Rapid Thermal Chemical Vapor Deposition of Germanium and Germanium/Silicon Alloys on Silicon: New Applications in the Fabrication of MOS Transistors

Abstract

AbstractIn this work, low pressure chemical vapor deposition (LPCVD) of pure Ge and SixGe1-x on Si and SiO2 has been considered for new applications in future ultra large scale integration (ULSI) technologies. Depositions were performed in a lamp heated cold-wall rapid thermal processor (rapid thermal chemical vapor deposition -RTCVD) using thermal decomposition of GeH4 and SiH2Cl2 in a carrier gas of H2. It is shown that RTCVD of Ge on Si is highly selective with no deposition occuring on SiO2. The selectivity of Ge/Si depends on the amount of germane in the gas phase. The processes are relatively low temperature/high throughput processes suitable to single wafer manufacturing. In this paper, we review potential applications of Ge and SixGe1−x in future MOS processes. Specifically, Ge and SixGe1−x have been considered for three new applications: i) fabrication of raised source/drain structures where selective Ge or SixGe1−x is used as a sacrificial layer to eliminate silicon consumption during silicide formation (by forming a germanide), ii) Formation of ultra-shallow junctions in silicon using selectively deposited and implanted polycrystalline SixGe1−x as a diffusion source, iii) Formation of MOS gate structures with SixGe1−x gate electrodes for lower dopant activation temperatures and better threshold control.