Abstract
In this article, we present a new technology platform for creating compact and loss-efficient wafer-scale integrated micromachined substrate-integrated waveguides with silicon-core (Si-SIWs) for the 230-330-GHz frequency range. The silicon dielectric core enables highly integrated sub-millimeter-wave systems, since it allows for downscaling the waveguide's cross section by a factor of 11.6, and the volume of components by a factor of 39.3, as compared to an air-filled waveguide. Moreover, geometrical control during fabrication of this type of waveguides is significantly better as compared to micromachined hollow waveguides. The measured waveguide's insertion loss (IL) is 0.43 dB/mm at 330 GHz (0.14 dB/λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , normalized to the guided wavelength). A low-loss ultrawideband coplanar-waveguide (CPW) transition is implemented to enable direct measurements of devices and circuits in this waveguide platform, and this is also the very first CPW-to-SIW transition in this frequency range. The measured IL of the transition is better than 0.5 dB (average 0.43 dB above 250 GHz), which is lower than for previously reported CPW-to-SIW transitions even at 3 times lower frequencies; the return loss is better than 14 dB for 75% of the band. As devices examples implemented in this platform, a filter and H-plane waveguide bends are shown. The waveguides and the devices are manufactured by deep-silicon etching using a cost-efficient two-mask micromachining process.
Highlights
C OMMERCIAL interest in highly integrated, costefficient, simple, and reliable ultra-high frequency platforms has grown dramatically in the last couple of decades [1]
Computer numerical control (CNC) milling of metal in split-block designs is the most established method to fabricate waveguide components, since this technology provides relatively high precision and relatively low surface roughness resulting in acceptable low insertion loss (IL) [2]
A promising alternative fabrication technology is siliconmicromachining using deep reactive-ion-etching (DRIE), which allows for batch fabrication, has superior precision, enables high-complexity geometries, as well as nanometer surface roughness and better insertion loss
Summary
C OMMERCIAL interest in highly integrated, costefficient, simple, and reliable ultra-high frequency platforms has grown dramatically in the last couple of decades [1]. Computer numerical control (CNC) milling of metal in split-block designs is the most established method to fabricate waveguide components, since this technology provides relatively high precision and relatively low surface roughness resulting in acceptable low insertion loss (IL) [2]. Due to the inserted dielectric, the losses in SIW are higher than in air-filled waveguides, but still substantially lower compared to planar transmission lines [17]. Probing interfaces require high geometrical accuracy, which limits SIW to frequencies below 100 GHz when using printed-circuit-board (PCB) fabrication techniques. In this article, which extends our conference publication [20], we present a new fabrication technology platform for implementing integrated rectangular waveguides in the 220–325-GHz frequency range using micromachining with DRIE. The platform can be used for integrating active components and building complex sub-THz and THz circuits
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