Fabrication of MEMS based structures for characterization of thin metal films by nanoindentation technique

Abstract

Micro-Electro-Mechanical systems based structures offer a reliable platform for investigating properties of thin metal film which are strongly influenced by the deposition process as well as post processing conditions during the wafer processing. The present work introduces a methodology to fabricate free standing structures based on silicon on Insulator (SOI) technology, which offers a tool to study material properties of silicon-thin metal interface under different conditions. A variety of micro structures such as straight/curved cantilevers, beams, as well as plus sign and theta specimens of varying dimensions have been fabricated. Different micro structures of silicon having thisckness of 2.8-3$\mu\mathrm{m}$ were deposited with copper films of 1000-3000 nm thicknesses. Among them, cantilevers of different dimensions have been used to study the varying grain size of copper from submicron to micrometer range. By using the nanoindentation technique, the stiffness and modulus of elasticity measurements were carried out for pure silicon cantilevers of varying width and Si-Cu compsite cantilvers of varying copper thicknesses with different grain size. This methodology of fabrication offers flexibility to characterize different kinds of thin films of various dimensions and study the impact of individual process conditions on properties of thin films.