Treatment of InP surfaces in radio frequency H{sub 2} and H{sub 2}/CH{sub 4}/Ar plasmas: {ital In} {ital situ} compositional analysis, etch rates, and surface roughness
- Department 5848, Sandia National Laboratories, Albuquerque, New Mexico 87185-0782 (United States)
- Department 1322, Sandia National Laboratories, Albuquerque, New Mexico 87185-0603 (United States)
- Department 1128, Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States)
The surface composition, etch rates, and surface roughness of indium phosphide (InP) surfaces have been investigated using {ital in} {ital situ} Auger spectroscopy and {ital ex} {ital situ} scanning electron microscopy and atomic force microscopy. In agreement with most previous studies, hydrogen plasmas are found to completely remove surface carbon and oxygen impurities, but at the expense of some degree of surface phosphorus depletion. This depletion can be minimized by utilizing brief plasma exposure times and low rf power settings. Oxygen removal is found to be rate limiting in the production of a clean surface. InP etching in hydrogen/argon/methane can be performed either in a low density, capacitively coupled plasma mode, or in a high density, inductively coupled plasma mode. For operation in the low density regime, the etched surfaces have a constant and nearly stoichiometric composition, independent of plasma parameters. Etch rates vary from {approximately}20{endash}400 A/min, while the root mean square (rms) surface roughness varies from {approximately}20 to {gt}400 A. Both of these quantities show definite trends with changing plasma parameters, and, in particular, high etch rates and low surface roughness are both favored by increasing total plasma pressure and methane flow rate. Within the ranges studied, the etch rate is most strongly affected by the amount of hydrocarbon species reaching the surface, which can remove indium in the form of indium alkyl products. However, sputtering effects are also shown to be significant. Etching InP in the high density plasma mode gives an etch rate of {approximately}700 A/min, but only at the expense of severe surface phosphorus depletion and rms surface roughness of {approximately}2000 A. The breakdown of methane within the plasma under these conditions may serve to inhibit indium alkyl formation, and hence lead to the observed phosphorus depletion. {copyright} {ital 1996 American Vacuum Society}
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 402518
- Journal Information:
- Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena, Vol. 14, Issue 6; Other Information: PBD: Nov 1996
- Country of Publication:
- United States
- Language:
- English
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