Abstract
The loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single-photon is stored, and analyzed with an independent two-level system defect model. Each a-SiNx:H film was deposited with different concentrations of hydrogen impurities. We find that quantum-regime dielectric loss tangent tan δ0 in a-SiNx:H is strongly correlated with N–H impurities, including NH2. By slightly reducing x we are able to reduce tan δ0 by approximately a factor of 50, where the best films show tan δ0≃3×10−5.
Highlights
The loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single-photon is stored, and analyzed with an independent two-level system (TLS) defect model
Superconducting quantum circuits use amorphous dielectric films for wiring crossovers and capacitors [1,2,3], but these films often cause loss at low temperatures in the quantum-regime where the resonator is occupied by a single photon
There has been recent interest in the low-temperature properties of dielectrics in superconducting devices [6, 7, 9] because they can increase the decoherence rate 1/T1 in a superconducting phase qubits [10] and the phase noise in microwave kinetic inductance detectors [8]. While both films are common in microelectronics, amorphous hydrogenated silicon nitride is found to exhibit less dielectric loss than silicon dioxide (SiO2) in the quantum regime [10]
Summary
The loss of amorphous hydrogenated silicon nitride (a-SiNx:H) is measured at 30 mK and 5 GHz using a superconducting LC resonator down to energies where a single-photon is stored, and analyzed with an independent two-level system (TLS) defect model. Superconducting quantum circuits use amorphous dielectric films for wiring crossovers and capacitors [1,2,3], but these films often cause loss at low temperatures in the quantum-regime where the resonator is occupied by a single photon. We present low-temperature loss measurements of the a-SiNx:H films using superconducting resonators.
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