Narrow trench corrosion of copper damascene interconnects

The effect of inorganic and organic acid solutions on the corrosion of copper interconnects is investigated as a function of the copper line width, the type and concentration of the chemical and the agitation speed. The chemical solutions used contained inorganic acids such as HNO3, H3PO4, HCl and organic acids such as citric acid, malic acid and acetic acid. Inorganic acid solutions resulted in strong line width dependent etching (line width; 0.2, 0.4 and 1.0 mum), as compared to the etch rate of the organic acid solutions which showed etch behavior independent of line width. The etch rate changed depending on the acid concentration, however, line width dependent/independent behavior remained the same. The etch behavior caused by the agitation also changes whether organic or inorganic acid solutions are used. The difference of the etching mechanism between inorganic and organic acid solutions is discussed based upon the pitting agent included in the inorganic acid and passivation layer effect of organic acid.