Homogeneous substrate heating using a CO2 laser with feedback, rastering, and temperature monitoring

We report results from a highly versatile and scalable raster-scanned conti nuous wave CO2 laser heater incorporating a dual wavelength photodiode-base d temperature monitoring system with feedback control. The system is able t o uniformly heat substrates inside a vacuum chamber, reduce the occurrence of substrate fracture and allow almost negligible heat loss to the depositi on chamber and surroundings. The minimum achievable temperature difference across the substrate is, in practice, limited by the fastest achievable ras ter scan speed. (C) 2000 American Institute of Physics. [S0034-6748(00)0131 1-3].