The Corrosion Behavior of Bimetallic Couples of Cu, Cr, and Ni in Polyamic Acid under Imidizing Conditions

Abstract

Polyamic acid is known to release water and possibly ions during imidization. In addition, it is a strong organic acid which can react with basic metal oxide surfaces. Consequently, questions are raised as to whether significant integrated circuit (IC) line corrosion and, in particular, galvanic corrosion occur during the initial stages of IC manufacture. This study examined the corrosion behavior of Cu, Cr, and Ni in a solution of polyamic acid (PI 2525) and solvent (T9039) at room and elevated temperature, as well as Cu‐Ni, Cu‐Cr, and Cr‐Ni galvanic couples. The anode‐cathode relationships of the galvanic couples at room and elevated temperature were predictable from open‐circuit behavior. Measured galvanic currents for some of the couples predicted significant material loss, particularly in the case of IC dimensions. Questions as to whether any of the anodic current might be partitioned into oxidation of the solvent or polyamic acid were answered by atomic absorption of solvent and polyamic acid/solvent solutions following potentiostatic, galvanostatic, and open‐circuit experiments. Copper ion concentrations measured ion solution were higher than those predicted by Faraday's law suggesting an additional mechanism such as chemical dissolution.