JPS61141179A - Turn-off thyristor - Google Patents

Abstract

PURPOSE:To contrive a reduction in current density and an augmentation in the maximum controllable current by a method wherein the respective passages for minority carriers and majority carriers, which are injected in the base region on one side, are separate-limited and high-impurity density regions, which have an inverse conductive type to the conductive type of the base region and are brought into a low-resistance state, and a gate are provided on the passage for the minority carriers. CONSTITUTION:When a positive voltage and a negative voltage and respectively impressed on an anode A1 and a cathode K, a positive pulse voltage is impressed on an N-type base layer Nb and a gate G is brought into a conducted state, electrons, which are injected in the layer Nb from an N-type emitter layer Ne, flow in a region B, the layer Nb and the N-type emitter layer Ne and bond with positive holes, while the majority of positive holes, which are injected in the layer Nb from the layer Ne, flow in low-resistance regions C as the potential of the region B is high and gap regions D are narrow, and further flow in a P type base layer Pb. Then, when a negative voltage is impressed on the gate G, the P-N junctions of the layer Nb and the P-type regions C are biased in the reverse direction, the positive holes which flowed in the regions C, are extracted through the gate G and the passage of the positive holes through the gap regions D is stopped by the gap regions D as the gap regions D respectively become the area of a depletion layer making a P-N junction. As a result, this turn-OFF thyristor is turned into an OFF-state layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called turn-off thyristor in which a voltage is applied to the gate of the thyristor and causes the thyristor to transition from a conducting state to a (reverse) blocking state, passing through the region of one base. In order to turn off the thyristor by blocking the flow of minority carriers into majority carriers and minority carriers, a turn-off device separates the paths of majority and minority carriers and cuts off the path of minority carriers. -Related to thyristors, which are suitable for switching large power supplies. p
apna! Considering a thyristor as a combination of a flfifl type transistor and an npn type transistor, and assuming that the current amplification factor of the pIIp type transistor is dpnp, and the current amplification wife of the npn type transistor is fXnpn, the conventional gate turn-off thyristor ( In order to increase turn-off gain in GTO), dpnp is generally used.
A gate G is provided at the base of the larger transistor of and σnpn. However, the base layer provided with this gate G cannot be made to have a low resistivity, and generally needs to be made small in thickness, resulting in a large base resistance. In a GTO that attempts to control large currents, the areas of the cathode and base regions are increased while keeping the base layer thickness thin, which increases the base resistance by 100%, which increases the turn-off time and increases the maximum possible There is a problem that the limiting a current cannot be increased.Also, if the thickness of the base layer is increased, there is a problem that the turn and off gain becomes smaller and the power loss within the thyristor increases.

The turn-off thyristor of the present invention is designed to eliminate the above-mentioned drawbacks of the conventional CTO, and the main points can be summarized as follows. The paths of minority carriers and majority carriers injected into one pace region (area A) are separated and restricted, and among these, the path of minority carriers is
A region C, which has a conductive type opposite to this pace region (region A) and has a low resistance due to a high impurity density, is formed so as to block the path of minority carriers, and a gate is provided in this region C. When the thyristor is in a conductive state, most of the minority carriers in region A pass through region C. To put the thyristor in a blocked state, the potential of region C is changed by biasing region C in the reverse direction with respect to region A. The method is to block the minority carriers in the base region A passing through the region C (extract them from the gate G) by changing the The potential change in the region C can be achieved in a manner similar to that of the conventional GTO, and the problem that the base in which the gate G is located has a large base resistance can be solved. Further, in the turn-off thyristor of the present invention, the base of the transistor with the larger current gain among the two transistors constituting the thyristor is usually not provided with a gate, or even if a gate is provided, the turn-off thyristor cannot be turned off. Since the transistor is not used as an additional gate, there is no need to increase the area of the base region of this transistor, and the area of the emitter region can be relatively increased, so that the current density can be reduced. Furthermore, since the majority carrier and minority carrier paths in the pace region A are separated, the current density in the base region A can be reduced, and local heating of the thyristor at high currents can be prevented, making it suitable for high power applications. Suitable.

Hereinafter, the turn-off risk of the present invention will be described in detail based on embodiments and with reference to the drawings. FIG. 1 is a cross-sectional diagram of a plane including an anode Ai cathode and a gate C of an example in which a turn-off thyristor having a pnpn structure according to the present invention is implemented with a lateral structure of silicon (SL), and shows the pH The point is p in the same figure, %pan@
a Corresponds to a. Furthermore, I) subscripts such as e+n&,
Electric and G correspond to the emitter and base, respectively. The thyristor made of fle n & Ph n, a is pn.
pn upper type resistor (composed of lee%%) and n
The current amplification factor IXnpn of the IIpn-type transistor is, in the embodiment shown in FIG.
It is assumed that the drift amplification factor C1pnp of the pnpn upper type transistor is larger than that of the pnpn transistor. An n-type silicon substrate (0"-3i substrate) plate with a high impurity density with a resistivity of about 0.015 fl-cm is defined as region B, and an n-type silicon substrate with a resistivity of about 10 Ω rcm on top of this plate has a resistivity of about 10 Ω rcm,
The n-type base layer n& corresponds to the base region A, and the n-type space layer nh is an epitaxially grown layer having a thickness of about 1 cm. In this n-type epitaxial growth layer, for example, a p-type emitter layer pe + a p-type base layer p with a depth of about gI, and an n-type emitter layer ne with a depth of about 9cm provided at the cathode are formed as shown in Fig. 1. Furthermore, as shown in the figure, a p-type low-resistance region C having a high impurity density is formed about Y distance from the n-type low-resistance region B. The operating mechanism of the turn-off thyristor having such a configuration will be explained as follows. From the DC power source, through the load, to anode A, positive.

When a negative voltage is applied to the cathode K and a positive pulse 1C voltage is applied to the gate G with respect to the n-type base Idnb to make the thyristor conductive, the n-type emitters from n to n The electrons with the majority carrier number in region A, which are injected into the type base layer n, flow into the region B, which has a low resistance, and flow from the partial region of region B at the bottom of the p-type emitter layer +1c to the n-type base layer na. ) flows out, and finally flows into the p-type emitter l1Iipe, and this emitter
recombines with the hole. On the other hand, p-type emitter npc to n
Most of the minority-carried holes injected into the shaped pace JFjn cannot flow into region B because it has a high potential for holes, and the gap region is narrow and has high resistance and low It flows into the region C of resistance. Furthermore, region C is charged until it becomes forward biased with respect to the n-type base layer nb (region A), and in a steady state, holes pass through region C and flow into the p-type base layer p-. . To shift this thyristor into the (reverse) blocking state, a negative voltage with respect to the n-type pace 11In6 can be applied to the gate G. At this time, between the n-type base layer n and the p shadow region C, pn! l! is backward biased, so the circulation C
The holes flowing into are extracted through the gate G and are returned to n
It is not possible to return to the shaped base layer 116. Also, the gap between area C and area B is 1% [the width of area 0 is narrow (approximately f
Since the reverse biased base layer fi- and the pn# of the region C become depletion layer regions, the passage of holes is also blocked through the gap region, and the p-type base II! Since the supply of holes to jp is cut off, the thyristor shifts to a blocking state (off state). Turn-off of the present invention
The thyristor can be manufactured using the same process as a conventional lateral thyristor. For example, p-type layers p, lpl and region C can be formed by thermal diffusion of boron, and n-type emitter layer n can be formed by thermal diffusion of phosphorus. Insulator Si
0. ! ! 4 + 4' + 4'' may be formed by thermal oxidation of 51 to a length of about 0.57 m, and the electrode 11 for the anode A1, the electrode 2 for the gate G and the cathode KffI electrode 4i1
3 is an ohmic electrode, which can be patterned by photolithography using a vacuum-deposited film of aluminum (AI) with a thickness of about 100 ml.

FIG. 2 is a cross-sectional structural diagram of an embodiment in which the turn-off thyristor of the present invention is made into a vertical na of St.
Components that function similarly to those of the embodiment shown in FIG. 1 are given the same reference symbols or numbers. In the embodiment shown in FIG. 2, p@n6 p
This is an example of a thyristor having a 4 structure, in which a gate CL is also provided in the p-type base layer 9k of the npn-type transistor section.Of course, the gist of the present invention is that the gate c
The presence or absence of l is irrelevant. Based on the embodiment of the vertical structure shown in FIG. 2, an example of the manufacturing method will be described in detail with reference to the drawings as follows. First, n-type St (approximately 10α
Thermal diffusion of boron is performed on both the front and back surfaces of the substrate 10' (thickness: approximately 150.cm), and p
A p-type emitter Np, which is a type layer, and a p-type high impurity density layer, which is to become a region C, are formed. At this time, by photolithography, a region of about 1 square inch where boron is not diffused is formed in the center of region C on the surface of the Si substrate d. Add phosphorus to this p-type region without Jg@ to form an n-type layer with a lagoon impurity density that should become region B. The width of the gap between region C and this region B is approximately → Next, in order to make this gap region 0 high in resistance, gold (An) or the like is diffused into the gap region. Of course, this gap area may be made into an insulator by ion implantation, or an insulating film may be formed to cover the gap area to increase the resistance. ni, f
An epitaxial layer 11' with a resistance of about 10Ω/C and a thickness of about 10/L is grown, and deep p-type impurity diffusion (boron diffusion) is performed to establish conduction from its surface to region C. , p forming a shadow region. Next, ll1
Similar to mwJ in Figure 1, a p-type base layer p6 and an n-type emitter layer n are formed by diffusion, and 5IO for insulation and surface protection is formed.
1 film 4.4', 4' is formed by thermal oxidation, and then AI
Pattern the electrodes 1.2, 2.3. The operating principle of the vertical turn-off thyristor shown in Figure 2 is as follows:
It is similar to the lateral type shown in the figure.

The operation of the gate G during turn-off of the turn-off thyristor of the present invention can be performed by an externally attached low-power transistor or thyristor.

As is clear from the above explanation, the turn and
An off-thyristor separates the majority carriers and minority carriers traveling in the base region, so the current density can be reduced. It is suitable for high power applications because the thickness can be reduced and the area of the emitter of the transistor can also be relatively large. In addition, since region C, which is a region that controls the passage of minority carriers in base region A, can have a high impurity density, it can also be made low in resistance and can easily draw out minority carriers in base region A. The control current becomes large and high-speed operation is possible.

[Brief explanation of drawings]

FIG. 1 shows an anode A of an embodiment of a turn-off thyristor according to the invention in a lateral configuration. , cross section rl in a plane including gate G and cathode K
Figures a and 2 show another embodiment of the present invention, which is a cross-sectional diagram similar to that of Figure 1 when it is implemented vertically. 10.10'...n-type substrate, dan, dan...■-type epitaxial layer, [...p-type diffusion region, 1,2
12.3...AI@pole, 4.4', 4...s
to, film, A...n-type base region, B...n
type high impurity density region, C...p@high impurity region,
O... Gap region, p,... P-type emitter island, n,... N-type base layer, pHl... P-type base layer, fil... N-type emitter Tang patent To the emergence of Mitsuteru Kimura

Claims (1)

[Claims] In a turn-off thyristor that has a pnpn structure and transitions from a conductive state to a blocking state by blocking the flow of minority carriers p_a (or n_a) in one base region A, the base region A is A region B of the same conductivity type as the base region A and a region C of the opposite conductivity type to the base region A are provided, and carriers in the base region A are distributed in regions other than regions B and C and a gap region D between the regions B and C. When the thyristor is in a conductive state, minority carriers p_a (or n
Region B and region C are made to have a high impurity density and are placed in close proximity so that at least 90% or more of __a) passes through region C and at least 90% or more of majority carrier n_a (or p_a) passes through region B. The gap region D is formed so that the minority carrier p_a (or n_a) cannot pass through the thyristor during transition from the conductive state to the blocked state, or the conductive state of the thyristor cannot be maintained even if the minority carrier p_a (or n_a) passes through. To move the thyristor from a conducting state to a blocking state, the minority carriers p_a (or A turn-off thyristor characterized in that the turn-off is performed by cutting off the flow of n_a).