JPH03172847A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To enable transfer high in resolution and precision irrespective of the shapes of pattern to be transferred by anisotropically etching a transparent film formed on a transparent substrate including a light-shielding member. CONSTITUTION:After the light-shielding member 2 has been formed on the surface of the transparent substrate 1, the transparent film 4 is formed on the whole surface of the substrate 1 including the member 2. At that time, the film 4 is formed in a thickness of thicker than the other places by the thickness of the member 2 near the circumferential part 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. Since the film 4 near the circumference 2a of the member 2 is thicker, 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 transmitted through only the substrate 1 and turning round into the regions of the members 3 and 2 by diffraction to interfere with the light transmitted through the member 3 and both to cancel each other, and accordingly, 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 [Industrial Application Field] The present invention relates to a method for manufacturing a photomask used in a phosphorography process when manufacturing semiconductor devices and the like.

[Conventional technology]

Generally, in a lithography 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) Thin Cr layer on top! (33), and further an electron beam resist J'ffl (34) is formed on the Cr 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 layer (34) is removed.

In the projected image of the photomask manufactured in this way, as shown in the amplitude distribution diagram of FIG.
). 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 l, T2...
and light shielding portions St, 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 a phase member (53) is formed. Phase member (
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 to 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 resist layers are left alternately on transparent parts (5
5) Form.

Using this resist pattern (55) as a mask, the transparent film (
After etching the resist pattern (54) to obtain a patterned phase member (53) as shown in FIG. 7D, the resist pattern (55) is finally 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 2 having the phase member (53) and the light transmitted through the adjacent transparent part 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 7C.
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 was made in order to solve these problems, and provides a photomask that can be easily and precisely manufactured to perform transfer with high resolution regardless of the shape of the transfer pattern. The purpose is to provide a manufacturing method.

[Means to solve the problem]

The photomask manufacturing method according to the present invention includes forming a light shielding member in a predetermined pattern on a transparent substrate, 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. This is a method of selectively and self-aligningly forming a phase member made of a transparent film on a transparent substrate and along the peripheral edge of a light shielding member.

[Effect]

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

〔Example〕

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

FIGS. 1A to 1C 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, HoS
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 layer using an electron beam, and then the thin film of the light-shielding material is selectively etched using the patterned electron beam resist layer as a mask. By doing so, the thin film is patterned 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. 1B, a transparent film (4) is formed over the entire surface of the transparent substrate (1) including the light shielding member (2). form. The transparent film (4) is made of a material transparent to irradiation light, such as 5iOz. At this time, as shown in FIG. 1B, the transparent film (4) is formed thicker near the peripheral edge (2a) of the light shielding member (2) by the thickness of the light shielding member (2) than at other locations.

Next, as shown in FIG. 1C, 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. 1B, the transparent film (4) located near the peripheral edge (2a) of the light shielding member (2)
) is formed thicker than other parts by the thickness of the light shielding member (2), so when the anisotropic etching is finished, the transparent substrate (1
) and along the peripheral edge (2a) of the light shielding portion 2), the transparent film (4) remains with approximately the same thickness as the light shielding member (2),
This results in the formation of the phase member (3) selectively and in a self-aligning manner.

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 filtered by 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).
), so by setting the thickness of the light shielding member (2) formed on the transparent substrate (1) to the value given by formula [1], for example, the phase member < 3) can be set to 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 that is transparent to the wavelength of the illumination light.
In addition to +02, Si, N, , CaF2 and l'l[rF2
An organic film such as polymethyl methacrylate (PMM^) or the like can be used. Also, transparent film (4)
may be made of the same material as the transparent substrate (1) or may be made of a different material. Furthermore, it may be made of two or more layers of transparent materials, such as Si3N or /SiO2.

In addition, when the transparent substrate (1) and the transparent M (4) are made of the same material, as shown in FIG. 3A or 3B, the gap between the transparent substrate (1) and the transparent IIK (4) Transparent material (5) or (6) made of a material different from these
If formed as an etching stopper, the transparent film (4)
Etching becomes easier.

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.

[Effects of the Invention] As explained above, according to the present invention, a light shielding member having a predetermined pattern is formed on a transparent substrate, a transparent film is formed over the entire surface of the transparent substrate including the light shielding member, and the transparent film is By anisotropically etching the entire surface, a phase member made of a transparent film is selectively and self-aligned on the transparent substrate and along the periphery of the light-shielding member, so that it can be etched easily regardless of the shape of the transferred pattern. A photomask that can perform transfer with high resolution can be easily and accurately manufactured.

[Brief explanation of the drawing]

1A to 1C 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. Figures 3A and 3B are cross-sectional views showing one step of another embodiment, and Figure 4A. The figure is a sectional view showing a conventional photomask.
Figures 4B and 4C are diagrams showing the amplitude distribution and light intensity distribution of the projected image by the photomask in Figure 4A, respectively.
Figures A to 5D are cross-sectional views showing a method for manufacturing the photomask shown in Figure 4A, Figure 6 is a cross-sectional view showing a photomask according to another conventional example, and Figures 7A to 7D are cross-sectional views showing a method for manufacturing the photomask shown in Figure 6. FIG. 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 a transparent substrate, a transparent film is formed over the entire surface of the transparent substrate including the light shielding member, and the entire surface of the transparent film is anisotropically etched. A method for manufacturing a photomask, comprising selectively and self-aligningly forming a phase member made of the transparent film on the transparent substrate and along the peripheral edge of the light shielding member.