JPH0378776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an X-ray exposure mask used in manufacturing semiconductor integrated circuits.

[Conventional technology]

Generally, in X-ray exposure, an X-ray exposure mask is used to transfer a fine resist pattern onto a silicon wafer, but the X-ray mask is used as a light source.
Because it uses lines, it is characterized by the ability to transfer patterns on the submicron order.
To transfer the pattern, use a mask to
It is necessary to selectively transmit lines.

FIG. 3 is a cross-sectional view showing the structure of a conventional X-ray exposure mask. In the figure, 1 is a ring-shaped support frame, and 2 is a mask substrate made of a silicon nitride film formed on this support frame 1. It is. 3 is an X-ray absorption pattern formed on the mask substrate 2 and made of heavy metal.

Next, the operation will be explained. The mask substrate 2 is
Silicon carbide (SiC), silicon oxide (SiO ₂ ),
A thin film of a material mainly composed of relatively light elements with high X-ray transmittance, such as silicon nitride (Si ₃ N ₄ ) and silicon (Si), is used. Furthermore, in order to efficiently absorb X-rays, the absorption pattern 3 is made of heavy metals such as tantalum (Ta), molybdenum (Mo), and tungsten (W), which have low X-ray transmittance.

When a resist thin film on a silicon wafer is irradiated with X-rays through a mask having the structure described above, a difference in transmitted X-ray intensity occurs in the resist film, and this causes the mask pattern to be transferred. The larger the size, the higher the contrast of the pattern can be transferred.

[Problem that the invention seeks to solve]

However, in the conventional X-ray exposure mask described above, the adhesion between the X-ray absorption pattern 3 and the mask substrate 2 is insufficient, so pattern defects due to peeling are likely to occur, and the service life is short. It was hot.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain an X-ray exposure mask having a structure with high adhesiveness between the X-ray absorption pattern and the mask substrate and a long life. .

[Means for solving problems]

In the X-ray exposure mask according to the present invention, between the X-ray absorption pattern made of heavy metal and the mask substrate,
It is formed by bonding layers of silicided absorption pattern material.

[Effect]

In this invention, "in general, it is possible to increase the adhesion force by preventing the material structure between the thin film and the substrate from changing abruptly."
Based on this fact, we came up with the idea of forming a silicide layer of the absorption pattern material metal as an intermediate compound layer between the mask substrate and the absorption pattern.
Since the silicide layer adheres the absorption pattern to the mask substrate with strong adhesive force due to cohesive energy, it is possible to manufacture an X-ray exposure mask in which the pattern does not easily peel off.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of an X-ray exposure mask according to an embodiment of the present invention, in which 1 is a ring-shaped support frame, 2 is a mask substrate made of a silicon nitride film formed on the support frame 1, and 3 4 is an X-ray absorbing pattern made of tantalum, and 4 is a silicide layer formed by siliciding tantalum, which is bonded between the mask substrate 2 and the X-ray absorbing pattern 3.

Next, a method for forming an X-ray absorption pattern including the silicide layer 4 described above will be described. Depressurize the silicon nitride film that will become mask substrate 2 on the silicon substrate.
It is formed by a CVD method or the like, and a tantalum silicide layer 4 is formed on the entire surface of the nitride film by a sputtering method or the like. Subsequently, a tantalum layer that will become the X-ray absorption pattern 3 is formed on the silicide layer 4 by sputtering, and a resist layer is further formed by spin coating. A desired resist pattern is obtained by exposing the resist layer to an electron beam and then performing a development process. Using this resist pattern as a mask, the tantalum layer and then the silicide layer are etched by reactive ion etching using CCl ₄ gas to obtain a desired X-ray absorption pattern.

As an example, FIG. 3 shows an X-ray exposure device in which an X-ray absorption pattern 3 consisting of a tantalum layer 3 with a thickness of 1 μm and a tantalum silicide layer 4 with a thickness of 300 Å is formed on a silicon nitride film mask substrate 2 with a thickness of 2 μm. This figure shows the change in pattern defect density over time when a mask is subjected to ultrasonic cleaning. The solid line in FIG. 2 shows the results of this example, and it can be seen that the pattern defect density is not dependent on the cleaning time and is a substantially constant value. Furthermore, the broken line in FIG. 2 shows the results obtained when the same procedure was performed on a conventional X-ray exposure mask that does not have a tantalum silicide layer.

X with a silicide layer 4 as shown in FIG.
The line absorption pattern 3 has better adhesion to the mask substrate 2 than the conventional pattern, and can significantly reduce pattern defect density.
In the above embodiment, by bonding the silicide layer 4, the change in pattern defect density over time can be suppressed to a constant low value. In addition, since the silicide thin film exists only at the boundary between the absorption pattern 3 and the mask substrate 2, the X-ray absorption ability is equivalent to that of the conventional pattern, and therefore the required It is possible to obtain contrast. moreover,
In the area where the silicide layer 4 does not exist, that is, the area where there is no absorption pattern 3 and allows X-rays to pass through,
An alignment method using laser light can be applied.

In addition, in the above embodiment, the case where a silicon nitride film is used for the mask substrate 2 and tantalum is used as the material for the absorption pattern 3 is shown, but the mask substrate 2
Similar effects can be expected by using other silicon-based substrate materials such as silicon, silicon carbide, and silicon oxide films, and by using other heavy metals such as molybdenum and tungsten for the absorption pattern 3.

[Effects of the Invention] As described above, according to the present invention, in a silicon-based X-ray exposure mask, a silicide layer is formed by bonding between the heavy metal X-ray absorption pattern and the mask substrate. This has the effect of providing a long-life X-ray exposure mask with high adhesiveness and few pattern defects.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an X-ray exposure mask according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating the ultrasonic cleaning time of X-ray absorption pattern defect density for explaining the operation and effect of the present invention. FIG. 3 is a cross-sectional view showing the structure of a conventional X-ray exposure mask. In the figure, 1 is a support frame, 2 is a mask substrate, and 3
4 is an X-ray absorption pattern, and 4 is a silicide layer.
In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. In an X-ray exposure mask using a silicon-based material as a substrate, a silicide layer made of a material obtained by siliciding the heavy metal between the X-ray absorption pattern made of a heavy metal and the mask substrate. A mask for X-ray exposure, characterized in that it is formed by bonding the above absorption pattern to a mask substrate. 2. The X-ray exposure mask according to claim 1, wherein the heavy metal is tantalum (Ta), tungsten (W), or molybdenum (Mo). 3. Claim 1, characterized in that the silicide layer is formed to match the absorption pattern.
X-ray exposure mask described in Section 1.