THERMAL-MODEL VALIDATION FOR RAPID THERMAL CHEMICAL-VAPOR-DEPOSITION OF POLYSILICON

A radiant heat-transfer model is verified for a susceptorless multizon e rapid thermal chemical vapor deposition (RTCVD) system. Qualitative agreement is shown between thermal model predictions and temperature m easurements as deduced via experimental film thickness measurements of polysilicon. The analysis is used to demonstrate that a wafer support mechanism overlapping the edge of the wafer in an RTCVD system contri butes significantly to spatial nonuniformities and nonsymmetries. The thermal model is also verified by demonstrating qualitative agreement between the lamp powers predicted by the model to be the optimal setti ngs with those that were determined experimentally to be approximately the optimal settings In addition, the applicability of the model is s tudied by examining the performance a closed-loop temperature controll er designed using the model. The model-based controller is demonstrate d to produce better repeatable film thicknesses than an open-loop meth od through comparative experimental studies of 24 consecutively proces sed wafers.