Transient Effects in Rapid Thermal Processing

Using a realistic model of a rapid thermal processing chamber including Navier-Stokes calculations of the gas losses, the stresses and yield strengths of silicon wafers were determined for several linear ramp rates. It was found that the stress to yield strength ratio is a sensitive function of the ramp rate and the radiant uniformity. Radiation patterns that produce good steady state thermal uniformity overheat the wafer edges during heating transients leading to high stress levels.