JPS6040192B2 - Thyristor for controlling voltage breakdown current and method for limiting voltage breakdown current - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to voltage sinks, and more particularly to localized regions where voltage breakdown begins when the forward anode-cathode voltage exceeds the breakover voltage in the normal direction. The present invention relates to a type of thyristor contained within a semiconductor body.

Switching the thyristor to a conducting state by exceeding its forward breakdown voltage is likely to damage the device.

One cause of damage is the small dimensions of the voltage breakdown region that is initially turned on. If the current rises rapidly to a large value before a sufficient part of the main current carrying part of the device is turned on, significant power consumption occurs. Localized overheating in the initial breakdown region results in device failure. Techniques have been developed to localize the initial breakdown region within the silicate tube.

One method is to create localized regions of low resistivity in the N-substrate. A region of low resistivity can be created by passing a neutron beam through a semiconductor material. By the known method of neutron modification, the silicon is partially converted to phosphorous, which increases the N-type doping level in the irradiated area. As a result, the resistivity decreases locally, which creates a localized initial breakdown region at the adjacent pn junction. This breakdown region can be located at any convenient location within the thyristor body. For example, it has been found that placing a voltage breakdown region under a centrally located gate electrode makes the thyristor turn on very quickly.
However, locating the voltage breakdown region locally in the thyristor does not solve the problem of high power consumption during the initial breakdown. The large current that occurs during breakdown must first pass through a very small junction area. Unless the initial current is controlled by external circuit conditions, overheating and destruction of the breakdown junction will cause the device to fail prematurely. A general object of the present invention is to provide a thyristor device with means for controlling the current flowing through the device when the forward breakdown voltage is exceeded.

Another object of the invention is to provide a method of making a thyristor device with a current controlled impedance that controls power consumption during voltage breakdown. Thus, a thyristor device is provided which controls the current flowing between a pair of terminals and switches from a blocking mode to a forward conductive state when the terminal voltage between the terminals exceeds a breakdown voltage. The thyristor device includes a semiconductor body having at least four regions of alternating conductivity type, which regions extend between terminals. One region is an emitter region in contact with one terminal.

Its adjacent region is the base region. A blocking pn junction forms a boundary between the base region and an adjacent third region. The semiconductor body is provided with means for localizing the breakdown portion of the blocking pn junction, which breakdown portion is where directional breakdown begins when the terminal fin pressure exceeds the breakdown voltage. The base region includes a first base portion disposed adjacent the breakdown portion of the blocking pn junction and a second base portion at least partially spaced apart from the first base portion. The emitter region contacts this second base portion. The thyristor device further includes current limiting means interconnecting the first base portion and the second base portion. A method of making a silister from a deposited semiconductor body comprises the steps of etching the semiconductor body so as to divide the base region into two base parts and at least partially separate them. This method also prevents p when the breakdown voltage is exceeded.
The method also includes creating a voltage limiting means interconnecting the first base portion and the second base portion to control current across the breakdown portion of the n-junction. ．． The present invention will be described in detail below with reference to the accompanying drawings. The syringe device according to the invention is formed starting from a basic semiconductor body 20 .

The semiconductor body 20 has opposed upper and lower surfaces 22 and 24, respectively. Typically, the semiconductor body 20 is formed of single crystal silicon, which is processed to create a PNP structure with an intermediate pn junction substantially parallel to the planes 22 and 24. A suitable method for forming this body 20 is N
Starting with a type silicon chip, the silicon chip is substantially diffused with impurities through its top and bottom surfaces. One or more conductive regions are created by epitaxial growth, ion implantation, or other suitable method. The resulting three layers include a lower layer 26 of P conductivity type, an intermediate layer 28 of N conductivity type, and an upper layer 30 of P conductivity type. The body 20 preferably includes a localized region of low resistivity in the N-type intermediate layer 28 to create a region of low breakdown voltage centrally located in the body 20. Forming such localized regions in body 20 can be accomplished by any suitable manufacturing technique that is well known. For example, arrow 3
A neutron beam can be passed through the body 20 in one direction. This neutron beam causes localized regions 32 of the body to be partially converted to phosphorous by a neutron-induced transformation process. The phosphorus increases the level of N-type dopant in region 28, creating a small region of low resistivity. Area 32 is the main body 20
Create a localized voltage breakdown region located in the center of. Main body 2
A method of forming a first embodiment of a thyristor according to the invention from scratch is illustrated in FIGS. 2-5.

As shown in FIG. 2, an additional region 35 is first added to the main body 2 to create a typical thyristor structure having at least four regions 26, 28, 30 and 35 of alternating conductivity types. be done. This upper region 35 is formed by any suitable method such as diffusion, epitaxial growth, or ion implantation. The resulting thyristor body has an NPNP structure, with layer 35 forming the emitter region and layer 30 adjacent thereto forming the base region. The third region of the body is the intermediate region 28. A pn junction 36 forms a boundary between base 30 and third region 28 . In FIG. 2, regions 35 and 28 are each N+
and N-, indicating that the level of N-type impurity doping in region 35 is relatively high. Following formation of this four-region structure, the top surface of body 20 is covered with a mask layer 38.

Any suitable photoresist mask can be used. Mask 38 initially covers the entire top surface 22 . Next, a portion of the mask is removed using a general photolithography technique to create a mask pattern as shown in FIG. This pattern has a large central checkpoint 40. A further small opening 42 is made outside this gate 40 to provide emitter shorting. Following the formation of the mask pattern of FIG. 2, the top surface 22 of the main body 20 is etched using conventional etching techniques.

An etching solution is used that will attack the silicon of the semiconductor body but not the mask layer 38. The etch is made within the gates 40 and 42 to a depth sufficient to penetrate the emitter region 35 and expose a portion of the base region 30. The resulting configuration after removing mask 38 is shown in FIG.

Emitter region 35 has been removed from within mask closure 40 . The portion of emitter 35 that remains forms the first or main emitter of the thyristor. Base region 30 extends within mask opening 40 to top surface 22 . emitter-based pn
The inner edge of the junction forms the thyristor turn-line 46. Emitter closure 47 corresponds to mask 38 closure 42 . Another etching step is then performed on the body.

This etching step results in a deep etch 48 in the base region 3, which extends from the top surface 22 as shown in FIG. Etched portion 48 is substantially annular and surrounds a central portion of the base region overlying voltage breakdown region 32 . To create etched portion 48, a suitable etchant-impermeable masking layer, such as silicon dioxide, is first grown or otherwise formed on top surface 22. Next, an annular gate corresponding to the etched portion 48 is formed in this mask layer by common photolithography and etching techniques. The exposed annular portion of surface 22 is then subjected to an etching solution that is of a type that etches the semiconductor body but does not attack the silicon dioxide mask. In this first embodiment, the etching is allowed to proceed to a predetermined depth in the base region 30. The resulting etched area 4
8 forms a closed ring cut deeply into the base region 30, which divides the base into a first base portion 50 and a second base portion 52, and the first base portion 5 forms a closed ring cut deeply into the base region 30, dividing the first base portion 5 into the region 32 in the center of the body. Overlying and surrounded by a second base portion 52 extending outwardly from etched portion 48 . These two base parts are only partially separated and are interconnected by a wide and relatively thin connection 53 that has not been removed in the base area. This connection 53 provides the current control mechanism for this first embodiment of the invention.

This connection 53 has a significantly higher resistivity than its adjacent base portion which has not been etched. The specific resistance value R of the base region between the inner first base portion 50 and the second inner base portion 52 is given by the following equation. R = Go 1
nWarning However, po is the sheet resistance value of the thin connection part 53,
mut and rin are the outer and inner radii of the deep etch, respectively (FIG. 7).

The value of R is controlled by the depth of the etched portion and the values of rout and rin. There is a wide margin for the value of R,
Thyristors can be tailored to specific circuit requirements. A typical value of the resistance value R of the connection portion 53 is, for example, 500.
It is 0. After removing the mask layer used to form etched portion 48, a layer of a suitable conductive metal, such as aluminum, is applied to top surface 22 by one step.

Then, to create a metallization pattern as shown in Figure 5,
A portion of this metal layer is removed by conventional photolithography and etching techniques. The metal that contacts the first emitter 35 outside the turn online 46 is the emitter electrode 55.
form. This electrode 55 extends into the opening 47 to touch the base 30 and provide an emitter connection line. Another metal electrode 58 remains within the turnline 46 and surrounds the first base portion 50. An electrode 58 extends around the etched portion 48 in contact with the second base portion 52 and forms the gate electrode of the thyristor. It is also desired to leave a metallized region 59 on the top surface of first base portion 50.
This electrode 59, herein referred to as the first base electrode, serves to more evenly distribute the current flowing through the first base portion 501 during voltage breakdown. The completed thyristor also includes a metallized electrode 62 on the bottom surface 24, which contacts the bottom layer 26 to form the anode electrode of the thyristor. This anode electrode 62 may be attached at the same time as the metallization of the upper surface, or may be attached at a different time. A pair of terminals provides external connections to the anode and cathode metallization.

Terminal 64 is connected to anode 62, and terminal 66 contacts first emitter 35 by means of emitter electrode 55.
Four regions of the device extend between these terminals 64 and 66. The resulting thyristor has terminals 64 and 66.
It acts as a switch device to control the current flowing between the

When anode terminal 64 is in a forward biased crest blocking mode with respect to cathode terminal 66, junction 36
Only a small leakage current flows through the device due to nearby carrier depletion. Junction 36 therefore acts as a forward blocking pn junction. Applying a small positive voltage to gate electrode 58 causes a large number of electrons to flow across the emitter-base junction starting at turn-on-line 46. The thyristor is then turned on by injecting electrons into the base 30, allowing a large forward current to flow. This on-switching is substantially uniform along turn-line 46. This is because the surrounding emitters 35 are spaced an equal minimum distance from the gate at any point. Such gate-triggered switching allows very large currents to be controlled between terminals 64 and 66 with relatively small gate currents. As is well known, by momentarily reversing the bias on terminals 64 and 66, the ``top blocking condition'' is restored. It is also possible to switch from the blocking mode to the forward conduction mode by increasing the voltage above the breakdown voltage.

This forward yield-on keratin process will be briefly explained. As the forward bias of the anode increases, the leakage current flowing through the device begins to increase. When the terminal voltage across the device reaches the forward breakdown voltage, leakage current causes avalanche breakdown in the blocking pn junction. This electron avalanche breakdown generates a large number of carriers in the base region. Electrons are drawn towards the anode and holes pass through the base towards emitter connection 47. The current in the hole in the base switches on the resistor at the emitter-base junction. Switching on by voltage breakdown does not require an external gate circuit. After momentarily reversing the terminal voltage, the blocking mode returns. The low resistivity region 32 of the N-substrate 28 provides a support 36 where forward voltage breakdown begins.
This serves as a means for localizing the yielding portion 70 of.

Yielding occurs first in this portion 70. This is because the strong doping of region 32 of adjacent region 28 reduces in the depletion layer and lowers the breakdown voltage. The high breakdown voltage along the rest of junction 36 prevents breakdown from occurring outside of this breakdown region 70 initially. In this first embodiment of the thyristor, when switched on by forward voltage breakdown, the current between terminals 64 and 66 first flows through connection base portion 53.

This is because most of the junction 36 is in the blocking state and only portion 70 is in the conducting state. Arrow 72 in FIG. 7 indicates the initial forward voltage breakdown current flowing through the thyristor. The tangential portion 53 of the base 30 has a significantly higher sheet resistance value than the rest of the base region due to the etched portion 48. The initial current between terminals 64 and 66 is therefore limited by the high resistivity of etched portion 53. This portion 53 provides a series resistance between the anode and cathode during breakdown, which prevents localized burning along junction 36. When current flows through this breakdown region 70 to the first base portion 50,
Metallized areas 59 help distribute the charge more evenly. The current flowing in the base region after voltage breakdown quickly switches the main current-carrying part of the thyristor into the forward-conducting state. Therefore, current flows substantially freely between terminals 64 and 66. Once the thyristor is turned on, it is bypassed by a resistance path through the yield section and other parts of the device. The present invention provides current control of the voltage breakdown region of the thyristor.

Power consumption in the voltage breakdown region is significantly reduced. The built-in impedance provided by etched portion 48 significantly limits the forward voltage breakdown current flowing through the thyristor device. By controlling the depth and depth of the etch 48, precise control of the magnitude of the impedance and thus the current limiting capability is achieved. The performance of the gate trigger portion outside the etched portion 48 of the thyristor is as follows:
It is not affected by the partial separation of the 4 parts of the base area. The dimensions and depth of the etch 48 can be varied to accommodate design requirements.

For example, if a relatively large breakdown current is expected, there is a potential problem of ohmic heating of the base connection 53. In order to compensate for the extra temperature, the volume of the connecting portion 53 must be increased by making the etched portion 48 shallower and wider. Alternatively, portion 53 can be expanded by increasing the overall length of the etch and increasing the diameter of central base portion 50. The shape and dimensions of etched portion 48 as shown in the accompanying drawings are for illustrative purposes only, and other shapes and dimensions may be used. Another embodiment of the invention using an external current limiting circuit impedance element is shown in FIG.

The method of forming this embodiment begins with the same manufacturing steps as illustrated in FIGS. 1-3 for the first embodiment.
A semiconductor body 20 is provided having at least four regions of alternating conductivity type. This semiconductor body has a centrally located region 32 of low resistivity in the N-substrate. Therefore, the pn junction 36 adjacent thereto is provided with the localized breakdown portion 70 of the first embodiment. The emitter pattern on the top surface is the same as in the first embodiment. In this embodiment, the second etching step creating etch 48 is performed for a slightly longer period of time, etching the semiconductor body even deeper. The resulting etch 78 extends through the base region 30 into the third region 28, dividing the base region into a first base portion 80 and a second base portion 82, respectively, and completely separating them. This alternative embodiment of the electrode includes a first base electrode 59 in contact with a central first base portion 801.

This first base electrode 59 is essentially the same as in the first embodiment. As in the first embodiment,
A base electrode 58 and an emitter electrode 55 are also provided. The formation of the electrodes in this example begins with the upper surface 2 of the semiconductor body.
This is accomplished by metallizing the entirety of 2 and removing selected portions of this metallization layer by common photolithography and etching techniques, leaving electrodes 55, 58 and 59. Manufacturing the thyristor device of this alternative embodiment includes the additional step of connecting an impedance element between gate electrode 58 and base electrode 59.

In the embodiment of FIG. 8, such an impedance is 1
Preferably, one or more resistors 86 are included. These resistors 86 correspond to the connections 5 of the first embodiment.
3 serves to interconnect separated base portions 80 and 82. The embodiment of FIG. 8 operates essentially the same as the first embodiment described above. If the terminal voltage between terminals 64 and 66 exceeds the forward breakdown voltage, forward breakdown begins at breakdown section 70. The first current path between the cathode and anode is through resistor 86. These resistors 86 reduce the initial breakdown current to a level that prevents unnecessary power dissipation in junction 36. The rest of the device is then switched on by the breakdown current flowing in the base region. As with the first embodiment, once the thyristor is fully turned on, the additional impedance of resistor 86 is effectively removed from the circuit. base part 80
The large faces of the more outer junctions 36 essentially provide an open circuit for current flowing between the terminals. The performance of the thyristor under normal gate-triggered switching is not affected by resistor 86. This external circuit element implementation of the invention can provide greater resistance than the partial etching of the first embodiment. Also, the difficulty of accurately controlling the depth of the etch is eliminated. A further embodiment with external impedance elements is shown in FIG.

This embodiment has exactly the same semiconductor body as the embodiment of FIG. 8, and its manufacturing method is also exactly the same. Etched portion 78 extends base region 30 to third region 28 and connects the base region to first base portion 80 and second base portion 8.
2 and completely separate these parts. A first base electrode 59 is provided on the base portion 80'. In the embodiment of FIG. 9, the gate electrode 58 and the base region 5
A conductive element 90 is connected between 9 and 9. The base portions of the two inductive elements are interconnected to provide another type of current limiting means in the breakdown region. The operation of the embodiment of FIG. 9 is exactly the same as that of the embodiment of FIG.

Forward breakdown begins at breakdown portion 70 of junction 36 when the terminal voltage between terminals 64 and 66 exceeds the forward breakdown voltage of the thyristor. The forward voltage breakdown current between the terminals flows through the inductive element 90. The conductive element 9 acts as a current limiting means during initial turn-on when the current gradient is large. Thus, extra power consumption in breakdown region 70 is avoided. As in the previous embodiment, the current flowing into the base region then switches on the rest of the device, effectively removing inductive element 90 from the circuit. Normal gate-triggered on-switching is not affected. The embodiment of FIG. 9 provides a type of current limiting impedance that cannot be easily achieved without the use of external circuit elements.

Other external impedance elements may also be used alone or in combination. Thus, the thyristor can be tailored to specific circuit conditions. A further embodiment of a thyristor according to the invention is shown in FIG.

In this embodiment, the built-in impedance feature of the present invention is applied to a multi-gate thyristor. In the method of forming the thyristor shown in FIG.
8, yet another annular portion within circle 40 is left unremoved. In a subsequent etching step, the emitter region is divided on the top surface 22 into a first emitter 35 and another enhancement stage emitter 94. As in the first embodiment, a deep etching process creates etches 48 which divide the base region 30 into a first base part 50 and a second base part 52, respectively, and partially separate these parts. Separate into Both emitters 35 and 94 remain in contact with the second base portion 52). In the metallization process, cathode electrode 55, base electrode 58 and first base electrode 59 are formed as described above. An intensifying gate electrode 96 is also formed on the top surface 22, which contacts the intensifying stage emitter 94 and the second portion 52 of the base 30. As in the first embodiment, the anode and cathode electrodes 62 and 55
is provided. To turn on the thyristor of FIG. 10 by a gate trigger, the positive gate current is applied to electrode 58.
supplied to

With the anode forward biased relative to the cathode, electrons flow out of the booster emitter 94 and across the base, turning the booster on. As a result, the electrode 96 of the booster stage becomes positive, switching on the main thyristor at the junction between the first emitter 92 and the base. If the terminal voltage between the anode and cathode exceeds the breakdown voltage of the thyristor, avalanche breakdown begins at breakdown portion 701 of junction 36. Since this yielding portion 7 is adjacent to the first base portion 50' and is partially separated from the rest of the base, the connecting base portion 53
A resistive current path is provided through . Connection base part 5
The high resistivity of 3 acts as a means to limit the initial breakdown current. As in the previous embodiment, the remainder of the thyristor is then switched on by the current flowing in the base, effectively removing impedance 53 from the circuit.
The example of FIG. 10 shows that the present invention can be easily applied to multi-gate thyristor configurations. This built-in impedance does not degrade the functionality of the gate trigger portion of the thyristor. It will be readily apparent that the external circuit element embodiment of the invention shown in FIGS. 8 and 9 can also be provided with the multiplication stage of FIG. A further embodiment of the invention is shown in FIG.

In this embodiment, a semiconductor body is used having at least four regions of alternating conductivity type as shown in FIGS. 2-4. As in the first mentioned embodiment, this semiconductor body is provided with a centrally located initial breakdown region 32, which forms a localized breakdown section 70 of the pn junction 36. In a first masking and etching step equivalent to FIGS. 2 and 3 of the first described embodiment, the N0 emitter region is etched to create the first emitter 100.

Within the circular turn-line 102, the exposed portion of the base region 30 extends to the top surface 22. ．． A second etching step, equivalent to FIG. 4 of the first embodiment, provides an annular etching 106, which extends from the top surface into the base region 30. This etching 106 divides the base into a first base part 108 and a second base part 110, which parts are partially separated, and the first base part 108 is located in the center of the body and the second base part 1
10 extends radially outward from the etched portion 106 .
These two base parts are joined by a connecting part 112, which provides a region of high resistivity at the base. As in the first described embodiment, the first base portion is located adjacent the yielding portion of the joint 36, and the first emitter 100 is in contact with the second base portion 11. Emitter electrode 114 and gate electrode 11
The metallization forming 6 is carried out in a conventional manner.

In the embodiment of FIG. 11, a gate electrode 116 is disposed on top surface 22 in contact with first base portion 108. In the embodiment of FIG. As previously discussed, an anode contact 62 is provided on the lower surface 24. Anode terminal 64 and cathode terminal 118 each allow external circuit connections to be made. In operation, the embodiment of FIG. 11 can be turned on when the cathode terminal 64 is biased forward with respect to the cathode terminal 118.
Gate triggered operation is also achieved by supplying a positive gate current to the gate electrode 116. This gate current is switched on along the emitter-base junction starting at turn-on-line 102. terminals 64 and 118
On-switching occurs due to voltage breakdown when the terminal voltage between the two terminals exceeds the forward breakdown voltage. This forward breakdown begins at yield portion 70 of junction 36. As in the previous embodiment, the initial current path between the anode and cathode terminals during breakdown is through the current limiting resistor 112 that is integrated with the base region 301. The resistive impedance provided by this connection 112 serves to reduce the initial breakdown current, thereby preventing extra power dissipation in the localized breakdown region.

As is well known to those skilled in the art, impedance 112 is
It can also be implemented as an external circuit in the form of external resistive elements, external inductive elements or other external impedance elements. In this case, the etching 106 is deep enough to completely divide the base into separate parts 108 and 11, and only another metallized electrode is provided outside this etching. As in the embodiment of FIGS. 8 and 9, external circuitry is then placed between these two base portions. The embodiment of FIG. 11 provides additional impedance to the gate circuit as well as during voltage breakdown.

Thus, this embodiment is only desirable if relatively large trigger gate voltages are available. Yet another embodiment of a sirensor according to the invention is shown in FIG.

This embodiment has essentially the same thyristor structure and manufacturing method as the first embodiment shown in FIGS. 1-7. The only difference is that it includes an additional N+ region extending to the top surface 22 in contact with the centrally located first base portion 501. This N+
The region forms the second emitter 125 extending to the top surface 22 and is easily produced during the manufacturing process described for the first embodiment above. To form the embodiment device of FIG. 12, the mask layer 38 shown in FIG. 2 is modified to include an additional circular mask portion centered over the voltage breakdown region 32. Ru. When the emitter region is etched in the next etching step, the second emitter 125 is formed separately from the first emitter 35. After the deep etching 48 is formed, the second emitter 125 remains in contact with the first base portion 50).
be made into The device of the embodiment of FIG. 12 is then formed using the metallization process of the first embodiment. The first base electrode 126 located in the center is the electrode 5 of the first embodiment.
9, but in contact with the first base portion 50 and the second emitter 125. Electrode 126 performs a current distribution function similar to electrode 59 in the first embodiment. A four-layer thyristor structure is provided in the voltage breakdown region outside the thyristor of the embodiment shown in FIG.

The importance of the second emitter 125 during the initial voltage breakdown is the 12th
As shown in the figure. As in the first embodiment,
The thyristor can be switched from a blocking mode to a forward conducting state by raising the terminal voltage between terminals 64 and 66 above the forward breakdown voltage. When the terminal voltage exceeds the forward breakdown voltage, current begins to flow across the localized breakdown portion 70 of the blocking pn junction 36. The path of positive Hall current is generally indicated by arrow 127. The pn junction 128 extending between the second emitter 125 and the first base portion 50 becomes forward biased when the initial voltage breakdown current increases significantly. This induces electrons to cross junction 128 as indicated by arrow 130. the result,
Localized thyristor action occurs, creating an instantaneous low resistance current path through the breakdown region. By injecting carriers from the second emitter 125, the voltage drop across the breakdown junction 70 is significantly reduced, reducing the risk of local combustion. The conductivity improvement that occurs during breakdown due to the presence of the second emitter 125 is only momentary.

Immediately after breakdown begins, the breakdown current is limited by the current limiting means described above. In the embodiment of FIG. 12, this current limiting means is a high resistance in the connection portion 53 of the base region. As in the first embodiment described above, the main current distal part of the device is eventually switched on by the positive Hall current flowing in the base region 30. 2nd emitter 125
The instantaneous reduction in box pressure drop caused by this is intended to further reduce the risk of local combustion of the joint. However, the risk of local combustion of this joint is already considerably reduced by the presence of the current limiting means of the invention. A further embodiment of the invention is shown in FIG.

This embodiment is essentially the same as the embodiment shown in FIG. 8, except that the second emitter 125 and the first emitter of the embodiment of FIG.
A base electrode 126 is also provided. The manufacture of the apparatus of the embodiment of FIG.
It will be readily apparent that the fabrication of the device is essentially the same as that of the embodiment of FIG. The operation of the apparatus of the FIG. 13 embodiment is essentially the same as the FIG. 8 embodiment.

The only difference in operation occurs during the initial voltage breakdown when the instantaneous thyristor action described for the embodiment of FIG. 12 takes place. As a result, the voltage drop along the breakdown zone 7 is instantaneously reduced, which serves to further reduce the risk of local combustion of the joint. Although the embodiment of FIG. 13 is shown with an external impedance element 86 which is a resistor as in FIG. 8, an inductive impedance element as shown in FIG. 9 may also be provided. can. A further embodiment of the invention is shown in FIG.

This embodiment is essentially the same as the embodiment shown in FIG. 10, but also includes the second emitter 125 and first base electrode 126 of the embodiment of FIG. The fabrication of the device of the embodiment of FIG. 14 is essentially the same as that of the device of the embodiment of FIG. 10, except that an additional N emitter is left in contact with the first base portion 50. It is. The operation of the apparatus of the embodiment of FIG. 14 is essentially the same as the embodiment of FIG.

The only difference in operation occurs during the initial voltage breakdown when the instantaneous silencing action described for the embodiment of FIG. 12 takes place. As a result, the voltage drop along the breakdown portion 70 is momentarily reduced, which serves to further reduce the risk of local combustion of the joint. A further embodiment of the invention is shown in FIG.

This embodiment is essentially the same as the embodiment shown in FIG. 11, but also includes the second emitter 125 of the embodiment of FIG. Electrode 132 serves as a gate electrode located on top surface 22 , which is in contact with first base portion 108 and second emitter 125 . This gate electrode 132
It works just like the gate electrode 116 of the illustrated embodiment. 1st
The fabrication of the device of the embodiment of FIG.
The fabrication of the device of the embodiment of FIG. 11 is essentially the same.
The operation of the apparatus of the embodiment of FIG. 15 is essentially the same as the embodiment of FIG.

The only difference in operation occurs when, during the initial voltage breakdown, the instantaneous thyristor action described for the embodiment of FIG. 12 takes place. As a result, there is an instantaneous reduction in the voltage drop along the breakdown section 70, which serves to further reduce the risk of local combustion of the joint. The present invention provides a thyristor device that effectively controls the effective power consumption in the voltage breakdown region. A number of simple steps carried out on the semiconductor body of the thyristor device effectively limit the forward voltage breakdown current flowing through the thyristor device. Splitting the base region of the semiconductor body serves to separate the portion of the base adjacent to the breakdown region from the other portion of the base that is in the main current carrying portion of the device. Current limiting means are then provided between these separated base portions. Since the initial forward voltage breakdown current is constrained to pass through the breakdown region into the base region and must flow far into the main portion of the device, the breakdown current will flow through this current limiting means. In each of the embodiments described above, whether using an etch that extends partially into the base region or completely through the base region, the current limiting impedance is During initial breakdown it becomes in series with the a/d and cathode. After switching on, the current limiting means is bypassed during all operations other than initial voltage breakdown, as current is no longer constrained to pass through the voltage breakdown region. Therefore, an effective reduction in voltage breakdown current is provided without undesirably degrading other thyristor performance parameters. Embodiments are provided that control either the level of initial breakdown current or the current distribution. Effective protection is therefore provided against failure of the sirensor during switching on of the sirens due to voltage breakdown. Further embodiments are possible within the scope of the invention.

For example, various external impedance elements can be installed. A combination of resistive and inductive impedances can also be used. Both an internal connection base part and an external impedance can be used in one thyristor. The external impedance need not necessarily be wire mounted, but could also be in the form of a ring bridging the depth etch. Other means may be provided to divide the base portion to isolate portions adjacent the voltage breakdown region. One such alternative technique is disclosed in US Pat. No. 4,047,21y, which involves forming deep regions of opposite conduction type in the base region that effectively control lateral current.

Further, the present invention can also be applied to those in which the emitter shape is not radial. In this case, it is only necessary to split the base so as to separate the initial voltage breakdown region from the rest of the thyristor in order to be able to install an intervening impedance. The base region can be made in separate parts from the beginning, eliminating the need for deep etching. Any of the embodiments described above may be provided with additional multiplication stages. Thus, a thyristor is provided with means for controlling the current flowing through the device when the forward breakdown voltage is exceeded.

Additionally, the present invention provides a method of forming a silencing device with a current controlled impedance that controls power consumption during voltage breakdown. The thyristor according to the invention can be applied even with considerably high power. 9 when voltage breakdown occurs in the forward direction
A resistance greater than KQ must be provided, but it is practically impossible to create a resistance of this magnitude using semiconductor manufacturing technology, such as etching 35 microns from a 40 micron P-base. Further, although it is not possible to obtain the high control resistance required by the present invention through the manufacturing process, the present invention allows the current limiting effect to be skillfully achieved.

[Brief explanation of the drawing]

1 to 5 are partial cross-sectional perspective views showing a method of forming a thyristor according to the present invention, FIG. 6 is a partial top view of the thyristor of FIG. 5, and FIG. 7 is a 7-7 of the thyristor of FIG. 6.
8 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the invention; FIG. 9 is a sectional view along the line, FIG. 10 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the invention, and FIG. 11 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the invention. 7 is a sectional view similar to FIG. 7, FIG. 12 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the present invention, and FIG. 13 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the present invention. 7 is a sectional view similar to FIG. 7, FIG. 14 is a sectional view similar to FIG. 7 showing another embodiment of the thyristor according to the invention, and FIG. 15 is a sectional view similar to FIG. 15 showing another embodiment of the thyristor according to the invention. FIG. 7 is a cross-sectional view similar to FIG. 7; 20...Semiconductor body, 22...Top surface, 24
... lower surface, 26 ... lower layer of P conductivity type,
28... N conductivity type intermediate layer, 30...
Upper layer of P conductivity type, 32... Localized region, 35...
...additional layer (emitter region), 36...
pn junction, 38... mask, 40, 42... Sekiguchi, 46... turn online, 48...
・Etched part, 50...First base part, 5
2...Second base portion, 53...Base region connection portion, 55...Emitter electrode, 58...
...Gate electrode, 59...First base electrode, 62...Anode, 64, 66...
・Terminal, 86...Resistor. Catty 76/'nG2 (763 'nG evening'nG5 'nG 60,767''G6 (nG 9 (n○^○ 'n6// catty JG ^2 stroke 7G'3 catty 70/4 〆′○′5

Claims (1)

[Claims] 1. The current between a pair of terminals is controlled, and when the terminal voltage between these terminals exceeds the breakdown voltage, the blocking mode is switched to the forward conduction state based on the gate electrode and the gate current. The thyristor device comprises a semiconductor body having at least four regions of alternating conductivity type extending between said terminals, said semiconductor body having a first region in contact with one of said terminals.
an emitter region having an emitter region, a base region adjacent to the emitter region, and a barrier p forming a boundary between the base region and a third region adjacent to the base region.
an n-junction and means in the semiconductor body for localizing a breakdown portion of the blocking pn junction, the breakdown portion being a portion that begins to breakdown in a forward direction when the terminal voltage exceeds the breakdown voltage. the base region includes a first base portion disposed adjacent to the breakdown portion of the blocking pn junction and a second base portion in contact with the first emitter; forming an on-switching channel for a gate current flowing through the second base portion between the gate electrode and the emitter region;
and an external device that limits current in the base region between the first and second base portions and provides an impedance between the first and second base portions that is greater than the resistance of the channel region. A thyristor device characterized in that a current limiting means is connected. 2. A method for limiting the forward voltage breakdown current flowing in a thyristor device, the thyristor device being of the type comprising a semiconductor body having at least four regions of alternating conductivity type extending between a pair of terminals. an emitter region having a first emitter in contact with one of the terminals; a base region adjacent to the emitter region;
a blocking pn junction forming a boundary between said base region and a third region adjacent said base region;
means in said semiconductor body for localizing a breakdown portion of the junction, said breakdown portion being a portion that begins to descend in a forward direction when the voltage across said terminals of said thyristor device exceeds a breakdown voltage; In a method, the base region includes a first base portion adjacent the breakdown portion of the blocking pn junction and a second base portion at least partially separated therefrom.
The second base part is divided into the first base part and the second base part.
A method characterized in that a current limiting means is created adjacent to the emitter and connecting the first base part and the second base part, thereby limiting the forward voltage breakdown current flowing through the thyristor device.