Generic modeling of surface reaction kinetics in plasma etching systems



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Texas Tech University


The complexity of both the bulk plasma phase physics and the substrate surface reaction chemistry indicate the need for simplified phenomenological modeling of etching systems. Simplified models are useful for design, analysis and control, within a reasonable time after data collection, and at modest cost. A current typical method in industry is a response surface model (an empirical polynomial), which has no predictive properties outside the range of fitted data, is completely arbitrary, and offers little physical understanding of the system.

A set of generic etch rate expressions based on simplified representations of physical phenomena are presented in this dissertation. The model parameter values are regressed firom data with a constrained, nonlinear optimization routine. Also presented are a statistical method for discriminating which model best represents the phenomenon of a particular etching system and a statistical model validation procedure.

The benefits of this approach are a predictive, statistically validated model; the small number of model parameters may reduce the number of data points required for regression; and there is no need to re-derive a polynomial fit for each new data set. The method will be demonstrated on experimental data for chlorine plasma etching of polysilicon; tetrafluoromethane/oxygen plasma etching of polysihcon and silicon dioxide; and oxygen plasma etching of photoresist.



Plasma engineering, Semiconductors, Plasma etching, Electrochemistry