In situ silicon-wafer temperature measurements during RF argon-ion plasma etching via fluoroptic thermometry

Abstract

In situ silicon-wafer temperature measurements during RF argon-ion plasma etching are reported for four different wafer cooling environments: (i) lying on the electrode; (ii) clamped to the electrode; with additional helium gas between wafer and electrode in both (i) and (ii), in order to enhance heat transfer. Fluoroptic thermometry is applied to measure the local surface temperature of the wafer during plasma processing. The measured heating and cooling curves can be fitted using a model which considers conductive heat losses only. Deviations are observed when high RF power is applied and surface temperatures higher than 120 degrees C are reached. The authors report on effective cooling via helium gas of the rear side of the wafer which is lying on an electrode without any clamping.