JP3332973B2 - Light exposure mask and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, the development of semiconductor technology has been remarkable,
Semiconductor devices having a minimum processing size of 0.5 μm have been mass-produced. Such miniaturization is based on a dramatic advance in a fine pattern forming technology called a lithography technology.

[0003] This lithography technique is roughly divided into steps of resist coating, exposure and development.
Pattern miniaturization has been achieved by improving resist materials, exposure apparatuses and exposure methods, development methods, and the like. In particular, pattern miniaturization has been remarkably promoted 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 drawing, cannot be ignored.

In other words, the above problem is caused by the fact that a pattern that is rectangular on a light exposure mask is transferred to a wafer with rounded corners due to the effect of diffraction in a projection optical system, with the corners of the pattern outline being removed. In the case of a fine pattern, as shown in FIGS. 5A and 5B, when a square pattern 1 is transferred onto a silicon wafer on a light exposure mask, a circular transfer pattern 2 is formed. Would. As described above, it is very generally observed that fine contact holes that are square on a light exposure mask are transferred in a circular shape on a wafer in a semiconductor manufacturing process, and that a transfer pattern cannot faithfully reproduce design data. May be a problem. For example, the pattern is rounded at the end of the gate, so that the leakage current from the gate increases, and the contact resistance increases because the area of the contact hole is reduced.

In order to prevent the corners of a pattern from being rounded as described above, a method of deforming a light exposure mask is disclosed in, for example, JP-B-62-7535 and JP-A-58-200238. And so on. As shown in FIGS. 6A and 6B, these methods use a small auxiliary pattern 4 which is not transferred to a wafer by itself at four corners of a rectangular mask pattern 3 in a light exposure mask. To make the transfer pattern 5 closer to the original design pattern. 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 pattern data amount is reduced. However, there is a problem that the number increases significantly.

That is, the design data is converted into drawing data for producing a light exposure mask, and electron beam drawing is mainly used at present for producing a light exposure mask.
The light exposure mask drawing data is composed of a group of a large number of rectangular figures obtained by dividing complicated design data into rectangles.

FIGS. 7A and 7B show an example in which the graphic 6 before the auxiliary pattern is added and the graphic 7 after the addition are divided into rectangular figures, respectively. It can be seen that the data is one rectangular figure, but becomes seven rectangular figures by adding the auxiliary pattern. Although data processing is possible even if the data amount is increased by a factor of seven if the data is simple data, the pattern data amount of the current VLSI is very large, and CAD processing is performed even for a normal mask pattern without an auxiliary pattern. The processing power of instruments and computers for data conversion is nearing its limits.

Therefore, if the data amount is increased several times by adding an auxiliary pattern to such data, the data processing capacity of the current computer may be exceeded and data processing may not be possible. Further, even when data processing is possible, the time required for data processing becomes long, which is not practical.

However, even when an auxiliary pattern is added to an VLSI, data compression is not so difficult if the pattern has complete periodicity in units of cells, such as a memory device. That is, a certain repeating unit is extracted, data in which an auxiliary pattern is added to only that portion is prepared, 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 mask ROM (read only memory) of a contact hole program type in which programming is performed depending on the presence or absence of a contact hole, the presence or absence of the contact hole in the mask pattern for forming the contact hole is determined by the program. As shown in (a), the periodicity of the mask pattern is lost. When an auxiliary pattern 9 is added to the light exposure mask 8, FIG.
, The data cannot be compressed, the data amount becomes several times 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 in the conventional method in which no auxiliary pattern is added, the mask data shown in FIG. It suffices that the obtained mask pattern generates 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.
Computer programs have to be changed significantly.

The present invention solves the above-mentioned problem, and can form a transfer pattern faithful to a design pattern even in a fine pattern without significantly increasing the amount of pattern data or changing the computer program significantly. It is an object of the present invention to provide a light exposure mask.

[0014]

In order to solve the above-mentioned problems, a light exposure mask according to the present invention comprises a main pattern comprising a rectangular figure.
Are partially missing from the state where they are arranged with periodicity
A first pattern arranged in a state having no periodicity
Pattern data and a plurality of auxiliary patterns are the same as the periodicity
Pattern data arranged in a state having a periodicity of
Pattern is not formed by overlapping each other
Where the main pattern is located,
Is formed in a partially overlapping or continuous shape
Where the main pattern is missing,
Only in an independent shape.

Further, a method of manufacturing a photo-exposure mask according to the present invention.
Indicates that the main pattern consisting of rectangular figures
Does not have a periodicity that is partially missing from the exposed state
Forming first pattern data arranged in a state
And the plurality of auxiliary patterns have the same periodicity as the periodicity.
Forming second pattern data arranged in a state having
And the first pattern and the second pattern
The main pattern is synthesized by superimposing
Where the main and auxiliary patterns partially overlap
The main putter
Where the auxiliary pattern is independent
Manufacturing a light exposure mask formed in a shape; and
It is characterized by having.

[0016]

According to the present invention , an auxiliary pattern is formed by using
Are formed not only at locations where the main pattern has a basic periodic structure, but also at locations corresponding to the pattern of the basic periodic structure, including locations that are different from the periodic structure. Can minimize the increase in the data amount due to the addition of the data, and can form a faithful transfer pattern corresponding to the data of the first pattern as the design pattern.

In this case, if there is a portion where the auxiliary pattern is arranged independently without overlapping with another pattern, the auxiliary pattern is formed to have a size that is not transferred to the semiconductor substrate by itself, so that unnecessary auxiliary patterns are formed. It is possible to prevent the pattern from being transferred to the semiconductor substrate.

Further, the light exposure mask having the above structure can be efficiently manufactured by the above-described method for manufacturing a light exposure 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.
FIG. 1 shows a mask ROM of a contact hole program type.
2 shows a data structure for manufacturing a light exposure mask for forming a contact hole.

As described above, the design pattern 11 for forming a contact hole shown in FIG. 1A does not have a perfect periodic structure, and it is difficult to compress data. However, the design pattern 11 has a hidden regularity (periodicity). Although the arrangement of the contact holes has lost regularity due to the programming depending on the presence or absence of the contact holes, the rectangular main pattern 12 is completely vertically and horizontally when considering the portion excluding the contact holes indicated by the dotted lines. Are arranged regularly. Focusing on this regularity, data compression can be performed. Assuming that the main pattern 12 is also present in the portion where the contact hole is omitted, data of only the auxiliary pattern 13 is created in a portion corresponding to the four corners of all the main patterns 12, and this is used as the data of the second layer. I 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
Data. The auxiliary pattern data and the data of the first layer (design pattern 1 shown in FIG.
1 at the time of drawing,
As shown in (c), all the main patterns 12 considered to have the main pattern 12 even in the portion where the contact hole is omitted are shown.
The light exposure mask 14 in which the auxiliary patterns 13 are formed in the portions corresponding to the four corners of the above can be manufactured.

In this case, the data of the first layer is exactly the same as the data of the conventional light exposure mask, and the data amount of the second layer can be reduced because the data is compressed. Note that, in the example shown in FIG.
Is compressed to 1/9, but the actual super LS
In the case of the pattern data of I, since the number of repetitions is much larger, the compression ratio of the data amount can be much larger. As a result of actually producing a light exposure mask for LSI by this method, the data amount of the light exposure mask 14 to which the auxiliary pattern 13 is added is larger than the data amount of the light exposure mask 11 as in the related art. It increased only about 10%. That is, the data of the second layer is only about 10% of the data of the first layer, and an increase of this degree is a range where the increase in the load on the data processing is almost negligible.

The mask data to be automatically generated based on the program code (see FIG. 1A) is the same as the conventional mask data. There is no need to create a program for creating a program, and a conventional program can be used as it is.

By the way, the light exposure mask 14 shown in FIG. 1C, which is obtained by combining the auxiliary pattern data and the data of the first layer, has the auxiliary pattern 13 even in a portion having no contact hole where the auxiliary pattern 13 is unnecessary. 13 are present. However, the auxiliary pattern 13 is designed so as to be a pattern that is not transferred to a semiconductor substrate alone, and the unnecessary auxiliary pattern 13 is not transferred to the wafer and does not adversely affect the device. . Actually, as a result of conducting a transfer experiment on the wafer using the prepared light exposure mask 14, even if the exposure energy is increased to twice the proper exposure amount, unnecessary auxiliary patterns are not transferred onto the wafer. Did not. However, if the size of the auxiliary pattern is too large, unnecessary auxiliary patterns may be transferred onto the wafer, so that the design of the auxiliary pattern 13 requires careful attention.

A detailed study was conducted on the case where the auxiliary pattern 13 was a square and the center of the auxiliary pattern 13 was located at the corner of the main pattern 12. As a result, the dimension L of one side of the auxiliary pattern 13 was L <L. It has been found that by setting the value to 0.5 · λ / NA, the auxiliary pattern 13 can be prevented from being independently transferred onto the wafer. Here, λ is the wavelength of the projection exposure apparatus using the light exposure mask 14, 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, the dimension L of one side of the auxiliary pattern 13 needs to be L> 0.2 · λ / NA.

Therefore, it is desirable that the dimension of the auxiliary pattern 13 be 0.2.lambda./NA<L<0.5.lambda./NA.

The auxiliary pattern 13 shown in FIG.
Is composed of four squares for one main pattern 12. As described above, the first pattern composed of the main pattern 12
When the data of the layer and the data of the second layer composed of the auxiliary pattern 13 are combined at the time of drawing, the part 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 very small area, the influence is not so large, but may cause a decrease in accuracy when producing a light exposure mask. To cope with this, by making the auxiliary pattern L-shaped as shown in FIG. 2B, the overlap with the main pattern 21 can be removed (see FIG. 2C). At this time, the data amount (data of the second layer) of the auxiliary pattern 22 is doubled. However, since the auxiliary pattern 22 is compressed and the data amount is not large, if the increase is about twice, the increase in the load on the data processing can be ignored. As shown in FIG. 2C, the light exposure mask 23 formed using the L-shaped auxiliary pattern data can reduce the area of the unnecessary portion of the auxiliary pattern 22 and can reduce the unnecessary auxiliary pattern. 2
2 can be reduced.

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

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 periodic data (see FIG. 3C). Data obtained by adding fine auxiliary patterns 33 to the corners of the four corners of the periodic main pattern 32 covering the contact holes is defined as data of the second layer. The data of the first layer is the contact hole part 3
It is assumed that the entire data is only the part connecting the two (the pattern shown in FIG. 3B is called a connection pattern, and the pattern data shown in FIG. 3C is called auxiliary pattern addition data).

By overlaying these two layers of data during electron beam drawing, a 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 has the same amount as the data of the conventional light exposure mask. 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 repetitions is much larger, so that the rate of data amount compression can be much larger. Also in this case, as a result of actually producing a light exposure mask for LSI, the amount of work and the processing time required for data processing 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. Therefore, the final mask pattern (see FIG. 3D)
The auxiliary pattern 33 has a shape protruding from the original design pattern 31. Also in this case, when the data of the first layer and the auxiliary pattern additional data of the second layer are combined at the time of drawing, the portion where the data overlaps is drawn twice.

To cope with this, if the connection pattern 36 is made to be a rectangle that fits between the auxiliary pattern 33 and the main pattern 32 as shown in FIG. 4A, data overlap will be eliminated. Even in this case, the data amount of the connection pattern 34 (data of the first layer) does not change because the data of the first layer remains a single rectangle only by changing the size of the pattern. When such connection data is used, the pattern on the light exposure mask 37 has large irregularities as shown in FIG. However, as a result of transferring the pattern onto the silicon wafer using the photo-exposure mask 37, the unevenness of the mask pattern hardly affected 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, and the irregularities on the light exposure mask 37 are not faithfully transferred. By averaging, a pattern was formed along the central portion 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 decreases. A problem arose. 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, and the like 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, the main pattern composed of rectangular figures has periodicity.
Has a periodicity in which some parts are missing from the
The first pattern data arranged without
State that the auxiliary pattern has a periodicity similar to the above periodicity
Each pattern with the second pattern data arranged in the
By superimposing the master, where there is a main pattern,
The pattern and the auxiliary pattern may partially overlap
Is formed in a continuous shape, where the main pattern is missing
In the light exposure, only the auxiliary pattern is formed into an independent shape
With the use mask, it is possible to form a transfer pattern faithful to the design pattern while minimizing an increase in the data amount due to the addition of the auxiliary pattern. In this case, if there is a portion where the auxiliary pattern is arranged independently without overlapping with other patterns, the auxiliary pattern is formed to a size that is not transferred to the semiconductor substrate by itself, thereby making the unnecessary auxiliary pattern unnecessary. Can be prevented from being transferred to the semiconductor substrate. Further, by using the light exposure mask of the present invention, a transfer pattern close to a design pattern can be obtained on a semiconductor substrate even for an LSI having a pattern having no complete periodicity.

The main pattern consisting of a rectangular figure is
A part that is partially missing from the state of being arranged with
First pattern data arranged in a state without period
Forming a plurality of auxiliary patterns with the periodicity
Second pattern arranged in a state having similar periodicity
Forming data, the first pattern and the second
By combining the two patterns so that they overlap,
Where there is a main pattern, the main pattern and auxiliary pattern
Is formed in a partially overlapping or continuous shape
And the auxiliary pattern is used where the main pattern is missing.
Only a light exposure mask that is formed in an independent shape
By including the manufacturing process, the light exposure mask having the above structure can be efficiently manufactured.

[Brief description of the drawings]

FIGS. 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 the 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.

FIGS. 2A and 2B show a data structure and a mask pattern for explaining a light exposure mask obtained by improving the first embodiment of the present invention, wherein 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,
(C) 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 producing a light exposure mask according to a second embodiment of the present invention, wherein 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 improved from the second embodiment of the present invention, wherein FIG. 4A is a plan view of first layer data, and FIG. Plan view of second layer data (auxiliary pattern additional data),
(C) is a plan view of a light exposure mask with an auxiliary pattern.

5A and 5B are diagrams for explaining the influence of diffraction in the projection optical system, wherein 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.

FIGS. 7A and 7B are plan views showing examples 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,
(B) 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 (5)

(57) [Claims] 1. A main pattern comprising a rectangular figure has periodicity.
The periodicity that some parts are missing from the arranged state
The first pattern data arranged without the
Number of auxiliary patterns have periodicity similar to the periodicity
Each pattern with the second pattern data arranged in the state
The main pattern and the auxiliary pattern are formed where the main pattern is located.
Is formed in a partially overlapping state or a continuous shape,
Where the main pattern is missing, only the auxiliary pattern
A light exposure mask formed in an independent shape . 2. In a place where a main pattern exists, an auxiliary putter is provided.
2. The light exposure mask according to claim 1, wherein the mask is superimposed on four corners of the main pattern . 3. The auxiliary pattern is formed in an independent shape.
Size is too large to be transferred to the semiconductor substrate.
The light exposure mask according to claim 1. 4. The auxiliary pattern is square, and
The dimension of one side of the auxiliary pattern is 0.2 · λ / NA (only
Is the wavelength of the projection exposure apparatus, and NA is the projection level of the exposure apparatus.
Larger than 0.5 · λ / NA
4. The mass for light exposure according to claim 3, wherein the mass is small.
H. 5. A main pattern comprising a rectangular figure has a periodicity.
The periodicity that some parts are missing from the arranged state
Form the first pattern data arranged without having
And the plurality of auxiliary patterns have the same periodicity as the periodicity.
To form the second pattern data arranged in the
And overlapping the first pattern and the second pattern
By combining so that the main pattern
If the main pattern and the auxiliary pattern partially overlap,
The main pattern is missing
Where only the auxiliary pattern is formed in an independent shape
Manufacturing a light exposure mask,
A method for manufacturing a light exposure mask, characterized in that: