Radiation and Strain Effects in Silicon-Germanium Bipolar Complementary Metal Oxide Semiconductor Technology
Haugerud, Becca Mary
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This work examines the effects of radiation and strain on silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) BiCMOS technology. First, aspects of the various SiGe HBT BiCMOS technologies and the device physics of the SiGe HBT are discussed. The performance advantages of the SiGe HBT over the Si BJT are also presented. Chapter II offers a basic introduction to key radiation concepts. The space radiation environment as well as the two common radiation damage mechanisms are described. An overview of the effects of radiation damage on Si-based semiconductor devices, namely bipolar and CMOS, is also presented. Next, the effects of proton and gamma radiation on a new first-generation SiGe HBT technology are investigated. The results of a differential SiGe HBT LC oscillator subjected to proton irradiation are also presented as a test of circuit-level radiation tolerance. Finally, a technology comparison is made between the results of this work and the three different previously reported SiGe technologies. All reported SiGe HBT technologies to date show acceptable proton radiation tolerance up to Mrad levels. Chapter IV investigates the effects of effects of mechanical planar biaxial strain in SiGe HBT BiCMOS technology. This novel strain method is applied post fabrication, unlike many other straining methods. We report increases in the nFET saturated drain current, transconductance, and effective mobility for an applied strain of 0.123%. The pFET device performance degrades for this type of low-level strain.