Reactive Ion Etching Of Silicon Research Articles

Generalized prism-array lenses for hard X-rays

A Fresnel-like X-ray lens can be constructed by a triangular array of identical prisms whose base corresponds to the 2pi-shift length. Each column of prisms is progressively shifted from the optical axis by an arbitrary fraction of the prism height. Similarly to the multi-prism lens, quasi-parabolic profiles are formed by a superposition of straight-line segments. The resulting projected lens profile is approximately linear with a Fresnel-lens pattern superimposed on it to provide the focusing. This geometry exhibits a significantly larger effective aperture than conventional parabolic refractive lenses. Prototype lenses were fabricated by deep reactive ion etching of silicon. These one-dimensionally focusing lenses were tested at a synchrotron beamline and provided focal line-widths down to 1.4 microm FWHM and an intensity gain of 39 at a photon energy of 13.4 keV. Fabrication imperfections gave rise to unwanted interference effects resulting in several intensity maxima in the focal plane. The presented design allows the focal length to be shortened without decreasing the feature size of the lens. Furthermore, this feature size does not limit the resolution as for real Fresnel optics.

Silicon bridge type micro-gas sensor array

Silicon bridge type micro-gas sensor array was fabricated for detecting hydrogen sulfide (H 2S) and ethanol (C 2H 5OH) gases simultaneously. Anisotropic wet etching of silicon in 25 wt.% KOH solution at 80 °C and silicon reactive ion etching (RIE) were applied to achieve the bridge type sensor for low power consumption. The fabricated device size and active region are 2 mm× 2 mm and 85 μm× 75 μm, respectively. SnO 2–CuO and SnO 2–Pt thin films were deposited on bridge type micro-heater in a simple way. The sensing characteristics of the packaged micro-sensor to target gases were also investigated.

Micro-ejector to supply fuel–air mixture to a micro-combustor

Micro-ejectors to supply fuel–air mixture to micro-combustors were fabricated and tested. The ejector sucks air using the jet of vaporized liquid gas ejected from a nozzle by its own vapor pressure, and needs no moving part and electric power supply. A tapered nozzle and a Laval nozzle were fabricated by the deep reactive ion etching of silicon. Using the Laval nozzle, which produces supersonic flow, the performance of the ejector becomes high, and the maximum entrainment ratio, which is defined as the volumetric ratio between ejected fuel flow and sucked air flow, reached 36.8. This entrainment ratio is stoichiometrically enough for the complete combustion of butane (>31). At this time, the flow rate of fuel–air mixture was 394 sccm. We investigated several characteristics of the prototyped ejectors. The most important problem that we found is that entrainment ratio considerably drops, when several tens Pa pressure is applied at the exit of the ejector by the pressure loss of a combustor. However, the performance of the ejector will be improved by optimizing the design of the Laval nozzle according to the supplied pressure of fuel.

Prevention method of a notching caused by surface charging in silicon reactive ion etching

This paper proposes a method to prevent silicon from a notching in a reactive ion etching (RIE) process by introducing a self-aligned metal interlayer to a silicon/glass bonded fixture. A metal interlayer prevents a charge buildup at the bottom of a silicon trench, therefore silicon structures do not suffer from charge-induced local damage. A self-aligning process of Ti/Au interlayer is accomplished by a lift-off process using a photoresist etch mask as a sacrificial layer. Titanium is a diffusion barrier of gold to silicon and gold is preferred due to its chemical stability in a pre-cleaning step. The effectiveness of the proposed method is verified by applying it to the fabrication of a simple trench and comb electrode. The applicability of the proposed methodology is examined by fabricating an optical knife edge device.

Anisotropic etching of silicon in SF6 plasma

The reactive ion etching of silicon in SF6 plasma is considered. During the experiment, silicon substrates are etched in SF6 plasma at different pressures and energies of incident ions. High etching anisotropy is achieved decreasing the pressure in the reactor and increasing the energy of the bombarding ions. The obtained experimental measurements are compared with theoretical calculations. It is determined that the temperature of the sidewalls decreases with the decrease of concentration of F atoms due to suppressed plasmochemical etching of silicon. The etching anisotropy increases with the decrease of concentration of F atoms due to decreased desorption of SiF4 molecules.

Vertically-coupled micro-resonators realized usingthree-dimensional sculpting in silicon

A modified separation by implantation of oxygen process has been developed to sculpt vertically coupled microdisk resonators in silicon. The approach involves the implantation of oxygen ions into a silicon substrate, patterned with thermal oxide, to define waveguides on the bottom silicon layer, and photolithography and reactive ion etching to define the microdisk resonators on the top silicon layer. The top and the bottom silicon layers are separated by the oxide layer that was formed after the oxygen implantation. Fabricated microdisk resonators show resonances with a Q value of 10 300 and a free spectral range of 5.4nm.

Bidirectional pumping properties of a peristaltic piezoelectric micropump with simple design and chemical resistance

A planar bidirectional valveless peristaltic micropump for controlling biosamples and reagent fluids was designed with a very simple structure and fabricated employing microelectromechanical system technologies, which include deep reactive ion etching in silicon and silicon–glass anodic bonding techniques. The proposed micropump consists of piezoelectric disks, silicon, and glass, thereby having the advantage of being resistant to aggressive media. The pump diaphragms are excited by applying pulse signal voltages to three lead zirconate titanate (PZT) disks on glass plates. For the channel and chamber in the silicon, the deep reactive ion etching process is utilized and a glass wafer is bonded to the pump-cavity side of the silicon wafer using an anodic bonding machine. The entire pump chip is 30×20×1 mm 3. The proposed micropump was able to control bidirectionally the flow rate of sample water at ∼12 μl/min (20 nl/stroke) and sample air at ∼60 μl/min (100 nl/stroke) based on a frequency of 10 Hz at 120 peak-to-peak voltage. In addition, actuation modeling of the PZT–glass actuator was performed using a Coventor simulator, CoventorWare, and the simulation results agreed well with the experimental measurements.

Electrostatic MEMS Variable Optical Attenuator With Rotating Folded Micromirror

The design and fabrication of an electrostatic MEMS variable optical attenuator (VOA) is described. The VOA is a reflection type with a folded micromirror actuated by a comb-drive actuator. The VOA is fabricated by a simple single-mask process. One photolithography and subsequent deep silicon reactive ion etching define all the microstructures of the VOA. The folded micromirror structure can reduce the overall size of the device by enabling the parallel alignment of an input fiber and an output fiber. Lensed fibers are used to maximize the coupling efficiency and the ease of assembly. The electrooptic characteristics and dynamic characteristics of fabricated VOA are measured. The initial insertion loss is 0.5 dB at 1550 nm and the maximum attenuation is 45 dB, respectively. The polarization dependent loss is measured to be 0.2 dB at 20-dB attenuation. The response time for maximum attenuation is less than 5 ms.

Robust SOI process without footing and its application to ultra high-performance microgyroscopes

A microgyroscope with flat bottom surfaces free from the notching effects of deep silicon reactive ion etching (RIE) is fabricated by combining the silicon on insulator (SOI) process with the sacrificial bulk micromachining (SBM) process. Roughened bottom surfaces and loose silicon fragments are common problems in the conventional deep silicon RIE process using SOI wafers. In this paper, the silicon fragments are removed and the roughened bottom surfaces are smoothed by the SBM process. An other problem in the SOI process is the stiction due to the relatively small sacrificial gap. In this paper, a large sacrificial gap of 20 μm is used to prevent the structure from sticking to the substrate. A gyroscope is fabricated by the proposed method. The measured noise equivalent resolution is 0.0044°/s, and the measured bandwidth is about 13 Hz. The angular random walk is 0.0012°/(s (Hz) 1/2).

Microfabrication of Piezoelectric MEMS

In this paper we present an overview of processes for fabrication of piezoelectric thin film devices using PZT (Pb(ZrxTi1−x)O3) in planar structures. These structures are used in cantilever-like and membrane configurations for sensing and actuation. Elaboration of a compatible wet and dry etching sequence for patterning of PZT, electrodes, SiO2 and silicon substrate is the key issues. The method for compensation of mechanical stresses to obtain flat, multilayer structures is demonstrated. Definition of membrane thickness and release of the structures are obtained by Deep Reactive Ion Etching of silicon or by surface micromachining. The complete process has been used for fabrication of cantilever arrays, ultrasonic transducers and pressure sensors. Excellent permittivity and transverse piezoelectric coefficient of PZT have been obtained with the final devices.

STUDY ON FEATURE OF SILICON MICROTRENCHES WITH A MULTIPLEXED INDUCTIVELY COUPLED PLASMA ETCHER

International Journal of Computational Engineering ScienceVol. 04, No. 02, pp. 319-322 (2003) Silicon MicromachiningNo AccessSTUDY ON FEATURE OF SILICON MICROTRENCHES WITH A MULTIPLEXED INDUCTIVELY COUPLED PLASMA ETCHERTIETUN SUN, JIANMIN MIAO, HONG ZHU, CIPRIAN ILIESCU and J. B. SUNTIETUN SUNSchool of M. P. E, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore Search for more papers by this author , JIANMIN MIAOSchool of M. P. E, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore Search for more papers by this author , HONG ZHUSchool of M. P. E, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore Search for more papers by this author , CIPRIAN ILIESCUInstitute of Bioengineering and Nanotechnology, 51 Science Park Road, The Aries, Singapore 117586, Singapore Search for more papers by this author and J. B. SUNSchool of M. P. E, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore Search for more papers by this author https://doi.org/10.1142/S1465876303001174Cited by:2 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractIn this paper, dry etching of silicon micro-trenches were completed with a time multiplexed inductively coupled plasma (ICP) etcher. By change the time of etching and passivation cycles, applied electrode and coil powers, gas flow rates and the gas flow overlap due to the finite time response of the mass flow controllers, the etch rate of silicon and mask materials, aspect ratio, the profiles of photoresist and silicon microtrenches were affected. The roughness of the sidewall has been decreased to 20 nm. The relationship between roughness of sidewall and process parameters for different width and depth of silicon trenches are presented.Keywords:Deep RIEmicrotrenchessidewall roughness References Kurt E. Petersen, Proceeding IEEE 70(5), (1982). Google Scholar Marc J. Madou , Fundamentals of microfabrication ( U.S.A. Press , 2001 ) . Google Scholar FiguresReferencesRelatedDetailsCited By 2Deep reactive ion etching of silicon using non-ICP-based equipmentZaifa Du, Junyang Nie, Dianlun Li, Weiling Guo and Qun Yan et al.19 June 2020 | Applied Physics A, Vol. 126, No. 7Silicon microneedle array with biodegradable tips for transdermal drug deliveryBangtao Chen, Jiashen Wei, Francis E. H. Tay, Yee Ting Wong and Ciprian Iliescu8 January 2008 | Microsystem Technologies, Vol. 14, No. 7 Recommended Vol. 04, No. 02 Metrics History KeywordsDeep RIEmicrotrenchessidewall roughnessPDF download

Deep reactive ion etching of silicon and diamond for the fabrication of planar refractive hard X-ray lenses

We report on the fabrication of diamond and silicon refractive X-ray lenses. These are made using e-beam lithography and deep reactive ion etching. The diamond lenses are promising candidates for optics meeting the extreme requirements of planned X-ray sources based on the free electron laser principle. The silicon lenses are well suited for micro-focusing applications at hard X-ray energies above 20 keV. We measured efficiencies up to 78% and a width of the line-focus down to 3 μm for these lenses. The possibility to compensate for lens aberrations using stacked lenses is discussed. A simple method for the stacking of two silicon devices (lenses) by means of micro-mechanical alignment marks is shown, giving an alignment accuracy in the micron range.

Formation of polymeric layer during silicon etching in CF2Cl2 plasma

The reactive ion etching of silicon in a CF2Cl2 plasma was considered. Different kinetics of the etching process at energies of bombarding ions of 100 and 400eV were observed. The polymeric layer is formed in both cases. Compositions of polymeric layers were measured by X-ray photoelectron spectroscopy (XPS) to explain the kinetics of etching rates. Significant variations of composition of polymeric layers were observed. It was found that the variations of concentrations of free and reacted carbon and alternation of bonds type on the surface influence the etching rate. XPS measurements showed that C–CF and CF–CCl species form Teflon-like polymer in later stages of the etching process. The polymer formed suppresses the etching process at low ion energy. Energy of bombarding ions of 400eV is sufficient to destroy partially the polymer and to produce etching. A theoretical model was proposed to explain the kinetics of composition of polymeric layers.

External cavity laser with a vertically etched silicon blazed grating

An external cavity laser based on a stripe waveguide semiconductor optical amplifier, a ball lens, and a blazed diffraction grating fabricated by vertical deep reactive ion etching of silicon is demonstrated. Bandpass characteristics for a 12th-order grating are given. Tuning of an external cavity laser over a 120-nm spectral range is demonstrated, with a maximum single-mode fiber-coupled power of 1 mW and side-mode suppression ratio of 30 dB.

Fabrication of multiple nano-electrodes for molecular addressing using high-resolution electron beam lithography and their replication using soft imprint lithography

Abstract We investigate the ability for High Resolution Electron Beam Lithography (HREBL) to fabricate multiple nano-electrodes with the smallest gap in the smallest area. By using both standard PolyMethylMethAcrylate (PMMA) as resist and standard MIBK/IPA development, we show that up to 10 nano-electrodes can be realized in an area as small as 65 nm. The obtained structures have been used either for the realization of embedded electrodes in SiO 2 by wet etching followed by lift-off, or for the fabrication of molds for Nano-Imprint Lithography using PMMA as a mask for Reactive Ion Etching of silicon. Preliminary results on the replication of these molds using a soft nano-imprint process are also presented.

Surface/bulk micromachined single-crystalline-silicon micro-gyroscope

A single-crystalline-silicon micro-gyroscope is fabricated in a single wafer using the recently developed surface/bulk micromachining (SBM) process. The SBM technology combined with deep silicon reactive ion etching allows fabricating accurately defined single-crystalline-silicon high-aspect-ratio structures with large sacrificial gaps, in a single wafer. The structural thickness of the fabricated micro-gyroscope is 40 /spl mu/m, and the sacrificial gap is 50 /spl mu/m. For electrostatic actuation and capacitive sensing of the developed gyroscope, a new isolation method which uses sandwiched oxide, polysilicon, and metal films, is developed in this paper. This triple-layer isolation method utilizes the excellent step coverage of low-pressure chemical vapor deposition polysilicon films, and thus, this new isolation method is well suited for high-aspect-ratio structures. The thickness of the additional films allows controlling and fine tuning the stiffness properties of underetched beams, as well as the capacitance between electrodes. The noise-equivalent angular-rate resolution of the SBM-fabricated gyroscope is 0.01/spl deg//s, and the bandwidth is 16.2 Hz. The output is linear to within 8% for a /spl plusmn/20/spl deg//s range. Work is currently underway to improve these performance specifications.

Fabrication of a silicon based electroluminescent device

In this paper we present a fabrication process for an electroluminescent device based on silicon nanopillars. The pillars were obtained by means of self-organized gold–chromium mask and reactive ion etching of silicon. Mask properties that influence pillar size distribution can be simply changed by means of thickness of metal layers. The electroluminescent device was made with the help of PMMA (polymethyl methacrylate) layer used for the structure planarization and semitransparent gold layer as electrode. Stable strong electroluminescence in visual and near IR range was observed. This effect was attributed to Si nanocrystallites and ‘hot’ electrons.

New Thermal Ink Jet Printhead with Improved Energy Efficiency Using Silicon Reactive Ion Etching

In thermal ink jet (TIJ) printhead design, in order to satisfy various market demands, it is important to consider how effectively the printhead transfers input energy to ejected drop performance. First, we defined energy efficiency as a ratio of ejected ink drop energy (the sum of kinetic and surface energy) to consuming electric energy in the heater of thermal ink jet printhead. We examined a method for increasing the energy efficiency in terms of printhead design, and we found that it relates with an inertance ratio of the rear fluid pass to the front. We proposed a new side shooter thermal ink jet printhead for improvement of the inertance ratio, and we tried to fabricate channels on silicon wafers by a reactive ion etching (RIE). The printhead achieved higher energy efficiency when compared with the conventional design and it has been proved that high energy efficiency enables low consuming energy or high drop energy, and other good characteristics have been also obtained by the printhead.

Bilayer resist used in e-beam lithography for deep narrow structures

A bilayer reist system developed by Olin Microelectronic Materials, consisting of a UV curable polystyrene bottom coat and a silicon loaded UV sensitive positive tone top coat ('bamboo resist'), has been investigated for its sensitivity and resolution in electron beam lithography, and its etch selectivity during subsequent use in Reactive Ion Etching of silicon. The ultimate resolution obtainable with the top coat appears to be around 80 nm, with a Dose-to-Clear of 28 @mC/cm^2 and a contrast value above 25. The mechanical and chemical stability of the bottom coat and its adhesion on silicon are excellent, allowing the fabrication of 30 nm thick free standing resist 'fences'. The best resolution obtained here in e-beam lithography, indicates that the resolution of this system will most probably not be limited by the resist performance down to at least 80 nm in optical lithography as well.

Application of Al Mask for SF6/N2 Reactive Ion Etching of Silicon

We researched SF6/N2 reactive ion etching of silicon using Al mask. It was established, that Al mask prevent formation of polymeric layers and rate of etching is higher, than using photoresistive mask. Etching directionality amount to 20 units, selectivity - 400 units.