Development of an ion energy flux sensor for plasma processing

Summary form only given, as follows. Ion bombardment on a substrate plays a crucial role in most plasma processing of materials. For instance, in the etching of poly-Si using chlorine discharges, in order to obtain a desired etch profiles, the process often is operated at the ion-enhanced regime where the etch rate and etched profile are strongly correlated with the total ion energy flux incident on the wafer surface. Therefore, a better process control can be achieved if one can monitor the ion energy flux in a real-time manner or even implement a real-time feedback control of the etch process by using a energy flux sensor. In this study, the relative value of ion energy flux is indirectly determined by combining the measurement results from two different diagnostic tools which both are real-time and non-intrusive measurements. To measure the ion energy, an impedance meter (AE-RFZ60) is used to measure the peak RF voltage on the wafer chuck, which has been shown to monotonically increases with the sheath voltage and hence the energy of ions incident on wafer surface. The ion flux information is extracted from the Cl/sup +/ line intensity of the optical emission spectroscopy measurements. The relative ion energy flux is determined by the product of these two measured values. Initial test of the idea in a Poly-Si high density plasma etcher with Cl/sub 2/ plasmas shows that the etch rate scales linearly with the measured "ion energy flux" for a wide range of operating conditions, which were designed by a standard CCD procedure. This tool will be further integrated with other sensors to form a real-time control system based on plasma properties.