JPH0453119A - X-ray mask - Google Patents

Abstract

PURPOSE:To facilitate sufficiently close exposure of a wafer by a method wherein the mask pattern mounting region of a mask membrane protrudes from its surroundings. CONSTITUTION:First, the circumferential part of an Si substrate 21 is removed by wet-etching so as to have a step S and protrusion 21A is formed. Then a membrane 22 made of SiN, etc., if formed on the upper surface of the Si substrate 21 by CVD, epitaxial growth, sputtering, etc. After that, the center part of the Si substrate 21 is removed by wet-etching from the rear to form a window 21B. After an X-ray absorbing metal film is applied to the membrane 22 by sputtering, etc., the metal film is patterned by electron beam exposure, etc., and dry-etching, etc., to form a mask pattern 23. Normally, a wafer 1 is kept sufficiently apart from a mask 10 and moved and, at a predetermined position, the wafer 1 is made to approach the X-ray mask 10 as close as a required exposure gap C and exposed in He gas at about 1atm. At that time, there is a possibility of breakdown of a mask substrate. However, even if the wafer is made to approach from a distance of several hundred mum to 15mum with a speed of 200mum/s, no breakdown occurs.

Description

[Detailed Description of the Invention] [Summary] Regarding the structure of an X-ray mask used for X-ray exposure, the purpose of this invention is to provide an X-ray mask that can expose a wafer sufficiently close to the wafer. The mask pattern 12'fJE area of No. 11 is configured to protrude from its surrounding area.

Regarding construction.

In recent years, patterns have become finer as semiconductor devices become more highly integrated, and this trend is certain to continue. For this reason, X-ray lithography is seen as a promising ultra-fine pattern forming technology, and research into its practical application is actively being carried out, but at present there are still unresolved problems. X
Ray lithography uses an X-ray mask with a mask pattern made of an X-ray absorber mounted on a mask membrane made of a thin film (membrane) of an X-ray transparent material, and the resist on the wafer is exposed to soft X-rays to create a pattern. However, this X-ray mask does not have a solid material that is sufficiently transparent to soft X-rays, so it is necessary to reduce the absorption loss by making the mask membrane thinner (for example, 2μjI).
However, there are problems caused by this thinning of the film, which imposes restrictions on its use. Therefore, a solution to such problems is desired.

[Industrial application field]

The present invention relates to the structure of an X-ray mask used for X-ray exposure [Prior art] The structure of a conventional X-ray mask will be explained with reference to FIG. Fourth
The figure is a schematic diagram showing the exposure state of a conventional X-ray mask.

In the figure, numeral 1 is a wafer to be exposed, the surface of which is coated with an X-ray resist. Reference numeral 40 denotes an XvA mask, which has a structure in which a support frame 43 supports the periphery of a mask membrane 410 having a mask pattern 42 mounted in the center. The mask membrane 41 is made of a solid material relatively transparent to soft X-rays, such as SiN, BNXSiC, etc.
It is a membrane (thin film) of about 100%. Mask pattern 42
are Ta, H, and Au, which have large absorption coefficients for soft X-rays.
etc., or their silicides, and the thickness is 0.
．． It is about 5 to 1°0μ. The diameter of the support frame 43 is 75~
25 x 2 in the center of a 100-m Si wall
A window 43A of approximately 5++a+ is provided. window 43
The reason why A is so small is that the mask membrane 41 is thin (and its mechanical strength is weak). The area where is provided is approximately 20×201.

X-ray exposure using this X-ray mask 40 is performed as follows. As mentioned above, the area of the mask pattern 42 is narrow;
On the other hand, since the diameter of the wafer 1 is usually much larger than this (for example, 100 to 150 IllI+), exposure is performed by a step-and-repeat method. usually,
Move the wafer 1 sufficiently away from the X-ray mask 40,
It is brought close to a desired exposure gap G at a predetermined position and exposed in an atmosphere of He gas or the like at about 1 atm.

[Problem to be solved by the invention]

In X-ray exposure, the exposure gap G is preferably small for highly accurate pattern transfer. However, the mask membrane of the X-ray mask is extremely thin and fragile, so when the wafer is brought close to the mask, the pressure of the atmospheric gas between the wafer and the X-ray mask may temporarily rise, causing the mask membrane to rupture. , the smaller the exposure gap G, the higher the risk. Therefore, the exposure gap G cannot be made sufficiently small.
There was a problem. SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide an X-ray mask that can expose a wafer sufficiently close to the wafer.

[Means to solve the problem]

According to the present invention, this object is achieved by providing an X-ray mask characterized in that the mask pattern 12 mounting area of the mask membrane 11 protrudes from its surrounding area.

[Effect]

In X-ray exposure, the mask must be brought close to the wafer only in the mask pattern mounting area. Since the ratio of this area to the total area is extremely low, if only this area is made to protrude and the gap between the wafer and the wafer is increased in other parts, the mask pattern mounting area when the mask and wafer are brought close to each other. Atmospheric gases can easily escape to the surrounding area, resulting in only a slight increase in atmospheric pressure.

Therefore, the risk of mask membrane destruction is reduced, and the exposure gap can be made sufficiently small.

〔Example〕

An embodiment of the X-ray mask based on the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 is a schematic diagram showing an exposure state of an X-ray mask according to an embodiment of the present invention. In the figure, 1 is a wafer to be exposed,
An X-ray resist is applied to the surface. Reference numeral 10 designates the X-ray mask of this embodiment, which has a structure in which a support frame 13 supports the peripheral portion of a mask membrane 110 having a mask pattern 12 mounted in the center thereof. Mask membrane 11 is soft X
SiN, BN, which is a solid material that is relatively transparent to wire
, is a thin film of about 2 μm such as SiC. Mask pattern 12 has a large absorption coefficient for soft X-rays.
, Au, etc., or their silicides,
The thickness is about 0.5 to 1.0 gyg. The support frame 13 has a diameter of about 75 to 100III and a thickness of about 0.5 to 1. h
A window 13A of about 25 x 25-m is provided in the center of the St substrate of about m, but the mask membrane 11
The supporting surface protrudes around the window 13A. The step S is about 100μ. Mask pattern 1 mentioned above
2 is provided at a position corresponding to this window 13A, so the area where the mask pattern 12 is provided is 20
It is about 20 mm.

The inventor manufactured the X-ray mask 10 of the present invention using the following two methods. First, the first manufacturing method will be explained with reference to FIG. First, the peripheral part of the Si substrate 21 is wet etched (using a mixed solution of hydrofluoric acid and nitric acid, etc.) to remove only the step S.
A convex portion 21A is formed (see (a) in the same figure). Next, a membrane 22 of SiN or the like is formed on the upper surface of the Si substrate 21 by CVD, epitaxial growth, sputtering, etc.
(See figure (b)). Next, the central portion of the Si substrate 21 is removed from the bottom surface by wet etching (using a mixed solution of hydrofluoric acid and nitric acid, etc.) to form a window 21B (see FIG. 2(c)).

Thereafter, a metal film of an X-ray absorber is deposited on the membrane 22 by sputtering or the like, and this is patterned by electron beam exposure or dry etching to form a mask pattern 23 (see FIG. 2D). This state corresponds to the X-ray mask 10 in FIG.

Next, a second method of manufacturing the X-ray mask 10 of the present invention will be explained with reference to FIG. First, a membrane 32 made of SiN or the like is formed on the upper surface of a Si substrate 31 by CVD, epitaxial growth, sputtering, or the like (see FIG. 3(a)). Next, S
Wet etching (
(using a mixed solution of hydrofluoric acid and nitric acid, etc.) to form a window 31B (see FIG. 3(b)).

Next, the peripheral part of the membrane 32 is dry etched (C
After removing with a mixed gas of F,・0□, etc.),
Wet etching (hydrofluoric acid,
(using a mixed solution of nitric acid, etc.) to form a step S (see the same figure (
c). Thereafter, a metal film of an X-ray absorber is deposited on the membrane 32 by sputtering or the like, and this is patterned by electron beam exposure or dry etching to form a mask pattern 33 (see figure (d)).
, this state corresponds to the X-ray mask 10 in FIG.

X-ray exposure using this X-ray mask 10 is performed as follows. As described above, since the area of the mask pattern 12 is narrow, exposure is performed in a step-and-repeat manner. Usually, the wafer 1 is moved sufficiently away from the X-ray mask 10 and brought close to the desired exposure gap G at a predetermined position,
Exposure in He gas at about 1 atm. There is a risk of destruction of the mask substrate 11 when approaching the desired exposure gap G, but in the case of the X-ray mask 10 of this embodiment, the distance from several hundred μm to 15 μm is approached at a speed of 200 μm/s. It didn't get damaged even if I did it. The X-ray mask 10 used has a supporting frame 13 of 100 gm in diameter and a window 13A of 25 gm in diameter.
X 25m+++, step S is 100μ-, one mask membrane is 2μ-thick SiN (withstand pressure is 10'P)
a), the atmosphere was He at 1 atm. A similar experiment was conducted using a conventional flat X-ray mask 40 (FIG. 4), and as a result, it was damaged at an amount of G=50 to 30μ. Therefore, the present invention makes it possible to significantly reduce the exposure gap G.

The present invention is not limited to the above embodiments, but can be implemented with various modifications. For example, the window 13A may be circular instead of square.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an X-ray mask that can expose a wafer sufficiently close to the wafer, which greatly contributes to the practical application of X-ray exposure technology.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the exposure state of an X-ray mask according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a first manufacturing method of an X-ray mask according to the present invention, and FIG. FIG. 4 is a schematic diagram showing a second method of manufacturing a ray mask. FIG. 4 is a schematic diagram showing an exposure state of a conventional X-ray mask. In the figure, ■ is a wafer, 10 and 40 are X-ray masks, 11 and 41 are mask membranes, 12 and 42 are mask patterns, 13 and 43 are support frames, 13A and 43A are windows, S is a step, and G is an exposure gap , is. Schematic diagram shown in Akira Akira's first page of x latitude square 7
2 illustration book Y Ming no Mi! ! Figure 1 shows the light production of the × strain mask of gI+. Figure 1 shows the deceptive state of the conventional Betsumo 2 illustration 3
figure

Claims (1)

[Claims] Mask pattern (12) of mask membrane (11)
An X-ray mask characterized by a mounting area that protrudes from its surrounding area.