Design study of a rapid thermal annealing system and temperature control

Abstract

A prototype rapid thermal annealing system using incoherent light sources has been assembled. The system is controlled by a microprocessor and a complete annealing process can be controlled automatically. Power distribution on the wafer has been simulated and optimal lamp positions has been found. Temperature profile has also been simulated, considering light absorption, light reflection, radiation from silicon wafer, conduction in silicon wafer and convection of ambient gas, and incident light spectrum. A control scheme, where the temperature control is executed with the real wafer temperature rather than measured thermocouple temperature, is proposed. The real wafer temperature is calculated by considering the thermocouple delay. This control scheme gives more accurate control of the wafer temperature and also very rapid heating.