JP2003282419A - Mask pattern verification method and mask pattern preparing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mask pattern verification method which can verify a complementary split pattern without developing special verification software, and to provide a mask pattern preparing method. <P>SOLUTION: The mask pattern verification method performs false complementary split application to a complementary split pattern, detects portions to be further split, and determines the complementary split pattern as being suitable when no portion for split has been detected. The mask pattern preparing method comprises first complementary split application for preparing the complementary split pattern, and a second complementary split application following the first application for performing the verification. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask pattern verification method and a mask pattern creation method for a mask used in a lithography process for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuit devices, the exposure wavelength has been shortened in photolithography, but a charged particle beam is used to form a fine pattern with higher resolution. Lithography is being developed. For example, an electron beam transfer apparatus has been proposed which irradiates a stencil mask with an electron beam to transfer a pattern onto a wafer. The stencil mask is a mask in which holes are formed in a thin film (membrane) in a predetermined mask pattern, and an electron beam passes through the holes.

When using a stencil mask, it is essential to use a complementary mask for transferring a specific pattern. The stencil mask membrane must be continuous at all but the holes. For example, in a donut-shaped pattern, the pattern cannot be transferred by one mask because the mask does not support a portion that is not continuous with the periphery of the center.

Therefore, a desired pattern is divided into a plurality of complementary division patterns (complementary division), and these complementary division patterns are formed on different stencil masks.
By using a stencil mask (complementary mask) on which complementary division patterns are formed and exposing the same place on the wafer, the pattern before division is complementarily transferred.

A pattern in which the central portion of the donut-shaped pattern is connected to the surrounding membrane at only one limited place is also called a leaf-shaped pattern.
In the leaf pattern, it is possible to hold the central part,
There is a problem in strength, and the portion surrounded by the pattern is likely to be deformed.

Alternatively, if holes are formed in the stencil mask by a long line pattern or a line and space (L / S) pattern in which a plurality of line patterns are arranged in parallel, the perimeter of the holes is affected by the internal stress of the membrane. Anisotropic distortion may occur and the line width may not be uniform, or stress may concentrate on the corners of the pattern and the membrane may be easily damaged. Therefore, the leaf-shaped pattern and the long line-shaped pattern are also divided into a plurality of rectangles or trapezoids as needed, and these are divided and formed into a plurality of complementary masks.

When the pattern is subjected to complementary division, the complementary division pattern is verified before the complementary division pattern is formed on the mask. As a result of the verification, if a pattern that cannot be actually formed on the stencil mask or a pattern that easily deforms is included in the complementary division pattern, the complementary division is performed again.

A mask pattern designing method involving complementary division is disclosed in, for example, Japanese Patent Laid-Open No. 2001-274072. According to the method described in this publication, the mask pattern is divided into lattice-shaped regions, and the patterns are distributed to two complementary masks so that the patterns of the regions adjacent to each other are not formed on the same complementary mask. Therefore, in each complementary mask, the areas to which the patterns are distributed are arranged like a checkerboard pattern.

With respect to each of the divided areas, it is determined whether or not a donut-shaped pattern exists inside. If no donut-shaped pattern exists in all areas, the complementary division pattern is determined at that time. If there is a donut pattern, change the grid size. This publication does not particularly show a method for determining a donut-shaped pattern.

Further, according to the mask manufacturing method described in Japanese Patent Laid-Open No. 2001-244192, it is determined whether or not donut-shaped or leaf-shaped patterns are present, and if these patterns are present, complementary division is performed. The complementary division pattern is corrected in consideration of the aspect ratio of the portion sandwiched between the patterns. The determination of the donut-shaped pattern or the like is performed based on whether the pattern coordinates are extracted and whether the pattern coordinates are continuous or discontinuous.

Japanese Patent Laid-Open No. 2001-185472 discloses that
A mask is disclosed in which a material through which an electron beam is transmitted is embedded in a hole portion of a stencil mask so that a donut-shaped pattern or the like can be formed without using a complementary mask. In this mask, a metal is used as a membrane material for blocking electron beams, and carbon, silicon carbide, or silicon nitride, for example, is embedded in the hole portions through which the electron beams pass.

Japanese Unexamined Patent Publication No. 2001-143996 discloses a stencil mask drawing pattern verification method, which discloses an algorithm capable of detecting a donut-shaped pattern or a leaf-shaped pattern. According to this algorithm, the drawing area is divided according to a predetermined rule, and the variable a = {0, 1, 2} is set in the divided area. Specifically, the drawing pattern portion, that is, the hole is set to {2}. In addition, the inner portion that is in contact with the hole closest to the side of the drawing area and is surrounded by the straight lines parallel to the side of the drawing area is {1}, and the outer portion of these straight lines is {0}.

Next, the first scan is performed in the X-axis direction and the Y-axis direction to check the variables in the portions on both sides of the variable {1}. Depending on how the variables are arranged in the X-axis direction and the Y-axis direction, the variables are reset to {0} or the variables are left as {1}. Further, the second and third scans are performed in the X-axis direction and the Y-axis direction to reconsider the arrangement of variables in the variable {1} portion and the portions adjacent to both sides.

The arrangement of variables in the variable {1} part and the parts on both sides of the variable {1} indicates the probability that the variable {1} part will be defective. Finally, if the variable is {1} and the arrangement of variables on both sides of the variable is {2} → {1} → {2}, it is detected as a donut pattern. Any other arrangement of variables is detected as a leaf pattern.

According to the charged particle beam projection exposure method disclosed in Japanese Patent Laid-Open No. 2000-124112, the complementary division pattern is formed by dividing it into two complementary masks, and the connecting portion of the drawing area (image field) is formed by each complementary mask. Make sure the pattern is not placed in. As a result, the accuracy of connecting the patterns between the drawing areas is improved, and the accuracy of controlling the exposure line width is improved in the connecting parts of the drawing areas. This publication does not show a method of verifying a complementary divided pattern.

Japanese Unexamined Patent Publication No. 5-36593 (Patent No. 31
According to the charged particle beam drawing mask making method described in No. 05580), when a stencil mask is irradiated with an electron beam in order to appropriately detect a pattern (prohibited pattern) that is easily damaged or cannot be realized. The temperature rise of is calculated by simulation. When the temperature rise of the mask is equal to or higher than the threshold value, the pattern formation is prohibited and the pattern division is changed.

Specifically, the stencil mask is divided into minute areas, and each minute area is set to 1 bit to create a bit map. In the bitmap, the hole portion is 0 and the portion other than the hole is 1. Next, an equation of heat conduction is created for each minute area, and the heat generation amount is calculated by solving the simultaneous equations. For example, the central portion of the donut-shaped pattern becomes extremely hot because the generated heat does not dissipate. In this way, the prohibited pattern is eliminated.

[0018]

A method of creating a complementary division pattern as described above is known, and a method of verifying a complementary division pattern is disclosed in JP 2001-244192 A or JP 2001-143996 A. And Japanese Patent Laid-Open No. 5-36593. However, in order to carry out these verification methods, it is necessary to develop dedicated verification software.

Further, according to the algorithm described in Japanese Patent Laid-Open No. 2001-143996, X is determined for each divided area.
Since it is necessary to perform the scanning in the axial direction and the scanning in the Y-axis direction a plurality of times to verify how the variables are arranged, the processing is complicated and the data processing amount is large. Since the amount of data processing increases with the miniaturization and high integration of patterns, the throughput of mask pattern creation decreases.

Also in the method described in Japanese Patent Laid-Open No. 5-36593, a fine region corresponding to 1 bit must be subdivided as the pattern is miniaturized, and when the temperature rise is simulated for each fine region, The amount of data processing becomes enormous. Therefore, the throughput of mask pattern creation is reduced.

In the manufacture of LSI, CAD (comput
The circuit pattern is designed by er-aided design). The layout-designed pattern data is complementarily divided by complementary division software. Further, the pattern data is corrected if necessary and finally inputted as electron beam drawing data to the electron beam drawing apparatus. A mask pattern is drawn on the resist on the mask by the electron beam drawing apparatus. A mask material is processed using this resist to form a mask.

When the dedicated verification software is used, the pattern data output from the complementary division software is
It is necessary to convert the pattern data into an internal format of the verification software for verification, and to convert the verified pattern data again into a format readable by the electron beam drawing apparatus. Therefore, even if dedicated verification software is developed, it is difficult to speed up the data processing due to a large amount of data processing in the verification and the format conversion accompanying the verification.

Generally, the data processing software for creating a mask has a relatively simple graphic calculation function such as a sizing function for enlarging / reducing a pattern. If the complementary division pattern can be verified by a relatively simple algorithm using such a function, the throughput of mask pattern creation is improved. In addition, format conversion is not required like when using dedicated verification software,
This also speeds up data processing.

The present invention has been made in view of the above problems. Therefore, the present invention is a mask pattern verification method and a mask pattern verification method capable of verifying complementary division patterns without developing dedicated verification software. The purpose is to provide a pattern creation method.

[0025]

In order to achieve the above object, the mask pattern verification method of the present invention performs a false complementary division process on complementary division patterns which are different parts of a desired pattern, and further, It is characterized in that the presence / absence of a divided portion is detected, and the complementary division pattern is determined to be appropriate when there is no divided portion.

Further, the mask pattern forming method of the present invention forms a mask pattern in which a thin film for blocking charged particle beams has holes in a predetermined pattern, and exposure is performed by the charged particle beam passing through the holes. A method of performing a first complementary division process on a designed pattern to form a plurality of mutually different complementary division patterns that are actually formed on a mask; and the complementary division. A second complementary division process is performed on the pattern, the presence or absence of a portion to be further divided is detected, and the verification of the first complementary division process is performed.

Preferably, the first complementary division processing is performed by extracting from the designed pattern a pattern that cannot be formed on one mask and a pattern that is deformed when formed on one mask. And a step of allocating the divided patterns to different complementary division patterns, and a step of allocating the undivided patterns that have not been extracted to the complementary division patterns.

Preferably, in the second complementary division processing, a plurality of complementary division patterns created in the first complementary division processing are overlapped with each other, and a contacting side is detected to detect a division position. Including steps. Alternatively, in the second complementary division processing, a plurality of complementary division patterns created in the first complementary division processing are enlarged and an AND operation processing is performed,
The process includes the step of detecting the division points. Preferably, the first and second complementary division processes are performed by different algorithms.

Thus, the complementary division pattern can be verified by using the comparatively simple graphic operation function of the existing complementary division software or general-purpose pattern data conversion software without developing special verification software. Is possible. According to the mask pattern verification method and the mask pattern creation method of the present invention, the amount of data processing for verification is relatively small, and pattern verification can be performed at high speed.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a mask pattern verifying method and a mask pattern creating method of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is an example showing complementary division and verification of a pattern by the mask pattern forming method of the present embodiment. In this embodiment, a single complementary division software is used.

FIG. 1A shows a pattern before performing complementary division, and includes patterns such as donut-shaped patterns and leaf-shaped patterns that need to be divided to form a stencil mask. 1B and 1C show complementary division patterns obtained by dividing the pattern of FIG. 1A by the first complementary division processing. According to the mask pattern creating method of the present embodiment, after the first complementary division processing,
Further, the second complementary division processing is performed.

If the first complementary division processing is correctly performed and the problematic pattern such as the donut-shaped pattern is eliminated, the output of the first complementary division processing (FIGS. 1B and 1C). It is considered that even if the second complementary division processing is performed again on each of the above, the patterns are not divided but are allotted (FIGS. 1D and 1E).

On the other hand, FIGS. 1 (f) and 1 (g) are shown in FIG.
The problematic pattern 1 in (c) includes complementary divided patterns 1a and 1b. As shown in FIGS. 1F and 1G, when there is a pattern divided in the second complementary division processing, the output of the first complementary division processing includes a pattern that cannot be formed on the stencil mask. Consider it to be. As described above, the complementary division processing is performed twice, and the second division is performed.
The complementary division pattern is verified by extracting the figure divided by the complementary division process.

Here, in the second complementary division processing, the condition of the pattern that can be formed on the stencil mask is relaxed more than in the first complementary division processing. If the second complementary division processing is performed under the same condition as that of the first complementary division processing or a stricter condition than the first complementary division processing, a pattern that does not need to be divided may be divided and correct verification may not be performed.

The determination as to whether or not the pattern is divided by the second complementary division processing and the extraction of the divided pattern are performed by the following method, for example. The output of the second complementary division processing is 2
With one layer, the design rules are checked with the two layers superposed, and the edges that are in contact are detected.

For this design rule check, for example, general-purpose design verification software can be used. The portion divided by the second complementary division processing is detected as a side that is in contact with each other when the two layers are superposed. For example, when this method is applied to FIGS. 1 (f) and 1 (g) (= FIGS. 2 (a) and 2 (b)) on which the second complementary division processing is performed, as shown in FIG. 2 (c). , Pattern 1 with side 2
Is detected.

Alternatively, the result of complementary division for verification (the output of the second complementary division processing) is expanded and ANDed.
Perform arithmetic processing. The magnification of expansion may be several grids.
The areas divided by the second complementary division processing are detected by the AND operation processing because the enlarged patterns overlap each other.

For example, when the complementary division patterns shown in FIGS. 1D and 1E are enlarged, the solid line patterns shown in FIGS. 3A and 3B are obtained. The dotted line patterns in FIGS. 3A and 3B correspond to the complementary division patterns in FIGS. 1D and 1E. FIG. 3C is the same as FIG.
The state which the pattern of (a) and (b) was piled up is shown.

Since FIG. 1 (b) is correctly complementary-divided, FIGS. 1 (d) and 1 (e) do not include a portion newly divided by the second complementary division processing, and thus FIG. Only the patterns were distributed. Therefore, FIG.
The solid line pattern in (c) corresponds to an enlarged version of the pattern in FIG. 1 (b). In FIG. 3C, the enlarged portion of the pattern (the portion between the dotted line and the solid line) does not overlap, so that the AND operation process does not leave a pattern (see FIG. 3D).

On the other hand, when the complementary division patterns shown in FIGS. 1F and 1G are enlarged, the solid line patterns shown in FIGS. 4A and 4B are obtained. The dotted line patterns in FIGS. 4A and 4B correspond to the complementary division patterns in FIGS. 1F and 1G. FIG.
The state which the pattern of (a) and (b) was piled up is shown. When the AND operation processing is performed, as shown in FIG. 4 (d), the pattern division portion 3 is detected.

As described above, when the output of the second complementary division processing is enlarged, if the pattern interval is narrow or the enlargement magnification is large, AND is performed even if division is not performed in the second complementary division processing. Patterns may remain in arithmetic processing. For example, if the magnification at the time of enlarging the complementary division patterns of FIGS. 1D and 1E is large, the solid line patterns of FIGS. 5A and 5B are obtained. The dotted line patterns in FIGS. 5A and 5B correspond to the complementary division patterns in FIGS. 1D and 1E.

FIG. 5C shows a state in which the patterns of FIGS. 5A and 5B are superposed. When the AND operation processing is performed, as shown in FIG. 5D, overlapping occurs in a pattern that does not cause a problem, and a false division location 4 is detected. In order to prevent this, it is desirable to determine the enlargement ratio based on the minimum number of grids that can detect a pattern by AND operation processing.

According to the mask pattern verifying method and the mask pattern creating method of the above-described embodiment of the present invention, the verification flow can be constructed by using the figure calculation function such as the widely used pattern data conversion software. Since complementary division patterns can be verified using existing software, there is no need to develop dedicated verification software. In addition, verification can be performed based on a relatively simple algorithm, and data processing can be speeded up.
Therefore, it is possible to improve the turn-around time for forming the mask pattern of the complementary mask.

(Embodiment 2) In this embodiment, 2
Embodiment 1 using two different complementary division software
Similarly, the complementary division pattern is verified. One complementary division software is used to perform the first complementary division processing, and the other complementary division software is used to perform the second complementary division processing.

When a single complementary division software is used, a pattern that needs division may not be divided in both the first and second complementary division processes due to a software defect. In the second complementary division processing, such complementary omission can be prevented by using complementary division software having a different algorithm from the first complementary division processing. For example, in the first complementary division processing, even if the pattern to be originally divided is not divided due to a software defect, it is divided by performing the second complementary division processing.

Alternatively, complementary division software of an algorithm suitable for the purpose of the processing can be adopted for each of the first and second complementary division processing. For example, complementary division software based on a geometric algorithm giving priority to processing speed can be used for the first complementary division processing for creating electron beam drawing data.

In the second complementary division processing for verification, complementary division software based on an analytical algorithm that takes into consideration the moment of the pattern and the like can be used. By combining such complementary division software to create and verify a complementary division pattern, it is possible to improve the accuracy of pattern verification and guarantee the quality of complementary division processing.

The embodiments of the mask pattern verifying method and the mask pattern creating method of the present invention are not limited to the above description. For example, the present invention can be applied to the case where a certain pattern is divided into three or more complementary division patterns. In this case, in the first complementary division processing, n (n is an integer of 3 or more) complementary division patterns are output, and in the second complementary division processing, the contact portion of the pattern is extracted between n layers. . Alternatively, each of the n complementary division patterns is enlarged, and an AND operation is performed on them to detect a pattern division location in the second complementary division processing. Besides, various modifications can be made without departing from the scope of the present invention.

[0049]

According to the mask pattern verifying method and the mask pattern creating method of the present invention, it is possible to verify the complementary division pattern without developing a dedicated verifying software. Can speed up.

[Brief description of drawings]

1A to 1G are views showing a mask pattern forming method of the present invention.

2A to 2C are diagrams showing an example of a mask pattern verification method of the present invention.

FIG. 3A to FIG. 3D are views showing an example of a mask pattern verification method of the present invention.

FIG. 4A to FIG. 4D are views showing an example of a mask pattern verification method of the present invention.

5A to 5D are diagrams showing an example in which a false division location is detected in the mask pattern verification method of the present invention.

[Explanation of symbols]

1, 1a, 1b ... Pattern, 2 ... Side, 3 ... Dividing location, 4
… Fake splits.

Claims (6)

[Claims] 1. A complementary division pattern that is a different part of a desired pattern is subjected to false complementary division processing, and the presence or absence of a portion to be further divided is detected. A mask pattern verification method that is determined to be appropriate. 2. A method for producing a pattern of a mask in which a thin film for blocking charged particle beams has holes in a predetermined pattern, and exposure is performed by the charged particle beam passing through the holes, which is a designed pattern. A first complementary division process to form the complementary division pattern which is a plurality of mutually different complementary division patterns and is actually formed on the mask; and a second complementary division process for the complementary division pattern. And a step of performing the verification of the first complementary division processing by detecting the presence or absence of a portion to be further divided. 3. The first complementary division processing comprises: a pattern which cannot be formed on one mask from a designed pattern;
A step of extracting a pattern that deforms when formed on one mask, a step of dividing the extracted pattern, a step of allocating the divided pattern to different complementary division patterns, and a pattern of the unextracted pattern that has not been extracted 3. The mask pattern creating method according to claim 2, further comprising a step of allocating to a divided pattern. 4. The second complementary division processing comprises a step of detecting a division position by superposing a plurality of complementary division patterns created in the first complementary division processing and detecting a contacting side. The mask pattern creating method according to claim 2, further comprising: 5. The second complementary division process enlarges a plurality of complementary division patterns created in the first complementary division process,
3. The mask pattern creating method according to claim 2, further comprising a step of performing AND operation processing to detect a division location. 6. The mask pattern creating method according to claim 2, wherein the first and second complementary division processes are performed by different algorithms.