Oxide via etching in a magnetically enhanced CHF 3/CF 4/Ar plasma

Abstract

Using a magnetically-enhanced reactive ion etching system, oxide films were etched in a CHF 3/CF 4/Ar plasma. Etch characteristics, etch rate and profile, are investigated as a function of process parameters, including radio frequency power, pressure, and CHF 3 flow rate. Important radicals (CF 1, CF 2, and F) along with the dc bias were collected to evaluate their relative contributions. The etch rate with the power was predominated by physical ion bombardment. The etch rate varied inconsistently with the pressure. Depending on the pressure, two different etch mechanisms were qualitatively identified. The etch rate at lower pressure was dominated by the etchant-driven chemical etching. However, physical ion bombardment dominated the etch rate at higher pressures. For variations in the CHF 3 flow rate, the etch rate varied randomly. Despite this randomness, it was reasonably estimated that the etch rate is governed by polymer deposition, particularly driven by the CF 2 radical. In separating physical and chemical contributions from radicals and ion bombardment effect, the variations in profile played a crucial role.