Ultra Deep Reactive Ion Etching of High Aspect-Ratio and Thick Silicon Using a Ramped-Parameter Process

Tang, Yemin; Sandoughsaz, A; Owen, K. J.; Najafi, K.

doi:10.1109/jmems.2018.2843722

Cited by 61 publications

(32 citation statements)

References 43 publications

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“…Deep reactive‐ion etching overcomes the limitations of reactive‐ion etching and allows the dry etching of nanostructures with aspect ratios typically in the region of 10:1 to 40:1, or in extreme cases up to 100:1, thanks to the use of alternating etch and passivation cycles that increase the overall anisotropy of the process. In the context of biointerfacing, deep reactive‐ion etching is most often used to fabricate solid silicon nanoneedles .…”

Section: Fabrication Techniquesmentioning

confidence: 99%

“…[39][40][41][42][43][44][45][46] The description "high aspect ratio" is loosely defined in the literature, but is typically applied to structures with an aspect ratio equal to or greater than 10:1. [6,[47][48][49][50] In this context, this means the majority of nanostructures we review here are less than 10 µm high, with sub-micron tips (with a few exceptions), see Figure 3. We do not consider micropatches (also referred to as microneedles) in this review, which can share similar aspect ratios, but have heights an order of magnitude larger.…”

Section: Scope Terminology and Takeaway Messagementioning

confidence: 99%

“…Here, we examine surfaces, rather than untethered high‐aspect‐ratio nanostructures, or single‐cell probes . The description “high aspect ratio” is loosely defined in the literature, but is typically applied to structures with an aspect ratio equal to or greater than 10:1 . In this context, this means the majority of nanostructures we review here are less than 10 µm high, with sub‐micron tips (with a few exceptions), see Figure .…”

Section: Introductionmentioning

confidence: 99%

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High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

et al. 2020

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Materials patterned with high‐aspect‐ratio nanostructures have features on similar length scales to cellular components. These surfaces are an extreme topography on the cellular level and have become useful tools for perturbing and sensing the cellular environment. Motivation comes from the ability of high‐aspect‐ratio nanostructures to deliver cargoes into cells and tissues, access the intracellular environment, and control cell behavior. These structures directly perturb cells' ability to sense and respond to external forces, influencing cell fate, and enabling new mechanistic studies. Through careful design of their nanoscale structure, these systems act as biological metamaterials, eliciting unusual biological responses. While predominantly used to interface eukaryotic cells, there is growing interest in nonanimal and prokaryotic cell interfacing. Both experimental and theoretical studies have attempted to develop a mechanistic understanding for the observed behaviors, predominantly focusing on the cell–nanostructure interface. This review considers how high‐aspect‐ratio nanostructured surfaces are used to both stimulate and sense biological systems.

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Section: Fabrication Techniquesmentioning

confidence: 99%

Section: Scope Terminology and Takeaway Messagementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

et al. 2020

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“…DRIE is the most promising micromachining technique to fabricate high-aspect-ratio and high-precision silicon structures to date [32]- [34]. However, at some sub-THz frequencies, where the cross section of rectangular waveguides ranges from 0.254 × 0.127 mm 2 (WR-1) to 2.032 × 1.016 mm 2 (WR-8), it has been always challenging to use DRIE to realize high-quality sidewalls, especially when etching superdeep (larger than 300 μm) and large-opening (wider than 500 μm) trenches [35], [36]. DRIE is an inherently geometry-dependent technology: different underetching for different cavities and feature sizes, as well as etching depths, seriously affects etching accuracy and verticality of the sidewalls [37], [38].…”

Section: Effects Of Fabrication Tolerances On Filter Performancementioning

confidence: 99%

Silicon Micromachined D-Band Diplexer Using Releasable Filling Structure Technique

Zhao

Glubokov

Campion

et al. 2020

IEEE Trans. Microwave Theory Techn.

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A D-band waveguide diplexer, implemented by silicon micromachining using releasable filling structure (RFS) technique to obtain high-precision geometries, is presented here for the first time. Prototype devices using this RFS technique are compared with devices using the conventional microfabrication process. The RFS technique allows etching large waveguide structures with nearly 90 • sidewall angles for the 400-µm-tall waveguides. The diplexer consists of two direct-coupled cavity six-pole bandpass filters, with the lower and the upper band at 130-134 and 141-148.5 GHz, respectively. The measured insertion loss of the two bands is 1.2 and 0.8 dB, respectively, and the measured return loss is 20 and 18 dB, respectively, across 85% of the passbands. The worst case adjacent channel rejection is better than 59 dB. The unloaded quality factors of a single cavity resonator are estimated from the measurements to reach 1400. Furthermore, for the RFS-based micromachined diplexer, an excellent agreement between measured and simulated data was observed, with a center frequency shift of only 0.8% and a bandwidth deviation of only 8%. In contrast to that, for the conventionally micromachined diplexer of this high complexity, the filter poles are not well controllable, resulting in a large center frequency shift of 3.5%, a huge bandwidth expanding of over 60%, a poor return loss of 6 and 10 dB for the lower and the upper band, respectively, and an adjacent channel rejection of only 22 dB.

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“…Fluorocarbon gases such as CF 4 , C 2 F 6 and C 4 F 8 have been used in microfabrication industries for over twenty years [1]. They are used for several purposes, especially the selective etching of Si and SiO 2 [2][3] and high aspect ratio structures through the Bosch process [4][5][6], and depositing intermetallic low-k dielectric films [7][8][9]. Fluoropolymer films are used as interlayer dielectrics because the C-F bonds have a much weaker tendency to polarise in external electric fields as compared to O-H and C-H bonds found in other common films [7].…”

Section: Introductionmentioning

confidence: 99%