Microwave Loss in Low-Temperature ICPCVD Silicon Nitride: Dependence on Precursor Ratio and RF Substrate Bias

Abstract

Low-loss dielectric films are an important component of superconducting circuits with applications ranging from quantum information to superconducting detectors for astrophysics. In millimeter-wave detector circuits, dielectric loss can be the limiting factor on efficiency and resonator performance. Some advantageous detector fabrication architectures require dielectric deposition at temperatures substantially lower than those conventionally used to achieve low dielectric loss. In this work, we characterize silicon nitride (SiN_x) films deposited by inductively coupled plasma chemical vapor deposition (ICPCVD) at 150 ^∘C for use in temperature-constrained superconducting detector fabrication. We measure the dielectric loss tangent of these films at ∼ 4−7 GHz using superconducting niobium microstrip resonators and extract the loss by fitting the temperature-dependent resonant frequency to a two-level-system model. We vary the N₂/SiH₄ precursor-flow ratio between dielectric depositions and find a clear trend of decreasing loss with decreasing N₂/SiH₄. We additionally find that applying an RF substrate bias during deposition reduces the loss compared to films deposited without bias. These results identify precursor ratio and substrate bias as practical process parameters for improving low-temperature SiN_x for superconducting detector circuits.

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BibTeX RIS

BibTeX

@misc{athreya2026microwave,
  title = {{Microwave Loss in Low-Temperature ICPCVD Silicon Nitride: Dependence on Precursor Ratio and RF Substrate Bias}},
  author = {H. Athreya and J. Cornelison and M. Mikhailov and R. J. H. van der Kolk and C. Chang and T. Cecil and M. N. Ali and J. A. Zebrowski},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.10767},
  eprint = {2610.10767},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.10767},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Microwave Loss in Low-Temperature ICPCVD Silicon Nitride: Dependence on Precursor Ratio and RF Substrate Bias
AU  - H. Athreya
AU  - J. Cornelison
AU  - M. Mikhailov
AU  - R. J. H. van der Kolk
AU  - C. Chang
AU  - T. Cecil
AU  - M. N. Ali
AU  - J. A. Zebrowski
PY  - 2026
DA  - 2026/10/07
PB  - arXiv
DO  - 10.48550/arxiv.2610.10767
UR  - https://arxiv.org/abs/2610.10767
AB  - Low-loss dielectric films are an important component of superconducting circuits with applications ranging from quantum information to superconducting detectors for astrophysics. In millimeter-wave detector circuits, dielectric loss can be the limiting factor on efficiency and resonator performance. Some advantageous detector fabrication architectures require dielectric deposition at temperatures substantially lower than those conventionally used to achieve low dielectric loss. In this work, we characterize silicon nitride (SiN_x) films deposited by inductively coupled plasma chemical vapor deposition (ICPCVD) at 150 ^∘C for use in temperature-constrained superconducting detector fabrication. We measure the dielectric loss tangent of these films at ∼ 4−7 GHz using superconducting niobium microstrip resonators and extract the loss by fitting the temperature-dependent resonant frequency to a two-level-system model. We vary the N_2/SiH_4 precursor-flow ratio between dielectric depositions and find a clear trend of decreasing loss with decreasing N_2/SiH_4. We additionally find that applying an RF substrate bias during deposition reduces the loss compared to films deposited without bias. These results identify precursor ratio and substrate bias as practical process parameters for improving low-temperature SiN_x for superconducting detector circuits.
ER  -

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