Fabrication of Au-Cu Alloy/Ti Layered Micro-Cantilevers and the Long-Term Structure Stability

This paper presents fabrication of micro-cantilevers with a layered structure of Au-Cu alloy top layer and titanium bottom layer and evaluation of the structure stability for applications as movable micro-components in MEMS inertial sensors. Gold-based materials are advantageous in miniaturization and sensitivity enhancement of MEMS inertial sensors because of the high mass density. The bottom titanium layer and alloying with copper are applied to reinforce the structure stability. The Au-Cu alloy/Ti micro-cantilevers are fabricated by electrodeposition with an electrolyte containing both gold and copper ions and lithography processes. Effects of the applied current density on shape, surface condition, and composition of the micro-cantilevers are studied. The long-term structure stability is revealed by vibration test. The micro-cantilevers are vibrated at a constant acceleration of 1 G (1G = 9.8 m/s
²
) and a constant frequency of 10.0 Hz for up to 10
⁷
cycles. Then, the structure stability is quantified by observing deflections of the micro-cantilevers by a 3D optical microscope.