JPH0992609A - Aligner and aligning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure high overlay accuracy when different layers on a wafer are exposed by a mix and match system even if the distortion characteristics of the projection image of a plurality of aligners corresponding to the different layers are different from each other. SOLUTION: A first layer on a wafer W is exposed by means of a first projection aligner SR1 and then a second layer on the wafer W is exposed by means of a second projection aligner SR2. A data indicative of distortion of the projection optical system in projection aligners SR1, SR2 is stored in a data base 2. When the wafer is exposed by means of the second projection aligner SR2, a correction value for the magnification of projection optical system PL2 in the second projection aligner SR2 is determined based on the distortion data, and the positional shift of the projection image obtained from an alignment sensor AS2 performing multi-point alignment measurement within a shot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transfers a mask pattern onto a photosensitive substrate in a photolithography process for manufacturing, for example, a semiconductor element, an image pickup element (CCD or the like), a liquid crystal display element, a thin film magnetic head or the like. The exposure method and the exposure apparatus for performing the exposure are particularly suitable for use in the case of performing the mix-and-match exposure using different exposure apparatuses for different layers on the photosensitive substrate.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device, a liquid crystal display device or the like by a photolithography process, a reticle pattern as a mask is formed on a wafer (or a glass plate or the like) coated with a photoresist through a projection optical system. A projection exposure apparatus (stepper or the like) that transfers to each shot area is used. For example, a semiconductor element is formed by stacking multiple layers of circuit patterns on a wafer in a predetermined positional relationship. Therefore, when projecting and exposing the circuit patterns of the second and subsequent layers onto the wafer, the circuit patterns already on the wafer have already been formed. It is necessary to perform highly accurate alignment between each shot area in which the marks have been formed and the pattern of the reticle to be exposed. Therefore, in the conventional projection exposure apparatus, the alignment sensor detects the position of the wafer mark attached to a predetermined shot area of the wafer, and the shot areas are aligned based on the detection result.

Recently, in order to increase the throughput (the number of processed wafers per unit time), different layers on the wafer are exposed by a mix-and-match method using different exposure apparatuses. There is. In this case, if the magnification of the projection image of the projection exposure apparatus used for the exposure of the first layer on the wafer and the magnification of the projection image of the projection exposure apparatus used for the exposure of the second layer are different, The overlay accuracy between the two layers deteriorates. Therefore, in order to improve the overlay accuracy, for example, the positions of a plurality of wafer marks indicating two-dimensional positions arranged in a predetermined shot area on the wafer in a predetermined positional relationship are detected. The linear magnification error of the pattern of the first layer in each shot area is obtained, and the magnification of the projection optical system of the projection exposure apparatus to be used is corrected in accordance with the linear magnification error. Such a method for detecting the positions of a plurality of wafer marks by converting into a two-dimensional mark in one shot area is also called an intra-shot multipoint alignment measurement method.

[0004]

As described above, in the conventional exposure method of the mix-and-match method, when the second layer of each shot area on the wafer is exposed, the pattern of the first layer is formed. The magnification of the projected image may be corrected in accordance with the magnification. However, the distortion (non-linear magnification error) characteristic of the projection exposure apparatus used for the exposure to the two layers is not taken into consideration, and when the difference in the distortion characteristics is large, the superposition between the two layers is performed. There was an inconvenience that the accuracy deteriorated.
This will be described with reference to FIGS. 5 and 6.

First, FIG. 5 shows an example of distortion. In FIG. 5, a predetermined square original image pattern is transferred to a wafer through a projection optical system having a predetermined magnification (for example, 1/5) free from distortion and linear magnification error. An image projected on the reference line 6 is a dotted line, and an image obtained by projecting the original image pattern on the first layer on the wafer through a projection optical system having a pincushion distortion is a solid line projection pattern 15. When measuring the distortion characteristics of the projection pattern 15, for example, the four measurement points 7A to 7D at the center of each side of the reference pattern 6 and the measurement points 8A to 8D on the four vertices of the reference pattern 6 are measured. At, the amount of positional deviation of the projected pattern 15 from the original position (in this case, the reference pattern 6) is measured. Then, the distortion characteristic of the projection pattern 15 is almost specified by the amount of positional deviation at these eight measurement points 7A to 7D, 8A to 8D, and more desirably at more measurement points.

On the other hand, in the intra-shot multipoint alignment measurement method, when the positions of a plurality of wafer marks in a predetermined shot area on the wafer are detected through the alignment sensor, each shot area is not detected. Since there is not much room to form a wafer mark and the measurement time needs to be shortened, the position of the wafer mark is detected at, for example, two or four measurement points. Therefore, since the number of measurement points by the alignment sensor is considerably smaller than the number of measurement points required to specify the distortion characteristic, it is difficult to correct the distortion.

Specifically, it is assumed that the projection optical system of the projection exposure apparatus for exposing the second layer on the wafer has neither distortion nor linear magnification error. Then, in the projection exposure apparatus, if the positional deviation amount of the wafer mark is measured at, for example, four measurement points 7A to 7D on the reference pattern 6 in FIG. 5, the projection pattern determined from this measurement result is as shown in FIG. A small projection pattern 16 of 6 (a) is obtained.
Therefore, when the exposure of the second layer is performed at a magnification that matches the projection pattern 16, the overlay error between the actual projection pattern 15 of the first layer and the projection pattern 16 of the second layer becomes large.

In the projection exposure apparatus, for example, the measurement points 8A to 8 on the four vertices of the reference pattern 6 shown in FIG.
If the amount of displacement of the wafer mark is measured with D, the projection pattern determined from this measurement result is as shown in FIG.
The large projected pattern 17 in (b) is obtained. Therefore, the second
If the layer is exposed at a magnification that matches the projection pattern 17, the overlay error between the first layer projection pattern 15 and the second layer projection pattern 17 becomes large.

As described above, in the conventional exposure method, even when the intra-shot multi-point alignment measurement method is applied, the overlay accuracy between the two layers on the wafer is largely influenced by the arrangement and number of measurement points by the alignment sensor. There was an inconvenience that it would end up. In view of the above point, the present invention is high even when the exposure characteristics of the two exposure apparatuses are different even when different exposure characteristics are used for the two layers on the wafer. An object of the present invention is to provide an exposure method that can obtain overlay accuracy. Another object of the present invention is to provide an exposure apparatus that can carry out such an exposure method.

[0010]

A first exposure method according to the present invention is a projection image of a first mask pattern (R1) on a first layer on a photosensitive substrate (W) by a first exposure device (SR1). And then exposing the second layer on the photosensitive substrate (W) to the second mask pattern (R2) by the second exposure device (SR2).
In the exposure method of exposing the projected images of the two in a superimposed manner, the first step of obtaining and storing the distortion data of the respective projected images by the first and second exposure devices, and the second layer on the photosensitive substrate (W). Before performing the exposure by the second exposure device (SR2), the positional deviation amount of the projected image of the first mask pattern (R1) is measured at a plurality of predetermined measurement points (5A to 5D) on the photosensitive substrate (W). The second exposure apparatus (S) based on the second step to be obtained, the distortion data stored in the first step, and the positional deviation amount measured in the second step.
R2) has a third step of correcting the magnification of the projected image, and the second exposure apparatus (SR) has the magnification corrected in the third step.
The exposure according to 2) is performed.

According to the present invention, the initial value of the magnification of the second exposure apparatus (SR2) for obtaining the best overlay accuracy can be obtained from, for example, the distortion data stored in advance. Then, by correcting the initial value of the magnification based on the positional deviation amount of the projected image of the first mask pattern (R1) actually measured at a plurality of measurement points on the photosensitive substrate (W), more accurate The magnification is determined.

Specifically, in the third step, the first data is stored in the first step based on the distortion data stored in the first step.
And the magnification of the projection image by the second exposure device (SR2) when the overlay accuracy of the respective projection images of the second exposure device (SR1, SR2) is the best, and with the thus obtained magnification Of the two projected images at a plurality of predetermined measurement points (7A to 7D) (11A to 11D)
And the positional deviation amount (14A to 1) obtained in the second step.
4D), it is desirable to correct the magnification of the projection image of the second exposure device (SR2).

The exposure apparatus according to the present invention is an exposure apparatus for projecting a mask pattern (R2) onto a photosensitive substrate (W) via a projection optical system (PL2). Exposure equipment (S
R1) projection image distortion data and projection optical system (PL2) projection image distortion data storage data (2), and the position of alignment marks (5A-5D) on the photosensitive substrate (W). Of the projection optical system (PL) based on the alignment sensor (AS2) for detecting the image, the detection data of the alignment sensor, and the distortion data stored in the storage means (2).
2) a calculation means (CNT2) for obtaining the correction value of the magnification,
Magnification correction means (BC2) for correcting the magnification of the projection optical system (PL2) based on the correction value obtained by this calculation means.
And The above-described exposure method can be implemented by the exposure apparatus of the present invention.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In this example, the present invention is applied to the case of performing exposure by a mix-and-match method using a plurality of stepper type projection exposure apparatuses. FIG. 1 shows an exposure system of this example. In FIG. 1, N (N is an integer of 2 or more) stepper-type projection exposure apparatuses SR1, SR2, ..., SRN are arranged in a predetermined arrangement. The operations of the projection exposure apparatuses SR1 to SRN are controlled online by the host computer 1. Further, the host computer 1 is connected to a database device 2 composed of a magnetic disk device or the like, and distortion data measured by the projection exposure apparatuses SR1 to SRN are respectively supplied to the database device 2 online to be updated as described later. And will be registered. Therefore, the database apparatus 2 always stores the latest distortion data of the projection exposure apparatuses SR1 to SRN. Projection exposure system SR
Each of 1 to SRN can take in the distortion data in the database device 2 via the host computer 1.

Next, the structure of each projection exposure apparatus will be described. First, in the first projection exposure apparatus SR1, the pattern area PA1 on the lower surface of the reticle R1 is illuminated by exposure light from an illumination optical system (not shown), and the pattern in the pattern area PA1 is magnified by the projection optical system PL1 at a magnification β (β. Is reduced by, for example, 1/5) and is projected and exposed to each shot area of the wafer on the wafer stage ST1. Wafer stage ST1 positions the wafer in a plane perpendicular to optical axis AX1 of projection optical system PL1, in a direction parallel to optical axis AX1, and the like. The two-dimensional coordinates of the wafer stage ST1 measured by a movable mirror (not shown) fixed on the wafer stage ST1 and an external laser interferometer are supplied to the control device CNT1, and the control device CNT1 is based on the supplied coordinates. The wafer W is positioned by stepwise driving the wafer stage ST1 in the two-dimensional direction. The control device CNT1 also has a function of transmitting and receiving various data and commands to and from the host computer 1, and a function of transmitting various data to the database device 1.

Further, in the projection optical system PL1 of the projection exposure apparatus SR1 of this example, a pressure adjuster BC as magnification correction means is provided.
1 is connected, and the control device CNT1 supplies the correction value of the magnification of the projection optical system PL1 to the pressure adjuster BC1. In response to this, the pressure adjuster BC1 changes the projection optical system PL.
By adjusting the pressure of the gas in the predetermined gas chamber surrounded by the predetermined lens and the lens barrel that form part 1,
The magnification β of the projection optical system PL1 is changed by the correction value. Instead of adjusting the pressure of the gas in the predetermined gas chamber in this way, for example, a predetermined lens in the projection optical system PL1 is driven in the optical axis direction, or a predetermined lens is attached to a plane perpendicular to the optical axis. The magnification of the projection optical system PL1 may be adjusted by adjusting the tilt angle or the like.

Further, on the side surface of the projection optical system PL1 of the projection exposure apparatus SR1 of this example, an off-axis type and image pickup type alignment sensor AS1 is arranged as an example. When exposing the second and subsequent layers on the wafer,
The coordinates of the wafer mark detected by the alignment sensor AS1 are supplied to the control device CNT1.
Then, the array coordinates of the corresponding shot area are obtained from the supplied coordinates. Then, the control device CNT1 applies, for example, an enhanced global alignment (hereinafter abbreviated as “EGA”) type alignment disclosed in Japanese Patent Laid-Open No. 61-44429 to a predetermined number of shot areas ( The array coordinates of sample shots) are statistically processed to calculate the array coordinates of all shot areas on the wafer. Then, by driving the wafer stage ST1 based on the calculated array coordinates, each shot area on the wafer is sequentially exposed (the projected image of the pattern area PA1).
Exposure is performed.

Further, for example, even if a plurality of two-dimensional wafer marks are formed in each shot area on the wafer and the coordinates of these wafer marks are detected by the alignment sensor AS1 by the multi-point alignment measurement method within a shot. Good. By processing this detection result,
It is possible to detect a magnification error of a pattern formed in the corresponding shot area, a rotation angle, and the like.

The other projection exposure apparatuses SR2 to SRN are also constructed similarly to the projection exposure apparatus SR1. For example, the second
In the projection exposure apparatus SR2, the pattern in the pattern area PA2 of the reticle R2 is β via the projection optical system PL2.
The image is reduced in size and projected onto the wafer on the wafer stage ST2, and the control device CNT2 can control the magnification of the projection optical system PL2 via the pressure adjuster BC2. Further, the coordinates of the wafer mark detected by the alignment sensor AS2 are supplied to the control device CNT2.

Next, an example of the operation in the case where each shot area on the wafer W is exposed by the mix-and-match method in the exposure system of this embodiment will be described with reference to FIGS. In the following, the first of each shot area on the wafer W is
When the second projection exposure apparatus SR2 exposes the second layer in each of the shot areas after the exposure of the layer is performed by the first projection exposure apparatus SR1 and the processing steps such as etching and film formation are performed. Will be explained.

First, prior to the exposure of the wafer W, as shown in FIG.
Using the test reticle R shown in FIG.
The distortion characteristics of the projection optical systems 1 to SRN are measured. As shown in FIG. 2A, the test reticle R
Pattern area PA of 9 cross-shaped imaging characteristic measurement marks 3A, 3B, ..., SH, 3I each having a predetermined pitch in two orthogonal directions (X direction and Y direction).
Are formed. For example, in the first projection exposure apparatus SR1, a test reticle R is loaded instead of the reticle R1, an unexposed wafer coated with photoresist is loaded on the wafer stage ST1, and the reticle of the projection optical system PL1 is transferred to the wafer. Is set to β (for example, ⅕), and the pattern image of the test reticle R is projected and exposed onto one shot area on the wafer. The magnification when there is distortion or the like is defined by, for example, the magnification at an image height of 70% of the maximum image height. Then, after developing the wafer, the wafer is loaded on the wafer stage ST1 and the positions of the formed images of the image-forming characteristic measuring marks 3A to 3I are measured using the alignment sensor AS1.
The measurement result is supplied to the control device CNT1.

FIG. 3A shows a first projection exposure apparatus SR1.
2 shows a measurement result of a square original image pattern obtained by connecting the imaging characteristic measurement marks 3A to 3I (excluding the center mark SE) of the test reticle R in FIG. Moreover, the pattern obtained by projecting on the wafer through the projection optical system having no distortion or linear magnification error is the reference pattern 6 in FIG. Also,
For measuring the image-forming characteristic, points on each side of the reference pattern 6 shown in FIG. 3 (a), which are conjugate with the image-forming characteristic measuring marks 3B, 3F, 3H and 3D shown in FIG. 2 (a), are set as measuring points 7A to 7D. Mark 3
The vertices of the reference pattern 6 that are conjugate with A, 3C, 3I, and 3G are measurement points 8A to 8D.

Then, the first projection exposure apparatus S having the imaging characteristic measurement marks 3A to 3D and 3F to 3I shown in FIG.
The projected image by R1 is formed by the image forming points 9a to 9d in FIG.
And 9f to 9i, measurement points 7A to 7D, 8A to 8
The two-dimensional positional deviation amount from D to the corresponding imaging point is obtained by the control device CNT1, and these positional deviation amounts are determined by the first
It is stored in the database device 2 of FIG. 1 as the distortion data of the projection exposure apparatus SR1. in this case,
The projected pattern 9 obtained by connecting the adjacent image forming points 9a, 9b, ..., 9g, 9d is a pincushion type.
It can be seen that the projection optical system PL1 of the projection exposure apparatus SR1 has a pincushion type distortion.

Similarly, the second projection exposure apparatus SR2 shown in FIG.
FIG. 3B shows a measurement result when the pattern of the test reticle R is projected with the magnification set to β by. 3B, the imaging characteristic measurement marks 3A, 3B, ..., 3 of FIG.
I projection image by the second projection exposure apparatus SR2
0a, 10b, ..., 10i, measurement points 7A to 7
The two-dimensional displacement amount from D, 8A to 8D to the corresponding image formation point is obtained by the control device CNT2, and these displacement amounts are stored in the database device 2 as distortion data of the second projection exposure device SR2. Is stored. In this case, the projection pattern 10 obtained by connecting the adjacent image formation points 10a, 10b, ..., 10d is barrel-shaped, and thus the projection optical system PL2 of the second projection exposure apparatus SR2 has barrel-shaped distortion. I understand.

Next, in the first projection exposure apparatus SR1 of FIG. 1, the reticle R1 is loaded and the wafer stage ST
The wafer W is loaded on the wafer 1, and the pattern image of the reticle R1 is exposed on each shot area of the wafer W by the step-and-repeat method. At this time, in the pattern area PA1 of the reticle R1, in addition to the circuit pattern, as shown in FIG.
Marks 3B, 3 for measuring the imaging characteristics of the test reticle R
Cross-shaped alignment marks are formed at the positions corresponding to F, 3H, and 3D, respectively.

Thereafter, the wafer W is subjected to processing steps such as development, etching, film formation, etc., and then the second projection exposure apparatus SR.
At 2, the wafer W is loaded on the wafer stage ST2 and the reticle R2 is loaded. The wafer W is pre-aligned on the basis of the outer shape, for example, as shown in FIG.
As shown in (b), in each shot area 4 of the wafer W, four cross-shaped wafer marks 5A to 5D are formed. Further, the moving directions of the wafer stage ST2 of the second projection exposure apparatus SR2 orthogonal to each other are defined as the X direction and the Y direction.

Prior to the exposure, the second projection exposure apparatus SR
The second controller CNT2 takes in the distortion data of the two projection exposure apparatuses SR1 and SR2 from the database apparatus 2 via the host computer 1. These distortion data are, as shown in FIGS. 3A and 3B, eight measurement points 7A to 7D and 8A to 8A, respectively.
It is represented as the amount of positional deviation between the projection patterns 9 and 10 with the magnification β in 8D. Then, in the control device CNT2,
As shown in FIG. 3C, when the magnification β of the projection pattern 10 by the second projection exposure apparatus SR2 is corrected to (β + Δβ), the projection patterns at the eight measurement points 7A to 7D and 8A to 8D 9 and the correction amount Δβ of the magnification that minimizes the overlay error between the projection pattern 10 and the pattern 10A after the magnification correction.

Specifically, in FIG. 3C, the measurement point 7
A vector 11A from the image formation point on the projection pattern 10A corresponding to A to the image formation point on the projection pattern 9 becomes a vector of the positional deviation amount at the measurement point 7A, and this vector is in the X direction and the Y direction. It consists of ingredients. Similarly,
At other measurement points 7B to 7D and 8A to 8D, the positional deviation amount vectors 11B to 11D and 12A to 12D are obtained, and the correction amount Δβ of the magnification is determined so that the sum of squares of the absolute values of these vectors is minimized. To be done. The correction amount Δβ of the magnification obtained in this way and the vector 11A to
11D and 12A to 12D are called distortion matching data, and the distortion matching data is stored in the storage unit in the control device CNT2.

The distortion matching data described above is used for the host computer 1 having a higher computing ability.
You may ask at. Furthermore, the required distortion
Store the matching data in the database device 2,
The stored distortion matching data may be repeatedly used until the distortion data is updated.

Next, in the second projection exposure apparatus SR2 of FIG. 1, using the alignment sensor AS2, a predetermined number of shot areas (sample shots) selected on the wafer W are shown in FIG. 2B, respectively. The coordinates of the four wafer marks 5A to 5D in the X and Y directions are measured. FIG. 4A shows a measurement result of four wafer marks 5A to 5D in a certain shot area on the wafer W.
In (a), the measurement points 7 on the square reference pattern 6
A to 7C are the projection optical system P of the first projection exposure apparatus SR1.
This corresponds to the projection position of the wafer marks 5A to 5C when the magnification of L1 is exactly β and there is no distortion or linear magnification error. Furthermore, a dotted cross-shaped mark 13A
13D set the magnification of the projection optical system PL2 of the second projection exposure apparatus SR2 to (β + Δβ), and project the pattern of the reticle R1 for the first layer onto the wafer W via the projection optical system PL2. The image of the wafer mark is shown, and the coordinates of the marks 13A to 13D are the same as those of the controller CNT2
Is calculated from the above distortion matching data and its own distortion data.

After that, the control device CNT2 makes the mark 13
The X and Y components of the vectors 14A to 14D from A to 13D toward the corresponding wafer marks 5A to 5D are obtained.
Then, for example, the vector 1 at the measurement point 7A in FIG.
Assuming that the absolute value of 1A is dA, the absolute value of the vector 14A at the measurement point 7A in FIG. 4A is dB, and the image height at the measurement point 7A is D, the control device CNT2 uses the following approximation formula on the wafer W. The correction amount Δβ ′ of the magnification of the projection optical system PL2 for minimizing the overlay error between the first layer and the second layer is calculated. This magnification correction amount Δβ ′ also includes the effect of expansion and contraction of the wafer W itself due to various processes.

Δβ ′ = 1 + (dA−dB) / L (1) Therefore, the final magnification of the projection optical system PL2 is (β + Δ
β) Δβ ′, and the control device CNT2 in FIG. 1 changes the magnification of the projection optical system PL2 via the pressure adjuster BC2 to (β
+ Δβ) Set to Δβ '. When obtaining the final correction value of the magnification of the projection optical system PL2, the absolute values of all the vectors 11A to 11D in FIG. 3C and the corresponding vectors 14A to 14D in FIG. It is desirable to use the average value of the differences of. In order to further enhance the averaging effect, it is desirable to use the average value of the measurement results for all the sample shots. Further, since the rotation angle of each sample shot is also detected by the intra-shot multi-point alignment measurement of this example, the overlay accuracy is further improved by rotating the reticle R2 in accordance with the average value of the rotation angles.

After that, the controller CNT2 calculates the array coordinates of all the shot areas on the wafer W by statistically processing the array coordinates of the wafer marks of each sample shot, and based on the calculated array coordinates, each shot. The regions are sequentially positioned at the exposure positions, and the pattern image of the reticle R2 is exposed through the projection optical system PL2. Thus, if the original circuit pattern on the first layer on the wafer W is the reference pattern 6 shown in FIG.
The actual projection image of the projection exposure apparatus SR1 of FIG.
The projection image by 2 becomes a projection pattern 10B, and the wafer W
The overlay error between the upper two layers is minimized.

In the following, in FIG. 1, when the third layer and subsequent layers on the wafer W are exposed by using a projection exposure apparatus different from the previous layer, calculation of distortion matching data and multipoint alignment within a shot are performed. By correcting the magnification based on the measurement result, the overlay error between different layers on the wafer W is maintained with high accuracy.
In addition, the multi-point alignment measurement within a shot is originally used to correct the error of the magnification of the pattern (chip magnification) in each shot area and the rotation of each shot area (chip rotation). According to the method, the former chip magnification can be corrected more accurately.

In the above example, as shown in FIG.
As the distortion matching data, the correction amount of the magnification of the second projection exposure apparatus for minimizing the overlay error between the two projection exposure apparatuses is obtained in advance. However, instead of this, for example, the position measurement results of the wafer marks 5A to 5D shown in FIG. 4A, and FIG.
Even if the distortion state of the projection image by the first projection exposure apparatus is obtained from the distortion data of 1 and the correction value of the magnification of the second projection exposure apparatus is directly obtained so that the overlay error with this projection image is minimized. Good.

Further, the present invention is not limited to the case where a stepper type (batch exposure type) projection exposure apparatus is used, but a step and step for performing exposure by synchronously scanning the reticle and the wafer with respect to the projection optical system. -It is also applicable when using a projection exposure apparatus of a scanning exposure method such as a scan method. As described above, the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the gist of the present invention.

[0037]

According to the exposure method of the present invention, the magnification of the projection image of the second exposure apparatus is corrected on the basis of the distortion data stored in advance and the positional deviation amount measured at a predetermined measurement point. 2 on the photosensitive substrate (wafer, etc.)
When performing exposure using two different exposure devices for layers,
Even if the distortion characteristics of the projected images of these two exposure apparatuses are different, there is an advantage that high overlay accuracy can be obtained.

Further, in the third step of the present invention, the distortion data stored in the first step is used for the second when the overlay accuracy of the projected images of the first and second exposure apparatuses becomes the best. Of the projection image by the exposure apparatus, and the positional deviation amount of the two projected images at the predetermined plurality of measurement points at the thus obtained magnification, and the positional deviation amount obtained in the second step. In the case of correcting the magnification of the projected image of the second exposure apparatus based on the above, the amount of calculation in actual exposure is reduced and the magnification of the projected image of the second exposure apparatus is corrected with high accuracy. There are advantages.

Further, according to the exposure apparatus of the present invention, there is an advantage that the above-mentioned exposure method can be carried out.

[Brief description of drawings]

FIG. 1 is a configuration diagram including a partial perspective view showing an exposure system used in an example of an embodiment of the present invention.

2A is a plan view showing the pattern arrangement of a test reticle, and FIG. 2B is a partial plan view showing the arrangement of wafer marks formed in a shot area of a wafer.

FIG. 3 is an explanatory diagram of distortion data and distortion matching data used in an example of the embodiment.

FIG. 4A is an enlarged view showing a measurement result of a wafer mark in the second projection exposure apparatus, and FIG. 4B is a virtual projection pattern of the first layer and a virtual projection pattern of the second layer. It is a figure which shows the state of the superposition.

FIG. 5 is a diagram showing an example of distortion of a projected image of a conventional projection exposure apparatus.

FIG. 6 is a diagram showing a state of superimposing projected images between two layers when exposure is performed by a conventional mix-and-match method.

[Explanation of symbols]

 1 Host Computer 2 Database Device R1, R2 Reticle W Wafer SR1-SRN Projection Exposure Device PL1, PL2 Projection Optical System CN1, CN2 Control Device AS1, AS2 Alignment Sensor BC1, BC2 Pressure Regulator

Claims (3)

[Claims] 1. A first layer on a photosensitive substrate is exposed with a projected image of a first mask pattern by a first exposure device, and then a second layer is exposed on a second layer by a second exposure device. In an exposure method of exposing the mask pattern projection images in an overlapping manner, a first step of obtaining and storing distortion data of the respective projection images by the first and second exposure devices; and a second layer on the photosensitive substrate. A second step of obtaining a positional deviation amount of the projected image of the first mask pattern at a plurality of predetermined measurement points on the photosensitive substrate before exposure by the second exposure device; A third step of correcting the magnification of the projected image of the second exposure apparatus based on the stored distortion data and the amount of positional deviation measured in the second step,
And an exposure method, wherein the exposure is performed by the second exposure apparatus at the magnification corrected in the third step. 2. The second step when, in the third step, the overlay accuracy of the respective projected images of the first and second exposure apparatuses is the best, based on the distortion data stored in the first step. Determining the magnification of the projection image by the exposure apparatus, and the amount of positional deviation between the two projection images at a plurality of predetermined measurement points at the obtained magnification,
The exposure method according to claim 1, wherein the magnification of the projection image of the second exposure apparatus is corrected based on the positional deviation amount obtained in the second step. 3. An exposure apparatus for projecting a mask pattern onto a photosensitive substrate via a projection optical system, wherein distortion data of a projected image by the exposure apparatus used for exposing the photosensitive substrate in the previous steps, and Storage means for storing distortion data of a projection image by the projection optical system, alignment sensor for detecting the position of the alignment mark on the photosensitive substrate, detection data by the alignment sensor and distortion stored in the storage means. And a magnification correction unit that corrects the magnification of the projection optical system based on the correction value obtained by the calculation unit. Exposure equipment.