JP2000331955A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or relax the fact where electrodes which comprise an Au (gold) or whose main component are Au chemically react to cause an accident with a semiconductor device, with a simple means. SOLUTION: The surfaces of a source electrode 2, drain electrode 3, and gate electrode 4 which are formed of Au or contain Au are covered with any of methyl-mercaptan, etyl-mercaptan, propyl-mercaptan, and isoproplyl mercaptan, a plurality of kinds of selected material, or a self-aggregation film which is generated by chemically adsorping a component dissociated from those all kinds of material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which prevents electrochemical corrosion of electrodes or wirings mainly composed of Au (gold) or Au and a method of manufacturing the same.

Generally, a GaAs-FET (field)
In a semiconductor device such as an effect transistor, a material of a source electrode or a drain electrode is
Au-based metals have been used.

In the semiconductor device, the surface of a semiconductor or an electrode is protected from moisture containing harmful chemical substances.
Multiple coating with an iN film or a polyimide film is also performed.

However, when the surface of the semiconductor device is covered with the insulating film as described above, the moisture adsorbed on the underlayer is confined at the interface between the surface and the covering film, and furthermore, the insulating film is formed. It is difficult to prevent moisture that penetrates from the surface of the surface or a portion where the coverage is poor.

FIG. 3 is a cutaway side view of a main part for explaining a standard GaAs-FET. In FIG.
s substrate, 2 a source electrode made of AuGe / Ni / Au, 3 a drain electrode also made of AuGe / Ni / Au, 4 a gate electrode made of Ti / Pt / Au, 5 a surface protection film made of SiN, 6 voltage V _ds adding a surface protective film made of polyimide, E ₁ between the source and drain
, And E ₂ denotes a power supply that generates a voltage V _gs applied between the gate and the source.

[0006] It is assumed that the same voltage is applied to each electrode of the illustrated FET, and if moisture containing a halogen element, for example, chlorine (Cl) permeates from the atmosphere, an anode is formed. Au on the drain electrode 3
Will result in a dissolution reaction. That is, a reaction of Au + 4Cl ⁻ → AuCl ₄ ⁻ + 3e ⁻ occurs.

The Au ions eluted as described above move to the gate electrode 4 along the potential gradient, and are reduced there to return to solid Au.
The solid Au precipitates toward the drain electrode 3 as indicated by the arrow in the figure. That is, a reaction of AuCl ₂ + e ⁻ Au + 2Cl ⁻ occurs.

[0008] The deposited Au grows and short-circuits between the gate electrode 4 and the drain electrode 3 to form an FET.
Will lead to destruction.

[0009]

SUMMARY OF THE INVENTION According to the present invention, it is possible to prevent or alleviate the occurrence of an accident in a semiconductor device due to a chemical reaction of Au or an electrode containing Au as a main component by simple means.

[0010]

According to the present invention, in order to prevent Au or an electrode containing Au as a main component from causing a chemical reaction through moisture, an organic molecule having a strong bonding force with Au is applied to a thin film on the surface of the electrode. The basic principle is to prevent Au from coming into contact with water due to the thin film organic molecules.

As described above, in the semiconductor device and the method of manufacturing the same according to the present invention, (1) Au or an electrode containing Au (for example, the source electrode 2,
The surface of the drain electrode 3 and the gate electrode 4: see FIG. 1) is methyl mercaptan, ethyl mercaptan, propyl mercaptan, or isopropyl mercaptan;
Alternatively, it is characterized by being covered with a self-assembled film generated by chemically adsorbing components dissociated from a plurality of selected types of substances, or all types of the substances, or

(2) A semiconductor substrate (for example, GaAs) on which Au or an electrode containing Au (for example, a source electrode 2, a drain electrode 3, and a gate electrode 4: see FIG. 1; the same applies hereinafter) is formed.
Substrate 1) was replaced with methyl mercaptan, ethyl mercaptan,
Propyl mercaptan, any substance of isopropyl mercaptan, or a plurality of selected substances,
Alternatively, a self-assembled film is formed by immersing in an organic solvent (for example, solution 7) containing all kinds of the substance to chemically adsorb components dissociated from the substance on the electrode surface. Do or

(3) The method according to (2), wherein at least an electrode of the semiconductor substrate is exposed to vapor of an organic solvent containing the substance instead of immersing the semiconductor substrate in the organic solvent. Or

(4) In the above (2) or (3), the organic solvent is any one of methyl alcohol, ethyl alcohol, propyl alcohol and isopropyl alcohol,
Alternatively, it is characterized in that it is a selected plural kinds of mixed liquids or all kinds of mixed liquids.

By adopting the above-mentioned means, the time for the occurrence of a short-circuit failure caused by corrosion of Au can be extended by about one digit, and the thin film of organic molecules utilizes the chemical adsorption phenomenon of molecules. Since the electrode is formed uniformly and densely without being affected by the processed shape of the electrode and the roughness of the surface, it is possible to favorably suppress the corrosion of Au.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are cutaway side views of a main part showing a semiconductor device and a processing apparatus (only FIG. 1) for explaining an embodiment of the present invention. The description will be made with reference to the drawings such as FIG. Note that the same symbols as those used in FIG. 3 represent the same parts or have the same meanings.

FIG. 1 (A) 1- (1) A resist film having openings in a source electrode formation region and a drain electrode formation region of a GaAs substrate 1 by applying a resist process in lithography technology. To form

1- (2) Thickness 1000 [Å] by applying a vacuum deposition method
An AuGe film / Ni film / Au film having a thickness of / 100 [Å] to 200 [Å] / 2000 [Å] is formed.

1- (3) AuGe film / Ni film / Au film by applying a lift-off method of dissolving and removing the resist film formed in step 1- (1) by dipping in a resist stripping solution The source electrode 2 and the drain electrode 3 are formed.

1- (4) A resist film having an opening in a region where a gate electrode is to be formed on the GaAs substrate 1 is formed by applying a resist process in the lithography technique.

1- (5) A thickness of 500 [Å] /
A Ti film / Pt film / Au film of 1000 [Å] / 3000 [Å] is formed.

1- (6) Ti film / Pt film / Au film by applying a lift-off method of dissolving and removing the resist film formed in step 1- (4) by dipping in a resist stripping solution Is formed.

1- (7) For example, ethyl alcohol (C ₂ H ₅ OH) and ethyl mercaptan (C ₂ H ₅ SH) are mixed in the container 8 so that the mixing volume ratio becomes 1: 0.05. And the semiconductor device is immersed for about 5 minutes.

1- (8) The semiconductor device taken out of the solution 7 is housed in a thermostat,
For example, drying is performed for 10 minutes while maintaining a temperature of about 100 ° C. by flowing nitrogen gas.

See FIG. 2 2- (1) Chemical vapor deposition
The surface protective film 5 made of SiN having a thickness of, for example, 1000 [Å] is formed by applying the position (CVD) method.

2- (2) A surface protection film 6 made of polyimide having a thickness of, for example, 2 [μm] is formed by applying the spin coating method.

Through the above steps, Au on the surface of the source electrode 2, the drain electrode 3, and the gate electrode 4 and the mercaptan react by Au + C ₂ H ₅ SH → Au SC ₂ H ₅ + ／ H ₂ chemical reaction. Then, moisture and oxygen adsorbed on the Au surface are released, and a dense self-assembled film having a strong bonding force mediated by sulfur (S) in the mercaptan is generated.

The chemicals for forming a self-assembled film on the surface of Au are limited, and any one of methyl mercaptan, ethyl mercaptan, propyl mercaptan, and isopropyl mercaptan, or a plurality of substances selected from the above substances Alternatively, all the above-mentioned types of substances can be used.

This self-assembled film is made of, for example, AuSC ₂ H ₅
A thin film having a thickness of about 5 to 6 molecules,
Since it is a thin film having a thickness of 20 [以下] or less and is chemically extremely stable, there is no inconvenience such as deterioration or peeling during the subsequent steps. In addition, the self-assembled film is A
AuSC ₂ H when u and methyl mercaptan are used.
_{The value is 5} , for example, when Au and ethyl mercaptan are used, the structure is such that AuS has an ethyl group.

In order to confirm the adsorption effect of the self-assembled film on Au, a corrosion resistance evaluation test was performed on the GaAs-FET described in the above embodiment.

Here, the load conditions given to the FET were as follows: temperature in a dedicated thermostat: 85 [° C.] Relative humidity in a dedicated thermostat: 85 [%] Drain-source voltage V _ds : 10 [V] Gate / source voltage V _gs : −4 [V].

There are 10 samples according to the present invention and 10 samples according to the prior art. The FET, which is a sample, fails when the above-described voltage is applied and it is electrically short-circuited. And the time until that was measured.

According to the measurement, the failure occurrence time of the sample according to the prior art: 82 hours!
136 [hours] Failure occurrence time of the sample according to the present invention: 963 [hours] to 1
215 [hours] were obtained, and it was confirmed that by performing the processing according to the present invention, the time until a failure occurred was extended by about one digit.

The present invention is effective in the case of Au or an electrode containing Au in relation to a chemical that forms a self-assembled film, but in the case of an electrode containing Au, when Au is 50 [atomic%] or more. The effect appears remarkably.

The concentration of the mercaptan in the organic solvent is preferably at least 0.01% by volume.

The present invention is not limited to the above-described embodiment, but can realize many modifications within the scope of the claims. For example, the relative concentration of mercaptan may be ethyl The volume was set to 0.05% [%] with respect to alcohol, but this may be appropriately selected as long as the pungent odor of mercaptan can be reduced.

[0037]

According to the semiconductor device and the method for manufacturing the same of the present invention, the surface of Au or an electrode containing Au is formed of methyl mercaptan, ethyl mercaptan, propyl mercaptan,
It is covered with a self-assembled film formed by chemically adsorbing any substance of isopropyl mercaptan, a plurality of selected substances, or a component dissociated from all the substances.

By adopting the above configuration, the time for the occurrence of the short-circuit failure caused by the corrosion of Au can be extended by about one digit, and the thin film of the organic molecule utilizes the chemical adsorption phenomenon of the molecule. Since the electrode is formed uniformly and densely without being affected by the processed shape of the electrode and the roughness of the surface, it is possible to favorably suppress the corrosion of Au.

[Brief description of the drawings]

FIG. 1 is a cutaway side view showing a main part of a semiconductor device and a processing apparatus for explaining an embodiment of the present invention.

FIG. 2 is a fragmentary side view showing a semiconductor device for explaining an embodiment of the present invention;

FIG. 3 is a fragmentary side view for explaining a standard GaAs-FET.

[Explanation of symbols]

Reference Signs List 1 GaAs substrate 2 Source electrode composed of AuGe / Ni / Au 3 Drain electrode composed of AuGe / Ni / Au 4 Gate electrode composed of Ti / Pt / Au 5 Surface protective film composed of SiN 6 Surface protective film composed of polyimide 7 Solution 8 Container E ₁ Power supply that generates voltage V _ds applied between source and drain E ₂ Power supply that generates voltage V _gs applied between gate and source

Continued on front page F-term (reference) 4M104 AA05 BB09 BB11 BB15 CC01 CC03 DD34 DD43 DD68 DD89 EE06 EE12 EE17 EE18 GG12 HH20 5F033 GG02 HH07 HH13 HH18 MM08 PP19 QQ00 QQ41 RR06 RR21 RR22 SS00 GS01 SS01 SS01 SS01 GB01 GT03 GT04 GV06 HC11 HC19

Claims (4)

[Claims] 1. The method according to claim 1, wherein the surface of the electrode containing Au or Au is selected from the group consisting of methyl mercaptan, ethyl mercaptan, propyl mercaptan, and isopropyl mercaptan, a plurality of selected substances, and all kinds of the substances. A semiconductor device comprising a self-assembled film formed by chemically adsorbing a component dissociated from a substrate. 2. The method according to claim 1, wherein the semiconductor substrate on which Au or an electrode containing Au is formed is made of any one of methyl mercaptan, ethyl mercaptan, propyl mercaptan, and isopropyl mercaptan, or a plurality of selected materials, or all of them. A method of manufacturing a semiconductor device, comprising immersing in a kind of an organic solvent containing the substance to chemically adsorb components dissociated from the substance on the electrode surface to form a self-assembled film. 3. The method of manufacturing a semiconductor device according to claim 2, wherein, instead of immersing the semiconductor substrate in the organic solvent, at least electrodes of the semiconductor substrate are exposed to a vapor of an organic solvent containing the substance. . 4. The method according to claim 1, wherein the organic solvent is any one of methyl alcohol, ethyl alcohol, propyl alcohol, and isopropyl alcohol, or a mixture of a plurality of types selected from the group consisting of:
4. The method for manufacturing a semiconductor device according to claim 2, wherein the liquid is a mixture of all types.