JPH0677204A - Photomask - Google Patents

Abstract

PURPOSE:To obtain a highly precise photomask in which the initial resist dimensions are reflected with fidelity. CONSTITUTION:A treatment substrate 1 and a light-shielding pattern 10, which is formed on the transparent substrate 1, are provided. The light-shielding pattern 10 is formed by a laminated layer film wherein at least two types of films 6 and 7 are laminated. The two types of films 6 and 7 are formed by the material which can be etched independently using different etchants.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to photomasks, and more particularly to a photomask with high accuracy in which initial resist dimensions are faithfully reflected.

[0002]

2. Description of the Related Art An optical lithography technique for forming a desired LSI pattern by reducing an enlarged pattern on a photomask on a wafer and repeatedly forming an image on the wafer is well known.

FIG. 3 shows the principle of a conventional method for producing a photomask substrate, and is a sectional view of the substrate in each step of the sequence.

Referring to FIG. 3A, a light-shielding pattern, for example, chromium (C) is formed on the main surface of synthetic quartz substrate 1.
The metal film 3 made of r) is formed by vapor deposition or the like. An electron beam resist 4 made of, for example, an organic polymer material is formed on the metal film 3 by a method such as spin coating.

Referring to FIGS. 3A and 3B, the electron beam resist 4 is exposed by using an electron beam exposure machine and developed to form a resist pattern 5.

Referring to FIG. 3C, the metal film 3 is made of, for example, chlorine (Cl ₂ ) with the resist pattern 5 as a mask.
A desired mask pattern 6 is formed by processing by dry etching using a gas such as the above.

Referring to FIGS. 3 (c) and 3 (d), the resist pattern 5 is removed by oxygen plasma or the like to produce a photomask.

In the above conventional example, the case where chromium is used for the metal film has been illustrated, but other metals such as MoSi may be used.

Further, although the dry etching method using chlorine gas has been exemplified for the processing of the metal film, the wet etching method may be used in which the etching is performed with an etching solution such as an aqueous solution of cerium ammonium nitrate.

[0010]

The conventional photomask manufacturing principle is as described above, and has the following problems.

Referring to FIG. 4, when the metal film 6 is etched using the resist 5 as a mask, etching is often observed, for example, during wet etching or dry etching with a gas pressure of 0.1 Torr or more. When the etching progresses in a horizontal direction, the metal film 6 under the resist 5 is etched. As a result, a so-called dimensional variation phenomenon occurs in which the dimensions of the resist 5 are not faithfully reflected. The dimensional variation of the light-shielding pattern is caused by the metal film 6 on one side.
The film thickness is about 0.1 μm on one side and about 0.2 μm on both sides, which is a non-negligible value.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly accurate photomask in which the initial resist dimensions are faithfully reflected.

[0013]

A photomask according to the present invention comprises a transparent substrate and a light-shielding pattern provided on the transparent substrate. The light shielding pattern is formed of a laminated film in which at least two kinds of films are laminated. The two types of films are formed of materials that can be independently etched by different etchants.

[0014]

According to the photomask according to the present invention, the light shielding pattern is formed of a laminated film in which at least two kinds of films are laminated, and these two kinds of films are independently etched by different etchants. It is made of the material you get.

The light-shielding pattern is obtained by etching a laminated film in which at least two kinds of films are laminated, which are formed of the above-mentioned materials that can be independently etched by different etchants. In the laminated film having such a structure, first, only the upper layer film can be etched,
Subsequently, the lower layer film can be etched using the obtained upper layer film pattern as a mask.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a substrate in each step of the order of the method for manufacturing a photomask according to an embodiment of the present invention.

Referring to FIG. 1 (a), for example, a MoSi film 2 serving as a light-shielding pattern is formed on the main surface of synthetic quartz substrate 1.
Is deposited to a thickness of about 0.05 μm by a sputtering method or the like. After that, for example, a Cr metal film 3 which becomes a light shielding pattern is formed.
Is deposited to a thickness of about 0.05 μm by a sputtering method or the like. The light-shielding film (MoSi film 2 + Cr metal film 3) has a film thickness of 1/1 for exposure light when used as a photomask.
000 or less is sufficient, and the film thickness is not limited to the above value.

In order to form the resist film 4 on the light-shielding film, about 5 ml of a liquid prepared by dissolving an organic polymer material such as polymethylmethacrylate in a solvent is dropped on the rotating substrate 1 and dried. Let As a result, the resist film 4 having a thickness of about 0.5 μm is formed on the Cr metal film 3.

Referring to FIGS. 1 (a) and 1 (b), the resist film 4 is irradiated with an electron beam at an accelerating voltage of, for example, 20 kV to about 100 μc / cm ² by an electron beam exposure machine or the like.
Decomposes resist molecules. Then, the resist pattern 5 is formed by developing the resist 4 with a solvent or the like.

Referring to FIGS. 1B and 1C, with the resist pattern 5 as a mask, the Cr metal film 3 is etched by dry etching using a gas such as chlorine (Cl ₂ ). The film pattern 6 is formed.

Referring to FIG. 1D, the MoSi film 2 is etched by dry etching using a gas such as carbon tetrafluoride (CF ₄ ) with the resist pattern 5 and the Cr metal film pattern 6 as a mask. , MoSi film pattern 7 is formed.

Then, referring to FIGS. 1 (d) and 1 (e),
By removing the resist pattern 5 with oxygen plasma or the like, the light shielding pattern 10 formed of a laminated film in which the Cr metal film pattern 6 and the MoSi film pattern 7 are laminated is obtained.

According to this method, a highly accurate photomask in which the initial resist pattern is faithfully reflected can be obtained. The reason for this will be described in more detail with reference to FIG.

FIG. 2A is an enlarged view of FIG. 1C,
FIG. 2 (b) is an enlarged view of FIG. 1 (d).

Referring to FIG. 2A, when isotropic etching is performed by dry etching using chlorine, for example, the Cr metal film pattern 6 has a dimensional variation corresponding to the thickness of the Cr metal film on one side. Occurs. However, since the film thickness is thinner (0.05 μm) than the film thickness (0.1 μm) of the conventional Cr metal, the variation amount is small. In this case, if the thickness of the Cr metal film pattern 6 is 0.05 μm, the dimensional variation is about 0.05 μm on one side and about 0.1 μm on both sides.

Referring to FIGS. 2A and 2B, the lower M
When the oSi film 2 is etched, the MoSi film 2 is etched using the lower end 6a of the Cr metal film 6 as a mask.
The variation amount is not added, and the dimension variation of the resist 5 is about 0.05 μm on one side and about 0.1 μm on both sides, and the dimension variation can be reduced.

In the above embodiment, the Cr metal film and the Mo film are
Although the case of using two layers of Si films has been illustrated, the present invention is not limited to this, and other films such as tungsten (W) can be used. If the number of multilayer films is increased, the film thickness for one layer can be reduced, and thus the dimensional variation amount can be further reduced. In the present invention, the number of multilayer films is not limited.

In the above embodiment, the case where polymethyl methacrylate is used for the electron beam resist is illustrated.
The present invention is not limited to this, and it is possible to use other electron beam resists, and it is also possible to use a photoresist for light exposure and patterning.

Further, in the above-mentioned embodiment, the dry etching using the gas for the etching of the metal film is exemplified, but the present invention is not limited to this, and the processing may be performed by the wet etching using the etching solution. It is possible.

[0031]

As described above, according to the photomask of the present invention, the light-shielding pattern is formed of a two-layer film in which at least two kinds of films are laminated, and these two kinds of films are different from each other. It is made of a material that can be independently etched by different etchants. The light-shielding pattern is obtained by etching a laminated film in which at least two kinds of films are laminated and formed of materials that can be independently etched with different etchants.
In the laminated film having such a structure, first, only the upper layer film can be etched by using a resist, and subsequently, the lower layer film can be etched by using the obtained pattern of the upper layer film as a mask. Consequently, it is possible to obtain a highly accurate light-shielding pattern that faithfully reflects the initial resist dimensions. As a result, it is possible to obtain a highly accurate photomask with a small dimensional variation from the resist.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a substrate in each step of the order of a method for manufacturing a photomask according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the reason why a light-shielding pattern in which a resist dimension is faithfully reflected is obtained by the present invention.

FIG. 3 is a cross-sectional view of the substrate in each step of the order of the method for manufacturing the conventional photomask.

FIG. 4 is a diagram for explaining the reason why an initial resist dimension is not faithfully reflected in a conventional photomask.

[Explanation of symbols]

 6 Cr metal film pattern 7 MoSi film pattern 10 Light-shielding pattern

Claims (1)

[Claims] 1. A transparent substrate and a light-shielding pattern provided on the transparent substrate, wherein the light-shielding pattern is formed by a laminated film in which at least two kinds of films are laminated, The film of is a photomask, which is formed of a material that can be independently etched with different etchants.