Large-Scale Magnetic Microcalorimeter Arrays for the Lynx X-Ray Microcalorimeter

The Lynx X-ray microcalorimeter (LXM) is an imaging spectrometer consisting of an array of greater than 100,000 pixels. Magnetic microcalorimeter (MMC) technology is a leading contender for detectors for the LXM. In this work, we detail the design of a full-size LXM MMC array fabricated using superconducting, multi-layer, buried wiring, with all pixels wired out on a full-size support wafer. We adopt a scheme that facilitates mixing and matching deep UV (DUV) and i-line (365 nm) steppers to stitch the high feature resolution detector array to the large field fanout wiring. To realize the main array of the microcalorimeter, we also employ a sandwich geometry. In this type of pixel, a superconducting ground plane placed above a paramagnetic sensor forces most of the magnetic flux to remain inside the sensor. This device aims to improve the coupling of the sensor to the pick-up coil, and thus enhance the energy resolution. Additionally, we introduce the integration of superconducting flux transformers to optimize the performance of the Ultra High Resolution Array. The wiring to each pixel terminates on bump bond pads, which allow future 2D microwave SQUID-based multiplexer chips to be indium bump bonded over the buried wiring. We present fabrication results and preliminary room temperature electrical measurements.