JPH03278471A - Light switch - Google Patents

Abstract

PURPOSE:To obtain a switch that is compact and superior in light responsibility by installing a thyristor which is formed by the same process as that of the anode in a semiconductor substrate together with the anode and providing a gate current when the light comes from the outside and then, feeding the switch with the gate current supplied by each solar cell. CONSTITUTION:Patterns 51 and 53 consisting of a P<+> type layer are formed by making an initial oxide film 8 act as a mask at the layer 1 of an Si substrate that is composed of an N<-> type layer 1, an N<p+> type layer 2, and a P<p+> type layer 3. Then, P-type layers 4 and 41 as well as a P<p+> type layer 52 are formed by making a polycrystal Si layer 9 that is provided on a gate oxide film 81 act as a mask and also, an N<p+> type layer 6 and an N<+> type emitter layer 61 are formed by making the layer 9 serve as a gate and an oxide film 83 act as a mask. After that, the patterning of a CVD oxide film is performed and a source electrode 10 and cathode electrodes 13 are provided by performing the patterning of an Al layer and further, a drain electrode 11 is formed at the rear of the substrate. Subsequently, solar cells 12 connected in series, a diode 14, a transistor 15, a resistor 16, and a phototransistor 17 are connected by wiring to obtain a light switch.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical switch that uses an insulated gate bipolar transistor (hereinafter referred to as IGBT) as a switching element and turns on and off a circuit using an optical signal. .

[Conventional technology]

Semiconductor switching elements include bipolar transistors and MOS gate transistors, and the latter include MOSFETs and IGETs whose on-resistance is reduced by utilizing conductivity modulation. Figure 2 is IGB
, T, and the rGBT part has a P-doped 142 layer 3 on one side of the N- layer 1 of the silicon substrate via an N+ buffer layer 2, and a P-doped 142 layer 3 on the surface layer of the other side. A base layer 4 is selectively provided, and a P''' diffusion layer 51 with a depth reaching the N- layer 1 is present in the central part of the P base layer 4, and a P+ diffusion layer 52 is present in the surface part. An N+ source layer 6 is formed between the periphery and the gap.

A region of the P base layer 4 sandwiched between the source layer 6 and the drain layer 1 is a channel forming region 7, and a gate electrode 9 made of polycrystalline silicon is provided thereon with a gate insulating film 81 interposed therebetween. A source electrode 10 covers the gate electrode 9 with an insulating film 82 in between.
Insulating film 82 on layer 51, 52 and N source layer 6
contact at the opening. Further, the drain electrode 11 is in contact with the P-doped 142 layer 3. When a positive voltage is applied to the gate electrode 9 of this I GET with respect to the source electrode 10, a channel is formed in the region 7 of the base layer 4 directly under the gate insulating film, and electrons pass through the channel from the source layer 6 to the drain layer. 1, 2.3, in response, from the P+ drain layer 3 through the N' buff layer 2 and the N- layer 1.
Holes are injected into the N-layer 1, causing conductivity modulation and resulting in low resistance. Further, by setting the gate electrode 9 to the same potential as the source electrode 10 or applying a negative bias, it enters a blocking state, so that it functions as a switching element.

In order to turn on and off this IGBT using an optical signal,
+ of the solar cell 12 in which a plurality of solar cells are connected in series
The side is connected to the gate electrode 9, and the - side is connected to the source electrode 10. The number of cells connected in series in the solar cell 12 is IG
It is determined depending on the threshold voltage of BT. solar cell 1
When the light 20 of No. 2 is irradiated, a photovoltaic voltage is generated in the solar cell, and when the voltage exceeds a threshold value, the IGBT is turned on. Also,
When the light 20 goes out, the output voltage of the solar cell 12 decreases, and when the voltage becomes lower than the threshold voltage, the IGBT turns off.

[Problem to be solved by the invention]

In the optical switch shown in FIG. 2, as the current capacity of the IGBT increases, the gate capacity increases, making it necessary to increase the area of the solar cell, which poses a problem that leads to an increase in cost. Furthermore, solar cells have the disadvantage that they turn off slowly even when the irradiated light disappears, and the turn-off speed of an optical switch is also slow.

The present invention solves the above problems and utilizes IGBT,
The purpose of the present invention is to provide an optical switch that can turn on and off a circuit at high speed.

[Means to solve the problem]

In order to achieve the above object, the present invention provides that a second layer of a second conductivity type is adjacent to a first layer of a first conductivity type, and selectively forms a surface portion of the second layer on the side opposite to the first layer. A first region of a first conductivity type is formed, a second region of a second conductivity type is selectively formed on the surface of the first region, and a second region of a second conductivity type is formed on the first region sandwiched between the second layer and the second region. A gate electrode is provided through an insulating film, and a first electrode is provided on the first layer.

-3 IGBT in which the second electrodes are in contact with each of the second regions
and a second conductive layer selectively formed on the extended portion of the first layer and the second layer, the third layer of the first conductivity type adjacent to the opposite side of the second layer, and the surface portion of the third layer. a third region having a shape, a third electrode connected to the first electrode on the second layer, a photothyristor having a fourth electrode in contact with the third region, and between the second electrode and the gate electrode. A solar cell that supplies a gate voltage to make the IGET conductive when light is incident, and a transistor that shorts the two poles of the solar cell when the incident light disappears are connected in parallel, and a photothyristor is connected between the fourth electrode and the gate electrode. Assume that diodes are connected in series with the forward direction and the forward direction in the same direction.

[Effect]

When a light signal is applied, a photovoltaic force is generated in the solar cell, and the potential between the two poles of the solar cell begins to rise, but since the gate capacity of the IGBT is large and the output current of the solar cell is small, the gate voltage increases. The speed is low. Therefore, rG
Even if a voltage is applied between the first and second electrodes of the BTO main electrode, the IGBT does not turn on. However, the optical thyristor built into the same semiconductor substrate as the IGBT is also turned on at the same time by the optical signal, and current flows into the gate electrode of the IGBT via the diode, so the IGBT is turned on as the gate potential rapidly rises. do. At this time, the transistor connected in parallel between the two poles of the solar cell is in an off state. When the I GET is turned on, the voltage between the first and second electrodes that had been rising decreases, and the thyristor in which the third electrode of one of the main electrodes is connected to the first electrode of the main electrode of the I GET is turned off. The gate potential is held at the output voltage of the solar cell, and the IGBT remains on.

When the optical signal disappears, the transistor circuit connected in parallel to the solar cell enters a short-circuit state discharging current, the gate voltage rapidly decreases, and the IGBT turns off.

〔Example〕

FIG. 1 shows an optical switch according to an embodiment of the present invention, and FIG.
Parts common to those in the figure are given the same reference numerals. Similar to FIG. 2, the silicon substrate on which each layer of an n-channel IGBT is formed is as follows: 24 layer 3 is formed as a P emitter layer, N+ layer 2 and N- layer 1 are formed as an N base layer, and N- layer 1 is formed as a surface layer. The optical thyristor has a built-in optical thyristor in which the two layers 41 are a P base layer, and the N layer 61 formed at a distance on the surface layer of the P base layer 41 is an N emitter layer. The light for igniting this thyristor can enter from the central surface of the two layers 41 in the gap between the N emitter layer 61 and enter the PN junction between it and the N-layer 1. Furthermore, below the N4 layer 61, P reaches the N− layer 1.
A layer 53 is formed on the surface of which the cathode electrode 13 of the optical thyristor is in contact. Cathode electrode 13 and IGB
A diode 14 is connected between the gate electrode 9 of T and the + side of the series-connected solar cell 12, with the anode facing the cathode electrode 13. Gate electrode 9 and IGBT
The collector and emitter of an npn) run risk 15 are connected between the source electrode 10 of the transistor 1, respectively.
A resistor 16. is connected between the base electrode of No. 5 and the gate electrode of the IGBT. A phototransistor 1 is connected between the source electrode 10 and the source electrode 10.
The collector and emitter of 7 are connected.

When the entire optical switch is irradiated with light 20 while the drain electrode 11 is at a high potential, the phototransistor 17 is turned on, so that the transistor 15 is turned off. On the other hand, the output voltage across the solar cell 12 starts to rise. Further, the optical thyristor is turned on by the incidence of the light 20 into the gap between the cathode electrodes 13, and the current flows between the cathode electrodes 13. It flows into the gate electrode 9 through the diode 14 and rapidly increases the gate potential.

When the potential of the gate exceeds the threshold, the IGBT is turned on, the potential of the drain electrode 11 is reduced, and the photothyristor is turned off. The potential of the gate electrode 9 is maintained at the output voltage of the solar cell 12. When the light 20 disappears, the phototransistor 17 is turned off, and the base potential of the transistor 15 becomes the resistance 1.
6, and the transistor 15 is turned on. As a result, the gate electrode 9 of the IGBT. The source electrodes 10 are short-circuited, and the IGBT is turned off. As a result, the photoresponsiveness is fast.

3(a) to 3(d) show the manufacturing process of the optical switch of FIG. 1.

FIG. 3(a) N-layer 1. N+ layer 2. Patterns 51 and 53 of the P+ layer are formed on the N- layer 1 of the silicon substrate consisting of the P+ layer 3 using the initial oxide film 8 as a mask.

FIG. 3(b) Two layers 4.4 are formed using the polycrystalline silicon layer 9 or photoresist on the gate oxide film 81 as a mask.
1 and P'' layers 52 are formed.

FIG. 3(C) Using the polycrystalline silicon gate 9 and oxide film 83 as a mask, an N'''' layer 63 and an emitter layer 61 are formed.

FIG. 3(d) The CVD oxide film 82 is patterned, and the A1 layer is further patterned to form a source electrode 10 and a cathode electrode 13. A drain electrode 11 is formed on the back surface.

After this, series-connected solar cells 12. diode 14,
Transistor 15. Resistance 16. Phototransistor 1
By connecting 7 with wiring, an optical switch is completed.

FIG. 4 shows another embodiment of the present invention, and like the following figures, parts common to those in FIG. 1 are given the same reference numerals. In this case, when forming the P middle layer 52 of the IGBT section, the P layer 54 was also formed on the second layer 41 of the optical thyristor section, but there was no particular change in characteristics.

FIG. 5 shows yet another embodiment of the present invention, in which the 21 layers 53 and 54 of the optical thyristor section of FIG. 4 were not formed, but there was no particular change in characteristics. Therefore, when building other elements near the optical thyristor, an appropriate structure can be selected.

FIG. 6 shows another embodiment of the present invention, in which a p-channel depletion type FET 18 is used, its drain and gate are short-circuited and connected to the gate electrode 9 of the IGET, and its source is connected to the source electrode of the IGBT. 10. The threshold value of the FET 18 is selected to be slightly lower than the output voltage of the solar cell 12. In this optical switch, when the light 20 is incident, the gate potential of IGET rises rapidly due to the current of the optical switch, and the IGBT turns on, but the FET
18 is turned off. When the incident light 20 disappears, the solar cell 1
The output of IG 2 decreases, FET 18 turns on, and the gate electrode 9 and source electrode 10 of I GET become short-circuited, and the IG
BT is turned off. This optical switch has the advantage of requiring fewer parts than the optical switch shown in FIG.

In each embodiment, when the IGBT is a p-channel, the conductivity types of each layer are all reversed, and the gate electrode of the IGET is connected to one side of the solar cell and the anode of the photothyristor via a diode of opposite polarity, and The connecting transistor is of the pnp type, and the FET is of the n-channel type.

〔Effect of the invention〕

According to the present invention, the gate current supplied from the solar cell can be supplemented by supplying the gate current when light is incident using a photothyristor that can be formed in the same semiconductor substrate in the same process as the anode. , there is no need to increase the area of the solar cell, and by connecting a transistor that shorts both poles of the solar cell when light fades, the current is discharged through the transistor and the gate voltage drops rapidly. The off speed becomes faster. In other words, an optical switch that is small and has fast photoresponsiveness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical switch according to an embodiment of the present invention, and FIG.
The figure is a cross-sectional view of a conventional optical switch, Figure 3 is a cross-sectional view showing the main parts of the manufacturing process of the optical switch in Figure 1 in the order of (a) to (6), Figures 4, 5, and 6. Each figure is a sectional view showing an optical switch according to a different embodiment of the present invention. IN-layer, 324 layer, 41G BTP base layer, 4
1 optical thyristor P base layer, 6. -,,, IG
BT source layer, 61 optical thyristor N emitter layer, 7 channel non-forming region, 81 gate oxide film, 9 gate electrode, 10 source electrode, 11 drain electrode, 12 solar cell, 13 anode electrode, 14 diode, 15 bipolar transistor , 17 7 Ototransistor, 18 Depletion type FET04
1 PA'-71 I visited Hirohiro. l Shadow; ii pole Fig. 3 1 Fig. 4

Claims (1)

[Claims] 1) A second layer of a second conductivity type is adjacent to the first layer of the first conductivity type, and a layer of the first conductivity type is selectively formed on the surface of the second layer on the side opposite to the first layer. A first region is formed, a second region of a second conductivity type is selectively formed on the surface of the first region, and an insulating film is formed on the first region sandwiched between the second layer and the second region. an insulated gate bipolar transistor in which a gate electrode is provided in the first layer, a first electrode is in contact with the first layer, and a second electrode is in contact with the first and second regions, an extension of the first layer and the second layer, and a second layer; a third layer of the first conductivity type adjacent to the side opposite to the first layer; and a third region of the second conductivity type selectively formed on the surface of the third layer;
An insulated gate bipolar transistor comprising a third electrode connected to the first electrode in the first layer and an optical thyristor in which the fourth electrode contacts the third region, and when light is incident between the second electrode and the gate electrode. A solar cell that supplies a gate voltage to make it conductive and a transistor that short-circuits both poles of the solar cell when the incident light disappears are connected in parallel, and a transistor is connected in parallel between the fourth electrode and the gate electrode in the same forward direction as the optical thyristor. An optical switch characterized by having diodes connected in series in different directions. 2) In the optical switch according to claim 1, the transistors connected in parallel so as to short-circuit both poles of the solar cell when the incident light disappears are FETs having a threshold voltage lower than the output voltage of the solar cell. Features an optical switch. 3) A second layer of a second conductivity type is adjacent to the first layer of the first conductivity type, and a first region of the first conductivity type is selectively formed on the surface of the second layer on the side opposite to the first layer. A second region of a second conductivity type is selectively formed on the surface of the first region, and a gate electrode is provided on the first region sandwiched between the second layer and the second region via an insulating film. , an insulated gate bipolar transistor in which a first electrode is in contact with the first layer, a second electrode is in contact with the first and second regions, extensions of the first and second layers, and a side of the second layer opposite to the first layer; a third layer of the first conductivity type adjacent to the third layer and a third region of the second conductivity type selectively formed on the surface of the third layer;
An insulated gate bipolar transistor comprising a third electrode connected to the first electrode in the first layer and an optical thyristor in which the fourth electrode contacts the third region, and when light is incident between the second electrode and the gate electrode. A solar cell that supplies a gate voltage to make it conductive is connected in parallel with a transistor that shorts the two poles of the solar cell when the incident light disappears.A resistor is connected between the gate and collector of this transistor, and a resistor is connected between the gate and emitter. A phototransistor is connected to each
The optical switch further comprises a diode connected in series between the fourth electrode and the gate electrode with the forward direction of the optical thyristor in the same direction.