Nano-indentation method for the measurement of the Poisson's ratio of MEMS thin films

A nano-indentation method is presented to measure the Poisson's ratio of thin films for micro-electro-mechanical systems (MEMS) applications. Double-ring shaped specimen is designed to facilitate the measurement of the Poisson's ratio. The Poisson's ratio can be obtained through analyzing the load-deflection data of the double ring specimen subjected to nano-indenter loading. The compatibility to the surface micromaching makes in situ measurement of the Poisson's ratio feasible. The Poisson's ratio is obtained as local quantity, not an average value over the wafer, due to the small size of the specimen. To validate the proposed method, the Poisson's ratio of LPCVD polysilicon with thickness of 2.33 mum is measured. Experimental results reveal that the Poisson's ratio of the polysilicon film is 0.254 +/- 0.0125. (C) 2003 Elsevier B.V. All rights reserved.