A Multistep DRIE Process for Complex Terahertz Waveguide Components

Jung-Kubiak, Cecile; Reck, Theodore; Siles, José V.; Lin, Robert; Lee, Choonsup; Gill, John; Cooper, Ken B.; Mehdi, Imran; Chattopadhyay, Goutam

doi:10.1109/tthz.2016.2593793

Cited by 54 publications

(41 citation statements)

References 13 publications

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“…We note that, although the OMT was designed for machining in metal, the proposed structure is also suitable for microfabrication processes such as silicon deep-reactive ion etching [15]- [17] with minimal additional redesign. In this way, batch-processing of many OMTs simultaneously could be done, which will be more suitable for focal plane array applications.…”

Section: B Full-wave Design and Optimizationmentioning

confidence: 99%

Compact Duplexing for a 680-GHz Radar Using a Waveguide Orthomode Transducer

Leal-Sevillano

Cooper

Decrossas

et al. 2014

IEEE Trans. Microwave Theory Techn.

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Abstract-A compact 680-GHz waveguide orthomode transducer (OMT) and circular horn combination has been designed, tested, and characterized in a radar transceiver's duplexer. The duplexing capability is implemented by a hybrid waveguide quasi optical solution, combining a linear polarization OMT and an external grating polarizer. Isolation between the OMT's orthogonal ports' flanges was measured with a vector network analyzer to exceed 33 dB over a >10% bandwidth between 630 and 710 GHz. Calibrated Y-factor measurements using a mixer attached to the OMT ports reveal losses through the transmit and receive paths that sum to an average of 4.7 dB of two-way loss over 660-690 GHz. This is consistent with radar sensitivity measurements comparing the new OMT/horn with a quasi-optical wire grid beam splitter. Moreover, the radar performance assessment validates the OMT as a suitable compact substitute of the wire grid for the JPL's short-range 680-GHz imaging radar.

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Section: B Full-wave Design and Optimizationmentioning

confidence: 99%

Compact Duplexing for a 680-GHz Radar Using a Waveguide Orthomode Transducer

Leal-Sevillano

Cooper

Decrossas

et al. 2014

IEEE Trans. Microwave Theory Techn.

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“…We made one modification for this work, using a photoresist mask for the etch of the highest-index layer (closest to bulk silicon), due to differences in process details. In particular, we found that the DRIE process has poorer selectivity between SiO 2 and silicon than in [25]. This may be due to the larger volumes of silicon being removed.…”

Section: B Antireflection Structure Fabricationmentioning

confidence: 83%

“…Combining multi-depth etching with wafer bonding may provide a viable technique for broadband AR treatment for powered silicon optics [24]. A multi-depth DRIE technique has been previously demonstrated [25], providing a means to pattern layers with different refractive indices in a single wafer. Multiple wafers could then be bonded together to obtain thick, high layer-count structures needed for very wide-bandwidth AR treatments.…”

Section: B a New Approachmentioning

confidence: 99%

“…In all cases, the desired etch depth divided by the DRIE process selectivity (the ratio of silicon to mask material etch rates) determines the mask thickness. For multi-layer AR structures, we began with the multi-step DRIE process previously reported in [25], where the SiO 2 mask was patterned with steps of different thicknesses, each in proportion to the desired etch depths of the silicon layers. We made one modification for this work, using a photoresist mask for the etch of the highest-index layer (closest to bulk silicon), due to differences in process details.…”

Section: B Antireflection Structure Fabricationmentioning

confidence: 99%

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16:1 bandwidth two-layer antireflection structure for silicon matched to the 190–310 GHz atmospheric window

et al. 2018

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Although high-resistivity, low-loss silicon is an excellent material for THz transmission optics, its high refractive index necessitates antireflection treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment by cutting subwavelength structures into the silicon surface using multi-depth deep reactive ion etching (DRIE). A wafer with this treatment on both sides has <−20 dB (<1%) reflectance over 187-317 GHz at 15°angle of incidence in TE polarization. We also demonstrated that bonding wafers introduces no reflection features above the −20 dB level (also in TE at 15°), reproducing previous work. Together these developments immediately enable construction of wide-bandwidth silicon vacuum windows and represent two important steps toward gradient-index silicon optics with integral broadband antireflection treatment.

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“…To our knowledge, the only previous silicon-micromachined OMT is a side-arm OMT design, which also achieved excellent performance, but was narrow-band (15% BW), and had a high fabrication complexity requiring 6 hard masks and sequential etch steps from one wafer surface [8].…”

Section: Introductionmentioning

confidence: 99%

Wideband 220 – 330 GHz Turnstile OMT Enabled by Silicon Micromachining

Gomez-Torrent

Shah

Oberhammer

2018

2018 IEEE/MTT-S International Microwave Symposium - IMS

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Abstract-This paper is the first publication on the first turnstile-junction orthogonal mode transducer (OMT) above 110 GHz, which is enabled by silicon micromachining. In contrast to other OMT concepts, turnstile OMTs are wideband and allow for co-planar ports, but require accurate and complex fabrication and have therefore, to the best of our knowledge, not been implemented above 110 GHz in any technology. As shown in this paper, the fabrication and assembly accuracy of silicon micromachining enables the realization of such complex OMT designs at 220 -330 GHz with excellent performance. The measured insertion loss is better than 0.7 dB for the whole waveguide band, with mean values of 0.34 dB and 0.48 dB for the vertical and horizontal polarizations, respectively. The measured return loss for both polarizations, even with an openended common port, is better than 14 dB for the whole waveguide band, and an average level of 18 dB. An estimation of the worst-case cross-polarization level, derived from measurements, results in at least 20 dB for the whole waveguide band, with an average of 25 dB for the upper half of the band.

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A Multistep DRIE Process for Complex Terahertz Waveguide Components

Cited by 54 publications

References 13 publications

Compact Duplexing for a 680-GHz Radar Using a Waveguide Orthomode Transducer

Compact Duplexing for a 680-GHz Radar Using a Waveguide Orthomode Transducer

16:1 bandwidth two-layer antireflection structure for silicon matched to the 190–310 GHz atmospheric window

Wideband 220 – 330 GHz Turnstile OMT Enabled by Silicon Micromachining

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