Semester

Spring

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Lane Department of Computer Science and Electrical Engineering

Committee Chair

Dimitris Korakakis

Abstract

Aluminum Nitride (AlN) is a group III--V compound that grows in a hexagonal wurtzite crystal structure and is a popular material for microelectromechanical systems (MEMS) due in part to its piezoelectricity, inertness and tolerance to high temperatures. High temperature stability is an essential characteristic for numerous MEMS applications, so one of the goals of this work is to determine how the material properties of AlN are affected by exposure to high temperatures and harsh environments. 3D AlN devices are also investigated to determine the effect of electric field isolation on the piezoelectric response of AlN.;A Rapid Thermal Annealing (RTA) system was used to anneal the AlN films at temperatures up to 1000°C in ambient and controlled environments. The oxygen content of films annealed in an ambient environment was measured along with the piezoelectric coefficient (d33) to determine the effect of oxygen incorporation on the piezoelectric response of the films. A high temperature test chamber was designed and built for in-situ high temperature piezoelectric measurements of AlN. The results of the ex-situ and in-situ high temperature experiments, the effects of oxidation on the piezoelectric response of AlN, and methods used to protect the films from oxidation are discussed.;Typically, a metal layer covering the entire AlN film is used as a top electrode in d33 measurements. In this work, circular AlN mesa structures, consisting of an AlN layer, with thicknesses between 200--1000nm, between two ∼200nm metal layers, have been created. By decreasing the contact size and limiting the surface area of the AlN film, clamping effects are reduced. This configuration also minimizes non-normal electric field lines between the top and bottom contacts and further isolates the d33 piezoelectric coefficient. The devices are constructed using two different fabrication methods and the piezoelectric and electrical properties have been studied.

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