JP2000231183A - Pattern forming method and phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form patterns of arbitrary sizes with high accuracy, to simplify stages and to improve throughput in photolithography. SOLUTION: A first mask pattern 13 consisting of a first phase shift region 11 which is offset in phase by 180 deg.C with respect to the phase of the exposure light transmitted through the transmissible region exclusive of the pattern part and a second mask pattern 14 consisting of a second phase shift region 12 are formed as a phase shift mask 100 on a mask substrate 100. The transmittance of the first phase shift region 11 is within a range from 60% to 100% and the transmittance of the second phase shift region 12 is within a range from 3% to 12%. The resist film on the semiconductor substrate is exposed by a diagonal incident illumination method by using the phase shift mask 100, by which resist patterns are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing technique in a manufacturing process of a semiconductor device or the like.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have been steadily miniaturized, and a pattern forming technology of 0.15 μm or less has become necessary. An ArF excimer laser (193 nm) has been required.
The importance of the development of lithography using is increasing.
On the other hand, with the advancement of functions of system LSIs, a technique for forming a high-speed and high-performance logic unit is required. In order to process a high-performance logic part, an exposure technique capable of forming a fine isolated pattern with high precision in photolithography is required. For example, H. H. Y. Liu et al. Have proposed a pattern forming method using a Levenson-type phase shift mask (Proc. SPIE, Vol. 333).
4, p. 2 (1998)).

Hereinafter, the conventional pattern forming method will be described with reference to FIG. A first arrangement in which an opening in which the phase of exposure light is 0 ° and an opening in which the phase is inverted to 180 ° are arranged on both sides of a desired isolated line pattern.
(A phase shift mask in FIG. 11A) and a second mask (a light-shield mask in FIG. 11B) in which a light-shielding pattern is arranged at a desired isolated line pattern.

First, when a positive resist film is applied on a silicon substrate and exposed using a first mask, it is sandwiched between an opening having a phase of 0 ° and an opening having a phase inverted to 180 °. A latent image of the isolated line portion and a latent image of the peripheral portion other than the opening are formed in the resist film. Next, the second image is formed such that the position of the projected image of the light-shielding pattern of the isolated line on the second mask matches the position of the latent image in the resist film of the desired isolated line formed using the first mask. When exposure is performed using a mask, only a latent image of a desired isolated line portion remains, and unnecessary latent images of peripheral portions are erased because they are exposed by the second mask. After the above two exposures, when the resist film is developed using a developing solution, a resist pattern is formed at a desired isolated line portion where a latent image is formed.

In the exposure using the first mask, the contrast of the latent image in the isolated line portion becomes extremely high due to the phase shift effect, so that a fine isolated line pattern can be formed. NA of the numerical aperture of the reduction projection optical system of the exposure machine
Assuming that the wavelength of the exposure light source is λ, the resolution limit is an isolated pattern having a dimension of 0.44 × λ / NA in the normal exposure method using one light-shielding mask. A fine isolated pattern having a size of .22 × λ / NA can be resolved.

[0006]

In the above method, two exposure steps are performed using two masks.
There is a problem of cost due to an increase in mask cost, and a problem of decrease in throughput due to an increase in the number of steps. For example, after unloading the first mask installed in the exposure apparatus, the second mask is loaded and the second mask is aligned, so that the first exposure step and the second exposure step are performed between the first exposure step and the second exposure step. It takes time to change the mask, and the number of exposure steps is twice as large as usual. Therefore, the processing time per wafer becomes longer, and the throughput decreases. Further, the above method has a problem that it is difficult to simultaneously form a pattern of an arbitrary size with high accuracy. For example, since the optimum exposure amount between a fine pattern and a large pattern is significantly different, a process margin when simultaneously forming a fine pattern and a large pattern is extremely small.

An object of the present invention is to simplify the manufacturing process of a semiconductor device using one phase shift mask. In particular, it is an object of the present invention to solve the above-described problems of a decrease in throughput and an increase in cost in forming a fine pattern of 0.22 × λ / NA or less. Another object of the present invention is to solve the problem of dimensional accuracy in a pattern having an arbitrary size.

[0008]

According to the pattern forming method of the present invention, a phase shift mask in which a pattern portion is formed by a plurality of phase shift regions having a transmittance corresponding to a pattern dimension is illuminated from a direction inclined from an optical axis. And exposing a desired pattern on the resist film.

In particular, the phase shift region has a first phase shift region having a transmittance in the range of 60% to 100% and a second phase shift region having a transmittance in the range of 3% to 12%. And an area.

The first phase shift region has a dimension in the short side direction of 0.44 when the numerical aperture of the reduction projection optical system of the exposure device is NA and the wavelength of the exposure light source is λ.
× λ / NA or less.

According to the present invention, a fine pattern is formed by illuminating the phase shift mask in which the phase of the pattern portion is inverted as compared with the phase of the non-pattern portion from a direction inclined from the optical axis. Since a fine pattern can be formed with only one mask, the process is very simple. Further, since the transmittance of the phase shift region is changed in accordance with the pattern size, the process windows (process margins) in each pattern size match, and any pattern having a large size to a large size can be simultaneously formed with high precision. be able to.

According to the present invention, the transmittance is 60%.
By forming a phase shift region in the range of to 100% on the mask, the effect of the phase shift can be obtained to the maximum, so that a very fine pattern of 0.22 × λ / NA or less can be resolved. Furthermore, by simultaneously forming a phase shift region having a transmittance in the range of 3% to 12% on the mask, a pattern having a large size can be simultaneously formed with high precision.

According to the present invention, the transmittance is 60%.
Dimensional accuracy of a pattern having a dimension in the vicinity of 0.44 × λ / NA is particularly improved by limiting the dimension of the phase shift region in the short side direction in the range from 0 to 100% to 0.44 × λ / NA or less. I do.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a plan view of a mask pattern of the phase shift mask 100 used in the present embodiment. As shown, a first mask pattern 13 including a first phase shift region 11 whose phase is shifted by 180 ° with respect to the phase of exposure light transmitted through a transmission region other than the pattern portion of the mask substrate 110, and, similarly, Second mask patterns 14 each including a second phase shift region 12 whose phase is shifted by 180 ° with respect to the phase of the exposure light transmitted through the transmission region other than the pattern portion were formed on the same mask substrate. First, the transmittance of the exposure light transmitting through the transmission region other than the pattern portion is set to 100%, and the transmittance of the first mask pattern is set to 6%, 60%, 8%.
The light intensity distribution on the image plane when calculated as 0% and 100% was calculated. The exposure light source is an ArF excimer laser (λ
= 193 nm), the numerical aperture NA is 0.6, the illumination method is the oblique incidence illumination method, and the annular illumination method (coherency σ at the outer periphery is 0.75, σ at the inner periphery is 0.55). Was. FIG. 2 shows that the line width of the first mask pattern is 0.05 μm.
7 shows the logarithmic gradient of the optical image intensity when changing from m to 0.16 μm. Since the pattern is resolved when the gradient of the optical image intensity is 15 or more, 0.09 μm when the transmittance is 6%.
It can be seen from the figure that the resolution is only up to the line width of. on the other hand,
0.06 μm (= 0.19 × λ /
NA) to 0.16 μm (= 0.50 × λ / NA) and 0.055 μm (= 0.50 μm) when the transmittance is 80%.
17 × λ / NA) to 0.15 μm (= 0.47 × λ / NA)
NA), 0.052 for 100% transmittance
μm (= 0.16 × λ / NA) to 0.14 μm (=
0.44 × λ / NA). From the above,
For a mask pattern having a line width of 0.14 μm (= 0.44 × λ / NA) or less, a phase shift region having a high transmittance of 60% or more is formed to maximize the phase shift effect. Can improve the resolution.
In particular, the transmittance of 60% is the lower limit for obtaining a sufficient phase shift effect, and the dimensional controllability is improved as compared with the case where the transmittance is as high as around 100%.

Next, when the transmittance of the exposure light transmitting through the transmission area other than the pattern portion is 100%, and the transmittance of the second mask pattern is 0%, 3%, 6%, 12% and 18%. The light intensity distribution on the image plane of was calculated. The same conditions as in the calculation of the first mask pattern were used for the exposure light source, the numerical aperture, and the illumination method. FIG. 3 shows a logarithmic gradient of the optical image intensity when the line width of the second mask pattern is changed from 0.08 μm to 0.20 μm. Transmittance 0
In the case of%, the gradient of the optical image intensity is near 15 in a pattern of 0.14 μm or more, and the contrast is not sufficient. When the transmittance was 3% or more, in the pattern of 0.14 μm or more, the gradient of the optical image intensity became large, and sufficient contrast was obtained. FIG. 4 shows the light intensity at the center of the pattern when the line width of the second mask pattern is changed from 0.08 μm to 0.8 μm. 0.
For a large pattern of 3 μm or more, the light intensity at the center of the pattern increases as the transmittance increases, and when the transmittance exceeds 18%, the light intensity at the center of the pattern exceeds a threshold value. become unable. From the above, 0.14 μm (= 0.44 × λ / NA)
3% to 12% for a mask pattern having the above line width.
%, A large pattern of 0.14 μm or more can be formed with high precision.

As described above, according to the first embodiment, when the pattern size is 0.44 × λ / NA or less, the pattern portion is formed in a phase shift region having a high transmittance of 60% or more. 3% to 12 in case of 44 × λ / NA or more
% By forming the pattern portion in a phase shift region having a low transmittance of up to 0.16 × λ
The resolution is improved to / NA, and a pattern of any size can be formed with high accuracy.

In this embodiment, an ArF excimer laser is used as a light source.
Light sources of other wavelengths such as ₂ excimer lasers may be used. In the present embodiment, an exposure apparatus having a numerical aperture NA of 0.6 is used, but the present invention is not limited to this. Further, in the present embodiment, the annular illumination method is used, but another oblique illumination method such as quadrupole illumination may be used.

Embodiment 2 FIG. A second embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a sectional view of a mask pattern of the phase shift mask 100 used in the present embodiment. The quartz substrate in an area other than the first mask pattern 42 and the second mask pattern 43 is
Engraved so that a phase difference of ° occurs. In the first mask pattern, the step of the quartz substrate is exposed, and in the second mask pattern, a chromium film 44 having a thickness of 100 ° (angstrom) is formed on the step of the quartz substrate.
The transmittance for F excimer laser light was reduced. Ar
The transmittance for F excimer laser light is as follows, assuming that the transmittance of the quartz substrate in the region other than the mask pattern is 100%.
It was 100% for the first mask pattern and 6% for the second mask pattern. 0.3 on silicon substrate
A chemically amplified resist film having a thickness of μm was formed. Next, NA
The resist film was exposed to light using an ArF excimer laser exposure machine with a thickness of 0.6, and a latent image of the mask pattern was formed. At this time, the quadrupole illumination method shown in FIG. 6 was used. After the exposure, a post-exposure bake at 110 ° C. is performed to obtain 2.38 wt%
The resist film was developed with the alkaline developer described above to form a resist pattern of the above mask pattern.

FIG. 7 shows the relationship between the design dimension of the resist pattern formed in this embodiment and the depth of focus. With the second mask pattern, a pattern up to 0.10 μm could be formed. On the other hand, in the first mask pattern,
A pattern of 0.14 μm to 0.06 μm was resolved.
Therefore, in the present embodiment, the design dimension is 0.14 μm.
m (= 0.44 × λ / NA) or less, transmittance 100
% Of the first mask pattern, and the design dimension is 0.14.
In the case of not less than μm, 0.06 μm (= 0.19 × λ) is obtained by using the second mask pattern having a transmittance of 6%.
A pattern of any size from a very fine pattern (/ NA) to a large pattern could be formed with high precision. In addition, since the first mask pattern and the second mask pattern can be simultaneously formed on one mask, the exposure process is simple.

In this embodiment, an ArF excimer laser is used as a light source.
Light sources of other wavelengths such as ₂ excimer lasers may be used. In the present embodiment, an exposure apparatus having a numerical aperture NA of 0.6 is used, but the present invention is not limited to this. Further, in the present embodiment, quadrupole illumination is used, but another oblique incidence illumination method such as annular illumination may be used. In the mask used in the present embodiment, the phase is inverted by digging a quartz substrate, but the phase may be inverted by selectively forming a phase shift film on the pattern portion.

Embodiment 3 A third embodiment of the present invention will be described below with reference to the drawings. FIG. 8 is a sectional view of a mask pattern of the phase shift mask 100 used in the present embodiment. The quartz substrate in an area other than the first mask pattern 82 and the second mask
Engraved so that a phase difference of ° occurs. In the first mask pattern, a chrome film 8 having a thickness of 30 ° is formed on the step of the quartz substrate.
4 was formed, and in the second mask pattern, a chrome film 85 having a thickness of 100 ° was formed on the step of the quartz substrate. The transmittance for the ArF excimer laser light was reduced by the chromium film, and was 80% in the first mask pattern and 6% in the second mask pattern.

A chemically amplified resist film having a thickness of 0.3 μm was formed on a silicon substrate. Next, ArF with NA of 0.6
Using an excimer laser exposure machine, expose the resist film,
A latent image of the above mask pattern was formed. At this time, FIG.
The quadrupole illumination method shown in FIG. After the exposure, a post-exposure bake at 110 ° C. was performed, and the resist film was developed with a 2.38 wt% alkaline developer to form a resist pattern of the mask pattern.

FIG. 9 shows the relationship between the design dimension of the resist pattern formed in this embodiment and the depth of focus. With the second mask pattern, a pattern up to 0.10 μm could be formed. On the other hand, in the first mask pattern,
A pattern of 0.15 μm to 0.06 μm was resolved.

Therefore, in the present embodiment, when the design size is 0.14 μm (= 0.44 × λ / NA) or less, the first mask pattern having a transmittance of 80% is used, and the design size is 0.14 μm. In the above case, by using the second mask pattern having a transmittance of 6%, 0.06 μm (=
A pattern of an arbitrary size from a very fine pattern (0.19 × λ / NA) to a large pattern could be formed with high accuracy. In addition, since the first mask pattern and the second mask pattern can be simultaneously formed on one mask, the exposure process is simple.

In this embodiment, an ArF excimer laser is used as a light source.
Light sources of other wavelengths such as ₂ excimer lasers may be used. In the present embodiment, an exposure apparatus having a numerical aperture NA of 0.6 is used, but the present invention is not limited to this. Further, in the present embodiment, quadrupole illumination is used, but another oblique incidence illumination method such as annular illumination may be used. In the mask used in the present embodiment, the phase is inverted by digging a quartz substrate, but the phase may be inverted by selectively forming a phase shift film on the pattern portion.

Embodiment 4 A fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a gate pattern of a logic device.
0 is shown. A gate portion having a line width of 0.07 μm has a first phase shift region 101 having a transmittance of 100% for ArF light.
The wiring portion and the wiring pad portion having a line width of 0.14 μm or more are formed in the second phase shift region 102 having a transmittance of 3%.
Formed. The mask has a first phase shift region 10.
Quartz substrates in regions other than the first and second phase shift regions 102 were dug so as to generate a phase difference of 180 °. In the first phase shift region, the quartz substrate step is exposed, and in the second phase shift region, 12
A 0 ° thick chromium film was formed.

Next, a pattern forming method using the above mask will be described. A 0.3 μm-thick chemically amplified resist film was formed on a silicon substrate. Next, when NA is 0.6
The resist film was exposed using an ArF excimer laser exposure machine of No. 1 to form a latent image of the mask pattern. At this time, an annular illumination method was used. After the exposure, a post-exposure bake at 110 ° C. was performed, and the resist film was developed with a 2.38 wt% alkali developing solution, whereby the resist pattern of the mask pattern could be formed with high precision.

Therefore, according to the present embodiment, when the design dimension is 0.14 μm (= 0.44 × λ / NA) or less, a mask pattern is formed in the first phase shift region having a high transmittance. Since the mask pattern is formed in the second phase shift region having a low transmittance when the design dimension is 0.14 μm or more, any pattern from a very fine pattern to a large pattern can be formed with high precision. Was.
Further, since the first mask pattern and the second mask pattern can be simultaneously formed on one mask, only one exposure step is required, and the throughput is improved as compared with the conventional case.

In this embodiment, an ArF excimer laser is used as a light source.
Light sources of other wavelengths such as ₂ excimer lasers may be used. In the present embodiment, an exposure apparatus having a numerical aperture NA of 0.6 is used, but the present invention is not limited to this. Further, in the present embodiment, annular illumination is used, but another oblique illumination method such as quadrupole illumination may be used. In the mask used in the present embodiment, the phase is inverted by digging a quartz substrate, but the phase may be inverted by selectively forming a phase shift film on the pattern portion. In the present embodiment, the transmittance of the first phase shift region is 10
0%, and the transmittance of the second phase shift region was 3%, but the transmittance of the first phase shift region was 60% to 1%.
The transmittance may be within the range of 00%, and the transmittance of the second phase shift region may be within the range of 3% to 12%.

[0030]

According to the pattern forming method of the present invention, since a pattern region having a transmittance corresponding to the pattern size exists on one mask, a pattern having an arbitrary size from an extremely fine pattern to a large pattern can be obtained. Can be transferred with high accuracy and high throughput.

According to the pattern forming method of the present invention, the pattern portion on the mask is divided into a high transmittance region of 60% or more and a low transmittance region of 3% to 12%.
The division simplifies the manufacture of the mask and limits the transmittance as described above to maximize the phase shift effect and improve the resolution.

Further, according to the pattern forming method of the present invention, the size of a pattern to be allocated to a region having a high transmittance of 60% or more is limited to 0.44 × λ / NA or less, so that a pattern from an extremely fine The dimensional accuracy of a wide range of patterns up to the pattern is further improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a mask pattern according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a logarithmic slope of an optical image intensity and a pattern size in the first mask pattern of FIG. 1;

FIG. 3 is a graph showing a relationship between a logarithmic slope of an optical image intensity and a pattern size in the second mask pattern of FIG. 1;

4 is a graph showing a relationship between a light intensity at a central portion of an optical image and a pattern dimension in the second mask pattern of FIG. 1;

FIG. 5 is a sectional view of a mask pattern according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an illumination shape of quadrupole illumination used in a second embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a pattern dimension and an experimental value of a depth of focus according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a mask pattern according to a third embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a pattern dimension and an experimental value of a depth of focus according to the third embodiment of the present invention.

FIG. 10 is a plan view of a mask pattern according to a fourth embodiment of the present invention.

FIG. 11 is a plan view of a mask pattern in a conventional example.

[Explanation of symbols]

11 first phase shift region, 12 second phase shift region, 13 first mask pattern, 14 second mask pattern, 41 quartz substrate, 42 first mask pattern, 43 second mask pattern, 44 chrome Film, 81 quartz substrate, 82 first mask pattern, 8
3 A second mask pattern, 84 a chrome film having a first thickness, 85 a chrome film having a second thickness, 101 a first phase shift region, and 102 a second phase shift region.

[Procedure amendment]

[Submission date] December 27, 1999 (1999.12.
27)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

4. A first phase shift area and a second phase shift area.
Both regions consist of halftone phase shift regions
Phase shift mask . ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 6, 2000 (200.3.6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junji Miyazaki 3-6-13-E864, Fujisawa, Fujisawa-shi, Kanagawa (72) Inventor Keisuke Nakazawa 4-41-12, Nogata 4-41-12, Nakano-ku, Tokyo (72) Inventor Uematsu Masaya 6-10-14 Shimonagaya, Konan-ku, Yokohama, Kanagawa Prefecture Sun Forest 203 F-term (reference) 2H095 BA02 BB03 5F046 AA25 BA04 BA08

Claims (4)

[Claims] 2. A pattern forming method comprising: exposing a desired pattern on a resist film using a mask in which a pattern portion is formed by a plurality of phase shift regions having a transmittance according to a pattern dimension. 2. The method according to claim 1, wherein the phase shift region is between 60% and 10%.
A first phase shift region having any transmittance in a range of up to 0% and a second phase shift region having any transmittance in a range of 3% to 12%. The pattern forming method according to claim 1, wherein 3. The pattern of the first phase shift region has a dimension in the short side direction of 0.44 × λ, where NA is a numerical aperture of a reduction projection optical system of an exposure machine, and λ is a wavelength of an exposure light source.
3. The pattern forming method according to claim 2, wherein the ratio is not more than / NA. 4. A phase shift mask, wherein a pattern portion is formed by a plurality of phase shift regions having a transmittance according to a pattern dimension.