Low temperature activation of Au/Ti getter film for application to wafer-level vacuum packaging

Abstract

Non-evaporable getter (NEG) thin films based on alloys of transition metals have been studied by various authors for vacuum control in wafer-level packages of micro electro mechanical systems (MEMS). These materials have typically a relatively high activation temperature (300–450 °C) which is incompatible with some temperature sensitive MEMS devices. In this work we investigate the potential of Au/Ti system with a thin or ultrathin non oxidizable Au layer as a low activation temperature getter material. In this bilayer system, gettering activation is produced by thermal outdiffusion of titanium atoms through the gold film. The outdiffusion kinetics of titanium was modelled and characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS) at various temperatures. Results confirm that Au/Ti bilayer is a promising getter material for wafer-level packaging with an activation temperature below 300 °C for 1 h annealing time.