JPH1197328A - Method for forming resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a high precision lift-off fine resist pattern with excellent resolution, by a method wherein, after first and second resist layers having different sensitivities are sequently formed on a processed substrate, exposure and development processes are performed to form a resist pattern. SOLUTION: After a resist film 3 is formed on a processed film of a processed substrate 1 such as a GaAs substrate, etc., in which a processed film such as SiO2 , etc., is formed, it is prebaked in a specified manner to carry out a crosslinking reaction. Next, after electron beams are irradiated on specified conditions and a space pattern of a specified dimension is drawn, a bake process after exposure is performed in the atmosphere by use of a hot plate at a specified temperature. Further, for example, the to-be-processed substrate is dipped in a developer based on tetraammonium hydroxide with alkali concentration 0.27, developing is performed to form a lift-off fine resist pattern 6. A resist layer of an upper layer with a large crosslinking rate is finished as a substantially prescribed dimension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resist pattern for forming a lift-off resist pattern.

[0002]

2. Description of the Related Art At present, as GaAs integrated circuits become more highly integrated and operate at higher speeds, there is a demand in lithography technology for forming resist patterns which are fine and have excellent dimensional controllability.

For the wiring of the GaAs integrated circuit, an Au-based metal is usually used because of its compatibility with the ohmic metal. However, this metal is RIE (Reactive Ion-Etchin
It is extremely difficult to process using the g) method, and the lift-off method is used for the processing.

Conventionally, when a resist pattern is formed using this lift-off method, a dye is added to an image reverse resist. The addition of this dye greatly reduces the transmittance of the resist to exposure light (eg, g-line) and increases the light absorption on the resist surface. In this state, the pattern is exposed, reversal baking is performed after the exposure, and development processing is performed to form an inversely tapered resist pattern suitable for lift-off.

[0005]

Conventionally, as described above,
When a resist pattern for lift-off is formed, an image reverse resist to which a dye is added has been used. Since the pattern formed by using this image reverse resist has an inverse tapered shape, when the pattern size is reduced, pattern collapse or the like occurs, the resolution is significantly reduced, and a fine resist pattern for lift-off is formed. There is a problem that is extremely difficult.

The present invention has been made in consideration of the above circumstances, and provides a method of forming a resist pattern capable of forming a fine resist pattern for lift-off with excellent resolution and high accuracy. With the goal.

[0007]

According to the method of forming a resist pattern according to the present invention, first resist patterns having different sensitivities are formed on a substrate to be processed.
And a step of sequentially forming a second resist layer, and a step of performing exposure and development processing.

Further, the first resist layer is formed by applying a resist to a substrate to be processed and then performing a pre-bake in an atmosphere at a first predetermined temperature, and the second resist layer is formed by the first resist layer. After applying a resist on the resist layer, the resist layer may be formed by performing pre-baking in an atmosphere at a second predetermined temperature lower than the first predetermined temperature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for forming a resist pattern according to the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing a process of forming a resist pattern according to the embodiment.

First, a chemically amplified negative electron beam resist (for example, SAL601 manufactured by Shipley Co.) is applied on the above-mentioned processed film of a substrate (for example, GaAs substrate) 1 on which a processed film (for example, SiO ₂ ) is formed. For example, a resist layer 3 having a thickness of, for example, 2 μm is formed (see FIG. 1A). Then 1
Pre-baking is performed for about 1 minute in an atmosphere of 45 ° C. The chemically amplified resist contains an acid, and when baked, a cross-linking reaction occurs continuously using the acid as a catalyst.

Next, a chemically amplified negative electron beam resist is applied on the resist layer to form a resist layer 5 having a thickness of, for example, 0.5 μm (see FIG. 1B). Then 6
Pre-bake is performed for about 1 minute in an atmosphere at 5 ° C.

[0012] Next acceleration voltage by using an electron beam of 50 KV, pattern size 0.2 under the conditions of irradiation dose 15 .mu.C / cm ²
A space pattern of μm is drawn (see FIG. 1C). Thereafter, using a hot plate set at 115 ° C., a post-exposure bake process is performed in the air for about 2 minutes.

Next, the substrate is immersed in, for example, a tetramethylammonium hydroxide-based developer having an alkali concentration of 0.27 for 10 minutes to carry out a development process, thereby forming a fine resist pattern 6 for lift-off. (See FIG. 1D).

As described above, in the present embodiment, the lower resist layer 3 is prebaked at a relatively high temperature (for example, 145 ° C.), and the upper resist layer 5 is prebaked at a relatively low temperature (for example, 65 ° C.). Accordingly, the cross-linking rate of the lower resist is reduced to lower the sensitivity, and the cross-linking rate of the upper resist layer 5 is increased to increase the sensitivity. When exposed and developed in this state, the lower resist layer 3 having a lower crosslinking rate has a higher dissolution rate, and the finished dimension is significantly reduced from the designed dimension (exposure dimension) (FIG. 1 (c)). ), (D)). However, the upper resist layer having a high cross-linking rate is almost finished as designed. For this reason, it is possible to form a fine resist pattern for lift-off with high accuracy and excellent resolution without pattern collapse.

In the above embodiment, the same effect can be obtained if the pre-bake temperature of the resist layer 3 is in the range of 140 to 150 ° C. The same effect can be obtained if the pre-bake temperature of the resist layer 5 is in the range of 60 to 70 ° C.

In the above embodiment, a negative electron beam resist is used as the resist in the chemical amplification system. However, the present invention is not limited to the chemical amplification system, and a negative resist having sensitivity to electron beams may be used. Needless to say.

[0017]

As described above, according to the present invention, it is possible to form a fine resist pattern for lift-off with excellent resolution and high accuracy.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a configuration of an embodiment of a method for forming a resist pattern according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate to be processed 3 resist layer 5 resist layer 6 resist pattern

Claims (3)

[Claims] 1. A method for forming a resist pattern, comprising: a step of sequentially forming first and second resist layers having different sensitivities on a substrate to be processed; and a step of exposing and developing. . 2. The first resist layer is formed by applying a resist on a substrate to be processed and then performing a pre-bake in an atmosphere at a first predetermined temperature, and the second resist layer is formed by applying the first resist layer to the first resist layer. 2. The method according to claim 1, wherein after the resist is applied on the resist layer, the resist pattern is formed by pre-baking in an atmosphere at a second predetermined temperature lower than the first predetermined temperature. 3. The method according to claim 1, wherein a negative electron beam resist is used for forming the resist layer.