Mechanical & Materials Engineering, Department of


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A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering, Under the Supervision of Professor Brian W. Robertson. Lincoln, Nebraska: May, 2011
Copyright 2011 Dhairyashil U. Aher


To the best of our knowledge, the mechanical properties of PECVD boron carbide (BC) grown using ortho-carborane as a source molecule have never been investigated before. Therefore, this thesis is an attempt to apply the bulge test and the nanoindentation technique for the mechanical characterization of PECVD BC thin films. Mechanical properties such as the Young’s modulus, hardness and residual stress were investigated. The bulge test system using an interferometry technique to measure the deflection of membrane has been designed. Commercially available LPCVD SiNx membrane windows were used as a substrate to deposit BC films for the bulge test. The effect of SiNx membrane configuration on the stability of SiNx/BC bi-layer membranes is also studied. The bulge test was used to investigate the residual stress in annealed BC films with two different thicknesses close to 59 and 74 nm.

The nanoindentation technique has been used to investigate the Young’s modulus and the hardness of as-deposited and annealed BC films deposited on silicon substrates. The properties of three film thicknesses close to 100, 200, and 300 nm have been investigated in each category. The compressive stress and the density of films were found to be the two important factors affecting the Young’s modulus and the hardness of BC films. The investigated properties are compared with literature values of BC films deposited by different forms of sputtering techniques. Spectroscopic ellipsometry was used to investigate film thickness.

Advisor: Brian W. Robertson