Temperature measurement and heat-treating methods and systems. One method includes identifying a temperature of a first surface of a workpiece, and controlling energy of an irradiance flash incident on the first surface of the workpiece, in response to the temperature of the first surface. Identifying may include identifying the temperature of the first surface during an initial portion of the irradiance flash, and controlling may include controlling the power of a remaining portion of the irradiance flash. The first surface of the workpiece may include a device side of a semiconductor wafer.