NASA's Langley Research Center has developed a new low-temperature method of SiGe/sapphire growth that produces the same single-crystal films with much less thermal loading effort to the substrate. This eliminates the time-consuming and costly high heating, long thermal soak times, and interfacial Si layer. Yield and throughput are increased as time to production is reduced from more than four hours to less than one hour. The same quality of SiGe/sapphire is produced with far less effort and time, bringing it to within the realm of mass production.
This innovation is based on a new fabrication method that alleviates the thermal loading requirement of the substrate, which previously required surface temperatures within the range of 850 to 900 °C. The method employs a new thermal loading requirement of sapphire substrate for growing single-crystal SiGe on sapphire substrate in the range of 450 to 500 °C. SiGe/sapphire wafers produced via this process show a high reflectivity without the discoloration that appears in low-quality films.