A Study on the Strain Stability of Si/SiGe Layer Structure in a Heterojunction Bipolar Transistor during Thermal Processing

摘要

Si/SiGe heterojunction layers grown by ultra-high-vacuum chemical vapor deposition (UHV/CVD) were characterized by Rutherford backscattering/Channeling (RBS/C). A high quality SiGe base layer was obtained. Enhancement of strain relaxation of the SiGe layer with increasing thickness of the Si cap layer is demonstrated. In addition, strain stability of the SiGe layer with an appropriate Si cap layer during real SiGe HBT fabrication has also been investigated. Rapid thermal annealing (RTA) at elevated temperature between 880 deg C and 910 deg C for a very short period of time had almost no influence on the strain in a Si_(0.84)Ge_(0.16) epilayer. However, high temperature (900 deg C) furnace annealing for 1 hr prompted the strain in the Si_(0.84)Ge_(0.16) layer to relax by approximately 15 percent relative to that in an as-grown structure.