Development of Techniques for Real-Time Monitoring and Control in Plasma Etching

Process control strategies have been developed for plasma etching of silicon (Si) and silicon dioxide (SiO2) in a CF4/O2 plasma. The analysis considered four measured variables, four manipulated variables, and up to seven performance variables. Empirical input-output models were developed by regression analysis. Relative gain array analysis and singular value decomposition were used to select manipulated/process variable control loop pairings and to evaluate potential difficulties in control system performance. Singular value decomposition was also used to determine process/performance variable pairings. Block relative gain analysis of multivariable interactions in the process indicated that partial decoupling was necessary for adequate control, which was verified by simulation.