Fabrication of bridge-type microcalorimeter arrays with Ti-Au transition-edge-sensors Available to Purchase

The present stage of cryogenic detector development is focused on fabrication of arrays. Arrays of superconducting-transition-edge-sensor (TES) microcalorimeters have generally been fabricated on $SiNX$ membranes. In conventional membrane structures fabricated by backside etching, it is difficult to realize arrays having both mechanical toughness and a large filling factor. It is possible to overcome these difficulties by using a bridge-type membrane structure, in which $SiNX$ membranes are raised above the Si substrate with a gap of 10–50 μm. In order to carry out etching and other processes, we have fabricated a small scale array with a bridge-type membrane structure. A preliminary version of a TES microcalorimeter array with a $5×5$ pixel structure had dimensions of $6×10 mm2.$ Each pixel consisted of a Ti/Au bilayer with a size of $0.5×0.7 mm2$ on a 1 μm-thick $SiNX$ membrane of $0.7×2 mm2.$ Although the current array exhibited a small filling factor of about 0.1, it is possible to obtain a high filling factor by fabricating mushroom-shaped absorbers.