CA1104726A - Thyristor fired by collapsing voltage - Google Patents
Thyristor fired by collapsing voltageInfo
- Publication number
- CA1104726A CA1104726A CA287,988A CA287988A CA1104726A CA 1104726 A CA1104726 A CA 1104726A CA 287988 A CA287988 A CA 287988A CA 1104726 A CA1104726 A CA 1104726A
- Authority
- CA
- Canada
- Prior art keywords
- region
- thyristor
- base region
- emitter region
- auxiliary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 239000004065 semiconductor Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 5
- 230000000903 blocking effect Effects 0.000 abstract description 5
- 238000010304 firing Methods 0.000 description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 241001663154 Electron Species 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- QHGVXILFMXYDRS-UHFFFAOYSA-N pyraclofos Chemical compound C1=C(OP(=O)(OCC)SCCC)C=NN1C1=CC=C(Cl)C=C1 QHGVXILFMXYDRS-UHFFFAOYSA-N 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/70—Bipolar devices
- H01L29/74—Thyristor-type devices, e.g. having four-zone regenerative action
- H01L29/7424—Thyristor-type devices, e.g. having four-zone regenerative action having a built-in localised breakdown/breakover region, e.g. self-protected against destructive spontaneous, e.g. voltage breakover, firing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/87—Thyristor diodes, e.g. Shockley diodes, break-over diodes
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Ceramic Engineering (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Thyristors (AREA)
- Power Conversion In General (AREA)
- Rectifiers (AREA)
Abstract
46,093 THYRISTOR FIRED BY COLLAPSING VOLTAGE
ABSTRACT OF THE DISCLOSURE
This invention is concerned with a thyristor device which can be fired by a collapsing voltage. The thyristor is switched from a forward blocking mode to a forward conducting mode when a displacement current produced by a collapsing voltage is concentrated under an auxiliary emitter, thereby causing sufficient carrier emission to fire the device.
ABSTRACT OF THE DISCLOSURE
This invention is concerned with a thyristor device which can be fired by a collapsing voltage. The thyristor is switched from a forward blocking mode to a forward conducting mode when a displacement current produced by a collapsing voltage is concentrated under an auxiliary emitter, thereby causing sufficient carrier emission to fire the device.
Description
BACK~ROUND OF THE IN~ENTION
10 Field of the _ ention: -The present invention pertains to semiconductor switching devices, and'more particularly to two terminal silicon thyristors.
De ~ he Prior Art:
In addition to the well known gating of thyristors by means of a third terminal, it is known in the art that thyristors may be switched from the forward blocking mode to the forward conducting mode by rapidly increasing the vol-tage across the thyristor. Thyristors which are designed to be fired by such positive dv/dt are sometimes referred to in the art as reverse switching rectifiers.
The thyristor device of the present invention dif-fers from a reverse switching rectifier in that a rapidly decreasing voltage (i.e., negative dv/dt) is used to initiate ~iring.
SUMMARY O~ THE INVENTION
The thyristor device of the present invention may be fired by a collapsing voltage. The collapsing voltage generates a displacement current which is used to effect ' '~ --1--, ~lt" uy~
7~6 firing of the thyristor. The word "firing" is used in this specification to describe the dynamic process in which a thyristor switches from the forward blocking mode to the forward conducting mode. The expression "turn-on" is also used in the art to describe this switching phenomenon.
In accordance with the present invention, the thy-ristor device has an emitter region and an auxiliary emitter region disposed in a body of semiconductor material. A
means for concentrating a displacement current, such as a moat, is disposed in a base region between the main emitter and the auxiliary emitter, whereby a collapsing voltage concentrates a lateral flowing portion of the displacement current. The concentrated displacement current causes carrier emission from the auxiliary emitter into the base region which generates a forward firing current.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plan view of a thyristor embodiment of the present invention;
Figure 2 is a cross-sectional view of the embodi-ment of Figure l;
Figure 3 is a plan view of a first practicalembodiment of the present invention;
Figure 11 is a cross-sectional view of the embodi-ment of Figure 3;
Figure 5 is a plan view of a second practical embodiment of the present invention;
Figure 6 is a cross-sectional view of the embodi-ment of ~igure 5;
Figures 7a and 7b are cross-sectional views of the 3o embodiment of Figure 1, schematically illustrating the .
46,093 l~U~726 firing process in tirne sequence;
Figure 8 is a graph illustrating the time sequence of events described in Figures 7a and 7b;
Figure 9 is a simplified circuit model of the thyristor of the present invention; and, Figures 10, 11 and 12 are practical examples of circuit applications of the thyristor of the present inven-tion.
DESCRIPTION OF THE PREFERRED EMB~DIMENTS
Figures 1 and 2 il]ustrate a basic thyristor embodiment 10 of the present invention comprising a body of semiconductor material 12, which is preferably silicon. The body 12 has four layers of alternate conductivity which, by way of example, are designated with the letters "N" and "P".
Those skilled in the art will recognize that a complementary device may be produced by interchanging the "N" and "P"
conductivity types in description which follows. Starting from top surface 13 of body 12, a first layer consists of two N-type emitter regions 14 and 16, which form PN junctions 15 and 17 with a second P-type layer or base region 18 as shown. A third layer, 20 of N- ~pe conductivity lies beneath base region 18, PN junction 19 being formed therebetween. A
fourth layer or anode emitter region 22 of P-type conductivity lies beneath layer 20, PN junction 21 being formed there-between. Electrodes 24 and 26 make ohmic contact with regions 14 and 16 respectively at top major surface 13.
Electrode 28 makes ohmic contact with region 22 at bottom major surface 29 as shown.
Base region 18 extends past emitter regions 14 and 3o 16 to surface 13 at at least three points. A first portion ~1~4 7Z6 46,093 30 of base region 18 extends to surface 13 as shown, thereby separating regions 14 and 16. A second portion 32 of base region 18 extends to surface 13 on a side of region 14 separated from portion 30 as shown. A third portion 34 of base region 18 extends to surface 13 on a side of region 16 separated from portion 30 as shown. Electrodes 24 and 26 make ohmic contact with portions 32 and 34 respectively at surface 13.
Disposed in portion 30 of region 18 is a barrier or means for concentrating or channelling lateral flowing current in region 18. What is meant by lateral flowing current is, for example, a current which flows from the portion of base region, 18 under emitter region 14 from rlght to left in the view of Figure 2, and which continues to flow through portion 30 of region 18 into the portion of region 18 under emitter region 16. A presently preferred current ` concentrating means is an etched moat 36. A suitable alter-,;1 I native to a moat is a N-type conductivity region which may -i be located in approximately the same position as moat 36.
. ~
An isthmus 38 lies in portion 30 of region 18 :, .
between portions of the moat 36 as shown in Figure 1, the isthmus 38 carrying a concentrated lateral flowing current near surface 13 in portion 30 of region 18. It is preferred that region 18 be produced by diffusion so that the resisti-vity in region 18 decreases as the distance from surface 13 decreases. Thus the isthmus 38 presents a relatively low resistance path to lateral flowing current.
~;~ While the embodiment of Figures 1 and 2 is symme-trical on elther side of moat 36, region 14 functions as a 30 main cathode emitter and region 16 functions as an auxiliary Ll6,093 1~4~6 emitter. Connections to an external circuit are made at cathode electrode 24 and anode electrode 28 as schematically illustrated by the letters "K" and "A".
Now referring to ~igures 3 and 4, a presently pre-ferred embodiment 110 is illustrated, which is particularly suited to applications in the hundreds of amperes range.
Thyristor 110 is circular in general con~iguration; however~
similar numerals designate parts similar to those described above in conjunction with basic thyristor device 10.
In particular, semiconductor body or wafer 112 has four layers of alternate conductivity, wherein the top layer comprises two N-type emitter regions 114 and 116. Auxiliary emitter region 116 is ring-shaped and surrounds circular-shaped main emitter region 114. Regions 114 and 116 form PN
junctions 115 and 117 respectively with P-type base region 118 disposed therebelow. N-type region 120 and P-type region 122 lie beneath region 118, PN junctions 119 and 121 i interfacing the regions as shown. Electrodes 124, 126 and 128 make ohmic contact to regions 114, 116 and 122 respec-20 tively. Base portions 130, 132 and 134 terminate at major surface 113. Portion 130 separates region 114 from region 116.
Disposed in portion 130 of base region 118 between regions 114 and 116 is a barrier or moat 136 similar in form and function to the barrier 36 described above. Moat 136 circumscribes main emitter region 114 almost entirely, a narrow isthmus 138 providing a path near surface 113 for current flowing laterally through portion 130 of base region 118. As a means of reducing surface recombination, an insulating layer 140, such as silicon dioxide, is disposed , : ~ - ., , , : ,.
~ 4~ 46,og3 on surface 113 covering at least the portion of ~unctions 115 and 117 in the vicinity of isthmus 138. The insulating layer 140 minimizes recombination of electrons injected by emitter regions 114 and 116 into base region 118 under layer ],i~o .
Portions 132 are hnown in the art as shorts or shunts since they provide direct contact between cathode electrode 124 and base region 118. Shunt portions 132 are disposed throughout emitter region 114 in a regular pattern known in the thyristor art, a preferred spacing between ad-jacent shunts being 25 to 40 mils and a preferred shunt dia-meter being 4 to 12 mils.
Semiconductor wafer 112 has a bevelled edge 141, for which the angle of inclination and method of forming are known in the art. Disposed on bevelled edge 141 is an insu-lating and protective coating 142, a high temperature curing silicon varnish being one of several suitable coating mate-rials.
A second preferred embodiment 210 is illustrated in Figures 5 and 6. The device 210 is fully analogous to device 110, similar parts being designated by similar nume-rals. However, device 210 differs from device 110 in that main emitter region 214 and associated electrode 224 sur-round an auxiliary emitter region 216 and associated elec-trode 226.
For purposes of comparison, the generic structure of Figure 2 is located in a portion of the cross-sections of devices 110 and 210 designated by numeral 10'. The opera-tion of the inventive devices 10, 110 and 210 is functionally similar apart from geometrical differences.
46,og3 '72 ~
~ or ease of illustration, the operation of device 13 will now be described diagrammatically with the aid of Figures 7a, 7b and 8.
At t=0 a forward blocking voltage VAK = VO exists across device 10 with the polarity shown at terminals "A"
and "K". At some later time t=tl, the voltage is caused to decrease sharply by means of external control~ causing a displacement current id to flow from cathode electrode 24 to ; anode electrode 28 along t~e solid line paths shown in Figure 7a. The current id is proportional to the capaci-tance of forward blocking junction 19 and the rate of de-crease in voltage. Some of the current id is channelled through isthmus 38 and then through a portion of base region ;~ 18 under auxiliary emitter region 16 as shown. A voltage drop "idr" therefore exists in base region 18 under aux~-liary emitter region 16, wherein "r" is the resistance along the current path, which is proportional to the resistivity of the base region 18. When a voltage drop of greater than about 0.7 volts exists under auxiliary emitter region 16, electrons are emitted from region 16 as shown. These elec-trons are replenished at the interface between metal elec-trode 26 and base region 18 where a positive current of holes flows from auxiliary emitter electrode 26 into base region 18 as illustrated by the dashed line.
At t=t2 the voltage VAK has dropped from an initial value of VO to about 0.25 VO as shown in Figure 8. By this time the electron emission from the edge of region 16 has caused localized lowering of junction resistance in PN
``I junction 19, which allows a localized forward firing current if to flow. The current if flows through isthmus 38 and ' ,,,,~
....
~,, . . ,. - -.. , : .. :. .. .
- . . . - ~ . . i . .
46,og3 1 1~ ~ 6 then through base region 18 under main emitter region 14 to cathode electrode 24, thus producing a voltage drop ("ifr") having the polarity shown in Figure 7b. When ifr exceeds about 0,7 volts, electrons are emitted from the edge of emitter region 14 as shown. Those skilled in the art will recognize that such electron emission will fire the thyristor.
Device embodiments 110 and 210 function similarly to device embodiment 10 as just described. Both devices 110 and 210 are fired by a collapsing voltage which produces a displacement current and resulting emission from an auxi-liary emitter.
In the case of thyristor device 110~ which is illustrated in Figures 3 and 4, the aforementioned displace-ment current flows from the cathode electrode 124 through the shunts 132 into base region 118. A portion of the displacement current then flows laterally (i.e., radially outward) until it encounters moat 136, which causes a con-centrated current to flow through isthmus 138. The con-centrated current continues laterally outward similarly as ' 20 described above in conjunction with the discussion of device 10 in Figure 7a. A voltage drop occurs under auxiliary emitter region 116 of device 110 in a portion of base region ~; 118 in the vicinity of isthmus 138. Electron emission then occurs from auxiliary emitter region 116 through a portion of PN junction 117 nearest isthmus 138. The junction resis-tance of a portion of PN junction 119 under the isthmus 138 is lowered as a result of the electron emission, which causes a localized forward firing current to flow from anode electrode 128 through the low resistance portion of PN junc-tion 119 and then through the shunts 132 to cathode electrode "
~, , . . ; .. :: . . , 46,093 ~47;~
124. The firing current produces a voltage drop in base region under main emitter region 114, causing electron emission from region 114 which fires the thyristor 110.
The positioning of shunts 132 is important. The nearest shunt 132 to isthmus 138 must be spaced at a dis-tance far enough from isthmus 138 so that the voltage drop under emitter region 114, as measured from the nearest shunt 132 to the isthmus 138, iS sufficiently high to cause elec-tron emission from the edge o~ emitter region 114 nearest the isthmus 138.
Again referring to Figures 5 and 6, thyristor device 210 functions in an analogous manner to device 110 discussed above. Briefly, when the voltage VAK collapses, a displacement current flows from cathode electrode 224 to anode electrode 228. Some of the displacement current flows laterally through isthrnus 238 causing electron emission from auxiliary emitter region 216. The electron emission from region 216 lowers the junction resistance of PN junction 219 ;; in the vicinity of the emission, which permits a forward 20 firing current to flow from anode electrode 228 to cathode - electrode 224 causing electron emission from emitter region 214 and a resulting firing of the device 210. The shunts 232 of device 210 serve the same purpose as shunts 132 of device 110 discussed above.
As a practical example of the invention, a working embodiment has been made having the basic geometry of thy-ristor device 110 shown in Figures 3 and ll. The working embodiment had the following dimensions: overall diameter equals 33 mm, diameter of cathode electrode 124 equals 22 mm, inside diameter of auxiliary emitter electrode 126 ~'~
, .
,~
,',, 46,093
10 Field of the _ ention: -The present invention pertains to semiconductor switching devices, and'more particularly to two terminal silicon thyristors.
De ~ he Prior Art:
In addition to the well known gating of thyristors by means of a third terminal, it is known in the art that thyristors may be switched from the forward blocking mode to the forward conducting mode by rapidly increasing the vol-tage across the thyristor. Thyristors which are designed to be fired by such positive dv/dt are sometimes referred to in the art as reverse switching rectifiers.
The thyristor device of the present invention dif-fers from a reverse switching rectifier in that a rapidly decreasing voltage (i.e., negative dv/dt) is used to initiate ~iring.
SUMMARY O~ THE INVENTION
The thyristor device of the present invention may be fired by a collapsing voltage. The collapsing voltage generates a displacement current which is used to effect ' '~ --1--, ~lt" uy~
7~6 firing of the thyristor. The word "firing" is used in this specification to describe the dynamic process in which a thyristor switches from the forward blocking mode to the forward conducting mode. The expression "turn-on" is also used in the art to describe this switching phenomenon.
In accordance with the present invention, the thy-ristor device has an emitter region and an auxiliary emitter region disposed in a body of semiconductor material. A
means for concentrating a displacement current, such as a moat, is disposed in a base region between the main emitter and the auxiliary emitter, whereby a collapsing voltage concentrates a lateral flowing portion of the displacement current. The concentrated displacement current causes carrier emission from the auxiliary emitter into the base region which generates a forward firing current.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plan view of a thyristor embodiment of the present invention;
Figure 2 is a cross-sectional view of the embodi-ment of Figure l;
Figure 3 is a plan view of a first practicalembodiment of the present invention;
Figure 11 is a cross-sectional view of the embodi-ment of Figure 3;
Figure 5 is a plan view of a second practical embodiment of the present invention;
Figure 6 is a cross-sectional view of the embodi-ment of ~igure 5;
Figures 7a and 7b are cross-sectional views of the 3o embodiment of Figure 1, schematically illustrating the .
46,093 l~U~726 firing process in tirne sequence;
Figure 8 is a graph illustrating the time sequence of events described in Figures 7a and 7b;
Figure 9 is a simplified circuit model of the thyristor of the present invention; and, Figures 10, 11 and 12 are practical examples of circuit applications of the thyristor of the present inven-tion.
DESCRIPTION OF THE PREFERRED EMB~DIMENTS
Figures 1 and 2 il]ustrate a basic thyristor embodiment 10 of the present invention comprising a body of semiconductor material 12, which is preferably silicon. The body 12 has four layers of alternate conductivity which, by way of example, are designated with the letters "N" and "P".
Those skilled in the art will recognize that a complementary device may be produced by interchanging the "N" and "P"
conductivity types in description which follows. Starting from top surface 13 of body 12, a first layer consists of two N-type emitter regions 14 and 16, which form PN junctions 15 and 17 with a second P-type layer or base region 18 as shown. A third layer, 20 of N- ~pe conductivity lies beneath base region 18, PN junction 19 being formed therebetween. A
fourth layer or anode emitter region 22 of P-type conductivity lies beneath layer 20, PN junction 21 being formed there-between. Electrodes 24 and 26 make ohmic contact with regions 14 and 16 respectively at top major surface 13.
Electrode 28 makes ohmic contact with region 22 at bottom major surface 29 as shown.
Base region 18 extends past emitter regions 14 and 3o 16 to surface 13 at at least three points. A first portion ~1~4 7Z6 46,093 30 of base region 18 extends to surface 13 as shown, thereby separating regions 14 and 16. A second portion 32 of base region 18 extends to surface 13 on a side of region 14 separated from portion 30 as shown. A third portion 34 of base region 18 extends to surface 13 on a side of region 16 separated from portion 30 as shown. Electrodes 24 and 26 make ohmic contact with portions 32 and 34 respectively at surface 13.
Disposed in portion 30 of region 18 is a barrier or means for concentrating or channelling lateral flowing current in region 18. What is meant by lateral flowing current is, for example, a current which flows from the portion of base region, 18 under emitter region 14 from rlght to left in the view of Figure 2, and which continues to flow through portion 30 of region 18 into the portion of region 18 under emitter region 16. A presently preferred current ` concentrating means is an etched moat 36. A suitable alter-,;1 I native to a moat is a N-type conductivity region which may -i be located in approximately the same position as moat 36.
. ~
An isthmus 38 lies in portion 30 of region 18 :, .
between portions of the moat 36 as shown in Figure 1, the isthmus 38 carrying a concentrated lateral flowing current near surface 13 in portion 30 of region 18. It is preferred that region 18 be produced by diffusion so that the resisti-vity in region 18 decreases as the distance from surface 13 decreases. Thus the isthmus 38 presents a relatively low resistance path to lateral flowing current.
~;~ While the embodiment of Figures 1 and 2 is symme-trical on elther side of moat 36, region 14 functions as a 30 main cathode emitter and region 16 functions as an auxiliary Ll6,093 1~4~6 emitter. Connections to an external circuit are made at cathode electrode 24 and anode electrode 28 as schematically illustrated by the letters "K" and "A".
Now referring to ~igures 3 and 4, a presently pre-ferred embodiment 110 is illustrated, which is particularly suited to applications in the hundreds of amperes range.
Thyristor 110 is circular in general con~iguration; however~
similar numerals designate parts similar to those described above in conjunction with basic thyristor device 10.
In particular, semiconductor body or wafer 112 has four layers of alternate conductivity, wherein the top layer comprises two N-type emitter regions 114 and 116. Auxiliary emitter region 116 is ring-shaped and surrounds circular-shaped main emitter region 114. Regions 114 and 116 form PN
junctions 115 and 117 respectively with P-type base region 118 disposed therebelow. N-type region 120 and P-type region 122 lie beneath region 118, PN junctions 119 and 121 i interfacing the regions as shown. Electrodes 124, 126 and 128 make ohmic contact to regions 114, 116 and 122 respec-20 tively. Base portions 130, 132 and 134 terminate at major surface 113. Portion 130 separates region 114 from region 116.
Disposed in portion 130 of base region 118 between regions 114 and 116 is a barrier or moat 136 similar in form and function to the barrier 36 described above. Moat 136 circumscribes main emitter region 114 almost entirely, a narrow isthmus 138 providing a path near surface 113 for current flowing laterally through portion 130 of base region 118. As a means of reducing surface recombination, an insulating layer 140, such as silicon dioxide, is disposed , : ~ - ., , , : ,.
~ 4~ 46,og3 on surface 113 covering at least the portion of ~unctions 115 and 117 in the vicinity of isthmus 138. The insulating layer 140 minimizes recombination of electrons injected by emitter regions 114 and 116 into base region 118 under layer ],i~o .
Portions 132 are hnown in the art as shorts or shunts since they provide direct contact between cathode electrode 124 and base region 118. Shunt portions 132 are disposed throughout emitter region 114 in a regular pattern known in the thyristor art, a preferred spacing between ad-jacent shunts being 25 to 40 mils and a preferred shunt dia-meter being 4 to 12 mils.
Semiconductor wafer 112 has a bevelled edge 141, for which the angle of inclination and method of forming are known in the art. Disposed on bevelled edge 141 is an insu-lating and protective coating 142, a high temperature curing silicon varnish being one of several suitable coating mate-rials.
A second preferred embodiment 210 is illustrated in Figures 5 and 6. The device 210 is fully analogous to device 110, similar parts being designated by similar nume-rals. However, device 210 differs from device 110 in that main emitter region 214 and associated electrode 224 sur-round an auxiliary emitter region 216 and associated elec-trode 226.
For purposes of comparison, the generic structure of Figure 2 is located in a portion of the cross-sections of devices 110 and 210 designated by numeral 10'. The opera-tion of the inventive devices 10, 110 and 210 is functionally similar apart from geometrical differences.
46,og3 '72 ~
~ or ease of illustration, the operation of device 13 will now be described diagrammatically with the aid of Figures 7a, 7b and 8.
At t=0 a forward blocking voltage VAK = VO exists across device 10 with the polarity shown at terminals "A"
and "K". At some later time t=tl, the voltage is caused to decrease sharply by means of external control~ causing a displacement current id to flow from cathode electrode 24 to ; anode electrode 28 along t~e solid line paths shown in Figure 7a. The current id is proportional to the capaci-tance of forward blocking junction 19 and the rate of de-crease in voltage. Some of the current id is channelled through isthmus 38 and then through a portion of base region ;~ 18 under auxiliary emitter region 16 as shown. A voltage drop "idr" therefore exists in base region 18 under aux~-liary emitter region 16, wherein "r" is the resistance along the current path, which is proportional to the resistivity of the base region 18. When a voltage drop of greater than about 0.7 volts exists under auxiliary emitter region 16, electrons are emitted from region 16 as shown. These elec-trons are replenished at the interface between metal elec-trode 26 and base region 18 where a positive current of holes flows from auxiliary emitter electrode 26 into base region 18 as illustrated by the dashed line.
At t=t2 the voltage VAK has dropped from an initial value of VO to about 0.25 VO as shown in Figure 8. By this time the electron emission from the edge of region 16 has caused localized lowering of junction resistance in PN
``I junction 19, which allows a localized forward firing current if to flow. The current if flows through isthmus 38 and ' ,,,,~
....
~,, . . ,. - -.. , : .. :. .. .
- . . . - ~ . . i . .
46,og3 1 1~ ~ 6 then through base region 18 under main emitter region 14 to cathode electrode 24, thus producing a voltage drop ("ifr") having the polarity shown in Figure 7b. When ifr exceeds about 0,7 volts, electrons are emitted from the edge of emitter region 14 as shown. Those skilled in the art will recognize that such electron emission will fire the thyristor.
Device embodiments 110 and 210 function similarly to device embodiment 10 as just described. Both devices 110 and 210 are fired by a collapsing voltage which produces a displacement current and resulting emission from an auxi-liary emitter.
In the case of thyristor device 110~ which is illustrated in Figures 3 and 4, the aforementioned displace-ment current flows from the cathode electrode 124 through the shunts 132 into base region 118. A portion of the displacement current then flows laterally (i.e., radially outward) until it encounters moat 136, which causes a con-centrated current to flow through isthmus 138. The con-centrated current continues laterally outward similarly as ' 20 described above in conjunction with the discussion of device 10 in Figure 7a. A voltage drop occurs under auxiliary emitter region 116 of device 110 in a portion of base region ~; 118 in the vicinity of isthmus 138. Electron emission then occurs from auxiliary emitter region 116 through a portion of PN junction 117 nearest isthmus 138. The junction resis-tance of a portion of PN junction 119 under the isthmus 138 is lowered as a result of the electron emission, which causes a localized forward firing current to flow from anode electrode 128 through the low resistance portion of PN junc-tion 119 and then through the shunts 132 to cathode electrode "
~, , . . ; .. :: . . , 46,093 ~47;~
124. The firing current produces a voltage drop in base region under main emitter region 114, causing electron emission from region 114 which fires the thyristor 110.
The positioning of shunts 132 is important. The nearest shunt 132 to isthmus 138 must be spaced at a dis-tance far enough from isthmus 138 so that the voltage drop under emitter region 114, as measured from the nearest shunt 132 to the isthmus 138, iS sufficiently high to cause elec-tron emission from the edge o~ emitter region 114 nearest the isthmus 138.
Again referring to Figures 5 and 6, thyristor device 210 functions in an analogous manner to device 110 discussed above. Briefly, when the voltage VAK collapses, a displacement current flows from cathode electrode 224 to anode electrode 228. Some of the displacement current flows laterally through isthrnus 238 causing electron emission from auxiliary emitter region 216. The electron emission from region 216 lowers the junction resistance of PN junction 219 ;; in the vicinity of the emission, which permits a forward 20 firing current to flow from anode electrode 228 to cathode - electrode 224 causing electron emission from emitter region 214 and a resulting firing of the device 210. The shunts 232 of device 210 serve the same purpose as shunts 132 of device 110 discussed above.
As a practical example of the invention, a working embodiment has been made having the basic geometry of thy-ristor device 110 shown in Figures 3 and ll. The working embodiment had the following dimensions: overall diameter equals 33 mm, diameter of cathode electrode 124 equals 22 mm, inside diameter of auxiliary emitter electrode 126 ~'~
, .
,~
,',, 46,093
2~
equals 28 mm, outside diameter of auxiliary emitter elec-trode 126 equals 32 mm, width of auxiliary emltter region equals 2 mm, width of moat 136 equals 1 mm, spacing between moat edge and adJacent emitter regions 114 and 116 equals 0.5 mm, width of isthmus 138 measured from the ends of moat equals 2 mm, peripheral overlap of electrode 126 onto base region 118 equals 0.25 mm. In addition, the working embo-diment employed a hexagonal arrangement of shunts 132, each shunt having approximately a 0.2 mm diameter and a 0.9 mm 10 spacing between nearest neighboring shunts. However, the shunts 132 were arranged so that the distance from the edge of emitter region 114 to the nearest shunt 132 (i.e., dis-tance "X" in Figure 4) was approximately 4.5 mm.
A better understanding of the dynamics of thyris-tor firing has lead to the above-described structure and presently preferred dimensions. As discussed in more detail above, it is necessary to produce a critical voltage of greater than about 0.7 volts under an emitter region in order to cause the desired electron emission from the emitter.
20 The distance "X" must therefore be long enough to produce a voltage drop in excess of 0.7 volts, and most preferably greater than about 1.0 volts. The working embodlment des-cribed above had a sheet resistivity of about 600 ohms/cm2 in base region 118. The distance "X" was therefore selected to be 4.5 mm so that the forward firing current passing .
laterally through base region 118 would produce the desired voltage drop of greater than about 1.0 volts. Similar r considerations affected the choice of the width of the auxiliary emitter region 116. The displacement current, 30 being concentrated as it passes through isthmus 138, has a - ~
.. .......
46,093 magnitude sufficient to produce the critical voltage drop in a distance of 2 mm given a shee~ resistivity of 600 ohms/cm2.
Now referring to Figure ~, a simplified circuit model 310 of the inventive thyristor device is shown, which by way of analogy further describes its operation. When the voltage VAK collapses~ a displacement current flows from ; capacitor C which fires thyristor Tl, which in turn fires the main thyristor T2.
Figure 10 shows a general circuit application for the inventive thyristor device 310. Initially no current flows through the circuit, the switch 350 being open-cir-cuited. When the switch 350 closes, the thyristor 310 is ` turned-on by the collapsing voltage, provided that the conduction state impedance of the switch 350 is greater than that of the thyristor 310. The switch may take any form, such as mechanical, electro-mechanical or solid-state elec-tronic.
Figure 11 shows an application having parallel operation of thyristors 310 and a conventional three-termi-nal thyristor 360. By applying a signal to the gate 362 in the usual manner known in the thyristor art, the three-terminal thyristor 360 is fired, which causes all thyristors i 310 to fire.
Series-parallel operation is also contemplated, as ! illustrated in Figure 12. Parallel banks of thyristors 310 i are connected in series as shown. Each bank has a control device 370 in parallel, the device 370 being capable of firing its entire bank. For example, a light activated switch may be used as a control device 370, which would enable simultaneous firing of all parallel banks. A light ~: . : . ,,, : , :, ,,, , ;,, ~, ,:
- . .,.: , . .:: .
4 6 , 093 `` 11~4726 activated switch has the advantage of enabling "gating" of each bank without regard to the voltage level at each bank.
These and other advantages of the thyristor device of the present invention will be appreciated by those skilled in the art. ~or example, it may be advantageous in certain applications to have conventional three-terminal thyristors constructed with the turn-on capability described herein.
If gate failure then occurs in such a device, firing will still take plaee under collapsing voltage coneitions.
, ~
P'i ~
' , ~ .
:~
, ,, ~ , ~ . .
equals 28 mm, outside diameter of auxiliary emitter elec-trode 126 equals 32 mm, width of auxiliary emltter region equals 2 mm, width of moat 136 equals 1 mm, spacing between moat edge and adJacent emitter regions 114 and 116 equals 0.5 mm, width of isthmus 138 measured from the ends of moat equals 2 mm, peripheral overlap of electrode 126 onto base region 118 equals 0.25 mm. In addition, the working embo-diment employed a hexagonal arrangement of shunts 132, each shunt having approximately a 0.2 mm diameter and a 0.9 mm 10 spacing between nearest neighboring shunts. However, the shunts 132 were arranged so that the distance from the edge of emitter region 114 to the nearest shunt 132 (i.e., dis-tance "X" in Figure 4) was approximately 4.5 mm.
A better understanding of the dynamics of thyris-tor firing has lead to the above-described structure and presently preferred dimensions. As discussed in more detail above, it is necessary to produce a critical voltage of greater than about 0.7 volts under an emitter region in order to cause the desired electron emission from the emitter.
20 The distance "X" must therefore be long enough to produce a voltage drop in excess of 0.7 volts, and most preferably greater than about 1.0 volts. The working embodlment des-cribed above had a sheet resistivity of about 600 ohms/cm2 in base region 118. The distance "X" was therefore selected to be 4.5 mm so that the forward firing current passing .
laterally through base region 118 would produce the desired voltage drop of greater than about 1.0 volts. Similar r considerations affected the choice of the width of the auxiliary emitter region 116. The displacement current, 30 being concentrated as it passes through isthmus 138, has a - ~
.. .......
46,093 magnitude sufficient to produce the critical voltage drop in a distance of 2 mm given a shee~ resistivity of 600 ohms/cm2.
Now referring to Figure ~, a simplified circuit model 310 of the inventive thyristor device is shown, which by way of analogy further describes its operation. When the voltage VAK collapses~ a displacement current flows from ; capacitor C which fires thyristor Tl, which in turn fires the main thyristor T2.
Figure 10 shows a general circuit application for the inventive thyristor device 310. Initially no current flows through the circuit, the switch 350 being open-cir-cuited. When the switch 350 closes, the thyristor 310 is ` turned-on by the collapsing voltage, provided that the conduction state impedance of the switch 350 is greater than that of the thyristor 310. The switch may take any form, such as mechanical, electro-mechanical or solid-state elec-tronic.
Figure 11 shows an application having parallel operation of thyristors 310 and a conventional three-termi-nal thyristor 360. By applying a signal to the gate 362 in the usual manner known in the thyristor art, the three-terminal thyristor 360 is fired, which causes all thyristors i 310 to fire.
Series-parallel operation is also contemplated, as ! illustrated in Figure 12. Parallel banks of thyristors 310 i are connected in series as shown. Each bank has a control device 370 in parallel, the device 370 being capable of firing its entire bank. For example, a light activated switch may be used as a control device 370, which would enable simultaneous firing of all parallel banks. A light ~: . : . ,,, : , :, ,,, , ;,, ~, ,:
- . .,.: , . .:: .
4 6 , 093 `` 11~4726 activated switch has the advantage of enabling "gating" of each bank without regard to the voltage level at each bank.
These and other advantages of the thyristor device of the present invention will be appreciated by those skilled in the art. ~or example, it may be advantageous in certain applications to have conventional three-terminal thyristors constructed with the turn-on capability described herein.
If gate failure then occurs in such a device, firing will still take plaee under collapsing voltage coneitions.
, ~
P'i ~
' , ~ .
:~
, ,, ~ , ~ . .
Claims (5)
1. A thyristor device comprising:
a body of semiconductor material;
said body having disposed therein a base region of a first conductivity type, a main emitter region of a second con-ductivity type, an auxiliary emitter region of said second conductivity type, said main emitter region and said auxiliary emitter region being separated by a first portion of said base region;
a cathode electrode in ohmic contact with said main emitter region and a second portion of said base region, said second portion of said base region being separated from said first portion of said base region by said main emitter region;
an auxiliary emitter electrode in ohmic contact with said auxiliary emitter region and a third portion of said base region, said third portion of said base region being separated from said first portion of said base region by said auxiliary emitter region; and means disposed in said first portion of said base region between said auxiliary emitter region and said main emitter region for concentrating a displacement current in said first portion of said base region.
a body of semiconductor material;
said body having disposed therein a base region of a first conductivity type, a main emitter region of a second con-ductivity type, an auxiliary emitter region of said second conductivity type, said main emitter region and said auxiliary emitter region being separated by a first portion of said base region;
a cathode electrode in ohmic contact with said main emitter region and a second portion of said base region, said second portion of said base region being separated from said first portion of said base region by said main emitter region;
an auxiliary emitter electrode in ohmic contact with said auxiliary emitter region and a third portion of said base region, said third portion of said base region being separated from said first portion of said base region by said auxiliary emitter region; and means disposed in said first portion of said base region between said auxiliary emitter region and said main emitter region for concentrating a displacement current in said first portion of said base region.
2. The device of claim 1 wherein said main emit-ter region circumscribes said auxiliary emitter region.
3. The device of claim 1 wherein said auxiliary emit-ter region circumscribes said main emitter region.
4. The device of claim 1 wherein said means comprises a moat forming an isthmus for concentrating current.
5. The device of claim 4 further comprising an oxide layer disposed on said body of semiconductor material covering at least said isthmus.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73679576A | 1976-10-29 | 1976-10-29 | |
| US736,795 | 1985-05-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1104726A true CA1104726A (en) | 1981-07-07 |
Family
ID=24961330
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA287,988A Expired CA1104726A (en) | 1976-10-29 | 1977-10-03 | Thyristor fired by collapsing voltage |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS5356979A (en) |
| AU (1) | AU516308B2 (en) |
| BE (1) | BE859992A (en) |
| BR (1) | BR7707015A (en) |
| CA (1) | CA1104726A (en) |
| DE (1) | DE2748528A1 (en) |
| FR (1) | FR2393432A1 (en) |
| GB (1) | GB1592877A (en) |
| HK (1) | HK64384A (en) |
| IN (1) | IN148845B (en) |
| PL (1) | PL117693B1 (en) |
| SE (1) | SE7712091L (en) |
| ZA (1) | ZA775629B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3000804A1 (en) * | 1980-01-11 | 1981-07-16 | SEMIKRON Gesellschaft für Gleichrichterbau u. Elektronik mbH, 8500 Nürnberg | THYRISTOR WITH SHORT-CLOSED EMITTER FOR SHORT CURRENT FLOW RATE |
| JPS5935689U (en) * | 1982-08-30 | 1984-03-06 | 株式会社東芝 | Refrigeration cycle equipment |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3573572A (en) * | 1968-09-23 | 1971-04-06 | Int Rectifier Corp | Controlled rectifier having high rate-of-rise-of-current capability and low firing gate current |
| US3731162A (en) * | 1969-09-25 | 1973-05-01 | Tokyo Shibaura Electric Co | Semiconductor switching device |
| FR2144581B1 (en) * | 1971-07-06 | 1976-03-19 | Silec Semi Conducteurs | |
| DE2141627C3 (en) * | 1971-08-19 | 1979-06-13 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Thyristor |
| US3914783A (en) * | 1971-10-01 | 1975-10-21 | Hitachi Ltd | Multi-layer semiconductor device |
| DE2210386A1 (en) * | 1972-03-03 | 1973-09-06 | Siemens Ag | THYRISTOR |
| GB1425651A (en) * | 1972-04-03 | 1976-02-18 | Motorola Inc | Channel firing thyristor |
| DE2346256C3 (en) * | 1973-09-13 | 1981-11-05 | Siemens AG, 1000 Berlin und 8000 München | Thyristor |
| JPS5413959B2 (en) * | 1973-10-17 | 1979-06-04 | ||
| JPS5927108B2 (en) * | 1975-02-07 | 1984-07-03 | 株式会社日立製作所 | Semiconductor controlled rectifier |
-
1977
- 1977-09-20 ZA ZA00775629A patent/ZA775629B/en unknown
- 1977-09-23 IN IN1434/CAL/77A patent/IN148845B/en unknown
- 1977-10-03 CA CA287,988A patent/CA1104726A/en not_active Expired
- 1977-10-13 GB GB42646/77A patent/GB1592877A/en not_active Expired
- 1977-10-14 AU AU29741/77A patent/AU516308B2/en not_active Expired
- 1977-10-20 BR BR7707015A patent/BR7707015A/en unknown
- 1977-10-21 BE BE181962A patent/BE859992A/en not_active IP Right Cessation
- 1977-10-25 FR FR7732103A patent/FR2393432A1/en active Granted
- 1977-10-27 SE SE7712091A patent/SE7712091L/en not_active Application Discontinuation
- 1977-10-28 PL PL1977201799A patent/PL117693B1/en unknown
- 1977-10-28 JP JP12883177A patent/JPS5356979A/en active Granted
- 1977-10-28 DE DE19772748528 patent/DE2748528A1/en not_active Withdrawn
-
1984
- 1984-08-16 HK HK643/84A patent/HK64384A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB1592877A (en) | 1981-07-08 |
| AU516308B2 (en) | 1981-05-28 |
| AU2974177A (en) | 1979-04-26 |
| IN148845B (en) | 1981-06-27 |
| HK64384A (en) | 1984-08-24 |
| PL117693B1 (en) | 1981-08-31 |
| BR7707015A (en) | 1978-07-18 |
| FR2393432A1 (en) | 1978-12-29 |
| BE859992A (en) | 1978-04-21 |
| PL201799A1 (en) | 1978-05-08 |
| FR2393432B1 (en) | 1983-08-26 |
| JPS5356979A (en) | 1978-05-23 |
| ZA775629B (en) | 1978-08-30 |
| JPS5649459B2 (en) | 1981-11-21 |
| DE2748528A1 (en) | 1978-05-03 |
| SE7712091L (en) | 1978-04-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0014098B1 (en) | Gate turn-off thyristor | |
| US4786959A (en) | Gate turn-off thyristor | |
| US9741839B1 (en) | Gate structure of thyristor | |
| US4454527A (en) | Thyristor having controllable emitter short circuits and a method for its operation | |
| JPS609669B2 (en) | thyristor | |
| CN111742411A (en) | Bidirectional thyristor device | |
| US3622845A (en) | Scr with amplified emitter gate | |
| JPS609668B2 (en) | thyristor | |
| US4060825A (en) | High speed high power two terminal solid state switch fired by dV/dt | |
| US4437107A (en) | Self-igniting thyristor with a plurality of discrete, field controlled zener diodes | |
| JPH0138381B2 (en) | ||
| JPH0117268B2 (en) | ||
| US4195306A (en) | Gate turn-off thyristor | |
| US4464673A (en) | Semiconductor component | |
| US4089024A (en) | Semiconductor switching device | |
| CA1104726A (en) | Thyristor fired by collapsing voltage | |
| US4951110A (en) | Power semiconductor structural element with four layers | |
| US4502072A (en) | FET Controlled thyristor | |
| JPS62109361A (en) | Thyristor | |
| US4214254A (en) | Amplified gate semiconductor controlled rectifier with reduced lifetime in auxiliary thyristor portion | |
| US4063278A (en) | Semiconductor switch having sensitive gate characteristics at high temperatures | |
| US4536783A (en) | High di/dt, light-triggered thyristor with etched moat current limiting resistors | |
| US4825270A (en) | Gate turn-off thyristor | |
| JPS5927108B2 (en) | Semiconductor controlled rectifier | |
| US3783350A (en) | Thyristor device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |