Silicon-on-sapphire technology for microwave power applications

Silicon-on-sapphire (SOS) MOSFETs offer many advantages such as reduced device and interconnect capacitance, availability of complementary devices with high microwave gain, and excellent device isolation, which make SOS technology a worthwhile choice for many applications. To meet future wireless communications demands, two areas must be addressed: aggressive scaling of device dimensions, which can reduce power consumption and increase speed; and development of power devices for radio frequency (RF) power amplifiers (PAs). RF PAs pose a number of device and modeling challenges. The objective of this dissertation is to demonstrate the inherent speed of 0.1 μm scaled CMOS technology and to characterize power MOSFETs for use in RF PAs.; A 0.1 μm gate length CMOS technology was used to demonstrate the speed advantages of deep sub-micron MOSFETs. A 2:1 digital dynamic frequency divider was designed and tested with operating frequency from 6.5GHz to a record 26.5GHz (55% faster than the previous MOSFET record of 17GHz using a 0.25μm process).; Large power MOSFETs were found to have microwave gain that decreased sharply with device size. To study this effect, power MOSFETs with different layout strategies were designed, fabricated, and tested. The effects of layout parasitics on RF performance were modeled using both lumped element models and distributed transmission line models. The RF characteristics of the power devices were accurately predicted. The effects of self-heating on SOS power MOSFETs were also investigated. Self-heating was found to play only a minor role in SOS technology.; Finally, an RF PA was demonstrated using SOS MOSFETs. The 1GHz class-B amplifier was designed using NMOS devices and measure to have 8dB gain. At 1dB gain compression, the PA has 21dBm output power and a power added efficiency of 27%. The performance can be further enhanced through device optimization. Although class-B, the amplifier has good linearity, meeting IS-95 linearity specifications for CDMA signals up to an output power of 20dBm.