Design and development of MEMS-based structures for in-situ characterization of thermo-mechanical behaviour of thin metal films

摘要

The reliability as well as performance of micro electronic devices strongly depends on the resistance to their thermal degradation induced during operation. In present work, a process flow is developed to fabricate Micro-Electro-Mechanical systems (MEMS) structures, which provide a reliable platform to study thermo-mechanical aspects of silicon-thin metal interface at different temperatures. Here different submicron structures such as cantilever, beams, plus sign, theta and curved cantilevers of varying dimensions are fabricated. The process demonstrates flexibility to manufacture different structures, where the thickness of silicon and of copper can be varied independent to each other. Features based on Si with thickness of 4 or 11 μm coated with Cu of 0.5–3 μm in thickness are manufactured and used as plus signs and curved cantilevers to study deformation over the temperature range of -50 °C to 400 °C. Deflections from 3 μm tensile to -8 μm compressive are observed. This study gives an experimental evidence of behaviour of copper over thermal cycling using MEMS structure. Moreover, Si-Cu based structures are subjected to high temperature cycling to induce degradation and microstructure of their interface is studied. This methodology offers flexibility to characterize different kinds of thin films of various dimensions under individual process conditions.