JPS633466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double-sided gate type electrostatic induction thyristor that performs high-speed switching in a large current region.

A static induction transistor (hereinafter referred to as SIT), which controls the amount of carrier injection from the source by controlling the potential barrier appearing in front of the source using the gate voltage and drain voltage, exhibits unsaturated current-voltage characteristics.
It allows a large current to flow, has a large conversion conductance, and can easily increase the withstand voltage.The gate capacitance can also be reduced, allowing high-power, high-frequency operation. There are two operating modes in junction-type SIT. When the gate is kept at the same potential as the source, it is in a conductive state, and in the main operating state, the gate is operated by applying a reverse bias (normally-on type), and when the gate is kept at the same potential as the source, it is in a conductive state. , the gate is in a cut-off state, and a forward bias is applied to the gate to make it conductive (normally-off type). When the gate is operated with a forward bias, minority carriers are inevitably injected from the gate into the channel. Of course, injection of a moderate amount of minority carriers into the channel increases the injection efficiency of majority carriers from the source, increasing the conversion conductance and current gain, and is effective, but if too many minority carriers are injected, the channel The accumulation effect of excess minority carriers inside becomes noticeable, resulting in a decrease in operating speed.

Split gate SIT proposed by the inventor of the present application (Patent No. 1302727 (Special Publication No. 60-20910) "Static Induction Transistor and Semiconductor Integrated Circuit", Patent No. 1236163
(Special Publication No. 59-12017) "Semiconductor integrated circuit", Patent No. 1247054 (Special Publication No. 59-21176) "Static induction transistor semiconductor integrated circuit", Patent No. 1231827 (Special Publication No. 59-8068) " (Details in “Semiconductor Integrated Circuits”)
This eliminates the accumulation effect of excess minority carriers mentioned above, reduces the gate capacitance without reducing the conversion conductance, and is extremely suitable for high-speed operation. Of course, the split gate structure is also effective for electrostatic induction thyristors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a double-sided gate type electrostatic induction thyristor that incorporates a split gate structure and is capable of high-speed switching of large currents.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of a double-sided gate type electrostatic induction thyristor of the present invention.

N ⁺ region 1 is a cathode, p ⁺ regions 2 and 3 are drive gates that control electron injection on the cathode side, respectively.
The fixed potential regions, n ^- region 4 and p ^- region 14 are channel regions on the cathode side and gate side, respectively;
The p ⁺ region 11 is an anode, and the n ⁺ regions 12 and 13 are drive gates and fixed potential gates that control hole injection on the anode side, respectively, 1', 2', 11', 1
Reference numerals 2' denote a cathode, a drive gate on the cathode side, an anode, and an electrode of the drive gate on the anode side, each made of a metal such as Al or Mo or low-resistance polysilicon. Region 6 contains SiO ₂ , Si ₃ N ₄ ,
It is an insulating layer such as Al ₂ O ₃ or a composite insulating layer that combines multiple of these. The impurity density in each region is approximately 10 ¹⁸ to 10 ²¹ cm ^-3 for 1 and 11, respectively.
2, 3, 12, 13 are about 10 ¹⁶ to 10 ²¹ cm ^-3 , 4,
14 may be approximately 10 ¹¹ to 10 ¹⁶ cm ⁻³ . The width of the channel sandwiched between the drive gate and the fixed potential gate varies depending on the voltage applied to the fixed potential gate, but when the potential of the drive gate is the same as that of the cathode and anode, the width of the channel is a depletion layer extending from both gates. It is chosen so that it is completely covered by , creating some potential barrier and being in a blocking state. This varies depending on the impurity density of the channel and the impurity density of the gate, and the higher the impurity density of the channel, the narrower the channel width usually has to be. The spacing between cathode and anode is
The transit time of electrons between the source and the drain may be set to a length that does not deteriorate the frequency characteristics of the operation. For example, if a switching speed of 1 nsec is to be obtained, the thickness should be about 20 μm or less. The fixed potential gates 3 and 13 may be directly connected to the cathode 1 or the anode 11, or may be biased in a predetermined reverse direction (in this case, a negative voltage). Also,
The operating voltages of the drive gates 2 and 12 are not limited to O and forward bias (positive voltage in this case), but are also set to reverse gate bias.
Therefore, it is possible to return to the O bias. but,
Normally, it is often easier to use a circuit that is cut off when the drive gate bias is zero and becomes conductive only when a predetermined forward bias is applied. For example, when a predetermined forward bias is applied to the drive gate, a large amount of electrons is injected from the cathode and holes are injected from the anode. The operation is performed by applying a positive voltage to electrode 11' with respect to electrode 1', applying a forward voltage (a slight positive voltage with respect to electrode 1') to electrode 2', and simultaneously applying a forward voltage (11' to electrode 12'). When a slightly negative voltage is applied to 1' and 11', electrons and holes are simultaneously injected from both sides, and the voltage between 1' and 11' decreases to a small holding voltage. At this time, most of the holes and electrons flow to the respective fixed potential gates 3 and 13' and do not flow to the drive gate. When shutting off, the bias applied to both drive gates can be returned to its original state. Compared to a single-sided gate type electrostatic induction thyristor having only one gate, the double-sided gate type electrostatic induction thyristor of the present invention has significantly shorter turn-on and turn-off times and a lower holding voltage.

Next, the planar configuration of the double-sided gate type electrostatic induction thyristor shown in FIG. 1 will be described. As is clear from the explanation of Fig. 1, each gate operates complementary to the cathode and anode, so the following explanation will be made regarding the cathode and the gate region on the cathode side, but the anode and the gate region on the anode side will be explained below. The same is true for FIG. 2 shows an example of the structure of a double-sided gate type static induction thyristor having a divided gate in which the gate is divided into a drive gate and a fixed potential gate. Figures 2a and b are plan views, Figure 2c is a sectional view taken along line A-A' in Figure 2a, and Figure 2d is a cross-sectional view taken along line A-A' in Figure 2b.
FIG. 3 is a sectional view taken along line B'. In FIGS. 2a to 2d, the electrode wiring and the structure on the anode side are not shown for the sake of simplicity. n ⁺ region 1 is cathode, p ⁺ region 2,
3 are drive gate, fixed potential gate, n ^-
Region 4 and p ^- region 14 are channels, respectively.
1' and 2' are a cathode electrode and a driving gate electrode, respectively. FIG. 2a shows a structure in which a fixed potential gate completely surrounds the cathode and drive gate. In FIG. 2b, the fixed potential gate has a structure in which a part of the fixed potential gate has a cut in order to reduce the capacitance between the drive gate electrode 2' and the fixed potential gate. As shown in FIG. 2d, the cathode electrode 1' is in direct contact with the fixed potential gate 3, illustrating the case where the fixed potential gate is kept at the same potential as the cathode. Of course, it is also possible to apply a predetermined constant bias to the fixed potential gate instead of setting it at the same potential as the cathode. FIG. 3 shows another embodiment of the double-sided gate type electrostatic induction thyristor of the present invention in which the capacitance of the drive gate is further reduced and the current gain is increased.

FIG. 3a is a plan view, and FIG. 3b is a sectional view taken along line A-A'. The drive gate 2 has a cylindrical shape, the source 1 has an annular shape, and the fixed potential gate 3 extends over the required entire surface. As shown in FIG. 3, when the drive gate is configured in a cylindrical or annular shape, a wide channel can be controlled even with a small drive gate, and the capacitance of the drive gate is small and the current gain is large. Since the minority carriers injected into the channel are immediately sucked out of the fixed potential gate, there is little effect of accumulation of minority carriers and the switching speed is extremely fast. The cathode electrode 1' opposes the fixed potential gate via the insulating layer 6, but since the cathode and the fixed potential gate are usually directly connected or kept at a constant voltage, an increase in the capacitance between them is not a problem. It doesn't affect me at all. The fact that normal switching operations are performed in a cathode-grounded circuit further confirms the above. The operation is almost the same as the example shown in FIG.

Although region 1 and regions 2 and 3 and region 11 and regions 12 and 13 are shown separated in FIG. 1, they may of course be in direct contact. Although FIG. 1 shows an example in which 1 and 11 face each other, it is not always necessary to do so.

In Figures 1, 2, and 3, the depths from the surface of the driving gate and the fixed potential gate are almost the same, but it goes without saying that they may be different. . Making the fixed potential gate deeper reduces the current flowing through the drive gates on the cathode and anode sides, further increasing the current gain.
Figures 1, 2, and 3 show the cross-sectional structure of a surface wiring type structure in which the cathode gate and anode gate are all on the same plane, but the capacitance of the drive gate is further reduced. In order to increase the current gain, a rectangular or V-shaped cut may be provided and a drive gate may be provided on the side surface of the cut.

The structure of the present invention can be manufactured by conventionally known crystal growth techniques, microfabrication techniques, selective diffusion techniques, selective etching techniques (dry chemical), ion implantation techniques, and the like.

The double-sided gate type electrostatic induction thyristor of the present invention has a plurality of units arranged in parallel, each having a cathode and an anode that supply a carrier to the channel, interposed between the drive gate and the fixed potential gate, and the capacitance of the drive gate is small. , there is almost no significant carrier effect in the channel, the current gain is large, and high-speed switching of large currents can be performed, so its industrial value is extremely high.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a double-sided gate type electrostatic induction thyristor of the present invention, Figures 2 a and b are plan views of a structural example of a double-sided gate type static induction thyristor of the present invention, and Figure 2 c is in Figure a. 2d is a sectional view taken along line A-A', FIG. 2d is a sectional view taken along line B-B' in FIG. FIG. 3b is a sectional view taken along line A-A' in FIG. 3a.

Claims (1)

[Scope of Claims] 1. A plurality of cathode regions each comprising a high impurity density region of the same conductivity type as the high resistance region of the first conductivity type, on one surface of the high resistance region of the first conductivity type, the first The first gate region includes a high impurity density region of a conductivity type opposite to the high resistance region of the conductivity type, one gate region of the cathode region is a drive gate region, and the drive gate region is opposite to the cathode region. The gate region on the opposite side is a fixed potential gate region, and the high resistance region of the second conductivity type is formed on the surface of the high resistance region of the second conductivity type that is in contact with the other surface of the high resistance region of the first conductivity type. a plurality of anode regions comprising high impurity density regions of the same conductivity type;
A second gate region is provided with a high impurity density region of a conductivity type opposite to the high resistance region of the conductivity type, one gate region of the anode region is a drive gate region, and the drive gate region is opposite to the anode region. The gate region on the opposite side is a fixed potential gate region,
A double-sided gate type electrostatic induction thyristor, wherein electrode wiring is provided in each of the first and second drive gate regions, and no external wiring is provided in the first and second fixed potential gate regions. 2. The double-sided gate type electrostatic capacitor according to claim 1, wherein the first fixed potential gate region is directly connected to a cathode region, and the second fixed potential gate region is directly connected to an anode region by an electrode. induction thyristor.