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Showing papers on "Silicon nitride published in 1998"


Journal ArticleDOI
01 Aug 1998
TL;DR: Surface micromachining is characterized by the fabrication of micromechanical structures from deposited thin films as discussed by the authors, which typically requires that they be freed from the planar substrate.
Abstract: Surface micromachining is characterized by the fabrication of micromechanical structures from deposited thin films. Originally employed for integrated circuits, films composed of materials such as low-pressure chemical-vapor-deposition polycrystalline silicon, silicon nitride, and silicon dioxides can be sequentially deposited and selectively removed to build or "machine" three-dimensional structures whose functionality typically requires that they be freed from the planar substrate. Although the process to accomplish this fabrication dates from the 1960's, its rapid extension over the past few years and its application to batch fabrication of micromechanisms and of monolithic microelectromechanical systems (MEMS) make a thorough review of surface micromachining appropriate at this time. Four central issues of consequence to the MEMS technologist are: (i) the understanding and control of the material properties of microstructural films, such as polycrystalline silicon, (ii) the release of the microstructure, for example, by wet etching silicon dioxide sacrificial films, followed by its drying and surface passivation, (iii) the constraints defined by the combination of micromachining and integrated-circuit technologies when fabricating monolithic sensor devices, and (iv) the methods, materials, and practices used when packaging the completed device. Last, recent developments of hinged structures for postrelease assembly, high-aspect-ratio fabrication of molded parts from deposited thin films, and the advent of deep anisotropic silicon etching hold promise to extend markedly the capabilities of surface-micromachining technologies.

663 citations


Journal ArticleDOI
Tso-Ping Ma1
TL;DR: In this article, high-quality silicon nitride (or oxynitride) films made by a novel jet vapor deposition (JVD) technique are described, which utilizes a high-speed jet of light carrier gas to transport the depositing species onto the substrate to form the desired films.
Abstract: To extend the scaling limit of thermal SiO/sub 2/ in the ultrathin regime when the direct tunneling current becomes significant, members of this author's research team at Yale University, in collaboration with the Jet Process Corporation, embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. In this paper, high-quality silicon nitride (or oxynitride) films made by a novel jet vapor deposition (JVD) technique are described. The JVD process utilizes a high-speed jet of light carrier gas to transport the depositing species onto the substrate to form the desired films. The film composition has been determined to consist primarily of Si and N, with some amounts of O and H. Metal-nitride-Si (MNS) capacitors based on the JVD nitride films deposited directly on Si exhibit relatively low densities of interface traps, fixed charge, and bulk traps. The interface traps at the nitride/Si interface exhibit different properties from those at the SiO/sub 2//Si interface in several aspects. In contrast to the conventional CVD silicon nitride, the high-field I-V characteristics of the JVD silicon nitride fit the Fowler-Nordheim (F-N) tunneling theory over four to five orders of magnitude in current, but do not fit at all the Frenkel-Poole (F-P) transport theory. This is consistent with the much lower concentration of electronic traps in the JVD silicon nitride. Results from the carrier separation experiment indicate that electron current dominates the gate current with very little hole contribution. Both theoretical calculation and experimental data indicate that the gate leakage current in JVD silicon nitride is significantly lower than that in silicon dioxide of the same equivalent oxide thickness. The breakdown characteristics of the JVD nitride are also respectable. Compared to their MOSFET counterparts, MNS transistors exhibit reduced low-field transconductance but enhanced high-field transconductance, perhaps due to the presence of border traps. As expected, the JVD silicon nitride films exhibit very strong resistance to boron penetration and oxidation at high temperatures. These properties, coupled with its room-temperature deposition process, make JVD silicon nitride an attractive candidate to succeed thermal SiO/sub 2/ as an advanced gate dielectric in future generations of ULSI devices.

357 citations


Journal ArticleDOI
TL;DR: In this paper, thin films of Ti-Si-N have been deposited by physical vapor deposition (PVD) with the intention to improve the wear resistance of TiN coatings, and they were prepared by reactive unbalanced magnetron sputtering using two separate Ti and Si targets and a rotating substrate holder.
Abstract: Thin films of Ti–Si–N have been deposited by physical vapor deposition (PVD) with the intention to improve the wear resistance of TiN coatings. The coatings are prepared by reactive unbalanced magnetron sputtering using two separate Ti and Si targets and a rotating substrate holder. The silicon concentration in the deposited films varies between 0 and 15 at.%. SEM observations and X-ray diffraction analysis (XRD) show that the addition of Si to TiN coatings transforms the [111] oriented columnar structure into a dense finely grained structure. From TEM investigations and XRD analyses, the crystallite sizes of TiN are observed to be below 20 nm. XPS analysis shows the presence of silicon nitride, while electron and X-ray diffraction results do not suggest the presence of crystalline Si3N4. This result clearly indicates that these films have a composite structure consisting of TiN nanocrystallites embedded in amorphous silicon nitride. The hardness of the nc-TiN/a-SiNx coatings reaches 3500 HV0.1. The abrasion resistance measured by ball cratering can be enhanced by a factor of 6 in comparison with TiN deposited under the same conditions.

316 citations


Journal ArticleDOI
20 Jan 1998-Langmuir
TL;DR: In this article, the results of probing adhesion and friction forces between surfaces with functional terminal groups with chemically modified scanning probe microscopy (SPM) tips were obtained by direct chemisorption of silane-based compounds on silicon/silicon nitride surfaces.
Abstract: We report the results of probing adhesion and friction forces between surfaces with functional terminal groups with chemically modified scanning probe microscopy (SPM) tips. Surfaces with terminal groups of CH3, NH2, and SO3H were obtained by direct chemisorption of silane-based compounds on silicon/silicon nitride surfaces. We studied surface properties of the resulting self-assembled monolayers (SAMs) in air and aqueous solutions with different pHs. Work of adhesion, “residual forces”, and friction coefficients was obtained for four different types of modified tips and surfaces. Absolute values of the work of adhesion between various surfaces, Wad, were in the range 0.5−8 mJ/m2. The work of adhesion for different modified surfaces correlated with changes of solid−liquid surface energy estimated from macroscopic contact-angle measurements. Friction properties varied with pH in a register with adhesive forces showing a broad maximum at intermediate pH values for a silicon nitride/silicon nitride mating pa...

305 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the thermal stresses in thin Cu films on silicon substrates as a function of film thickness and presence of a silicon nitride passivation layer and found that at room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model.
Abstract: Thermal stresses in thin Cu films on silicon substrates were examined as a function of film thickness and presence of a silicon nitride passivation layer. At room temperature, tensile stresses increased with decreasing film thickness in qualitative agreement with a dislocation constraint model. However, in order to predict the stress levels, grain-size strengthening, which is shown to follow a Hall–Petch relation, must be superimposed. An alternative explanation is strain-hardening due to the increase in dislocation density, which was measured by x-ray diffraction. At 600 °C, the passivation increases the stress by an order of magnitude; this leads to a substantially different shape of the stress-temperature curves, which now resemble those of aluminum with only a native oxide layer. The effect of passivation is shown to be very sensitive to the deposition and test conditions.

264 citations


Journal ArticleDOI
TL;DR: In this paper, the Cat-CVD a-Si, p-Si and SiNx films are compared with those obtained by the conventional plasma CVD (PCVD) method.
Abstract: This paper is a review of the catalytic chemical vapor deposition (Cat-CVD) method and properties of silicon-based thin films, such as amorphous-silicon (a-Si), polycrystalline-silicon (p-Si) and silicon nitride (SiNx) films, prepared by the Cat-CVD method. In the Cat-CVD method, also known as the hot-wire CVD (HWCVD) method, deposition gases are decomposed by catalytic cracking reactions with a heated catalyzer placed near the substrates, so that films are deposited at low substrate temperatures around 300°C without any help from the plasma. After explaining the deposition system and deposition mechanism, the properties of Cat-CVD a-Si, p-Si and SiNx films are described and the results are compared with those obtained by the conventional plasma CVD (PCVD) method. The superiority of the Cat-CVD method over the PCVD method is demonstrated.

226 citations


Patent
06 Mar 1998
TL;DR: In this article, a chemical downstream etching (CDE) that is selective to silicon nitrides (SiN) over silicon oxide (SiO) was proposed, using at least one of a CH 3 F/CF 4 /O 2 recipe.
Abstract: A chemical downstream etching (CDE) that is selective to silicon nitrides (SiN) over silicon oxides (SiO) uses at least one of a CH 3 F/CF 4 /O 2 recipe and a CH 2 F 2 /CF 4 /O 2 recipe. Inflow rates are mapped for the respective components of the input recipe to find settings that provide both high nitride etch rates and high selectivity towards the SiN material. A pins-up scheme is used for simultaneously stripping away backside nitride with topside nitride.

189 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of the deposition parameters (temperature, total pressure and NH3/SiH4 gaseous ratio) on the film deposition rate, refractive index, stoichiometry and thermomechanical stress are investigated and correlated.
Abstract: Varied SiNx films have been deposited by low pressure chemical vapor deposition from silane SiH4 and ammonia NH3 and the influences of the deposition parameters (temperature, total pressure and NH3/SiH4 gaseous ratio) on the film deposition rate, refractive index (assessed at a 830 nm wavelength), stoichiometry and thermomechanical stress are investigated and correlated. Low stress (≈600 MPa) Si3N4 films are obtained for the highest deposition temperature and the lowest total pressure but the gaseous ratio is shown to be the dominant parameter. According to the SiNx stoichiometry, silicon-rich silicon nitride and nitrogen-doped silicon (called NIDOS) depositions are obtained and compressive to tensile stresses are reported. A maximum in compressive stress is put into evidence for N/Si ratio roughly equal to 0.7 and is related to the cumulated effects of silicon nitridation and crystallization, characterizing the transition between nitrogen-doped silicon and silicon-rich silicon nitride. Finally, by consid...

187 citations


Journal ArticleDOI
TL;DR: In this paper, the electrical properties of electron beam (EB) evaporated silicon dioxide (SiO2)/n-GaN, plasma enhanced chemical vapor deposited (PECVD) SiO2/n-GAN, and PECVD silicon nitride (Si3N4)/nGaN interfaces were investigated using high frequency capacitance-voltage measurements.
Abstract: The electrical properties of electron beam (EB) evaporated silicon dioxide (SiO2)/n-GaN, plasma enhanced chemical vapor deposited (PECVD) SiO2/n-GaN, and PECVD silicon nitride (Si3N4)/n-GaN interfaces were investigated using high frequency capacitance–voltage measurements. Compositions of the deposited insulating layers (SiO2 and Si3N4) were analyzed using x-ray photoelectron spectroscopy. Metal-insulator-semiconductor structures were fabricated on the metalorganic chemical vapor deposition grown n-type GaN layers using EB, PECVD grown SiO2 and PECVD grown Si3N4 layers. Minimum interface state density (2.5×1011 eV−1 cm−2) has been observed in the PECVD grown SiO2/n-GaN interface when it was compared with EB evaporated SiO2/n-GaN interface (5.3×1011 eV−1 cm−2) and PECVD Si3N4/n-GaN interface (6.5×1011 eV−1 cm−2). The interface state density (Nf) depends on the composition of deposited insulating layers.

184 citations


Patent
23 Jan 1998
TL;DR: Tantalum and titanium source reagents are described in this article, including tantalum amide and tantalum silicon nitride precursors for the deposition of tantalum nitride material on a substrate by processes such as chemical vapor deposition, assisted chemical vapor, ion implantation, molecular beam epitaxy and rapid thermal processing.
Abstract: Tantalum and titanium source reagents are described, including tantalum amide and tantalum silicon nitride precursors for the deposition of tantalum nitride material on a substrate by processes such as chemical vapor deposition, assisted chemical vapor deposition, ion implantation, molecular beam epitaxy and rapid thermal processing. The precursors may be employed to form diffusion barrier layers on microelectronic device structures enabling the use of copper metallization and ferroelectric thin films in device construction.

180 citations


Journal ArticleDOI
Xin Guo1, Tso-Ping Ma1
TL;DR: In this paper, the authors examined the gate leakage current as a function of the oxygen and nitrogen contents in ultrathin silicon oxynitride films on Si substrates and showed that, provided that electron tunneling is the dominant current conduction mechanism, the leakage current in the direct tunneling regime increases monotonically with the oxygen content for a given equivalent oxide thickness, such that pure silicon nitride passes the least amount of current while pure silicon oxide is the leakiest.
Abstract: It is widely known that the addition of nitrogen in silicon oxide, or the addition of oxygen in silicon nitride, affects its reliability as a gate dielectric. The authors examine the gate leakage current as a function of the oxygen and nitrogen contents in ultrathin silicon oxynitride films on Si substrates. It is shown that, provided that electron tunneling is the dominant current conduction mechanism, the gate leakage current in the direct tunneling regime increases monotonically with the oxygen content for a given equivalent oxide thickness (EOT), such that pure silicon nitride passes the least amount of current while pure silicon oxide is the leakiest.

Journal ArticleDOI
TL;DR: In this paper, a single crystalline wurtzite GaN was grown on the buffer layers of amorphous-like silicon nitride formed on Si (111) substrates by taking the following relationship with the substrate: GaN [0001]//Si [111] and GaN (1120)//Si (110).
Abstract: Wurtzite GaN films were grown on silicon nitride buffer layers formed on Si (111) substrates by radio frequency plasma-assisted molecular beam epitaxy. Reflection high energy electron diffraction, Auger electron spectroscopy, transmission electron microscopy, and photoluminescence results indicate that the single crystalline wurtzite GaN was grown on the buffer layers of amorphouslike silicon nitride formed on Si (111) substrates by taking the following relationship with the substrate: GaN [0001]//Si [111] and GaN (1120)//Si (110). Both faces of the silicon nitride buffer layer were found to be flat and sharp, the thickness of the buffer layer (1–1.5 nm) being constant across the interface. Efficient bound exciton emission was observed at 3.46 eV. The growth technique described was found to be simple but very powerful for growing high quality GaN films on Si substrates.

Journal ArticleDOI
TL;DR: In this article, an empirical potential for interactions between Si and N to describe silicon nitride systems using the Tersoff functional form was developed using a set of ab initio and experimental results of the crystalline phase.
Abstract: We developed an empirical potential for interactions between Si and N to describe silicon nitride systems using the Tersoff functional form. The fitting parameters were found using a set of ab initio and experimental results of the crystalline phase. Using this empirical model, we explored the structural properties of amorphous silicon nitride through Monte Carlo simulations, and compared them to available experimental data. The good description of the $a\ensuremath{-}{\mathrm{SiN}}_{x}$ system for a wide range of nitrogen contents $(0lxl1.5)$ shows the reliability of this model.

Patent
Tadashi Oshima1
25 Feb 1998
TL;DR: In this paper, a silicon nitride layer on a silicon layer or a silicon oxide layer is formed by loading the silicon or the silicon oxide layers and the silicon n-oxide layer in a dry etching atmosphere, and selectively etching the silicon polysilicon oxide layer with respect to the silicon and silicon oxide by flowing a fluorine gas consisting of any one of CH 2 F 2, CH 3 F, or CHF 3 and an inert gas.
Abstract: There are included steps of forming a silicon nitride layer on a silicon layer or a silicon oxide layer, loading the silicon layer or the silicon oxide layer and the silicon nitride layer in a dry etching atmosphere, and selectively etching the silicon nitride layer with respect to the silicon layer or the silicon oxide layer by flowing a fluorine gas consisting of any one of CH 2 F 2 , CH 3 F, or CHF 3 and an inert gas to the dry etching atmosphere Hence, in the etching process of the silicon nitride layer, the etching selectivity of the silicon nitride layer to Si or SiO 2 can be enhanced and also etching anisotropy can be enhanced

Patent
01 Oct 1998
TL;DR: In this paper, a hydrogen barrier encapsulation technique for the control of hydrogen induced degradation of ferroelectric capacitors in nonvolatile integrated circuit memory devices is presented, which is applicable to all known perovskite dielectrics including PZT, PLZT and layered Perovskites (whether doped or undoped).
Abstract: A hydrogen barrier encapsulation technique for the control of hydrogen induced degradation of ferroelectric capacitors in non-volatile integrated circuit memory devices. The resultant device structure ameliorates the hydrogen induced degradation of ferroelectric capacitors by completely encapsulating the capacitor within a suitable hydrogen barrier material, such as chemical vapor deposition (“CVD”) or sputtered silicon nitride, thus ensuring process compatibility with industry standard process steps. Although the deposition process for CVD Si3N4 itself contains hydrogen, the deposition time may be kept relatively short thereby allowing the TiN local interconnect layer to act as a “short term” hydrogen barrier. The techniques of the present invention are applicable to all known ferroelectric dielectrics including Perovskites and layered Perovskites (whether doped or undoped) including PZT, PLZT, BST, SBT and others while simultaneously allowing for a potentially broader choice of electrode materials and the use of a forming gas anneal process step on the completed IC structure.

Patent
Bin Zhao1
25 Sep 1998
TL;DR: In this paper, a dual damascene method and structures for IC interconnects which use a dual-damascene process incorporating a low-k dielectric material, high conductivity metal, and an improved hard mask scheme are provided.
Abstract: Dual damascene methods and structures are provided for IC interconnects which use a dual-damascene process incorporating a low-k dielectric material, high conductivity metal, and an improved hard mask scheme. A pair of hard masks are employed: a silicon dioxide layer and a silicon nitride layer, wherein the silicon dioxide layer acts to protect the silicon nitride layer during dual damascene etch processing, but is subsequently sacrificed during CMP, allowing the silicon nitride layer to act as a the CMP hard mask. In this way, delamination of the low-k material is prevented, and any copper-contaminated silicon dioxide material is removed.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the thermal conductance of 1 μm thick low stress silicon nitride membranes over the temperature range, 0.06 4 K, indicating that the thermal transport is determined by bulk scattering.
Abstract: We have measured the thermal conductance, G, of ≈1 μm thick low stress silicon nitride membranes over the temperature range, 0.06 4 K, G is independent of surface condition indicating that the thermal transport is determined by bulk scattering. For T<4 K, scattering from membrane surfaces becomes significant. Membranes which have submicron sized Ag particles glued to the surface or are micromachined into narrow strips have a G that is reduced by a factor as large as 5 compared with that of clean, solid membranes with the same ratio of cross section to length.

Journal ArticleDOI
TL;DR: Lauinger et al. as discussed by the authors showed that low effective surface recombination velocities Seff of 4 cm/s have been obtained at ISFH on low resistivity p-type crystalline silicon using microwave-excited remote plasmaenhanced chemical vapor deposition (RPECVD) of silicon nitride at low temperature (300-400
Abstract: In a recent letter [Lauinger et al., Appl. Phys. Lett. 68, 1232 (1996)] we have shown that record low effective surface recombination velocities Seff of 4 cm/s have been obtained at ISFH on low-resistivity (1 Ω cm) p-type crystalline silicon using microwave-excited remote plasma-enhanced chemical vapor deposition (RPECVD) of silicon nitride at low temperature (300–400 °C). As an important application, this technique allows a simple fabrication of rear-passivated high-efficiency silicon solar cells with monofacial or bifacial sensitivity. In this work, we present details of the required optimization of the PECVD parameters and a characterization of the resulting silicon nitride films. All deposition parameters are shown to strongly affect Seff as well as the stability of the films against the ultraviolet (UV) photons of terrestrial sunlight. A clear correlation between Seff and the film stoichiometry is observed, allowing a simple control and even a rough optimization of the surface passivation quality by ...

Journal ArticleDOI
TL;DR: In this paper, the influence of negative substrate bias on the microstructural, compositional, chemical, mechanical, and optical properties of silicon nitride (SiNx) thin films was systematically investigated.
Abstract: Silicon nitride (SiNx) thin films have been deposited by radio frequency (rf) magnetron sputtering of a silicon target in reactive nitrogen-argon atmospheres without intentional substrate heating. The influence of negative substrate bias Vs on the microstructural, compositional, chemical, mechanical, and optical properties of the SiNx films was systematically investigated. An extensive analysis of the films was carried out using ellipsometry, transmission electron microscopy (TEM), atomic force microscopy (AFM), Rutherford backscattering spectrometry, secondary ion mass spectrometry (SIMS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy, stress and chemical etch rate measurements. TEM and AFM studies revealed that films produced at low bias voltages had a porous columnar structure containing large void, typical of zone 1, but that films produced at higher bias voltages had relatively smooth surfaces with a highly condensed structure, typical of zone T. Both FTIR and SIMS ...

Journal ArticleDOI
TL;DR: The known properties of nitrogen as an impurity in, and as an alloy element of, the germanium network are reviewed in this paper, where the existing data are compared with similar properties of other group IV nitrides, in particular with silicon nitride.
Abstract: The known properties of nitrogen as an impurity in, and as an alloy element of, the germanium network are reviewed in this article. Amorphous and crystalline germanium–nitrogen alloys are interesting materials with potential applications for protective coatings and window layers for solar conversion devices. They may also act as effective diffusion masks for III-V electronic devices. The existing data are compared with similar properties of other group IV nitrides, in particular with silicon nitride. To a certain extent, the general picture mirrors the one found in Si–N systems, as expected from the similar valence structure of both elemental semiconductors. However, important differences appear in the deposition methods and alloy composition, the optical properties of as grown films, and the electrical behavior of nitrogen-doped amorphous layers. Structural studies are reviewed, including band structure calculations and the energies of nitrogen-related defects, which are compared with experimental data. ...

Patent
18 Jun 1998
TL;DR: A layer for protecting an underlying functional coating stack for example a single silver layer or double silver layer Low-E coating stack includes silicon oxynitride or silicon aluminum oxide layer as mentioned in this paper.
Abstract: A layer for protecting an underlying functional coating stack for example a single silver layer or double silver layer Low-E coating stack includes silicon oxynitride or silicon aluminum oxynitride layer. The protective film may have a uniform composition throughout its thickness i.e. homogeneous protective layer, a constantly increasing or decreasing index of refraction throughout its thickness i.e. a graded protective layer, or a combination of all or some of the foregoing i.e. a non-homogeneous protective layer. The graded and non-homogeneous layers may have an outer surface of silicon nitride, silicon aluminum nitride, silicon dioxide, silicon oxynitride or silicon aluminum oxynitride. The protective layer of the invention may be the last layer deposited on the functional coating stack or may have a film deposited thereon.

Journal ArticleDOI
TL;DR: In this paper, high performance amorphous silicon thin-film transistors (a-Si:H TFTs) were fabricated on 2 mil. (51 µm) thick polyimide foil substrates.
Abstract: We have fabricated high-performance amorphous silicon thin-film transistors (a-Si:H TFTs) on 2 mil. (51 µm) thick polyimide foil substrates. The TFT structure was deposited by r.f.-excited plasma enhanced chemical vapor deposition (PECVD). All TFT layers, including the gate silicon nitride, the undoped, and the n+ amorphous silicon were deposited at a substrate temperature of 150°C. The transistors have inverted-staggered back-channel etch structure. The TFT off-current is ∼ 10−12 A, the on-off current ratio is > 107, the threshold voltage is 3.5 V, the sub-threshold slope is ∼ 0.5V/decade, and the linear-regime mobility is ∼ 0.5 cm2V−1s−1. We compare the mechanical behavior of a thin film on a stiff and on a compliant substrate. The thin film stress can be reduced to one half by changing from a stiff to a compliant substrate. A new equation is developed for the radius of curvature of thin films on compliant substrates.

Journal ArticleDOI
TL;DR: Si 3 N 4 thin films were deposited with atomic layer control on Si(100) substrates using sequential surface chemical reactions as mentioned in this paper, which was accomplished by separating the binary reaction 3SiCl 4 +4NH 3 →Si 3N 4 +12HCl into two half-reactions.

Journal ArticleDOI
TL;DR: Friction and wear properties of silicon nitride were investigated using ball-on-disk tribometer under various relative humidity levels (RHL), and the results showed that the influence of humidity depends on the material of the couples as mentioned in this paper.
Abstract: Friction and wear properties of silicon nitride were investigated using ball-on-disk tribometer under various relative humidity levels (RHL). Friction tests were conducted against various metals (copper, nickel, titanium, aluminium). The results show that the influence of humidity depends on the material of the couples. Tribological behaviour of silicon nitride sliding on very reactive metals such as titanium and aluminium is not influenced by RHL. In contrast, the friction coefficient and wear mechanism of nickel and copper are strongly affected by adsorbed films of water vapour. Tribological properties of Si 3 N 4 /Si 3 N 4 couple were also studied and the effect of humidity was analyzed.

Journal ArticleDOI
TL;DR: In this article, the authors performed calorimetric measurements on 200 nm thin silicon nitride membranes at temperatures from 0.07 to 1 K. Besides full windows, membranes cut into a thermally isolating suspended bridge geometry were investigated.
Abstract: We have performed calorimetric measurements on 200 nm thin silicon nitride membranes at temperatures from 0.07 to 1 K. Besides full windows, membranes cut into a thermally isolating suspended bridge geometry were investigated. Based on dc and ac measurements employing normal-metal/insulator/superconductor (NIS) tunnel junctions both as a thermometer and a heater, we report on heat transport and thermal relaxation in silicon nitride films. The bridge structure improves thermal isolation and, consequently, energy sensitivity by two orders of magnitude over those of the full membrane with the same size, and makes such a structure very attractive for bolometric and microrefrigeration applications.

Journal ArticleDOI
TL;DR: In this paper, a top-gate staggered hydrogenated amorphous silicon (a-Si:H) thin-film transistors were fabricated over large-area glass substrates using a selective phosphorus-treatment (PT) of indium-tinoxide (ITO) source/drain electrodes.
Abstract: Top-gate staggered hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) were fabricated over large-area glass substrates using a selective phosphorus-treatment (PT) of indium-tin-oxide (ITO) source/drain electrodes. The ohmic contact between a-Si:H and ITO had a specific contact resistivity of about 0.18 Ωcm2. For a 100-µm channel length TFT, the source/drain series resistance contributes less than 5% of the total drain-to-source resistance. This contribution increases to about 25% for a 10-µm channel length TFT. Our study also indicated that the interface quality of a-Si:H/a-SiNx:H is amorphous silicon nitride (a-SiNx:H) and a-Si:H thickness independent and dependent, respectively. Effective interface state densities of about 1.5×1012 cm-2eV-1 and 3.2×1012 cm-2eV-1 were obtained for top-gate TFTs with a 1300 and 300 A thick a-Si:H films, respectively. Channel conductance activation energy of about 0.1 eV was measured for this top-gate TFT with 300 A a-Si:H.

Journal ArticleDOI
TL;DR: In this article, a SrBi2Ta2O9 thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film was used to make ferroelectric memory capacitors.
Abstract: We have made ferroelectric memory capacitors by depositing a SrBi2Ta2O9 thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film. The hysteresis in the capacitance–voltage curves suggests a sizable memory window of 2 V with a programming voltage swing of ±7 V. The switching time is estimated to be on the order of nanosecond based on the results of a one-shot pulse experiment. The results from the fatigue test indicate a slight degradation of the memory window after 1011 switching cycles. These properties are encouraging for the development of ferroelectric memory transistors.

Journal ArticleDOI
TL;DR: In this paper, two different electron energy loss spectroscopy (EELS) quantitative analytical methods for obtaining complete compositions from interface regions are applied to ultrathin oxide-based amorphous grain boundary (GB) films of ∼ 1 nm thickness in high-purity HIPed Si3N4 ceramics.
Abstract: Two different electron energy loss spectroscopy (EELS) quantitative analytical methods for obtaining complete compositions from interface regions are applied to ultrathin oxide-based amorphous grain boundary (GB) films of ∼ 1 nm thickness in high-purity HIPed Si3N4 ceramics. The first method, 1, is a quantification of the segregation excess at interfaces for all the elements, including the bulk constituents such as silicon and nitrogen; this yields a GB film composition of SiN0.49±1.4O1.02±0.42 when combined with the average film thickness from high resolution electron microscopy (HREM). The second method, II, is based on an EELS near-edge structure (ELNES) analysis of the Si–L 2,3 edge of thin GB films which permits a subtraction procedure that yields a completeEELS spectrum, e.g., that also includes the O–K and N–K edges, explicitly for the GB film. From analysis of these spectra, the film composition is directly obtained as SiN0.63±0.19O1.44±0.33, close to the one obtained by the first method but with much better statistical quality. The improved quality results from the fewer assumptions made in method II; while in method I uniform thickness and illumination condition have to beassumed, and correction of such effects yields an extra systematic error. Method II is convenient as it does not depend on the film thickness detected by HREM, nor suffer from material lost by preferential thinning at the GB. In addition, a chemical width for these films can be deduced as 1.33 ± 0.25 nm, that depends on an estimation of film density based on its composition. Such a chemical width is in good agreement with the structural thickness determined by HREM, with a small difference that is probably due to the different way in which these techniques probe the GB film. The GB film compositions are both nonstoichiometric, but in an opposite sense, this discrepancy is probably due to different ways of treating the surface oxidation layers in both methods.

Journal ArticleDOI
TL;DR: In this article, the etch rate of silicon nitride (Si3N4) and silicon dioxide (SiO2) in the afterglow of NF3 and NF3/O2 microwave discharges was characterized.
Abstract: The etching of silicon nitride (Si3N4) and silicon dioxide (SiO2) in the afterglow of NF3 and NF3/O2 microwave discharges has been characterized. The etch rates of both materials increase approximately linearly with the flow of NF3 due to the increased availability of F atoms. The etch rate of Si3N4 is enhanced significantly upon O2 injection into the NF3 discharge for O2/NF3 ratios of 0.3 and higher, whereas the SiO2 etch rate is less influenced for the same flow ratios. X-ray photoelectron spectroscopy of processed Si3N4 samples shows that the fluorine content of the reactive layer, which forms on the Si3N4 surface during etching, decreases with the flow of O2, and instead oxidation and nitrogen depletion of the surface occur. The oxidation of the reactive layer follows the same dependence on the flow of O2 as the etch rate. Argon actinometry and quadrupole mass spectrometry are used to identify reactive species in the etching of both materials. The atomic fluorine density decreases due to dilution as O...

Journal ArticleDOI
TL;DR: In this article, a very high selectivity silicon nitride etch process has been developed on an inductively coupled plasma etching system which uses a NF3/O2/NH3 (nonchlorine) chemistry.
Abstract: A very high-selectivity silicon nitride etch process has been developed on an inductively coupled plasma etching system which uses a NF3/O2/NH3 (nonchlorine) chemistry. Etch selectivity of low-pressure chemical vapor deposition nitride to thermal oxide greater than 100:1 was achieved at a nitride etch rate of 500 A/min. A NF3/O2 chemistry was optimized for nitride to oxide selectivity of about 12:1, with a nitride etch rate of 1200 A/min. The addition of NH3 inhibits oxide etching thus enhancing selectivity. The net etch rate for oxide may be reduced to zero while maintaining a reasonably high etch rate for nitride thus resulting in essentially infinite selectivity. The process is stable, repeatable and creates no particles. A split lot test on device wafers against standard wet etch process demonstrates superior process and device performance.