Surface Reaction and Topography Modeling of Fluorocarbon Plasma Etching

Fluorocarbon plasma etching is a key enabling technology for modern semiconductor fabrication processes. Particularly, fluorocarbon etching of SiO
2
via structures finds a wide variety of applications in logic and memory devices. The etching technology’s development is, however, hindered by the complexity of the surface phenomena and by the intricacy of the etchant flux distribution on the feature scale. We thus propose a revised surface reaction model for fluorocarbon plasma etching processes to study these effects. The surface model is integrated into a TCAD workflow and is applied to a via etch process of SiO
2
by C
4
F
8
/O
2
/Ar. The model is calibrated with experimental data and is able to accurately reproduce the via shape, overall etch rate (560 nm/min), and mask faceting angle (60°). We then apply the workflow to investigate essential process information that would otherwise require substantial experimental effort. The etch rate dependence with time throughout the 90 s process is analyzed and correlated with the aspect ratio dependent etching lag effect. We find that for aspect ratios > 7 the etch rate falls below 500 nm/min, which causes a substantial increase in total etch time for deeper vias.