	US 12,068,322 B2
	Method of forming a multi-layer epitaxial source/drain region having varying concentrations of boron and germanium therein
Han-Yu Tang, Hsinchu (TW); Hung-Tai Chang, Hsinchu (TW); Ming-Hua Yu, Hsinchu (TW); and Yee-Chia Yeo, Hsinchu (TW)
Assigned to TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD., Hsinchu (TW)
Filed by Taiwan Semiconductor Manufacturing Co., Ltd., Hsinchu (TW)
Filed on Jan. 29, 2021, as Appl. No. 17/161,978.
Prior Publication US 2022/0246611 A1, Aug. 4, 2022
Int. Cl. H01L 29/66 (2006.01); H01L 21/8234 (2006.01); H01L 21/8238 (2006.01); H01L 27/092 (2006.01); H01L 29/04 (2006.01); H01L 29/08 (2006.01); H01L 29/417 (2006.01); H01L 29/78 (2006.01)

CPC H01L 27/0924 (2013.01) [H01L 21/823418 (2013.01); H01L 21/823431 (2013.01); H01L 21/823468 (2013.01); H01L 29/045 (2013.01); H01L 29/0847 (2013.01); H01L 29/41791 (2013.01); H01L 29/66545 (2013.01); H01L 29/6656 (2013.01); H01L 29/66575 (2013.01); H01L 29/66636 (2013.01); H01L 29/66795 (2013.01); H01L 29/7851 (2013.01); H01L 21/823814 (2013.01); H01L 29/7848 (2013.01)]

20 Claims

1. A method comprising:

depositing a first dummy gate over and along sidewalls of a first fin, the first fin extending from a substrate;

forming a first gate spacer along a sidewall of the first dummy gate;

forming a first recess in the first fin adjacent the first gate spacer; and

epitaxially growing a first source/drain region in the first recess, the first source/drain region having a first layer and a second layer, the first layer having a higher germanium concentration than the second layer, the first layer having a lower boron concentration than the second layer, the first layer being the innermost layer of the first source/drain region, an outer surface of the second layer of the first source/drain region having more than eight facets in a first plane, the first plane being orthogonal to a top surface of the substrate, the first layer having a boron concentration in a range from 3E20 cm⁻³to 5E20 cm⁻³, the second layer having a boron concentration in a range from 6E20 cm⁻³to 1E21 cm⁻³.

10. A method comprising:

forming a first dummy gate over and along sidewalls of a first fin extending upwards from a substrate;

forming gate spacers along sidewalls of the first dummy gate and the first fin;

etching a first recess in the first fin adjacent the first dummy gate, the gate spacers being on opposing sides of the first recess;

epitaxially growing a first source/drain region in the first recess with a first ratio of etchant precursors to deposition precursors, the first ratio being in a range from 0.05/1 to 0.25/1, the first source/drain region contacting the gate spacers on opposing sides of the first recess, the first source/drain region having a top surface extending above a top surface of the gate spacers on opposing sides of the first recess, wherein epitaxially growing the first source/drain region in the first recess further comprises:

epitaxially growing a first epitaxial layer from the first fin in the first recess; and

epitaxially growing a second epitaxial layer from the first epitaxial layer, the second epitaxial layer having a greater concentration of boron than the first epitaxial layer, the first epitaxial layer having a greater concentration of germanium than the second epitaxial layer, the second epitaxial layer being the outermost layer of the first source/drain region; and

replacing the first dummy gate with a first functional gate stack disposed over and along sidewalls of the first fin.

13. A method comprising:

forming a first fin extending from a substrate;

forming a first gate stack over and along sidewalls of the first fin;

forming a first gate spacer disposed along a sidewall of the first gate stack; and

forming a first epitaxial source/drain region in the first fin and adjacent the first gate spacer, an outer surface of the epitaxial first source/drain region having more than eight facets in a first plane, the first plane being orthogonal to a top surface of the substrate, wherein the first epitaxial source/drain region comprises:

a first epitaxial layer on the first fin, the first epitaxial layer having a first doping concentration of boron; and

a second epitaxial layer on the first epitaxial layer, the second epitaxial layer having a second doping concentration of boron, the second doping concentration being greater than the first doping concentration, the first epitaxial layer having a higher germanium concentration than the second epitaxial layer, the first epitaxial layer being the innermost layer of the first epitaxial source/drain region, the first epitaxial layer having a boron concentration in a range from 3E20 cm⁻³to 5E20 cm⁻³, the second epitaxial layer having a boron concentration in a range from 6E20 cm⁻³to 1E21 cm⁻³.