JPH06275482A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve focus depth at both a basic pattern and a periphery pattern, by, with a mask where a basic repetition pattern and a peripheral repetition pattern are drawn used, obliquely letting partially coherent light from a light source, impinge on a semiconductor device for exposure. CONSTITUTION:As an optimum light source by which an optimum light intensity distribution corresponding to periodicity of a pattern A is obtained for a basic repetition pattern A and peripheral repetition pattern, two-piece rod-like light source, for example, is decided. Then, to obtain an optimum light intensity distribution for the two-piece rod-like light source, the pattern B is corrected, thus a pattern TB is generated. Then, with a mask where the patterns B and TB are drawn used, partially coherent light is made to be incident from the two-piece rod-like light source for exposure. With this arrangement, the resolution in both the basic repetition pattern A and the peripheral repetition pattern is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device in which a mask on which a fine pattern near the limit resolution of an exposure device is drawn by obliquely illuminating partial coherent light. Regarding In recent years, miniaturization of semiconductor devices has been rapidly progressing, and it has become difficult to deal with resolution in conventional exposure by circular illumination using a circular light source. Therefore, a method such as an oblique incident illumination exposure method in which the shape of the light source of the illumination system is arranged at a pitch corresponding to the periodicity of the pattern shape drawn on the mask and the oblique incident illumination is performed is being studied.

However, there is no universal light source shape for mask patterns having various periodicities, and therefore, how to match the mask pattern and the light source shape is a major issue.

[0003]

2. Description of the Related Art In conventional exposure by circular illumination using a circular light source, as shown in FIG.
In the case of a circular light source of × NA / λ (where σ ≦ σmax), the resolution r is generally r = 0.8 × λ / NA, where λ: exposure wavelength NA: numerical aperture. Therefore, it lacks the ability to form a fine pattern that requires a higher resolution.

Therefore, when a resolution of 0.7 × λ / NA is required, or when an L & S (line
When it is required to improve the depth of focus (focus margin) of the (and space) pattern, as shown in FIG. 6B, a circular light source having a radius σ max × NA / λ is formed by a slit called a σ diaphragm. Divide the radius of each circular light source by σ ′ × NA / λ, and the distance between circular light sources σ′−
This has been dealt with by changing to a four-divided light source in which σ ′ is 2 × 0.7 × NA / λ.

When such a 4-division light source is used to expose and transfer a simple L & S pattern with a duty d = 0.5 drawn on a mask, as shown in the graph of FIG. The depth of focus was greater than when used and therefore the resolution was also improved.

[0006]

However, the improvement of the depth of focus by changing the light source shape from the circular light source to the four-division light source tends to depend on the pattern shape. For example, FIG. 8 shows a photograph of a transfer pattern formed by exposing and transferring a predetermined repeating pattern using a four-divided light source. As is clear from this figure, in the case of a simple L & S pattern with a constant duty, Although the depth of focus is improved and the transfer pattern is cut well (see FIG. 8A), the depth of focus is reduced and the transfer pattern is not cut well in a portion where there is a pad or the like and the space width is small. (See FIG. 8B).

Therefore, for a mask in which pattern shapes having different line widths and duty ratios such as a basic pattern and a peripheral pattern are mixed, the resolution can be improved even if the light source shape is changed. There was a problem that some patterns could not be created. Therefore, it is an object of the present invention to provide a method of manufacturing a semiconductor device capable of improving the depth of focus for both the basic pattern and the peripheral pattern when exposing with a common light source.

[0008]

[Means for Solving the Problems] The above problem is that a basic repetitive pattern is formed on a mask, and the shape of a light source is determined so as to obtain an optimum light intensity distribution for the basic repetitive pattern. In order to obtain an optimal light intensity distribution for the shape of the light source, a peripheral repeating pattern is created on the mask, and the mask is used to draw the basic repeating pattern and the peripheral repeating pattern,
This is achieved by a method for manufacturing a semiconductor device, which comprises exposing the partially coherent light from the light source by oblique incidence illumination.

Further, the above problem is that the shape of the light source is determined so that the light intensity distribution is optimum for the basic repetitive pattern already drawn on the mask, and the optimum light intensity is determined for the shape of the light source. Partial coherent light from the light source is corrected by correcting the peripheral repeating pattern already drawn on the mask so that the intensity distribution is obtained, and using the mask in which the basic repeating pattern and the corrected peripheral repeating pattern are drawn. Is performed by obliquely illuminating and exposing.

In the method of manufacturing a semiconductor device described above, the correction of the peripheral repetitive pattern is performed by correcting the pitch of the peripheral repetitive pattern. . Also, in the method for manufacturing a semiconductor device described above, the method for manufacturing a semiconductor device is characterized in that the correction of the peripheral repetitive pattern is to correct the line width of a line pattern in the peripheral repetitive pattern. To be done.

Further, in the above-described semiconductor device manufacturing method, the pitch of the peripheral repetitive pattern before correction is equal to or larger than the pitch of the basic repetitive pattern. Achieved by In addition, in the above-described method for manufacturing a semiconductor device, the peripheral repetitive pattern is divided into a plurality of pattern groups having different pitches and / or line widths of line patterns. To be done.

[0012]

According to the present invention, a basic repetitive pattern is created, a light source shape is determined so that an optimum light intensity distribution is obtained for this basic repetitive pattern, and an optimum light intensity is obtained for this light source shape. Since the peripheral repetitive pattern is created so as to have a distribution, the light source having the determined shape becomes a common optimum light source for both the basic repetitive pattern and the peripheral repetitive pattern. Therefore, by using a mask in which a basic repeating pattern and a peripheral repeating pattern are drawn and exposing a partial coherent light from a common optimum light source by oblique incidence illumination, both the basic repeating pattern and the peripheral repeating pattern are exposed. The depth of focus can be improved.

When the basic repetitive pattern and the peripheral repetitive pattern have already been drawn, the light source shape is determined so that the light intensity distribution is optimum for the basic repetitive pattern. In order to correct the peripheral repetitive pattern so that the light intensity distribution is optimum for the shape, a common optimum light source is used for both the repetitive pattern based on the light source of the determined shape and the corrected peripheral repetitive pattern. Become. Therefore, by using a mask in which a basic repetitive pattern and a peripheral repetitive pattern after the correction are drawn, partial coherent light from a common optimum light source is obliquely illuminated to expose the basic repetitive pattern and the corrected repetitive pattern. Both the depth of focus of the surrounding repeating pattern can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on illustrated embodiments. 1A and 1B are pattern plan views showing a basic repetitive pattern A and a peripheral repetitive pattern B among the patterns drawn on the mask.

For example, the repetitive pattern A, which is the basis of the cell portion of the integrated circuit, is the line pattern 1 in
The line width WA1 of 0, the pitch PA1 of the first type, and the pitch PA2 of the second type are WA1 = 0.30 to 0.35 μm PA1 = 0.80 to 0.85 μm PA2 = 1.00 to 1.05 μm, respectively. Yes, therefore average pitch (PA1 + PA2) / 2
Is (PA1 + PA2) /2=0.90 to 0.95 μm.

On the other hand, for example, in the peripheral repetitive pattern B constituting the peripheral circuit portion of the integrated circuit, the line width WB1 of the line pattern 12 therein, the first type pitch PB1 and the second type pitch PB2 are respectively WB1. = WA1 PB1 = PA1 PB2 = PA2, which is the same as the pattern A, but the pad portion 14 is provided in the middle of the line pattern 12, and the line width WB2 of the pad portion 14 is, for example, WB2 = 0. 6 μm.

Next, ideal light intensity distributions for forming the patterns A and B of FIGS. 1A and 1B are shown in FIGS. 2A and 2B, respectively. The light intensity distribution RA and the light intensity distribution RB are obtained. That is, the light intensity distribution RA and the light intensity distribution RB are respectively shown in FIG.
The distribution has a shape obtained by inverting the pattern A and the pattern B in (b). The shaded area in the figure indicates that the light intensity is 1, and the white area indicates that the light intensity is 0.

Next, for the repetitive pattern A, the shape of the light source having the optimum light intensity distribution is determined. First, FIG.
As shown in (a), a circular light source E having a radius σ max × NA / λ for irradiating the partially coherent light is divided into meshes, and the light intensity on the image plane is calculated for each divided region. Then, by matching with the ideal light intensity distribution RA of the pattern A and selecting a region having a matching degree of 60% or more, for example, a light source SA having a shape as shown in FIG. 3B is obtained. That is, the parallel rod-shaped light source SA divided into two
Is an optimum light source that can obtain an optimum light intensity distribution corresponding to the periodicity of the pattern A.

Next, the two-divided rod-shaped light source S shown in FIG.
Using A, the pattern B is corrected so that the ideal light intensity distribution RB of the repeating pattern B is obtained. In this embodiment, the line width W of the line pattern 12 in the pattern B is
Since B1 and the average pitch (PB1 + PB2) / 2 are the same as the line width WA1 and the average pitch (PA1 + PA2) / 2 of the line pattern 10 in the pattern A, respectively, the line of the pad portion 14 is not corrected. Width W
Correct only B2.

That is, the line width WB1 of the line pattern 12 'and the pad portion 14' in the corrected repeated pattern TB.
The line width TWB2 of the pad portion 14 of the pattern B is W
When the correction term for B2 is ΔWB2, TWB1 = WB1 TWB2 = WB2-ΔWB2, respectively. In the case of the present embodiment, ΔWB2 = 0.02 μm, so TWB1 = 0.30 to 0.35 μm TWB2 = 0. It becomes 58 μm. In this way, the pattern TB in which the pattern B is corrected corresponding to the light source of FIG. 3B is as shown in FIG.

Next, the pattern A and the corrected pattern T
Using a mask on which B is drawn, partial coherent light is obliquely incident from a common optimum light source, which is a two-divided rod-shaped light source SA, and is exposed to transfer pattern A and pattern TB. As described above, a photograph of the transfer pattern actually formed is
As shown in FIG. When the photograph of FIG. 5 is compared with the photograph of FIG. 8 showing the transfer pattern in the conventional case, the improvement in resolution due to the improvement in the depth of focus is obvious.

That is, in the case of a simple repetitive pattern with a constant duty, the transfer pattern is well cut off since both are optimum light sources corresponding to the periodicity of the pattern (FIG. 5).
(A) and FIG. 8 (a)). On the other hand, when the space width is small due to a pad portion or the like in the middle of the line, the depth of focus is reduced in the area where the space width is conventionally small, so that the cut of the transfer pattern is also poor. However (see FIG. 8B), by applying this embodiment, the depth of focus is improved because the correction corresponding to the optimum light source is made even for the portion where the space width is small. , The transfer pattern is well cut off (see FIG. 5B).

As described above, according to this embodiment, in the basic repeating pattern A and the peripheral repeating pattern B, the line widths WA1 and W of the line patterns 10 and 12 are formed.
B1 and average pitch (PA1 + PA2) / 2, (PB1
+ PB2) / 2 are equal, but the line width WB2 of the pad portion 14 of the pattern B is the line width WB of the line pattern 12.
If it is larger than 1 (see FIGS. 1A and 1B), the optimum two-divided rod-shaped light source SA that obtains an ideal light intensity distribution RA corresponding to the periodicity of the pattern A is determined (see FIG. b)), the pattern B is corrected to the pattern TB so as to obtain the ideal light intensity distribution RB for the pattern B with respect to the two-part rod light source SA (see FIG. 4). It can be a common optimum light source for both pattern A and pattern TB.

Therefore, when the mask on which the pattern A and the pattern TB are drawn is used to illuminate the partial coherent light from the common split light source SA, which is a two-divided rod light source SA, at an oblique incidence.
Since the optimum light intensity distribution RA and light intensity distribution RB are obtained,
The focal depths of both the transfer pattern A and the transfer pattern B formed by transferring the pattern A and the pattern TB can be improved, and the yield can be improved.

In the above embodiment, the pitches PA1 and PA2 of the basic repeating pattern A and the pitches PB1 and PB2 of the peripheral repeating pattern B are equal to each other, so that the average pitch of both repeating patterns A and B ( The case where PA1 + PA2) / 2 and (PB1 + PB2) / 2 are the same has been described, but the pitch PB of the pattern B is
When 1 and PB2 are different from the pitches PA1 and PA2 of the pattern A and the average pitch (PB1 + PB2) / 2 of the pattern B is larger than the average pitch (PA1 + PA2) / 2 of the pattern A, the pattern B is corrected to the pattern TB. At this time, it is desirable to correct the pitches PB1 and PB2.

That is, the corrected pitches are respectively set to PTB.
1 and PTB2, these pitches PTB1 and PT
B2 becomes PTB1 = (PA1 + PA2) / 2 PTB2 = (PA1 + PA2) / 2.

Further, in the above embodiment, the case where the peripheral repeating pattern B is one kind has been described, but of course, plural kinds of peripheral repeating patterns B1 and B are provided.
Even if there are 2, ..., By applying the present invention to each of them, it is possible to improve the depth of focus for all patterns of the basic repeating pattern A and the peripheral repeating patterns B1, B2 ,. it can.

When there are a plurality of types of peripheral repeating patterns B1, B2, ..., Such a plurality of peripheral repeating patterns have different line widths, pitches, pattern shapes, etc. of the line patterns therein. It is desirable to divide into a plurality of pattern groups. By dividing the level code into a plurality of pattern groups, it becomes possible to easily correct each data in each pattern group when applying the present invention.

Further, in the above embodiment, the basic repeating pattern A and the peripheral repeating pattern B are already drawn, the pattern B is corrected to the pattern TB, and the pattern A and the corrected pattern TB are drawn. Although the depth of focus is improved by exposing using a mask, the present invention can be applied not only when correcting such an existing mask, but also when designing a pattern from now on. Therefore, it can be said that the effect of applying the present invention is great only in such a case.

That is, when designing a basic repeating pattern and peripheral repeating patterns, first, a basic repeating pattern A as shown in FIG. Next, the optimum light source shape as shown in FIG. 3B is determined so that the optimum light intensity distribution can be obtained corresponding to the periodicity of the pattern A. Next, a peripheral repeating pattern TB as shown in FIG. 4 is created so that the light intensity distribution is optimum for the two-divided rod-shaped light source SA.

Then, using the mask on which the pattern A and the pattern TB are drawn, the partial coherent light from the common optimum light source SA, which is a two-divided rod-shaped light source SA, is obliquely illuminated to expose the pattern A and the pattern TB. To form a transfer pattern A and a transfer pattern B. By adopting such a pattern design method, rather than correcting the pattern of the mask once created, the basic repeating pattern A and the peripheral repeating pattern are improved so that the depth of focus is improved with respect to a common light source. It is possible to easily design the pattern TB from the beginning.

[0032]

As described above, according to the present invention, when a mask on which a predetermined pattern is drawn is irradiated with partial coherent light from a predetermined light source for exposure, a basic repeating pattern is created and The light source shape is determined by deciding the light source shape so that the optimum light intensity distribution is obtained for the repetitive pattern and the peripheral repeating pattern is created so that the light intensity distribution is optimum for this light source shape. Is a common optimum light source for both the repeating pattern and the surrounding repeating pattern. As a result, by using a mask in which a basic repeating pattern and peripheral repeating patterns are drawn, partial coherent light is obliquely illuminated from a common optimum light source to expose the basic repeating pattern and peripheral repeating patterns. Both depths of focus can be improved.

When the basic repeating pattern and the peripheral repeating pattern are already drawn, the light source shape is determined so that the light intensity distribution is optimum for the pattern shape of the basic repeating pattern. By correcting the pattern shape of the peripheral repetitive pattern so that the light intensity distribution is optimal for the light source shape, a common optimum light source for both the repetitive pattern on which the light source is based and the peripheral repetitive pattern after correction is obtained. Therefore, the depth of focus of both the basic repeating pattern and the peripheral repeating pattern can be improved.

Therefore, the resolution of both the basic repetitive pattern and the peripheral repetitive pattern can be improved, and the characteristics of the semiconductor device and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a pattern plan view showing a basic repeating pattern A and a peripheral repeating pattern B drawn on a mask.

2 is an ideal light intensity distribution R of patterns A and B in FIG.
It is a figure which shows A and RB.

FIG. 3 is a diagram for explaining determination of an optimum light source shape for pattern A in FIG.

4 is a pattern plan view showing a corrected pattern TB of the pattern B of FIG. 1. FIG.

FIG. 5 is a photograph showing a repeating pattern formed by applying the present invention specifically.

FIG. 6 is a diagram showing a conventional circular light source and a conventional four-divided light source.

FIG. 7 is a graph for explaining the improvement of the depth of focus when a conventional four-divided light source is used.

FIG. 8 is a photograph showing a repeating pattern formed using a conventional four-divided light source.

[Explanation of symbols]

10 ... Line pattern 12 ... Line pattern 12 '... Line pattern 14 ... Pad part 14' ... Pad part WA1, WB1, WTB1 ... Line width of line pattern WB2, WTB2 ... Line width of pad part PA1, PA2, PB1, PB2, PTB1 and PTB2
…pitch

Claims (6)

[Claims] 1. A basic repeating pattern is created on a mask, and the shape of a light source is determined so that an optimum light intensity distribution is obtained with respect to the basic repeating pattern. A peripheral repetitive pattern is created on the mask so as to obtain an optimum light intensity distribution, and the partially coherent light is obliquely emitted from the light source using the mask in which the basic repetitive pattern and the peripheral repetitive pattern are drawn. A method of manufacturing a semiconductor device, which comprises exposing by illuminating incident light. 2. The shape of a light source is determined so as to have an optimum light intensity distribution with respect to a basic repeating pattern already drawn on a mask, and the light intensity distribution is optimum with respect to the shape of the light source. As described above, the peripheral repetitive pattern already drawn on the mask is corrected, and the partially repeated coherent light is obliquely illuminated from the light source using the mask on which the basic repetitive pattern and the corrected peripheral repetitive pattern are drawn. And exposing the semiconductor device. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the correction of the peripheral repeated pattern is correction of the pitch of the peripheral repeated pattern. 4. The semiconductor device manufacturing method according to claim 2, wherein the correction of the peripheral repetitive pattern is correction of the line width of the line pattern in the peripheral repetitive pattern. Device manufacturing method. 5. The semiconductor device manufacturing method according to claim 2, wherein the pitch of the peripheral repetitive pattern before correction is equal to or larger than the pitch of the basic repetitive pattern. Manufacturing method. 6. The method of manufacturing a semiconductor device according to claim 2, wherein the repeating pattern in the periphery is divided into a plurality of pattern groups having different pitches and / or line widths of line patterns. Device manufacturing method.