Phononic Isolated Kinetic Inductance Detector Fabrication Process
sensors
Phononic Isolated Kinetic Inductance Detector Fabrication Process (GSC-TOPS-252)
A fabrication process that can integrate a phononic crystal into a kinetic inductance detector architecture to reduce the loss of athermal phonons
Overview
Kinetic Inductance Detectors (KIDs) are highly sensitive superconducting cryogenic detectors which can be scaled to very large format arrays. However, KID detectors are not as sensitive as transition edge sensor bolometers. Currently, no detector technology exists that meets the requirements for next generation space telescopes which have specific noise-equivalent power (NEP) and stability requirements. NEP is a measure of the sensitivity of a detector system. Many space telescopes also require large format arrays. KIDs are highly scalable to large format arrays, but have not demonstrated adequate NEP, since they are often limited by the generation recombination rate of quasi-particles in the superconducting film. The Phononic Isolated KID Fabrication Process reduces the NEP without sacrificing scalability.
The Technology
The Phononic Isolated KID Fabrication Process utilizes a silicon on insulator, or a silicon wafer coated with a thin film bilayer of silicon oxide and silicon nitride (or amorphous silicon), to be used as the starting wafer. The silicon or silicon nitride thin films act as the structural material. The films thicknesses are chosen based on the desirable phononic crystal properties. The phononic crystal is patterned with electron beam lithography to get minimum features. The structures are etched in a fluorine plasma chemistry stopping on the oxide layer. The niobium or other superconductor layer is deposited, patterned, and etched. This can be done in a liftoff process so as not to damage the SiN or Si underlayer. A hafnium or other superconductor is deposited, patterned, and etched to function as the kinetic inductance material. A silicon handle wafer is patterned and etched using deep reactive ion etching which stops on the silicon oxide. The silicon oxide is etched in hydroflouric acid and a wax bonding material used as a temporary bonding material is dissolved. The final structure is removed from the temporary handle wafer. This process is beneficial in that it is simple aside from the incorporation of the nanostructured membranes.
The Phononic Isolated KID Fabrication Process is an implementation of incorporation of a phononic crystal into a KID architecture. The process can also incorporate a second dieletric material such as nanocrystalline diamond that can be used as a stiffening material for the phononic crystal.
Benefits
- Improves detector performance
- Enables salability for cryogenic detectors
Applications
- High performance cryogenic detector technology
- Single photon calorimetry
Technology Details
sensors
GSC-TOPS-252
GSC-18244-1
GSC-18400-1
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