scispace - formally typeset
Search or ask a question

Showing papers on "Silicon nitride published in 2011"


Journal ArticleDOI
TL;DR: In this paper, the authors explore how dielectric polymer composites with high thermal conductivity have been developed and explore how fillers can be used to increase the thermal conductivities of a polymer.
Abstract: The continuing miniaturization of electronic devices and the increasing power output of electrical equipment have created new challenges in packaging and insulating materials. The key goals are to develop materials with high thermal conductivity, low coefficient of thermal expansion (CTE), low dielectric con stant, high electrical resistivity, high breakdown strength, and most importantly, low cost. Polymeric materials have attracted increasing interest because of their excellent processability and low cost; however, most polymers are thermally insulating and have a thermal conductivity between 0.1 and 0.5 W-m-ι-K"1. One approach to increase the thermal conductivity of a polymer is to introduce high-thermal-conductivity fillers, such as aluminum oxide, aluminum nitride, boron nitride, silicon nitride, beryllium oxide, or diamond. In this review paper, we explore how dielectric polymer composites with high thermal conductivity have been developed.

581 citations


Journal ArticleDOI
31 Mar 2011-ACS Nano
TL;DR: Novel toughening mechanisms were observed that show GPL wrapping and anchoring themselves around individual ceramic grains to resist sheet pullout and the resulting cage-like graphene structures that encapsulate the individual grains were observed to deflect propagating cracks in not just two but three dimensions.
Abstract: The majority of work in graphene nanocomposites has focused on polymer matrices. Here we report for the first time the use of graphene to enhance the toughness of bulk silicon nitride ceramics. Ceramics are ideally suited for high-temperature applications but suffer from poor toughness. Our approach uses graphene platelets (GPL) that are homogeneously dispersed with silicon nitride particles and densified, at ∼1650 °C, using spark plasma sintering. The sintering parameters are selected to enable the GPL to survive the harsh processing environment, as confirmed by Raman spectroscopy. We find that the ceramic's fracture toughness increases by up to ∼235% (from ∼2.8 to ∼6.6 MPa·m(1/2)) at ∼1.5% GPL volume fraction. Most interestingly, novel toughening mechanisms were observed that show GPL wrapping and anchoring themselves around individual ceramic grains to resist sheet pullout. The resulting cage-like graphene structures that encapsulate the individual grains were observed to deflect propagating cracks in not just two but three dimensions.

575 citations


Journal ArticleDOI
TL;DR: Second- and third-harmonic generation in a centrosymmetric CMOS-compatible material using ring resonators and integrated optical waveguides is demonstrated and phase matching of the harmonic processes occurs due to the near coincidence of indices of refraction of the fundamental mode at the pump frequency.
Abstract: We demonstrate second- and third-harmonic generation in a centrosymmetric CMOS-compatible material using ring resonators and integrated optical waveguides. The χ(2) response is induced by using the nanoscale structure of the waveguide to break the bulk symmetry of silicon nitride (Si3N4) with the silicon dioxide (SiO2) cladding. Using a high-Q ring resonator cavity to enhance the efficiency of the process, we detect the second-harmonic output in the visible wavelength range with milliwatt input powers at telecom wavelengths. We also observe third-harmonic generation from the intrinsic χ(3) susceptibility of the silicon nitride. Phase matching of the harmonic processes occurs due to the near coincidence of indices of refraction of the fundamental mode at the pump frequency and the corresponding higher-order modes of the harmonic fields.

314 citations


Journal ArticleDOI
TL;DR: In this paper, a single-wire radial p-n junction solar cell was fabricated with amorphous silicon and silicon nitride surface coatings, achieving up to 9.0% apparent photovoltaic efficiency, and exhibiting up to ∼600 mV open circuit voltage with over 80% fill factor.
Abstract: Crystalline Si wires, grown by the vapor–liquid–solid (VLS) process, have emerged as promising candidate materials for low-cost, thin-film photovoltaics. Here, we demonstrate VLS-grown Si microwires that have suitable electrical properties for high-performance photovoltaic applications, including long minority-carrier diffusion lengths (Ln ≫ 30 µm) and low surface recombination velocities (S ≪ 70 cm·s−1). Single-wire radial p–n junction solar cells were fabricated with amorphous silicon and silicon nitride surface coatings, achieving up to 9.0% apparent photovoltaic efficiency, and exhibiting up to ∼600 mV open-circuit voltage with over 80% fill factor. Projective single-wire measurements and optoelectronic simulations suggest that large-area Si wire-array solar cells have the potential to exceed 17% energy-conversion efficiency, offering a promising route toward cost-effective crystalline Si photovoltaics.

202 citations


Journal ArticleDOI
TL;DR: A new Si 3 N 4 ceramic is shown that possesses a very high thermal conductivity along with a high fracture toughness and is expected to be used as the next-generation insulating substrate material for high-power electronic devices.
Abstract: IO N The world is shifting energy sources from fossil fuel to electric power in order to cope with the energy and environmental problems. Driven by the demand for effi cient control and conversion of electric power, power electronic device technology is advancing toward higher voltage, larger current, greater power density, and smaller size, and this trend is poised to be accelerated with the replacement of Si by the wide-bandgap semiconductors (SiC and GaN) in the near future. [ 1 , 2 ] However, the high power will induce large thermal stresses in the devices, which pose great challenges for the assembly of the devices and the packaging materials, in particular the brittle ceramic substrates that provide functions of electrical insulation and heat dissipation. In many occasions, even the two high-grade ceramic substrate materials, AlN and Si 3 N 4 , become cracked due to low mechanical strength and fracture toughness (for AlN) or insuffi cient thermal conductivity (for Si 3 N 4 ). [ 3 , 4 ] The reliability problem caused by the ceramic substrates has become a bottleneck hindering the advancement of power device technology. Search for new ceramic materials with better thermomechanical properties is an urgent issue. Here, we show a new Si 3 N 4 ceramic that possesses a very high thermal conductivity (177 W m − 1 K − 1 ) along with a high fracture toughness (11.2 MPa m 1/2 ) and a high fracture strength (460 MPa). We expect this Si 3 N 4 will be used as the next-generation insulating substrate material for high-power electronic devices. Silicon nitride mainly exists in two hexagonal polymorphs, namely α and β -Si 3 N 4 , which are generally regarded as lowand high-temperature crystal forms, respectively. [ 5 , 6 ] As a highly covalent compound, Si 3 N 4 transports heat primarily by phonons at room temperature and below. In 1995, Haggerty and Lightfoot predicted that the intrinsic thermal conductivity of Si 3 N 4 might be 200 to 320 W m − 1 K − 1 at room temperature. [ 7 ] Later, Hirosaki et al. estimated that the intrinsic thermal conductivities of a β -Si 3 N 4 crystal were 170 and 450 W m − 1 K − 1 along the a -axis and c -axis, respectively. [ 8 ] However, the thermal conductivity of Si 3 N 4 ceramics is much lower than the intrinsic values. Si 3 N 4 ceramics are polycrystalline materials consolidated by liquid-phase sintering. During sintering, Si 3 N 4 raw powder, which is usually α phase, converts to the more stable β phase. In the microstructure of Si 3 N 4 ceramics,

181 citations


Patent
07 Apr 2011
TL;DR: In this paper, a method for manufacturing a high-performance bipolar transistor in which emitter size dependence of the transistor characteristics is reduced was proposed, in which an opening on an N epitaxial layer was provided, and a polysilicon containing boron and in contact with the N epitaxis layer around the opening, a silicon oxide film with a thickness about 60% with respect to that of the BSG film was formed.
Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-performance bipolar transistor in which emitter size dependence of the transistor characteristics is reduced SOLUTION: A silicon oxide film 102 provided with an opening on an N epitaxial layer 101, a polysilicon 103 containing boron and in contact with the N epitaxial layer around the opening, a silicon nitride film 104, a silicon oxide film 105 and a silicon nitride film 106 are formed Next, a base region 108 is formed by depositing and heat-treating a BSG film 107, the BSG film 107 is exposed by depositing and etching back a silicon nitride film 109 with anisotropic etching, and a P-base region is exposed by etching back with anisotropic etching Next, a silicon oxide film with a thickness about 60% with respect to that of the BSG film 107 is formed, an undercut under a lower portion of the silicon nitride film is etched back by embedded isotropic etching, the film thickness of arsenic-doped polysilicon is uniformized by decreasing the undercut, and impurity concentration and depth of an emitter region are uniformized

172 citations


Journal ArticleDOI
TL;DR: In this article, an invisibility carpet cloak was designed using quasi conformal mapping and fabricated in a silicon nitride waveguide on a specially developed nanoporous silicon oxide substrate with a very low refractive index (n < 1.25).
Abstract: We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nanoporous silicon oxide substrate with a very low refractive index (n<1.25). The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequencies.

164 citations


Patent
14 Sep 2011
TL;DR: In this paper, a method of etching exposed silicon oxide on patterned heterogeneous structures is described and includes a remote plasma etch formed from a fluorine-containing precursor, which is used to conformally trim silicon oxide while removing little or no silicon, polysilicon, silicon nitride, titanium or titanium nitride.
Abstract: A method of etching exposed silicon oxide on patterned heterogeneous structures is described and includes a remote plasma etch formed from a fluorine-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents combine with water vapor. The chemical reaction resulting from the combination produces reactants which etch the patterned heterogeneous structures to produce, in embodiments, a thin residual structure exhibiting little deformation. The methods may be used to conformally trim silicon oxide while removing little or no silicon, polysilicon, silicon nitride, titanium or titanium nitride. In an exemplary embodiment, the etch processes described herein have been found to remove mold oxide around a thin cylindrical conducting structure without causing the cylindrical structure to significantly deform.

155 citations


Patent
22 Dec 2011
TL;DR: A trench embedding method includes forming an oxidization barrier film on a trench, forming an expandable film on the oxidisation barrier film, embedding an embedding material that contracts by being fired on the trench, and firing the embedding materials as mentioned in this paper.
Abstract: A trench embedding method includes forming an oxidization barrier film on a trench; forming an expandable film on the oxidization barrier film; embedding an embedding material that contracts by being fired on the trench; and firing the embedding material, wherein the forming of the oxidization barrier film includes: forming a first seed layer on the trench by supplying an aminosilane-based gas; and forming a silicon nitride film on the first seed layer, wherein the forming of the expandable film includes: forming a second seed layer on the silicon nitride film by supplying an aminosilane-based gas; and forming a silicon film on the second seed layer.

154 citations


Journal ArticleDOI
TL;DR: An invisibility carpet cloak device, which is capable of making an object undetectable by visible light, is reported, which can be a general scheme for implementation of transformation optical devices at visible frequencies.
Abstract: We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nano-porous silicon oxide substrate with a very low refractive index. The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequency.

153 citations


Patent
20 Dec 2011
TL;DR: In this paper, the authors describe a method for fabricating micro-scale or nanoscale polymer or metal structures on a substrate by photolithography and/or nano imprinting lithography.
Abstract: Devices, systems and techniques are described for producing and implementing articles and materials having nanoscale and microscale structures that exhibit superhydrophobic, superoleophobic or omniphobic surface properties and other enhanced properties. In one aspect, a surface nanostructure can be formed by adding a silicon-containing buffer layer such as silicon, silicon oxide or silicon nitride layer, followed by metal film deposition and heating to convert the metal film into balled-up, discrete islands to form an etch mask. The buffer layer can be etched using the etch mask to create an array of pillar structures underneath the etch mask, in which the pillar structures have a shape that includes cylinders, negatively tapered rods, or cones and are vertically aligned. In another aspect, a method of fabricating microscale or nanoscale polymer or metal structures on a substrate is made by photolithography and/or nano imprinting lithography.

Journal ArticleDOI
TL;DR: In this article, a large-area solar cell with passivated homogeneous emitter and rear achieving energy conversion efficiencies of up to 19.4% on 125 × 125 mm2 p-type 2-3 Ω cm boron-doped Czochralski silicon wafers is presented.
Abstract: We demonstrate industrially feasible large-area solar cells with passivated homogeneous emitter and rear achieving energy conversion efficiencies of up to 19.4% on 125 × 125 mm2 p-type 2–3 Ω cm boron-doped Czochralski silicon wafers. Front and rear metal contacts are fabricated by screen-printing of silver and aluminum paste and firing in a conventional belt furnace. We implement two different dielectric rear surface passivation stacks: (i) a thermally grown silicon dioxide/silicon nitride stack and (ii) an atomic-layer-deposited aluminum oxide/silicon nitride stack. The dielectrics at the rear result in a decreased surface recombination velocity of Srear = 70 cm/s and 80 cm/s, and an increased internal IR reflectance of up to 91% corresponding to an improved Jsc of up to 38.9 mA/cm2 and Voc of up to 664 mV. We observe an increase in cell efficiency of 0.8% absolute for the cells compared to 18.6% efficient reference solar cells featuring a full-area aluminum back surface field. To our knowledge, the energy conversion efficiency of 19.4% is the best value reported so far for large area screen-printed solar cells. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Journal ArticleDOI
TL;DR: Numerical simulations based on the Poisson−Nernst−Planck equations are applied to study the effect of pore size, electrolyte concentration, and half-cone angles on ICR at glass nanopore membranes and show that for the occurrence of ICR the pore mouth radius r0 has to be in the order of magnitude of the Deb...
Abstract: Conical nanopores from various materials (e.g., glass, silicon nitride, PET) were found to rectify ionic currents in electrolytes. Several models and simulations have been developed to explain and ...

Journal ArticleDOI
TL;DR: In this article, an experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations through measurement of the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap.
Abstract: An experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations. Results are obtained primarily through measurement of the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Measured heat-flux data are used in a formula based on Direct Simulation Monte Carlo (DSMC) simulations to determine the coefficients. The assembly also features a complementary capability for measuring the variation in gas density between the plates using electron-beam fluorescence. Surface materials examined include 304 stainless steel, gold, aluminum, platinum, silicon, silicon nitride, and polysilicon. Effects of gas composition, surface roughness, and surface contamination have been investigated with this system; the behavior of gas mixtures has also been explored. Without special cleaning procedures, thermal accommodation coefficients for most materials and surface finishes were determined to be near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Surface cleaning by in situ argon-plasma treatment reduced coefficient values by up to 0.10 for helium and by ∼0.05 for nitrogen and argon. Results for both single-species and gas-mixture experiments compare favorably to DSMC simulations.

Journal ArticleDOI
TL;DR: In this paper, large-area uniform carbon films with graphene-like properties are synthesized by chemical vapor deposition directly on Si3N4/Si at 1000 degrees C without metal catalysts.
Abstract: Large-area uniform carbon films with graphene-like properties are synthesized by chemical vapor deposition directly on Si3N4/Si at 1000 degrees C without metal catalysts. The as deposited films are atomically thin and wrinkle- and pinhole-free. The film thickness can be controlled by modifying the growth conditions. Raman spectroscopy confirms the sp(2) graphitic structures. The films show ohmic behavior with a sheet resistance of similar to 2.3-10.5 k Omega/square at room temperature. An electric field effect of similar to 2-10% (V-G=-20 V) is observed. The growth is explained by the self-assembly of carbon clusters from hydrocarbon pyrolysis. The scalable and transfer-free technique favors the application of graphene as transparent electrodes.

Journal ArticleDOI
TL;DR: In this paper, an analytical model for the sensitivity with which they optimize the temperature response of resonant strings by varying geometry and material was presented, and the relative change in resonant frequency per temperature change of −1.74±0.04% was measured.
Abstract: Resonant strings are a promising concept for ultra sensitive temperature detection. We present an analytical model for the sensitivity with which we optimize the temperature response of resonant strings by varying geometry and material. The temperature sensitivity of silicon nitride and aluminum microstrings was measured. The relative change in resonant frequency per temperature change of −1.74±0.04%/°C of the aluminum strings is more than one order of magnitude higher than of the silicon nitride strings and of comparable state-of-the-art AuPd strings.

Patent
22 Aug 2011
TL;DR: In this article, an atomic layer deposition using a precursor having both nitrogen and silicon components is described, where silicon-nitrogen bonds are present in the precursor molecule, but hydrogen and/or halogens may also be present.
Abstract: Atomic layer deposition using a precursor having both nitrogen and silicon components is described. The deposition precursor contains molecules which supply both nitrogen and silicon to a growing film of silicon nitride. Silicon-nitrogen bonds may be present in the precursor molecule, but hydrogen and/or halogens may also be present. The growth substrate may be terminated in a variety of ways and exposure to the deposition precursor displaces species from the outer layer of the growth substrate, replacing them with an atomic-scale silicon-and-nitrogen-containing layer. The silicon-and-nitrogen-containing layer grows until one complete layer is produced and then stops (self-limiting growth kinetics). Subsequent exposure to a plasma excited gas modifies the chemical termination of the surface so the growth step may be repeated. The presence of both silicon and nitrogen in the deposition precursor molecule increases the deposition per cycle thereby reducing the number of precursor exposures to grow a film of the same thickness.

Journal ArticleDOI
01 Oct 2011-Carbon
TL;DR: In this article, the electrical conductivity of these composites is investigated at the nanoscale by conducting force microscopy to understand the influence of the carbon phase content when above the percolation threshold.

Journal ArticleDOI
TL;DR: In this paper, a bulge test setup was used to determine the fracture toughness of amorphous low-pressure chemical vapor deposited (LPCVD) silicon nitride films with various thicknesses in the range 40-108nm.

Journal ArticleDOI
TL;DR: In this article, the authors identify the silicon nitride matrix itself as responsible for the photoluminescence, and conclude that silicon nanocrystal films are inappropriate if one aims at investigating photolumininescence from silicon nanoparticles within such a matrix.
Abstract: Silicon nitride compounds emit photoluminescence all over the visible range. Recent studies ascribed this luminescence to quantum-size effects within silicon nanocrystals that were either shown or assumed to form inside the silicon nitride matrix; the luminescence of the matrix itself was ignored. In contrast, observing the same luminescence even without the presence of silicon crystallites, our work identifies the silicon nitride matrix itself as responsible for the photoluminescence. All experimental observations are well explained by band tail luminescence from the silicon matrix. In contrast to the silicon nanocrystal approach, our model explains all aspects of the luminescence. As a consequence, we conclude that silicon nitride films are inappropriate if one aims at investigating photoluminescence from silicon nanocrystals within such a matrix.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the minority carrier lifetime in Czochralski silicon solar cells with surface passivation and showed that the recombination activity is likely to be dependent on the precipitate surface area.
Abstract: Supersaturated levels of interstitial oxygen in Czochralski silicon can lead to the formation of oxide precipitates. Although beneficial from an internal gettering perspective, oxygen-related extended defects give rise to recombination which reduces minority carrier lifetime. The highest efficiency silicon solar cells are made from n-type substrates in which oxide precipitates can have a detrimental impact on cell efficiency. In order to quantify and to understand the mechanism of recombination in such materials, we correlate injection level-dependent minority carrier lifetime data measured with silicon nitride surface passivation with interstitial oxygen loss and precipitate concentration measurements in samples processed under substantially different conditions. We account for surface recombination, doping level, and precipitate morphology to present a generalised parameterisation of lifetime. The lifetime data are analysed in terms of recombination activity which is dependent on precipitate density or on the surface area of different morphologies of precipitates. Correlation of the lifetime data with interstitial oxygen loss data shows that the recombination activity is likely to be dependent on the precipitate surface area. We generalise our findings to estimate the impact of oxide precipitates with a given surface area on lifetime in both n-type and p-type silicon.

Journal ArticleDOI
TL;DR: In this paper, surface recombination velocities (SRVs) below 10 cm/s on low resistivity (1.4 cm) p-type crystalline silicon wafers passivated with plasma assisted and thermal atomic layer deposited (ALD) aluminium oxide (Al2O3) films were measured.

Patent
22 Feb 2011
TL;DR: A nonvolatile semiconductor memory device having high charge retention characteristics and capable of improving leakage characteristics of a dielectric film disposed between a charge storage layer and a control gate electrode, and manufacturing method thereof is disclosed.
Abstract: A nonvolatile semiconductor memory device having high charge retention characteristics and capable of improving leakage characteristics of a dielectric film disposed between a charge storage layer and a control gate electrode, and manufacturing method thereof is disclosed. According to one aspect, there is provided a semiconductor memory device comprising a first electrode disposed on a first insulator on a semiconductor substrate, a second insulator disposed on the first electrode, a second electrode disposed on the second insulator, and diffusion layers disposed in the semiconductor substrate, wherein the second insulator including a silicon-rich silicon nitride film containing more silicon than that in a stoichiometric silicon nitride film, and a silicon oxide film formed on the silicon-rich silicon nitride film, and wherein the silicon-rich silicon nitride film has a ratio of a silicon concentration and a nitrogen concentration set to 1:0.9 to 1:1.2.

Journal ArticleDOI
TL;DR: In this paper, the microstructure, morphology and mechanical characteristics of the as-deposited graphite-like carbon (GLC) films were investigated by Raman spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and nano-indention tester.
Abstract: Silicon nitride (Si3N4), silicon carbide (SiC) and cemented carbide (WC) are good material candidates in the applications of water hydraulic systems and related water-lubrication fields. But high friction and severe wear would arise from the unavoidable solid–solid contact during running-in period, frequent starting/stopping due to the absence of effective water lubrication. Graphite-like carbon (GLC) films with high hardness was successfully deposited on above different ceramics to improve their durability and stability under different working conditions. The microstructure, morphology and mechanical characteristics of the as-deposited GLC films were investigated by Raman spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and nano-indention tester. The tribological behaviors of GLC-coated Si3N4, SiC and WC were comparatively studied by a ball-on-disc tribo-meter when compared with un-coated ceramic substrates under both dry and water-lubricated sliding conditions. Results show that the friction coefficient of coated-GLC films kept a relatively lower value of 0.04–0.07 whereas the above three ceramic substrates demonstrated a much higher value in the range of 0.1–0.3 under both dry and water-lubricated conditions. In addition, the wear rate of Si3N4, SiC and WC substrates could be significantly reduced after the deposition of GLC films and interestingly the GLC-coated WC exhibited unique super-low wear rate (nearly non-wear properties). The tribological performance of coated-GLC films greatly depended on the ceramic substrates and the corresponding friction-reduction and anti-wear mechanisms related with different wear conditions and substrates were also revealed. Such GLC films are considered as potential protective and lubricating surfaces for water-lubricated parts such as water-lubricated bearing, mechanical seals and other moving parts used in water environment.

Journal ArticleDOI
TL;DR: It is shown how an inhomogeneous thickness of the sample affects the spectra and how this can be avoided, and how the fine structure of the x-ray absorption spectra is not affected by the sample thickness.
Abstract: A novel sample holder for soft x-ray absorption spectroscopy of liquids in transmission mode based on sample cells with x-ray transparent silicon nitride membranes is introduced. The sample holder allows for a reliable preparation of ultrathin liquid films with an adjustable thickness in the nm–μm range. This enables measurements of high quality x-ray absorption spectra of liquids in transmission mode, as will be shown for the example of liquid H2O, aqueous solutions of 3d-transition metal ions and alcohol-water mixtures. The fine structure of the x-ray absorption spectra is not affected by the sample thickness. No effects of the silicon nitride membranes were observed in the spectra. It is shown how an inhomogeneous thickness of the sample affects the spectra and how this can be avoided.

Journal ArticleDOI
TL;DR: In this paper, a double layer of amorphous silicon-rich oxynitride (SiNx) was used to obtain a nearly perfect surface passivation after subsequent rapid thermal process (RTP) and light soaking.
Abstract: Excellent surface passivation of crystalline silicon (c-Si) is desired for a number of c-Si based applications ranging from microelectronics to photovoltaics. A plasma-enhanced chemical vapor deposition double layer of amorphous silicon-rich oxynitride and amorphous silicon nitride (SiNx) can provide a nearly perfect passivation after subsequent rapid thermal process (RTP) and light soaking. The resulting effective minority carriers’ lifetime (τeff) is close to the modeled maximum on p-type as well as on n-type c-Si. Restrictions on the RTP of passivated surfaces, typical of other common passivation schemes (e.g., amorphous Si), are relieved by this double layer. Harsher thermal treatments can be adopted while still obtaining salient passivation. Furthermore, characterization of the same, such as, surface photovoltage, capacitance voltage, and electron paramagnetic resonance, enables the reproducibility and the understanding of the passivation scheme under test. It is shown that the strong quality of surf...

Journal ArticleDOI
TL;DR: In this paper, a new mechanistic theory for the evolution of the R-curve is proposed, which is attributed to the formation of elastic bridges that experience no debonding.

Journal ArticleDOI
TL;DR: In this paper, the effects of ceria abrasives in chemical mechanical polishing (CMP) slurries were investigated on silicon dioxide (SiO 2 ) and silicon nitride (Si 3 N 4 ) polishing process.

Journal ArticleDOI
TL;DR: In this article, the laser assisted machining (LAM) method was proposed to cut and remove softened parts by locally heating the ceramic with laser, where the laser power is the machining factor that controls the temperature.
Abstract: This paper describes the Laser Assisted Machining (LAM) that cuts and removes softened parts by locally heating the ceramic with laser. Silicon nitride ceramics can be machined with general machining tools as well, because YSiAlON, which was made up ceramics, is soften at about 1,000°C. In particular, the laser, which concentrates on highly dense energy, can locally heat materials and very effectively control the temperature of the heated part of specimen. Therefore, this paper intends to propose an efficient machining method of ceramic by deducing the machining governing factors of laser assisted machining and understanding its mechanism. While laser power is the machining factor that controls the temperature, the CBN cutting tool could cut the material more easily as the material gets deteriorated from the temperature increase by increasing the laser power, but excessive oxidation can negatively affect the quality of the material surface after machining. As the feed rate and cutting depth increase, the cutting force increases and tool lifespan decreases, but surface oxidation also decreases. In this experiment, the material can be cut to 3mm of cutting depth. And based on the results of the experiment, the laser assisted machining mechanism is clarified.

Journal ArticleDOI
TL;DR: In this paper, a series of multicrystalline silicon ingots of ultrapure feedstock material were cast with intentional addition of typical transition metal impurities (Fe, Cu, Cr) and Ge as doping elements.
Abstract: Defects in multicrystalline silicon for photovoltaic applications and their impact on solar cell parameters have been investigated in the material research network project SolarFocus. A series of multicrystalline silicon ingots of ultrapure feedstock material were cast with intentional addition of typical transition metal impurities (Fe, Cu, Cr) and Ge as doping elements. The results of lifetime measurements, NAA and FTIR analysis, solar cell processing and microscopic investigations are presented in this study. For ingots intentionally contaminated with transition metals, the combined analysis reveals that despite the overall high impurity content, good solar cell efficiencies can be reached. A strong influence of the in-diffusion of metal impurities from the crucible as well as the back-diffusion from the top region of the ingot ca still be observed. All metals show a strong precipitation behaviour throughout the whole ingot. The solar cell efficiency is both limited by multiple recombination active defects and shunts, induced by a high metal contamination via indirect mechanisms. Solar cells with efficiencies up to 15.2% for material contaminated with 20 ppma Fe in the melt, 15.7% for 20 ppma Cu and 15.1% for 20 ppma Cr were processed. A positive effect of Cu added to the feedstock could not be found. Ge-rich ingots showed strong effects of increasing silicon carbide and silicon nitride formation with increasing Ge content larger than 0.5 wt.% thus reducing solar cell efficiency. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)