New polymerizing chemistries for through-silicon via etching

This study investigates a new fluorocarbon (FC) as an environmentally friendly gas chemistry for sidewall passivation during time-multiplexed plasma etch processes for through-silicon vias (TSVs). The effect of plasma processing conditions on TSV etch rate, etch selectivity, and sidewall roughness was examined. In addition, blanket fluorocarbon films were deposited, etched, and characterized with x-ray photoelectron spectroscopy (XPS) to study the effect of film chemistry on polymer growth and etch rates. XPS analysis of films deposited by low fluorine/carbon (F/C) ratio gases showed similarly low F/C ratios in the deposited films. This low F/C ratio also corresponded to an increased film deposition rate and etch resistance. Compared to octafluorocyclobutane (C₄F₈) processes, recipes with this FC had slightly lower etch rates while selectivity was slightly increased. Sidewall roughness of TSVs was the same between the two gases, and trench profiles were generally vertical.