Measuring the permittivity of fused silica with planar on-wafer structures up to 325 GHz

Published

February 12, 2024

Author(s)

Nicholas Jungwirth, Florian Bergmann, Bryan Bosworth, Jerome Cheron, Christian Long, Nathan Orloff

Abstract

Fused silica has become an interesting alternative to silicon for millimeter-wave (mmWave) applications. Unfortunately, there are few reports on the measurement of fused silica's permittivity above 110 GHz using electrical rather than optical methods. However, electrical circuitry is the preferred infrastructure for mmWave applications. To test the feasibility of electrical methods, we apply on-wafer techniques based on coplanar waveguide transmission lines to measure the complex permittivity of fused silica to 325 GHz. Our approach applied the multiline thru reflect line algorithm on the scattering parameter measurements of transmission lines. Our method combined these results with dc measurements of the resistivity of the metals, simulations of the coplanar waveguide cross section, and dimensional metrology. The resulting complex permittivity was ϵ_r =3.87±0.04 and a loss tangent tanδ< 0.005 from 320 MHz to 325 GHz. To support our conclusions, we performed an uncertainty analysis considering several sources of uncertainty. In the broader context, these results show that fused silica is a suitable substrate for mmWave electronics where the loss tangent must be less than 0.005 up to 325 GHz.

Citation

Applied Physics Letters

Volume

124

Issue

7

Pub Type

Journals

Download Paper

https://doi.org/10.1063/5.0188240

Local Download

Keywords

Microwave, mmWave, Wafer, Coplanar Waveguide, Permittivity, Fused Silica

Citation

Jungwirth, N. , Bergmann, F. , Bosworth, B. , Cheron, J. , Long, C. and Orloff, N. (2024), Measuring the permittivity of fused silica with planar on-wafer structures up to 325 GHz, Applied Physics Letters, [online], https://doi.org/10.1063/5.0188240, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956320 (Accessed January 14, 2025)