JPH0786149A - Formation of mask for x-ray exposure - Google Patents

Abstract

PURPOSE:To provide a method for forming an X-ray exposure mask which can stabilize the intensity of alignment light regardless of the thickness of a translucent supporting film while allowing easy and positive alignment. CONSTITUTION:A supporting film 2 transmitting exposing X-rays and an alignment light beam is formed on the main surface of a silicon substrate 1 having the rear side formed with a protective film 3. A surface side antireflection film 4 for the alignment light and a patterned X-ray absorber layer 5 are sequentially formed on the translucent supporting film 2. The central part of the protective film 3 is then removed and the substrate 1 exposed on the rear side is etched to form a frame body having an X-ray transmission window and the translucent supporting film 2 is exposed on the rear side. An antireflection film 6 is then formed on the rear side on the exposed supporting film 2 thus forming a mask for X-ray exposure. This method protects the antireflection film on the rear side against corrosion due to hot alkali at the time of formation of frame body as compared with a conventional method thus sustaining the characteristics of antireflection film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an X-ray exposure mask used in X-ray lithography, and more particularly,
The present invention relates to a method for manufacturing an X-ray exposure mask that can improve the alignment accuracy between the X-ray exposure mask and a wafer or the like.

[0002]

2. Description of the Related Art An X-ray exposure mask of this type is generally
As shown in FIG. 3, a frame body a having an X-ray transmission window a1 in the center portion, and a transparent support film b having its peripheral portion held by the frame body a and transmitting both the exposure X-rays and the alignment light rays.
And an X-ray absorber layer c and an alignment mark c provided in a pattern on the main surface on the surface side of the transparent support film b.
The main part is composed of 2 and.

In the figure, d indicates a protective film which acts as an etching resist when the central portion of the substrate constituting the frame a is etched to form the X-ray transmission window a1. Further, the alignment mark c2 for position alignment is usually formed by a part of the X-ray absorber layer c.

The X-ray exposure mask is used as follows. That is, the X-ray exposure mask is superposed on the X-ray sensitive resist film applied on a semiconductor wafer or the like, alignment light rays are irradiated, and the alignment mark c2 of the X-ray exposure mask and An alignment mark provided on a semiconductor wafer or the like is optically detected to align them, and then a soft X-ray is irradiated to expose the X-ray sensitive resist film in a pattern. The pattern exposed on the X-ray sensitive resist film corresponds exactly to the X-ray absorber pattern, and the X-ray sensitive resist film exposed in the pattern is developed to expose the semiconductor wafer etc. in the pattern. As a result, it becomes possible to selectively process the semiconductor wafer or the like at the exposed portion.

By the way, the alignment light beam that has entered the transparent support film b repeats multiple reflections, and these multiple reflection light beams are emitted from the transparent support film b while interfering with each other. The thickness of the permeable support film b is 1 to 2 μm.
Since it is thin, the intensity of emitted light varies greatly with a slight variation in the film thickness. As described above, in the related art, the alignment mark c2 is detected by the light intensity that easily changes depending on the film thickness of the transparent support film b. Therefore, it is difficult to detect the alignment mark c2 accurately, and the detection result tends to be inaccurate. Had the problem. On the other hand, in JP-A-5-129190, as shown in FIG. 4, X-rays capable of preventing multiple reflections by providing anti-reflection films e and f for alignment light rays on both front and back surfaces of the transparent support film b. I am proposing an exposure mask. According to the mask for X-ray exposure described in Japanese Patent Laid-Open No. 5-129190, the transparent support film b is emitted without causing multiple reflection, so that the transparent support film b is used.
The emission intensity of the alignment light beam is stable irrespective of the film thickness, and the alignment mark can be detected easily and accurately.

The X-ray exposure mask described in Japanese Patent Laid-Open No. 5-129190 was manufactured by the following method. That is, as shown in FIG. 5A, the back surface side antireflection film e is formed on the main surface side of the silicon substrate a ′, and the transparent support film b is formed on the back surface side antireflection film e. , A substrate a ′ made of the same material as the permeable support film c
A protective film d is formed on the back surface and the side surface side of (see FIG. 5B). Next, the front-side antireflection film f and the X-ray absorber layer c are sequentially formed on the transparent support film b (see FIG. 5C). Then, a resist pattern g is formed on the X-ray absorber layer c (see FIG. 5D), and the X pattern is formed by RIE (reactive ion etching) using the resist pattern g as a mask.
The X-ray absorber layer c is patterned to form the patterned X-ray absorber layer c and the alignment mark c2 (FIG. 5E).
reference). Next, a resist pattern is formed in the peripheral portion on the back surface side of the protective film d, and the protective film d is etched by RIE using this resist pattern as a mask to expose the central portion of the substrate a ′ (see FIG. 5F). Then, finally, the exposed central portion of the substrate a'is removed by etching with a hot alkali to form a frame a having an X-ray transmission window a1, and the X-ray exposure mask shown in FIG. 4 is manufactured.

[0007]

By the way, according to this conventional manufacturing method, when the central portion of the substrate a'is etched with hot alkali, the backside antireflection film e comes into contact with the hot alkali and penetrates. However, the characteristics may be deteriorated. Then, if the characteristics of the back surface side antireflection film e are deteriorated, the antireflection function for the alignment light beam becomes insufficient, so that the intensity of the alignment light beam fluctuates greatly with a slight change in the thickness of the transparent support film b, and the alignment mark. There is a problem that it is difficult to accurately detect c2, and the detection result tends to be inaccurate.

The present invention has been made by paying attention to such problems, and the problem is that the permeable support film b is used.
An object of the present invention is to provide a method for manufacturing an X-ray exposure mask, which stabilizes the emission intensity of the alignment light beam regardless of the thickness of the film, and by which the position can be reliably and easily aligned.

[0009]

That is, in the invention according to claim 1, a frame body having an X-ray transmission window in the center, and a peripheral portion of the frame body held by the frame body transmits both alignment light and X-rays. A transparent support film and front and back antireflection films for alignment light provided on both surfaces of at least a portion of the transparent support film corresponding to the X-ray transmission window;
A method for manufacturing an X-ray exposure mask, comprising an X-ray absorber layer provided in a pattern on the main surface on the front surface side of the transparent support film, and a protective film provided on the side surface and the back surface side of the frame body. On the premise of the manufacturing method of 1., a transparent support film is formed on the front surface of the frame substrate, and a coating film forming a protective film is formed on the back surface and the side surface of the substrate, and a front side antireflection film is formed on the transparent support film. And forming the X-ray absorber layer on the front-surface-side antireflection film, and then removing the protective film coating on the portion corresponding to the X-ray transmission window by etching to form a frame substrate. After partially exposing the frame body substrate at the exposed portion by etching to form a frame body having an X-ray transmission window, the backside antireflection film is formed on the backside of the exposed transparent support film. It is characterized by forming.

According to the first aspect of the invention, the frame-side substrate is removed by etching to form the frame having the X-ray transmission window, and then the backside antireflection film is formed. As compared with the conventional manufacturing method, since the back side antireflection film is not attacked by the hot alkali during substrate etching, it is possible to reliably form the back side antireflection film having a desired antireflection function. Become. Therefore,
It becomes possible to reliably manufacture the X-ray exposure mask that stabilizes the emission intensity of the alignment light beam and that can position-align reliably and easily.

According to the first aspect of the invention, as in the conventional manufacturing method, the front side antireflection film is formed prior to the formation of the patterned X-ray absorber layer. The pattern of the X-ray absorber thus obtained can be maintained with high accuracy without being distorted in the subsequent steps, and the pattern inspection accuracy is also improved. When the substrate is etched, the front side antireflection film is protected by a jig or the like, or the hot side alkali is selectively supplied from the back side so that the front side antireflection film is eroded by the hot alkali. It is possible to prevent

Next, in the invention according to claim 1, the above-mentioned transparent support film physically supports and fixes the X-ray absorber layer to allow the exposure X-rays and the alignment light rays to pass therethrough, and is excellent in mechanical strength. Those having high X-ray transmittance and alignment light transmittance and having excellent X-ray irradiation resistance can be used. As such a permeable support film, for example, Si
Thickness of 1 to 2 μm composed of N, SiC, Si, B, etc.
Thin films of SiN are mentioned, and among them, SiN is preferable.

The front-side antireflection film and the back-side antireflection film are provided in close contact with the front and back surfaces of the transparent support film, respectively, to prevent reflection of alignment light rays on the front and back surfaces of the transparent support film. Alternatively, a transparent thin film having a refractive index n that is the same as the refractive index of the transparent support film and is approximately the square root of the refractive index of the transparent support film can be applied. Examples of such a transparent thin film include SiO ₂ , SiO, MgF, MgO, and Al _2.
O ₃ , HfO ₂ , ZrO, TiO ₂ , CeO ₂ , ZnS
A thin film such as can be used. Further, the optical thickness nd of these antireflection films (where n is the refractive index of the antireflection film, d
Represents the film thickness) is preferably approximately equal to ¼ of the wavelength λ of the alignment light beam.

Further, in the invention according to claim 1, the above X
The X-ray absorber layer is, for example, a pattern-wise X-ray exposure of an X-ray sensitive resist provided on a semiconductor wafer. At the site where the X-ray absorber layer exists, the X-ray is blocked to expose the resist. On the other hand, on the other hand, at the site where the X-ray absorber is absent, X-rays pass through the transparent support film and the antireflection films on the front and back thereof to expose the resist. As such an X-ray absorber layer, a metal thin film such as Ta, W, Au or the like having an excellent X-ray absorption ability can be applied, and it can be patterned by well-known reactive ion etching. When patterning the X-ray absorber layer, it is desirable to form an alignment mark in addition to the pattern to be exposed on the X-ray sensitive resist.

In the invention according to claim 1, a silicon substrate can be applied as the frame substrate,
Further, a thin film made of the same material as the permeable support film can be applied as the protective layer.

[0016]

According to the method of manufacturing an X-ray exposure mask of the first aspect of the present invention, a transparent support film is formed on the front surface of the frame substrate, and a coating film forming a protective film is formed on the rear surface and the side surface of the substrate. A portion corresponding to the X-ray transmission window after forming each of them, forming a surface-side antireflection film on the transparent support film, and forming the X-ray absorber layer on the surface-side antireflection film. The protective film is removed by etching to expose a part of the frame substrate, and then the exposed frame substrate is removed by etching to form a frame having an X-ray transmission window. The backside antireflection film is formed on the backside of the exposed transparent support film.

That is, since the backside antireflection film is formed after the frame substrate is removed by etching to form a frame having an X-ray transmission window, the substrate is more difficult than the conventional manufacturing method. Since the backside antireflection film is not attacked by the hot alkali during etching, the backside antireflection film having a desired antireflection function can be reliably formed.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1A, a refractive index of 2.1 is provided on the main surface side of a disk-shaped silicon substrate 1 having a thickness of 2 mm and a diameter of 3 inches.
SiN 8 was deposited to a thickness of 2.0 μm to form the permeable support film 2. At the same time, thin films of the same material were formed on the back surface and side surfaces of the substrate 1 to form the protective film 3.

Next, a SiO ₂ film having a refractive index of 1.46 was deposited to a thickness of 105 nm on the transparent support film 2 to form a front side antireflection film 4 (see FIG. 1A). The square root of the refractive index 2.18 of the transparent support film 2 is about 1.47, and it can be seen that the refractive index of the front side antireflection film 4 is substantially equal to this value.

Next, a Ta film 5 having a thickness of 750 nm was formed on the antireflection film 4 on the front surface side (see FIG. 1A). Subsequently, a resist pattern R is formed on the Ta film 5 (see FIG.
B), the Ta film 5 was etched by reactive ion etching using the resist pattern R as a mask, and the Ta film 5 was patterned (see FIG. 1C).

In FIG. 1C, 5a indicates an alignment mark formed by etching the Ta film 5 and made of the same material as the Ta film 5.

Next, the peripheral portion of the protective film 3 on the back surface of the substrate 1 was covered with a mask, and the exposed central portion was removed by reactive ion etching to expose a part of the substrate 1 (see FIG. 1D). . Next, the substrate 1 is housed in a jig to protect the front side antireflection film 4 and the Ta film 5, and hot alkali is supplied from the back side to remove the substrate 1 exposed at the center of the back side by etching. Then, a frame having an X-ray transmission window was formed and the back surface side of the transparent support film 2 was exposed (see FIG. 1E).

Next, SiO ₂ having a refractive index of 1.46 is deposited to a thickness of 105 nm on the exposed back surface of the transparent support film 2 to form a back surface side antireflection film 6 to form an X-ray exposure mask. It was manufactured (see FIG. 1F).

The spectral transmittance of the X-ray exposure mask thus manufactured is shown in FIG.

For comparison, FIG. 2 also shows the spectral transmittance of a conventional X-ray exposure mask that does not have both the front-side antireflection film and the back-side antireflection film.

As is clear from this figure, in the conventional X-ray exposure mask, the transmittance greatly fluctuates with a slight change in wavelength, whereas in the X-ray exposure mask according to the embodiment. The transmittance does not substantially fluctuate due to slight fluctuations in wavelength, and maintains a constant transmittance.

As a result, it can be seen that the X-ray exposure mask according to the example maintains a constant transmittance even when the wavelength is constant and the film thickness varies slightly.

[0029]

According to the first aspect of the invention, the backside antireflection film is formed after the frame substrate is removed by etching to form the frame having the X-ray transmission window. As compared with the conventional manufacturing method, since the back side antireflection film is not attacked by the hot alkali during the substrate etching, it is possible to reliably form the back side antireflection film having a desired antireflection function. Become.

Therefore, there is an effect that the emission intensity of the alignment light beam can be stabilized and the X-ray exposure mask which can surely and easily perform the position alignment can be reliably manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of an X-ray exposure mask manufacturing process according to an embodiment.

FIG. 2 is a graph showing the spectral transmittance of X-ray exposure masks according to examples and comparative examples.

FIG. 3 is a cross-sectional explanatory view of a conventional X-ray exposure mask.

FIG. 4 is an explanatory cross-sectional view of a conventional X-ray exposure mask.

FIG. 5 is an explanatory cross-sectional view of a conventional X-ray exposure mask manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Transparent support film 3 Protective film 4 Front-side antireflection film 5 X-ray absorber layer 5a Alignment mark 6 Back-side antireflection film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tadashi Matsuo 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (1)

[Claims] 1. A frame body having an X-ray transmission window in the center, a transparent support film whose peripheral portion is held by the frame body and which transmits both alignment light and X-rays, and at least the above transparent support film. Front and back antireflection films for alignment light provided on both surfaces of a portion corresponding to the X-ray transmission window, and an X-ray absorber layer provided in a pattern on the main surface of the front surface of the transparent support film. And a protective film provided on the side surface and the back surface side of the frame body, wherein a transparent support film is provided on the front surface of the frame body substrate, and the back surface and the side surface of the substrate are protected. The X-rays are formed after forming the respective coatings that form the films, forming the surface-side antireflection film on the transparent support film, and forming the X-ray absorber layer on the surface-side antireflection film. Coating for the protective film of the part corresponding to the transmission window Is removed by etching to expose a part of the frame body substrate, and then the frame body substrate at the exposed portion is removed by etching to form a frame body having an X-ray transmission window,
A method for manufacturing an X-ray exposure mask, comprising forming the backside antireflection film on the backside of the exposed transparent support film.