Silicon to tungsten ratio determination in tungsten silicide using XRF

The use of X-ray fluorescence (XRF) to measure the silicon to tungsten (Si-to-W) ratio in sputter-deposited tungsten silicide films from a sintered WSi/sub x/ target has been described. It is important to know and control the Si-to-W ratio to maintain good gate stack properties and hence a quick and simple measurement technique is needed for Si-to-W ratio determination. Other techniques such as Rutherford back scattering (RBS) are expensive and time consuming, whereas methods like secondary ion mass spectroscopy (SIMS) are destructive. XRF is less time consuming, simple and noncontact, and hence is preferred in the semiconductor industry since it can be used on product wafers. Certain limitations have been clarified and assumptions have been tested based on theory and experimental results. The results obtained from XRF are compared with those from Rutherford back scattering (RBS) and a good correlation is seen.