Microwave Spoof Surface Plasmon Sensor for Dielectric Material Characterization

Abstract

A microwave planar resonator sensor design supporting spoof surface plasmon waves is used for wafer dielectric characterization. The proposed circuit guides the microwave as a surface wave across the metal signal line, from port to port of the device. The surface wave effectively interacts with the sample being measured, placed on top of the planar sensor. The proposed planar sensor is fabricated on an RF-35 substrate, resulting in a low-cost implementation. The sensor is used to discriminate between wafers with different dielectric permittivity and thickness. Quartz, borosilicate, BK7 glass, and Silicon wafers have been characterized using the proposed sensor. The sensor resonant frequency and losses change according to the permittivity and the thickness of the samples, with an achieved sensor sensitivity of 60.22 MHz/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ_r</i> . Simulation and measurements demonstrate that the proposed spoof surface plasmon resonator sensor can be used to create a high sensitivity sensor for dielectric material characterization. The dielectric constant and loss tangent of the samples are inferred from a polynomial fit obtained from sample simulations and confirmed through measurements.