The low‐energy (about 30 eV) ion etching of InP with an excellent vertical sidewall profile, smooth surface, and a high etch rate (more than 1000 A˚/min) has been demonstrated in an electron cyclotron resonance plasma using a Cl2/N2mixture. Surface analysis by x‐ray photoelectron spectroscopy and plasma diagnostics by optical emission spectroscopy suggest that the etching mechanism is dominated by the reduction of Cl neutral radical density by N2dilution and the formation of InN and P3N5due to the reaction between the atomic nitrogen in the Cl2/N2plasma and the InP substrate. The success of this technique appears to be based on a new InP dry etching concept which controls the volatility of PClx(x=1–5) products, thus balancing the desorption rate of InClx(x=1–3) products, in contrast to the conventional reactive ion etching method which enhances the desorption of nonvolatile InClxproducts by high‐energy ion bombardment. ©1995 American Institute of Physics.