Steady-state regression analysis and optimization of multivariable plasma etching system

The steady-state model, which relates the manipulated conditions to both the process and performance quantities, has been developed in this work for plasma etching process by regression analysis. Non-intrusive techniques, namely optical emission spectroscopy and laser interferometry, are employed to estimate the relative plasma species concentrations and electron energy of the process and real-time etch rate respectively in order to maintain the integrity of the etching environment. This information can be used to find the correlations and also feed into the model to track back proper operating conditions. Correlations are developed to directly relate inputs, semi-outputs and outputs in the SF₆/Ar etching system. Response surface methodology is used as a basis for further modelling of nonlinear plasma etching. Results presented in this paper are compared favourably to the known discharge characteristics, experimental data and some interpretations of etching and discharge mechanism as well as the comprehensive reactor model