JPH0786561A - Static-induction type semiconductor device - Google Patents

Abstract

PURPOSE:To control a voltage by using a voltage control electrode without drawing holes to the outside from a gate region by newly forming an N-type inversion layer on the side of the voltage control electrode in a first-conductivity type gate region between an ON gate region and a low-impurity-density region, and electrically connecting the ON region and the low-impurity-density region. CONSTITUTION:To turn OFF a static-induction-type semiconductor device, a negative voltage is applied on a voltage control electrode 14. Thus, a P-type inversion layer, which is formed by the application of the voltage, is formed on the surface of a low-impurity-density region 6 between a gate region 3a and a cathode shorting region 4. The gate region 3a and the cathode shorting region 4 become the short-circuit state. Thus, the potential of the gate region 3a becomes the same potential of the cathode shorting region. Holes in a channel region 6a are drawn to the outside from a first main electrode 7. The potential of the channel region 6a with respect to electrons becomes high. Thus, the injection of the electrons from the cathode region 2 is stopped, and the static induction type semiconductor device is turned OFF.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated gate type electrostatic induction type semiconductor device which operates at high speed.

[0002]

2. Description of the Related Art From the viewpoint of effective use of electric energy and high accuracy of power control, various control systems have been developed for cutting off current or the like at high speed and precisely controlling power. As a semiconductor device used in this control system, an element capable of high-speed operation with a large current and having a small loss during conduction is required. Conventionally, an electrostatic induction type semiconductor device is considered promising as a semiconductor device that realizes high-speed interruption of this large current.

An example of a conventional static induction semiconductor device will be described with reference to FIG. This example is an example of an n-channel static induction thyristor, and FIG. 9 shows the sectional structure of only the basic unit.

On the upper surface of the static induction thyristor 1,
A cathode region 2 made of an n-type semiconductor of the second conductivity type and gate regions 3, 3 made of a p-type semiconductor of the first conductivity type.
a is formed, and a cathode short-circuit region 4 made of a p-type semiconductor is formed so as to sandwich the gate region 3 with the cathode region 2.

On the lower surface portion of the static induction thyristor 1, an anode region 5 made of a p-type semiconductor is provided over the entire surface. A low impurity density region 6 is provided in the middle part of the electrostatic induction thyristor 1 sandwiched between these surface parts.

On the upper surface of the static induction thyristor 1,
First connected to the cathode region 2 and the cathode short-circuit region 4
A gate electrode 8 connected to the main electrode 7 and the gate region 3 is provided. An insulator 9 is arranged between the gate region 3 and the first main electrode 7 to prevent the two from being electrically connected. Further, a second main electrode 10 connected to the anode region 5 is provided on the lower surface portion of the static induction thyristor 1.

In such an electrostatic induction type thyristor 1, when the gate electrode 8 and the first main electrode 7 are kept at the same potential, for example, the electrostatic induction type thyristor (which is normally off) is not brought into conduction. Static induction type thyristor). In the non-conductive state, a predetermined voltage is applied between the first main electrode 7 and the second main electrode 10 of this normally-off static induction thyristor, and the anode region 5 has a predetermined high potential with respect to the cathode region 2. Even if kept in the state, no electric current is conducted between the main electrodes.

In order to make the electrostatic induction thyristor conductive, that is, to turn it on, a positive voltage is applied to the gate electrode 8 so that the gate regions 3 and 3a have a positive potential with respect to the cathode region 2. To be As a result, the static induction thyristor 1 becomes conductive, and a current flows between the first main electrode 7 and the second main electrode 10.

That is, when the gate regions 3 and 3a have a positive potential, a small amount of holes are injected from the gate regions 3 and 3a into the channel region 6a, and this hole injection causes the low impurity density region 6 from the cathode region 2. A large amount of electrons is injected into the low impurity density region 6 from the anode region 5 by the electrons. As a result, the electrostatic induction thyristor 1 becomes conductive. In addition,
The channel region 6a is a portion of the low impurity density region 6 sandwiched between the gate regions 3 and 3a below the cathode region 2.

In order to turn off the static induction type thyristor 1, that is, to bring it into a cutoff state, the gate regions 3 and 3a are formed.
It is necessary to apply a negative voltage to and quickly draw out the holes in the channel region 6a to the outside. By extracting the holes in the channel region 6a, the potential of the channel region 6a with respect to the electrons is increased, and the injection of electrons from the cathode region 2 is stopped. Subsequently, the injection of holes from the anode region 5 is stopped, so that the static induction thyristor 1 is turned off and the current flow between the first main electrode 7 and the second main electrode 10 is stopped. .

[0011]

In the conventional static induction thyristor 1, in the conductive state, the holes injected from the anode region 5 are present at a high density throughout the low impurity density region 6, These holes flow to the cathode region 2 and the cathode short-circuit region 4 through the channel region 6a. The amount of holes flowing to the cathode region 2 through the channel region 6a depends on the area of the cathode short-circuit region 4, but in a normal static induction thyristor, the cathode region 2
In order to extract a large electron current from the holes, holes of a considerably high density are accumulated in the channel region 6a.

In order to bring the electrostatic induction thyristor 1 in such a state into the cutoff state, it is necessary to draw out the holes accumulated in the channel region 6a to the gate regions 3 and 3a as described above.

In order to extract the holes to the gate regions 3 and 3a, it is necessary to apply a negative voltage to the gate electrode 8 to allow a current to flow to an external circuit, which increases the current value between the main electrodes and causes the gate electrode 8 to have a large current. When the current value to be drawn increases, the drive power for drawing the current and shutting off the static induction thyristor 1 increases. Usually, the current value drawn from the gate electrode 8 needs to be about ¼ of the main current, and therefore a large current can be passed through the drive circuit and a large drive power is required. It was so-called current control.

In order to reduce the driving power, the amount of charges extracted from the gate electrode 8 at the time of turn-off may be reduced, and for that purpose, the amount of holes accumulated in the channel region 6a in the conductive state may be reduced. Good. However, when the amount of holes accumulated in the channel region 6a is reduced, the injection amount of electrons from the cathode region 2 is reduced and the charge amount in the low impurity density region 6 is reduced, so that the voltage drop in the conductive state is reduced. It becomes large, which causes an increase in loss during conduction.

Therefore, the conventional electrostatic induction type thyristor 1 requires a drive circuit of high power in order to realize a high-speed cutoff while keeping the conduction loss small, so that the drive circuit becomes large and the number of parts increases. There was a problem with.

The present invention has been made to solve such a problem, and is a so-called voltage that can realize turn-on / turn-off by using an insulated voltage control electrode without extracting holes from the gate region to the outside. The purpose is to provide a controllable electrostatic induction type semiconductor device.

[0017]

According to a first aspect of the present invention, there is provided an electrostatic induction type semiconductor device (claim 1), wherein an anode region made of a first conductivity type semiconductor is provided on one surface portion of a semiconductor substrate. A cathode region made of a second conductive type semiconductor provided on the other surface of the semiconductor substrate; a gate region made of a first conductive type semiconductor provided adjacent to the cathode region of the semiconductor substrate; A semiconductor substrate, an on-gate region of the second conductivity type provided so as to be surrounded by the gate region, a low impurity density region provided in an intermediate portion between the anode region and the cathode region, and the cathode region. A cathode short circuit region made of a semiconductor of a first conductivity type provided at a position sandwiching the gate region therebetween, and a first main electrode connected to the cathode region and the cathode short circuit region. Connecting the gate region and the on-gate region to a voltage control electrode disposed on the surface of the on-gate region and the cathode short-circuit region via an insulating film at a position sandwiched between the on-gate region and the cathode short-circuit region. And a second main electrode connected to the anode region.

[0018]

The operation of the static induction semiconductor device according to the first aspect of the present invention having the above structure will be described using an example of an n-channel normally-off static induction semiconductor device.

In the electrostatic induction type semiconductor device of the first invention, a positive voltage is applied to the voltage control electrode when the electrostatic induction type semiconductor device is made conductive, that is, when the turn-on operation is performed. As a result, an n-type inversion layer is newly formed on the voltage control electrode side of the first conductivity type gate region between the on-gate region and the low impurity density region, and the on-gate region and the low impurity density region are electrically connected. .

As a result, the voltage applied to the anode region is applied to the gate region through the low impurity density region, the n-type inversion region, the on-gate region and the short-circuit electrode, and the potential of the gate region rises. The increase in the potential of the gate region causes a decrease in the potential of electrons in the channel region immediately below the cathode region, and electrons are injected from the cathode region into the low impurity density region. With this as a trigger, the electrostatic induction semiconductor device of the first invention is turned on.

In the conductive state, the holes injected from the anode region maintain the potential of the gate region to continue the injection of electrons from the cathode region, and a part of the holes pass through the cathode short-circuit region to the first main region. It flows to the electrode. Therefore, the hole density of the channel region is adjusted to an appropriate amount for maintaining the electrostatic induction type semiconductor device in the ON state, and does not increase more than necessary.

In order to turn off the electrostatic induction type semiconductor device in this state, that is, to perform the turn-off operation,
A negative voltage is applied to the voltage control electrode. As a result, a p-type inversion layer is newly formed on the surface of the low impurity density region between the gate region and the cathode short-circuit region, and the gate region and the cathode short-circuit region are short-circuited.

As a result, the gate region has the same potential as the cathode short-circuit region, and the holes existing in the channel region are extracted from the first main electrode to the outside through the gate region, the p-type inversion layer and the cathode short-circuit region. As a result, the potential of electrons in the channel region becomes high, so that the injection of electrons from the cathode region is stopped and the electrostatic induction semiconductor device is turned off.

As described above, the electrostatic induction semiconductor device of the first invention can be turned on / off by applying a positive or negative voltage to the voltage control electrode. The voltage control electrode is an insulated gate type, and the current passed through this electrode is sufficient to charge and discharge the capacitance of the electrode and change the voltage to a voltage at which the electrostatic induction semiconductor device can be sufficiently turned on or off. 1 compared to
/ 10 is sufficient, and the electric power of the drive circuit can be significantly reduced.

In the electrostatic induction type semiconductor device of the second invention (claim 2), a semiconductor of the second conductivity type having a higher impurity density than the low impurity density region between the anode region and the low impurity density region. Is provided with a buffer area.

That is, in the electrostatic induction type semiconductor device of the second invention, since the buffer region having the second conductivity type and the higher impurity density than the low impurity density region is provided between the anode region and the low impurity density region. Since the injection of holes from the anode region is suppressed to a low level, the total amount of carriers in the low impurity density region in the conductive state is low, and the effective carrier lifetime at turn-off is shortened. High-speed operation can be expected by application of the negative voltage.

Further, in the electrostatic induction type semiconductor device of the third invention (claim 3), a second conductivity type anode short-circuit region is formed in a part of the anode region, and the second main electrode is formed. It is characterized by being connected. That is, the electrostatic induction semiconductor device of the third invention has an anode short-circuit structure in which the anode region is composed of the first conductivity type and the second conductivity type. For this reason, in particular, at the time of turn-off, the electrons existing in the low impurity density region smoothly flow out to the anode region, the injection of holes from the anode region is quickly stopped, the turn-off time is further shortened, and the speed is further increased. Various operations are possible. Of course, the turn-on / turn-off operation can be performed only by applying positive and negative voltages to the voltage control electrode.

The static induction semiconductor device according to the first to third inventions may be a p-channel static induction semiconductor device, and in this case, the same operational effect as described above can be obtained. it can.

[0029]

As described above, according to the present invention,
It is possible to obtain an electrostatic induction type semiconductor device capable of high-speed operation only by applying a voltage to the voltage control electrode without applying a large current to the gate electrode as in the conventional case.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. First Embodiment FIG. 1 shows a part of a sectional structure when an electrostatic induction type semiconductor device of the first invention is applied to an n-channel electrostatic induction type thyristor 11. Incidentally, the same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

The electrostatic induction type thyristor 11 of this example is constructed as follows. The impurity density is about 1 × 10 ¹⁴ cm ^-3 ,
Ion implantation of boron is performed from one surface of an n-type silicon substrate having a thickness of about 400 μm to form p-type gate regions 3 and 3a of the first conductivity type and p-type cathode short-circuit region 4. The formation depth of these p-type regions is about 4 μm, and the impurity density on the surface is 1 × 10 ¹⁸ cm ⁻³ . Then, boron ions are implanted also on the other surface to form the p-type anode region 5. The formation depth of this region is about 5 μm,
The impurity density on the surface is 2 × 10 ¹⁹ cm ⁻³ .

Next, the low impurity density region 6 sandwiched between the p-type gate regions 3 and 3a has an n-type cathode region 2 of the second conductivity type, and the p-type gate region 3a has arsenic ion-implanted therein. Thus, the on-gate region 12 is formed. The formation depth of these regions is about 0.2 μm, and the impurity density on the surface is about 1 × 10 ²⁰ cm ⁻³ .

After that, a gate insulator 13 is formed on a part of the on-gate region 12, the p-type gate region 3a, the low impurity density region 6 and the p-type cathode short-circuit region 4, and a voltage of n-type polysilicon is formed thereon. The control electrode 14 is formed. Further, a short-circuit electrode 15 that short-circuits the on-gate region 12 and the p-type gate region 3a, a first main electrode 7 made of an aluminum electrode so that the cathode region 2 and the cathode short-circuit region 4 have the same potential, and an anode. The second main electrode 10 made of an aluminum electrode is wired in the region 5. An insulator 9 is interposed at a position where the gate regions 3 and 3a and the first main electrode 7 may come into contact with each other to insulate them.

Therefore, the electrostatic induction type semiconductor device of the first embodiment performs the following operation, and the appearance thereof is shown in FIGS.
This will be described with reference to FIGS. 4 and 5. When the electrostatic induction type semiconductor device is made conductive, that is, when the turn-on operation is performed, a positive voltage is applied to the voltage control electrode 14 as shown in FIG. As a result, as shown in FIG. 3, in the gate region 3a between the on-gate region 12 and the low impurity density region 6, the n-type inversion layer 16a is formed on the surface side on the insulator 13 side, and as a result, the on-gate region 12 is formed. Are electrically connected to the low impurity density region 6.

As a result, as shown in FIG. 4, the voltage applied to the anode region 5 is the low impurity density region 6, the n-type inversion region 16a generated by the voltage application, and the on-gate region 1.
2 and is applied to the gate region 3a through the short-circuit electrode 15 to raise the potential of the gate region 3a. The increase in the potential of the gate region 3a causes a decrease in the potential of the channel region 6a immediately below the cathode region 2 for electrons, and the injection of electrons from the cathode region 2 into the low impurity density region 6 occurs. With this as a trigger, the electrostatic induction semiconductor device is turned on.

In the conductive state, the holes injected from the anode region 5 maintain the potential of the gate region 3a to continue the injection of electrons from the cathode region 2, and part of the holes pass through the cathode short circuit region 4. It flows out to the first main electrode 7.

In order to turn off the electrostatic induction type semiconductor device in this state, that is, to perform the turn-off operation,
As shown in FIG. 5, a negative voltage is applied to the voltage control electrode 14. As a result, the p inversion layer 16b generated by the voltage application is formed on the surface of the low impurity density region 6 between the gate region 3a and the cathode short-circuit region 4, and as a result, the gate region 3a and the cathode short-circuit region 4 are short-circuited. Becomes

As a result, the gate region 3a has the same potential as the cathode short-circuit region 4, and the holes existing in the channel region 6a pass through the gate region 3a, the p-type inversion layer 16b, and the cathode short-circuit region 4 to generate the first potential. The electrons are extracted from the main electrode 7 and the potential of electrons in the channel region 6a increases, so that the injection of electrons from the cathode region 2 is stopped and the electrostatic induction semiconductor device is turned off. As described above, the electrostatic induction semiconductor device of the first embodiment can be turned on / off by applying positive and negative voltages to the voltage control electrode 14.

FIG. 6 shows an example of the anode current and control current waveforms when the electrostatic induction thyristor 11 of this embodiment and the conventional electrostatic induction thyristor 1 are turned off.

The forward voltage drop of each of these static induction type semiconductor devices is 1.2 at an anode current density of 100 A / cm ² .
Although about V, the extraction current for the turn-off operation of the electrostatic induction thyristor 11 of this embodiment is about 1/10 that of the conventional electrostatic induction thyristor 1. Therefore, the current capacity of the element used for turn-off can be small, and the control power can be small.

A turn-on / turn-off operation can be realized by applying a voltage of ± 20 V to the voltage control electrode 14 of the electrostatic induction thyristor 11 of this embodiment. Further, since no voltage is applied to the gate region from the outside, the distance to the cathode short-circuit region can be shortened,
The gate region can be effectively short-circuited to the cathode short-circuit region at turn-off. Further, the cathode short circuit rate can be increased, and in this example, it is about 1000%. Therefore, due to these effects, high-speed turn-off can be realized with low driving power.

Second Embodiment FIG. 7 shows the second invention of the n-channel static induction type thyristor 1.
An example applied to No. 7 is shown. This example is applied to the electrostatic induction thyristor 11 of the first embodiment. The same parts will be denoted by the same reference numerals and the description thereof will be omitted.

The static induction thyristor 17 diffuses phosphorus from the surface where the anode region 5 is to be formed and forms a region to be the buffer region 18 before the ion implantation of boron to form the anode region 5. , Boron ion implantation is performed to form the anode region 5. The impurity density on the anode region 5 side of the buffer region 18 thus formed is about 1 × 10 ¹⁷ cm ⁻³ , and the thickness of the region is about 10 μm.

The basic turn-on / turn-off operation is the same as that of the electrostatic induction thyristor of the first embodiment, but the hole density in the low impurity density region 6 in the conductive state is about 3.
The turn-off speed is 30% higher than that of the electrostatic induction thyristor 11 because it is smaller than that of the electrostatic induction thyristor 11 of the first embodiment and the effective carrier lifetime is about 10% smaller.

That is, in the electrostatic induction type semiconductor device of the second embodiment, an n-type buffer region 18 having a higher impurity density than the low impurity density region 6 is provided between the anode region 5 and the low impurity density region 6. Since the injection of holes from the anode region 5 is suppressed low, the total amount of carriers in the low impurity density region 6 in the conductive state is low, and the effective carrier lifetime at turn-off is shortened. Therefore, high-speed operation can be expected by applying a negative voltage to the voltage control electrode 14.

Third Embodiment FIG. 8 shows the third invention of the n-channel static induction type thyristor 1.
An example applied to No. 9 is shown. In this example, the surface structure of the thyristor is applied to the static induction thyristor 11 of the first embodiment. The same parts will be denoted by the same reference numerals and the description thereof will be omitted.

The static induction thyristor 19 has a p-type anode region 5 of the static induction thyristor 11 of the first embodiment.
The structure is such that the type anode region 20 and the n-type anode short-circuit region 21 are replaced. By making the anode a short-circuit structure, the electrons accumulated in the low impurity density region 6 at the time of turn-off smoothly flow out through the anode short-circuit region 21, so that the electrons and holes in the low impurity density region 6 disappear. The speed is increased, and the electrostatic induction thyristor 19 is turned off at high speed.

Of course, the turn-on / turn-off operation is controlled by the positive and negative voltages applied to the voltage control electrode 14. However, the electrostatic induction thyristor 1 of this embodiment is
In No. 9, it cannot be used such that a negative voltage is applied to the anode region.

Although the first, second and third embodiments have been described with respect to the n-channel static induction type thyristor, they are not limited to these examples and can be applied to the p-channel static induction type thyristor. In the above-mentioned embodiment, the anode region is formed by ion implantation and diffusion, but a Si substrate to be the anode region is used and a Si crystal having a low impurity density is formed by crystal growth to form a region to be the low impurity density region. Formed,
It can also be realized by forming a cathode region, a gate region, a cathode short-circuit region, an on-gate region, a gate insulator, a voltage control electrode, an insulator, and a first main electrode on the surface.

Further, in order to obtain the normally-off characteristic that the current does not flow when the voltage control electrode 14 is 0 V, an appropriate impurity may be introduced into the channel region of the static induction thyristor to control the potential for electrons.

Needless to say, the semiconductor material may be a compound semiconductor such as SiC or GaAs other than Si shown in the above-mentioned embodiment.

Further, the impurity density and the diffusion depth of each region shown in the above embodiment may be changed without being restricted thereto within a range in which the performance as the electrostatic induction type semiconductor device can be maintained, and the manufacturing process also. It may be manufactured using a semiconductor manufacturing process that is normally available.

[0053]

[Brief description of drawings]

FIG. 1 is a sectional view of an electrostatic induction thyristor that is a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of the electrostatic induction thyristor of the same embodiment.

FIG. 3 is an operation explanatory view of the static induction thyristor of the same embodiment.

FIG. 4 is an operation explanatory view of the static induction thyristor of the same embodiment.

FIG. 5 is an operation explanatory view of the static induction thyristor of the same embodiment.

FIG. 6 is a characteristic diagram showing a current interruption operation of the electrostatic induction thyristor of the same embodiment.

FIG. 7 is a sectional view of an electrostatic induction thyristor that is a second embodiment of the present invention.

FIG. 8 is a sectional view of an electrostatic induction thyristor that is a third embodiment of the present invention.

FIG. 9 is a sectional view of an electrostatic induction type thyristor which is an example of a conventional electrostatic induction type semiconductor device.

[Explanation of symbols]

 2 ・ ・ ・ ・ Cathode region 3 ・ ・ ・ ・ ・ ・ Gate region 4 ・ ・ ・ ・ Cathode short-circuit region 5 ・ ・ ・ ・ ・ ・ Anode region 6 ・ ・ ・ Low Impurity density region 6a ... Channel region 7 ... First main electrode 8 ... Gate electrode 9 ... Insulator 10 ... ... Second main electrode 12 ... On-gate region 13 ... Gate insulator 14 ... Voltage control electrode 15 ... Short-circuit electrode 16a, 16b ... Inversion layer 18 ... Buffer region 20 ... Anode region 21 ... Anode short-circuit region

Claims (3)

[Claims] 1. An anode region made of a first conductivity type semiconductor provided on one surface of a semiconductor substrate, and a cathode region made of a second conductivity type semiconductor provided on the other surface of the semiconductor substrate. A gate region made of a first conductive type semiconductor provided adjacent to the cathode region of the semiconductor substrate, and a second conductive type provided on the semiconductor substrate so as to be surrounded by the gate region. An on-gate region, a low-impurity-density region provided in an intermediate portion between the anode region and the cathode region, and a first conductivity type semiconductor provided at a position sandwiching the gate region between the cathode region and the cathode region. It is sandwiched between a cathode short-circuit region, a first main electrode connected to the cathode region and the cathode short-circuit region, the on-gate region and the cathode short-circuit region. A voltage control electrode disposed on the surface of the on-gate region and the cathode short-circuit region via an insulating film, a short-circuit electrode connecting the gate region and the on-gate region, and a second electrode connected to the anode region. An electrostatic induction type semiconductor device comprising: 2. A buffer region made of a second conductivity type semiconductor having an impurity density higher than that of the low impurity density region is provided between the anode region and the low impurity density region. Item 1. The electrostatic induction semiconductor device according to item 1. 3. A second conductivity type anode short circuit region is formed in a part of the anode region, and the second main electrode is connected to the anode short circuit region. The electrostatic induction type semiconductor device according to the paragraph.