JPH03172848A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To enable transfer high in resolution and precision irrespective of the form of pattern to be transferred by forming a light-shielding member specified in pattern on a transparent substrate, selectively etching parts free from the light-shielding member, then forming a transparent film on the whole surface, and anisotropically etching it. CONSTITUTION:After the light-shielding member 2 has been formed on the surface of the transparent substrate 1, the surface of the substrate 1 is etched to the prescribed depth d1, and the transparent film 4 is formed on the whole surface of the substrate 1. At that time, the film 4 is formed in a thickness of thicker than the other places by the sum of the thickness of the member 2 d2 and the etching depth d1 near the circumference 2a of the member 2. Then, all the film 4 is anisotropically etched until one of the member 2 or the substrate 1 is disclosed. The film 4 remains along the circumference 2a of the member 2 in a thickness of almost the same as the member 2, and the phase member 3 is selectively and self-matchingly formed, thus permitting the light intensity distribution of the projected image of the photomask to be sharpened and high resolution to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a photomask used in a photomask process for manufacturing semiconductor devices and the like.

[Conventional technology]

Generally, in the phosphorography process, a photomask is used in which a predetermined transfer pattern is formed from a portion that is transparent to illumination light and a light-shielding portion that is opaque.

Such a photomask is projected by a lens system onto a substrate to be processed having a photosensitive material layer, thereby transferring a pattern.

FIG. 4A shows a cross-sectional view of a conventional photomask.

Cr,
A light shielding member (32) made of MoSi or the like is formed.

A transfer pattern is formed by this light shielding member (32).

Such a photomask has been manufactured, for example, in the following manner. First, as shown in FIG. 5A, a transparent substrate (3
1) Form a Cr thin film (33) thereon, and further form an electron beam resist layer (34) on the C thin film (33).

Next, pattern transfer is performed by drawing and developing a predetermined pattern on the electron beam resist layer (34) using an electron beam (35), and the electron beam resist layer (34) is patterned as shown in FIG. 5B. do. Thereafter, the Cr thin film (32) is etched using the electron beam resist layer (34) as a mask, thereby obtaining a patterned light shielding member (32) as shown in FIG. 5C. Finally, as shown in FIG. 5D, the electron beam resist I-layer (34) is removed.

In the projected image of the photomask manufactured in this way, as shown in the amplitude distribution diagram of FIG.
) has extended into the realm of Since the actual light intensity is obtained as the square of the amplitude, as shown in FIG. 4C, the light wraps around to the area of the light shielding member (32) similarly to the amplitude distribution. For this reason, the resolution of pattern transfer is reduced, making it difficult to transfer fine patterns with high precision.

There is a phase shift method as a method for preventing the decrease in resolution caused by the diffraction phenomenon. In this method, as shown in FIG. 6, transparent molecules I, T2...
and light-shielding portions S1, S2, S3, . . . are arranged periodically, and a phase member (53) is arranged on every other transparent portion. That is, in the transparent part molecule 2, the transparent substrates (51
) on which the phase member (53) is formed.
53) is 1 depending on whether the light passes through it or not.
The thickness is set to produce a phase difference of 80°.

Therefore, the light that passes through the transparent molecules 1 and T2 and wraps around the light-shielding portion S2 cancels each other out due to interference. Therefore, resolution is improved.

The photomask shown in FIG. 6 is manufactured, for example, as follows. First, in the same manner as in Figures 5A-5D,
As shown in Figure A, a light shielding member (52) in a predetermined pattern is formed on a transparent substrate (51). Next, as shown in FIG. 7B, a transparent film (54) is formed on the transparent substrate (51) and the light shielding member (52). Furthermore, a resist layer is formed on the transparent film (54), and a pattern is transferred by drawing and developing it with an electron beam or the like, and a light shielding member (52) is provided as shown in FIG. 7C. A resist pattern in which layers of resist 1 to 1 remain alternately on transparent parts (
55).

Using this resist pattern (55) as a mask, the transparent film <
After obtaining a patterned phase member (53) as shown in FIG. 7D by etching 54),! & After that, the resist pattern (55) is removed.

[Problem to be solved by the invention]

However, in the photomask shown in FIG. 6, since the interference between the light transmitted through the transparent part molecule 2 provided with the phase member (53) and the light transmitted through the adjacent transparent part molecule 1 is utilized, There is a problem in that this technique can only be applied to repeating patterns in which transparent and opaque areas are periodically arranged with respect to each other.

In addition, in order to manufacture such a photomask, patterning of the resist layer (34) shown in FIG. 5A and step C.
Two pattern transfer steps are required for each patterning of the resist pattern (55) shown in the figure, complicating the manufacturing process and causing pattern defects. Furthermore, since pattern transfer is performed twice, pattern positioning during transfer must be performed with extremely high precision.

This invention has been made to solve these problems, and provides a method for manufacturing a photomask that can easily and accurately produce a photomask that can perform transfer with high resolution regardless of the shape of the transfer pattern. The purpose is to provide a method.

[Means to solve the problem]

A method for manufacturing a photomask according to the present invention includes forming a light shielding member in a predetermined pattern on the surface of a transparent substrate, and selectively etching a portion of the surface of the transparent substrate where the light shielding member is not formed to a predetermined depth. , by forming a transparent film over the entire surface of the transparent substrate including the light-shielding member and anisotropically etching the entire surface of the transparent film, a phase member made of the transparent film is selected on the transparent substrate and along the periphery of the light-shielding member. This is a method of forming the material in a self-aligning manner.

[Effect]

In this invention, by anisotropically etching the transparent film formed on the selectively etched surface of the transparent substrate and over the light shielding member, the phase member made of the transparent film is formed along the periphery of the light shielding member. formed selectively and self-aligned.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1A to 1D are cross-sectional views showing a method for manufacturing a photomask according to an embodiment of the present invention in the order of steps. First, as shown in FIG. 1A, a light shielding member (2) in a predetermined pattern is formed on the surface of a transparent substrate (1) made of quartz glass or the like. This light shielding member (2) is made of, for example, Cr, MoS
It is made of a light shielding material that is opaque to the irradiation light such as
It is formed by the method shown in Figures A to 5D. That is, a thin film of a light-shielding material is formed on a transparent substrate (1), and an electron beam resist layer is formed on this thin film. Next, pattern transfer is performed by drawing and developing a predetermined pattern on the electron beam resist l-layer using an electron beam, and then using this patterned electron beam resist layer as a mask, a thin film of light-shielding material is selectively applied. The thin film is buttered by etching to obtain a light shielding member (2) with a predetermined pattern. After that, the electron beam resist layer is removed.

After forming the light shielding member (2) on the transparent substrate (1) in this way, as shown in FIG. Etch until. Furthermore, as shown in FIG. 1C, a transparent film (4) is formed over the entire surface of the transparent substrate (1) including the light shielding member (2). The transparent film (4) is, for example, 5i02.
It is made of a material that is transparent to irradiated light such as. At this time, as shown in FIG. 1C, near the peripheral edge (2a) of the light shielding member (2), the sum d of the thickness d2 of the light shielding member (2) and the etching depth d of the transparent substrate (1), The transparent film (4) is formed thicker than the pond portion by +d2.

Next, as shown in FIG. 1D, the entire surface of the transparent film (4) is anisotropically etched by reactive ion etching or the like until at least one of the light shielding member (2) and the transparent substrate (1) is exposed. As described in the step of FIG. 1C, the transparent film (4) located near the peripheral edge (2a) of the light shielding member (2)
) is formed thicker than other parts by the sum of the thickness d2 of the light shielding member (2) and the etching depth d of the transparent substrate (1). A transparent film (4) is placed along the peripheral edge (2a) of the light shielding member (2).
) remains at approximately the same height as the surface of the light shielding member (2), thereby forming the phase member (3) selectively and self-aligned.

In the manner described above, a photomask as shown in FIG. 2A is manufactured. Next, a method of pattern transfer using this photomask will be explained. First, the photomask shown in FIG. 2A is irradiated with illumination light, and the substrate to be processed having a photosensitive material layer (
(not shown) onto which a photomask image is projected. At this time,
Since the phase member (3) is formed on the peripheral edge (2a) of the light shielding member (2), the light transmitted through this phase member (3) and the transparent substrate (1) is transmitted through the phase member (3). A phase difference corresponding to the thickness D of the phase member (3) is generated for the light that has passed through only the portion of the transparent substrate (1) that is not covered.

Here, assuming that the wavelength of the illumination light is λ and the refractive index of the phase member (3) is n, for example, the thickness D of the phase member (3) is D−λ/2(
n-1) ...If set to [1], the phase difference is 1
It becomes 80°. The amplitude distribution of the projected image of the photomask in this case is shown in FIG. 2B.

The light that passes only through the transparent substrate (1) and wraps around the phase member (3) and the light shielding member (2) due to diffraction interferes with and cancels out the light that has passed through the phase member (3). Therefore, the light intensity distribution of the projected image of the photomask is
As shown in Fig. C, it becomes steep, and high resolution can be obtained.

As mentioned above, the thickness D of the phase member (3) is the same as the thickness D of the phase member (3).
) and the etching depth d of the transparent substrate (1). Therefore, by controlling the etching depth dl of the transparent substrate (1), the phase member (3) can be easily etched by 180°. It can be formed to a thickness that produces a phase difference of .

According to this embodiment, the light shielding member (2) with a predetermined pattern
Since the phase member (3) is formed along the peripheral edge (2a) of the light shielding member (2), a photomask that can perform highly accurate pattern transfer even if the light shielding member (2) does not have a repeating pattern that appears periodically can be manufactured. Ru. Furthermore, in the method of this embodiment, the pattern transfer only needs to be performed once when forming the light shielding member (2) with a predetermined pattern on the transparent substrate (1), thereby simplifying the manufacturing process.

The transparent film (4) for forming the phase member (3) may be made of any material as long as it is transparent to the wavelength of the illumination light (,5
In addition to in2, inorganic films such as Si, N, CaF2, and MgF2, and organic films such as polymethyl methacrylate (PMN^) can be used. Further, the transparent film (4) may be made of the same material as the transparent substrate (1) or may be made of a different material. Furthermore, for example, like SiJ</5i02,
It may also be one in which two or more layers of transparent materials are laminated.

In addition, when the transparent substrate (1) and the transparent film (4) are formed from the same material, as shown in FIG.
) and the transparent film (4), if a transparent material (5) made of a material different from these materials is formed as an etching stopper, the transparent film (4>) can be easily etched.

Further, the method of etching the transparent film (4) is not limited to the reactive ion etching method, and other anisotropic etching methods may be used.

Furthermore, in the above embodiment, the transparent substrate (1) was etched using the light shielding member (2) as a mask, but the patterning of the light shielding member (2) as shown in the electron beam resist layer (34) in FIG. For this purpose, the transparent substrate (1) is etched using the resist layer formed on the light shielding member (2) as a mask.
The resist layer can then be removed.

〔Effect of the invention〕

As explained above, according to the present invention, a light shielding member in a predetermined pattern is formed on the surface of a transparent substrate, and a portion of the surface of the transparent substrate where no light shielding member is formed is selectively etched to a predetermined depth. Then, by forming a transparent film over the entire surface of the transparent substrate including the light shielding member and anisotropically etching the entire surface of the transparent film, the phase member made of the transparent film is formed on the transparent substrate and along the periphery of the light shielding member. Since it is formed selectively and in self-alignment, it is possible to easily and accurately manufacture a photomask that can perform transfer with high resolution regardless of the shape of the transfer pattern.

[Brief explanation of the drawing]

1A to 1D are cross-sectional views showing a method for manufacturing a photomask according to an embodiment of the present invention in the order of steps, and FIG. 2A is a cross-sectional view showing a photomask manufactured according to the embodiment.
Figures B and 2C are diagrams showing the amplitude distribution and light intensity distribution of the projected image by the photomask in Figure 2A, respectively, Figure 3 is a sectional view showing one step of another embodiment, and Figure 4A is a diagram showing the conventional example. 4B and 4C are diagrams showing the amplitude distribution and light intensity distribution of a projected image by the photomask of FIG. 4A, respectively, and FIGS. 5A to 5D are cross-sectional views showing a method of manufacturing the photomask of FIG. 4A. 6 is a sectional view showing a photomask according to another conventional example, and FIGS. 7A to 7D are sectional views showing a method for manufacturing the photomask shown in FIG. 6. In the figure, (1) is a transparent substrate, (2) is a light shielding member, (
2a) is a peripheral portion, (3) is a phase member, and (4) is a transparent film. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A light shielding member having a predetermined pattern is formed on the surface of a transparent substrate, and a portion of the surface of the transparent substrate where the light shielding member is not formed is selectively etched to a predetermined depth; A transparent film is formed over the entire surface of the transparent substrate including the light shielding member, and the transparent film is formed on the transparent substrate and along the peripheral edge of the light shielding member by anisotropically etching the entire surface of the transparent film. A method for manufacturing a photomask, characterized in that a phase member is formed selectively and in self-alignment.