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Journal of Undergraduate Research

Keywords

atomic layer deposition techniques, tungsten, hydrogen as a reducing agent

College

Physical and Mathematical Sciences

Department

Physics and Astronomy

Abstract

Introduction: Traditional micro fabrication processes are confined to a small subset of possible materials due to limitations on etching. They are also confined to low aspect ratio fabrication due to limits in both etching process and stability of thicker film deposition processes. Carbon Nanotube Templated Microfabrication (CNT-M) technology has introduced a dramatically different approach to micro fabrication that fabricates without significant etching processes and achieves thick features with the equivalent of thin depositions. This is achieved by forming the desired structure in carbon nanotubes and then filling, or infiltrating, that structure with the material of choice. Optimal materials infiltration for CNT-M should be limited not by mass transfer into the structure, but by sticking of the reacting species to the carbon nanotubes. This technology has been developed at BYU using materials like silicon and carbon; however, a suitable process for metals has not yet been found. Micro fabrication of metals is sought after for their higher density, and improved electrical and mechanical properties as compared to silicon and other traditional micro fabrication materials. I began the project to develop atomic layer deposition (ALD) of tungsten (W), using a gaseous form of W and atomic hydrogen (H) as the reactive agent. This agent is needed for abstracting the nonmetal atoms such as C, O or F that act as ligands for the gaseous form of W. This process has a high likelihood of success for CNT-M application. This success stems from the ability to decouple the mass transfer of the metal from the deposition on the nanotubes. If these processes are successful, a whole new range of micro fabricated devices such as high sensitivity inertial sensors, x-ray collimators, and high strength micro sieve filters will be enabled. All three of these potential applications have commercialization routes either through interest from companies or forming of a company.

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