Effect of showerhead electrode materials on high aspect ratio etching of SiO₂

High aspect ratio dielectric etching can lead issues such as pattern distortion and twisting due to uneven polymer deposition on the sidewalls of high aspect ratio dielectric structures. In this study, to reduce charge related issues during the etching of high aspect ratio dielectric structure using a capacitively coupled plasma (CCP) etcher, as a showerhead electrode material, W instead of conventional Si was used and the effect of W inclusion to the polymer layer formed on the sidewall of the etched feature on the etch characteristics of a high aspect ratio SiO₂ etching was investigated and compared with the conventional Si showerhead electrode by DC-biasing the electrodes. The results showed that the addition and increase of DC voltage to both electrodes improved etch selectivity of SiO₂ over amorphous carbon layer (ACL). In the case of W showerhead electrode, DC-bias voltage to the electrode improved the pattern distortion due to the charge removal in the polymer formed at the SiO₂ sidewall by the inclusion of W. It is believed that our findings provide valuable insights into the intricate interplay between electrode material reactivity and the resulting etching characteristics in CCP-based high aspect ratio etching processes.