Review on copper chemical-mechanical polishing (CMP) and post-CMP cleaning in ultra large system integrated (ULSI)—An electrochemical perspective

The current review describes electrochemical evaluation and study of copper chemical-mechanical polishing (CMP) slurries and post-CMP cleaning solutions. Electrochemical and surface analyses of commercial and new developed CMP slurries over the last decade are discussed. It is stated that the main CMP requirement needed from slurries, to provide copper passivity, is not being complied in all commercial slurries, since copper is being actively dissolved in all of them. Two novel systems based on alkaline weak acid salts (K-sorbate and K-carbonate) are being reviewed, as well. Once considering post-CMP slurries it is shown that HNO₃ based solutions are highly effective in copper layers etching. Simultaneous etching of silicon oxide and copper layers can be efficiently conducted in diluted HF solutions. The composition of etching solution usually includes inhibitors, and surface active compounds. However, copper etching in aqueous solutions is usually accompanied with a deposition of corrosion products (Cu(1) compounds). Formation of such deposition is being determined electrochemically subsequent to an etching process (at OCP) in some of the recommended post-CMP cleaning solutions. Cautious consideration should be taken once choosing the most appropriate etching solution for Cu post-CMP cleaning.