Analysis of submicron Cu-Ta-SiO2 structures by highly charged ion secondary ion mass spectroscopy

We have analyzed wafers with submicron copper lines on Ta/SiO2/Si by time-of-flight secondary ion mass spectrometry with highly charged projectiles. The goal of the study was to diagnose the effectiveness of different cleaning solutions during brush scrubbing after chemical mechanical polishing. The advantage of projectiles like Xe44+ lies in the fact that they produce up to three orders of magnitude more secondary ions than singly charge projectiles. Detection of molecular ions (e.g., Cu oxide, Cu hydrocarbon, and alumina ions) enables a detailed assessment of surface conditions on wafers. Analysis of correlations in secondary ion emission from individual impacts gives insight into the chemical structure and homogeneity on a length scale of about 10 nm. (C) 1999 American Vacuum Society. [S0734-211X(99)04605-3].