JP2854050B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] With regard to a method of manufacturing a semiconductor device, more specifically, in order to align a pattern on a mask with a pattern on a wafer, light for position detection is used to align the alignment mark on the mask with light. The present invention relates to a method for manufacturing a semiconductor device including a method of aligning an alignment mark on a wafer and a method for manufacturing a semiconductor device capable of performing accurate alignment even when irradiated with light for position detection whose direction is not fixed. A mask made of a light-transparent material having an alignment mark made of a translucent material with respect to light is placed between the light source and the wafer on which another alignment mark is formed. And irradiating the wafer with light from the light source through the mask to reflect images reflected from the respective alignment marks on the mask and on the wafer by image processing. And performing position adjustment such that the peak value of the intensity distribution of the synthesized gray-scale signal is maximized.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and more specifically, to align a pattern on a mask with a pattern on a wafer, and to use a position detection light to align the alignment mark on the mask with the alignment mark on the wafer. And a method for manufacturing a semiconductor device including a method for aligning the semiconductor device.

[Conventional technology]

FIGS. 3A to 3C are views for explaining a conventional alignment method for aligning an alignment mark on a mask with an alignment mark on a wafer by an image processing method. FIG. 2 is a configuration diagram of a positioning device used in this positioning method.

In FIG. 2, 9 is a stage, 10 is a microscope for confirming alignment marks on the mask 4 and the wafer 1, and light is irradiated from a light source 12 through a half mirror 11 in the microscope 10, and Half mirror image of alignment mark
The light passes through 11 and is guided to the image processing device 13. Then, the obtained grayscale image is analyzed by the image processing device 13, and the position information of the alignment mark is given to the stage controller 14, and the stage 9 is moved to adjust the positions of the mask 4 and the wafer 1.

Next, when positioning is performed using this positioning apparatus, as shown in FIG. 3A, the wafer 1 is moved while irradiating light from the microscope 10 and the positioning mark formed by patterning chrome on the mask 4 is used. 3 and images of the alignment marks 2a and 2b patterned on the wafer are collected via the half mirror 11 in the microscope 10. Then, the obtained image is cut out by the image processing apparatus 3 as indicated by E in FIG. 2B (in this figure, the x method is used as the alignment direction). Y
The averaging process is performed in the direction to obtain the grayscale signal shown in FIG. As shown in FIG. 3C, the peak position of the grayscale signal of the alignment mark 3 of the mask 4 obtained as a result of such image processing is the peak position and position of the grayscale signal of the alignment mark 2a on the wafer 1. The stage is adjusted so that it is exactly at the center of the peak position of the grayscale signal of the alignment mark 2b (1 = l2). As a result, a mask pattern (not shown) on the mask 4 and a pattern (not shown) on the wafer 1 are aligned. FIG. 2B shows a top view of FIG. 2A, and the reference numerals in the figure denote the same elements as those shown in FIG. 1A.

[Problems to be solved by the invention]

By the way, as shown in FIG. 4 (a), when the irradiation light is deviated from the direction perpendicular to the alignment marks 2a, 2b, 3 and is irradiated obliquely, the respective alignment marks
Since 2a, 2b, and 3 are kept at a constant interval, FIG.
Each alignment mark 2 corresponds to the irradiation angle as shown in
The positions of the peak values of the gray-scale signals a, 2b, and 3 are slightly shifted from the centers of the alignment marks 2a, 2b, and 3.

Therefore, when the peak position of the density signal of the alignment mark 3 of the mask 4 is exactly centered between the peak position of the density signal of the alignment mark 2a on the wafer 1 and the peak position of the density signal of the alignment mark 2b. But mask 4
The position of the actual alignment mark 3 above is deviated from the center between the position of the actual alignment mark 2a and the position of the alignment mark 2b on the wafer 1. As a result, there is a problem that the mask pattern on the mask 4 is not accurately aligned with the pattern on the wafer 1, and the transferred pattern is shifted from a normal position.

Accordingly, the present invention has been made in view of such a conventional problem, and provides a method of manufacturing a semiconductor device capable of performing accurate alignment even when irradiated with position detection light having an inconstant direction. It is intended to provide.

[Means for solving the problem]

The above object is achieved by placing a mask made of a material transparent to light on which an alignment mark made of a material translucent to light is formed between a wafer on which another alignment mark is formed and a light source. Irradiating the wafer with light from the light source through the mask, and combining reflected images from the respective alignment marks on the mask and the wafer by using an image processing method; and intensity distribution of the synthesized grayscale signal. Is achieved so as to maximize the peak value of the semiconductor device.

[Action]

In the method of manufacturing a semiconductor device according to the present invention, light is irradiated through a mask having alignment marks made of a material that is translucent to light, and alignment marks on the mask and alignment marks on the wafer are irradiated. Both images have been synthesized using an image processing technique.

For this reason, the alignment can be performed by utilizing the fact that the peak value of the synthesized grayscale signal changes depending on the degree of overlap of the alignment marks on the mask and the wafer.

As a result, even if the direction of light irradiation changes and the grayscale distribution from each alignment mark becomes asymmetric, the deviation of the peak position of each grayscale signal is almost the same because the alignment marks at almost the same position are used. Be equivalent. Furthermore,
Since the sum from the peak to the base of each gray signal is taken, the peak value of these sum signals becomes insensitive to the deviation between the peak position of the gray signal of the mask and the peak position of the gray signal of the wafer. Therefore, the position where the peak value of the sum signal becomes maximum coincides with the position where the respective alignment marks substantially overlap. For this reason, it is possible to perform accurate alignment by fixing the wafer at a position where the maximum value of the peak value of the combined grayscale signal is obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

1 (a) to 1 (c) illustrate a conventional alignment method for aligning an alignment mark on a mask with an alignment mark on a wafer using light for position detection according to an embodiment of the present invention. FIG. FIG. 2 is a configuration diagram of a positioning device used in this positioning method.

In FIG. 2, 9 is a stage on which the wafer 5 is mounted, 10 is a microscope for confirming the alignment 6, 7 of the wafer 5 and the mask 8, and light is transmitted from a light source 12 to a half mirror in the microscope 10. The alignment mark image is irradiated through the half mirror 11 and guided to the image processing device 13 through the half mirror 11. Then, the obtained gray scale image is
The position of the alignment mark is detected by analyzing the position of the alignment mark. Thereafter, the position information is provided to the stage controller 14, and the stage 9 is moved to adjust the positions of the mask 8 and the wafer 5.

Next, the case of performing positioning using this positioning apparatus will be described with reference to FIGS. 1 (a) to 1 (c).

1A is a cross-sectional view showing the position of a wafer and a mask during alignment, FIG. 1B is a top view showing the position of an alignment mark in FIG. 1, and FIG. FIG. 3 is a diagram showing a gray-scale signal processed by the image processing apparatus 14.

5A, reference numeral 5 denotes a wafer on the stage 9;
Is an alignment mark patterned on the wafer 5, positions indicated by reference numerals B and C indicate positions in the middle of the movement of the wafer 5, and the position B is exactly overlapped with the position A of the alignment mark 7 on the mask 8. Indicates a state in which Reference numeral 7 denotes an alignment mark made of a PSG film having a thickness of about 0.5 μm on a mask 8 made of quartz glass, which is translucent to light, partially transmits irradiation light, and partially reflects irradiation light. With.

First, while irradiating the wafer 5 with light from the microscope 10, the wafer 5 is moved to a position C in FIG.
Are collected via the half mirror 11 in the microscope 10.
Then, the image processing device 13 cuts out the obtained synthesized image in the image processing device 13 as indicated by D in FIG. 2B (the x direction is defined as the alignment direction), and then the cut out image D When the averaging process is performed in the y direction, a composite value A + C of the gray scale signals indicated by A and C in FIG. Note that the intensity of the reflected light from the alignment mark 6 at the position C is weak at the portion where the light overlaps with the position A. That is, when transmitted through the alignment mark 7 of A, a part of the irradiation light is reflected and only a part of the irradiation light reaches the alignment mark 6 on the wafer 5.

Next, when the wafer 5 is moved to the position B, the grayscale signal becomes a combined value A + B of A and B as shown in FIG. In this state, the alignment marks 6 on the wafer 5
Since the position and the alignment mark 7 on the mask 8 just overlap, the peak values of the reflected light intensities of A and B overlap. At this time, since the light applied to the alignment mark 6 at the position B is transmitted through the alignment mark 7 on the mask 8, the peak value of the intensity of the reflected light of B is the peak value of the intensity of the reflected light of C. However, the peak value of the synthesized grayscale signal is larger than that at the position C.

Furthermore, when the wafer 5 is moved to the right, the position of the peak value of the intensity of each reflected light is separated, so that the peak value of the synthesized grayscale signal is lower than that in the case of B.

From the above description, when the alignment mark 6 on the wafer 5 and the alignment mark 7 on the mask 8 just overlap, the peak value of the intensity of the synthesized grayscale signal becomes the largest. Therefore, if the wafer 5 is fixed at this position, accurate positioning can be performed.

By the way, even when the light is applied obliquely and the intensity distribution of the grayscale image becomes asymmetric, the deviation of the peak value of each grayscale signal is almost the same because the alignment marks 6 and 7 are almost at the same position. Further, since the sum from the peak to the base of the grayscale signal is obtained, the peak value of the sum signal becomes insensitive to the shift between the peak positions of the image signal from the mask and the image signal from the wafer. For this reason, it is possible to perform accurate alignment by fixing the wafer at a position obtained from the maximum value of the peak value of the combined image signal.

〔The invention's effect〕

As described above, according to the method for manufacturing a semiconductor device of the present invention, alignment is performed using a mask having a translucent alignment mark with respect to light for position detection. It is possible to combine the images of the alignment marks on the wafer using an image processing technique, and perform alignment using the fact that the peak value of the synthesized grayscale signal varies depending on the degree of overlap between the alignment marks. it can.

Therefore, even when the direction of light irradiation changes and the intensity distribution of the image signal of each alignment mark becomes asymmetric, the positional relationship between both the alignment mark on the mask and the alignment mark on the wafer is different from the related art. Since the alignment can be performed at substantially the same position, the deviation of the peak position of the grayscale signal of each alignment mark becomes substantially equal. Furthermore, since the sum from the peak to the base of each grayscale signal is taken,
The peak values of these sum signals become insensitive to the shift of each peak position. Therefore, the peak value of the image signal also overlaps at the position where each alignment mark just overlaps. Thus, if the wafer is fixed at a position where the maximum value of the peak value of the synthesized grayscale signal is obtained, accurate alignment can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a positioning method according to an embodiment of the present invention, FIG. 2 is a diagram illustrating a positioning device, FIG. 3 is a diagram illustrating a positioning method of a conventional example, FIG. FIG. 7 is a diagram for explaining a problem of the conventional example. [Explanation of symbols] 1,5 ... wafer, 2a, 2b, 3,6,7 ... alignment mark, 4,8 ...
Mask, 9 stage, 10 microscope, 11 half mirror, 12 light source, 13 image processing device, 14 stage controller.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/207

Claims (1)

(57) [Claims] A mask made of a light-transparent material having an alignment mark formed of a translucent material with respect to light is provided between a light source and a wafer having another alignment mark formed thereon. And irradiating the wafer with light through the mask by the light source to combine reflection images from the respective alignment marks on the mask and the wafer by using an image processing technique, and to obtain an intensity of the synthesized gray signal. A method for manufacturing a semiconductor device, comprising: performing alignment so that a peak value of a distribution becomes maximum.