JPH0795509B2 - Method of forming resist pattern - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a resist pattern using electron beam exposure.

2. Description of the Related Art As semiconductor device patterns have become finer, electron beam exposure has come to be used for pattern formation. Further, in order to improve the resolution and reduce the influence of the unevenness of the substrate, consideration is given to making the resist a multilayer structure. Further, in electron beam exposure using a multi-layered resist film, if the thickness of the lower layer resist is large, the lower layer resist is charged by the incident electrons, and the electron beam is bent to cause misalignment of the drawing pattern. A conductive silicon (Si) thin film is placed in between to prevent the lower layer resist from being charged.

Problems to be Solved by the Invention In such a conventional method, it is necessary to form an electrically conductive Si thin film, which is originally unnecessary, between resists having a multi-layer structure. Since it is necessary to perform processing such as plasma CVD or vapor deposition, and these steps are different from the photoresist step including coating and heat treatment steps, there is a problem that the steps are complicated.

Means for Solving the Problems In order to overcome the above problems, the present invention sequentially forms at least an electron beam resist film and an ammonium polystyrenesulfonate film on a substrate, and then performs heat treatment and electron beam exposure treatment. This is a method of forming a resist pattern, in which the application is performed, then the polystyrene sulfonate ammonium film is removed, and then the electron beam resist film is developed to form a pattern.

Effect According to the method for forming a resist pattern of the present invention, it is possible to prevent the charging phenomenon without using a Si thin film, and a highly accurate resist pattern free from pattern distortion and displacement can be realized.

EXAMPLES Hereinafter, the method for forming a resist pattern of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 shows a first method of forming a resist pattern according to the present invention.
FIG. 4 is a diagram for explaining the embodiment of the present invention. In this method, first, a polymethylmethacrylate (PMMA) film is applied as the electron beam resist film 2 on the surface of the semi-insulating GaAs substrate 1 to a thickness of 0.5 μm. Then, pre-bake at 160 ° C for 30 minutes. Next, as a conductive polymer thin film 3, an ammonium polystyrene sulfonate film is formed to a thickness of 0.2 μm, and then heat treatment is performed at 100 ° C. for 30 minutes [FIG. 1A].

Then, a predetermined area is exposed to an electron beam. Further, the conductive polymer thin film 3 is removed by using an organic alkali developing solution for positive photoresist, and finally, the electron beam resist film 2 is developed by a methyl isobutyl ketone (MIBK) developing solution to form a pattern 4 on the PMMA film. Are formed [Fig. 1b].

In the pattern formed in this way, no pattern distortion or pattern positional deviation was observed. The electron beam resist pattern formed by using the same semi-insulating GaAs substrate as described above and subjecting it to electron beam exposure and development without forming an ammonium polystyrene sulfonate film has very large pattern distortion and pattern displacement. It was confirmed. Since ammonium polystyrene sulfonate is water-soluble, it can be easily applied on PMMA. Further, even if it is applied on various resists other than PMMA, it can be applied without mixing in the vicinity of the boundary between the two.
In addition, since ammonium polystyrene sulfonate can be removed with an organic alkaline developer or water, PM
MA and other electron beam resists are not affected. By the way, the structure of ammonium polystyrene sulfonate is composed of an anion group of polystyrene sulfonate and a salt of a positively charged ammonium group as shown in FIG. 2, and has ion conductivity. Also,
The ammonium group is composed of nitrogen and hydrogen and does not contain a metal. Therefore, the ammonium group has no risk of contaminating the semiconductor substrate and is particularly suitable for forming a resist pattern in the manufacturing process of a semiconductor device. Of course, a group having a positive charge other than the ammonium group can be used.

FIG. 3 is a diagram showing changes in the sheet resistance of the ammonium polystyrenesulfonate film when the heat treatment temperature is changed and the sheet resistance of the Si film formed by sputter deposition. As is clear from this figure, the sheet resistance of the ammonium polystyrenesulfonate film increases as the heat treatment temperature increases. However, at a heat treatment temperature of 200 ° C., a sheet resistance of 6 × 10 ⁷ Ω / □ is obtained, which is slightly higher than the sheet resistance of the Si film formed by sputter deposition. Therefore, a resistance value low enough to discharge the incident electrons at the time of electron beam exposure is obtained, and the incident electrons are not charged.

FIG. 4 shows that a silicon substrate is used as the substrate,
It is a figure which shows the other Example which forms the three-layer resist whose uppermost layer is a polystyrene sulfonate ammonium film on this board | substrate, and patterns this.

In this method, a silicon substrate 5 is prepared, and a novolac-based positive resist film 2 μ is first formed as an organic thin film 6 on the silicon substrate 5.
It is applied to a thickness of m and heat-treated at 270 ° C for 30 minutes. Next, a coated silicon oxide film (SOG) 7 is coated to a thickness of 0.2 μm and heat-treated at 250 ° C. for 30 minutes. Furthermore, a chloromethylated polystyrene film was used as the electron beam resist 2.
After applying a thickness of 5 μm and performing a pre-baking treatment at 130 ° C. for 30 minutes, apply an ammonium polystyrene sulfonate film as a conductive polymer thin film 3 to a thickness of 0.2 μm, and apply 100
Heat treatment is performed at 30 ° C for 30 minutes [Fig. 4a].

Next, after performing an exposure amount of 6 μC / cm ² electron beam exposure,
The ammonium polystyrene sulfonate film was removed with an organic alkaline developer, and the chloromethylated polystyrene film 2 was developed with a developer in which isoamyl acetate and ethyl cellosolve were mixed at a ratio of 1: 4 to form a predetermined pattern 4. (Fig. 4b).

Finally, the coated silicon oxide film 7 is selectively removed by CHF ₃ / O ₂ plasma etching using the chloromethylated polystyrene film 2 as a mask.
A predetermined pattern 8 is formed by subjecting the organic thin film 6 to etching treatment with O ₂ plasma using the mask as a mask (FIG. 4c).

In the pattern formed through such a process, ± 0.1μ
A high overlay accuracy of m (3σ) was obtained. It was confirmed that when the pattern was formed without using the conductive polymer thin film, the positional deviation due to charging occurred, and the overlay accuracy was lowered to ± 0.7 μm (3σ).

EFFECTS OF THE INVENTION As is apparent from the above description, according to the method for forming a resist pattern of the present invention, electron beam exposure can be performed without charging the resist film with incident electrons, and therefore the electron beam can be bent. It is possible to form a resist pattern which has no pattern distortion and pattern displacement. Further, the conductive polymer thin film can be easily formed and removed, and there is no fear that the electron beam resist is adversely affected or the substrate is contaminated at this time.

[Brief description of drawings]

1A and 1B are cross-sectional views showing a process of forming a resist pattern by the method for forming a resist pattern of the present invention, FIG. 2 is a molecular structure diagram showing the structure of ammonium polystyrene sulfonate, and FIG. 3 is a heat treatment temperature. Is a characteristic diagram showing a change in sheet resistance of the ammonium polystyrene sulfonate film and a sheet resistance of the Si film formed by sputter deposition when the value is changed, and FIGS. 4A to 4C show the resist pattern forming method of the present invention. FIG. 7 is a cross-sectional view showing a process of forming a resist pattern according to another embodiment. 1 ... Semi-insulating GaAs substrate, 2 ... Electron beam resist,
3 ... Conductive polymer thin film, 4 ... Pattern, 5 ... Silicon substrate, 6 ... Organic thin film, 7 ... Coated silicon oxide film, 8 ... Pattern.

Claims (1)

[Claims] 1. At least an electron beam resist film and a polystyrene sulfonate ammonium film are sequentially formed on a substrate, followed by heat treatment and electron beam exposure treatment, and then,
Removing the polystyrene ammonium sulfonate membrane,
After that, the resist pattern is formed by developing the electron beam resist film to form a pattern.