JPH0897406A - Gate turn-off thyristor and semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] A P-type emitter layer 1, an N-type base layer 2 provided on the P-type emitter layer 1, and a P-type base layer 3 provided on the N-type base layer 2. A plurality of N-type emitter regions 4 formed by partially subdividing the surface layer of the P-type base layer 3, an anode electrode 5 provided on the P-type emitter layer 1, and a plurality of N-type emitter regions. In a pressure contact type gate turn-off thyristor provided with a cathode metal electrode 16 provided on each surface of the mold emitter region 4, even if the cathode electrode is deformed due to biased pressure during pressure contact, the cathode electrode and the gate electrode are short-circuited or Make sure that there is no insulation failure. [Structure] In the cathode electrode 16, a layer close to the cathode region is made of hard metal 16a, and a layer close to the external pressure welding electrode is made of soft metal 16b. Warpage and bias of the pressure contact surface during pressure contact are alleviated by the elastic deformation of the soft metal 16b.
Even if the bias pressure exceeds a certain level, the hard metal 16a does not cause the plastic deformation.

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 gate turn-off thyristor which is a self-turn-off switching device.

[0002]

2. Description of the Related Art Gate turn-off thyristor (hereinafter GT
Abbreviated as O) is increasingly exerting its characteristics as a self-extinguishing element for electric power in the field of large current control.
A device capable of turning off the anode current of 500 A has been developed. In particular, do not braze a thermal buffer plate such as tungsten as an electrode on the anode region of the Si semiconductor part,
The so-called alloy-free structure has been attracting attention in terms of performance and cost. One of the features of the alloy-free GTO is that it is advantageous for miniaturization. This is because the thermal buffer plate is not brazed, so that a highly accurate miniaturization device used in the IC or LSI wafer process can be used.

However, in the GTO, it is necessary to etch the semiconductor surface in order to form the gate electrode, and the inactive region generated by this etching has prevented miniaturization. Therefore, as shown in FIG. 3, G having a gate structure suitable for an alloy-free GTO that can be further miniaturized.
TO is proposed.

In the GTO shown in FIG. 3, a metal gate thin film (gate electrode) 10 having a thickness smaller than that of the cathode electrode 6 is provided on the P-type high impurity concentration layer 12, and the cathode electrode 6 and the cathode electrode 6 are formed at the time of pressure welding for electrode extraction. An insulating film 8 such as polyimide is provided on the metal gate thin film 10 so that the gate electrode 10 is not short-circuited, and the sum of the thicknesses of the metal gate thin film 10 and the insulating film 8 does not exceed the thickness of the cathode electrode 6. This is a gate structure that does not use etching as in the past.

In FIG. 3, 1 is a P-type emitter layer, and 2 is N.
A type base layer, 3 is a P type base layer, 4 is an N type emitter region, 5 is an anode electrode, 6 is a cathode electrode, and 11 is an insulating thin film.

[0006]

In the conventional structure shown in FIG. 3, the cathode electrode and the gate electrode formed on the same plane are short-circuited or the insulation is defective. This is because when a biased pressure is applied to the cathode electrode, the specific cathode electrode is deformed, and the height of the cathode electrode and the height of the gate electrode approach each other at that portion. Of course, an insulating film is formed on the gate electrode in preparation for this case, but the deformation of the cathode electrode causes pressure contact load on the insulating film, which is problematic in terms of reliability.

Usually, the cathode region is divided into several thousands of minute slits, and it is required that the external electrodes are pressed against all the cathode electrodes provided in these slits during pressure contact. For this reason, the cathode electrode is made of a soft metal such as aluminum, and even if there is some warp or bias in the pressure contact surface during pressure contact, the cathode electrode is deformed to a uniform pressure contact state. However,
On the contrary, when the bias pressure exceeds a certain level, the above-mentioned inconvenience occurs due to the elastic deformation of the electrodes.

The present invention has been made in view of the above problems, and an object thereof is high reliability that the cathode electrode and the gate electrode are not short-circuited or have poor insulation even if the cathode electrode is deformed due to biased pressure during pressure welding. To provide a gate turn-off thyristor and a semiconductor device having added characteristics.

[0009]

According to the present invention, there is provided a P-type emitter layer, an N-type base layer provided on the P-type emitter layer, and a P-type base layer provided on the N-type base layer. A plurality of N-type emitter regions formed by partially subdividing the surface layer of the P-type base layer, and a P formed on the surface layer of the P-type base layer so as to surround the N-type emitter region. An anode metal electrode is provided on the surface of the P-type emitter layer, a cathode metal electrode is provided on each surface of the plurality of N-type emitter regions, and a gate metal electrode is provided on the surface of the P-type gate region. The thickness of the portion of the gate metal electrode that is not directly connected to the external electrode is thinner than the thickness of the cathode electrode, and an insulating film is provided on the thin gate metal electrode to reduce the thickness of the thin gate metal electrode. The thickness of the insulating film The thickness of the cathode metal electrode is smaller than that of the cathode metal electrode, and a gate signal is applied to the gate metal electrode to turn on or off a current between the anode and cathode metal electrodes. 2 electrodes
At least the layer near the cathode region is made of a hard metal such as tungsten, molybdenum, and titanium, and the layer near the external pressure welding electrode is made of a soft metal such as aluminum.

[0010]

The warp and bias of the pressure contact surface during pressure contact are alleviated by the soft deformation of the soft metal of the cathode metal electrode. Also, even if the bias pressure exceeds a certain level, it does not deform due to the hard metal that does not easily deform. Therefore, the cathode metal electrode and the gate metal electrode do not short-circuit or have poor insulation. As a result, a highly reliable element can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1, the same parts as those in FIG. 3 are indicated by the same reference numerals. 1 is different from FIG. 3 in that
The cathode electrode (16) is composed of two layers, a hard metal 16a on the N-type emitter region side and a soft metal 16b on the pressure contact surface side, and the other parts are configured the same as in FIG. The hard metal 16a is tungsten, molybdenum,
The soft metal 16b is made of aluminum or the like.

In the GTO configured as described above,
Warpage and bias of the pressure contact surface during pressure contact are alleviated as in the conventional case by the elastic deformation of the soft metal 16b. However, since the hard metal 16a is less likely to undergo elastic deformation even if the bias pressure exceeds a certain level, the cathode electrode 16 does not have enough weight to the gate electrode portion (metal gate thin film 10) and the insulating film 8. It does not deform. For this purpose, hard metal 16
The thickness of a is preferably equal to or more than the sum of the thickness of the metal gate thin film 10 and the thickness of the insulating film 8.

The hard metal 16a of the cathode electrode 16
Instead of, a low resistance polysilicon that can also be used as a hard electrode may be used. Although the cathode electrode 16 is composed of two layers in FIG. 1, it is not limited to this and may be composed of three or more layers.

The present invention may be applied to the GTO having the structure shown in FIG. 2 in which the cathode electrode of the GTO having the structure shown in FIG. 3 is used as a common electrode. That is, in FIG. 2, the metal thin film 13 provided to make the cathode electrode the common electrode is made of a soft metal such as aluminum. Also in the case of such a configuration, the same operation and effect as described above can be obtained. In addition, in FIG.
The same parts as are indicated by the same reference numerals.

Further, the present invention may be applied to an electrostatic induction type thyristor (SI thyristor) or an insulated gate type bipolar transistor having the same pressure contact structure, and in that case, the same action and effect as described above can be obtained.

[0016]

As described above, according to the present invention, in the pressure contact type gate turn-off thyristor or semiconductor element, the cathode metal electrode is composed of two or more metal films, and at least the layer close to the cathode region is made of tungsten or molybdenum. ,
Since the layer made of a hard metal such as titanium and the layer close to the external pressure welding electrode is made of a soft metal such as aluminum, even if the cathode electrode is deformed due to biased pressure during pressure welding, the cathode electrode and the gate electrode are There is no short circuit or poor insulation, which results in a highly reliable element.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a gate turn-off thyristor according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a gate turn-off thyristor according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing an example of a conventional gate turn-off thyristor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... P-type emitter layer 2 ... N-type base layer 3 ... P-type base layer 4 ... N-type emitter region 5 ... Anode electrode 6, 16 ... Cathode electrode 8 ... Insulating film 10 ... Metal gate thin film 11 ... Insulating thin film 12 ... P -Type high impurity concentration layer 13 ... Metal thin film 16a ... Hard metal 16b ... Soft metal

Claims (7)

[Claims] 1. A P-type emitter layer, an N-type base layer provided on the P-type emitter layer, a P-type base layer provided on the N-type base layer, and a surface of the P-type base layer. A plurality of N-type emitter regions formed by being partially subdivided into layers, and a P-type gate region formed on the surface layer of the P-type base layer so as to surround the N-type emitter regions, P
An anode metal electrode is provided on the surface of the type emitter layer, a cathode metal electrode is provided on each surface of the plurality of N type emitter regions, and a gate metal electrode is provided on the surface of the P type gate region. The thickness of the portion not directly connected to the external electrode is thinner than the thickness of the cathode electrode, an insulating film is provided on the thin gate metal electrode, and the thickness of the thin gate metal electrode is the thickness of the insulating film. In a pressure contact type gate turn-off thyristor configured to be thinner than the thickness of the cathode metal electrode and applying a gate signal to the gate metal electrode to turn on or off the current between the anode and the cathode metal electrode, wherein the cathode metal electrode is It is composed of two or more metal films, and at least the layer close to the cathode region is made of tungsten, molybdenum, or titanium. Hard a metal, and a layer close to the external pressure electrode gate turn-off thyristor, comprising the soft such as aluminum metals. 2. The thickness of the layer near the cathode region of the cathode metal electrode is thicker than the thickness of the thin gate metal electrode plus the thickness of the insulating film. Gate turn-off thyristor. 3. The gate turn-off thyristor according to claim 1, wherein the layer of the cathode metal electrode near the cathode region is formed of a low resistance polysilicon layer. 4. A P-type emitter layer, an N-type base layer provided on the P-type emitter layer, a P-type base layer provided on the N-type base layer, and a surface of the P-type base layer. A plurality of N-type emitter regions formed by being partially subdivided into layers, and a P-type gate region formed on the surface layer of the P-type base layer so as to surround the N-type emitter regions, P
An anode metal electrode is provided on the surface of the type emitter layer, a cathode metal electrode is provided on each surface of the plurality of N type emitter regions, and a gate metal electrode is provided on the surface of the P type gate region. The thickness of the portion not directly connected to the external electrode is thinner than the thickness of the cathode electrode, an insulating film is provided on the thin gate metal electrode, and the thickness of the thin gate metal electrode is the thickness of the insulating film. Is thinner than the thickness of the cathode metal electrode, a metal thin film for making the cathode electrode a common electrode is provided on the surface of the insulating film and the cathode metal electrode, and a gate signal is applied to the gate metal electrode to apply the anode signal to the anode.・ In a pressure contact type gate turn-off thyristor that turns on or off a current between cathode metal electrodes, the metal thin film is soft A gate turn-off thyristor characterized by being made of a metal. 5. An n base layer and ap anode layer are laminated, and a plurality of p gate layers and n cathode layers are alternately formed at predetermined intervals on the surface of the n base layer in a direction orthogonal to the laminating direction. In a pressure contact type semiconductor device in which a gate electrode is formed on the upper surface of the p gate layer and a cathode electrode is formed on the upper surface of the n cathode layer, the cathode electrode is formed of two or more metal films, A semiconductor element characterized in that a layer close to the n cathode layer is made of a hard metal such as tungsten, molybdenum, or titanium, and a layer close to the external pressure welding electrode is made of a soft metal such as aluminum. 6. The semiconductor device according to claim 5, wherein the semiconductor device is composed of an electrostatic induction thyristor. 7. The semiconductor device according to claim 5, wherein the semiconductor device is composed of an insulated gate bipolar transistor.