Semiconductor switching device

• US 5,285,100 A
• Filed: 12/04/1992
• Issued: 02/08/1994
• Est. Priority Date: 07/22/1988
• Status: Expired due to Fees

• Current Assignee: Power Innovations Ltd. (Bourns Incorporated)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Byatt, Stephen
• Primary Examiner(s): CARROLL, JAMES J
• Application Number:
  US07/985,543
• Time in Patent Office: 431 Days
• Field of Search: 357/13, 357/38, 257/109, 257/146, 257/154, 257/162, 257/173-175, 257/566, 257/577, 257/587, 361/91
• US Class Current: 257/566
• CPC Class Codes: H01L 27/0664 Vertical bipolar transistor in combination with diodes
• CPC Class Codes: H01L 29/7408 the device being a capacitor or a resistor
• CPC Class Codes: H01L 29/7412 the device being a diode
• CPC Class Codes: H01L 29/87 Thyristor diodes, e.g. Shockley diodes, break-over diodes
• CPC Class Codes: H03K 17/30 Modifications for providing a predetermined threshold before switching shaping pulses by thresholding H03K5/08
• CPC Class Codes: H04M 3/301 Circuit arrangements at the subscriber's side of the line

Abstract

A semiconductor switching device that is suitable for use as a remote isolation device (RID) in telephone networks. The semiconductor switching device is a two-terminal voltage sensitive device that switches from an open-circuit condition to a short-circuit condition at a fixed breakover voltage, appears as an open-circuit below the breakover voltage, and appears as a short-circuit above the breakover voltage. When semiconductor switching devices are installed in a telephone network, they are held in their short-circuit condition by the network voltage supply and do not affect the normal operation of the network but will switch to their open-circuit condition if the network voltage supply is reduced to below the breakover voltage, and therefore, parts of the network may be isolated from each other by reducing the voltage supply. Isolation of the parts of the network from each other facilitates testing for maintenance purposes.

Claims

1. In a circuit system having a supply line to an apparatus and having a remote isolation device to disconnect the apparatus in response to a remote command, the improvement in which the remote isolation device comprises a semiconductor switching device comprising a PNP transistor having a P-type emitter region, an N-type base region, and a P-type collector region, an NPN transistor having an N-type emitter region, a P-type base region, and an N-type collector region, and a reverse breakdown PN diode having a P-type region and an N-type region, wherein the respective emitter regions of the transistors are connected in series in the supply line to serve as terminals of the semiconductor switching device, the collector region of the NPN transistor is connected to the base region of the PNP transistor and to the N-type region of the reverse breakdown PN diode, and the collector region of the PNP transistor is connected to the base region of the NPN transistor and to the P-type region of the reverse breakdown PN diode, the semiconductor switching device comprising a P-type semiconductor body that is both the base region of the NPN transistor and the collector region of the PNP transistor, an N-type island, at a surface of the P-type body, that is both the base region of the PNP transistor and the collector region of the NPN transistor, a P⁺ -type island, in the N-type island, that is the emitter region of the PNP transistor, an N-type island, at the surface of the P-type body, that is the emitter region of the NPN transistor, and conductive contact regions providing respective terminals for the P⁺ -type island and the N-type island, the semiconductor switching device including a further P⁺ -type island that extends across the junction between the N-type island and the P-type body, which further P⁺ -type island provides a part of the reverse breakdown diode and has a N^- -type region in the P-type body immediately adjacent to the further P⁺ -type island.

2. A system for a telephone network having a semiconductor switching device as claimed in claim 1, wherein the impurity concentration of the N^- -type region is of the order 10¹⁵ to 10¹⁷ atoms per cubic centimeter.

3. In a circuit system having a supply line to an apparatus and having a remote isolation device to disconnect the apparatus in response to a remote command, the improvement in which the remote isolation device comprises a semiconductor switching device comprising a PNP transistor having a P-type emitter region, an N-type base region, and a P-type collector region, an NPN transistor having an N-type emitter region, a P-type base region, and an N-type collector region, and a reverse breakdown PN diode having a P-type region and an N-type region, wherein the respective emitter regions of the transistors are connected in series in the supply line to serve as terminals of the semiconductor switching device, the collector region of the NPN transistor is connected to the base region of the PNP transistor and to the N-type region of the reverse breakdown PN diode, and the collector region of the PNP transistor is connected to the base region of the NPN transistor and to the P-type region of the reverse breakdown PN diode, the reverse breakdown PN diode being formed at a junction of the collector and base region in one of the transistors, the semiconductor switching device comprising a P-type semiconductor body that is both the base region of the NPN transistor and the collector region of the PNP transistor, an N-type island, at a surface of the P-type body, that is both the base region of the PNP transistor and the collector region of the NPN transistor, a P⁺ -type island, in the N-type island, that is the emitter region of the PNP transistor, and N-type island, at the surface of the P-type body, that is the emitter region of the NPN transistor, and conductive contact regions providing respective terminals for the P⁺ type island and the N-type island, the semiconductor switching device including a further P⁺ -type island that extends across the junction between the N-type island and the P-type body, which further P⁺ -type island provides a part of the reverse breakdown diode and has a N^- -type region in the P-type body immediately adjacent to the further P⁺ -type island.

4. A system for a telephone network having a semiconductor switching device as claimed in claim 3 wherein the impurity concentration of the N^- -type region is of the order 10¹⁵ to 10¹⁷ atoms per cubic centimeter.

5. In a circuit system having a supply line to an apparatus and having a remote isolation device to disconnect the apparatus in response to a remote command, the improvement in which the remote isolation device comprises a monolithic semiconductor switching device comprising a NPN transistor having a N-type emitter region, an P-type base region, and a N-type collector region, an PNP transistor having an P-type emitter region, a N-type base region, and an P-type collector region, and a reverse breakdown NP diode having a N-type region and an P-type region, wherein the respective emitter regions of the transistors are connected in series in the supply line to serve as terminals of the semiconductor switching device, the collector region of the PNP transistor is connected to the base region of the NPN transistor and to the P-type region of the reverse breakdown NP diode, and the collector region of the NPN transistor is connected to the base region of the PNP transistor and to the N-type region of the reverse breakdown NP diode, the semiconductor switching device comprising a N-type semiconductor body that is both the base region of the PNP transistor and the collector region of the NPN transistor, an P-type island, at a surface of the N-type body, that is both the base region of the NPN transistor and the collector region of the PNP transistor, a N⁺ type island, in the P-type island, that is the emitter region of the NPN transistor, an P-type island, at the surface of the N-type body, that is the emitter region of the PNP transistor, and conductive contact regions providing respective terminals for the N⁺ -type island and the P-type island, the semiconductor switching device including a further N⁺ -type island that extends across the junction between the P-type island and the N-type body, which further N⁺ -type island provides a part of the reverse breakdown diode and has a P^- -type region in the N-type body immediately adjacent to the further N⁺ -type island.

6. A system having a semiconductor switching device as claimed in claim 5 wherein the impurity concentration of the P^- -type region is of the order of 10¹⁵ to 10¹⁷ atoms per cubic centimeter.

7. In a circuit system having a supply line to an apparatus and having a remote isolation device to disconnect the apparatus in response to a remote command, the improvement in which the remote isolation device comprises a semiconductor switching device comprising a NPN transistor having a N-type emitter region, an P-type base region, and a N-type collector region, an PNP transistor having an P-type emitter region, a N-type base region, and an P-type collector region, and a reverse breakdown NP diode having a N-type region and an P-type region, wherein the respective emitter regions of the transistors are connected in series in the supply line to serve as terminals of the semiconductor switching device, the collector region of the PNP transistor is connected to the base region of the NPN transistor and to the P-type region of the reverse breakdown NP diode, and the collector region of the NPN transistor is connected to the base region of the PNP transistor and to the N-type region of the reverse breakdown NP diode, the reverse breakdown NP diode being formed at a junction of the collector and base region in one of the transistors, the semiconductor switching device comprising a N-type semiconductor body that is both the base region of the PNP transistor and the collector region of the NPN transistor, an P-type island, at a surface of the N-type body, that is both the base region of the NPN transistor and the collector region of the PNP transistor, a N⁺ -type island, in the P-type island, that is the emitter region of the NPN transistor, and P-type island, at the surface of the N-type body, that is the emitter region of the PNP transistor, and conductive contact regions providing respective terminals for the N⁺ -type island and the P-type island, the semiconductor switching device including a further N⁺ -type island that extends across the junction between the P-type island and the N-type body, which further N⁺ -type island provides a part of the reverse breakdown diode and has a P^- -type region in the N-type body immediately adjacent to the further N⁺ -type island.

8. A system for a telephone network having a semiconductor switching device as claimed in claim 7 wherein the impurity concentration of the P^- -type region is of the order 10¹⁵ to 10¹⁷ atoms per cubit centimeter.