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Title: Development of a micromechanical characterisation process for thin film MEMS materials and its application to electro-thermal actuators
Author: He, J. H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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This thesis describes a fast and inexpensive test method for the characterisation of mechanical properties, particularly Young’s modulus, of thin films. This technique is based on micro-machined beam bending, and it can be used on a wide range of materials. Firstly, laser micromachining is used to pattern the beam of the thin film material (e.g. silicon nitride on silicon). Next, dry or wet etching (e.g. SF6 or KOH) is used to release the cantilever. Finally, a surface profilometer is used to bend the cantilevers. Beam deflection yields position-displacement traces from which the thin film’s elastic modulus is extracted. Different data analysis methods are investigated and compared. Among them, taking the cube root of the data with force superposition (One large-force profile subtracted from another small-force profile) techniques produces the most consistent results, which are independent of fitting range, loading force, process and samples. Finite Element Method (FEM) simulations, analytical and experimental results are presented to support the extraction and error analysis in terms of root undercut, anticlastic curvature and misalignment effects. A comprehensive analysis of the possible errors is presented. The final result is consistent with the modulus derived from nano-indentation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available