Polysilicon residue removal in nanosheet mosfets

Patent metadata

Field	Value
Publication number	US-2018090315-A1
Application number	US-201715466420-A
Country	US
Kind code	A1
Filing date	Mar 22, 2017
Priority date	Sep 28, 2016
Publication date	Mar 29, 2018
Grant date	—

Abstract

A method is presented for forming a semiconductor device. The method includes depositing a sacrificial layer on a fin structure formed on a substrate and then filled with polysilicon, etching a portion of the polysilicon material via a first etching process, and pre-cleaning the surface native oxide layer. The method further includes etching the remaining polysilicon material via a second etching process, and removing polysilicon etch residue formed adjacent the fin structure by a cleaning process. The pre-cleaning is performed by applying ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ) or by applying buffered hydrofluoric acid (BHF). The first etching process is reactive ion etching (RIE) and the second etching process involves applying nitrogen trifluoride (NF 3 ) and hydrogen gas (H 2 ).

First claim

1 . A method of forming a semiconductor device, the method comprising:
etching a portion of a polysilicon material deposited over a dielectric layer of a fin via a first etching process such that remaining polysilicon material covers the fin; etching the remaining polysilicon material via a second etching process resulting in polysilicon etch residue formed on portions of the fin; and removing the polysilicon etch residue by a cleaning process.

2 . The method of claim 1 , wherein the fin is formed by alternating layers of silicon (Si) and silicon germanium (SiGe).

3 . The method of claim 1 , wherein the cleaning process exposes the dielectric layer.

4 . The method of claim 1 , wherein the cleaning process is a wet etch cleaning process.

5 . The method of claim 1 , further comprising pre-cleaning a surface of the remaining polysilicon material.

6 . The method of claim 5 , wherein the pre-cleaning is performed by applying ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ).

7 . The method of claim 5 , wherein the pre-cleaning is performed by applying buffered hydrofluoric acid (BHF).

8 . The method of claim 1 , wherein the first etching process is reactive ion etching (RIE) and the second etching process involves applying nitrogen trifluoride (NF 3 ) and hydrogen gas (H 2 ).

9 . The method of claim 8 , wherein the nitrogen trifluoride (NF 3 ) flow is about 100 sccm-300 sccm and the H 2 flow is about 1000 sccm-5000 sccm.

10 . The method of claim 8 , wherein the second etching process has an etch rate of about 200 Å/minute and an anneal time of about 1 minutes to about 5 minutes.

11 . A method of forming nanosheet metal oxide semiconductor field effect transistors (MOSFETs), the method comprising:
forming a plurality of fins each including a first material and a second material arranged in an alternating configuration; forming a polysilicon material over the plurality of fins; etching a portion of the polysilicon material deposited via a first etching process such that remaining polysilicon material covers the plurality of fins; etching the remaining polysilicon material via a second etching process resulting in polysilicon etch residue formed on the plurality of fins; removing the polysilicon etch residue by a cleaning process; and removing either the first material or the second material to form the nanosheet MOSFETs.

12 . The method of claim 11 , wherein the first material is silicon (Si) and the second material is silicon germanium (SiGe).

13 . The method of claim 11 , wherein the cleaning process is a wet etch cleaning process.

14 . The method of claim 11 , further comprising pre-cleaning a surface of the remaining polysilicon material.

15 . The method of claim 14 , wherein the pre-cleaning is performed by applying ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ).

16 . The method of claim 14 , wherein the pre-cleaning is performed by applying buffered hydrofluoric acid (BHF).

17 . The method of claim 14 , wherein the pre-cleaning involves an isotropic process.

18 . The method of claim 11 , wherein the first etching process is reactive ion etching (RIE) and the second etching process involves applying nitrogen trifluoride (NF 3 ) and hydrogen gas (H 2 ).

19 . The method of claim 11 , wherein the plurality of fins include a dielectric liner formed before deposition of the polysilicon material.

20 . The method of claim 19 , wherein the cleaning process exposes the dielectric layer.

Assignees

• IBM

Inventors

• Bi Zhenxing
• Canaperi Donald F
• Devarajan Thamarai S
• Loubet Nicolas J

Classifications

• H10P70/273 Primary

  the processing being a delineation of conductive layers, e.g. by RIE · CPC title

• H10P70/23

  during, before or after processing of insulating materials · CPC title

• H10P50/283

  by chemical means · CPC title

• H10P14/6903

  containing silicon · CPC title

• H10P14/6528 Primary

  In-situ cleaning after layer formation, e.g. removing process residues · CPC title