Promoted bending strength in micro-cantilevers composed of nanograined gold toward MEMS applications

In this research, micro-bending tests of electrodeposited gold with various crystal structure were conducted using micro-cantilever specimens with dimensions at 10 μm × 10 μm × 50 μm for design of gold-based movable structures in MEMS devices. The gold film fabricated by pulse-current electrodeposition with a sulfite-based gold electrolyte (PE-Su) had the finest average grain size, which was at 15.5 nm. The PE-Su gold micro-cantilever showed ductile deformation behavior and the highest yield stress, which was at 800 MPa, because of the grain boundary strengthening mechanism also known as the Hall-Petch relationship. The gold film fabricated by constant-current electrodeposition with a cyanide-based gold electrolyte (CE-Cy) had an average grain size at 17.6 nm. The CE-Cy gold micro-cantilever showed brittle fracture and the yield stress at 480 MPa. The brittle fracture was suggested to be a result of the columnar texture structure in the CE-Cy gold film.