Base for a NPN bipolar transistor

• US 20030230789A1
• Filed: 06/12/2002
• Published: 12/18/2003
• Est. Priority Date: 06/12/2002
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Beasom, James D.
• Granted Patent: US 6,822,314 B2
• Time in Patent Office: Days
• US Class Current: 257/591
• CPC Class Codes: H01L 29/1004 Base region of bipolar transistors
• CPC Class Codes: H01L 29/1008 of lateral transistors
• CPC Class Codes: H01L 29/167 further characterised by the doping material H01L29/1604 takes precedence
• CPC Class Codes: H01L 29/6625 Lateral transistors H01L29/66242 and H01L29/66265 take precedence
• CPC Class Codes: H01L 29/66272 Silicon vertical transistors H01L29/66242, H01L29/66257 and H01L29/66265 take precedence
• CPC Class Codes: H01L 29/7322 having emitter-base and base-collector junctions leaving at the same surface of the body, e.g. planar transistor
• CPC Class Codes: H01L 29/735 Lateral transistors

Abstract

An improved base for a NPN bipolar transistor. The base region is formed with Boron and Indium dopants for improved beta early voltage product and reduced base resistance.

Claims

1. A base region for a NPN transistor, the base region comprising:

Boron dopants; and

Indium dopants, wherein the boron and indium dopants form the base region of P conductivity type;

2. The base region of claim 1, wherein the concentration of Indium dopants is greater than the concentration of Boron dopants at a base-collector junction.

3. The base region of claim 1, wherein the concentration of Boron dopants is greater than the concentration of Indium dopants at a base-emitter junction.

4. The base region of claim 1, wherein a peak concentration of the Indium dopants is formed deeper from a working surface of a substrate in which the NPN transistor is formed than a peak concentration of boron dopants is formed.

5. The base region of claim 1, wherein the Boron dopants are diffused and the Indium dopants are implanted.

6. The base region of claim 1, wherein at least one of the Boron dopants and the Indium dopants are diffused.

7. The base region of claim 1, wherein at least one of the Boron dopants and the Indium dopants are implanted.

8. The base region of claim 1, wherein base is formed by epitaxial growth.

9. The base region of claim 1 wherein the Indium to Boron ratio is selected to achieve a desired current gain temperature coefficient.

10. A NPN transistor comprising:

a collector of a N conductivity type formed in a substrate, the substrate having a working surface,

a base of a P conductivity type formed in the collector adjacent the working surface of the substrate, wherein the P conductivity type is formed with both Boron and Indium dopants; and

an emitter of the N conductivity type formed in the base adjacent the working surface of the substrate.

11. The NPN transistor of claim 10, wherein the concentration of Indium dopants is greater than the concentration of Boron dopants at a base-collector junction.

12. The NPN transistor of claim 10, wherein the concentration of Boron dopants is greater than the concentration of Indium dopants at an emitter-base junction.

13. The NPN transistor of claim 10, wherein the ratio of Boron to Indium in the base is adjusted to provide a desired beta temperature coefficient.

14. The NPN transistor of claim 10, wherein the collector is low density N conductivity type and the emitter is high density N conductivity type.

15. The NPN transistor of claim 13, further comprising:

a collector contact of the N conductivity type with high density formed in the collector a select distance from the emitter and adjacent the working surface of the substrate.

16. A base region for a NPN transistor, the base region comprising:

Boron dopants; and

Indium dopants, wherein the ratio of Indium dopants to Boron dopants is selected to create a desired current gain temperature coefficient.

17. The base region of claim 16, wherein the concentration of Boron dopants is greater than the concentration of Indium dopants adjacent an emitter-base junction to set base resistance with the Boron dopants.

18. The base region of claim 16, wherein the concentration of Indium dopants is greater than the concentration of Boron dopants adjacent a base-collector junction to achieve relatively high early voltage.

19. A method of forming a base region in an NPN transistor, the method comprising:

diffusing Boron dopants through a select region of working surface of a substrate; and

implanting Indium dopants through the select region of the working surface of the substrate.

20. The method of claim 19, wherein a peak concentration of Indium dopants are formed deeper from the working surface of the substrate than a peak concentration of the Boron dopants.

21. The method of claim 19, wherein the Boron dopants have a gaussain profile with a peak concentration approximate the working surface of the substrate.

22. The method of claim 19, wherein the location of the Indium dopants is approximately determined by implant.

23. The method of claim 19 wherein the indium dopants have approximately a Gaussian profile with the peak concentration below the working surface.

24. The method of claim 19, wherein the ratio of Boron dopants to Indium dopants is selected to achieve a desired beta temperature coefficient.

25. A method of forming a base region in an NPN transistor, the method comprising:

epitaxially growing the base region with Boron and Indium dopant profiles.

26. The method of claim 25, wherein a peak concentration of Boron dopants adjacent a base-emitter junction is grown greater than a peak concentration of Indium dopants and a peak concentration of Indium dopants at a base-collector junction is grown greater than the concentration of Boron dopants.

27. A method of forming a NPN transistor, the method comprising:

forming a collector in a substrate with N conductivity type dopants, the substrate having a working surface;

forming a base region in the collector adjacent the working surface of the substrate with P conductivity type dopants, wherein the P type conductivity type dopants are both Boron and Indium dopants; and

forming an emitter region in the base region adjacent the working surface of the substrate with the N conductivity type dopants.

28. The method of claim 27, wherein forming the Boron and Indium dopants in the base region further comprises:

diffusing the Boron dopants; and

implanting the Indium dopants.

29. The method of claim 27, wherein at least one of the Boron and Indium dopants formed in the base region further comprises:

diffusing the dopants.

30. The method of claim 27, wherein at least one of the Boron and Indium dopants formed in the base region further comprises:

implanting the dopants.

31. The method of claim 27, wherein the forming the Boron and Indium dopants in the base further comprises:

epitaxially growing the base and incorporating the Boron and Indium dopants in the base during the epitaxial growth.

32. The method of claim 27, wherein the concentration of Boron dopants adjacent a base-emitter junction is greater than the concentration of Indium dopants to set base resistance of the NPN transistor with the Boron dopants.

33. The method of claim 27, wherein the concentration of Indium dopants at a base-collector junction is greater than the concentration of Boron dopants to achieve relatively high early voltage that is set by the Indium dopants.

34. The method of claim 27, wherein a peak concentration of Indium dopants are formed deeper from the working surface of the substrate than a peak concentration of the Boron dopants.

35. The method of claim 27, wherein the Boron dopants have a gaussain profile with a peak concentration approximate the working surface of the substrate.

36. The method of claim 27, wherein the location of the Indium dopants is approximately determined by implant.

37. The method of claim 27 wherein the Indium dopants have approximately a Gaussian profile with the peak concentration below the working surface.

38. The method of claim 27, wherein the collector N conductivity type is made with a low density of dopants and the emitter N type conductivity type is made with a high density of dopants.

39. The method of claim 38, further comprising:

forming a collector contact a select distance from the emitter adjacent the working surface of the substrate, the collector contact having N conductivity type with a high density of dopants.

40. A method of forming a base region in a NPN transistor, the method comprising:

introducing a select amount of Indium dopants to the base region; and

introducing a select amount of Boron dopants to the base region, wherein the ratio of the select amount of the Indium dopants to the select amount of Boron dopants is selected to determine the beta temperature coefficient of the NPN transistor.

41. The method of claim 40, wherein introducing the Boron and Indium dopants in the base region further comprises:

diffusing the Boron dopants; and

implanting the Indium dopants.

42. The method of claim 40, wherein at least one method of introducing the Boron and Indium dopants in the base region further comprises:

diffusing the dopants.

43. The method of claim 40, wherein at least one method of introducing the Boron and Indium dopants in the base region further comprises:

implanting the dopants.

44. The method of claim 40, wherein the introducing of the Boron and Indium dopants in the base further comprises:

epitaxially growing the base and incorporating the Boron and Indium dopants in the base during the epitaxial growth.