Enhanced process stability for the low temperature sputter deposition of aluminium nitride thin films

Abstract

MEMS(micro electro-mechanical systems)operated in resonance and excited piezoelectrically arenowadays used for a broad range of different application scenarios. To enhance the process stabilityand hence, the reproducibility of keyfilm parameters of sputter-deposited aluminium nitride such asthefilm stress, the piezoelectric coefficientd33and low leakage current levels, a novel aluminiumclamped substrate holder is reported. Compared to the standard molybdenum based solution, wherethe thermal contact between the wafer and substrate holder varies during deposition, as the wafer canmove freely, the substrate temperature variations are substantially reduced due to clampedconfiguration. Independent of AlNfilm thickness ranging between 0.5μm and 2.0μm the scatter inpiezoelectric constantd33and leakage current characteristics represented by the barrier height and theactivation energy is reduced up to a factor of 3. These results demonstrate the importance to controlcarefully the temperature conditions during low-temperature AlN deposition to ensure a highreproducibility infilm properties.