Investigations of Residual Chlorine on Etched AlCu Metal Lines by Total Reflection X-Ray Fluorescence (TXRF)

The present trend in the silicon IC industry is toward the replacement of AlSi metallization by AlCu(Si). However, the addition of Cu to Al(Si) increases the sensitivity of the metallization to moisture corrosion. Total reflection X-Ray Fluorescence (TXRF) with a detection limit in the 1012 atoms/cm2 range is used to measure the residual Cl on Al(Cu) as a function of processing. The results indicate that significant Cl can remain even after standard ash and chemical solvent resist removal. Furthermore, a need is identified to study some unexpected sources of Cl (e.g., air) and the chemistry of its removal from Al films, and this can be now be done easily using TXRF.