Showing papers on "Silicon nitride published in 1992"

A new bulge test technique for the determination of Young's modulus and Poisson's ratio of thin films

Abstract: A new analysis of the deflection of square and rectangular membranes of varying aspect ratio under the influence of a uniform pressure is presented. The influence of residual stresses on the deflection of membranes is examined. Expressions have been developed that allow one to measure residual stresses and Young's moduli. By testing both square and rectangular membranes of the same film, it is possible to determine Poisson's ratio of the film. Using standard micromachining techniques, free-standing films of LPCVD silicon nitride were fabricated and tested as a model system. The deflection of the silicon nitride films as a function of film aspect ratio is very well predicted by the new analysis. Young's modulus of the silicon nitride films is 222 ± 3 GPa and Poisson's ratio is 0.28 ± 0.05. The residual stress varies between 120 and 150 MPa. Young's modulus and hardness of the films were also measured by means of nanoindentation, yielding values of 216 ± 10 GPa and 21.0 ± 0.9 GPa, respectively.

An infrared dielectric function model for amorphous solids

Abstract: For the modeling of infrared spectra it is a common approach to use a dielectric function that treats the vibrational modes as damped harmonic oscillators. This model was found to be rather crude for some applications to amorphous solids. A dielectric function model yielding a Gaussian shape of the absorption lines and satisfying Kramers–Kronig relations is suggested. The model function is constructed by a convolution of a Gaussian function with the dielectric function of the damped harmonic oscillator model. An analytical solution of this integral is given. It is demonstrated that this model describes the spectra of thermally grown ultrathin (1.3 nm) silicon oxide films, plasma‐deposited silicon films, plasma‐deposited silicon nitride films, and amorphous aluminum oxide films very well. The physical motivation of the dielectric function model suggested is the randomness of the vibrational frequencies in an amorphous structure.

Methods of forming an interconnect on a semiconductor substrate

Abstract: A device and methods of forming an interconnection within a prepatterned channel in a semiconductor device are described. The present invention includes a method of forming an interconnect channel within a semiconductor device. A first dielectric layer is deposited over a substrate and patterned to form a contact opening that is subsequently filled with a contact plug. A second dielectric layer is deposited over the patterned first dielectric layer and the contact plug. The second dielectric layer is patterned to form the interconnect channel, wherein the first dielectric layer acts as an etch stop to prevent etching of the substrate. The present invention also includes a method of forming an interconnect. A dielectric layer is deposited over a substrate and patterned to form an interconnect chapel. A metal layer is deposited over the patterned dielectric layer and within the interconnect channel. The metal layer is polished with an alkaline solution to remove the metal layer that does not lie within the interconnect chapel to form an interconnect. The present invention further includes a method of forming an interconnect over a silicon nitride layer. The silicon nitride layer is deposited over a semiconductor substrate and patterned to form a contact opening that is subsequently filled with a conductive material. A metal layer is deposited on the patterned silicon nitride layer and the contact plug and patterned to form the interconnect such that all of the interconnect lies on the contact plug and part of the patterned silicon nitride layer.

Oxygen mobility in silicon dioxide and silicate glasses: a review

Abstract: Silicon dioxide and silicate glass films are formed on silicon nitride and silicon carbide ceramics during exposure to high-temperature oxidising atmospheres, and oxygen transport through the film is potentially a rate-controlling step. Recent published literature concerning oxygen permeation and diffusion through amorphous and crystalline silicon dioxide, and silicate glasses, is reviewed. Data for diffusion coefficients are collected to facilitate the assessment of probable dominant oxygen transport mechanisms, and associated rates, under given sets of oxidation conditions.

Paramagnetic point defects in amorphous silicon dioxide and amorphous silicon nitride thin films

Abstract: In this paper the authors review paramagnetic point defects in amorphous silicon nitride thin films. We will discuss two intrinsic paramagnetic defects: a trivalent silicon center, named the K-center, and the recently observed nitrogen dangling-bond center. We examine the structural identification, and the electronic properties of the K-center, as well as consider why a SiN{sub x}:H is generally a very effective charge trapping dielectric. In addition, this paper compares and contrasts special features of the structure and electronic role of the paramagnetic point defects in both silicon dioxide and silicon nitride thin films; this may provide insight for further studies on the physics and chemistry of these dangling-bond centers in both materials.

Fabrication and Secondary‐Phase Crystallization of Rare‐Earth Disilicate–Silicon Nitride Ceramics

Abstract: The fabrication and intergranular-phase devitrification of silicon nitride densified with rare-earth (RE) oxide additives has been investigated. The additions of the oxides of Sm, Gd, Dy, Er, and Yb, having high melting points and behaving similarly to Y2O3, were compositionally controlled to tailor a microstructure with a crystalline secondary phase of RE2Si2O7. The lanthanide oxides were found to be as effective as Y2O3 in densifying Si3N4, resulting in identical microstructures and densities of 98–99% of theoretical density. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a thin residual amorphous film which was observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification.

Process for selectively etching a layer of silicon dioxide on an underlying stop layer of silicon nitride

Abstract: More specifically, a process is provided for etching a multilayer structure to form a predetermined etched pattern therein. The subject process comprises providing the multilayer structure having a plurality of structural layers. The structural layers of the multilayer structure comprise a silicon dioxide outer layer on an underlying silicon nitride stop layer. Then, a chemical etchant protective layer is formed on a major surface of the multilayer structure having a predetermined pattern of openings, thereby exposing areas of the silicon dioxide outer layer corresponding to the predetermined pattern of openings. The exposed areas of the silicon dioxide outer layer are then etched down to the silicon nitride stop layer, at a high SiO 2 etch rate and at a high level of selectivity of the SiO 2 etch rate with respect to the Si 3 N 4 etch rate, with a fluorinated chemical etchant system. The fluorinated chemical etchant system includes an etchant material and an additive material. The additive material comprises a fluorocarbon material in which the number of hydrogen atoms is equal to or greater than the number of fluorine atoms. The etching step forms a substantially predetermined etch pattern in the silicon dioxide outer layer in which the contact sidewalls of said SiO 2 outer layer are substantially upright.

Fabrication of silicon condenser microphones using single wafer technology

Abstract: A condenser microphone design that can be fabricated using the sacrificial layer technique is proposed and tested. The microphone backplate is a 1- mu m plasma-enhanced chemical-vapor-deposited (PECVD) silicon nitride film with a high density of acoustic holes (120-525 holes/mm/sup 2/), covered with a thin Ti/Au electrode. Microphones with a flat frequency response between 100 Hz and 14 kHz and a sensitivity of typically 1-2 mV/Pa have been fabricated in a reproducible way. These sensitivities can be achieved using a relatively low bias voltage of 6-16 V. The measured sensitivities and bandwidths are comparable to those of other silicon microphones with highly perforated backplates. The major advantage of the new microphone design is that it can be fabricated on a single wafer so that no bonding techniques are required. >

The Hessian biased force field for silicon nitride ceramics: Predictions of thermodynamic and mechanical properties for α‐ and β‐Si3N4

Abstract: A force field (MSXX) for molecular dynamics simulations of silicon nitride is derived using the Hessian biased technique from ab initio calculations on N(SiH3)3 and Si(NH2)4 clusters. This is used to model the nitrogen and silicon centers of the α and β forms of crystalline Si3N4 for prediction of crystal structures, lattice expansion parameters, elastic constants, phonon states, and thermodynamic properties. Experimental measurements on many of these important physical constants are lacking, so that these calculations provide the first reliable data on such fundamental properties of silicon nitride. This MSXX force field is expected to be useful for molecular dynamics simulations of dislocations and grain boundaries and for studying the reconstruction and energetics of clean, reduced, and oxidized surfaces.

Chemical aspects of ceramic tribology

Abstract: Chemical interactions with ambient gases and with lubricant liquids have been found to influence friction forces and wear rates of ceramics and to determine the mechanisms by which these materials wear. In the presence of water vapor, for example, tribochemical reactions (which are accelerated by simultaneous friction) produce smooth surfaces and decrease wear by several orders of magnitude in silicon nitride and chemisorption embrittlement increases wear rates of zirconia. Hydrocarbon lubricants produce similar effects, decreasing wear by surface reaction in some cases and increasing it by grain boundary attack in others. These interactions can be understood in terms of the surface chemistry of ceramics, which is dominated by charge transfer with ambients through acid-base reactions. The surface chemistry of ceramics is reviewed and related to their electronic structure. Tribochemical maps are proposed for the interaction with water and selected hydrocarbons by comparing the electronic structure of the ceramics and fluids. The ability to generalize the behavior of lubricants on ceramics by the use of these maps indicates an improved understanding of the lubricant-surface interaction and provides a tool for the development of new lubricant systems. 71 refs., 14 figs.

R‐Curve Behavior and Strength for In‐Situ Reinforced Silicon Nitrides with Different Microstructures

Abstract: R-curves for two in-situ reinforced silicon nitrides A and B of nominally the same composition are characterized using the Griffith equation and indentation fracture mechanics. These R-curves are calibrated against fine-grained silicon nitrides which have a known chevron-notch (long-crack) toughness and with a nearly flat R-curve behavior. Silicon nitride A, with its coarser microstructure and higher chevron-notch toughness, shows lower resitance to crack growth than silicon nitride B if the crack size is less than ∼200 μm. These results are consistent with the indentation–Strength measurements which show a crossover of strength between the two materials at an indentation load between 49 and 98 N, and below the crossover A has a lower strength. The toughening behavior is explained using an elastic-bridging model for the short crack, and a pullout model for the long crack. The effects of R-curve properties on design are discussed.

Electrical and optical characteristics of vacuum-sealed polysilicon microlamps

Abstract: A silicon-filament vacuum-sealed incandescent light source has been fabricated using IC technology and subsurface micromachining. The incandescent source consists of a heavily doped p/sup +/ polysilicon filament coated with silicon nitride and enclosed in a vacuum-sealed ( approximately=80-mT) cavity in the silicon-chip surface. The filament is formed beneath the surface and later released using sacrificial etching to obtain a microstructure that is protected from the external environment. The filament is electrically heated to reach incandescence at a temperature near 1400 K. The power required to achieve this temperature (for a filament 510*5*1 mu m) is 5 mW. The emitted optical power is 250 mu W, and the peak in the spectrum distribution is near 2.5 mu m. The radiation approximately follows Lambert's cosine law. The subsurface micromachining technique used to produce the evacuated cavity has applications in other micromechanical devices. >

High performance induction plasma torch with a water-cooled ceramic confinement tube

Abstract: A high performance induction plasma torch (1) comprises a cylindrical torch body (2) made of cast ceramic or composite polymer, a coaxial cylindrical plasma confinement tube (9) located inside the torch body (2), a gas distributor head (11) secured to one end of the torch body (2) to supply the confinement tube (9) with gaseous substances, a cylindrical and coaxial induction coil (3) completely embedded in the ceramic or polymer material of the torch body (2), and a thin annular chamber (25) separating the coaxial torch body (2) and confinement tube (9). This confinement tube can be made of pure or composite ceramic materials based on sintered or reaction bonded silicon nitride, boron nitride, aluminum nitride or alumina, or any combinations of them with varying additives and fillers. The annular chamber (25) is about 1 mm thick and high velocity cooling water flows therein to efficiently cool the plasma confinement tube (9).

Crack healing behavior of hot pressed silicon nitride due to oxidation

Abstract: It is shown that limited oxidation of an MgO-containing, hot-pressed silicon nitride ceramic at 800 deg C and above results in increased strength due to crack healing. Slight oxidation of the surface produces enstatite and cristobalite which fills in cracks. More extensive oxidation leads to strength degradation due to the formation of new flaws by the evolution of N2 gas at the surface. The apparent fracture toughness also increased at 800 deg C and above due to oxidation. Bonds formed between the two surfaces of the crack during oxidation leads to a reduction in stress intensity at the crack tip, suggesting that valid high-temperature toughness values cannot be obtained in an air environment. The increase in strength due to crack healing by oxidation can be achieved without compromising the fatigue properties of the silicon nitride ceramic.

Internal stress compensation and scaling in ultrasensitive silicon pressure sensors

Abstract: The pressure sensitivity of boron-doped silicon membranes has been characterized as a function of diaphragm dimensions and internal membrane stress. Using an electrostatic technique based on silicon microbridges, the internal stress for p/sup ++/ silicon (on glass), LPCVD silicon dioxide, and LPCVD silicon nitride was measured; typical values are 40, -300, and 950 MPa, respectively. Silicon membranes with several different edge lengths and deposited oxide and/or nitride coatings were characterized for sensitivity. While the pressure sensitivity can be reduced by more than a factor of twenty in the membranes due to boron-induced internal stress, the use of stress-compensating dielectrics can improve this sensitivity by a factor of six or more. Based on this theory and the measured material parameters, scaled experimental devices show typical sensitivities within 10-20% of the theoretical design targets. Pressure sensitivities as high as 2900 ppm/Pa have been achieved. >

Silicon fusion bonding and its characterization

Abstract: The basic principles of wafer fusion bonding including pretreatment, room temperature mating, and thermal annealing are presented. Techniques for the characterization of the bond quality are reviewed. Results for fusion bonding of other materials such as silicon nitride and polysilicon are discussed with a view to bond quality and application. Examples of fusion processes for power device fabrication show the feasibility of the technique.

Plasma-Enhanced Chemical Vapor Deposition of Silicon Nitride

Abstract: The optimum condition of plasma-enhanced chemical vapor deposition to deposite silicon nitride (SiNx) film and its application as a gate insulator of a-Si thin-film transistor (TFT) have been investigated. The internal stress of SiNx in the range of 4.3×109 dyn/cm2 tensile to 8.0×109 dyn/cm2 compressive is found to be controllable by changing the ratio of H2 and N2 in the source gases without affecting the optical band gap. Satisfactory TFT characteristics and high reliability are realized by using a gate insulator of SiNx having either stoichiometric or N-rich composition which shows the large optical band gap.

Method of fabricating semiconductor devices and integrated circuits using sidewall spacer technology

Abstract: The base layer of high quality spacers, such as those used on the sidewalls of the gate stack of submicron devices (e.g. MOSFETs, EPROMs), are formed as composite, multi-layered structures (22.1-22.3) of silicon oxides or of silicon oxides and silicon nitride.

Fracture toughness and thermal shock behavior of silicon nitride-boron nitride ceramics

Abstract: Fracture toughness behavior, stress–strain behavior, and flaw resistance of pressureless-sintered Si3N4-BN ceramics are investigated. The results are discussed with respect to the reported thermal shock behavior of these composites. Although the materials behave linear-elastic and exhibit no R-curve behavior, their flaw resistance is different from that of other linear-elastic materials. Whereas the critical thermal shock temperature difference (ΔTc) is enhanced by adding BN, the content of BN has no influence on the strength loss during severe thermal shocks.

Corrosion of High-Performance Ceramics

Abstract: 1 Introduction- 2 Oxidation in Oxygen and Air- 21 Silicon Nitride Ceramics- 211 Thermodynamics of Si3N4 Oxidation- 212 Composition of Oxide Layer- 213 Effect of Phase and Chemical Composition of Ceramics- 214 Oxidation of Porous Ceramics- 215 Oxidation of Dense Ceramics- 216 Peculiarities of Oxidation Kinetics- 22 Silicon Carbide Ceramics- 221 Thermodynamics of SiC Oxidation- 222 Composition of Oxide Layer- 223 Hot-Pressed and Sintered SiC- 224 Self-Bonded and Recrystallized SiC- 23 Aluminium Nitride Ceramics- 24 Boron Carbide Ceramics- 25 Boron Nitride Ceramics- 26 Ceramic Matrix Composites- 261 Nonoxide Matrix Composites- 262 Oxide Matrix Composites- 3 Gaseous Corrosion of Ceramics- 31 Hot Corrosion- 311 Silicon Nitride Ceramics- 312 Silicon Carbide Ceramics- 313 Oxide Ceramics- 32 Water Vapour Corrosion- 321 Nonoxide Ceramics- 322 Zirconia Ceramics- 33 Corrosion in Carbon Oxide Environments- 34 Corrosion in Halogen- and Chalcogen-Containing Environments- 4 Corrosion in Liquid Media- 41 Corrosion in Solutions- 411 Silicon Nitride Ceramics- 412 Silicon Carbide Ceramics- 413 Aluminium Nitride Ceramics- 414 Boron Carbide Ceramics- 415 Boron Nitride Ceramics- 416 Oxide Ceramics- 42 Molten Salt and Alkali Corrosion- 5 Corrosion Effect on Ceramic Properties- 51 Preoxidation of Ceramics- 511 Silicon Nitride Ceramics- 512 Silicon Carbide Ceramics- 513 Aluminium Nitride Ceramics- 514 Zirconia Ceramics- 52 Effect of Corrosion in Different Environments- 521 Hot Corrosion- 522 Molten Salt Corrosion- 523 Corrosion in Solutions- 6 Mechanical Properties and Corrosion- 61 Effect of Oxidation on Results of High-Temperature Mechanical Tests- 611 Silicon Nitride Ceramics- 612 Silicon Carbide Ceramics- 613 Boron Carbide Ceramics- 62 Effect of Salts on High-Temperature Strength- 63 Failure of Ceramics Affected by Long-Term Mechanical Loading in Corrosive Environment- 631 Silicon Nitride Ceramics- 632 Silicon Carbide Ceramics- 633 Alumina Ceramics- 634 Zirconia Ceramics- 635 Salt-Assisted Strength Degradation- 636 Triboxidation- 64 Lifetime Prediction in View of Environmental Effects- 7 Corrosion Protection and Development of Corrosion-Resistant Ceramics- 71 Chemical-Vapour Deposited Coatings- 72 Sprayed and Sputtered Coatings- 73 Impregnation and Other Methods of Protection- 74 Choice of Optimum Ceramic Composition- References

Process for fabricating multiple pillars inside a dram trench for increased capacitor surface

Abstract: A method is disclosed for fabricating a DRAM trench capacitor with multiple-pillars inside the trench for increased surface area. A thin pad oxide of a few tens of nonometers is grown on a silicon substrate. A layer of silicon nitride is deposited and another layer of oxide is then deposited. This provides the ONO stack. Then a layer of polysilicon, a layer of nitride, and a layer of large-grained polysilicon are deposited sequentially. Then, a trench is defined by a lithographic mask and the exposed large-grained polysilicon is etched in CF4. Since CF4 etches the polysilicon and nitride 20 at almost the same rates, the topographical features existed in the polysilicon layer is copied to the nitride layer. The nitride layer is partially etched. The RIE etching gas is then changed to a mixture of HBR, SiF4, Helium, and NF3 which gives a very directional polysilicon etching with a good selectivity to nitride and a very high selectivity to oxide. Consequently, the topographical features on the nitride layer is enhanced and is transferred to the polysilicon layer which is used as a mask to etch the oxide nitride and pad oxide to form pillars.

A study of static friction between silicon and silicon compounds

Abstract: Presents results from measurements of static coefficient of friction between materials of interest to microelectromechanical systems (MEMS). The materials studied include silicon, silicon dioxide, and silicon nitride. Two measurement techniques have been used to this study. In the first technique, static friction between two millimeter-sized flat components was measured in a 10-6 Torr vacuum chamber. In the second technique, static friction between a three-millimeter radius aluminum bullet coated with a material of interest and a flat substrate was measured in a approximately 5*10-10 Torr ultra-high vacuum (UHV) chamber. The results show that the coefficient of friction, mu , between silicon and silicon compound contacts in vacuum is in the range 0.2 to 0.7. The coefficients of friction between silicon dioxide/silicon dioxide and silicon dioxide/silicon contacts increase by 55% to 157% with increased exposure to humidity. Additionally, friction between similar materials behaves differently than that between dissimilar materials.

Silicon nitride formation by low energy N + and N + 2 ion beams

Abstract: Reactions of N+ and N+2 ions with Si(100) surface are examined as a function of both ion kinetic energy and dose using a low energy ion beam instrument. The Si surface is exposed to low energy (1–300 eV) ion beams in an ultrahigh vacuum environment and the resulting surface species are characterized by Auger electron spectroscopy and ultraviolet photoelectron spectroscopy. The absolute reaction probability Pr is measured for nitridation processes. Pr(N+) has a value of ∼0.25 and stays constant in the energy range of 1–25 eV. Pr(N+2) increases from zero to ∼0.25 in the same range. Continued exposure of the ion beams to a dose ≳5×1015 ions/cm2 leads to a saturation and formation of a dense and stable silicon nitride layer. Variation of Pr with energy and dose is explained in terms of elementary reaction steps such as charge neutralization of the projectile ion, collisional dissociation of N+2, nitridation reaction, and chemically induced desorption of surface nitrogen species. A mechanism is proposed to exp...

Silicon nitride sintered body

Abstract: A silicon nitride sintered body comprising α-silicon nitride including α'-sialon and β'-sialon including β-silicon nitride in which the content of the α-silicon nitride including α'-sialon in the surface part thereof is less than its content in the inner part thereof. The silicon nitride sintered body is excellent in mechanical strength at ordinary temperature, productivity and cost efficiency.

Bias-stress-induced creation and removal of dangling-bond states in amorphous silicon thin-film transistors

Abstract: We report on the threshold voltage shift in amorphous silicon thin‐film transistors, subjected to a gate bias for a prolonged period of time (bias stress). For transistors made with a silicon nitride gate insulator, the threshold voltage shift for low positive bias is due to dangling‐bond‐state creation in the amorphous silicon layer. For low negative bias, the threshold voltage shift is due to the bias‐stress‐induced removal of dangling‐bond states. These results are contrasted with previously published results for oxide transistors, but both results are consistent with a defect pool model for the dangling‐bond states. The difference for oxide and nitride transistors is due to a different zero‐bias Fermi energy position at the interface. For nitride transistors at much larger applied bias, the dominant mechanism changes and the threshold voltage shift is dominated by charge trapping in the gate dielectric. This is found for both large negative and large positive bias.

Microstructure of an Extruded β‐Silicon Nitride Whisker‐Reinforced Silicon Nitride Composite

Abstract: β-Si3N4 whisker-reinforced β′SiAlON composites were fabricated by extrusion and densified, using pressureless sintering. Whisker alignment was observed in both the green and sintered microstructures. SEM analysis of polished, sintered samples showed a microstructure consisting of the original β-Si3N4 whiskers in a matrix of fine SiAlON grains. SEM of plasma-etched samples and TEM analysis showed that the whiskers, as a result of grain growth, consisted of two phases, a core and a sheath layer. X-ray mapping and EDS analysis revealed that the core material contained no trace of Al, confirming the presence of original β-Si3N4 whiskers. The composition of the sheath was qualitatively identical to that of the fine β′ SiAlON grains in the matrix. The sheath was thus formed by the precipitation of the β′SiAlON during liquid-phase sintering and led to substantial growth of the whiskers. Microdiffraction showed that the β′SiAlON grew epitaxially on the β-Si3N4 whiskers, resulting in a heavily faulted SiAlON layer.