JPH02192714A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To mitigate the approximation effect by a method wherein a substrate is coated with a material comprising light atoms; an intermediate layer comprising another material comprising heavy atoms or in high density is formed; furthermore, the intermediate layer is coated with electron beam resist. CONSTITUTION:An X-ray transmissive thin film 2 and an etching protective film 3 are formed respectively on the surface and rear surface of a substrate 1. Next, an X-ray absorber layer 4 is formed on the film 2 and then the layer 4 is coated with novolak base photoresist to form an electron beam buffer layer 5 on the layer 4. Furthermore, after forming an intermediate layer 6 on the layer 5, an electron beam resist 7 mainly composed of polymethylmethacrylate is coated on the layer 6. Later, the surface is electron beam-exposed using electron beams 8. At this time, the insident electrons generate reflected electrons and secondary electrons on the boundary surface of the layer 4 however, the energy is attenuated in the running process and reflected again on the layer 6 not to reach the resist 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to l, SI (Large 5cal In
The present invention relates to a method for forming a resist pattern when forming a circuit pattern for a high-density integrated circuit such as a VLSI or a VLSI by electron beam writing.

[Conventional technology]

In recent years, demands for higher performance and higher integration of semiconductor integrated circuits have been increasing. Therefore, instead of conventional photolithography using ultraviolet rays, lithography using electron beams has been used to create ultra-fine patterns. There is a need to establish processing technology to form . Particularly with respect to photomasks, production by electron beam lithography has already been put into practical use industrially, and attempts have also been made to directly write electron beams onto wafer substrates.

On the other hand, in order to enable electron beam lithography technology that forms ultra-fine patterns, the drawing precision required of electron beam exposure equipment has become stricter, and the resist materials used must also have characteristics that correspond to the required drawing precision. Furthermore, the resist process is also very important.

In the resist process, proximity effects, resist heating effects, charge-up effects, etc. are known to be causes of deterioration in pattern drawing accuracy that occurs during electron beam lithography. It is believed that the proximity effect is a major cause of the deviation from the design value.

The influence of the proximity effect is thought to be caused by backscattering of the electron beam, so the conventional method is to absorb and attenuate the backscattered electrons by forming a buffer layer between the substrate and the electron beam resist. It was adopted by

[Problem to be solved by the invention]

However, if the substrate is made of heavy atoms or a material with high density, the backscatter of the electron beam will be extremely large, so simply providing a buffer layer will not be sufficient to absorb and attenuate the backscattered electrons. The problem was that it was difficult.

[Means for solving problems]

The present invention solves the above problems, and includes coating a material made of heavy atoms on a substrate in a resist pattern forming process, forming an intermediate layer made of heavy atoms or a material with high density, and further By applying an electron beam resist, electrons backscattered by a substrate made of heavy atoms or a high-density material during electron beam writing are scattered by an intermediate layer made of a heavy atom or a high-density material. , which is characterized by making it possible to form a resist pattern with reduced proximity effects.

The film thickness of the electron beam resist is 0.05 to 3 μm1.
Examples of the material of the intermediate layer made of heavy atoms or high-density materials include heavy metals such as N Au1 Ta1 W, WN1
Using a compound such as WSi, the film thickness is 0.01 to 0.5 μm
As a coating material made of heavy atoms on the substrate, a novolak resist, polyimide, etc.
The film thickness is μm, and the substrate is Au1Tas wN.
It is preferable to use an X-ray mask substrate or a GaAS wafer substrate on which a predetermined thin film is formed, such as WN.

[Effect]

According to the present invention, a material made of heavy atoms is coated on a substrate, an intermediate layer made of heavy atoms or a high-density material is formed, and an electron beam resist is further coated on top of the intermediate layer. It is possible to reduce the

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiment, an example of manufacturing an X-ray mask having a polymeric X-ray absorber layer will be taken up.

FIGS. 1(a) to 1(f) are cross-sectional views of an X-ray mask in the manufacturing process of an X-ray mask employing the resist pattern forming method of the present invention, in which 1 is a Si wafer substrate;
2 is an X-ray transparent thin film, 3 is an etching protective film, 4 is an X-ray absorber layer, 5 is an electron beam buffer layer, 6 is an intermediate layer, 7 is an electron beam resist, 8 is an electron beam, and 9 is a window. .

First, as shown in FIG. 1(a), a SiN film with a thickness of 1 μm is formed on both sides of a mirror-polished Si wafer substrate 1 with a thickness of 2 μm by the CVD method, and the upper surface side is coated with X-rays. A transparent thin film 2 and an etching protection film 3 are formed on the lower surface side. Note that the etching protection film 3 can be formed by etching away unnecessary portions using a photoresist pattern as a mask.

Thereafter, an X-ray absorber layer 4 made of a Ta film or the like with a thickness of 1 μm is formed on the X-ray transparent thin film 2 on the upper surface side by sputtering, and a novolac-based photoreceptor layer 4 is formed on the X-ray absorber layer 4. 1 resist, such as Hoechst AZ-1350.
μm coating to form an electron beam buffer layer 5, and further on the electron beam buffer layer 5, an intermediate layer 6 made of Ta film with a thickness of 0.1 μm.
After forming by sputtering method, an electron beam resist 7 containing polymethyl methacrylate as a main component, such as 0EBR-1000 manufactured by Tokyo Ohka Co., Ltd., is applied to a thickness of 0.5 μm on the intermediate layer 6.

Thereafter, electron beam lithography is performed using the electron beam 8 accelerated at an acceleration voltage of 20 kV.

Figure 2 shows the trajectory of the electrons at this time. That is, the incident electrons 10 are reflected at the boundary surface of the X-ray absorber layer 4 or collide with the X-ray absorber layer 4 to generate secondary electrons, but the reflected electrons and secondary electrons do not travel. During the process, the energy is attenuated and reflected again by the intermediate layer 6, so that the electron beam resist 7
It will never reach that point. This makes it possible to reduce the influence of the proximity effect caused by backscattering of electrons.

Next, as shown in FIG. 1(b), after developing the electron beam resist door, RIE (
After removing the intermediate layer 6 by etching with CF4 plasma using a reactive fan etching (reactive fan etching) device, as shown in FIG. The electron beam buffer layer 5 is etched away using plasma, and the electron beam resist 7 on the intermediate layer 6 is also removed.

Next, as shown in FIG. 1(d), an RIE apparatus is used with the pattern of the electron beam buffer layer 5 as a mask, and the CF
4. After etching and removing the X-ray absorber layer 4 with plasma and removing the intermediate layer 6 on the electron beam buffer layer 5,
As shown in FIG. 1(e), using an RIE device, o2
The electron beam buffer layer 5 is ashed and removed by plasma.

Finally, as shown in FIG. 1(f), the NS is etched with a 30% KOH aqueous solution using the etching protective film 3 on the back side as a mask.
If the windows 9 are formed by etching the I-wafer substrate 1 from the back side, an X-ray mask having a desired pattern can be manufactured.

In the above embodiments, the production of an X-ray mask was taken as an example, but the present invention is not limited to the above embodiments, and may be applied to cases where a GaAs substrate or the like is produced by electron beam lithography, etc. It is clear that this method can be generally applied to multilayer plate making using IJ sogelafy.

〔Effect of the invention〕

As is clear from the above description, the present invention has the advantage that the influence of the proximity effect can be reduced when a resist pattern is formed on a substrate where electron beam backscattering is large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the manufacturing process of an X-ray mask according to the present invention,
FIG. 2 is a diagram showing the trajectory of electrons. 1...Si wafer substrate, 2...X-ray transparent thin film,
3... Etching protective film, 4... X-ray absorber layer, 5
...Electron beam buffer layer, 6... Intermediate layer, 7... Electron beam resist, 8... Electron beam, 9... Window, 10... Electron trajectory. Applicant: Dai Nippon Printing Co., Ltd.

Claims (1)

[Claims] (1) In the process of forming a desired pattern on a substrate by electron beam photolithography, a material made of light atoms is applied onto the substrate, and an intermediate layer made of heavy atoms or a high-density material is further formed on top of the material. A method for forming a resist pattern, which further comprises applying an electron beam resist thereon.