Fabrication of Magnetic Calorimeter Arrays With Buried Wiring

Future astrophysics missions such as the Lynx X-ray Microcalorimeter will comprise a very large array of X-ray microcalorimeters with greater than 100 000 pixels. One of the major challenges associated with the realization of large format arrays is the fabrication of high-density, high-yield, superconducting wiring between the pixels of the array. An attractive way to overcome this challenge is to use buried layers of multilayer wiring. Here we report on the fabrication of prototype arrays of magnetically coupled microcalorimeters (MMCs) using multiple niobium layers of buried wiring. In order to successfully scale MMCs to large arrays, so that the stray inductance of the wiring is sufficiently low and the sensor meander coil inductance is sufficiently high, the meander coil pitch is decreased. We have investigated linewidths as narrow as 400 nm. Fabricated devices have demonstrated high critical currents of 30 mA for the narrowest pitch.