OXYNITRIDE SHALLOW TRENCH ISOLATION AND METHOD OF FORMATION

• US 20020177270A1
• Filed: 05/23/2001
• Published: 11/28/2002
• Est. Priority Date: 05/23/2001
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Varekamp, Patrick R., Jamin, Fen F., Beyer, Klaus D.
• Granted Patent: US 6,498,383 B2
• Time in Patent Office: Days
• US Class Current: 438/221
• CPC Class Codes: H01L 21/76224 using trench refilling with dielectric materials trench filling with polycristalline silicon H01L21/763; together with vertical isolation, e.g. trench refilling in a SOI substrate H01L21/76264

Abstract

An oxynitride material is used to form shallow trench isolation regions in an integrated circuit structure. The oxynitride may be used for both the trench liner and trench fill material. The oxynitride liner is formed by nitriding an initially formed oxide trench liner. The oxynitride trench fill material is formed by directly depositing a high density plasma (HDP) oxide mixture of SiH₄ and O₂ and adding a controlled amount of NH₃ to the plasma mixture. The resultant oxynitride structure is much more resistant to trench fill erosion by wet etch, for example, yet results in minimal stress to the surrounding silicon. To further reduce stress, the nitrogen concentration may be varied by varying the proportion of O₂ to NH₃ in the plasma mixture so that the nitrogen concentration is maximum at the top of the fill material.

Claims

1. A method for forming a semiconductor structure, comprising the steps of:

providing a substrate;

forming a trench region within said substrate;

forming a trench liner region within said trench region; and

directly filling said trench region with an oxynitride material formed from the deposition of a fill material containing oxygen and nitrogen.

2. The method as set forth in claim 1 wherein said step of directly filling comprises directly filling said trench region using a dense plasma oxide containing a controlled amount of said nitrogen.

3. The method as set forth in claim 2 wherein said nitrogen is in the form of a gas.

4. The method as set forth in claim 3 wherein said gas is NH₃ and the rage of flow ratios of NH₃ to oxygen in said plasma mixture is 0.1 to 10.

5. The method as set forth in claim 4 wherein said ratio is varied to increase the nitrogen concentration is said plasma as the trench is filled with said oxynitride.

6. The method as set forth in claim 5 wherein said ratio is varied to increase the nitrogen concentration at the top portion of said trench.

7. The method as set forth in claim 6 wherein said step of forming a trench liner region comprises the steps of forming an oxide trench liner region and then nitriding said oxide trench liner region to form as oxynitride trench liner region.

8. The method as set forth in claim 7 wherein said step of nitriding the oxide trench liner region comprises annealing said oxide trench liner region in a nitrogen containing ambient.

9. The method as set forth in claim 7 wherein said step of nitriding the oxide trench liner comprises nitriding by plasma nitridation.

10. The method as set forth in claim 7 wherein said step of nitriding the oxide trench liner region includes nitriding said oxide trench liner so as to form a higher nitrogen concentration in said liner region at the top of the trench sidewall than the nitrogen concentration in said liner region at the lower portion of said trench sidewall.

11. The method as set forth in claim 10 wherein said higher nitrogen concentration is formed by ion implant.

12. The method as set forth in claim 4 including the further steps of etching back said oxynitride material to form an oxynitride trench plug and then nitriding a layer of up to 50 Å

at the exposed surface of said oxynitride trench plug.

13. The method as set forth in claim 12 including the further step of ion implanting nitrogen below said layer of nitriding at the exposed surface of said oxynitride trench plug.

15. The method as set forth in claim 14 wherein said step of filling said trench region with an oxynitride material comprises filling said trench region using a high density plasma oxide mixture including nitrogen.

16. The method as set forth in claim 15 wherein the amount of said nitrogen in said plasma oxide mixture is varied during the filling of said trench region.

17. The method as set forth in claim 16 wherein the said nitrogen in said plasma oxide mixture is increased during the filling of said trench so that the nitrogen concentration in said oxynitride material is higher at the top of said trench region.

18. The method as set forth in claim 17 wherein said plasma oxide mixture including nitrogen is formed from a mixture of SiH₄ and O₂ with a controlled amount of NH₃ added thereto.

19. The method as set forth in claim 18 wherein the proportion of NH₃ to O₂ in said plasma is in the range of 0.1 to 10.

20. The method as set forth in claim 19 wherein said step of nitriding said oxide liner to form an oxynitride liner includes nitriding by annealing in a nitrogen containing ambient.

21. The method as set forth in claim 19 wherein said step of nitriding said oxide liner to form an oxynitride liner includes nitriding by plasma nitridation.

22. The method as set forth in claim 19 wherein said step of nitriding said oxide liner to form an oxynitride liner includes nitriding said oxide liner with a greater concentration of nitrogen at the top portion of the sidewall of said trench.

23. The method as set forth in claim 22 wherein said step of nitriding said oxide liner with a greater concentration of nitrogen at the top of the said sidewall of said trench includes nitriding by ion implant.

24. The method as set forth in claim 23 comprising the further steps of etching said oxynitride material to form an oxynitride trench plug the top surface of which extends above the surface of said substrate and then nitriding the top surface of said oxynitride trench plug.

25. The method as set forth in claim 24 wherein at least the sidewall portions of said oxynitride trench plug extending above the said surface of said substrate are nitrided.

26. The method as set forth in claim 25 wherein said sidewall portions are nitrided by ion implant.

14. A method of forming an isolation structure for a semiconductor device, comprising the steps of:

forming a trench region within a semiconductor substrate;

forming an oxide liner within said trench region;

nitriding said oxide liner to form an oxynitride liner within said trench region; and

directly filling said trench region with an oxynitride material formed from the deposition of a fill material including oxygen and nitrogen.

27. A method of forming an isolation structure for a semiconductor device, comprising:

forming a trench region within a semiconductor substrate;

forming an oxide liner within said trench region;

nitriding said oxide liner to form an oxynitride liner within said trench region; and

filling said trench region with an oxynitride material with the concentration of nitrogen within said oxynitride material being greater toward the top portion of said trench than toward the bottom portion of said trench.

28. A method of forming an isolation structure for a semiconductor device, comprising:

forming a trench region within a semiconductor substrate;

forming an oxide liner within said trench region;

nitriding said oxide liner to form an oxynitride liner within said trench region;

directly filling said trench region with an oxynitride filler material using a plasma mixture including O₂ and a controlled amount of NH₃;

removing the top portion of said oxynitride filler material to form an oxynitride trench plug; and

plasma nitriding said oxynitride trench plug to form additional nitrogen concentration at the top surface of said plug.

29. A method of forming an isolation structure for a semiconductor device, comprising:

forming a trench region within a semiconductor substrate;

forming an oxide liner within said trench region;

nitriding said oxide liner to form an oxynitride liner within said trench region;

directly filling said trench region with an oxynitride material using a plasma mixture including O₂ and a controlled amount of NH₃;

varying the ratio of NH₃ to O₂ so that the nitrogen concentration increases as said trench fills with said oxynitride material;

removing the top portion of said oxynitride filler material to form an oxynitride trench plug; and

plasma nitriding said oxynitride trench plug to form additional nitrogen concentration within the top 50 Å

of said plug.

30. A semiconductor device trench isolation structure, comprising a substrate having a trench region filled with an oxynitride material to form an oxynitride trench plug with the nitrogen concentration of said oxynitride material being greater at the top portion of said trench plug than at the bottom portion of said trench plug.

31. The trench isolation structure as set forth in claim 30 wherein the said nitrogen concentration of said oxynitride material is graded so that the nitrogen concentration increases from the bottom of said trench plug to the top of said trench plug.

32. The trench isolation structure as set forth in claim 30 wherein said trench region includes an oxynitride liner lining the walls of said trench region with the sidewalls of said oxynitride liner at the top portion of said trench region having a nitrogen concentration greater than the nitrogen concentration in the sidewalls of said oxynitride liner at the lower portion of said trench region.

33. The trench isolation structure as set forth in claim 32 wherein the nitrogen concentration within the top 50 Å

of the sidewalls said oxynitride trench plug is higher than the nitrogen concentration below the said top 50 Å

of the sidewalls of said oxynitride trench plug.

34. The trench isolation structure as set forth in claim 33 wherein said oxynitride trench plug extends above the surface of said substrate and wherein at least the portion of said trench plug extending above the surface of said substrate has a nitrogen concentration greater than the portion of said trench plug extending below the surface of said substrate.

35. The trench isolation structure as set forth in claim 33 wherein said oxynitride trench plug extends above the surface of said substrate and wherein the sidewall portions of said trench plug extending above the surface of said substrate have a nitrogen concentration greater than the interior portions of said trench plug.

36. A semiconductor device trench isolation structure, comprising:

a substrate having a trench region lined with an oxynitride liner and with the oxynitride lined trench region filled with an oxynitride fill material to form an oxynitride trench plug with the concentration of said trench plug being greater at the top portion of said trench plug than at the bottom portion of said trench plug.

37. A semiconductor device trench isolation structure, comprising a substrate having a trench region lined with an oxynitride liner with the portion of the sidewalls of said oxynitride liner at the top of said trench region having a nitrogen concentration greater than the nitrogen concentration of the sidewalls in the lower portion of said trench region, and with said trench region lined therein with said oxynitride liner filled with an oxynitride fill material to form an oxynitride trench plug with the nitrogen concentration of said oxynitride fill material being greater at the top portion of said oxynitride trench plug than at the bottom portion of said oxynitride trench plug.

38. A semiconductor device trench isolation structure, comprising a substrate having a trench region lined with an oxynitride liner with at least 500 Å

of the sidewall of said oxynitride liner immediately below the surface of said substrate having a nitrogen concentration greater than the nitrogen concentration of the sidewalls of said liner in the lower portion of said trench, and with said trench region lined therein with said oxynitride liner filled with an oxynitride fill material to form an oxynitride trench plug with the nitrogen concentration of said oxynitride fill material being greater at the top portion of said oxynitride trench plug than at the bottom portion of said oxynitride trench plug.

39. A semiconductor device trench isolation structure, comprising a substrate having a trench region lined with an oxynitride liner with at least 500 Å

of the sidewall of said oxynitride liner immediately below the surface of said substrate having a nitrogen concentration greater than the nitrogen concentration of the sidewalls of said liner in the lower portion of said trench, and with said trench region lined therein with said oxynitride liner filled with an oxynitride fill material to form an oxynitride trench plug with the nitrogen concentration of said oxynitride fill material being greater within 50 Å

of the top surface of said trench plug.