Examining process induced contamination: plasma etching and chemical vapor deposition reactors coupled to an in situ surface analytical capability

A comprehensive approach developed for the systematic examination of process induced contamination and reaction mechanisms seen during electronics processing is discussed. The approach is based on a tool which models a cluster tool environment, incorporating both plasma and thermal processing, and coupling them in vacuo to a surface analytical instrument. This tool has been used to examine a number of contamination issues including those arising from the use of fluorine-containing plasma exposed to aluminum and anodized aluminum. It was found that coupons of aluminum and anodized aluminum alloys exposed to NF₃ /Ar or C₂F₆/O₂ plasmas were fluorinated by similar chemical mechanisms but at different rates. These rates correlate with fluorine atom concentrations in the respective plasmas and with DC self bias or ion bombardment. Using in vacuo transfer of the exposed samples, both the extent of reaction between the plasma and substrate and plasma/substrate reaction mechanisms were determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The results suggest that to take advantage of chemical differences between various plasma-cleaning gases, process times should be optimized for fluorine atom concentrations and etch rates