US 10,892,328 B2
Source/drain extension regions and air spacers for nanosheet field-effect transistor structures
Yi Song, Albany, NY (US); Zhenxing Bi, Schenectady, NY (US); Kangguo Cheng, Schenectady, NY (US); and Chi-Chun Liu, Altamont, NY (US)
Assigned to International Business Machines Corporation, Armonk, NY (US)
Filed by International Business Machines Corporation, Armonk, NY (US)
Filed on Mar. 4, 2019, as Appl. No. 16/291,443.
Prior Publication US 2020/0286992 A1, Sep. 10, 2020
Int. Cl. H01L 29/786 (2006.01); H01L 29/66 (2006.01); H01L 21/02 (2006.01); H01L 21/762 (2006.01); H01L 29/423 (2006.01); H01L 29/08 (2006.01); H01L 21/8234 (2006.01); H01L 21/324 (2006.01); H01L 21/764 (2006.01); H01L 27/088 (2006.01); H01L 29/10 (2006.01); H01L 29/06 (2006.01)
CPC H01L 29/0847 (2013.01) [H01L 21/0228 (2013.01); H01L 21/02532 (2013.01); H01L 21/324 (2013.01); H01L 21/764 (2013.01); H01L 21/823412 (2013.01); H01L 21/823418 (2013.01); H01L 21/823431 (2013.01); H01L 21/823437 (2013.01); H01L 21/823468 (2013.01); H01L 21/823481 (2013.01); H01L 27/0886 (2013.01); H01L 29/0653 (2013.01); H01L 29/0673 (2013.01); H01L 29/1037 (2013.01); H01L 29/66545 (2013.01); H01L 29/66553 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of forming a semiconductor structure, comprising:
forming a nanosheet stack over a substrate, the nanosheet stack comprising alternating sacrificial layers and channel layers, the channel layers providing nanosheet channels for one or more nanosheet field-effect transistors;
forming one or more vertical fins in the nanosheet stack and at least a portion of the substrate;
forming indents in sidewalls of the sacrificial layers at vertical sidewalls of the one or more vertical fins;
forming nanosheet extension regions in portions of the channel layers which extend from the indented sidewalls of the sacrificial layers to the vertical sidewalls of the one or more vertical fins, the nanosheet extension regions increasing in thickness from a first thickness proximate the indented sidewalls of the sacrificial layers to a second thickness proximate the vertical sidewalls of the one or more vertical fins; and
forming inner spacers using a conformal deposition process that forms air gaps in spaces between the nanosheet extension regions and the indented sidewalls of the sacrificial layers;
wherein the nanosheet extension regions have a curved thickness profile that gradually increases from the first thickness proximate the indented sidewalls of the sacrificial layers to the second thickness proximate the vertical sidewalls of the one or more vertical fins.