Characterization of sio2 over poly-si mask etching in ar/c4f8 capacitively coupled plasma

Abstract

This research involved an experimental investigation of the relationship between the plasma parameters and etching properties of SiO2 over poly-Si mask in Ar/C4F8 capacitively coupled plasma (CCP). In these experiments, the etching process was conducted in CCP and the external conditions such as the applied power, pressure, and gas ratio were varied. In addition, the density of radicals, which dominantly participate in surface reactions, the electron density, and the self-bias voltage were measured. As a result, deposition of the CFx polymer film on the poly-Si mask lowered the electron density and self-bias voltage and the etch rate of the target and the mask increased as the internal parameters of the plasma increased. This result indicated that the electron density and the self-bias voltage, which represent the physical etch elements of ion flux and energy, respectively, have a marked influence on the etching process. Consequently, our work led us to propose a critical value, which is the product of the electron density and self-bias voltage, neVbias, to analyze the etching mechanism. Our results are also expected to serve as a basic processing database that enables an in-depth understanding of etching.