	US 7,524,740 B1
	Localized strain relaxation for strained Si directly on insulator
Yaocheng Liu, White Plains, N.Y. (US); Devendra Kumar Sadana, Pleasantville, N.Y. (US); and Kern Rim, Yorktown Heights, N.Y. (US)
Assigned to International Business Machines Corporation, Armonk, N.Y. (US)
Filed on Apr. 24, 2008, as Appl. No. 12/108,917.
Int. Cl. H01L 21/36 (2006.01); H01L 21/20 (2006.01)

U.S. Cl. 438—479 [438/480; 438/481; 438/482; 438/486; 438/507]

2 Claims

1. A method of forming a localized region of relaxed Si within a strained Si layer comprising strained silicon directly on insulator (SSDOI) semiconductor substrate, the strained Si layer formed on a buried oxide (BOX) layer disposed on a SI substrate base, the method comprising steps of:

forming a thin oxide layer on the strained Si layer using heat;

depositing a nitride hard mask pattern upon the thin oxide layer above a region in the strained Si layer in which enhanced electron mobility is desired, the hard mask pattern leaving an exposed region on the thin oxide layer above the strained Si layer in which enhanced hole mobility is desired;

performing one of step branches (a), (b) or (c):

(a):

implanting high temperature silicon (Si I/I) into the unmasked region of the strained Si layer to realize a localized relaxed Si region;

amorphization implanting one of Si, Ge or Xe at normal temperature into the localized relaxed Si region to form an amorphous silicon layer above a thinner localized relaxed Si layer;

stripping the nitride hard mask pattern, and cleaning; and

solid-phase epitaxial annealing to crystallize the amorphous silicon region and realize a relaxed SPE Si region from the thinner localized relaxed Si layer and amorphous Si layer;

(b):

selectively growing an EPI Si region upon the unmasked region of the strained Si layer;

using pre-amorphization implantation, modifying the EPI Si region and the unmasked region of the strained Si layer to realize a buried amorphous Si region below a thinner relaxed EPI Si region;

using SPE regrowth, modifying the buried amorphous Si region to realize a relaxed SPE Si region, below thinner relaxed EPI Si region; and

oxidizing the thinner relaxed EPI Si region, and part of the relaxed SPE Si region to realize an oxide region, and a thinner relaxed SPE Si region below the formed oxide region; and

stripping the nitride pattern and oxide region;

(c):

growing an EPI SiGe region on an unmasked region of the strained Si layer;

using pre-amorphization implantation of Ge I/I, forming a buried amorphous SiGe region in a portion of the EPI SiGe region, and an amorphous Si region, in what was the strained Si region below the amorphous silicon region;

using SPE regrowth, modifying the amorphous SiGe and amorphous Si regions to realize respective SPE SiGe and relaxed SPE Si regions, both below the EPI SiGe region;

etching the EPI SiGe and SPE SiGe regions to leave the relaxed SPE Si region above the buried oxide layer; and

stripping the nitride pattern.