Characterization of post-copper CMP surface with scanning probe microscopy: Part II: Surface potential measurements with scanning Kelvin probe force microscopy

We demonstrate in this paper for the first time the use of Scanning Kelvin Probe Force Microscopy (KFM) to characterize post-CMP copper structures with varying line width and spacing. This work is in the continuity of previously published results concerning surface leakage measurements with conductive Atomic Force Microscopy. The feasibility of KFM will be shown by studying patterned samples and post-CMP copper samples. Results show clearly the capability of this technique in the detection of metallic contamination. It has also been observed that a post-CMP cleaning solution impacts the copper work function. A special study has been done by varying the pH of a cleaning solution. Moreover, electrostatic simulations have been performed to analyse the results obtained for patterned wafers.