JPH08162382A - Projection exposure device and method - Google Patents

Abstract

PURPOSE: To enable a slit image to be optimally focused by a method wherein a reflected light from a pattern image projected on a stage is photoelectrically detected to find an imaging state of the pattern image, and the pattern image is focused on a photosensitive substrate basing on the imaging state. CONSTITUTION: A main control system MCS arranges an area sensor 201 at a point where its center intersects with an optical axis AX and projects a slit image SP onto a sensor 201. Then, the main control system MCS moves a stage ST2 by a very small distance in a direction of Z, and the width of the slit image SP in the direction of Z is obtained through an image processing device 202. A height Z0 is obtained at a point where the slit image SP becomes minimum in width, and a height difference ΔZ between a height Z0 and a height Z1 at the detection of a focal point is obtained. The picture image processing device 202 stores the detection signals of the slit image corresponding to the position of the picture elements of the sensor 201, and the detection signals are processed to calculate the position and width of the slit image SP and inputted into the main control system MCS.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and method for manufacturing semiconductor elements, liquid crystal display elements and the like, and more particularly to a projection exposure apparatus and method capable of focusing a photosensitive substrate.

[0002]

2. Description of the Related Art In a conventional projection exposure apparatus, when a mask (reticle) pattern is imaged on a photosensitive substrate (wafer) via a projection optical system, the wafer surface is accurately aligned with the image plane of the pattern. That is, focusing is essential. In recent years, the depth of focus of the projection optical system has become narrower, but even with the i-line having a wavelength of 365 nm as the illumination for exposure, only the depth of focus of about ± 0.7 μm can be obtained. Therefore, the focus detection system provided in this type of projection exposure apparatus is required to detect the deviation amount between the image plane of the projection optical system and the wafer surface in the optical axis direction of the projection optical system with high accuracy.

As a method for detecting the deviation amount between the image plane of the projection optical system and the wafer surface in the direction of the optical axis of the projection optical system with high accuracy and focusing, as described above, for example, Japanese Patent Laid-Open Publication No.
The technique disclosed in Japanese Patent Laid-Open No. 8-113706 is known. This is because a laser beam (a beam that is non-photosensitive to the resist on the wafer) is projected onto the wafer as a pattern image, and the reflected light is photoelectrically detected by the synchronous detection method and the image formation surface of the projection optical system and the wafer. The amount of deviation from the surface in the optical axis direction of the projection optical system is detected with high accuracy.

If the optical axis direction of the projection optical system is the Z direction and the coordinate system that defines the moving position of the stage in the plane perpendicular to the Z direction is the XY coordinate system, the height position of the wafer surface is detected. At this time, the formation position (XY coordinate position) of the pattern image (hereinafter referred to as “slit image”) projected on the wafer by the focus detection system is the optical axis position of the projection optical system in the image plane of the projection optical system. Is set in advance as a set position. Therefore, the focus detection system performs focus detection by projecting a slit image at the center point of each shot area that has already been exposed on the wafer.

[0005]

However, in the conventional projection exposure apparatus, even if the slit image is projected at the optical axis position of the projection optical system, the slit image is formed on the wafer (focused state). Varies depending on the projection exposure apparatus, and the focus of the slit image is not always the best on the wafer. The focus shift of the slit image causes an error in focus detection.

Further, when the projection position of the slit image varies from device to device, unevenness existing in the shot area on the wafer causes variations in the height position of the point where the slit image is irradiated on the substrate. I will end up. This also causes an error in the result of focus detection. In such an exposure apparatus, it becomes difficult to arrange the wafer surface within a focal depth as narrow as ± 0.7 μm.

The present invention has been made in view of the above problems, and provides a projection exposure apparatus which can optimize the focus of a slit image projected on a wafer and can always perform highly accurate focus detection. The purpose is to provide a method.

[0008]

An embodiment of the present invention will be described with reference to FIG. In order to solve the above-mentioned problems, the apparatus of the present invention is a projection optical system (PL) for projecting an image of a pattern of a mask (R) onto a photosensitive substrate (W), and a projection optical system (PL) holding and projecting. A stage (ST) movable in the optical axis direction of the optical system (PL) and in a direction perpendicular to the optical axis.
By projecting the pattern image (SP) on the photosensitive substrate (W) and photoelectrically detecting the reflected light from the photosensitive substrate (W), the image plane of the projection optical system (PL) and the photosensitive substrate (W) are detected. Focus detection means (15-2) for outputting a detection signal corresponding to the deviation of the projection optical system from the surface in the optical axis (AX) direction.
1) and the detection signal (Sa) from the focus detection means (15-21), the optical axis (AX) of the stage (ST).
A projection exposure apparatus including control means (MCS, 2) for controlling movement in a direction, the light receiving means (201) having a light receiving surface arranged on a part of a stage (ST), and a pattern image ( When the SP is projected onto the light receiving surface, the light receiving means (20
1) A detection means (202, MCS) for detecting the image formation state of the pattern image (SP) on the light receiving surface based on the photoelectric signal output from the light receiving surface, and a pattern image obtained by the detection means (202, MCS). Adjusting means (18c, 17) for adjusting the focus of the pattern image (SP) on the photosensitive substrate (W) on the basis of the image formation state.

Here, the focus detection means (15-21) are
It has a light projecting system (15-18) for projecting a pattern image on the substrate, and the adjusting means (18c, 17) controls at least one of a plurality of optical members constituting the light projecting system to emit light from the light projecting system. It is desirable to have a drive means (18c) that drives in the axial direction. Further, it is desirable that the light receiving means (201) has an image pickup means for picking up a pattern image.

Further, in the projection exposure method of the present invention, the photosensitive substrate (W) is exposed before the pattern formed on the mask is exposed on the photosensitive substrate (W) mounted on the stage through the projection optical system. ) By projecting a pattern image onto the photosensitive substrate (W) and photoelectrically detecting reflected light from the photosensitive substrate (W), the optical axis direction of the projection optical system between the image plane of the projection optical system and the surface of the photosensitive substrate (W). Of the pattern image (SP) irradiated on the stage (ST) by obtaining a detection signal corresponding to the deviation in the step (1) and arranging the surface of the photosensitive substrate (W) on the image plane based on the detection signal. , Or stage (ST)
The first step of detecting the image formation state of the pattern image by photoelectrically detecting the reflected light from, and the focus of the pattern image (SP) on the photosensitive substrate based on the detected image formation state of the pattern image. A second step of adjusting.

[0011]

According to the present invention, the detecting means (202, MC) is based on the photoelectric signal when the reference member arranged on the stage photoelectrically detects the pattern image (SP) by the light receiving means (201).
S) determines the image formation state of the pattern image. Adjustment means (18
(c, 17) adjusts the image formation state of the pattern image so that the focus of the pattern image on the reference member becomes the best. Therefore, focus detection can always be performed with high accuracy, and variations in detection error between devices can be eliminated.

[0012]

1 is a view showing the schematic arrangement of a projection exposure apparatus according to a first embodiment of the present invention and a focus detection system incorporated therein. A description will be given below with reference to FIG. Illumination light for exposure (g-line, i-line from a mercury lamp, or ultraviolet pulsed light from an excimer laser light source) IL passes through a fly-eye lens FL, then a condenser lens CL,
The pattern area PA of the reticle R is illuminated with a uniform illuminance via the mirror M. The illumination light IL that has passed through the pattern area PA reaches the wafer W placed on the wafer stage ST via the projection optical system (both-side telecentric in FIG. 1, but may be one-side telecentric) PL. Wafer stage ST is XY stage ST1 and Z
The stage ST2. The XY stage ST1 can be moved by the XY drive system 1 in a direction (XY direction) perpendicular to the optical axis AX of the projection optical system PL,
The Z stage ST2 is a projection optical system PL driven by the Z drive system 2.
Can be moved in the optical axis AX direction (Z-axis direction). The position (XY coordinate value) of the XY stage ST1 is sequentially measured by the stage interferometer 3. The position (Z coordinate value) of the Z stage ST2 in the Z axis direction is obtained by an encoder provided in the Z stage drive system 2. The wafer stage controller WSC receives the XY coordinate values from the stage interferometer 3, the Z coordinate values from the Z drive system 2, the commands from the main control system MCS, and the like via the XY drive system 1 and the Z drive system 2. It controls the movement and positioning of the XY stage ST1 and the Z stage ST2.

The reticle R is held by a reticle holder RH, and this reticle holder RH is provided on the reticle stage RST. The reticle stage RST is movable in the XY directions by the reticle drive system 4, and the coordinate value of the reticle R is sequentially measured by the reticle interferometer 5. The reticle stage controller RSC has coordinate values from the reticle interferometer 5 and the main control system M.
The movement and positioning of reticle stage RST is controlled via reticle drive system 4 based on commands from CS and the like.

FIG. 2 shows the reticle R viewed from the mirror M side (upper side in FIG. 1). In the circuit pattern area PA inside the reticle R, a circuit pattern for manufacturing a semiconductor element is formed. The pattern area PA is substantially square, and alignment marks RMx and RMy are provided adjacent to the pattern area PA on the outside of the two sides (outside of the pattern area) that are adjacent to the square.
The alignment mark RMx has a rectangular mark portion extending in the X direction, and the alignment mark RMy has a rectangular mark portion extending in the Y direction. Openings are provided on both sides of each mark portion (direction perpendicular to the longitudinal direction of each mark portion). Then, the center point (center point of the pattern area) RC of the reticle R exists on the extension of the center line in the longitudinal direction of each mark. These alignment marks RMx and RMy are used when measuring the position of the reticle R. Also, as shown in FIG. 2, the reticle R has two opposite sides (the Y direction in FIG. Reticle marks RMa and RMb are provided adjacent to (two sides parallel to). The reticle marks RMa and RMb each have a cross-shaped mark portion extending in the X direction and the Y direction, and a center point M of each mark portion.
Ca and MCb are respectively present on the straight lines that pass through the center point RC of the reticle R and extend in the Y direction. This reticle mark R
Ma and RMb are read by a reticle alignment system described later when positioning the reticle R at a predetermined position.

In FIG. 1, a reticle alignment system (6, 7) including a mark detection system 6 and a mirror 7 is provided above the reticle R. The reticle alignment system (6, 7) is used for the reticle mark R shown in FIG.
Detect Mb. In addition, the projection exposure apparatus of the present embodiment,
An alignment system having the same configuration as the reticle alignment system (6, 7) and detecting the reticle mark RMa is provided (not shown). The reticle alignment system (6, 7) irradiates the reticle mark RMb with a laser beam such as a He-Ne laser and detects the reflected light. The main control system MCS controls the position of the reticle R via the reticle stage controller RSC so that the image of the reticle mark RMb matches the index in the mark detection system 6. The reticle mark RMa is similarly detected by an alignment system (not shown), and the reticle R is positioned by these reticle alignment systems so that the center point RC coincides with the optical axis AX.

Further, a reference plate FM is provided on the stage ST (Z stage ST2 in FIG. 1). The surface of the reference plate FM and the surface of the wafer W are substantially in the same plane. On the reference plate FM, a light-transmissive light emitting mark 31 having longitudinal directions in the X direction and the Y direction and a mark for baseline measurement are formed. Each of these marks is arranged at a predetermined position on the reference plate FM, and the main control system MCS stores in advance the distance between the marks (interval between the center points of the marks).

Next, with respect to this reference plate FM, the projection optical system P
An illumination system that irradiates the light emitting mark 31 provided on the reference plate FM with light from the side opposite to L (the lower side in FIG. 1),
Also, a light receiving system for receiving the light transmitted through the light emitting mark will be described with reference to FIG. This detection system (hereinafter referred to as "ISS
System)) is for measuring the position of the reticle R. For details of the configuration, see, for example, Japanese Patent Laid-Open No.
Since it is disclosed in Japanese Patent No. 0105, a brief description will be given here.

In FIG. 1, a light source 8 is an illumination light IL for exposure.
Of the illumination light IE with a wavelength equal to or near
To live. This illumination light IE has a lens 9 and a fiber 10.
Sent to the inside of the stage ST (below the reference plate FM)
Be done. The illumination light IE emitted from the fiber 10 is the lens 1
The light-emission mark 3 is condensed by 1 and passes through the mirror 12
Irradiate 1 from below. The image of the emission mark 31 is a reticle
Form an image on the alignment mark RMy provided on R
It At this time, the main control system MCS moves the wafer stage WS
By scanning in the Y direction, the alignment mark R
The My and the emission mark 31 are relatively scanned. Align Men
The light transmitted through the Tomark RMy is mirror M, condenser
Photoelectric detection via lens CL, beam splitter 13, etc.
The light is received by the container 14. Here, the image of the emission mark is aligned.
When the measurement mark RMy overlaps with the mark part,
Since the transmitter 14 hardly receives the illumination light IE,
The signal level is bottom. The signal processing device 101 is
Signal S from the tage interferometer 3 ₂Based on this bottom
The center position Yrm is detected.

Similarly, the main control system MCS scans the alignment mark RMx with the image of the light emitting mark 31 formed on the pattern surface of the reticle R. Then, the signal processing device 101 detects the position Xrm at which the detection signal obtained from the photoelectric detector 14 at this time is the bottom. Then, the main control system MCS inputs these measured values (Xrm, Yrm) from the signal processing device 101.

Since the main control system MCS stores in advance the positional relationship between the alignment marks RMx, RMy and the center point RC of the reticle R, the above-mentioned two measured values (Xrm,
The position of the center point RC of the reticle R can be detected based on Yrm). Returning to FIG. 1 again, the configuration of the focus detection system incorporated in this apparatus will be described. The focus detection system in this embodiment is a light transmission system (15, 16, 1).
7) and a light receiving system (19, 20, 21).

The light projector 15 emits light (for example, infrared light) having a wavelength that does not sensitize the photosensitive agent applied to the wafer W. Since a slit plate for light transmission is provided in the projector 15, light transmitted through the slit plate is emitted from the projector 15. Then, this light passes through a parallel plate glass (plane parallel glass) 16 and a condenser lens 17, and is irradiated onto the wafer W as a slit image SP.
The center point of this slit image SP is located at the point where the image plane of the projection optical system and the optical axis AX of the projection optical system PL intersect.
In FIG. 1, the wafer surface is arranged on the image plane of the projection optical system PL. The parallel plate glass 16 is arranged near the slit plate for light transmission. Further, the parallel flat plate glass 16 has rotation axes in a direction perpendicular to the paper surface of FIG. 1 (Y direction) and in a direction parallel to the paper surface, and can rotate a minute amount about these rotation axes. The driving unit 18a rotates the parallel flat plate glass 16 around each rotation axis within a predetermined angle range. Due to this rotation, the image forming position of the slit image SP is displaced in a direction (XY direction) substantially parallel to the surface of the wafer W. Further, the driving unit 18c adjusts the focus state of the slit image on the surface of the wafer W by moving the lens 17 in the optical axis direction of the light sending system.

The light beam (reflected light) reflected by the wafer W passes through the lens 19 and the parallel plate glass 20 and is received by the light receiver 21. A slit plate for receiving light is provided in the light receiver 21, and light passing through the slit plate for receiving light is photoelectrically detected. The parallel flat plate glass 20 also has a rotation axis in the Y direction. The drive unit 18b adjusts the irradiation position of the reflected light on the slit plate arranged in the light receiver 21 by rotating the parallel flat plate glass 20 within a predetermined angle range. The detection signal Sa from the light receiver 21 is output to the signal processing device 103. The signal processing device 103 detects the deviation amount in the optical axis AX direction between the surface of the wafer W and the reference plane defined by the focus detection system. This deviation amount is output to the main control system MCS. In this embodiment, the reference plane of the focus detection system is calibrated so as to coincide with the image plane of the projection optical system PL.

An area sensor 201 for receiving the slit image from the focus detection system is arranged on the Z stage ST2. FIG. 3 shows the slit image SP on the area sensor 201.
It is a figure which shows a mode that is being irradiated. At this time, the center point of the area sensor 201 is the optical axis AX of the projection optical system.
Will be placed to match. This area sensor 201
Captures the slit image SP irradiated on the light receiving surface of the area sensor 201 and outputs the image signal to the image processing device 202. The image processing device 202 detects the position of the slit image SP and the image formation state of the slit image based on the signal from the area sensor 201.

Further, the present apparatus further includes an off-axis type alignment system for detecting a mark on the wafer W. The detailed structure of this alignment system is disclosed in Japanese Patent Application Laid-Open No. 62-171125, and will be briefly described here. In FIG. 1, the optical axis l of the alignment optical system 22 is the optical axis AX of the projection optical system PL.
The distance L is away from in the X-axis direction. Then, the alignment optical system 22 irradiates the wafer W with illumination light having a broad wavelength distribution having a certain bandwidth. Then, the detection center P ₂ on the wafer W of the alignment optical system 22
Are determined so as to coincide with the measurement axis of the stage interferometer 3.

The reflected light from the mark on the wafer W again enters the alignment optical system 22, and the image of the mark is formed on the lower surface of the index plate provided in the alignment optical system 22. Then, the image of the mark on the wafer W is formed on the image pickup surface of the image pickup tube 23 together with the image of the index mark formed on the index plate. The image signal from the image pickup tube 23 is output to the signal processing device 102. The signal processing device 102 detects the positional deviation amount (Δx, Δy) of the mark on the wafer W with respect to the detection center point P ₂ defined by the index plate.

Further, in this embodiment, the display device CRT is used.
Is provided, for example, various measurement results of this device are displayed on the screen to notify the operator of the measurement results. The operator can also use the display device CRT to display the main control system MC.
The condition of the exposure operation or the like can be input to S.
Further, in FIG. 1, the main control system MCS is a signal processing device 1.
Wafer stage controller WSC and reticle stage controller R based on signals from 01 to 103
In addition to outputting the control signal S ₁ to the SC, it controls the entire device.

Now, the operation of this embodiment will be described with reference to the flow chart shown in FIG. Further, in the present embodiment, it is assumed that the reticle R is positioned by the reticle alignment system or the ISS system described above so that the center point RC and the optical axis (AX) coincide with each other. First, in step 110, the main control system MC
In S, the area sensor 201 is arranged at a position where the center point thereof intersects the optical axis AX, and the slit image SP is arranged in the area sensor 201.
Irradiate on top. Next, the main control system MCS is the Z stage S
While moving T2 by a small amount in the Z direction, the image processing apparatus 202 obtains the width of the slit image SP at each Z direction position (height position). Then, the height position Z ₀ when the width of the slit image SP has the minimum value is obtained. And the amount of deviation ΔZ (= Z ₀ − from the height position Z ₁ at the time of focus detection)
Z ₁ ) is calculated. (Step 130). Slit image SP
When the width of the slit image becomes the minimum value, the focus of the slit image becomes the best. Therefore, the shift amount ΔZ of the slit image in the height direction is a value corresponding to the defocus amount of the slit image SP. Here, the image processing device 202 stores the detection signal of the slit image corresponding to each pixel position of the area sensor 201, and processes the signal to determine the position of the slit image SP and the width of the slit image SP. calculate.
These measurement results are input to the main control system MCS.

Next, in step 140, the measurement result of the focus shift of the slit image SP is displayed on the display device CRT. The operator determines the slit image SP according to the image formation state of the slit image SP displayed on the display device CRT.
It is determined whether or not the focus is adjusted (step 17).
0). When it is necessary to adjust the focus of the slit image SP in step 170, the operator determines the slit image S
A command for adjusting the focus of P is sent to the main control system MCS via the display device CRT. Main control system MC based on this command
S adjusts the focus of the slit image on the wafer by moving the lens 17 in the optical axis direction of the light sending system via the drive unit 18c (step 180). After the adjustment, the process returns to step 130 again to check the focus deviation of the slit image.

Here, the main control system MCS may automatically determine whether to adjust the focus of the slit image SP. Further, the operator may manually adjust the focus of the slit image SP. Also, step 110,
Steps 130, 140, 170 and 180 may be performed at the time of manufacturing the projection exposure apparatus, or may be performed immediately before the actual exposure operation. This embodiment is the latter.

When the focus adjustment of the slit image SP is completed, the exposure process of exposing the reticle pattern to each shot area is started. First, in step 190, the wafer W
Are arranged on the wafer stage ST. Then, the first shot area to be exposed is arranged below the projection optical system PL,
The focus of the shot area is detected. Then, after arranging the shot area on the image plane of the projection optical system PL, the pattern of the reticle R is superimposed and exposed on the shot area (step 200). Then, step 190 and step 200 are repeated until exposure to all shot areas on the wafer W is completed (step 210).

By the above operation, when the focus of each shot area is detected, the slit plate in the projector 15, the point on which the slit image on the wafer surface is projected, and the slit plate in the light receiver are three points. The relationship can be almost conjugate.
Therefore, stable and highly accurate focus detection is always possible.
Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, an operation for detecting the position of the slit image SP is added to the first embodiment. Therefore, the steps for performing the same operations as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The operation of the second embodiment will be described below.

First, in step 110, the slit image SP is projected onto the area sensor 201. Then, in step 120, the image processing apparatus 202 sets the optical axis AX as the origin based on the detection signal from the area sensor 201. Coordinate position (σx, σy) of the center point of the formed slit image SP
Ask for. Next, the image processing device 202 displays the Z stage ST.
The width of the slit image SP at each position (height position) in the Z direction is obtained while moving 2 in the small amount in the Z direction. Then, the height position Z ₀ when the width of the slit image SP becomes the minimum value is obtained, and the deviation amount ΔZ (= Z ₀ −Z) from the height position Z ₁ when the coordinate position (σx, σy) is measured. ₁ ) ask. (Step 130).

Next, in step 140, the main control system MCS displays the positional deviation of the slit image SP from the optical axis AX and the image formation state of the slit image SP on the display device CRT. FIG. 6 is a diagram showing an example of the display screen.
The set position of the slit image SP is the position (0, 0) of the optical axis AX.
This set position is the center point in the frame shown in FIG. The position of the slit image SP with respect to this set position is indicated by "A" on the map. Further, the image processing device 20
The deviation amount ΔZ obtained by 2 is displayed in the unit of μm below the display of “A”.

The inner square frame in FIG. 6 indicates the slit image S.
The allowable range of positional deviation from the set position of P is shown, and when the position is outside of this frame, it is necessary to adjust the position of the slit image SP. This allowable range can be freely set by the operator. The operator determines whether or not to adjust the position of the slit image SP according to the positional deviation state and the image formation state of the slit image SP displayed on the display device CRT (steps 150 and 170).

When it is necessary to adjust the position of the slit image SP in step 150, the operator sends a command to adjust the position of the slit image SP to the main control system MCS via the display device CRT. Based on this command, the main control system M
The CS adjusts the rotation angle of the parallel plate glass 16 via the drive unit 18a and adjusts the position of the slit image SP to match the set position (step 160). After the adjustment, the process returns to step 120 and the position of the slit image is confirmed.

When it is necessary to adjust the image formation state of the slit image SP in step 170, the operator sends a command for focus adjustment of the slit image to the main control system MCS via the display device CRT. Based on this command, the main control system MCS drives the lens system 17 via the drive device 18c and adjusts the focus of the slit image to the best focus (step 180). After adjustment, step 130 again
Go back and check the focus of the slit image.

Here, the main control system MCS may automatically determine whether or not to adjust the position of the slit image SP. Further, the position and focus of the slit image SP may be manually adjusted by the operator, or may be automatically adjusted by the main control system MCS when the positional deviation is within the allowable range. When the position of the slit image SP and the focus adjustment are completed, the process proceeds to step 190 of FIG. 4, and the exposure process of exposing the reticle pattern to each shot area is started. This exposure process is the same operation as that of the first embodiment.

By the above operation, when the focus of each shot area is detected, the focus of the slit image on the wafer becomes the best and the slit image SP is always formed at the center position of each shot area. It is possible to always perform stable and highly accurate focus detection regardless of the unevenness of. In the present embodiment, the focus detection system for irradiating the single slit image SP on the wafer W and measuring the focus position of one point in the shot area has been described. However, the present invention can be similarly applied to a focus detection system for detecting focus at a plurality of points in a shot area on a wafer, as disclosed in, for example, Japanese Patent Laid-Open No. 5-190423.

Next, a third embodiment of the present invention will be described with reference to the flowchart shown in FIG. The apparatus used in this embodiment is exactly the same as that in the first embodiment. This embodiment is different from the first embodiment in that the position of the slit image is adjusted in consideration of the positional deviation of the reticle R. By the same operation as in the second embodiment (steps 110 to 130), the main control system MCS determines the position (σx, σy) of the slit image SP on the XY coordinate system and the height direction of the slit image SP. The deviation amount ΔZ is detected. Next, the emission mark 3
The alignment marks RMx and RMy are detected by using 1 to obtain the projection position (Rx, Ry) of the center point of the reticle R by the projection optical system PL (step 135). FIG. 8 is a diagram showing the positional relationship of the slit image SP, the optical axis AX, and the projection point (center point of the shot area) RC ′ of the center point RC of the reticle R on the wafer W by the projection optical system PL. When performing overlay exposure, each shot area
The center point of the reticle R is arranged so as to coincide with the projected position of the center point. That is, if the projection position of the center point of the reticle is displaced from the optical axis AX, the center point of the shot area is naturally displaced from the optical axis AX. Therefore, even if the slit image of the focus detection system is on the optical axis AX, it is not always irradiated to the center point of the shot area. Therefore, the main control system MCS determines the coordinate value (σ) of the previously detected slit image SP.
x, σy) and the coordinate value (Rx, Ry) of the point RC ′, the position of the slit image SP and the center point R of the shot area.
Positional shift amount from the position of C ′ (ΔX, ΔY) = (Rx−σ
x, Ry−σy) is measured. And display device CRT
Displays the slit image forming position as shown in FIG. 6 with reference to the projection position of the center point of the reticle R (step 140). Then, the center point of the slit image SP and the center point RC ′ of the shot area are made to coincide with each other by the same operation as the operation after step 150 in the first embodiment. As a result, the slit image can always be formed at the center point of each shot area.

In the third embodiment described above, the position of the slit image SP is adjusted, but the reticle R may be moved so that the projection position of the center point of the reticle R is aligned with the position of the slit image SP. However, when the reticle R is moved, the alignment position of the shot area on the wafer W,
The interval (baseline amount) between the shot area and the exposure position changes. Therefore, when the reticle R is moved, it is necessary to measure this baseline amount.
Therefore, the main control system MCS stores the position (X coordinate value) Xb ₁ where the light emitting mark 31 on the stage ST and the alignment mark RMx on the reticle R overlap. Next, the main control system MCS detects the position (X coordinate value) X where the baseline measurement mark provided on the reference plate FM is detected by the off-axis alignment system (22, 23).
Remember b ₂ . Letting ΔXb be the amount of deviation between the emission mark 31 and the baseline measurement mark in the X direction, the main control system MCS determines the amount of the baseline in the X direction as (Xb ₁
−Xb ₂ −ΔXb) is calculated and stored. Further, similarly to this, the Y-direction baseline amount is also obtained. When the reticle R is moved in this way, the baseline check may be performed as described above.

Next, a fourth embodiment of the present invention will be described. This embodiment also uses the device described in the first embodiment. The present embodiment is the slit image SP measured in the previous third embodiment.
The amount of deviation (ΔX, ΔY) between the position of and the position of the center point RC ′ of the shot area, and a typical alignment method are used. In the present embodiment, an enhancement global alignment (EGA) method is used which achieves both high throughput and high alignment accuracy. The details of this EGA method are disclosed in Japanese Patent Application Laid-Open No. 61-44429, so a brief description will be given here.

In the EGA method, a plurality of (3 to
9) The positions of the marks MYn and MXn of the shot areas Sn are measured, and based on the measured values, a minute rotation in the running coordinate system of the stage ST of the wafer W, that is, the XY coordinate system defined by the stage interferometer. Error θ, orthogonality w of the shot array on the wafer (or the running of the stage ST),
Scaling error Rx due to linear expansion and contraction of the wafer,
Parameters related to Ry and a minute positional deviation of the wafer in the X and Y directions, that is, offset errors Ox and Oy are obtained by least-squares approximation. Then, the designed shot arrangement coordinates are converted into the actual shot arrangement coordinates by using these respective parameters as interpositions, and the stepping position at the time of exposure is obtained.

In the present embodiment, it is assumed that there are _eight shot areas S _{1 to} S ₈ as shot areas for sample alignment on the wafer W. Then, in each of the sample shots S _{1 to} S ₈ , marks MXn and MYn (n is 1 to 8) are formed by projecting and exposing the alignment marks RMx and RMy shown in FIG. 2 on the wafer W. In addition, the center points of the sample shots S _{1 to} S ₈ are RCn (n
Is 1 to 8). The main control system MCS above each of the eight marks MXn sample shot S ₁ to S _8, an off-axis alignment system for MYn (22, 23) controls the stage drive system 1 to detect. Main control system M
The CS detects the alignment mark of each sample shot and obtains the stepping position (Xn, Yn) at the time of exposure.

Now, before the main control system MCS positions the stage ST at the stepping position (Xn, Yn), the focus detection system shown in FIG. 1 performs focus detection.
The coordinate values of the slit image SP at this time are (ΔX, ΔY) from the center point RC ′ of the shot in the XY directions as shown in FIG.
Just shifted. This is obtained by steps 110 to 135 in the third embodiment. The main control system MCS adjusts the focus of the slit image SP via the drive device 18c, and then the coordinate values (Xn + ΔX, Yn + ΔY)
The stage ST is positioned at a position where Then, the wafer surface is placed on the image plane of the projection optical system PL, and the stage ST is moved to the stepping position (Xn, Yn).
After positioning to, exposure is performed.

With the above sequence, it is possible to always irradiate the central point RC 'in the shot area with the slit image SP for focus detection. Further, even when the parallel flat plate glass 16 shown in FIG. 1 is not provided, that is, even when the position of the slit image cannot be adjusted, the same effects as those of the first and second embodiments can be obtained by this embodiment. In the first to fourth embodiments described above, the area sensor 201 detects the formation position of the slit image SP and the focus shift. For example, a rectangular shape having a low reflectance with respect to the peripheral portion on the reference plate FM. By forming the reference mark (1) and relatively scanning the mark and the slit image SP, the formation position of the slit image SP and the focus shift can be measured. Hereinafter, description will be made with reference to FIGS. 9A and 9B.

As shown in FIG. 9A, the reference mark 30
a is a mark in a low reflection region made of, for example, quartz,
It is formed in the high reflection region 30b coated with the chrome layer. The reference mark 30a is a reference plate FM shown in FIG.
Formed on. In step 110 shown in FIG. 11, the main control system MCS irradiates the slit image SP on the reference mark and moves the wafer stage ST in the X direction to relatively scan the slit image SP and the reference mark 30a. For convenience, FIG. 9A shows a state in which the slit mark SP is scanned with the reference mark 30a fixed.
FIG. 9B shows the level of the photoelectric signal obtained by the light receiver 21 at that time. Here, the slit image SP is the peripheral portion 30.
The level of the photoelectric signal when scanning b is Sh, and the level of the photoelectric signal when the slit image SP scans the mark portion 30a is Sl. Then, as shown in FIG. 9B, the point where the signal level decreases from Sh to Sl is A ₁ , the point when the signal level reaches Sl is A ₂ , and the point from Sl to S is S.
The point where the level increases toward h is A ₃ , and the point when the level reaches Sh again is A ₄ . The photoelectric signal from the light receiver 21 is output to the signal processing device 103.

The signal processing device 103 uses the X coordinate value Xsa of the midpoint between the points A ₁ and A ₂ and the X coordinate value Xsa of the midpoint between the points A ₃ and A _4.
The coordinate value Xsb is measured, and each X coordinate value Xsa, Xsb
Is measured as the X coordinate position Xsc of the slit image SP. Similarly, the slit image SP and the reference mark 30a are set to Y
The Y coordinate value Ysp of the slit image SP is measured by performing relative scanning in the direction. These coordinate signals are sent to the main control system M
It is output to CS. Then, the main control system MCS obtains the position (σx, σy) of the slit image SP in the XY coordinate system based on these coordinate signals (step 120).

Further, the signal processing device 103 has points A ₁ and A ₂
The width of the slit image SP is obtained according to the inclination of the straight line connecting the points and the inclination of the straight line connecting the points A ₃ and A ₄ . And
As described in the first embodiment, the height position of the stage ST is changed and the width of the slit image is obtained to obtain the shift amount ΔZ of the slit image SP in the height direction.
Is calculated (step 130).

As described above, the position and focus shift of the slit image SP are detected based on the change in the photoelectric signal from the light receiver 21 when the slit image SP is relatively scanned in two regions having different reflectances. be able to. Further, the algorithm for calculating the XY coordinate values of the slit image SP is not limited to the above embodiment. In addition, parallel plate glass 16
The slit image SP may be scanned with respect to the reference mark by driving. At this time, the main control system MCS matches the center point of the reference mark with the optical axis AX or the projection position of the center point of the reticle R. Then, the rotation angle of the parallel flat glass is measured when the center point of the slit image passes the center point of the reference mark, and if the angle is adjusted to this angle, the slit image is projected onto the optical axis AX or the center point of the reticle R. Is formed.

Further, in each of the above-mentioned four embodiments, at the time of focus detection, the slit image S is formed at the center point RC 'of each shot area.
Although the slit image SP, the reticle R, or the wafer W is moved so that P is formed, it is not always necessary to form the slit image SP at the center point RC ′ of each shot area.
For example, if the main control system MCS stores in advance information about the height position (unevenness) at an arbitrary position in each shot area, the height position at the center point RC ′ and the height at the point where the slit image is formed. Depending on the amount of deviation from the position
The detection result by the focus detection system may be corrected. As a result, focus detection can be performed at any position within the shot area.

The slit image S is not formed at the center point RC 'of the shot area but at the same height position as the center point RC'.
P may be projected. At this time as well, similarly to the above, the main control system MCS needs to store in advance information about the height position (concavo-convex) at an arbitrary position in each shot area. Further, in the focus detection system of each of the above-described embodiments, the center point RC ′ of the shot area is set in advance as the focus detection position, but the setting of the focus detection position is not limited to the center point of the shot area and the shot area is naturally set. It may be set at any position inside.

[0052]

As described above, according to the present invention, the image formation state of the pattern image (slit image) projected on the substrate can be detected with high accuracy, and the focus of the slit image on the wafer is optimized. Since it is adjusted so that the focus detection can always be performed with high accuracy. Further, by adjusting the position where the slit image is formed, it is possible to always perform highly accurate focus detection even if unevenness exists in the shot area. Further, it is possible to eliminate a detection error in focus detection between a plurality of exposure apparatuses.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an arrangement of marks on a reticle R.

FIG. 3 shows a state in which a slit image is projected on an area sensor 201.

FIG. 4 is a flow chart diagram in the first embodiment of the present invention.

FIG. 5 is a flow chart diagram in the second embodiment of the present invention.

FIG. 6 is a diagram showing an example of display of a formation position of a slit image SP on a display device CRT.

FIG. 7 is a flow chart diagram in the third embodiment of the present invention.

FIG. 8: Slit image SP, optical axis A on wafer W
FIG. 6 is a diagram showing a positional relationship between X and a projection position RC ′ of a center position RC of a reticle R.

9A is a slit image SP and a reference mark 30. FIG.
FIG. 9B is a diagram showing a change in the photoelectric signal obtained by the light receiver 21 at that time.

[Explanation of symbols]

 R ... Reticle PL ... Projection optical system W ... Wafer FM ... Reference plate MCS ... Main control system CRT ... Display device WSC ... Wafer stage controller RSC ... Reticle stage controller ST1 ... XY stage ST2 ... Z stage SP ... Slit image 15 ... Projector 16, 20 ... Parallel plate glass 18a, 18b ... Drive part 21 ... Photoreceiver 101, 102, 103 ... Signal processing device

Claims (11)

[Claims] 1. A projection optical system for projecting an image of a pattern of a mask onto a photosensitive substrate, and a movable optical system of the projection optical system holding the photosensitive substrate and movable in a direction perpendicular to the optical axis. By projecting a pattern image on the stage and the photosensitive substrate and photoelectrically detecting reflected light from the photosensitive substrate, the image forming surface of the projection optical system and the surface of the photosensitive substrate of the projection optical system. Projection provided with focus detection means for outputting a detection signal corresponding to deviation in the optical axis direction, and control means for controlling movement of the stage in the optical axis direction based on the detection signal from the focus detection means. In the exposure apparatus, a light receiving unit having a light receiving surface arranged on a part of the stage, and a photoelectric signal output from the light receiving unit when the pattern image is projected on the light receiving surface, on the light receiving surface, A detection means for detecting the image formation state of the pattern image, and an adjustment means for adjusting the focus of the pattern image on the photosensitive substrate based on the image formation state of the pattern image obtained by the detection means. A projection exposure apparatus characterized by the above. 2. The focus detecting means has a light projecting system for projecting the pattern image on the substrate, and the adjusting means is at least one of a plurality of optical members constituting the light projecting system. 2. The apparatus according to claim 1, further comprising drive means for driving the light source in the optical axis direction of the light projecting system. 3. The apparatus according to claim 2, wherein the light receiving unit has an image pickup unit that picks up the pattern image. 4. A position detecting means for detecting a formation position of the pattern image on a stationary coordinate system which defines a moving position of the stage in a direction perpendicular to the optical axis based on a photoelectric signal from the light receiving means. A moving unit that moves the pattern image forming position so that the pattern image is formed at a predetermined setting position on the stationary coordinate system based on the pattern image forming position obtained by the position detecting unit. The device of claim 1, comprising: 5. The focus detecting means includes an optical member that shifts the position of the pattern image in a plane perpendicular to the optical axis, and the moving means includes a driving means that drives the optical member. The device according to claim 4, characterized in that 6. A projection optical system for projecting an image of a pattern of a mask onto a photosensitive substrate, and holding the photosensitive substrate, movable in the optical axis direction of the projection optical system and in a direction perpendicular to the optical axis. By projecting a pattern image on the stage and the photosensitive substrate and photoelectrically detecting reflected light from the photosensitive substrate, the image forming surface of the projection optical system and the surface of the photosensitive substrate of the projection optical system. Projection provided with focus detection means for outputting a detection signal corresponding to deviation in the optical axis direction, and control means for controlling movement of the stage in the optical axis direction based on the detection signal from the focus detection means. In the exposure apparatus, a reference part provided on a part of the stage and provided with a reference pattern having at least two regions having different reflectances in a predetermined direction in a plane perpendicular to the optical axis. And, based on a change in intensity of a detection signal output from the focus detection system when the reference pattern and the pattern image are relatively moved in the predetermined direction, an image forming state of the pattern image on the reference member is set. A projection exposure apparatus comprising: detection means for detecting; and adjustment means for adjusting the focus of the pattern image on the photosensitive substrate based on the image formation state of the pattern image obtained by the detection means. . 7. The focus detecting means has a light projecting system for projecting the pattern image on the substrate, and the adjusting means is at least one of a plurality of optical members constituting the light projecting system. 7. The apparatus according to claim 6, further comprising drive means for driving the light source in the optical axis direction of the light projecting system. 8. A formation position of the pattern image on a stationary coordinate system that defines a movement position of the stage in a direction perpendicular to the optical axis based on a change in intensity of the detection signal from the focus detection means. Position detecting means, and based on the pattern image forming position obtained by the position detecting means, the pattern image forming position so that the pattern image is formed at a predetermined setting position on the stationary coordinate system. 7. The apparatus according to claim 6, further comprising a moving means for moving the. 9. The focus detection means has an optical member that shifts the position of the pattern image in a plane perpendicular to the optical axis, and the moving means has a drive means that drives the optical member. 9. The device according to claim 8, characterized in that 10. Prior to exposing a pattern formed on a mask onto a photosensitive substrate placed on a stage via a projection optical system, a pattern image is projected onto the photosensitive substrate and the photosensitive substrate is exposed. By photoelectrically detecting the reflected light of, the detection signal corresponding to the deviation in the optical axis direction of the projection optical system between the image plane of the projection optical system and the surface of the photosensitive substrate is obtained, and based on the detection signal In a projection exposure method in which the surface of the photosensitive substrate is arranged on the image plane, the pattern image formed on the stage or the reflected light from the stage is photoelectrically detected to form an image of the pattern image. And a second step of adjusting the focus of the pattern image on the photosensitive substrate based on the detected image formation state of the pattern image. A projection exposure method. 11. A step of detecting a position where the pattern image is formed in a plane perpendicular to the optical axis by photoelectrically detecting the pattern image formed on the stage or reflected light from the stage. A step of moving the formation position of the pattern image based on the detected formation position of the pattern image so that the pattern image is formed at a predetermined measurement point on the photosensitive substrate. The method according to claim 10, wherein