JPS625639A - Lift-off method - Google Patents

Abstract

PURPOSE:To enable the form action of a polyimide layer of an overhanging structure by patterning the first layer made of polyimide formed on a substrate in the desired shape, so forming the second layer made of polyimide having smaller bonding force to the substrate than the first layer to coat it, and then organically treating it. CONSTITUTION:The first layer 2 of polyimide is formed on a substrate 1. A resist film 3 is selectively laminated on the layer 2. then, the layer 2 of trapezoidal section directly under the film 3 is allowed to remain and the other layer 2 is removed by etching with an etchant. Then, after the film 3 on the layer 2 is removed, the second layer 4 and the second resist film 5 made of polyimide are formed on the substrate 1. Then, with the film 5 as a mask the layer 4 except the portion directly under the film 5 is removed by etching and the film 5 is then removed. Subsequently, the end 4a of the layer 4 secured to the substrate 1 is separated from the substrate 1, and formed in an overhanging structure for the substrate 1.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to a lift-off method.

(B) Prior art In current semiconductor processes, materials that are difficult to pattern using photoetching are often patterned using lift-off.

When using the lift-off method, a photoresist or the like is usually used as a lift-off material, but resist is altered by high-temperature heat treatment, so lift-off must be performed before heat treatment. However, if AI, 4, etc. are to be deposited again to improve bondability after alloying the electrode, it is necessary to perform lift-off after heat treatment.

If a metal or an oxide film such as Si02 is used as the lift-off material, lift-off is possible after heat treatment. However, if metal is used, there is a risk of contact with the base during heat treatment, and if the material is The oxide film cannot be used if it is used in areas other than lift-off materials.

Polyimide can be etched even after heat treatment at about 400° C. and is chemically stable, so it is a material that can be lifted off after heat treatment.

(c) The problem that the invention attempts to solve.
ical 5ociety: SQL ID-8
TATE5CIENCE AND TECHN
OLOGY), January 1983 + Vo
1, 130, No, 1゜As described in P129-P134, when polyimide is chemically etched, its cross-sectional shape becomes trapezoidal (Fig. 2), and an overhang structure (inverted trapezoidal cross-section) ideal for lift-off (Fig. Figure 3). In addition, (11) (12) ¥' in Figures 2 and 3
i indicates the substrate and lift-off material, respectively.

2) Means for Solving the Problems of Wholesalers The present invention has been made in view of the above-mentioned problems, and its structural feature is that it consists of polyimide on a substrate. a first step of forming an IJl spring; a second step of patterning the first layer into a desired shape; A third step of forming a second layer made of polyimide, which has a low adhesion to the substrate, on the substrate; The present invention further includes a fourth step of forming the second layer into an overhanging structure with respect to the substrate by performing an organic treatment after the step No. 43.

(e) Effect: It is possible to form a layer made of polyimide into an overhanging structure by using such a method.

FIG. 1(a) shows the first step, in which a substrate made of, for example, GaAs single crystal (for example, 5P-
A 111+2 layer of polyimide consisting of 510 is formed. Specifically, first, a V-run coupling material made of aminosilane was applied onto the substrate (Ij) using a spinner (5000 ~
6000pp+n, 30 seconds), then apply 5P-510 with a spinner (4000-50001)pm, 30 seconds]
do. Thereafter, by baking at 170 to 180° C. for 20 to 30 minutes, @1 layer (2) with a thickness of about 1 μm can be formed.

! ! Figure 1(b) shows the second step, in which a resist film (3) is selectively formed on the first layer (2) using photolithography technology.
) are stacked. After that, etching was carried out for 1 minute using an etching solution containing anhydrous and dofusine: ethylenediamine = 7:3 (third step), as shown in Figure 1 (C).
Ku resist film i31! ! [The other parts (2) are removed by etching, leaving the first part (2) of the trapezoidal shape below.

@17(d)r/if)”< 4 Engineering, El is shown,
11th + 2) Remove the upper Luzithro parrot 3) and the 9th board (1)
A second resist film (41) and a second resist film (6) made of polyimide are formed thereon.

Specifically, 5P-510 is applied with a spinner (4000 to 5000 ppm, 30 seconds) onto the trenchless substrate (11), and then baked at 170 to 180°C for 20 to 30 minutes. A second layer (4) of approximately 1 μm is formed, and then an eleventh layer is formed using photolithography technology.
1211 A second resist film (5) is selectively formed on the surface of the second layer 14).

In addition, the substrate (
1 (e) shows the fifth step. , the second V cyst f
Etching is performed using the i+51'i mask to remove the 21-+4+ portions other than those immediately below the resist film (5), and then the second resist film +5) is removed. Note that the above etching is performed using the same etching solution as in step #S3.

FIG. 1(f) shows the sixth step, in which the end portion (4a
) (4a) is peeled off from the substrate (1) to form an overhang structure with respect to the substrate [1j]. Specifically, first, ultrasonic cleaning is performed using acetone for 3 minutes to remove moisture on the substrate (1). Next, by performing ultrasonic cleaning for 3 minutes with boiled trichlorene, the adhesion between the substrate (11) and the second layer (4) is weakened, and the above-mentioned overhang structure is obtained.

Then, ultrasonic e-cleaning for 3 minutes with acetone, methanol/I/3
The trichlene on the substrate (1) is completely removed through the steps of ultrasonic cleaning for 5 minutes, running water for 5 minutes, isopropyl alcohol cleaning, and drying.

FIG. 1(g) shows the seventh step, in which a deposit (6) of gold or the like is deposited on the upper surface of the substrate (1). In such vapor deposition, the second j! lt+l end (
4a) (4a) is the rounded end portion (4a) where (4a) acts as a wall for a part of the substrate (1);
No vapor deposits (6) are deposited on top. Also, the second layer (4)
A step is formed between the deposited material (6) on the upper part and the deposited material (6) on the substrate +1), and the end part (4a) of @ 2 +1) is formed.
The bottom is an opening (7).

Figure 1 (h) shows the final step, in which the first and second layers (2
The H4 layer is removed and the deposit (θ) on the second layer (4) is selectively lifted off. In the etching process, the etching liquid reaches the second hole (t41) through the first hole (7), so that lift-off can be carried out efficiently.

In this example, 5P-510 manufactured by Toshi Co., Ltd. was formed on the substrate (1) as I1 Hibiki (2) using a coupling material, but for example, 5P-710 manufactured by Toshi Co., Ltd. ,8
If the material is a highly adhesive material such as polyimide such as No. 10, a coupling material is not necessary. Furthermore, when such a highly adhesive polyimide is used as the material for the first layer (4), it is necessary to use a low adhesive polyimide as the material for the second layer (4).

(G) Effects of the Invention According to the present invention, even when polyimide is used as the lift-off material, it is possible to obtain an overhang structure that is optimal for lift-off.

[Brief explanation of the drawing]

Figures 1 (a) to (h) are cross-sectional views showing steps of embodiments of the present invention, and Figures 2 and 3 show the shape of the lift-off material.
W+There is a drawing

Claims (1)

[Claims] (1) A first step of forming a first layer made of polyimide on a substrate, and a second step of patterning the first layer into a desired shape.
a third step of forming a second layer made of polyimide, which has a smaller adhesion force to the substrate than the first layer, on the substrate so as to cover the first layer patterned in the second step; and a fourth step of forming the second layer into an overhanging structure with respect to the substrate by performing an organic treatment after the third step.