JP2868548B2 - Alignment device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus for performing high-accuracy relative positioning between an original such as a mask and a substrate to be exposed such as a semiconductor wafer in a so-called step-and-repeat exposure apparatus. .

2. Description of the Related Art In an exposure apparatus for manufacturing a semiconductor integrated circuit, a mask on which a pattern of an integrated circuit is formed and a semiconductor wafer to which the pattern is to be transferred need to be overlapped with high accuracy before exposure. is there. For example, in the case of an integrated circuit of 256 mechabit DRAM class, the line width of the pattern is 0.25
It is on the order of microns, and the overlay accuracy is required to be 0.06 microns or less.

In order to achieve such high precision, a so-called die-by-die alignment method is commercially available, in which the exposed pattern on the wafer and the transfer pattern of the mask are aligned and exposed at each exposure position (shot) on the wafer. Adopted.

The alignment apparatus measures the amount of linear displacement between the alignment mark formed on the mask and the alignment mark formed on the semiconductor wafer in a direction parallel to the X and Y coordinate axes, and performs multiple pairs of marks on the mask and on the wafer. From the plurality of linear deviation amount data ΔX _m and ΔY _n obtained from the mask, and the linear deviation amount (ΔX, Δ
Y) and the amount of rotation deviation (Δθ) are calculated. The mask and the wafer are positioned relative to each other by relatively driving the mask and the wafer based on the calculation result.

[Problems to be Solved by the Invention] By the way, in such an alignment apparatus,
A mark that can detect the amount of displacement in one direction with one mark is used as an alignment mark.
As shown in FIGS. 12 (a) and 12 (b), when they are arranged near the end of each side of each shot, there is a disadvantage that the positioning accuracy is not always sufficient. This is because the alignment apparatus uses only the linear deviation measurement values ΔX _m and ΔY _n to elongate or distort the shot as shown in FIG. 12 (a) and the rotational deviation Δθ as shown in FIG. 12 (b). This is because it is not possible to distinguish between In FIGS. 12 (a) and (b), ΔX _U , ΔX _D , ΔX _L , and ΔX _R indicate linear deviation amounts measured by respective alignment marks, a solid line indicates a mask shot pattern, and a broken line indicates a wafer shot. 3 shows a shot pattern.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in the related art, and has as its object to provide an alignment apparatus that enables more accurate alignment.

[Means for Solving the Problems] In order to achieve the above object, an alignment apparatus according to the present invention provides a die-by-die alignment, in which an on-substrate mark provided for each shot on a substrate and an original corresponding to each on-substrate mark are provided. A mark measuring means for measuring a relative displacement amount in a linear direction in the XY plane with the upper mark; a shot distortion detecting means for detecting a shot distortion for each shot in the XY plane due to expansion and contraction of the substrate; Correction means for correcting the relative displacement output from the mark measurement means based on the shot distortion detected by the shot distortion detection means, and positioning the substrate and the original based on the output of the correction means. Calculating means for calculating the correction drive amount;
It is characterized by having.

In one embodiment of the present invention, the alignment marks, which can detect the amount of displacement in one direction with one mark, are respectively assigned to the original priority mark for position shift measurement and the priority mark when the priority mark cannot be used. The shot distortion detection means is provided as a spare mark to be used instead, and detects the shot distortion based on the positional deviation measurement values of both the priority mark and the preliminary mark.

These priority marks and spare marks are provided, for example, on each side of each shot. As a means for measuring the displacement of the priority mark and the preliminary mark in the shot distortion detecting means, a dedicated measuring means may be provided, but the mark measuring means originally provided for alignment may be shared. Cut off.

In another aspect of the present invention, the distortion of the entire substrate is detected by measuring several shots in the substrate. In this case, as the distortion of each shot, one distortion detection value for the entire substrate is used, or the distortion distribution on the substrate is stored in a polynomial, a table, or the like, and is determined according to the shot position coordinates.

[Operation and Effect] In the present invention, the distortion of each shot is detected, and the measured value of the relative displacement for alignment is corrected based on the detected distortion information. Due to this, the expansion or contraction or distortion of the substrate to be exposed and the rotation (rotational deviation) between the substrate and the original plate
Even if the substrate to be exposed has expansion or contraction or distortion, as shown in FIG. 12 (a), the exposed pattern on the substrate and the transfer pattern of the original are most shifted. Can be superimposed in a state where the number is small.

The original purpose of alignment (alignment) is not to align the alignment marks, but to align the chips.

According to the present invention, particularly, alignment accuracy in the sense of aligning chips can be improved.

Embodiment FIG. 1 shows a configuration of a mask wafer alignment and an exposure stage portion of a step and repeat exposure apparatus (stepper) according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes exposure light, for example, X-rays emitted from SOR. Reference numeral 2 denotes a mask on which a pattern to be transferred is formed. Reference numeral 3 denotes a wafer to which a pattern of a mask is transferred, 4 denotes a mask θ stage for rotating the mask 2 in its plane, 5 denotes a θ coarse movement stage for rotating the wafer 3 in its plane, and 6 denotes a wafer 3 When the wafer 3 is made to face the mask 2 via a predetermined proximity gap, the wafer 3 is moved in the direction toward the exposure light, ω _X (rotated around the X axis), ω _Y
(Rotating around Y axis) Z tilt stage for driving,
Reference numeral 7 denotes a θ fine movement stage for minutely rotating the wafer 3 in the plane thereof, and reference numeral 8 denotes an X axis for minutely driving the wafer in the X direction.
A fine movement stage, 9 is a Y fine movement stage for finely driving the wafer in the Y direction, 10 is an X coarse movement stage, and 11 is a Y coarse movement stage. The θ coarse movement stage 5, the Z tilt stage 6, the θ fine movement stage 7, the X fine movement stage 8, the Y fine movement stage 9, the X coarse movement stage 10, and the Y coarse movement stage 11 constitute a wafer stage 24.

Reference numeral 12 denotes a pickup that irradiates light to alignment marks formed on the mask 2 and the wafer 3 and detects scattered light from these marks. In this embodiment, a total of eight alignment marks are formed on the scribe line of each shot on the wafer 3 in the vicinity of each side of the shot, one priority mark and one spare mark. As shown in FIG. 2, one alignment mark includes an AA mark 201 for detecting a mask-wafer overlay error in a direction parallel to a side where the mark is arranged, and an AA mark 201 for detecting a mask 2 and a wafer 3. A diffraction grating serving as an AF mark 202 for detecting an interval is formed together with a semiconductor circuit pattern in a preceding process. Eight alignment marks 203 and 204 that are paired with the alignment marks on the wafer 3 are also formed on the mask 2 with gold or the like together with the semiconductor circuit pattern to be transferred.

In FIG. 2, reference numeral 205 denotes a semiconductor laser as a light emitting element; 206, a collimator lens for converting a light beam output from the semiconductor laser 205 into parallel light; and 207, a projection light output from the semiconductor laser 205 and converted to parallel light by a collimator lens 206. Light beam 208, AA mark 210 on wafer and AA mark 203 on mask
AA light-receiving beam to which positional deviation information (AA information) is given by an optical system constituted by 209. Gap information (AF information) is given to 209 by an optical system constituted by an AF mark 202 on a wafer and an AF mark 204 on a mask. AA sensor 210 which is a line sensor such as a CCD for converting the position of the AA light receiving spot 211 formed by the AA light receiving beam 208 into an electric signal as AA information, and 212 is formed by the AF light receiving beam 209. The position of the received AF spot 213
It is an AF sensor that is a line sensor such as a CCD that converts the information into an electric signal.

FIG. 3 shows a configuration of a control system of the exposure apparatus shown in FIG.
The apparatus shown in FIG. 1 includes a mirror unit that expands an X-ray radiated from an SOR into a sheet beam in a horizontal direction in the vertical direction to form a planar beam, an alignment unit that aligns a mask and a wafer, and an aligned mask. A body unit including an exposure unit for exposing the wafer with the planar X-ray, a posture control unit for controlling the postures of the mirror unit and the body unit, and a chamber and an air conditioning unit for controlling the atmosphere of the mirror unit and the body unit Etc. are provided.

In FIG. 3, reference numeral 301 denotes a main processor unit for controlling the operation of the entire apparatus, 302 denotes a communication line connecting the main processor unit 301 and the main unit, 303 denotes a main body side communication interface, 302 denotes a main unit control unit, 305 is a pickup stage control unit, and 307 and 306, 308 are fine AA / AF control units 309a, 309b, for driving the θ, X, Y fine movement stage and the mask θ stage for fine alignment with the main unit control unit 304 and the main unit in the main unit. Communication line and communication interface connecting to 309c, 309d, 311 and 310,312
Reference numeral denotes a communication line and a communication interface for connecting the main body control unit 304 and the stage control unit 313 for controlling pre-alignment and step movement of the wafer in the main body unit.

FIG. 4 is a diagram showing a step-and-repeat exposure method. For simplicity, for FIG. 1,
The mask θ stage 4 as a driving unit of the mask 2, the wafer stage 24 as a driving unit of the wafer 3, and the pickup 12
The pickup stage 13 which is a driving means of the above is omitted.

In the figure, reference numeral 12 (12a to 12d) denotes a mask 2 and a wafer 3
418 is a transfer pattern drawn on the mask, 419 is a transferred pattern formed on the wafer by the preceding process, and 420 is a mask alignment mark for aligning the mask with the wafer stage Reference numeral 412 denotes an alignment mark on a mask for aligning the transfer pattern 418 with the transferred pattern 419, reference numeral 422 denotes an alignment mark on the wafer for the same purpose, reference numeral 423 denotes a light beam projected from the pickup 12 for the same purpose, reference numeral 40 denotes
Reference numeral 1 denotes a scribe line between shots, on which an alignment mark 421 on a mask and an alignment mark 422 on a wafer are drawn.

To align the mask 2 and the wafer 3, first,
In a state where the mask 2 and the wafer 3 are supported to face each other, light beams 423 are projected from the pickups 12a to 12d, and a gap between the mask and the wafer is formed through the corresponding alignment mark 421 on the mask and alignment mark 422 on the wafer. Measure. Based on information obtained from the four pickups, a gap correction driving amount is calculated, and the wafer stage is driven.
By driving 24 (not shown), the gap between the mask and the wafer is set to the exposure gap.

Next, light beams 423 are projected from the pickups 12a to 12d, and the corresponding alignment marks 421 on the mask are respectively projected.
Of the mask and the alignment mark 422 on the wafer in the plane direction of the mask and the wafer are measured. Based on the information obtained from the four pickups, the correction drive amount of the entire shot is calculated, and the mask is moved on the mask by driving the mask θ stage 4 (not shown) and the wafer stage 24 (not shown). The transferred pattern 418 is aligned with the transferred pattern 419 on the wafer. When the alignment is achieved, exposure is performed to transfer the transfer pattern 418 onto the wafer 3. Then, the wafer stage 24 (not shown) is driven so that the next exposure shot comes under the mask. Similarly, the alignment and the exposure are repeated to expose all the shots.

FIG. 5 is a flowchart for one batch of the step-and-repeat exposure sequence. One batch is a unit that can be printed on one wafer without replacing the mask in the middle. In the start state, the mask 2 and the wafer 3 are chucked by the mask θ stage 4 and the wafer stage 24, respectively, and the pickup 12 aligns the projection beam 423 on the mask for AF (auto focus) / AA (auto alignment) measurement. Each of the marks 421 is irradiated.

First, in step 501, it is determined whether or not the mask needs to be replaced. The process proceeds to step 504 when exposing with the currently chucked mask, and proceeds to step 502 when exposing with the mask replaced. In step 502, the currently chucked mask is detached from the mask stage 4 using a mask traverser (not shown) and stored in a mask cassette (not shown), and the mask used for exposure is removed from the mask cassette using a mask traverser. Take it out and chuck it on the mask stage 4. In step 503, the pickup 12 is used to align the mask alignment mark 420 drawn on the mask 2 with a reference mark (not shown) provided on the wafer stage.

Next, in step 504, the wafer stage 24 is driven,
The position (shot position, that is, the transferred pattern 419) on the wafer to be exposed now is opposed to the transfer pattern 418 on the mask. In step 505, the gap between the mask and the wafer is measured using the on-mask alignment mark 421 and the on-wafer alignment mark 422, and the z-direction and tilt correction driving is performed. When the AF is completed, in step 506, the alignment mark 421 on the mask is set.
AA is performed by performing a correction drive by measuring a displacement in the X and Y directions between the mask and the wafer using the wafer alignment mark 422 and the wafer alignment mark 422. Detailed processing contents of AA (step 506) will be described later.

When AA is completed, one-shot exposure is performed in step 507, and the presence or absence of the next exposure shot is determined in step 508. If there is, the process returns to step 504;

FIG. 6 is a flowchart showing the contents of the AA process in step 506 in FIG. It shows AA measurement for one shot, X, Y, θ deviation amount calculation, and correction driving.

First, in step 601, a layout check on the wafer of the shot to be exposed (current shot) is performed. 1
FIG. 7 shows an example of a shot layout of a wafer.
S1 to S3 are shots. FIG. 8 shows the alignment mark arrangement for one shot. a to d are priority marks for measuring the displacement between the mask and the wafer, and a 'to d' are preliminary marks, which are provided on both the mask and the wafer. Each mark can detect either a shift in the X or Y direction at that position, and a, a ', b, b'
In the directions c, c ', d, d', a shift in the Y direction can be detected. Therefore, in order to know the X, Y, θ shift of one shot, at least 3
Measurement of marks on two sides is required.

When the shot S1 is to be exposed, all marks a to d can be measured because the entire shot is on the wafer. Therefore, proceed to step 602 to select each pickup 1
By projecting the light projecting beam 423 for AA from 2, measurement is performed at four points, and the measurement result is checked in step 603. Here, a measurement error caused by a measurement failure due to a missing or crushed mark or a large shift between the mask 2 and the wafer 3 is repelled.

FIG. 9 is a graph showing the characteristics of the output signal from the pickup 12 with respect to the amount of displacement between the wafer and the mask in the X and Y directions. Zones I and II will be described in step 604, but this range is the AA measurement range, and zone III is a region in which a measurement error occurs and is rejected in step 603. When all four marks can be measured, four points are determined to be OK, and the X, Y, and θ shift amounts are calculated in step 604.
The correction drive of θ is performed. Then, at step 606, the correction drive amount is checked. If this correction amount, that is, the deviation amount calculation value in step 604 is within the tolerance, this A
The process A is terminated, and if the tolerance is out of tolerance, the process returns to step 601. A specific X, Y, θ shift amount calculation method in step 604 will be described later with reference to FIG. 10 and subsequent figures. Steps
If only three marks can be measured in 603, it is determined that three points are OK, and merges with the above-described four-point measurement sequence (steps 602 to 604) to step 609 of the three-point measurement sequence (steps 607 to 609) branched in step 601. I do. In addition, when only two marks or less can be measured, the step of the measurement sequence (steps 610 to 613) of two points or less is determined as NG.
Proceeding to 612, a preliminary mark corresponding to the NG mark is measured.

When the shot S2 in FIG. 7 is to be exposed, the mark a in FIG.
The point is measured, branching from step 601 and step 607
Performs AA measurement at three points excluding mark a. In step 608, the measurement result is checked in the same manner as in step 603. If three points are OK, the process proceeds to step 609; In step 609, X, Y, and θ correction amounts are calculated based on the three-point data, including those branched in step 603 of the four-point measurement sequence. Assuming that a cannot be measured and that displacement measurement data ΔX _D , ΔY _L , and ΔY _{R of the} mask and the wafer are obtained from b, c, and d, respectively, the displacements ΔX, ΔY, Δθ of the entire shot are represented by ΔX = ΔX _D + Δθ · L _X / 2 ΔY = (ΔX _L + ΔY _R / 2 Δθ = (ΔY _L −ΔY _R / L _Y. The sign of each shift amount is inverted to be the correction amount. L _X and L _Y are the distances between marks for detecting displacement in the same direction, respectively.
The value or design value obtained in 1006 is used. When marks other than a cannot be measured, 3
Three unknowns ΔX, ΔY, Δθ can be obtained from the measured data of the points. Then, in step 605, correction driving of X, Y, θ is performed.

When shot S3 in FIG. 7 is to be exposed, only b and c in FIG. 8 can be measured. Although the measurement of d 'is possible, in the present embodiment, the measurement of d' is performed later because the pickups interfere with each other depending on the shape and mark arrangement of the pickup.

First, the process branches from step 601 to step 610.
AA measurement of 2 marks is performed. In step 611, the measurement result is checked, and in step 612, the missing data is supplemented. In step 612, the error branch from the four-point measurement or the three-point measurement merges. When only two points or less can be measured as in the shot S3, d 'can be measured as described above, so that the pickup 12 corresponding to d is measured.
d is driven using the pickup stage 13d to move over the preliminary mark d ', and d' is measured. When the NG is merged from the four-point measurement or the three-point measurement, the preliminary mark corresponding to the NG mark is measured. If the pickup 12 is moved here, after the measurement is completed, it is necessary to return the pickup position to the original position for the measurement of the next shot. Then, check the total number of valid data in step 613,
If there are four points, the process proceeds to step 604, and if there are three points, the process proceeds to step 609 to calculate the X, Y, and θ shift amounts. If still less than two points are obtained, an error is terminated and manual alignment is performed or the shot is skipped and the next shot is started. Alternatively, it is also possible to perform alignment by estimating from information of surrounding shots and performing alignment.

In the present embodiment, when four points are measured in step 602 and three points are OK in step 603, the shot shift amount is obtained from the data of the three points. The process may proceed to step 612 instead of 609 to measure the preliminary mark corresponding to the NG mark. The effect of the measurement error can be reduced at four points than at three points.
Since the measurement data at another point is obtained by picking up an object that can be aligned at a point and the measurement data at the other point is obtained, the throughput is reduced. Therefore, which one to select is a trade-off between time and accuracy.

FIG. 10 is a flowchart showing the processing content of step 604 in FIG. 4 shows a calculation sequence for calculating X, Y, and θ shift amounts for one shot from four measurement data. First, in step 1001, it is determined whether or not the calculation of the elongation percentage of this shot is necessary. If the expansion / contraction of the wafer occurs almost uniformly over the entire wafer due to the process, this elongation ratio calculation is necessary only for the first shot, and correction calculation based on the elongation ratio calculated for the first shot after the second shot. So go to step 1007.

If the elongation percentage needs to be calculated, it is determined in step 1002 whether the elongation percentage can be calculated. For elongation calculation,
Since at least one preliminary mark in each of the X and Y directions must be measured, the elongation rate calculation is performed when both preliminary marks in the X or Y direction are used to obtain four points of measurement data. Can not. If the elongation cannot be calculated in this way, the process proceeds to step 1008, and if possible, the process proceeds to step 1003.

In step 1003, the pickup 12 is moved above the preliminary mark, and in step 1004, the deviation between the mask and the wafer is measured using the preliminary mark. In step 1005, the measurement result is checked in the same manner as in step 603 in FIG. 6, and if at least one preliminary mark has been measured in each of the X and Y directions,
If it is not, the process proceeds to step 1006. If the process is not completed, the elongation cannot be calculated, and the process proceeds to step 1008.

In step 1006, the elongation percentage of the wafer is calculated from the measured values of the priority marks measured in steps 602, 607, and 610 of FIG. 6 and the measured values of the preliminary marks measured in step 1004, and the distances L _X and L between the marks are calculated accordingly. Perform _Y correction. A specific calculation method will be described with reference to FIG.

In FIG. 11, the solid line is the design size of one shot, the broken line is the size of one expanded shot, and the solid line can be considered as the shot shape on the mask and the broken line is the shot shape on the wafer. 'To determine the growth rate of the x-direction using a mark a, and mark a as seen from the shot center' mask a and a respectively designed X-coordinate of the X _U, as X _U ',
The measured values of the mark a and the mark a ′ are Δ
X _U, 'elongation [rho _xu in the x direction when A _{ρ xu = (ΔX U' ΔX} U becomes _{-ΔX U) / (X U '} -X U). Similarly, marks b and b ', marks c and c', 'when seeking respective elongation _{using, ρ XD = (ΔX L -ΔX} L' mark d and _{d) / (X L -X L} ' ) Ρ _YL = (ΔY _L ′ −ΔY _L ) / (Y _L ′ −Y _L ) ρ _YR = (ΔY _R −ΔY _R ′) / (Y _R −Y _R ′). When only one preliminary mark can be measured in each of the X and Y directions, the obtained elongation percentages may be used as they are, and ρ _X and ρ _Y may be used as they are. It is sufficient to calculate and set ρ _X = (ρ _XU + ρ _XD ) / 2 ρ _Y = (ρ _YL + ρ _YR ) / 2.

Next, the distances L _X and L _Y between marks are corrected in accordance with the elongation percentage obtained as described above. Assuming that the design value of the distance between marks is L _X and L _Y shown in FIG. 11, the actual distance between marks for calculating the θ rotation amount of the shot changes due to the expansion of the wafer. Therefore, the correction can be made again by setting L _X ← L _X (1 + ρ _X ) L _Y ← L _Y (1 + ρ _Y ).

In step 1007, the measurement data is corrected based on the elongation percentage obtained in step 1006. For the shots for which it is determined in step 1001 that the elongation rate calculation is unnecessary, the elongation rates already calculated for the first shot and the like are used. The measurement data is the displacement between the mask and the wafer at the mark position, but the displacement in the sense of aligning the shot center excludes the elongation, so that ΔX _U ← ΔX _U −ρ _X・ X _U ΔX _D ← ΔX _D −ρ _X・ X _D ΔY _L ← ΔY _L −ρ _Y・ Y _L ΔY _R ← ΔY _R −ρ _Y・ Y _R By performing such a correction, it is possible to remove the displacement due to the expansion of the wafer as shown in FIG. 12 (a), and it is possible to identify the displacement from the rotation shown in FIG. 12 (b).

Next, in step 1008, the shot shift amounts ΔX, ΔY, Δ
Calculate θ _X and Δθ _Y. As the inter-mark distance and measurement data used here, the values after correction are used for those for which the elongation rate has been calculated. The calculation formula is shown below.

ΔX = (ΔX _U + ΔX _D ) / 2 ΔY = (ΔY _L + ΔY _R ) / 2 Δθ _X = (ΔX _U + ΔX _D ) / L _X Δθ _Y = (ΔY _L + ΔY _R ) / L _Y where Δθ _X and Δθ _Y is the θ rotation shift amount obtained from the measurement data in the X and Y directions, respectively.

In the present embodiment, a mark that can measure only one direction of displacement is used. However, if a mark that can be measured in both X and Y directions is used, the same correction can be performed without using a spare mark.
For example, in FIG. 11, when a mark that can be measured in both X and Y directions is used as the marks a, b, c, and d, the elongation of the upper side of the shot in the X direction from the marks a and d is represented by the marks c and b. , The extension rate in the X direction of the lower side of the shot, the marks a and c, the extension rate in the Y direction of the left side of the shot, and the marks d and b, the extension rate in the Y direction of the right side of the shot.

In step 1009, the measurement accuracy in the X direction and the measurement accuracy in the Y direction are compared. Although Δθ _X and Δθ _Y obtained in step 1008 should originally have the same value, they actually have different values depending on measurement accuracy, distortion of the wafer and mask, and the like. Therefore, an attempt is made to use the one with higher accuracy for the correction drive.

Further, at present, if the resolution of the measurement optical system is increased in order to perform precise alignment, the measurement range in which the signal output of the measurement system with respect to the amount of displacement between the mask and the wafer is linearly reduced. Therefore, for the optical system having the characteristics shown in FIG. 9, even the non-linear regions (Zone II) on both sides of the linear region (Zone I) are included in the measurement range. As a matter of course, since the measurement accuracy in the zone II is lower than that in the zone I, it is indispensable to perform the correction drive and perform the measurement again in the zone I.

When the mask and the wafer are displaced as shown in FIG. 13, since the drift amount in the X direction is large and also has a θ rotation component, ΔX _D , ΔY _L , and ΔY _R fall within zone I. , ΔX _U are in zone II. Then, it is reliable for [Delta] [theta] _Y than [Delta] [theta] _X obtained in step 1008 of FIG. 10, the θ rotation shift amount [Delta] [theta] requires only a little rotation of the thrust towards using [Delta] [theta] _Y. Therefore, Y
If the two measured values in the direction are both zone I and at least one of the measured values in the X direction is zone II, step 10
If the θ rotational deviation Δθ is set to Δθ _Y at 10 and at least one of the two measured values in the X direction is Zone II in Zone I, the rotational deviation Δθ is set to Δθ _{X in} Step 1011. And If both zones are the same, the process proceeds to step 1012.

In step 1012, when the measurement accuracy in the X direction and the Y direction is equal, a weighting coefficient n (0 ≦ n ≦ 1) for calculating the θ rotation shift amount Δθ by temporarily combining Δθ _X and Δθ _Y is calculated.
As is clear from the calculation formulas, Δθ _X and Δθ _Y have higher accuracy if the denominator is larger if the mark measurement accuracy is equal. Therefore, the weighting coefficient n is expressed as n = L _x / (L _x + L _y ), and the θ rotation deviation Δθ is set to Δθ = n · Δθ _x + (1−n) Δθ _Y as shown in step 1013. Enables weighting according to the accuracy.

Here, L _X and L _Y used in the calculation of the weighting coefficient n are the values corrected by the elongation in Step 1006, but the elongation cannot be calculated in Step 1002 or 1005, and L _X and L _Y
Is the design value, there is a method for calculating the weighting coefficient n described below. This method can be used when it is known that the wafer easily expands and contracts in the X direction and the Y direction depending on the crystal growth direction of the wafer. Assuming that the uncertainty rate (uncertain length / basic length) of the length of the wafer in the X direction is α _X , and that in the Y direction is α _Y , L _X ← L _X · (1−α _X ) L _Y ← L _Y If (1−α _Y ), the weighting coefficient n can be obtained by the same equation as in the above example. Further, the weighting coefficient n may be determined according to other conditions.

Further, in FIG. 10, Δx, Δy, and Δθ were obtained after correcting the measured values based on the elongation rate. However, when at least one of the measured values was in zone II, the accuracy was more nonlinear than the accuracy degradation due to elongation. If the deterioration is greater, a branch is made before the step 1008 by branching at the step 1009, and the extension is not corrected for the steps 1010 and 1011.

Further, in the above-described embodiment, only the step 604 in FIG.
The elongation rate calculation and the L _X , L _Y correction processing of step 6 are executed. However, when calculating the X, Y, θ shift amount based on the three-point data in step 609, two or one point measurement data The same elongation rate calculation processing can be performed even when only the values are obtained. In this case, step 1005 in FIG.
It is determined whether the priority mark and the preliminary mark on the same side have been measured together, and the step is performed only when the measurement has been performed.
What is necessary is just to go to 1006 elongation rate calculation processing. In addition,
If only two or one measurement data is available,
Although the X, Y, and θ shift amounts in the current shot cannot be calculated (step 1008 in FIG. 10), the elongation data when only two or one measurement data is obtained is based on the fact that the expansion and contraction of the wafer is This is effective when elongation ratio calculation is performed with only one shot as in the case of almost uniform, or when elongation ratios of several shots are calculated to obtain the average elongation ratio or strain distribution of the entire wafer. . In addition, three or more points of measurement data including the preliminary mark are obtained in the adjacent shot, but this is also effective as supplementary data when the elongation rate cannot be calculated by using up the preliminary mark.

Although the AA sequence has been described above, the AF sequence can be applied to selecting a sequence according to shot layout information or occurrence of a measurement error, and supplementing measurement data using a spare mark.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a step-and-repeat exposure apparatus according to an embodiment of the present invention. FIG. 2 is an explanation of a fine AA / AF system for detecting a deviation between a wafer and a mask in a plane direction and a vertical direction. Schematic diagram, FIG. 3 is a hardware configuration diagram of a control system of the exposure apparatus of FIG. 1, FIG. 4 is an explanatory diagram of a step-and-repeat exposure method, and FIG.
FIG. 6 is a flowchart showing the contents of the AA process in step 506 of FIG. 5, FIG. 7 is an explanatory diagram showing a shot layout of one wafer, and FIG. 8 is a diagram of one shot. FIG. 9 is a graph showing the characteristics of the output signal from the pickup with respect to the amount of displacement between the wafer and the mask in the X and Y directions. FIG. 10 shows the processing contents of step 604 in FIG. FIG. 11 is an explanatory view of the calculation of the elongation rate of the wafer, FIGS. 12 (a) and (b) are explanatory views of the deviation due to the elongation of the wafer and the deviation due to the rotation, and FIG. 13 is the alignment on the wafer FIG. 4 is an explanatory diagram of a state where one of the marks has deviated from a high-precision measurement zone. 1: X-ray (exposure light) 2: Mask (original plate) 3: Wafer (substrate to be exposed) 4: Mask θ stage 12, 12a to 12d: Pickup 13: Pickup stage 24: Wafer stage 304: Main unit control unit 305: Pickup Stage controller 309a, 309b, 309c, 309d: Fine AA / AF controller 421: Alignment mark on wafer 422: Alignment mark on mask 423: Projection beam ΔX _U , ΔX _D , ΔY _L , ΔY _R : Misalignment of alignment mark Quantity measurement

Continued on the front page (72) Inventor Shunichi Uzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Satoshi Nose 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-3-77310 (JP, A) JP-A-1-283927 (JP, A) JP-A-1-243419 (JP, A) JP-A-64-53545 (JP, A) 1986-201427 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (4)

(57) [Claims] In a step-and-repeat type exposure apparatus, a relative position of a mark on a substrate provided for each shot on a substrate and a mark on an original corresponding to the mark on the substrate in a linear direction in an XY plane. A mark measuring unit that measures a shift amount; a shot distortion detecting unit that detects shot distortion for each shot in the XY plane due to expansion and contraction of the substrate; and a shot distortion detected by the shot distortion detecting unit. Correction means for correcting the relative shift amount output from the mark measurement means based on the correction means; andcalculation means for calculating a correction drive amount for aligning the substrate and the original based on the output of the correction means. An alignment apparatus, comprising: 2. The mark on the substrate and the mark on the original are a mark capable of detecting a relative positional deviation amount in one direction with one mark on the substrate and the mark on the original, and is originally used for alignment between the substrate and the original. A priority mark to be used and a preliminary mark to be used in place of the priority mark when the priority mark is inappropriate for alignment are provided. 2. The alignment apparatus according to claim 1, wherein the shot distortion is detected based on a shift amount between both marks. 3. The alignment apparatus according to claim 2, wherein said preliminary mark is provided on each side of said shot. 4. The alignment apparatus according to claim 1, wherein said shot distortion detecting means measures the shot distortion for a part of shots on the substrate and detects distortion of the entire substrate.