Fabrication Process Control to Realize High Yield, Uniform, Repeatable Low-Frequency Detector Arrays for the LiteBIRD CMB Experiment

The LiteBIRD experiment is an international spaceborne mission, led by JAXA, the Japan Aerospace Exploration Agency, to observe cosmic microwave background (CMB) radiation. The satellite will be deployed to measure and characterize the signature of the primordial gravitational waves from cosmic inflation in the B-mode polarization of the CMB radiation. LiteBIRD will also explore the nature of quantum gravity as well as attempt to detect the recombination peak and reionization peak with greater than 5σ significance for a tensor-to-scalar value of r = 0.01. These observations and measurements will take place over 15 separate frequency bands in the range of 34–448 GHz. The 15 frequency channels are separated into three telescopes—low, medium, and high frequency. This paper will describe the process flow developed to fabricate the low frequency detectors, covering bands from 34 to 161 GHz. The detector wafer itself has a device side and a sky side. The device side contains the trichroic polarization sensitive sinuous antennae coupled to transition-edge sensor detectors. The skyside contains the cosmic ray mitigation structure.