JP3303280B2 - Position detection device, exposure device, and exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device ,
Positioning and exposure method , in particular, by synchronously scanning the reticle and the photosensitive substrate with respect to a slit-shaped illumination area, such as a rectangular or arc shape, the pattern on the reticle to each shot on the substrate The present invention is suitably applied to an autofocus mechanism or an autoleveling mechanism of a so-called step-and-scan exposure system for sequentially exposing an area.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device, a liquid crystal display device, a thin film magnetic head, or the like is manufactured by using photolithography technology, a photomask or a reticle (hereinafter, referred to as a "reticle") has been used.
A projection exposure apparatus that exposes a pattern of a “reticle” to a wafer (or a glass plate or the like) coated with a photoresist or the like through a projection optical system is used. Generally, projection exposure apparatuses require high resolution,
Since the numerical aperture of the mounted projection optical system is high, the depth of focus (focus margin) of the projected image decreases in inverse proportion to the square of the numerical aperture. Therefore, in order to align each shot area of the wafer with respect to the imaging plane of the projection optical system within the range of the depth of focus, conventionally, the projection exposure apparatus has a focus on the wafer at a predetermined reference point in the exposure field. An auto-focus mechanism for adjusting the position to the image plane formed by the projection optical system and an auto-leveling mechanism for setting the tilt angle of the exposure surface of the wafer in the exposure field parallel to the image plane are provided.

The conventional auto-focus mechanism detects a defocus amount from a focusing plane (a position in a direction of an optical axis of a projection optical system) of a predetermined measurement point in each shot area of a wafer. And a servo system for keeping the defocus amount within an allowable range. On the other hand, the auto-leveling mechanism has a leveling sensor that detects the amount of deviation of the inclination angle of each shot area of the wafer from the inclination angle of the imaging surface, and a servo system that keeps the deviation amount of the inclination angle within an allowable range. It is composed of

[0004] In this regard, in a projection exposure apparatus (stepper or the like) of the collective exposure method generally used in the past, since the wafer whose focus position is to be detected is stationary during exposure, the numerical aperture of the projection optical system is further increased. Even if it becomes larger, it is possible to cope with a decrease in the depth of focus by improving the resolution and accuracy of the AF sensor for detecting the defocus amount and increasing the accuracy of the mechanism of the Z stage in the servo system. . Similarly, for the auto-leveling mechanism, the batch exposure method was able to cope with higher precision.

[0005]

Recently, one chip pattern such as a semiconductor element has been increasing in size. In a projection exposure apparatus, a pattern having a larger area on a reticle is exposed on a wafer. The area is required to be increased. Further, as the pattern of a semiconductor element or the like becomes finer, it is required to improve the resolution of the projection optical system. However, in order to improve the resolution of the projection optical system, the exposure field of the projection optical system must be improved. However, there is an inconvenience that it is difficult from the viewpoint of design or manufacture to increase the value. In particular, when a catadioptric system is used as the projection optical system, the shape of the aberration-free exposure field may be an arc-shaped region.

In order to increase the area of the pattern to be transferred and to respond to the limitation of the exposure field of the projection optical system, for example, a rectangular, circular or hexagonal illumination area (this is referred to as a "slit illumination area"). A so-called step-and-scan projection exposure in which a pattern having a larger area than the slit-shaped illumination area on the reticle is sequentially exposed to each shot area on the wafer by scanning the reticle and the wafer in synchronization with each other. Equipment is being developed.

This type of projection exposure apparatus also requires an autofocus mechanism and an autoleveling mechanism for aligning the exposure surface of the wafer during scanning exposure with the image forming surface. However, in the case of the step-and-scan method, since the wafer whose focus position is to be detected moves during exposure, the AF sensor and the servo system have a predetermined response speed. Simply increasing the accuracy of the mechanism of the system or the like is disadvantageous in that it is difficult to adjust the exposure surface of the wafer to the imaging plane within the range of the depth of focus.

SUMMARY OF THE INVENTION In view of the above, according to the present invention, when performing exposure by the step-and-scan exposure method, the focus position (height) of the exposure surface of the moving wafer or the average inclination angle of the surface is determined. and an object thereof is to allow feedback to the servo system to accurately detect.

[0009]

According to the position detecting device of the present invention, as shown in FIGS. 1 and 6, for example, a mask (7) in which a pattern for transfer is formed on an illumination area (8) of a predetermined shape. ) In a predetermined direction, and a substrate stage (20) for scanning the photosensitive substrate (15) in a predetermined direction in synchronization with the mask stage.
And the substrate (1) provided on this substrate stage in accordance with the height of the exposure surface of the substrate (15) in the mask direction (Z direction).
Height adjusting means (17, 19, 2) for adjusting the height of (5)
4) is provided in a scanning type exposure apparatus for sequentially exposing the pattern of the mask (7) onto the substrate (15) while adjusting the height of the substrate (15), and the height adjusting means (17, 19,
This device detects a signal corresponding to the height of the exposure surface of the substrate (15) to be supplied to the substrate (24).

The present invention relates to a measurement point (PB2) in an area on the near side in the scanning direction with respect to the measurement point (PA2) in the exposure area (16) of the pattern of the mask (7) and the exposure area (16). ) Height detecting means (25A2, 25B2) for detecting the height of the exposed surface of the substrate (15) at a plurality of measurement points
And the measurement signals (SA2, SB2) corresponding to the heights of the plurality of measurement points, which are output from the height detection means, are transferred to the moving speed of the substrate stage (20), the exposure area (16) of the mask pattern. By adding the weights (K1, K2) determined in accordance with the width in the scanning direction and the arrangement of the plurality of measurement points, so that the substrate at a predetermined reference point in the exposure area (16) of the pattern of the mask is added. (15) height calculating means (33) for obtaining a signal (SD2) corresponding to the height of the exposure surface, and a signal (SD2) corresponding to the height obtained by the height calculating means is converted to a high level. Adjustment means (17, 1
9, 24).

In this case, a plurality of measurement points detected by the height detecting means are distributed on a plurality of different straight lines parallel to the scanning direction (X direction) of the substrate as shown in FIG. 2, for example. Or more measurement points (PA1 to PA3, PB1 to PB
As 3), the heights of the plurality of measurement points detected by the height detection means are processed by the least square method, and the substrate (1) is processed.
The surface shape calculation means (3) for calculating the surface shape of the exposure surface of (5).
It is desirable to provide 3). Next, exposure according to the present invention
The device scans the mask on which the pattern is formed in a predetermined direction.
Mask stage to be inspected and synchronized with the mask stage
A substrate stage that scans the substrate in a predetermined direction,
Projection optical system that projects the image of the laser pattern onto the substrate
And an exposure surface of the substrate and its projection optics during scanning of the substrate.
Adjusting means for matching the image plane of the system,
By scanning the mask and its substrate synchronously,
Scan to expose the pattern of the mask on the substrate sequentially
Type exposure apparatus, the projection optical system
Placed in the exposure area where the image of the disc pattern is projected
The first measurement point and the scanning method of the substrate with respect to the first measurement point
A second measurement point that is away from the first measurement point,
At each of the second measurement points, the focus information on the exposed surface of the substrate
Detection means for detecting the information, and the detection means detected at the first measurement point.
Focus information and focus detected at the second measurement point
And weighting each of the
Control the adjustment means based on the focus information
And control means for controlling. In addition, the present invention
Exposure method uses a projection optical system to project the image of the mask pattern
And the mask and its
By moving the substrate synchronously, the mask
In an exposure method for exposing a pattern on the substrate,
At each of the number measurement points, the focus information on the exposed surface of the substrate
Information is detected, and the detected focus information is
Of the substrate in the exposure area where the image of the disk pattern is projected
Weighting according to the width in the scanning direction is performed, and the weight
Exposure surface of the substrate based on the attached focus information
Adjusts the positional relationship between the image plane of the projection optical system and
is there.

[0012]

The principle of the present invention will be described. First, FIG.
As shown in the figure, the exposure area (1) on the moving substrate (15)
Assuming that the pattern of the mask is exposed in 6), the substrate (15) is scanned rightward with respect to the exposure area (16). For example, consider the case where the height of a central point (PA2) in the exposure area (16) is detected by the height detecting means (25A2). Assuming that there is no delay time, if the output signal from the height detecting means (25A2) is shown in time series, it indicates the unevenness of the surface of the substrate (15) as shown by the curve (34A) in FIG. Signal. This signal is supplied to height adjusting means (17, 19, 24) to supply the substrate (1).
By adjusting the height of 5), dynamic autofocus during scanning can be realized.

However, actually, the detection signal from the height detecting means (25A2) is represented by the curve (3) in FIG.
In addition to the delay as shown in FIG. 5A), since the entire control system in the case where a servo loop is formed has a limited response, a tracking error occurs, which becomes a focus residual. Although the focus residual is small while the moving speed of the substrate (15) is low, the moving speed of the substrate (15) is increased, and the time series frequency of the observed output signal and the response frequency of the control system are reduced. Are the same order, a large focus residual remains.

In the present invention, in order to solve such inconvenience,
As shown in FIG. 3, the measurement point (PA) in the exposure area (16)
Height detection means (25A2) for detecting the height of 2), and a measurement point (PB2) preceding the measurement point in the exposure area (16)
Height detecting means (25B2) for detecting the height of
The output signals from the plurality of height detection means are weighted and then added, thereby improving the phase delay due to the limitation of the response of the entire control system. The principle will be described below.

FIG. 2A shows an example of the arrangement of the height detecting means according to the present invention. In FIG. 2A, measurement of one line in the non-scanning direction in the exposure area (16) of the mask pattern is performed. Points (PA1 to PA3) and two rows of measurement points (PB1 to PB3 and PC1 to PC3) on both sides of this one row of measurement points
Height detecting means for detecting the height of the object is provided. Each height detecting means is provided at the substrate (1) at the corresponding measuring point.
What is necessary is just to be able to detect the height of 5), and any method may be used. FIG. 2A is an example of the arrangement of the measurement points, and the arrangement of at least three rows is sufficient, and the arrangement is not limited to the arrangement of FIG. When the substrate (15) is scanned in the X direction, the measurement points (PA1 to PA3) in row A
And the detection results of the measurement points (PB1 to PB3) in the B column are used, and when the substrate (15) is scanned in the −X direction,
Measurement points in row A (PA1 to PA3) and measurement points in row C (P
The detection results of C1 to PC3) are used.

As shown in FIG. 3, it is assumed that the substrate (15) is scanned in the right direction (X direction).
A2, PB2) (25A2, 25)
The detection result of B2) is used. In this case, the height detecting means (25A2, 25B
The output signal from 2) (this is called the "original signal")
The solid curve (34A) in FIGS. 4 (b) and 4 (a), respectively.
And (34B), the actual height detecting means (25A) to which a phase delay is added due to the limitation of the response of the control system.
2 and 25B2) are respectively shown in FIG.
And (a) are shown by the dotted curves (35A) and (35B). That is, the signal at the measurement point (PB2) has a phase advance with respect to the signal at the measurement point (PA2), and each signal has a predetermined phase delay with respect to the original signal due to the delay of the entire control system. .

FIG. 5 shows the height detecting means (25A2, 25B).
The output signal from 2) is represented by a vector, and the solid line vectors <SB2 ₀ > and <SA2 ₀ > represent the original signals at the measurement point (PB2) and the measurement point (PA2), respectively. <SB2> and <SA2> represent signals to which actual phase delays are added at the measurement points (PB2) and (PA2), respectively. What is to be obtained is the original signal represented by the vector <SA2 ₀ > at the measurement point (PA2). Then, after multiplying the actually detected vectors <SB2> and <SA2> by an appropriate weighting coefficient, and adding these, the vector <SD
2> is obtained, and this vector <SD2> represents a signal close to the original vector <SA2 ₀ >. Such addition on a vector is actually performed by simple addition on a time series. By controlling the height of the substrate (15) using a signal corresponding to the vector <SD2>,
The phase lag is compensated.

Next, as shown in FIG. 6, a signal (SD2) obtained by multiplying the output signals of the height detecting means (25B2, 25A2) by weighting factors (gains) K1 and K2, respectively, and adding them. Height adjusting means (17, 19, 24)
And the height adjusting means (17, 19, 24) internally generates a servo signal to drive the stage (17) on which the substrate (15) is mounted. The driving of the substrate (15) in the height direction by the servo signal is reflected in the output signals of the height detecting means (25B2, 25A2), and as a result, the entire control system forms a closed loop control system. In this case, the ratio of the weighting factors K1 and K2 depends on the frequency of the time-series signal (SA2, SB2) of the displacement in the height direction, and this is a parameter that depends on the moving speed of the substrate (15).

[0019] Now, the response limit of the whole system (the cutoff frequency) and F _n, this system results in a delay of [pi / 8 with respect to the signal of frequency F _n. Here, the system is regarded as a first-order delay. Also, consider the unevenness of the substrate (15), which is one cycle in the exposure area (16). When auto-focusing or auto-leveling is performed on an exposure region (16) having a finite area, irregularities on the surface of the substrate (15) having a period smaller than the width of the exposure region (16) in the scanning direction are as follows. Since it is impossible to follow in principle, this frequency _Fn is the highest frequency that the system must follow. The frequency F _n is the width of the scanning direction of the exposure region (16) D, when the moving speed of the substrate (15) is D,
It is expressed as the following equation.

[0020]

[Number 1] and F _n = D / V, the measurement points as shown in FIG. 6 (PA2) and the measurement point interval in the scanning direction with the (PB2) is d, the measurement points in the signal of the frequency (PA2) Signal and measurement point (P
The phase difference φ _AB between the signal B2) and the signal B2) is as follows.

[0021]

Φ _AB = π (d / D) Then, as shown in FIG. 5, in order to compensate for the phase delay by the vector addition, the ratio of the weighting coefficients K1 and K2 (K1
/ K2) is 1, the phase difference φ _AB is π / 4
If, the vector <SD2> after the addition has the same phase as the original vector <SA2 ₀ >. At this time, the following relationship is derived from (Equation 2).

[0022]

Π (d / D) = π / 4, that is, d = D / 4 When the spatial frequency of the unevenness of the substrate (15) is shifted to the lower frequency side, the measurement point (PA2) is measured. It is sufficient to reduce the distance d from the point (PB2), but changing the distance between the height detecting means during operation generally involves many difficulties.
Therefore, in the present invention, for example, the weighting factors K1 and K1
By changing the ratio K1 / K2 of 2, an operation effect equivalent to changing the interval d is obtained. When the spatial frequency distribution of the irregularities on the surface of the substrate (15) is actually unknown, for example, the ratio K1 / K2 may be adjusted while monitoring the focus residual.

Next, assuming that the substrate (15) is scanned in the X direction in FIG. 2 (a), a plurality of measurement points detected by the height detecting means are detected, for example, in the scanning direction of the substrate (X direction). As three or more measurement points (PA1 to PA3, PB1 to PB3) distributed on a plurality of different straight lines parallel to, the heights of the plurality of measurement points detected by the height detection means are calculated by the least square method. When a surface shape calculating means (33) for processing and calculating the surface shape of the exposed surface of the substrate (15) is provided, the average surface of the exposed surface of the substrate (15) is determined based on the height data read in advance. Is required. By making this average plane parallel to a reference plane (for example, in the case of having a projection optical system, an imaging plane formed by the projection optical system), auto-leveling is performed.

[0024]

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an autofocus mechanism and an autoleveling mechanism of a projection exposure apparatus of a step-and-scan method. FIG. 1 shows the overall configuration of a projection exposure apparatus according to the present embodiment. In FIG. 1, an exposure light IL from a light source system 1 including a light source and an optical integrator is used for a first relay lens 2 and a reticle blind (variable field stop). 3) illuminate the rectangular illumination area 8 on the reticle 7 with uniform illuminance via the second relay lens 4, mirror 5, and main condenser lens 6. Reticle blind 3 is placed on reticle 7
Conjugate with the pattern forming surface of reticle blind 3
The position and shape of the illumination area 8 on the reticle 7 are set according to the position and shape of the opening. The light source in the light source system 1 is an ultra-high pressure mercury lamp, an excimer laser light source, or a Y light source.
An AG laser harmonic generator or the like is used.

The image of the pattern in the illumination area 8 of the reticle 7 is projected and exposed through a projection optical system PL into a rectangular exposure area 16 on a wafer 15 coated with a photoresist. The Z axis is taken in parallel with the optical axis AX of the projection optical system PL, the X axis is taken in a direction parallel to the plane of FIG. 1 in a two-dimensional plane perpendicular to the optical axis AX, and the Y axis is taken in the direction perpendicular to the plane of FIG. Take the axis. In this embodiment, the scanning direction of the reticle 7 and the wafer 15 when performing exposure by the scanning method is parallel to the X axis.

The reticle 7 is held on a reticle stage 9, and the reticle stage 9 is supported on a reticle base 10 so as to be driven at a predetermined speed in the X direction by, for example, a linear motor. The laser beam from the laser interferometer 12 is reflected by the movable mirror 11 fixed to one end of the reticle stage 9 in the X direction, and the coordinates of the reticle 7 in the X direction are constantly measured by the laser interferometer 12. The coordinate information of the reticle 7 measured by the laser interferometer 12 is supplied to a main control system 13 for controlling the operation of the entire apparatus, and the main control system 13 moves and moves the reticle stage 9 via a reticle drive system 14. Control the speed.

On the other hand, the wafer 15 is
The wafer holder 17 held above is supported by a fulcrum composed of three telescopic piezo elements (fulcrums 18A to 18 in FIG. 6).
C) is placed on the Z leveling stage 19 via
The Z leveling stage 19 is mounted on an XY stage 20, and the XY stage 20 is supported on a wafer base 21 so as to be slidable two-dimensionally. The Z leveling stage 19 finely adjusts the position (focus position) of the wafer 15 on the wafer holder 17 in the Z direction via three fulcrums, and finely adjusts the tilt angle of the exposure surface of the wafer 15. Further, the Z leveling stage 19
A coarse adjustment of the position in the direction is also performed. XY stage 2
0 is a Z leveling stage 19, a wafer holder 17
In addition, the wafer 15 is positioned in the X and Y directions, and the wafer 15 is scanned at a predetermined scanning speed in parallel with the X axis during scanning exposure.

Moving mirror 22 fixed to XY stage 20
Reflect the laser beam from the external laser interferometer 23, and the XY stage 2
3 are constantly monitored, and the detected XY coordinates are supplied to the main control system 13. The main control system 13 controls the operations of the XY stage 20 and the Z leveling stage 19 via the wafer drive system 24. When performing exposure with scanning method, the scanning as the projection magnification of the projection optical system PL beta, via the reticle stage 9 at a speed V _R in the -X direction (or X direction) with respect to the reticle 7 illumination region 8 In synchronization with the operation of the wafer 1 via the XY stage 20.
The pattern image of the reticle 7 is sequentially exposed on the wafer 15 by scanning the exposure area 16 with respect to the exposure area 16 in the X direction (or the −X direction) at the speed V _W (= β · V _R ).

Next, the configuration of an AF sensor (focus position detection system) for detecting the position (focus position) of the exposure surface of the wafer 15 in the Z direction in this embodiment will be described. In this embodiment, nine AF sensors having the same configuration are arranged, but FIG. 1 shows three AF sensors 25A2, 25B2, and 25C2. First, the center AF
In the sensor 25A2, non-photosensitive detection light with respect to the photoresist emitted from the light source 26A2 illuminates a slit pattern in the light transmission slit plate 27A2, and an image of the slit pattern passes through the objective lens 28A2.
The exposure region 16 is oblique to the optical axis AX of the projection optical system PL.
Is projected onto the measurement point PA2 on the wafer 15 located at the center of the measurement. The reflected light from the measurement point PA2 is collected by the condenser lens 29A.
2, a slit pattern image focused on the vibration slit plate 30A2 and projected onto the measurement point PA2 on the vibration slit plate 30A2 is formed again.

The light passing through the slit of the vibration slit plate 30A2 is photoelectrically converted by a photoelectric detector 31A2, and the photoelectric conversion signal is supplied to an amplifier 32A2. Amplifier 3
2A2 performs synchronous detection of the photoelectric conversion signal from the photoelectric detector 31A2 based on the drive signal of the vibration slit plate 30A2, and amplifies the obtained signal, so that it is substantially linear within a predetermined range with respect to the focus position of the measurement point PA2. A changing focus signal is generated, and the focus signal is supplied to the surface position calculation system 33. Similarly, the other AF sensor 25B2
Projects a slit pattern image at the measurement point PB2 on the −X direction side with respect to the measurement point PA2, photoelectrically converts light from this slit pattern image with the photoelectric detector 31B2, and supplies the light to the amplifier 32B2. The amplifier 32B2 is connected to the measurement point PB2
Is supplied to the surface position calculation system 33. Similarly, the AF sensor 25C2
Projects a slit pattern image at the measurement point PC2 on the X direction side with respect to the measurement point PA2, photoelectrically converts light from this slit pattern image with the photoelectric detector 31C2, and
2C2. The amplifier 32C2 supplies a focus signal corresponding to the focus position of the measurement point PC2 to the surface position calculation system 33.

In this case, the AF sensors 25A2 to 25C
The focus signals obtained by the amplifiers 32A2 to 32C2 from the photoelectric conversion signals from the measurement points PA2
Calibration is performed so as to become 0 when PC2 matches the image plane formed by the projection optical system PL. Therefore, each focus signal is measured at the measurement point PA
2 corresponds to the shift amount (defocus amount) of the focus position of the PC2 from the image forming plane.

FIG. 2A shows the distribution of measurement points on the wafer 15 in this example. In FIG. 2A, the width in the X direction is the center of the rectangular exposure area 16 having the width D in the Y direction. The three measurement points PA1 to PA3 are arranged along a straight line extending in the direction, and the measurement points PB1 to PB3 are arranged at positions separated from the measurement points PA1 to PA3 by a distance d in the -X direction, respectively. The measurement points PC1 to PC3 are arranged at positions separated from the PA3 by a distance d in the X direction. The measurement point PA2 is located at the center of the exposure area 16, and the focus positions of the nine measurement points are independently set to the AF points in FIG.
It is measured by an AF sensor having the same configuration as the sensor 25A2. In this embodiment, when scanning the wafer 15 in the X direction, the measurement points PA1 to PA
3, and when the wafer 15 is scanned in the −X direction using the measurement values of the focus signals at the measurement points PB1 to PB3 in the scanning direction, the measurement points PA1 to PA3 in the exposure area 16 are used.
PA3 and the measured values of the focus signals at the measurement points PC1 to PC3 in the scanning direction are used.

In the following description, it is assumed that the wafer 15 is scanned in the X direction as shown in FIG. 3, that is, the reticle 7 is scanned in the -X direction. First, an autofocus mechanism for matching the focus position of the wafer 15 at the central portion in the exposure area 16 with the image plane will be described. In this case, as shown in FIG. 3, the focus position at the measurement point PA2 at the center in the exposure area 16 and the focus position at the measurement point PB2 on the near side in the scanning direction (X direction) with respect to the measurement point PA2. To the AF sensors 25A2 and 25B, respectively.
2 and the photoelectric conversion signals from the AF sensors 25A2 and 25B2 are passed through amplifiers 32A2 and 32B2, respectively, to obtain focus signals SA2 and SB2. The focus signals SA2 and SB2 are signals corresponding to the amounts of shift of the focus positions (positions in the Z direction) of the measurement points PA2 and PB2 from the image plane.

At this time, assuming that the detection system and the servo system have no phase delay and no limit of the response frequency, the focus signals SB2 and SA2 are respectively represented by the solid line curve 34B in FIG. As shown by a solid line curve 34A), the unevenness of the exposed surface of the wafer 15 is faithfully reproduced.
However, in actuality, the focus signals SB2 and SB2 are determined by the phase delay and response frequency of the detection system and the servo system.
A2 represents the wafer 15 as shown by the dotted curve 35B in FIG. 4A and the dotted curve 35A in FIG. 4B, respectively.
Is approximated by a predetermined phase delay.

FIG. 5 shows the focus signals SB2 and SA2 in vector notation, and the vector <SB
2 ₀ > and <SB2> correspond to the curve 34 in FIG.
4A and 4B show focus signals corresponding to B and 35B, respectively, and vectors <SA2 ₀ > and <SA2> show focus signals corresponding to curves 34A and 35A in FIG. 4B, respectively. What is to be obtained is the original focus signal with no phase delay corresponding to the focus position at the center measurement point PA2 in the exposure area 16 in FIG. 3, that is, the focus signal corresponding to the vector <SA2 ₀ >. As can be seen from FIG. 5, when the vectors <SB2> and <SA2> are respectively weighted and added, a vector <SD2> is obtained. However, by adjusting the weighting coefficients, the vector <SA2 ₀ > is substantially obtained.
Can be obtained.
Actually, the vector addition is performed by weighting and adding the focus signals SB2 and SA2 on the time axis.

FIG. 6 shows an example of the surface position calculating system 33 for performing the weighted addition of the focus signal.
In FIG. 6, focus signals SA2 and SB2 include:
Weighting coefficients K1 and K2 are multiplied by multipliers 36A2 and 36B2 in the surface position calculation system 33, respectively. The output signals of the multipliers 36A2 and 36B2 are added to the adder 3
7D2 is added to obtain a focus signal SD2. The focus signal SD2 is supplied from the surface position calculation system 33 to the wafer drive system 24. The wafer drive system 24 adjusts the amounts of expansion and contraction of the three fulcrums 18A to 18C of the Z leveling stage 19 in the Z direction in parallel so that the focus signal SD2 becomes 0. Thus, even when exposure is performed by scanning the wafer 15 in the X direction, the focus position at the central measurement point PA2 in the exposure area 16 is maintained in a state in which the focus position coincides with the imaging plane.

At this time, the values of the weighting factors K1 and K2 are
Scanning speed V of wafer 15 in X direction _WOn the wafer 15
Of the exposure area (reticle pattern projection area) 16
Scanning of the width D in the direction and the measurement points PA2 and PB2
It is determined by the distance d in the direction. In practice, for example, weights
By setting the values of the coefficients K1 and K2 variously,
Perform a test print and check that the defocus amount after exposure is
Use the values of the weighting factors K1 and K2 when they become smaller.
I just need.

Next, the configuration and operation of a control system for performing autofocusing and autoleveling of the wafer 15 in this embodiment will be described. FIG. 7 shows a surface position calculation system 3 in this case.
3 and an example of the configuration of the wafer drive system 24.
, Three AF sensors 25A1 to 25A3 for detecting the focus positions of the measurement points in the exposure region 16, and three AF sensors 25B1 to 25 for detecting the focus positions of the measurement points on the near side in the scanning direction of these measurement points. 25B3
Is used. AF sensors 25A1 to 25A3, 25
The photoelectric conversion signals from B1 to 25B3 are
Multiplexer 3 in surface position calculation system 33 as a focus signal via 2A1-32A3 and 32B1-32B3
8 is supplied. Amplifiers 32A1-32A3, 32B1
In ~ 32B3, noise components due to disturbance light and the like are removed from the input photoelectric conversion signal, and the signal components are conditioned. FIG.
The focus signals corresponding to the three measurement points PC1 to PC3 in FIG. 7A are also supplied, but are not used in this case, so that the display is omitted.

The multiplexer 38 includes amplifiers 32A1 to 32A1.
The analog / digital (A / D) converter 3 sequentially converts the focus signals from the 32A3 and 32B1 to 32B3 in a time-division manner.
9, and the digitized focus signal from the A / D converter 39 is sequentially stored in a memory in the main control system 13. In the main control system 13, the focus signal selected from the supplied focus signals is weighted and added in the same manner as the circuit in FIG. 6 to generate a reference focus signal, and the current exposure area From the focus signals at each point on the exposure surface of the wafer 15 in the wafer 16, an average exposure surface in the exposure region 16 is obtained by the least square method. Then, the main control system 13 uses the reference focus signal and the average surface tilt angle to adjust the position of the Z leveling stage 19 to match the exposure surface of the wafer 15 in the exposure region 16 with the imaging surface. The amount of expansion and contraction of the three fulcrums 18A to 18C is calculated, and the information of these three expansion and contraction amounts is converted into a digital / analog (D / A) converter 40 in the wafer drive system 24.
To supply.

In the wafer drive system 24, the D / A converter 40
Are supplied to the demultiplexer 41, and the three signals representing the amount of expansion and contraction output from the demultiplexer 41 are transmitted to the fulcrums 18A to 18C of the Z leveling stage 19 via the servo amplifiers 42A to 42C, respectively.
Supplied to Then, the amount of expansion and contraction of the fulcrums 18A to 18C is adjusted, and the focus position and the inclination angle of the exposure surface of the wafer 15 are adjusted. The focus position of the wafer 15 is determined by the AF sensors 25A1 to 25A3, 25B1 to 25B3.
, And is fed back, and the entire system of FIG. 7 functions as a closed-loop servo system. As a result, control is performed so that the average exposure surface of the wafer 15 in the exposure region 16 matches the imaging surface.

In the above embodiment, as shown in FIG. 2A, a total of nine measurement points are set in three rows in the exposure area 16 and in the vicinity thereof. May be set. Also, for example, as shown in FIG. 2B, four measurement points QA1 to QA4 are set in the exposure area 16, and the measurement points QA1 to QA1 are located in front of these one row of measurement points.
Five measurement points QB1 to QB5 may be set by changing the position in the non-scanning direction (Y direction) from QA4. In this case, on the straight line passing through the measurement points QB1 to QB5, the measurement points QA1 and Y
When a focus position at the measurement point QB6 having the same position in the direction is required, the data may be interpolated by, for example, an average value of the focus positions at the measurement points QB1 and QB2 on both sides.

In the above embodiment, when only focusing is performed, at least two measurement points separated by a predetermined distance in the scanning direction may be set, and when one-dimensional (or two-dimensional) leveling is performed, At least two sets, ie four measurement points (or at least three sets,
That is, six measurement points) may be set. However, when performing two-dimensional leveling, at least three
It is necessary to set so that two measurement points do not line up on the same straight line.

In the above embodiment, the present invention is applied to a projection exposure apparatus on which a projection optical system is mounted. In addition, for example, a reflection type projection exposure apparatus, a proximity type exposure apparatus, or The present invention can be applied to a contact type exposure apparatus. Furthermore, other than the exposure apparatus, even if it is an inspection apparatus or a processing apparatus that detects the height or inclination of the moving body, the present invention can be applied to obtain the same effect. Also, for example, the surface position calculation system 3 in FIG.
Reference numeral 3 may be composed of either hardware or software. As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention. Less than
As above, according to the above embodiment, the measurement in the exposure area
Signal corresponding to the height detected at the point and the preceding measurement point
Is added with a weighting factor to correspond to the height at the reference point
Step and scan method because you are looking for a signal
In a scanning type exposure apparatus such as
Of the exposure surface of the substrate (wafer, etc.)
Position (height) is accurately detected and feedback to the servo system is provided.
There is an advantage that can be checked. In addition, the height detection means
Multiple measurement points parallel to the substrate scanning direction.
As three or more measurement points distributed on a straight line of numbers,
Height of the plurality of measurement points detected by the height detection means
Exposure of the substrate by processing the signal corresponding to
When calculating the surface shape of a surface,
Accurately detect the average tilt angle of the exposed surface of the substrate
There is an advantage that feedback can be made to the servo system.

[0044]

According to the present invention, in a scanning type exposure apparatus such as a step-and-scan method, a focus position (high position) of an exposure surface of a moving substrate (wafer or the like) at a reference point thereof. ) Can be accurately detected and fed back to the servo system.

Another advantage is that the average inclination angle of the exposure surface of the moving substrate can be accurately detected and fed back to the servo system.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an entire projection exposure apparatus according to an embodiment of the present invention.

2A is a diagram illustrating an example of an arrangement of measurement points on a wafer 15 in FIG. 1, and FIG. 2B is a diagram illustrating another example of an arrangement of the measurement points.

FIG. 3 is an AF for scanning the wafer 15 in a predetermined direction.
FIG. 7 is a schematic diagram for explaining an operation of detecting a focus position by a sensor.

4A is a waveform diagram showing a focus signal by an AF sensor 25B2 in FIG. 3, and FIG. 4B is a waveform diagram showing a focus signal by an AF sensor 25A2 in FIG.

FIG. 5 is a diagram showing a state where the focus signal of FIG. 4 is represented by a vector.

FIG. 6 is a configuration diagram of a main part showing an example of an autofocus mechanism of the embodiment.

FIG. 7 is a configuration diagram of a main part showing another example of the auto focus mechanism and the auto leveling mechanism of the embodiment.

[Explanation of symbols]

Reference Signs List 3 reticle blind 7 reticle PL projection optical system 13 main control system 15 wafer 16 exposure area 18A to 18C fulcrum 19 Z leveling stage 20 XY stage 23 wafer side laser interferometer 24 wafer drive system 25A1 to 25A3, 25B1 to 25B3 AF sensor PA1 ＰＡPA3, PB1 to PB3, PC1 to PC3 Measurement points 32A1 to 32A3, 32B1 to 32B3 Amplifier 33 Surface position calculation system

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/207

Claims (10)

(57) [Claims] 1. A mask stage for scanning a mask having a transfer pattern formed on an illumination area of a predetermined shape in a predetermined direction, and a photosensitive substrate is scanned in a predetermined direction in synchronization with the mask stage. Adjusting the height of the substrate in accordance with the height of the exposure surface of the substrate in the mask direction provided on the substrate stage, and adjusting the height of the substrate. A scanning type exposure apparatus that sequentially exposes the pattern of the mask onto the substrate while detecting the signal corresponding to the height of the exposure surface of the substrate to be supplied to the height adjusting means. Position detection device
In the arrangement , a plurality of measurement points including measurement points in an exposure region of the pattern of the mask and measurement points in a region on the near side in the scanning direction with respect to the exposure region correspond to the height of the exposure surface of the substrate. Height detecting means for detecting a signal, a signal corresponding to the height of the plurality of measurement points detected by the height detecting means, a moving speed of the substrate stage, a scanning direction of an exposure area of the pattern of the mask, The signal corresponding to the height of the exposure surface of the substrate at a predetermined reference point in the exposure area of the pattern of the mask is obtained by adding the width and the weight coefficient determined from the arrangement of the plurality of measurement points. And a height calculating unit for obtaining a signal corresponding to the height, and supplying a signal corresponding to the height calculated by the height calculating unit to the height adjusting unit. 2. The plurality of measurement points to be detected by the height detection means are three or more measurement points distributed on a plurality of different straight lines parallel to a scanning direction of the substrate. 2. A surface shape calculating means for calculating a surface shape of an exposure surface of the substrate by processing a signal corresponding to a height of the plurality of measurement points detected by a least square method. An apparatus according to claim 1. 3. A mask stage for scanning a mask on which a pattern is formed in a predetermined direction, a substrate stage for scanning a substrate in a predetermined direction in synchronization with the mask stage, and an image of the mask pattern on the substrate. A projection optical system for projecting the projection optical system, and an adjusting unit for matching an exposure surface of the substrate and an image plane of the projection optical system during scanning of the substrate,
In a scanning exposure apparatus that sequentially exposes the pattern of the mask onto the substrate by scanning the mask and the substrate in synchronization, an image of the pattern of the mask is projected through the projection optical system. A first measurement point disposed in an exposure area, and a second measurement point separated from the first measurement point in the scanning direction of the substrate, wherein the first measurement point and the second measurement point Detecting means for detecting focus information on the exposure surface of the substrate in each of the first and second focus information detected at the first measurement point;
An exposure apparatus, comprising: weighting each of focus information detected at a measurement point and control means for controlling the adjusting means based on the weighted focus information. Wherein said exposure region is a rectangular shape extending in the non-scanning direction perpendicular to the scanning direction of the substrate, said first measurement point, a plurality of measurement points arranged along the non-scanning direction 4. The device according to claim 3, comprising: Wherein said exposure region is a rectangular shape extending in the non-scanning direction perpendicular to the scanning direction of the substrate, the second measurement point, a plurality of measurement points arranged along the non-scanning direction The device according to claim 3 or 4, comprising: 6. weighting factor for the focus information, claims 3,4, characterized in that determined in accordance with the width of the exposure area in the scanning direction of the substrate, or 5
An apparatus according to claim 1. 7. The apparatus according to claim 3 , wherein a weight coefficient for the focus information is determined according to a scanning speed of the substrate. 8. The apparatus according to claim 3 , wherein a weighting factor for the focus information is determined according to an interval between the first measurement point and the second measurement point in the scanning direction of the substrate. An apparatus according to claim 1. 9. An image of a pattern of a mask is projected onto a substrate through a projection optical system, and the pattern of the mask is exposed onto the substrate by moving the mask and the substrate in synchronization. In the exposure method, focus information of an exposure surface of the substrate is detected at each of a plurality of measurement points; weighting is performed on the detected focus information according to a scanning speed of the substrate, and the weighted focus information is obtained. Adjusting the positional relationship between the exposure surface of the substrate and the image surface of the projection optical system based on 10. An image of a pattern of a mask is projected onto a substrate through a projection optical system, and the pattern of the mask is exposed onto the substrate by moving the mask and the substrate in synchronization. In the exposure method, focus information of an exposure surface of the substrate is detected at each of a plurality of measurement points; a scanning direction of the substrate in an exposure region where an image of the pattern of the mask is projected on the detected focus information. An exposure method, wherein weighting is performed in accordance with the width of the projection optical system, and the positional relationship between the exposure surface of the substrate and the image surface of the projection optical system is adjusted based on the weighted focus information.