METHODS FOR FABRICATING BULK FINFET DEVICES HAVING DEEP TRENCH ISOLATION

• US 20110045648A1
• Filed: 08/20/2009
• Published: 02/24/2011
• Est. Priority Date: 08/20/2009
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: GlobalFoundries, Inc.
• Inventors: JOHNSON, Frank Scott, KNORR, Andreas
• Granted Patent: US 8,039,326 B2
• Time in Patent Office: Days
• US Class Current: 438/296
• CPC Class Codes: H01L 21/76232 of trenches having a shape other than rectangular or V-shape, e.g. rounded corners, oblique or rounded trench walls H01L21/76229 takes precedence
• CPC Class Codes: H01L 29/66795 with a horizontal current flow in a vertical sidewall of a semiconductor body, e.g. FinFET, MuGFET
• CPC Class Codes: H01L 29/7851 with the body tied to the substrate

Abstract

Methods are provided for fabricating Bulk FinFET devices having deep trench isolation. One or more deep isolation trenches are formed in a bulk silicon wafer. Mandrel-forming material is deposited overlying the bulk silicon wafer and dielectric pad layer thereon and simultaneously into the trench(es) as filler material. Mandrels are formed, overetching thereof creating a recess at the trench upper end. A conformal sidewall spacer material from which sidewall spacers are fabricated is deposited overlying the mandrels and into the recess forming a spacer overlying the filler material in the trench(es). Mandrels are removed using the spacer as an etch stop. Fin structures are formed from the bulk silicon wafer using the sidewall spacers as an etch mask. The mandrel-forming material is amorphous and/or polycrystalline silicon.

Claims

1. A method for fabricating a bulk FinFET device having deep trench isolation comprising the steps of:

forming one or more deep isolation trenches in a bulk silicon wafer;

depositing a mandrel-forming material on the bulk silicon wafer, the mandrel-forming material also substantially filling the one or more deep isolation trenches as filler material, wherein the mandrel-forming material comprises at least one of amorphous and polycrystalline silicon;

fabricating a plurality of mandrels from the mandrel-forming material and overetching the mandrel-forming material at an upper end of the one or more deep isolation trenches to form a recess;

depositing a sidewall spacer material overlying the plurality of mandrels and into the recess to form a spacer therein;

fabricating sidewall spacers from the sidewall spacer material, the sidewall spacers adjacent sidewalls of the plurality of mandrels;

removing the plurality of mandrels using the spacer as an etch stop;

etching the bulk silicon wafer to form a plurality of fin structures therefrom using the sidewall spacers as an etch mask.

2. The method of claim 1, wherein the step of forming one or more deep isolation trenches comprises forming one or more deep isolation trenches with an aspect ratio of from about 12:

1 to about 3;

1.

3. The method of claim 1, wherein the step of depositing mandrel-forming material on the bulk silicon wafer comprises simultaneously filling the one or more deep isolation trenches.

4. The method of claim 1, wherein the step of substantially filling the one or more deep isolation trenches precedes the step of depositing mandrel-forming material on the bulk silicon wafer.

5. The method of claim 1, further comprising the steps of:

forming a source electrode adjacent a first end of each of the fin structures and a drain electrode adjacent a second end of each of the fin structures with deep trench isolation in the bulk silicon wafer separating unrelated source and drain electrodes; and

forming a gate over the plurality of fin structures.

6. The method of claim 1, wherein the step of depositing the sidewall spacer material into the recess to form the spacer comprises depositing sidewall spacer material overlying the filler material in the one or more deep isolation trenches.

7. The method of claim 1, wherein the step of forming one or more deep isolation trenches in the bulk silicon wafer further comprises the step of forming a trench liner in the one or more deep isolation trenches, the trench liner comprised of a material having a lower etch rate than the mandrel-forming material.

8. The method of claim 1, wherein the step of depositing the sidewall spacer material comprises depositing silicon nitride.

9. A method, comprising:

forming one or more deep isolation trenches in a bulk silicon wafer having a silicon oxide pad layer thereon;

forming an insulating trench liner in the one or more deep isolation trenches;

depositing a mandrel-forming material overlying the silicon oxide pad layer, the mandrel-forming material simultaneously substantially filling the one or more deep isolation trenches, wherein the mandrel-forming material comprises at least one of amorphous and polycrystalline silicon;

fabricating a plurality of mandrels from the mandrel-forming material and overetching the mandrel-forming material at an upper end of the one or more deep isolation trenches to form a recess therein;

depositing a conformal sidewall spacer material overlying the plurality of mandrels and filling the recess at the upper end of the one or more deep isolation trenches to form a spacer therein;

fabricating sidewall spacers from the sidewall spacer material, the sidewall spacers adjacent sidewalls of the plurality of mandrels;

removing the plurality of mandrels using the spacer as an etch stop; and

etching the bulk silicon wafer to form a plurality of fin structures therefrom using the sidewall spacers as an etch mask.

10. The method of claim 9, wherein the step of forming one or more deep isolation trenches comprises forming one or more deep isolation trenches with an aspect ratio of from about 12:

1 to about 3;

1.

11. The method of claim 9, wherein the step of depositing the sidewall spacer material into the recess to form the spacer comprises depositing sidewall spacer material overlying the filler material in the one or more deep isolation trenches.

12. The method of claim 9, wherein the step of forming the insulating trench liner comprises one of depositing and growing an insulating material having a lower etch rate than the mandrel-forming material.

13. The method of claim 9, wherein the step of depositing a conformal sidewall spacer material comprises depositing silicon nitride.

14. A method of forming inter-well isolation in a bulk FinFET device comprising the steps of:

forming one or more isolation trenches in a bulk silicon wafer having a dielectric pad layer, the one or more isolation trenches adapted to coincide with p- and n-well boundaries in the bulk silicon wafer;

filling the one or more isolation trenches with at least one of amorphous and polycrystalline silicon to form filled isolation trenches;

forming a plurality of fin structures from the bulk silicon wafer.

15. The method of claim 14, wherein the step of forming the plurality of fin structures comprises the steps of:

depositing at least one of amorphous and polycrystalline silicon overlying the dielectric pad layer and the filled isolation trenches;

fabricating a plurality of mandrels from the at least one of amorphous and polycrystalline silicon;

depositing a sidewall spacer material overlying the plurality of mandrels;

fabricating sidewall spacers from the sidewall spacer material, the sidewall spacers adjacent sidewalls of the plurality of mandrels;

removing the plurality of mandrels; and

etching the bulk silicon wafer to form the plurality of fin structures therefrom using the sidewalls spacers as an etch mask.

16. The method of claim 15, wherein the step of depositing the at least one of amorphous and polycrystalline silicon overlying the dielectric pad layer and the filled isolation trenches is substantially simultaneous with the step of filling the one or more isolation trenches.

17. The method of claim 15, wherein the step of fabricating the plurality of mandrels further comprises:

overetching the at least one of amorphous and polycrystalline silicon at an upper end of the one or more deep isolation trenches to form a recess therein; and

wherein the step of depositing the sidewall spacer material further comprises filling the recess with sidewall spacer material that is used as an etch stop during the mandrel removal step.

18. The method of claim 14, wherein the step of forming one or more isolation trenches comprises forming one or more deep isolation trenches with an aspect ratio of from about 12:

1 to about 3;

1.

19. The method of claim 14, wherein the step of forming one or more isolation trenches in the bulk silicon wafer further comprises the step of forming a trench liner in the one or more deep isolation trenches, the trench liner comprised of a material having a lower etch rate than the at least one amorphous and polycrystalline silicon.

20. The method of claim 15, wherein the step of depositing the sidewall spacer material comprises depositing silicon nitride.