JPH0457050A - Formation of drawing pattern - Google Patents

Abstract

PURPOSE:To irradiate a resist film of the parts exclusive of heated parts with an in beam and to selectively and easily remove only these parts by subjecting only the parts to be left as a mask of the resist film to a heat treatment to lower sensitivity. CONSTITUTION:A resist material essentially consisting of nitrocellulose is applied on a substrate 1 to form the resist film 2. The parts to be irradiated with the ion beam have the relatively high sensitivity if the parts to be left as the mask of the resist film 2 are selectively heated. Exposing and developing are simultaneously executed and drawn patterns are successively formed when the non-heated parts are thereafter successively irradiated with the ion beam. Apertures 3 are formed in desired patterns on the resist film 2 in this way. The drawn patterns which are less disturbed in shape are formed without applying the damages by the ion beam to a substrate, etc., which are the substrate for the nitrocellulose resist. Since the nitrocellulose of the parts to be removed is maintained at the high sensitivity, there is no need for using a powerful ion beam irradiating device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a resist film containing nitrocellulose as a main component. The present invention relates to a method for forming a drawing pattern by irradiating B (focused ion beam).

[Conventional technology]

In the semiconductor manufacturing process, a technology that forms a desired resist pattern by irradiating a nitrocellulose resist with an ion beam is attracting attention.

That is, since the nitrocellulose resist is exposed and developed simultaneously by ion beam irradiation, the manufacturing process can be simplified and shortened.

However, since nitrocellulose is highly sensitive to ion beams, it has the disadvantage that the shape of the drawn pattern tends to be irregular at the edges.

Therefore, as a conventional technique for improving this, there is a technique shown, for example, in the 37th Japan Society of Applied Physics Conference Proceedings 31a-ZG-1+ and 31a-ZG-9. The former technique deposits PMMA (polymethyl methacrylate) on top of the nitrocellulose resist to form a two-layer resist film, while the latter technology heat-treats the nitrocellulose resist film to reduce its sensitivity to ion beams. This is followed by ion beam irradiation.

[Problem to be solved by the invention]

However, the former technique requires a two-layer resist film, which increases the number of steps. Furthermore, in the latter technique, a resist film with reduced sensitivity is exposed and developed, so it is necessary to increase the intensity of the ion beam or to irradiate it for a long time. Therefore, the underside of the resist film (substrate, etc.) is likely to be damaged during beam irradiation.

It is an object of the present invention to provide a method for forming a drawing pattern that eliminates the drawbacks of such conventional techniques.

[Means to solve the problem]

The method for forming a drawing pattern according to the present invention is a method of forming a drawing pattern by irradiating a resist film mainly composed of nitrocellulose with an ion beam, in which a portion of the resist film to be left as a mask is selectively removed. It is characterized by comprising a first step of heating, and a second step of irradiating the resist film other than the selectively heated portions with an ion beam and selectively removing the resist film at the irradiated portions.

[Effect]

According to the configuration of the present invention, only the portion that should remain as a mask has its sensitivity reduced, so that only the portion irradiated with the ion beam can be selectively removed.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective sectional view of each step showing a method for forming a drawing pattern according to an embodiment. First, a resist material containing nitrocellulose as a main component is applied onto a substrate 1 to form a resist film 2 (as shown in FIG. 3A). Note that, depending on each stage of the manufacturing process, an impurity region may already be formed in the substrate, or an insulating film may be formed on the upper surface of the substrate 1.

Next, only the portion of the resist film 2 to be left as a mask is selectively heated. As a result, the portion to be irradiated with the ion beam becomes relatively sensitive. Thereafter, when the non-heated portion is irradiated with an ion beam, exposure and development are performed simultaneously (in-situ development), and a drawn pattern is formed (as shown in FIG. 3(b)). As a result, openings 3 are formed in the resist film 2 in a desired pattern (
Figure (C) shown). Here, the ions to be irradiated include, for example, gallium ions (Ga), beryllium (Be)
), argon (Ar), gold (Au).

+ Hydrogen (H) ions can be used.

Since the present invention is characterized in that it combines selective heating of mask portions and ion beam irradiation of unheated portions, it is necessary to heat the mask so that the temperature gradient with respect to the unheated portions is steep.

The first method is flash lamp heating using a mask pattern (for example, a reticle). That is, a reticle with a light-shielding film (for example, a chrome film) formed on the part corresponding to the part to be irradiated with the ion beam is prepared and heated for a short time with a powerful flash lamp. Next, the semiconductor wafer subjected to such local heat treatment is set in an ion beam irradiation device, aligned, and then exposed to ion beam irradiation and developed.

A second method is a heating method using a laser beam. That is, only the portion to be left as a mask is scanned or projected exposed with a laser beam to reduce the sensitivity of the resist. Thereafter, only the high-sensitivity areas are developed and exposed by ion beam irradiation. In this case, since local heating with an extremely steep temperature gradient is achieved by the laser beam, a fine drawing pattern on the order of submicrons can be easily formed. Note that when a resist is heated with a laser beam, the temperature gradient generally has a Gaussian distribution.

Various methods other than those described above can be considered as specific methods for local heating. For example, if it is possible to achieve local heating treatment using an ion beam by changing the type of ions to those used for exposure and development, the local heating process, exposure, and development process can be performed continuously using the same ion beam irradiation device. obtain. In this case, alignment of the semiconductor wafer can be made unnecessary, so that the drawing process can be further simplified.

〔Effect of the invention〕

As described in detail above, according to the present invention, only the portion that should remain as a mask has its sensitivity reduced by heat treatment, so that only the portion irradiated with the ion beam can be selectively and easily removed. For this reason, for the substrate etc. that is the base of the nitrocellulose resist,
It is possible to form a drawing pattern with less disturbance in shape without causing damage due to the ion beam. Further, since the nitrocellulose in the portion to be removed is kept highly sensitive to ion beam irradiation, a drawing pattern can be formed in a short time without using a powerful ion beam irradiation device.

It is a perspective sectional view by process explaining the formation method.

1... Substrate, 2... Nitrocellulose resist film,
3...Opening.

Claims (1)

[Claims] In a method of forming a drawn pattern by irradiating a resist film mainly composed of nitrocellulose with an ion beam, the first step includes selectively heating a portion of the resist film that is to be left as a mask. and a second step of irradiating the resist film other than the selectively heated portions with the ion beam and selectively removing the resist film at the irradiated portions. How to form.