Reduction of Loading Effect in Reactive Ion Etching Using Real-time Closed Loop Control

Real-time, in-situ control of reactive ion etching is shown to reduce loading disturbance in an Applied 8300 reactive ion etch system. The etch process vehicle is CF4 etching of polysilicon. A real-time, multivariable feedback control strategy where key plasma parameters are fed back has been developed. This strategy is experimentally compared with standard industry practice and is shown to reduce the loading e ect by 80%. This quanti cation of improvement is carried out in terms of a model from the literature which is reviewed and experimentally validated for the etch equipment and process used.