JPS5931220B2 - reverse conducting thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a reverse conduction thyristor that reduces the off-state current of the reverse conduction thyristor.

An example of the structure of a so-called reverse conduction thyristor in which a thyristor and a diode are arranged in antiparallel in one semiconductor substrate is shown in the sectional view of FIG.

In FIG. 1, reference numeral 1 denotes an n-type high-resistance substrate, which constitutes an n-type second base layer 2. In FIG. 3 is a P-type first base layer that is adjacent to the second base layer 2 and forms a junction J2 with the second base layer 2; 4 is a P-type first base layer that is adjacent to the second base layer 2 and forms a junction J2 with the second base layer 2; The second emitter layer constituting the junction J1, 5 is the first
Junction J3 adjacent to the base layer 3 and between the first base layer 3
The first emitter layer 6 and T constituting are the first base layer and the second base layer exposed on the main surfaces 8 and 9, respectively.

Further, 10 is a first base layer exposed on the main surface 8 and constitutes a gate. 11 is a gate electrode that makes electrical contact with the gate 10, 12 is a cathode electrode, 13 is an anode electrode, and 14 is between the second base layer and the anode electrode, and is provided on the second base layer to make ohmic contact with the anode electrode. 15 is a sloped surface for surface stabilization, 16 is a thyristor part, 1? is the diode part, 1
8 is an inclined portion.

The method of manufacturing a reverse conduction thyristor having such a configuration is well known, and therefore will not be described here. Since reverse conduction thyristors are used in inverters and chopper devices, short turn-off times are required.

In order to shorten the turn-off time, it is necessary to introduce into the thyristor section 16 a heavy metal or a lattice defect that will kill the lifetime, and gold or platinum electron beam irradiation is generally used. Furthermore, after energizing the diode section 17, if ten voltages are applied to the anode side and one voltage is applied to the cathode side, the holes that have penetrated into the second base layer 2 of the thyristor section 16 when the diode section 17 is energized are transferred to the thyristor section. 16 into the first emitter layer 5 to fire the thyristor, causing what is called a commutation loss. In order to prevent this loss of sales due to commutation, lifetime killers such as heavy metals have conventionally been introduced into the diode section 17 as well. Furthermore, it is necessary to maintain the accumulated charge at a constant value after energizing the diode section 17 in the circuit, but in the conventional structure,
Diode current also flows to the vertically projected part of the inclined part, so if the lifetime of this part is not controlled,
Accumulated charge could not be controlled. For this reason, the reverse conduction thyristor of the conventional structure has the disadvantage that the off-state current increases due to the introduction of heavy metals into the sloped portions which do not work effectively when energizing the diode portion 17.

The object of the present invention is to eliminate the drawbacks of the conventional reverse conduction thyristors and provide a reverse conduction thyristor with reduced off-state current.

An embodiment of the present invention will be described using a cross-sectional view shown in FIG.

In FIG. 2, 1 is an n-type high-resistance semiconductor substrate;
This constitutes the second base layer 2 of the mold.

3 is a p-type first base layer adjacent to the second base layer 2 and forms a junction J2 with the second base layer 2; 4 is adjacent to the second base layer 2 and forms a junction J2 with the second base layer 2; A p-type second emitter layer 5 is adjacent to the first base layer 3 and forms a junction J3 with the first base layer; 6 and 7 are respective main surfaces; 8 and 9 are the first base layer 3 and the second base layer 4 exposed.

Further, 10 is a first base layer exposed on the main surface 8 and constitutes a gate. 11 is a gate electrode that makes electrical contact with the gate 10; 12 is a cathode electrode; 13 is an anode electrode;
4 is an n+ layer provided on the second base layer 2 between the second base layer 4 and the anode electrode 13 to make ohmic contact with the anode electrode; 15 is the semiconductor substrate 1 tilted for surface stabilization; surface, 16 is the thyristor part, 17
18 is a diode portion, and 18 is a tilted portion.

Reference numeral 19 denotes a third emitter layer of a conductivity type different from that of the second base layer, which is provided in the vertical projection part of the surface inclined part into the second base region 2 toward the anode side, and J4 denotes the third emitter layer 19 and the second emitter layer. This is a Pn junction formed by the base layer 2.

The main point of the invention is that such a third emitter layer is present in the vertical projection of the sloped portion 18 towards the anode side. Therefore, almost no carriers flow into the vertically projected portion of the inclined portion 18 toward the anode side when the diode is energized, so that the accumulated charge in the inclined portion 18 becomes almost zero.

Therefore, it is no longer necessary to shorten the carrier lifetime in this region, and the amount of lifetime killer introduced into the inclined portion 18 is extremely small compared to the reverse conduction thyristor of the conventional structure, and the vertical projection of the inclined portion 18 is Even if the lifetime of the lower first base layer 3 and second base layer 2 is made longer than the lifetime of the first base layer 3 and second base layer 2 of the diode part, the amount of accumulated charge can be controlled to be the same. In normal power semiconductors, the depth of the J2 junction is about 80 to 90 μm,
Since the inclination is performed at an inclination angle of about 1 to 3 degrees, approximately 3 mm is required for the inclination.

When a semiconductor substrate with a diameter of 50 mm is used, the area required for tilting is 4.2 d, which is 20% of the total area.

In conventional reverse conduction thyristors, heavy metals are also introduced into the inclined portions, so the share of off-current in areas other than the thyristor portions is approximately 70? It was moderately hot. For example, 2500V, 40
In a high-speed switching reverse conduction thyristor with characteristics and ratings of 0A/150A, 30μm, of the 80mA of off-state current at a junction temperature of 125°C, the off-state current is 25mA only in the thyristor part, and the off-state current is 25mA in the thyristor part only, that is, the diode part and the inclined part. The off-state current at the sloping part was about 55 mA, but in the present invention, the off-state current is 20 to 30 mA only at the thyristor part, and the off-state current at parts other than the thyristor part shows that the amount of heavy metal introduced into the slanted part 18 is small. Therefore, the total off-state current was reduced by +20mA to 30mA. As described above, the present invention has a remarkable effect on reducing off-state current, and since the present invention is implemented in an area that does not contribute to actual current conduction, it does not have any adverse effect on the characteristics and ratings. Needless to say.

The embodiment of the present invention was explained using FIG. 2, but an n-type high resistance layer (ml layer) was formed in place of the third emitter layer 19 made of the p+ layer in FIG. Good too.

This is because the high resistance layer (n-) existing between the second base layer (ml) 2 of the first conductivity type and the anode electrode 13 acts to prevent injection of electrons from the anode electrode 13, and the slope When the diode is energized, carrier hardly flows into the vertically projected part of the attached part 18, so the inclined part 1
The accumulated charge of 8 becomes almost O. Therefore, the high resistance n layer produces exactly the same effect as the p+ third emitter layer 19. Furthermore, although it is preferable that the inner edge 20 of the third emitter layer 19 be located inside the inner edge of the vertically projected portion of the inclined portion, it has been confirmed that the same effect can be obtained even if it is located slightly outside. . As described above, according to the present invention, a reverse conduction thyristor in which a diode is arranged around a semiconductor substrate has a remarkable effect in reducing off-state current.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a conventional reverse conduction thyristor, and FIG. 2 is a longitudinal cross-sectional view of a reverse conduction thyristor embodying the present invention. In the figure, 5 is a first emitter of the first conductivity type. 3 is a first base layer of a second conductivity type, 2 is a second base layer of a first conductivity type, 4 is a second emitter layer of a second conductivity type, and 6 is a second base layer of a second conductivity type forming a diode. 1 base layer; 7 a second base layer of the first conductivity type forming a diode; 8;
9 is a pair of main surfaces, 19 is a third emitter layer of the second conductivity type adjacent to the second base, 18 is a vertical projection of the inclined portion, 17 is a diode portion, and 20 is a vertical projection of the inclined portion. 21 is the inner end of the third emitter layer.

Claims (1)

[Claims] 1. A first emitter layer of a first conductivity type and a first base layer of a second conductivity type forming a pn junction J_3, which are adjacent to the first base layer and form a pn junction J_2. a thyristor portion including a second base layer of a first conductivity type to be formed, a second emitter layer of a second conductivity type adjacent to the second base layer and forming a pn junction J_1 with the second base layer, and the pn junction J_2.
and a diode portion formed by exposing a first base layer and a second base layer to a pair of main surfaces, respectively, the diode portion is arranged around the thyristor portion, and the second base layer is formed at the periphery of the semiconductor substrate. A third emitter layer of the second conductivity type or a high resistance layer of the first conductivity type forming a pn junction J_4 with the second base layer around the outer periphery of the diode is provided adjacent to the layer;
A first base layer in which the outermost peripheral edge of the semiconductor substrate is sloped, and the lifetime of minority carriers of at least a portion of the first base layer and the second base layer under the vertical projection of the sloped portion constitutes a diode portion. and a reverse conduction thyristor characterized by having a lifetime longer than the minority carriers of the second base layer. 2. The end of the third emitter layer or the high resistance layer of the first conductivity type that faces the second emitter layer of the thyristor section is located inside the end of the vertically projected part of the inclined semiconductor substrate. A reverse conducting thyristor according to claim 1, characterized in that: 3. The end of the third emitter layer or the high resistance layer of the first conductivity type opposite to the second emitter layer of the thyristor section is on the inner end of the vertically projected part of the inclined semiconductor substrate or on the outside. A reverse conducting thyristor according to claim 1, characterized in that: 4 Claims characterized in that the lifetime of the region including at least the second base layer is controlled using heavy metals such as gold, platinum, Fe, Ni, etc., and radiation such as neutron beams, electron beams, and γ rays. The reverse conducting thyristor according to item 1.