Etching parylene-N using a remote oxygen microwave plasma

Abstract

The etching characteristics of parylene-N in a remote microwave oxygen plasma have been studied. The etch rate was measured over a range of pressures from 0.4 to 2.0 Torr and oxygen flow rates from 25 to 125 sccm using an applied plasma power of 250 W. In order to describe the etching behavior of the polymer as a function of different process parameters, a model has been developed to predict the concentration of reactive species at the polymer surface. The model uses two different plasma physics models to predict the net molecular oxygen dissociation rate in the microwave plasma. The species concentrations at the plasma outlet are used as the inlet condition for a model of the afterglow region, which includes a delivery tube and an etching chamber. The afterglow region is modeled using momentum and mass conservation equations. The predicted atomic oxygen concentrations at the polymer surface are inserted into a simple etch rate model and an etch rate is calculated and compared to etch rate data. The best agreement between theory and experiment was found using a plasma physics model developed by the Joint Institute for Laboratory Astrophysics and an etch rate model that has a reaction order of 0.5 with respect to the oxygen atom concentration.