JPH07106223A - X-ray mask and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To provide a high-precision X-ray mask having the capacity of sufficiently obstructing the X-ray as well as fine absorber patterns in high density. CONSTITUTION:The first X-ray absorber patterns 4 are buried in concave patterns formed in an X-ray transmissive film while the second X-ray absorber patterns 5 are laminatedly formed on the first X-ray absorber patterns 4 by transferring the first X-ray absorber patterns 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray mask used in a semiconductor device manufacturing process and a method for manufacturing the X-ray mask.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices, especially large-scale integrated circuits (LSI), have become higher in density and higher in speed, miniaturization of elements has been required. In the LSI manufacturing process, the shorter the wavelength of light used in the photo-etching process is, the finer the element can be formed. Therefore, a soft X-ray with a wavelength of about 1 nm (hereinafter simply referred to as X
X-ray exposure method, in which a fine resist pattern is formed using (for example, a line) as a light source, is considered promising.

A conventional X-ray mask used in the X-ray exposure method will be described below with reference to FIG. In FIG.
2 is a Si3N4 film, and 5 is a W pattern.

As shown in FIG. 6, in the conventional X-ray mask, the exposed area is a supporting frame having a thickness of 2
A 2 μm thick Si3N4 film 3, which is an X-ray transparent support film, is held on a Si wafer 1 mm, and a 0.7 μm thick W pattern 5 that is an X-ray absorber is held on the Si3N4 film 2.
Are formed.

In X-ray exposure, since there is no refracting lens for X-rays having a short wavelength, the X-ray mask and the wafer are opposed to each other with a small gap and irradiated with X-rays to form an X-ray mask. It is necessary to transfer the formed pattern as it is to the wafer. Therefore, the W pattern 5 is required to have a sufficient thickness to prevent the irradiated X-rays from passing therethrough, and also needs to have the same size as the pattern to be transferred. Therefore, for example, when transferring a pattern having a width of 0.15 μm, the W pattern 5 is required to have a thickness of 0.7 μm and a width of 0.15 μm.

To form the W pattern 5, a W film having a thickness of 0.7 μm is formed, and then a resist pattern is formed by an electron beam exposure method (hereinafter referred to as an EB exposure method). A method of selectively etching the W film by a dry etching method or the like using a reactive gas using this resist pattern as a mask is used.

[0007]

However, it is difficult to form a high-density fine pattern on the resist formed on the W film by the EB exposure method. That is, when the W film on which the resist is formed is irradiated with an electron beam, electrons are also irradiated to the resist in the vicinity of the pattern formation region due to backscattering by the W film (proximity effect), so that a desired fine resist pattern is formed.
Difficult to form. In addition, the higher the density of the pattern to be formed, the more likely it is to be affected by the proximity effect when drawing adjacent patterns, and it becomes more difficult to form fine patterns with high accuracy.

An object of the present invention is to provide a high-precision X-ray mask having a high density and fine absorber pattern while having a thickness sufficient to block X-rays and a method for manufacturing the same. It is to be.

[0009]

In order to achieve the above object, the X-ray mask of the invention of claim 1 is formed by embedding in a concave pattern formed in an X-ray transparent film. From the second X-ray absorption pattern formed by laminating the first X-ray absorption pattern on the first X-ray absorption pattern by transferring the first X-ray absorption pattern. It is characterized by having the following X-ray absorption pattern.

A second aspect of the present invention is a method for manufacturing the X-ray mask according to the first aspect of the present invention, which comprises a step of forming an X-ray transparent support film on the surface of the support, and an X-ray transparency. Forming a film and selectively etching the same to form a concave pattern identical to the X-ray absorption pattern; forming a first X-ray absorber film; and forming a first pattern on the X-ray transparent film. Forming the first X-ray absorption pattern by removing the first X-ray absorption film and leaving the X-ray absorption film only in the concave pattern; and etching the support in the exposed region from the back surface. The step of forming a support frame by the second X
Forming the X-ray absorber film, forming a resist film on the second X-ray absorber film, and using the first X-ray absorption pattern as a mask from the back surface side of the support frame to form the resist film. A step of irradiating the resist with X-rays to selectively expose the resist, and then developing the resist film to form a resist pattern; and using the resist pattern as a mask to form the second X-ray absorber film. The second layer formed on the first X-ray absorption pattern is selectively etched.
And a step of forming an X-ray absorption pattern.

[0011]

With the structure of claim 1, the X-ray absorption pattern is
The first X-ray absorption pattern embedded in the X-ray transparent film and the second X-ray absorption pattern having the exact same pattern by transferring the first X-ray absorption pattern are laminated, and therefore, The thickness of each of the first and second X-ray absorption patterns may be smaller than that of the conventional X-ray absorption pattern.

According to the structure of claim 2, the first X-ray absorption pattern is formed by forming the first X-ray absorber film on the X-ray transmissive film having a concave pattern formed by selective etching. By removing the X-ray absorber film other than the concave pattern, the concave pattern is embedded. Therefore, the first X-ray absorption pattern is formed without forming a resist pattern on the X-ray absorber film by the EB exposure method. Further, the resist film formed on the second X-ray absorber film formed on the front surface is irradiated with X-rays from the back surface side of the supporting frame using the first X-ray absorption pattern as a mask to form the resist pattern. To form, a resist pattern identical to the first X-ray absorption pattern is formed, and therefore a second X-ray absorption pattern identical to the first X-ray absorption pattern is formed.
Since the line absorption patterns are formed by stacking, both have a thickness necessary to block X-rays.

[0013]

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

FIG. 1 is a schematic sectional view of an X-ray mask of the present invention, in which 1 is a Si wafer, 2 is a Si3N4 film, and 3 is Si.
Membrane 4, 4 is a first W pattern, and 5 is a second W pattern.

In the X-ray mask of this embodiment, a Si 3N 4 film 2 having a thickness of 2 μm, which is an X-ray transparent support film, is formed on the surface of a Si wafer 1 having a thickness of 2 mm, which is a support frame.
4 has a W pattern 4 which is a first X-ray absorption pattern embedded in a concave pattern of the Si film 3 formed on the film 2 and is formed by transferring the first W pattern 4 on the W pattern 4. The formed second W pattern 5 is formed by stacking.

2 to 5 are partial sectional views showing respective steps in manufacturing the X-ray mask. 50 is the second W film,
6 is a resist.

As shown in FIG. 2, a 2 μm thick Si 3 N 4 film 2 is formed on the surface of a 2 mm thick Si wafer 1, and a 0.3 μm thick Si film 3 is further formed. Then EB
A concave pattern identical to the X-ray absorption pattern is formed on the Si film 3 by using an exposure method, and the first W film 4 having a thickness of 0.4 μm is formed.
Form 0.

Next, the first W film 40 is polished by chemical mechanical polishing until the Si film 3 is exposed from the surface,
As shown in FIG. 3, the W film is left only in the concave pattern of the Si film 3, and the first W film pattern 4 is formed.

As shown in FIG. 4, the thickness O. 4 μm
After forming the second W film 50, the back surface of the exposed region of the Si wafer 1 is etched with an alkaline etching solution such as KOH.

Further, as shown in FIG. 5, a positive resist 6 is applied and X-rays are irradiated from the back surface. The X-rays applied to the region where the first W pattern 4 is not formed are transmitted while exposing the resist 6 while attenuating the intensity of the W film 50 having a thickness of 0.4 μm. On the other hand, since the intensity of X-rays transmitted through the W pattern is exponentially attenuated with respect to the thickness, the X-rays transmitted through both the first W pattern 4 and the W film 50 are transmitted only through the W film 50. It is much lower than the intensity of X-rays. Therefore, if a resist sensitive to the intensity of X-rays is selected, the resist in the region without the first W pattern 4 is exposed, but the resist on the W pattern 4 is not exposed.

By developing thereafter, a resist pattern in which the W pattern 4 is transferred is formed on the second W film 50. Then, dry etching using a reactive gas is performed on the first W pattern. 2nd W pattern 5
Is formed.

In the present embodiment described above, when the first W pattern is formed, the resist on the Si film is exposed by the EB exposure method, so that there is no influence of the proximity effect due to the scattering of electrons, and it is fine and fine. A high-density resist pattern can be formed. The concave pattern formed by etching the Si film 3 using this resist pattern as a mask has a depth of 0.3 μm and a width of 0.15 μm.
After that, the inside can be sufficiently filled by forming the first W film 3 by the sputtering method or the like.

Further, when the chemical mechanical polishing method is used thereafter, when the W film is polished from the surface and the surface of the SiO 2 film 3 is exposed, the polishing is stopped so that the W film is formed only in the concave pattern. Is left.

When forming the second W pattern 5, the W film 50 having a thickness of 0.4 μm may be selectively etched. Therefore, the fine W pattern 5 can be accurately formed without the resist being greatly damaged or the side etch becoming large during the etching.

The X-ray absorption pattern of the X-ray mask thus formed is formed by stacking the first and second W patterns 4 and 5 of the same pattern, and the X pattern is formed during exposure.
It can absorb the rays and sufficiently reduce its strength.

In the embodiment described above, Si3 is used as the support film.
Although W is used as the N4 film and the X-ray absorber, it is not limited to this and may be a support film made of a dielectric film such as a SiC film or an absorber made of another heavy metal such as Ta. Nor.

A chemical mechanical polishing method is used from the surface of the W film 40 in order to embed the first W film 40 in the concave pattern formed in the Si film 3. However, the method is not limited to this method and is thick. It is also possible to use another method such as an etch back method in which the resist film and the W film are etched at the same speed after forming the resist film.

Further, instead of the Si film 3 on the support film, SiO 2
By forming the film, an antireflection effect against visible light during alignment is produced. Further, in order to enhance the antireflection effect, a SiO2 film may be formed under the support film.

Further, the X-rays irradiated from the back surface to form the second W pattern do not have to have the same wavelength as the X-rays used for exposure using this X-ray mask, and the first W
It is desirable to select an X-ray having a wavelength such that it is blocked in the area where the pattern and the second W film overlap, and is transmitted in the area where only the second W film is transmitted.

[0030]

According to the first aspect of the present invention, the second X-ray absorption pattern faithfully formed by using this pattern as a mask is laminated on the first X-ray absorption pattern formed with high precision. In addition, it is fine and has a high density, but has a thickness sufficient to block X-rays.

According to the second aspect of the invention, in forming the first X-ray absorption pattern, the X-ray absorbing thin film made of a heavy metal film having a large proximity effect is not directly EB drawn, but a Si film, a SiO2 film or the like. Since the concave pattern is formed on the second X-ray transparent film, it is possible to easily form a fine and high-density X-ray absorption pattern that is not affected by the proximity effect.
Further, when forming the second W pattern in order to obtain a sufficient thickness to block X-rays, it is not necessary to etch the W film that is thicker than in the conventional case, so that the accuracy of the first W pattern is high. A fine X-ray absorption pattern can be formed without impairing the thickness.

[Brief description of drawings]

FIG. 1 is a structural sectional view of an X-ray mask according to an embodiment of the present invention.

FIG. 2 is a process sectional view of an X-ray mask manufacturing method.

FIG. 3 is a process sectional view of an X-ray mask manufacturing method.

FIG. 4 is a process cross-sectional view of an X-ray mask manufacturing method.

FIG. 5 is a process cross-sectional view of a method for manufacturing an X-ray mask.

FIG. 6 is a structural cross-sectional view of a conventional X-ray mask.

[Explanation of symbols]

 1 Si Wafer 2 SiN Film 3 Si Film 4 First W Pattern 5 Second W Pattern 6 Resist

Claims (2)

[Claims] 1. A first X-ray absorption pattern formed by being embedded in a concave pattern formed on an X-ray transparent film, and the first X-ray absorption pattern transferred to the first X-ray absorption pattern. First
An X-ray mask having an X-ray absorption pattern composed of a second X-ray absorber pattern formed by being laminated on the X-ray absorption pattern. 2. A step of forming a support film on the surface of a support frame substrate,
A step of forming a thin film having a predetermined thickness, a step of selectively etching the thin film to form a concave pattern equal to the X-ray absorption pattern, a first X-ray absorption inside the concave pattern. A step of forming a body film, a step of etching the supporting frame substrate including at least an exposed region from the back surface, a step of forming a second X-ray absorber film, and a resist film on the second X-ray absorber film. A step of forming, a step of selectively exposing the resist by irradiating X-rays from the back surface, a step of selectively developing the resist and then etching the second X-ray absorber film to absorb the second X-ray A method of manufacturing an X-ray mask, comprising the step of forming a pattern.