Selective SiGe Nanostructures
Massachusetts Institute of Technology, 2001 - 215 ページ
Selective epitaxial growth (SEG) of SiGe on patterned SiO2/Si substrates by ultra-high vacuum chemical vapor deposition (UHVCVD) shows promise for the fabrication of novel SiGe microelectronic structures. This work explores selective growth conditions in the SiH2Cl2/SiH4/GeH4/H2 system between 650-850°C, without the addition of C12 or HC1, on substrates patterned by both conventional and interferometric lithography. We have achieved several important milestones for the fabrication of vertical MOSFETs by selective growth in 100 nm SiO2 features patterned by interferometric lithography. We have observed excellent selectivity to SiO2 masks with SiH2C12 at 750°C, perfect epitaxial Si filling of SiO2 features, the facet morphology during growth, and the effects of n-type doping on selective growth. We have also fabricated extremely sharp p-n diode doping profiles. With the above accomplishments we have demonstrated the feasibility of vertical MOSFET fabrication through selective epitaxial growth. To realize the advantages of advanced MOSFET designs on silicon-on-insulator (SOI) substrates, we have developed a facet-free raised source/drain process utilizing moderate n-type doping of Si selective growth and 110-oriented vertical SiO2 sidewalls. However, to improve SiO2 spacer dimension fidelity and eliminate Si substrate overetching, a novel SiO2/Si3N4 spacer process was developed. The keys to the SiO2/Si3N4 spacer process are removal of the Si3N4 layer prior to growth and increased Si ELO growth by moderate in situ n-type doping. This process has wide ranging application to both SOI and bulk Si technologies for fabrication of low-resistance contacts in advanced devices.
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100 nm features buffer contamination Cross-section TEM image decrease defect density defect reduction depletion region deposition device diamond cubic dielectric dielectric mask diodes dopant dry-etched ELO defects ELO fronts epitaxial lateral overgrowth epitaxial necking fabrication facet behavior facet morphology facet-free fluoropolymer Ge/Si GeH4 grown H2 flow HF dip image force image showing increase incubation leakage currents masking material minimize minority carrier minute oxygen plasma misfit mismatch morphology mTorr n-type doping Note nuclei observed oxide sidewall patterned substrates photodetectors photodiode piranha clean poly-Si nucleation prior to growth PVTEM image raised source/drain contacts RCA clean reactive ion etching reactor reduced RIE overetch Selected area diffraction selective epitaxial growth selective growth series resistance shown in Figure SiGe SiH2Cl2 SiH4 pressure silicide SiO2 mask SiO2 sidewall stacking faults submicron substrate interface substrate patterning substrates surface diffusion surface morphology temperature thermal threading dislocation density unpattemed unpatterned vertical MOSFETs wafers wet-etched