KR20100059512A - Photo mask and method for forming the pattern using the same - Google Patents

Abstract

PURPOSE: An exposure mask and a pattern forming method using the same are provided to improve the process margin by using an exposure mask including an assist feature. CONSTITUTION: A first line pattern(210a) is formed on the domain A on a transparent substrate(200). A second line pattern(210b) is formed on the domain B on the transparent substrate. The first pattern and the second pattern are line pattern. The second patterns have the pitch smaller than the pitch of the first patterns. An assist feature(210c) is arranged between the first patterns. The line width of the assist feature is formed to be smaller than the line width of the first line pattern.

Description

Exposure mask and pattern formation method using the same {PHOTO MASK AND METHOD FOR FORMING THE PATTERN USING THE SAME}

The present invention relates to an exposure mask and a pattern forming method using the same. In particular, it relates to an exposure mask comprising an assist feature.

In recent years, as the degree of integration of semiconductor devices has sharply increased, the pitch between the patterns formed on the wafer is also getting narrower. Accordingly, the photolithography process for forming a pattern is also showing a further limit. Accordingly, a short wavelength laser and a projection lens having a high numerical aperture (NA) may be used to form a pattern requiring high resolution. However, as the numerical aperture increases, a phenomenon in which a section in which a specific pattern is formed is not defined occurs. Such a section is called a forbidden pitch.

Forbidden pitch will be described with reference to FIGS. 1, 2A and 2B.

FIG. 1 illustrates an exposure mask defining a flash memory device, and illustrates a portion corresponding to a connection section of a core region in a cell region.

First line patterns 110a and second line patterns 110b are formed in regions A and B on the transparent substrate 100, respectively. Here, area A is a core area and area B represents a cell area. Hereinafter, the A region and the B region will be described as core regions and cell regions, respectively.

The pitch P1 of the first line pattern 110a formed in the core region is larger than the pitch P2 of the second line pattern 110b formed in the cell region. That is, when two patterns are formed in the cell region, one pattern is formed in the core region. For example, if the second line patterns 110b of the cell region are designed with a pitch of 100 nm, the first line patterns 110a of the core region are designed with a pitch of 200 nm, which is twice that of the cell region.

2A and 2B illustrate photographs of patterns formed using the exposure mask shown in FIG. 1.

FIG. 2A is a photograph showing a DI profile of a pattern in the case of best focus, and FIG. 2B is a photograph showing a DI profile of the pattern in the case of defocus.

Here, in the case of the best focus, all the patterns to be patterned are patterned, but in the case of defocus, the pattern of the core region having a large pitch of the pattern is not formed. In the core region having a large pitch of the pattern, the process margin was reduced, and thus the pattern was not formed. That is, although the pitch of the pattern of the cell region is twice as small as that of the pattern formed in the core region, the process margin is very large.

In this case, a phenomenon in which patterning is not performed in a section of a specific pattern, such as a pattern formed in the core region, occurs, and this is called a forbidden pitch.

When a pattern having a forbidden pitch is designed as described above, even if the pattern has a large pitch, a process margin is rapidly reduced during the exposure process, thereby causing a problem in that patterning is not performed.

In the past, a method of forbidden pitch section is reflected in a design rule and a designer is not allowed to design the pattern of the section of the forbidden pitch. However, since the designer is subject to various restrictions in designing the pattern layout, a design time and effort are required.

In addition, a method of designing a pattern of a forbidden pitch section to have a larger pitch may be used, which causes a problem of increasing chip size.

The present invention intends to change the layout of the exposure mask to form the same pattern as the original design.

The exposure mask according to the present invention

And first patterns, second patterns having a pitch smaller than the pitch of the first patterns, and an assist feature disposed between the first patterns.

In this case, the first pattern and the second pattern are line patterns, and the first pattern and the second pattern are light blocking patterns or light transmitting patterns.

The first patterns are formed in a core region, and the second patterns are formed in a cell region.

In addition, the pitch of the first pattern is twice the pitch of the second pattern, the assist feature is formed spaced apart from the first patterns by a predetermined distance, the assist feature is formed in the center between the first patterns Is formed. The line width of the assist feature is smaller than the line width of the first pattern, and the pitch between the first pattern and the assist feature is equal to the pitch of the second pattern.

In addition, the pattern forming method using an exposure mask according to the present invention

Forming an etched layer and a photoresist on the substrate, first patterns, second patterns having a pitch smaller than the pitch of the first patterns, and an assist feature disposed between the first patterns; Patterning the photoresist layer using the formed exposure mask to form a photoresist pattern, and etching the etched layer using the photoresist pattern as a mask.

The exposure mask according to the present invention can design the original design irrespective of the forbidden pitch, and can minimize the size of the chip as the limit of the forbidden pitch is eliminated.

In addition, there is an effect that the process margin is improved by using an exposure mask including an assist feature.

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention will be described in detail.

3 is a plan view showing an exposure mask according to the present invention.

Referring to FIG. 3, first line patterns 210a are formed in an area A of the transparent substrate 200, and a second line having a pitch smaller than a pitch of the first line pattern 210a is formed in an area B of the transparent substrate 200. Patterns 210b are formed. The exposure mask layout may be applied to a flash memory device. However, the present invention is not limited to flash memory devices but can be applied to all semiconductor devices such as DRAM and PRAM.

Here, area A corresponds to the core area and area B corresponds to the cell area. The first line pattern 210a and the second line pattern 210b may be light blocking patterns or light transmitting patterns.

An assist feature 210c is formed between the first line patterns 210a. Here, the assist features 210c are formed one by one in the center portion between the first line patterns 210a and are spaced apart from the first line patterns 210a by a predetermined distance. The line width of the earth feature 210c is smaller than the line width of the first line pattern 210a. In this case, since the assist feature 210c is present on the exposure mask but should not be patterned on the wafer, the assist feature 210c is preferably formed with a line width below the limit resolution that can be patterned.

Here, the pitch P1 between the first line pattern 210a and the assist feature 210c is preferably equal to the pitch P2 of the second line pattern 210b. That is, the line width of the region in which the first line pattern 210a and the assist feature 210c are formed, as in the region indicated by the point islands in FIG. 3, is the width of the region in which the second line pattern 210b is formed. Make it the same as the line width.

For example, if the second line patterns 210b of the B region are designed to have a pitch of 100 nm, in the A region, the assist feature 210c is inserted adjacent to the first line pattern 210a and the pitch of 100 nm, which is the same pitch as the B region, is inserted. do.

Although not shown, a pattern forming method using the exposure mask of FIG. 3 will be described.

First, an etched layer and a hard mask layer are formed on the substrate, and a photosensitive film is coated on the hard mask layer.

Next, an exposure process using the exposure mask of FIG. 3 is performed on the photosensitive film to form a photosensitive film pattern. In this case, since the assist feature 210c shown in FIG. 3 does not affect forming a pattern, the assist feature 210c is not formed as a photoresist pattern. The assist feature 210c is formed with a line width less than or equal to the limit resolution that can be patterned to increase the resolution when the first line patterns 210a on both sides of the assist feature 210c form a pattern, thereby changing the focus or energy of the exposed light. Nevertheless, it serves to form an accurate pattern within the process margin.

Accordingly, the first line pattern 210a and the second line pattern 210b to be patterned in the exposure mask of FIG. 3 are patterned. In particular, the first line pattern 210a formed at the forbidden pitch is accurately patterned.

Next, the hard mask layer is etched using the photoresist pattern as a mask to form a hard mask pattern, and the etched layer is etched using the hard mask pattern as a mask to form an etched layer pattern.

As described above, when the pattern formation is performed using an exposure mask in which an assist feature is formed between the patterns formed at the Forbidden pitch, the same pattern as the original design is formed even if the pattern at the Forbidden pitch is designed.

Thus, the design can be designed regardless of the forbidden pitch, and the chip size can be minimized as the forbidden pitch is not limited. And process margins improve.

It will be apparent to those skilled in the art that various modifications, additions, and substitutions are possible, and that various modifications, additions and substitutions are possible, within the spirit and scope of the appended claims. As shown in Fig.

1 is a plan view showing an exposure mask according to the prior art.

2A and 2B are photographic views showing patterns formed using the exposure mask of FIG.

3 is a plan view of an exposure mask according to the present invention;

<Explanation of Signs of Major Parts of Drawings>

200: transparent substrate 210a: first line pattern

210b: second line pattern 210c: assist feature

Claims (11)

First patterns; Second patterns having a pitch smaller than that of the first patterns; And Assist Feature disposed between the first patterns Exposure mask comprising a. The method of claim 1, And the first pattern and the second pattern are line patterns. The method of claim 1, And the first pattern and the second pattern are light blocking patterns or light transmitting patterns. The method of claim 1, The first pattern may be formed in the core area. The method of claim 1, And the second patterns are formed in a cell region. The method of claim 1, The pitch of the first pattern is twice the pitch of the second pattern. The method of claim 1, The assist feature may be formed to be spaced apart from the first patterns by a predetermined distance. The method of claim 1, And the assist feature is formed at a central portion between the first patterns. The method of claim 1, The line width of the assist feature is smaller than the line width of the first pattern. The method of claim 1, And the pitch between the first pattern and the assist feature is equal to the pitch of the second pattern. Forming an etched layer and a photosensitive film on the substrate; The photoresist pattern is patterned by patterning the photoresist layer using an exposure mask having first patterns, second patterns having a pitch smaller than the pitch of the first patterns, and an assist feature disposed between the first patterns. Forming a; And Etching the etched layer using the photoresist pattern as a mask Pattern formation method using an exposure mask comprising a.

Images