Various evolution trends of sample thickness in fluorocarbon film deposition on SiO2

Recently, fluorocarbon (FC) film deposition on a SiO2 surface has become one of the most important processes in semiconductor manufacturing because the formation of a passivation layer on SiO2 during the deposition process plays a crucial role in atomic layer etching and high aspect ratio contact (HARC) etching, areas that are attracting intense interest in the semiconductor industry. In this work, various trends of sample thickness change, namely, decreasing, increasing, and anomalously increasing trends with time, were observed during FC film deposition on a SiO2 surface. The total thickness including both SiO2 and FC film was found to change during the deposition process in various ways depending on the plasma conditions. This can be successfully explained by considering the mechanism of SiO2 etching with FC plasma, taking into account the dependence of the SiO2 etch rate on FC film thickness. This result is expected to be utilized in semiconductor processes such as HARC etching where a precise control of film thickness is needed.