Subscriber interface protection circuit

• US 7,019,338 B1
• Filed: 12/29/1998
• Issued: 03/28/2006
• Est. Priority Date: 12/30/1997
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV), STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Ballon, Christian
• Primary Examiner(s): Nadav, Ori
• Application Number:
  US09/367,645
• Time in Patent Office: 2,646 Days
• Field of Search: 257173-174, 257355-363
• US Class Current: 257/173
• CPC Class Codes: H01L 27/0248 for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
• CPC Class Codes: H02H 9/043 Protection of over-voltage protection device by short-circuiting

Abstract

The present invention relates to a monolithic component of protection of a line against overvoltages than a determined positive threshold or smaller than a determined negative threshold, including in antiparallel a cathode-gate thyristor (Th1) and an anode-gate thyristor (Th2), the gate of the cathode-gate thyristor being connected to a negative threshold voltage (−V) via a gate current amplification transistor (T1), the gate of the anode-gate thyristor being connected to a positive threshold voltage (+V). The monolithic component is made in a substrate divided into wells separated by isolating walls (3, 4), the smaller surfaces of which are coated with insulating layers (5, 6), the smaller surface of the substrate being uniformly coated with a metallization (M1).

Claims

1. A monolithic component protecting a line against overvoltages greater than a determined positive threshold or lower than a determined negative threshold, including in antiparallel a cathode-gate thyristor and an anode-gate thyristor connected between a first terminal of the line to be protected and a reference voltage, the gate of the cathode-gate thyristor being connected to a negative threshold voltage via a gate current amplification transistor, the gate of the anode-gate thyristor being connected to a positive threshold voltage, characterized in that:

the monolithic component is made in a substrate of a first conductivity type divided into wells separated by isolating walls, lower surfaces of the isolating walls being coated with insulating layers, a lower surface of the substrate being uniformly coated with a lower surface metallization,

the gate current amplification transistor of the cathode-gate thyristor is made in vertical form in a first well,

the cathode-gate thyristor is implemented in vertical form in a second well,

the lower surface metallization links up the collector of the transistor, the anode of the cathode-gate thyristor, and the cathode of the anode-gate thyristor,

a first front surface metallization connects the cathode of the cathode-gate thyristor to the anode of the anode-gate thyristor,

a second front surface metallization connects the gate of the cathode-gate thyristor to the emitter of the transistor, and

a third front surface metallization is in contact with the gate of the anode-gate thyristor.

2. The component of claim 1, further including a diode, the anode of which is connected to the gate of the anode-gate thyristor, characterized in that the diode is implemented in the form of a P-type region itself formed in an N-type region, the latter being formed in the cathode-gate region of the anode-gate thyristor, on the upper surface side of the component.

3. The component of claim 1, wherein the gate of the cathode-gate thyristor is connected to a second terminal of the line to be protected.

4. The component of claim 1, further ensuring a protective function against overcurrents, in which the gates of the cathode-gate and anode-gate thyristors are interconnected and connected to a second terminal of the line to be protected.

5. The component of claim 4, further including a gate current amplification transistor associated with the anode-gate thyristor, characterized in that this transistor, of PNP type, is formed on the upper surface of the component, a collector region extending via isolating walls towards the lower surface and being in contact with the lower surface metallization.

6. A monolithic component for protecting a line against overvoltages, comprising:

a substrate of a first conductivity type divided into wells separated by isolating walls, lower surfaces of the isolating walls being coated with insulating layers;

a gate current amplification transistor fabricated in vertical form in a first well in the substrate;

a cathode-gate thyristor fabricated in vertical form in a second well in the substrate;

an anode-gate thyristor fabricated in vertical form in a third well in the substrate;

a lower surface metallization connecting the collector of the transistor, the anode of the cathode-gate thyristor, and the cathode of the anode-gate thyristor;

a first front surface metallization connecting the cathode of the cathode-gate thyristor to the anode of the anode-gate thyristor; and

a second front surface metallization connecting the gate of the cathode-gate thyristor to the emitter of the transistor.

7. A monolithic component as defined in claim 6, further comprising a third front surface metallization in contact with the gate of the anode-gate thyristor.

8. A monolithic component as defined in claim 6, further comprising a diode, an anode of which is connected to the gate of the anode-gate thyristor.

9. A monolithic component as defined in claim 8, wherein the diode is implemented as a P-type region formed in an N-type region, the N-type region being formed in the cathode-gate region of the anode-gate thyristor on the front surface of the substrate.

10. A monolithic component as defined in claim 6, further comprising a second gate current amplification transistor associated with the anode-gate thyristor.

11. A monolithic component as defined in claim 10, wherein the second transistor is formed on the front surface of the substrate, a collector region extending via isolating walls toward the lower surface and being in contact with the lower surface metallization.

12. A monolithic component as defined in claim 6, wherein the cathode-gate thyristor and the anode-gate thyristor are connected in antiparallel between a first terminal of the line to be protected and a reference voltage, the gate of the cathode-gate thyristor being connected to a negative threshold voltage via the gate current amplification transistor and the gate of the anode-gate thyristor being connected to a positive threshold voltage.

13. A monolithic component as defined in claim 12, wherein the gate of the cathode-gate thyristor is adapted for connection to a second terminal of the line to be protected.

14. A monolithic component as defined in claim 12, wherein the gates of the cathode-gate and anode-gate thyristors are interconnected and are configured for a connection to a second terminal of the line to be protected.