It is demonstrated that the polymer byproduct of methane/hydrogen RIE (reactive ion etching) can be used advantageously in forming thin, yet durable etch masks. The thin masking layers are consistent with high-resolution pattern transfer, and are made possible by the etch chemistry itself. A 1000 AA mask can be used to delineate features microns deep in InP. They are particularly useful in in situ processes, such as the metal protection process, where the films are not subjected to the atmosphere until the etch is complete. Although the surface cleaning was sufficient to obtain a patterned etch, the polymer film eventually peeled. In any case, these polymer masks can easily be removed in an oxygen plasma without adversely affecting device materials or structures.<<ETX>>