Analytical study of polymer deposition distribution for two-dimensional trench sidewall in low-k fluorocarbon plasma etching process

In this study, a new polymer deposition distribution model for a two-dimensional low-k porous SiOCH trench structure during the fluorocarbon plasma etching process is described so as to investigate the bowing effect in a nanoscale trench. The model consists of three processes, namely, (1) polymer reflection, (2) ion-assisted polymer deposition, and (3) ion-assisted polymer emission. To calculate the distribution of the polymer, the polymer flux arrived at the surface points of the trench was calculated based on the model. To estimate the profile of the trench, the flux of the etchants at the point of the trench surface was also considered. The simulated etching process is based on a simple flux model, which takes into account angular distributions for ions and radicals from the sheath edge to the trench. Simulation results show that the lower section of the sidewall had a larger number of polymer particles than the other positions of the sidewall did. According to the simulated results, the sidewall bowing amount was estimated to be about 2.9 nm and the bowing position was approximately 29.8 nm at a trench depth of about 148.5 nm. With the proposed polymer distribution model, the bowing effect during fluorocarbon plasma etching can be further understood for a nanoscale process.