A study on the dry thermal oxidation of a graded SiGe layer was performed. To reduce the Ge pileup effect during the thermal oxidation, the SiGe layer was deposited with much lower Ge content near the free surface than near the SiGe/Si heterointerface. After dry thermal oxidation at 900°C, the Ge composition in the pileup layer was significantly reduced and strain relaxation by defect formation was prevented due to the graded Ge distribution. To homogenize the Ge distribution between the pileup layer and remaining SiGe layer, the oxidized layers were postannealed. The homogenization is significantly enhanced by strain-induced diffusion, and it was confirmed by uphill diffusion of Ge. This result can propose an alternative oxidation method of strained SiGe/Si heterostructures.
Bibliographical noteFunding Information:
The authors acknowledge the support of this research by the Ministry of Science and Technology of Korea through the National Research Laboratory Program.
- Strain-induced diffusion