The dry etching characteristics of InP and GaAs using CH4/H2plasmas produced by two different electron cyclotron resonance (ECR) source configurations were examined in terms of surface morphology, stoichiometry, etch rate and anisotropy and finally the etch uniformity on 3‘φ wafers. Both the multipolar resonant cavity ECR source and the more conventional high‐profile magnetic mirror configuration produce high ion densities (∼7×1011cm−3at 1000 W) in 1 mTorr CH4/H2/Ar discharges, although the mirror source has slightly faster etch rates for both InP and GaAs. The etching becomes more anisotropic as the rf power to the chuck position is increased, and the rates fall for substrate temperatures below −10 °C, although the stoichiometry of the near‐surface region of InP is slightly better under these conditions. The optimized etch uniformity is ≤±2% for both sources and in general is better for high rf and microwave powers. Manual tuning of the multipolar source is simpler than for the mirror source and it is a little more stable during operation, with fewer of the mode jumps observed for the mirror configuration.