Dry etching of silicon carbide

• US 4,865,685 A
• Filed: 11/03/1987
• Issued: 09/12/1989
• Est. Priority Date: 11/03/1987
• Status: Expired due to Term

• Current Assignee: North Carolina State University (University of North Carolina System)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Palmour, John W.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/116,467
• Time in Patent Office: 679 Days
• Field of Search: 156/643, 156/646, 156/657, 156/659.1, 156/662, 204/192.32, 204/192.37, 427/38, 427/39, 252/79.1, 437/228, 437/234
• US Class Current: 438/718
• CPC Class Codes: H01L 21/0475 Changing the shape of the semiconductor body, e.g. forming recesses, etching of the semiconductor body H01L21/302
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: Y10S 438/931 Silicon carbide semiconductor

Abstract

The invention comprises a method of etching silicon carbide targets. In one embodiment, a reactive ion plasma is formed from a gas which is easily dissociated into its elemental species in the plasma, for which all of the dissociated elemental species are volatile in the plasma, and for which at least one of the elemental species is reactive with silicon carbide. The silicon carbide target to be etched is positioned on one of the electrodes which is formed from a material with a low sputter yield and which material reacts with a dissociated species to thereby prevent contamination of the target with either sputtered materials from the electrode or polymerized species from the plasma.

Claims

1. A method of etching a silicon carbide target, the method comprising:

applying a plasma generating potential across two electrodes;

generating a plasma between the two electrodes by introducing a gas between the electrodes, and wherein the gas is easily dissociated substantially into its elemental species in the plasma and wherein substantially all of the dissociated species from the gas are volatile in the plasma and wherein at least one of the dissociated species is reactive with silicon carbide; and

positioning a silicon carbide target to be etched on one of the electrodes, and wherein the electrode is formed from a material with a low sputter yield and wherein the electrode material is reactive with the dissociated species; and

reacting the plasma with the silicon carbide to thereby etch the silicon carbide while the reaction of the dissociated species with the electrode, and the electrode'"'"'s low sputter yield prevents contamination of the target with either sputtered materials from the supporting electrode or unreacted dissociated species from the plasma.

2. A method according to claim 1 wherein the step of generating a plasma comprises forming a reactive ion plasma from nitrogen trifluoride.

3. A method according to claim 2 wherein the step of generating a reactive ion plasma comprises applying a direct current bias to the plasma.

4. A method according to claim 1 wherein the step of positioning a silicon carbide target on one of the electrodes comprises positioning the silicon carbide target on the cathode.

5. A method according to claim 4 wherein the step of positioning the silicon carbide target on the cathode comprises positioning the silicon carbide target on a carbon cathode.

6. A method according to claim 1 wherein the step of positioning a silicon carbide target comprises positioning a silicon carbide thin film.

7. A method according to claim 6 wherein the step of positioning a silicon carbide thin film comprises positioning a thin film of beta silicon carbide.

8. A method according to claim 6 wherein the step of positioning a silicon carbide thin film comprises positioning a thin film of alpha silicon carbide.

9. A method according to claim 1 wherein the step of applying a plasma generating potential comprises applying between about 10 and about 400 watts of power to the electrodes.

10. A method according to claim 1 wherein the step of applying a plasma generating potential comprises applying a power density of between about 0.04 and about 2 watts per square centimeter to the powered electrode.

11. A method according to claim 1 wherein the step of applying a plasma generating potential comprises applying a power density of between about 0.4 and about 0.9 watts per square centimeter to the powered electrode.

12. A method according to claim 1 wherein the step of introducing a gas between the electrodes comprises introducing the gas at a pressure of between about 5 milliTorr and about 10 Torr.

13. A method according to claim 1 wherein the step of introducing a gas between the electrodes comprises introducing the gas at a pressure of about 40 milliTorr.

14. A method according to claim 1 wherein the step of introducing a gas comprises introducing a gas at a flow rate of between about 1 and about 500 standard cubic centimeters per minute.

15. A method according to claim 1 wherein the step of introducing a gas comprises introducing a gas at a flow rate of between about 20 and about 60 standard cubic centimeters per minute.

16. A method according to claim 1 wherein the step of introducing a gas comprises introducing a gas at a flow rate of about 25 standard cubic centimeters per minute.

17. A method according to claim 1 wherein the step of introducing a gas comprises introducing a mixture of nitrogen trifluoride and oxygen.

18. A method according to claim 1 wherein the step of introducing a gas comprises introducing a mixture of nitrogen trifluoride and argon.

19. A method according to claim 1 wherein the step of introducing a gas comprises introducing a mixture of nitrogen trifluoride, oxygen and argon.

20. A method of etching of a silicon carbide target comprising:

applying a plasma generating potential across an anode and a carbon cathode;

generating a plasma between the anode and the carbon cathode by introducing nitrogen trifluoride therebetween;

positioning a silicon carbide target to be etched on the carbon cathode whereby the carbon cathode exhibits a low sputter yield and is reactive with dissociated fluorine from the nitrogen trifluoride; and

reacting the plasma with the silicon carbide to thereby etch the silicon carbide while the reaction of dissociated fluorine with the carbon cathode, and the cathode'"'"'s low sputter yield prevents contamination of the target with either sputtered carbon materials from the cathode or polymerized fluorine species from the plasma.

21. A method according to claim 20 wherein the step of positioning a silicon carbide target comprises positioning a doped silcon carbide target.

22. A method according to claim 21 wherein the step of positioning a doped silicon carbide target comprises positioning a doped beta silicon carbide target.

23. A method according to claim 21 wherein the step of positioning a doped silicon carbide target comprises positioning a doped alpha silicon carbide target.

24. A method according to claim 20 wherein the step of generating a plasma further comprises applying a direct current bias to the plasma.

25. A method of reactive ion beam etching of a silicon carbide target comprising:

applying a plasma generating potential and a direct current bias across two electrodes positioned in a source chamber;

generating a reactive ion plasma between the two electrodes in the source chamber by introducing a gas which is easily dissociated into its elemental species in the plasma and wherein substantially all of the dissociated species are volatile in the plasma and wherein at least one of the species is reactive with silicon carbide;

positioning a silicon carbide target in a target chamber on a support formed from a material with a low sputter yield and wherein the material reacts with the elemental species in the plasma to thereby prevent contamination of the target with either sputtered materials from the support or polymerized species from the plasma, and wherein the target chamber is in communication with the source chamber; and

applying a negative bias to the target so that a reactive ion plasma beam is directed from the source chamber to the target chamber to thereby etch the silicon carbide target.

26. A method according to claim 25 wherein the step of introducing a gas comprises introducing nitrogen trifluoride.

27. A method according to claim 25 wherein the step of positioning a silicon carbide target comprises positioning the silicon carbide target on a carbon support.

28. A method according to claim 25 further comprising maintaining the target chamber at a lesser pressure than the source chamber.

29. A method of patterning silicon carbide in the formation of electronic devices using reactive ion etching, the method comprising

forming a masked pattern on a silicon carbide substrate;

positioning the masked silicon carbide substrate as a target on a cathode in a reactive ion plasma system having an anode opposite the cathode; and

applying a plasma generating potential and a direct current bias across the anode and cathode in the reactive ion system;

generating plasma in the system by introducing a gas which is easily dissociated in the plasma and wherein substantially all of the dissociated species are volatile in the plasma and wherein at least one of the dissociated species is reactive with silicon carbide;

wherein the cathode is formed from a material with a low sputter yield and wherein the material reacts with the dissociated species in the plasma to thereby prevent contamination of the target with either sputtered materials from the cathode or polymerized species from the plasma; and

reacting the plasma with the silicon carbide substrate to thereby etch the silicon carbide.

30. A method according to claim 29 further comprising the step of removing the mask from the silicon carbide substrate following the step of reacting the plasma with the silicon carbide.

31. A method according to claim 29 wherein the step of introducing a gas comprises introducing nitrogen trifluoride.

32. A method according to claim 29 wherein the step of positioning the silicon carbide masked substrate on the cathode comprises positioning the masked silicon carbide substrate on a carbon cathode.