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Published online by Cambridge University Press: 10 February 2011
Selective deposition of SiGe alloys by rapid thermal deposition has been studied using a commercially available Rapid Thermal Chemical Vapor Deposition (RTCVD) cluster tool. The precursors used in this work were dichlorosilane and germane diluted in either hydrogen or argon. An initial characterization was performed to find the appropriate temperature and GeH4 flow ranges to deposit epitaxial layers with low surface roughness. For layers with higher germanium concentration lower deposition temperatures are required to minimize surface roughness. The effects of the dilutant gas on the deposition were examined. An H2 dilutant affects the deposition by consuming chlorine released by the SiCl2H2 and forming HCI. When Ar is used as the dilutant, more chlorine is available for other reactions that can result in etching of the silicon surface. Finally, the effects of pre-deposition treatment were determined. When compared to a wet HF dip, a gas/vapor phase HF/methanol native oxide removal treatment appears to increase the initiation time for the epitaxial deposition reaction. This is most likely due to increased fluorine termination of the surface. When a wet HF or HF/methanol native oxide removal is followed by a UV-Cl2 process, the deposition reaction initiation time is reduced. The UV-Cl2 process was also found to etch silicon through the native oxide.