JPH0682603B2 - X-ray exposure mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to X used for manufacturing a semiconductor integrated circuit.
The present invention relates to a line exposure mask.

[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, a sub-micron order pattern can be transferred. It is characterized by being. In order to transfer the pattern, it is necessary to selectively transmit X-rays with a mask.

FIG. 3 is a cross-sectional view showing the structure of a conventional X-ray exposure mask, in which 1 is a ring-shaped support frame and 2 is a mask substrate made of silicon carbide or the like formed on the support frame 1. Is. Reference numeral 3 is an X-ray absorption pattern made of a heavy metal formed on the mask substrate 2.

Next, the operation will be described. The mask substrate 2 has carbon (C), silicon carbide (SiC), boron carbide (B ₄ C), in order to have a high transmittance for X-rays.
A thin film of a material mainly composed of a relatively light element having a high X-ray transmittance such as aluminum carbide (AlC ₃ ) is used. Further, the absorption pattern 3 is made of a heavy metal such as tantalum (Ta) or tungsten (w) having a low X-ray transmittance as a material in order to efficiently absorb X-rays.

When the resist thin film on the silicon wafer is irradiated with X-rays through the mask having the above-described structure, a difference in transmitted X-ray intensity occurs in the resist film, which causes the mask pattern to be transferred. A pattern with high contrast can be transferred.

[Problems to be solved by the invention]

However, in the conventional X-ray exposure mask described above,
Since the adhesiveness between the X-ray absorption pattern 3 and the mask substrate 2 is insufficient, there is a problem that pattern defects due to peeling are likely to occur and the life is short.

The present invention has been made to solve the above problems, and an object thereof is to obtain an X-ray exposure mask having a structure in which the X-ray absorption pattern and the mask substrate have high adhesiveness and a long life. To do.

[Means for solving problems]

The mask for X-ray exposure according to the present invention is made of a heavy metal X.
It is formed by joining a layer of the absorption pattern material, which is made into a carbide, between the line absorption pattern and the mask substrate.

[Action]

In the present invention, the adhesive force can be generally increased by preventing the material structure between the thin film and the substrate from abruptly changing. The idea has been to form a carbide layer of absorption pattern material metal as an intermediate compound layer with the pattern. Since this carbide layer adheres the absorption pattern to the mask substrate by a 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.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows the structure of an X-ray exposure mask according to one embodiment of the present invention. In the figure, 1 is a ring-shaped support frame, and 2 is a mask substrate made of a silicon carbide film formed on the support frame 1. Reference numeral 3 is an X-ray absorption pattern made of tungsten, and 4 is a carbide layer formed by joining tungsten between the mask substrate 2 and the X-ray absorption pattern 3 and forming a carbide of tungsten.

Next, a method of forming the X-ray absorption pattern provided with the above-mentioned carbide layer 4 will be described. A silicon carbide film serving as 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.
Are formed by a sputtering method or the like. Then, a tungsten layer to be the X-ray absorption pattern 3 is formed on the carbide layer 4 by a sputtering method, and a resist layer is further formed by a spin coating method. The desired resist pattern is obtained by exposing the resist layer with an electron beam and further developing it. Using this resist pattern as a mask, the tungsten layer and then the carbide layer can be etched by reactive ion etching using CF ₄ gas to obtain a desired X-ray absorption pattern.

FIG. 2 shows, by way of example, an X consisting of a tungsten layer 3 having a thickness of 1 μm and a tungsten carbide layer 4 having a thickness of 300 Å on a silicon carbide film mask substrate 2 having a thickness of 2 μm.
For the X-ray exposure mask on which the line absorption pattern is formed,
It shows the change over time in the pattern defect density when ultrasonic cleaning is performed. The solid line in FIG. 2 shows the result in the case of this embodiment, and it can be seen that the pattern defect density has a substantially constant value regardless of the cleaning time. Further, the result when the same is performed on the conventional X-ray exposure mask having no tungsten carbide layer is shown by a broken line in FIG.

As shown in FIG. 2, the X-ray absorption pattern 3 provided with the carbide layer 4 has better adhesiveness to the mask substrate 2 than the conventional one which does not, and significantly reduces the pattern defect density. You can

In the above-mentioned examples, by joining the carbide layer 4, it was possible to suppress the temporal change of the pattern defect density to a constant low value. Further, since the silicide thin film exists only at the boundary portion between the absorption pattern 3 and the mask substrate 2, the X-ray absorption capacity is equivalent to that of the conventional pattern, and therefore, the absorption pattern 3 is required without increasing the aspect ratio. It is possible to obtain contrast. Further, an alignment method using a laser beam can be applied to a portion where the carbide layer 4 does not exist, that is, an area that does not have the absorption pattern 3 and transmits X-rays.

In the above embodiment, the mask substrate 2 is made of a silicon carbide film and the absorption pattern 3 is made of tungsten. However, the mask substrate 2 is made of other materials such as carbide, boron carbide and aluminum carbide. The same effect can be expected when other heavy metals such as tantalum are used for the carbon-based substrate material and the absorption pattern 3.

〔The invention's effect〕

As described above, according to the present invention, in the carbon-based X-ray exposure mask, the heavy metal X-ray absorption pattern and the mask substrate are bonded to each other and the carbide layer is bonded to each other. It has an effect of obtaining a long-life mask for X-ray exposure, which has a high adhesiveness, and has few pattern defects.

[Brief description 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 an ultrasonic cleaning time for X-ray absorption pattern defect density for explaining the function and effect of the present invention. 3 is a 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, 3 is an X-ray absorption pattern, and 4 is a carbide layer. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (5)

[Claims] 1. An X-ray exposure mask using a substrate made of a carbon-based material as a mask substrate, wherein the heavy metal is formed between the X-ray absorption pattern made of a heavy metal and the mask substrate. An X-ray exposure mask comprising a carbide layer made of a material obtained by converting the above into a carbide. 2. The mask for X-ray exposure according to claim 1, wherein the mask substrate is made of carbon, silicon carbide, boron carbide or aluminum carbide. 3. The X-ray exposure mask according to claim 1, wherein the heavy metal is tantalum or tungsten. 4. The X-ray exposure mask according to claim 1, wherein the heavy metal is an alloy containing either tantalum or tungsten. 5. The mask for X-ray exposure according to claim 1, wherein an edge of the carbide layer is formed so as to match the absorption pattern.