JPS62188271A - Semiconductor device including static induction thyristor - Google Patents

Abstract

PURPOSE:To enable the conduction and interruption of current to be controlled by means of light by a method wherein the resistance of a photosensitive semiconductor element in a conducting state at the time of light irradiation is selected to be much lower than a gate resistance. CONSTITUTION:The figure furnishes an example of a photosensitive conductor element D inserted between a gate and a source in parallel therewith. When the element D is not radiated with light, the gate of an Si thyristor Q is impressed with -Vg to be interrupted. But when it is irradiated with light and brought into a conducting state, the Si thyristor Q is changed-over to the conducting state since the potential of gate becomes almost equal to that of a source. Resultantly, the resistance of the element D in the conducting state is selected to be much lower than the gate resistance Rg.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device using an electrostatic induction thyristor whose gate includes a light-controlled element.

Conventional thyristors, which basically consist of a pnpn four-layer structure, have the disadvantage that it is difficult to switch off using the gate electrode, and even if it is possible to switch off the thyristor using the gate, the speed is extremely slow. On the other hand, the electrostatic induction thyristor (hereinafter referred to as S1 thyristor), which has a diode structure with a gate on its right side, has the advantage that it is extremely easy to shut off using the gate and that the shutoff time is fast.SI A cross-sectional view of a typical structural example of a thyristor is not shown in FIG.

FIGS. 1A to 1D are cross-sectional views of a structural example of a Stt Nyristor in a circuit configuration of the present invention, which will be described later.

FIGS. 1(a) and 1(b) are cross-sectional views of typical examples of surface gate structures of SI Zyristors. Figure 1(C) is an example of a buried gate structure, and Figure 1(d) is an example of an insulated gate type S.
It is an example of the cross-sectional structure of a t-thyristor.

In FIGS. 1(a), (b), and (C), p'' regions 11 and 14 are 7 node regions and gate regions, and n+ regions 13
is the cathode region, and the n-region or i-region 12 constitutes the channel. Typically the semiconductor material I1 is silicon.

0+ region 13 is a cathode region. 11'. 13
, 14' is an anode electrode, cathode electrode, or gate electrode made of AJL, Mo, W, Au, etc. or other metals, or low resistance polysilicon or a multilayer structure thereof, 15 is S b O 2, SLaN4,
These are AfL203, AIN, etc. or other insulating layers, or composite insulating layers or multilayer insulating layers thereof.

The n region 16 has a relatively high impurity density, is formed into a thin layer, and is a layer for suppressing hole injection from the anode.

In FIG. 1(d), the p1 region 21 is the anode region, the i region 22 is the range that constitutes the channel, and the n+ region! 23 is a cathode region 1, and an I1 region 27 is a region for suppressing hole injection from the anode. The n area 28 is
It has a structure in which it reaches the surface at a predetermined point in the vertical direction in the figure, and is usually directly connected to the cathode region by an electrode. 25 is the above-mentioned insulating layer. 21', 23'
, 24 are anode electrodes, cathode electrodes, and insulated gate electrodes. The operation of the Si4 thyristor, the dimensions of each region, and the impurity density are detailed in the specification of the 3R electrostatic induction thyristor j published by the present inventors in Japanese Patent Application Laid-Open No. 55-997743.

SI thyristors control the potential distribution in the vicinity of the cathode using gate voltage to control conduction and cutoff, so they have the advantage of being able to easily cut off direct current and at high speed. The structure shown in FIG. 1(a) can produce a device with approximately the same forward blocking voltage and reverse breakdown voltage, but the structures shown in FIG.
Compared to structure a), the same forward blocking voltage can be achieved with an element that is approximately half the thickness, the operating speed is faster, and the forward voltage drop is smaller. It has the disadvantage that it becomes small. Therefore, in order to use the SI thyristors shown in FIGS. 1(b), 1(c), and 1(d) where reverse breakdown voltage is required, a Schottky diode or the like is connected in series.

Figure 2 <a>, (b') shows junction type and insulated gate type S.
■Shows the thyristor symbol mark.

A diode is formed on the drain side of a static induction transistor (hereinafter referred to as SIT).

FIG. 3 shows a typical structural example of a conventionally well-known photosensitive semiconductor element. FIGS. 3(a) to 3(d) show structural examples of a photosensitive element integrated or connected to the gate of an 81 thyristor in a circuit configuration of the present invention to be described later.

(a) is a photoconductive element. An i region 32, which can almost be regarded as an insulator, is provided on the n+ region 31. 31' and 32 are ohmic electrodes, and in this example, 32' is a transparent electrode such as 1n2Q3.5no2. When the electrode 32' is difficult to serve as an ohmic electrode, the transparent electrode 32' may be provided on the surface of the i region 32 after providing a very thin n+ region. When light is irradiated and electron-hole pairs are generated in the i-region 32, a current starts to flow. In this figure (a), when the electrode 32' is a Schottky electrode, the Schottky electrode side is 31'
If a voltage is applied so that the potential is lower than that of the diode, it can also be used as a Schottky diode that is sensitive to light.

L represents light that divides into large parts. The figure (b) shows a phototransistor. n+ region 44, n region 43, n- region 4
2 and n+fr4 regions 41 are an emitter region, a base region, a high resistance layer, and a collector region, respectively. Reference numeral 41' is a rector electrode, and 44' is an emitter transparent electrode. The n+ region 44 and the n region 43 are made thin like a normal bipolar transistor. Most of the light is absorbed in the n-region 42. When a positive voltage is applied to 41', photoexcited electrons flow into the n+ collector region and are absorbed, and holes flow into the p base region, which is the floating region, and are accumulated.

When holes are accumulated in excess, the potential barrier to electrons in the base region decreases, allowing electrons to flow from the emitter region into the base region and into the collector region. (C
) The figure shows a zyristor that is excited by light. n+ area 55
, p+ region 51 is a cathode region and an anode region.

55' is a transparent electrode, and 51' is an anode electrode. 51
When irradiated with light while a positive voltage is applied to ′,
Electrons and holes photoexcited in the i-region flow into the n-region 52 and n-region 54, respectively. The barrier potential is lowered, and electrons are injected from the cathode region and balls are injected from the anode region, resulting in conduction. ,(C)
The optical Nyristor shown in the figure has carrier injection amplification mechanisms on both sides. However, it is highly sensitive to light. (d
) The figure is an example of a p"in+ photodiode. 63' is a transparent electrode, 61' is an electrode. 61' is applied to a positive voltage. 〈a), (kl), (C), (d ) In either case, most of the irradiated light is in the i region or n
It is absorbed in the ``'' region and generates electron and ball pairs.

Therefore, if the electric field strength in this region is set to a level slightly lower than the avalanche electric field (J5), a large amount of carriers will be generated by the avalanche multiplication mechanism, and the sensitivity will be further improved. Third
The figure shows a very representative and very simple example, so it goes without saying that there are many other variations.
It is.

Of course, any photosensitive semiconductor device exhibiting the photopolquick effect may be used.

So far, the S1 thyristor and the photosensitive semiconductor device have been described. The 51 thyristor is extremely unique in that it can operate at a high operating voltage and current, and can perform high-speed switching. However, when considering high power applications such as DC power transmission, one Sl thyristor can
It is almost difficult to handle all this large amount of power.

Therefore, for example, a forward blocking voltage of 5000 volts or a current of 100 volts when conducting 10000 pols 1-1
A series-parallel connection of Sl thyristors is required, such as connecting a plurality of Sl thyristors such as 0Δ in series to increase the withstand voltage, and further connecting them in parallel to generate current. In such cases, S
It will be easier to control with light. On the other hand, the 31 thyristor which is controlled by light has already been described by the inventors of the present application in the application specification of Japanese Patent Publication No. 1908/1988 entitled "Silence IR3 Induced Optical Thyristor". However, the invention described in Japanese Patent Publication No. 61-1908 mentioned above is based on light control l'7.
The method for turning on the gate circuit is related to the turn-on operation, that is, the light 1 to the start operation, and the method for the turn-off operation is based on the electric turn A) applied to the gate circuit. That is, although conduction is performed by light, electrical gate turn-off is performed for interruption.

An object of the present invention is to provide an electrostatic induction thyristor whose conduction and interruption can be controlled by light and a device including the electrostatic induction thyristor.

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

FIG. 1 is an example of a circuit of an SL thyristor whose operation is controlled by light according to the present invention, in which the aforementioned photosensitive semiconductor element is connected to the gate of an 81 thyristor. In FIG. 4, Q is an SI iris resistor, and D is a photosensitive semiconductor element. Rg is resistance. Vt is a bias power supply.

S [There are various types of thyristors, so the value of Vt should be selected according to them. For example, forward voltage 5
If 000 volts can be stopped by adding a reverse gate bias of -30 volts to Goo1~, then Vt is -30
It is sufficient to choose a value of Pol 1 or higher.

Figure 4 (a) is an example in which D is inserted in parallel between the gate and the source. When not irradiated with light, -V is applied to the Sl thyristor's G1~, which means that it is in the cut-off state and the light is not irradiated. When D is irradiated and D becomes conductive, the gate becomes almost the same potential as the source, so S[thyristor becomes conductive;
transfer.

The resistance of D when conductive is sufficiently small compared to R7).

The Sr thyristor is
) In cases where the reverse breakdown voltage is not very high, as in the example of
However, if reverse withstand voltage is required during operation, the fourth
As shown in Figure (b), a Schottky diode or the like may be connected in series with the S[thyristor].

For example, when constructing an AC/DC converter for direct current transmission of 1 million volts using Sl thyristors with a maximum forward blocking voltage of 5000 volts, at least 200,111 81 thyristors must be connected in series. In such a case, as shown in FIG. 5, 81 thyristors may be connected in series for the required number of UA. Since the gates are controlled by light, it is easy to operate all Sl thyristors simultaneously and synchronously, even if many are connected in i+:i columns.

The light may be irradiated by using an optical fiber or the like to uniformly irradiate a predetermined location on the photosensitive element. In any case, since the operation is not as fast as each other, a cladding type fiber is sufficient. Further, in the case of the clad type, the light intensity within the cross section of the fiber is more likely to be uniform. Of course, depending on the application, it may be effective to use a focusing fiber.

FIG. 5(b) is an example in which a resistor R7 is connected in parallel to Sr thyristors connected in series.

This is because resistors of equal value are connected in parallel so that the voltage applied to each Sl thyristor becomes uniform when the Sr thyristor is in the cut-off state. The higher the resistance value, the better, as long as it can be considered to be smaller than the resistance value of the Sr thyristor in the cut-off state. For example, a value such as 1 MΩ is selected. J: for use in mulling, it may be larger or smaller than this.

Further, to handle a large current, the necessary number of switches configured as shown in FIG. 5 may be connected in parallel. 4 and 5 show junction type Sll thyristors, but Mo5s r thyristors may also be used.

Until now, the gate of the Sl thyristor has been made with a photosensitive type '' conductor (A
By connecting the element with VC7), the optically controlled S[
An example of configuring a thyristor circuit has been described. It goes without saying that the SI thyristor itself can be made into an element controlled by light, and in that case, the operation shown in FIGS. Figure 1 (a) includes the operation of direct light irradiation by providing 1,000 stages to introduce light into the thyristor.
, (11), (c), and (d), and by constructing transparent electrodes on either side so that the light reaches the high resistance region, a light-controlled Sl thyristor can be obtained. becomes. The side on which light is emitted may be either the cathode side or the anode side. If either side is connected to a transparent electrode, it is J. If the semiconductor material is SQ, the predetermined incident depth of light is about 20 to 30 μm. Therefore, in the structure shown in FIG. 1, when light is irradiated from the anode side, the thickness of the p+ region vA11 or the sum of the thicknesses of the p+ region 11 and the nff region 16 (p+ region 21 and n region 27) can be It is desirable that the layer be thin, and it must be at least sufficiently thinner than the depth of incidence of the light. For example, the p-region thickness is about 1 μm or less, the impurity density is 1×10″Cl1−
The thickness of the n-region 16 is about 1 μm or less, and the impurity density is about 1×10 cm 2 or more. The depth of the gate region is usually on the order of several μm, although it depends on the gate interval and the impurity density in the respective region.

Therefore, if the electrodes are made transparent, they can be controlled using light. If only transparent electrodes such as fn, o, and sno are used, the resistance will be high. In such a case, metal electrodes such as ΔL may be placed at key points. This will be explained using the example shown in FIG. 1(b). Electron-hole pairs are generated in the i-region 12 by the light irradiation. If a positive voltage is applied to the anode, the generated electrons flow into the n-region 16 and charge the n-region 1G to Ω. When the amount of charge increases to a certain extent, hole injection from the anode region /)r + occurs. Photoexcited holes and holes injected from the anode flow toward the cathode. A portion flows into the p+gegu region and a portion flows into the cathode region.

At this time, the barrier to electrons that had been formed on the entire surface of the cathode is lowered. Electron injection begins to occur from the cathode and it becomes conductive. In order to further reduce the forward voltage drop during conduction, a resistor of a predetermined size may be inserted between the gate and source.

The magnitude of the insertion resistance R is given by the current I flowing through the gate, R. (marked on the gate)
) J3 should be approximately equal to the applied reverse bias. This gate-source resistance can be easily made of polysilicon.

1(a), (1, and (d)) may be set in the same manner. In FIG. 1(C), a resistor is inserted between the n region 28 and the power bond region.

6 to 8 show structural examples of the Sl thyristor according to the present invention, similar to FIGS. 1(a) to 8(d).

Compared to the structure shown in FIG. 1, FIG. 6 shows a structure in which the current flowing through the gate is reduced to increase the main current. The structure is such that an absolute $1 layer 17 such as 5j02 is provided on the lower surface of the p+ region 14. A polysilicon resistor is inserted between the gate and the source, making it 4Mm thick. Polysilicon resistors are provided at predetermined locations in the vertical direction in the figure. The equivalent circuit is shown in FIG. 6(b). Of course, the gate-source resistance R may also be connected externally.

FIG. 7 shows an example in which the potential FF wall on the cathode side is also eliminated by accumulation of carriers, instead of connecting a resistor between the gate and the source. For example, a negative voltage is applied to the gate electrode 14', but this voltage is completely masked by the holes flowing into the vicinity of the gate, the potential barrier across the entire surface of the cathode disappears, and electron injection from the cathode occurs intensely. The mechanism of hole injection from the anode is the same as in the previous examples.

In FIGS. 6 and 7, the electrodes 13' and 14' are made of low resistance polysilicon or a transparent electrode of ln 203.3n 021 so that light can be incident from the cathode side. This is done to allow heat sinking from the anode side. If you do not need to be too particular about the heat sink, you can use a transparent electrode as the anode electrode and irradiate light from the anode side. Of course, it goes without saying that light may be irradiated from both sides.

Although FIGS. 6 and 7 show a structure in which a gate is provided only on the cathode side, a gate 1 structure may be provided on the anode side. If the electrons accumulated in the n-region 16 remain as they are, they will have to go through annihilation due to recombination or the like. If the Goo-h structure is introduced on the 7 node side as well, this problem will disappear.

An example of this is shown in FIG. One insulating area is provided. If a reverse bias is applied between the anode region 11 and the n+ region 18 on the anode side as well as on the cathode side, the region 12 may be an i region having a very high resistance instead of the n- region. In the structure shown in FIG. 8, a polysilicon resistor may be built between the p+ region 11 and the n+ region [18(7)]. ff1l+! The impurity density and thickness of 212 and 16 are disclosed in JP-A-55-99774@
"r Electrostatic Induction Thyristor" application specification and Japanese Patent Application Laid-open No. 55-10
The selection may be made as described in the application specification No. 8768 "Electrostatic Induction Thyristor". The gist of the present invention is to integrate or connect a photosensitive element to the gate of the S1 thyristor so that the thyristor can be quenched by light (A by light).
When the thyristor is turned off, the carriers accumulated in the gate of the thyristor are turned on by shining light on the photosensitive element connected to the gate of the thyristor, causing them to conduct and discharge, thereby turning off the thyristor. At the point. That is, Example 4
The circuit configurations shown in Figures (a) to (b) and Figures 5 (a) and (b) are the main parts of the present invention. In the end, the important part of the present invention is that the gate is turned on by light, and moreover, the gate is turned off by light.

It goes without saying that the configuration of the 81 Nyristor that is exposed to the light of the present invention is not limited to the example described here. Of course, a light-controlled SI thyristor may be used as the light-sensitive semiconductor device shown in FIGS. 4 and 5. Furthermore, it goes without saying that the conductivity type may be completely reversed, as long as the polarity of the voltage is reversed. In the case of a junction type, it is preferable to sandwich an insulating layer such as SNO02 between the cathode and gate because it reduces the capacitance and increases the breakdown voltage at the same time.Also, even in the case of a junction gate type, it is also possible to provide a gate in the notch area. It is valid. Even in a structure in which the gate is provided on the anode side, it is often effective to sandwich an insulating layer. In the case of a junction gate, it may be a Schottky gate instead of a pn junction.

The light source for controlling the SI thyristor may be any light source that can generate electron-hole pairs in the semiconductor and can switch at high speed. It may be a semiconductor or a light emitting diode. For example, a Ga AiAS-based heterojunction laser or a light emitting diode may be used. Of course, a semiconductor laser or a light emitting diode made of other materials may also be used. Of course, other lasers may also be used. In short, a light source that has the necessary intensity of 11 and can perform high-speed modulation is fine. Depending on the type, solid or gas lasers may be used to
) Nii. These lights may be directly illuminated 4, or may be guided to a predetermined location using a fiber.

The optically controlled SI thyristor of the present invention can be easily manufactured using conventionally known lithography technology, diffusion/ion implantation technology, crystal technology, shrimp growth technology, etching technology, oxidation technology, CVD technology, wiring technology, etc.

The semiconductor device of the present invention, which allows the S1 thyristor to perform high-speed switching of large voltages and large currents, to be controlled by light, is extremely effective when connecting S1 thyristors in series or parallel, or in series and parallel. It is a technology and its industrial value is high.

[Brief explanation of drawings]

Figures 1 (a) to (d) are cross-sectional grooves) Δ examples of electrostatic induction thyristors, Figures 2 (a) and (b) are symbol marks of electrostatic induction thyristors, and Figure 3 are various optical Ll control semiconductors. In the element (a > is a photoconductive element, (b) is a phototransistor,
(C) is an optical thyristor, (d) is a photodiode, FIGS. 4(a) and (b) are the circuit configurations of the present invention, and FIGS.
) and (b) are examples of the present invention in which an S1 thyristor circuit including a photosensitive semiconductor element is connected in series to the gate,
6(a), 7, and 8 are diagrams showing structural examples of the electrostatic induction thyristor portion in the circuit configuration, which is the main part of the present invention, and FIG. 6(b) shows the forward direction voltage drop. It is a circuit explanatory diagram for lowering.

Claims (12)

[Claims] (1) A gate circuit consisting of one gate resistor R_g and a reverse gate bias power supply connected in series with it is connected in parallel between the gate and cathode of the static induction thyristor, and one photosensitive semiconductor element D is connected to the static induction thyristor. In a configuration where the gate and cathode of an induction thyristor are connected in parallel,
A means for irradiating light to the photosensitive semiconductor element D is provided, and the light pulse L from the light irradiation means is irradiated to the photosensitive semiconductor element D to make the electrostatic induction thyristor conductive, and the light pulse L In order to cause the electrostatic induction thyristor to transition to a cut-off state by being cut off, the resistance value of the photosensitive semiconductor element D when it is conductive when irradiated with light is selected to be sufficiently smaller than the value of the gate resistance R_g. A semiconductor device containing a static induction thyristor. (2) A semiconductor device including a capacitive induction thyristor according to claim 1, characterized in that a Schottky diode or a pin diode having a predetermined reverse breakdown voltage is connected in series to the capacitive induction thyristor. (3) A semiconductor device including a static induction thyristor, characterized in that a plurality of semiconductor devices each including a static induction thyristor according to the above item 1 or 2 are connected in series. (4) In order to equalize the voltage applied to each electrostatic induction thyristor when all of the plurality of electrostatic induction thyristors are in a cut-off state, resistors R_n of equal value are connected in parallel between the anode and cathode of each electrostatic induction thyristor. A semiconductor device including the electrostatic induction thyristor according to claim 3, characterized in that the electrostatic induction thyristor is connected to. (5) A semiconductor device including a static induction thyristor, characterized in that a semiconductor device including a static induction thyristor according to claim 4 is further connected in parallel. (6) Electrostatic induction according to any one of claims 1 to 5, wherein the light irradiation to the photosensitive element is guided by an optical fiber. Semiconductor devices including thyristors. (7) A semiconductor including the electrostatic induction thyristor according to any one of claims 1 to 6, characterized in that a photo-controlled electrostatic induction thyristor is used as the photosensitive semiconductor element. Device. (8) A semiconductor device including the electrostatic induction thyristor according to any one of claims 1 to 7, wherein the electrostatic induction thyristor has a surface junction gate structure. (9) A semiconductor device including the electrostatic induction thyristor according to any one of claims 1 to 7, wherein the electrostatic induction thyristor has a buried gate structure. (10) A semiconductor device including the electrostatic induction thyristor according to any one of claims 1 to 7, wherein the electrostatic induction thyristor has an insulated gate structure. (11) Claim 1, wherein the electrostatic induction thyristor is a light-controlled electrostatic induction thyristor.
A semiconductor device comprising the electrostatic induction thyristor according to any one of Items 7 to 7. (12) The electrostatic induction thyristor is an optically controlled electrostatic induction thyristor, and includes means for irradiating light, and includes an operation of transitioning to a conductive state by directly introducing a light pulse. A semiconductor device comprising the electrostatic induction thyristor according to any one of claims 1 to 7.