Virtual plasma equipment model: a tool for investigating feedbackcontrol in plasma processing equipment

摘要

As microelectronics device feature sizes continue to shrink andnwafers continue to increase in size, it is necessary to have tighterntolerances during the fabrication process to maintain high yields.nFeedback control has, therefore, become an important issue in plasmanprocessing equipment design; comprehensive plasma equipment modelsnlinked to control algorithms would greatly aid in the investigation andnoptimal selection of control strategies. This paper reports on annumerical plasma simulation tool, the virtual plasma equipment modeln(VPEM), which addresses this need to test feedback control strategiesnand algorithms on plasma processing equipment. The VPEM is an extensionnof the hybrid plasma equipment model which has been augmented by sensorsnand actuators, linked together through a programmable controller. Thensensors emulate experimental measurements of species densities, fluxes,nand energies, while the actuators change process parameters such asnpressure, inductive power, capacitive power, electrode voltages, andnmole fraction of gases. Controllers were designed using a responsensurface based methodology. Results are presented from studies in whichnthese controllers were used to compensate for a leak of N2ninto an Ar discharge, to stably control drifts in process parametersnsuch as pressure and power in Ar and Ar/Cl2, and to nullifynthe effects of long term changes in wall conditions in Cl2ncontaining plasmas. A new strategy for improving the ion energy fluxnuniformity in capacitively coupled discharges using feedback controlntechniques is also explored