Critical Factors for Enhancement of Compressive Strain in SGOI Layers Fabricated by Ge Condensation Technique

Abstract

SGOI layers with high compressive strain and high Ge content are promising channel materials for high current drive pMOSFETs under future technology nodes. In order to clarify the way of maximizing strain in SiGe-On-Insulator (SGOI) structures with high Ge fraction fabricated by th Ge condensation technique, we have examined the strain relaxation behaviors of the SGOI layers during the condensation process. The relationship among compressive strain in SGOI, the oxidation recipe and the substrate structures before oxidation has been quantitatively evaluated. With increasing the Ge fraction, the compressive strain in the SGOI layers linearly increases in lower Ge contents and rapidly decreases after it reaches peak values. It is found that the higher oxidation temperature and the Ge content in the SiGe epitaxial layers before oxidation are influential factors in mitigating the strain relaxation, in addition to the use of the strained Si-On-Insulator (sSOI) substrates As a result of optimizing these structural parameters, we have successfully obtained SGOI with 2.5% compressive strain under the Ge content of 0.86.