Investigation of the Impact of Pre-Etching Mechanisms on the Deposition of Fluorocarbon Passivation Layers

Abstract—This study examines the influence of plasma pre-etching on the deposition and surface properties of fluorocarbon passivation layers under low-pressure plasma conditions. Single-crystal silicon wafers with (100) orientation were cleaned with deionized water and acetone before treatment. A tubular capacitively coupled radio-frequency plasma reactor operating at 13.56 MHz was used, with external copper electrodes to prevent contamination. Industrial-grade sulfur hexafluoride (SF6) and octafluorocyclobutane (C4F8) gases of 99.999% purity served as process gases. Fluorocarbon films were first deposited using C4F8 plasma; the samples were then subjected to an SF6 plasma pre-etching step between two deposition runs to modify the surface before the subsequent deposition. SF6 pre-treatment generated fluorinated, micro-roughened surfaces, enhancing film nucleation and adhesion. Wettability was evaluated using the automated sessile drop method, and surface free energy was calculated via the Owens–Wendt–Rabel–Kaelble model. Morphological changes were analyzed by scanning electron microscopy. The results showed that SF6 pre-etching significantly increased hydrophobicity, reduced surface energy, and improved film uniformity. These findings highlight the synergistic relationship between plasma etching and deposition processes, offering a controllable route to enhance fluorocarbon passivation layer performance.