JP2003318089A - Method of analyzing errors of exposed position, pattern for analyzing errors of exposed position, exposure mask, and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of analyzing errors of exposed positions which separates and detects factors causing errors in accuracy of exposed positions in superimposed exposure. <P>SOLUTION: A transfer pattern 7 is formed by performing a plurality of superimposed exposures in which one of three factors, an exposure optical system, a substrate W, and an exposure mask, which are used for superimposed exposure, is rotated by relatively 90 degrees each relative to the other two factors for superimposition to a ground pattern 5 on the substrate. The amount of misregistration in the transfer pattern 7 relative to the ground pattern 5 is measured for each rotation angle. Coordinate conversion is performed that returns the amount of misregistration measured for each rotation angle by the rotated angle. An average value of a plurality of amounts of misregistration acquired for each coordinate position that is coordinate-converted is acquired. The average value is assumed as an error in accuracy of exposed positions that may occur in each coordinate position caused by distortion in one factor that is rotated. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects an error in exposure position accuracy when overlay exposure is performed on an underlying pattern formed on a substrate by using an exposure mask by detecting each error factor separately. The present invention relates to a possible exposure position accuracy analysis method, and further to an exposure position accuracy analysis pattern, an exposure mask, and an exposure apparatus used in this analysis method.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, a resist pattern serving as a mask for etching or implanting impurities is formed on a substrate by a lithographic process. In a series of lithographic processing,
Pattern exposure (overlay exposure) is performed in which an exposure position is corrected on the basis of a detection position of a base alignment mark formed on a substrate, that is, so-called alignment is performed and the base pattern is superimposed.

By the way, in recent semiconductor device manufacturing processes, overlay exposure (so-called mix-and-match) using an exposure apparatus suitable for each step is performed, and overlay accuracy between different exposure apparatuses is required. ing. Therefore, when overlay exposure is performed, pattern exposure of the transfer pattern for position accuracy measurement as well as the transfer pattern for forming the actual device is also performed. The transfer pattern for measuring the position accuracy is formed so as to overlap with the base pattern for measuring the position accuracy formed on the substrate, and constitutes a set of measurement marks together with the base pattern. And
For each measurement mark, the amount of displacement of the transfer pattern with respect to the underlying pattern is measured by an alignment accuracy measuring device, and the measured amount of deviation is detected as an error in exposure position accuracy in overlay exposure.

Then, based on the detected error, the overlay accuracy between the exposure apparatuses is guaranteed, and when the error is large, the setting of the exposure optical system of the exposure apparatus is corrected so as to cancel this error. Overlay exposure is performed for manufacturing an actual product by using an appropriately corrected exposure apparatus.

[0005]

However, in the exposure position accuracy error detected as described above, in addition to the systematic error of the exposure optical system peculiar to the exposure apparatus, the pattern formed on the exposure mask Position error (exposure mask distortion) and position error of the underlying pattern formed on the substrate (substrate distortion).

Therefore, even if the setting of the exposure optical system in the exposure apparatus is corrected on the basis of the detected error, the correction cannot be performed with high accuracy.

Therefore, the present invention is an exposure position accuracy analysis capable of separately detecting the systematic error of the exposure optical system of the exposure position accuracy in the exposure apparatus, the distortion of the exposure mask, and the distortion of the underlying substrate. An object of the present invention is to provide a method, an exposure position accuracy analysis pattern, an exposure mask, and an exposure apparatus used in this analysis method.

[0008]

The exposure position accuracy analysis method of the present invention for achieving the above object is a method of performing overlay exposure using an exposure mask on a substrate on which a base pattern is formed. The method of analyzing the exposure position accuracy is characterized by being performed as follows. First, one of the three elements of the exposure optical system of the exposure apparatus used for overlay exposure, the substrate, and the exposure mask is arranged in a plurality relative to the other two elements and centered on the exposure optical axis. Perform multiple overlay exposures rotated at the rotation angle of
A transfer pattern is formed by superimposing each base pattern on the substrate. After that, the shift amount of the transfer pattern with respect to the base pattern is measured, and further, the coordinate conversion for returning each shift amount measured corresponding to each rotation angle by the rotation angle is performed. Then, an average value of a plurality of shift amounts obtained for each coordinate-converted coordinate position is obtained, and the average value is caused by the distortion of one element rotated during the above-described overlay exposure. This is the error in the exposure position accuracy that occurs at the coordinate position.

In such an analysis method, one of the three elements of the exposure optical system of the exposure apparatus, the substrate, and the exposure mask is rotated at a predetermined rotation angle with respect to the other two elements, and is superimposed. Since the alignment exposure is performed, in the overlay exposure at each rotation angle, only the error component caused by one rotated element follows this rotation. Therefore, by measuring the amount of deviation between the underlying pattern and the transfer pattern formed by superposition exposure at each rotation angle, and averaging the measured values by coordinate conversion, the error caused by the rotated element is measured. The shift amount obtained by extracting only the component is obtained.

Further, the exposure position accuracy analysis pattern of the present invention is an exposure position accuracy analysis pattern for carrying out the above-described analysis method of the present invention, and uses a base pattern provided on a substrate and an exposure mask. And a transfer pattern formed on the substrate by exposure. Then, in particular, the exposure is performed so that the layout diagrams obtained by rotating the exposure area surface by 360 / n degrees (n is a positive number of 2 or more) by about the normal line to the exposure area surface on the substrate are all in agreement. Measurement marks are arranged on the area surface.

In the exposure position accuracy analysis pattern having such a structure, the layout diagram of the transfer pattern is rotated by 360 / n degrees (n is a positive number of 2 or more) at a time and overlapped with the layout diagram of the base pattern. Also, the relationship between each base pattern and the transfer pattern is kept the same. That is, the substrate and the exposure mask are set to 360 / n degrees (n is 2
Even if the exposure position accuracy analysis patterns are formed by rotating each of the above positive numbers), the relationship between each base pattern and the transfer pattern is kept the same in each measurement mark constituting them. . Therefore, when the exposure position accuracy analysis method described above is performed, it becomes possible to uniformly handle the deviation amount relating to the measurement mark obtained at each rotation angle.

In the exposure mask of the present invention, the layout diagrams obtained by rotating the exposure area surface by 360 / n degrees (n is a positive number of 2 or more) by the normal line of the exposure area surface are all in agreement. Similarly, an exposure pattern for exposure position accuracy analysis is arranged on the exposure area surface.

In such an exposure mask, the exposure area surface is 360 / n degrees (n is 2) with the normal line of the exposure area surface as an axis.
The pattern exposure with the same layout is performed in all the exposures rotated by the above positive number).

Further, the exposure apparatus of the present invention is an exposure apparatus for carrying out the above-described analysis method of the present invention, and the exposure mask is 360 / n degrees (n is a positive number of 2 or more) with its normal line as an axis. ) And a mask holder that can be held in each state, and the substrate to be exposed 360 /
and a stage that can be held in each state rotated by n degrees.

In the exposure apparatus having such a structure, one element of the exposure optical system, the substrate, and the exposure mask is set at 360 / n degrees relative to the other two elements about the exposure optical axis. Overlay exposure is performed in each state rotated to.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in the order of an exposure position accuracy analysis pattern in overlay exposure, an exposure apparatus, an exposure mask, and an exposure position accuracy analysis method using these.

<Exposure Position Accuracy Analysis Pattern> FIG.
FIG. 1A is a plan view showing an example of an exposure position accuracy analysis pattern, and FIG. 1B is a plan view showing an example of measurement marks constituting the exposure position accuracy analysis pattern of FIG. 1A. Is.

The exposure position accuracy analysis pattern 1 (hereinafter, simply referred to as an analysis pattern) 1 shown in these figures has a plurality of measurement marks 3 at predetermined coordinates in an exposure area plane A on a substrate W. It is arranged at the position (x, y).

Each measurement mark 3 is composed of a base pattern 5 formed as a main scale, and a transfer pattern 7 formed as a sub-scale on the base pattern 5. The base pattern 5 and the transfer pattern 7 are configured to detect the amount of deviation of the transfer pattern 7 with respect to the base pattern 5 in the xy directions based on their positional relationship. As an example of such a measurement mark 3,
Here, a similar and smaller rectangle is formed in the center of the base pattern 5, which is a rectangle formed by two lines extending in the x direction and two lines extending in the y direction. Although the configuration in which the transfer pattern 7 formed by the above is provided is shown, the configuration of the measurement mark 3 is not limited to this.

The measurement mark 3 as described above has the exposure area surface A with the normal to the center O of the exposure area surface A as an axis.
Are arranged in the exposure area plane A in a so-called n-fold rotational symmetry form in which all the layout diagrams rotated by 360 / n degrees (n is a positive number of 2 or more) all match. Further, it is preferable that the measurement marks 3 are evenly arranged in the exposure area surface A so that the exposure position accuracy can be analyzed in the entire area of the exposure area surface A.

Here, as an example, the case where the measurement marks 3 are arranged in a matrix of 6 columns in the x direction and 6 rows in the y direction in the square exposure area surface A is shown. In the analysis pattern 1 formed by arranging the measurement marks 3 in this way, the exposure area surface A is 90 degrees (= 3
It becomes a four-fold rotational symmetry, in which all layout diagrams rotated by 60/4 degrees all match.

In the analysis pattern 1 having such a structure, a resist film is formed on the substrate W on which the underlying pattern 5 as the main scale is previously formed, and an exposure mask described below is applied to the resist film. The transfer pattern 7 made of a resist film is formed by performing the exposure used and then performing the development process.
Is obtained by forming. At this time, the layout of the base pattern 5 formed on the exposure area surface A of the substrate W and the layout of the transfer pattern 7 formed on the exposure area surface A by the exposure with the exposure mask are accurately overlapped, and each base pattern 5 is formed. Aligning the exposure mask with the exposure area surface A of the substrate W by using the alignment mark 4 so that the center of the transfer pattern 7 overlaps the center coordinate, that is, the center coordinate (x, y) of each measurement mark 3. is important. Regarding the alignment mark 9,
The details will be described below. The base pattern 5 is formed by forming a resist pattern by exposure using an exposure device different from the formation of the transfer pattern 7 and subsequent development, and etching the surface material of the substrate W using the resist pattern as a mask. ing.

In such an analysis pattern 1, even if the layout of the transfer pattern 7 is rotated 90 degrees with respect to the layout of the base pattern 5, the relationship between each base pattern 5 and the transfer pattern 7 is kept the same. , The same measurement mark 3 is configured. Therefore, even if the exposure position accuracy analysis pattern 1 is formed by rotating the substrate W or the exposure mask by 360 / n degrees (n is a positive number of 2 or more) about the exposure optical axis, these are configured. For each measurement mark 3
The relationship between each base pattern 5 and the transfer pattern 7 is kept the same. Therefore, when the exposure position accuracy analysis method described below is performed, it is possible to uniformly handle the deviation amount relating to the measurement mark 3 obtained at each rotation angle.

<Exposure Mask> FIG. 2 is a plan view of the exposure mask 10 for obtaining the above-described analysis pattern. On the exposure area surface 10A of the exposure mask 10 shown in this figure, an exposure pattern 11 for forming the transfer pattern (7) shown in FIG. 1 on a substrate, an exposure device pattern for an actual device (not shown) and An exposure alignment pattern 11a for alignment is formed. Then, in the empty space where the exposure device pattern is arranged, the exposure pattern 1 is arranged in the same arrangement as the above-mentioned measurement mark (3).
1 is provided, and an exposure alignment pattern 11a is provided in these empty spaces.

Of these, the exposure pattern 11 is in the same arrangement as the measurement mark (3) described with reference to FIG. 1, that is, with the normal line to the center O ′ of the exposure area surface 10A as an axis, as described above. The exposure area surface 10A is rotated by 360 / n degrees (here, 90 degrees) by n times rotational symmetry (here, n = 4 four times symmetry rotational symmetry) in which the respective layout diagrams are all matched. It is supposed to be arranged within 10A. Here, as an example, as in the case of the exposure marks shown in FIG. 1, a case where the exposure patterns 11 are evenly arranged in a matrix of 6 columns in the x direction and 6 rows in the y direction within the square exposure region surface 10A. Illustrated.

Further, the exposure alignment pattern 11a
Is for aligning the exposure mask 10 with respect to the exposure area surface by combining with the underlying alignment pattern formed on each exposure area surface of the substrate to be exposed. Especially here, with respect to the exposure area surface of the substrate,
In each case where the exposure area surface 10A of the exposure mask 10 is rotated by 90 degrees, the layout of the base pattern formed on the exposure area surface of the substrate and the exposure area surface of the substrate are formed by the exposure by the exposure mask 10. It is assumed that the exposure alignment pattern 11a that allows the exposure mask 10 to be aligned with the exposure region surface of the substrate is configured so as to accurately overlap the layout of the transfer pattern.

Here, when the exposure mask 10 is a stencil mask for equal-magnification exposure, each exposure alignment pattern 11a consisting of a plurality of lines of lines is used as the exposure area surface 1
It is assumed that they are arranged on the peripheral portion of 0A in a state of being rotated and moved by 360 / n degrees (here, 90 degrees) with respect to the center O ′. In the arranged state, each of the exposure alignment patterns 11a is arranged so that the line is kept vertical or horizontal with respect to the side forming the exposure area surface 10A.

This exposure alignment pattern 11a is
It is used in combination with a base alignment pattern formed on a substrate to be exposed.

That is, as shown in FIG. 3, on the exposure area surface A of the substrate W to be exposed, in addition to the underlying pattern 5 and the underlying device pattern (not shown) for an actual device shown in FIG. The underlying alignment pattern 5a for alignment is provided. The base alignment pattern 5a is composed of a plurality of lines of lines.
Then, in a state where the layout of the exposure pattern of the exposure mask projected on the substrate W matches the layout of the underlying pattern 5 on the substrate W, as shown in FIG. 4, the center of the array of lines forming the exposure alignment pattern 11a. It is assumed that each alignment pattern 5a is arranged at a position such that c ′ and the array center c of the line of the underlying alignment pattern 5a seen through the membrane all match.

Therefore, in the alignment of the exposure mask with respect to the surface of the exposure area of the substrate, the array center c of the lines forming the underlying alignment pattern 5a and the array center c'of the lines forming the exposure alignment pattern 11a are all aligned. As described above, the position of the exposure mask is relatively moved with respect to the exposure area surface of the substrate.

As shown in FIG. 4, each line forming the base alignment pattern 5a and each line forming the exposure alignment pattern 11a may be formed by an array of dots. In addition, an alignment mark (alignment mark 9 in FIG. 1) is formed on the substrate after the overlay exposure, on which the exposure alignment pattern 11a is transferred so as to be superimposed on the underlying alignment pattern 5.

As described above, in the exposure mask 10 having the structure described with reference to FIG. 2, the exposure area surface 10A is 360 / n degrees (here, 90 degrees) each with the normal line to the center O'of the exposure area surface 10A as an axis. In all the rotated exposures, it is possible to perform the pattern exposure with the same layout on the exposure area of the substrate.

<Exposure Device> Next, the structure of an exposure device for performing overlay exposure using the above-mentioned exposure mask will be described. FIG. 5 shows an example of such an exposure apparatus. The exposure apparatus 20 shown in this figure is a low acceleration electron exposure (LEEP).
L: Low energy E-beam Proximity Projection Lithogr
a exposure device for apy), in which the exposure pattern formed on the exposure mask 10 is exposed to the exposure area surface A on the substrate W at the same magnification.

The exposure apparatus 20 shown in this figure has an electron gun 21 for generating an electron beam e (charged particle beam) as exposure light.
(Irradiation unit). Then, on the path of the electron beam e emitted from the electron gun 21, a mask holding unit for holding the exposure mask 10 having the above-described configuration with the path (exposure optical axis) of the electron beam e as a normal line. 23, and a stage 25 that holds the substrate W at a distance d from the exposure mask 10 is arranged. Also,
Between the electron gun 21 and the mask holder 23, a condenser lens 27a, an aperture 27b for limiting the electron beam e, and an electron beam e in a state of enclosing the path of the electron beam e.
Deflectors 27c to 27 for controlling the irradiation position of
An exposure optical system 27 for controlling the exposure light (electron beam e) composed of f is arranged.

Then, in particular, the mask holding unit 23 sets the exposure mask 10 to 3 with the normal line of the exposure area surface 10A as an axis.
60 / n degrees (n is a positive number of 2 or more, where n = 4
It can be held in each state rotated by 90 degrees). In addition, the mask holding unit 23 is the mask holding unit 2
3 itself may be configured to be rotatable by 360 / n degrees, or may be configured to be capable of holding the exposure mask 10 in a state of being rotated by the predetermined angle.

Furthermore, the stage 25 is an xy stepper stage, and the substrate W is exposed to each exposure area surface A
It is configured such that it can be held in each state rotated by 360 / n degrees (n is a positive number of 2 or more, and here, 90 degrees of n = 4) about the normal line of. In addition, this stage 25
The stage 25 itself may be configured to be rotatable by 360 / n degrees, or may be configured to be capable of holding the substrate W rotated by the predetermined angle.

In the exposure apparatus having such a configuration, one element of the exposure optical system 27, the substrate W, and the exposure mask 10 is set at 360 / n degrees with respect to the other two elements about the exposure optical axis. It is possible to perform overlay exposure in each state in which the relative rotation is performed.

<Exposure Position Accuracy Analysis Method> Next, a method of analyzing the exposure position accuracy in overlay exposure using the above-described exposure mask and exposure apparatus with the above-described analysis pattern will be described.

First, in the exposure apparatus 20 shown in FIG. 5, the substrate W to be exposed and the exposure mask 10 are set in the reference state. The substrate W is the substrate W on which the base pattern 5 described with reference to FIG. 3 is formed, and the exposure mask 10 is
It is the exposure mask 10 on which the exposure pattern 11 described with reference to FIG. 2 is formed.

In the reference state where the substrate W and the exposure mask 10 are installed, the rotation state of the exposure mask 10 with respect to the exposure optical system 27 and the substrate W is θ = 0 degree. Then, in this reference state (r0), after aligning the exposure mask 10 with respect to one exposure area surface A (r0) on the substrate W, the first exposure area surface A (r0) is aligned with the first exposure area surface A (r0). Exposure.

Next, with respect to the exposure optical system 27 and the substrate W, only the exposure mask 10 is rotated, for example, 360 / n degrees (here, 90 degrees) counterclockwise with respect to the exposure optical axis, and the mask holder 23 is rotated. To the first rotation state (r90) held by. The first rotation state (r90) is the reference state (r90).
From 0), only the exposure mask 10 is relatively rotated with respect to the exposure optical system 27 and the substrate W by r = + 90 °. Then, in the first rotation state (r90), after aligning the exposure mask 10 with respect to the next exposure area surface A (r90) on the substrate W, with respect to this exposure area surface A (r90). Second exposure is performed.

Thereafter, with respect to the exposure optical system 27 and the substrate W, only the exposure mask 10 is moved to the first rotation state (r9).
0) to 360 / n degrees counterclockwise (+90 here)
The second rotation state (r180) held by the mask holding section 23 is rotated. This second rotation state (r1
In 80), from the reference state (r0), only the exposure mask 10 is relatively r = + with respect to the exposure optical system 27 and the substrate W.
It is rotated 180 degrees. Then, in the second rotation state (r180), after the exposure mask 10 is aligned with the next exposure area surface A (r180) on the substrate W, the exposure area surface A (r180) is aligned with the exposure area surface A (r180). And perform the third exposure.

Thereafter, similarly, only the exposure mask 10 is rotated counterclockwise from the second rotation state (r180).
In the third rotation state (r270) in which the mask holder 23 is rotated by 60 / n degrees (here, +90 degrees), it is the fourth time with respect to the new exposure area surface A (r270) on the substrate W. Expose.

As described above, n (four in this case) exposure area surfaces A (r0), A (r90), A (r1) on the substrate W are formed.
80) and A (r270) are exposed, and then development processing is performed to form a transfer pattern on each exposed area surface A of the substrate W. As a result, the four exposure area surfaces A (r0) and A (r9
0), A (r180), and A (r270) have the analysis pattern 1 as described with reference to FIG. The above four exposure area surfaces A (r0), A (r90), A (r180), A (r270)
May be on wafers W having the same history.

Here, FIG. 6A shows the analysis pattern 1 (r0) formed on the exposure area surface A (r0) which has been exposed in the reference state (r0) described above. 6 (2) shows the analysis pattern 1 (r90) formed on the exposure area surface A (r90) that has been exposed in the first rotation state (r90) described above. In addition, in order to simplify the description, in each of these drawings, the plurality of measurement marks 3 constituting the analysis patterns 1 (r0) and 1 (r90) are represented by four measurement marks 3 as representatives. .

Then, with respect to the analysis pattern 1 (r0) formed on the exposure area surface A (r0), the shift amount (xd, yd) of the exposure position in all the measurement marks 3 constituting them.
Measure ^r0 . Then, the coordinates (x,
y) ^r0 is associated with the shift amount (xd, yd) ^r0 measured for each measurement mark 3. Therefore, with respect to the exposure area surface A (r = 0), data as shown in (1) below in which the coordinates and the deviation amount are associated with each other are obtained by the number of the measurement marks 3. (X, y) ^r0 , (xd, yd) ^r0 (1)

Further, with respect to the analysis pattern 1 (r90) formed on the exposure area surface A (r90), the exposure position deviation amount (xd, y) in all the measurement marks 3 constituting them.
d) ^{r9 0} to measure. Then, the coordinates (x, y) ^r90 of each measurement mark 3 and the deviation amount (xd, yd) ^r90 measured for each measurement mark 3 are associated with each other. Therefore, as for the exposure area surface A (r90), the data as shown in (2) below in which the coordinates and the deviation amount are associated with each other are obtained by the number of the measurement marks 3. (X, y) ^r90 , (xd, yd) ^r90 (2)

Similarly, the other exposure area surfaces A (r180) and A (r27)
Regarding 0), as in the following (3) and (4), data associating the coordinates with the deviation amount is obtained for each of the measurement marks 3. (X, y) ^r180 , (xd, yd) ^r180 (3) (x, y) ^r270 , (xd, yd) ^r270 (4)

Next, (1) to (1) obtained as described above
The coordinates of the data of (4) are converted. Here, coordinate conversion is performed so that the rotation state of the exposure mask at the time of exposing each exposure area surface A (r0), A (r90), A (r180), A (r270) is returned to the reference state (r0). I will do it. Specifically, the data regarding each exposure area surface A (r0) is used as it is, the data regarding A (r90) is subjected to the coordinate conversion of −90 degrees, and the data regarding A (r180) is subjected to the coordinate conversion of −180 degrees. , A (r270)
The data related to the coordinate conversion is -270 degrees.

By this surface coordinate conversion, the following conversions (5) to (8) are performed on all the measurement marks 3. The left side of the arrow indicates each exposure area surface A (r0), A (r90),
It is the original data regarding A (r180) and A (r270), and the right side of the arrow is the data after coordinate conversion. (X, y) ^r0 , (xd, yd) ^r0 → (x, y) ^r0 , (xd, yd) ^r0 (5) (x, y) ^r90 , (xd, yd) ^r90 → (x, y) ^r0 , (xd, yd) ^r0 (6) (x, y) ^r180 , (xd, yd) ^r180 → (x, y) ^r0 , (xd, yd) ^r0 ... (7) (x, y) ^r270 , ( ^Xd , yd) ^r270 → (x, y) ^r0 , (xd, yd) ^r0 (8)

By performing the coordinate conversion as described above, data having the same coordinate value is generated every n sets (4 sets in this case).

Therefore, after the coordinate conversion processing as described above is performed, n = 4 deviation amounts associated with the same coordinate value are averaged, and the average value calculated for each coordinate value is
The error is the exposure position accuracy error that occurs at each coordinate position due to the distortion of the exposure mask.

Then, the distortion of the exposure mask is corrected based on such an error in the exposure position accuracy. At this time, if the distortion of the exposure mask is within a range that can be corrected by adjustment of the exposure optical system of the exposure apparatus, the exposure optical system is corrected so as to cancel the distortion of the exposure mask based on the obtained error. Then, overlay exposure for forming an actual device is performed. On the other hand, when the distortion of the exposure mask cannot be corrected by adjusting the exposure optical system of the exposure apparatus, the exposure pattern itself for the actual device in the exposure mask is corrected so as to cancel the distortion, or the exposure mask is exposed. Re-form the mask.

In the above, the exposure optical system 27 and the substrate W shown in FIG. 5 are exposed a plurality of times by rotating only the exposure mask 10 to cause the exposure mask 10 to distort. Although the case of obtaining the error of the exposure position accuracy that occurs at the coordinate position has been described, similarly, it is also possible to obtain the error of the exposure position accuracy that occurs at each coordinate position due to the distortion of the exposure optical system 27 and the substrate W. .

For example, when obtaining an error in the exposure position accuracy caused by the distortion of the substrate W, the exposure in the reference state (r0) similar to the above and the exposure optical system 27 and the exposure mask 10 are performed. , The substrate W is 360 / n with respect to the exposure optical axis
The exposure is performed a plurality of times by rotating each time (here, for example, +90 degrees).

After that, in the same manner as described above, the deviation amount is measured for each measurement mark of the exposure position accuracy analysis pattern obtained by this exposure. Then, the coordinates of each measurement mark and each measured deviation amount are associated with each other, coordinate conversion is performed so that the rotation state of the exposure optical system 27 returns to the reference state (r0), and a plurality of coordinates associated with the same coordinate value are obtained. Obtain the average value of the deviation. This average value is defined as an exposure position accuracy error that occurs at each coordinate position due to the distortion of the substrate W.

Then, the distortion of the substrate W is corrected based on such an error in the exposure position accuracy. At this time, this substrate W
If the distortion is within a range that can be corrected by adjusting the exposure optical system of the exposure apparatus, the distortion of the substrate (deviation of the formation position of the underlying pattern) is canceled based on the obtained error.
The exposure optical system is corrected to perform overlay exposure for forming an actual device. On the other hand, when the distortion of the substrate cannot be corrected by adjusting the exposure optical system of the exposure apparatus, the underlying pattern itself for the actual device is corrected or the underlying pattern is reformed so as to cancel the distortion. I do.

Further, in order to obtain an error in the exposure position accuracy caused by the distortion of the exposure optical system 27, the exposure in the reference state (r0) as described above and the exposure optical system 27 are performed. The mask 10 and the substrate W are rotated by 360 / n degrees (here, -90 degrees) with respect to the exposure optical axis, and exposure is performed a plurality of times. Thus, the exposure mask 10 and the substrate W are exposed a plurality of times by rotating only the exposure optical system 27 by +90 degrees.

After that, in the same manner as described above, the deviation amount is measured for each measurement mark of the exposure position accuracy analysis pattern obtained by this exposure. Then, the coordinates of each measurement mark and each measured deviation amount are associated with each other, coordinate conversion is performed so that the rotation state of the exposure optical system 27 returns to the reference state (r0), and a plurality of coordinates associated with the same coordinate value are obtained. Obtain the average value of the deviation. This average value is defined as an exposure position accuracy error that occurs at each coordinate position due to the distortion of the exposure optical system 27.

Then, based on such an error in the exposure position accuracy, the exposure optical system of the exposure apparatus is corrected so as to cancel this distortion, and overlay exposure for forming an actual device is performed using the corrected exposure apparatus. .

Further, the exposure in which one element of the exposure optical system 27, the substrate W, and the exposure mask 10 as described above is rotated with respect to the other two elements is performed for each of the three elements. Thus, it is possible to obtain all the errors in the exposure position accuracy that occur at each coordinate position due to the three elements.

In the above embodiment, the measurement mark 3 of the exposure position accuracy analysis pattern 1 described with reference to FIG. 1 and the exposure pattern 11 of the exposure mask 10 described with reference to FIG. The case where the layout diagrams rotated by 90 degrees about the normal to the center O of the planes A and 10A are arranged in the same so-called four-fold rotational symmetry form has been described. However, the present invention is not limited to this, and the exposure position accuracy in which the measurement marks 3 are arranged so that all the layout diagrams rotated by 360 / n degrees (n is a positive number of 2 or more) match each other. Analysis pattern 1,
With the exposure mask 10 on which the exposure pattern 11 is arranged, the same analysis method can be performed, and the same effect can be obtained. However, in the overlay exposure for performing the analysis method, the substrate W and the exposure mask are rotated by 360 / n degrees.

The larger n is, the more accurate position accuracy analysis can be performed. Further, as shown in the embodiment, by setting n = 4, the measurement mark 3 and the exposure pattern 11 are efficiently arranged on the rectangular exposure region surfaces A and 10A, and highly accurate position accuracy analysis is performed. It is possible. Further, by setting n = 4, the rotation angle of the exposure mask and the substrate becomes 90 degrees. Therefore, if the substrate and the exposure mask have a rectangular shape, the storability in the exposure apparatus can be secured. .

[0064]

As described above, according to the exposure position accuracy analysis method of the present invention, one of the three elements of the exposure optical system of the exposure apparatus, the substrate to be exposed, and the exposure mask used for exposure is used. By rotating one of the other two elements at a predetermined rotation angle and performing overlay exposure, it is possible to extract only the error component caused by the rotated element. It becomes possible to analyze the exposure position accuracy with the components separated. As a result, when the error in the exposure position accuracy is corrected, it is possible to perform the correction based on the error obtained by separately separating each element, and it is possible to perform the overlay exposure with higher position accuracy accuracy. It will be possible. Further, by using the exposure position accuracy analysis pattern, the exposure mask, and the exposure apparatus of the present invention, the above-described exposure position accuracy analysis method of the present invention can be performed.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of an exposure position accuracy analysis pattern of the present invention.

FIG. 2 is a plan view showing an example of an exposure mask of the present invention.

FIG. 3 is a plan view showing a layout of a base pattern forming the exposure position accuracy analysis pattern of FIG.

FIG. 4 is a plan view showing details of alignment marks for forming an exposure position accuracy analysis pattern of the present invention.

FIG. 5 is a configuration diagram of an exposure apparatus for performing analysis using the exposure position accuracy analysis pattern of the present invention.

FIG. 6 is a plan view (No. 1) for explaining the exposure position accuracy analysis method of the present invention.

FIG. 7 is a plan view (No. 2) for explaining the exposure position accuracy analysis method of the present invention.

[Explanation of symbols]

1 ... Analysis pattern, 3 ... Measurement mark, 5 ... Underlayer pattern, 7 ... Transfer pattern, 10 ... Exposure mask, 10A ... Exposure area surface (exposure mask), 11 ... Exposure pattern, 20 ...
Exposure device, 23 ... Mask holding part, 25 ... Stage, 27
... exposure optical system, O, O '... center, A ... exposure area surface (substrate), W ... substrate

Claims (8)

[Claims] 1. A method of analyzing exposure position accuracy when overlay exposure using an exposure mask is performed on a substrate on which an underlying pattern is formed, the exposure optical system of an exposure apparatus used for the overlay exposure, One of the three elements of the substrate and the exposure mask
One is subjected to a plurality of overlay exposures, which are rotated at a plurality of rotation angles about the exposure optical axis relative to the other two elements, and are overlaid on each underlying pattern on the substrate. A step of forming a transfer pattern, a step of measuring a displacement amount of the transfer pattern with respect to the base pattern for each of the rotation angles, and a displacement amount measured corresponding to each of the rotation angles, for each rotation angle. And a step of performing coordinate conversion to return only the average value of a plurality of displacement amounts obtained for each coordinate position subjected to the coordinate conversion, and the average value is caused by the distortion of the rotated one element. An exposure position accuracy analysis method, wherein the exposure position accuracy error occurs at a coordinate position. 2. The exposure position accuracy analysis method according to claim 1, wherein the measurement of the deviation amount is performed with the exposure area surface being 360 / n degrees (n is 2) with the normal line of the exposure area surface of the substrate as an axis. Exposure performed by using a measurement mark composed of the underlying pattern and the transfer pattern, which is arranged on the exposure area surface so that all the layout drawings rotated by the above positive numbers) match each other. Position accuracy analysis method. 3. An exposure position accuracy analysis pattern used for analyzing the overlay accuracy of a base pattern provided on a substrate and a transfer pattern formed on the substrate by exposure using an exposure mask. Then, the exposure pattern is rotated by 360 / n degrees (n is a positive number of 2 or more) by 360 ° about the normal to the exposure pattern surface of the substrate so that all the layout diagrams match with each other. An exposure position accuracy analysis pattern, characterized in that a measurement mark composed of the transfer pattern is arranged on the exposure area surface. 4. The exposure position accuracy analysis pattern according to claim 3, wherein the measurement marks are provided on the exposure area surface such that all layout diagrams obtained by rotating the exposure area surface by 90 degrees are all in agreement. An exposure position accuracy analysis pattern characterized by being arranged. 5. An exposure mask used for overlay exposure, wherein the exposure area surface is 360 /
An exposure mask in which an exposure pattern for exposure position accuracy analysis is arranged on the exposure area surface so that all the layout diagrams rotated by n degrees (n is a positive number of 2 or more) match each other. . 6. The exposure mask according to claim 5, wherein the exposure pattern is arranged on the exposure area surface so that all layout diagrams obtained by rotating the exposure area surface by 90 degrees match each other. An exposure mask characterized by the above. 7. An exposure apparatus used for pattern exposure using an exposure mask, wherein the exposure mask in each state rotated by 360 / n degrees (n is a positive number of 2 or more) with respect to the exposure optical axis. An exposure apparatus comprising: a mask holding unit capable of holding, and a stage capable of holding a substrate in each state rotated by 360 / n degrees with respect to an exposure optical axis. 8. The exposure apparatus according to claim 7, wherein the exposure mask and the substrate are held in respective states rotated by 90 degrees.