JPS60247948A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a high accurate and fine wiring on a substrate by a method wherein photosensitive polyimide is used as a lift-off material, in case that the wiring is formed by means that metal is deposited partially onto the substrate. CONSTITUTION:Photosensitive polyimide material 5 is applied as a mask for lift- off onto the surface of a substrate 1. Thereafter, sensitization is performed using ultraviolet ray through a mask 3. After sensitization, development is performed and unexposed part of a photosensitive polyimide film is dissolved and removed, and forms a patternized photosensitive polyimide layer 6. Next, metal such as Al and the like, is evaporated on all over the surface and Al layer 7a is deposited directly to the portion where polyimide film 6 is not formalized and Al layer 7a is deposited to the portion where polyimide film is formalized. Electrodes which are consist of the required patterning of Al layer 7a is obtained by means of removing the polyimide film at the same time as the Al layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technology for forming wiring in a semiconductor device, and in particular to a technology for microfabrication of wiring using photosensitive polyimide.

[Background technology]

2. Description of the Related Art As semiconductor devices become smaller and more highly integrated, fine processing of wiring formed on the surface of a substrate has become a problem.

In the conventional method of forming electrodes (wirings) in which the metal is etched through a photoresist mask formed on a metal vapor-deposited film, side etching errors occur because the metal film is etched in the lateral direction. Since 1
The lift-off method is used to form fine wiring with a width of .mu.m (Page 80-P83 of the January 1983 issue of Denshi Materials).

According to this lift-off method, as shown in FIG. 1, a photoresist (positive photoresist) film 2 is formed on a substrate 1 on which wiring is to be formed, exposed to light through a mask 3, and the exposed portion of the photoresist is removed by development. . After that, metal 4 is deposited over the entire surface, and the remaining photoresist is then dissolved and removed simultaneously with the metal part above it.
A metal film pattern as shown in FIG. 3 is obtained.

Conventionally, cyclized rubber-based resists used as positive photoresists do not have sufficient heat resistance, and the resist softens due to the heat of vapor deposition (approximately 150°C) when metal is vapor-deposited, as shown in Figure 2. This causes "sagging" 2a, making it difficult to cut the metal and reducing the dimensional accuracy of the pattern.

If a negative resist is used instead of a positive resist, it has relatively high heat resistance, but the processability is poor due to the fact that light wraps around the wiring portion, and the pattern is also susceptible to sagging.

Polyimide resin is a material that can be used in the lift-off method and has excellent heat resistance. However, in order to pattern polyimide resin, a separate layer of photoresist is layered on top of the photoresist and etching is performed using this as a mask, which reduces dimensional accuracy and complicates the process for the same reasons as mentioned above. This was made clear by a review by a person.

[Purpose of the invention]

The present invention has been made in view of the above points,
The purpose is to provide a wiring processing technology using a lift-off method that uses materials with excellent heat resistance and allows fine processing with high precision.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, when metal is partially deposited on a substrate to form wiring, a photosensitive polyimide film, which is an insulating film that is photosensitive and heat resistant, is applied over the entire surface of the substrate, and a portion of it is exposed and developed. Therefore, by forming a photosensitive polyimide pattern that excludes the portion where wiring is to be formed, depositing metal to cover it, and then removing the photosensitive polyimide, a fine pattern is formed on the substrate with high precision. Thus, the above object can be achieved.

〔Example〕

FIG. 4 to FIG. 7 are process cross-sectional views showing an embodiment of this process.

In the following description, a case will be described in which a photosensitive polyimide resin developed by the present inventor is used for an insulating film having photosensitivity and heat resistance, but the present invention is not limited thereto. Furthermore, hereinafter, the photosensitive polyimide resin will also be referred to as photosensitive polyimide.

Each step will be explained in detail below.

(1) Referring to FIG. 4, a photosensitive polyimide material 5 is coated on the surface of the substrate 1 as a lift-off mask.

When applying the photosensitive polyimide material, a photosensitive polyimide film 5 is formed by applying a photosensitive polyimide having a resin concentration of 14% and a viscosity of 30 poise using a spinner at a rotational speed of 300 rpm for 30 seconds.

This photosensitive polyimide is made from polyamic acid, a bisamide photocrosslinking agent, an amine compound having a carbon-carbon double bond, and a compound containing one or more hydroxyl groups in the molecule and whose boiling point is 150°C or higher at normal pressure. In the photosensitive polymer composition, a polyamic acid whose structure is represented by a repeating unit of the general formula (wherein R' represents a divalent aromatic ring-containing organic group or a silicon-containing organic group) A photopolymer composition is used. After coating with a spinner, prebaking is performed at 80° C. for 20 minutes. At this time, the thickness of the photosensitive polyimide film is approximately 4.5 μm.

Thereafter, as shown in FIG. 4, exposure is performed using ultraviolet light of 350 to 430 nm (nanometers) through a mask 3, as in the case of a normal photoresist.

The appropriate photosensitive energy is 100 mJ/-, but considering pattern processing accuracy, etc., it is 20 to 200 mJ/d.
can be arbitrarily selected within the range.

Since the photosensitive polyimide 5 used here is of a negative type, when light enters through other than the dark areas (bright areas) of the mask 3, only those areas undergo a photoreaction and begin to polymerize and harden.

(2) NMP (n-methylpyrrolidone) after exposure
: Water = 4:1 (volume ratio) developer solution at 25°C.

Immerse for 10 minutes and develop. At this time, the film thickness of the photosensitive polyimide is approximately 4 μIn. By this development, the unexposed portions of the photosensitive polyimide film are dissolved and removed, resulting in a patterned photosensitive polyimide layer 6 as shown in FIG. In this case, it is dissolved and removed so that it enters the bottom portion 6a of the portion exposed to light. This occurs because the photosensitive polyimide film is a surface-curing type, so the surface is first cured by the photoreaction of ultraviolet rays, and the bottom part is not completely cured. Therefore, part of the unexposed area at the bottom is dissolved by the developer and the fifth layer is exposed.
The shape is as shown in the figure, that is, the opening is narrow at the top and wide at the bottom.

Thereafter, heat treatment is performed at 200°C for 30 minutes and at 400°C for 30 minutes to harden the polyimide film 6 having a heat resistance of 400°C.

(3) A metal such as aluminum is deposited (or sputtered) on the entire surface, and as shown in FIG. 6, an aluminum layer 7a is directly deposited on the areas where the polyimide film 6 is not formed, and the areas where the polyimide film is formed are Then an aluminum layer 7b is deposited thereon. An aluminum electrode is formed by a so-called lift-off method.

(4) By dissolving the polyimide film using a plasma asher method or a suitable organic solvent and simultaneously removing the aluminum layer thereon, the aluminum layer 7a with the desired pattern is formed into an electrode, as shown in FIG. get.

〔effect〕

According to the present invention described in the above embodiments, the following effects are brought about.

(1) Photosensitive polyimide itself can not only be used as a lift-off material, but also has a heat resistance of 400° C. or higher after curing (Electronic Materials, January 1983, p. 80). Therefore, it can withstand high temperature vapor deposition and light radiation, and the pattern Kl'-sag.
Further, since the adhesiveness with the substrate 1 is good, a highly accurate fine pattern can be obtained.

(2) Due to the photoreaction through the mask, the bottom part is widened and etched, so that the deposited metal 7 is etched as shown in Figure 6.
The "cut" between a and 7b is good, and fine processing with high accuracy, for example, fine processing with a width of 0.4 to 0.5 μm is possible.

[Example 2] FIGS. 8 to 15 show another example using the riff-off method according to the present invention, and a GaAs LSI FET
FIG. 3 is a cross-sectional view of the process.

Regarding GaAs LSI FETs, a technology to bury a p-type layer under the gate has been proposed in order to simultaneously achieve high speed and high integration in GaAs integrated circuits (Electronic Materials 1).
Although the process is introduced in January 1983 issue P80-83 PM-embedded FET for GaAs LSI (Yasunari Umemoto et al.), this example mainly describes the ultra-fine electrode formation technique using the lift-off method.

(1) A semi-insulating GaAs substrate 8 is prepared, and a mask 9 made of, for example, chemical vapor deposition (CVD) or Sin is formed on the surface as shown in FIG.
Ion implantation (150KeV, I Xl 013
atms/i).

(2) Remove the gate mask and implant Si ions at a slightly lower concentration (150 KeV) as shown in FIG.

5X10' snow/d).

(3) Annealing is performed at 850° C. for 20 minutes to diffuse Si into the substrate 8 to form n+ type regions (source, drain) 10 and n− type region (channel portion) 11 as shown in FIG.

(4) As shown in FIG. 11, a mask 12 is formed to cover the source and drain, and Be ion implantation is performed (125-175 KeV, 20×10”y
n-”), followed by capless annealing (7
00°C for 20 minutes), a p
! A buried layer 13 is formed.

(5) Remove the mask material, coat the entire surface with photosensitive polyimide, and expose and develop it through a mask with a predetermined pattern to form a lift-off mask 14 with window openings for the source and drain portions as shown in FIG. . Formation of this photosensitive polyimide.

The processing is carried out in the same manner as steps (1) and (2) of Example 1 above.

(6) Perform the vapor deposition method or sputtering method on the entire surface and
As shown in Figure 3, 5 is a metal layer 15 for electrode (AuGe-N
i-Au) was sequentially deposited and alloyed at 400°C for 30 minutes to obtain ohmic properties.

By dissolving the photosensitive polyimide and removing it simultaneously with the metal layer thereon, metal electrodes S and D are left only on the source and drain portions.

(7) After coating the entire surface with photosensitive polyimide 16 and opening the gate portion by exposure and development, the electrode metal (T
i-Pt-Au) 17 is formed.

(8) The unnecessary portion of the metal layer is removed by dissolving and removing the photosensitive polyimide 16, leaving the Schottky gate electrode G. Fig. 15 shows the microelectrode S.

It shows the completed form of a p-layer embedded FET having D and G.

〔effect〕

According to the present invention described in the embodiments above, by using photosensitive polyimide as an off-cutting material, highly accurate fine electrodes can be formed and a high-speed, highly integrated semiconductor device can be provided.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the present invention can be applied to the formation of fine electrodes for LSIs and very large scale integrated circuits.

[Application field]

The present invention can be applied to semiconductor devices having fine wiring in general.

The present invention is particularly applicable to fine wiring such as GaAs FET, LS
This is effective when applied to I wiring.

[Brief explanation of drawings]

1 to 3 are process cross-sectional views showing an example of a conventional lift-off method. FIGS. 4 to 7 are cross-sectional views of an electrode forming process showing an embodiment of the present invention. FIG. 8 to FIG. 15 are FE showing another embodiment of the present invention.
FIG. 3 is a process cross-sectional view of the electrode formation process of T. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Photoresist, 3... Mask, 4... Aluminum, 5... Photosensitive polyimide film, 7... Metal layer, 8... GaAs substrate, 9...・Mask, 10...n+ type region source, drain), 1
DESCRIPTION OF SYMBOLS 1... N-type region (channel part), 12... Mask, 13... P-type buried layer, 14... Photosensitive polyimide film, 15... Metal layer, 16... Photosensitive Polyimide film, 17...metal layer. Figure 1 Figure 3 Figure 5 Figure 6 Figure 7 Figure 7 Figure 8 Figure 11

Claims (1)

[Claims] 1. When partially depositing metal on the surface of a semiconductor substrate to form a metal layer in a predetermined pattern, a photosensitive and heat-resistant insulating film is applied over the entire surface of the substrate, and one of the A pattern of a photosensitive and heat-resistant insulating film is formed by exposing and developing the photosensitive and heat-resistant insulating film from which the metal layer is to be formed, and after depositing metal on the entire surface, the photosensitive and heat-resistant A method for manufacturing a semiconductor device, comprising forming a metal layer in a desired pattern on a substrate by removing a heat-resistant insulating film. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the photosensitive and heat-resistant insulating film is made of a photosensitive polyimide 2-based resin, and the metal layer is formed as an electrode or wiring of the semiconductor device. .