XAFS and HAXPES analyses of the oxidation state of a copper surface buried under a phenolic resin nanofilm

Abstract

The oxidation state of a buried copper surface under a phenolic resin insulating layer was investigated by nondestructive analysis methods using conversion electron yield X-ray absorption fine structure (CEY-XAFS) and hard X-ray photoelectron spectroscopy (HAXPES). The formation of Cu2O and CuO during heat treatment at 180 °C in air and the formation of Cu(OH)2 and CuCO3 during long-term storage under atmospheric conditions at room temperature proceeded on the buried copper surface to a depth of tens of nanometers. The phenolic resin nanofilm suppressed the thermal oxidation of the underlying Cu to Cu2O and CuO by 20% but did not suppress the formation of native oxides Cu(OH)2 and CuCO3 under atmospheric conditions because of the high water absorption and high permeability of the phenolic resin nanofilm. This study demonstrated that CEY-XAFS and HAXPES technique are the powerful tools for investigation of oxidation states of the copper surface buried under the phenolic resin insulating layer.