JPH10256148A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner which is used in a photolithographic process at the time of manufacturing a semiconductor device or liquid crystal display device and can perform projection alignment with high accuracy by suppressing the occurrence of transfer errors as much as possible even when the pattern of a reticle to be transferred has a curvature of field. SOLUTION: A projection aligner is provided with a projection optical system 2 which projects the pattern of a reticle 3 upon a photosensitive substrate 11 placed on a substrate stage 12, a shape measuring means 20 which measures the shape of the image forming surface of the system 2, a wafer deforming means 16 which deforms the wafer 11 placed on the stage 12, and a control means 10 which controls the deforming means 16 based on the measured results of the measuring means 20 so that the image forming surface may be nearly aligned with the exposed surface area of the wafer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection exposure apparatus used in a photolithography process in manufacturing a semiconductor device or a liquid crystal display device.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing a semiconductor device or a liquid crystal display device, an image of a circuit pattern drawn on a photomask or a reticle (hereinafter referred to as a reticle) is formed on a semiconductor wafer or glass coated with a photoresist. A projection exposure apparatus that performs projection exposure on a photosensitive substrate such as a substrate is used.

[0003] A projection exposure apparatus mounts a reticle on an X-ray.
A reticle stage movable on the Y plane, and a substrate stage on which the photosensitive substrate is placed and movable on the XY plane,
Using a positioning mark provided on the reticle and the photosensitive substrate, they are aligned, and the image of the circuit pattern by the illumination light applied to the reticle is projected onto a predetermined exposure area on the photosensitive substrate via the projection optical system. And expose.

In order to transfer a reticle pattern onto a photosensitive substrate with high precision, it is necessary to illuminate the reticle with a uniform illuminance distribution and to reduce the aberration of the projection optical system.
In the case where a glass substrate for a liquid crystal display device, whose substrate size has been increasing in size in recent years, is to be dividedly exposed, not only the flatness of the glass substrate itself but also the substrate stage substrate on which the glass substrate is mounted. The flatness of the mounting surface also affects the exposure accuracy. If the board flatness is out of the allowable range,
Even if the aberration of the projection optical system is suppressed to a predetermined range, a transfer error such as a variation in the line width of the transferred circuit pattern does not disappear. Therefore, it is necessary to measure the flatness of the reticle and the photosensitive substrate prior to exposure, and adjust and correct them so that they fall within an allowable range.

[0005]

On the other hand, even if the flatness of the substrate is ideally adjusted and corrected, if the aberration of the projection optical system (especially the curvature of field) exceeds an allowable range, the transferred image is transferred. The transfer error such as the variation in the line width of the circuit pattern does not disappear. Aberrations in the projection optical system are caused by factors such as residuals in the design stage of the device, manufacturing errors in the device manufacturing stage, and fluctuations in the surrounding environment during use of the device, especially temperature, pressure, humidity, and the like. It changes dynamically. Therefore, it is necessary to make adjustments and corrections to reduce the aberration of the projection optical system prior to exposure.

However, in order to adjust and correct the aberration of the projection optical system or to adjust and correct the flatness of the substrate, a complicated and large-scale mechanism is required, and the entire apparatus is large and expensive. There is a problem that it becomes a thing. In addition, there is a problem that these adjustments and corrections are accompanied by extremely complicated and troublesome work.

An object of the present invention is to provide a projection exposure apparatus capable of performing high-precision projection exposure while minimizing a transfer error even when an image of a reticle pattern to be transferred has a field curvature. .

[0008]

FIG. 1 shows an embodiment of the present invention.
The object of the present invention is described in association with FIG. 4 and FIG. 4. The purpose of the projection optical system (2) is to expose a pattern of a reticle (3) onto a photosensitive substrate (11) mounted on a substrate stage (12).
And a shape measuring means (20) for measuring the shape of the image plane of the projection optical system (2) and a shape of a photosensitive substrate (11) mounted on a substrate stage (12). Substrate deformation means (16, 21, 24, 26, 2
8, 30) and the substrate deforming means (16, 21, 24, 2) based on the measurement result of the shape measuring means (20) such that the image plane and the surface of the exposure area of the photosensitive substrate (11) substantially match.
And control means (10) for controlling (6, 28, 30).

In the above-mentioned projection exposure apparatus, the substrate deforming means includes a photosensitive substrate (11) on a substrate stage (12).
Air pressure changing means (1) for changing the air pressure between the plurality of recesses (21) provided on the mounting surface of the substrate and the back surface of the photosensitive substrate (11) on each of the plurality of recesses (21) and each recess (21).
6, 24). Further, in the above-described projection exposure apparatus, the shape measuring means (20) can measure the shape of the surface of the photosensitive substrate (11) mounted on the substrate stage (12).

According to the present invention, after the shape of the image plane of the projection optical system is measured in advance, the projection area of the photosensitive substrate is forcibly deformed to match the image plane of the projection optical system based on the measured value. Like that.

By doing so, the deterioration of the image of the reticle pattern due to the curvature of field of the projection optical system can be reduced, and the depth of focus can be increased, so that a finer pattern can be accurately exposed. Will be able to

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection exposure apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG.
1 shows a schematic configuration of a projection exposure apparatus according to the present embodiment. In FIG. 1, a reticle 3 having a reticle pattern on a lower surface is held on a reticle stage 3a. The reticle 3 faces the substrate stage 12 via the projection optical system 2 and is illuminated by the exposure illumination system 4 during projection exposure. Substrate stage 1 on which photosensitive substrate 11 is mounted
2 can move an arbitrary position on the substrate stage 12 directly below the projection optical system 2 by the XY drive system 15, and can adjust the entire substrate stage 12 to an arbitrary height and inclination by the Zθ drive system 9. A reference plate 1 on which a predetermined opening pattern 1a is formed is provided on the substrate stage 12, and the opening pattern 1a includes an illumination optical system including an illumination light source 8, a glass fiber cable 13, etc., a glass fiber cable 13, A shape measuring unit 20 for measuring the shape of the imaging surface of the projection optical system 2 including the light amount detector 7, the detection optical system including the half mirror 14, and the like is connected. A projection system 5 and a light receiving system 6 for an oblique incidence focus sensor for detecting a photosensitive substrate surface are fixed to the projection optical system 2. Outputs of the light receiving system 6 and the detector 7 are input to a control system 10, and the Zθ drive system 9 and the XY drive system 15 are controlled by the control system 10.

In the shape measuring section 20, the illumination light output from the illumination light source 8 is guided to the reference plate 1 via the glass fiber cable 13, and the opening pattern 1 of the reference plate 1 is formed.
a, and is projected upward through the projection optical system 2 to form a projection image of the aperture pattern 1a on the pattern surface of the reticle (the lower surface of the reticle). The projected image is moved to an arbitrary position on the reticle pattern by moving the substrate stage 12 two-dimensionally using the XY drive system 15 and scanning the reference plate 1 within the field of view of the projection optical system 2. It is possible to individually detect the focal point, that is, the image forming position of the reticle pattern at each location.

Further, optical information from the projected image of the pattern surface of the reticle 3 forms an image on the conjugate plane of the projection optical system 2 of the reticle pattern by going back the optical path of the illumination light. At this time, the height of the opening pattern 1a surface of the reference plate 1 is
If the pattern surface of the reticle 3 and the projection optical system 2 have a conjugate positional relationship, the projected image on the pattern surface of the reticle 3 will have a clear boundary with focus, and the reflected light of the projected image will cause the aperture pattern of the reference plate 1 to be opened. The reflection projection image formed on 1a also has an in-focus boundary. Here, the reflection projection image of the aperture pattern 1a is, of course,
Since it has the same shape, the same size, and the same posture as the aperture pattern 1a, the optical information from the projected image of the reticle pattern surface enters the aperture pattern 1a to the maximum extent and travels through the detection optical system.
The light reaches the detector 7 and gives a peak of the amount of received light. On the other hand, when the height of the opening pattern 1a surface of the reference plate 1 is shifted from the conjugate plane of the pattern surface of the reticle 3, the projected image of the pattern surface of the reticle 3 and the reflected projected image on the reference plate 1 are out of focus. The border is blurred. Accordingly, the optical information is lost by the amount of the reflected projection image protruding from the opening pattern 1a, and the reflected light enters the opening pattern 1a.
To reduce the amount of light received.

Accordingly, the substrate stage 12 is moved by the XY drive system 15, and the projected image of the opening pattern 1a of the reference plate 1 is sequentially positioned at a plurality of locations defined on the pattern surface of the reticle 3, and The control system 10 adjusts the height of the substrate stage 12 to the height at which the detector 7 detects a change in the amount of light by the Zθ driving system 9 to obtain the height information of the substrate stage 12, that is, the image formation position information of the reticle pattern. Accumulate one after another. The control system 10 uses the information on the image forming surface of the pattern of the reticle 3 obtained in this manner to change the shape of a photosensitive substrate 11 mounted on a substrate stage 12 which will be described later. The surface shape driving system 16 is controlled so that the shape of the surface of the exposure area of the placed photosensitive substrate 11 matches the image forming surface of the reticle pattern.

After the shape of the photosensitive substrate 11 is adjusted, the projected image of the aperture pattern 1a is moved to the center of the pattern surface of the reticle 3 again, and is driven again by Zθ until the reference plate 1 is at the height of the focal point. The height of the substrate stage 12 is adjusted by the system 9. Thereafter, the light projecting system 5 and the light receiving system 6 of the oblique incidence focus sensor are used by using the reference plate 1 adjusted to the focal point height.
Is performed. That is, the height of the reflected beam / spot on the reference plate 1 is stored as the origin. Thereafter, when the field of view of the projection optical system 2 is scanned at an arbitrary position on the substrate stage 12, the projection system of the oblique incidence focus sensor is scanned. The exposure surface height of the photosensitive substrate 11 is measured based on the height of the reflected beam and the spot in the light receiving system 5 and the light receiving system 6, and the control system 10 controls the height of the substrate stage 12 by the Zθ drive system 9 so that the height becomes the height of the origin. To adjust.

Next, an example of detection of the pattern image forming position of the reticle 3 by the shape measuring section 20 for measuring the shape of the image forming surface of the projection optical system 2 will be described in detail. FIG. 2 is a diagram showing a change in the amount of light detected by the detector 7 above and below a pattern image forming plane (focus point) of the reticle 3. In FIG. 1, light transmitted through an aperture pattern 1a provided in a reference plate 1 is projected onto a pattern surface of a reticle 3 via a projection optical system 2,
The projection image reflected by the pattern surface of the reticle 3 is re-imaged on the aperture pattern 1a by the projection optical system 2, and again passes through the aperture pattern 1a to enter the detector 7 and the pattern image position of the reticle 3. Shows the relationship.

In FIG. 2, the horizontal axis represents the height of the substrate stage 12, with Z- being closer to the projection optical system 2 and Z + being farther from the focal point height Z0. The vertical axis is the amount of light detected by the detector 7. When the substrate stage 12 is moved up and down, there is a height at which the amount of light is maximized, and this is the focal height (the image forming position of the pattern of the reticle 3) Z0. To find this, the light receiving system 6 of the oblique incidence focus sensor
The substrate stage 12 is moved up and down along the optical axis of the projection optical system 2 on the basis of the above signal. At the same time, if the light amount of the detector 7 is monitored, the diagram of FIG. 2 can be obtained.

Incidentally, it is preferable that the signal as shown in FIG. 2 has as large a slope as possible at the light amount changing portion. For that purpose, the pattern of the opening pattern 1a projected from the reference plate 1 needs to have an appropriate line width. For example, a line as shown in FIG.
Think and space. The line and space pitch is p, the width of the opening is a, and the duty ratio (a /
Assuming that p) is 50%, the change of the detection light with respect to the focus position in FIG.

| Z0−Z− | = | Z + −Z0 | = a / 2 tan θ where θ is a tilt angle of a light ray and is an estimate when diffraction is ignored. For example, NA = 0.5, σ = 0.5, a =
In the case of 2 μm, θ = 14.5 degrees, and | Z0−Z− | becomes 3.9 μm.

Next, the substrate deforming means in this embodiment will be described with reference to FIGS. FIG. 4 is a partial cross-sectional view including one exposure area on the substrate mounting surface of the substrate stage 12. A concave portion 21 having a shape corresponding to the size of the exposure region and having an open top is formed on the substrate mounting surface. A suction hole 26 is provided between the adjacent concave portions 21 for sucking the photosensitive substrate 11 and sucking it in vacuum. At approximately the center of the bottom of the concave portion 21, a pressurizing / depressurizing hole 24 for adjusting the pressure in a space formed by the concave portion 21 and the back surface of the photosensitive substrate 11 to deform the photosensitive substrate 11 is provided. The pressurizing / depressurizing hole 24 and the suction hole 26 are connected to the substrate surface shape driving system 16 via a pressurizing / depressurizing path 28 and a depressurizing path 30, respectively. The board surface shape drive system 16 is connected to the control system 10,
In accordance with a command from the control system 10, the pressure in the space formed between the back surface of the photosensitive substrate 11 and the concave portion 21 is adjusted through the pressurizing and depressurizing holes 26 while adsorbing the photosensitive substrate 11 with a predetermined suction force through the suction holes 26, and The substrate 11 is deformed according to the field curvature of the projection optical system 2.

For example, in FIG. 5, which shows only the reticle 3, the projection optical system 2, and the photosensitive substrate 11 in a simplified manner, the field curvature amount FC shown by a broken line is the same as the shape measurement unit 2 described above.
It is assumed that it is measured in advance by 0. In response to such a curvature of field, the gas in the space formed by the back surface of the photosensitive substrate 11 and the concave portion 21 is sucked from the suction hole 26,
The photosensitive substrate 11 is moved so as to follow the field curvature shown by the broken line in FIG.
Can be transformed. The photosensitive substrate 11 deformed so as to follow the curvature of field is shown by a broken line in FIG.

In the case where the image plane is inclined like the field curvature amount FC 'shown by a dashed line in FIG.
By tilting the entire substrate stage 12 by the Zθ drive system 9 of the substrate stage 12, the projection area of the photosensitive substrate 11 can be deformed so as to follow the curvature of field in the same manner as described above. When the curvature of field FC of the projection optical system 2 does not have a constant curvature, the substrate can be deformed with a small error by performing a quadratic approximation.

The above description is based on the premise that the flatness of the photosensitive substrate 11 sucked on the substrate stage 12 is within a predetermined allowable range. Is considered to be outside the allowable range, it is necessary to measure the flatness of the photosensitive substrate 11 in a state where the photosensitive substrate 11 is vacuum-adsorbed by the substrate stage 12 in advance. Also in this case, by using the light projecting system 5 and the light receiving system 6 of the oblique incidence focus sensor of the shape measuring unit 20 in the present embodiment, the height of the exposed surface of the photosensitive substrate 11 can be changed from the height of the reflected beam / spot. By measuring points, the flatness of the photosensitive substrate 11 can be obtained. The flatness of the photosensitive substrate 11 obtained in advance and the measured field curvature amount F
C, the optimum image plane is calculated, and the back surface of the photosensitive substrate 11 and the concave portion 2 are also considered in consideration of the tension of the photosensitive substrate 11 and the like.
1 to adjust the air pressure in the space formed by the photosensitive substrate 1
The first exposure region may be deformed.

In the case where the same reticle pattern is repeatedly exposed to a plurality of shot areas on the photosensitive substrate 11 as in a step-and-repeat type projection exposure apparatus, the flatness of the substrate is constant. In this case, the compression / decompression of the plurality of recesses 21 may be controlled by the same expansion / contraction pattern in accordance with the arrangement pitch of the shot areas.

As described above, the projection exposure apparatus according to the present embodiment detects the curvature of field of the pattern image forming surface of the reticle, and matches the surface of the exposure area of the photosensitive substrate with the detected curvature of field. Since the pattern exposure is performed, the reticle pattern can always be exposed in the best focus state over the entire exposure area on the photosensitive substrate.

Next, a projection exposure apparatus according to a second embodiment of the present invention will be described with reference to FIG. The projection exposure apparatus according to the present embodiment is the same as the projection recording apparatus according to the first embodiment except that the substrate deformation means shown in FIG. 6 is different from that of the first embodiment. The description and illustration are omitted. In the first embodiment, the inside of the exposure region of the photosensitive substrate 11 is uniformly pressurized and depressurized. However, the present embodiment is characterized in that the exposure region is divided into a plurality of regions and finer deformation is performed. have.

FIG. 6 is a partial sectional view including one exposure area on the substrate mounting surface of the substrate stage 12. On the substrate mounting surface, a plurality of concave portions 21 whose upper sides are open are formed in one exposure area. A suction hole 26 is provided between the adjacent concave portions 21 for sucking the photosensitive substrate 11 and sucking it in vacuum. At approximately the center of the bottom of the concave portion 21, a pressurizing / depressurizing hole 24 for adjusting the pressure in a space formed by the concave portion 21 and the back surface of the photosensitive substrate 11 to deform the photosensitive substrate 11 is provided. The pressurizing and depressurizing holes 24 and the suction holes 26 are respectively connected to the substrate surface shape driving system 1 through pressurizing and depressurizing paths 28 and 30.
6 is connected. The board surface shape drive system 16 is the control system 1
0, and the pressure of the space formed between the back surface of the photosensitive substrate 11 and the concave portion 21 through the pressurizing / depressurizing hole 26 while adsorbing the photosensitive substrate 11 with a predetermined suction force by the suction hole 26 according to a command of the control system 10. Is adjusted, and the photosensitive substrate 11 is deformed in accordance with the field curvature of the projection optical system 2.

It is assumed that the field curvature amount FC and the flatness of the photosensitive substrate 11 after adsorption are measured in advance by the shape measuring unit 20 described above. The control system 10 uses the result calculated using the information on the pattern image plane of the reticle 3 as described above,
A command is issued to the substrate surface shape drive system 16 to control the pressure values of the plurality of concave portions 21, respectively, so that the substrate surface shape of the exposure area matches the image forming surface of the pattern of the reticle 3.

In the case where the curvature of field locally exceeds the allowable range but swells, but the overall shape is substantially flat, or the curvature of field is within the predetermined allowable range, In a case where the substrate 11 locally has undulations exceeding an allowable range, the substrate deforming means according to the present embodiment suitably functions. That is, the substrate deforming means according to the present embodiment includes a plurality of recesses 2 in one exposure area.
1 is formed, the pressure in each space formed by the back surface of the photosensitive substrate 11 and each concave portion 21 can be changed by the pressurizing and depressurizing holes 26 provided at the bottom of each concave portion 21. The shape of the photosensitive substrate 11 can be deformed in accordance with a local change in the image forming position in the projection area.

In FIG. 6, the deformation of the photosensitive substrate 11 is indicated by a broken line. For example, in the figure, the pressure of the space formed by the back surface of the photosensitive substrate 11 and the concave portion 21 like the photosensitive substrate on the central concave portion 21 is shown. It is also possible to pressurize by sending gas through the pressurizing / depressurizing hole 26 to raise the substrate surface to the projection optical system 2 side. As described above, by using the substrate deforming means in the present embodiment, the photosensitive substrate 11 in the projection area can be deformed for each smaller area, so that a fine pattern can be transferred with high precision. Become.

According to the first and second embodiments, the surface of the exposure area of the photosensitive substrate 11 substantially coincides with the pattern image forming surface of the reticle 3, and the pattern of the reticle 3 is in the best focus state over the entire exposure area. Exposure can be performed.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above-described embodiment, the shape measuring unit 20 is provided as one component of the projection exposure apparatus. However, it is also possible to use a dedicated apparatus separate from the projection exposure apparatus without attaching to the projection exposure apparatus. .

[0034]

As described above, according to the present invention, even if the image of the pattern of the reticle to be transferred has a field curvature, it is possible to perform high-precision projection exposure with a transfer error minimized. .

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a detected light amount in a shape measuring unit of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an example of an aperture pattern projected by a shape measuring unit of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a schematic configuration of a substrate deforming means of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of field curvature.

FIG. 6 is a view showing a schematic configuration of a substrate deforming means of a projection exposure apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1a Opening pattern 2 Projection optical system 3 Reticle 3a Reticle stage 4 Exposure illumination system 5 Projection system 6 Light reception system 7 Detector 8 Illumination light source 9 Zθ drive system 10 Control system 11 Photosensitive substrate 12 Substrate stage 13 Glass fiber cable 14 Half mirror 15 XY drive system 16 Substrate surface shape drive system 21 Concave portion 24 Pressurizing / depressurizing hole 26 Suction hole

Claims (3)

[Claims] 1. A projection exposure apparatus having a projection optical system for exposing a pattern of a reticle onto a photosensitive substrate mounted on a substrate stage, wherein a shape measuring means for measuring a shape of an image forming surface of the projection optical system. Substrate deformation means for deforming the shape of the photosensitive substrate placed on the substrate stage; and a measurement result of the shape measurement means such that the image plane and the exposed area surface of the photosensitive substrate substantially match. Control means for controlling the substrate deforming means based on the information. 2. The projection exposure apparatus according to claim 1, wherein said substrate deforming means includes a plurality of concave portions provided on a surface of said substrate stage on which said photosensitive substrate is placed, and said plurality of concave portions and said plurality of concave portions. A projection exposure apparatus comprising: air pressure changing means for changing the air pressure between the photosensitive substrate and the rear surface thereof. 3. The projection exposure apparatus according to claim 1, wherein said shape measuring means also measures a shape of a surface of said photosensitive substrate mounted on said substrate stage. .