RF systems based on silicon-on-sapphire technology

The major issues which confronted the formation of very thin layers of silicon (30-100 nm) on sapphire substrates for application to mm-wave communication and sensors were investigated. The focus of the investigation was to achieve a structure in which modern CMOS technology can be affordably continued. In this context the application of device-quality thin film silicon-on-sapphire (TFSOS), obtained by solid phase epitaxy (SPE), and the growth of strained silicon-germanium (SiGe) layers on these improved thin silicon films on sapphire have demonstrated enhanced device and circuit performance. We have fabricated 250 nm and 100 nm T-gated devices with noise figures as low as 0.9 dB at 2 GHz with an associated gain of 21 dB, and 2.5 dB at 20 GHz, with an associated gain of 7.5 dB, respectively. These performances resulted in distributed wide-band amplifiers (10 GHz BW) and tuned amplifiers (15 dB peak gain, 4 GHz BW), among others. Additionally, VCOs (25.9 GHz) and frequency dividers in excess of 30 GHz were fabricated with devices with f/sub t/(f/sub max/) of 105 GHz (50 GHz) for n-channel and 49 GHz (>110 GHz) for p-MODFETs with 100 nm T-gates (strained Si/sub 0.2/Ge/sub 0.8/ on a relaxed Si/sub 0.7/Ge/sub 0.3/ heterostructure).