Even a cursory glance at the International Technology Roadmap for Semiconductors (ITRS) readily shows that the damascene process ― the filling of high-aspect-ratio vias and lines with copper ― will prove to be difficult in the immediate future. The detection of subtle fill defects or voids in these features continues to be a very serious problem in search of a solution. However, this may soon be resolved with the use of X-ray fluorescence (XRF). XRF has always proven useful for quick qualitative and quantitative analysis. It is a very attractive technology for use in composition and thickness analysis because it accommodates solid samples, metals and insulators, and production wafers. When it is properly calibrated, it can monitor metal film thickness between 0.2 nm and several microns with up to 0.01% precision, depending on which elements are being measured. In a grazing incidence configuration (total reflection X-ray fluorescence, or TXRF), it provides fast, nondestruc- tive, full-wafer monitor capabilities for wafer metal contamination control.
展开▼
