In situ electrical monitoring of SiO2/Si structures in low-temperature plasma using impedance spectroscopy

Abstract

To investigate the electrical properties and degradation features of dielectric materials during plasma exposure, we developed an in situ impedance spectroscopy (IS) system. We applied the proposed system to monitor SiO2/Si structures exposed to Ar plasma. By analyzing the measured data based on an equivalent circuit model considering the plasma and SiO2/Si structures, we obtained the resistance (R) and capacitance (C) values for the SiO2 film and SiO2/Si interface. In a cyclic experiment of in situ IS and high-energy ion irradiation, we characterized dielectric degradation by ion irradiation based on the variations in the R and C values of the SiO2 film. A continuous in situ IS measurement revealed temporal variations in the electrical properties of the film and interface independently. The thickness-dependent degradation observed for the RC variation was analyzed and compared with the results of previous ex situ measurement studies. This study demonstrates that the in situ IS measurement technique is promising for monitoring plasma-assisted dry processes.