JPS6237930A - Electron beam exposing method - Google Patents

Abstract

PURPOSE:To form a fine pattern with high dimensional accuracy, by forming a resist pattern whose cross-sectional form is nearly vertical, by a method wherein the distribution of the electron absorption energy in a resist film is made uniform by the effect of a dual exposure applying both a high acceleration voltage and a low acceleration voltage. CONSTITUTION:After a resist film 6 sensitive to electron beams is coated on a semiconductor substrate 3, a predefined pattern is drawn on a resist film 6 by electron beams with acceleration voltage to penetrate the resist film 6. Then, the pattern is drawn on the resist film 6 by the electron beams 8 with acceleration voltage insufficient to penetrate the resist film 6. Thus the distribution of electron absorption energy in the resist film 6 is made uinform. Thereby, resist pattern 9 whose cross-sectional form is nearly vertical is formed, and a fine pattern with high dimensional accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electron beam exposure method for forming fine resist patterns with good dimensional accuracy by double exposure.

2. Description of the Related Art In recent years, in an effort to miniaturize and increase the integration of semiconductor elements built into semiconductor substrates, an electron beam exposure method suitable for forming a fine pattern 2 basis has been used.

In this electron beam exposure method, after applying a resist film that reacts to electrons (electron beam sensitive resist film) on a semiconductor substrate,
This is a method in which a predetermined pattern is drawn on a resist film by controlling the scanning of an electron beam using a computer, and then a development process is performed to form a predetermined resist pattern on a semiconductor substrate. FIG. 2 is a distribution curve of the amount of electron absorption energy due to isoenergetic lines in the resist film exposed by this method. The electron beam 2 incident on the resist film 1 passes through the resist film 1, and the Since the electrons that have reached are scattered by the silicon substrate 3,
The amount of electron absorption energy inside the resist film increases as it approaches the surface of the silicon substrate 3, and the distribution curve of the amount of electron absorption energy shows a tendency to spread horizontally along the surface of the silicon substrate 3.

Problems to be Solved by the Invention FIG. 3 shows a cross-sectional view of the resist pattern after developing the resist 3-7 film exposed under such a tendency. FIG. 3a shows a case where a positive resist 4 is applied on a silicon substrate 3, and the resist film in the area irradiated with the electron beam 2 is removed, and moreover, it has an undercut shape in which much of the silicon substrate side of the resist film is removed. becomes. Third
The figure shows a case where a negative resist 6 is applied on a silicon substrate 1, and the resist remains in the area irradiated with the electron beam 2, and has a trapezoidal cross section. In either case, the problem arises that the pattern shape has low dimensional accuracy.

Means to Solve the Problems The electron beam exposure method of the present invention aims to make the electron absorption energy distribution within the resist film uniform, and to form a resist pattern whose side surfaces are approximately perpendicular to the substrate. After applying an electron beam sensitive resist film on a conductor substrate, a predetermined pattern is formed on the electron beam sensitive resist film using an electron beam at an accelerating voltage that penetrates the electron beam sensitive resist film. The method comprises a first exposure for drawing, and a second exposure for drawing the pattern on the electron beam-sensitive resist film using an electron beam at an accelerating voltage that does not penetrate the electron-beam-sensitive resist film. be.

Function: In this electron beam exposure method, after exposing the resist film with an electron beam at an accelerating voltage that penetrates the resist film, the electron beam is superimposed with an accelerating voltage that does not penetrate the resist film because the electron absorption energy is large on the resist film surface. Since the resist film is exposed to light, the distribution of electron absorption energy within the resist film can be made uniform.

Embodiment An embodiment of the electron beam exposure method of the present invention will be described with reference to the process flowchart of FIG.

First, a negative resist for electron beam (chloromethylated polystyrene resin) (hereinafter referred to as 0M polystyrene resin) commercially available from Toyo Soda Co., Ltd. under the trade name
S resist) 6 was applied to a thickness of 0.6 μm, and 1
Pre-bake for 30 minutes at a temperature of 30°C (Fig. 1 Δ
) Next, the acceleration voltage 5x, - which penetrates this resist film thickness is
A predetermined pattern is entirely drawn on the OMS resist film 6 at an exposure dose of 6 μO/cA while controlling the scanning of the electron beam 7 with a voltage of 20 KV by a computer (FIG. 1b).

Next, while controlling the scanning of the electron beam 8 with an acceleration voltage of 6KY by a computer, a 2μ
Draw the same pattern with an exposure amount of Q/cA (Fig. 1C
).

Here, the electron absorption energy distribution in the incident direction of the electron beam in the OMS resist film at an accelerating voltage of 5 KV is shown in the table below.

(Left below) 6. When the accelerating voltage is 5 KV, electrons penetrate to a depth of 0.6 μm, but the number decreases as the depth increases from the resist film surface, and when the depth becomes deeper than 0.6 μm, there are no penetrating electrons. . Therefore, the resist film thickness should be set to 0.6μ.
If a thickness exceeding mf is selected, electrons rejected from the silicon substrate 3 will not be scattered. Because the electron absorption energy is large at the surface, the electron absorption energy distribution spreads horizontally due to surface scattering near the surface. Therefore, by superimposing the electron absorption energy distribution with an accelerating voltage of 5 KV on the electron absorption energy distribution with an accelerating voltage of 20 KV, it is possible to obtain a substantially uniform electron absorption energy distribution from the resist film surface to the silicon substrate.

In this way, cM with a uniform electron absorption energy distribution
s The resist film 6 is developed for 1 minute using a developer containing isoamyl acetate and ethyl cellulone in a ratio of 1:3, and rinsed for 1 minute with isopropyl alcohol, so that the cross-sectional shape is approximately the same in the area irradiated with the electron beam. A vertical resist pattern 9 can be obtained (FIG. 1d).

In addition, in the example, an example is given in which the electron acceleration voltage is 20 Ω and 5 Ω, but this value varies depending on the type of resist, film thickness, etc., and the acceleration voltage that penetrates the resist film and the resist film Any accelerating voltage that does not penetrate can be used.

Effects of the Invention According to the electron beam exposure method of the present invention, double exposure using a high accelerating voltage that penetrates the resist film and a low accelerating voltage that does not penetrate the resist film makes the electron absorption energy distribution inside the resist film uniform. In this way, a resist pattern with a substantially vertical cross-sectional shape can be formed, and a fine pattern with high dimensional accuracy can be formed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a resist pattern formed by the electron beam exposure method of the present invention. 3... Silicon substrate, 6... 0MS resist, 91, -7 7... Electron beam with acceleration voltage of 20 KV, 8...
...Electron beam with accelerating voltage of 5KV, 9...
...Resist pattern. Name of agent: Patent attorney Toshio Nakao and 1 other person3-
--Silico
,～---Column size L2---Electric beam 3---Silicone 1 and Q=Io'' eV/c 6m2 Figure 3 2=-Electric)ji''-4 3---Silicoshi base 4 -Ichimasa °Gilet Q-S L

Claims (1)

[Claims] After applying an electron beam sensitive resist film on a semiconductor substrate, a first exposure of drawing a predetermined pattern on the electron beam sensitive resist film using an electron beam at an accelerating voltage that penetrates the electron beam sensitive resist film; and a second exposure of drawing the pattern on the electron beam-sensitive resist film using an electron beam at an accelerated voltage that does not penetrate the electron beam-sensitive resist film. .