DETERMINATION OF FLUX IONIZATION FRACTION USING A QUARTZ-CRYSTAL MICROBALANCE AND A GRIDDED ENERGY ANALYZER IN AN IONIZED MAGNETRON SPUTTERING SYSTEM

A diagnostic which combines a quartz crystal microbalance (QCM) and a gridded energy analyzer has been developed to measure the metal flux i onization fraction in a modified commercial de magnetron sputtering de vice. The sensor is mounted on a linear motion feedthrough and embedde d in a slot in the substrate plane to allow for measuring the uniformi ty in deposition and ionization throughout the plane of the wafer. Rad io-frequency (rf) power is introduced through a coil to ionize the Al atoms. The metal flux ionization fraction at the QCM is determined by comparing the total deposition rate with and without a bias that scree ns out the ions, but that leaves the plasma undisturbed. By varying th e voltage applied to the grids, the plasma potential is determined. At a pressure of 35 mTorr, a magnetron power of 2 kW, and a net rf power of 310+/-5 W, 78+/-5% ionization was found. (C) 1997 American Institu te of Physics.