| Summary: | 博士 === 國立中興大學 === 精密工程學系所 === 100 === In this dissertation, the design, construction and use of a novel capacitance measurement system is described. The system can be used to measure the mechanical properties (such as stress – strain curve, energy loss, and fatigue behavior) of ultra thin metal films. In order to measure the metal film samples on the very small scale, a paddle like silicon test specimen has been designed. It is used to carry a metal film on top because a metal film can’t support itself in very small dimension. The dissertation includes the motivation, sample design and fabrication, system design, setup and calibration. In the final two chapters it discusses measurement results of energy loss in Cu and Al thin films and suggestions for future work.
Aluminum and copper thin films are widely used in the semiconductor industry. They are used either in the electronic interconnections or MEMS structures. There have been many previous studies of their mechanical properties, but they have usually focused on the quasistatic properties or dynamic properties in larger scale.
A major goal of this dissertation is to experimentally investigate the dynamic properties of Al and Cu thin films at room temperature under high vacuum conditions. We measured energy loss through decay of oscillation amplitude of a vibrating structure following resonant excitation. We closely examine the film thickness and grain size with respect to the dynamic properties of the films.
The measurement results in this dissertation include gas damping effect on sample decay, resonance frequency changes of various thicknesses paddle samples, stiffness and mass influence on resonance frequencies, and the thickness dependence of internal friction in Cu and Al films. In these results, we found that even at high vacuum the environmental pressure makes a significant contribution to the sample decay rate which changes linearly with pressure. Resonance frequencies of paddle samples have been obtained and the values were compared with fundamental theory calculation and Finite Element Method simulation. We also determine the internal friction of the thin and ultra thin metal films. The internal friction of the thin and ultra thin metal films depend strongly on the film thickness but present entirely different trends in Cu and Al films.
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