System and method for electrostatic discharge protection using lateral PNP or PMOS or both for substrate biasing

• US 6,628,493 B1
• Filed: 04/11/2000
• Issued: 09/30/2003
• Est. Priority Date: 04/15/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Vrotsos, Thomas A., Amerasekera, E. Ajith, Chen, Zhiliang Julian
• Primary Examiner(s): Jackson, Stephen W.
• Application Number:
  US09/546,988
• Time in Patent Office: 1,267 Days
• Field of Search: 257/360, 257/361, 257/362, 257/566, 257/567, 361/56, 361/58, 361/111, 361/117, 361/118, 361/119, 361/127, 361/91.5, 327/310, 327/318, 327/313, 327/327, 327/328, 327/534
• US Class Current: 361/111
• CPC Class Codes: H01L 27/0259 using bipolar transistors as protective elements
• CPC Class Codes: H01L 27/027 specially adapted to provide an electrical current path other than the field effect induced current path
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

The invention comprises a system and method for providing electrostatic discharge protection. In one embodiment of the invention, an integrated circuit (10) comprising at least one input element (20) is protected by a protective circuit (40). The protective circuit (40) is operable to protect the integrated circuit (10) from damage due to electrostatic discharge and may be coupled to the input element (20). The protective circuit (40) comprises a lateral NPN transistor (T1) coupled to the input element (20) and operable to activate when the input element voltage exceeds threshold, the threshold greater than or equal to the ordinary operating voltage of circuitry coupled to the input element (20). The protective circuit (40) also may comprise a lateral PNP transistor (T2) coupled to the input element (20) and to the lateral NPN transistor (T1). The lateral PNP transistor (T2) is operable to aid in raising a potential of the base of the lateral NPN transistor (T1). Alternatively, the protective circuit (40) also may use a PMOS traisistor (P1), or a PMOS transistor (P1) in combination with the lateral NPN transistor (T1), coupled to the input element (20) and to the lateral NPN transistor (T1). The PMOS transistor (P1) is operable to aid in raising the potential of the base of the lateral NPN transistor (T1).

Claims

1. An integrated circuit comprising:

at least one input element; and

a protective circuit coupled to the input element, the protective circuit operable to protect the integrated circuit from electrostatic discharge, the protective circuit comprising;

a lateral NPN transistor coupled to the input element, and operable to activate when the input element voltage exceeds a threshold, the threshold greater than or equal to the ordinary operating voltage of circuitry coupled to the input element; and

a lateral PNP transistor coupled to the input element and to the lateral NPN transistor, the lateral PNP transistor supplying collector current to raise a potential of the base of the lateral NPN transistor responsive to the input element voltage exceeding said threshold.

2. The integrated circuit of claim 1 wherein the collector of the lateral PNP transistor is connected to the base of the lateral NPN transistor.

3. The integrated circuit of claim 1 wherein the lateral PNP transistor comprises the drain, source and channel regio n of a p-channel MOSFET.

4. The protective circuit of claim 1 wherein the protective circuit further comprises a vertical PNP operable to aid in raising the potential of the base of the lateral NPN transistor, the vertical PNP transistor coupled to the lateral NPN transistor and to the input element.

5. The integrated circuit of claim 1 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors connected in parallel, and surrounded by a substrate biasing area.

6. The integrated circuit of claim 1 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, each of the plurality located near a positively-doped diffusion in the substrate.

7. The integrated circuit of claim 1 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, each of the plurality located within approximately five microns of a positively-doped diffusion in the substrate.

8. A protective circuit for electrostatic discharge protection, comprising:

a lateral NPN transistor operable to couple to an input element, the lateral NPN transistor further operable to activate when the input element voltage exceeds a threshold, the threshold greater than or equal to the ordinary operating voltage of circuitry coupled to the input element; and

a lateral PNP transistor operable to couple to the input element and to the lateral NPN transistor, the lateral PNP transistor raising a potential of the base of the lateral NPN transistor by supplying collector current responsive to the input element voltage exceeding said threshold.

9. The protective circuit of claim 8 wherein the collector of the lateral PNP transistor is connected to the base of the lateral NPN transistor.

10. The protective circuit of claim 8 wherein the lateral PNP transistor comprises the drain, source and channel region of a p-channel MOSFET.

11. The protective circuit of claim 8 wherein the protective circuit further comprises a vertical PNP operable to aid in raising the potential of the base of the lateral NPN transistor, the vertical PNP transistor operable to couple to the lateral NPN transistor and to the input element.

12. The protective circuit of claim 8 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors connected in parallel and surrounded by a substrate biasing area.

13. The protective circuit of claim 8 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, ones of the plurality including a positively-doped diffusion in the substrate between them.

14. The protective circuit of claim 8 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, each of the plurality located within approximately five microns of a positively-doped diffusion in the substrate.

15. A method for providing electrostatic discharge protection, comprising:

coupling internal circuitry of an integrated circuit to an input element;

coupling to the input element a lateral NPN transistor operable to activate when the input element voltage exceeds a threshold, the threshold greater than or equal to the ordinary operating voltage of the internal circuitry; and

coupling to the input element, the internal circuitry of the integrated circuit, and the lateral NPN transistor a lateral PNP transistor operable to aid in raising a potential of the base of the lateral NPN transistor by supplying collector current responsive to the input element voltage exceeding said threshold.

16. The method of claim 15 wherein the collector of the lateral PNP transistor is connected to the base of the lateral NPN transistor.

17. The method of claim 15 wherein the lateral PNP transistor comprises the drain, source and channel region of a p-channel MOSFET.

18. The method of claim 15 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors connected in parallel, and surrounded by a substrate biasing area.

19. The method of claim 15 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, each of the plurality located near a positively-doped diffusion in the substrate.

20. The method of claim 15 wherein the lateral NPN transistor comprises a plurality of lateral NPN transistors in parallel, each of the plurality located within approximately five microns of a positively-doped diffusion in the substrate.