Fabrication of MKIDS for the MicroSpec Spectrometer

Abstract

Microspec is a new class of submillimeter and millimeter (250-700 μm wavelength) spectrometer, in which the wavelength separation and detection of incident light is done on a single substrate. The instrument is designed for space exploration by offering high spectral resolving power over a broad band, while being orders of magnitude smaller in mass and volume than the present state-of-the-art. The key enabling components for Microspec are background-limited microwave kinetic inductance detectors, which operate over the full bandwidth of the spectrometer. Here we present our fabrication strategy for making these sensitive detectors. A microstrip architecture utilizing a 0.45-μm crystalline silicon dielectric with a molybdenum nitride kinetic inductor material has been adopted. We have optimized wafer-scale lithographic patterning, and have developed processes that allow us to minimize surface roughness that may contribute to detector noise. Additionally, we have optimized the low-temperature wafer bonding process; this process allows us to build superconductors on both sides of the silicon dielectric layer. We present a final fabricated device and resonator operation at cryogenic temperatures.