Real-time control and modelling of plasma etching

Summary form only given. To meet the challenge of real-time advanced process control, the instantaneous process state needs to be determined. The relatively high process rates in high density plasma tools as well as the shrinking thickness of the films, require a fast estimate of the process state in order to implement process control. The research objective is to determine within a second the process rates and to implement real-time control of the films etch rate. Several in-situ, non-invasive and non-destructive sensors such as a laser interferometer and a full wafer interferometer are used to monitor the process state in a magnetically confined ICP tool. The advantages of two-color laser interferometry for real-time process monitoring and control is described. Langmuir kinetics modeling of the measured etch rates of polysilicon and SiO/sub 2/ films using Cl/sub 2/, CF/sub 4/ and CHF/sub 3/ gases over a large parameter space of antenna and wafer-stage RF power, gas flow, pressure and gas additives is described. Etch modeling enabled us to develop a real-time control algorithm. The results of real-time etch rate control of unpatterned SiO/sub 2/ and polysilicon films is described.