Oxygen plasma etching of thick polymer layers

Reactive ion etching of thick (≳100 μm) epoxy, polyester, and photoresist layers in oxygen was studied as a function of gas flow, gas pressure, gas purity, and rf power density. Etch rates greater than 2500 A/min were obtained with low substrate temperatures. The etch was found to be extremely directional so that structures with aspect ratios as large as 30 to 1 were measured. Both the etch geometry and mask material appear to have some effect on this directionality. In addition the etch was found to smooth the etched surface so that surface finishes better than 200 A were possible.