Plasma-induced damage of GaAs during etching of refractory metal contacts
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
- University of Florida, Gainesville, Florida 32611 (United States)
The effect of plasma-induced damage on the majority carrier transport properties of {ital p}-type GaAs has been studied by monitoring changes in sheet resistance ({ital R}{sub {ital s}}) of thin conducting layers under various plasma conditions including etch conditions for refractory metal contacts. {ital R}{sub {ital s}} determined from transmission line measurements are used to evaluate plasma-induced damage for electron cyclotron resonance (ECR) and reactive ion etch (RIE) conditions by varying the thickness and doping of epitaxial layers. Damage depths calculated from {ital R}{sub {ital s}} data show a strong dependence on doping levels. This can be explained by a plasma-damage-induced trap density profile which tails off into the sample. Consistent trends have been observed where {ital R}{sub {ital s}} increases with increasing dc bias, increasing microwave power, and decreasing pressure, thus showing {ital R}{sub {ital s}} increases as either the ion energy or ion flux increases. The lowest plasma-induced damage observed in this study occurs with ECR at low microwave power and no rf biasing. Under rf-bias conditions, samples exposed to the ECR (1 mTorr total pressure) show more damage than those exposed to the RIE (8 mTorr total pressure) at comparable dc bias. We have also observed {ital R}{sub {ital s}} dependence on ECR plasma chemistry where {ital R}{sub {ital s}} is lower in SF{sub 6}/Ar plasmas than Ar and N{sub 2} plasmas possibly related to interactions of F or S atoms with the GaAs surface. Moderate anneal temperatures (200--500 {degree}C) have shown significant {ital R}{sub {ital s}} recovery. {copyright} {ital 1995} {ital American} {ital Vacuum} {ital Society}
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 57118
- Journal Information:
- Journal of Vacuum Science and Technology, A, Journal Name: Journal of Vacuum Science and Technology, A Journal Issue: 3 Vol. 13; ISSN 0734-2101; ISSN JVTAD6
- Country of Publication:
- United States
- Language:
- English
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