JPS61105875A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to form correct wiring patterns by a method wherein a resist film, which is formed on the surface of the substrate, is removed in the interior of a closed and heated high-pressure container by a lift-off method. CONSTITUTION:Before a photo resist film 16is formed on a gallium arsenid semiconductor substrate 11, openings 14a and 14b are formed on insulating films 13. Subsequently, second openings 17a and 17b are formed and metal wiring layers 15 consisting of gold and germanium are formed by evaporation on the surface of the substrate 11. These are dipped in a resist dissolving liquid 19 in the interior of a closed container 18, which is heated by a heating coil L at high temperatures. The pressure in the interior of the closed container 18 rises by heating and is turned into a high pressure, the biling point of the resist dissolving liquid 19 rises, a reaction of the resist film 16 to dissolution is rapidly promoted and the gold-germanium layers 15 other than metal layers 15a and 15b, which are evaporated on the surface of the substrate 11, are securely removed along with the resist film 16. Accordingly, ohmic metal wirings 15a and 15b consisting of gold and germanium are correctly patterned corresponding to the prescribed wiring patterns. As a result, the highly reliable semiconductor device can be manufactured.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention is used for forming wiring/mother turns on the surface of a gallium arsenide (GaAs) semiconductor substrate on which semiconductor elements such as ■S FETs are formed. The present invention relates to a method for manufacturing a semiconductor device.

[Technical background of the invention and its problems]

Generally, in the case of a semiconductor device using a silicon substrate, aluminum can be used as the ohmic metal that requires ohmic contact. This is because there are not many levels on the silicon surface, and the height of the Schottky barrier can be easily adjusted by changing the type of metal, and the implantation limit (solid solution limit) of impurity ions is approximately 1020m-2
This is due to the fact that ohmic contact can be obtained due to the tunnel effect.

On the other hand, when manufacturing a semiconductor device using a compound semiconductor substrate such as gallium arsenide, the surface level is set in the forbidden band that exists two-thirds from the bottom of the energy conductor. Therefore, as in the case of silicon,
Even if the ohmic metal is changed, the height of the Schottky barrier does not change easily.
Since it is about 2, it is difficult to utilize the tunnel effect. For this reason, a method of obtaining ohmic contact by depositing gold-dalmanium (AuGe) to form an alloy has been considered.

Here, in the case of the aluminum electrode used in the silicon substrate, an ohmic electrode can be obtained by etching a wiring pattern formed by a well-known photolithography method. In the case of gold germanium electrodes used in substrates, the following problems arise when etching is performed in the same manner as in the case of silicon.

(1) If wet etching is performed using a gold-rumanium solution, the surface of the gallium arsenide substrate will be damaged.

(2) Gold and rumanium are difficult to remove by RIE (dry etching).

(3) In the case of suttering, the selectivity between gold germanium, the protective film, and the gallium arsenide substrate is low.

For this reason, when using a gallium arsenide substrate (GaAs), a lift-off method is used in which a resist stripping solution with low etching strength, such as acetone, is heated under normal pressure. It is not possible to easily remove the resist from unnecessary parts.

Therefore, methods have been considered to apply ultrasonic waves to promote the resist peeling during etching using the lift-off method, or to promote the peeling using water pressure from water spray treatment. G
There is a risk that the aAs substrate may crack, and even if water spray is used in combination with the latter, the peeling effect is not sufficient. Therefore, until highly reliable etching is completed, a lot of time and manpower are required for one inspection using a blunt microscope, which is an obstacle to the mass production of semiconductor devices using gallium arsenide substrates.

[Purpose of the invention]

This invention was made in view of the problems mentioned above.
To provide a semiconductor device that enables formation of an accurate wiring pattern through highly reliable etching in a short time without the need for two inspections before etching is completed when forming a wiring arm turn using a lift-off method. The purpose is to provide a manufacturing method for.

[Summary of the invention]

That is, in the method for manufacturing a semiconductor device according to the present invention, a compound semiconductor substrate on which a resist film and a wiring metal layer are formed, in which openings are formed corresponding to wiring lines and turns, is heated in a closed container at high temperature and high pressure. By immersing it in the Lennost solution, the dissolution reaction of the resist film is strongly promoted.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Figures 1 (A) to (D) and Figure 2 show the manufacturing process. First, as shown in Figure (A), the surface of a compound semiconductor, for example, gallium arsenide (GaAs) semiconductor substrate 1 is coated. In this method, a high concentration layer and a low concentration MN are formed in accordance with a predetermined circuit pattern using an impurity diffusion technique or the like. Next, a gate electrode 12 is formed corresponding to the dirt position of the circuit/mother turn made of N using the above impurity diffusion technique, and an insulating film (Si) is formed on the surface of the substrate 11 including the dirt electrode 12.
n2) form 7 s. Then, in this insulating film 13, first openings (contact holes) 14a, 14b are formed by photoetching or the like in correspondence with a predetermined wiring pattern.
A photoresist film 16 is formed on the surface of the substrate 11 including the openings 14m and 14b, as shown in FIG. Form.

Next, as shown in FIG. 1(C), the photoresist film 16 is provided with the openings 14a of the insulating film 13.

Second openings (contact holes) 17a and 17b corresponding to the wiring/mother turn following 14b are formed, and this opening 17
The aforementioned gold-dalmanium metal wiring layer (AuGa) 15 is formed by vapor deposition on the surface of the substrate 11 including regions a and 17b. Then, the gallium arsenide substrate 11 on which the metal layer 15 has been formed by vapor deposition is immersed in a resist solution 19 such as acetone stored in a closed container 18 heated to a high temperature by a heating coil L, for example, as shown in FIG. .

In this case, the pressure inside the closed container 18 increases due to heating and becomes high pressure. Therefore, the boiling point of the resist solution (acetone) 19 is 563°C under atmospheric pressure (1 atm).
However, its boiling point under high pressure increases as shown below.

In general, the rate constant that represents the rate of a chemical reaction is
-Ea/RT. Here, T is the absolute temperature, Ea is the activation energy, R is the gas constant, and A is the constant. Although these values vary depending on the type of resist and the solution, the above reaction rate usually increases by 2 to 3 for every 10°C increase in the temperature of the solution.
It's twice as fast.

As a result, the dissolution reaction of the resist film 16 is promoted intensely and quickly, and as shown in FIG. 1(b),
The gold-dalmanium layer 15 other than the metal layers 15h and 15b deposited on the surface of the substrate 11 is reliably removed together with the resist film 16. Here, the above gold germanium (
For example, lOa
tm.

When carried out under the condition of 144.5°C, the above resist film 1
6 can be reliably peeled off in a few minutes, and etching of 100 layers can be achieved by the lift-off method. Therefore, gold germanium (AuG) is
The ohmic metal wirings 15m and 15b consisting of e) can be accurately turned, making it possible to manufacture a highly reliable semiconductor device.

In the above embodiment, the case where acetone is used as the resist dissolving solution has been described, but the same effect can be obtained by using a dissolving solution such as methyl, ethyl, ketone, etc.

〔Effect of the invention〕

As described above, according to the present invention, when patterning four turns of predetermined wiring on the surface of a compound semiconductor substrate by the lift-off method, the photoresist film is removed using a high-temperature, high-pressure solution in a sealed heating container. Therefore, the dissolution reaction for the resist film can be strongly promoted.
A short and reliable no'? Turning allows manufacturing of highly reliable semiconductor devices. Thereby, mass productivity of semiconductor devices using compound semiconductor substrates can be improved.

[Brief explanation of drawings]

1(A) to υ) are cross-sectional configuration diagrams showing a method for manufacturing a semiconductor device according to an embodiment of the present invention in the order of manufacturing steps;
FIG. 2 is a diagram showing the etching process by high-pressure lift-off in the above manufacturing process. 11... Gallium arsenide semiconductor substrate, 15... Wiring metal layer, 16... Photoresist film, 17a, Ilb...
・Open hole, 18... Sealed container, 19... Resist solution, L... Heating coil.

Claims (1)

[Claims] means for forming a resist film in which openings are formed corresponding to a wiring pattern on the surface of a compound semiconductor substrate; means for forming a wiring metal layer on the surface of the semiconductor substrate on which the resist film is formed; 1. A method for manufacturing a semiconductor device, comprising means for removing a resist film formed on a surface of a substrate by a lift-off method in a sealed heated high-pressure container.