DIODE-LASER-BASED ATOMIC-ABSORPTION MONITOR USING FREQUENCY-MODULATION SPECTROSCOPY FOR PHYSICAL VAPOR-DEPOSITION PROCESS-CONTROL

We have developed an atomic monitoring system for physical vapor depos ition process control based on a frequency-modulation (FM) spectroscop y scheme using a 670 nm external cavity diode laser. FM detection made it possible to measure absorption as low as 10(-6). For electron-beam evaporated yttrium, deposition rate control with a relative accuracy better than 1% at a rate of 3.5 Angstrom/s has been realized, correspo nding to a deposition rate resolution of 0.03 Angstrom/s. Variations i n Doppler shifts due to the velocity distribution of the atomic vapor within the deposition chamber have been measured, demonstrating the po ssibility of velocity mapping of evaporated atoms in the deposition pr ocess. (C) 1995 American Institute of Physics.