JPH04290421A - Method of forming photoresist pattern suitable for liftoff method - Google Patents

Abstract

PURPOSE:To form a photoresist pattern suitable for liftoff method, where the under-cut shape can be made surely even to a thick resist film and besides the thickness and the length of the eaves of the undercut part can be controlled. CONSTITUTION:A positive resist 2 is made on the substrate 1, and this positive resist 2 is exposed and developed using a positive pattern mask 10mum in pattern width and is made into a resist pattern 2A. Then, negative resist 3 is applied all over the topside of the substrate 1, and then using a negative pattern mask 6mum in pattern width, the negative resist 3 on the above resist pattern 10mum in width is removed by exposure and development, and lastly only the resist pattern 2A is removed by dissolution by acetone or the like. The negative resist pattern in the shape of the undercut having eaves 4 can be obtained.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for forming a photoresist pattern suitable for lift-off method, and in detail,
The present invention relates to a method for forming a photoresist pattern using a photolithography technique suitable for a lift-off method applied to the manufacture of thin film devices such as semiconductor devices.

0002

[Prior Art] In the lift-off method, a photoresist (hereinafter referred to as "resist") film on a substrate on which a photoresist pattern has been formed by photolithography is used as a mask to form a vapor deposited film, and then the vapor deposited film on the resist is transferred to the resist. In this method, a deposited film pattern is formed on the substrate by removing the deposited film pattern on the substrate.

When applying this lift-off method, it is important that the cross-sectional shape of the resist, which serves as a mask on the substrate during vapor deposition, is formed so that the portion where the resist is removed has an undercut shape. That's true.

Conventionally, known methods for forming a resist with an undercut shape on a substrate include a single-layer resist method using chlorobenzene treatment and a two-layer resist method using two types of resists with different exposure sensitivities. ing.

FIG. 2 is a schematic process diagram of a single-layer resist method using chlorobenzene treatment, and the formation of a resist having an undercut shape is performed roughly in the following manner.

First, a positive resist layer 7 is formed on the substrate 1 [see FIG. 2(a)]. Next, this substrate 1 is immersed in chlorobenzene, and the positive resist layer 7 is divided into a layer 8 penetrated by chlorobenzene and a layer 9 not penetrated by chlorobenzene. As a result, a layer 8 having low solubility in the developer is formed on the surface of the positive resist layer 7 [see FIG. 2(b)]. Thereafter, the target pattern is exposed to ultraviolet light and developed. Due to this development, the pattern widths 10 and 11 of the resists of layers 8 and 9 are removed due to the difference in dissolution rate of layers 8 and 9 in the developer.
is different, and the pattern width 10 formed in layer 8 is different from the pattern width 10 formed in layer 9.
Since the pattern width 11 formed in the pattern is larger, an undercut shape is obtained [see FIG. 2(c)].

Further, FIG. 3 is a schematic process diagram of the two-layer resist method, and the formation of a resist having an undercut shape is performed roughly in the following manner.

First, a first resist layer 12 and a second resist layer 13 are formed on the substrate 1. At this time, a resist having higher sensitivity to exposure (hereinafter referred to as sensitivity) than the second resist layer 13 is used for the first resist layer 12.
See Figure 3(a)]. Thereafter, the target pattern is exposed to ultraviolet light and developed. Due to this development, due to the difference in dissolution rate in the developer between the first resist layer 12 and the second resist layer 13,
The pattern widths 14 and 15 of the resists removed in the first resist layer 12 and the second resist layer 13 are different, and the pattern width 15 formed in the first resist layer 12 is wider than the pattern width 15 formed in the second resist layer 13. 14 is larger, an undercut shape is obtained [Figure 3(b)
reference〕.

[0009]

[Problems to be Solved by the Invention] In the former single-layer resist method using chlorobenzene treatment described above, chlorobenzene is impregnated into the surface of the positive resist layer 7 to form a low-sensitivity layer (infiltrated layer 8). Therefore, there is a limit to the penetration of chlorobenzene, and there is also a limit to the thickness of the layer 8, so that the eaves 16 cannot be formed to a sufficient thickness, as shown in FIG. 2(c). Also layer 8 and layer 9 2
Since the difference in sensitivity between layers is small, exposure and development conditions are extremely limited, and there is a problem in that an undercut shape cannot be formed, especially in the case of a thick resist of 2 μm or more.

On the other hand, in the latter two-layer resist method, two types of resists with different sensitivities are used, but even in this case, there is a problem that exposure and development conditions are limited due to the limit of the sensitivity difference between the two layers. As shown in FIG. 3(b), the length of the eaves 16 varies depending on the exposure and development conditions for all resist layers (layer 1).
If the thickness of layer 2 and layer 13) is large, there is a problem that an undercut shape cannot be formed.

In view of the above-mentioned problems, the present invention makes it possible to reliably form an undercut shape even on a resist film thicker than that obtained by the above-mentioned method. The present invention provides a method for forming a photoresist pattern suitable for a lift-off method whose length can be controlled.

0012

[Means for Solving the Problems] In order to achieve the above object, a method for forming a photoresist pattern suitable for the lift-off method according to the present invention includes a method for forming a photoresist pattern using a first photoresist for forming an undercut on a substrate. After forming a resist pattern and forming a film of a second photoresist of a predetermined thickness using a developer and a solution different from that of the first photoresist, a second photoresist covering the first photoresist is formed. is removed according to the target pattern shape, and then the first photoresist is dissolved and removed.

[0013]

[Operation] In the present invention, two types of resists with different developing solutions and dissolving solutions are used, and an undercut shape is formed on the substrate in advance with the first resist, so that a reliable undercut shape can be formed.

[0014] The thickness of the resist film formed on the substrate and the thickness of the eaves of the undercut portion are determined according to the above 2.
By changing the viscosity of the seed resist and the spin coating rotation speed during coating, it can be controlled within a range of approximately 0.1 μm to 20 μm. Furthermore, the length of the eaves can be controlled within a range in which the eaves are not deformed by the weight of the eaves by changing the shape of the undercut formed on the substrate by the first resist.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic process diagram for explaining a method for forming a photoresist pattern suitable for the lift-off method according to the present invention. Hereinafter, the method for forming a photoresist pattern according to the present invention will be described in detail with reference to this figure.

First, a positive resist 2 was formed on a substrate 1. At this time, AZ1375 manufactured by Hoechst Japan Co., Ltd. was used as the positive resist 2, and the film was formed to a thickness of about 4 μm, and after the formation, it was heated (dried) at 85° C. for 30 minutes. [See Figure 1(a)]

Next, a positive pattern mask with a pattern width of 10 μm was used for exposure and development, and heating (drying) after development.
A resist pattern 2A having a width of 10 μm was formed. [See Figure 1(b)]

Next, a negative resist 3 was applied to the entire upper surface of the substrate 1. At this time, OMR83-35CP manufactured by Tokyo Ohka Co., Ltd. was used as negative resist 3, and the coating rotation speed was 1500.
Apply to a film thickness of approximately 1.5μm at rpm, and after application
Heating (drying) was carried out under the conditions of 30 minutes at °C. [See Figure 1(c)]

Thereafter, using a negative pattern mask with a pattern width of 6 μm, the negative resist 3 on the resist pattern 2A with a width of 10 μm was exposed, developed, and removed. [See Figure 1(d)]

Finally, only the resist pattern 2A was dissolved and removed using acetone or the like. As a result, an undercut shape 5 having an eave 4 with a thickness of approximately 4.5 μm is formed.
A negative resist pattern 6 was obtained. [See Figure 1(e)]

[0021] In the above embodiment, an optimal example was explained in which a positive resist was used as the first resist and a negative resist was used as the second resist. However, the present invention is not limited to this example, and the main points are as follows. , two types of resists may be used as long as they have different exposure sensitivities and use different developing solutions and dissolving solutions. Also,
The resist film thickness can be reduced to 20μ by changing the coating conditions.
The thickness can be changed to a desired thickness within about 100 m.

[0022]

As explained above, according to the method of forming a photoresist pattern suitable for the lift-off method according to the present invention, an undercut shape can be reliably formed even on a relatively thick resist film of about 20 μm. can. Also,
The thickness and length of the eaves of the undercut portion can be controlled, and an undercut of a desired shape can be formed.

[Brief explanation of the drawing]

FIG. 1 is a schematic process diagram for explaining a method for forming a photoresist pattern suitable for a lift-off method according to the present invention.

FIG. 2 is a schematic process diagram of a single layer resist method using chlorobenzene treatment.

FIG. 3 is a schematic process diagram of a two-layer resist method.

[Explanation of symbols]

Claims (1)

[Claims] 1. A photoresist pattern is formed using a first photoresist to form an undercut on a substrate, and a second photoresist pattern having a predetermined thickness different from the first photoresist and a developer and a solution is formed on the photoresist pattern. After forming a resist film, the second photoresist covering the first photoresist is removed according to the desired pattern shape, and then the first photoresist is dissolved and removed. A method for forming a photoresist pattern.