Selective metal-carbides hardmask strip with chlorine and oxygen plasma

Metal carbides (MCs) are novel hardmask materials tailored for high aspect ratio etching processes, and their strip technologies are presented. Unlike conventional plasma strip methods that target amorphous carbon layers and photoresists composed of C–H–O organic compounds, MCs require a chemically distinct approach involving Cl2-based plasma. We present an MC strip method characterized by high selectivity toward SiO2 layers. We analyze the dissociation rate of Cl2 by using optical emission spectroscopy to identify the strippable region of the MCs as a next-generation etch hardmask. We use a design of experiment to systematically investigate the influence of process parameters on the strip rate and selectivity. We optimize the gas flow rate ratio of Cl2 to O2 to identify the appropriate process conditions for stripping MCs with a sufficiently high strip rate suitable for semiconductor manufacturing standards. Notably, we observe a consistent relationship between the normalized intensity ratio of oxygen and chlorine species obtained from the optical emission spectroscopy data and the normalized strip rate of the MCs, thereby underscoring the strip mechanism of MCs with high selectivity toward SiO2.