JPH07115187A - Semiconductor device - Google Patents

Abstract

PURPOSE:To avoid crackings which are developed in an interlayer insulating film when an Al lead wire is connected to a cathode pad part by ultrasonic bonding. CONSTITUTION:An interlayer insulating type surface p-type gate static induction thyristor has an aluminum gate electrode 3, a silicon oxide film which is formed on the aluminum gate electrode 3 by a plasma-exciting chemical vapor phase growth apparatus and a cathode 1 formed on the silicon oxide film. In this thyristor, a reiforcing film 4 which protects an interlayer insulating film 2 which is the silicon oxide film is provided between the aluminum gate electrode 3 and the interlayer insulating film 2. With this constitution, crackings which are developed in the interlayer insulating film when an aluminum lead wire is bonded to a cathode pad part by ultrasonic bonding can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a technique for preventing cracking of an interlayer insulating film of an interlayer insulating type surface p gate type static induction thyristor.

[0002]

2. Description of the Related Art The basic structure of an interlayer insulating surface type electrostatic induction thyristor in which a gate electrode is buried under a cathode electrode through a silicon oxide film and its manufacturing process will be described with reference to FIG. explain.

On the surface of the n-type silicon substrate 11, an n ⁺ cathode layer 6 and a p ⁺ gate layer 5 are alternately formed by a diffusion method or an ion implantation (implantation) method in a comb-shaped fine pattern having a width of about 1 to 5 μm. Arrange with.

A p ⁺ anode layer 9 is formed on the back surface of the n-type silicon substrate 11.

An insulating film 7 is formed between the p ⁺ gate layer 5 and the n ⁺ cathode layer 6 in a comb-shaped fine pattern.

Aluminum (Al) is deposited on the p ⁺ gate layer 5 by vapor deposition or sputtering to form an Al gate electrode 3 (hereinafter abbreviated as Al gate electrode).
The film thickness of the Al gate electrode 3 is 0.3 to 1.2 μm.

Since the interlayer insulating film 2 having a film thickness of 1 to 2 μm is formed on the Al gate electrode 3, a plasma enhanced chemical vapor deposition (hereinafter abbreviated as plasma CVD) apparatus capable of forming a film at a low temperature is used for 300 to 500. Create a silicon oxide film at ℃.

Aluminum is deposited on the n ⁺ cathode layer 6 and the interlayer insulating layer 2 by vapor deposition or sputtering to form an Al cathode electrode 1.

Aluminum is deposited on the p ⁺ anode layer 9 by vapor deposition or sputtering to form an Al anode electrode 1
Form 0.

As shown in FIG. 3, the diameter is 300 to 400 μm.
The Al lead wire 12 of m is connected to the cathode electrode 1 and the gate electrode 3 by ultrasonic bonding, and wiring is performed on the element. Since it is not possible to directly bond an Al lead wire having a diameter of 300 to 400 μm to the fine gate and cathode electrodes having a width of 1 to 5 μm, a bonding pad portion is formed for both the cathode and the gate, and the Al lead wire is ultrasonically bonded to this pad. Connected by bonding.

The bonding pad portion of the gate electrode extends below the interlayer insulating film 2 to the outer peripheral portion of the element, and the pad portion is formed there. On the other hand, the pad portion of the cathode electrode is formed as shown in FIG. The entire cathode electrode 1 formed on the n ⁺ cathode layer 6 and the interlayer insulating film 2 serves as a pad portion.

[0012]

The problem of the present technology is shown in the interlayer insulation when the Al lead wire is connected to the pad portion of the cathode electrode by ultrasonic bonding as shown in FIGS. 2 and 3. As described above, the gate electrode and the cathode electrode, which are separated and insulated by the interlayer insulating film, are short-circuited, and the element function as the SI thyristor is completely impaired.

The present invention has been made based on the background described above, and an object thereof is to prevent cracking of an interlayer insulating film which occurs when an Al lead wire is connected to a cathode electrode pad portion by ultrasonic bonding. And

Applications of the metal material are firstly a lead wire and secondly a gate electrode. In order to use it as a lead wire or a gate electrode, it must have a high electric conductivity, be in ohmic contact with a substrate material such as silicon, and have a certain current capacity.

Generally, copper, silver, gold and aluminum are often used. Particularly, aluminum is most widely used because it has a stable property in contact with silicon.
Silicon compounds such as molybdenum, tungsten, tantalum and platinum have been studied as refractory metal materials.

Such a wiring technique holds an important key for future device development in both material selection and processing technique.

[0017]

In order to solve the above problems, the present invention provides an interlayer insulation type semiconductor device having a cathode electrode formed on an aluminum gate electrode via an interlayer insulation film, wherein There is provided a semiconductor element characterized in that a reinforcing film layer made of a material having higher mechanical strength than aluminum is formed between the interlayer insulating film and the interlayer insulating film.

The thickness of this reinforcing film is preferably about 0.5 to 2 μm, though it depends on the material, and it is preferable that it has the same shape as the aluminum gate electrode. As the material, for example, tungsten, titanium, tungsten silicide,
Titanium polysilicide, polysilicon, or those having mechanical strength and hardness equivalent to these are preferable.

[0019]

A method of increasing the strength of the interlayer insulating film itself and a method of preventing the interlayer insulating film from cracking when the Al lead wire is connected to the cathode electrode pad portion by ultrasonic bonding There is a method of relaxing or reducing stress to prevent cracking.

One of the reasons why the interlayer insulating film cracks when bonding the Al lead wire to the cathode electrode pad portion is that the stress generated by the deformation of the Al cathode electrode 1 is shared by the Al gate electrode 3. Instead, it may be concentrated on the interlayer insulating film.

The reason is that the gate electrode 3 is made of aluminum, which is a soft metal having a very low hardness, so that the gate electrode is easily deformed and has plasticity against distortion.

Therefore, it is possible to protect the interlayer insulating film by providing a reinforcing film between the interlayer insulating film and the gate electrode using a material having excellent strength.

When a metal such as titanium having a hardness sufficiently higher than that of aluminum or polysilicon doped with a high concentration of impurities is used as the material of the reinforcing film, the Al lead wire is ultrasonically bonded to the cathode electrode pad portion. The stress applied to the interlayer insulating film can be shared, and the occurrence of cracks in the interlayer insulating film can be suppressed.

Titanium, polysilicon and the like have electric resistances several to hundreds of times higher than that of aluminum and significantly impair the current cut-off resistance of SI thyristors, so that they have not been used as electrode materials until now. By utilizing these electrode materials as a reinforcing film, an interlayer insulating film forming method having an electric resistance equal to that of Al and no cracks in the interlayer insulating film has been developed.

[0025]

EXAMPLES Examples of the present invention will be described in detail below.
The present invention is not limited to the examples below.

The structure of the embodiment of the present invention and the manufacturing process thereof will be described with reference to FIG. 1, but the reference numerals are the same in all the drawings, and the explanation of the above-mentioned reference numerals will be omitted.

(1) p ⁺ gate layer 5 and n ^{+ on a} silicon substrate
The cathode layer 6 is formed.

(2) On the p ⁺ gate layer 5, a film thickness of 0.3 to
An Al gate electrode 3 of 1.2 μm is formed.

Up to this point, the method is the same as the conventional method.

(3) A reinforcing film 4 having the same shape as the Al gate electrode is formed on the Al gate electrode 3.

The role of this reinforcing film is that the Al gate electrode is made of Al.
The purpose is to prevent the lead wire from being deformed during ultrasonic bonding to the cathode electrode pad portion, and to reduce the stress applied to the interlayer insulating film 2.

Therefore, this reinforcing film must have high hardness and high mechanical strength and can be formed by a low temperature process of 400 to 500 ° C. or lower because it is formed on the Al gate electrode.

As the material of the reinforcing film, a metal having a high hardness such as tungsten (W) or titanium (Ti), or a WSi ₂ , TiSi ₂ film or a polysilicon film which is a silicide of these metals can be used. Although the thickness of the reinforcing film varies depending on the material, if it is 0.5 to 2 μm, cracking of the interlayer insulating film can be prevented.

(4) After forming the reinforcing film, an interlayer insulating film is formed.

(5) An Al cathode electrode is formed on the interlayer insulating film.

(6) The Al lead wire is bonded to the Al cathode electrode pad portion by ultrasonic bonding.

As described above, by introducing the reinforcing film, it is possible to prevent the interlayer insulating film from being cracked when the Al wire is bonded to the cathode electrode pad portion. Since they are the same, there is no reduction in the current proof capability of SI thyristors.

[0038]

As described above, according to the present invention, various effects as described below can be obtained.

(1) When an Al lead wire is connected to the cathode electrode of an inter-layer insulation type surface p-gate type SI thyristor by ultrasonic bonding, cracks occurring in the inter-layer insulation film can be prevented.

(2) A short circuit between the cathode electrode and the gate electrode due to cracking of the interlayer insulating film does not occur.

(3) Since the p ⁺ gate electrode is made of aluminum and the reinforcing film is formed on the Al gate electrode, the current blocking resistance of the SI thyristor does not decrease.

(4) The manufacturing yield of the SI thyristor element can be improved.

(5) Since the interlayer insulating film of the SI thyristor element is protected by the reinforcing film, the reliability of its electric characteristics can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a reinforced interlayer insulating film.

FIG. 2 is a vertical sectional view of a conventional SI thyristor.

FIG. 3 is an explanatory diagram of ultrasonic bonding of an Al lead wire and a breaking point of an interlayer insulating film.

FIG. 4 is an explanatory diagram of a short circuit due to a crack in an interlayer insulating film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Al cathode electrode 2 ... Interlayer insulation film 3 ... Al gate electrode 4 ... Reinforcement film 5 ... p ⁺ gate layer 6 ... n ⁺ cathode layer 7 ... Insulation film 8 ... n ^- Base layer 9 ... p ⁺ Anode layer 10 ... Al Anode electrode 11 ... Silicon substrate 12 ... Al lead wire 13 ... Break point of interlayer insulating film 14 ... Crack of interlayer insulating film

Claims (1)

[Claims] 1. An interlayer insulating semiconductor device having a cathode electrode formed on an aluminum gate electrode via an interlayer insulating film, wherein a mechanical strength higher than that of aluminum is provided between the aluminum gate electrode and the interlayer insulating film. A semiconductor element having a reinforcing film layer made of a high-quality material.