A high resolution dry etch process for InP via holes is presented. Using Cl2:HBr:BCl3:Ar reactive ion etching, etch rates in excess of 1 mum/min have been obtained on InP substrates with feature sizes as small as 15 X 15 mum2. The etch rate selectivity between InP and the photoresist was found to improve with the addition of HBr. The tapered sidewall profiles, suitable for subsequent metallization steps, can easily be achieved with this process.