3D-printed fixture for capacitance measurements of very low permittivity dielectrics.

Abstract

The significant increase in the density of modern integrated circuits (ICs) introduces technological challenges, including in-line parasitic capacitance, which can lead to interactions extending beyond the intended electrical architecture. Extensive research has therefore been conducted on developing novel, low dielectric permittivity (ɛr < 2) materials for IC interlayer coatings. A potentially successful approach is that of introducing porosity into common substrate materials; for example, nanoporous silica aerogels are promising candidates as low permittivity dielectrics. However, accurately measuring the dielectric permittivity of materials is particularly difficult when sample capacitance is low, thereby impeding rapid surveying and optimization of material compositions. In this article, we describe a 3D-printed polymer fixture that simplifies the measurement of low dielectric permittivity via impedance measurements, while the parasitic capacitance of the measuring system itself is maintained at an acceptably low level. To characterize our polymer fixture, we have successfully measured the relative dielectric permittivity of dry nitrogen, dry oxygen, dry helium, and amorphous SiO2 wafers in the very low frequency (VLF) range, 10-27 kHz. Systems that operate in the VLF range include (i) circuits for biological signal processing, characterized by low amplitude and frequency, and (ii) circuits that operate in marine environments, where the frequency range is limited by acoustic signal deterioration. SiO2-based aerogel has the potential to replace the conventional dielectric SiO2 due to its lower relative dielectric permittivity, high dielectric strength, and good gap-fill capabilities. 3D-printing enables the impedance measurement fixture to be highly adaptable, readily adjusted to various size samples and tailored for specific purposes.