Characterization of elastomer degradation in O₂/Ar plasma via mass and surface morphology changes

The degradation of fluoroelastomer, perfluoroelastomer (FFKM), and fluorosilicone materials were compared between three O₂/Ar plasma conditions: full plasma (ions plus radicals), radical only, and ion only. These elastomer materials are used extensively in plasma processing equipment used to manufacture semiconductors, and understanding the plasma environments that enhance degradation will inform material choice and further material development. Langmuir probe measurements were made to quantify the electron temperature and plasma density; radical probe measurements were made to quantify the oxygen radical density. The results suggested that plasma radicals were required to drive significant mass loss rates, with ions speeding up the mass loss rate further in the full plasma case. Additionally, it was determined that plasma radicals were the main driver of surface changes of the elastomer, with similar surface roughening in plasma versus radical only conditions and less significant roughening in ion-only conditions. The O₂/Ar plasma discharge had an electron temperature of 4.6 ± 0.1 eV and a plasma density of 2.9 ± 0.07 × 10¹⁶ m⁻³. It was observed that the fluorosilicone material had the lowest mass loss rate, the unfilled FFKM had the highest mass loss rate, and the silica-filled FFKM had the lowest mass loss rate among the FFKMs tested. The presence of oxygen radicals during exposure conditions significantly changed surface roughness.