JPS605227B2 - thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thyristor with improved dv/dt characteristics and gate trigger current characteristics.

FIG. 1 shows a longitudinal sectional view of the main parts of a conventional thyristor. In FIG. 1, 1, 2, and 3 are a first emitter region of a first conductivity type, a first base region of a second conductivity type, and a second base of the first conductivity type, which are successively formed in contact with each other. area, 4
is a second base region formed at a required portion of the surface portion of the second base region.
5 is the first emitter region 1 of conductivity type.
6 is a second main electrode bonded to the surface of the second emitter region 4; 7 is a portion of the second base region 3 where the second emitter region 4 is not formed; A gate electrode 3 is bonded to the surface of the gate electrode 3, and a passivation region 8 is made of a glass film or the like. First emitter region 1, first base region 2, second base region 3 and second emitter region 4
constitutes the semiconductor substrate. FIG. 2 is an impurity concentration distribution diagram of the semiconductor substrate of the thyristor shown in FIG.

In Figure 2, the axis is the distance from the surface of the second emitter region to the inside of the semiconductor substrate, and the vertical axis is the impurity concentration (both the impurity of the first conductivity type and the impurity of the second conductivity type are taken in the same direction). ), the broken line A shows the concentration distribution of the second conductive type impurity of the semiconductor substrate whose non-diffused region becomes the first base region 2, and the broken line B shows the first conductivity during diffusion to form the first emitter region 1. The broken line C shows the concentration distribution of the first conductivity type diffused impurity during diffusion to form the second base region 3, and the broken line D shows the concentration distribution of the first conductivity type diffused impurity during diffusion to form the second emitter region 4. The concentration distribution of the diffused impurity of the second conductivity type, and the solid line is the impurity concentration distribution of the semiconductor substrate after the impurities of the opposite conductivity type are compensated for. The intersection of the broken line C and the broken line D shown by A in FIG. 2 is called a "working point."

The concentration of the diffused impurity of the first conductivity type or the second conductivity type at this working point (hereinafter abbreviated as "impurity concentration at the working point") is an extremely important factor that determines various characteristics of the thyristor. In conventional thyristors, the impurity concentration at the working point is constant within a range of variation at each location. Generally, when the impurity concentration at the working point is high, the characteristics of the syringe tend to be as follows.
First, the gate trigger current increases. Second, the gate trigger voltage increases. Thirdly, the temperature dependence of the gate trigger current becomes large. Fourth, the dv/dt characteristics become better, but the di/d stability becomes worse. In recent years, thyristors have come to be required to have very good specific characteristics depending on the conditions of use. dv/d
Another important example is a thyristor, which has an extremely good t characteristic, a small gate trigger current, and a small temperature dependence of the gate trigger current. When manufacturing such a thyristor, conflicting requirements are raised in determining the impurity concentration at the aforementioned working point. If the impurity concentration at the working point is approximately constant at each location, as in conventional thyristors, the above requirements cannot be fully met. This invention has been made in view of the above points, and by forming a region near the gate electrode in which the impurity concentration at the working point is lower than that in other regions, the impurity concentration at the working point and the impurity concentration at the working point can be reduced. The object of the present invention is to provide a thyristor that can meet the conflicting demands of the semiconductor industry, has good dv/dt, and has low gate trigger current and its temperature dependence.

Having a region where the impurity concentration at the working point is lower than other regions allows the gate trigger current to be reduced because the gate trigger current is determined by that region.

Furthermore, the temperature dependence of the gate trigger current can be reduced because it is determined in the region of low impurity concentration at the working point. The dv/dt characteristics are improved by arranging a region with low impurity concentration at the working point near the gate electrode so that the displacement current generated by the forward rising voltage is more easily absorbed by the gate electrode than flowing into the low working point region. is almost determined by the region of high impurity concentration at the working point, and can be made to be almost unaffected by the region of low impurity concentration at the working point. FIG. 3 shows a main part of a semiconductor substrate of an embodiment of a thyristor according to the present invention, which is arranged so that a region with a low impurity region at a working point satisfies the above requirements, viewed from the second emitter region side. FIG.

In FIG. 3, numeral 41 is a second emitter region for lowering the impurity concentration at the working point than in other regions. FIG. 4 is an impurity concentration distribution diagram of the semiconductor substrate of the thyristor of this embodiment. In Figure 4, the horizontal axis,
The vertical axis and broken lines A, B, C, and D represent the same as in FIG. The thin solid line represents the same thing as the solid line in FIG. The broken line E shows the concentration distribution of the second conductivity type diffusion impurity during diffusion to form the second emitter region 41 in the region with low impurity concentration at the working point, and the opening is the broken line C.
The intersection point between and the broken line E, that is, the working point in a region where the impurity concentration at the working point is lower than other regions, and the thick solid line indicates the impurity distribution of the semiconductor substrate in a certain region where the impurity concentration at the working point is lower than other regions. ing. FIG. 5 is a longitudinal sectional view of the main parts of the thyristor of the embodiment.

In Figure 5, the same reference numerals as in Figures 1 and 3 refer to 1.
It represents something similar to that shown in Figures 3 and 3. FIG. 3 shows a plan view of the second emitter region side of the semiconductor substrate, FIG. 4 shows its impurity concentration distribution map, and FIG. 5 shows a vertical cross-sectional view.
It is possible to improve the characteristics, reduce the gate trigger current, and reduce the temperature dependence of the gate trigger current.

A conventional thyristor having the structure shown in FIG. 1 and the impurity concentration distribution shown in FIG. 2, and a conventional thyristor having the structure shown in FIGS. 3 and 5 and the impurity concentration distribution shown in FIG. 4. A comparison of the characteristics with a thyristor according to an embodiment of the present invention having the following characteristics is shown in FIGS. 6 and 7. FIG. 6 shows an example of dv/dt characteristics, where the horizontal axis shows the critical off-voltage increase rate dv/dt, and the vertical axis shows the breakover voltage. FIG. 7 shows an example of the gate trigger current and its temperature dependence, where the vertical axis shows the junction temperature and the vertical axis shows the gate trigger current. In both FIGS. 6 and 7, the broken line shows the characteristics of the conventional thyristor, and the solid line shows the characteristics of the thyristor of the embodiment. From FIG. 6 and FIG. 7, it can be seen that the thyristor of the example has improved dv/dt characteristics as compared to the conventional thyristor, and the gate trigger current and its temperature dependence are reduced.

Next, the main points of a method for forming a region in which the impurity concentration at the working point is lower than in other regions will be explained. 8th
Figures a and b are longitudinal cross-sectional views of a semiconductor wafer for explaining an example of a forming method.

In FIG. 8, the same reference numerals as in FIG. 1 represent the same components as shown in FIG. As shown in FIG. 8a, the impurity concentration at the working point of the surface portion of the second base region 3 of the semiconductor wafer on which the first emitter region 1, the first base region 2, and the second base region 3 are formed is determined. A diffusion region 9 in which impurities of the second conductivity type are diffused is formed in a region lower than the region. Next, as shown in FIG. 8b, a second emitter region 4 is formed in the same manner as in the conventional method. In the region 41 where the diffusion region 9 of the second emitter region 4 was formed, the diffusion depth is deep and the impurity concentration at the working point is lower than in other regions. FIGS. 9a and 9b are longitudinal cross-sectional views of a semiconductor wafer for explaining another example of forming a region in which the impurity concentration at the working point is lower than in other regions.

As shown in FIG. 9a, the impurity concentration at the working point of the surface portion of the second base region 3 of the semiconductor wafer on which the first emitter region 1, the first base region 2, and the second base region 3 are formed is A recess 10 is formed by etching a region that is to be lower than the other region. Next, as shown in FIG. 9b, the second emitter region 4 is formed in the same manner as in the conventional method. In the region 41 of the second emitter region 4 where the recess 10 is formed, the diffusion depth is deep and the impurity concentration at the working point is lower than in other regions. In addition to the above two methods, it is possible to perform selective diffusion when forming the second base region 3 and form the second base region 3 so that the impurity concentration differs depending on the location.
The impurity concentration of the second base region 3, which is a region where the impurity concentration at the working point is to be lowered, is made lower than that of other regions of the second base region 3.The second emitter region 4 is formed by a conventional method. However, it is possible to partially lower the impurity concentration at the working point.

Although the above description has been made regarding the case where the present invention is applied to a three-terminal reverse blocking thyristor, the present invention can also be applied to bidirectional thyristors, reverse conductive thyristors, and the like. As described in detail above, in the thyristor according to the present invention, the second base region to which the gate electrode is bonded and the second emitter region formed in a predetermined portion of the surface of the second base region form a PN. Since a region is provided near the gate electrode of the junction where the impurity concentration at the working point is lower than other regions, the dv node and dt are extremely good, and the gate trigger current and its temperature dependence are also small.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the main part of a conventional thyristor, FIG. 2 is an impurity concentration distribution diagram of the semiconductor substrate of the thyristor shown in FIG. 1, and FIG. 4 is an impurity concentration distribution diagram of the semiconductor substrate of the thyristor of the example, FIG. 5 is a vertical cross-sectional view of the main part of the thyristor of the example, and FIG. 6 is a diagram of the conventional thyristor and the thyristor of the example. A graph showing the dv/dt characteristics, FIG. 7 is a graph showing the gate trigger current of the conventional thyristor and the thyristor of the example and its temperature dependence, and FIG.
Figures a and b are longitudinal cross-sectional views showing main intermediate steps of one method for manufacturing a thyristor according to the present invention, and Figures 9 a and b are longitudinal cross-sectional views showing main intermediate steps of another method for manufacturing a thyristor according to the present invention. It is. In the figure, 1 is the first emitter layer, 2 is the first base layer,
3 is a second base layer, 4 is a second emitter layer, 41 is a second emitter region in which the impurity concentration at the working point is lower than other regions, 5 is a first main electric castle, 6 is a second main electric castle, 7 is a gate electrode. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1 A first emitter region of a first conductivity type, a first base region of a second conductivity type, and a second base region of the first conductivity type are arranged adjacent to each other in order, and a surface portion of the second base region a semiconductor substrate having a second emitter region formed in a predetermined portion thereof, and a first main electrode, a second main electrode, and a gate electrode bonded to the first emitter region, the second emitter region, and the second base region, respectively. In those equipped with
The second base region and the second emitter region form a PN junction near the gate electrode.
The concentration of the diffused impurity at the point where the concentration of the diffused impurity of the first conductivity type for forming the base region and the concentration of the diffused impurity of the second conductivity type for the formation of the second emitter region is equal to the concentration of the diffused impurity of the PN junction. A thyristor characterized by having a region lower than other regions of the thyristor.