JPH06242595A - Mask for photoexposure and its production - Google Patents

Abstract

PURPOSE:To provide a mask for photoexposure for production of semiconductor integrated circuits capable of forming transfer patterns faithful to a design pattern without largely increasing a data quantity. CONSTITUTION:The mask 14 for photoexposure is produced by extracting a part having a basic periodic structure among design patterns 11 of the semiconductor integrated circuits, forming auxiliary pattern data provided with the very small auxiliary patterns 13 which are not transferred to a semiconductor substrate above in places corresponding to the corner parts of the main pattern 12 of the basic periodic structure and synthesizing this auxiliary pattern data and the main pattern data corresponding to the design pattern 11. Since the auxiliary patterns 13 are formed in the places corresponding to the corner parts of the main pattern 12 including the points varying from the periodic structure, the transfer patterns faithful to the design pattern 11 are formed while the increase in the data quantity by addition of the auxiliary patterns 13 is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoexposure mask used in photolithography.

[0002]

2. Description of the Related Art In recent years, the development of semiconductor technology has been remarkable.
A semiconductor device having a minimum processing size of 0.5 μm has been mass-produced. Such miniaturization is rooted in a breakthrough in fine pattern formation technology called lithography technology.

This lithographic technique is roughly divided into steps of resist application, exposure and development.
The miniaturization of the pattern has been achieved by improving the resist material, exposure apparatus and exposure method, development method and the like. In particular, the patterning has been remarkably made finer by improving the exposure apparatus and the exposure method. But,
As the pattern becomes finer, the problem that the pattern transferred onto the wafer, which is a semiconductor substrate, differs from that of the light exposure mask, which is the original pattern, cannot be ignored.

That is, the above problem is that a rectangular pattern on the light exposure mask is transferred to the wafer with a rounded corner due to the influence of diffraction in the projection optical system. In a fine pattern, as shown in FIGS. 5 (a) and 5 (b), a square pattern 1 is transferred to a silicon wafer on a photo-exposure mask to form a circular transfer pattern 2 in a fine pattern. Will end up. As described above, it is very generally observed that a fine contact hole, which is a square on the light exposure mask, is transferred to a circle on the wafer in the semiconductor manufacturing process, and the transfer pattern cannot faithfully reproduce the design data. May be a problem. For example, since the pattern is rounded at the end of the gate, the leak current from the gate is increased, or the area of the contact hole is decreased, so that the contact resistance is increased.

In order to prevent the corners of the pattern from being rounded as described above, a method of deforming the light exposure mask is disclosed in, for example, Japanese Patent Publication No. 62-7535 and Japanese Patent Laid-Open No. 58-200238. Etc. As shown in FIGS. 6 (a) and 6 (b), these methods use small auxiliary patterns 4 which are not transferred onto the wafer by themselves at the four corners of the rectangular mask pattern 3 in the light exposure mask. Is added to bring the transfer pattern 5 closer to the original design pattern, and this method is a very effective method for increasing the fidelity of the transfer pattern 5 to the design pattern.

[0006]

However, in the method of adding the auxiliary patterns 4 to the four corners of the rectangular light exposure mask pattern to bring the transfer pattern 5 closer to the original design pattern, the amount of pattern data is increased. However, there is a problem in that

That is, the design data has been converted into drawing data for making a light exposure mask, and currently electron beam drawing is mainly used for making a light exposure mask.
The data for drawing the mask for light exposure is composed of a collection of many rectangular figures obtained by dividing complicated design data into rectangles.

FIGS. 7 (a) and 7 (b) show an example in which the figure 6 before the auxiliary pattern is added and the figure 7 after the auxiliary pattern are divided into rectangular figures, respectively, before the auxiliary pattern is added. It can be seen that the data, which was one rectangular figure, becomes seven rectangular figures by adding the auxiliary pattern. Although data processing is possible with simple data even if the amount of data increases by a factor of 7, the current VLSI pattern data amount is very large, and even for ordinary mask patterns to which auxiliary patterns are not added, CAD processing is possible. The processing capacity of computers for equipment and data conversion is near the limit.

Therefore, when an auxiliary pattern is added to such data to increase the data amount several times, the processing capacity of the current computer may be exceeded and data processing may become impossible. Further, even when data processing is possible, the time required for data processing becomes long and not practical.

However, even when the auxiliary pattern is added to the VLSI, it is not so difficult to compress the data as long as the pattern has complete periodicity in cell units such as a memory device. That is, a certain repeating unit may be extracted, data in which an auxiliary pattern is added only to that portion is produced, this data is converted into drawing data, and this data may be arranged at the time of drawing.

On the other hand, when the pattern has a random arrangement, such data compression is not easy. For example, in the case of a contact hole programming type mask ROM (read only memory) that performs programming with or without contact holes, the presence or absence of contact holes in the mask pattern for forming contact holes is determined by the program. As shown in (a), the periodicity of the mask pattern is lost. When the auxiliary pattern 9 is added to the light exposure mask 8, (b) in FIG.
As shown in (3), the data cannot be compressed, the data amount becomes several times as large as the original data, and the data processing becomes very difficult.

The mask data for the mask ROM is automatically generated by a computer program based on the code of the program to the mask ROM, and is shown in FIG. 8A in the conventional method in which the auxiliary pattern is not added. It suffices that the formed mask pattern generate a rectangle at each position on the light exposure mask 8 based on the program code.
However, in order to automatically generate the mask pattern with the auxiliary pattern 9 shown in FIG. 8B on the light exposure mask 8,
Computer programs have to be changed significantly.

The present invention solves the above problems, and a transfer pattern faithful to a design pattern can be formed even in a fine pattern without significantly increasing the pattern data amount or significantly changing the computer program. It is intended to provide a mask for light exposure.

[0014]

In order to solve the above problems, the present invention is directed to a semiconductor integrated circuit in which a design pattern has a basic periodic structure and a part of the design pattern is different from the periodic structure. In the photoexposure mask used when a circuit is formed on a semiconductor substrate by photolithography, a small auxiliary pattern for preventing circularization of corners of a transfer pattern is provided only at a portion having the basic periodic structure. Instead, it is formed at a location corresponding to a corner of the pattern of the basic periodic structure, including a portion different from the periodic structure.

Further, according to the present invention, a semiconductor integrated circuit in which a design pattern has a basic periodic structure and a part of the design pattern is different from the periodic structure is formed on a semiconductor substrate by photolithography. In the method of manufacturing a light exposure mask used in some cases, a basic periodic structure is extracted from a design pattern, and a small auxiliary pattern that is not transferred to a semiconductor substrate by itself corresponds to a corner portion of the pattern of the basic periodic structure. Auxiliary pattern data provided at a location is created, and the auxiliary pattern data and the main data corresponding to the design pattern are converted into drawing data and are combined at the time of drawing to manufacture a light exposure mask, or a transfer pattern is created. A small auxiliary pattern that prevents circularization of the corners of the A method for producing a mask for light exposure by creating added auxiliary pattern additional data, converting the minute auxiliary pattern additional data and data having no periodic structure in the design pattern into drawing data, and synthesizing them at the time of drawing Is.

[0016]

With the light exposure mask having the above-described structure, a minute auxiliary pattern for preventing the corners of the transfer pattern from being rounded is provided not only at the basic periodic structure but also at the periodic structure. Since it was formed at the location corresponding to the corner of the pattern of the basic periodic structure, including the location where it is, it is possible to minimize the increase in the amount of data due to the addition of the auxiliary pattern, and to adhere to the design pattern. Transfer patterns can be formed.

In this case, when there is a portion where the auxiliary pattern is arranged independently without overlapping with other patterns, the auxiliary pattern is formed to a size such that the auxiliary pattern cannot be transferred to the semiconductor substrate by itself. It is possible to prevent the pattern from being transferred to the semiconductor substrate.

Further, the photoexposure mask having the above-mentioned structure can be efficiently manufactured by the above-mentioned method for manufacturing a photoexposure mask.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. First, the first embodiment will be described in detail with reference to FIG.
Figure 1 shows a contact hole programming mask ROM.
2 shows a data structure for manufacturing the contact hole forming photoexposure mask.

As described above, the design pattern 11 for forming contact holes shown in FIG. 1A does not have a perfect periodic structure, and it is difficult to compress data. However, this design pattern 11 has hidden regularity (periodicity). The arrangement of contact holes loses regularity because programming is performed depending on the presence or absence of contact holes. However, considering the contact holes omitted in dotted lines, the rectangular main pattern 12 is completely vertical and horizontal. Are regularly arranged. Focusing on this regularity, data can be compressed. Considering that the main pattern 12 is also present in the portion where the contact holes are omitted, data for only the auxiliary pattern 13 is created in the portions corresponding to the four corners of all the main patterns 12, and this is used as the data for the second layer. To do. Since the data of the second layer is completely regularly arranged, the data can be compressed.

In the auxiliary pattern data shown in FIG. 1B, the data amount is compressed to 1/9 of the whole. By expanding this compressed data over the entire surface, the auxiliary pattern 13
Can be data. This auxiliary pattern data and the data of the first layer (design pattern 1 shown in FIG.
1) and the data at the time of drawing,
As shown in (c), all the main patterns 12 that are considered to have the main pattern 12 even in the portion where the contact holes are omitted.
It is possible to manufacture the light exposure mask 14 in which the auxiliary patterns 13 are formed in the portions corresponding to the four corners.

In this case, the data of the first layer is exactly the same as the data of the conventional light exposure mask, and since the data of the second layer is compressed, the data amount can be made small. In the example shown in FIG. 1B, the auxiliary pattern 13
Data amount is compressed to 1/9, but the actual super LS
In the case of I pattern data, the number of repetitions is much larger, so the compression ratio of the data amount can be much larger. As a result of actually creating a light exposure mask for LSI by this method, the data amount for the light exposure mask 14 to which the auxiliary pattern 13 is added is larger than the data amount of the exposure mask 11 similar to the conventional one as a whole. The increase was only about 10%. That is, the amount of the data of the second layer is only about 10% of the amount of the data of the first layer, and if the amount of increase is such an amount, the increase of the load on the data processing can be almost ignored.

Further, since the mask data to be automatically generated based on the program code (see FIG. 1A) is the same as the conventional mask data, a new mask data based on the program code is added. There is no need to create a program to create a, and conventional programs can be used as they are.

By the way, in the photoexposure mask 14 shown in FIG. 1C, which is formed by synthesizing the auxiliary pattern data and the data of the first layer, the auxiliary pattern 13 is not necessary even in a portion having no contact hole. There are thirteen. However, the auxiliary pattern 13 is designed so as not to be transferred onto the wafer, which is a semiconductor substrate, by itself, so that the unnecessary auxiliary pattern 13 is transferred onto the wafer and does not adversely affect the device. . As a result of actually performing a transfer experiment on a wafer using the created light exposure mask 14, even if the exposure energy is increased to twice the proper exposure amount, an unnecessary auxiliary pattern is not transferred onto the wafer. There wasn't. However, when the size of the auxiliary pattern is too large, an unnecessary auxiliary pattern may be transferred onto the wafer, and therefore the design of the auxiliary pattern 13 requires sufficient care.

When the auxiliary pattern 13 has a square shape and the center of the auxiliary pattern 13 is located at a corner of the main pattern 12, a detailed study is conducted. As a result, the dimension L of one side of the auxiliary pattern 13 is L < It was found that by setting 0.5 · λ / NA, it is possible to prevent the auxiliary pattern 13 from being independently transferred onto the wafer. Here, λ is the wavelength of the projection exposure apparatus in which this light exposure mask 14 is used, and NA is the numerical aperture of the projection lens of the exposure apparatus.

On the other hand, in order to suppress the roundness of the corners of the transfer pattern by the auxiliary pattern 13, it is necessary to set the dimension L of one side of the auxiliary pattern 13 to L> 0.2 · λ / NA.

Therefore, it is desirable that the size of the auxiliary pattern 13 is 0.2 · λ / NA <L <0.5 · λ / NA.

The auxiliary pattern 13 shown in FIG.
Is composed of four squares for one main pattern 12. As described above, the first pattern including the main pattern 12
When the data of the layer and the data of the second layer including the auxiliary pattern 13 are combined at the time of drawing, a portion where the data overlaps is drawn twice. Auxiliary pattern 13
Since the overlapping portion of the main pattern 12 and the main pattern 12 has a small area, the influence is not so great, but it may cause a decrease in accuracy when the mask for light exposure is formed. As a measure against this, the auxiliary pattern can be formed in an L shape as shown in FIG. 2B to remove the overlap with the main pattern 21 (see FIG. 2C). At this time, the data amount of the auxiliary pattern 22 (second layer data) is doubled. However, since the auxiliary pattern 22 is compressed and the data amount is not large, the increase in the data processing load can be ignored if the increase is about twice. As shown in FIG. 2C, the light exposure mask 23 formed by using the L-shaped auxiliary pattern data can reduce the area of the unnecessary portion of the auxiliary pattern 22, and thus the unnecessary auxiliary pattern. Two
The influence of 2 can be reduced.

Next, the second embodiment of the present invention will be described in detail with reference to FIG. FIG. 3A shows a design pattern 31 of the mask of the wiring of the gate array, which is a pattern for connecting the contacts with polysilicon wiring. At first glance, the design pattern 31 does not seem to have periodicity. However, in this case, unlike the first embodiment, the contact holes (portions shown by dotted lines in FIG. 3B) of the base substrate to be connected by the polysilicon wiring are completely regularly arranged.

The polysilicon wiring is divided into a case where each contact hole is connected and a case where only the contact hole is filled. In this case, if only the pattern covering the contact hole portion 32 is extracted as the main pattern 32, the data can be compressed as data having periodicity (see (c) of FIG. 3). The data in which the fine auxiliary patterns 33 are added to the corners of the four corners of the periodic main pattern 32 that covers the contact hole is the data of the second layer. The data of the first layer is the contact hole part 3
The entire surface data of only the portion connecting the two is defined (the pattern shown in FIG. 3B is called a connection pattern, and the pattern data shown in FIG. 3C is called auxiliary pattern additional data).

By overlapping the data of these two layers at the time of electron beam drawing, the light exposure mask 35 with an auxiliary pattern shown in FIG. 3D can be formed. Also in this case, the data of the first layer is the same amount as the data of the conventional light exposure mask. Further, the auxiliary pattern additional data of the second layer is compressed to 1/9 in the example shown in FIG. In the case of actual VLSI pattern data, the number of times of repetition becomes much larger, so the rate of data amount compression can be made much larger. Also in this case, as a result of actually creating a mask for light exposure for LSI, the amount of work required for data processing and the processing time were almost the same as those of the conventional method.

Here, the connection pattern 34 shown in FIG. 3B has the same width as the main pattern 32, so that the final mask pattern (see FIG. 3D) is as follows.
The auxiliary pattern 33 has a shape protruding from the original design pattern 31. Also in this case, when the first layer data and the second layer auxiliary pattern additional data are combined at the time of drawing, a portion where the data overlaps is drawn twice.

In order to deal with this, if the connection pattern 36 is formed into a rectangle that fits between the auxiliary pattern 33 and the main pattern 32 as shown in FIG. 4A, the data does not overlap. Even in this case, the data of the first layer remains as one rectangle only by changing the size of the pattern, and therefore the data amount of the connection pattern 34 (data of the first layer) does not change. When such connection data is used, as shown in FIG. 4C, the pattern on the light exposure mask 37 has large irregularities. However, as a result of transferring a pattern onto a silicon wafer using this light exposure mask 37, the unevenness of the mask pattern had almost no effect on the wafer, and a pattern close to a straight line could be formed. This is because the auxiliary pattern 33 on the light exposure mask 37 is a fine pattern that cannot be transferred alone on the wafer. The patterns were averaged to form a pattern along the center of the unevenness. On the other hand, when the light exposure mask 35 shown in FIG. 3D is used, the amount of light transmitted between the auxiliary patterns 33 decreases, and the line width of the transfer pattern between the auxiliary patterns 33 becomes thin. There was a problem. From these results, it can be concluded that it is most desirable that the connection pattern has a shape as shown in FIG.

By using these light exposure masks, a gate array integrated circuit, a standard cell integrated circuit, a mask program ROM, etc. can be manufactured with a transfer pattern that faithfully reproduces design data.

[0035]

As is apparent from the above description, according to the present invention, a minute auxiliary pattern for preventing circularization of a corner portion of a transfer pattern is provided only at a portion having the basic periodic structure. In addition, the increase in the amount of data due to the addition of the auxiliary pattern is minimized by forming the pattern in the position corresponding to the corner of the pattern of the basic periodic structure, including the part different from the periodic structure. It is possible to form a transfer pattern that is faithful to the design pattern while being suppressed. In this case, if there is a portion where the auxiliary pattern does not overlap with other patterns and is arranged independently, by forming the auxiliary pattern to a size that is not transferred to the semiconductor substrate by itself, unnecessary auxiliary patterns are formed. Can be prevented from being transferred to the semiconductor substrate.
Furthermore, by using the light exposure mask of the present invention, it is possible to obtain a transfer pattern close to a design pattern on a semiconductor substrate even for an LSI having a pattern that does not have perfect periodicity.

Further, a basic periodic structure is extracted from the design pattern, and auxiliary pattern data in which a minute auxiliary pattern that is not transferred to the semiconductor substrate by itself is provided at a position corresponding to a corner of the pattern of the basic periodic structure is created. Then, the auxiliary pattern data and the main data corresponding to the design pattern are converted into drawing data and are combined at the time of drawing to manufacture a light exposure mask, or prevent the corners of the transfer pattern from being rounded. Auxiliary pattern additional data is created by adding a minute auxiliary pattern to a location corresponding to a corner of a basic periodic structure pattern, and this minute auxiliary pattern additional data and data without a periodic structure in the design pattern are used for drawing. By converting to data and synthesizing at the time of drawing to manufacture an optical exposure mask, It can be produced an exposure mask efficiently.

[Brief description of drawings]

1A and 1B show a data structure and a mask pattern for manufacturing a light exposure mask according to a first embodiment of the present invention, FIG. 1A is a plan view of design pattern data of a light exposure mask, and FIG. ) Is a plan view of auxiliary pattern data, and (c) is a plan view of a light exposure mask with an auxiliary pattern.

2A and 2B show a data structure and a mask pattern for explaining a light exposure mask which is an improved first embodiment of the present invention, and FIG. 2A is a plan view of design pattern data of the light exposure mask; (B) is a plan view of the auxiliary pattern data,
FIG. 3C is a plan view of a light exposure mask with an auxiliary pattern.

3A and 3B show a data structure and a mask pattern for manufacturing a light exposure mask that is a second embodiment of the present invention, FIG. 3A is a plan view of design pattern data of the light exposure mask, and FIG. ) Is a plan view of the first layer data, (c) is a plan view of the second layer data (auxiliary pattern additional data), and (d) is a plan view of the light exposure mask with the auxiliary pattern.

4A and 4B show a data structure and a mask pattern for explaining a light exposure mask which is an improved second embodiment of the present invention. FIG. 4A is a plan view of first layer data, and FIG. A plan view of the second layer data (auxiliary pattern additional data),
FIG. 3C is a plan view of a light exposure mask with an auxiliary pattern.

5A and 5B are diagrams for explaining an influence of diffraction in a projection optical system, FIG. 5A is a plan view of a mask pattern of a light exposure mask, and FIG. 5B is a plan view of a transfer pattern.

6A and 6B are views for explaining a conventional mask with an auxiliary pattern, in which FIG. 6A is a plan view of a mask pattern of a light exposure mask, and FIG. 6B is a plan view of a transfer pattern.

7A and 7B are plan views showing an example in which a figure before adding an auxiliary pattern and a figure after adding an auxiliary pattern are each divided into rectangular figures.

FIG. 8A is a plan view of a conventional light exposure mask,
FIG. 6B is a plan view of a conventional mask with an auxiliary pattern.

[Explanation of symbols]

11, 31 Design pattern 12, 21, 32 Main pattern 13, 22, 33 Auxiliary pattern 14, 35, 37 Light exposure mask with auxiliary pattern 34, 36 Connection pattern

Claims (4)

[Claims] 1. A semiconductor integrated circuit in which a design pattern has a basic periodic structure and a part of the design pattern is different from the periodic structure is used for producing a semiconductor substrate on a semiconductor substrate by photolithography. In the mask for light exposure, a minute auxiliary pattern for preventing circularization of the corners of the transfer pattern, including not only the portion having the basic periodic structure but also the portion different from the periodic structure, A photoexposure mask formed at a location corresponding to a corner of the pattern of the basic periodic structure. 2. The photoexposure mask according to claim 1, wherein the minute auxiliary pattern is formed in a size such that it is not transferred to the semiconductor substrate by itself. 3. A semiconductor integrated circuit in which a design pattern has a basic periodic structure and a part of the design pattern is different from the periodic structure is used for photolithographically fabricating a semiconductor integrated circuit on a semiconductor substrate. In the method of manufacturing a mask for light exposure, a basic periodic structure is extracted from a design pattern, and a small auxiliary pattern that is not transferred to a semiconductor substrate by itself is provided at a position corresponding to a corner of the pattern of the basic periodic structure. A method for manufacturing a photoexposure mask, which creates auxiliary pattern data, converts the auxiliary pattern data and main pattern data corresponding to a design pattern into drawing data, and combines the auxiliary pattern data during drawing to manufacture an optical exposure mask. 4. A semiconductor integrated circuit in which a design pattern has a basic periodic structure and a part of the design pattern is different from the periodic structure is used in the case of manufacturing a semiconductor substrate by photolithography. In a method of manufacturing a mask for light exposure, a basic periodic structure is extracted from a design pattern, and a minute auxiliary pattern for preventing circularization of a corner portion of a transfer pattern corresponds to a corner portion of the pattern of the basic periodic structure. The auxiliary pattern additional data added to the location is created, and the minute auxiliary pattern additional data and the data having no periodic structure in the design pattern are converted into drawing data and are combined at the time of drawing to produce a light exposure mask. Method for manufacturing exposure mask.