Extraction of process-induced damage in low-k/Cu damascene structure

This paper describes the extraction of process-induced damage in low-k/Cu damascene by comparing measured data of interline capacitances of Cu interconnects and parasitic capacitances between the line and the substrate with simulation results. The effective dielectric constants were extracted by fitting the simulated results to the measured capacitances. The extracted dielectric constant of the low-k film increased from 2.1 to 4.5 with decreasing the spacing from 800 nm to 140 nm, indicating that the interfacial damage was induced between low-k and cap layer. It is shown that the interfacial damaged layer with a thickness of 10 nm and a k-value of 34.5 could be formed due to wet chemicals during CMP or Cu electrochemical plating or wet cleaning. The simulated interlines capacitance fitted well to measured data, assuming the void-like damage in the low-k film. Lateral sidewall damage could be caused by dry etching and ashing.