JPH06349707A - Alignment method - Google Patents

Abstract

PURPOSE:To perform alignment with high throughput and accuracy even if a sample shot has a nonlinear array error. CONSTITUTION:The coordinate value in a stage coordinate system (X, Y) is measured and then array coordinates in terms of calculation of each sample shot in the EGA system are obtained from the measurement result for sample shots SA1SA19 selected from a wafer W. The coordinate values in the stage coordinate system of adjacent substitution shots SB1. SB7, and SB15 are calculated for specifical sample shots SA1, SA7, and SA15 where the amount of nonlinear error obtained by subtracting the array coordinates in terms of calculation from the measurement result is large. By comparing the specifical sample shots with the amount of nonlinear error of the substitution shot, a shot used for calculating coordinates is determined.

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 which sequentially exposes a pattern image of a reticle on each shot area of a wafer on the basis of array coordinates calculated by statistical processing. The present invention relates to a position alignment method suitable for application in alignment.

[0002]

2. Description of the Related Art When a semiconductor device, a liquid crystal display device, or the like is manufactured by a photolithography process, a photosensitive material is applied with a pattern image of a photomask or reticle (hereinafter referred to as "reticle") through a projection optical system. A projection exposure apparatus is used to project each shot area on a wafer.
In recent years, as a projection exposure apparatus of this type, a wafer is placed on a stage that is two-dimensionally movable, and the wafer is stepped by this stage to form a pattern image of a reticle on each shot area on the wafer. A so-called step-and-repeat type exposure apparatus that repeats the operation of sequentially performing exposure, especially a reduction projection type exposure apparatus (stepper) is often used.

For example, since a semiconductor element is formed by stacking multiple layers of circuit patterns on a wafer, when projecting and exposing the circuit patterns of the second and subsequent layers, the circuit patterns are already formed on the wafer. Further, it is necessary to accurately align each shot area with the pattern image of the reticle, that is, accurately align the wafer and the reticle. A conventional wafer alignment method in a stepper or the like is roughly as follows (for example, Japanese Patent Laid-Open No. 61-61).
44429).

That is, a plurality of shot areas (chip patterns) each including a positioning mark called a wafer mark are formed on the wafer, and these shot areas are arranged in advance on the wafer. Are regularly arranged based on. However, even if the wafer is stepped based on the designed array coordinate values (shot arrays) of a plurality of shot areas on the wafer, the wafer is not always accurately aligned due to the following factors.

(1) Remaining rotation error of wafer θ (2) Orthogonal error of stage coordinate system (or shot arrangement) w (3) Linear expansion and contraction (scaling) of wafer Rx, Ry (4) Wafer (center position) Offset (translation) O
x, Oy

At this time, the coordinate transformation of the wafer based on these four error amounts (six parameters) can be described by a linear transformation equation. Therefore, for a wafer in which a plurality of shot areas including wafer marks are regularly arranged, the coordinate system (x, y) on the wafer is converted to the coordinate system (X, Y) on the stage as a stationary coordinate system. The first-order conversion model can be expressed as follows using the six conversion parameters a to f.

[0007]

[Equation 1]

The six conversion parameters a to f in this conversion equation are enhanced global alignments (hereinafter referred to as "EGA") using the least square approximation method as follows.
Called) method. In this case, a plurality of shot areas to be exposed on the wafer (hereinafter,
The design coordinates on the coordinate system (x, y) associated with each of several exposure shots (hereinafter referred to as “sample shots”) selected from among “exposure shots” are (x1, y). y1), (x2, y2), ..., (x
The wafer mark (n, yn) is aligned with a predetermined reference position. Then, the actual coordinate values (XM1, YM1), (XM2, YM2), ..., (XM in the coordinate system (X, Y) on the stage at that time
n, YMn) is measured.

Further, the calculated array coordinates (xi, yi) (i = 1, ..., N) of the selected wafer marks are substituted into the above-mentioned linear transformation model to obtain the calculated array coordinates. (Xi, Yi) and the measured coordinates (X
The difference (Δx, Δy) from Mi, YMi) is considered as an alignment error. The one alignment error Δx is represented by, for example, the sum of (Xi-XMi) ² with respect to i, and the other alignment error Δy is represented by, for example, the sum of (Yi-YMi) ² with respect to i.

Then, the alignment errors .DELTA.x and .DELTA.y are sequentially partially differentiated with the six conversion parameters a to f, an equation is set so that the value becomes 0, and these six simultaneous equations are solved. For example, six conversion parameters a to f are obtained. After this, the alignment of each exposure shot of the wafer can be performed based on the array coordinates calculated using the primary conversion formula with the conversion parameters a to f as coefficients.

Further, in the above EGA method, since linear approximation is performed, when the wafer to be exposed has nonlinear distortion,
There is an inconvenience that the residual error corresponding to the nonlinear distortion becomes a positioning error. Therefore, when such a distortion is present, the smaller the distance from the exposure shot position is, the smaller the influence of the non-linear error due to the distortion is. Therefore, the sample shot having a smaller distance from the exposure shot position to be calculated is weighted more. A weighted EGA method has also been proposed (for example, Japanese Patent Laid-Open No. 62-291133).
(See the official gazette). In this method, linear approximation of weighting is performed, and the offset, rotation, scaling, and orthogonality correction components of the wafer are obtained for each exposure shot, and then each exposure shot is placed at the position where only those correction components are corrected. Exposure is performed by sequentially positioning.

[0012]

When performing the alignment by the above method, the position of the selected sample shot is greatly different from the arrangement of other exposure shots due to the distortion of the wafer, the loss of the measurement mark, or the like. Consider the case of being measured as. First, in the EGA method, since it is assumed that such a sample shot is included in an array common to other exposure shots, information of a sample shot having a large array error is also included when calculating the shot array by linear approximation. Therefore, there is an inconvenience that the positional deviation of the sample shot affects the arrangement position of the entire shot. Further, when the cause of the array error is the distortion of the wafer, there is a disadvantage that the difference between the array by the linear approximation and the array including the actual distortion causes the alignment error.

When the weighted EGA method is used,
The position of each exposure shot is estimated by performing weighted least square approximation using a weighting function according to the distance between the exposure shot and the sample shot. Therefore, when a mark defect or the like occurs in the sample shot and the measurement error of the position of the wafer mark is large, the position measurement error of this sample shot and the alignment accuracy of the exposure shot around this sample shot are There is the inconvenience of having a large impact.

As described above, in the conventional method, when the sample shot has a non-linear array error, it is possible to judge whether the non-linear array error is caused by the wafer distortion or the measurement error (mark loss, etc.). Since this is not possible, there is the inconvenience that the alignment error becomes large. In view of the above-mentioned problems, it is an object of the present invention to provide an alignment method capable of aligning each exposure shot of a wafer with high accuracy and high throughput even when a sample shot has a non-linear array error. And

[0015]

As shown in FIGS. 1 and 5 to 7, a positioning method according to the present invention is performed on a sample coordinate system (x, y) set on a substrate (W). Each of the plurality of processed regions (ES1 to ESN) arranged on the substrate (W) based on the arrangement coordinates is set in a predetermined coordinate system (X, Y) that defines the moving position of the substrate (W). At the time of aligning with respect to the processing position, the coordinate positions of at least three processing regions among the plurality of processing regions on the stationary coordinate system (X, Y) are measured, and the plurality of measured positions are measured. By statistically calculating the coordinate position,
To calculate the array coordinates of each of the plurality of processed regions on the substrate (W) on the static coordinate system (X, Y) and control the moving position of the substrate (W) according to the array coordinates thus calculated. Depending on the plurality of processed regions (ES1 to ES
In the method of aligning each of N) with respect to the processing position, among the plurality of processed regions (ES1 to ESN),
At least four preselected sample areas (SA1
To SA19), the first step (step 101) of measuring the coordinate position on the stationary coordinate system (X, Y), and the first step
The second step of obtaining the nonlinear error amount which is the difference between the coordinate positions of those sample areas calculated by linear approximation from the measurement results of the step and the coordinate positions of the sample areas (SA1 to SA19) measured in the first step ( Steps 102 to 1
05) and.

Further, according to the present invention, the sample area (SA1 to S1
A19), the static coordinate system (X, X) of the alternative area (SB15) consisting of the processed area near the specific sample area (SA15) whose nonlinear error amount is larger than a predetermined allowable value.
Y) A third step (steps 106 and 107) of measuring the coordinate position on the step, the measurement result of the first step and the coordinates of the alternative area (SB15) calculated by linear approximation from the measurement result of the third step. A fourth step (steps 108 and 109) for obtaining a non-linear error amount which is a difference between the position and the coordinate position of the alternative area (SB15) measured in the third step.
And the non-linear error amount of the specific sample area (SA15) and the non-linear error amount of the alternative area (SB15) are compared to determine the coordinate position used in the calculation of the actual array coordinates (step 5). 110 to 115), and based on the coordinate position determined to be used in the fifth step and the coordinate position measured for the sample region other than the specific sample region, a plurality of processed regions (ES1 to ES1 E
The array coordinates of the (SN) on the stationary coordinate system (X, Y) are calculated.

[0017]

In general, when non-linear distortion is present in the substrate (W), the EGA performing the simple least-squares approximation and the weighted EGA performing the weighted least-squares approximation have the same sample area ( Even if the measurement result of the sample shot) is used, the target position for alignment is different. The same can be said when the measurement error of the alignment mark is large.

Here, the change in the array due to the non-linear distortion of the substrate (W) is continuous to some extent, whereas the error due to the measurement error is peculiar to this sample area and is different from the adjacent processed area. There is usually no special relationship between. In the present invention, by utilizing the difference in the change in strain between the processed regions between the non-linear strain and the measurement error in the specific sample region as described above, the processed region (ES1
~ ESN) to determine which is the cause of the sequence change. That is, if the non-linear error amount in the specific sample area (SA15) and the non-linear error amount in the alternative area (SB15) have the same tendency and the cause of the non-linear error is the non-linear distortion on the substrate (W), Using the measurement results of the sample area (SA15) and the alternative area (SB15) together with the measurement results of other sample areas, alignment is performed by, for example, the EGA method.

On the other hand, a specific sample area (SA15)
If the non-linear error amount of 1 is different from the non-linear error amount of the alternative area (SB15) and the cause of the non-linear error is the measurement error of the sample area, the measurement result of this sample area (SA15) is eliminated and the EGA method is used. Alternatively, the alignment is performed by the weighted EGA method. As a result, highly accurate alignment can be performed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the alignment method according to the present invention will be described below with reference to the drawings. FIG. 2 shows a schematic configuration of a projection exposure apparatus suitable for applying the alignment method of this embodiment. In FIG.
Illumination light IL generated from the ellipsoidal mirror 2 is reflected by the ellipsoidal mirror 2 and once condensed at its second focus, and then includes illumination optical including a collimator lens, an interference filter, an optical integrator (fly-eye lens), an aperture stop (σ stop), and the like. It is incident on the system 3. Although not shown, the fly-eye lens is arranged in the in-plane direction perpendicular to the optical axis AX so that the reticle-side focal plane of the fly-eye lens substantially coincides with the Fourier transform plane (pupil conjugate plane) of the reticle pattern.

A shutter (for example, a four-blade rotary shutter) 37 for closing and opening the optical path of the illumination light IL by a motor 38 is arranged near the second focal point of the elliptic mirror 2. As the illumination light for exposure, laser light such as an excimer laser (KrF excimer laser, ArF excimer laser) or a harmonic wave of a metal vapor laser or a YAG laser is used in addition to the bright line of the ultra-high pressure mercury lamp 1 or the like. It doesn't matter.

In FIG. 2, illumination light (i-line, etc.) in a wavelength range in which the photoresist layer emitted from the illumination optical system 3 is exposed to light.
Most of the IL is reflected by the beam splitter 4, and then passes through the first relay lens 5, the variable field stop (reticle blind) 6 and the second relay lens 7 to reach the mirror 8. Then, the illumination light IL reflected by the mirror 8 in a substantially vertically downward direction illuminates the pattern area PA of the reticle R with substantially uniform illuminance via the main condenser lens 9. The arrangement surface of the reticle blind 6 and the pattern formation surface of the reticle R are in a conjugate relationship (image formation relationship), and the drive system 3
By opening and closing a plurality of movable blades constituting the reticle blind 6 by 6 to change the size and shape of the opening, the illumination field of the reticle R can be arbitrarily set.

In the reticle R of the present embodiment, reticle marks serving as alignment marks are formed at substantially central portions of the four sides of the pattern area PA surrounded by the light-shielding band. By projecting the images of these reticle marks onto the photoresist layer of the wafer W, the images of these reticle marks are formed as latent images on the photoresist layer. Further, in the present embodiment, these reticle marks are also used as alignment marks when aligning each shot area of the wafer W with the reticle R. The four reticle marks have the same configuration (however, the directions are different). For example, one certain reticle mark is a diffraction grating mark composed of seven dot marks arranged in the Y direction, and is separated by a predetermined distance in the X direction. It is a multi-mark arranged in 5 columns. The reticle marks are formed by a light-shielding portion such as chrome inside a transparent window provided in the light-shielding band of the reticle R. Further, on the reticle R, alignment marks composed of two cross-shaped light-shielding marks are formed facing each other in the vicinity of the outer periphery of the reticle R. These two alignment marks are used for alignment of the reticle R (positioning with respect to the optical axis AX of the projection optical system 13).

The reticle R is mounted on a reticle stage RS which can be finely moved in the direction of the optical axis AX of the projection optical system 13 by a motor 12, and can be two-dimensionally moved and finely rotated in a horizontal plane perpendicular to the optical axis AX. It is placed. At the end of the reticle stage RS, a movable mirror 11m that reflects a laser beam from a laser light wave interferometer (laser interferometer) 11
Is fixed, and the two-dimensional position of the reticle stage RS is constantly detected by the laser interferometer 11 with a resolution of, for example, about 0.01 μm. Reticle alignment systems (RA systems) 10A and 10B are arranged above the reticle R, and these RA systems 10A and 10B are mounted on the reticle R.
Two cross-shaped alignment marks formed near the outer periphery of the are detected. By finely moving the reticle stage RS based on the measurement signals from the RA systems 10A and 10B, the reticle R is positioned so that the center point of the pattern area PA coincides with the optical axis AX of the projection optical system 13.

The illumination light IL that has passed through the pattern area PA of the reticle R enters the projection optical system 13 that is telecentric on both sides, and is projected by the projection optical system 13 to a projected image of the circuit pattern of the reticle R that is reduced to 1/5. However, a photoresist layer is formed on the surface, and the surface is projected (imaged) so as to be superposed on one exposure shot on the wafer W held so that the surface substantially coincides with the best imaging plane of the projection optical system 13. It

The wafer W is vacuum-sucked by a finely rotatable wafer holder (not shown), and is held on the wafer stage WS via this wafer holder. The wafer stage WS is configured to be two-dimensionally movable in a step-and-repeat manner by a motor 16,
When the transfer exposure of the reticle R for one exposure shot is completed, the wafer stage WS is stepped to the next shot position. A movable mirror 15 that reflects the laser beam from the laser interferometer 15 is provided at the end of the wafer stage WS.
m is fixed, and the two-dimensional coordinates of the wafer stage WS are constantly detected by the laser interferometer 15 with a resolution of about 0.01 μm, for example. The laser interferometer 15 is
The coordinates of one direction perpendicular to the optical axis AX of the projection optical system 13 of the wafer stage WS (referred to as the X direction) and the Y direction perpendicular thereto are measured, and the coordinates in the X direction and the Y direction are measured. A stage coordinate system (stationary coordinate system) (X, Y) of wafer stage WS is defined. That is, the coordinate value of the wafer stage WS measured by the laser interferometer 15 is the coordinate value on the stage coordinate system (X, Y).

On the wafer stage WS, a reference member (glass substrate) 14 provided with a reference mark used when measuring a baseline amount (described later) or the like has almost the same height as the exposed surface of the wafer W. Is provided. The reference member 14 has, as a reference mark, a slit pattern composed of five light-transmitting L-shaped patterns and two sets of reference patterns formed of light-reflecting chrome (duty ratio is 1:
1) and are provided. One set of reference patterns is
A diffraction grating mark formed by arranging 7 dot marks arranged in the Y direction in three rows in the X direction, a diffraction grating mark formed by arranging three linear patterns in the X direction, and 12 extending in the Y direction. The bar marks of the book are arranged in the X direction. The other set of reference patterns is the one set of reference patterns rotated by 90 °.

Now, the slit pattern formed on the reference member 14 is illuminated from below (inside the wafer stage) by the illumination light (exposure light) transmitted below the reference member 14 using an optical fiber (not shown) or the like. Is configured to. The illumination light transmitted through the slit pattern of the reference member 14 forms a projected image of the slit pattern on the back surface (pattern surface) of the reticle R via the projection optical system 13. Further, the illumination light passing through any of the four reticle marks on the reticle R reaches the beam splitter 4 through the main condenser lens 9, the relay lenses 7 and 5, and the like.
The illumination light transmitted through the beam splitter 4 is received by a photoelectric detector 35 arranged near the pupil conjugate plane of the projection optical system 13. The photoelectric detector 35 outputs a photoelectric signal SS corresponding to the intensity of the illumination light to the main control system 18. In the following, an optical fiber (not shown), the reference member 14 and the photoelectric detector 3
5 is collectively called an ISS (Imaging Slit Sensor) system.

Further, in FIG. 2, an image formation characteristic correction unit 19 capable of adjusting the image formation characteristic of the projection optical system 13 is also provided.
The imaging characteristic correction unit 19 in this embodiment is the projection optical system 1
Some of the lens elements that make up part 3, especially reticle R
By independently driving (moving or tilting in a direction parallel to the optical axis AX) each of the plurality of lens elements close to each other by using a piezoelectric element such as a piezo element, For example, it corrects projection magnification and distortion.

Next, an off-axis type alignment sensor (hereinafter referred to as "Field Imag") is provided on the side of the projection optical system 13.
e Alignment system (FIA system) ”is provided. In this FIA system, the light generated by the halogen lamp 20 is converted into the condenser lens 21 and the optical fiber 22.
It is guided to the interference filter 23 through the light source, and the light in the photosensitive wavelength region and the infrared wavelength region of the resist layer is cut off there. The light transmitted through the interference filter 23 enters the telecentric objective lens 27 via the lens system 24, the beam splitter 25, the mirror 26 and the field stop BR. The light emitted from the objective lens 27 is reflected by a prism (or mirror) 28 fixed around the lower part of the lens barrel of the projection optical system 13 so as not to block the illumination visual field of the projection optical system 13, and the wafer W is almost vertical. To irradiate.

The light from the objective lens 27 is applied to the partial area including the wafer mark (base mark) on the wafer W, and the light reflected from the area is the prism 28, the objective lens 27, the field stop BR, and the mirror 26. , Is guided to the index plate 30 via the beam splitter 25 and the lens system 29. Here, the index plate 30 is arranged in a plane conjugate with the wafer W with respect to the objective lens 27 and the lens system 29, and the image of the wafer mark on the wafer W is formed in the transparent window of the index plate 30. Further, the index plate 30 is formed with two linear marks extending in the Y direction at predetermined intervals in the X direction as index marks in the transparent window.
The light that has passed through the index plate 30 receives the first relay lens system 31,
The image of the wafer mark and the image of the index mark are formed on the light receiving surface of the image pickup device 34 by being guided to the image pickup device (CCD camera etc.) 34 via the mirror 32 and the second relay lens system 33. The image pickup signal SV from the image pickup device 34 is supplied to the main control system 1
8, the position (coordinate value) of the wafer mark in the X direction is calculated. Although not shown in FIG. 2, in addition to the FIA system having the above configuration (FIA system for X axis),
Another set of FIA for detecting mark position in Y direction
A system (FIA system for Y axis) is also provided.

Next, TT is provided on the upper side of the projection optical system 13.
An L (through the lens) type alignment sensor 17 is also arranged, and the position detection light from the alignment sensor 17 is transmitted through the mirrors M1 and M2 to the projection optical system 1.
It is led to 3. The light for detecting the position is the projection optical system 1
The wafer W on the wafer W is irradiated with the reflected light from the wafer W via the projection optical system 13, the mirror M2, and the mirror M1, and the alignment sensor 17
Returned to. The alignment sensor 17 obtains the position of the wafer mark on the wafer W from the signal obtained by photoelectrically converting the returned reflected light.

FIG. 3 shows a detailed configuration of the TTL type alignment sensor 17 in FIG. 2. In FIG. 3, the alignment sensor 17 of this example is a two-beam interference type alignment system (hereinafter referred to as “LIA system”). ) And a laser step alignment type alignment system (hereinafter referred to as “LSA system”), and the optical members thereof are maximally shared. Although briefly described here, a more specific configuration is disclosed in Japanese Patent Laid-Open No. 2-272305.

In FIG. 3, a laser beam emitted from a light source (He-Ne laser light source or the like) 40 is split by a beam splitter 41, and the laser beam reflected here is passed through a shutter 42 to a first beam shaping optical system. (LI
A optical system) 45. On the other hand, the laser beam transmitted through the beam splitter 41 enters the second beam shaping optical system (LSA optical system) 46 via the shutter 43 and the mirror 44. Therefore, the shutters 42 and 43
Can be used by switching between the LIA system and the LSA system by appropriately driving.

The LIA optical system 45 includes two sets of acousto-optic modulators and the like, and emits two laser beams having a predetermined frequency difference Δf substantially symmetrically with respect to the optical axis.
Further, the two laser beams emitted from the LIA optical system 45 reach the beam splitter 49 via the mirror 47 and the beam splitter 48, and the two laser beams transmitted therethrough are a lens system (inverse Fourier transform lens). 5
The light enters the reference diffraction grating 55, which is fixed on the apparatus, from two different directions at a predetermined crossing angle, and forms an image (crossing) through the mirror 3 and the mirror 54. The photoelectric detector 56 receives the interference light of the diffracted lights that are transmitted through the reference diffraction grating 55 and generated in substantially the same direction, and outputs a sinusoidal photoelectric signal SR corresponding to the intensity of the diffracted light to the main control system 18 (FIG. 2))
It is output to the A arithmetic unit 58.

On the other hand, the two laser beams reflected by the beam splitter 49 intersect once at the opening of the field stop 51 by the objective lens 50, and then the mirror M2 (see FIG. 2).
The inside mirror M1 is incident on the projection optical system 13 via a mirror (not shown). Further, the two laser beams incident on the projection optical system 13 become substantially symmetrical with respect to the optical axis AX on the pupil plane of the projection optical system 13 and once converged in a spot shape. The parallel luminous fluxes are inclined with respect to the direction (Y direction) with respect to each other with the optical axis AX in between, and become parallel luminous fluxes, which are incident on the wafer mark from two different directions at a predetermined crossing angle. A one-dimensional interference fringe that moves at a speed corresponding to the frequency difference Δf is formed on the wafer mark, and the ± first-order diffracted light (interference light) generated in the same direction from the mark, that is, the optical axis direction in this case, is projected by the projection optical system. The light is received by the photoelectric detector 52 via the system 13, the objective lens 50, etc., and the photoelectric detector 52 receives the sine-wave photoelectric signal S corresponding to the cycle of the change in brightness of the interference fringes.
Dw is output to the LIA operation unit 58. The LIA calculation unit 58 calculates the position deviation amount of the wafer mark from the phase difference on the waveforms of the two photoelectric signals SR and SDw, and uses the position signal PDs from the laser interferometer 15 to calculate the position deviation amount. The coordinate position of the wafer stage WS when it becomes zero is obtained, and this information is output to the alignment data storage unit 61 (see FIG. 4).

The LSA optical system 46 includes a beam expander, a cylindrical lens, etc., and the laser beam emitted from the LSA optical system 46 enters the objective lens 50 via the beam splitters 48 and 49. Further, the laser beam emitted from the objective lens 50 once converges into a slit shape at the opening of the field stop 51, and then enters the projection optical system 13 via the mirror M2. The laser beam incident on the projection optical system 13 passes through almost the center of its pupil plane, then extends in the X direction within the image field of the projection optical system 13 and is directed to the optical axis AX as an elongated strip-shaped spot light on the wafer. Projected onto W.

When the spot light and the wafer mark (diffraction grating mark) on the wafer W are moved relative to each other in the Y direction, the light generated from the wafer mark passes through the projection optical system 13, the objective lens 50 and the like and is a photoelectric detector. The light is received at 52. The photoelectric detector 52 has ± 1st order of the light from the wafer mark.
Only the third-order diffracted light is photoelectrically converted, and the photoelectric signal SDi corresponding to the light intensity obtained by photoelectrically converting in this manner is used as the main control system
It is output to the LSA calculation unit 57 in the inside. The LSA arithmetic unit 57 has a position signal PDs from the laser interferometer 15.
Also, the LSA calculation unit 57 samples the photoelectric signal SDi in synchronization with the up / down pulse generated for each unit movement amount of the wafer stage WS. Furthermore, LS
The A calculation unit 57 converts each sampling value into a digital value and stores it in the memory in the order of addresses, then calculates the position of the wafer mark in the Y direction by a predetermined calculation process, and stores this information in the alignment data storage of FIG. It is output to the unit 61.

Next, the structure of the main control system 18 shown in FIG. 2 will be described with reference to FIG. FIG. 4 shows the main control system 18 of this example and the members related thereto. In FIG.
Arithmetic unit 57, LIA arithmetic unit 58, FIA arithmetic unit 59, alignment data storage unit 61, EG
A calculation unit 62, storage unit 63, shot map data unit 64, system controller 65, wafer stage controller 66, and reticle stage controller 6
A main control system 18 is composed of 7. Among these members, the LSA arithmetic unit 57 and the LIA arithmetic unit 5
8 and the FIA arithmetic unit 59 obtains the coordinate position of each wafer mark in the stage coordinate system (X, Y) from the supplied photoelectric signal, and supplies the obtained coordinate position to the alignment data storage unit 61. Information on the measured coordinate position of the alignment data storage unit 61 is supplied to the EGA arithmetic unit 62.

The shot map data storage unit 64 stores the designed array coordinate values of the wafer marks belonging to each exposure shot on the wafer W in the coordinate system (x, y) on the wafer W. The array coordinate value of is also supplied to the EGA calculation unit 62. Based on the measured coordinate values and the designed coordinate values, the EGA calculation unit 62 uses the least squares method to convert the designed array coordinate values in the coordinate system (x, y) on the wafer W into the stage coordinate system (X , Y) to obtain six conversion parameters (corresponding to the conversion parameters a to f of (Equation 1)) for calculating the calculated array coordinate value,
The conversion parameters a to f are supplied to the storage unit 63.

Further, the EGA arithmetic unit 62 uses the conversion parameters a to f stored in such a manner as the wafer W.
Calculate the calculated array coordinate value in the stage coordinate system (X, Y) from the designed array coordinate value in the above coordinate system (x, y),
The calculated array coordinate value is supplied to the system controller 65. In response to this, the system controller 65
2 drives the wafer stage WS of FIG. 2 via the motor 16 while monitoring the measurement value of the laser interferometer 15 via the wafer stage controller 66, thereby positioning each shot area on the wafer W and each shot area. Exposure to. At this time, off-axis FIA system, LI
Observation center of alignment sensor of A system and alignment sensor of LSA system, and optical axis AX of projection optical system 13
The baseline amount, which is the interval between and, has been measured in advance,
Each exposure shot on the wafer W is positioned at the coordinate value obtained by adding the baseline amount to the calculated array coordinate value obtained as described above. Further, the system controller 65 is a reticle stage controller 67.
While monitoring the measurement value of the laser interferometer 11 via
The reticle stage RS shown in FIG. 2 is driven via the motor 12 to adjust the position of the reticle R.

Next, with reference to the flow chart of FIG. 1, the operation of positioning each exposure shot of the wafer to be exposed in this example and projecting and exposing the pattern image of the reticle R on each exposure shot will be described. explain. First, the wafer W to be exposed is loaded on the wafer stage WS shown in FIG. FIG. 5A shows an array of exposure shots on the wafer W. In FIG. 5A, the wafer W is regularly arranged along the coordinate system (x, y) set on the wafer W. Exposure shots ES1, ES2, ..., ESN are formed, and a chip pattern is formed on each exposure shot ESi by the steps up to that point. Further, each exposure shot ESj is separated by a street line having a predetermined width in the x direction and the y direction, and a wafer mark Mxj in the X direction is formed at the center of the street line extending in the x direction in the vicinity of each exposure shot ESj. Each exposure shot E
A wafer mark Myj in the Y direction is formed at the center of the street line extending in the y direction near the Si. X
The wafer mark Mxj for the direction and the wafer mark Myj for the Y direction are 3 at a predetermined pitch in the x direction and the y direction, respectively.
The linear patterns of a book are arranged, and these patterns are formed as concave or convex patterns on the base of the wafer W. In FIG. 5, only the wafer marks attached to the exposure shot ESj and the sample shot SAi described later are shown.

Then, in step 101 of FIG.
As shown in FIG. 5A, 19 sample shots SA1 preselected from all exposure shots of the wafer W
Up to SA19, the coordinates <Am (i)> on the stage coordinate system (X, Y) are measured (i = 1 to 19). Wafer marks for the X direction and the Y direction are also formed close to each of the sample shots SA1 to SA19.
In this example, by measuring these positions, the stage coordinate system (X,
Y) Measure the coordinate position on. Specifically, the imaging signal of the wafer mark Mxi belonging to the sample shot SAi is
For example, the wafer mark Mx is supplied to the FIA calculation unit 59 shown in FIG. 4 via the image pickup device 34 shown in FIG.
The position of i in the X direction is detected.

FIG. 6 shows a state of the wafer mark Mxi imaged by the FIA type image pickup device 34 of FIG. 2, and an image pickup signal obtained at that time is supplied to the FIA arithmetic unit 59 of FIG. As shown in FIG. 6, within the imaging visual field VSA of the image sensor 34, the wafer marks Mxi each having three linear patterns and the index mark FM1 formed on the index plate 30 in FIG. , FM2 are arranged. The image sensor 34 electrically scans the images of the wafer mark Mx1 and the index marks FM1 and FM2 along the horizontal scanning line VL. At this time, since only one scanning line is disadvantageous in terms of SN ratio, it is possible to add and average the levels of the imaging signals obtained by a plurality of horizontal scanning lines within the imaging visual field VSA for each pixel in the horizontal direction. desirable. As a result, the position of the wafer mark Mxi in the X direction is measured, and the sample shot SA is similarly measured by the FIA system for the Y direction.
The position of the wafer mark Myi belonging to i in the Y direction is measured.

FIG. 5 (b) shows another example of the wafer mark. In FIG. 5 (b), a wafer mark MAX formed of a diffraction grating pattern having a predetermined pitch in the X direction, which is the measurement direction, is formed. Has been done. This wafer mark M
In order to detect the position of Ax, the two laser beams BM ₁ and BM ₂ emitted from the LIA optical system 45 (see FIG. 3) in the alignment sensor 17 of FIG. Irradiate on. Its pitch in the X direction of the crossing angle and the wafer mark MAx is the laser beam BM ₁ -1 order diffracted light B ₁ from the wafer mark MAx by (-1) and the laser beam BM ₂ +1 order diffracted light B ₂ from the wafer mark MAx by (+) Is set to be parallel. The interference light of the -1st-order diffracted light B ₁ (-1) and the + _1st-order diffracted light B ₂ (+) is converted into a photoelectric signal SDw by the photoelectric detector 52 of FIG. 3, and this photoelectric signal SDw is supplied to the LIA operation unit 58. In the LIA arithmetic unit 58,
The amount of misalignment of the wafer mark MAx in the X direction is calculated from the phase difference between the photoelectric signal SR as the reference signal and the photoelectric signal SDw.

FIG. 5C shows still another example of the wafer mark. In FIG. 5C, the dot marks are arranged at a predetermined pitch in the Y direction perpendicular to the X direction which is the measurement direction. The wafer mark MBx is formed.
To detect the position of the wafer mark MBx, the LSA optical system 46 (see FIG. 3) in the alignment sensor 17 of FIG.
The laser beam emitted from the laser beam is emitted as slit-shaped spot light LXS that is long in the Y direction in the vicinity of the wafer mark MBx. When the wafer stage WS of FIG. 2 is driven and the wafer mark MBx is scanned with respect to the spot light LXS, in a range in which the spot light LXS scans the wafer mark MBx, the wafer mark MBx is moved in a predetermined direction from the wafer mark MBx. Diffracted light is emitted to. A photoelectric signal SDi obtained by photoelectrically converting the diffracted light by the photoelectric detector 52 of FIG. 3 is supplied to the LSA operation unit 57, and LS
The A calculation unit 57 obtains the position of the wafer mark MBy in the X direction based on the set measurement parameter. Similarly, the coordinate values of the other sample shots SA2 to SA9 in the stage coordinate system (X, Y) are measured, and these measured coordinate values are sent to the EGA operation unit 62 via the alignment data storage unit 61 of FIG. Supplied.

Next, at step 102, the values of the coordinate conversion parameters a to f satisfying (Equation 1) are obtained from the measurement results (alignment data) of the sample shots SA1 to SA19 by the least square method. This is called EGA calculation. Specifically, the EGA calculation unit 62 of FIG.
Are the six conversion parameters a to satisfy (Equation 1) based on the designed coordinate values of the wafer mark and the measured coordinate values.
The value of f is obtained using, for example, a simple least square method. That is, the measured coordinate value of the nth sample shot SAn on the stage coordinate system is (XM _n , YM _n ), and the coordinate value calculated from the designed coordinate value based on (Equation 1) is (X _n , Y _n ), the residual error component is expressed by the following equation.
However, in the example of FIG. 5A, the value of m is 19.

[0048]

[Equation 2]

Then, the values of the conversion parameters a to f of (Equation 1) are determined so that this residual error component is minimized.
Next, in step 103, the initial value of the variable i is set to 1, and in step 104, the EGA arithmetic unit 62
Is the design coordinate value and the conversion parameter a obtained in step 102 for the i-th sample shot SAi.
The calculated array coordinate value (X _i , Y _i ) is obtained using ~ f. The calculated array coordinate value (X _i , Y _i ) is represented by the vector format coordinate <Ae (i)>.

Next, at step 105, the coordinate <Ae (i)> is subtracted from the coordinate <Am (i)> measured at step 101 to obtain a sample shot SAi.
Error vector <NLa (i)> of the array error of
Ask for. Then, in step 106, it is judged whether or not the absolute value of the nonlinear error vector <NLa (i)> is larger than the set nonlinear error allowable value NLc. If | <NLa (i)> | ≦ NLc, the nonlinear error amount in the sample shot SAi is small, the process proceeds to step 114, and the alignment data of the sample shot SAi is valid, and then step 113
Proceed to.

On the other hand, in step 106, | <NLa
If (i)>|> NLc, the process proceeds to step 107,
The exposure shot adjacent to the sample shot SAi is selected as the alternative shot SBi, and the coordinates <Bm (i)> of the wafer mark attached to the alternative shot SBi in the stage coordinate system (X, Y) are measured. FIG. 7A is a diagram of FIG.
Sample shots SA1 to SA19 of the wafer W in (a)
The exaggerated example of the non-linear error amount of is shown in FIG.
, The nonlinear error amount in the sample shot SAi is represented by the nonlinear error vector <NLa (i)>, and the starting point Pi of this nonlinear error vector <NLa (i)> is
The calculated coordinate value of the sample shot SAi (the coordinate value including the linear error amount) and the end point Qi of the vector represent the measured coordinate value of the sample shot SAi. The non-linear error amounts of the other sample shots are also represented by the non-linear error vector. Then, in the example of FIG.
The nonlinear error vector of sample shots SA1, SA7 and SA15 is large. Therefore, for example, the coordinate values in the stage coordinate system (X, Y) of the alternative shots SB1, SB7, and SB15 adjacent to the sample shots SA1, SA7, and SA15 are measured.

At the next step 108, EGA calculation is performed using the alternative shot SBi and the alignment data results of all other sample shots. That is, the values of the conversion parameters a to f that satisfy (Equation 1) are obtained. Then, for the substitute shot SBi, the calculated array coordinates <Be (i)> are calculated using the design coordinate values and the conversion parameters a to f obtained as described above.

Next, at step 109, the coordinate <Bm (i)> measured at step 107 is subtracted from the coordinate <Be (i)> to obtain the non-linear error vector <NLb (i) of the array error of the alternative shot SBi. 〉 Is required. Then, in step 110, it is judged whether or not the absolute value of the nonlinear error vector <NLb (i)> is larger than the nonlinear error allowable value NLc. Where | <NLb
If (i)>|> NLc, the process proceeds to step 111. On the contrary, if | <NLb (i)> | ≦ NLc, it is determined that the non-linear error amount of the alignment data measured by the sample shot SAi is due to the measurement error, and step 1
In step 15, the alignment data of the alternative shot SBi is validated, and the process proceeds to step 113. Therefore, the alignment data of the sample shot SAi is no longer used.

In step 111, the non-linear error vector <NLa (i)> and the non-linear error vector <NLb
(I)>. Absolute value of the difference | <NLb
If (i)>-<NLa (i)> | is larger than a predetermined nonlinear error change allowable amount ΔNL0, the sample shot S
It is assumed that the cause of the difference in the non-linear error amount between Ai and the alternative shot SBi is not the non-linear distortion of the wafer but the measurement error. That is, it is determined that the random non-linear error amount is large, and the process proceeds to step 112, where the alignment data of both the sample shot SAi and the alternative shot SBi is valid, and then the process proceeds to step 113.

On the other hand, in step 111, the non-linear error change amount | <NLb (i)>-<NLa (i)> | is Δ.
If it is smaller than NL0, it is determined that the main cause of the change in the non-linear error is the non-linear distortion of the wafer, and the alignment data of the sample shot SAi is validated in step 114, and the process proceeds to step 113. In this step 113,
It is determined whether the variable i has reached the number m of sample shots. When i <m, the value of the variable i is incremented by 1 in step 116, and then the process returns to step 104. If i = m in step 113, the process proceeds to step 117.

In step 117, the values of the conversion parameters a to f that satisfy (Equation 1) are determined by the weighted EGA method using the alignment data that has been validated so far. In the following, the weighted EGA method is shown in FIG.
The explanation will be given with reference to. For simplicity, it is assumed that the total number of the sample shots and the alternative shots for which the alignment data is valid is nine, and these nine shots are sample shots SA1 to SA9 in FIG. 9 again. In FIG. 9, when determining the calculated coordinate position of the i-th exposure shot ESi on the wafer W, between this exposure shot ESi and m (m = 9 in FIG. 9) sample shots SA1 to SA9. A weight W _in is given to each of the measured coordinate positions (alignment data) of the nine sample shots according to the distances LK1 to LK9. Therefore, the following residual error component Ei is defined.

[0057]

[Equation 3]

Then, the conversion parameter a of (Equation 1) is set so that the residual error component Ei defined in this way is minimized.
The value of ~ f is determined. Here, the sample shots SA1 to SA9 used for each exposure shot ESi are the same, but naturally the distance to each sample shot SAn is different for each exposure shot ESi. Therefore, the weight W _in given to the alignment data of the sample shot SAn changes for each exposure shot ESi. Then, the conversion parameters a to f are determined for each exposure shot ESi,
By calculating the calculated coordinate position from (Equation 1),
The calculated array coordinates (shot array) of all exposure shots on the wafer W are determined. The exposure shot ESi is positioned at the coordinate value obtained by correcting the baseline amount in the array coordinates calculated in this way, and the pattern of the reticle is exposed in that state. When the exposure for all the exposure shots on the wafer is completed in this way, the wafer is replaced, and the next wafer is replaced with step 10 in FIG.
1 to 117 are repeated.

[0059] In this method, for each of the exposure shot ESi on the wafer W, the weight W _in changes with respect to the alignment data of each sample shot SAn. As an example, the weight W _in is expressed as follows as a function of the distance LKn between the i-th exposure shot ESi and the n-th sample shot SAn. However, the parameter S is a parameter for changing the degree of weighting.

[0060]

[Equation 4]

As is clear from this (Equation 4), the shorter the distance LKn to the i-th exposure shot ESi, the shorter the sample shot SAn, the greater the weight W _in given to the alignment data. Further, in (Equation 4), when the value of the parameter S is sufficiently large, the result of the statistical calculation processing is almost equal to the result obtained by the method of the first embodiment. On the other hand, when all the exposure shots ESi on the wafer are sample shots SAn and the value of the parameter S is made sufficiently close to zero, the position of the wafer mark is measured for each exposure shot to perform alignment, that is, a so-called die-by-die method. Is almost equal to the result obtained in. That is, W1-EG
In the method based on the A method, an intermediate effect between the EGA method and the die-by-die method can be obtained by setting the parameter S to an appropriate value. Furthermore, the weighting function of (Equation 4) is the wafer mark Mxi for the X direction.
And the wafer mark Myi for the Y direction are separately prepared, and the weight W _in can be set independently for the X direction and the Y direction. Therefore, the degree of nonlinear distortion of the wafer (magnitude), regularity or step pitch, that is, the center-to-center distance between two adjacent shot areas (depending on the width of the street line on the wafer, a value approximately corresponding to the shot size) ) Is different in the X and Y directions, the shot arrangement error on the wafer can be corrected with high accuracy by setting the value of the parameter S independently. At this time, the value of the parameter S may be different in the X direction and the Y direction as described above, and the parameter S may be the same or different in the X direction and the Y direction. The value of S is
It may be appropriately changed according to the magnitude of the “regular non-linear distortion”, the regularity, the step pitch, the measurement reproducibility of the alignment sensor, or the like.

Next, a modified example of the above-mentioned weighted EGA method will be described with reference to FIG. Here, in order to simplify the explanation, it is assumed that the wafer W is regularly and particularly point-symmetrically subjected to non-linear distortion, and the center of the point symmetry coincides with the center of the wafer W (wafer center). Figure 10
Shows a wafer W to be exposed in this example. In FIG. 9, the deformation center point of the wafer W (the center of point symmetry of the nonlinear distortion), that is, the wafer center Wc, and the i-th exposure shot ESi on the wafer W are shown. The distance (radius) between the two is LEi, and the wafer center Wc is m (m = 9 in FIG. 10).
The distance (radius) between each of the sample shots SA1 to SA9 is LW1 to LW9. Then, similarly to the example of FIG. 9, a weight W _in ′ is given to each of the alignment data of the nine sample shots SA1 to SA9 according to the distance LEi and the distances LW1 to LW9. In this method, the two sets of wafer marks (M
After detecting (xi, Myi), the residual error component Ei ′ is defined by the following (Equation 5) as in (Equation 3).
The values of the conversion parameters a to f in (Equation 1) are determined so that

[0063]

[Equation 5]

Also in this method, the weight W _in ′ given to the alignment data changes for each exposure shot ESi.
A statistical calculation is performed for each exposure shot ESi to determine the conversion parameters a to f, and the calculated array coordinate values are determined. Then, each exposure shot E on the wafer W
Each Si, 'to change the weights W _in the equation (5)' weight W _in for each sample shots, i th exposure shot ESi and the wafer center W on the wafer W
It is expressed as a function of the distance (radius) LEi from c as follows. However, the parameter S is a parameter for changing the degree of weighting.

[0065]

[Equation 6]

As is clear from this (Equation 6), the distance L from the sample shot SAn to the wafer center Wc.
A sample shot in which Wn is closer to the distance LEi between the wafer center Wc and the i-th exposure shot ESi on the wafer W has a weight W _in ′ given to the alignment data.
Is becoming larger. In other words, the largest weight W _in ′ is given to the alignment data of the sample shot located on the circle having the radius LEi centered on the wafer enter Wc, and the weight W to the alignment data is increased as the distance from the circle in the radial direction increases. _in ′ is getting smaller.

Further, according to this method, a plurality of shot areas located substantially equidistant from the center of point symmetry on the wafer W, that is, a plurality of shot areas located on the same circle centered on the center of point symmetry are used. Of course, the weights W _in ′ given to the alignment data of the sample shots are the same. For this reason, when a plurality of exposure shots are located on the same circle centered on the point symmetry center, the above-mentioned weighting and statistical calculation are performed in only one of the shot areas to convert the conversion parameters a to f. If calculated, the previously calculated parameters a to f are calculated for the remaining shot areas.
Can be used as is to determine its coordinate position. This has the advantage of reducing the amount of calculation for determining the coordinate position.

Next, a method of determining the parameter S representing the degree of weighting in the above weighted EGA method will be described. First, as an example, the value of the parameter S can be determined by the following equation. In this equation, D is a weighting parameter, and the operator sets the value of the weighting parameter D to a predetermined value to automatically determine the parameter S, and thus the weightings W _in and W _in ′.

[0069]

S = D ² / (8 · log _e 10) The physical meaning of this weight parameter D is that the range of sample shots effective for calculating the coordinate position of each shot area on the wafer (hereinafter, simply "Zone").
That is, when the zone is large, the number of effective sample shots is large, and the result is close to the result obtained by the conventional EGA method. On the contrary, when the zone is small, the number of valid sample shots is small, and the result is close to the result obtained by the die-by-die method. However, the zone referred to here is just a reference value for weighting, and even if all the sample shots exist outside the zone, the sample shot closest to the shot area where the coordinate position should be determined. The statistical calculation is performed by maximizing the weight related to the alignment data of.

The equation for determining the parameter S is (Equation 1
Not limited to (0), the following (Equation 11) can be used, for example. However, the area of the wafer is A [mm ² ], the number of sample shots is m, and the correction coefficient (positive real number) is C.

[0071]

[Equation 8] S = A / (m · C) This (Equation 11) reflects the change in the wafer size (area) and the number of sample shots in the determination of the parameter S, and is a correction coefficient to be used in the determination. The optimum value of C does not fluctuate too much. When the correction coefficient C is small, the value of the parameter S becomes large, and EG
The result is close to the result obtained by the method based on the A method, and when the correction coefficient C is large, the value of the parameter S is small, and thus it is close to the result obtained by the die-by-die method. Therefore, the parameter S indicating the degree of weighting for the alignment data can be obtained from (Equation 8) only by inputting the correction coefficient C determined in advance by experiments or simulations to the exposure apparatus via the operator or the identification code reading apparatus. Further, the weights W _in and W _in ′ are automatically determined from (Equation 4) and (Equation 6).

FIG. 7B shows the distribution of the residual error component (non-linear error amount) when the wafer W having the shot arrangement error as shown in FIG. 7A is aligned using the above method. Show. In FIG. 7A, 19 sample shots SA1 to SA19 are selected, and there are three sample shots SA1, SA7, and SA15 having a large non-linear error amount. On the other hand, alternative shots SB1, SB7, S
B15 are sample shots SA1, SA7, S respectively
An exposure shot on the side closer to the center of the wafer with respect to A15 was selected. Then, in that case, the weight parameter D used in (Equation 7) is set to 100 mm, and the nonlinear error allowable value NLc is set.
Is 0.1 μm, and the allowable amount of nonlinear error change ΔNL0 is 0.0
It was 4 μm.

In FIG. 7B, the exposure shot ESj
For, the nonlinear error vector <NLa (j)> indicates the error from the calculated array coordinates to the actual array coordinates. Also, only for sample shot SA15,
Although the amount of non-linear error is large, alignment may be performed by a die-by-die method for such a specific sample shot. Further, in step 105 of FIG. 1, if the absolute values of the non-linear error vectors of all the sample shots are equal to or less than a predetermined allowable value (allowable value for using EGA) NL0, alignment may be performed by the normal EGA method. good. An example of the allowable value NL0 is 0.1 μm.

For reference, the wafer W shown in FIG.
On the other hand, FIG. 8A shows the state of the nonlinear error when the alignment is performed by the conventional normal EGA method, and FIG. 8A shows the state of the nonlinear error when the alignment is performed by the conventional weighted EGA method. Shown in b). 7 (b) and 8
By comparing (a) and (b), it can be seen that the nonlinear error amount is reduced as a whole in the method of this embodiment.

The present invention is not limited to the above-described embodiments, but is also applicable to alignment in a projection exposure apparatus of so-called slit scan exposure system, for example. Further, the shot arrangement on the wafer, the number and position of sample shots, the method of determining alternative shots, the size of each allowable value, and the like may be those other than the above values and methods. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0076]

According to the present invention, when there is a specific sample area having a large arrangement error in the sample area on the substrate, the specific sample area is compared with the measurement result in the alternative area. Whether the area is due to the nonlinear distortion of the substrate,
It is possible to determine whether the damage is due to mark destruction or measurement error. Then, since the optimum alignment method and the sample area used for each can be selected according to the determination result, the alignment can be performed with high throughput and high accuracy.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of a positioning method according to the present invention.

FIG. 2 is a configuration diagram showing a projection exposure apparatus to which the alignment method of the embodiment is applied.

FIG. 3 is a TTL alignment sensor 1 shown in FIG.
7 is a block diagram showing a detailed configuration of No. 7.

FIG. 4 is a block diagram showing a detailed configuration of a main control system 18 and the like in FIG.

5A is a plan view showing an arrangement of shot areas on a wafer exposed in the embodiment, FIG. 5B is an explanatory view of a wafer mark detection method for LIA system, and FIG. 5C is for LSA system. FIG. 3 is an explanatory diagram of a wafer mark detection method of FIG.

FIG. 6 is a diagram showing an observation region of an image sensor of an FIA alignment sensor.

7A is a plan view showing an example of a distribution of a non-linear error amount of a sample shot, and FIG. 7B is a position alignment of each exposure shot of the wafer of FIG. 7A by the alignment method of the embodiment. It is a top view showing distribution of the amount of nonlinear error of each subsequent exposure shot.

8A is a plan view showing a distribution of a non-linear error amount after each exposure shot of the wafer of FIG. 7A is aligned by a conventional normal EGA method, and FIG. Figure 7
It is a top view which shows the distribution of the non-linear error amount after aligning with the conventional weighted EGA system with respect to each exposure shot of the wafer of (a).

FIG. 9 is a plan view showing an example of an array of sample shots on a wafer when performing alignment by a weighted EGA method in an example of the present invention.

FIG. 10 is a plan view showing an example of an array of sample shots on a wafer when performing alignment by a method in which the weighted EGA method is modified in the embodiment.

[Explanation of symbols]

 1 Mercury lamp 3 Illumination optical system 9 Main condenser lens R Reticle 13 Projection optical system W Wafer WS Wafer stage 15 Laser interferometer 17 TTL type alignment sensor 18 Main control system ESj Exposure shot SA1 to SA19 Sample shot SB1, SB7, SB15 Alternative Shot Mxj X-direction wafer mark Myj Y-direction wafer mark

Claims (1)

[Claims] 1. A plurality of processed regions arranged on the substrate based on arrangement coordinates on a sample coordinate system set on the substrate are defined in a stationary coordinate system that defines a moving position of the substrate. When aligning with the predetermined processing position,
By measuring coordinate positions on the stationary coordinate system of at least three processed regions among the plurality of processed regions, and statistically calculating the measured plurality of coordinate positions,
Each of the plurality of processed regions is calculated by calculating array coordinates of each of the plurality of processed regions on the substrate on the stationary coordinate system and controlling the moving position of the substrate according to the calculated array coordinates. In the method of aligning with respect to the processing position, a first step of measuring coordinate positions on the stationary coordinate system of at least four preselected sample areas among the plurality of processing areas; A second step of obtaining a nonlinear error amount which is a difference between the coordinate position of the sample area calculated by linear approximation from the measurement result of the one step and the coordinate position of the sample area measured in the first step; On the stationary coordinate system of an alternative region consisting of the processed region in the vicinity of a specific sample region in which the nonlinear error amount is larger than a predetermined allowable value, among the regions. A third step of measuring the coordinate position, the measurement result of the first step and the coordinate position of the alternative area calculated by linear approximation from the measurement result of the third step and the alternative measured in the third step. A fourth step of obtaining a non-linear error amount which is a difference from the coordinate position of the region, and a non-linear error amount of the specific sample region and a non-linear error amount of the alternative region are compared to calculate an actual array coordinate. A fifth step of determining a coordinate position to be used, based on the coordinate position determined to be used in the fifth step and the coordinate position measured for the sample area other than the specific sample area, An alignment method, wherein array coordinates of the plurality of processed regions on the stationary coordinate system are calculated.