Strain evolution in SiGe-on-insulator fabricated by a modified germanium condensation technique with gradually reduced condensation temperature

Strain evolution in SiGe-on-insulator fabricated by a modified germanium condensation technique was studied. As enrichment of Ge content, the condensation temperature was proposed to decrease from 1150 to 900 degrees C through five steps, rather than only two different temperatures (1150 degrees C and 900 degrees C) were used as reported previously. Compared to condensation recipe with only two different temperatures, the modified condensation recipe was beneficial to obtain more uniform SiGe layers with lower surface roughness, thus better material quality. As Ge content enriched to 0.54, the strain in SiGe is almost fully relaxed with surface roughness RMS of less than 0.59 nm at condensation temperature of >= 1050 degrees C. After further condensation at 900 degrees C, the strain in SiGe accumulated dramatically to -1.23% with a surface roughness RMS of 0.66 nm. At the final stage of Ge condensation process, most of the compressive strain was sustained in Ge-rich SiGe layer. However, when pure GOI was obtained, the compressive strain could be almost fully relaxed by intensive over-oxidation without surface deterioration. The fully relaxed SiGe-on-insulator and germanium-on-insulator with low surface roughness could be a good template for secondary growth of strained Si and Ge, respectively.