Plasma induced wafer charging sensor

Abstract

An on-wafer surface charging sensor was developed for real-time measurement of the local charging voltage during plasma processing. This sensor is based on a modified MOS capacitor structure with charging voltage built up between an electrode and the substrate across a thick oxide as an indicator of charging. An array of electrodes are designed to measure the local plasma charging condition across the wafer. The processes needed for this sensor manufacturing are fully compatible with present CMOS processes. Comparisons between different characterization methods of plasma charging are also discussed. This sensor can differentiate the charging condition for different process stages (on-transient, steady state, off-transient). In addition, this sensor provides a faster reading method of charging without further device measurements after plasma processing. From the experimental results of probe measurements in Ar, SF 6 and C 2 CIF 5 plasma, this probe shows excellent capability on real-time monitoring of charging voltage. This sensor can be applied to IC plasma processing and equipment development, and trouble shooting in the future.