Inductively coupled plasma (ICP) etching of GaAs, GaP, and InP is reported as a function of plasma chemistry, chamber pressure, rf power, and source power. Etches were characterized in terms of rate and anisotropy using scanning electron microscopy, and root-mean-square surface roughness using atomic force microscopy. ICP etch rates were compared to electron cyclotron resonance etch rates for Cl2/Ar, Cl2/N2, BCl3/Ar, and BCl3/N2 plasmas under similar plasma conditions. High GaAs and GaP etch rates (exceeding 1500 nm/min) were obtained in Cl2-based plasmas due to the high concentration of reactive Cl neutrals and ions generated as compared to BCl3-based plasmas. InP etch rates were much slower and independent of plasma chemistry due to the low volatility of the InClx etch products. The surface morphology for all three materials was smooth over a wide range of etch conditions.

Wet chemical etching of A1N and In3A11_N was investigated in KOH-based solutions as a function of etch temperature and material quality. The etch rates for both materials increased with increasing etch temperatures, which was varied from 20 to 80°C. The crystal quality of A1N prepared by reactive sputtering was improved by rapid thermal annealing at temperatures to 1100°C, with a decreased wet etch rate of the material measured with increasing anneal temperature. The etch rate decreased approximately an order of magnitude at 80°C etch temperature after an 1100°C anneal. The etch rate for In0 19A1081N grown by metallorganic molecular beam epitaxy was approximately three times higher for material on Si than on GaAs. This corresponds to the superior crystalline quality of the material grown on GaAs. Etching of InAl1_N was also examined as a function o In composition. The etch rate initially increased as the In composition changed from 0 to 36%, and then decreased to 0 A/mm for InN. We also compared the effect of doping concentration on etch rate. Two mAIN samples of similar crystal quality were also etched; one was fully depleted with n c 1016 cm3 (2.6% In) and the other n 5 >< 10's cm3 (3.1% In). At low etch temperature, the rates were similar, but above 60°C the n-type sample etched faster, approximately three times faster at 80°C. The activation energy for these etches is very low, 2.0 0.5 kcal mot' for the sputtered A1N. The activation energies for mAIN were dependent on In composition and were in the range 2 to 6 kcal mol . GaN and InN layers did not show any etching in KOH at temperatures up to 80°C. * Electrochemical Society Student Member.

REC El VED JMAl9 9997'Plasma-Them, Inc., St. Petersburg, FL 33716The wide band gap group-IIt nitride materials continue to generate interest in the s e m i c o n d a r s T I ---community with the fabricition of green, blue, and ultraviolit light emitting diodes (LEDs), blue lasers, and high temperature transistors. Realization of more advanced devices requires pattern transfer processes which are well controlled, smooth, highly anisotropic and have etch rates exceeding 0.5 pdmin. The utilization of high-density chlorine-based plasmas including electron cyclotron resonance (ECR) and inductively coupled plasma (ICP) systems has resulted in improved GaN etch quality over more conventional reactive ion etch (RIE) systems.

Etch rates 5000 A min were obtained for Cu in electron cyclotron resonance C12/Ar discharges at a sample temperature of 200°C for ion-neutral ratios 0.02. The rates are a strong function of ion-neutral ratio, ion flux, and ion energy through the need to have CuCl desorption rate faster than the CuCl, generation rate in order to avoid formation of a chlorinated selvedge layer. Postetch, in situ El2 plasma cleaning removes most of the chlorine residues and allows creation of clean, anistropic Cu features.