JP2985089B2 - Exposure control apparatus, exposure apparatus and method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of irradiation energy amount to a sensitive object and control of uniforming illuminance. For example, a pulse laser such as an excimer is used as exposure light. The present invention relates to an exposure control device suitable for controlling an exposure amount and illuminance uniformity of an exposure device.

[Conventional technology]

Conventionally, the exposure amount control based on the exposure value using a pulsed laser as the light source generally has a variation of about ± 10% for each pulse and there is a short-term and long-term decrease in the laser density. Therefore, the light amount for each pulse is detected and integrated, and the light emission is continued until the integration result reaches a desired value. The decrease in laser density is remarkable when a gas laser is used, and an active medium (eg, KrF, Xr) sealed inside a laser gas chamber is used.
The output decreases with the deterioration of the gas mixture such as eCl). Usually, when the internal gas deteriorates and the output decreases, the applied voltage between two electrodes provided in parallel along the optical axis of the laser light inside the chamber may be increased, or in some cases, In order to reduce the decrease in output by performing a typical gas exchange, it is difficult to always control the actually detected integrated exposure amount to a desired exposure amount with a substantially constant pulse number. Was.

Under these circumstances, for example, as an exposure control apparatus for an apparatus requiring more accurate exposure amount control, such as an exposure apparatus for manufacturing a semiconductor element (stepper, aligner, etc.),
For example, there is one disclosed in JP-A-60-169136.

In this type of apparatus, the exposure energy to be applied to a sensitive body (a wafer with a resist or the like) is divided into two types: a rough exposure that provides an exposure energy slightly smaller than an appropriate exposure amount, and a correction exposure that provides the remaining required exposure energy. By dividing into stages, the variation (error) of the integrated exposure energy with respect to the appropriate exposure energy is controlled to, for example, about ± 2%. In other words, when one-shot exposure is performed with the pulse light of duplication, by setting the energy amount of the final pulse small, the variation of the integrated exposure amount is kept within the allowable error of the exposure amount control accuracy, and the one-shot exposure is appropriately performed. Exposure is obtained.

Here, one shot means that the entire surface of the wafer is exposed to exposure energy through a mask or a reticle (hereinafter, simply referred to as a reticle) in the case of the batch exposure method.
On the other hand, in the case of the step-and-repeat method (described later), exposure energy is applied to one partial area on the wafer.

In recent years, in a photolithography process for manufacturing semiconductor devices, a step-and-repeat type reduction projection exposure apparatus (a so-called stepper) has been frequently used as an apparatus for transferring a reticle pattern onto a wafer with high resolution. ing. In this type of stepper, when exposing one wafer, an area to be exposed is divided into a plurality of exposure areas, and when exposure to one exposure area is completed, the stepper is moved to the next exposure area and exposed again. Is performed repeatedly, thereby finally exposing the entire surface of the wafer.

Therefore, in order to increase the production amount of semiconductor elements per unit time, it is important to shorten the movement time between exposure regions as much as possible and to shorten the exposure time for one exposure region. For this reason, even when performing exposure using the apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 60-169136, it is important to shorten the correction exposure time by performing rough exposure with as much energy as possible.

[Problems to be solved by the invention]

However, in the prior art as described above, since no consideration is given to the variation in the amount of energy contained in the final pulse, the amount of exposure is still not properly controlled, and the appropriate exposure cannot be performed. There is.

In addition, since the set energy amount of the final pulse is a value obtained by subtracting the coarse exposure amount from the appropriate exposure amount, the dynamic range of the means for setting the exposure amount of the final pulse must be widened, and the apparatus becomes complicated. In addition, there is a problem that high control accuracy cannot be obtained.

Therefore, for example, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent Publication No. 81882, the correction exposure is performed by a plurality of pulses, and the energy amount for each pulse is set so as to be sequentially reduced, so that the variation in the exposure energy as a whole is reduced and the proper exposure is performed. Methods for obtaining quantities have also been proposed. However, even in such an apparatus, the problem that the exposure time becomes longer due to the plural pulses of the correction exposure and that a wide dynamic range is required as the exposure amount setting means cannot be solved.

Further, in the method of adjusting the exposure amount by the correction exposure using a plurality of pulses as described above, the energy amount of one pulse and the number of exposure pulses at the time of the correction exposure depend on the integrated exposure amount at the time when the coarse exposure is completed. Will be. For this reason,
There is a disadvantage that the energy amount of one pulse and the number of exposure pulses are not constant for each shot (exposure area). That is, when the exposure energy source is a pulse laser light source, a regular interference pattern is generated on the exposure surface (reticle or wafer) due to the coherence of the laser light. Further, a large number of light beams having different phases are generated due to scratches, dust, surface defects, and the like in the illumination optical system, and an irregular interference pattern (speckle) in which the light beams overlap is also generated. Irradiation unevenness may occur on the exposure surface due to these interference patterns, but the interference pattern cannot be effectively reduced by the above-described exposure amount control method. Therefore, the problem of the illuminance uniformity will be described below.

The above two interference patterns, especially regular interference patterns, have a significant effect on the control of the pattern line width in the photolithography process of manufacturing a semiconductor device. Therefore, for example, it is considered that a regular interference pattern or speckle (hereinafter, collectively referred to as an interference pattern) is smoothed by a method equivalent to the method disclosed in JP-A-59-226317. .

In the above-mentioned publication, the interference pattern is smoothed (incoherent) by one-dimensional or two-dimensional movement (raster scan) of a laser beam by a vibrating mirror (a galvanometer mirror, a polygon mirror, or the like) at a constant period to spatially coherency. Is to be reduced. In other words, the interference pattern is moved on the reticle by changing the incident angle of the laser beam to the illuminance uniforming means (optical integrator) for each pulse, and finally the interference pattern is smoothed, in other words, the illuminance This is to improve uniformity.

When passing pulse energy such as excimer laser light to the illumination optical system of such a method, a plurality of pulses are irradiated in synchronization with one-dimensional or two-dimensional scanning by a vibrating mirror. Normally, the oscillation pulse width of an excimer laser is extremely short, about 20 nsec. Even if the oscillating mirror is oscillated at about 10 Hz, one pulse of the excimer laser behaves as if it is stationary during the oscillation cycle of the oscillating mirror.

Japanese Patent Laid-Open No. 59-226317 (illumination uniformity)
Combining the method of JP-A-63-81882 (exposure amount control) and optimizing the exposure amount and smoothing the interference pattern at the same time, the method disclosed in JP-A-59-226317 is disclosed. As shown, it is necessary to distribute the secondary light source image (laser spot) on the pupil plane of the projection lens as uniformly as possible in the pupil plane. To achieve this, it is necessary to keep the laser intensity constant during exposure.

However, in the method described in Japanese Patent Application Laid-Open No. 63-81882, the energy amounts of a plurality of pulses are sequentially changed during correction exposure. Therefore, only in the time region corresponding to the correction exposure, the integrated exposure energy is lower than in the other time regions (corresponding to the coarse exposure), and as a result, the interference pattern cannot be sufficiently smoothed.

The present invention has been made in view of such a point, and can control the exposure amount in accordance with the required accuracy, can effectively uniform the illuminance, and can shorten the exposure time. An object of the present invention is to provide an exposure control device.

[Means for solving the problem]

In order to solve such a problem, the present invention includes a pulse light source 1 that emits coherent pulse light, and an illumination optical system that irradiates the first object (reticle R) with the pulse light. For transferring a pattern formed on a first object by a predetermined amount of exposure (appropriate amount of exposure S) to a second object (wafer W) by irradiating the second object with a predetermined amount of exposure. A first light amount adjusting means (light reducing unit 3) for uniformly adjusting the light amount of each pulse light irradiated to the first object at a predetermined adjustment degree.
The number of pulses Nsp required to move and smooth the interference pattern generated on the first object or the second object by the irradiation of the pulse light with each irradiation of the pulse light, and the second by the irradiation of the plurality of pulse lights. Based on the number of pulses Ne required to control the integrated light amount given to the object with a predetermined setting accuracy and a predetermined exposure amount, the degree of adjustment of the first light amount adjusting means and the average light amount of the pulse light (· B And a second calculating means for determining, for each predetermined unit pulse, a target integrated light quantity to be given to the second object when irradiating the pulse light under an average light quantity value. Light quantity measuring means (light receiving element 9 and light quantity monitoring unit 18) for detecting the actual integrated light quantity given to the second object; and the actual light quantity given to the second object by the previously irradiated pulse light. Integrated light quantity and it A third calculating means for calculating a difference D from the corresponding target integrated light quantity; and a second adjusting means for correcting the light quantity of pulse light to be irradiated next from the average light quantity value based on the calculated difference. And a light amount adjusting means (second light amount control unit 15).

Also, an energy source that emits pulse energy,
An illumination system for irradiating the first object with the pulse energy; and irradiating a pattern formed on the first object by irradiation of the plurality of pulse energies with a second light-sensitive pattern at a predetermined exposure dose.
An exposure control device for transferring an exposure amount to the second object to the predetermined exposure amount, wherein the energy amount of each pulse energy applied to the first object is adjusted by a predetermined adjustment degree. A first energy amount adjusting means for uniformly adjusting the number of pulses required to control the integrated energy given to the second object by irradiation of a plurality of pulse energies with a predetermined setting accuracy, a predetermined exposure amount, The first energy amount adjusting means and the average energy value of the pulse energy are determined in advance based on
Calculation means; and second calculation means for determining, for each predetermined unit pulse, a target integrated energy amount to be given to the second object when the pulse energy is irradiated under the average energy value; given to the second object. Energy amount measuring means for detecting an actual integrated energy amount; calculating a difference between the actual integrated energy amount given to the second object by the previously irradiated pulse energy and the target integrated energy amount corresponding thereto. Third
Calculating means; and second energy amount adjusting means for adjusting the energy amount of the pulse energy to be irradiated next by correcting the average energy value based on the calculated difference.

Also, an energy source that emits pulse energy,
An irradiation system for irradiating the first object with the pulse energy, and irradiating a pattern formed on the first object by irradiation of a plurality of pulse energies with a second light-sensitive pattern at a predetermined exposure dose.
An exposure apparatus for transferring an object to an object, a first energy amount adjusting means for uniformly adjusting an energy amount of each pulse energy applied to the first object at a predetermined adjustment degree; Second calculating means for determining a target integrated energy amount to be provided for each predetermined unit pulse; energy amount measuring means for detecting information on an actual integrated energy amount applied to the second object; a pulse previously irradiated Second energy amount adjusting means for adjusting the energy amount of the pulse energy to be irradiated next based on the actual integrated energy amount given to the second object by the energy and the target integrated energy amount corresponding thereto. I decided to prepare.

Also, an energy source that emits pulse energy,
An illumination system for irradiating the object with the pulse energy,
An energy control device for controlling an amount of energy applied to the object by irradiation of a plurality of pulse energies, wherein a first energy amount adjustment for uniformly adjusting an energy amount of each pulse energy applied to the object at a predetermined adjustment degree. Means; and second energy amount adjusting means capable of adjusting each pulse energy amount irradiated onto the object for each predetermined unit pulse.

An exposure method for irradiating a first object with pulse energy from an energy source and transferring a pattern formed on the first object by irradiation of a plurality of pulse energies to a sensitive second object at a predetermined exposure dose. Adjusting the pulse energy uniformly with a predetermined degree of adjustment for a plurality of pulse energies; calculating a target integrated energy amount to be given to the second object when irradiating the pulse energy; Detecting information on the provided actual integrated energy amount; and adjusting the energy amount of the pulse energy for each predetermined unit pulse based on the integrated energy amount and the target integrated energy amount.

(Operation)

In the present invention, the first light amount adjusting means for uniformly adjusting the light amounts of all the pulse lights and the second light amount adjusting means for adjusting the light amounts for each pulse are provided, and all of the pulse lights necessary for one-shot exposure are provided. , The exposure energy is controlled to be substantially equal to a predetermined average light amount value, and the number of pulses for each shot is kept constant. For this reason, by optimizing the exposure amount and moving the interference pattern in synchronization with the irradiation of the pulse light, the interference pattern can be finally almost completely smoothed (uniform illuminance).

In the present invention, since the correction exposure is not performed by reducing the light amount of the last several pulses or one pulse as in the related art, the exposure time for each shot can be shortest and constant.

Further, since the light amount is actually measured for each pulse and the light amount is finely adjusted, the light amount is actually measured in comparison with the conventional case where the light amount is adjusted at a stage very close to the target exposure amount. The dynamic range of the light amount measuring means and the second light amount adjusting means for adjusting the light amount of the next pulse can be small, and the control accuracy of the exposure amount can be improved.

Further, even when the exposure condition for the photosensitive second object (for example, an appropriate exposure amount per one shot in accordance with the sensitivity characteristic of the resist) greatly changes, all the pulse light Can be adjusted uniformly, so that it is possible to easily respond to changes in exposure conditions without increasing the dynamic range of the second light amount adjusting means.

〔Example〕

FIG. 1 is a plan view showing a schematic configuration of an exposure control apparatus according to an embodiment of the present invention. Here, a configuration applied to a stepper for projecting and exposing a pattern of a reticle R onto a wafer W is shown.

In FIG. 1, a trigger controller 13 that outputs an external trigger pulse controls the oscillation (number of pulses, oscillation interval, and the like) of the pulse laser light source 1 that emits pulse light such as excimer laser light. Further, the second light quantity control unit 15 as the second light quantity adjusting means of the present invention controls the high discharge voltage of the pulse laser light source 1, and in the present embodiment, a command signal from the main control system 10 described later. , And finely adjust the exposure energy for each pulse.

The pulsed laser light source 1 includes an etalon at a part between two resonance mirrors disposed at both ends of the laser tube,
It has a narrow band wavelength stabilizing mechanism composed of dispersive elements and the like,
It is configured as a laser light source having a stable resonator. By generating a high-voltage discharge between two electrodes provided in parallel along the optical axis of the laser light in the pulse laser light source 1, DeepUV having a wavelength that makes the resist layer photosensitive is provided.
Light, for example, KrF excimer laser light (wavelength 248 nm) is oscillated. The laser beam LB ₀ emitted from the pulse laser source 1, a rectangular cross section corresponding to the arrangement shape of the two electrodes, i.e., the aspect ratio of the beam cross section has a 1 / 2-1 / 5 of about rectangular. Therefore, the laser beam LB ₀ is incident on a beam expander 2 (beam cross-sectional shape conversion optical system) in which two sets (irregularities) of cylindrical lenses are combined,
Expander 2 to expand the width of the lateral direction of the beam LB _0, the beam cross section is emitted as a beam LB ₁ that has been converted into a substantially square shape.

Emerging beam LB ₁ from the expander 2 from incident on the first light reduction unit 3 is a light amount adjusting means of the present invention, the dimming section 3 the beam light intensity (energy) 0% (completely transparent)
Attenuate continuously or stepwise between 100% (complete shading). As will be described later, the dimming rate (or transmittance) of the dimming unit 3 is determined by the number of pulses Nsp required to smooth an interference pattern generated on the reticle R or the wafer W and the integration given to the wafer W. The number of pulses Nexp required for actual exposure, which is determined from the number of pulses Ne required to control the amount of light with desired exposure amount control accuracy, and an appropriate exposure amount.

Here, for example, assuming that the dimming rate of the dimming unit 3 is set to six discrete steps, the dimming rate is selected based on the pulse number Nexp and the appropriate exposure amount before the start of exposure, and at least 1 It is not changed to another value during the exposure of one shot. In other words, the dimming unit 3 always reduces the light amounts of all the pulse lights by a predetermined amount as long as the exposure condition for the wafer W (for example, an appropriate exposure amount per shot according to the sensitivity characteristic of the resist) does not change. The light amount is uniformly attenuated by the light rate, and a light amount adjusting mechanism having a relatively low response speed (light-changing rate switching speed) may be used.

The light reducing unit 3 in the present embodiment employs a method in which six types of mesh filters having different attenuation rates (transmittances) are attached to a turret plate and the turret plate is rotated. FIG. 2 shows an example of the structure of a rotating turret plate 16 and six types of mesh filters 16a to 16f. The filter 16a is a mere opening (transparent) part, and the attenuation rate is 0%.
(That is, 100% transmittance). Each of the filters 16a to 16f is disposed at about six positions along a circle centered on the rotation axis of the rotary turret plate 16 at an interval of about 60 °, and one of the filters is a substantially square beam LB ₁ from the expander 2. Are arranged in the optical path.

FIG. 3 shows the relationship between the amount of rotation of the rotating turret plate 16 shown in FIG. 2 and the transmittance. Here, it is shown as a filter 16a is a rotation amount zero when positioned in the optical path of the beam LB _1, it rotates the rotary turret plate 16 counterclockwise in the drawing sheet of FIG. 2. Third
In the figure, when the rotary turret plate 16 by about 16 ° (π / 3), the beam LB ₁ is dimmed at a predetermined rate. still,
When the rotation amount is 2π (360 ° or 0 °), the filter 16a is selected, and the transmittance becomes 100%.

Here, as the dimming element attached to the rotating turret plate 16, a dielectric mirror having a different transmittance may be used other than the mesh filter. Further, two sets of rotating turret plates 16 are provided so as to be relatively rotatable at a fixed interval, and for example, the transmittance of the dimming element of the first rotating turret plate is set to 100%, 90%, 80%, 70%, 60%. , 50%, and the transmittance of the dimming element of the second rotating turret plate is 100%, 40%, 30%, 20%.
If set to%, 10%, and 5%, a total of 36 transmittances can be realized by a combination of the two.

In addition, a method in which a predetermined short aperture and a zoom lens system are combined as the light reduction unit 3 to continuously reduce light by changing the zoom ratio and the aperture diameter, and two glass plates (quartz or the like) are used. A method of rotating a so-called etalon, which is held substantially in parallel at intervals, a method of relatively moving two phase gratings or light and dark gratings, or rotating a polarizing plate when linearly polarized laser light is used as exposure light. A system or the like may be adopted.

Returning to the description of FIG. 1, the substantially parallel beam LB ₁ ′ which has undergone a predetermined attenuation in the light reduction unit 3 enters an interference pattern reduction unit 4 which smoothes an interference pattern. The interference pattern reduction unit 4 has a vibrating mirror (galvano mirror, polygon mirror, or the like) that vibrates one-dimensionally (or two-dimensionally) by an actuator (piezo element or the like), and the beam LB to the fly-eye lens 6 for each pulse. By changing the angle of incidence of ₁ ', the interference pattern is moved one-dimensionally (or two-dimensionally) on the reticle to finally smooth it, in other words, to improve the illuminance uniformity.

Now, the beam LB ₁ ′ that has passed through the interference pattern reduction unit 4
Is turned into a vibrating beam that swings one-dimensionally (or two-dimensionally) at a minute angle, is then turned back by a mirror 5 and enters a fly-eye lens 6 as an optical integrator.
Therefore, the beam LB ₁ ′ incident on the fly-eye lens 6
The incident angle of the fly-eye lens 6 on the incident surface changes every moment. Here, the fly-eye lens 6 is formed by bundling a plurality of rod-shaped element lenses, and the exit end thereof has the same number of secondary light source images (here, the collection of the partial light beams of the beam LB ₁ ′) as the number of element lenses. (Light spot).

FIG. 4 shows the relationship between the incident beam of the fly-eye lens 6 and the secondary light source image (spot light).
FIG. 2 is a schematic explanatory diagram according to the principle disclosed in Japanese Patent Application Publication No. H10-115,004.
Each rod lens 6a of the fly-eye lens 6 is a quadrangular prism made of quartz glass having convex spherical surfaces formed at both ends. When the beam LBb (parallel light beam) is incident on the fly-eye lens in parallel with the optical axis AX, the exit end of each rod lens 6a of the fly-eye lens 6 or the position where a predetermined amount has exited from the exit end into the air,
The spot light SPb is collected. Although this spot light SPb is shown for only one rod lens in FIG. 4, it is actually formed on all the emission sides of the rod lens irradiated with the beam LBb. Moreover, each spot light SPb is focused on the beam LBb substantially at the center of the exit surface of the rod lens. On the other hand, when the parallel beam LBc inclined rightward with respect to the optical axis AX enters the fly-eye lens 6, it is collected as a spot light SPc on the left side of the exit surface of each rod lens 6a. Similarly, the parallel beam LBa inclined leftward with respect to the optical axis AX is focused as spot light SPa on the right side of the exit surface of the rod lens 6a.

Therefore, the parallel beam L by the interference pattern reduction unit 4
Due to the one-dimensional vibration of B ₁ ′, all of the plurality of spot lights generated on the exit side of the fly-eye lens 6 reciprocate simultaneously in one direction with respect to the fly-eye lens 6 (optical axis AX).

In this way, a plurality of beams LB ₂ forming each spot light formed on the exit side of the fly-eye lens 6 are transmitted through the beam splitter 7 as shown in FIG. 1, and are incident on the condenser lens CL. , On the reticle R. As a result, the reticle R is illuminated with a substantially uniform illuminance distribution, and the pattern of the reticle R is transferred by the projection lens PL onto the resist layer of the wafer W mounted on a stage (not shown) at a predetermined exposure amount. . At this time, a plurality of spot lights formed at the exit end of the fly-eye lens 6 are re-imaged at least on the pupil (entrance pupil) Ep of the image (wafer) side telecentric projection lens PL, and a so-called Koehler illumination system is configured. You.

As described above, the interference pattern reduction unit 4 vibrates the beam incident on the fly-eye lens 6 to move the interference fringes (two-dimensional interference pattern) generated on the reticle surface or the wafer surface by a very small amount. In (2), light and dark fringes transferred to the resist layer are consequently smoothed to reduce the visibility of interference fringes. In this embodiment, when smoothing the interference pattern, the laser light incident on the fly-eye lens 6 is vibrated. In addition to this, for example, a configuration in which the rotating diffuser is rotated in synchronization with the emission of the pulse light is used. Is also good.

Next, the beam LB ₂ split by the beam splitter 7
Is condensed on the light receiving surface of the light receiving element 9 by the light condensing optical system 8. The light receiving element 9, and outputs a photoelectric signal corresponding to the amount (light intensity) of each of the beam LB ₂ pulses correctly, composed of a PIN photodiode or the like having a sufficient sensitivity in the ultraviolet region. The photoelectric signal output from the light receiving element 9 is input to the light amount monitor unit 18, and the light amount monitor unit 18 sequentially integrates the light amount for each pulse emission. Therefore, the light receiving element 9 and the light amount monitoring unit 18 constitute a light amount measuring unit in the present invention, and the actually measured value (a value corresponding to the actually measured integrated light amount may be used. Is not sent to the main control system 10). This measured value (integrated light amount value) is controlled by the main control system 10 to control the exposure amount, that is, to control the voltage applied to the pulse laser light source 1 for each pulse, and to control the trigger controller 13
This is the basic data of the oscillation control for each shot of the trigger pulse oscillated from. The relationship between the actual light amount of the laser beam and the sensitivity of the light receiving element 9 is obtained in advance by a power meter or the like for the light receiving element 9 and stored in the memory 11.

The main control system 10 has a memory 11 and an input / output device 12, and outputs a control command to the trigger control unit 13 based on the actual measurement value of the light amount monitor unit 18 described above.
(4) A predetermined command signal is sent to each of the second light amount control unit 15 and the interference pattern control unit 17 to totally control the operation of the entire stepper. The input / output device 12 is a man-machine interface between the operator and the stepper main body, receives various parameters required for exposure from the operator, and notifies the operator of the operation state of the stepper.

The memory 11 stores parameters (constants) and tables required for the exposure operation and various calculations input from the input / output device 12, or the sensitivity characteristics of the light receiving element 9 and the like. In particular, in the present embodiment, while the beam LB ₁ ′ is oscillated by a half cycle by the interference pattern reduction unit 4, the minimum number of pulses (Nv
ib) is stored. here,
The half cycle of the beam is defined as the spot light SPa in FIG.
To move in the order of SPb → SPc (or vice versa), move the beam
This corresponds to tilting by the swing angle α ゜ in the order of LBa → LBb → LBc (or the reverse). Note that the actual tilt amount of the oscillating mirror is α ゜ / 2 from the double angle theorem.

In the main control system 10, the number of pulses Nsp required to smooth the interference pattern stored in advance in the memory 11 and the number of pulses required to achieve the desired exposure amount control accuracy in one-shot exposure are set. First calculating means (not shown) of the present invention based on Ne and data on an appropriate exposure amount S per shot according to the sensitivity characteristic of the resist.
Calculates the dimming rate β of the dimming unit 3 and the average light amount per pulse (· β) described later.

Further, the main control system 10 calculates a target integrated light amount to be given to the wafer W by the second calculating means (not shown) when each pulse is irradiated with the average light amount value. The difference D from the actually measured value sent from the monitor unit 18 is calculated by a third calculating means (not shown). Then, based on the difference D, the second
A command for adjusting the light amount by controlling the applied voltage of the pulse laser light source 1 is output to the second light amount control unit 15 as the light amount adjusting means. In other words, the main control system 10 determines the difference D
The second light quantity control unit 15 controls the applied voltage of the pulse laser light source 1 based on the corrected light quantity of the pulsed light source 1 based on the average light quantity value (· β). That is, the applied voltage is corrected by the amount corresponding to the above-mentioned correction value and applied to the pulse laser light source 1. FIG. 5 shows an example of the relationship between the voltage applied to the pulse laser light source 1 and the light amount (pulse energy) of the emission pulse.

Further, the main control system 10 outputs a drive signal to the interference pattern control unit 17 so that the pulse emission of the pulse laser light source 1 and the deflection angle of the beam by the interference pattern reduction unit 4 are synchronized. Note that this synchronization follows the output of a detector that monitors the beam deflection angle with high precision, and sends an oscillation start and stop signal to the trigger control unit 13 so as to trigger a pulse emission of the pulse laser light source 1. You may make it output.

Here, the second light amount adjusting means of the present invention is not limited to the method of controlling the voltage applied to the pulse laser light source 1 as in the present embodiment, but may be, for example, a continuous transmittance (light reduction ratio).
May be obtained. Specifically, as an example of the light reduction unit 3, a combination of the aperture and the zoom lens system described above, an etalon, two phase gratings or bright and dark gratings, a rotating polarizing plate (in the case of a linearly polarized laser), or the like is used. May be.

Therefore, for example, FIG.
A description will be given of a case where a high-speed dimming unit including two light / dark gratings 20a and 20b and a grating driving unit 20c as shown in FIG. The two light and dark gratings 20a and 20b are formed on a glass plate (quartz) made of a material having a high transmittance with respect to ultraviolet light, by chromium or the like being vapor-deposited to provide an opaque portion (light-shielding portion) with ultraviolet light at an appropriate interval. And are arranged in parallel at appropriate intervals. And one of the light and dark gratings 20a is a laser beam LB.
And the other light-dark grid 20b is connected to a grid driving unit 20c, which can be finely moved in the pitch direction of the grid by a command from the main control system 10.

FIGS. 8B and 8C are partially enlarged views of two light and dark grids, in which the pitch of the grid is Gp and the width of the opaque portion (light shielding portion) is Gw. FIG. 8 (B) shows a case where the two light and dark gratings are not displaced at all, and the light transmitting part and the light shielding part coincide with each other, and the extinction ratio for the laser beam LB is Gw / G
becomes p. FIG. 8 (C) shows a case where the light and dark grid 20a (fixed) and the light and dark grid 20b (movable) are shifted by Δd.
The dimming rate for the laser beam LB is {(Gw + Δd) / Gp}
Becomes However, the deviation amount Δd is in the range of Gw> Δd.

Here, the grating pitch Gp is 10 μm, and the width Gw of the light shielding portion is 2.5
When the thickness is set to μm, the above configuration enables the emission beam LB ′ to be reduced from 75% to 50% with respect to the laser beam LB.
At this time, since the maximum relative movement amount (maximum deviation amount Δdmax) of the light and dark grids 20a and 20b is defined by the width Gw, the light and dark grid 20b may be moved by a maximum of 2.5 μm. Therefore, a piezoelectric element (such as a piezo element) can be used as the grating driving unit 20c, and the repetition frequency of a general excimer laser or the like is 100 Hz to 500 Hz.
With respect to Hz, the extinction ratio can be set completely following pulse emission, and high-speed extinction can be realized.

In the case where the high-speed dimming unit having the above configuration is used, a pair of photocouplers is arranged with the two light / dark gratings 20a and 20b interposed therebetween so as not to block the incident beam to the rear fly-eye lens 6. . For example, a light emitting element such as a semiconductor laser or an LED is arranged outside the optical path of the beams LB and LB 'on the incident side of the light and dark grid, and a photoelectric detector (such as a silicon photodiode) is provided on the emitting side so as to face the light emitting element. Is provided.
If the grating drive unit 20c is servo-controlled using the output of the detector (a photoelectric signal corresponding to the amount of transmitted light of the high-speed darkening unit), the two light-dark gratings 20 can be more accurately controlled.
It is possible to adjust the relative movement amount of a and 20b, that is, the transmittance of the high-speed darkening unit.

At this time, although it depends on the stability of the output of the light emitting element, as described above, the moving amount of the light / dark grating 20b is at most about 2.5 μm. , The measurement accuracy of the transmittance and the setting accuracy thereof also decrease. Therefore, in practice, a part of the beam emitted from the light emitting element is received by the photoelectric detector and its light amount is detected, and the output (transmitted light amount) of the detector is divided by using this value. It is desirable to accurately measure the transmittance (actually measured value) of the high-speed darkening portion. still,
Even if a photocoupler is not used, two photoelectric detection values may be simply arranged before and after the high-speed darkening portion (incident side and emitting side), and division may be performed using the outputs of the two detectors.
Similarly, the transmittance of the high-speed darkening portion can be accurately measured.

The case where two light-dark gratings are used as the second light amount adjusting means has been described above. However, in other methods (such as a phase grating), high-speed driving is possible by using a piezo element or the like as a driving means (actuator). Thus, the light amount adjustment (light reduction ratio setting) can be performed accurately following the oscillation of the pulse laser light source 1 sufficiently.

The dimming unit 3 is not limited to the position shown in FIG.
The same effect can be obtained by inserting the light source between the pulse light source 1 and the expander 2 or between the cavity mirrors in the pulse light source 1. Further, when the method of causing the beam to vibrate at a small angle by the interference pattern reduction unit 4 described above is not employed, the beam may be inserted between the interference pattern reduction unit 4 and the fly-eye lens 6. However, in any case, the dimming unit 3 needs to be placed in a stage before the laser light is incident on the fly-eye lens 6. This is because a dimming element such as a mesh filter often causes deterioration of illuminance uniformity in a beam cross section, and it is necessary to eliminate the deterioration by the fly-eye lens 6. In the case where a high-speed dimming unit (two light / dark gratings or the like) is used as the second light amount adjusting means, the high-speed dimming unit is connected to any one of the optical paths in front of the fly-eye lens 6 similarly to the dimming unit 3. Just place it inside.

Next, the minimum number of pulses Nsp required for smoothing the interference pattern (uniform illuminance) will be described. For the smoothing of the interference pattern, see, for example, JP-A-1-257327.
Since it is disclosed in the official gazette, it will be briefly described here. In the above publication, when an optical integrator, particularly an illumination optical system having a fly-eye lens is employed, a plurality of pulsed lights are irradiated while moving an interference pattern formed on a reticle (or a wafer) within a certain range. Therefore, when performing the smoothing, the minimum number of pulses to be irradiated during the movement of the interference pattern by one pitch is limited to a predetermined value in advance, and the pulse light of the number equal to or more than the minimum number of pulses must be irradiated. It uses the principle that it must be.

Now, as shown in FIG. 4, the interference pattern is generated when the spot lights generated by the rod lenses of the fly-eye lens 6 interfere with each other. At this time, a case where only the spot lights of two rod lenses adjacent to each other interfere with each other, or a case where three spot lights in the arrangement direction of the rod lenses interfere with each other may be used. What is necessary is just to consider a case where a number of spot lights interfere with each other.

Therefore, the number of pulses Nsp necessary for smoothing an excellent interference pattern is theoretically determined according to the number of spot lights that interfere with each other among the numbers in the arrangement direction of the rod lenses constituting the fly-eye lens. And the minimum number of pulses Nvib to be applied during a half cycle of the beam swing by the vibrating mirror required for one pitch movement of the interference pattern (Nvib is Nvib ≧ Ns
p, an arbitrary integer).

For example, when only two adjacent spot lights interfere with each other, the intensity distribution of the interference pattern is mathematically and theoretically a simple sine wave. In order to smooth this interference pattern, it is sufficient to irradiate two pulses, one pulse before and after shifting the phase difference between the two spot lights by π (movement of a half cycle of the interference pattern). . In general, when n spot lights interfere with each other, theoretically, the interference pattern is shifted by 1 / n period while being 1 / n.
Irradiation with pulses enables smoothing with a total of n pulses.

Here, considering the intensity distribution in one direction (for example, the Y direction) of the interference pattern generated on the reticle when one pulse is emitted, generally, bright stripes and dark stripes alternate with a predetermined pitch Yp in the Y direction. line up. However, the pitch Yp determined by the arrangement pitch of the rod lenses of the fly-eye lens, the wavelength of the laser beam, and the like depends on the configuration of the fly-eye lens, such as a two-stage structure.
In addition to the basic component, weak interference fringes whose intensity changes at a finer pitch may appear in a superimposed manner. Therefore, in practice, complete smoothing is rarely achieved under the above conditions, and the optimum value of the minimum pulse number Nsp required for smoothing the interference pattern needs to be determined by experiments or the like.

In the present embodiment, the angle change of the vibrating mirror (not shown) and the light emission pulse interval (frequency) are set based on the minimum pulse number Nsp obtained by experiments so as to satisfy the relationship of n · ΔY ≧ Yp. Then, an interference pattern is sequentially formed on the resist layer in the Y direction by a minute amount ΔY (ΔY <Y
By shifting by p), the interference pattern is smoothed (illumination uniformity) at the time of completion of exposure, and an approximately constant illuminance distribution including a minute amount of ripple is obtained so as not to affect accuracy. It is.

Then, considering the conditions required for uniformity of illuminance, the following two conditions are given.

(1) Half cycle of mirror oscillation (beam swing angle is from 0 ° to α
Within a period that changes to N), pulse light emission of a certain number Nsp or more is performed substantially uniformly.

Here, the pulse number Nsp is determined by the visibility of the interference pattern, and the larger the visibility, the larger the value of Nsp. Also, if the pulse number is Nsp
Is determined in advance by an experiment such as trial printing, and the numerical value differs between apparatuses having different optical systems. Therefore, when the pulse light emission of a number smaller than Nsp is almost uniformly distributed within a half cycle of the beam swing angle change (0 ° → α ゜), it is desirable in terms of uniform illuminance (illumination unevenness on the image plane). Within the precision of

(2) The average exposure energy per pulse at a predetermined angle of the vibrating mirror is within the beam swing range (0 ° → α).
゜) It should be substantially constant for any angle in (1).

The second condition is that the total number of pulses Nexp actually required for one-shot exposure is an integral multiple of the number of pulses Nvib in a half cycle of the beam oscillation, and that the first pulse light is subjected to mirror oscillation ( 0 ° to α ゜ / 2) (eg, beam LBa in FIG. 4)
Is achieved by emitting light at an angle of 0 °). When the pulse number Nexp is an integral multiple of the number of pulses in one cycle of the mirror oscillation (0 ° to α ゜ / 2), the first pulse light is transmitted to the mirror oscillation (0 ゜ to α ゜ / 2). The light emission may be started at an arbitrary angle in (3).

From the above, the above two conditions (1) and (2)
, The average exposure energy per pulse is adjusted to determine the optimal number of pulses, so that uniformity of illuminance and control of the amount of exposure can both be extremely efficiently achieved. Further, if not only the exposure energy but also the oscillation period (oscillation speed) of the oscillation mirror is changed, the number of exposure pulses is not increased more than necessary, which is advantageous in throughput.

By the way, the degree of adjustment of the second light amount adjusting means (that is, in the second light amount control unit 15 of the present embodiment, the voltage applied to the pulse laser light source 1 and the high-speed dimming unit (two light / dark gratings, etc.) Is the dimming rate or transmittance) to a value slightly smaller than the maximum value of the exposure energy control range of the second light amount adjusting means in consideration of the variation of the exposure energy for each pulse oscillated from the pulse laser light source 1. After the first pulse light is emitted under the above set value in one shot exposure, the main control system 10 sequentially controls the control value to be calculated for each of the second and subsequent pulses. You.

Therefore, an exposure energy control range of the second light amount adjusting means will be described. The average exposure energy per pulse (under the dimming rate of the dimming unit 3 is 1), the variation between the pulses of the exposure energy is Δ, and the pulse emission is performed N times in one shot exposure. Then, the actual integrated light amount I with respect to the target integrated light amount · N (appropriate exposure amount S)
The variation of the (actually measured value) is expressed by the following equation (1).

As is apparent from the above equation (1), the control ratio of the second light amount adjusting means is {1 ± (Δ /) / (1−Δ /)}.
Becomes Therefore, the maximum value of this control ratio ｛1 / (1−Δ
/)｝ Does not exceed the maximum value of the exposure energy control range, the average control value of the second light amount adjusting means set before the exposure is changed to (1) of the maximum value of the control range.
-Δ /) times or less.

Here, in the present embodiment, as a second light amount adjusting means, a second light amount control unit 15 for controlling an applied voltage of the pulse laser light source 1 is used.
Is used. Therefore, the second light quantity control unit 15 determines that the average exposure energy is the maximum output of the pulse laser light source 1 (1−Δ
The voltage applied to the pulse laser light source 1 (discharge voltage between the electrodes) may be set based on the relationship shown in FIG. For example, in the case of an excimer laser,
Because it is usually (delta /) = about 10%, and the maximum output of the pulse laser light source 1 and 10 mJ / cm ^2, the exposure energy may be set to the applied voltage so that the 9 mJ / cm ² or less. In practice, the applied voltage should be set so that the exposure energy is, for example, 5 mJ / cm ² or less, in consideration of the phenomenon of laser density decrease (output decrease due to deterioration of the mixed gas) and the life of optical components. Is desirable.

On the other hand, when a high-speed dimming section is used as the second light quantity adjusting means, the dimming rate is set in advance to about 90% (when Δ / = 10%), and the second and subsequent shots are set based on this set value. The extinction ratio is set sequentially for each pulse. On this occasion,
The applied voltage of the pulse laser light source 1 is controlled only to prevent a decrease in the laser density of the pulse light and to keep the exposure energy per pulse substantially constant.

In this embodiment, since the extinction ratio of the extinction unit 3 is changed in accordance with the exposure condition on the wafer W, the exposure energy of the second and subsequent pulsed light is determined by the error of the integrated light amount due to variation between pulses. Fine adjustment will be made only for correction. Therefore, the discharge voltage between the electrodes in the pulse laser light source 1,
Alternatively, it is not necessary to largely change the extinction ratio of the high-speed extinction section, and the dynamic range of the second light amount adjusting means can be small.

Next, the number of pulses Ne required to achieve a desired exposure amount control accuracy A (A = I / N) in one shot exposure
Will be described briefly. In the exposure amount control in this embodiment, while adjusting the exposure energy for each pulse,
Since the actual integrated light amount I and the target integrated light amount / N are made to substantially match, the error of the final integrated light amount is a variation in the exposure energy of the final pulse light. Therefore, in order to achieve the exposure control accuracy, the variation in the exposure energy of the final pulse light must be within the tolerance of the exposure control accuracy. That is, the exposure energy must be set to a small value, and the number of pulses N (N = S /) required for one-shot exposure must be a relatively large number. From this, in the above equation (1), (Δ /)
^{Since N} can be regarded as zero, dividing each side by .N and rearranging it, the exposure amount control accuracy A becomes It is expressed as Here, in equation (2), the exposure amount control accuracy A
Is the maximum permissible error, ie , The number N of pulses required to achieve the exposure amount control accuracy becomes the smallest. Thus, the pulse number Ne is expressed by the following equation (4).

Therefore, at least the number of pulses represented by the above equation (4)
If exposure is performed with pulse light of a number equal to or greater than Ne, the final integrated light amount I is ± A (for example, 1%
In the case of A, the control accuracy of A = 0.01) is guaranteed.

Next, a method of determining the number Nexp of exposure pulses for one shot will be described. Generally, the number of exposure pulses Nexp is Nexp =
iNT (S /). Note that iNT (ω) indicates that the real value ω is rounded up to the nearest whole number and converted to an integer value.

Now, the pulse light oscillated from the pulse laser light source 1 is uniformly attenuated by the dimming unit 3 at a predetermined dimming rate β (0 ≦ β ≦ 1) and is irradiated on the reticle R. For this reason, the number Nexp of exposure pulses is required to satisfy the following conditional expression (5).

As described above, in order to achieve the exposure amount control accuracy A, it is necessary to satisfy the following expression (6).

Nexp ≧ Ne (6) Further, in order to smooth the interference pattern, the number Nexp of exposure pulses must be an integral multiple of the number Nvib of pulses in a half cycle of the vibrating mirror. Therefore, the number of exposure pulses Nexp
Is represented by the following equation (7).

Nexp = m · Nvib ≧ m · Nsp (m: m ≧ 1) (7) Therefore, the extinction ratio β of the extinction unit 3 is obtained from the equations (4) to (6). It is expressed as

Further, the integer m is expressed by the following expression (9) from the expressions (4), (6), and (7).

Further, since the dimming rate β is 1 or less, (5) and (7)
From the formula, it is expressed as follows.

From the above, in the present embodiment, first, the dimming rate of the dimming unit 3 is determined so as to satisfy Expression (8), that is, the filter of the rotating turret plate 16 is selected, and the dimming of the selected filter is performed. It is checked whether the pulse number Nexp calculated from the equation (5) under the rate satisfies the equations (6) and (7). If not satisfied, a filter satisfying the expression (8) and having a smaller dimming rate is selected so that the number Nexp of exposure pulses satisfies the expressions (6) and (7). When the number of exposure pulses Nexp is determined in this way, (9) and (1)
It suffices to determine m and Nvib so as to simultaneously satisfy the expression (0).

As an example, assuming that the variation Δ / between pulses of the average exposure energy is 10% (Δ / = 0.1) and the exposure amount control accuracy A is 1% (A = 0.01), the number of pulses is obtained from the equation (4).
Ne has 12 pulses. On the other hand, when the dimming rate β of the dimming unit 3 is 1, the average exposure energy is ² mJ / cm ² , the appropriate exposure amount S is 80 mJ / cm ² , and the number of pulses Nsp required for smoothing the interference pattern is 50 pulses. From equation (5), the number of exposure pulses N
Although exp is 40 pulses, this pulse number Nexp does not satisfy the expression (7). Therefore, the extinction ratio of the extinction section 3 is set to be smaller than 1, and the extinction ratio, that is, the number of exposure pulses Nexp calculated from the expression (5) under the average exposure energy · β, Try to meet.

Here, when the dimming rate of the dimming unit 3 can be continuously set, since Ne = 12 and Nsp = 50 pulses,
M and Nvib are set based on equations (9) and (10). At this time, the combination of (m, Nvib) is, for example, (1,50), (1,6)
0), (2,100), etc., but in order to minimize the number of exposure pulses Nexp (Nexp = mNvib) in consideration of the throughput, here, m = 1 and Nvib = 50 are set. The number of exposure pulses Nexp is set to 50 pulses. If exposure is performed with Nexp = 50, optimization of the exposure amount and smoothing of the interference pattern can be performed with the minimum number of pulses Nexp. As a result, the dimming rate β of the dimming unit 3 is set to 0.80 according to the equation (5). Also, Δ is ± 0% from Δ / = ± 10%.
² mJ / cm ² and the average light amount
β is ± 0.160 mJ / cm ² . Accordingly, since the variation of the average light amount of the final pulse light, that is, the error of the final integrated exposure amount can be considered to be about ± 0.160 mJ / cm ² , the exposure amount control accuracy (1%) is sufficiently achieved. You can see that

On the other hand, when the setting of the dimming rate of the dimming unit 3 is discontinuous (when the dimming unit 3 is a rotary turret plate or the like), a mesh filter of the rotary turret plate 16 satisfying the expression (8) is selected. The number of pulses Nexp calculated from the equation (5) under the dimming rate of this filter (for example, β = 0.5)
(7) Check whether the expression is satisfied. Here Ne
In order to minimize xp, among the filters satisfying the expression (8), the filter having the largest dimming rate is selected. Nex when β = 0.50 (ie, β = 1mJ / cm ² )
p = 80 pulses, which satisfies the equations (6) and (7). If the number of pulses Nexp is determined in this way, since Nexp = 80, it is only necessary to determine m and Nvib that simultaneously satisfy the expressions (9) and (10). Here, m = 1 and Nvib
= 80.

As is apparent from the above, when the setting of the dimming rate of the dimming unit 3 is discontinuous, the dimming rate cannot always be set to the optimum value obtained from the calculation. , The number of pulses Nexp becomes large, which may be disadvantageous in throughput. For this reason, the dimming unit 3 can continuously set the dimming rate, or can set the attenuation rate (transmittance) finely even if it is discontinuous (for example, two rotations). It is desirable to use a combination of a turret plate).

Next, the operation of the apparatus according to the present embodiment will be described with reference to the flowchart of FIG. First, in the first step 100, the optimum (target) total exposure amount S corresponding to the register applied to the wafer, the pulse number Nsp necessary for smoothing the interference pattern stored in the memory 11 in advance, and the exposure amount control Based on the data of the number of pulses Ne required to achieve the accuracy, the first arithmetic means provided in the main control system 10 as described above uses the first arithmetic means to reduce the extinction rate β (the average Value β) is calculated.

Subsequently, in step 101, the rotary turret plate 16 is rotated to set the dimming rate of the dimming unit 3 to β, and in step 10
In step 2, a value Sa corresponding to the integrated light amount of the pulse counter n and the light amount monitor unit 18 is set to Nexp and zero, respectively.

In the next step 103, the main control system 10 determines whether or not the pulse counter n is zero, and if not, proceeds to the next step 104. Then, a trigger pulse is sent from the trigger control unit 13 to the pulse laser light source 1 to emit one pulse, and a value Pa corresponding to the actual light amount of the pulse light oscillated by the light receiving element 9 is detected. In the following step 105, the integrated light amount setting in the light amount monitor unit 18 is set to Sa + Pa, and the pulse counter setting is set to (Ne
xp-1).

Next, at step 106, the second integrated means obtains the target integrated light quantity to be given by the average light quantity value β determined at the previous step 100 according to the equation (5), and obtains the third integrated light quantity.
Difference D between target integrated light quantity and actual measured integrated light quantity by arithmetic means
Ask for.

D = (Nexp−n) · β-Sa (11) Then, based on the difference D in step 107, the light quantity 'of the pulse light to be irradiated next is determined in step 100 by the equation (12). It is obtained by correcting from the average light amount value β obtained.

In the next step 108, the second light quantity control unit 15 sets the applied voltage corresponding to the light quantity 'to the pulse laser light source 1, and then returns to step 103. In this step 103, it is determined whether or not the pulse counter n is zero, as in the operation described above. If it is not zero, the process proceeds to step 104, performs the same operation as described above in steps 104 to 108, returns to step 103 again, and repeatedly executes steps 103 to 108 until the pulse counter n becomes zero. The exposure operation ends when n becomes zero.

Here, when a high-speed dimming unit is used as the second light-amount adjusting unit, if the average light amount value β determined in step 100 is a value under the initial dimming rate of the high-speed dimming unit, In 107, the extinction ratio γn of the high-speed extinction unit when the pulse light to be irradiated next is oscillated is determined by the following equation (13). Here, the average exposure energy of the pulse light oscillated from the pulse laser light source 1 is P.

Therefore, the extinction rate of the high-speed extinction unit is set to γn in the next step 108, and steps 103 to 108 may be repeatedly executed by the same operation as that of the present embodiment until the pulse counter n becomes zero.

Next, the state of exposure amount control in the apparatus according to the present embodiment will be described with reference to FIG. FIG. 7 is a graph showing the relationship between the number of pulses and the integrated exposure amount when exposing one shot, and here, a case where the exposure is completed by eight pulses is shown. For simplicity of explanation, it is assumed that the dimming rate β of the dimming unit 3 is set to 1.

In FIG. 7, a straight line indicated by a two-dot chain line
A target value of the integrated exposure amount to be given by the pulse light of the average light amount value / β determined at 0 is shown. Therefore,
In the present invention, the light amount is adjusted for each of the second and subsequent pulses so that the exposure amount control is performed according to the target value.

Now, the first pulse light is emitted with a target of an exposure amount of ₁ , and the actually detected exposure amount after the emission is
_'When were, pulsed light of the second shot th target exposure amount 2 ₁ and _{1' 1} the difference between _- would be light emission performed is set to (2 1 1 _') = ₂ becomes the light amount. At this time, the second light amount control unit 15 only needs to apply an applied voltage corresponding to the light amount ₂ to the pulse laser light source 1. Similarly, _'When a was the third shot th pulsed light (3 1 _- 1' _- measured value of the second shot th pulse light amount ₂ 2 _') = is set to ₃ comprising light amount emission line Will be

Therefore, by repeating the above operation, the exposure is completed at the eighth pulse in a state where the displacement of the two-dot chain line from the target line is small. At this time, it is clear that the final exposure amount control accuracy (variation of the actually measured value with respect to the appropriate exposure amount) is a light amount error (variation) of the eighth pulse light.

As described above, in one embodiment of the present invention, when exposing one shot with a plurality of pulsed lights, the target value of the integrated exposure amount up to the (i + 1) -th shot and the integrated exposure in the past (up to the i-th shot) Based on the difference with the quantity, the (i + 1)
The light quantity of the first pulse light was set. However,
If there is any tendency in the variation from pulse to pulse,
A new target value may be set by averaging the ratio between the target value for each unit pulse and the actually measured value for each unit pulse over a plurality of past pulses, and dividing the target value by the average value of this ratio.

Further, in the above embodiment, the case where the pulse energy oscillated from the exposure amount illumination light source is a coherent laser beam has been described.However, the case where the light source of the exposure apparatus emits incoherent pulse light, for example, When emitting pulse energy other than light such as an electron beam, there is no need to consider reduction (smoothing) of an interference pattern at all.
Therefore, the minimum number of pulses (the number of pulses necessary to control the variation of the actual integrated exposure amount given to the wafer W by the irradiation of the plurality of pulse lights with the desired exposure amount control accuracy with respect to the target appropriate exposure amount). (Corresponds to the pulse number Ne in this embodiment)
May be determined from the fluctuation range of the pulse energy per pulse and the exposure amount control accuracy, and the target value of the pulse energy may be set for each pulse based on the number of pulses and the optimum exposure amount. That is, since the error of the final integrated exposure amount with respect to the proper exposure amount is determined by the light amount error of the final pulse light, the variation of the final pulse falls within the allowable error of the exposure amount control accuracy (4). )), The number of pulses is determined, and an average energy amount per pulse is set according to the expression (5).

〔The invention's effect〕

As described above, in the present invention, the number of pulses ejected during one-shot exposure is always a predetermined constant value, and the light amount (energy amount) for each pulse required for one-shot exposure ) Is actually measured and finely adjusted to control the exposure amount. For this reason, by moving the interference pattern in synchronization with the irradiation of the pulse light, it is convenient to almost completely smooth the final interference pattern (uniform illuminance). Since one-shot exposure is performed with the minimum necessary number of pulses while performing pattern smoothing, productivity can be improved. In addition, the exposure amount control can be performed with higher accuracy as compared with the related art, and the light amount measuring means for actually measuring the light amount for each pulse and the means for finely adjusting the light amount of the next pulse light (first There is an effect that the dynamic range of (2 light amount adjusting means) can be small. Further, even when the exposure condition for the photosensitive second object changes, a means (first light amount adjusting means) for uniformly attenuating the light amounts of all the pulse lights is provided, so that the second light amount adjusting means is provided. It is possible to easily respond to changes in exposure conditions without increasing the dynamic range of the means.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of a stepper provided with an exposure control device according to an embodiment of the present invention, and FIG. 2 is a rotation suitable for application to a dimming unit (first light amount adjusting means). FIG. 3 is a configuration diagram illustrating an example of a turret plate, FIG. 3 is a diagram illustrating a relationship between a rotation amount of a dimming element and transmittance when dimming is performed by the rotating turret plate illustrated in FIG. 2, and FIG. FIG. 5 schematically shows a relationship between a beam incident on an integrator (fly-eye lens) and its secondary light source image (spot light). FIG. 5 shows a relationship between an applied voltage and its output (pulse energy) in a pulse laser light source. Diagram showing an example of
FIG. 6 is a flowchart showing the operation of the exposure control apparatus according to the embodiment of the present invention shown in FIG. 1, FIG. 7 is a graph showing the state of exposure control according to the embodiment shown in FIG.
FIGS. 8A to 8C are views for explaining an example of a high-speed darkening section as a second light amount adjusting means. [Description of Signs of Main Parts] 1... Pulse laser light source, 3... Dimming unit, 4... Interference pattern reducing unit, 6... Fly-eye lens, 10. , 14... First light quantity control unit, 15
... Second light quantity control unit, 16 rotating turret plate, 17
Interference pattern control unit, 18: Light amount monitor unit, R: Reticle, PL: Projection lens, Ep: Entrance pupil, W: Wafer,

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-11-238681 (JP, A) JP-A-10-92744 (JP, A) JP-A-2-135723 (JP, A) JP-A-1- 274021 (JP, A) JP-A-1-274022 (JP, A) JP-A-1-257327 (JP, A) JP-A-63-316430 (JP, A) JP-A-63-190332 (JP, A) JP-A-61-14720 (JP, A) JP-A-60-169136 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F ^7/ 20-7/24 G03F 9/00 -9/02 H01L 21/027

Claims (11)

(57) [Claims] A pulse light source for emitting coherent pulse light; and an illumination optical system for irradiating the pulse light to a first object.
An apparatus for transferring a pattern formed on the first object by irradiation of a plurality of pulsed lights to a photosensitive second object at a predetermined exposure amount, wherein the exposure amount on the second object is changed to the predetermined exposure amount. A first light amount adjusting means for uniformly adjusting the light amount of each pulse light irradiated on the first object at a predetermined adjustment degree; and the first object or the first object by the irradiation of the pulse light. Second
The predetermined number of pulses required to move and smooth the interference pattern generated on the object every time the pulse light is irradiated and the integrated light amount given to the second object by the irradiation of the plurality of pulse lights are set to a predetermined accuracy. A first calculating means for determining in advance the degree of adjustment of the first light quantity adjusting means and the average light quantity value of the pulsed light based on the number of pulses required to control the light quantity and the predetermined exposure amount; Second calculating means for determining, for each predetermined unit pulse, a target integrated light amount to be given to the second object when irradiating the pulse light with an average light amount value; actual integration given to the second object Light quantity measuring means for detecting light quantity; third calculating means for calculating a difference between the actual integrated light quantity given to the second object by the previously irradiated pulse light and the target integrated light quantity corresponding thereto. The calculation And a second light amount adjusting means for adjusting the light amount of the pulse light to be irradiated next based on the average light amount value based on the difference. 2. The apparatus according to claim 1, wherein said second light amount adjusting means adjusts the light amount of said pulse light by controlling a predetermined oscillation condition of said pulse light source for each said predetermined unit pulse. Exposure control device described at the time. 3. The apparatus according to claim 1, wherein the first light amount adjusting means switches the degree of adjustment of the light amount of the pulse light continuously or stepwise only when an exposure condition for the second object changes. 3. The exposure control device according to claim 1 or 2. 4. An energy source for emitting pulse energy, and an illumination system for irradiating the pulse energy to a first object, wherein a pattern formed on the first object by irradiation of a plurality of pulse energies is exposed to a predetermined light. An exposure control device for controlling the amount of exposure to the second object to the predetermined amount of exposure, wherein the pulse energy of each pulse energy applied to the first object is First energy amount adjusting means for uniformly adjusting the energy amount at a predetermined adjustment degree; necessary for controlling the integrated energy given to the second object by irradiation of the plurality of pulse energies with a predetermined setting accuracy. Based on the number of pulses and the predetermined exposure amount, the degree of adjustment of the first energy amount adjusting means and the average energy value of the pulse energy are determined in advance. A second calculating means for determining, for each predetermined unit pulse, a target integrated energy amount to be given to the second object when the pulse energy is irradiated under the average energy value; Energy amount measuring means for detecting an actual integrated energy amount given to the two objects; and the second energy is measured by the previously applied pulse energy.
Third calculating means for calculating a difference between the actual integrated energy amount given to the object and the target integrated energy amount corresponding thereto; based on the calculated difference, the energy of the pulse energy to be irradiated next And a second energy amount adjusting means for adjusting the amount by correcting the average energy value. 5. An energy source for emitting pulse energy, and an irradiation system for irradiating the pulse energy to a first object, wherein a pattern formed on the first object by irradiation of a plurality of pulse energies is exposed to a predetermined light. An exposure apparatus for transferring an amount of energy of each pulse energy applied to the first object to a second object responsive to an amount, the first energy amount adjusting unit uniformly adjusting an energy amount of each pulse energy with a predetermined adjustment degree; Second calculating means for determining, for each predetermined unit pulse, a target integrated energy amount to be given to the second object when energy is irradiated; an energy amount for detecting information on an actual integrated energy amount given to the second object Measuring means; and said second energy by a previously applied pulse energy.
Second energy amount adjusting means for adjusting the energy amount of the pulse energy to be irradiated next based on the actual integrated energy amount given to the object and the target integrated energy amount corresponding thereto. Exposure control device characterized by the above-mentioned. 6. An energy control apparatus comprising: an energy source for emitting pulse energy; and an illumination system for irradiating the object with the pulse energy, wherein the energy control device controls the amount of energy applied to the object by irradiating the plurality of pulse energies. A first energy amount adjusting means for uniformly adjusting the energy amount of each pulse energy applied to the object at a predetermined adjustment degree; and adjusting the pulse energy amount applied to the object for each predetermined unit pulse. An energy control device, comprising: a possible second energy amount adjusting means. 7. The apparatus according to claim 6, wherein said second energy amount adjusting means adjusts said pulse energy amount for each of said predetermined units by controlling a predetermined oscillation condition of said energy source. An energy control device according to claim 1. 8. The energy source is a pulse laser light source whose output varies according to a given discharge voltage, and the second energy amount adjusting means controls the discharge voltage to adjust the pulse energy amount for each of the predetermined units. The energy control device according to claim 7, wherein the energy control is performed. 9. A first object is irradiated with pulse energy from an energy source, and a pattern formed on the first object by irradiation of a plurality of pulse energies is transferred to a sensitive second object with a predetermined exposure amount. In the exposure method, for the plurality of pulse energies, uniformly adjusting the pulse energy at a predetermined adjustment degree; calculating a target integrated energy amount to be given to the second object when the pulse energy is irradiated. Detecting information on the actual integrated energy amount given to the second object; adjusting the energy amount of the pulse energy for each predetermined unit pulse based on the integrated energy amount and the target integrated energy amount; An exposure method, comprising: 10. The apparatus according to claim 9, wherein the second energy amount adjusting means adjusts the pulse energy amount for each of the predetermined units by controlling a predetermined oscillation condition of the energy source. An energy control device according to claim 1. 11. The energy source is a pulse laser light source whose output changes according to a given discharge voltage, and the second energy amount adjusting means controls the discharge voltage to adjust the pulse energy amount for each of the predetermined units. 11. The energy control device according to claim 10, wherein