JPH0513754A - High speed turn-on device - Google Patents

Abstract

PURPOSE:To ensure a high speed turn-on device which is capable of turning on at high speed with lower loss and which is prevented from erroneous arcing even though anode voltage is raised in a short time after a current is attenuated by setting a diode carrier life time in a thyristor including an insulating gate. CONSTITUTION:Once positive voltage is applied to a gate electrode 10, a channel region CH of a p type base layer 4 is inverted to inject electrons from an n<+> type emitter layer 5 into an n<-> type base layer 3. Once positive holes corresponding to those electrons are injected from a p<+> type emitter layer 1 into the n<-> type base layer 3, a thyristor is turned on. Herein, the lifetime of the electron in the n<-> type base layer 3 is set to be longer than a time required for a pulsed current to be conducted to the device to increase to one 0.1 times the peak value thereof, and the lifetimes of the electron and of the hole are set to be shorter than a time interval until anode voltage is applied after the pulsed current is conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high speed turn-on device capable of high speed turn-on by an insulated gate.

[0002]

2. Description of the Related Art A thyristor with an insulated gate is known as a high speed turn-on element. The basic structure is that a p-type emitter layer is formed on one surface of a high resistance n-type base layer,
It has a pnpn structure in which a p-type base layer and an n-type emitter layer are selectively formed on the other surface, and a gate insulating film is formed in a region of the p-type base layer sandwiched between the n-type emitter layer and the n-type base layer. A gate electrode is formed via the. When turned on, this thyristor with an insulated gate shifts from the MOSFET operation to the IGBT operation to the thyristor operation.

In this type of insulated gate thyristor, when high-speed repetitive pulse driving is performed, unless the peak current is set to a small value, there is a problem that the anode voltage is erroneously fired after the current is attenuated. This is because residual carriers remain in the high resistance n-type base layer for a while even after the current is attenuated. If the frequency of repetitive driving is about several hundreds Hz or less, there is no problem because residual carriers disappear until the anode voltage rises after current decay, but several kHz
This is a major problem in applications requiring high-speed repetitive pulse driving. More concretely, this problem will be described by taking the case of using a thyristor with an insulated gate as a switching element of an excimer laser power supply as an example.

FIG. 6 shows an LCR in which a laser power supply circuit is formed by connecting an inductance L, a capacitance C and a resistance R in series.
When simulating the circuit is a diagram showing the waveform of the anode voltage V _A and the anode current I _A of the insulated gate with thyristor. The anode voltage V _A at the applied state to the device, a positive voltage is applied to the insulated gate electrode of the element is fast turned on, the anode current rise rate di / dt, peak anode current i _p, sinusoidal pulse width t _W Energize with pulse current. In case of excimer laser power supply, di / dt is 1k
A / μsec / cm ² Or more and a number peak current i _p thousand A / cm ²
It may take the above value. Pulse width t _W is 0.1
It takes a value of about 3.0 μsec. After the oscillating current is attenuated by the resistor R, the anode voltage is raised at the voltage rising rate dv / dt with the rest time Δt as a preparation period for passing the next pulse current. The pause time Δt is required to be about 20 μsec when the number of repetitions is 5 kHz.

In the case of using a high-speed turn-on element in such a circuit, it has been known that shortening the carrier lifetime of the element increases the on-voltage, so that the carrier lifetime has not been shortened so far. It was However, conventionally, the number of laser repetitions per second was at most several hundreds Hz, and Δt was sufficiently large at 1 msec or more. Therefore, no carrier remained at the time of raising the anode voltage. But in recent years, become a laser with a repetition rate of several kHz is required, unless a smaller peak current i _p in the devices so far, a problem of false firing at a displacement current by rising the anode voltage Came up.

[0006]

As described above, in the conventional thyristor with an insulated gate, there is a problem that the peak current is set to a small value in the high repetition pulse driving, and a false ignition occurs when the anode voltage rises. .

An object of the present invention is to solve such problems and to provide a high speed turn-on element which can be turned on at a high speed with a low loss and which is not erroneously fired even if the anode voltage is raised in a short time after the current is attenuated. And

[0008]

According to the present invention, a first-conductivity-type emitter layer, a second-conductivity-type base layer provided in contact with the first-conductivity-type emitter layer, and a surface portion of the second-conductivity-type base layer are selectively formed by diffusion. The first conductivity type base layer, the second conductivity type emitter layer selectively diffused on the surface of the first conductivity type base layer, the second conductivity type emitter layer of the first conductivity type base layer and the second layer.
A gate electrode formed on the region sandwiched by the conductivity type base layer as a channel region with a gate insulating film interposed therebetween, a first main electrode provided on the first conductivity type emitter layer, and a second conductivity type emitter layer. In the high-speed turn-on device including the second main electrode provided in the second conductivity type carrier, the lifetime of the second conductivity type carrier in the second conductivity type base layer is 0.1 times the peak value of the pulse current flowing through the device. It is set longer than the time required to increase to a double current value, and the lifetime of the first conductivity type carrier and the second conductivity type carrier in the second conductivity type base layer is until the anode voltage is applied after the pulsed current is applied. It is characterized in that it is set shorter than the time interval of.

[0009]

If the carrier lifetime of the device is set in such a range, the second conductivity type base layer is turned on when the device is turned on.
Since carriers do not disappear until the carriers of the conductivity type are sufficiently accumulated, the resistance of the device can be promptly reduced, and therefore turn-on loss does not increase. On the other hand, since carriers disappear promptly after the current is attenuated, false firing does not occur even if the anode voltage is raised in a short time.

If the lifetime of the second conductivity type carrier is set to be longer than the time width of the pulsed current that is applied to the device, the turn-on loss can be further reduced.
When a larger current is flown, the loss from the start of the thyristor operation becomes a problem, so the lifetime of the carriers of the first conductivity type and the carrier of the second conductivity type should be set longer than the time width of the pulsed current for energizing the device. This can reduce turn-on loss.

[0011]

EXAMPLES Examples of the present invention will be described below. In the following embodiments, the first conductivity type is p-type and the second conductivity type is n-type. Therefore, the first conductivity type carriers are holes, and the second conductivity type carriers are electrons.

FIG. 1 shows an element structure of a thyristor with an insulated gate according to an embodiment. A p ⁺ type emitter layer 1 is formed on the back surface of a high-resistance n ⁻ type base layer 3 with an n ⁺ type buffer layer 2 interposed therebetween. On the surface of the n ⁻ -type base layer 3, p is selectively
The p-type base layer 4 is formed by diffusion, and n ⁺ is further formed in the p-type base layer 4. The type emitter layer 5 is formed by diffusion. p
N ^{+ of the} mold base layer 4 Type emitter layer 5 and n ⁻ Mold base layer 3
A gate electrode 10 is formed on the surface of the region sandwiched by the above as a channel region CH with a gate insulating film 9 interposed therebetween. p ⁺ An anode electrode 7 is formed on the mold emitter layer 1. n ⁺ A cathode electrode 8 is provided on the mold emitter layer 5 so as to be separated from the gate electrode 10 by an interlayer insulating film 11 and cover the gate electrode 10. The cathode electrode 8 is also in contact with the p-type base layer 4, and the contact portion has p ⁺ The mold layer 6 is formed. The cathode electrode 8 is electrically connected to the p-type base layer 4 because the p-type base layer 4 serves as a well region of the insulated gate transistor and its potential needs to be fixed.

The operation of this thyristor with an insulated gate is as follows. When a positive voltage is applied to the gate electrode 10,
The channel region CH of the p-type base layer 4 is inverted to n ⁺ Type emitter layer 5 to n ⁻ Electrons are injected into the mold base layer 3.
And the amount of holes corresponding to this is p ⁺ Type emitter layers 1 to n ⁻ When injected into the mold base layer 3, the thyristor turns on.

In the thyristor having such a structure, electrons pass through the channel CH and n ⁻ The high-speed injection into the mold base layer 3 increases the electron concentration in a short time, which enables high-speed turn-on. However, since the cathode electrode 8 is also in contact with the p-type base layer 4 in this structure, n ⁺ Electrons are not injected from the end of the mold emitter layer 5, and a sufficient current driving capability cannot be obtained.

In order to solve such a problem, as shown in FIG. 2, p ⁺ formed on the p-type base layer 4 is formed. Mold layer 6
On the other hand, the control electrode 12 may be formed separately from the cathode electrode 8. With such a structure, the potential of the p-type base layer 4 can be fixed by the control electrode 14 separately from the potential of the cathode electrode 8. Therefore n ⁺ Electrons can be injected over the entire area of the type emitter layer 5, and high current drive capability can be obtained in addition to high-speed turn-on capability. Further, since the base current can be extracted from the control electrode 12, a high dV / dt withstand capability can be obtained.

In the element structure shown in FIG. 1 or FIG. 2 above, in this embodiment, n ⁻ The carrier lifetime in the mold base layer 3 is set so as to satisfy the following conditions. First,
The electron lifetime is set to be longer than the time required for the pulsed current flowing through the element to increase to a current value 0.1 times the peak value. In particular, in order to sufficiently reduce the turn-on loss, the lifetime of electrons is set longer than the time width of the pulsed current that is passed through the device. Second
In addition, the lifetimes of electrons and holes are set to be shorter than the time interval from the application of the pulsed current to the application of the anode voltage. The carrier lifetime in the device as described above can be controlled, for example, by irradiating the device with an electron beam. Next, the effect of this embodiment will be described based on concrete data.

FIG. 3 is a diagram showing a change in element resistance at high speed turn-on of the thyristor with an insulated gate according to the embodiment. A change in the element resistance is caused by a MOSFET mode in which electrons passing through the channel region CH contribute to conduction, and IG in which holes start injection.
BT mode, n ⁺ The thyristor mode in which electrons are injected from the mold emitter layer 5 is divided into three modes. When a positive voltage is applied to the gate electrode 10, the channel region CH of the p-type base layer 4 is inverted and n ⁺ Type emitter layer 5 to n ⁻
Electrons are injected into the mold base layer 3. Element resistance is first n ^-
It is sharply lowered by the accumulation of electrons in the mold base layer 3 (M
OSFET mode). Then p ⁺ Type emitter layers 1 to n ⁻ Although holes are injected into the mold base layer 3, a large amount of holes are injected and the device resistance starts decreasing again after the anode current starts rising (IGBT mode).
Large number of holes n ⁻ When injected into the mold base layer 3, eventually n ⁺ The electron injection from the type emitter layer 5 to the p-type base layer 4 starts, and the thyristor turns on. After that, n
^- The carrier concentration in the mold base layer 3 increases and the element resistance gradually decreases (thyristor mode).

As is apparent from FIG. 3, it is the channel region CH to n ⁻ that causes the element resistance to drop sharply in the high speed turn-on operation. The electrons are injected into the mold base layer 3. Therefore, in the IGBT mode, the anode current starts to rise and a large amount of holes are n ^−. If the electrons do not disappear until they are injected into the mold base layer 3, the electrons can be efficiently accumulated and the element resistance can be rapidly reduced. The starting point of the rising of the anode current is 0.
It is appropriate to take the time when the current value reaches about 1 time.
Further, if the lifetime of electrons is set longer than the time width of the pulsed current flowing through the element, the element resistance after entering the thyristor mode can be reduced. When a larger current is flown, the device resistance in the thyristor mode can be further reduced by setting the lifetime of holes longer than the time width of the pulsed current.

FIG. 4 shows the dv / dt after the pulsed current is applied.
It is the figure which showed the electron beam irradiation dose dependency of tolerability. i _p = 6
00A / cm ² , T _W = 0.7 μsec was applied, and after the current decay, the anode voltage was applied when the dwell time Δt passed 5 μsec to measure the dv / dt withstand capability. The higher the electron beam irradiation amount, the higher the dv / dt resistance. This is considered to be because the carrier lifetime is reduced when the electron beam is irradiated, and the carriers inside the element disappear immediately after the pulsed current is passed.

FIG. 5 is a diagram showing the dependence of the turn-on loss on the electron beam dose. It can be seen that the turn-on loss does not change even if the electron beam irradiation amount is increased. The actually measured amount of electron beam irradiation and ^{(× 10 13 cm -2) n} - Electrons in the base layer 3,
The relationship between hole lifetimes (μsec) is as shown below.

[0021]   Electron beam dose 1 2 3 4 5 8   Electronic lifetime 1.19 0.80 0.58 0.47 0.38 0.25   Hole lifetime 0.22 0.12 0.08 0.06 0.05 0.03

As described above, in the range of the electron beam dose shown in FIGS. 4 and 5, the lifetime of the electron is 1/2 of the conduction width t _W = 0.7 μsec of the pulsed current, that is, the sinusoidal pulsed current. Since the time is set to be larger than the peak time, the turn-on loss does not increase.
On the other hand, the lifetime of electrons and holes is the rest time Δt.
= 5 μsec, which is a sufficiently small value,
High dv / dt tolerance is obtained. Therefore, a great effect can be obtained when used for high-speed pulse driving such as an excimer laser power source.

[0023]

As described above, according to the present invention, the second
The lifetime of the second conductivity type carrier in the conductivity type base layer is set to be longer than the time required for the pulsed current passing through the element to increase to a current value 0.1 times the peak value. By setting the lifetime of the second conductivity type carrier to be shorter than the time interval from the application of the pulsed current to the application of the anode voltage, fast turn-on is performed with a small turn-on loss, and the anode voltage is reduced in a short time after the current decay. A thyristor with an insulated gate that can be activated can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a thyristor with an insulated gate according to an embodiment.

FIG. 2 is a diagram showing a thyristor with an insulated gate according to another embodiment.

FIG. 3 is a diagram showing a change in element resistance during high-speed turn-on.

FIG. 4 is a diagram showing the electron beam irradiation dose dependency of the dv / dt withstand amount after pulsed current application.

FIG. 5 is a diagram showing the dependence of turn-on loss on electron beam dose.

FIG. 6 is a switching waveform diagram when an excimer laser power supply is simulated.

[Explanation of symbols]

1 ... p ⁺ Type emitter layer, 2 ... n ⁺ Type buffer layer, 3 ... n ^- Type base layer, 4 ... p type base layer, 5 ... n ⁺ Type emitter layer, 6 ... p ⁺ Mold layer, 7 ... Anode electrode, 8 ... Cathode electrode, 9 ... Gate insulating film, 10 ... Gate electrode, 11 ... Interlayer insulating film, 12 ... Control electrode, CH ... Channel region.

Claims (3)

[Claims] 1. A first conductivity type emitter layer and a second conductivity type base layer provided in contact with the first conductivity type emitter layer,
A first conductivity type base layer selectively diffused and formed on a surface portion of the second conductivity type base layer, and a second conductivity type emitter layer selectively diffused and formed on a surface portion of the first conductivity type base layer A gate electrode formed on the first conductive type base layer sandwiched by the second conductive type emitter layer and the second conductive type base layer as a channel region with a gate insulating film interposed therebetween; A first main electrode provided on the one-conductivity type emitter layer and a second main electrode provided on the second-conductivity type emitter layer;
In the high-speed turn-on device including the main electrode of, the lifetime of the second conductivity type carrier in the second conductivity type base layer is up to 0.1 times the peak value of the pulse current flowing through the device. It is set to be longer than the time required to increase, and the lifetimes of the first conductivity type and second conductivity type carriers are set to be shorter than the time interval from application of the pulsed current to application of the anode voltage. Characteristic high-speed turn-on element. 2. The high speed according to claim 1, wherein the lifetime of the second conductivity type carrier in the second conductivity type base layer is set to be longer than the time width of the pulsed current flowing through the device. Turn-on element. 3. The lifetime of the first conductivity type carrier and the second conductivity type carrier in the second conductivity type base layer is set to be longer than the time width of the pulsed current passed through the device. A high-speed turn-on device according to item 1.