JPH07321026A - Projection aligner - Google Patents

Abstract

PURPOSE:To obtain a projection aligner in which superposition and synthesis of screen are effected with high accuracy by deriving an optimal correction amount or difference in the alignment therefor easily. CONSTITUTION:A plurality of marks are put around a region on an original plate 3 where a pattern is present and the positions of a plurality of images of the marks projected onto a substrate 5 are detected. Correction amount in the positioning of the substrate 5 or correction amount in the focus characteristics of a projection optical system 4 is then determined depending on the positional shift from the design position thereof for the plurality of marks 3A. Finally, the position of the substrate 5 or the focus characteristics of the projection optical system 4 is corrected based on each correction amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and can be applied to, for example, a liquid crystal display or an apparatus for projecting a semiconductor pattern onto a substrate.

[0002]

2. Description of the Related Art Conventionally, an L formed on a reticle has been used as a projection exposure apparatus for manufacturing a liquid crystal display (LCD).
There is a so-called step-and-repeat method in which after exposing a predetermined area of a plate with a CD pattern, the plate is stepped a certain distance and the LCD pattern of the reticle is exposed again. This LCD
The exposure apparatus 1 for use is configured as shown in FIG.
That is, the pattern of the LCD formed on the reticle 3 by being illuminated by the illumination optical system 2 is X-rayed by the projection lens 4.
It is transferred to the plate 6 placed on the Y stage 5.
The position coordinate of the XY stage 5 is accurately monitored by the laser interferometer 7 and the position is controlled.

A reticle alignment system 8 for aligning the reticle 3 and a plate alignment system 9 for aligning the plate 6 are arranged as alignment systems for performing alignment. Further, the stepper type LCD exposure apparatus 1 is equipped with a reticle exchanging mechanism 10 for exchanging the reticle 3 in order to perform stitching exposure while exchanging the reticle 3.

[0004]

By the way, the pattern of the LCD is formed in the stepper type LCD exposure apparatus 1 by the normal screen compositing method. In this screen compositing method, for example, as shown in FIG. 14, the LCD pattern is divided into four patterns A, B, C and D and exposed. Here, each pattern A, B, C, D corresponds to one reticle 3.
The patterns A, B, C, and D are exposed on the plate 6 by exchanging the reticle 3 using the four reticles 3, and the patterns A, B, C, and D are combined on the plate 6 in this manner. Forming an LCD pattern.

In the exposure using such a screen synthesizing method,
There are error factors as shown in FIG. That is, if the pattern to be transferred has a rotation error when the screens are combined, or if there is an error in the positions of the patterns A and B to be transferred, it shifts to the joint as shown in FIGS. Occurs. Further, as shown in FIG. 15C, for example, the patterns A and B formed by the first exposure are represented by dotted lines, and the patterns A ′ and B ′ to be superimposed by the second exposure are represented by solid lines. If the exposure patterns A ′ and B ′ of 1 have a magnification error, a misalignment or an overlay error occurs at the joint. In addition to this, there are errors due to misalignment of the joint portion due to lens distortion and overlay errors, and errors due to patterning errors in the pattern of the reticle 3.

However, as described above, due to various factors,
If an error occurs during overlaying or screen composition, an LCD or semiconductor with sufficient performance cannot be manufactured as a result of exposure. As a method for solving this problem, various correction amounts (values) during exposure may be optimized. However, deriving the correction amount is not easy because it involves test exposure and measurement by another inspection device, and there are many problems in that accuracy cannot be expected because it includes another error factor.

The present invention has been made in consideration of the above points, and it is possible to easily derive an optimum correction amount or deviation for exposure for overlay or screen composition to perform exposure with high accuracy in overlay or screen composition. It is intended to propose a possible exposure apparatus.

[0008]

In order to solve such a problem, in the present invention, the original plate 3 and the substrate 6 are positioned,
In a projection exposure apparatus 20 that projects a pattern on the original plate 3 onto a predetermined area of a substrate 6 via a projection optical system 4 having a predetermined image forming characteristic, a plurality of marks are provided around the area where the pattern on the original plate 3 exists. 3A is provided and the positions of the images of the plurality of marks 3A projected on the surface substantially the same as the surface of the substrate 6 are respectively detected by the position detecting means 21 and 22, and the position detecting means 21 and 22. Based on the deviation amount of the positions of the plurality of marks 3A from the designed position where the plurality of marks 3A should be projected by the projection optical system 4, the original plate 3
Deviation detection means for determining at least one of a positional deviation of the substrate 6 with respect to the substrate 6 and a deviation of the imaging characteristic of the projection optical system 4 from a predetermined imaging characteristic, and a correction amount for positioning the substrate 6 based on the determined positional deviation. Projection optical system 4 based on the obtained deviation
Correction amount calculation means for determining at least one of the correction amounts of the image forming characteristics, and the position of the substrate 6 is corrected based on the calculated correction amounts, or the image forming characteristic of the projection optical system 4 is corrected based on the deviation. And a correction means for doing so.

[0009]

A plurality of marks 3A are provided around the area where the pattern exists on the original plate 3, and the positions of the images of the plurality of marks 3A projected on the surface substantially the same as the surface of the substrate 6 are detected, respectively. The mark 3A of 3 is calculated according to the amount of deviation from the designed position to be projected by the projection optical system 4, and the correction amount of the positioning of the substrate 6 and / or the correction amount of the imaging characteristic of the projection optical system 4 is obtained. By correcting the position of the substrate 6 and / or the image forming characteristic of the projection optical system 4 based on each correction amount, the optimum correction amount and deviation for exposure for superposition and screen composition can be easily derived to obtain high accuracy. It can be exposed by superimposing and screen composition.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 12 are designated by the same reference numerals, 20 is an LCD according to the present invention as a whole.
The exposure optical system 2 provides uniform illumination on the reticle 3, and the pattern on the reticle 3 is the projection lens 4
An image is formed on a plate (not shown) on the XY stage 5 through A light receiving portion mark 21 is provided at the image forming position on the XY stage 5.

This light receiving portion mark 21 is shown in FIG.
As shown in (A), a slit-shaped opening pattern is formed. The light that has passed through the light receiving portion mark 21 is converted into the photoelectric conversion element 2
2 is photoelectrically converted and processed as an electric signal. XY
The movement amount of the stage 5 is accurately monitored by the laser interferometer 7, and the positioning is precisely controlled. That is, the laser interferometer 7
It moves along the movement coordinate system (stage coordinate system) determined by. Further, a mark 3A having a slit-shaped opening pattern as shown in FIG. 2B is arranged on the reticle 3, and the position of the mark 3A in the stage coordinate system projected through the projection optical system 4 is obtained. . This is obtained by scanning the projected image of the mark 3A with the light-receiving portion mark 21 in the direction orthogonal to the longitudinal direction of the slit, and FIG. 3A shows the coordinate of the laser interferometer 7 taken on the horizontal axis. A bright signal waveform as shown is obtained.

If the coordinate measuring mark 3A on the reticle 3 is a slit slit mark instead of an opening, a dark signal waveform as shown in FIG. 3B is obtained. By processing these waveforms, the position of the projected image of the mark 3A on the reticle 3 can be obtained. Since the light-receiving unit mark 21 and the mark 3A on the reticle 3 are measured in the X and Y directions, the mark 3A having slits in the X and Y directions is formed as shown in FIG. Further, in order to obtain a signal having a good SN ratio or average the measurement patterns to perform accurate measurement, a plurality of slits may be provided as the mark 3A in the X and Y directions as shown in FIG.

Now, an exposure method according to this embodiment using these coordinate measuring functions will be described. First, FIG. 6 shows the actual arrangement of the coordinate measuring marks 3A on the reticle 3.
The mark 3A is a mark for measuring the X and Y directions, and a plurality of points are arranged around the LCD pattern 3B. First, the reticle 3 is aligned by using the alignment mark 3C, and then the plurality of coordinate measuring marks 3A are attached to the light receiving unit mark 21 described above in FIG.
Also, the reticle coordinate measuring function including the photoelectric conversion element 22 is used for measurement, and optimal parameters for overlaying and screen composition are derived based on the measurement result.

This measurement includes the patterning error of the reticle 3 and the distortion of the projection lens 4, and the correction amount and the deviation are obtained by measuring at the position actually transferred onto the plate 6, and therefore these errors are included. Can be corrected. For example, the amount of deviation between the position of the coordinate measuring mark 3A on the reticle 3 and the ideal point that should be designed for each mark 3A is obtained, and the rotation correction amount of the reticle 3, the XY shift correction amount, and the XY magnification offset amount are calculated. It can be obtained by least-squares approximation or approximation by an n-order formula. The reticle 3 is positioned based on these correction amounts, the imaging characteristics of the projection optical system are changed, and the exposure operation starts.

In this embodiment, a plurality of reticle coordinate measuring marks 3A are arranged on the outer peripheral portion of the LCD pattern 3B, so that the correction amount that optimizes the outer peripheral portion can be obtained. It is possible to suppress the error and the difference in overlay accuracy at the joint portion, which is effective for screen composition.

FIG. 7 shows the effect of superimposing the first exposure and the second exposure. The pattern shift at the time of the first exposure is shown in FIG. The two-dot chain line in the figure is the ideal position. Similarly, FIG. 7B shows the deviation of the pattern at the time of the second exposure. If these are exposed without correction, a large misalignment occurs as shown in FIG. 7 (C). In FIG. 7C, the shift of the pattern at the first exposure is shown by a solid line, and the shift of the pattern at the second exposure is shown by a dotted line.

When the first exposure is performed, the pattern of FIG. 7A is optimized so as to be close to the ideal position, parameters are obtained, and the pattern of FIG. Figure 7
As shown in FIG. 7D, the error can be significantly reduced as compared with FIG.

In the example of FIG. 7, the correction amount is derived with emphasis on the superposition, but if the correction amount is obtained by each reticle 3 in the same layer, the splicing error can be reduced in the same layer. Whether superposed or spliced, not only in the X and Y directions, but also in the X or Y direction depending on the directionality of the pattern.
Of the correction amount by giving priority to only one direction, or X or Y
The correction amount can be derived by weighting in the direction.

This method is effective when the overlaying accuracy or the joining accuracy is strict in only one direction due to the nature of the pattern of the transistors constituting the LCD. Also L
When the CD is divided and exposed, it is possible to give priority to the information of only the divided portion and derive the correction amount so that the difference in overlay accuracy at the joint portion reduces the joint error. Further, since each layer is optimized to the ideal position, it is effective even when the LCD exposure device 20 is used interchangeably. Of course, correction is not performed in the first exposure, and only the coordinate position information of the reticle 3 is held, and this information is used in the second exposure for the coordinate position of the reticle 3 in the first exposure. It is also possible to derive the correction amount to be optimized.

Actually, this exposure is executed along the exposure processing procedure SP0 as shown in FIG. That is, first, at step SP1, the reticle 3 is loaded on the LCD exposure device 20, and at subsequent step SP2, the reticle 3 is loaded.
Align. Next, in step SP3, the mark 3A for coordinate measurement on the aligned reticle 3 is moved to X by the reticle coordinate measuring functions 21 and 22.
The position is measured on the coordinates of the Y stage 5.

Then, in step SP4, for example, an optimum correction amount is calculated from the position information so that an ideal design position can be exposed, and the calculated result is used in step SP4.
Set the correction amount with 5. Next, the magnification, rotation, etc. are corrected by the set correction amount, the reticle 3 is aligned again, and the coordinates are measured again at step SP7.

Next, at step SP8, it is judged whether the measured position is within the permissible range with respect to the position after correction, and if it is insufficient, the process returns to step SP4 and the setting of the correction amount is repeated. If it is within the allowable range, the process proceeds to step SP9 to determine whether or not the designated number of reticles 3 has been completed. If not completed, the process returns to step SP1 to measure the next reticle 3. On the other hand, when the processing is completed, the process proceeds to step SP10 and the exposure processing procedure SP0 is completed.

These measurements may be performed at different times in advance and managed as reticle data.
For example, it may be executed each time at the beginning of the lot. Further, it is possible to omit the determination in step SP8 as to whether it is within the allowable range and the repeated measurement based on the determination result.

According to the above construction, a plurality of marks 3A for coordinate position measurement are provided on the reticle 3, and the XY stage 5 is provided.
With the reticle coordinate measurement functions 21 and 22 placed above,
By measuring these coordinate position measuring marks 3A in the coordinate system of the XY stage 5 and determining the exposure optimization parameters, it is possible to easily obtain the optimum correction amount and deviation for the exposure of overlay or screen composition. It is possible to obtain a high-precision LCD pattern by performing the superimposing or screen-synthesizing exposure with high accuracy.

Further, according to the above configuration, the pattern directly transferred on the coordinates of the XY stage 5 including the patterning error of the reticle 3, the lens distortion component, the alignment error of the reticle 3, etc. is measured and superposed. To improve the accuracy, or to reduce the error of the screen joint, to easily find the exposure optimization correction amount to reduce the overlay accuracy difference of the joint part, and perform the exposure by the correction amount. As a result, these errors can be suppressed.

Here, as a stitching exposure pattern, FIGS. 9A to 9D show an embodiment of the arrangement of the marks on the reticle in the case described above with reference to FIG. In this embodiment, the marks are arranged on the reticle only in the vicinity of the joints, and only the joints are focused to reduce the error of the screen joint, or to reduce the overlay accuracy difference of the joints. The exposure optimization correction amount for the above is obtained, and these errors are reduced by performing exposure according to the correction amount. As a result, focusing on only the joint portion, the exposure of the joint portion with the highest priority of precision can be performed, and the screen composition can be performed with high precision.

In this mark, the marks on the reticle are arranged only in the vicinity of the spliced portion, but the marks are arranged on the entire outer periphery of the pattern to be exposed, and only the mark data of the joint portion is selected or weighted. Even if the correction amount is obtained, the same effect can be expected. Further, as in this embodiment, it is possible to dispose the mark at a portion to be emphasized.

In the above embodiment, the reticle 3
The case where the above pattern is measured at the coordinates on the XY stage 5 has been described, but instead of this, as shown in FIG.
Illumination system 3 in which the light-receiving unit mark 21 is provided in the XY stage 5
1, the pattern of the light-receiving portion mark 21 is back projected onto the reticle 3 by the lens 4, and the XY stage 5 is scanned, so that the image of the light-receiving portion mark 21 forms an image on the reticle 3.
You may make it measure by scanning the upper mark 3A.
In this case, the light passing therethrough is split by the light splitter 32 provided in the illumination system 11 and photoelectrically converted by the light receiving unit 33.
With this measuring function, a signal similar to that in FIG. 1 can be obtained.

Further, in the above-mentioned embodiment, the case where the optimized correction amount is obtained for the ideal position has been described, but instead of this, the optimization is performed by the information for another reticle or another device. Is also possible. In this case, the exposure processing procedure SP11 is as shown in FIG. In this exposure processing procedure SP11, consideration such as lot management is necessary, and if necessary, coordinate position information (SP by another reticle device).
17) will be used.

In the above embodiment, the reticle 3 is used.
The case where a plurality of the above marks 3A are provided on the outer periphery of the pattern 3B has been described. However, if there is a space to be placed inside the pattern 3B of the reticle 3 instead of this, as shown in FIG. A plurality of 3A may be arranged. If you want to determine the constants for exposure equipment management,
It is effective to dispose the marks 3A on the entire surface of the pattern in this way. However, when such a reticle is used for exposure device constant management, it is necessary to measure and correct the patterning error on the reticle by another inspection device.

[0032]

As described above, according to the present invention, a plurality of marks are provided around the area where the pattern exists on the original plate,
Positions of the images of the marks projected on the board are respectively detected, and the correction amount for the positioning of the board is calculated according to the deviation from the designed position where the marks should be projected by the projection optical system. Optimum for exposure of overlay or screen composition by obtaining the correction amount of the image forming characteristic of the projection optical system and correcting the position of the substrate and / or the image forming characteristic of the projection optical system based on each correction amount. It is possible to realize a projection exposure apparatus capable of easily deriving various correction amounts and deviations and performing exposure with high accuracy by superimposing and screen composition.

[Brief description of drawings]

FIG. 1 shows L as an embodiment of a projection exposure apparatus according to the present invention.
It is a schematic diagram which shows the exposure apparatus for CD.

FIG. 2 is a schematic diagram showing the shapes of a light receiving unit mark and a reticle mark.

FIG. 3 is a signal waveform diagram showing a mark detection signal by the mark of FIG.

FIG. 4 is a schematic diagram showing the shapes of a light-receiving portion mark and a reticle mark in the X and Y directions.

5 is a schematic diagram showing the shapes of a light-receiving portion mark and a reticle mark in the X and Y directions, as in FIG.

FIG. 6 is a schematic diagram showing an arrangement of reticle marks according to the embodiment.

FIG. 7 is a schematic diagram for explaining overlay exposure of an example.

FIG. 8 is a flow chart used for explaining the exposure processing procedure of the embodiment.

FIG. 9 is a schematic diagram showing another embodiment of the LCD exposure apparatus.

FIG. 10 is a schematic diagram showing an arrangement of marks on a reticle by stitching exposure.

FIG. 11 is a schematic diagram illustrating another example of the exposure processing procedure.

FIG. 12 is a schematic diagram showing another embodiment of the reticle mark.

FIG. 13 is a schematic diagram showing a conventional LCD exposure apparatus.

FIG. 14 is a schematic diagram used for explaining joint exposure.

FIG. 15 is a schematic diagram for explaining an error factor in stitching exposure.

[Explanation of symbols]

1, 20, 30 ... Exposure device for LCD, 2 ... Illumination optical system, 3 ... Reticle, 4 ... Projection lens, 5 ... XY stage, 6 ... Plate, 7 ... Laser interferometer, 8 ... …
Reticle alignment system, 9 ... Plate alignment system, 10 ... Reticle exchange mechanism, 21 ... Photosensitive mark, 22 ... Photoelectric conversion element, 31 ... Illumination system, 32 ...
Light splitter, 33 ... Light receiving part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Muneyasu Yokota 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (5)

[Claims] 1. A projection exposure apparatus for positioning a master plate and a substrate and projecting a pattern on the master plate onto a predetermined region of the substrate via a projection optical system having a predetermined image forming characteristic. A plurality of marks are provided around the area where the pattern is present, and position detecting means for respectively detecting the positions of the images of the plurality of marks projected on substantially the same surface as the surface of the substrate; and the position detecting means. The position of the image of the plurality of marks detected by the, based on the amount of deviation from the design position where the plurality of marks should be projected by the projection optical system, relative to the substrate of the original plate. A deviation detection unit that determines at least one of a positional deviation and a deviation of the imaging characteristic of the projection optical system with respect to the predetermined imaging characteristic, and a correction amount for positioning the substrate based on the determined positional deviation. Correction amount calculation means for obtaining at least one of the correction amount of the image forming characteristic of the projection optical system based on the obtained deviation, and correcting the position of the substrate based on each of the obtained correction amounts, or the deviation And a correction means for correcting the image formation characteristic of the projection optical system based on the above. 2. The projection exposure apparatus according to claim 1, wherein the position detecting means detects the positions of the images of the marks by detecting the plurality of marks via the projection optical system. . 3. The correction amount is a rotation correction amount of the original plate, X
The projection exposure apparatus according to claim 1, wherein the Y shift correction amount and / or the XY magnification offset amount are used. 4. The projection exposure apparatus according to claim 1, wherein the exposure is performed while the correction is performed and the pattern is overlapped on the predetermined area or is connected to an area adjacent to the predetermined area. . 5. When the pattern is connected to an area adjacent to the predetermined area, or when the pattern is exposed by overlapping the pattern and exposing the predetermined area, the shift amount of the connection area or the connection area 2. The projection exposure apparatus according to claim 1, wherein the correction amount is obtained so as to optimize the amount of overlay misalignment of the matching portions.