Oxygen content dependent etch rate of single polymer microparticles confined in the sheath region of a low pressure radiofrequency argon/oxygen plasma

To study the etching of polymer microparticles confined in low pressure radiofrequency plasmas, the size and refractive index of single 2 μm particles are experimentally obtained as a function of both time and oxygen content (0%-50%) added to the argon background gas. The etch rate was found to depend heavily on the oxygen (O2) content, especially for mixtures with low fractions of O2. As expected the etch rate was found to be close to zero in absence of O2 and increases to a value of 2 nm min−1 for 0.5% O2 and to roughly 3.5 nm min−1 for 5% O2. Above 5% O2 the etch rate saturates. It is shown that these results are consistent with a steady state etch model taking the effects of both atomic oxygen and positive ions into account.