Full Wafer Process for Microfabrication of Superconducting Tunnel Junctions as Phonon Detectors

A thesis submitted to the faculty of
San Francisco State University
in partial fulfillment of the
requirements for the

Master of Science


Mark Forrest Cunningham

San Francisco, California

December, 1996


The motivation for the development of a new class of elementary particle detector arises primarily from the search for dark matter and from the rapidly evolving field of x-ray astronomy. A promising category of detector measures the low energy phonons created when an incident particle interacts with a nucleus or electron in an ultra cold crystal of silicon or germanium. This thesis describes a thin film microfabrication Full Wafer Process used to make superconductor-insulator-normal tunnel junctions as phonon detectors. It also describes pulse data from an x-ray source used to determine the effect of superconducting lead geometry and normal - normal tunneling resistance on the removal of hot quasiparticles from the tunneling region of the detector.