A radiant heat-transfer model is verified for a susceptorless multizone rapid thermal chemical vapor deposition (RTCVD) system. Qualitative agreement is shown between thermal model predictions and temperature measurements 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 contributes 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 settings with those that were determined experimentally to be approximately the optimal settings In addition, the applicability of the model is studied by examining the performance a closed-loop temperature controller designed using the model. The model-based controller is demonstrated to produce better repeatable film thicknesses than an open-loop method through comparative experimental studies of 24 consecutively processed wafers.