JP2002100561A - Aligning method and aligner and method for fabricating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance uniformity in the distribution of light exposure without substantially deteriorating uniformity in the coherence factor of exposing beam. SOLUTION: A reticle 28 is irradiated with an exposing light IL from an exposure light source 1 through an illumination optical system ILS comprising a first fly eye lens 6, a second fly eye lens 9, lens systems 12 and 13, blinds 14A and 14B, and condenser lenses 17 and 18. Pattern of the reticle 28 is projected onto a wafer W through a projection optical system PL and transferred onto the wafer W by scanning exposing system. In the vicinity of a plane conjugate with an image plane between the second lens system 13 and the blind 14A, a density filter plate 51 carrying a pattern of specified transmittance distribution is disposed rotatably and the rotational angle of the density filter plate 51 is controlled to correct unevenness of illuminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for transferring a mask pattern onto a substrate in a lithography process for manufacturing a device such as a semiconductor device, a liquid crystal display device, a plasma display device, or a thin film magnetic head. An exposure method and an exposure apparatus.

[0002]

2. Description of the Related Art A lithography process (typically, a resist coating process, an exposure process, and a resist development process) for manufacturing a semiconductor device is performed in order to cope with an improvement in the degree of integration and fineness of a semiconductor device. In an exposure apparatus, it is required to improve the uniformity of the exposure amount distribution (exposure amount accuracy) to further improve the line width uniformity.
The improvement of the exposure accuracy is mainly due to the improvement of the uniformity of the illuminance distribution of the exposure light in the exposure field, that is, the reduction of "illuminance unevenness" and the exposure energy (pulse energy for pulsed light).
And the control accuracy is improved.

The illuminance unevenness is mainly illuminance unevenness axially symmetrical with respect to the optical axis (central symmetrical unevenness), ie, quadratic functional unevenness, and inclination in which the illuminance gradually increases or decreases in a region crossing the optical axis. Unevenness, that is, linear functional unevenness. In a batch exposure type exposure apparatus such as a stepper, it is necessary to correct these uneven illuminance with high accuracy in two orthogonal directions. On the other hand, in a scanning exposure type exposure apparatus such as a step-and-scan method, the illuminance unevenness in the scanning direction is averaged to a level that causes little problem by the scanning exposure operation. It is required to correct illuminance unevenness in a direction with high accuracy.

Conventionally, correction of uneven illuminance is performed by driving a predetermined lens group in the illumination optical system in the optical axis direction, or
This has been done by driving to change the tilt angle around the axis. In general, the state of uneven illuminance differs depending on lighting conditions. In particular, in the case of the central symmetry unevenness, the degree of unevenness of the illuminance changes in accordance with the change in the position through which the light beam passes in the lens group depending on the numerical aperture of the exposure light (illumination light). Therefore, the optimal position of the lens group to be adjusted is stored in advance for each illumination condition as an example, and the lens group is driven to the optimal position every time the illumination condition is switched.

Further, it is known that the exposure light in the ultraviolet region reacts with a trace amount of organic substances in the gas around the optical element, so that a fogging substance adheres to the surface of the optical element. Normally, a gas from which organic substances are removed through a chemical filter or the like is supplied around each lens of the illumination optical system and the projection optical system. The fogging of each lens gradually increases, and in particular, the central symmetric unevenness in which the illuminance at the central portion decreases may progress with time. In this case, the operator re-adjusts the position of the corresponding lens group according to the degree of progress of the central symmetry unevenness. Further, in the case where the central symmetry unevenness has progressed extremely in the course of using the exposure apparatus for several years, the lens group itself to be adjusted may be replaced with a lens group having a stronger correction effect.

[0006]

As described above, the correction of uneven illuminance of the conventional exposure apparatus involves controlling the position and tilt angle of a predetermined lens group including a lens having a certain curvature (refractive power) in the optical system. Or by replacing the lens group with another lens group. However, when trying to correct illuminance unevenness by driving a lens having a certain curvature other than a plane, coherence of illumination light in an illumination area on a reticle as a mask and further in an exposure area on a wafer as a substrate to be exposed. The uniformity of the factor (σ value) may be deteriorated. As described above, when the uniformity of the σ value is deteriorated in the exposure region, there is a disadvantage that the line width uniformity, which is an original purpose of suppressing the unevenness of the illuminance, is reduced.
On the other hand, if the correction amount of the illuminance unevenness is set so as to suppress the deterioration of the uniformity of the σ value, the line width control accuracy is limited.

In particular, in recent years, the design rules (standard line width) of semiconductor devices have been miniaturized year by year. In order to further improve the line width control accuracy, the uniformity of the σ value has not been degraded. The development of an exposure method capable of improving the uniformity of the dose distribution has been desired. In view of the above, it is a first object of the present invention to provide an exposure method that can improve the uniformity of the exposure amount distribution.

Another object of the present invention is to provide an exposure method capable of improving the uniformity of the dose distribution without substantially deteriorating the uniformity of the coherence factor of the exposure beam. Still another object of the present invention is to provide an exposure apparatus capable of performing the exposure method, and a device manufacturing method capable of manufacturing a device with high line width control accuracy using the exposure method.

[0009]

A first exposure method according to the present invention is an exposure method for exposing a second object (W) through a first object (28) with an exposure beam. In the optical path of the exposure beam, the transmittance distribution for the exposure beam is two-dimensionally variable in the vicinity of the exposure surface of the second object or in a plate-like region near the surface conjugate to the exposure surface. It is controlled by.

According to the present invention, instead of adjusting the illuminance unevenness by driving an optical element having a predetermined curvature other than a plane, the flat area is corrected so as to correct the illuminance unevenness. The transmittance distribution is controlled two-dimensionally.
This makes it possible to control the illuminance distribution without substantially deteriorating the uniformity of the coherence factor of the exposure beam in the exposure area of the second object. Therefore, by controlling the illuminance distribution so as to correct the unevenness of the integrated exposure amount on the second object, the uniformity of the exposure amount distribution can be improved so that the line width uniformity can be surely improved. Further, since the transmittance distribution is not fixed but is two-dimensionally variable, an optical element such as an illumination system may be fogged or the like, and the second element may be degraded over time.
When the illuminance distribution on the object changes, the uniformity of the exposure distribution can always be maintained high by controlling the transmittance distribution so as to cancel the change.

In this case, as an example, the transmittance distribution for the exposure beam is controlled by a concentric distribution and a distribution rotatable about the optical axis so as to correct the unevenness of the exposure distribution for the second object. Is done. With such a concentric distribution, uneven illuminance that is axially symmetric with respect to the optical axis (uneven central symmetry) can be corrected well. Further, by rotating the transmittance distribution, the central symmetry unevenness can be corrected substantially continuously within a predetermined range.

Further, as another example, the transmittance distribution for the exposure beam is controlled in a variable one-direction with a predetermined distribution so as to correct the unevenness of the exposure amount distribution for the second object. That is, the transmittance distribution is controlled by a one-dimensional predetermined distribution whose direction is variable. Thus, when the one-dimensional transmittance distribution is used, it is possible to correct the unevenness of the integrated exposure amount in the non-scanning direction (the direction orthogonal to the scanning direction) when performing the scanning exposure. That is, when the predetermined distribution is a distribution that changes one-dimensionally symmetrically with respect to the optical axis as a center, the central symmetry unevenness (quadratic functional unevenness) is substantially continuously reduced within a predetermined range after the scanning exposure. When the predetermined distribution is a distribution that gradually increases or decreases across the optical axis, after scanning exposure, inclination unevenness (linear function-like unevenness) is substantially continuously corrected within a predetermined range. it can.

The transmittance distribution for the exposure beam may be further controlled in a direction intersecting the direction of the predetermined distribution with the same distribution as the predetermined distribution or another distribution. By combining a plurality of one-dimensional transmittance distributions in this manner, it is possible to correct two-dimensional unevenness in illuminance such as uneven central symmetry and uneven tilt in a stationary state. It can also be applied to devices. Also, a mechanism for driving a large lens group to correct uneven illuminance can be omitted.

In the scanning exposure method in which the first object and the second object are moved in synchronization with each other in the scanning direction when exposing the second object, the exposure of the second object by the exposure beam is performed. It is desirable to control the transmittance distribution for the exposure beam so that the exposure distribution (exposure distribution in the non-scanning direction) obtained by integrating the amounts in the scanning direction is uniform. In this case, since the illuminance unevenness in the scanning direction is averaged by the scanning exposure, by making the exposure amount distribution in the non-scanning direction orthogonal to the scanning direction uniform,
The integrated exposure amount distribution is made uniform over the entire surface of the second object,
High line width control accuracy can be obtained.

Next, a second exposure method according to the present invention is an exposure method for illuminating a first object (28) with an exposure beam and exposing a second object (W) with the exposure beam via the first object. In the method, the illumination condition of the first object is changed according to the pattern to be transferred onto the second object, and the illuminance unevenness in the irradiation area of the exposure beam is divided into a tilt component and a centrally symmetric component. The center symmetric component is adjusted without adjusting the tilt component within a predetermined period after the adjustment.

According to the present invention, when the illumination condition is changed, after adjusting the inclination component and the centrally symmetric component of the illuminance unevenness first, the centrally symmetric component is adjusted, thereby making it relatively simple. The uniformity of the exposure distribution can be improved by a simple adjustment process. In this case, the first and second objects are relatively moved with respect to the exposure beam, and the second object is scanned and exposed with the exposure beam via the first object. When the illumination condition is changed, A tilt component in a non-scanning direction orthogonal to the scanning direction in which the first and second objects are moved may be adjusted. In the scanning exposure method, since the illuminance unevenness in the scanning direction is averaged, the uniformity of the exposure amount distribution can be easily improved by adjusting the tilt component in the non-scanning direction in the illuminance unevenness.

The tilt component and its center symmetry are obtained so that the light amount distribution in the non-scanning direction, which is obtained by integrating the light amount in the scanning direction within the irradiation area of the exposure beam, is substantially uniform. The components may be adjusted. By obtaining the integrated exposure distribution, the actual exposure distribution after the scanning exposure can be adjusted.
Next, the first exposure apparatus according to the present invention includes an illumination system (1 to 10, 12, 1) for illuminating the first object (28) with an exposure beam.
3, 14A, 14B, 16 to 18), which exposes a second object through the first object, the exposure of the second object on the optical path of the exposure beam to the second object. One or a plurality of flat filter members (51, 51) disposed near the surface or near a surface conjugate to the exposure surface and having a predetermined transmittance distribution for the exposure beam.
55, 61, 63).

According to the present invention, the transmittance distribution is made substantially continuous by, for example, mechanically rotating the filter member or electrically rotating the transmittance distribution of the filter member. , The exposure method of the present invention can be implemented. In this case, it is desirable to have a drive device (52) for controlling the rotation angle of the filter member itself or controlling the transmittance distribution of the filter member to be electrically rotated. This makes it possible to automatically correct the exposure unevenness.

In this case, the illumination system includes one or more stages of optical integrators (6, 9) for equalizing the illuminance distribution of the exposure beam, and the second stage of the exposure beam from the optical integrator. When a field stop (14A) that defines an illumination area on one object is provided, the filter member is provided on a surface near the field stop or a surface near the irradiated surface of the first object. It is desirable to be arranged. Thereby, the filter member can be easily arranged.

Further, the filter member is composed of two filter members (51A, 51B) having the same transmittance distribution in one-dimensional direction symmetrically with respect to the optical axis, respectively. You may make it drive rotationally in mutually opposite phases. This makes it possible to continuously correct central symmetry unevenness with simple control. Also, the first
A stage system (31, 39) for moving the object and the second object in synchronization with the scanning direction;
An exposure distribution measuring device (42) for measuring a distribution of an integrated value of the exposure amount on the object in the scanning direction, and a filter provided via the driving device according to the exposure distribution measured by the distribution measuring device It is desirable to further have a control device (22) for controlling the rotation angle of the member. This means that the present invention is applied to a scanning exposure type exposure apparatus, and the distribution measuring apparatus measures the distribution of the integrated value in the non-scanning direction, and the distribution is measured so that the distribution becomes uniform. By rotating the filter member, the exposure unevenness can be corrected with high accuracy.

Next, a second exposure apparatus of the present invention illuminates a first object (28) with an exposure beam, and exposes a second object (W) with the exposure beam via the first object. In the apparatus, the first object can be illuminated under a plurality of illumination conditions, and the illuminance distribution of the exposure beam has the same tendency under the plurality of illumination conditions. 14A, 14B, 16-1
8) and an optical member (51, 5) arranged on the optical path of the exposure beam to the second object and adjusting the illuminance distribution thereof.
5, 61, 63).

According to the present invention, when the illumination conditions are switched from, for example, normal illumination to deformed illumination, small σ value illumination, or the like, when the degree of central symmetry unevenness or tilt unevenness slightly changes, By canceling out the variation in the illuminance unevenness by the optical member, the uniformity of the exposure amount distribution can be improved. In this case, it is desirable that the illumination optical system is adjusted so that the illuminance distribution has illuminance unevenness substantially symmetric with respect to the optical axis of the illumination optical system. This facilitates correction of uneven illuminance. The optical member includes, for example, at least one optical filter that is disposed apart from the exposure surface of the second object or the conjugate surface thereof and has a predetermined transmittance distribution with respect to the exposure beam.

The device manufacturing method of the present invention includes a step of transferring a device pattern (28) onto a substrate (W) using any of the exposure methods or any of the exposure apparatuses of the present invention. According to the present invention, high-performance devices with high line width control accuracy can be mass-produced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention is applied to a step-and-scan type scanning exposure type projection exposure apparatus. FIG. 1 shows a schematic configuration of a projection exposure apparatus of this embodiment. In FIG. 1, an ArF excimer laser light source (wavelength 193 nm) is used as an exposure light source 1. However, as the exposure light source 1, KrF excimer laser (wavelength 248 nm), F ₂ laser (wavelength 15
7 nm), a Kr ₂ laser (wavelength 146 nm), a harmonic generator of a YAG laser, a harmonic generator of a semiconductor laser, a mercury lamp, or the like. Exposure light IL (exposure beam) composed of ultraviolet pulse light having a wavelength of 193 nm from the exposure light source 1 passes through a beam matching unit (BMU) 2 for positionally matching an optical path with an exposure apparatus main body, and passes through an optical attenuator. To the variable attenuator 3. An exposure control unit 21 for controlling the amount of exposure to the photoresist on the wafer controls the start and stop of light emission of the exposure light source 1 and the output (oscillation frequency, pulse energy), and the light reduction in the variable dimmer 3. The luminous efficiency is adjusted stepwise or continuously.

The exposure light IL that has passed through the variable dimmer 3 passes through a beam shaping system 5 composed of a first lens system 4A and a second lens system 4B arranged along a predetermined optical axis, and a first-stage optical system. The light enters the first fly-eye lens 6 as an integrator (uniformizer or homogenizer). The exposure light IL emitted from the first fly-eye lens 6 passes through a first lens system 7A, a mirror 8 for bending the optical path, and a second lens system 7B as a second stage optical integrator. The light enters the eye lens 9.

An aperture stop plate 10 is provided on the exit surface of the second fly-eye lens 9, that is, on the optical Fourier transform surface (pupil surface of the illumination system) with respect to the pattern surface (reticle surface) of the reticle 28 as a mask to be exposed. , Are rotatably arranged by a drive motor 10e. The aperture stop plate 10 has a circular aperture stop 10a for normal illumination, an aperture stop 10b for orbicular illumination as an example of modified illumination, and an aperture stop (a plurality of eccentric small apertures as another example of modified illumination). (Not shown) and a small circular aperture stop (not shown) for a small coherence factor (σ value) are arranged to be switchable. An “illumination condition switching system” for switching the illumination condition to one of a plurality of illumination conditions (normal illumination, deformed illumination, and small σ value illumination) by the aperture stop plate 10 and the drive motor 10e is configured, and the operation of the entire apparatus is configured. Is set by the main control system 22 for controlling the lighting conditions via the drive motor 10e.

In FIG. 1, an aperture stop 10a for normal illumination is provided on the exit surface of the second fly-eye lens 9, and the aperture stop 10a is emitted from the second fly-eye lens 9 to emit light.
The exposure light IL that has passed through 0a is incident on the beam splitter 11 having a high transmittance and a low reflectance. The exposure light reflected by the beam splitter 11 is incident on an integrator sensor 20 composed of a photoelectric detector via a converging lens 19, and a detection signal S 1 of the integrator sensor 20 is supplied to an exposure control unit 21. The relationship between the detection signal of the integrator sensor 20 and the illuminance of the exposure light IL on the wafer W as a substrate to be exposed is measured in advance with high accuracy.
It is stored in a memory in the exposure control unit 21. The exposure control unit 21 is configured to be able to indirectly monitor the illuminance (average value) of the exposure light IL on the wafer W and the integral value (average value of the integrated exposure amount) from the detection signal of the integrator sensor 20. .

Exposure light I transmitted through beam splitter 11
L is a fixed blind (fixed field stop) 14A and a movable blind (movable field stop) 14B sequentially through the first lens system 12, the second lens system 13, and the rotatable density filter plate 51 along the optical axis IAX. Incident on. The latter movable blind 14B is disposed on a conjugate plane with respect to the reticle plane, and the former fixed blind 14A is disposed on a plane defocused by a predetermined amount from the conjugate plane. Also,
The filter member of the present invention and a density filter plate 51 (details described later) corresponding to a flat region having a variable transmittance distribution are provided.
It is arranged on a surface further defocused by a predetermined amount from the fixed blind 14A, that is, a surface slightly defocused from a conjugate surface with the reticle surface. By arranging the density filter plate 51 on the surface slightly defocused from the conjugate plane with the reticle surface, the density filter plate 5
The transfer of an image of a foreign substance such as dust adhered to the wafer 1 onto the wafer W can be prevented.

Instead of arranging the density filter plate 51 on the defocus surface or in combination therewith, for example, an optical element (for example, the lens system 16) disposed between the density filter plate 51 and the reticle 28 is used. ~ 1
8 or a diffuser plate (not shown)) to make the density filter plate 51 and the image of the foreign matter unclear in the illumination area 35, thereby lowering the illuminance uniformity and consequently on the wafer W. May be prevented from lowering the uniformity of the exposure amount distribution.

The fixed blind 14A is disclosed in, for example,
As disclosed in Japanese Patent Application Laid-Open No. 196513, the optical axis AX is substantially at the center in the projection field of view of the projection optical system PL, and is orthogonal to the scanning direction (Y direction) in which the reticle 28 and the wafer W are moved during scanning exposure. Straight slit shape or rectangular shape (hereinafter collectively referred to as “slit shape”) in the non-scanning direction (X direction)
). That is, in the present example, the fixed blind 14A includes the illumination area 35 on the reticle 28 to which the exposure light IL is irradiated, and the wafer W
The upper exposure area 35P (the projection area in which the image of the pattern in the illumination area 35 is formed conjugate with the illumination area 35 with respect to the projection optical system PL) is defined, and at least the opening having a fixed width in the scanning direction is fixed. Have.

On the other hand, the movable blind 14B
Used to change the width in the scanning direction of the illumination area 35 and the exposure area 35P defined by the fixed blind 14A in order to prevent unnecessary exposure at the start and end of the scanning exposure to each of the above shot areas. Is done. The movable blind 14B is also used for making the width thereof variable in the direction orthogonal to the scanning direction (non-scanning direction) according to the size of the pattern area of the reticle 28. The information on the aperture ratio of the movable blind 14B is also supplied to the exposure control unit 21, and the value obtained by multiplying the illuminance obtained from the detection signal of the integrator sensor 20 by the aperture ratio is the actual illuminance on the wafer W.

The arrangement of the fixed blinds 14A, the movable blinds 14B, and the density filter plate 51 is as shown in FIG.
The invention is not limited to this, and the point is that it may be disposed on a surface substantially conjugate to the surface of the wafer W (the image forming surface of the projection optical system PL) or a surface separated by a predetermined distance from the conjugate surface. May be arranged close to the surface of the wafer W.

The exposure light IL that has passed through the fixed blind 14A during exposure passes through a mirror 15 for bending the optical path, a lens system 16 for imaging, a sub-condenser lens system 17, and a main condenser lens system 18 to serve as a mask. The illumination area (illumination visual field area) 35 on the pattern surface (reticle surface) of the reticle 28 is illuminated. Under the exposure light IL, an image of the circuit pattern in the illumination area of the reticle 28 is projected at a predetermined projection magnification β (β
Are, for example, 1/4, 1/5, etc.), which are transferred to a slit-like exposure area 35P of a photoresist layer on a wafer W as a substrate (substrate to be exposed) disposed on an image plane of the projection optical system PL. You. The reticle 28 and the wafer W correspond to the first object and the second object of the present invention, respectively,
r) W is, for example, a semiconductor (such as silicon) or SOI (silicon)
on insulator). The projection optical system PL as the projection system in this example is a diopter system (refractive system), but it goes without saying that a catadioptric system (reflective system) or a reflective system can also be used. Hereinafter, the Z axis is taken in parallel with the optical axis AX of the projection optical system PL, the Y axis is taken in the scanning direction (here, the direction parallel to the plane of FIG. 1) in a plane perpendicular to the Z axis, and orthogonal to the scanning direction. The description will be made by taking the X axis in the non-scanning direction (in this case, the direction perpendicular to the paper surface of FIG. 1).

In FIG. 1, in this example, the beam matching unit 2, the variable dimmer 3, the beam shaping system 5, the first fly-eye lens 6, the lens systems 7A and 7B, the mirror 8, the second fly-eye lens 9, Aperture stop plate 10, lens system 1
2, 13, fixed blind 14A, movable blind 14
The illumination optical system ILS is constituted by B, the imaging lens system 16, the sub-condenser lens system 17, the main condenser lens system 18, and the like. The exposure light source 1 and the illumination optical system ILS correspond to the illumination system of the present invention. In this example, the density filter plate 51 is arranged in the illumination optical system ILS, and the illumination optical system ILS
The optical axis IAX of the LS is projected on the reticle 28 by the projection optical system PL.
Of the optical axis AX.

The density filter plate 51 may be arranged not on the entrance side of the fixed blind 14A but on the surface close to the exit side of the movable blind 14B. Alternatively, for example, the fixed blind 14A is arranged on a surface near the pattern surface (reticle surface) of the reticle 28, for example, a surface close to the upper surface of the reticle 28, and the density filter plate 51 is set on the input side of the movable blind 14B in FIG. It may be arranged on a surface defocused by an interval. Thus, the density filter plate 51 can be easily arranged.

In addition, the density filter plate 51 is provided with a conjugate plane (that is, a reticle plane) with another image plane different from the plane (conjugate plane with the image plane) on which the movable blind 14B is arranged in the illumination optical system ILS. (A conjugate plane). As an example, in FIG.
With the fixed blind 14A arranged near 4B,
The density filter plate 51 may be arranged on a surface in the vicinity of the pattern surface of the reticle 28, for example, on the upper surface or the lower surface of the reticle 28 at a predetermined interval. Further, when the projection optical system PL internally forms an intermediate image, the density filter plate 51 may be disposed on a surface separated from the surface on which the intermediate image is formed. In addition, the movable blind 14B may be arranged, for example, close to the reticle surface.

The lens units 12 and 13 and the density filter plate 51 of this embodiment are provided with the drive units 24 and 2 respectively.
5, and 52 are mounted. FIG. 2 is a perspective view showing the relationship between the optical system from the second fly-eye lens 9 to the fixed blind 14A in FIG. 1 and the illumination area 35. In FIG. The directions on the fixed blind 14A corresponding to the (Y direction) and the non-scanning direction (X direction) are defined as the Y direction and the X direction, respectively. Note that the fixed blind 14A (fixed field stop) shows only the slit-shaped opening.

In this case, the drive unit 24 adjusts the position of the first lens system 12 in the direction of the optical axis IAX. Further, the drive unit 25 of FIG. 1 includes the drive unit 25R of FIG.
Of the illumination area 35 in the direction corresponding to the non-scanning direction of the illumination area 35 is adjusted. Further, the drive unit 52 shown in FIG. 1 includes a gear unit 52 mounted around a disc-shaped density filter plate 51 shown in FIG. 2 via a ring-shaped holder (not shown).
G and a drive unit 52W including a gear and a motor for rotationally driving the gear unit 52G.
Thus, the density filter plate 51 can be rotated by a desired angle θ within a range of 90 ° around the optical axis IAX.

As the driving units 24 and 25R, for example, an electric micrometer or a driving device that displaces a holder of an optical element to be driven by a driving element such as a piezo element can be used. In this case, the driving unit 2
The encoders (rotary encoders and the like) (not shown) each indicating the amount of displacement of the optical element within the drivable range (drive stroke) are incorporated in the 4, 25R, and the drive unit 52W. The signal is supplied to the drive system 26 of FIG.
The drive system 26 controls the states of the lens systems 12 and 13 and the density filter plate 51 via the drive units 24, 25 and 52 based on the drive information from 2.

In this case, as an example, the first lens system 12
Is driven in the optical axis direction, thereby correcting central symmetric unevenness (quadratic functional unevenness), which is illuminance unevenness axially symmetric with respect to the optical axis, and controlling the tilt angle of the second lens system 13 by In the region crossing the optical axis, the illumination unevenness is gradually increased or decreased. Then, finally, the rotation angle of the density filter plate 51 is controlled to keep the uniformity of the exposure amount distribution on the wafer W within a predetermined allowable range (details will be described later). In this example, since the central symmetry unevenness can be substantially corrected by controlling the rotation angle of the density filter plate 51, the drive unit 24 of the first lens system 12 may be omitted. Thereby, the mechanism of the illumination optical system can be simplified.

Returning to FIG. 1, the reticle 28 is sucked and held on the reticle stage 31, and the reticle stage 31
Is mounted on the reticle base 32 so as to be able to move at a constant speed in the Y direction and to be finely movable in the X direction, the Y direction, and the rotation direction. Reticle stage 31 (reticle 28)
The two-dimensional position and rotation angle of the drive control unit 34
It is measured in real time by a laser interferometer inside. Based on the measurement result and the control information from the main control system 22, the drive motor (such as a linear motor or a voice coil motor) in the drive control unit 34 controls the scanning speed and the position of the reticle stage 31.

An evaluation mark plate 33 made of a glass substrate is fixed near the reticle 28 on the reticle stage 31 in the scanning direction. A plurality of two-dimensional identical evaluation marks 36A are formed in a substantially uniform distribution in an area of the evaluation mark plate 33 having substantially the same size as the illumination area 35. The image of the evaluation mark 36A is projected onto the wafer side via the projection optical system PL, and the position of the spatial image is measured, whereby the distortion of the projection optical system PL, imaging characteristics such as field curvature, and illumination. The amount of collapse of the telecentricity of the optical system can be measured.

In FIG. 1, a wafer W is held by suction on a wafer stage 39 via a wafer holder 38. The wafer stage 39 is placed on a wafer base 40 along an XY plane parallel to the image plane of the projection optical system PL. Move two-dimensionally.
That is, the wafer stage 39
, And at a constant speed, and stepwise in the X and Y directions. Further, the wafer stage 39 also incorporates a Z leveling mechanism for controlling the position (focus position) of the wafer W in the Z direction and the tilt angles around the X axis and the Y axis. A multipoint autofocus sensor (not shown) for measuring a focus position at a measurement point is also provided. At the time of exposure, the surface of the wafer W is focused on the image plane of the projection optical system PL by driving the Z leveling mechanism by the autofocus method based on the measurement value of the autofocus sensor.

The position of the wafer stage 39 in the X and Y directions and the rotation angles around the X, Y and Z axes are measured in real time by a laser interferometer in the drive control unit 41. The drive motor (such as a linear motor) in the drive control unit 41 controls the scanning speed and the position of the wafer stage 39 based on the measurement result and the control information from the main control system 22. The main control system 22 sends various information such as the moving position, moving speed, moving acceleration, and position offset of each of the reticle stage 31 and the wafer stage 39 to the drive control units 34 and 41. At the time of scanning exposure, the wafer stage 39 is moved in synchronization with the reticle 28 being scanned at a speed Vr in the + Y direction (or -Y direction) with respect to the illumination area 35 of the exposure light IL via the reticle stage 31. The wafer W moves at a speed β · Vr in the −Y direction (or + Y direction) with respect to the exposure region 35P
(Β is a projection magnification from the reticle 28 to the wafer W). At this time, at the start and end of the scanning exposure, a drive control unit 34 is provided to prevent unnecessary portions from being exposed.
Thus, the opening and closing operation of the movable blind 14B is controlled.

Further, the main control system 22 reads from the exposure data file various exposure conditions for scanning and exposing the photoresist in each shot area on the wafer W with an appropriate exposure amount, and optimally cooperates with the exposure control unit 21. A simple exposure sequence. That is, when a command to start scanning exposure to one shot area on the wafer W is issued from the main control system 22 to the exposure control unit 21, the exposure control unit 21
Starts the light emission of the exposure light source 1 and the illuminance of the exposure light IL to the wafer W via the integrator sensor 20 (the sum of the pulse energy per unit area and unit time).
Is calculated. The integrated value is 0 at the start of scanning exposure.
Has been reset to Then, the exposure control unit 21
Then, the integrated value of the illuminance is sequentially calculated, and according to the result, the output of the exposure light source 1 (the oscillation frequency, the oscillation frequency, and the like) is obtained so that the appropriate exposure amount can be obtained at each point of the photoresist on the wafer W after the scanning exposure. And the pulse energy) and the dimming rate of the variable dimmer 3. Then, at the end of the scanning exposure on the shot area, the emission of the exposure light source 1 is stopped.

In the vicinity of the wafer holder 38 on the wafer stage 39 of the present embodiment, an illuminance unevenness sensor 42 as an exposure distribution measuring device is installed, as shown in FIG. Is a pinhole-shaped light receiving section 4
A first sensor composed of a photoelectric sensor having a second sensor 2a and a line sensor 42b (a second sensor) having a row of photoelectric conversion elements (pixels) elongated in the scanning direction SD (Y direction).
Is provided, and according to control information from the main control system 22,
The photoelectric conversion signal of either the first sensor or the second sensor is supplied to the exposure control unit 21 of FIG. 1 as a detection signal S4.

In FIG. 3A, the line sensor 42b
In the scanning direction SD of the exposure region 35P.
When the illuminance unevenness in the non-scanning direction (X direction) in the exposure area 35P is set to be wider than the width of D, the wafer stage 39 in FIG.
Line sensor 42b of uneven illuminance sensor 42 on the side in the direction
And the photoelectric conversion signal read from the line sensor 42b is supplied to the exposure control unit 21 as the detection signal S4. Thereafter, light emission of the exposure light source 1 is started, the wafer stage 39 is driven, and the line sensor 42b is moved to a plurality of measurement points arranged at predetermined intervals in the X direction so as to cross the exposure area 35P, and each measurement is performed. At this point, the exposure control unit 21 obtains an integrated signal obtained by integrating the detection signal of the line sensor 42b in the Y direction, and supplies the integrated signal to the main control system 22. Actually, since the exposure light IL has a certain degree of energy variation for each pulse emission,
The integrated signal is standardized using the detection signal S1 of the integrator sensor 20 in FIG. The main control system 22 includes:
The standardized integrated signal (also called S4) is stored in the storage device in correspondence with the position X of the line sensor 42b in the non-scanning direction.

FIG. 3B shows an example of the integrated signal S4. In FIG.
The position X in the non-scanning direction of 2b, and the vertical axis is the integrated signal S4. The integration signal S4 is an exposure amount obtained by integrating the exposure amount of the exposure area 35P in the scanning direction at each measurement point in the non-scanning direction, that is, the exposure amount (integration amount) given to a predetermined point on the wafer by the scanning exposure. Exposure).
Therefore, the integrated signal S4 substantially represents the distribution (non-uniformity of exposure) in the non-scanning direction of the exposure amount (integrated exposure amount) after each shot area on the wafer is scanned and exposed by the exposure area 35P. Become.

In FIG. 3B, when the integrated signal S4 is flat with respect to the position X as indicated by the straight line 53A, it indicates that there is no unevenness in the exposure amount in the non-scanning direction. High uniformity of distribution (high exposure dose accuracy) is obtained. On the other hand, the integrated signal S4 is represented by a curve 53B.
As shown in the figure, when the distribution of the central concave portion becomes smaller at the center portion including the optical axis AX, the exposure dose unevenness is axially symmetric with respect to the optical axis.
That is, it can be seen that the illuminance unevenness (central symmetric unevenness) is axisymmetric. To correct this, the transmittance near the optical axis may be relatively increased using, for example, the density filter plate 51 in FIG. Further, the integrated signal S4 is a straight line 53C.
As shown in the above, when the tilt unevenness gradually increases so as to cross the optical axis AX, the tilt angle of the second lens system 13 in FIG.
In this example, by using the line sensor 42b in this way, it is possible to easily measure the unevenness of the exposure amount after the scanning exposure in the non-scanning direction, that is, the illuminance unevenness in the non-scanning direction. In addition, the pinhole-shaped light receiving portion 42a in FIG. 3A is moved to a plurality of measurement points two-dimensionally set in the exposure region 35P, and the illuminance is measured, thereby obtaining the light in the exposure region 35P. Irradiance unevenness in the X direction and the Y direction can also be measured.

Further, at each position in the non-scanning direction (X direction) within the exposure area 35P, the illuminance at each measurement point in the scanning direction (Y direction) is integrated to calculate the integrated light amount (exposure amount) of the exposure light IL. By calculating, the exposure amount distribution (non-uniform exposure amount) in the non-scanning direction can be obtained in the same manner as in the light receiving unit 42b. At this time, at each position in the non-scanning direction,
Illuminance at each measurement point may be measured while stepping 2a in the scanning direction. At each position in the non-scanning direction, the light receiving section 42a is relatively moved with respect to the exposure area 35P along the scanning direction, and the wafer W It is preferable to control the oscillation (oscillation frequency and pulse energy) of the exposure light source 1 and the moving speed of the wafer stage 39 under the same conditions as the scanning exposure.
Thereby, while the light receiving section 42a crosses the exposure area 35P, the exposure light IL having the same number of pulses as in the scanning exposure is applied to the light receiving section 4a.
2a, the integrated light amount (exposure amount) of the exposure light IL can be accurately measured at each position in the non-scanning direction.
Therefore, in this example, the irradiation unevenness sensor 42 includes the light receiving unit 42a,
Although the illuminance unevenness sensor 42 need only be provided with one of the light receiving portions 42a and 42b. The light receiving section 42b is used to measure the integrated light amount (exposure amount) of the exposure light IL at each position in the non-scanning direction.
It is preferable that the number of light receiving elements (arrays) arranged in 5P is the same as the number of pulses applied to each point on the wafer W during scanning exposure. At this time, for example, it is preferable to irradiate the same number of exposure lights IL as during the scanning exposure, and integrate outputs of different light receiving elements for each pulse to determine the integrated light amount.

Returning to FIG. 1, although not shown, a radiation dose monitor having a light receiving portion that covers the entire exposure area 35P is also provided on the wafer stage 39, and a detection signal of the radiation dose monitor and a signal of the integrator sensor 20 are provided. Based on the detection signal and the detection signal of the integrator sensor 20, the wafer W
A coefficient for indirectly obtaining the above illuminance is calculated. Further, a scanning plate 43 made of a glass substrate is provided near the wafer holder 38 on the wafer stage 39, and a substantially square opening pattern 43a is formed in the light shielding film on the scanning plate 43. Then, a condenser lens 44 and a photoelectric detector 45 are provided on the bottom side of the scanning plate 43 in the wafer stage 39.
Are arranged, and a scanning image 43, a condenser lens 44, and a photoelectric detector 45 constitute an aerial image measurement system 46, and a detection signal of the photoelectric detector 45 is supplied to an arithmetic unit in the exposure control unit 21. The position of the image of the evaluation mark 36A formed on the evaluation mark plate 33 on the reticle stage 31 can be measured by the aerial image measurement system 46.

The exposure light IL of this embodiment has a wavelength of 200 nm.
The following almost vacuum ultraviolet light (VUV light: Vacuum Ultraviolet)
ray), and absorption by light-absorbing substances such as water vapor and carbon dioxide is large. Also, the absorption by oxygen increases gradually. Therefore, in the optical path of the exposure light IL from the exposure light source 1 to the wafer W in FIG. 1, those light absorbing substances are removed, and a chemical filter or a HEPA filter (high e
A purge gas, which is a gas from which organic substances and fine dusts have been removed using a fficiency particulate air-filter, is supplied. Dry air, nitrogen gas, helium gas, or the like can be used as the purge gas.

Even when a purge gas from which organic substances and the like are highly removed is used, a trace amount of the remaining organic substances and the like cause a chemical reaction with the exposure light IL, and each of the components in the illumination optical system ILS and the projection optical system PL is removed. The cloudy substance gradually adheres to the surface of the optical element, the transmittance distribution changes, and uneven illuminance occurs in the exposure area 35P on the wafer W with time. The illuminance unevenness caused by the cloudy substance tends to be axially symmetrical (quadratic functional unevenness) with respect to the optical axis AX (which coincides with the exposure center in this example). There is a tendency to cause illuminance unevenness in which the illuminance is reduced at the center (hereinafter, referred to as “center concave unevenness”). Therefore, in the present embodiment, the central symmetry unevenness (particularly, the concave unevenness) that occurs mainly over time is corrected using the rotatable density filter plate 51 of FIG.

Hereinafter, the rotatable density filter plate 51 will be described.
An example of the configuration and the method of using the same will be described in detail. FIG. 4A shows an arrangement of the density filter plate 51 in FIG. 1 (or FIG. 2) in an initial state. In FIG. 4A, the density filter plate 51 is a flat circular plate that transmits exposure light. A predetermined light-blocking material such as metal (for example, chromium) or a dimming material is coated on one surface of the glass substrate by vapor deposition or the like so that a one-dimensional predetermined transmittance distribution can be obtained axially symmetrically with respect to the optical axis IAX. It is what I wore.

In FIG. 4A, the direction having the transmittance distribution of the density filter plate 51 is in the Y direction (scanning direction) with respect to the fixed blind 14A (represented by a slit-like opening; the same applies hereinafter). Is set, and the transmittance T in the Y direction is set.
(Y) is expressed as follows using the coefficient a. T (Y) = 1 / (a · Y ² +1) (1) This function cancels out the quadratic functional irregularities due to the fact that the central symmetry irregularities usually become quadratic functional irregularities. Has been determined. This function is determined in several ways by the amount of (expected) occurrence of the actual central symmetry unevenness.
The coefficient a in the equation (1) is a parameter for determining the maximum correction amount of the density filter plate 51. The radius of the density filter plate 51 is R, and the maximum correction amount of the transmittance at the outermost contour of the density filter plate 51 is D. Then, the coefficient a becomes as follows.
The maximum correction amount D is, for example, 0.1 (10%).

A = D / {(1−D) R ² } (2) In this example, even if the projection exposure apparatus of FIG. 1 is operated in the actual exposure process for about two years or more, Irradiation unevenness due to a cloudy substance that gradually adheres to the optical element can be corrected by the single density filter plate 51. Assuming that the degree of central symmetry unevenness in the exposure area 35P, particularly the center concave unevenness in the exposure area 35P after using the projection exposure apparatus for two years is about 10% in the range, the value of the coefficient a in the equation (2) becomes Become like

A = 0.1 / (0.9 · R ² ) (2A) As shown in FIGS. 4A to 4C, the density filter plate 51 has an angle of 90 ° about the optical axis IAX. It can be rotated by any angle θ within the range. FIG. 4A shows a state in which the density filter plate 51 is not rotated, that is, the angle θ.
Indicates a state of 0 °, in which state the fixed blind 14
Average transmittance T in the non-scanning direction (X direction) in the opening of A
(X) is flat as shown by the straight line 54A, and the function of adjusting the illuminance unevenness in the non-scanning direction does not work. In addition,
In the following figures, the X coordinate on the optical axis IAX is set to 0. Further, in the scanning direction (Y direction), the transmittance distribution is higher at the center, but the illuminance unevenness in the scanning direction is averaged by scanning exposure.

On the other hand, FIG. 4 (c) shows a case where the density filter plate 51 is rotated by 90 ° in order to correct the indentation unevenness which has progressed extremely due to aging. In this case, the transmittance T (X) in the non-scanning direction is as follows. T (X) = 1 / (a · X ² +1) (3) At this time, the distribution of the transmittance T (X) has a maximum difference between the maximum value and the minimum value as shown by the curve 54C, and the density filter The effect of correcting the unevenness of the concave portion by the plate 51 is maximized. Also,
From the equation (2), the minimum value T ′ of the curve 54C is 0.9 (9
0%).

FIG. 4B shows the density filter plate 5.
1 is rotated 45 ° (θ = 45 °), and the transmittance T corresponding to each point in the opening (corresponding to the exposure area 35P on the wafer) of the fixed blind 14A in this case is shown.
(X, Y, θ) is as follows. T (X, Y, θ) = 1 / {a (Xsin θ−Ycos θ) ² +1} (4) Then, the transmittance T (X) in the non-scanning direction obtained by averaging the transmittance in the Y direction. ) Is represented by a curve 54B, and it can be seen that the correction effect of the middle concave unevenness at an intermediate level between θ = 90 ° and θ = 0 ° is obtained.

As shown in FIGS. 4A to 4C, the average transmittance distribution in the non-scanning direction can be adjusted to an arbitrary characteristic by rotating the density filter plate 51 at an arbitrary angle. It is possible to successively correct the unevenness of the hollow due to the irradiation variation over time. Moreover, since the density filter plate 51 is a thin flat plate installed near the conjugate plane with the image plane,
When the illuminance unevenness is corrected, the uniformity of the coherence factor (σ value) of the illumination optical system is hardly affected. That is, if the uniformity of the σ value is adjusted within a predetermined allowable range in the initial state, the uniformity of the σ value does not deteriorate even when the illuminance unevenness due to the aging change is corrected, and a high line is always obtained. Width uniformity is obtained.

Further, since the rotating mechanism of the density filter plate 51 is of an electric type (automatic control type), for example, during the regular maintenance, the unevenness of the exposure amount in the non-scanning direction is obtained by using the uneven illuminance sensor 42 as shown in FIG. Irradiation unevenness) is measured, and the density filter plate 51 can be rotationally driven at an optimum angle so as to offset the exposure unevenness on the spot.
Also, the projection exposure apparatus is managed for a long period of time, or the total irradiation amount is controlled, the degree of the concave pit unevenness at an arbitrary elapsed time is obtained by rough estimation, and the concave pit unevenness is automatically corrected so as to be corrected. The density filter plate 51 can also be rotated (in real time).

Further, it is possible to correct the difference between a plurality of illumination conditions of the illuminance unevenness which is initially generated. Although the density filter plate 51 of the present case has only the function of flattening the unevenness in the concave portion, for example, the density filter plate 5 shown in FIG.
By inserting a fixed density filter plate or the like in the vicinity of 1 in advance to make the illuminance unevenness slightly uneven in all the illumination conditions, and correcting the difference by rotation of the density filter plate 51, the illumination condition is reduced. Even in the case of switching between the normal illumination and the modified illumination, it is possible to suppress the occurrence of uneven illuminance. Since the density filter plate 51 of this example can be controlled electrically, the density filter plate 51 is changed every time the illumination condition is switched.
Can be rotated to an optimal angle. In all cases, a slight loss of illuminance occurs initially, but in practice, the illuminance loss can be suppressed to about 5% or less.

The density filter plate 51 can be manufactured by various manufacturing methods as shown in FIG. The density filter plate 51 shown in FIG. 5A continuously changes in the Y direction by depositing a light reducing substance such as chromium (Cr) on a light-transmitting substrate while continuously changing the film thickness. Is obtained. Note that a metal such as chromium becomes a light-shielding substance at a normal film thickness, but in this example, it is used as a light-reducing substance in a region having a film thickness through which chrome or the like transmits light to some extent. Further, the density filter plate 51 shown in FIG.
G is obtained by dividing one surface of the substrate into a plurality of band-shaped regions in the Y direction, and forming a dielectric multilayer film on each of these band-shaped regions so as to obtain a predetermined transmittance. That is,
In the density filter plate 51G, the transmittance distribution changes stepwise in the Y direction. By increasing the number of divisions to, for example, about 10 or more, the illuminance substantially equal to the transmittance distribution that changes continuously is obtained. An uneven correction effect can be obtained.

On the other hand, the density filter plate 51D shown in FIG.
Is a pattern in which a large number of fine light-shielding dot patterns such as chrome are deposited on a substrate with a probability of existence such that a predetermined transmittance distribution (macroscopic density distribution) can be obtained as a whole in the Y direction. Even when this is used, uneven illuminance can be corrected as in the case of FIG. Density filter plate 51D
Also, the dot pattern is placed at a position slightly defocused from the conjugate plane of the image plane, and is partially formed with a random distribution, so that the dot pattern is not transferred onto the image plane. The random dot pattern is, for example, a fine circular pattern having a diameter of about 25 μm. If the maximum correction amount of the concave unevenness is about 10%, the existence probability of the dot pattern at an arbitrary position in the density filter plate 51D. Is expected to fall within the range of about 0 to 15%.

Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment is an embodiment in which the center symmetry unevenness can be corrected not only after scanning exposure but also in a static exposure state. The basic configuration of the projection exposure apparatus of this embodiment is the same as that of FIG. 1, but in this embodiment, two rotatable density filter plates are provided instead of one density filter plate 51 of FIG. Is different. In FIG. 6, portions corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 6 shows the relationship between the optical system from the fly-eye lens 9 to the fixed blind 14A of the projection exposure apparatus of this embodiment and the slit-shaped illumination area 35. In FIG. 6, the arrangement surface of the fixed blind 14A is shown. That is, the first density filter plate 51A and the first density filter plate 51A are located adjacent to a position slightly defocused from the plane conjugate with the reticle surface (the plane conjugate with the image plane) to the second lens system 13 side. Second
Is disposed rotatably around the optical axis IAX. Two density filter plates 51A, 51
B have the same characteristics as the density filter plate 51 of FIG. 1 and have a one-dimensional transmittance distribution formed axially symmetrically with respect to the optical axis.

Also, the gear filter 52GA mounted around the first density filter plate 51A and the drive unit 52WA allow the density filter plate 51A to be rotated counterclockwise within 90 ° around the optical axis IAX. It is rotationally driven by the angle θA. On the other hand, the gear portion 52GB mounted around the second density filter plate 51B and the driving portion 52WB enable
The density filter plate 51B is rotated clockwise about the optical axis IAX by an angle θB within a range of 90 °. Furthermore, in the initial state of the present example, the two density filter plates 51
The rotation angles of A and 51B correspond to the density filter plate 5 shown in FIG.
Similar to 1, the average transmittance distribution in the non-scanning direction is set to be flat.

When correcting central symmetry unevenness (especially, center concave unevenness), two density filter plates 51A and 51B are used.
Are driven in the opposite phase by the same rotation angle, that is, by the same rotation angle in the opposite direction. Thereby, the transmittance distribution is changed to the optical axis IAX.
Can be corrected with an axially symmetric two-dimensional distribution centered on
In the stationary state, a uniform illuminance distribution can be obtained over the entire surface of the illumination area 35 (and thus the exposure area 35P). Moreover, the uniformity of the σ value of the illumination optical system does not deteriorate.

FIG. 7 shows such a density filter plate 51.
FIG. 7A shows a state in which A and 51B are rotated in opposite phases.
In the above, the density filter plate 51A is 45 ° counterclockwise.
(ΘA = 45 °), and in FIG. 7B, the density filter plate 51B is rotated clockwise by 45 ° (θB = 45 °).
Has been rotated. In this case, the transmittance distribution in the opening of the fixed blind 14A by the density filter plates 51A and 51B is as shown in FIGS. 7B and 7D, respectively. The transmittance distribution is concentric with the optical axis IAX as the center as shown in FIG. That is, the light and dark areas in FIG. 7B and FIG. 7D cancel each other out, and X does not need to be integrated in the scanning direction.
An ideal centrally symmetric secondary transmittance distribution is obtained in both the direction and the Y direction. Correcting the normal unevenness of the concave portion with this transmittance distribution makes it possible to simultaneously correct the uneven illuminance in the still exposure state. Such two-dimensional uneven illuminance can be measured by a sensor having a pinhole-shaped light receiving portion 42a in the uneven illuminance sensor 42 in FIG.

At the time of actual maintenance of the scanning exposure type projection exposure apparatus, there is a case where exposure is performed in a stationary state without scanning, so that the illumination unevenness correction in the stationary state according to the present embodiment is effective. Further, the two density filter plates 51A and 51B of this example are used not only for scanning exposure type exposure apparatuses but also for correcting illuminance unevenness with batch exposure type (static exposure type) exposure apparatuses such as steppers. It can be adopted. That is, the present invention can be applied to a batch exposure type exposure apparatus.

Next, a third embodiment of the present invention will be described with reference to FIGS. In the present example, the present invention is applied to a case in which inclination unevenness (linear function-like unevenness) in which the illuminance gradually increases or decreases so as to cross the optical axis in the non-scanning direction. The tilt unevenness does not change over time due to the fogging of the optical element such as the illumination optical system, and the correction range does not need to be so wide, but for example, the amount to be corrected at startup after assembly adjustment of the projection exposure apparatus It is.

In the projection exposure apparatus shown in FIG.
Although the tilt unevenness is corrected by controlling the tilt angle of 3, the uniformity of the σ value of the illumination optical system may be deteriorated.
In order to avoid this, in this example, the density filter plate 5 shown in FIG.
1 is replaced with a density filter plate 55 for correcting uneven inclination.
Note that a density filter plate 55 for correcting inclination unevenness may be arranged close to the density filter plate 51 for correcting central symmetry unevenness. In addition, the density filter plate 55 for correcting uneven inclination
(52G, 52W) drives the density filter plate 55 ± 90 ° around the optical axis IAX (18 degrees in the range).
(0 °).

FIG. 8A shows the positional relationship between the density filter plate 55 for correcting unevenness of inclination and the fixed blind 14A in the initial state. In FIG. 8A, the density filter plate 55 having a disk shape is shown. Has a transmittance distribution of + from the end in the -Y direction.
The one-dimensional distribution is set so as to gradually increase across the optical axis toward the end in the Y direction. That is, the transmittance T (Y) of the density filter plate 55 in the Y direction is expressed by the following equation using the coefficient b. The origin of the Y coordinate is the optical axis, and the radius of the density filter plate 55 is R.

T (Y) = b · Y + (1−b · R) (5) The maximum value of the transmittance is 1 (Y = R), and the minimum value is 1-2b
R (Y = −R), and the maximum correction amount is 2b · R. Since the unevenness of inclination does not change with time as in the case of unevenness of center symmetry, the correction amount may be very small and the coefficient b takes a very small value. Therefore, when the filter plate is not rotating, the illuminance loss is reduced at a very small rate. Accordingly, the average transmittance T (X) in the non-scanning direction in FIG.
Becomes constant at a value slightly lower than 1 (100%) as shown by the straight line 56A. Actually, when the unevenness of the exposure amount in the non-scanning direction measured by using the uneven illuminance sensor 42 of FIG. 3 is the uneven inclination, by rotating the density filter plate 55 so as to cancel the uneven unevenness, The inclination unevenness can be corrected.

In this example, the maximum correction amount of the uneven inclination is θ = ±
Obtained at 90 °. FIG. 8C shows that θ = + 90 °
And the transmittance T in the non-scanning direction at this time.
(X) is obtained by subtracting Y from equation (5) as shown by a straight line 56C.
It is expressed by an expression replaced with X (however, the origin of the coordinate X is the optical axis). At this time, assuming that the optical system according to the present embodiment can generate a maximum of ± 1% in the peripheral portion with respect to the vicinity of the optical axis, for example, in order to correct the unevenness,
What is necessary is just to set the coefficient b as follows.

B = 0.98 / (2 · R) (6) Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this example, the central symmetry unevenness in the still exposure state is corrected using one density filter plate without adversely affecting the uniformity of the σ value of the illumination optical system. This embodiment also basically uses the projection exposure apparatus shown in FIGS. 1 and 2, but uses a rotatable density filter plate having a substantially concentric transmittance distribution instead of the density filter plate 51 of FIG. Are different.

FIG. 9A shows a rotatable density filter plate 61 for correcting concave and uneven unevenness used in the present embodiment. In FIG. 9A, the density filter plate 61 has a light transmitting property. A light-shielding substance or a light-reducing substance is applied to one surface of a circular thin substrate with a predetermined substantially concentric transmittance distribution.
The center of the density filter plate 61 coincides with the optical axis of the illumination optical system, and the y-axis is set in the direction corresponding to the scanning direction through the optical axis, and the x-axis is set in the direction corresponding to the non-scanning direction. Will be explained.

In order to explain the transmittance distribution of this example,
In the transmittance T (Y) of the equation (1), the coefficient a is replaced by a function a (φ) of the angle φ, and the position Y is replaced by the radius r, so that the transmittance T (r, φ) in the polar coordinate display is as follows. To Further, the maximum correction amount D in the equation (2) is calculated by the function D of the angle φ.
As (φ), the coefficient a (φ) is expressed as follows. T (r, φ) = 1 / {a (φ) · r ² +1} (11) a (φ) = D (φ) / {(1-D (φ)) R ² } (12) In this case, the polar coordinate system (φ, r) can be converted to the rectangular coordinate system (x, y) using the following relational expression.

Φ = tan ⁻¹ (y / x) (13) r = (x ² + y ² ) ^1/2 (14) Then, using this relational expression, the expression (11) is expressed as follows. Expressed in a rectangular coordinate system (x, y). T (x, y) = 1 / {a (x, y) · (x ² + y ² ) +1} (15) Further, if the coefficient a is determined by considering the change in transmittance as “constant angular velocity”, A (φ) in the expression 12) is as follows.

A (φ) = φ · D / ｛(π / 2−φ · D) R ² … (16) Then, the orthogonality after rotating the density filter plate 61 of FIG. 9A by the angle θ. The transmittance T (x, y) in the coordinate system (x, y)
y, θ) is expressed as follows.

[0081]

(Equation 1)

From equation (17), the transmittance at an arbitrary position (x, y) at an arbitrary rotation angle θ can be obtained. Specifically, FIG. 9B shows that the rotation angle θ (rad) is 3
A value T of the transmittance T (x, y, θ) at a position of a radius r in the non-scanning direction from the center (optical axis) when the type is set,
In FIG. 9B, a flat straight line 62A indicates a transmittance T when the rotation angle θ is 0, and a curve 62B indicates a rotation angle θ of π / 4.
(45 °), the transmittance T and the curve 62C are represented by the rotation angle θ.
Represents the transmittance T when π / 2 (90 °). As the rotation angle θ approaches π / 2, the transmittance T of the peripheral portion decreases as a quadratic function of the radius r, and the rotation angle θ becomes π /
It can be seen that the amount of decrease in the transmittance of the peripheral portion with respect to the central portion at the time of 2 is the maximum correction amount D, and the correction amount for the concave unevenness is maximum.

The above-mentioned density filter plate 61 is used for correcting the concave unevenness. Similarly, the unevenness of the illuminance where the illuminance increases quadratically in the vicinity of the optical axis (hereinafter, referred to as “center convex unevenness”) is corrected. A density filter plate can also be manufactured. For this purpose, a transmittance distribution that is the inverse of the transmittance distribution of the density filter plate 61 may be provided. Furthermore, by changing the rotation angle of one density filter plate, it is also possible to manufacture a density filter plate capable of correcting both the concave and convex unevenness.

FIG. 10 (a) shows a rotatable density filter plate 63 capable of correcting both the central concave unevenness and the central convex unevenness. In FIG.
Are aligned with the optical axis of the illumination optical system, and the x-axis and the y-axis will be described in the directions corresponding to the non-scanning method and the scanning direction through the optical axis. Regarding the density filter plate 63 as well, it is assumed that the change in the correction amount for the irregular concave and convex irregularities at an arbitrary rotation angle is proportional to the change in the angle. When the correction amount of the central convex unevenness is set to M, and the rotation angle when switching from the correction of the central convex unevenness to the correction of the central concave unevenness is set to φ ′, the coordinates (x, y) when the rotation angle θ is φ ′ are set. ) And the rotation angle θ is 0 and the coordinates (x, y) are the maximum value (the value at the position farthest from the optical axis).
(X _max , y _max ), the transmittance T (x _max , y
_max , 0) are as follows.

T (x, y, φ ′) = 1−M (18A) T (x _max , y _max , 0) = 1 (18B) Using this, the maximum correction amount D (φ) and The maximum correction amount D (x, y, θ) at the rotation angle θ is as follows.

[0086]

(Equation 2)

When the maximum correction amount D (x, y, θ) is used, the transmittance T (x, y, θ) at the rotation angle θ in equation (17) is obtained.
θ) is as follows.

[0088]

(Equation 3)

From this equation (21), the transmittance at an arbitrary position (x, y) at an arbitrary rotation angle θ can be obtained. Specifically, FIG. 10B shows the transmittance T (x, y, θ) at a position with a radius r from the center (optical axis) in the non-scanning direction when the rotation angle θ (rad) is set to three types. 10 (b), the upward curve 64A indicates the transmittance T when the rotation angle θ is 0, and the flat line 64B indicates that the rotation angle θ is φ ′ (0 <φ ′ < π / 2), the transmittance T,
A downward curve 64C represents the transmittance T when the rotation angle θ is π / 2 (90 °). Rotation angle θ is φ '
In a smaller range, the transmittance T increases in a quadratic function of the radius r, and the unevenness of the convexity can be corrected. In a range where the rotation angle θ is larger than φ ′, the transmittance T is a quadratic function of the radius r. It can be seen that the unevenness can be reduced and the unevenness in the center can be corrected. Further, when the rotation angle θ is 0, the amount of increase in the transmittance of the peripheral portion with respect to the center portion is the maximum correction amount M, and the correction amount for the central unevenness is the maximum. Then, when the rotation angle θ is π / 2, the correction amount for the concave unevenness is the maximum correction amount D
Becomes

[0090]

(Equation 4)

In this embodiment, the density filter plate 6 shown in FIGS.
Since the transmittance distribution is optimized two-dimensionally, 1, 63 can be used not only for a scanning exposure type projection exposure apparatus but also for a batch exposure type (static exposure type) projection exposure apparatus. . In the above embodiment, the density filter plates 51, 61, 63 and the like are used as the filter members. Instead, for example, a transmission type liquid crystal panel capable of controlling the internal pattern is used, and the internal liquid crystal panel is used. The pattern (transmittance distribution) may be controlled electrically.

In each of the above embodiments, the adjustment is performed at the time of measuring the illuminance unevenness (exposure amount unevenness). However, the adjustment of the illumination characteristic may be performed other than at the time of the measurement. For example,
The change in the illumination characteristics may be calculated (simulation or the like), and the illuminance unevenness (exposure amount unevenness) may be sequentially adjusted based on the calculation result. In addition, the illuminance unevenness (exposure amount unevenness) may be periodically measured and adjusted, and the illuminance unevenness (exposure amount unevenness) may be adjusted by the above calculation during the periodic measurement. . Further, when the illumination condition, that is, the intensity distribution of the exposure light IL (particularly, its shape) on the pupil plane of the illumination optical system is changed, both the inclination unevenness and the central symmetry unevenness (unevenness unevenness) are adjusted. May be adjusted only by changing the central symmetry unevenness.

Although the fly-eye lenses 6 and 9 are used as optical integrators in the above embodiment, the present invention is also applicable to a case where an internal reflection type integrator (rod integrator) is used as an optical integrator. Clearly what you can do. Further, in the above embodiment, a so-called double fly-eye type illumination optical system ILS using two-stage fly-eye lenses 6 and 9 is used, but a one-stage optical integrator (fly-eye lens, rod integrator) is used. The present invention can also be applied to a case where adjustment of an illumination optical system using only the above-described method is performed.

When an internal reflection type integrator is used as the optical integrator, the internal reflection type integrator has its entrance surface arranged on the pupil plane of the illumination optical system and its exit plane arranged conjugate with the pattern plane of the reticle 28. Is done. When a fly-eye lens is used as the optical integrator, a surface light source composed of a plurality of light source images, that is, a secondary light source is formed on the exit surface side. When an internal reflection type integrator is used, a plurality of light sources are provided on the entrance surface side. Is formed. Therefore, the change of the illumination condition in each of the above embodiments means that the intensity distribution of the exposure light IL on the pupil plane of the illumination optical system is changed, and that the secondary light source formed on the pupil plane of the illumination optical system is changed. This is equivalent to changing at least one of the size and the shape.

Further, in the above embodiment, the modified illumination,
An illumination condition switching system that changes the light amount distribution of illumination light (exposure light) on the Fourier transform plane (pupil plane) in the illumination optical system ILS for performing normal illumination, illumination with a small σ value, and the like includes an aperture stop. Although the plate 10 is included, the illumination condition may be changed by another configuration. That is, the illumination condition switching system may be constituted only by the aperture stop plate 10, but, for example, between the exposure light source (1) and the optical integrator (9), the illumination condition (that is, on the pupil plane of the illumination optical system). In accordance with the intensity distribution of the exposure light IL in the optical integrator (9), in this example, one of a plurality of aperture stops 10a to 10d arranged in the illumination light path), the condition (fly-eye In the case of a lens, the light amount distribution of the exposure light IL on its incident surface, and in the case of an internal reflection type integrator (such as a rod lens), the exposure light IL for its incident surface
It is preferable to dispose an optical member capable of changing the incident angle and the incident angle range of the light source to reduce the loss of the illumination light amount due to the change of the illumination condition. As an example, the optical member is exchangeably arranged in the optical path of the illumination optical system, and includes a plurality of diffractive optical elements (DOE) that generate exposure light (diffractive light) IL having different incident conditions as described above, a zoom optical system, It is desirable to include at least one of a pair of prisms (such as a conical prism (axicon) or a quadrangular pyramid prism) that can relatively move in the optical axis direction of the illumination optical system. This optical member may be used together with the aperture stop plate 10 or may be used instead of the aperture stop plate 10. The above-described diffractive optical element may also be used as at least one optical integrator in the illumination optical system, and the configuration of the illumination optical system can be slightly simplified by this dual use.

In the above embodiment, the present invention is applied to a scanning exposure type projection exposure apparatus, but the present invention is applied to a step-and-repeat type (batch exposure type).
The present invention can also be applied to a projection exposure apparatus (stepper) described above and an exposure apparatus of a proximity system or the like that does not use a projection system. Further, the exposure light (exposure beam) is not limited to the above-described ultraviolet light, and may be, for example, a laser plasma light source or an S beam.
EUV light in the soft X-ray region (wavelength 5 to 50 nm) generated from an OR (Synchrotron Orbital Radiation) ring may be used. In the EUV exposure apparatus, the illumination optical system and the projection optical system each include only a plurality of reflection optical elements. Therefore, the above-mentioned density filter plates 51, 61 and the like may also be constituted by a reflection member.

Then, semiconductor devices can be manufactured from the wafer W shown in FIG. The semiconductor device has a step of designing the function and performance of the device, a step of manufacturing a reticle based on this step, a step of manufacturing a wafer from a silicon material, and a step of forming a reticle pattern on the wafer by the projection exposure apparatus of the above-described embodiment. , A device assembling step (including a dicing step, a bonding step, and a package step), an inspection step, and the like.

The application of the exposure apparatus is not limited to an exposure apparatus for manufacturing semiconductor devices, but may be, for example, a liquid crystal display element formed on a square glass plate or an exposure apparatus for a display apparatus such as a plasma display. The present invention can be widely applied to an apparatus and an exposure apparatus for manufacturing various devices such as an imaging device (CCD or the like), a micromachine, a thin-film magnetic head, and a DNA chip. Further, the present invention can be applied to an exposure step (exposure apparatus) when manufacturing a mask (photomask, reticle, or the like) on which a mask pattern of various devices is formed by using a photolithography step.

The present invention is not limited to the above-described embodiment, but can take various configurations without departing from the gist of the present invention.

[0100]

According to the first exposure method of the present invention, the uniformity of the coherence factor of the exposure beam is almost deteriorated because the transmittance distribution of the plate-shaped region or the plate-shaped filter member is controlled. There is an advantage that the uniformity of the exposure amount distribution can be improved without performing this. Also, by using one rotatable filter member having a one-dimensional transmittance distribution, it is possible to correct the central symmetry unevenness or the tilt unevenness after scanning exposure.

Further, by using two filter members having a one-dimensional transmittance distribution in combination or using one filter member having a concentric transmittance distribution, various filters can be obtained even in a static exposure state. Can be corrected. Further, according to the second exposure method of the present invention, when the illumination condition is changed, the uneven illuminance is adjusted by dividing it into a tilt component and a centrally symmetric component, and the tilt component is adjusted within a predetermined period after the adjustment. Since the center symmetric component is adjusted without adjustment, there is an advantage that, when switching to various illumination conditions, the adjustment process is simplified and the uniformity of the exposure amount distribution can be improved.

According to the exposure apparatus of the present invention, the exposure method of the present invention can be implemented. Further, according to the device manufacturing method of the present invention, a device can be manufactured with high line width control accuracy using the exposure method of the present invention.

[Brief description of the drawings]

FIG. 1 is a partially cutaway configuration view showing a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a relationship between an optical system from a second fly-eye lens 9 to a fixed blind 14A in FIG. 1 and an illumination area 35.

3A is a plan view illustrating an exposure area and an uneven illuminance sensor 42, and FIG. 3B is a diagram illustrating an example of a detection signal obtained from the uneven illuminance sensor 42. FIG.

FIG. 4 shows a density filter plate 51 according to the first embodiment.
FIG. 6 is a diagram showing a state in which the rotation angles of the three are changed to three types.

FIG. 5 is a view showing a density filter plate 51 and a filter plate equivalent thereto.

FIG. 6 is a perspective view illustrating a relationship between an illumination system 35 and an optical system from a second fly-eye lens 9 to a fixed blind 14A of the projection exposure apparatus according to the second embodiment of the present invention.

FIG. 7A is a diagram illustrating a first density filter plate 51A according to a second embodiment, and FIG. 7B is a diagram illustrating the density filter plate 5A.
FIG. 1C is a diagram showing a transmittance distribution of FIG. 1A, FIG. 2C is a diagram showing a second density filter plate 51B of the second embodiment, FIG. 2D is a diagram showing a transmittance distribution of the density filter plate 51B, and FIG. () Is a diagram showing a final transmittance distribution.

FIG. 8 is a diagram illustrating a state in which the rotation angle of the density filter plate 55 according to the third embodiment of the present invention is changed to three types.

9A is a diagram illustrating a first density filter plate 61 according to a fourth embodiment of the present invention, and FIG. 9B is a view illustrating transmittance distributions of the density filter plate 61 at various rotation angles. FIG.

FIG. 10A is a diagram showing a second density filter plate 63 of the fourth embodiment, and FIG. 10B is a diagram showing transmittance distribution at various rotation angles of the density filter plate 63. is there.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure light source, 5 ... Beam shaping system, 6 ... 1st fly-eye lens, 9 ... 2nd fly-eye lens, 10 ... Aperture stop plate, 12 ... 1st lens system, 13 ... 2nd lens system, 14A
... fixed blind, PL ... projection optical system, W ... wafer, 2
0: integrator sensor, 21: exposure control unit,
22 main control system, 24, 25, 52 drive unit, 2
Reference numeral 6: drive system, 28: reticle, 31: reticle stage, 42: uneven illuminance sensor, 51, 51A, 51B: density filter plate for correcting central symmetric unevenness, 55: density filter plate for correcting tilt unevenness, 61, 63 … Density filter plate for correcting central symmetry unevenness

Claims (22)

[Claims] 1. An exposure method for exposing a second object with an exposure beam through a first object, comprising: an optical path of the exposure beam up to the second object, near an exposure surface of the second object, or An exposure method, wherein a transmittance distribution for the exposure beam is controlled in a two-dimensionally variable distribution in a flat area near a plane conjugate with the exposure plane. 2. The method according to claim 1, wherein the transmittance distribution for the exposure beam is controlled by a concentric distribution and a distribution rotatable about an optical axis so as to correct the unevenness of the exposure distribution for the second object. The exposure method according to claim 1, wherein: 3. The exposure according to claim 1, wherein the transmittance distribution for the exposure beam is controlled in a variable direction in a predetermined distribution so as to correct the unevenness of the exposure amount distribution for the second object. Method. 4. The method according to claim 3, wherein the transmittance distribution for the exposure beam is further controlled in a direction intersecting the direction of the predetermined distribution with the same distribution as the predetermined distribution or another distribution. Exposure method. 5. The exposure method according to claim 3, wherein the predetermined distribution is a distribution that changes one-dimensionally symmetrically about an optical axis. 6. The exposure method according to claim 3, wherein the predetermined distribution is a distribution that gradually increases or decreases so as to cross the optical axis. 7. When exposing the second object, the first object and the second object are moved in synchronization with a scanning direction, and the exposure amount of the exposure beam for the second object is scanned. The exposure method according to any one of claims 1 to 6, wherein a transmittance distribution for the exposure beam is controlled such that an exposure amount distribution obtained by integrating in the direction is uniformed. 8. An exposure method for illuminating a first object with an exposure beam and exposing a second object with the exposure beam through the first object, wherein the second object is exposed according to a pattern to be transferred onto the second object. First
While changing the illumination condition of the object, illuminance unevenness in the irradiation area of the exposure beam is adjusted by dividing it into a tilt component and a centrally symmetric component, and the tilt component is adjusted within a predetermined period after the adjustment. An exposure method, wherein the centrally symmetric component is adjusted without using the method. 9. A method according to claim 1, wherein the first and second objects are relatively moved with respect to the exposure beam, and the second object is scanned and exposed with the exposure beam via the first object, and the illumination condition is changed. 9. The exposure method according to claim 8, wherein an inclination component in a non-scanning direction orthogonal to a scanning direction in which the first and second objects are moved is adjusted. 10. An exposure amount distribution in the non-scanning direction, which is obtained by integrating light amounts in the scanning direction in an irradiation area of the exposure beam, so as to be substantially uniform.
10. The exposure method according to claim 9, wherein the tilt component and the central symmetric component are adjusted. 11. The illuminance information in the irradiation area of the exposure beam is measured to adjust at least the centrally symmetric component, and the measured illuminance information is calculated until the illuminance information is measured next. 11. The exposure method according to claim 8, wherein at least the central symmetric component is adjusted based on the updated illuminance information. 12. An exposure apparatus, comprising: an illumination system that illuminates a first object with an exposure beam, and exposing a second object via the first object. One or more flat filter members having a predetermined transmittance distribution with respect to the exposure beam are disposed near the exposure surface of the second object or near a surface conjugate to the exposure surface. An exposure apparatus comprising: 13. The illumination system according to claim 1, wherein one or more stages of an optical integrator for equalizing the illuminance distribution of the exposure beam, and illumination of the exposure beam from the optical integrator on the first object. A field stop that defines an area, wherein the filter member is disposed on a surface near the field stop or a surface near an irradiated surface of the first object, and is configured to control a rotation angle of the filter member. 13. The exposure apparatus according to claim 12, further comprising an apparatus. 14. The exposure apparatus according to claim 12, wherein the filter member has a concentric transmittance distribution. 15. The exposure apparatus according to claim 12, wherein the filter member has a predetermined transmittance distribution in a one-dimensional direction symmetrically with respect to an optical axis. 16. The filter member according to claim 1, wherein each of the filter members has the same transmittance distribution in a one-dimensional direction symmetrically with respect to an optical axis.
14. The exposure apparatus according to claim 12, wherein the two filter members are rotatable in opposite phases to each other. 17. A stage system for moving the first object and the second object in synchronization with a scanning direction, and a distribution of an integrated value of an exposure amount of the exposure beam on the second object in the scanning direction. The apparatus according to claim 1, further comprising: an exposure distribution measuring device for measuring, and a control device for controlling a rotation angle of the filter member via the driving device according to the exposure distribution measured by the distribution measuring device. Item 12-1
7. The exposure apparatus according to claim 6. 18. An exposure apparatus for illuminating a first object with an exposure beam and exposing a second object with the exposure beam via the first object, wherein the first object can be illuminated under a plurality of illumination conditions. An illumination optical system in which the illuminance distribution of the exposure beam has the same tendency under the plurality of illumination conditions; and an optical member arranged on an optical path of the exposure beam to the second object to adjust the illuminance distribution An exposure apparatus comprising: 19. The exposure apparatus according to claim 18, wherein the illumination optical system is adjusted such that the illuminance distribution has illuminance unevenness substantially symmetric with respect to an optical axis of the illumination optical system. 20. The optical element according to claim 20, wherein the optical member includes at least one optical filter arranged at a distance from an exposure surface of the second object or a conjugate surface thereof and having a predetermined transmittance distribution with respect to the exposure beam. Claim 18 or 19
3. The exposure apparatus according to claim 1. 21. A device manufacturing method including a step of transferring a device pattern onto a substrate using the exposure method according to claim 1. 22. A device manufacturing method including a step of transferring a device pattern onto a substrate using the exposure apparatus according to claim 12.