A generalized plasma etching model

Abstract

A generalized plasma etching model has been developed. The new model is a generalization of our previous model presented in a recent paper [E. Zawaideh and N. S. Kim, J. Appl. Phys. 62, 2498 (1987)]. The new model includes the effects of multi-ion and multineutral gas species. New generalized plasma transport equations are also introduced. These equations are derived for multi-ion species. No restrictions on the anisotropy of the ion distribution functions are imposed. The new generalized plasma transport equations are valid for collisional to weakly collisional plasma [λ/L≤0(1)], where λ is the ion mean free path and L is the smallest of the scale lengths of the gradient in the electric field or in the macroscopic plasma parameters. A new particle balance model has also been introduced which incorporates the effects of gas composition, gas flowrate, pumping rate, ion and neutral gas chemistry, and atomic reactions on the neutral gas and plasma parameters (e.g., densities and pressures of the various neutral gas and plasma species). As an example, silicon dioxide (SiO2) plasma etching using carbon tetrafluoride (CF4) gas is used to illustrate this new generalized model. The model has shown good agreement with the experimental etch rates of SiO2 for various plasma and reactor parameters (e.g., neutral gas pressure, CF4 flowrate, and rf power).