Materials development for auxiliary components for large compact Mo/Au TES arrays

Pursuing the feasibility of scaling conventionally-micromachined transition-edge-sensor (TES) arrays, we have undertaken a study of materials suitable for array integration. A potential limitation of increased pixel count is adequate heatsinking of each detector element to its base temperature. We describe technical approaches for heat sinking large compact TES microcalorimeter arrays and calculate the achievable heatsinking based on measured material parameters. Techniques include backside-deposited thick film copper on arrays with deep-etched wells in the substrates and electroplated gold and copper-filled micro-trenches on the substrate surface. Another limitation is the sensitivity of the thin film circuit elements to applied stress, which can arise in fabrication and mounting of arrays of increasing size. We have explored stress and deposition temperature sensitivity in our molybdenum-based bilayers. Such process parameters can impact options for array heat sinking and electrical interconnects.