JP3403123B2 - Photothyristor element and bidirectional photothyristor element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in commercial frequency lines, etc.
The present invention relates to a photothyristor element having a built-in T and a bidirectional photothyristor element in which the photothyristor element is connected in anti-parallel, and particularly to a photothyristor element and a bidirectional photothyristor element capable of surely performing a zero-cross operation during actual AC operation. Regarding thyristor element.

[0002]

2. Description of the Related Art Conventionally, as a so-called ignition SSR (solid sot relay), for example, a bidirectional thyristor is formed on an N-type silicon substrate or the like, and a gate trigger signal is generated by irradiating the bidirectional thyristor with light. A bidirectional photothyristor element that gives and controls a voltage is widely used.

This SSR generally produces less noise due to switching, but noise occurs when switching is performed at a high AC voltage, which adversely affects control equipment. Therefore, it is desired to perform switching only in a place where the AC power source is low (zero cross point), and in order to realize this, in general, a MOSFET (Metal) is used.
Oxide Semiconductor Field
d Effect Transistor) is used.

FIG. 12 is a sectional view showing a schematic structure of a conventional photothyristor element having a zero-cross function.

The N-type silicon substrate 1 generally has an impurity concentration of 10 ¹³ atoms / cm ³ to 10 ¹⁵ atoms / cm ³ , and an N-type channel stopper region 10 is provided around the portion where the photothyristor element is formed. Has been.

A P type anode diffusion region 2 is formed on the surface of the N type silicon substrate 1, and an anode terminal A is connected to the P type anode diffusion region 2 through an electrode layer 20 made of Al or the like. A certain distance is provided on the left side of the anode diffusion region 2, and P
A type P gate diffusion region 3 is provided, and an N type cathode diffusion region 4 is formed therein. A P gate terminal PG and a cathode terminal K are connected to the P gate diffusion region 3 and the cathode diffusion region 4 via an electrode layer 20, respectively. This anode diffusion region 2, silicon substrate 1, P
P by the gate diffusion region 3 and the cathode diffusion region 4
A lateral type thyristor 30 having an NPN structure is configured. Reference numeral 18 denotes a gate resistance RGK formed by P-type diffusion.

On the left side of these, diffusion regions 5 and 6 forming the NPN type phototransistor 21 are formed. Furthermore, on the left side of the P
Type well diffusion region 7 is formed, and N type source diffusion region 8 and drain diffusion region 9 are formed on the surface side thereof. This MOSFET 14 is provided to realize the zero-cross function, and the phototransistor 21 is a MOS.
It is provided to drive the gate 15 of the FET 14.

Au or the like is formed on the back surface of the N-type silicon substrate 1.
An electrode layer 11 made of is provided. Also, N type
The surface of the con board 1 is made of Al or the like for electrical connection.
The wiring layer (electrode layer) 20 is provided to provide electrical insulation.
SiO in the required parts ₂Membrane 12 and oxygen doping
A high passivation film composed of the semi-insulating film 13 is formed.
ing. Furthermore, input an optical signal as a photothyristor
P gate diffusion region (light receiving portion) 3 for
Phototran for optically controlling the gate 15 of the ET14
In the P-type diffusion region (base part) 5 of the transistor 21,
Is not shown, but for removing the wiring layer 20, etc.
More open.

FIG. 13 is an equivalent circuit diagram of one side of the bidirectional photothyristor element. Here, two transistors T1 and T2 are connected between the anode terminal A and the cathode terminal K. The emitter of the transistor T1 is connected to the anode terminal A, the base of the transistor T1 is connected to the collector of the transistor T2, the collector of the transistor T1 is connected to the base of the transistor T2, and the cathode terminal K via the resistor RGK. Has been done. The emitter of the transistor T2 is connected to the cathode terminal K. Then, the MOSFET 1 for the zero-cross function so as to straddle the resistor RGK
Source S and drain D of 4 are connected, and
The gate G of T14 is connected to the middle of the base of the transistor T1 and the collector of the transistor T2 via the phototransistor 21. This phototransistor 21
A junction capacitance Cj2 is connected in parallel with.

Such a circuit operates as follows. The MOSFET 14 is provided between the P gate diffusion region 3 and the cathode diffusion region 4 of the thyristor 30, and the MOSFET 14 is
The gate G of the ET 14 is controlled by the potential of the N-type silicon substrate 1 via the phototransistor 21 for driving the gate of the MOSFET. At this time, when the voltage applied to the MOSFET 14 by the voltage V _AK between the anode and the cathode exceeds the threshold voltage of the MOSFET 14, the MO
When the SFET 14 is turned on, the gate and cathode of the thyristor 30 are short-circuited, and the operation of the photothyristor is limited. This realizes the zero-cross function.

The two photothyristor elements thus configured are connected in reverse parallel to each other as CH (channel) 1 and CH2, and basic light control is performed by directly irradiating the surface of the photothyristor element with light. Type SSR for ignition, operating as a bidirectional photothyristor
Used as.

The above-mentioned photothyristor element is the MOSFET 14 provided for the zero-cross function,
A phototransistor for optically controlling the gate 15 of the MOSFET 14 is incorporated in order to improve lightning resistance surge resistance and electrostatic breakdown resistance of the gate insulating film. Hereafter, this is Vp
It is called a circuit 16. With this structure, even if a high voltage (rated at a maximum of 800 V) is applied between the elements A and K, the MO
The voltage is clamped so that the voltage between the gate 15 and the source 8 of the SFET 14 does not become higher than a certain voltage.

FIG. 14 is a sectional view for explaining the structure around the phototransistor portion for driving the MOSFET.

The design parameters for determining the clamp voltage are as shown in FIG. 1 when the specific resistance of the N-type silicon substrate 1 is constant.
The base-collector junction j of the phototransistor shown in FIG.
2 and a P-type diffusion region 3 adjacent to surround the same,
7 is the distance Lp from the junction j1. The larger the value of Lp, the higher the clamp voltage. The reason for this is as follows. That is, when the voltage between the anode and the cathode is forward biased and the voltage rises, the junction j1 is also reverse biased, and the depletion layer 19 extends as indicated by. The reason is that when reaching the junction j2 as shown in (3), a punch-through state is established and further voltage increase is suppressed.

Regarding the structure of the Vp circuit 16, the structure
From the viewpoint of the reliability of the through-thru voltage
Considering the change of the charge Qss17 at the interface of S,
iO ₂High breakdown voltage passivation in which a semi-insulating film 14 is formed on the film 12.
If you provide a basation film, for example, from the package resin
Seal that is not affected by external charges such as ions
It is preferable because it can obtain the effect. In addition, this high voltage
Since the passivation film is a transparent film that transmits light,
Phototransistor for optically driving the gate voltage of SFET
The optical output of the transistor rises, and the efficiency is good.
is there. The oxygen-doped semi-insulating film 13 is, for example, a low pressure CV.
SiH by D device_FourAnd N₂About 650 using O gas
Grow at ℃, N₂Change the mixing ratio of O gas
The oxygen resistance is changed by and the resistance value of the film is controlled.
I am Normally, the oxygen concentration is about 30%.
It

[0016]

However, when the high breakdown voltage passivation film in which the semi-insulating film is formed on the SiO ₂ film as described above is provided in the Vp circuit 16 portion, the following zero-cross operation failure occurs. . In this structure, the gate 15 and the source 8 (GND) of the MOSFET 14 are
The resistance Rx25 of the semi-insulating film 13 is parasitically entered between the voltage and the potential. Therefore, this parasitic resistance Rx25 causes
As shown in (b), especially when the AC voltage drops, the MOS
The gate potential of the FET 14 easily drops. Then, under a certain evaluation condition, the value Vox (F) when the AC voltage of the zero-cross voltage decreases is about three times as large as the value Vox (R) when the AC voltage increases, and a defect exceeding the specification occurs.
Further, the resistance Rx25 of the semi-insulating film 13 also enters between the gate 15 of the MOSFET 14 and the cathode K of the thyristor, but since the source 8 of the MOSFET 14 and the cathode K of the thyristor are connected by wiring, the same problem occurs. Occurs.

The present invention has been made in order to solve the problems of the prior art, and has a high breakdown voltage in which a MOSFET for obtaining a zero-cross function is built in and an oxygen-doped semi-insulating film is provided on the insulating film. An object of the present invention is to provide a photothyristor element and a bidirectional photothyristor element capable of preventing a zero-cross operation failure due to a parasitic capacitance of a semi-insulating film in a structure having a passivation film.

[0018]

A photothyristor element of the present invention has a built-in MOSFET for obtaining a zero-cross function, and includes a photodiode or a phototransistor for driving the gate of the MOSFET, and
In a photothyristor element having a high breakdown voltage passivation film in which a semi-insulating film is provided on a SiO ₂ film, the MOS
The semi-insulating film is patterned so that the parasitic resistance due to the semi-insulating film does not enter between the gate and the source of the FET, thereby achieving the above object.

The semi-insulating film may be patterned so that parasitic resistance due to the semi-insulating film does not enter between the gate of the MOSFET and the cathode of the thyristor.

The photothyristor element of the present invention comprises a first conductivity type semiconductor substrate, second conductivity type first diffusion regions and second diffusion regions provided on the surface of the semiconductor substrate, and the second diffusion region. A thyristor is composed of a third diffusion region of the first conductivity type provided inside, a fourth diffusion region of the second conductivity type provided on the surface of the semiconductor substrate, and a substrate surface in the fourth diffusion region. A MOSFET for obtaining a zero-cross function is formed from the fifth diffusion region and the sixth diffusion region of the first conductivity type which are provided on the side and serve as the source and the drain, and between the second diffusion region and the fourth diffusion region. A seventh diffusion region of the second conductivity type is provided on the surface portion of the semiconductor substrate, and a photodiode for driving the gate of the MOSFET is configured from the seventh diffusion region and the semiconductor substrate, or , The An eighth diffusion region of the second conductivity type is provided on the semiconductor substrate surface portion between the second diffusion region and the fourth diffusion region, and a ninth diffusion region of the first conductivity type is provided on the substrate surface side in the eighth diffusion region. A region is provided to form a phototransistor for driving the gate of the MOSFET from the eighth diffusion region, the ninth diffusion region and the semiconductor substrate, and a SiO ₂ film is formed so as to cover the surface of the semiconductor substrate. In a photothyristor element having a high breakdown voltage passivation film having a semi-insulating film formed thereon, a parasitic resistance due to the semi-insulating film does not enter between the gate and the source of the MOSFET,
The semi-insulating film is divided at a portion that covers between the seventh diffusion region and the fourth diffusion region or a portion that covers between the eighth diffusion region and the fourth diffusion region, whereby the above object is achieved. Is achieved.

The semi-insulating film is formed between the gate of the MOSFET and the cathode of the thyristor so that a parasitic resistance due to the semi-insulating film does not enter.
It may be divided by a portion that covers the diffusion region or a portion that covers the eighth diffusion region and the second diffusion region.

It is preferable that the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region adjacent so as to surround the junction are covered with a semi-insulating film or a metal layer. Alternatively, it is preferable that the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region adjacent to surround the phototransistor or the photodiode are covered with two layers of a semi-insulating film and a metal layer.

In the metal layer, an overlay distance Lo from the junction of the P-type diffusion region is larger than 0 μm, and a distance Lp between the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region is larger than the distance Lp. Is preferably small, and more preferably the distance Lo of the overlay from the junction of the P-type diffusion region is 10 μm or more.

The metal layer has an overlay distance Lo ′ from the junction of the phototransistor or the photodiode of more than 0 μm, and the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region. It is preferably smaller than the distance Lp, more preferably the distance L of the overlay from the junction of the phototransistor or the photodiode.
o'is 10 μm or more.

In the metal layer, the sum Lo + Lo ′ of the distance Lo of the overlay from the junction of the P-type diffusion region and the distance Lo ′ of the overlay from the junction of the phototransistor or the photodiode is represented by the phototransistor or It is preferably smaller than the distance Lp between the junction of the photodiode and the junction of the P-type diffusion region.

The metal layer has a width Lw of 10 μm or more and 20 μm between the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region.
It is preferable to have a window opening of m or less.

The bidirectional photothyristor element of the present invention comprises:
The photothyristor elements of the present invention are connected in anti-parallel so that the above object is achieved.

The operation of the present invention will be described below.

The mechanism that causes the above-mentioned failure of the zero-cross operation is as follows. -DV when the voltage drops with AC voltage applied between the anode and cathode
If the voltage VG supplied from the phototransistor drops sharply below the threshold value Vth of the MOSFET during the transition period when the voltage VG supplied from the phototransistor sharply decreases with respect to the voltage / dt.
The ET is turned off and the thyristor is turned on. A normal zero-cross operation is shown in FIG. In this figure, the region in which the thyristor can be turned on is indicated by diagonal lines. In this case, the value Vox (F) of the zero-cross voltage when the AC voltage decreases and the value Vox (R) of the AC voltage increase are almost the same. However, in the conventional structure, the VG voltage is likely to drop at a faster timing than the AC voltage in this transition period. For this reason, as shown in FIG. 6B, the zero-cross voltage Vox (F) at the time of the AC voltage drop is likely to be large, which causes a malfunction. The cause of such a zero-cross malfunction is the MO that realizes the zero-cross function.
This is because the resistance Rx formed by the semi-insulating film is parasitically formed between the gate and the source (GDN potential) of the SFET, so that the gate potential leaks through this resistance and the VG voltage easily decreases. Further, the larger −dV / dt, such as when the AC voltage is high or the frequency is high, the larger Vox (F) is.

Therefore, in the present invention, the MOSFET
The semi-insulating film is patterned in consideration of design so that the parasitic resistance due to the semi-insulating film does not enter between the gate and the source. As a result, when the anode voltage drops in the AC voltage applied state, it is possible to suppress the decrease in the gate potential VG of the MOSFET, and it is possible to perform a stable zero-cross operation with respect to the voltage. Furthermore, MOSF
Since the source of ET and the cathode of the thyristor are connected, the same problem arises when a parasitic resistance due to the semi-insulating film enters between the gate of the MOSFET and the cathode. Therefore, the semi-insulating film is patterned so that the parasitic resistance due to the semi-insulating film does not enter between the gate and the cathode.

For example, if the semi-insulating film is divided at the portion covering the diffusion region of the phototransistor or the photodiode and the well diffusion region for the MOSFET adjacent thereto, the semi-insulating film is provided between the gate and the source of the MOSFET. It is possible to prevent parasitic resistance from entering. In addition, if the semi-insulating film is divided at the part covering the diffusion region of the phototransistor or photodiode and the diffusion region of the thyristor adjacent to it, the parasitic resistance due to the semi-insulating film is formed between the gate of the MOSFET and the cathode of the thyristor. Can be prevented from entering.

Further, from the viewpoint of device reliability, in order to stabilize the punch-through voltage, the base-collector junction of the phototransistor or the junction j of the photodiode j
2 and a region (a portion of distance Lp) between and on the junction j1 of the P-type diffusion regions adjacent so as to surround it,
It is preferable to shield by covering with a metal layer such as a semi-insulating film or Al wiring. Alternatively, it may be covered with two layers of a semi-insulating film and a metal layer. If the entire area is not covered with a semi-insulating film or a metal layer, the voltage (punch through voltage) that clamps between the gate and the source of the MOSFET rises, and in the worst case, the gate insulation of the MOSFET is isolated. The membrane may be destroyed.

However, when the junctions j1 and j2 and the region between them are covered with a metal layer, the photodiodes and phototransistors may be shielded from light and the driving efficiency of the MOSFET may be lowered. It is necessary to optimize the compatibility of the contradictory characteristics. Therefore, the overlay distance Lo from the junction j1 of the P-type diffusion region of the metal layer and the overlay distance Lo ′ from the junction j2 of the phototransistor or photodiode are set to be larger than 0 μm so as to cover the junctions j1 and j2. The thickness is preferably 10 μm or more in order to surely cover the junction j1 and the junction j2. Further, the preferable ranges of the distance Lo and the distance Lo ′ change depending on the distance Lp between the joint j1 and the joint j2. In order to obtain the light efficiency in the phototransistor or the photodiode, the distance Lo and the distance Lo ′ are the distance L.
It should be smaller than p, and L so that they do not overlap.
It is preferable that o + Lo ′ is smaller than the distance Lp. This distance Lp is a parameter that determines the clamp voltage. For example, in order to set the punch through voltage to about 50V, the distance Lp is set to 50 μm. Therefore, assuming that the distance Lp is 500 μm, the distance Lo and the distance Lo ′ are preferably less than 50 μm so that the photodiode and the phototransistor are not completely shielded from light and the efficiency is not reduced. Moreover, it is preferable that the distance Lp is less than 100 μm, assuming that the distance Lp is expanded to 100 μm.
Furthermore, in order to obtain sufficient light efficiency, the metal layer has a width Lw of 10 μm or more between the junction j2 of the phototransistor or photodiode and the junction j1 of the P-type diffusion region,
In addition, it is preferable to form it so as to have a window opening of 20 μm or less.

By connecting the photothyristor elements of the present invention in anti-parallel, the zero cross function is not defective.
A bidirectional photothyristor element suitable for a commercial frequency power supply circuit having excellent reliability can be realized.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing a schematic structure of a photothyristor element of the present embodiment, and FIG. 2 is an equivalent circuit diagram of one side portion as the bidirectional photothyristor element. FIG. 3 is a cross-sectional view for explaining the structure around the phototransistor portion that drives the MOSFET.

In the lateral type photothyristor element having the PNPN structure of the present embodiment, the difference from the conventional photothyristor element shown in FIG. 11 is that (1) SiO ₂ film is provided as shown in FIGS. 1 and 3. The oxygen-doped semi-insulating film 13 is formed on the passivation film 12 for high breakdown voltage and high reliability by selectively patterning in the peripheral portion of the Vp circuit 16 to form a gate and a source (GND) of the MOSFET 14. Between, and MOSFET
The point where the gate of 14 and the cathode of the thyristor 30 are not electrically connected by the semi-insulating film 13,
(2) At least on the base / collector junction j2 of the phototransistor and on the junction j1 of the P-type diffusion region adjacent to and surrounding the base-collector junction j2 of the phototransistor in the region (distance Lp) that determines the punchthrough voltage around the Vp circuit 16. A semi-insulating film 1
The point covered with 3.

As a result, the parasitic resistance Rx25 due to the semi-insulating film 13 formed in the conventional photothyristor element shown in FIG. 12 can be eliminated as shown in FIG. In addition, in the present embodiment, since the semi-insulating film 13 covers the region (distance Lp) that determines the punch-through voltage around the Vp circuit 16 except for the divided portion, a sufficient shielding effect can be obtained. You can further,
The passivation film including the semi-insulating film 13 and the SiO ₂ film 12 is a transparent film, and the output of the phototransistor 21 can be increased.

The two photothyristor elements thus configured are connected in antiparallel with each other as CH (channel) 1 and CH2, as shown in FIG. 4, for example, so that the bidirectional photothyristor of this embodiment is connected. The device is obtained. By irradiating light directly on the surface of the bidirectional photothyristor element, the bidirectional photothyristor element operates as a basic light control type bidirectional photothyristor and can be used as a so-called ignition SSR.

The result of the reliability test performed on the bidirectional photothyristor element of the present embodiment is shown by ◯ in FIG.
Here, a chip is simply assembled to TC-5, which is used as a simple evaluation method in a general can package, and an AC voltage of 360 Vrms, Ta = 100 ° C., and an input current IF = 0 (cut-off state) are set to 5000. Tested up to time. The AC voltage of 360 Vrms is a voltage condition in which a voltage margin is added to the AC voltage of 200 Vrms which is the actual use condition, and Ta = 100 ° C. is a temperature condition for performing an acceleration test by temperature. The clamp voltage was obtained by measuring the breakdown voltage between the gate of the MOSFET 14 and the cathode of the thyristor 30 in FIG. Further, for comparison, a result of a reliability test conducted on a bidirectional photothyristor element having a conventional structure is shown by ● in FIG. 5, and as shown in FIG. The result of the reliability test performed on the photothyristor element is shown by x in FIG.
In FIG. 5, the dotted line indicates the dielectric strength (about 250 V) of the gate insulating film of the MOSFET, and if the fluctuation exceeds this value, the reliability becomes poor. As can be seen from FIG. 5, the bidirectional photothyristor element of the present embodiment can have better reliability than the unshielded structure.

Further, in the bidirectional photothyristor element of this embodiment, a semi-insulating film is provided between the gate and the source of the MOSFET 14 and between the gate of the MOSFET 14 and the cathode of the thyristor 30 as in the conventional photothyristor element. Since the parasitic resistance due to 13 does not occur, the MOS is not applied when the AC voltage drops in the AC voltage applied state.
It is possible to suppress the decrease in the gate potential VG of the FET and prevent the zero-cross operation failure as shown in FIG. 6B. Therefore, as shown in FIG. 6A, Vo when the AC voltage rises
By making the x (R) value and the Vox (F) value at the time of AC voltage drop equal, a stable zero-cross operation can be performed.

(Embodiment 2) FIG. 7 is a sectional view for explaining the structure around the phototransistor portion for driving the MOSFET in the photothyristor element of this embodiment.

The photothyristor element of this embodiment is different from the photothyristor element of Embodiment 1 in that the junctions j1 and j2 are covered with two layers of the metal layer 20 and the semi-insulating film 13.

The two photothyristor elements having the above-described structure are similar to those of the first embodiment in that CH (channel) is used.
The bidirectional photothyristor element of the present embodiment can be obtained by connecting 1 and CH2 in antiparallel with each other. By irradiating light directly on the surface of the bidirectional photothyristor element, the bidirectional photothyristor element operates as a basic light control type bidirectional photothyristor and can be used as a so-called ignition SSR.

Also in the bidirectional photothyristor element of the present embodiment, similar to the first embodiment, the parasitic resistance due to the semi-insulating film is present between the gate and the source of the MOSFET 14 and between the gate of the MOSFET 14 and the cathode of the thyristor 30. Since it does not occur, Vox (R) when the AC voltage rises
The value can be made equal to the Vox (F) value at the time of AC voltage drop, and stable zero-cross operation can be performed. Further, as in the first embodiment, since the region around the Vp circuit 16 that determines the punch-through voltage (the portion having the distance Lp) is covered with the semi-insulating film 13, a sufficient shielding effect can be obtained. Further, since the metal layer 20 is opened in this portion, the output of the phototransistor 21 can be sufficiently obtained. In the present embodiment, the joints j1 and j
Although the upper part of 2 is covered with two layers of the metal layer 20 and the semi-insulating film 13, it may be covered only with the metal layer 20 or only with the semi-insulating film 14.

(Third Embodiment) FIG. 8 is a sectional view for explaining the structure around the phototransistor portion for driving the MOSFET in the photothyristor element of the present embodiment.

The photothyristor element of this embodiment is different from the photothyristor element of Embodiment 1 in that the semi-insulating film 13 is not provided on the junctions j1 and j2 and the junction is covered with a metal layer 20 such as an Al wiring. is there.

The two photothyristor elements having the above-described structure are similar to those in the first embodiment in that CH (channel) is used.
The bidirectional photothyristor element of the present embodiment can be obtained by connecting 1 and CH2 in antiparallel with each other. By irradiating light directly on the surface of the bidirectional photothyristor element, the bidirectional photothyristor element operates as a basic light control type bidirectional photothyristor and can be used as a so-called ignition SSR.

Also in the bidirectional photothyristor element of the present embodiment, similar to the first embodiment, the parasitic resistance due to the semi-insulating film is present between the gate and the source of the MOSFET 14 and between the gate of the MOSFET 14 and the cathode of the thyristor 30. Since it does not occur, Vox (R) when the AC voltage rises
The value can be made equal to the Vox (F) value at the time of AC voltage drop, and stable zero-cross operation can be performed. Also, Vp
Since the region around the circuit 16 that determines the punch-through voltage (the portion having the distance Lp) is covered with the metal layer 20, a sufficient shielding effect can be obtained.

In this embodiment, the joint j1,
Since the j2 and the region between them are covered with a metal layer, the phototransistor is completely shielded from light and is not visible in the MOSFE.
The distance Lo of the overlay of the P-type diffusion regions 3 and 7 of the metal layer 20 from the junction j1 is larger than 0 μm so that the driving efficiency of T does not decrease and the junctions j1 and j2 are surely covered, and , Less than 100 μm, and the overlay distance L from the junction j2 of the phototransistor
It is preferable that o ′ is greater than 0 μm and less than 100 μm. More preferably, the distance Lo and the distance L
o ′ is 10 μm or more and less than 50 μm. However, the distance Lo and the distance Lo ′ also change depending on the distance Lp between the junction j1 and the junction j2. Furthermore, in order to obtain sufficient light efficiency, it is preferable to provide a window opening having a width Lw of 10 μm or more and 20 μm or less between the junction j1 and the junction j2 as shown in FIG. The same applies to the metal layer when the junction is covered with two layers of the metal layer 20 and the semi-insulating film 13 as in the second embodiment. In this embodiment, the distance Lp is 50 μm and the distance Lo is 30 μm.
A window opening having a width Lw of 10 μm was provided with μm and a distance Lo ′ of 10 μm.

(Embodiment 4) FIG. 9 is a sectional view showing a schematic structure of the photothyristor element of the present embodiment, and FIG. 10 is an equivalent circuit diagram of one side portion as the bidirectional photothyristor element. FIG. 11 is a cross-sectional view for explaining the structure around the photodiode portion that drives the MOSFET.

The difference between the photothyristor element of the present embodiment and the photothyristor element of the first embodiment is M
Phototransistor 2 that optically drives the gate of OSFET
The point is that a photodiode 22 is provided instead of 1.

The two photothyristor elements having the above-described structure are similar to those of the first embodiment in that CH (channel) is used.
The bidirectional photothyristor element of the present embodiment can be obtained by connecting 1 and CH2 in antiparallel with each other. By irradiating light directly on the surface of the bidirectional photothyristor element, the bidirectional photothyristor element operates as a basic light control type bidirectional photothyristor and can be used as a so-called ignition SSR.

Also in the bidirectional photothyristor element of the present embodiment, similar to the first embodiment, the parasitic resistance due to the semi-insulating film is present between the gate and the source of the MOSFET 14 and between the gate of the MOSFET 13 and the cathode of the thyristor 30. Since it does not occur, Vox (R) when the AC voltage rises
The value can be made equal to the Vox (F) value at the time of AC voltage drop, and stable zero-cross operation can be performed. Further, as in the first embodiment, since the region around the Vp circuit 16 that determines the punch-through voltage (the portion having the distance Lp) is covered with the semi-insulating film 13, a sufficient shielding effect can be obtained. Further, since the metal layer 20 is opened in this portion, the output of the photodiode 22 can be sufficiently obtained. However, in this embodiment, since the photodiode 22 is used to optically drive the gate of the MOSFET, the amount of charge from the photodiode 22 is relatively small compared to the case where the phototransistor is used. When the pulse width is short, the gate 15 of the MOSFET 14 may not be sufficiently charged, the conduction of the MOSFET 2 may be delayed, and the ON resistance may increase.

[0055]

As described in detail above, according to the present invention,
Built-in MOSFET to obtain zero-cross function, M
In a photothyristor element having a photodiode or phototransistor for optically driving the gate of the OSFET and having a high breakdown voltage passivation film in which an oxygen-doped semi-insulating film is provided on the insulating film, a zero-cross operation failure due to the parasitic capacitance of the semi-insulating film Can be prevented and stable operation can be performed with respect to the AC voltage. Further, in order to stabilize the punch through voltage, the junctions j1 and j2 and the region between them are selectively covered with a semi-insulating film or a metal layer to be shielded, thereby realizing a highly reliable photothyristor element. be able to. Therefore, it is possible to realize a highly reliable bidirectional photothyristor element without causing a defect in the zero-cross function, and it is possible to suitably use it in a commercial frequency line or the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a photothyristor element according to a first embodiment.

FIG. 2 is an equivalent circuit diagram of one side of the bidirectional photothyristor element of the first embodiment.

FIG. 3 shows M in the photothyristor element of the first embodiment.
FIG. 6 is a cross-sectional view for explaining a structure around a phototransistor portion that drives an OSFET.

FIG. 4 is an equivalent circuit diagram of the bidirectional photothyristor element according to the first embodiment.

FIG. 5 is a diagram showing reliability test results for the photothyristor elements of the first embodiment, the conventional and comparative examples.

6A is a diagram for explaining a normal zero-cross operation when an AC voltage is applied, and FIG. 6B is a diagram for explaining a malfunction thereof.

FIG. 7 shows M in the photothyristor element of the second embodiment.
FIG. 6 is a cross-sectional view for explaining a structure around a phototransistor portion that drives an OSFET.

FIG. 8 shows M in the photothyristor element of the third embodiment.
FIG. 6 is a cross-sectional view for explaining a structure around a phototransistor portion that drives an OSFET.

FIG. 9 is a cross-sectional view showing a schematic configuration of a photothyristor element according to a fourth embodiment.

FIG. 10 is an equivalent circuit diagram of one side of the bidirectional photothyristor element according to the fourth embodiment.

FIG. 11 is a cross-sectional view for explaining a structure around a photodiode portion that drives a MOSFET in the photothyristor element according to the fourth embodiment.

FIG. 12 is a cross-sectional view showing a schematic configuration of a conventional photothyristor element.

FIG. 13 is an equivalent circuit diagram of one side of a conventional bidirectional photothyristor element.

FIG. 14 is a MOS in a conventional photothyristor element.
FIG. 4 is a cross-sectional view for explaining a structure around a phototransistor portion that drives an FET.

FIG. 15 is an MO in a photothyristor device of a comparative example.
FIG. 6 is a cross-sectional view for explaining a structure around a phototransistor portion that drives an SFET.

[Explanation of symbols]

1 N-type silicon substrate 2 P-type anode diffusion region 3 P-type P gate diffusion region 4 N-type cathode diffusion regions 5 and 6 Phototransistor diffusion region 5a Photodiode diffusion region 7 P-type well diffusion region 8 N-type source diffusion region 9 N-type drain diffusion region 10 N-type channel stopper region 11 Au, etc. electrode layer 12 SiO ₂ film 13 Oxygen-doped semi-insulating film 15 MOSFET gate 18 Gate resistance RGK 19 Depletion layer 20 Metal layer 21 made of Al etc. Phototransistor 22 Photodiode 25 Parasitic resistance due to semi-insulating film 30 Thyristor A Anode terminal PG P Gate terminal K Cathode terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-11-45993 (JP, A) JP-A-10-242449 (JP, A) JP-A-6-169081 (JP, A) JP-A-61- 222172 (JP, A) JP-A-4-249370 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/74

Claims (14)

(57) [Claims] 1. A MOSFE for obtaining a zero-cross function.
In a photothyristor element having a built-in T, a photodiode or a phototransistor for driving the gate of the MOSFET, and a high breakdown voltage passivation film provided with a semi-insulating film on a SiO ₂ film, the gate of the MOSFET is provided. A photothyristor element in which the semi-insulating film is patterned so that a parasitic resistance due to the semi-insulating film does not enter between the source and the source. 2. The photothyristor element according to claim 1, wherein the semi-insulating film is patterned so that parasitic resistance due to the semi-insulating film does not enter between the gate of the MOSFET and the cathode of the thyristor. 3. A semiconductor substrate of a first conductivity type, a first diffusion region and a second diffusion region of a second conductivity type provided on the surface of the semiconductor substrate, and a first diffusion region provided in the second diffusion region. A thyristor is composed of a first conductivity type third diffusion region, a second conductivity type fourth diffusion region provided on the surface of the semiconductor substrate, and a substrate surface side in the fourth diffusion region. And M for obtaining a zero-cross function from the fifth diffusion region and the sixth diffusion region of the first conductivity type which become the drain.
An OSFET is configured, and a seventh diffusion region of a second conductivity type is provided in the semiconductor substrate surface portion between the second diffusion region and the fourth diffusion region,
A photodiode for driving the gate of the MOSFET is formed from the seventh diffusion region and the semiconductor substrate, or on a surface portion of the semiconductor substrate between the second diffusion region and the fourth diffusion region. An eighth diffusion region of the second conductivity type is provided, a ninth diffusion region of the first conductivity type is provided on the substrate surface side in the eighth diffusion region, and the eighth diffusion region and the ninth diffusion region are provided. In a photothyristor element comprising a phototransistor for driving the gate of the MOSFET from the semiconductor substrate, and having a high breakdown voltage passivation film provided with a semi-insulating film on a SiO ₂ film so as to cover the surface of the semiconductor substrate. A part covering the seventh diffusion region and the fourth diffusion region with the semi-insulating film so that parasitic resistance due to the semi-insulating film does not enter between the gate and the source of the MOSFET, Is a photothyristor element divided by a portion covering between the eighth diffusion region and the fourth diffusion region. 4. The semi-insulating film is provided between the seventh diffusion region and the second diffusion region so that parasitic resistance due to the semi-insulating film does not enter between the gate of the MOSFET and the cathode of the thyristor. Is divided by a portion that covers the first diffusion region or a portion that covers between the eighth diffusion region and the second diffusion region.
The photothyristor element according to claim 3 . 5. The metal layer covers the junction of the phototransistor or the photodiode and the junction of a P-type diffusion region adjacent to and surrounding the phototransistor or the photodiode. The photothyristor element according to any one of the above. 6. The semi-insulating film covers the junction of the phototransistor or the photodiode and the junction of a P-type diffusion region adjacent to and surrounding the phototransistor or the photodiode. 5. The photothyristor element according to any one of 1. 7. The junction between the phototransistor or the photodiode and the junction between adjacent P-type diffusion regions surrounding the phototransistor or the photodiode are covered with two layers of a semi-insulating film and a metal layer. The photothyristor element according to any one of claims 1 to 4. 8. The metal layer has an overlay distance Lo from the junction of the P-type diffusion region greater than 0 μm, and a distance between the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region. The photothyristor element according to claim 5, which is smaller than Lp. 9. The photothyristor element according to claim 8, wherein the metal layer has an overlay distance Lo from the junction of the P-type diffusion regions of 10 μm or more. 10. The metal layer has an overlay distance Lo ′ from the junction of the phototransistor or the photodiode of more than 0 μm, and the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region. 6. The distance Lp is smaller than the distance Lp.
Alternatively, the photothyristor element according to claim 7. 11. The photothyristor element according to claim 10, wherein the metal layer has an overlay distance Lo ′ of 10 μm or more from a junction of the phototransistor or the photodiode. 12. The metal layer has a sum Lo + Lo ′ of a distance Lo of an overlay from a junction of the P-type diffusion region and a distance Lo ′ of an overlay from a junction of the phototransistor or the photodiode. The photothyristor element according to any one of claims 8 to 11, which is smaller than a distance Lp between a junction of a transistor or the photodiode and a junction of the P-type diffusion region. 13. The metal layer has a width Lw of 10 μm or more between the junction of the phototransistor or the photodiode and the junction of the P-type diffusion region, and 2
13. A window opening part having a size of 0 .mu.m or less.
5. The photothyristor element according to any one of 1. 14. A bidirectional photothyristor device in which the photothyristor device according to claim 1 is connected in antiparallel.