Surface oxide evolution on Al–Si bond wires for high-power RF applications

Abstract

Contact is often made to bond pads of semiconductor chips using bond wires made of materials such as Al–Si. During device operation, such bond-wires can reach relatively high temperatures. Air exposure at such temperatures can cause oxidation of the wires. Increased wire-resistance can result. The oxidation behavior of bond-wires is therefore of interest. In the present study, Al–Si wires were annealed at technologically relevant temperatures, 240 and 300 °C. Wires with and without such annealing were characterized using transmission electron microscopy (TEM) and scanning Auger microscopy (SAM). Surface oxide was found, initially as a single layer. Upon annealing, the chemical nature of the oxide changed, leading ultimately to a dual-layer oxide. Thicknesses of the oxide layers, however, were three to four orders of magnitude smaller than the wire radius even after extended annealing up to 3000 h.