Emission feedback control system for sub-millisecond laser spike anneal

Abstract

For the successful implementation of any advanced annealing system in a production environment, real-time measurement and control of wafer peak temperature is critical. For sub-millisecond laser anneal (SMA), the uniformity and repeatability of wafer peak temperature is limited by a variety of local and global effects. Two examples are variations in substrate temperature, and optical power fluctuations which are primarily caused by changes in the transmittance of the beam delivery system. We report on characterization and temperature uniformity performance of a laser spike anneal (LSA) system utilizing a closed loop feedback control system based on thermal emission from the local anneal site. We also report on the results of a characterization of a silicon wafer’s thermal response to temporal variations in incident optical power. Finally, we show that a properly designed measurement and control system enables the achievement of uniform and repeatable peak anneal temperatures.