Development of Superconducting Multilayer Wiring for a 400-Pixel TES X-ray Microcalorimeter Array

Aiming at a large array of transition edge sensors for future astrophysical missions such as DIOS, we have been developing a multilayer readout wiring. Superconducting signal and return lines made of Al sandwich a SiO₂ insulation layer. With this approach, self and mutual inductances are minimized and self fielding of bias leads can be reduced. We fabricated a 20 × 20 transition-edge sensor (TES) array on the multilayer wiring. A series of TES fabrication processes including absorber deposition and membrane formation were tested. However, resistance measurements at room temperature suggest that process yield is not high (~50 %). At low temperature, sharp superconducting transitions were observed for normal TES pixels, while their residual resistances were high (>;10 mΩ) and the critical currents were low (<;10 μA). Reasons for these phenomena and plans for a future TES array fabrication are discussed.