Auger method to characterize metal oxides on titanium tungsten barrier layer for copper pad

Abstract

Titanium-tungsten (TiW) barrier layers were treated with process chemicals like palladium sulfate (PdSO4), diluted hydrofluoric acid (DHF), O2 plasma etc and the metal oxides change post treatments were investigated. The changes of metal oxides on surface and inside the TiW layer were characterized with Auger surface scan and depth profiling. The dominant species were identified as tungsten oxide (W-O) and copper oxide (Cu-O). Qualitative chart featuring atomic peak intensity (%) in response to the thickness (min) were plotted to show the trends of both W-O and Cu-O across the samples treated with different conditions. DHF can etch away Cu-O but at the same time enhanced W-O. Cu-O was enhanced under slow wet/dried condition at ambient air and by O2 plasma while W-O is not affected in both conditions.