A dishing model for STI CMP process

It is well known that field-oxide dishing occurring in STI CMP leads to considerable sidewall and edge-parasitic conduction as well as high electric fields in the gate oxide at the active-area edge. Thus, a closed-form solution for quantitative prediction of oxide dishing is needed. A contact-mechanics-based approach to describe the steady-state oxide dishing occurring in STI CMP process is presented. The theory is validated through comparison with experimental data in the literature. Once validated, the model is used to quantify the effect of pattern geometry on oxide dishing. Oxide dishing is found to be strongly dependent on field-oxide width and reach the maximum value at a certain pattern density.