JPH10209447A - Semiconductor switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor switch, wherein an IEGT(injection enhanced gate transistor) with the reinforced reverse breakdown strength is utilized, both currents of a DC and an AC can be controlled, and a reduction in cost and a reduction in an ON-voltage are possible. SOLUTION: IEGTs 1 and 3 formed by an isolation diffusion method are reversely parallel-connected with each other, an anode of the IEGT 1 and a cathode of the IEGT 3 are commonly connected with an I/O terminal 5 and a cathode of the IEGT 1 and an anode of the IEGT 3 are commonly connected with an I/O terminal 7. Photodiode arrays 9a and 11a, which respectively bias a gate of the IEGT 1 and a gate of the IEGT 3, are respectively connected between the gate of the IEGT 1 and the terminal 7 and between the gate of the IEGT 3 and the terminal 5 and resistors 9b and 11b are parallel-connected with each other. Input/output of an LED(light emitting diode) 23, which is optically coupled with the arrays 9a and 11a, are connected with contact signal ends 25 and 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor switch for controlling both DC and AC currents in an integrated circuit, and more particularly to an IEGT (Injection Enhanced Gate Transistor).
or) using a semiconductor switch.

[0002]

2. Description of the Related Art Normally, both a direct current and an alternating current flow in an integrated circuit such as a programmable controller.
In the past, mechanical relays were used to control the flow of these currents, but recently they have been replaced with semiconductor switches composed of transistors.

FIG. 5 shows an example of a conventional semiconductor switch, which is constituted by MOS FETs. In this semiconductor switch, two MOS FETs 51 and 53 are connected in reverse series, and the emitter and the collector are commonly connected together. A floating power supply (for example, a solar cell or a photodiode) 55 is connected in series between the emitter and the collector, and input / output terminals 57 and 59 are connected to respective sources.

However, the MOS FET has a high on-voltage per unit area, and the MOS FETs 51, 5
3 are connected in reverse series, the on-voltage further doubles. If the on-state voltage is high, the power consumption increases and the temperature becomes high. To prevent this, the chip must be enlarged and the current density must be reduced. As a result, there is a disadvantage that the cost is increased.

Therefore, a semiconductor switch constituted by an IGBT (gate-insulated bipolar transistor) having a low on-state voltage has been considered. FIG. 6 shows an example. In this semiconductor switch, two IGBTs 61 and 63 are connected in anti-parallel, an anode of the IGBT 61 and a cathode of the IGBT 63 are commonly connected to an input / output terminal 65, and an IGBT 6
The first cathode and the anode of the IGBT 63 are commonly connected to the input / output terminal 67.

Floating power supplies (for example, solar cells and photodiodes) 69 and 71 are connected in series between the gate of the IGBT 61 and the input / output terminal 67 and between the gate of the IGBT 63 and the input / output terminal 65, respectively. I have.

In this semiconductor switch, the ON voltage per unit area of the IGBT is 1/3 of that of the MOSFET, and two IGBTs 61 and 63 are connected in anti-parallel. Compared with a semiconductor switch, the on-voltage can be reduced to about 1/6 with the same chip area and the same cost. However, with the recent integrated circuit technology, further cost reduction and lower on-voltage are required.

[0008] Then, what is considered is IEGT (Inject).
ion Enhanced Gate Transistor). FIG. 7 shows the IE
FIG. 3 is a cross-sectional structural diagram of a GT. This IEGT is connected to the cathode electrode 13 which contacts the n ⁺ source at a certain interval.
And a gate control type bipolar transistor comprising a trench gate electrode 15 formed at a minute interval on the surface on the cathode electrode side and ap ⁺ anode electrode 17 on the back surface of the chip.

As shown in FIG. 7, when a positive voltage is applied to the anode electrode 17 and a negative voltage is applied to the cathode electrode 13, holes injected from the anode p emitter 19 are supplied to the cathode electrode 13 by the trench gate electrode 15. Spillage is prevented. On the other hand, when the gate electrode 15 is positively biased with respect to the cathode electrode 13, the cathode electrode 13
Is injected from the MOS channel without any limitation, so that the injection of electrons becomes much higher than the outflow of holes, so that the on-resistance of the high-resistance n-base layer can be suppressed low.

FIG. 8 shows the IEGT (solid line) and the IGBT.
6 is a graph showing a difference between a current voltage characteristic and a (dashed line).
For the same current density, the ON voltage of IEGT is IGBT
It can be seen that it is about 1/3 compared to that of. It is expected that a semiconductor switch using IEGT having such characteristics and having a lower on-voltage and lower cost will be realized.

[0011]

As described above, the IGB
A semiconductor switch using an IEGT having an ON voltage lower than T is expected, but the IEGT shown in FIG. 8 is the reverse of when a negative voltage is applied to the anode 17 and a positive voltage is applied to the cathode 13. Because of its low withstand voltage, it was possible to control the DC current but not the AC current.

The present invention has been made in view of the above problems, and an object thereof is to provide an IEGT having an enhanced reverse withstand voltage.
It is an object of the present invention to provide a semiconductor switch which can control both DC and AC currents and can reduce the cost and the ON voltage more than before.

[0013]

In order to achieve the above-mentioned object, a first aspect of the present invention is a semiconductor switch for performing DC and AC current control using an IEGT, comprising an anti-parallel connection. The first and second IEGTs, the anode electrode of the first IEGT, and the second IEGT
A first input / output terminal commonly connected to a cathode electrode of the first IEGT; a cathode electrode of the first IEGT;
A second input / output terminal commonly connected to an anode electrode of the EGT; a first floating power supply for biasing a gate electrode of the first IEGT; and a second floating power supply for biasing a gate electrode of the second IEGT. And a floating power supply.

According to the first aspect, since the IEGTs having a low current density and a low on-state voltage are connected in anti-parallel, both DC and AC current control can be performed with a small area and at low cost. Further, since the gate electrodes are biased by the floating power supply, the gate electrodes of the two IEGTs can be biased at different voltages.

According to a second aspect of the present invention, in the first aspect, both the first and second floating power supplies are photodiode arrays, and the first and second floating power supplies are optically coupled simultaneously with the first and second photodiode arrays. It has a device.

According to the second aspect of the present invention, photo-electromotive force is generated in the photodiode array by optical coupling with the issuing element which is electrically insulated, and the first and second input / output terminals are turned on. Therefore, the two input / output terminals can be used at different potentials.

A feature of the third invention is that in the first invention, the first and second IEGTs both have a structure formed by using an isolation diffusion method.

A feature of the fourth invention is that, in the first invention, both the first and second IEGTs have a structure formed by using a glass passivation method.

According to the third and fourth aspects of the invention, the reverse withstand voltage characteristics when a negative voltage is applied to the anode electrode and a positive voltage is applied to the cathode electrode can be improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a semiconductor switch according to an embodiment of the present invention. In the semiconductor switch shown in the figure, two IEGTs 1 and 3 are connected in anti-parallel.
The anode of the EGT1 and the cathode of the IEGT3 are commonly connected to the input / output terminal 5, and the cathode of the IEGT1 and the IEGT are connected.
The anode of T3 is commonly connected to the input / output terminal 7. Between the gate of the IEGT 1 and the input / output terminal 7;
Between the gate of the EGT 3 and the input / output terminal 5, a floating power supply (eg,
Photodiode arrays and insulating transformers) 9 and 11 are connected in series.

Here, a specific sectional structural view of IEGTs 1 and 3 is shown in FIG. This IEGT has a structure formed using an isolation diffusion method, and the cathode electrode 1
3, the gate electrode 15, the anode electrode 17, and the anode p emitter 19 are the same as those shown in FIG.
Is formed between them. The isolation 21 can enhance the reverse breakdown voltage characteristics when a negative voltage is applied to the anode electrode 17 and a positive voltage is applied to the cathode electrode 13.

By configuring the IEGTs 1 and 3 formed by using the isolation diffusion method as shown in FIG. 1, both DC and AC current control can be performed. Since the respective gate electrodes 13 can be biased with different voltages by the floating power supplies 9 and 11, when a current flows from the input / output terminal 5 to the input / output terminal 7, the IEGT 1 turned on by the floating power supply 9 causes a current to flow.
When a current flows in the opposite direction, the floating power supply 11
The current is controlled so that the IEGT 3 turned on by the current flows a current.

FIG. 3 is a configuration diagram when a photodiode array is used for the floating power supplies 9 and 11. I
Between the gate of the EGT 1 and the input / output terminal 7, and the IEGT
The photodiode arrays 9a and 11a are connected between the gate of the input terminal 3 and the input / output terminal 5, and the resistors 9b and 11
b are connected in parallel. Further, an LED (light emitting diode) 23 electrically insulated from the semiconductor switch is provided near the semiconductor switch, and its input and output are connected to control signal terminals 25 and 27.

According to this semiconductor switch, the control signal from the microcomputer or the like is transmitted to the control signal terminal 25,
27, LED 23 emits light and LED 2
The photodiode arrays 9a and 11a optically coupled to 3 simultaneously generate photovoltaic power. With this voltage, IEGT
The gates 1 and 3 are biased, and the input / output terminals 5 and 7 are turned on to perform current control. Therefore, the two input / output terminals 5 and 7 can be used at different potentials.

As described above, according to the semiconductor switch of the present invention, since the IEGT having an extremely low on-voltage is formed by the isolation diffusion method and connected in anti-parallel, both DC and AC current control is performed. In addition, the cost and on-voltage can be further reduced as compared with the conventional case. Further, since the photodiode array is used as the floating power supply, it is possible to use different potentials between the input and output terminals.

The structure of the IEGT is not limited to the structure by the isolation diffusion method, but may be a structure by a glass passivation method as shown in FIG. With this IEGT, the reverse breakdown voltage is enhanced by the glass layer 29 formed near the surface on the cathode electrode side and near the anode electrode 17.

[0028]

As described above, according to the semiconductor switch of the present invention, since two IEGTs having an enhanced reverse breakdown voltage are connected in anti-parallel, both DC and AC current control can be performed, which is more effective than in the prior art. Low cost and low on-voltage are possible. Since the gate electrodes are biased by the floating power supply, the gate electrodes of the two IEGTs can be biased at different voltages.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a semiconductor switch according to an embodiment of the present invention.

FIG. 2 is a sectional structural view of an IEGT constituting the semiconductor switch according to one embodiment of the present invention.

FIG. 3 is a configuration diagram when a photodiode array is used for the configuration of the semiconductor switch according to one embodiment of the present invention;

FIG. 4 is a sectional structural view of the IEGT different from FIG. 2;

FIG. 5 is a configuration diagram showing an example of a conventional semiconductor switch using a MOS FET.

FIG. 6 is a configuration diagram showing an example of a conventional semiconductor switch using an IGBT.

FIG. 7 is a sectional structural view of a conventionally known IEGT.

FIG. 8 is a graph showing a difference in current-voltage characteristics between IEGT and IGBT.

[Explanation of symbols]

 1,3 IEGT 5,7 Input / output terminal 9,11 Floating power supply 9a, 11a Photodiode array 9b, 11b Resistance 13 Cathode electrode 15 Gate electrode 17 Anode electrode 19 Anode p emitter 21 Isolation 23 LED (Light emitting diode) 25,27 Control signal end 29 Glass layer

Claims (4)

[Claims] 1. A semiconductor switch for performing DC and AC current control using an IEGT, comprising: first and second IEGTs connected in anti-parallel;
A first input / output terminal in which an anode electrode of the IEGT and a cathode electrode of the second IEGT are connected in common, and a cathode electrode of the first IEGT and an anode electrode of the second IEGT are connected in common. A second input / output terminal,
A semiconductor switch comprising: a first floating power supply for biasing a gate electrode of the first IEGT; and a second floating power supply for biasing a gate electrode of the second IEGT. 2. The method according to claim 1, wherein the first and second floating power supplies are both photodiode arrays.
2. The semiconductor switch according to claim 1, further comprising a light emitting element that is optically coupled simultaneously with the photodiode array. 3. The semiconductor switch according to claim 1, wherein each of the first and second IEGTs has a structure formed by using an isolation diffusion method. 4. The semiconductor switch according to claim 1, wherein each of the first and second IEGTs has a structure formed by using a glass passivation method.