Narrow trench corrosion

Chemical corrosion, which is caused by the CMP slurries, is investigated as a function of the chemicals used, copper line width and pH of the solution. Chemical solutions are prepared using several kinds of acids such as HNO3, H3PO4, HCl, citric acid, malic acid and acetic acid with different concentrations. The solutions that contained inorganic acids resulted in a high etch rate of the isolated copper lines, with widths of 0.2, 0.4 and 1.0 um, as compared to the etch rate caused by the solutions that contained organic acids. Special attention is drawn to the fact that inorganic solutions caused line width dependent etching which increased while line width decreased. On the other hand, organic ones had line width independent behavior. The data are fitted by an empirical equation which correlates the etch rate of copper to line width, with a power dependency. Focused Ion Beam images are presented to demonstrate the results.