JPH09213653A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesiveness of, a protective film, which consists of a nitride film or an oxide film, to the gold in a gold electrode and to prevent water or the like from being mixed in between the protective film and the gold electrode by a method wherein a film consisting of a material, which has a high adhesiveness to either of the gold electrode and the protective film, is interposed between the gold electrode and the protective film. SOLUTION: A film 4 consisting of a material, which has a high adhesiveness to either of a gold electrode 2 and a protective film 3, is interposed between the gold electrode 2, which is formed on a semiconductor substrate 1, and the film 3, which consists of a silicon nitride film or a silicon oxide film. As this film 4, a silicon film is selected to be concrete. The silicon film formed by a vacuum deposition method or a plasma CVD method makes an eutectic with the gold in the gold electrode 2 at a comparatively low temperature when the film 3 is formed or by a heat treatment in the following process and is bonded strongly to the electrode 2, while as the silicon film and the film 3 have a high adheveness, the electrode 2 and the film 3 can be made to bond together via the silicon film and the silicon film is the optimum film as the film 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a protective film made of a nitride film or an oxide film for protecting the surface of a semiconductor device using gold as an electrode metal, and more particularly to an electrode metal and a protective film. The present invention relates to a semiconductor device having improved adhesiveness.

[0002]

2. Description of the Related Art A semiconductor substrate on which elements such as transistors and resistors are formed is covered with a protective film such as a nitride film or an oxide film in order to physically and chemically protect the surface of the semiconductor substrate.

On the other hand, in gallium arsenide ICs, gold is generally used as an electrode metal. However, gold is the most chemically stable of the metals, and it is hard to form a passivation, etc., and is bonded to a protective film such as a nitride film only by Van der Waals force. Therefore, the adhesion between the protective film and the gold electrode is very weak.

[0004]

The protective film, which has weak adhesion to the gold electrode, cannot sufficiently prevent invasion of moisture and the like, which causes a problem in reliability of the semiconductor device. Further, when the semiconductor device is sealed with resin, there is a problem that the force of peeling the protective film acts due to the contraction of the resin, and the protective film is easily cracked or peeled off. The present invention provides a semiconductor device which improves adhesion between a protective film made of a nitride film or an oxide film and gold of an electrode metal, prevents intrusion of water and the like, and prevents peeling of the protective film due to resin sealing. The purpose is to do.

[0005]

In order to achieve the above object, the present invention is characterized in that a film made of a substance having high adhesiveness to both gold and an oxide film is interposed between a gold electrode and a protective film. To do.

Specifically, the film is made of silicon, a silicon-rich nitride film, or a silicon-rich oxide film.

The film may be a metal film containing at least one of nickel, titanium and chromium.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described. In FIG. 1, 1 is a semiconductor substrate, 2 is a gold electrode, 3 is a protective film, and 4 is a film. The gold electrode 2 and the protective film 3 are provided between the gold electrode 2 and the protective film 3 made of silicon nitride or silicon oxide formed on the semiconductor substrate 1.
In both cases, the film 4 having high adhesiveness is inserted.

For this film 4, silicon is specifically selected. For example, the gold electrode 2 is formed by a lift-off method in which an ohmic electrode is formed on the semiconductor substrate 1, gold is vapor-deposited on the ohmic electrode via titanium, platinum, or the like.
Then, silicon is formed on the gold electrode to a thickness of about several hundred angstroms by a vacuum vapor deposition method using an electron beam as a heating source or a plasma CVD method using silane as a source gas. By forming a protective film on the film 4 made of silicon by a plasma CVD method or the like, a semiconductor device having a structure shown in FIG. 1A can be obtained. The thickness of silicon is
It is appropriately selected depending on the silicon forming conditions, the type of protective film, and the like.

Silicon formed by the vacuum vapor deposition method or plasma CVD method forms a eutectic with gold at a relatively low temperature (eutectic temperature 370 ° C.) when forming a protective film or by heat treatment in a subsequent step, and the gold electrode And adhere strongly. On the other hand, since the silicon and the protective film have high adhesiveness, the gold electrode and the protective film can be bonded to each other through the silicon, which is optimal as the film 4 of the present invention.

The silicon film formed here may be either amorphous silicon or polysilicon. The silicon thus formed can be removed by ordinary dry etching or wet etching, and since the wire bonding is performed, the protective film can be removed and the gold electrode can be easily exposed.

Next, a second embodiment of the present invention will be described. The film 4 described in the first embodiment is a silicon-rich nitride film or oxide film instead of silicon. The silicon-rich nitride film or oxide film can be formed by a normal plasma CVD method or the like, so that a semiconductor device having a structure shown in FIG. 1A can be obtained. Here, the silicon-rich nitride film or oxide film means a nitride film or oxide film in which the proportion of silicon is stoichiometrically higher than that of trisilicon tetranitride or silicon dioxide. The ratio and film thickness of silicon having high adhesiveness are appropriately selected depending on the formation conditions of the nitride film and the like.

The silicon-rich nitride film or oxide film is
As in the first embodiment, the silicon contained in the film 4 is eutectic with gold to improve the adhesion with the gold electrode. The silicon-rich nitride film or oxide film can be easily removed by ordinary dry etching or wet etching.

The silicon-rich nitride film or oxide film has a continuous composition so as to increase the silicon content in the portion in contact with the gold electrode 2 and decrease the silicon content in the portion in contact with the protective film 3. It is also possible to change to.

In the case of forming a nitride film, for example, in the case of forming a nitride film, the film 4 whose composition is continuously changed is obtained by using monosilane and nitrogen gas as source gases by a plasma CVD method and gradually increasing the ratio of nitrogen. It can be formed by changing the composition of the deposited film. Further, if the protective film is continuously formed, the protective film 3 can be formed without an interface. Further, the composition of the protective film 3 may be continuously changed.

It is also possible to have a structure in which a nitride film and an oxide film are laminated, and the composition of the film 4 may be a silicon oxynitride film.

Next, a third embodiment of the present invention will be described. It is also possible to interpose a protective film 3 and a metal film 4 having a strong adhesive force on the gold electrode 2. Metal film with strong adhesion to protective film 4
Examples include nickel, titanium, and chromium.

These metal films can be formed, for example, by depositing gold and then continuously depositing several hundred angstroms of these metals and lifting off when forming the gold electrode 2 by the lift-off method. it can. After that, when a protective film is formed by a plasma CVD method or the like, as shown in FIG.
A semiconductor device having the structure shown in (B) can be obtained. These metal films can be removed by normal dry etching or wet etching, and the gold electrode 2 can be easily exposed because of wire bonding. The thickness of the metal film formed is appropriately selected depending on the conditions for forming the metal film and the type of the protective film.

Among the metal films thus formed, nickel, for example, is eutectic with gold (eutectic temperature 340 ° C.) at a relatively low temperature such as heat treatment for forming a protective film, and is strongly strong with gold. To glue. These metals have high adhesiveness to the protective film and are suitable as the film of the present invention. Further, the composition of the protective film may be continuously changed in order to improve the adhesion between these metals and the protective film.

Further, even titanium and chromium which do not form a mixed crystal with gold have high adhesiveness to both gold and the protective film and are suitable as the film 4 of the present invention.

As described above, the semiconductor device formed by interposing the film 4 for improving the adhesiveness between the protective film and the gold electrode is resin-sealed, and at 120 ° C. under 2 atmospheres of steam, As a result of conducting a reliability test on moisture penetration between the gold electrode and the protective film, as compared with the conventional structure in which no film is interposed,
About twice as long life was obtained.

[0022]

As described above, according to the present invention, since the protective film made of silicon nitride or silicon oxide and the film for firmly adhering the gold electrode are interposed, it is possible to prevent the intrusion of water. You can Further, during resin sealing, peeling or cracking of the protective film due to shrinkage of the resin can be effectively prevented.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

[Explanation of symbols]

 1 semiconductor substrate 2 gold electrode 3 protective film 4 film

Front page continuation (72) Inventor Seiichi Ishihara 2-1-1 Fukuoka, Kamifukuoka-shi, Saitama Inside Nippon Express Co., Ltd. Kawagoe Manufacturing (72) Inventor Keizo Takahashi 2-1-1 Fukuoka, Kamifukuoka, Saitama No. Nihonhon Radio Co., Ltd. Kawagoe Works

Claims (4)

[Claims] 1. A semiconductor device in which a gold electrode is formed on a semiconductor substrate and a protective film is formed on the gold electrode, wherein a material having high adhesion to both gold and the protective film is provided between the gold electrode and the protective film. A semiconductor device in which a film made of is interposed. 2. The semiconductor device according to claim 1, wherein the film is made of silicon. 3. The semiconductor device according to claim 1, wherein the film is made of a silicon-rich nitride film or oxide film. 4. The semiconductor device according to claim 1, wherein the film is a metal film containing at least one of nickel, titanium, and chromium.