Modeling and simulation of rapid thermal processing has been studied extensively in the past. This work presents the results of a combined simulation and measurement study of a commercial multilamp RTP chamber. The simulations were used to estimate the contributions of different geometrical, material, process, and physical effects on temperature uniformity. The physical effects considered in the simulations included radiation, thermal conduction, transient effects during ramp up and cool down and the effects of patterns on the wafer surface. The effects were corroborated by direct temperature measurements using thermocouple embedded wafers, and the results were used to reliably calculate stress effects. The stress distributions were determined analytically in cases without surface films on the wafer. In the case of wafers with surface films, stress distributions were calculated based on thermal strains. This study allows us to concentrate efforts on increasing temperature uniformity to those areas where the greatest benefits in terms of yield and film uniformity can be obtained.