JPS593867B2 - reverse conducting thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a reverse conduction thyristor that improves commutation ability, reduces on-state voltage, and reduces off-state current.

10 As an example of a conventional structure in which a so-called reverse conduction thyristor, in which a thyristor and a diode are built in antiparallel in the same semiconductor substrate, has a high breakdown voltage and a large capacity, Fig. 1 shows a vertical cross-sectional view of its main parts. The fully diffused type shown below was common.

15 FIG. 2 is a diagram showing the impurity concentration distribution in a cross section taken along the line ■-■ shown in FIG.

In FIG. 1, A is a thyristor section, B is a diode section, C is a separation band, and 1 is an N-type silicon 20-con board (semiconductor substrate) that is shared by the N base region of the thyristor section and the N-type region of the diode section. , 2 is a P type region (first second conductivity type region) shared by the P base region of the thyristor section and the P type region of the diode section, and 3 is a P emitter region of the thyristor section (second second conductivity type region). 4 is an N← type region for the ohmic contact 25 of the diode section, 5 is an N emitter region (third first conductivity type region) of the thyristor section, 6
is a gate region of the thyristor portion, □ is an anode electrode, 8 is a cathode electrode, and 9 is a gate electrode. J1 is a PN junction formed by N type silicon substrate 1 and P emitter region 3, J2 is a PN junction formed by N type silicon substrate 1 and P type region 2, and J3 is P type region 2 and N emitter region 3. This is a PN junction formed by region 5. In the reverse conduction thyristor with the above structure, the structural force S of the thyristor part is the same as that of the reverse blocking thyristor with the PNPN structure, so the characteristics and ratings of the thyristor part of the reverse conduction thyristor are as follows:
It was not possible to exceed the characteristics and ratings of a reverse blocking thyristor with the same cathode area.

For this reason, it has high breakdown voltage, large capacity, and high-speed switching characteristics, with a breakdown voltage of 2500V, a current capacity of 400A for the thyristor section, a current capacity of 150A for the diode section, and a switching time of 30I.
It has been difficult to realize a tS reverse conduction thyristor. In order to overcome this difficulty, we focused on the fact that in reverse conduction thyristors, the withstand voltage of the J1 junction only needs to be several times the transient on-voltage drop of the diode built in parallel. As shown in the top view, the thyristor part is PN+NPN.
A reverse conducting thyristor with a structure has been devised. In this structure, although the withstand voltage of the J1 junction is lower than that of the PNPN structure, in order to obtain the same off-voltage, it is necessary to increase the specific resistance of the N-type silicon substrate 1, which is the central N base layer. The width of the base layer can be shortened. Therefore, PN′+
In the NPN structure, N is shortened compared to the PNPN structure.
The on-voltage drop and off-state current can be reduced by the width of the base layer. As a result, the breakdown voltage is over 2500V,
It has become possible to manufacture a reverse conduction thyristor with a turn-off time of 30 μs or less. To realize the PN+NPN structure, epitaxial growth is generally used to form the N+ type region 10 (second first conductivity type region) shown in FIG.

FIG. 4 is a diagram showing the impurity concentration distribution in a cross section along the HV line shown in FIG. 3. The manufacturing method of the conventional reverse conduction thyristor of PN+NPN structure shown in FIG. 3 in which the N+ type region 10 is formed is as follows.

First, aluminum (A
t) A P-type region is formed by diffusing an impurity such as gallium (Ga), and one P-type region 2 is left and the other P-type region is removed by lapping and mirror polishing. Subsequently, the mirror-polished surface of the N-type silicon substrate 1 is cleaned by a well-known method, and then an N+-type region 10 is formed on the mirror-polished surface by epitaxial growth. in this case,
The thickness of the epitaxially grown layer is limited to about 50 μm due to mass productivity and defects introduced into the crystal.
Next, a P emitter layer 3 in which P type impurities are diffused to form a J1 junction in the N+ type region 10, and an N+ type emitter layer 3 in which N type impurities are selectively diffused to form an ohmic contact in the diode part. After forming the region 4, N-type impurities are selectively diffused into the P-type region 2 from its surface to form an N-emitter region 5 and a gate region 6, thereby forming a reverse conduction thyristor with a desired PN+NPN structure. obtain.
In the reverse conduction thyristor thus obtained, an isolation region of a PN+NP structure called an isolation band (indicated by C in the figure) is provided at the boundary between the thyristor section and the diode section. If this separation band is not present, the thyristor is turned on,
Next, the voltage between the anode and cathode is reversed, the diode is energized, and then the voltage is reversed, and the remaining holes in the diode part are transferred to the N emitter region 5 of the adjacent thyristor.
VC is injected, electrons are injected from the N emitter region 5, and the thyristor is turned on. This phenomenon is called commutation failure. A major challenge for reverse conducting thyristors is to improve this commutation ability. Improvement in commutation capability is particularly desired for reverse conduction thyristors with large capacity and high speed switching characteristics. However, in a reverse conduction thyristor with a PN+NPN structure in which the N+ type region 10 is formed by epitaxial growth, the larger the area, the larger the
It becomes difficult to obtain the required breakdown voltage over the entire area of 0. This is thought to be caused by the inclusion of foreign matter introduced during epitaxial growth or by crystal defects. In addition, the J1 junction is formed by epitaxially growing the N+ type region 1.
The required soil to be formed within 0, the depth of J1 joint is at most 30
Molybdenum (MO)
When adhering to a temperature compensator such as , tungsten (W), etc., the J1 joint may be destroyed and pressure resistance may not be obtained due to local digging of the brazing material. In this way, if the withstand voltage of the J1 junction of the thyristor section is not a partial one, the short emitter is provided on the cathode side, resulting in a structure in which the thyristor section has a built-in diode. In this case, since there is no separation structure between the built-in diode and the thyristor, the commutation ability is reduced. For this reason, large diameter (
For example, using a silicon wafer (with a diameter exceeding 50Tm0), the N+ type region 1 is grown by epitaxial growth.
It has been difficult to realize a reverse conduction thyristor with a PN+NPN structure in which 0 is formed. This invention was made to eliminate the above-mentioned drawbacks, and by forming the J1 junction at a position deeper than the boundary between the epitaxial growth layer and the silicon substrate, it is possible to ensure the breakdown voltage of the J1 junction. The object of the present invention is to provide a reverse conduction thyristor which prevents a reduction in pressure resistance due to biting of the brazing material when bonded to a temperature compensator.

The present invention will be explained below with reference to Examples.

FIG. 5 is a longitudinal cross-sectional view of a main part of an embodiment of a reverse conduction thyristor according to the present invention, and FIG. 6 is a diagram showing an impurity concentration distribution in a cross section taken along the line - shown in FIG.

5 and 6, reference numeral 11 denotes a ▼-shaped diffusion region (a first first conductive shape area). A ▼-shaped region 10 with a thickness of about 50 μm is formed by epitaxial growth on the surface of the N+ type diffusion region 11. The main portion of the J1 junction is formed beyond the N+ type region 10 and into the N+ type diffusion region 11. The manufacturing method of the reverse conduction thyristor shown in FIG. 5 will be briefly described as follows.

At. from both main surfaces of the N-type silicon substrate. ．． P-type impurities such as Ga are diffused to form P-type regions, and one P-type region 2
, and remove the other P-shaped region by wrapping and mirror polishing. Subsequently, N-type impurities are diffused from the surface of the mirror-polished N-type silicon substrate to a depth of about 30 μm to form a meter-shaped diffusion region 11. Next, an N+ type region 10 with a thickness of about 50 μm is formed on the surface of the N type diffusion region 11 by epitaxial growth. Next, from the surface of the N+ type region 10, a P type impurity is diffused into the thyristor portion to form a P emitter layer 3, and an N type impurity is diffused into the diode portion to form an N-type region 4. Furthermore, N-type impurities are selectively diffused from the surface of P-type region 2 to form N-emitter region 5 and gate region 6. In the reverse conducting thyristor of the above embodiment, the main part of the J1 junction is not the N+ type region 10 formed by epitaxial growth;
Since it is formed in the N+ type diffusion region 11 formed by diffusing N type impurities into the silicon substrate, it is not affected by foreign matter contamination in the epitaxial growth layer, crystal defects, etc.
Regardless of the area of the silicon wafer, the J1 junction can provide the required breakdown voltage.

Further, since the depth of the J1 joint can be set to about 60 μm, it is possible to prevent a decrease in the withstand voltage of the J1 joint due to biting of the brazing material during adhesion to the temperature compensator. As a result, even if the silicon substrate has a diameter of 60 mn0 or more, the PN+NPN structure prevents the commutation ability from decreasing. Therefore, by shortening the N base region, reducing on-voltage, reducing off-current, and improving commutation ability, silicon of 50 m0 or more can be used. It has become possible to realize a reverse conduction thyristor with high withstand voltage, large capacity, and high-speed switching characteristics using a body.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the main parts of a conventional reverse conduction thyristor.
Figure 2 shows the impurity concentration in the cross section along the - line shown in Figure 1. Figure 3 is a longitudinal sectional view of the main parts of an improved conventional reverse conduction thyristor, and Figure 4 is a diagram showing the distribution.
Figure 5 is a longitudinal sectional view of the main part of a reverse conduction thyristor which is an embodiment of the present invention, and Figure 6 is a diagram showing the impurity concentration distribution along the line shown in Figure 5. 2 is a diagram showing an impurity concentration distribution in a cross section along . In the figure, 1 is an N-type silicon substrate, 2 is a P-type region, and 3
is a P emitter region, 4 is an N+ type region, 5 is an N emitter region, 6 is a gate region, 1 is an anode electrode, 8 is a cathode electrode, 9 is a gate electrode, 10 is an N+ type region, 11 is an N
It is a +-shaped diffusion region.

Claims (1)

[Claims] 1. A semiconductor substrate having a first conductivity type and having a low impurity concentration; a first second semiconductor substrate formed on a first main surface portion of the semiconductor substrate;
a conductivity type region, a first conductivity formed by introducing impurities of a first conductivity type at a high concentration into a second main surface portion of the semiconductor substrate opposite to the first main surface portion; a second first conductivity type region with a high impurity concentration formed by epitaxial growth on the surface of the first first conductivity type region; a predetermined portion of the surface of the first second conductivity type region; impurities of a second conductivity type from a position opposite to the third first conductivity type region on the surface of the third first conductivity type region formed in the second conductivity type region and from the vicinity thereof. a second second conductivity type region formed such that its leading edge is located within the first first conductivity type region, the second first conductivity type region and the second second conductivity type region; a cathode electrode that electrically connects the first second conductivity type region and the third first conductivity type region; and a cathode electrode that electrically connects the first second conductivity type region and the third first conductivity type region; and a gate electrode connected to the region. 2. The reverse conduction thyristor according to claim 1, wherein the outer edge of the second second conductivity type region is located outside the position facing the outer edge of the third first conductivity type region.