JPS61110427A - Formation of pattern - Google Patents

Abstract

PURPOSE:To improve accuracy of pattern formation by providing a resist film on a substrate to be processed after providing a protection film for reducing strength of secondary electron generated from the substrate to be processed with the exposure by radioactive ray. CONSTITUTION:As a substrate 10 to be processed, a W film (film to be processed) 2 is provided on a silicon wafer 1 and a polycrystalline silicon film 3 is formed thereon by the CVD method as a protection film. Next, an X-ray resist film 4 is deposited on the polycrystalline silicon film 3 and baking is carried out. Next, the X-ray resist film 4 is exposed by the X-ray 6 through the X-ray mask 5. Next, a resist pattern 4' is formed by the developed process and then post-baking is carried out. Thereafter, the protection film and W film are etched by reactive ion etching using the sulfur hexafluoride (SF6) with the resist pattern 4' used as the mask. Next, the remaining resist film is removed to form a pattern.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of forming a fine pattern using X-rays,
In particular, the present invention relates to a method of forming highly accurate patterns by reducing secondary electrons from a substrate to be processed due to X-ray exposure.

[Background of the invention]

It is known that in radiation lithography, especially in Xa lithography, secondary electrons generated from the absorber of the X-ray mask spread and act on the resist, reducing the dimensional accuracy of the resist pattern. An example is Ja
pan J, of Appl, Phys.

Vol. 20 (1981) P, L20-24.

However, no report has been found regarding the influence of secondary electrons from the substrate to be processed due to XjIA exposure.

[Purpose of the invention]

An object of the present invention is to provide a highly accurate resist pattern forming method in radiation lithography.

[Summary of the invention]

In radiation lithography, the inventor developed a film (workpiece film) of a substance that easily generates secondary electrons, such as heavy metals such as gold (Au) and tungsten (W), which is provided on a semiconductor substrate.
It has been found that when processing materials such as heavy metals, secondary electrons generated by irradiation with radiation spread and irradiate the resist film, reducing the precision of the resist pattern. Furthermore, it was found that the maximum penetration depth of the secondary electrons into the resist film (η (escape depth)) was 1,000.

Next, we considered this countermeasure and added a material, in other words, a material that emits less secondary electrons when exposed to radiation than the film to be processed, on a workpiece substrate that has a film to be processed on such a substrate. For example, we have invented a method of forming a resist film after forming a thin film of a substance (hereinafter referred to as a protective film) composed of an element with a lower atomic number than the elements constituting the film to be processed. Konoho 1119
The film thickness varies slightly depending on the material, but the maximum is 1,000 people. It was found that &Small was effective even with about 50 people, which is the limit of film-forming technology. However, it can be easily inferred that the present invention can be applied to a film having a thickness smaller than this depending on improvements in film forming technology.

Furthermore, the main types of radiation that cause secondary electrons to be emitted from elements are X-rays and ultraviolet rays, and the radiation that is often used in phosphorography is also X-rays and ultraviolet rays.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1 This will be explained using FIG.

First, a substrate 10 to be processed was prepared in which a W film (film to be processed) 2 having a thickness of 0.2 μm was provided on a silicon wafer 1 . On top of that is a polycrystalline silicon film 3 as a protective film.
was formed by CVD method. This CVD reaction uses monosilane (S i H,) as a reaction gas and the substrate temperature is 60°C.
The temperature was 0°C. A Xa resist film 4 with a thickness of 1 μm was deposited on the primary polycrystalline silicon film 3 with a film thickness of 200 μm using NPR (manufactured by Hitachi Chemical) as an X-ray resist. Baking was performed for 1 minute. Next, X-rays 6 are applied to the film 1 through the X-ray mask 5.
to expose. X-ray 6 is M. , alpha rays, exposure amount is 100m
J/aJ.

Next, a developing process was performed for 3 minutes using developer NMD-3 (manufactured by Tokyo Ohka) to form a resist pattern 4', and then post baking was performed at 80° C. for 20 minutes. Subsequently, using this resist pattern 4' as a mask, the protective film and W film were etched by reactive ion etching using sulfur hexafluoride (SF). The SF gas pressure was 20 Pa and the etching time was 2 minutes.The remaining resist film was removed after the first step, and the pattern formation was completed.

As a result, a 0.3 μm pattern could be formed on the W film. In addition, when a protective film was not used, the formation of a pattern of 0.5 μm was the limit.

In this etching, since the etching rate of polysilicon IPJ3 is about six times the etching rate of wg, the increase in etching time due to the introduction of the protective film hardly poses a practical problem.

Further, the remaining protective film may or may not be removed as necessary.

In the present invention, it is not necessary for the substrate to be processed to have a film to be processed formed on the entire surface of the semiconductor base, and it goes without saying that the present invention can be applied even when there are two or more layers of films to be processed. Further, the protective film does not necessarily have to be one layer, but may be formed of two or more layers, and the present invention could be carried out even if a film that does not function as a protective film is provided between the layers.

In this embodiment, polysilicon was used as the material for the protective film, but SiO, SilN, and other elements with small atomic numbers or compounds made of these may also be used.

It goes without saying that various organic substances can also be used.

Example 2 A protective film was provided on the substrate to be processed in the same manner as in Example 1, and a photoresist (Δzt3so, I: manufactured by Hoechst) was applied thereon.
was applied to a film thickness of 0.7 μm.

Next, a pattern was formed by performing exposure of 45IIIJ/aJ using an ultra-high pressure mercury lamp. When no protective film was provided, a pattern of 2 μm or less could not be formed, but when a protective film was provided, a 1.5 μm pattern could be formed.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the influence of secondary electrons emitted from the substrate to be processed along with the x and wtn tips on the resist film surrounding the x, thereby improving the accuracy of pattern formation.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the first embodiment. 1... Silicon wafer, 2... Tungsten (workpiece) 1

Claims (1)

[Scope of Claims] 1. In a pattern forming method in which a resist pattern is formed on a substrate to be processed by radiation lithography, secondary electrons generated from the substrate to be processed due to radiation exposure are placed on the substrate to be processed. A pattern forming method characterized in that a resist film is provided after a protective film is provided to reduce the strength of the pattern. 2. The pattern forming method according to claim 1, wherein the radiation is an X-ray. 3. The pattern forming method according to claim 1, wherein the radiation is ultraviolet rays. 4. The pattern forming method according to claim 1, wherein the protective film is composed of an element having an atomic number smaller than an element constituting the film to be processed on the substrate to be processed. 5. The pattern forming method according to claim 4, wherein the protective film is obtained by oxidizing the surface of the film to be processed. 6. The pattern forming method according to claim 1, wherein the protective film is formed of polycrystalline silicon. 7. The pattern forming method according to any one of claims 1 to 4, wherein the protective film has a thickness of 1,000 Å or less. 8. Claim 1 or 4, characterized in that the protective film is composed of one layer or two or more layers.
8. The pattern forming method according to any one of Items 7 to 7.