Standard Silicon Technology Research Articles

2-D MMI Devices Based on Integrated Hollow ARROW Waveguides

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, the design, fabrication, and characterization of 2-D multimode interference (MMI) devices based on integrated silicon hollow antiresonant reflection optical waveguides (ARROW) is presented. Unlike conventional waveguides, the field in ARROW is not confined in the core region by total internal reflection but by dielectric cladding layers designed to form-high reflectivity Fabry–Perot mirrors. This peculiar structure permits to realize integrated hollow-core waveguides using standard silicon technology. In this paper, we show that these waveguides can be usefully applied in the fabrication of 2-D MMI devices. With a 130 <formula formulatype="inline"><tex>$\mu$</tex></formula>m<formula formulatype="inline"><tex>$\,\times\,$</tex></formula> 130 <formula formulatype="inline"><tex>$\mu$</tex></formula>m cross-section waveguide, multiple images are observed from 1<formula formulatype="inline"><tex>$\,\times\,$</tex></formula>1 to 6<formula formulatype="inline"><tex> $\,\times\,$</tex></formula>6 image matrices. These devices also exhibit interesting bandpass spectral properties that can be usefully applied in several fields ranging from telecommunications to sensing. </para>

Fast Ge-on-Si Photodetectors for the Near Infrared

We report on the state of the art of near infrared photodetectors based on germanium on silicon. After a brief review on material and devices, we describe our approach to the fabrication of fast Ge/Si p-i-n detectors based on a simple process with reduced thermal budget for compatibility with standard silicon technology. The diodes, fabricated by chemical vapor deposition at 600ºC, exhibit responsivities of 0.4 and 0.2A/W at 1.3μm and 1.55μm, respectively, and operation at 10Gbit/s.

Design of a silicon RCE Schottky photodetector working at 1.55 μm

In this paper, the design of a resonant cavity-enhanced (RCE) Schottky photodetector, based on internal photoemission effect and working at 1.55 μm, is presented. In order to estimate the theoretical quantum efficiency we take the advantage of analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films, while for the optical analysis of device a numerical method, based on the transfer matrix method, has been implemented. Finally, we complete our design calculating bandwidth and bandwidth-efficiency product. Our numerical results prove that a quantum efficiency of 0.1% is obtained at resonant wavelength (1.55 μm) with a very thin absorbing metal layer (30 nm). Theoretical values of 100 GHz and 100 MHz were obtained, respectively, for the carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency. The proposed photodetector can work at room temperature and its fabrication is completely compatible with standard silicon technology.

Silicon-on-insulator microcavity light emitting diodes with two Si/SiO 2 Bragg reflectors

Light emitting pn-diodes were fabricated on a 5.8 μm thick n-type Si device layer of a silicon-on-insulator (SOI) wafer using standard silicon technology and boron implantation. The thickness of the Si device layer was reduced to 1.3 μm, corresponding to a 4 λ-cavity for λ=1150 nm light. Electroluminescence spectra of these low Q-factor microcavities are presented. Addition of Si/SiO 2 Bragg reflectors on the top and bottom of the device (3.5 and 5.5 pairs, respectively) is predicted to lead to spectral emission enhancement by ∼270.

Interaction between rare-earth ions and amorphous silicon nanoclusters produced at low processing temperatures

Temperatures of 1000 °C and higher are a significant problem for the incorporation of erbium-doped silicon nanocrystal devices into standard silicon technology, and make the fabrication of contacts and reflectors in light emitting devices difficult. In the present work, we use energy-filtered TEM imaging techniques to show the formation of size-controlled amorphous silicon nanoclusters in SiO films annealed between 400 and 500 °C. The PL properties of such films are characteristic of amorphous silicon, and the spectrum can be controlled via a statistical size effect—as opposed to quantum confinement—that has previously been proposed for porous amorphous silicon. Finally, we show that amorphous nanoclusters sensitize the luminescence from the rare-earth ions Er, Nd, Yb, and Tm with excitation cross-sections similar in magnitude to erbium-doped silicon nanocrystal composites, and with a similar nonresonant energy transfer mechanism.

Large Area Printing of Organic Electronics

Organic electronic systems offer the possibility of lightweight, flexibility and large area coverage, properties not easily achievable with standard silicon technology, and at potentially lower manufacturing costs. DuPont has focused on the development of conducting and semiconducting organic materials that allow for the printing of active and passive electronic devices. A number of groups have focus in improving device performance by designing organic semiconducting materials of higher mobility. We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The method, based on creating subpercolating conducting networks, would enable the printing of submicron features with conventional commercial engines. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in effective mobility without reduction of the on/off ratio.These conducting and semiconducting composites are compatible with various large area printing processes such as thermal and ink jet. However, the manufacturing of complex multi-layer circuits over large areas in a reel-to-reel configuration has been one of the driving forces in the organic electronics field. We are currently evaluating the feasibility of micro-contact printing as a path to high-resolution reel-to-reel electronics. Thus extending flexography into the high-resolution arena. Unlike conventional lithography, micro-contact printing; not requiring sacrificial resists, developers, and etchants; maybe compatible with a wider range of materials and substrates currently utilized in plastic electronics.

Silicon waveguides produced by wafer bonding

X-ray waveguides are successfully produced employing standard silicon technology of UV photolithography and wafer bonding. Contrary to theoretical expectations for similar systems even 100μm broad guides of less than 80nm height do not collapse and can be used as one dimensional waveguides to excite single guided modes at typical x-ray energies.

Development of pNH4-isfets microsensors for water analysis

Front-side connected, N-channel, normally-off, SiO2/Si3N4 chemical field effect transistor (ChemFET) microsensors have been fabricated using a standard P-well silicon technology. These ChemFETs microsensors were adapted to ammonium ion detection thanks to photosensitive polysiloxane (PSX) polymer containing nonactine as an ionophore. The ammonium-sensitive membrane has been deposited either manually by micropipette, either by spin coating and patterned using photolithography technique. Both processes have been studied and compared through the ammonium ion determination. The manually deposed layers have been characterised by thickness non-reproducibility. Therefore, spin-coated layers have good reproducibility, but their thickness of 30μm has been responsible for an increase of the ISFET threshold voltage and a decrease of its bias current. Nevertheless, in both cases, good sensitivities have been shown on the (1–5) pNH4 range even if saturation phenomena have been evidenced for the lowest concentrations. These pNH4-ISFETs microsensors are developed for the monitoring of environmental pollution and more precisely for ground water analysis.

Highly explosive nanosilicon‐based composite materials

AbstractWe present a highly explosive binary system based on porous silicon layers with their pores filled with solid oxidizers. The porous layers are produced by a standard electrochemical etching process and exhibit properties that are different from other energetic materials. Its production is completely compatible with the standard silicon technology and full bulk silicon wafers can be processed and therefore a large number of explosive elements can be produced simultaneously. The application‐relevant parameters: the efficiency and the long‐term stability of various porous silicon/oxidizer systems have been studied in details. Structural properties of porous silicon, its surface termination, the atomic ratio of silicon to oxygen and the chosen oxidizers were optimized to achieve the highest efficiency of the explosive reaction. This explosive system reveals various possible applications in different industrial fields, e.g. as a novel, very fast airbag igniter. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Application of Magnetic Ferrite Electrodeposition and Copper Chemical Mechanical Planarization for On-Chip Analog Circuitry

AbstractInductors are important components of analog circuit designs, from matching circuitry to passive filters. In this study, the application of electrophoretically deposited nano-ferrite material has been investigated as a technique to increase the inductance of integrated copper planar inductors fabricated using copper plating and chemical mechanical planarization. Sintered Mn-Zn ferrite particles are suspended in a medium of isopropyl alcohol with magnesium nitrate and lanthanum nitrate salts. The transportation of the particles to the substrate surface is assisted by applied electric field and particles adhere to the substrate surface by a glycerol based surfactant. Electrophorectic deposition process forms a self aligned polymeric thin film on the surface of a p-type silicon substrate selectively with respect to copper. This ferrite deposition method yields high selectivity to the inductor coils and patterned silicon substrates compatible with standard silicon technology.

Microfluidic sensor based on integrated optical hollow waveguides.

A simple integrated optical refractometric sensor based on hollow-core antiresonant reflecting optical waveguides is proposed. The sensor uses the antiresonant reflecting guidance mechanism and permits one to measure the refractive index of a liquid filling the core by simply monitoring the transmitted spectrum. The device has been made with standard silicon technology, and the experimental results confirm numerical simulations performed in one- and two-dimensional geometry. The sensor exhibits a linear response over a wide measurement range (1.3330-1.4450) and a resolution of 9 x 10(-4) and requires a small analyte volume.

Characterization of Embedded Rhomboidal Microchannels Formation on Silicon (100) Surface

Several techniques are routinely used to fabricate arrays of microchannels embedded in crystalline silicon. They are commonly based on plasma or anisotropic etch of silicon and on subsequent wafer bonding to close the cavities on top. These techniques are quite complex and usually work on (110) oriented silicon wafers. In this paper we present an innovative microchannel formation process, entirely based on front side wafer silicon bulk micromachining, which allows us to produce rhomboidal microchannels embedded on (100) silicon wafers. Compared to the traditional techniques, the proposed process is very compatible with the standard microelectronics silicon technology. The kinetics of rhomboidal microchannel formation are monitored by cyclic voltammetry measurements and the results are compared with a detailed structural characterization performed by scanning electron microscopy. The effectiveness of this process is discussed in view of the possible applications in the microfluidic field. © 2004 The Electrochemical Society. All rights reserved.

Silicon Germanium Strained Layers and Heterostructures

The integration of strained-Si1–xGex into Si technology has enhanced the performance and extended the functionality of Si based circuits. The improvement of device performance is observed in both AC as well as DC characteristics of these devices. The category of such devices includes field effect as well as bipolar families. Speed performance in some based circuits has reached limits previously dominated by III-V heterostructures based devices. In addition, for some optoelectronics applications including photodetectors it is now possible to easily integrate strained-Si1–xGex based optical devices into standard Silicon technology. The impact of integrating strained and relaxed Si1–xGex alloys into Si technology is important. It has lead to stimulate Si research as well as offers easy options for performances that requires very complicated and costly process if pure Si has to be used. In this paper we start by discussing the strain and stability of Si1–xGex alloys. The origin and the process responsible for transient enhanced diffusion (TED) in highly doped Si containing layers will be mentioned. Due to the importance of TED for thin highly doped Boron strained-Si1–xGex layers and its degrading consequences, possible suppression design methods will be presented. Quantum well pchannel MOSFETs (QW-PMOSFETs) based on thin buried QW are solution to the low speed and weak current derivability. Different aspects of designing these devices for a better performance are briefly reviewed. Other FETs based on tensile strained Si on relaxed Si1–xGex for n-channel and modulation doped field effect transistors (MODFETs) showed excellent performance. Record AC performance well above 200GHz for fmax is already observed and this record is expected to increase in the coming years. Heterojunction bipolar transistors (HPTs) with thin strained-Si1–xGex highly doped base have lead to optimize the performance of the bipolar technology for many applications easily. The strategies of design and the most important designs of HBTs for optimum AC as well as DC are discussed in details. This technology is now mature enough and that is manifested in the appearance in the market nowadays. Si1–xGex based FETs circuits compatible with standard Si CMOS processes are soon expected to appear in the market. Finally, we briefly discuss the recent advances in Si1–xGex based infrared photodetectors.

Development of a microcalorimeter array for wide energy band X-ray astronomy

Some experience has been acquired by the CEA/DSM/DAPNIA/SAp in IR bolometer arrays realization in collaboration with the LETI (Grenoble). From this basis, we are undertaking a development of an X-ray sensitive array for X-ray astronomy imaging spectroscopy missions. We are conservative in using only standard and well-known silicon processing technologies. An implanted and diffused silicon MESA structure is used, in place of ionic multi-implanted silicon, to provide the thermal sensor. Using this technology, we expect to obtain a set of homogeneous sensor of high volume, and low noise. The absorber will be a high Z material. HgTe is a candidate, high Z superconducting alternatives are explored. The absorber is hybridized, with indium beads providing a thermomechanical coupling, to the sensor plate. The microcalorimeter is decoupled from the cold sink by narrow silicon beams, following the structure already used for the IR arrays. The extrapolation of the X-ray thermal sensor is presently being pursued. Measurements of the characteristics of the sensors of the last batch of array prototypes are presented. With this standard silicon technology, we expect to obtain a low spread in sensor parameters, as is required by a multiplexed readout scheme.

Study of front-side connected chemical field effect transistor for water analysis

Front-side connected, N-channel, normally-off, chemical field effect transistor (ChemFET) microsensors including a SiO 2/Si 3N 4 pH-sensitive gate have been fabricated using a standard P-well silicon technology. The fabrication and packaging processes are described and sensor properties and performances are demonstrated through pH measurements. Finally, the front-side connected ChemFETs microsensors have been adapted to the detection of ions thanks to polyHEMA/siloprene-based ionosensitive membranes. Application is performed through the NH 4 + and NO 3 − ions detection in artificial solutions, evidencing quasi-Nernstian responses ( s≈50 mV/pH) in the appropriate detection ranges. This microsensor will be used for the monitoring of environmental pollution and more precisely for ground water analysis.

Planar antiresonant reflecting optical waveguides as integrated optical refractometer

This paper reports on an integrated refractometer sensor, useful for measuring chemical quantities, based on antiresonant reflecting optical waveguides (ARROWs). We show that, by a suitable design, the attenuation in ARROW waveguides can strongly depend on the refractive index of the superstrate layer. We use this property to design and realize an integrated refractometer. The proposed sensor structure is unique in that it consists in the ARROW waveguide itself acting like a vertical interferometer. The device is fabricated using standard silicon technology fully compatible with bipolar and CMOS integrated circuit process. The measurement results show a sensing resolution of /spl Delta/n = 6e - 4 when used in a solution with a refractive index of 1.4600.

Integrating a micro fuel cell on Si

A research group of the Institute for Microelectronics and Microsystems (IMM) of the National Council of Research (CNR) in Catania, Italy is working to integrate fuel cells and conventional electronic devices on the same silicon chip. By using innovative micromachining processes, based on advanced and smart material engineering, they succeeded in fabricating electrocatalytic porous membranes, with a wide and tunable surface, positioned above a micro-channel system. These processes only consist of surface micromachining, fully compatible with the standard ULSI silicon technology. This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.

Development of chemical field effect transistors for the detection of urea

Low cost, disposable, chemical field effect transistor (ChemFET) microsensors including a SiO2/Si3N4 pH-sensitive gate, a ChemFET/ReFET structure and a titanium/gold pseudo-electrode have been fabricated using a standard P-well silicon technology. The fabrication process is described and sensor properties and performances are demonstrated through pH measurements. The pH-ChemFET is adapted to biochemical applications owing to photosensitive polyvinyl alcohol (PVA) layers patterned by standard photolithography techniques. Application is performed through the development of urease-based enzymatic field effect transistor (U-EnFET) for the detection of urea. The microsensor will be used for blood analysis and more precisely for hemodialysis.

Enhanced channel mobility of 4H–SiC metal–oxide–semiconductor transistors fabricated with standard polycrystalline silicon technology and gate-oxide nitridation

This work presents improved channel mobility of n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) on 4H–SiC, achieved by gate-oxide nitridation in nitric oxide. Lateral enhancement mode MOSFETs were fabricated using standard polycrystalline silicon gate process and 900 °C annealing for the source and drain contacts. The low field mobility of these MOSFETs was as high as 48 cm2/Vs together with a threshold voltage of 0.6 V, while the interface state density—determined from the subthreshold slope—was about 3×1011 eV−1 cm−2. The 43-nm-thick gate oxide of coprocessed metal–oxide–semiconductor structures exhibited a breakdown field strength of 9 MV/cm.

Optimized silicon antiresonant reflecting optical waveguides for sensing applications

The development of an evanescent field sensor with an integrated Mach-Zehnder interferometric (MZI) configuration requires the fabrication of optical waveguides with two main characteristics: (1) monomode behavior and (2) high surface sensitivity for sensing biomolecular interactions in a direct way (without labels). In this paper, we present an experimental study for the optimization of the different parameters of the waveguides that will be the basis of a highly sensitive optical sensor. After optimization, an MZI sensor has been fabricated and some sensing applications are shown. The designed waveguides are based on antiresonant reflecting optical waveguide (ARROW) structures and are fabricated with standard silicon technology.