A model-based automatic control algorithm for a laser anneal processing system

A physical model dealing with the laser-matter interaction is developed. The model is then adopted as the core of an algorithm that is coded to automatically control a laser annealing system. Doped impurities can be activated during the laser annealing process. In such a process, the total energy that is deposited onto surface of a semiconductor wafer must be carefully controlled, because less laser energy may not efficiently activates the impurities, or more laser energy may melt and destroy the wafer (surface). Given the ratio of activated to total impurities, desired laser dose can be calculated by using our model. Known the laser power, scan speed of the wafer stage can be precisely determined so as to meet the process requirement on the laser dose. One distinct property of our model is: non-heat factors such as the photon absorption are regarded as more critical, whereas in other models, the heat effects are emphasized.