Showing papers on "Silicon published in 1997"
TL;DR: In this paper, dense periodic arrays of holes and dots have been fabricated in a silicon nitride-coated silicon wafer and transferred directly to the underlying silicon oxide layer by two complementary techniques.
Abstract: Dense periodic arrays of holes and dots have been fabricated in a silicon nitride–coated silicon wafer. The holes are 20 nanometers across, 40 nanometers apart, and hexagonally ordered with a polygrain structure that has an average grain size of 10 by 10. Spin-coated diblock copolymer thin films with well-ordered spherical or cylindrical microdomains were used as the templates. The microdomain patterns were transferred directly to the underlying silicon nitride layer by two complementary techniques that resulted in opposite tones of the patterns. This process opens a route for nanometer-scale surface patterning by means of spontaneous self-assembly in synthetic materials on length scales that are difficult to obtain by standard semiconductor lithography techniques.
1,921 citations
TL;DR: A biosensor has been developed based on induced wavelength shifts in the Fabry-Perot fringes in the visible-light reflection spectrum of appropriately derivatized thin films of porous silicon semiconductors based on Binding of molecules induced changes in the refractive index of the porous silicon.
Abstract: A biosensor has been developed based on induced wavelength shifts in the Fabry-Perot fringes in the visible-light reflection spectrum of appropriately derivatized thin films of porous silicon semiconductors. Binding of molecules induced changes in the refractive index of the porous silicon. The validity and sensitivity of the system are demonstrated for small organic molecules (biotin and digoxigenin), 16-nucleotide DNA oligomers, and proteins (streptavidin and antibodies) at pico- and femtomolar analyte concentrations. The sensor is also highly effective for detecting single and multilayered molecular assemblies.
1,392 citations
TL;DR: In this article, a simple technique for precisely controlling the interfacial energies and wetting behavior of polymers in contact with solid surfaces is described, where end-functionalized statistical random copolymers of styrene and methylmethacrylate are synthesized, with the styrene fraction f varying from 0 to 1, and were end-grafted onto silicon substrates to create random polymers about 5 nanometers thick.
Abstract: A simple technique for precisely controlling the interfacial energies and wetting behavior of polymers in contact with solid surfaces is described. End-functionalized statistical random copolymers of styrene and methylmethacrylate were synthesized, with the styrene fraction f varying from 0 to 1, and were end-grafted onto silicon substrates to create random copolymer brushes about 5 nanometers thick. For f < 0.7, polystyrene (PS) films (20 nanometers thick) rapidly dewet from the brushes when heated well above the glass transition temperature. The contact angle of the resulting polymer droplets increased monotonically with decreasing f . Similar behavior was observed for poly(methylmethacrylate) (PMMA) films but with an opposite dependence on f . The interfacial energies of the random copolymer brushes with PS and PMMA were equal when f was about 0.6. Thus, precise control of the relative surface affinities of PS and PMMA was possible, demonstrating a way to manipulate polymer-surface interactions.
1,293 citations
TL;DR: The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for different Er-doped thin film photonic materials.
Abstract: Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+ intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can be used to fabricate planar optical amplifiers or lasers that can be integrated with other devices on the same chip. Semiconductors, such as silicon, can also be doped with erbium. In this case the Er may be excited through optically or electrically generated charge carriers. Er-doped Si light-emitting diodes may find applications in Si-based optoelectronic circuits. In this article, the synthesis, characterization, and application of several different Er-doped thin film photonic materials is described. It focuses on oxide glasses (pure SiO2, phosphosilicate, borosilicate, and soda-lime glasses), ceramic thin films (Al2O3, Y2O3, LiNbO3), and amorphous and crystalline silicon, all doped with Er by ion implantation. MeV ion implantation is a technique that is ideally suited to dope these materials with Er as the ion range corresponds to the typical micron dimensions of these optical materials. The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for the various materials.
1,089 citations
Patent•
24 Jun 1997
TL;DR: In this article, the authors proposed a method for programming and reading a programmable read only memory (EPROM) having a trapping dielectric layer (20) sandwiched between two silicon dioxide layers (18, 20) that greatly reduced the programming time of conventional PROM devices.
Abstract: A novel apparatus and method for programming and reading a programmable read only memory (EPROM) having a trapping dielectric layer (20) sandwiched between two silicon dioxide layers (18, 20) is disclosed that greatly reduces the programming time of conventional PROM devices. Examples of the trapping dielectric material are silicon oxide-silicon, nitride-silicon oxide (ONO) and silicon dioxide with buried polysilicon islands. A nonconducting dielectric layer functions as an electrical charge trapping medium. This charging trapping layer is sandwiched between two layers of silicon dioxide acting as an electrical insulator. A conducting gate layer (24) is placed over the upper silicon dioxide layer (22). The memory device (10) is programmed in the conventional manner. The device, however, is read in the opposite direction from which it was written, meaning voltages are applied to the gate (24) and the source (14) while the drain is grounded. For the same applied gate voltage, reading in the reverse direction greatly reduces the potential across the trapped charge region.
855 citations
Book•
01 Jan 1997
TL;DR: In this paper, the authors present a collection of 50 commissioned essays on the subject from scientists in Europe, America and Japan, with the focus on the luminescence of silicon chips.
Abstract: Porous silicon has been the focus of much research activity in recent years, in view of its luminescence, which may enable light emitting devices to be integrated with silicon chips. This work comprises over 50 commissioned essays on the subject from scientists in Europe, America and Japan .
775 citations
TL;DR: The thermal conductivity of Si-Ge superlattices with relatively longer periods, L>130 A, has smaller thermal conductivities than the short-period samples.
Abstract: The thermal conductivity of Si–Ge superlattices with superlattice periods 30 2 × 109 W m−2 K−1 at 200 K. Superlattices with relatively longer periods, L>130 A, have smaller thermal conductivities than the short-period samples. This unexpected result is attributed to a strong disruption of the lattice vibrations by extended defects produced during lattice-mismatched growth.
660 citations
TL;DR: In this article, a light-emitting device operating at 1.5 µm was presented that incorporates β-FeSi2 into a conventional silicon bipolar junction, which demonstrates the potential of this material as an important candidate for a silicon-based optoelectronic technology.
Abstract: Although silicon has long been the material of choice for most microelectronic applications, it is a poor emitter of light (a consequence of having an ‘indirect’ bandgap), so hampering the development of integrated silicon optoelectronic devices. This problem has motivated numerous attempts to develop silicon-based structures with good light-emission characteristics1, particularly at wavelengths (∼1.5 μm) relevant to optical fibre communication. For example, silicon–germanium superlattice structures2 can result in a material with a pseudo-direct bandgap that emits at ∼1.5 μm, and doping silicon with erbium3 introduces an internal optical transition having a similar emission wavelength, although neither approach has led to practical devices. In this context, β-iron disilicide has attracted recent interest4,5,6,7,8,9,10,11,12 as an optically active, direct-bandgap material th might be compatible with existing silicon processing technology. Here we report the realization of a light-emitting device operating at 1.5 μm that incorporates β-FeSi2 into a conventional silicon bipolar junction. We argue that this result demonstrates the potential of β-FeSi2 as an important candidate for a silicon-based optoelectronic technology.
649 citations
TL;DR: In this article, the authors review applications of the near-edge X-ray absorption fine structure (NEXAFS) technique in the investigations of electronic and structural properties of transition metal compounds.
518 citations
TL;DR: In this paper, the optical properties of porous silicon are discussed in a wide spectral range from the infrared to the ultraviolet and the analysis is done by a simulation method which adjusts parameters of dielectric function models to fit experimentally obtained reflectance spectra.
452 citations
TL;DR: In this article, the authors examined the kinetics and mechanism of local oxidation of silicon and how factors such as the strength of the electric field, ambient humidity, and thickness of the oxide affect its rate and resolution.
Abstract: Atomic force microscope induced local oxidation of silicon is a process with a strong potential for use in proximal probe nanofabrication. Here we examine its kinetics and mechanism and how such factors as the strength of the electric field, ambient humidity, and thickness of the oxide affect its rate and resolution. Detection of electrochemical currents proves the anodization character of the process. Initial very fast oxidation rates are shown to slow down dramatically as a result of a self-limiting behavior resulting from the build up of stress and a reduction of the electric field strength. The lateral resolution is determined by the defocusing of the electric field in a condensed water film whose extent is a function of ambient humidity.
TL;DR: In situ hybridization with complementary oligomer strands, performed at the surface of modified electrodes, is clearly reflected by negative shifts of about 100 mV in the flat-band potential of the semiconductor.
Abstract: Homo-oligomer DNA strands were immobilized onto silicon/silicon dioxide electrodes using 3-aminopropyltriethoxysilane. These modified substrates were used as working electrodes in a three-electrode electrochemical cell. In-phase and out-of-phase impedances were measured in the range −1 to +1 V with respect to an Ag/AgCl reference electrode, with a superimposed 10 mV ac signal at frequencies of 20 and 100 kHz. Ex situ hybridization with complementary oligomer strands, performed at the surface of modified electrodes, is clearly reflected by negative shifts of about 100 mV in the flat-band potential of the semiconductor. Consecutive hybridization−denaturation steps show that the shifts are reproducible and the process is reversible. The in situ hybridization of complementary strands has also been observed with impedance measurements at Si/SiO2 substrates and with the use of a field effect device. The direct detection of hybridization with a field effect device was performed under constant drain current mode,...
TL;DR: In this paper, the authors reported the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure, which is 40% harder than β-Si 3N4 and is equally strong and tough.
Abstract: Silicon nitride (Si3N4) is a light, hard and strong engineering ceramic1,2. It can withstand harsh environments and support heavy loads at temperatures beyond those at which metals and polymers fail. It can also be manufactured reliably at a reasonable cost and in large quantities. There are two forms of silicon nitride3: α-Si3N4 and β-Si3N4. The former is harder, but only the latter is currently used in engineering applications, because only this form can be given a microstructure resembling a whisker-reinforced composite1,2,4, which gives it the necessary toughness and strength. Here we report the synthesis of a tough α-Si3N4 solid solution with this kind of microstructure. This material is 40% harder than β-Si3N4 and is equally strong and tough. Its hardness (22 GPa) is exceeded only by boron carbide and diamond (which are both brittle). These properties mean that this form of α-Si3N4 should be preferred over β-Si3N4 for all engineering applications, and it should open up new potential areas in which the ceramic can be applied.
TL;DR: In this paper, the authors combine hardness indentation tests and micro-Raman spectroscopy to show that metallic Si-II is produced near the interface of a diamond indenter and silicon to a depth of about 0.5 μm.
Abstract: Combining hardness indentation tests and micro-Raman spectroscopy it is shown that metallic Si-II is produced near the interface of a diamond indenter and silicon to a depth of about 0.5 μm, where the highest stresses (hydrostatic and deviatoric) exist. At fast unloading rates Si-II transforms to the amorphous state, whereas a mixture of the r8 high pressure polymorph Si-XII and the bc8 phase Si-III forms upon a slow load release. The region of Si-III+Si-XII is surrounded by the wurtzite structured Si-IV, where the stresses during the indentation had not been high enough to cause the transition to the metallic state. Thus, because of shear deformation a direct transformation to Si-IV takes place. Outside the phase-transformed regions the classical aspects of indentation-induced deformation by dislocation glide, twinning and crack formation are observed. Annealing of the high pressure phases leads to the formation of Si-IV at moderate temperatures and to the reversal to the original diamond structure (Si-I...
TL;DR: The authors measured the thermal conductivity of single-crystal silicon layers in SOI substrates at temperatures between 20 and 320 K using Joule heating and electrical-resistance thermometry in microfabricated structures.
Abstract: Temperature fields in microdevices made from silicon-on-insulator (SOI) wafers are strongly influenced by the lateral thermal conductivity of the silicon overlayer, which is diminished by phonon scattering on the layer boundaries. This study measures the thermal conductivity of single-crystal silicon layers in SOI substrates at temperatures between 20 and 320 K using Joule heating and electrical-resistance thermometry in microfabricated structures. Data for layers of thickness between 0.4 and 1.6 μm demonstrate the large reduction resulting from phonon-boundary scattering, particularly at low temperatures, and are consistent with predictions based on the phonon Boltzmann transport equation.
TL;DR: In this paper, the fundamental mechanism underlying hydrogen-induced exfoliation of silicon, using a combination of spectroscopic and microscopic techniques, was investigated, and the evolution of the internal defect structure as a function of implanted hydrogen concentration and annealing temperature was studied.
Abstract: We have investigated the fundamental mechanism underlying the hydrogen-induced exfoliation of silicon, using a combination of spectroscopic and microscopic techniques. We have studied the evolution of the internal defect structure as a function of implanted hydrogen concentration and annealing temperature and found that the mechanism consists of a number of essential components in which hydrogen plays a key role. Specifically, we show that the chemical action of hydrogen leads to the formation of (100) and (111) internal surfaces above 400 °C via agglomeration of the initial defect structure. In addition, molecular hydrogen is evolved between 200 and 400 °C and subsequently traps in the microvoids bounded by the internal surfaces, resulting in the build-up of internal pressure. This, in turn, leads to the observed “blistering” of unconstrained silicon samples, or complete layer transfer for silicon wafers joined to a supporting (handle) wafer which acts as a mechanical “stiffener.”
TL;DR: In this paper, a micro-reactor with submillimeter flow channels with integrated heaters and flow and temperature sensors is described, and the potential application of this reactor to partial-oxidation reactions is explored by using Pt-catalyzed NH 3 oxidation as a model reaction.
Abstract: Silicon-based microfabrication of a novel chemical reactor (microreactor) having submillimeter flow channels with integrated heaters, and flow and temperature sensors is described. The potential application of this reactor to partial-oxidation reactions is explored by using Pt-catalyzed NH 3 oxidation as a model reaction. Investigation of reactor behavior as a function of operating conditions shows that conversion and selectivity behavior of conventional laboratory reactors can be reproduced and demonstrates the feasibility of conducting chemical reactions in microfabricated systems. Ignition-extinction behavior is explored, along with high-temperature microreactor materials degradation. Potential applications and scale-up of microreactors are also discussed.
IBM1
TL;DR: In this article, a fabrication method that attains the "ideal" double-gate MOSFET device structure is reported, where the top and bottom gates are inherently self-aligned to the source/drain.
Abstract: In this paper, we report a fabrication method that attains the "ideal" double-gate MOSFET device structure. The top and bottom gates are inherently self-aligned to the source/drain. The source/drain is a fanned-out source/drain structure, which provides a low parasitic resistance. Channel silicon thickness is determined by a planar film deposition process with good uniformity control in principle. N-channel double-gate MOSFET's with a 25 nm thick silicon channel were successfully demonstrated.
TL;DR: In this paper, the oxidation of hydrogen-terminated porous silicon surfaces produced by electrochemical etching has been studied using transmission FTIR spectroscopy and two reactions are observed.
Abstract: The oxidation of hydrogen-terminated porous silicon surfaces produced by electrochemical etching has been studied using transmission FTIR spectroscopy. The surface is passivated to oxidation by surface hydrogen below about 523 K. Above this temperature as hydrogen depletion occurs by H2 evolution, Si surface dangling bond sites, capable of O2 dissociation, are involved in initiating the first stage of oxidation. Two reactions are observed. The first, O insertion into Si−Si back-bonds, leads to −OySiHx surface species which exhibit frequency shifts to the blue compared to parent SiHx stretching modes. In addition, Si−O−Si modes are also observed to form. The second reaction involves oxygen atom insertion into Si−H bonds to produce isolated Si−OH surface species.
TL;DR: Although silicon is not considered an essential element; plant development, growth and yield has been increased in many graminaceous and some nongraminaceous crop species and silicon also is known to reduce plant diseases especially in rice.
TL;DR: Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques in this paper, and a net optical gain of 4.1 dB at 1.535 μm was achieved.
Abstract: Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques. The Er concentration was 5.3×1020 cm−3. By pumping the waveguide at 980 nm with a power of ∼21 mW, a net optical gain of 4.1 dB at 1.535 μm was achieved. This high gain per unit length at low pump power could be achieved because the Er–Er cooperative upconversion interactions in this heavily Er-doped phosphate glass are very weak [the upconversion coefficient is (2.0±0.5)×10−18 cm3/s], presumably due to the homogeneous distribution of Er in the glass and due to the high optical mode confinement in the waveguide which leads to high pump power density at low pump power.
TL;DR: In this article, the hardness, elastic modulus, and scratch resistance of polysilicon films were measured by nanoindentation and microscratching using a nanoindenter, and wear properties were measured using an accelerated ball-on-flat tribometer.
Abstract: Microelectromechanical systems (MEMS) devices are made of doped single-crystal silicon, LPCVD polysilicon films, and other ceramic films. Very little is understood about tribology and mechanical characterization of these materials on micro- to nanoscales. Micromechanical and tribological characterization of p-type (lightly boron-doped) single-crystal silicon (referred to as “undoped”), p+-type (boron doped) single-crystal silicon, polysilicon bulk, and n+-type (phosphorous doped) LPCVD polysilicon films have been carried out. Hardness, elastic modulus, and scratch resistance of these materials were measured by nanoindentation and microscratching using a nanoindenter. Friction and wear properties were measured using an accelerated ball-on-flat tribometer. It is found that the undoped silicon and polysilicon bulk as well as n+-type polysilicon film exhibit higher hardness and elastic modulus than the p+-type silicon. The polysilicon bulk and n+-type polysilicon film exhibit the lowest friction and highest resistance to scratch and wear followed by the undoped silicon and with the poorest behavior of the p+-type silicon. During scratching, the p+-type silicon deforms like a ductile metal.
TL;DR: In this paper, the authors describe subwavelength surfaces etched into silicon wafers that exhibit antireflection characteristics for visible light, which are fabricated by holographically recording a crossed-grating in a photoresist mask followed by reactive-ion etching to transfer the primary mask onto the silicon substrate.
Abstract: We describe subwavelength surfaces etched into silicon wafers that exhibit antireflection characteristics for visible light. The wafers are fabricated by holographically recording a crossed-grating in a photoresist mask followed by reactive-ion etching to transfer the primary mask onto the silicon substrate. The dependence of reflectivity on the wavelength and angle of incidence is measured. The overall antireflection performance of the corrugated silicon wafers is compared with that of standard thin-film stacks, and is interpreted with the effective medium theory and with simulation results obtained from rigorous computations.
TL;DR: In this article, it is shown that in a reflecting cavity with negligible absorption one is able to perform a time reversal of elastic waves using a single element, where the field is measured at one point over a long period of time and the time reversed signal is reinjected at the same position.
Abstract: Acoustic time-reversal experiments usually need large arrays of transducers. It is shown that in a reflecting cavity with negligible absorption one is able to perform a time reversal of elastic waves using a single element. The field is measured at one point over a long period of time and the time-reversed signal is reinjected at the same position. Numerical simulations illustrate the process. Experiments carried out in silicon wafers show that it is possible to obtain an excellent temporal and spatial focusing quality.
TL;DR: In this article, the microstructural properties of amorphous silicon (a-Si) alloy solar cells were investigated using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy.
Abstract: We investigate why high levels of hydrogen dilution of the process gas lead to enhanced light soaking stability of amorphous silicon (a-Si) alloy solar cells by studying the microstructural properties of the material using high-resolution transmission electron microscopy (TEM) and Raman spectroscopy. The TEM results show that a-Si alloy (with or without hydrogen dilution) is a heterogeneous mixture of amorphous network and linear-like objects that show evidence of order along their length. The volume fraction of these ordered regions increases with increasing hydrogen dilution.
TL;DR: In this article, a simple technique for size-controllable nanostructure array formation has been developed, using self-assembled polystyrene beads whose diameters can be arbitrarily reduced by reactive ion etching.
Abstract: A simple technique for size-controllable nanostructure array formation has been developed, using self-assembled polystyrene beads whose diameters can be arbitrarily reduced by reactive ion etching. We have produced a hole array of 83 and 157 nm diameter with 200 nm pitch on Si substrate. This technique can find potential applications in many areas of science and technology.
TL;DR: In this paper, the thermal conductivity of electrochemically etched porous silicon (PS) layers was determined over a wide temperature range (T = 35 - 320 K) using the dynamic technique.
Abstract: The thermal conductivity of electrochemically etched porous silicon (PS) layers was determined over a wide temperature range (T = 35 - 320 K) using the dynamic technique. Both the doping level of the silicon wafers (p and ) and the porosity P of the porous layers (P = 64 - 89%) were varied. The measured thermal conductivities were three to five orders of magnitude smaller than the values for bulk silicon. Furthermore, they increase with increasing the wafer doping level and with decreasing the porosity P of the layers. For all investigated PS layers the thermal conductivity increases with temperature. The results are discussed in terms of a simple model for heat conduction in PS based on the phonon diffusion model.
TL;DR: In this article, tight-binding molecular dynamics simulations are performed to study self-diffusion, interstitial-vacancy recombination, and formation volumes of point defects in crystalline silicon.
Abstract: Tight-binding molecular dynamics simulations are performed to study self-diffusion, interstitial-vacancy recombination, and formation volumes of point defects in crystalline silicon. The results show that (i) self-diffusion is dominated by vacancies (V) at low temperature and by interstitials (I) at high temperature; (ii) interstitial-vacancy recombination at room temperature leads to formation of a metastable I-V complex, which has an annihilation energy barrier of 1.1 eV; (iii) interstitial and vacancy relaxation volumes in silicon are approximately equal in magnitude and opposite in sign.
TL;DR: On narrow lines, the Ge islands locate preferentially at the edges of the raised Si(001) regions, and the preference is strongest on the narrowest patterns aligned along a 〈100〉 direction as discussed by the authors.
Abstract: Ge islands were deposited on Si(001) partially covered with patterned oxide. Selective Si was deposited on some wafers before Ge deposition to form raised Si(001) plateaus with well-defined sidewall facets. On narrow lines, the Ge islands locate preferentially at the edges of the raised Si(001) regions, and the preference is strongest on the narrowest patterns aligned along a 〈100〉 direction. For a 450 nm wide plateau aligned in this direction, all the islands are positioned along the edges of the pattern, with a 300 nm space near the center of the pattern free of Ge islands. The islands appear to be uniformly spaced along the pattern edges. On wider lines, several rows of islands are aligned near the edges of the pattern, with the order decreasing farther from the edge.