High-germanium-content SiGe islands formed on compliant oxide by SiGe oxidation

Abstract

The oxidation of Si1−xGex islands on a compliant viscous borophosphorosilicate glass (BPSG) was utilized to achieve nearly fully relaxed Si1−xGex with germanium content up to 57%. After Si1−xGex islands were formed on BPSG by layer transfer, dry oxidation was carried out to form pure silicon dioxide on the top and to increase germanium content in the Si1−xGex layer. Surface roughening and the nonuniformity of the enhanced germanium content during the SiGe oxidation were improved by depositing a silicon dioxide capping layer before oxidation. The strain arising from the increase of germanium content was relaxed by lateral expansion of the SiGe islands, showing that dislocations were not required in the process.