JPH1154410A - Projection aligner, its method, and manufacture of element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently adjust inclination of a shot area even when the shot area exists in the fringe section of a photosensitive substrate, by temporarily shifting a movable stage so that the point at which a straight line passing through a specific point in the shot area and the center of the substrate intersects a boundary line may be aligned with the center of an inclination detecting area. SOLUTION: A main control system sets a straight line K1 which connects the center CCw of a wafer with the center SC1 of a shot area SA1 and calculates the coordinate position of the point Pff at which the line K1 intersects a boundary line LL. Then, the control system moves an X-Y stage so that the calculated coordinate position of the point Pff may become a target value. After moving the X-Y stage, the control system calculates the point P1 at which the extension of the straight line K2 connecting a specific point SC2 with the center CCw of the wafer intersects the boundary line LL, and the coordinate position of a point Psf which divides the segment between the points P1 and the specific point SC2 at a specific ratio (of, preferably, 1/2 when the convenience of calculation is taken into consideration) on the straight line K2 . Then, the X-Y stage is moved to the calculated coordinate position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mask (reticle).
When exposing the pattern to the photosensitive substrate via the projection optical system, the projection exposure apparatus of the method of moving the photosensitive substrate in a step-and-repeat manner, and particularly optimized the tilt alignment with respect to the shot area to be exposed on the photosensitive substrate It concerns the device.

[0002]

2. Description of the Related Art In a step-and-repeat type projection exposure apparatus (stepper), a wafer mounted on a two-dimensional moving stage is stepped at a fixed pitch in an x-direction or a y-direction to obtain a projected image of a reticle pattern. Exposure is repeated. At this time, for each shot area to be exposed on the wafer (the area where the pattern projection image of the reticle is transferred), the wafer surface is matched with the best image plane of the projection optical system, that is, focusing is performed. Then, the wafer is finely moved in the projection optical axis direction by the Z stage on the moving stage. For example, Japanese Patent Application Laid-Open No. 58-11370 discloses a focus sensor for focusing.
As disclosed in Japanese Unexamined Patent Application Publication No. 6-206, an oblique incident light type focus detection system that projects an imaging light beam (non-exposure wavelength) obliquely onto the surface of a wafer and photoelectrically detects the reflected light is used. The image-forming light beam from the focus detection system usually forms a spot image or a slit image on a part of the wafer surface located substantially at the center in the projection field of view of the projection optical system. For this reason, the position shift amount in the optical axis direction of the wafer surface, that is, the focus shift amount, is determined based on the light receiving position of the reflected light that is photoelectrically detected when the wafer surface matches the best imaging plane of the projection optical system. , And is measured based on the photoelectrically detected signal. Then, the position of the Z stage in the optical axis direction is servo-controlled so that the detected defocus amount becomes zero, so that automatic focusing (auto f.
ocus) is achieved. Also, parallel light is obliquely incident on the surface of the wafer, the reflected light is received, the inclination of the wafer surface is detected, and the inclination of the Z stage is controlled so as to correct the inclination. Is being done.
In the case of a stepper, such automatic focusing and automatic tilting are usually performed each time each shot area on a wafer is exposed. That is, immediately after the moving stage is stepped so that the center point of one shot area coincides with the center point of the projected image of the reticle pattern (substantially in the projection field), autofocus is performed by the focus detection system and the tilt detection system. Is performed, and after the automatic tilt adjustment is performed, an exposure is started when the Z stage is settled.

[0003]

In the case of a stepper for exposing a wafer, the shape of a projected reticle pattern is generally rectangular, whereas the wafer is circular. , Y, a portion of the shot area is missing near the circular outer periphery of the wafer. The manner of the chipping varies depending on the arrangement of the shot areas on the wafer. Therefore, stepping is performed on a shot area located in the peripheral portion of the wafer, and the shot area is positioned at the center of the projection field of view, and the detection area of the tilt detection system (the irradiation area formed by the projection of oblique incident light) ) May be located outside the wafer.

In this case, since the tilt adjustment with respect to the shot area is no longer possible, the exposure is performed without performing the tilt alignment, or the tilt position (Z) in the shot area immediately before the tilt alignment is normally performed. (Position of leveling stage). For this reason, such a shot area is composed of multiple chips, and even if there is a chip that can be obtained effectively, the chip is exposed without being correctly aligned with the chip. Had occurred. This is contrary to the demand for efficiently obtaining chips up to the peripheral portion of the wafer. In view of the above, the present invention solves the above-described problems, and enables efficient tilt alignment to be performed even in a shot region located in the peripheral portion of a photosensitive substrate such as a wafer, thereby relieving chips existing in the peripheral portion as much as possible ( An object of the present invention is to provide a projection exposure apparatus equipped with a tilt alignment method for performing normal tilt alignment exposure.

Another object of the present invention is to provide an exposure method and an element manufacturing method in which even when the detection area of the tilt detection system overlaps with an unexposed area, exposure is performed with normal tilt alignment.

[0006]

In the present invention, when a substantially constant width from the outer peripheral edge (WE) of the photosensitive substrate (wafer W) is defined as a forbidden band, a plurality of shot areas (SA1, SA2...) Based on the design layout information (shot map data reflecting the result of wafer global alignment in the case of second print), all shots located outside the forbidden zone boundary line (LL) The area (SA1) is determined as the first type, and among the shot areas located in the projection field of view (PLF) at the time of exposure, the inclination detecting means (the projector ALP, the light receiver AL)
R, the shot area (SA2, SA3) in which the detection area SB (illumination area) of the control system AFU is located in the forbidden zone and at the same time partly exists inside the boundary line (LL) is determined as the second type. A specific shot discriminating means (step 104), and a first type shot area (S
When tilting A1), the shot area (S
A1) and the center point (CC) of the photosensitive substrate
w) to temporarily shift the moving stage (21) so that the point (Pff) at which the straight line (K1) passing through the boundary line (LL) intersects the boundary line (LL) matches the center of the tilt detection area SB (illumination area). 1 shift control means (steps 106, 110, 1
12) and a second type shot area (SA) during exposure.
When tilting 2), the shot area (SA
Point (SC) closest to the center of the photosensitive substrate (CCw) in 2)
2) and a straight line (K) passing through the center point (CCw) of the photosensitive substrate.
2) The moving stage (21) such that a point (Psf) located on the shot area (SA2) above and inside the boundary line (LL) is aligned with the center of the tilt detection area SB (illumination area). And second shift control means (steps 108, 116, and 118) for temporarily shifting.

According to the structure of the present invention, it is impossible to detect inclination at the time of exposure with a chipped shot located around the photosensitive substrate,
Alternatively, even in the case of an unstable state (such as a case where all the detection points cannot be detected in the multi-point AF system), a chip area to be relieved within the missing shot can be correctly aligned and exposed. In addition, for a shot area (first type) in which a part enters only into the forbidden band and does not exist at all in the effective tilt detectable range, it is highly possible that the chip area itself to be relieved is also missing.
The moving distance of the stage is set to be the shortest in order to realize shift leveling while suppressing a decrease in throughput.

[0008]

FIG. 1 shows an overall configuration of a projection exposure apparatus (stepper) to which the present invention is applied. A rectangular putter area PA formed on a reticle (mask) R is a condenser of an illumination system for exposure. The illumination light is uniformly emitted from the lens CL. The light transmitted through the pattern area PA reaches the wafer W via the bilateral telecentric or image-side telecentric projection lens PL, and the image of the pattern area PA is transferred to a predetermined shot area on the wafer W (the area where the pattern area PA is transferred). ). Reticle alignment microscopes RA1 and RA2 detect marks formed around reticle R and project reticle R onto projection lens PL.
Of the reticle R and the wafer W by detecting the relative positional deviation between the mark on the reticle R and the mark on the wafer W. A TTL (through-the-lens) alignment system WA for detecting a mark on the wafer W via only the projection lens PL is provided within a circular projection field of view of the projection lens PL and a projection range (rectangular) of the pattern area PA of the reticle R. Outside the mark detection area. The same TTL alignment system WA is provided in two sets so that the mark detection areas are arranged at two places in the projection visual field.
On the other hand, the wafer W is held on a Z stage 20, and the Z stage 20 is held on an XY stage 21. The Z stage 20 is driven by a drive system such as a motor 19 to move the XY stage 2
1 is configured to be finely movable in the optical axis AX direction (Z direction). As a result, the surface on the wafer W becomes the projection lens PL.
Is performed so as to coincide with the best image plane of.
The position of the surface of the wafer W in the optical axis AX direction is detected by an oblique incident light type focus position detection system, and the non-exposure light (red broadband wavelength light) from the projector AFP is projected obliquely onto the wafer W, The reflected light is received by the light receiver AFR. A detection signal (a signal whose state changes according to the magnitude of defocus) from the photodetector AFR is a focus control system AFU
Sent to The control system AFU sequentially detects the amount of deviation of the surface of the wafer W from the best image plane based on the detection signal,
The motor 19 for the Z stage 20 is driven until the deviation amount falls within a predetermined allowable value. The leveling light projector ALP emits collimator light into the shot of the wafer W, and the reflected light is received by the light receiver ALR. Receiver AL
R has a detector in which the light receiving surface is divided into four (quadrant detector), and the position of the reflected light from the wafer W incident on the light receiving surface of the four-divided detector changes according to the inclination of the wafer W. Therefore, the inclination of the shot on the wafer W is detected by detecting the position of the reflected light on the light receiving surface of the four-divided detector. The position of the reflected light can be determined by detecting the position of the center of gravity of the amount of the reflected light in the light receiving surface based on, for example, the outputs of the four divided detectors. An auto-collimator type auto-leveling such as a projector ALP and a photodetector ALR is disclosed in detail in Japanese Patent Application Laid-Open No. 58-113706.

The wafer W is exposed by a step-and-repeat method, and its stepping position is detected as a two-dimensional coordinate value by a laser interferometer IFM.
This laser interferometer IFM uses the moving plane (xy) of the wafer W.
A coordinate position within a plane is detected with a resolution of about 0.01 μm, and is also used for mark position measurement during alignment.
The motor 40 moves the XY stage 21 (that is, the wafer W) in each of the x direction and the y direction, and is controlled by the stage control STU. When data of the movement target position of the wafer W is sent from the main control system MC, the control system STU calculates a difference from the current position measured by the laser interferometer IFM, and sets the motor at an optimum speed according to the difference. The motor 40 is driven and the motor 40 is servo-controlled so that the count value of the laser interferometer IFM with respect to the target position is within, for example, ± 5 counts (± 0.05 μm).

The main control system MC inputs measurement results by the reticle alignment microscopes RA1 and RA2, mark position measurement results by the TTL alignment system WA, and the like, and bidirectionally exchanges data and commands with the focus control system AFU. Interact. In particular, in this embodiment,
The main control system MC is a step and repeat type wafer W
Target position when moving the XY stage, that is, the XY stage 21
(Design value in the case of the first print, actual measured value determined by the measurement result of the mark position on the wafer W in the case of the second print). This will be described in detail later.

FIG. 2 is a diagram showing in detail each configuration of the control system AFU, the light projector AFP, and the light receiver AFR in FIG. The broadband illumination light IL having a band in the red or infrared region illuminates the slit 1. Light from the slit 1 is projected obliquely to the surface of the wafer W via a lens system, a mirror 3, an aperture stop 4, an objective lens 5, and a mirror 6. At this time, the image of the slit 1 is formed on the wafer W. The reflected light of the slit image is mirror 7,
Objective lens 8, lens system 9, vibrating mirror 10, angle-variable parallel flat glass (hereinafter referred to as plane parallel) 12
Are re-imaged on the slit 14 for detection. The photomultiplier 15 photoelectrically detects the light flux of the slit image transmitted through the slit 14 and outputs the photoelectric signal to a synchronous detection circuit (PSD) 17. The vibrating mirror 10
Oscillator (OSC.) Via drive circuit (M-DRV) 11
In response to a sinusoidal signal of a constant frequency from 16 oscillated in a fixed angle range. As a result, the image of the slit 1 re-imaged on the detection slit 14 slightly vibrates in a direction orthogonal to the longitudinal direction of the slit, and the photoelectric signal of the photomultiplier 15 becomes OSC. It is modulated in correspondence with 16 frequencies. PSD 17 is OSC. The phase of the photoelectric signal from the photomultiplier 15 is detected with reference to the original signal from the photomultiplier 16, and the detected signal SZ is processed by the processing circuit (CPX) 30 and the driving circuit (Z-DRV) 18 of the motor 19 for the Z stage 20. Output to Detection signal SZ
Becomes zero level when the surface of the wafer W is coincident with the best image plane (reference plane), and becomes positive level when the wafer W is deviated upward along the optical axis AX from that state, When the signal is displaced in the reverse direction, the signal is output as an analog signal having a negative level. Therefore, Z-DRV18
Is up to the servo amplifier based on the zero level, Z-
The DRV 18 drives the actuator 19 so that the detection signal SZ becomes zero level. Thereby, automatic focusing of the wafer W is achieved.

On the other hand, the processing circuit (CPX) 30 adjusts the inclination of the plane parallel 12 with respect to the optical axis by a driving unit (H).
-DRV) 13 to output the drive signal DS. This HD
The RV13 has a driving motor and a plane parallel 1
And an encoder for monitoring the amount of inclination of 2. The up / down pulse output ES from the encoder is CPX.
It is read into 30.

When the CPX 30 performs focusing on a stepping position (shot area to be exposed) determined by the main control system MC or a position shifted from the original position by a certain amount, the signal FLS ( The focus lock signal) is output to the Z-DRV 18 as disabled, and the servo loop for automatic focusing is operated as usual. When performing focus lock (shift / focus), the focus servo is settled and the signal SZ is set.
Is read by the CPX 30 and becomes zero level, the signal FLS is enabled and output to the Z-DRV 18 to prohibit the driving of the Z stage 20 (the driving of the actuator 19). FIG. 3 shows the control system AFU of FIG.
FIG. 3 is a detailed view of a light emitter ALP and a light receiver ALR. Red or infrared broadband light (illumination light) ILL from a light source (not shown) is collimated by a pinhole 41 and a lens system 42, and is incident on the wafer W via a mirror 43. The illumination light ILL reflected by the wafer W is reflected by the mirror 44 and then condensed by the lens system 45 to form a light spot on the quadrant detector 46. The photoelectric conversion signals LZ from the four detectors are output from C in the control system AFU.
PX30 is input. The CPX 30 calculates the position of the illumination light (the position of the light spot) on the divided detector 46 by comparing the photoelectric conversion signals LZ from each of the four detectors. The position of the illumination light on the split detector 46 indicates the rolling and pitching of the wafer W (inclination around the X and Y axes). When performing the tilt adjustment (auto leveling: AL) with respect to the stepping position (shot area to be exposed) determined by the main control system MC, the CPX 30 disables the signal LLS (leveling lock signal) to disable the Z-DRV 18. The actuator 19 is controlled so that the servo loop of the auto-leveling works as usual and the wafer W is in a desired posture. When leveling lock (shift / leveling) is performed, the signal LLS is enabled when the level of the signal LZ is read to the zero level by the CPX 30 after the servo of the auto leveling is settled and the Z-DRV 18 is enabled.
To drive the Z stage 20 (actuator 19
FIGS. 4 and 5 show an example of the wafer surface that appears in the projection field PLF of the projection lens PL during step-and-repeat exposure. FIG. 4 shows a state in which a certain shot area SA inside the wafer W is exposed. Usually, the optical axis AX of the projection lens PL is set to pass through the center point of the shot area SA to be exposed. This is because the alignment is performed so that the center point of the pattern area PA of the reticle R coincides with the optical axis AX.

A light beam from the projector ALP of the tilt detection system is projected as an illumination area SBL at the center of the projection field PLF. The center of the illumination area SBL, that is, the point through which the optical axis AX passes is the detection point of the tilt detection system. FIG. 5 shows a state in which a shot area SA ′ located around the wafer W is exposed, and shows a case where the illumination area SBL is located outside the outer peripheral edge (edge) WE of the wafer W. In this case, when the exposure for the shot area SA ′ is performed, the tilt detection system does not operate, and the exposure is conventionally performed ignoring the leveling. However, the shot area SA '
Has a multi-chip configuration, one chip area CP may be normally included inside the wafer edge WE as shown in FIG. Accordingly, it is an object of the present invention to improve the chip acquisition rate by performing normal exposure even on such a chip area.

Next, the operation of the first embodiment of the present invention will be described with reference to FIG. In FIG.
0 is mainly executed before the first print (exposure of the first layer), and step 102 is executed at the time of the second print (overlay exposure of the second and subsequent layers). In step 100, the main control system MC sets the wafer W based on the external dimensions of the wafer W, the size of the shot area, the step pitch, and the like.
Create optimal shot map data corresponding to the external shape of. The shot map data indicates how to arrange the shot areas in the wafer from the outer shape of the wafer W, and is automatically determined by calculation.
It is registered in the memory as the stepping coordinate position of the XY stage 21. Further, in step 100, based on the determined shot map data, the coordinate position of the center point of the wafer, the boundary line position of the forbidden band, and the like are set by calculation.

FIG. 7 schematically shows an example of shot map data determined corresponding to the wafer outer shape.
One of the rectangles in FIG. 7 represents a shot area. As shown in FIG. 7, the forbidden zone means an area in which leveling detection is prohibited within a certain width (about 1 to several tens of mm) from the outer peripheral edge WE of the wafer W. The boundary line determined in step 100 is a line LL in FIG. 7 and is defined by a radius from the center CCw of the wafer W. Further, with respect to the linear notch (orientation flat) portion OF, a forbidden zone (boundary line LL) having a fixed width is set along the orientation notch portion OF. In addition, the forbidden band generally indicates uneven coating of the resist,
This is set because non-defective chips can hardly be obtained due to non-uniformity of various processes, or loss of the wafer edge WE. Therefore, the width of the forbidden band may be fixed to a substantially constant value, but the forbidden band width may be made inputtable so as to be slightly changed according to the chip size.

If the center of the illumination light SBL of the tilt detection system is inside the boundary line LL, there is no problem in the leveling operation. At the time of first printing, step 100 is completed only by the above-described operations. At the time of second printing, the Z stage 20 (holder) of the wafer at the time of first printing is determined based on the result of the wafer global alignment in step 102. The offset amount from the above mounting position is obtained, and the offset amount is used as a correction value when calculating the wafer center point and the forbidden band boundary line position in step 100. By doing so, the deviation between the shot map (matrix in FIG. 7) generated in the second print and the wafer outline in the X and Y directions is corrected, and the state in the first print is always maintained.

Next, in step 104, the main control system MC determines the state of the shot area to be exposed based on the shot map data. In this step 104,
It is determined how the position of the wafer edge WE and the position of the boundary line LL on the shot map are with respect to the shot area to be exposed. For example, in FIG. 7, the shot area SA at the upper leftmost position on the shot map
1 as a first shot, and shot areas SA1, SA2,
After step-and-repeat exposure in the X direction up to the shot area SA7 in the order of SA3,..., Stepping is performed to the shot area SA8 diagonally lower right, and step-and-repeat exposure is performed in the opposite direction to the X direction. Note that FIG.
, The center point of each of the shot areas SA1, SA2, and SA3 is represented by the intersection of a cross mark.

In the case of the first shot area SA1 in FIG. 7, a part of the first shot area SA1 exists on the wafer W, but the whole is outside the boundary line LL of the forbidden zone, and the shot center point is also the wafer edge WE. Located outside of. The main control system MC determines the shot area in such a state as the first type. In addition, a part of the adjacent second shot area SA2 exists inside the boundary line LL, but a shot center point (a point that coincides with the detection point of the tilt detection system at the time of exposure) exists in the forbidden zone. The main control system MC determines the shot area in such a state as the second type. The same applies to the third shot area SA3. Further, regarding the ninth shot area SA9, the shot center point is located inside the boundary line LL. In this case, the tilt can be normally adjusted at the exposure position.

Whether the shot is the first type shot or the second type shot depends on whether a line connecting the center point CCw of the wafer W and the center point of the shot area of interest intersects the boundary line LL or the wafer edge WE. Is calculated by a mathematical method. In other words, the line connecting the center point of the shot area and the wafer center point CCw is the wafer edge W
When it crosses both E and the boundary line LL, it is determined to be the first type, and when it crosses only the boundary line LL, it is determined to be the second type.

Next, the main control system MC executes steps 106, 1
At 08, one of the three modes according to the situation of the shot area to be exposed is executed. Assuming that the shot area to be exposed is, for example, the area SA9, it is determined in steps 106 and 108 that the shot is a normal focusing shot that is neither of the first type nor the second type, and the sequence proceeds to step 120. In step 120, the main control system MC determines the shot area S on the wafer W based on the shot map data.
A9 calculates a coordinate position that overlaps with the projected image of the pattern area PA of the reticle R, and outputs it to the stage control system STU as a target value. XY stage 2 in response
1 performs stepping. And the next step 122
In step, the main control system MC checks the state of the leveling lock signal LLS via the CPX 30, and if enabled (leveling lock is being executed), the sequence proceeds to step 126. The main control system MC outputs the signal LL
If S is disabled (the focus lock is released), automatic leveling (tilt adjustment by fine movement of the actuator 19) is executed in step 124. In the case of the shot area SA9 in FIG. 7, the signal LLS is disabled, and the auto-leveling is performed as in the related art.

Then, at step 126, an exposure operation is performed. After the exposure is completed, at step 128, the signal LLS is set to disable. This step 128 is for releasing the state where the shot area exposed in step 126 is leveling lock. If the signal LLS has already been disabled at the time of step 126, step 128 is executed. It will be ignored.

When the exposure of one shot area is completed, it is determined in step 130 whether or not the exposure of all shot areas has been completed. If the exposure has not been completed, the first shot area is exposed for the exposure of the next shot area. The sequence from step 104 is repeated. If it is determined in step 106 that the shot area to be exposed belongs to the first type such as SA1, the main control system MC executes steps 110, 112, and 114, and then executes step 12
Execute 0. Therefore, these steps 110, 112,
The operation of 114 will be described with reference to FIG.

First, in step 110, the shot area S
Since all of A1 are outside the boundary line LL of the forbidden zone, an operation for forcibly moving the leveling point to somewhere in the adjacent shot area is performed. As shown in FIG. 8, the main control system MC has a wafer center point C
A straight line K1 connecting Cw and the center point SC1 of the shot area SA1 is set, and a coordinate position FF of a point Pff at which the straight line K1 intersects the boundary line LL is calculated. This calculation is based on the position of the center point CCw in the moving coordinate system of the XY stage 21,
Since the position of the shot center point SC1 and the radius of the boundary line LL are known in advance, it can be immediately executed by a geometrical mathematical solution. As described above, in the case of the shot area belonging to the first type, the point detected by the shift leveling is set on the boundary line LL in the shot area adjacent to the wafer center side with respect to the shot area.

Next, in step 112, the main control system MC moves the XY stage 21 so that the calculated coordinate position (also referred to as a forced shift focus position) FF of the point Pff becomes a target value. Thus, the slit image SB of the focus detection system is projected on the point Pff. The Z stage 2 responds to the detection signal LZ of the tilt detection system.
0 (actuator 19) is driven, and auto-leveling (AL) is executed at the point Pff.

When the Z stage 20 is settled and AL is completed, the main control system MC proceeds to step 114 where the CPX 30
, The signal LLS is switched to enable, and the leveling lock state is set. Then immediately step 12
The sequence proceeds to 0, and the XY stage 21 is moved to a position where the shot area SA1 is exposed. Then, exposure is performed, a resist is applied through process steps such as development and etching, and exposure is performed by repeating the above-described sequence. By repeating these series of operations several times, semiconductor elements are formed on the wafer W.

As described above, in the case of the first type shot area, since there is no portion existing inside the forbidden zone, even if leveling adjustment is not performed at all, there is no chip to be rescued. Should not be. Therefore, in response to a request to perform tentative leveling adjustment even for such a first type shot area, in consideration of throughput, a levelable position closest to the shot center point SC1 (that is, the boundary line LL).
The wafer is moved upward (or in the vicinity thereof). In this way, when the XY stage 21 is moved to the shot center point SC1, which is the exposure position, after performing the leveling operation (AL) at the point Pff, the amount of movement becomes the shortest distance.

On the other hand, if it is determined in step 108 in FIG. 6 that the shot area to be exposed is the second type, the main control system MC executes steps 116 and 118 and then performs the leveling lock operation in step 114. Execute. Therefore, steps 116 and 118 will be further described with reference to FIG. The shot area SA2 in FIG. 8 is considered as the second type shot area. In this case, the shot area SA2
Is located within the leveling detectable range inside the boundary line LL, so that the main control system MC sets the shot area SA2
, A specific point existing inside the boundary line LL and closest to the center of the wafer is calculated. This calculation includes the position of the center point of the shot area SA2, the position of the wafer center point CCw,
It is easily executed based on the size of the shot area SA2 and the radius of the boundary line LL. As a result, in the case of the shot area SA2 in FIG. 8, the position of the corner in the shot closest to the center of the wafer is determined as the specific point SC2.

Next, the main control system MC sets a straight line K2 connecting the specific point SC2 and the wafer center point CCw, and calculates a point P1 at which an extension of the straight line K2 intersects the boundary line LL. Further, the main control system MC calculates the coordinate position SF of the point Psf on the straight line K2 that divides the point P1 and the specific point SC2 at a predetermined ratio (preferably 1/2 in consideration of the simplicity of calculation). This point Psf is the point at which shift leveling is performed, and in the next step 118, the XY stage 21
Is moved to a coordinate position SF, where auto-leveling is performed. Thereafter, the sequence from step 114 described above is executed.

As described above, in the case of the shot area of the second type, the point at which leveling is performed is shifted to the leveling detectable range within the shot area. I will call it. Now, as is clear from the arrangement of the shot areas in FIG. 8 and the sequence in FIG.
The stepping movement to the first exposure position (shot center point) is necessarily performed after the movement by shift leveling. Therefore, in the case of FIG. 8, when global alignment (EGA or the like) of the wafer is completed and step-and-repeat exposure is performed from the first shot area SA1, the stepping movement of the XY stage 21 is performed at a point Pff (leveling alignment) → shot center. Point SC1 (exposure) → point Psf
(Leveling adjustment) → the center point (exposure) of the shot area SA2.

In the sequence shown in FIG. 6, after the exposure of one shot area is completed, the type of the next shot area is determined, and the shift leveling point is calculated (steps 104, 106, 108, 110, 116).
However, since these calculation times can be sufficiently shorter than the exposure time (0.1 to 0.5 seconds) of one shot area, the shift leveling point is obtained during the exposure operation of the previous shot area. Alternatively, the sequence may be such that step 112 or 118 is executed simultaneously with the completion of exposure.

When the algorithm shown in FIG. 8 is applied to the second type of shot area, an inconvenient point occurs depending on how the boundary line LL is applied in the shot area. Therefore, an algorithm that solves the disadvantage will be described as a second embodiment with reference to FIG. This algorithm is executed in step 116 in the sequence of FIG. 6, and does not change the sequence entity.

Now, consider the shot area SA3 (same as that in FIG. 7) shown in FIG. This shot area SA3 belongs to the second type because the shot center point SS3 exists in the forbidden zone, and in the case of the first embodiment, the specific point SC3 closest to the wafer center in this shot area SA3 is The straight line K determined and further passing through the specific point SC3
3, and an intersection P3 between the straight line K3 and the boundary line LL is determined. Thereby, the point of the normal shift leveling position SF is set somewhere on the line segment connecting the point P3 and the specific point SC3.

However, in the case of the shot area SA3, the portion where the straight line K3 passes is located at the very end of the effective portion existing within the leveling detectable range in the shot area SA3, and is determined by the above-described algorithm. It is hard to say that shift leveling position SF typically reflects the effective portion thereof. Therefore, in the present embodiment, the first
A judgment function is added to the algorithm of the embodiment of the present invention to further optimize the shift / leveling position. First, a point P3 and a specific point SC3 are obtained according to a normal algorithm.
A point Psf which bisects both points on the straight line K3 is obtained. Then, a point SC3 'which is the second corner in the shot area SA3 closest to the wafer center is found, and the point SC3'
A straight line K3 'connecting 3' to the wafer center point CCw and a straight line K3 "connecting the center point SS3 of the shot area SA3 and the wafer center point CCw are set. The point SC3 'is inside the boundary line LL. Under the condition, a straight line K3 "
Is determined between the two straight lines K3 and K3 '. When the straight line K3 "is sandwiched substantially at the center, the shift leveling point P on the straight line K3 previously obtained
A length equal to the distance connecting sf and the wafer center point CCw is set on a straight line K3 ″ from the wafer center point CCw, and that point is set as an actual shift leveling point.

Alternatively, an intersection point SC3 ″ between a straight line connecting the point SC3 ′ and the specific point SC3 and the straight line K3 ″ and an intersection point P3 ″ between the straight line K3 ″ and the boundary line LL are obtained, and the point P3 ″ and the point SC are determined.
A point that bisects 3 ″ on the straight line K3 ″ may be set as an actual shift leveling point. According to the above-described algorithm, shift / leveling can be performed as a position almost accurately representing an area partially within the leveling detectable range in the shot area.

Next, a shift leveling operation according to the third embodiment will be described. In the third embodiment, in order to suppress a decrease in throughput as much as possible, a forced shift / leveling operation is not performed for all of the shot regions belonging to the first type.
A sequence is set up in which forced shift / leveling is performed only when the shot is of the first type, and a shot of the first type that appears during the progress of the step-and-repeat exposure is dealt with by leveling lock.

Hereinafter, a sequence according to the third embodiment will be described with reference to FIG. The flowchart of FIG. 10 is basically the same as the flowchart of FIG. 6, except that the signal LL is provided between steps 106 and 108 in FIG.
Step 132 for switching S to disable (leveling servo mode) is added, and step 10 in FIG.
When the determination of step 6 is true (Yes), step 134 is added to execute steps 110, 112, and 114 only for the first shot, and AL execution of step 124 in FIG. This means that the signal LLS is changed to step 124 'for switching to the enable (leveling lock mode) after execution.

In FIG. 10, if it is determined in step 106 that the shot to be exposed is of the first type, it is further determined in step 134 whether or not the shot is the first (head) shot. If it is not one shot, steps 120 and 122 are executed. If it is determined in step 134 that the shot is the first shot, steps 110, 112, and 11 are performed for forced shift leveling.
4 is executed, and the sequence proceeds to step 120. For example, in the case of the shot maps shown in FIGS.
06, 134, 110-114, 120, 122, 12
The sequence proceeds in the order of 6, and exposure is performed. At this time, the leveling lock state is set in step 114, but this state is kept unless step 132 in the processing routine for the next shot is executed. Then, for the next shot area SA2, step 10
6, 132, and 108, and is determined to be of the second type, so that steps 116, 118,
The processing is performed in the order of 114, 120, 122, and 126.

It is assumed that step-and-repeat exposure is sequentially performed as described above, and that the next shot area to be exposed is determined to be of the first type in step 106. In this case, when the exposure of the immediately preceding shot area is completed,
Since the leveling lock is locked in step 124 ', the process proceeds to step 134 without proceeding to step 132. In this case, since it is determined in step 134 that the shot is other than the first shot, the process immediately proceeds to step 120. That is, shot areas other than the first shot and of the first type include steps 106, 134, 120, 1
Exposure is performed in the order of steps 22 and 126, and instead of omitting the forced shift leveling operation (steps 110 to 114), exposure is performed in a state of leveling adjustment for the immediately preceding shot area.

When the first shot is of the first type and the second shot is normal (neither of the first or second type), step 106 is executed for the second shot area. 132, 108, 120, 12
2, 124 'and 126 are performed in this order, and a normal auto-leveling operation is performed. Further, when both the first shot and the second shot are of the first type, steps 106 and 134 are executed for the second shot area.
The sequence proceeds in the order of 120, 122, and 126, and exposure is performed at the same leveling position as the forced shift / leveling state in the first shot. As described above, as in the present embodiment, the forced shift leveling for the first type shot is limited to only the first shot, and the other first type shots remain in the leveling state performed in the immediately preceding shot. If the exposure is performed, the XY stage 21
, The number of movements at the time of forced shift leveling is greatly reduced, and a decrease in throughput can be suppressed. Next, FIG.
A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the shift amount at the time of shift leveling is set to an integral multiple of the step pitch P when performing exposure by the step-and-repeat operation. That is, during shift leveling, leveling is detected at the same position in the shot. In FIG. 11, shots SA1, SA
Since shots such as SA2 and SA3 are outside the leveling prohibited zone LL, the center of the nearby shot and the leveling illumination area SBL is shifted to the center of the shots SA7, SA8, and SA9 that are inside the leveling prohibited zone LL. And apply leveling. By doing so, it is possible to prevent a change in the leveling measurement value due to the surface shape in the shot.

Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment provides the following optimum shift leveling for a process wafer. (1) Small shot size, leveling illumination area SB
When L protrudes from the shot. (2) This is a process after the second exposure, and a case where an unexposed region MR (shaded portion in FIG. 12) exists in the periphery. In such a process wafer, the peripheral unexposed portion MR
And the inclination and height in the shot may greatly differ from each other, and the presence of the unexposed portion MR in the leveling illumination area SBL causes an error in the leveling measurement value. In this case, the information within the levelable boundary line LL is no longer sufficient, and the unexposed area MR is included in the leveling illumination area SBL from the shot size, the step pitch, and the shot map (information of the shot position in the wafer W). It is sufficient to calculate the shift amount to be shifted to a place where there is no shift, and execute the above-described shift leveling.

Further, this shift amount is set in the same manner as in the fourth embodiment.
It may be an integral multiple of the step pitch. FIG. 12 shows a case where the leveling operation is performed by shifting the shot SA1 to the shot SA6 and a case where the shot SA4 is shifted to the shot SA1.
3 shows a case where the leveling operation is performed by shifting to 3.

Each shot is given a shot number,
The shot map is displayed on the screen together with the shot number. Shots in which at least a part of the leveling illumination area SBL is located in the unexposed area MR, such as the shots SA1 and SA4, are displayed on the shot map on the screen by changing the color of the shot, and the like. Alternatively, the shot number to be manually shift-leveled may be specified in association with the shot numbers of the shots SA1 and SA4. In the case where a shift error of the stage occurs during the shift leveling and shift focus as described above, the error is measured in advance and the control system AFU is controlled.
And the travel error may be corrected during shift leveling and shift focus. For example, by using a wafer with a very high degree of flatness and parallelism called a super flatness wafer and performing AF and AL measurements at a plurality of arbitrary positions within the wafer, the stage travel error can be calculated as a function of location ( X, Y).

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments and can take various modifications. For example, in the case of the normal shift leveling operation, the area centroid of a portion existing inside the boundary line LL in the shot area to be exposed may be obtained, and the centroid point may be set as the shift leveling point position SF. Also, when calculating the leveling point for the normal shift leveling operation for the second type shot, the leveling point may always be found only on the straight line connecting the shot center point and the wafer center point CCw. Recently, an obliquely incident light type focus detection system (multipoint focus sensor) having a large number of detection points in addition to the center point in the projection field of view PLF has been proposed in, for example, JP-A-6-283403. Tilt detection can be performed using this multipoint focus sensor. In this case, if at least one or two or more of the detection points are in the exposure state and a shot area not located inside the boundary line LL is to be subjected to shift leveling (shift focus), the present invention is applied. Each embodiment of the invention can be applied as it is. When the multipoint focus sensor is used as a tilt detection system, a shot in which at least a part of the leveling illumination area SBL (the detection point of the multipoint focus sensor) is located in the unexposed area MR as in the fifth embodiment is described.
As for the auto focus, the shift focus may be performed similarly to the shift leveling of the fifth embodiment. The shift focus method is disclosed in detail in Japanese Patent Application Laid-Open No. 6-29186. Further, in each embodiment of the present invention, the detection point (the illumination area SBL, the center of the slit image in the case of the multi-point focus sensor) of the tilt detection system is located at the center of the projection visual field PLF. If the positional relationship with the optical axis AX (shot center point) is known in advance, it may be set anywhere. The present invention can be applied not only to the exposure of a circular wafer but also to the exposure of a plurality of shot areas on a square photosensitive substrate. Further, the present invention is also applicable to a scanning type exposure apparatus that performs exposure while moving a reticle and a wafer in synchronization with each other, and the scanning type exposure apparatus is disclosed in Japanese Patent Application Laid-Open No. 6-283403. Further, the present invention is similarly applicable to an X-ray exposure apparatus and an EB exposure apparatus.

[0045]

As described above, according to the present invention, among the chips in the shot area formed around the photosensitive substrate, those which are located inside the forbidden band having a fixed width from the edge of the substrate are almost normally tilt-aligned. Exposure is performed under the following conditions, so that there is an advantage that the chip collection rate is improved. Further, according to the present invention, since the leveling detection points are shifted in the direction of a straight line (radius) passing through the center of the photosensitive substrate, there is also an effect that the amount of movement of the substrate can be reduced. In addition, even when the detection area of the tilt detection system covers an unexposed area, the points to be leveled are shifted, so that almost normal tilt adjustment can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a projection exposure apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a focus detection system.

FIG. 3 is a diagram illustrating a configuration of a tilt detection system.

FIG. 4 is a diagram showing an arrangement of a focus detection point and a projection visual field at the time of exposure to a normal shot area.

FIG. 5 is a diagram illustrating an arrangement of a focus detection point and a projection visual field in a peripheral shot area at the time of exposure;

FIG. 6 is a flowchart illustrating a sequence according to the first embodiment.

FIG. 7 is a diagram illustrating an example of a relationship between a wafer outer shape and a shot map;

FIG. 8 is a partially enlarged view of a shot map.

FIG. 9 is a partially enlarged view of a shot map for explaining a method of the second embodiment.

FIG. 10 is a flowchart illustrating a sequence according to a third embodiment.

FIG. 11 illustrates a shift operation according to a fourth embodiment.

FIG. 12 is a diagram illustrating a shift operation according to a fifth embodiment.

[Explanation of symbols] [Explanation of symbols]

 R Reticle PA Pattern area PL Projection lens W Wafer AFU Focus position control system ALP Tilt detection system (light projector) ALR Tilt detection system (light receiver) SB Slit image (detection point) SBL Tilt detection system Illumination area MC Main control system WE Wafer outer shape Edge LL Boundary line SA Shot area Pff Forced shift focus point Psf Normal shift focus point CCw Wafer center point

Claims (8)

[Claims] 1. A step-and-repeat method in which a projection image of a rectangular pattern area formed on a mask by a projection optical system is applied to each of a plurality of shot areas on a circular photosensitive substrate mounted on a two-dimensional moving stage. A projection exposure apparatus for exposing at a predetermined position in a field of view of the projection optical system, wherein the inclination detection means detects an inclination of the surface of the photosensitive substrate with respect to a projection image plane of the projection optical system; When a substantially constant width is defined as a forbidden band from the outer peripheral edge of the photosensitive substrate, based on design layout information of the plurality of shot areas with respect to the outer shape of the photosensitive substrate, all of the forbidden bands are located outside a boundary line of the forbidden band. The position of the shot area is determined as the first type, and the detection point of the inclination detecting means is set at the boundary of the forbidden band in the shot area positioned within the field of view of the projection optical system at the time of exposure. A specific shot determining means for determining a shot area partially located inside the boundary line as the second type at the same time as the second type; when the shot area belonging to the first type is tilted at the time of exposure Temporarily moving the moving stage so that a point where a straight line passing through a specific point in the shot area and the center point of the photosensitive substrate intersects with the boundary line, or the vicinity thereof, is adjusted to a detection point of the inclination detecting means. A first shift control means for shifting the position of the photosensitive substrate; and a step of aligning the shot area belonging to the second type at the time of exposure with a point closest to the center of the photosensitive substrate in the shot area. A point located on a straight line passing through the center point and within the shot area inside the boundary line or in the vicinity thereof is adjusted to a detection point of the inclination detecting means. And a second shift control means for temporarily shifting the moving stage. 2. A projection for exposing a projection image of a rectangular pattern area formed on a mask by a projection optical system to each of a plurality of rectangular shot areas on a photosensitive substrate mounted on a two-dimensional moving stage. An exposure apparatus having at least one detection point substantially at the center of the field of view of the projection optical system;
Inclination detecting means for detecting the position of the surface of the photosensitive substrate in the direction of the projection optical axis at the detection point for inclination adjustment; and a substantially constant dimension from the outer peripheral end of the photosensitive substrate smaller than the dimension of the shot area. When the width is a forbidden band, a center point of the plurality of shot regions is located outside a boundary line of the forbidden band, based on design layout information of the plurality of shot regions with respect to the outer shape of the photosensitive substrate. A specific shot determining means for determining a specific shot area to be positioned; and, at the time of the exposure, when adjusting the inclination with respect to the specific shot area, a specific point in the shot area and a center point of the photosensitive substrate. A point located in the shot area or a shot area adjacent to the shot area on the straight line connecting Projection exposure apparatus characterized by comprising a shift control means for temporarily shifting the moving stage so as to match the detection points of the tilt detecting means. 3. A step-and-repeat method of projecting an image of a rectangular pattern area formed on a mask by a projection optical system onto each of a plurality of shot areas on a circular photosensitive substrate placed on a two-dimensional moving stage. A projection exposure apparatus for exposing at a predetermined position in a field of view of the projection optical system, wherein the inclination detection means detects an inclination of the surface of the photosensitive substrate with respect to a projection image plane of the projection optical system; When the forbidden zone has a substantially constant width from the outer peripheral edge of the photosensitive substrate, when the detection point is located in the forbidden zone in exposing the shot area, the detection point is located in a shot area near the shot area to be exposed. And a control system for controlling the stage so that the position is located and detecting the inclination in the vicinity shot. 4. The apparatus according to claim 3, wherein the control system controls the stage based on a tilt at the near shot. 5. A projection for exposing a projection image of a rectangular pattern area formed on a mask by a projection optical system to each of a plurality of rectangular shot areas on a photosensitive substrate mounted on a two-dimensional moving stage. An exposure apparatus having at least one detection point substantially at the center of the field of view of the projection optical system;
An inclination detecting means for detecting an inclination of a surface of the photosensitive substrate with respect to a predetermined reference plane; and a control unit for controlling the moving stage so that a measurement area of the inclination detecting means is always located within the shot area. A projection exposure apparatus. 6. A projection for exposing a projection image of a rectangular pattern area formed on a mask by a projection optical system to each of a plurality of rectangular shot areas on a photosensitive substrate mounted on a two-dimensional moving stage. In the exposure apparatus, an inclination detecting means for detecting an inclination of the projection optical system with respect to an image forming surface; and a determining unit for determining whether at least a part of a detection area of the inclination detecting means is located in an unexposed area. A projection exposure apparatus comprising: a shift control unit that shifts a detection area of the tilt detection unit from the shot area based on a determination result of the determination unit. 7. A plurality of rectangular shot areas on a photosensitive substrate mounted on a two-dimensional moving stage, the inclination of which is determined with respect to a predetermined reference plane by a tilt detecting means. In a projection exposure method for exposing a projection image of a rectangular pattern area formed on a mask by a projection optical system, when detecting the inclination of the shot area, the arrangement information of the shot area and the position of the shot area on the substrate are determined. Based on the exposure area information, the detection area of the inclination detection means and the shot area are relatively moved, and the inclination of the substrate in the detection area after the movement is detected, and based on the detection result, A projection exposure method characterized by performing a tilt adjustment of a shot area. 8. A plurality of rectangular shot areas on a photosensitive substrate are detected by a tilt detecting means to detect inclinations of a plurality of rectangular shot areas with respect to a predetermined reference plane. In a device manufacturing method for exposing a projection image of a pattern region by a projection optical system to form a semiconductor device on the substrate, the tilt is determined based on arrangement information of the shot region and unexposed region information on the substrate. After relatively moving the detection area of the detection means and the shot area, detecting the inclination of the substrate in the detection area after the movement, after performing the tilt adjustment of the shot area based on the detection result, A method for manufacturing an element, comprising exposing an image of the pattern area.