JPS63192235A - Mask for x-ray exposure - Google Patents

Abstract

PURPOSE:To improve bonding properties among heavy metallic X-ray absorption patterns and a mask substrate, to decrease pattern defects and to lengthen a lifetime by joining and forming carbide layers while each being cemented among the heavy metallic X-ray absorption patterns and the mask substrate in a mask for X-ray exposure consisting of a carbon system. CONSTITUTION:A mask substrate 2 composed of an silicon carbide film shaped onto a ring-shaped housing 1, X-ray absorption patterns 3 made up of tungsten, and carbide layers 4, which are formed joined among the mask substrate 2 and the X-ray absorption patterns 3 respectively and shaped by changing tungsten into carbide, are formed. The absorption patterns are attached to the mask substrate by strong adhesion by the cohesive energy of the carbide layers 4, thus forming a mask for X-ray exposure from which the patterns are difficult to be peeled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to
This invention relates to a mask for line exposure.

[Conventional technology]

Generally, in X-ray exposure, an X-ray exposure mask is used to transfer a fine register pattern onto a silicon wafer, but since X-rays are used as a light source, it is possible to transfer patterns on the submicron order. It is characterized by certain things. In order to transfer the pattern, it is necessary to selectively transmit X-rays using a mask.

FIG. 3 is a cross-sectional view showing the structure of a conventional X-ray exposure mask. In the figure, l is a ring-shaped support frame, and 2 is a mask substrate made of silicon carbide or the like formed on this support frame l. 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 made of X-rays such as carbon (C), silicon carbide (S i C), boron carbide (84C), and aluminum carbide (Alc) in order to have high transmittance to X-rays. A thin film made of a material mainly composed of relatively light elements with high radiation transmittance is used. In addition, absorption pattern 3 is made of tantalum (Ta), which has low X-ray transmittance, in order to efficiently absorb X-rays.
, tungsten (W), and other heavy metals are used as materials.

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. It is possible to transfer patterns with high contrast.

[Problem that the invention seeks to solve]

However, in the conventional X-ray exposure mask mentioned above,
Since the adhesion between the X-ray absorbing pattern 3 and the mask substrate 2 is insufficient, there are problems in that pattern defects are likely to occur due to peeling and the service life is short.

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

[Means for solving problems]

The X-ray exposure mask according to the present invention comprises X-rays made of heavy metals.
A layer made of a carbide absorbing pattern material is bonded between the line absorbing pattern and the mask substrate.

[Effect]

In this invention, based on the fact that "in general, it is possible to increase the adhesion force by preventing the material structure between the thin film and the substrate from changing rapidly," the mask substrate and the absorbent As an intermediate compound layer with the pattern,
The idea was to form a carbide layer of metal as an absorbing pattern material.

Since this carbide layer adheres the absorption pattern to the mask substrate with strong adhesion force due to cohesive energy, it is possible to manufacture an X-ray exposure mask in which the pattern does not easily peel off.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the structure of an X-ray exposure mask according to an embodiment of the present invention. In the figure, l is a ring-shaped support frame, and 2 is a mask substrate made of a silicon carbide film formed on the support frame 1. , 3 is an X-ray absorbing pattern made of tungsten, and 4 is a carbide layer made of tungsten carbide, 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 above carbide layer 4 will be described. A silicon carbide film, which will become a mask substrate 2, is formed on a silicon substrate by a low pressure CVD method or the like, and a tungsten carbide layer 4 is formed on the entire surface of the nitride film by a sputtering method or the like. Subsequently, a tungsten layer that will become the X-ray absorption pattern 3 is formed on the carbide layer 4 by sputtering, and a resist layer is further formed by a spin code method. A desired resist pattern is obtained by exposing the resist layer to an electron beam and further performing a development process. Using this resist pattern as a mask, the tungsten layer and then the carbide layer are etched by reactive ion etching using CF4 gas to obtain a desired X-ray absorption pattern.

FIG. 2 shows, for example, an X-ray absorption pattern formed on a silicon carbide film mask substrate 2 with a thickness of 2 μm, consisting of a tungsten layer 3 with a thickness of 1 μm and a tungsten carbide layer 4 with a thickness of 300 μm. This figure shows the change in pattern defect density over time when a line exposure 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 almost constant regardless of the cleaning time. Further, the broken line in FIG. 2 shows the result when the same process was performed on a conventional X&LI optical mask that does not have a tungsten carbide layer.

As shown in FIG. 2, the X-ray absorbing pattern 3 with the carbide layer 4 has better adhesion to the mask substrate 2 than the conventional pattern without the carbide layer 4, and can significantly reduce pattern defect density. Can be done.

In the above example, by bonding the carbide layer 4, it was possible to suppress the change in pattern defect density over time 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. Furthermore, an alignment method using a laser beam can be applied to a portion where the carbide layer 4 is not present, that is, a region where there is no absorption pattern 3 and allows X-rays to pass through.

In the above embodiment, the mask substrate 2 is made of silicon carbide film, and the absorption pattern 3 is made of tungsten. Similar effects can be expected even if other heavy metals such as tantalum are used for the carbon-based substrate material and the absorption pattern 3.

〔Effect of the invention〕

As described above, according to the present invention, in a carbon-based X-ray exposure mask, a carbide layer is bonded between the heavy metal X-ray absorption pattern and the mask substrate, thereby making it possible to bond both 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 adhesion and few pattern defects.

[Brief explanation of the drawing]

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 is an XvA
Absorption pattern 4 is a carbide layer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (5)

[Claims] (1) In an X-ray exposure mask using a substrate made of carbon-based material as a mask substrate,
A mask for X-ray exposure, comprising a carbide layer made of a material obtained by converting the heavy metal into carbide, which is bonded between the radiation absorption pattern and the mask substrate. (2) The X-ray exposure mask according to claim 1, wherein the mask substrate is made of carbon, silicon carbide, boron carbide, or aluminum carbide. (3) X according to claim 1, wherein the heavy metal is either tantalum or tungsten.
Mask for line exposure. (4) Claim 1, wherein the heavy metal is an alloy containing either tantalum or tungsten.
X-ray exposure mask described in Section 1. (5) The X-ray exposure mask according to claim 1, wherein the carbide layer has an edge formed to match the absorption pattern.