Non-Invasive Millimeter-Wave Profiler for Surface Height Measurement of Photoresist Films

Abstract

-This work presents a low-cost non-invasive millimeter-wave surface-height measurement sensor of dielectric and polymer films on glass and quartz substrates. The surfaceheight profiler utilizes near-field resonance measurement technique operating at 96 GHz implemented by using a single complementary split-ring resonator (CSRR) integrated with a tailor-made WR10 rectangular waveguide. By placing a glass or quartz substrate uniformly coated with SU-8 photoresist on top of the CSRR, the thickness of the SU-8 polymer can be extracted based on the reflected and transmitted electromagnetic-wave energy interacting at the electrical boundary between the substrate and polymer film. Uniform single layers of SU-8 polymer with thicknesses from 3 to 13 m, coated on top of glass substrate are measured and characterized. The extracted polymer-film thicknesses from the sensor in this work show an agreement of higher than 95% as compared to the commercial surface profiler instrument, while offering various advantages e.g. non-invasion, ease of measurement setup, low-cost and miniaturization.Index Terms-non-invasive measurement, millimeter-wave sensor, thickness characterization, SU-8 photoresist, W-band.

In-Situ Self-Aligned NaCl-Solution Fluidic-Integrated Microwave Sensors for Industrial and Biomedical Applications

“…The propagating incident microwave signal is then split into two signals, due to the impedance mismatch of the combline resonator; 1) the transmitted signal propagating towards port 2, the output terminal, and 2) the reflected signal propagating back to the input port. By measuring the reflected signal at the input terminal, the percent concentration of the NaCl in aqueous solution can be numerically computed from the amplitude attenuation and the resonant frequency shift, as compared to the incident input signal, using resonant technique [18], [31]. The EM effect of the Teflon tube in the measurement is negligible only when the combline NaCl sensor is first calibrated with an empty Teflon tube used in the measurement setup before an actual measurement with an unknown concentration of the NaCl-aqueous solution under test is performed.…”

“…With microwave measurement techniques, there are several methods to indicate liquid ingredients from liquid-mixture solutions, e.g., resonance frequency [18], [30]- [32], transmission level [17], [32]- [33], phase and quality factor (Q-factor) [23]. Various liquid-mixture sensors based on microwave technologies have been extensively investigated, such as split-ring resonator [34]- [36], complementary split-ring resonator (CSRR) structures [17], [31]- [32], [37]- [38], interdigital structures [8], substrate integrated-waveguide (SIW) structures [18], waveguide structures [30] and mushroom-like structures [23]. These techniques offer a good measurement accuracy [17]- [18], [31], with, generally, nondestructive measurement and short assay time.…”

“…Various liquid-mixture sensors based on microwave technologies have been extensively investigated, such as split-ring resonator [34]- [36], complementary split-ring resonator (CSRR) structures [17], [31]- [32], [37]- [38], interdigital structures [8], substrate integrated-waveguide (SIW) structures [18], waveguide structures [30] and mushroom-like structures [23]. These techniques offer a good measurement accuracy [17]- [18], [31], with, generally, nondestructive measurement and short assay time.…”

An Integrated 3D-Printed Lens with Ultra-Wideband Flower-Shaped Stub Antenna for Ethanol-Water Mixture Characterization

“…In [1], the sensors provide high sensitivity by discriminating ethanol content of approximately 2% in the liquid mixture. Additionally, in [3], the modified H-plane split waveguide is designed for detecting the thickness of the photoresist film by using the resonance technique. The extracted results can discriminate the level of SU-8 layer in micrometer scale.…”