JPS6364908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to buried gate gate turn-off (GTO) thyristor structures.

In contrast to the normal surface gate type shown in Fig. 1, the buried gate type GTO thyristor is a P thyristor that is formed embedded in a _P2 base layer using an epitaxial growth method, as shown in Fig. 2. ^A ₂₊ high concentration impurity layer is provided in a distributed manner, and ^the P ₂₊ layer is used as a gate layer. In the surface gate type GTO thyristor shown in Fig. 1, the cathode K has a short fence-like narrow structure and the _N2 emitter layer is divided in order to improve off-state characteristics.
In a buried gate type GTO thyristor, an N ₂ emitter layer is formed over the entire surface of the P ₂ ⁺ buried gate layer. this is,
The buried gate type GTO thyristor utilizes the fact that the main current flows through the gate slit S and the P ₂ ⁺ gate part does not operate as a thyristor. Therefore, the buried gate type GTO thyristor has the advantage that short circuits between the gate and the cathode are less likely to occur, making it easier to manufacture.

However, a buried gate GTO thyristor has a P ₂ ⁺
Since the part corresponding to the buried gate does not operate as a thyristor, the part of the on-gate current I _gt that flows from the P ₂ ⁺ buried gate to the N ₂ emitter layer, which is the part where the thyristor does not operate, is turned on, as shown in _Figure 3. Does not contribute to operation, that is, on-gate current I _gt
becomes larger than necessary, lowering the turn-on gain as a ratio to the main current I _L. To reduce this, reducing the P ₂ ⁺ buried gate area makes the P ₂ ⁺ layer removed part more prone to turn-off failure to operate as a thyristor.

The present invention was made in view of the above circumstances, and
By keeping the total resistance of the P ₂ ⁺ buried gate layer within the range necessary to draw the off-gate current, equivalently the extra P ₂ ⁺
Split the cathode N ₂ layer to remove the layer P ₂ ⁺ the anode opposite it without forming the central part P ₁
The purpose of this invention is to provide a buried gate type GTO thyristor with reduced on-gate current by having a divided structure with layers removed.

FIG. 4 shows an embodiment of the present invention. The same figure is the third
The difference from the diagram is that the area of the P ₂ ⁺ buried gate layer is set to the range necessary to draw out the off-gate current, and no P ₂ ⁺ layer is formed in the central part (shaded area) where the invalid on-gate current flows. Directly below this central part
The structure is such that the _P1 emitter layer is not formed, but is left as the _N1 base layer and is shot by the anode electrode A.

In this structure, the resistance of the _P2 ⁺ buried gate layer is
Since it is much smaller than the P ₂ base resistance, the current density of the on-gate current increases by removing the P ₂ ⁺ layer.
In addition to this, since the reactive portion of the on-gate current is also reduced, the on-gate current I _gt can be reduced. Furthermore, although epitaxial growth is usually used to form a P ₂ ⁺ buried gate layer, P ₂ ⁺
The reduction in the area of the layer has the effect of reducing autodoping, making the resulting I _gt reduction more effective. In addition,
Directly below the deleted part of the _P2 ⁺ buried gate layer, the _P1 emitter layer is not formed and it operates only as a transistor,
Erroneous thyristor operation does not occur even when the device is turned off.

In this example, the rate of decrease in the on-gate current I _gt was reduced by about 60% compared to that in FIG.

FIG. 5 shows another embodiment of the invention. The difference between this figure and FIG. 3 is that the N ₂ emitter layer facing the central part of the P ₂ ⁺ layer, which is the ineffective portion of the on-gate current, is not formed and is left as a P ₂ ^- layer, and the short part of the cathode emitter is The point is that the cathode electrode K and the P ₂ ^-base layer are separated by an insulating film such as a Si oxide film to prevent this from occurring.

With this structure, the on-gate current reactive component is reduced and the on-gate current density near the gate slit is increased. In other words, turn-on can be achieved with a reduced on-gate current I _gt . Furthermore, when turning off the device by reverse biasing the degree of the N ₂ emitter, an increase in leakage current due to the N ₂ emitter short is prevented.

In this example, the rate of decrease in on-gate current I _gt was reduced by about 70% compared to that in FIG.

In this way, ⁱⁿ the present invention, _{N 2}
Since the structure reduces the current flowing to the emitter layer, it is possible to reduce the reactive component of the on-gate current and increase the turn-on gain.

[Brief explanation of drawings]

Fig. 1 is a structural diagram a of a conventional surface gate type GTO thyristor and a partially sloped view b; Fig. 2 is a structural diagram a of a conventional buried gate type GTO thyristor and a partially sloped view b;
Figure 3 is a diagram for explaining the on-gate current in a conventional buried gate GTO thyristor.
The figure is a structural diagram showing one embodiment of the present invention, and FIG. 5 is a structural diagram showing another embodiment of the present invention. A... Anode electrode, K... Cathode electrode, G
...Gate electrode, P ₂ ⁺ ...Buried gate layer.

Claims (1)

[Claims] A four-layer structure of 1 P ₁ N ₁ P ₂ N ₂ , with a highly concentrated impurity layer P ₂ ⁺ dispersed in the P ₂ base layer, and the layer P ₂ ⁺ used as a gate layer. In the embedded gate type gate turn-off thyristor, the N ₂ emitter layer does not form a portion facing the center portion of the gate layer so as to reduce the current flowing from the center portion of the gate layer that does not contribute to the thyristor operation to the N ₂ emitter layer. A buried gate type gate turn-off thyristor characterized by a structure in which a P ₂ base layer is left in the split portion and an insulating film is formed between the P ₂ base layer in the split portion and a cathode electrode. 2 A buried gate type gate turn-off thyristor with a four-layer structure of P ₁ N ₁ P ₂ N ₂ , with a highly concentrated impurity layer P ₂ ⁺ dispersed in the P ₂ base layer, and using the layer P ₂ ⁺ as the gate layer. In this case, the gate layer is formed without forming the central portion so as to reduce the current flowing from the central portion that does not contribute to the thyristor operation to the _N2 emitter layer.
A buried gate type gate turn-off thyristor characterized by a divided structure in which a _P2 base layer is left and an anode _P1 layer facing the central portion is not formed and left as an _N1 base layer.