JPH088419A - Semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a semiconductor device that improves withstand voltage during breakdown and improves allowable current. The same conductivity type as that of the first semiconductor layer is provided between a fourth semiconductor layer 4 forming a cathode and a second semiconductor layer 2 separating the wafer from the surface of the first semiconductor layer 1 serving as a substrate wafer. Thus, the sixth semiconductor layer 13 having an impurity concentration higher than that of the first semiconductor layer was provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a thyristor and a triac, and more particularly to a semiconductor device having high withstand voltage.

[0002]

2. Description of the Related Art Semiconductor devices such as thyristors and triacs are known as shown in FIG. FIG. 1A is a sectional view of this type of semiconductor device, and FIG. 1B is a plan view schematically showing a plane excluding electrodes and an oxide film. Reference numeral 1 is, for example, an N-type first semiconductor layer, and 2 is, for example, a P-type second semiconductor layer provided so as to selectively penetrate between both surfaces of the first semiconductor layer 1. One surface of the first semiconductor layer 1 separated and diffused by the second semiconductor layer 2 is entirely covered,
Further, the other surface is selectively formed, for example, in the P-type third semiconductor layer 3
And the fourth semiconductor layer 4 is formed. For example, an N-type fifth semiconductor layer 5 is formed in the fourth semiconductor layer 4, and the first semiconductor layer 1 and the second semiconductor layer 2, the first semiconductor layer 1 and the fourth semiconductor layer 4, An oxide film 6 is formed including the bonding surfaces of the fourth semiconductor layer 4 and the fifth semiconductor layer 5, and after the oxide film 6 is formed, the cathode electrode 7 and the third semiconductor layer 3 are formed on the fifth semiconductor layer 5. On the anode electrode 8 and the fourth semiconductor layer 4 on the gate electrode 9
To form a semiconductor device (thyristor).

When a positive voltage is applied to the anode electrode 8 and a negative voltage is applied to the cathode electrode 7, depletion layers are formed on both sides of the junction J2 between the first semiconductor layer 1 and the fourth semiconductor layer 4. Generally fourth
Since the concentration of the semiconductor layer 4 is designed to be higher than that of the first semiconductor layer 1, most of the depletion layer is formed in the first semiconductor layer 1.
Occur on the side. When the applied voltage is increased, the depletion layer expands in the direction of the junction J1 between the first semiconductor layer 1 and the third semiconductor layer 3 and the junction J1 between the first semiconductor layer 1 and the second semiconductor layer 2. At the same time, the electric field strength of the junction J2 increases. In this state, the semiconductor device exhibits a cutoff characteristic. At this time, when a positive voltage is applied to the gate electrode 9 and a negative voltage is applied to the cathode electrode 7, a gate current flows through the gate electrode 9, the fourth semiconductor layer 4, the fifth semiconductor layer 5, and the cathode electrode 7, and the fourth voltage is applied. The electrons injected into the semiconductor layer 4 are attracted toward the anode electrode 8, and the anode electrode 8, the third semiconductor layer 3, the first semiconductor layer 1, the fourth semiconductor layer 4, the fifth semiconductor layer 5, and the cathode are formed. A current flows through the electrode 7 and the semiconductor device becomes conductive.

Further, without applying a voltage between the gate electrode 9 and the cathode electrode 7, the anode electrode 8 and the cathode electrode 7
When the voltage applied to the junction is increased, the depletion layer expands with the applied voltage, and the electric field strength of the junction J2 becomes higher and higher.
When the depletion layer reaches the junction J1 or the electric field strength of the junction J2 reaches a certain electric field, a current flows from the anode electrode 8 to the cathode electrode 7 to cause a breakdown phenomenon. Therefore, the withstand voltage of the semiconductor device is determined by the distance between the junction J1 and the junction J2 or the electric field strength of the junction J2.

[0005]

However, when the withstand voltage of the semiconductor device is designed so as to be determined by the distance between the junction J1 and the junction J2, the withstand voltage at a high temperature is remarkably reduced, and the use at a high temperature is prevented. I had a problem with. Further, when the withstand voltage of the semiconductor device is designed by the electric field strength of the junction J2, the position of the junction J2 varies due to the heat treatment, and the breakdown phenomenon occurs at the place where the electric field strength is the strongest. There is a problem that the semiconductor device is damaged due to local concentration of breakdown current.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is provided between the first conductivity type first semiconductor layer and both surfaces of the first semiconductor layer. A second semiconductor layer of a second conductivity type that selectively penetrates the first semiconductor layer, a third semiconductor layer of the second conductivity type provided on one surface of the first semiconductor layer, and the third semiconductor layer. Second semiconductor layer of the second conductivity type selectively provided on the surface facing the semiconductor layer, and a fifth semiconductor layer of the first conductivity type selectively provided in the fourth semiconductor layer. In a semiconductor device having a semiconductor layer, an impurity concentration of the first semiconductor layer is of a first conductivity type between the surface of the first semiconductor layer and the fourth semiconductor layer and the second semiconductor layer. The sixth semiconductor layer having a higher impurity concentration is provided.

When the surface shape of the fourth semiconductor layer and the surface shape of the second semiconductor layer have curved portions,
The sixth semiconductor layer is a semiconductor layer excluding a curved portion facing the curved portion.

A wiring layer having a low resistance is provided on the surface of the sixth semiconductor layer.

[0009]

The second semiconductor layer of the second conductivity type is formed so as to penetrate between both surfaces of the first semiconductor layer of the first conductivity type.
The third semiconductor layer of the second conductivity type is formed on one surface of the semiconductor layer, and the fourth semiconductor layer of the second conductivity type is selectively formed on the other surface of the first semiconductor layer. A fifth semiconductor layer of the first conductivity type is selectively formed in the fourth semiconductor layer. Further, a sixth semiconductor layer of a first conductivity type and an impurity concentration higher than that of the first semiconductor layer is provided between the surface of the first semiconductor layer and the fourth semiconductor layer and the second semiconductor layer, When a positive voltage is applied to the electrode connected to the third semiconductor layer and a negative voltage is applied to the electrode connected to the fifth semiconductor layer to increase the voltage, the depletion layer becomes the first semiconductor layer and the sixth semiconductor layer. The electric field near the surface of this junction rises, and when it reaches a certain value, the yield phenomenon occurs.

When the surface shape of the fourth semiconductor layer has a curved line, the electric field is prevented from concentrating on the curved line portion of the sixth semiconductor layer except for the curved line portion of the sixth semiconductor layer.

Further, by providing the low resistance wiring layer on the surface of the sixth semiconductor layer, the potential variation in the surface direction of the sixth semiconductor layer 13 is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIG. In FIG. 1, the same reference numerals as those in FIG. 6 indicate the same functions. 1 is different from FIG. 6 in that it is the other surface of the first semiconductor layer 1 and has the same conductivity type as the first semiconductor layer between the second semiconductor layer 2 and the fourth semiconductor layer 4. The sixth semiconductor layer 13 is provided. This sixth semiconductor layer 13
Are formed with an impurity concentration higher than that of the first semiconductor layer 1.

Now, the anode electrode 8 is positive and the cathode electrode 7 is
When a negative voltage is applied to the depletion layer to increase the applied voltage, the depletion layer spreads from the junction J2 in the direction of the junction J1 on the third semiconductor layer 3 side and in the direction of the sixth semiconductor layer 13, and the depletion layer becomes the first depletion layer. 1
To the junction J4 between the semiconductor layer 1 and the sixth semiconductor layer 13. After the depletion layer reaches the junction J4, the sixth semiconductor layer 6
Is higher than that of the first semiconductor layer 1, the junction J4
It does not spread from the vicinity, and thereafter the electric field strength near the surface of the junction J4 rises, and when it reaches a certain value, a breakdown phenomenon occurs.

Since the distance between the sixth semiconductor layer 13 and the junction J2 governs the breakdown, the variation in the breakdown can be considered by the patterning accuracy of the sixth semiconductor layer 13, and the pattern accuracy can be improved. By improving
In contrast to the conventional Svotte-like breakdown, the part that causes the breakdown becomes a junction line (hereinafter, the breakdown that occurs in the junction line is referred to as a line breakdown), and the allowable current at the time of breakdown becomes large, causing damage even at the time of device breakdown. A semiconductor device that is difficult to manufacture can be obtained.

FIGS. 2 to 5 show another embodiment, and FIG. 2 (a) is a sectional view taken along line AA of the semiconductor device.
FIG. 6B is a plan view schematically showing a plane excluding the electrodes and the oxide film. In the embodiment shown in FIG. 1, the electric field strength is highest at the curved portion of the corner of the sixth semiconductor layer 6.
For this reason, in the embodiment of FIG. 2, the sixth semiconductor layer 13 excluding the curved portion of the corner is provided. Therefore, in the breakdown phenomenon, a line breakdown occurs in the sixth semiconductor layer, the permissible current at the time of breakdown becomes large, and a semiconductor device which is not easily broken even at the time of device breakdown can be obtained.

Further, the sixth embodiment of the invention shown in FIG.
The low resistance wiring layer 15 is provided on the surface of the semiconductor layer 13. Moreover, what is shown in FIG. 4 is the sixth semiconductor layer 1
The wiring layer 15 having a low resistance is provided on the surface of the sixth semiconductor layer 13 except for the curved portion of the third corner. Also, FIG.
What is shown in FIG. 6 is a wiring in which a low resistance wiring layer 15 is provided on the surface of the sixth semiconductor layer 13 and the surface of the oxide film 6 except for the corner portion of the sixth semiconductor layer 13, and the cross section AA is shown 4 A-A
It is the same as the cross section. In the examples shown in FIGS. 3 to 5, the potential variation in the surface direction of the sixth semiconductor layer 13 can be reduced.

Further, in the above embodiment, an example of a P-gate thyristor is shown, but it can also be applied to an N-gate thyristor in which all conductive layers are inverted, and can also be applied to a triac.

[0018]

As described above, the breakdown phenomenon can be extended from the point to the line, the allowable current at the breakdown can be increased, and the semiconductor device is less likely to be damaged. In addition, the leak current at breakdown acts as a gate current, and by appropriately selecting the gate sensitivity, the semiconductor device can be ignited, and the semiconductor device can protect itself against overvoltage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a semiconductor device of the present invention and a plan view excluding electrodes and oxide films.

FIG. 2 is a cross-sectional view of another embodiment of the semiconductor device of the present invention and a plan view excluding electrodes and oxide films.

FIG. 3 is a cross-sectional view of another embodiment of the semiconductor device of the present invention and a plan view from which electrodes and oxide films are removed.

FIG. 4 is a cross-sectional view of another embodiment of the semiconductor device of the present invention and a plan view excluding electrodes and oxide films.

FIG. 5 is a cross-sectional view of another embodiment of the semiconductor device of the present invention and a plan view excluding electrodes and oxide films.

FIG. 6 is a cross-sectional view of a conventional semiconductor device and a plan view with electrodes and oxide films removed.

[Explanation of symbols]

 1 1st semiconductor layer 2 2nd semiconductor layer 3 3rd semiconductor layer 4 4th semiconductor layer 5 5th semiconductor layer 6 oxide film 7 cathode electrode 8 anode electrode 9 gate electrode 13 6th semiconductor layer 15 wiring Layer J1, J2, J3, J4 Joining

Claims (3)

[Claims] 1. A first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type that selectively penetrates between both surfaces of the first semiconductor layer, and the first semiconductor layer. A third semiconductor layer of the second conductivity type provided on the surface of one side of the semiconductor layer;
A fourth semiconductor layer of a second conductivity type selectively provided on the surface facing the third semiconductor layer, and a fourth semiconductor layer of a first conductivity type selectively provided in the fourth semiconductor layer. In a semiconductor device having a fifth semiconductor layer, the first semiconductor layer of the first conductivity type is provided between the surface of the first semiconductor layer and the fourth semiconductor layer and the second semiconductor layer. A semiconductor device having a sixth semiconductor layer having an impurity concentration higher than the impurity concentration of. 2. When the surface shape of the fourth semiconductor layer and the surface shape of the second semiconductor layer have a curved portion, the sixth semiconductor layer is a semiconductor excluding a curved portion facing the curved portion. The semiconductor device according to claim 1, which is a layer. 3. The semiconductor device according to claim 1, wherein a wiring layer having a low resistance is provided on the surface of the sixth semiconductor layer.