Superconducting Tunnel Junction Arrays for UV Photon Detection

An innovative method is described for the fabrication of superconducting tunnel junction (STJ) detector arrays offering true "three dimensional" imaging throughout the UV, visible and near-IR spectrum. Current state-of-the-art STJ detectors are fabricated from thin epitaxial Ta films that must be deposited at high temperatures on sapphire substrates. The subsequent metal films necessary to complete the STJ may be deposited at ambient temperature, but all of these films must be deposited uniformly with low stress and tight thickness control if acceptable device yields are to be achieved. We propose to develop a reliable and reproducible Ta STJ fabrication process using an advanced thin-film deposition tool that features a precision backside heater for reproducible depositions of high-quality epitaxial films and computer-controlled deposition modes that ensure excellent reproducibility and film uniformity (better than 98%) across an entire wafer. The combination of these unique deposition features is essential for the reproducible fabrication of reliable STJ detector arrays with uniform device properties and high production yields.