Shallow trench isolation process

• US 6,750,117 B1
• Filed: 12/23/2002
• Issued: 06/15/2004
• Est. Priority Date: 12/23/2002
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Hung, Yung-Tai, Chen, Lee-Jen
• Primary Examiner(s): FOURSON III, GEORGE R
• Application Number:
  US10/248,164
• Publication Number:
  US 20040121555A1
• Time in Patent Office: 540 Days
• Field of Search: 438/437, 257/E21.546
• US Class Current: 438/437
• CPC Class Codes: H01L 21/76235 trench shape altered by a local oxidation of silicon process step, e.g. trench corner rounding by LOCOS

Abstract

A shallow trench isolation (STI) process is described. A patterned mask layer is formed on a substrate, and then a trench is formed in the substrate with the mask layer as a mask. A portion of the mask layer around the trench is removed, and a portion of the substrate around the top portion of the trench is removed with the remaining mask layer as a mask. A liner layer is formed in the trench. The liner layer on the top portion of the trench is then removed with a pre-deposition process of an HDP-CVD process. Thereafter, an insulating material is filled into the trench, and the mask layer is removed with an etchant. In STI process, the liner layer comprises a material that can also be etched by the etchant.

Claims

1. A shallow trench isolation (STI) process, comprising:

forming a patterned mask layer on a substrate;

forming a trench in the substrate with the mask layer as a mask;

removing a portion of the mask layer around the trench;

removing a portion of the substrate around a top portion of the trench with the remaining mask layer as a mask;

forming a liner layer in the trench;

removing the liner layer on the top portion of the trench;

filling an insulating material into the trench covering the liner layer remaining in the trench; and

removing the mask layer with an etchant, wherein

the liner layer comprises a material that can also be etched by the etchant.

2. The method of claim 1, wherein removing the liner layer on the top portion of the trench comprises performing a pre-deposition process of a high-density plasma chemical vapor deposition (HDP-CVD) process.

3. The method of claim 2, wherein the insulating material is filled with the same HDP-CVD process after the pre-deposition process.

4. The method of claim 2, wherein reaction gases used in the pre-deposition process of the HDP-CVD process comprise O₂, He and SiH₄.

5. The method of claim 4, wherein a flow rate of O₂ is 215 sccm, a flow rate of He is 155 sccm, and a flow rate of SiH₄ is 147 sccm.

6. The method of claim 2, wherein the pre-deposition process of the HDP-CVD process is conducted under a low frequency power of 4000 W and a high frequency power of 2400 W.

7. The method of claim 1, wherein the liner layer comprises a material capable of reducing stress in the substrate around the trench.

8. The method of claim 1, wherein the mask layer and the liner layer both comprise silicon nitride.

9. The method of claim 8, further comprising forming a pad oxide layer before the mask layer is formed.

10. The method of claim 8, wherein the mask layer is removed by using an etchant comprising hot phosphoric acid.

11. The method of claim 1, further comprising forming a silicon oxide liner layer in the trench before the step of forming the liner layer in the trench.

12. The method of claim 11, wherein the silicon oxide liner layer is formed with a thermal oxidation process.

13. The method of claim 1, further comprising forming a silicon oxide liner layer on the liner layer.

14. The method of claim 1, wherein removing a portion of the mask layer around the trench comprises performing an isotropic etching process.

15. The method of claim 1, wherein the insulating material comprises silicon oxide.

16. A shallow trench isolation (STI) process, comprising:

forming a mask layer on a substrate;

forming a trench-like opening in the mask layer;

forming spacers on sidewalls of the trench-like opening;

forming a trench in the substrate with the mask layer and the spacers as a mask;

forming a thermal oxide layer on surfaces of the trench with a thermal oxidation process, such that bird'"'"'s beaks are formed under the spacers;

forming a liner layer in the trench;

removing the liner layer on a top portion of the trench;

filling an insulating material into the trench covering the liner layer remaining in the trench; and

removing the mask layer with an etchant, wherein

the liner layer comprises a material that can also be etched by the etchant.

17. The method of claim 16, wherein removing the liner layer on the top portion of the trench comprises performing a pre-deposition process of an HDP-CVD process.

18. The method of claim 17, wherein the insulating material is filled with the same HDP-CVD process after the pre-deposition process.

19. The method of claim 17, wherein reaction gases of pre-deposition process of the HDP-CVD process comprise O₂, He and SiH₄.

20. The method of claim 19, wherein a flow rate of O₂ is 215 sccm, a flow rate of He is 155 sccm, and a flow rate of SiH₄ is 147 sccm.

21. The method of claim 17, wherein the pre-deposition process of the HDP-CVD process is conducted under a low frequency power of 4000 W and a high frequency power of 2400 W.

22. The method of claim 16, wherein the liner layer comprises a material capable of reducing stress in the substrate around the trench.

23. The method of claim 16, wherein the mask layer and the liner layer both comprise silicon nitride.

24. The method of claim 23, wherein the mask layer is removed by using an etchant comprising hot phosphoric acid.

25. The method of claim 16, further comprising forming a silicon oxide liner layer on the liner layer.

26. The method of claim 16, wherein the insulating material comprises silicon oxide.