JP3359620B2 - Photomask manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a photomask used in a lithography process such as semiconductor manufacturing, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a lithography process is used to form a predetermined design pattern on a silicon substrate. In the lithography process, a photosensitive resin called a resist is applied on a silicon substrate, and a predetermined pattern formed in advance on a photomask (or a photomask) is baked using a reduction projection type exposure apparatus. To form

[0003] A photomask consists of C on a transparent glass substrate.
A predetermined pattern is formed using a metal film such as r or MoSi or a metal silicide. FIG. 6 shows a principle diagram of a general reduction projection type exposure apparatus. In the reduction projection type exposure apparatus, irradiation light 61 is emitted from an illumination light source 60 and a photomask 62 is irradiated.
The transmitted light 63 transmitted through the (reticle) forms an image on a substrate 68 (semiconductor wafer) as transmitted light 66 through a projection lens 65. However, the transmitted light 63 transmitted through the photomask 62 is reflected on the surface of the projection lens 65 to generate a reflected light 64, and the transmission hole 66 transmitted through the projection lens 65 is reflected by the substrate 68 to be exposed and reflected light 67.
Is generated. Then, the reflected light is again applied to the photomask 6.
2 is irradiated from below.

FIG. 7 is a diagram showing an example of the photomask 62 of FIG. 6 and the state of reflected light. In FIG. 7, the photomask 62 has a light shielding film 72 formed on the lower surface of a glass substrate 70. After the irradiation light 61 passes through the photomask 62,
The reflected light 64 and the like are reflected from the lower surface. for that reason,
When a metal film is used for the light-shielding film 72, the metal film generally has a high reflectance of 50% or more with respect to the exposure wavelength, so that the reflected light from the projection lens 65 and the substrate 68 to be exposed is reflected again on the lower surface of the photomask 62. This reflected light again becomes stray light 74.
Thus, there is a problem that the contrast of the optical image is reduced without contributing to the original image formation.

FIG. 8 shows an example of the structure of a conventional photomask. FIG. 8A shows a photomask having a single-layer type light shielding film.
FIG. 8B is a cross-sectional view of a photomask having a two-layer type light shielding film. In order to reduce the re-reflection of the light-shielding film as described above, a two-layer photomask shown in FIG. 8B has recently been used instead of the conventional single-layer photomask shown in FIG. In the two-layer photomask 62 shown in FIG. 8B, a light-shielding film 72 and an anti-reflection film 76 are formed in two layers on the lower surface of a glass substrate 70. As a specific example, for example, metal Cr and C
A two layer structure of rOx is used. By forming a Cr oxide film on the Cr surface, the reflectance with respect to exposure light can be reduced to 20% or less. This allows wafers,
The reflected light from the lens reaches the wafer surface as stray light,
This prevents the contrast of the optical image from lowering.

[0006]

However, in recent reduction projection exposure apparatuses, an increase in the projection side NA, an increase in σ,
The illumination side NA is increased due to a decrease in the projection magnification or the like. For example, in the quadruple system, the projection side NA = 0.7, σ = 0.8
In the case of, the illumination side NA = 0.56 / 4 = 0.14. For this reason, the influence of the oblique component of the light incident on the photomask cannot be ignored. FIG. 9 shows a cross section of a conventional photomask having a two-layer film structure. In FIG. 9, the photomask 62 has a light-shielding film 72 (Cr light-shielding film) and an anti-reflection film 76 formed on the lower surface of a glass substrate 70. Light shielding film 7 of photomask 62
When 2 is illuminated with oblique light, reflected light is generated as stray light 74 from the side surface of the light shielding film 72. There is a problem that the contrast of the optical image deteriorates due to the reflected light. Further, as shown in FIG. 10, there is also a problem that the reflected light 64 from the projection lens or the substrate to be exposed is reflected on the side surface of the light shielding film 72 to generate stray light 74.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem that the contrast of an optical image is degraded by reflected light generated from the side surface of a light shielding film of a photomask. An antireflection film suitable for the wavelength of the exposure light is provided on the side surface. Thereby, the reflected light from the side surface of the light shielding film can be reduced, and the deterioration of the optical image can be prevented.

[0008]

[0009]

[0010]

A method of manufacturing a photomask according to the present invention is a method of manufacturing a photomask used in a lithography process, comprising: forming a pattern of a light-shielding film on a light-transmitting substrate; forming an anti-reflection film on the surface of the one in which to d Tchibakku the antireflection film by anisotropic etching and a step of leaving the anti-reflection film on the side surface of the light shielding film.

[0012]

[0013]

[0014]

[0015]

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a diagram showing a cross-sectional structure of a photomask according to Embodiment 1 of the present invention. The photomask 100 according to this embodiment includes a glass substrate 70 (light-transmitting substrate).
Light-shielding films 82 and 84 are formed on the lower surface of
2, 84, the antireflection film 8 according to the present embodiment.
0 is formed. The light shielding film 82 is made of, for example, Cr, Mo, W
The light shielding film 84 is made of, for example, CrO, Mo, or the like.
It is composed of a single-layer film or a laminated film of a metal oxide such as Si or a silicide.

The antireflection film 80 formed on these side surfaces has a reflectance of 25% with respect to an exposure wavelength, for example, g-line, i-line of a high pressure mercury lamp, KrF, ArF, F2 of a laser light source, and the like.
The following films, for example, CrO, CrOF, MoSi, MoS
metal oxides such as iON, WSi, WSiON, silicides,
An oxynitride, an oxynitride fluoride, or the like is used.

According to the present embodiment, as shown in FIG. 2, an anti-reflection film 80 for preventing reflection of the exposure wavelength is provided on the side surfaces of the light-shielding films 82 and 84 of the photomask 100, so that irradiation light from above can be obtained. It is possible to reduce the reflection of the reflected light 64 from below from the side surfaces of the light shielding films 82 and 84 and the reflection of stray light 74 due to the reflected light 64 from below. as a result,
Deterioration of the optical image can be prevented. The light shielding film 8
4 may be regarded as an antireflection film on the lower surface of the light shielding film 82.
Further, the light shielding film 84 may be omitted and only the light shielding film 82 may be used.

This embodiment can be summarized as follows. In the photomask 100 used in the lithography process in this embodiment, the patterns of the light-shielding films 82 and 84 are formed on the light-transmitting substrate 70, and the reflectance of the side surface of the light-shielding film with respect to the exposure wavelength is 25% or less. In the photomask 100 according to this embodiment, a pattern of light-shielding films 82 and 84 is formed on the light-transmitting substrate 70, and at least the side surfaces of the light-shielding film have a reflectance of 2 with respect to the exposure wavelength.
The antireflection film 80 is formed so as to have a concentration of 5% or less. Preferably, the antireflection film 80 is made of a metal oxide film, a metal nitride film, a metal silicide film, or a composite film thereof.

Embodiment 2 FIG. 3 shows a flow of a method for manufacturing a photomask according to the second embodiment of the present invention. First, as shown in FIG. 3A, a light-shielding film having a two-layer structure of a light-shielding film 82 made of metal chromium and a light-shielding film 84 made of chromium oxide is formed on a transparent substrate 70 made of synthetic quartz or the like. An electron beam resist is spin-coated on the substrate 70. A predetermined semiconductor circuit pattern is drawn on the substrate 70 using an electron beam drawing apparatus, and a predetermined resist pattern is formed by development. Next, after etching is performed using this resist pattern as a mask, the resist is removed, and a predetermined pattern is formed on the light shielding films 82 and 84 as shown in FIG.

Next, as shown in FIG. 3C, a film having a low reflectivity, for example, 20% or less in reflectivity with respect to an exposure wavelength of, for example, 248 nm or 193 nm of an exposure apparatus used is formed as the antireflection film 80. I do. The film is, for example, a light shielding film 82, 8
As a material different from 4, a metal oxide film such as MoSiO or a metal oxynitride film is used. As a film forming method, a vacuum deposition, a sputtering method, a CVD method, or the like is used.

Next, as shown in FIG. 3D, the entire surface of the antireflection film 80 is etched back using anisotropic dry etching such as RIE. Thus, the antireflection film 80 can be formed on the side surfaces of the predetermined patterns of the light shielding films 82 and 84. Note that the light shielding film 84 is a light shielding film 82.
May be regarded as an anti-reflection film on the lower surface of. Also, the light shielding film 8
4 and only the light shielding film 82 may be used.

This embodiment can be summarized as follows. In the manufacturing method of the photomask 100 used in the lithography process in this embodiment, the patterns of the light shielding films 82 and 84 are formed on the light transmitting substrate 70. Then, an anti-reflection film 80 is formed on the surface of the light-transmitting substrate 70 including the light-shielding films 82 and 84, and the anti-reflection film 80 is selectively etched away by anisotropic etching.
The anti-reflection film 80 is left on the side surface of 84.

Embodiment 3 FIG. FIG. 4 shows a flow of a method for manufacturing a photomask according to the third embodiment of the present invention. In this embodiment, a light-shielding film 82 made of metal chromium is formed on a transparent substrate 70 made of synthetic quartz or the like. Light shielding film 82 in this case
Can be applied to a high-reflection film made of a metal film or a low-reflection film having a multilayer structure made of a metal oxide or the like.

An electron beam resist is spin-coated on the substrate 70. A predetermined semiconductor circuit pattern is drawn on the substrate 70 using an electron beam drawing apparatus, and a predetermined resist pattern is formed by development. Next, after etching is performed using this resist pattern as a mask, the resist is removed, and a predetermined pattern is formed on the light shielding film 82 as shown in FIG. Next, the surface of the Cr film serving as the light-shielding film 82 is oxidized using O2 plasma.
The photomask substrate 7 is placed on the electrode stage in the vacuum chamber.
After introducing 0 and reducing the pressure to a predetermined pressure, oxygen gas is introduced and an electric field is applied to the counter electrode above the photomask to generate oxygen plasma.

As a result, as shown in FIG. 4C, a Cr oxide layer having a predetermined thickness, for example, about 10 to 50 nm, which oxidizes the metal Cr surface and has a low reflectance with respect to the exposure wavelength, is formed on the anti-reflection film 86. Form as Since this oxide layer is also formed on the side surface of the Cr film, the reflectance of the side surface is also reduced. Here, a single-layer Cr film was used as the light-shielding film 82,
A light-shielding film having a two-layer structure in which an r layer is formed may be used. Although the oxide film layer is formed using oxygen plasma here, the same effect can be obtained by forming a fluoride film or a nitride film. Further, the oxide film layer can be formed by liquid treatment using a solution such as hydrogen peroxide solution instead of plasma treatment.

This embodiment can be summarized as follows. In the manufacturing method of the photomask 100 used in the lithography process in this embodiment, a pattern of the light shielding film 82 is formed on the light transmitting substrate 70. Then, the light-shielding film 82 is oxidized, nitrided or silicided to form an anti-reflection film 86 on its surface. Preferably, the surface of the light shielding film 82 is nitrided or oxidized by plasma including nitrogen plasma or oxygen plasma. Preferably, the surface of the light shielding film 82 is oxidized with an oxidizing liquid.

Embodiment 4 Embodiment 4 of the present invention
The present invention relates to a method for manufacturing a semiconductor device using the photomask of the present invention exemplified in each of the above embodiments or the method for manufacturing the same. The process of transferring the mask pattern of the photomask to the wafer by the reduction exposure apparatus and manufacturing the semiconductor device uses a known method, and thus the details are omitted.

FIG. 5 shows a result of simulating the focus dependence of the contrast when a pattern is formed using the photomask according to the present invention. That is, this is a simulation of contrast reduction at the time of day focus. In FIG. 5, a curve A indicates the case where the photomask of the present invention is used, and a curve B indicates the case where the conventional photomask is used. As is apparent from FIG. 5, the contrast of an optical image at the time of pattern formation can be improved by applying the photomask according to the present invention.

[0030]

As described above, in the present invention, an anti-reflection film suitable for the exposure wavelength is provided on the side surface of the light-shielding film of the photomask used in the lithography process. And the deterioration of the optical image can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a photomask according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view illustrating an effect of the photomask according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a method for manufacturing a photomask according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a method for manufacturing a photomask according to a third embodiment of the present invention.

FIG. 5 is a view showing a simulation result of a decrease in contrast at the time of defocusing when a pattern is formed using a photomask according to the present invention.

FIG. 6 is a diagram showing the principle of a general reduction type projection exposure apparatus.

FIG. 7 is a view for explaining a problem of a conventional single-layer photomask.

FIG. 8 is a diagram showing a conventional single-layer photomask and two-layer photomask structures.

FIG. 9 is a view for explaining a problem of a conventional two-layer photomask.

FIG. 10 is another view for explaining the problem of the conventional two-layer photomask.

[Explanation of symbols]

70 glass substrate, 80 anti-reflection film, 82 light-shielding film, 84, 86 anti-reflection film, 100 photomask.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-227156 (JP, A) JP-A-52-58375 (JP, A) JP-A-8-64492 (JP, A) JP-A-7-57 281411 (JP, A) JP-A-1-166046 (JP, A) JP-A-2-101457 (JP, A) JP-A-6-334793 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 1/00-1/16

Claims (1)

(57) [Claims] 1. A method for manufacturing a photomask used in a lithography step, comprising: forming a pattern of a light-shielding film on a light-transmitting substrate; and forming an anti-reflection film on a surface of the light-transmitting substrate including the light-shielding film. process and, photomask manufacturing method which comprises a step of leaving the anti-reflection film on the side surface of the light shielding film and d Tchibakku the antireflection film by anisotropic etching to form.