Silicon carbide switching devices having near ideal breakdown voltage capability and ultralow on-state resistance

• US 5,742,076 A
• Filed: 06/05/1996
• Issued: 04/21/1998
• Est. Priority Date: 06/05/1996
• Status: Expired due to Term

• Current Assignee: Intellectual Ventures Holding 81 LLC (Intellectual Ventures LLC)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Baliga, Bantval Jayant, McLarty, Peter Kerr, Sridevan, Srikant
• Primary Examiner(s): JACKSON JR, JEROME
• Application Number:
  US08/658,733
• Time in Patent Office: 685 Days
• Field of Search: 257/77, 257/78, 257/295, 257/289, 257/331, 257/341, 257/410
• US Class Current: 257/77
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/517 the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A silicon carbide switching device having near ideal electrical characteristics includes an electrical insulator with an electrical permittivity greater than about ten times the permittivity of free space (ε_o) and more preferably greater than about fifteen times the permittivity of free space, as a gate electrode insulating region. The use of electrical insulators having high electrical permittivities relative to conventional electrical insulators such as silicon dioxide significantly improves the breakdown voltage and on-state resistance characteristics of a silicon carbide switching device to the point of near ideal characteristics, as predicted by theoretical analysis. Thus, the preferred advantages of using silicon carbide, instead of silicon, can be more fully realized. Electrical insulators having low critical electric field strengths relative to conventional electrical insulators such as silicon dioxide can also be used even though these insulators are relatively more susceptible to field induced dielectric breakdown for a given electric field strength. Such electrical insulators include titanium dioxide.

Claims

1. A silicon carbide switching device, comprising:

a silicon carbide substrate having first and second opposing faces;

a silicon carbide drift region of first conductivity type in said silicon carbide substrate;

a silicon carbide base region of second conductivity type in said silicon carbide substrate, said silicon carbide base region forming a P-N rectifying junction with said silicon carbide drift region;

a silicon carbide source region of first conductivity type in said silicon carbide substrate, said silicon carbide source region forming a P-N rectifying junction with said silicon carbide base region;

a trench in said silicon carbide substrate, said trench having a bottom extending adjacent said silicon carbide drift region and a sidewall extending from said silicon carbide drift region, adjacent said silicon carbide base region and to the first face;

a gate electrode in said trench for modulating the conductivity of said silicon carbide base region upon application of a gate bias thereto;

a first electrode on the first face and ohmically contacting said silicon carbide source region;

a second electrode on the second face and ohmically contacting said silicon carbide substrate; and

a gate electrode insulating region disposed in said trench, between said gate electrode and said silicon carbide drift and base regions, said gate electrode insulating region comprising a material selected from the group consisting of electrical insulators having electrical permittivities greater than about ten times the permittivity of free space.

2. The silicon carbide switching device of claim 1, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

3. The silicon carbide switching device of claim 1, wherein said gate electrode insulating region comprises titanium dioxide.

4. The silicon carbide switching device of claim 2, wherein said gate electrode insulating region comprises titanium dioxide.

5. The silicon carbide switching device of claim 2, wherein said silicon carbide substrate comprises 4H--SiC.

6. The silicon carbide switching device of claim 2, wherein said drift region has a first conductivity type doping concentration greater than 2×

10¹⁶ cm^-3.

7. The silicon carbide switching device of claim 6, wherein said base region has a second conductivity type doping concentration greater than 5×

10¹⁷ cm^-3.

9. A silicon carbide switching device, comprising:

a silicon carbide substrate;

a silicon carbide drift region of first conductivity type in said silicon carbide substrate;

a silicon carbide base region of second conductivity type in said silicon carbide substrate, said silicon carbide base region forming a P-N rectifying junction with said silicon carbide drift region;

a silicon carbide source region of first conductivity type in said silicon carbide substrate, said silicon carbide source region forming a P-N rectifying junction with said silicon carbide base region;

gate electrode means, disposed adjacent said silicon carbide base region, for modulating the conductivity of said silicon carbide base region upon the application of a gate bias thereto;

a first electrode on said silicon carbide substrate;

a second electrode on said silicon carbide substrate; and

a gate electrode insulating region disposed between said gate electrode means and said silicon carbide base region, said gate electrode insulating region comprising a material selected from the group consisting of electrical insulators having electrical permittivities greater than about ten times the permittivity of free space (ε

_o).

10. The silicon carbide switching device of claim 9, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

11. The silicon carbide switching device of claim 9, wherein said gate electrode insulating region comprises titanium dioxide.

12. The silicon carbide switching device of claim 10, wherein said gate electrode insulating region comprises titanium dioxide.

13. The silicon carbide switching device of claim 9, further comprising a trench having a sidewall extending adjacent said silicon carbide base region.

14. A silicon carbide switching device, comprising:

a silicon carbide substrate having first and second opposing faces;

a silicon carbide drift region of first conductivity type in said silicon carbide substrate;

a silicon carbide base region in said silicon carbide substrate, between said silicon carbide drift region and the first face;

a trench in said silicon carbide substrate, said trench having a bottom extending adjacent said silicon carbide drift region and a sidewall extending from said silicon carbide drift region, adjacent said silicon carbide base region and to the first face;

a gate electrode in said trench for modulating the conductivity of said silicon carbide base region upon the application of a gate bias thereto;

a first electrode on the first face and ohmically contacting said silicon carbide substrate;

second electrode on the second face and ohmically contacting said silicon carbide substrate; and

a gate electrode insulating region disposed in said trench, between said gate electrode and said silicon carbide drift and base regions, said gate electrode insulating region comprising a material selected from the group consisting of electrical insulators having dielectric constants greater than the dielectric constant of silicon dioxide.

8. The silicon carbide switching device of claim 14, wherein said base region comprises a layer having a thickness of less than about 0.6 μ

m.

15. The silicon carbide switching device of claim 14, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

16. The silicon carbide switching device of claim 14, wherein said drift region has a first conductivity type doping concentration greater than 2×

10¹⁶ cm^-3.

17. The silicon carbide switching device of claim 16, wherein said base region is of second conductivity type and has a second conductivity type doping concentration greater than 5×

10¹⁷ cm^-3.

18. The silicon carbide switching device of claim 17, further comprising a silicon carbide source region of first conductivity type disposed between said silicon carbide base region and the first face and wherein said base region comprises a layer having a thickness of less than about 0.6 μ

m.

19. A silicon carbide switching device, comprising:

a silicon carbide substrate having first and second opposing faces;

a silicon carbide drift region of first conductivity type in said silicon carbide substrate;

a silicon carbide base region of second conductivity type in said silicon carbide substrate, said silicon carbide base region forming a P-N rectifying junction with said silicon carbide drift region;

a silicon carbide source region of first conductivity type in said silicon carbide substrate, said silicon carbide source region forming a P-N rectifying junction with said silicon carbide base region;

a trench in said silicon carbide substrate, said trench having a bottom extending adjacent said silicon carbide drift region and a sidewall extending from said silicon carbide drift region, adjacent said silicon carbide base region and to the first face;

a gate electrode in said trench for modulating the conductivity of said silicon carbide base region upon the application of a gate bias thereto;

a first electrode on the first face and ohmically contacting said silicon carbide source region;

a second electrode on the second face and ohmically contacting said silicon carbide substrate; and

a gate electrode insulating region comprising titanium dioxide, said gate electrode insulating region extending between said gate electrode and said silicon carbide drift and base regions.

20. The silicon carbide switching device of claim 19, wherein said gate electrode insulating region has an effective permittivity in a range between about fifteen and eighty times a permittivity of free space.

21. The silicon carbide switching device of claim 19, wherein a critical electrical field strength of said gate electrode insulating region is less than a critical electrical field strength of silicon dioxide.

22. The silicon carbide switching device of claim 20, wherein a critical electrical field strength of said gate electrode insulating region is less than a critical electrical field strength of silicon dioxide.

23. A silicon carbide field effect transistor, comprising:

a silicon carbide substrate having first and second opposing faces;

a silicon carbide drift region of first conductivity type in said silicon carbide substrate;

a silicon carbide base region of first conductivity type in said silicon carbide substrate;

a silicon carbide source region of first conductivity type in said silicon carbide substrate, said silicon carbide source region having a doping concentration greater than a doping concentration of said silicon carbide base region;

a trench in said silicon carbide substrate, said trench having a bottom extending adjacent said silicon carbide drift region and a sidewall extending from said silicon carbide drift region, adjacent said silicon carbide base region and to the first face;

a gate electrode in said trench for modulating the conductivity of said silicon carbide base region upon the application of a gate bias thereto;

a first electrode on the first face and ohmically contacting said silicon carbide source region;

a second electrode on the second face and ohmically contacting said silicon carbide substrate; and

a gate electrode insulating region disposed in said trench, between said gate electrode and said silicon carbide drift and base regions, said gate electrode insulating region comprising a material selected from the group consisting of electrical insulators having electrical permittivities greater than about ten times the permittivity of free space.

24. The silicon carbide switching device of claim 23, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

25. The silicon carbide switching device of claim 23, wherein said gate electrode insulating region comprises titanium dioxide.

26. The silicon carbide switching device of claim 24, wherein said gate electrode insulating region comprises titanium dioxide.

27. The silicon carbide switching device of claim 24, wherein said silicon carbide substrate comprises 4H--SiC.

28. A silicon carbide power semiconductor device, comprising:

a silicon carbide substrate; and

an insulated gate power semiconductor device in said silicon carbide substrate, said insulated gate power semiconductor device including a gate electrode, a silicon carbide drift region of first conductivity type, a silicon carbide base region of second conductivity type adjacent said drift region and a gate electrode insulating region disposed between said gate electrode and said base and drift regions, said gate electrode insulating region selected from the group consisting of electrical insulators having electrical permittivities greater than about ten times the permittivity of free space.

29. The silicon carbide power semiconductor device of claim 28, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

30. A silicon carbide power semiconductor device, comprising:

a silicon carbide substrate; and

an insulated gate power semiconductor device in said silicon carbide substrate, said insulated gate power semiconductor device including a silicon carbide drift region with a first conductivity type doping concentration therein and a gate electrode insulating region selected from the group consisting of electrical insulators having dielectric constants greater than about 9.75×

10^-3 N_dr⁰.131 ε

_SiC, where ε

_SiC and N_D are the dielectric constant and first conductivity type doping concentration of the silicon carbide drift region, respectively, and where N_D is greater than about 2×

10¹⁶ cm^-3.

31. The silicon carbide power semiconductor device of claim 30, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.

32. The silicon carbide power semiconductor device of claim 30, wherein said insulated gate power semiconductor device includes a trench in said silicon carbide drift region, extending to a face of said silicon carbide substrate, wherein said gate electrode insulating region extends in said trench and adjacent a bottom thereof and wherein N_D is greater than about 4×

10¹⁶ cm^-3 adjacent the bottom of said trench.

33. A power semiconductor device, comprising:

a wide bandgap semiconductor substrate; and

an insulated gate power semiconductor device in said wide bandgap semiconductor substrate, said insulated gate power semiconductor device including a gate electrode, a wide bandgap semiconductor drift region of first conductivity type, a wide bandgap semiconductor base region of second conductivity type adjacent said drift region and a gate electrode insulating region disposed between said gate electrode and said base and drift regions, said gate electrode insulating region selected from the group consisting of electrical insulators having electrical permittivities greater than about ten times the permittivity of free space.

34. The power semiconductor device of claim 33, wherein said gate electrode insulating region comprises a material having a critical electric field strength which is less than a critical electric field strength of silicon dioxide.