Quartz Crystal Microbalance Based System for Angularly Resolved Sputter Yield Measurements

摘要

A quartz crystal microbalance (QCM) based system for high sensitivity differential sputter yield measurements of different target materials due to ion bombardment is presented. Detailed knowledge of differential sputter yield profiles can aid optimization of coating processes based on ion beam etching. The setup uses gridded ion sources to provide mono-energetic and collimated beams at different ion energies (~30-3000 eV). To obtain sputter measurements, the QCM deposition monitor is moved to a series of locations above the sputtered target. At each location the rate of mass deposition is measured and the set of measurements provides the differential sputter yield profile. The profiles are fit with analytic expressions using two free parameters to provide a compact description of the profiles. The differential sputter yields can be integrated to find total yields. Examples of differential sputter yield profiles are presented for gold targets that are both bulk materials and films, as well as for multi-component boron nitride targets. In many cases, azimuthally asymmetric profiles with clear non-diffuse behavior are observed. Validation experiments are presented that confirm high sensitivity and accuracy of sputter yield measurements even at ion energies close to sputtering threshold.