JPH0136712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thyristor with increased di/dt tolerance and high sensitivity.

[Technical background of the invention and its problems]

As the capacity and voltage of power conversion devices such as thyristor valves for DC power transmission become larger and higher, there is a strong demand for replacing the thyristors in use with optically triggered thyristors. Using optically triggered thyristors in high-voltage power conversion equipment facilitates electrical insulation between the main circuit and control circuit and measures against inductive disturbances.
The device can be made significantly smaller and lighter.

However, currently available optical trigger energy is weaker than electrical trigger energy, so it was necessary to increase the optical sensitivity of an optical trigger thyristor by several tens of times the gate sensitivity of an electrically triggered thyristor. In general, increasing the gate sensitivity of a thyristor makes it easier for the thyristor to operate against voltage noise with a steep rise that enters from the main circuit side, such as lightning surges. The permissible rate of voltage increase without malfunction even when overvoltage is applied is called dv/dt tolerance. By reducing the area of the light receiving part and reducing the displacement current generated in this part, it is possible to increase the dv/dt tolerance without sacrificing photosensitivity. The ability to withstand the steep rising on-current that occurs at the beginning of turn-on (di/dt ability)
decreases. An important technical challenge is to realize a photo-triggered thyristor with high photosensitivity without sacrificing major thyristor characteristics such as dv/dt and di/dt tolerance.

FIG. 1 shows a cross-sectional view of a typical optical trigger thyristor. Four semiconductor layers of different conductivity types are formed on a semiconductor wafer such as silicon. 1 is a P emitter layer, 2 is an N base layer, 3 is a P base layer, and 4 is a P emitter layer.
is called the N emitter layer. A pilot thyristor 10 consisting of an N emitter layer 4a is arranged concentrically in the center of the semiconductor wafer, and a P base layer 3 is exposed at the center to form a light receiving section 5. An electrode 5a made of a vapor-deposited layer of aluminum or the like is formed on the N emitter layer 4a. A main thyristor 11 is formed concentrically with the pilot thyristor 10 , and a cathode electrode 5b is deposited on its N emitter 4b. Short circuit parts 7 are provided in the N emitter layer 4b, and P
The base layer 3 and the cathode electrode 5b are short-circuited.
A dv/dt compensation electrode 8 is provided on the outer periphery of the main thyristor 11 , and the dv/dt compensation electrode 8 is electrically coupled to the electrode 5a by a conductor 9. An anode electrode 6 made of metal such as tungsten is attached to the P emitter layer 1 by a method such as an alloy method.

When the light receiving part 5 of the phototrigger thyristor configured in this manner is irradiated with a phototrigger signal having a light amount φ, depletion layers on both sides of the central junction J ₂ formed by the N base layer 2 and the P base layer 3 are formed. The photocurrent Iph, which mainly occurs in the region, begins to flow. The photocurrent Iph shown by the broken line in FIG. 1 flows laterally through the P base layer 3, passes through the short circuit part 7 provided in the main thyristor 11 , and the cathode electrode 5b, and is connected to an external circuit consisting of a load 12 and a power source 13. flows. P where the photocurrent Iph flows
The voltage drop V ₁ occurring across the base layer 3 and the P base lateral resistance R ₁ forward biases the junction J ₃ consisting of the P base layer 3 and the N emitter layer 4a. When the voltage V ₁ at the inner peripheral part 4a' of the deepest forward biased N emitter 4a becomes larger than the diffusion potential of _J3 , the injection of electrons from the 4a' part increases rapidly, and the pilot thyristor 10 is photo-turned on from the 4a' part. do. This turn-on current Ip is 4a-5a-9-8
It flows out to the external circuit via -3-7-5b.
Ip functions as a gate current for the main thyristor 11 , and the main thyristor 11 is turned on by Ip, and this photo-triggered thyristor is turned on. As is clear from the above description, the photosensitivity of the photo-triggered thyristor is determined by the P-base lateral resistance _R1 , and the larger _R1 is, the higher the photosensitivity is.

Next, the anode electrode 6 of this photo-triggered thyristor
Consider a case where voltage noise with a steep rise is applied between the electrode 5b and the cathode electrode 5b. Unlike when the light-receiving section is irradiated with a photo-trigger signal, when voltage noise is applied between the anode electrode 6 and the cathode electrode 5b of the photo-trigger thyristor, the displacement current Id flows through the entire junction area of the photo-trigger thyristor. Assuming that the junction capacitance of the central junction J ₂ directly below the light receiving section is C ₁ , the displacement current Id ₁ flowing through C ₁ flows along the same path as the photocurrent Iph, as shown by the solid line. On the other hand, the displacement current Id ₂ flowing through the junction capacitance C ₂ near the dv/dt compensation electrode 8 flows through the short circuit portion 7 provided in the main thyristor 11 . The equivalent circuit of the optical trigger thyristor at this time is shown in FIG. 2. Point A corresponds to the cathode electrode 5b. The bias voltage Vj of the diode D consisting of the N emitter layer 4a and the P base layer 3 of the pilot thyristor 10 can be expressed as the difference _V1' - _V2 ' between the voltages _V1 ' and _V2 ' across _R1 and _R2 . Vj=
When the value of V ₁ '-V ₂ ' crosses the diffusion potential of J ₃ , the pilot thyristor 10 triggers dv/dt. in this case,
By adjusting the value of R ₂ and keeping the value of Vj low, J ₃ will be less likely to be forward biased even if voltage noise is applied, and the dv/dt tolerance of the pilot thyristor 10 will be
The improvement can be made independently of the value of _R1 .

By using the methods described above, conventional photo-triggered thyristors have been able to improve their light sensitivity and dv/dt tolerance. However, conventional optically triggered thyristors have the following drawbacks.

That is, in a conventional optically triggered thyristor, R ₁ and
By increasing R ₂ and using the effect of the dv/dt compensation electrode,
Although the optical sensitivity and dv/dt tolerance are improved, if _R2 is increased unnecessarily, the gate sensitivity of the main thyristor 11 increases, and the dv/dt of the main thyristor 11 increases.
There was a problem that the tolerance level decreased. R ₂ is the second
As is clear from the equivalent circuit in the figure, the P base layer resistance R ₂ ' directly under the groove 14 in FIG. 1 and the main thyristor 1
P base layer resistance directly under the N emitter layer 4a' of 1
is the sum of R ₂ ″.N emitter 4a′ and P base layer 3
The bias voltage at the junction J ₃ ′ formed by is
Since it is determined by R ₂ ″, by making the groove 14 deeper and increasing R ₂ ′, R ₂ can be increased without reducing the dv/dt tolerance of the main thyristor 11 .
Although the photosensitivity of the pilot thyristor 10 can be increased, the gate sensitivity of the main thyristor 11 is reduced, so there is a problem that the turn-on of the main thyristor 11 is delayed compared to the turn-on of the pilot thyristor 10 . As a result, the on-current at the initial stage of photo-turn-on is concentrated in the pilot thyristor 10 , and the di/dt withstand capability is significantly reduced. In this way, dv/
Conventional thyristors had limitations in improving photosensitivity without compromising dt and di/dt tolerance.

[Purpose of the invention]

The present invention was made in consideration of these circumstances, and its purpose is to improve light sensitivity (gate sensitivity) and di/dt tolerance without impairing characteristics such as dv/dt tolerance. The object of the present invention is to provide a highly practical thyristor with a significant improvement in performance.

[Summary of the invention]

In the present invention, a plurality of pilot thyristors are arranged so as to be surrounded by a current collecting electrode formed on a base layer,
and a gate electrode is formed on each base layer surrounded by the emitter layer of the pilot thyristor,
The gate electrode of each of these pilot thyristors is sequentially electrically connected to the emitter electrode provided on the emitter layer of the pilot thyristor in the previous stage, and the emitter electrode of the pilot thyristor in the final stage is shared with the current collecting electrode. The cathode emitter bias voltage of the other pilot thyristors is set to be smaller than or equal to the cathode emitter bias voltage of the final stage of the pilot thyristor, which is caused by displacement current due to overcurrent or overvoltage application. .

〔Effect of the invention〕

According to the present invention, the gate sensitivity of each pilot thyristor can be increased without reducing the dv/dt withstand capability, and the diameter of the light receiving portion can also be increased by 2 to 3 times or more compared to the conventional one. As a result of increasing the size of the light receiving section, it is possible to significantly improve photosensitivity and optical coupling efficiency. In addition, when the diameter of the light receiving part is increased, the leakage current generated in this part generally increases and the withstand voltage tends to decrease during high temperature operation, but in the present invention, the leakage current flows along the same path as the displacement current. It is also effective in preventing false triggers due to stray current. Furthermore, in the present invention, since a plurality of pilot thyristors are turned on in sequence, the current flowing through the first pilot thyristor at the initial stage of turn-on decreases in proportion to the number of pilot thyristors in the subsequent stage, so that the turn-on current to the first pilot thyristor decreases. can reduce concentration,
The di/dt capacity can be greatly expanded without compromising the dv/dt capacity.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. 3 and 4 show the configuration of a thyristor according to an embodiment of the present invention.
The figure is a plan view of the gate electrode, and FIG. 4 is a cross-sectional view.

The surface of the P base layer 23 adjacent to the N emitter layer 24f of the main thyristor MT is composed of four stacked semiconductor layers: the P emitter layer 21, the N base layer 22, the P base layer 23, and the N emitter layer 24f. An electrode 25 is formed, and this current collecting electrode 2
5, a plurality of pilot thyristors are formed. Here, the first
A total of five pilot thyristors, from the pilot thyristor PT ₁ to the fifth pilot thyristor PT ₅ whose emitter electrode is shared with the current collector electrode 25.
PT ₁ to PT ₅ are formed. The periphery of the current collecting electrode 25, that is, each pilot thyristor PT ₁ to PT ₅
around which the main thyristor MT is formed. The first pilot thyristor _PT1 has an N emitter layer 24a formed in an annular shape around the light receiving part 26,
An emitter electrode 27 is arranged on the surface thereof. Further, the second to fifth pilot thyristors PT ₂ to _{PT 5} are provided in the P base layer 23, surrounded by the current collecting electrode 25, and provided with N emitter layers 24b, 25c,
24d, 24e are formed respectively, emitter electrodes 28, 29, 30, 31 are formed on these N emitter layers 24b, 24c, 24d, 24e, respectively, and gate electrodes 32, 33, 31 are formed on P base layer 23, respectively. 34 and 35 are formed.
Among these, the emitter electrode 31 of the fifth pilot thyristor PT ₅ is shared with the current collecting electrode 25 . However, the pilot thyristor of each stage
Each gate electrode 32, 3 of PT ₂ , PT ₃ , PT ₄ , PT ₅
3, 34, and 35 are wiring layers 36 such as Al wires on the emitter electrodes 27, 28, 29, and 30 of the pilot thyristors PT ₁ , PT ₂ , PT ₃ , and PT ₄ in the previous stage, respectively.
are sequentially electrically connected via. Therefore,
Pilot thyristors in each stage PT ₂ , PT ₃ , PT ₄ ,
Each PT ₅ is a pilot thyristor in the previous stage.
The turn-on operation is performed by receiving the turn-on currents of PT ₁ , PT ₂ , PT ₃ , and PT ₄ as gate currents. 37 and 38 are a cathode electrode and an anode electrode, respectively.

Now, when the light gate signal hν is irradiated to the light receiving section 26 of the present thyristor configured in this way, the first
The photocurrent Iph generated mainly in the depletion layer region of the central junction of the pilot thyristor PT ₁ flows through the P base layer 2.
Flows into 3. This photocurrent Iph is
flows laterally, passes through the collector electrode 25 provided on the P base layer 23, and then flows into the cathode electrode 37 via the short circuit 39 provided between the P base layer 23 and the cathode electrode 37. As a result, the photocurrent Iph generates a lateral potential difference in the P base layer 23 of the first pilot thyristor _PT1 region, which causes the N emitter layer 24a of the first pilot thyristor _PT1 to move in the forward direction. You will be biased. The deepest potential of this forward bias voltage is between the N emitter layer 24a and the P base layer 24.
When the diffusion potential approaches the value of the junction between the N emitter layer 24a and the P base layer 23,
The injection of electrons into the thyristor PT1 increases rapidly, and the first pilot thyristor _PT1 is turned on from the junction. This first pilot thyristor
The turn-on current of PT ₁ is transferred to the second through the wiring layer 36.
A gate current is applied to the gate electrode 32 of the second pilot thyristor PT ₂ , thereby turning on the second pilot thyristor PT ₂ . Similarly, by turning on the pilot thyristor _PT2 , the third to fifth pilot thyristors _PT3 to _PT5 are sequentially turned on. The turn-on current of the fifth pilot thyristor PT ₅ flows from the current collecting electrode 25 to the short circuit 39.
The turn-on current flows to the cathode electrode 37 via the gate current, and at this time, the turn-on current functions as a gate current of the main thyristor MT, so that the main thyristor MT is turned on.

By the way, the light sensitivity (gate sensitivity) of the thyristor
In order to increase the
N emitter layer 24a of pilot thyristor PT ₁
It is sufficient to increase the lateral resistance of the P base layer 23 immediately below. However, in the thyristor having the structure according to the present invention, in addition to this, the second pilot thyristor
It is better to reduce the resistance value Rp ₂ between the gate electrode 32 of PT ₂ and the current collecting electrode 25.

Fig. 5 shows the minimum optical trigger power φ ^* and Rp ₂ of the first pilot thyristor PT ₁ , which were determined by the inventors.
shows the relationship between It can be seen that when Pp ₂ >100Ω, φ ^* increases rapidly and the photosensitivity decreases. This means that a part of the photocurrent Iph is transferred to the N emitter layer 24a of the first pilot thyristor _PT1 , the wiring layer 36, and the second pilot thyristor PT1.
Gate electrode 32 of pilot thyristor PT ₂ , N emitter layer 24 of second pilot thyristor PT ₂
b Via the P base layer 23 directly below the current collecting electrode 2
5, the current collector electrode 25 and the gate electrode 32
This is because a voltage that biases the N emitter 24b in the reverse direction is generated during this period. Therefore, the resistance Rp ₂ between the gate electrode 32 and the current collecting electrode 25 is reduced,
The smaller the reverse bias voltage applied to the N emitter layer 24b, the better the photosensitivity. Next, consider a case where voltage noise with a large dv/dt value is applied between the anode and cathode of a thyristor having such a structure. FIG. 6 shows an equivalent circuit of a thyristor according to the present invention. N emitters 24a, 24b, 24c, 24 from the first pilot thyristor _PT1 to the fifth pilot thyristor _PT5 with the light receiving section
The junction capacitances that supply the displacement current flowing through the P base layer 23 directly under d and 24e are respectively C ₁ ~
Represented by C ₅ . _CM is a junction capacitance that supplies a displacement current flowing into a short circuit portion 39 arranged on the inner circumference of the main thyristor MT. The diodes D ₁ to D ₅ are connected to the N emitter layer and P of each pilot thyristor PT ₁ to _{PT 5} .
This is a diode formed from the base layer 23.
Similarly, A _M is the N emitter layer 2 of the main thyristor MT.
4f and a P base layer 23. In the figure, A represents the cathode electrode, K represents the cathode electrode, B represents the light receiving part, and C represents the cathode electrode.
-F represent gate electrodes 32-35, respectively. Further, H ₁ to _{H 5} correspond to the current collecting electrodes 25 . Assuming that the density of the displacement current flowing through each junction capacitance C ₁ to C _M is Jd, as the displacement current is generated, the current collector electrodes H ₁ to _{H 5} , the light receiving part B, and the gate electrode C to
The potential difference V ₁ to _{V 5} generated between F is proportional to Jd.
Each proportionality constant is R ₁ (=V ₁ /Jd), R ₂ (=V ₂ /Jd), R ₃
(=V ₃ /Jd), R ₄ (=V ₄ /Jd), and R ₅ (=V ₅ /Jd).

The maximum value of the forward bias of each pilot thyristor PT ₁ to PT ₅ is determined by the diode D ₁ in FIG.
~D is the voltage across ₅ . Forward bias applied across D ₁ to D ₅ V ₁₂ , V ₂₃ , V ₃₄ , V ₄₅ and
_V5 can be expressed by the difference in voltage across _R1 and _R2 , _R2 and _R3 , _R3 and _R4 , _R4 and _R5 , and the voltage across _R5 . Since Jd is the product of junction capacitance Cj and dv/dt value, V ₁₂ , V ₂₃ , V ₃₄ , V ₄₅ and V ₅ are as follows.

V ₁₂ =V ₁ −V ₂ =(R ₁ -R ₂ )・Cj・dv/dt …(1) V ₂₃ =V ₂ −V ₃ =(R ₂ -R ₃ )・Cj・dv/dt …( 2) V ₃₄ =V ₃ −V ₄ =(R ₃ -R ₄ )・Cj・dv/dt …(3) V ₄₅ =V ₄ −V ₅ =(R ₄ -R ₅ )・Cj・dv/dt …(4) V ₅ = V ₅ = R ₅・Cj・dv/dt When the values of V ₁₂ , V ₂₃ , V ₃₄ , V ₄₅ and V ₅ reach the diffusion potential of each diode D ₁ to D ₅ , the pilot thyristor The injection of electrons from the thyristor rapidly increases, and the pilot thyristor whose bias voltage first exceeds the diffusion potential triggers dv/dt. In this example, V ₁₂ , V ₂₃ ,
The values of R ₁ to R ₅ are selected so that the values of V ₃₄ and V ₄₅ are smaller than or equal to V ₅ . _V12 , _V23 , _V34 ,
If designed so that V ₄₅ is equal to V ₅ then R ₅ =
R ₄ - R ₅ = R ₃ - R ₄ = R ₂ - R ₃ = R ₁ - R ₂ , and from these relationships, R ₅ = R ₄ /2 = R ₃ /3 = R ₂ /4 =
A relationship of R ₁ /5 is obtained. Therefore, to satisfy the above-mentioned conditions, at least R ₅ R ₄ /2, R ₅
The values of R 1 to R 5 must be selected so as to satisfy the relationships R ₃ /3, R ₅ R ₂ /4, and R ₅ R _{1 / 5} .

In addition, in the present invention, as described above, the gate electrode 32 of the second pilot thyristor PT ₂ and the current collecting electrode 2
It is necessary to keep the resistance value between 5 and 5 below 100Ω to prevent a decrease in photosensitivity. While R ₂ depends on the width of the N emitter of the second pilot thyristor PT ₂ , the resistance value between the gate electrode 32 and the current collecting electrode 25 can be lowered by increasing the length of the N emitter. Therefore, the conditions of R ₁ to _{R 5} and the condition of the resistance value between the current collecting electrode 25 and the gate electrode 32 can be realized without contradicting each other.

Incidentally, in such a structure, the dv/dt tolerance is determined by the P-base effective resistance Rn of the final stage pilot thyristor _PT5 . As shown in the example,
When the pilot thyristor has five stages, _R5 may be determined so as to satisfy the dv/dt value of the predetermined specifications. At that time, R ₁ can be up to 5 times larger than R ₅ .
If you try to increase the diameter of the light receiving part in order to increase the optical sensitivity of the first pilot thyristor PT ₁ , which has the light receiving part, or to increase the optical coupling efficiency with the optical signal transmission system, it is generally necessary to increase R ₁ . There is.
In the present invention, R ₁ can be easily increased without sacrificing dv/dt tolerance, so photosensitivity and optical coupling efficiency can be significantly improved.
For example, according to an experiment using a 4KV optically triggered thyristor, when the diameter of the light receiving part is d = 1.5mmφ,
In the conventional example, the minimum optical trigger power φ ^* was 4 mw when dv/dt=1500 V/μs, but in the optical trigger thyristor of the 5-stage pilot thyristor according to the present invention, it was possible to reduce the minimum optical trigger power φ ^* to 2 mw. Same φ ^*
= 4 mw, when the present invention is implemented,
We were able to achieve a two-fold improvement to d=3mmφ. 1.5
When a light-emitting diode is used as a light source in an optical signal transmission system consisting of a bundled optical fiber of mmφ and that of a bundled optical fiber of 3mmφ, the light output of the light-emitting diode and the optical coupling efficiency of the bundled optical fiber can be improved by more than three times. In either case, the driving current of the light emitting diode can be significantly improved. Since the driving current value of the light emitting diode greatly affects the life of the light emitting diode, by implementing the present invention, the reliability of the optical trigger system can be greatly improved. Especially for thyristor valves for DC power transmission, which require high reliability in optical trigger systems.
When the optically triggered thyristor of the present invention is installed, great effects can be achieved. In addition, when the diameter of the light receiving part is increased, the leakage current generated in this part increases, and the withstand voltage tends to decrease during high temperature operation. However, since the leakage current flows along the same path as the displacement current, the present invention The implemented thyristor is also effective in preventing false triggering due to leakage current. As a result, a thyristor with excellent forward blocking voltage characteristics at high temperatures can be realized.

Furthermore, in the present invention, the following effects can be obtained by the current collecting electrode. As shown in Figure 2, in the conventional example, R ₁ and R ₂ are electrically coupled via a cathode electrode, and the voltage generated in R ₁ due to the displacement current is transferred to R ₂
The voltage generated at both ends cancels it out, improving dv/dt tolerance. However, as mentioned above, if we try to prevent the main thyristor's dv/dt tolerance from decreasing,
There was a problem that the di/dt tolerance decreased.

On the other hand, in the present invention, since R ₁ to Rf are electrically coupled via the current collecting electrode, the number of stages of pilot thyristors can be easily increased. That is, in the present invention, as shown in _FIG .
Since one end of the resistors R ₁ , R ₂ ,... is short-circuited by H ₂ ,..., the junction capacitance of the first stage pilot thyristor C ₁
The displacement current flowing through the junction capacitance _C2 of the second stage pilot thyristor flows through the resistor _R2 to the current collecting electrode and does not provide _a bias to the second stage. This is because it has the effect of not flowing to the current collecting electrode and becoming a third stage bias. Since the current flowing through the first pilot thyristor PT ₁ in which the light receiving section is located at the initial stage of turn-on decreases in proportion to the number of pilot thyristors in the subsequent stage, the thyristor according to the present invention prevents the concentration of turn-on current to the first pilot thyristor PT ₁ . It can be reduced. Also, when a displacement current flows due to dv/dt noise, for example, the capacitance
The displacement current flowing through C ₂ creates a reverse bias on the diode D ₁ through the resistor R ₂ , and the displacement current flowing through the capacitor C ₃ creates a reverse bias on the diode D ₂ through the resistor R ₃ . This effect can be obtained. Even when the first-stage pilot thyristor is turned on, the turn-on current flows from the diode D ₁ through the resistor R ₂ to the current collecting electrode, and a reverse bias is also generated for the diode D ₁ . As a result of these, in the present invention,
Gate sensitivity can be increased while maintaining high di/dt tolerance and dv/dt tolerance. In addition, in the thyristor of the present invention, the area of the light receiving area can be easily increased without sacrificing photosensitivity or dv/dt tolerance, so the initial turn-on area is expanded and the on-current density at the initial turn-on stage is significantly lowered. can do. For this reason, in the present invention,
Compared to the conventional example, di/dt tolerance can be greatly expanded. According to the prototype results, the thyristor of the example
di/dt600A and 2 to 3 times as much as the conventional example.
We were able to achieve di/dt tolerance.

In this way, this embodiment achieves high performance with dramatically improved di/dt tolerance and light sensitivity (gate reduction) without impairing the main characteristics required of a thyristor such as dv/dt tolerance. A highly practical thyristor can be realized.

FIG. 7 shows a schematic plan view of another embodiment of the present invention. A first pilot thyristor PT ₁ having a light receiving part in the center is formed, and three second pilot thyristors PT ₂₁ to PT ₂₃ and three third pilot thyristors PT ₂₁ to _{PT 23} are arranged radially alternately. An array is formed. The outer circumference of the N emitter of the first pilot thyristor _PT1 has 3
An N emitter electrode is provided here as well, and this protrusion and the second pilot thyristor are connected to each other.
Each of the gate electrodes PT ₂₁ to _{PT 23} is connected by bonding with an aluminum wire. Furthermore, protrusions are also provided on the N emitter layers of the second pilot thyristors PT ₂₁ to PT ₂₃ , and N emitter electrodes _are also _provided on these. A bonding connection is made between the gate electrode and the gate electrode using an aluminum wire. In the third pilot thyristors PT ₃₁ to _{PT 33} , the radially arranged current collecting electrodes 40 also serve as emitter electrodes, as in the previous embodiment. Each pilot thyristor and main thyristor MT is
> plane, and the peripheral length directions of the N emitter of each pilot thyristor and the current collecting electrode 40 are crystal axes [011], [011], [110], [110], [
Ten
1] and [101] directions. Half of the peripheral length of each N emitter and current collecting electrode 40 is [011],
The [110] and [101] crystal axes are in this direction, and the crystal axes in this direction are suitable for maintaining the conduction region at the initial stage of turn-on, and reliable turn-on can be achieved.

Note that the present invention is not limited only to the above embodiments. In the embodiment, an optical thyristor is illustrated, but the present invention can be similarly applied to an electrically triggered thyristor in which a gate electrode is formed in a light receiving section. In addition, the number of stages of pilot thyristors and their arrangement can be determined according to the specifications, and the key is to arrange each pilot thyristor so that it is surrounded by current collecting electrodes provided on the base layer. The electrical connection may be made sequentially by the method described above.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional thyristor, FIG. 2 is an equivalent circuit diagram thereof, FIG. 3 is a plan view of a thyristor according to an embodiment of the present invention, and FIG. 4 is a sectional view of the thyristor. 5 is a diagram for explaining the operating characteristics of the thyristor, FIG. 6 is an equivalent circuit diagram of the thyristor, and FIG. 7 is a schematic plan view of a thyristor according to another embodiment of the present invention. MT...Main thyristor, _ST1 to _ST5 ...Pilot thyristor, 24a to 24f...N emitter layer, 2
5... Current collecting electrode, 26... Light receiving part, 27-31... Emitter electrode, 32-35... Gate electrode, 36... Wiring, 37... Cathode electrode, 38... Anode electrode.

Claims (1)

[Scope of Claims] 1. A main thyristor comprising four semiconductor layers laminated with alternating conductivity types, including a plurality of semiconductor layers that share three semiconductor layers other than the emitter layer of the main thyristor in the base layer. In the thyristor in which the emitter layer of the pilot thyristor is formed to have the same conductivity type as the emitter layer of the main thyristor, each of the pilot thyristors has a current collector electrode provided on the base layer adjacent to the emitter layer of the main thyristor. A gate electrode is formed on the base layer surrounded by the emitter layer of each pilot thyristor, and the gate electrode of each pilot thyristor is sequentially connected to the previous pilot stage. It is electrically connected to the emitter electrode provided on the emitter layer of the thyristor, and the emitter electrode of the pilot thyristor in the final stage is shared with the current collecting electrode, so that the final stage generated by displacement current due to leakage current or overvoltage application. A thyristor characterized in that the forward bias voltages of the cathodes and emitters of the other pilot thyristors are set to be smaller than or equal to the forward bias voltage of the cathodes and emitters of the pilot thyristors. 2. The thyristor according to claim 1, wherein the resistance value between the gate electrode of the second stage pilot thyristor of the plurality of pilot thyristors and the current collecting electrode is 100Ω or less. 3. The emitter layer of the plurality of pilot thyristors and a part of the emitter electrode thereon are provided with a protrusion for electrically connecting the emitter layer to the gate electrode of an adjacent pilot thyristor. Thyristor according to range 1. 4. Claim 1, characterized in that the pilot thyristor at the first stage among the plurality of pilot thyristors is driven by an optical trigger signal.
Thyristor described in section.