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Selective Removal of Silicon-Germanium: Chemical and Reactive Ion Etching

Published online by Cambridge University Press:  25 February 2011

F. Scott Johnson ,
Veena Misra ,
J. J. Wortman ,
Leanne R. Martin ,
Gari A. Harris  and
Dennis M. Maher
F. Scott Johnson
Affiliation:
North Carolina State University, Department of Electrical and Computer Engineering, Raleigh, NC 27695-7911
Veena Misra
Affiliation:
North Carolina State University, Department of Electrical and Computer Engineering, Raleigh, NC 27695-7911
J. J. Wortman
Affiliation:
North Carolina State University, Department of Electrical and Computer Engineering, Raleigh, NC 27695-7911
Leanne R. Martin
Affiliation:
North Carolina State University, Department of Materials Science and Engineering, Raleigh, NC 27695-7916
Gari A. Harris
Affiliation:
North Carolina State University, Department of Materials Science and Engineering, Raleigh, NC 27695-7916
Dennis M. Maher
Affiliation:
North Carolina State University, Department of Materials Science and Engineering, Raleigh, NC 27695-7916
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Abstract

The use of both chemical and reactive ion etching for the selective removal of SixGe1-x alloys with respect to both silicon and silicon dioxide has been investigated. We have found that a solution of NH4OH:H2O2:H2O is effective in selectively etching the SixGe1-x films with respect to both of these materials. The chemical composition of the substrate surface after removal of insitu doped SixGe1-x films was evaluated using EDS and SIMS. Diffusion from insitu doped Si0.7Ge0.3, followed by selective removal, was used to demonstrate self-aligned npn dopant profiles with narrow base widths. Reactive ion etching of SixGe1-x alloys was investigated using SF6, CF4, and Cl2 based chemistries. Pressure, power, and gas flow ratios were optimized to provide the least isotropic etch possible for SixGe1-x films containing approximately 40% Ge. Selectivity and degree of anisotropic etching were determined as a function of Ge content for samples with 0% to 100% Ge. Samples were analyzed using SEM and ellipsometry. Highest selectivities were achieved using SF6 and O2.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 298: Symposium B – Silicon-Based Optoelectronic Materials , 1993 , 157
Copyright
Copyright © Materials Research Society 1993

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