Showing papers on "Silicon nitride published in 1987"

Relationships between processing, microstructure and properties of dense and reaction-bonded silicon nitride

Abstract: Some aspects of processing, microstructure and properties of the various types of silicon nitride are discussed. Special emphasis is placed on the relationships between powder properties, process conditions, densification and microstructure, as well as the interdependence between microstructure and properties. After summarizing the areas of crystal structure and thermodynamic properties, and processing of the different types of Si3N4, the state-of-the-art of dense and reaction-bonded silicon nitride is given. For both types the formation mechanisms and microstructure, relationships between powder properties, additives (in the case of dense Si3N4), process conditions, and densification and microstructure, as well as data and microstructural effects of various mechanical, thermal and thermo-mechanical properties, are outlined. Advanced processing techniques, such as sintering, gas-pressure sintering, post-sintering, and the different routes of hot-isostatic pressing (starting with powder compacts, reaction-bonded Si3N4 or pre-sintered Si3N4 and the resulting properties, are discussed.

On the Equilibrium Thickness of Intergranular Glass Phases in Ceramic Materials

Abstract: The fundamental question as to whether thin intergranular films can adopt an equilibrium thickness in polycrystalline ceramics is addressed. Two continuum approaches are presented, one based on interfacial energies and the other on the force balance normal to the boundary. These indicate that there will exist a stable thickness for the intergranular film and that it will be of the order of 1 nm. The origin of an equilibrium thickness is shown to be the result of two competing interactions, an attractive van der Waals-disperson interaction between the grains on either side of the boundary acting to thin the film and a repulsive term, due to the structure of the intergranular liquid, opposing this attraction. As both of these interactions are of short range (

Method of making programmable low impedance interconnect diode element

Abstract: A programmable low impedance interconnect diode element is disclosed having a lower electrode formed of a semiconductor material of a first conductivity type covered by an insulating dielectric layer which may be in a preferred embodiment comprised of an initial layer of silicon dioxide, a second layer of silicon nitride and a third layer of silicon dioxide, covered by a layer of semiconductor material of a second conductivity type. A programmable read only memory array and a programmable logic array comprising a plurality of the above-described cells are also disclosed.

Non-volatile memory cell having Si rich silicon nitride charge trapping layer

Abstract: A non-volatile storage cell comprising a field effect transistor having source, gate, and drain electrodes. The gate electrode includes a gate stack having a dielectric layer, a charge storage structure comprising a layer of silicon-rich silicon nitride having sufficient excess silicon to provide appreciable charge storage enhancement, without providing appreciable charge conductance enhancement, as compared to stoichiometric silicon nitride, and a charge injection means. A control electrode is disposed on the gate stack for effecting charge transfer to and from the silicon-rich silicon nitride layer through the charge injection means. An array of these cells is formed by disposing the FETs within independently biased substrate portions. Thus the cells can be overwritten without an intervening erasure cycle.

Ion-sensing devices with silicon nitride and borosilicate glass insulators

Abstract: Ion-sensitive field-effect transistors (ISFET's) with silicon dioxide, silicon nitride, and borosilicate glass as the active gate material were fabricated and tested for pH-sensing applications. The borosilicate glass and silicon nitride devices were found to have a linear potential/pH response and previous theories of ISFET function were inadequate to explain this. A two-site theory is presented that can explain the features of the potential/pH response of both silicon nitride and borosilicate glass ISFETs. The model is easily extended to any two-site system.

Method of fabricating a LDDFET with self-aligned silicide

Abstract: A method of fabricating a lightly-doped drain field effect transistor (LDDFET) with or without self-aligned silicide (salicide) on a substrate is disclosed. The initial steps include either (1) anisotropic silicon nitride and polysilicon etching steps, an isotropic photoresist erosion step, and a second anisotropic etching of part of the silicon nitride to obtain a ladder-shaped polysilicon gate having a silicon nitride thereon; or (2) an anisotropic polysilicon etch step, an isotropic photoresist erosion step to expose part of the unetched polysilicon, and a second anisotropic polysilicon etch step to remove completely the unmasked polysilicon to obtain the ladder-shaped polysilicon gate. The LDD structure is formed by the implantation of ions to form a heavily-doped source and drain regions and lightly-doped regions under the step of the ladder-shaped polysilicon gate layer. Thereafter, the thin polysilicon step is oxidized completely. After the silicon nitride and silicon dioxide layers are removed, the self-aligned silicide may be applied to form the LDD with salicide.

Oxygen distribution in silicon nitride powders

Abstract: The oxygen content of ten different silicon nitride powders was determined by bulk chemical analysis and surface-sensitive X-ray photoemission spectroscopy (XPS). In silicon nitride powders prepared from silicon and silica by nitridation and carbothermal reduction in a nitrogen atmosphere, respectively, only a minor part of the total oxygen content of 0.9 to 2.5 wt% was found in a surface layer of less than 1 nm thick, whereas an appreciable amount can be attributed to oxygen dissolved in the bulk. Powders made by silicon diimide decomposition, however, are characterized by a higher oxygen concentration at the particle surface relative to the bulk, which may be further reduced by chemical treatment. The surface layer composition corresponds to an intermediate state between silica and silicon oxynitride.

Controlled Crystallization of the Amorphous Phase in Silicon Nitride Ceramics

Abstract: The controlled crystallization of amorphous second phases in SiAlON is demonstrated in two systems. In a magnesia-containing SiAlON, cordierite crystallized on annealing after hot-pressing. Similarly, garnet crystallized in yttria-contain-ing SiAlON. The resulting microstructures are characterized by TEM and qualitatively related to changes on room-temperature toughness and high-temperature deformation.

Synchrotron radiation-excited chemical-vapor deposition and etching

Abstract: Photoexcited chemical‐vapor deposition (CVD) and etching using synchrotron radiation as an exciting light source were experimentally demonstrated. CVD of silicon nitride film and etching of Si and SiO2 by SF6+O2 gases are described in detail. In several reaction systems, it was found that the surface photoexcitation was an important mechanism. Reaction models for gas‐phase excitation and surface excitation were proposed.

Low Pressure CVD of Silicon Nitride

Abstract: A model of the hot wall tubular reactor for low pressure chemical vapor deposition (LPCVD) is applied to the study of silicon nitride film growth from dichlorosilane and ammonia. The model predicts the effects of process conditions and reactor configuration on distributed wafer growth rate profiles. The model formulation includes contributions from convection, multicomponent diffusion, and gas and surface reactions of several chemical species. Rival chemical mechanisms are compared to experimental data obtained in a conventional LPCVD reactor over widely varying conditions. Results indicate that the in‐wafer film thickness nonuniformities may be explained by the effect of diffusion‐limited film growth from highly reactive gas‐phase intermediates, with simultaneous uniform deposition from less reactive dichlorosilane. Model predictions agree well with experimental data over the composition, pressure, and temperature ranges considered. The model is also used in the design of optimal operating conditions for 100 and 150 mm wafer processes.

Synchrotron radiation‐excited chemical‐vapor deposition and etching

Abstract: Photoexcited chemical‐vapor deposition (CVD) and etching using synchrotron radiation as an exciting light source were experimentally demonstrated. CVD of silicon nitride film and etching of Si and SiO2 by SF6+O2 gases are described in detail. In several reaction systems, it was found that the surface photoexcitation was an important mechanism. Reaction models for gas‐phase excitation and surface excitation were proposed.

Electronic structure of silicon nitride and amorphous silicon/silicon nitride band offsets by electron spectroscopy

Abstract: The film thickness, chemical state, and polarization screening for a‐SiN1.4 :H films deposited by glow discharge over hydrogenated amorphous silicon (a‐Si:H) were determined by x‐ray photoelectron spectroscopy (XPS) and Auger spectroscopy. The nitride films were observed to be single phase and the escape depth for 1400‐eV electrons in the a‐SiN1.4 :H film was determined to be 30 A. The band offsets for the a‐Si:H/a‐SiN1.4 :H interface were determined by XPS and Bremsstrahlung isochromat spectroscopy (BIS) to be 1.2 eV for the valence band and 2.2 eV for the conduction band, while the band gap for a‐SiN1.4 :H was found to be 5.3 eV in accordance with the optical gap. By combining optical absorption measurements with the valence‐band density of states and conduction‐band density of states determined by electron spectroscopy, a semiquantitative estimate of the band tailing within the nitride gap was obtained. Correlation of the defect absorption with the electron spin resonance measurements suggest that the ...

Method for producing substoichiometric silicon nitride of preselected proportions

Abstract: An apparatus and method for producing films of silicon nitride whose index of refraction varies continuously with film depth by preselected amounts between n=3.9 and n=1.99. This is done by producing an amorphous film of silicon nitride, Si1-x Nx, of pre-selected stoichiometry between x=0 and x=0.57. In a vacuum-chamber, a target substrate is exposed to vaporized silicon while being simultaneously bombarded with an ion beam of relatively high kinetic energy, ionized, nitrogen particles. The nitrogen embeds in the silicon film deposited on the substrate to form amorphous silicon nitride, the stoichiometry of which depends on the intensity of the ion beam. Instruments measure during the deposition the relative rate of arrival at the target for silicon and nitrogen, and, with pre-generated calibration data for the apparatus, enable an operator to selectively control the film's stoichiometry by controlling the ion beam's intensity response to the measured rate of silicon deposition.

Laser Processing of Thin Films and Microstructures: Oxidation, Deposition and Etching of Insulators

Abstract: 1. Introduction.- 1.1 Historical Background.- 1.2 Advantages of Laser Technology.- 1.3 Requirements for Laser Processing.- 1.4 Outline.- 2. Interaction and Kinetics.- 2.1 Laser Excitation of Matter.- 2.2 Laser Excitation of the Gas Species.- 2.2.1 Selective Vibrational Excitation.- 2.2.2 Selective Electronic Excitation.- 2.3 Interaction of Laser Radiation with Solids.- 2.3.1 Metals.- 2.3.2 Insulators and Semiconductors.- 2.3.3 Non linear Optical Absorption.- 2.3.4 Plasma Formation.- 2.4 Interactions with Surfaces and Adsorbates.- 2.4.1 Adsorbates.- 2.4.2 Desorption.- 2.4.3 Adsorption.- 2.5 Laser-Induced Heating.- 2.5.1 Thermalization.- 2.5.2 Heating Models.- 2.5.3 Impurity Incorporation.- 2.6 Nucleation and Growth.- 2.7 Chemical Reactions and Growth Rates.- 2.7.1 Low Intensity Levels.- 2.7.2 High Intensity Levels.- 2.7.3 CW Laser Controlled Reaction Rates.- 3. Experimental Considerations.- 3.1 Properties of Laser Beams.- 3.2 Spatial Resolution.- 3.3 Modes of Laser Processing.- 3.3.1 Geometrical Configurations.- 3.3.2 Pattern Generation.- 3.3.3 Process Uniformity and Reproducibility.- 3.3.4 Beam Profile Measurements.- 3.4 The Choice of Laser.- 4. Laser-Assisted Oxidation and Nitridation.- 4.1 Oxidation.- 4.2 Background and Theory.- 4.3 Metal Oxidation.- 4.4 Silicon Oxidation.- 4.4.1 Alternative Processing Techniques.- 4.4.2 Laser-induced Growth.- 4.4.3 Mechanisms of Photonically Enhanced Oxidation.- 4.4.4 Rapid Thermal Oxidation.- 4.5 Oxidation of Compound Semiconductors.- 4.6 Nitridation.- 4.6.1 Thermal Nitridation.- 4.6.2 Laser Nitridation.- 4.7 Laser Curing.- 5. Passivation by Laser Annealing and Melting.- 5.1 Modes of Laser Annealing.- 5.2 Laser Annealing in Oxygen.- 5.3 Oxygen Implantation.- 5.4 Nitrogen Implantation.- 5.5 Impurity Effects.- 5.6 Laser Cleaning of Surfaces.- 6. Laser-Induced Deposition.- 6.1 Background.- 6.2 Metal Oxides.- 6.3 Silicon Oxide.- 6.4 Silicon Nitride.- 6.5 Organic Polymer Formation.- 7. Material Removal.- 7.1 Introduction and Background.- 7.2 Etching.- 7.3 Ablation.- 7.4 Trimming.- 7.5 Cutting and Drilling.- 8. Summary and Conclusions.- 8.1 Properties and Applications.- 8.2 Future Prospects.- 8.3 Postscript.- References.

Plasma enhanced chemical vapor deposition of thin films of silicon nitride from cyclic organosilicon nitrogen precursors

Abstract: This invention relates to a process for the production of a solid thin film containing silicon and nitrogen on a substrate, said film having an aggregate low concentration of inorganic carbon and oxygen of less than about 51 atom percent, which process comprises: (A) contacting the substrate with a gaseous mixture itself comprising: (i) a volatile cyclic organic silicon-nitrogen source, and (ii) a reactant independently selected from hydrogen or a hydrogen-nitrogen source, under plasma enhanced chemical vapor deposition conditions of pressure lower than 10 Torr and temperature greater than ambient temperature for a time sufficient to produce a silicon nitride thin film. In another aspect, the invention relates to the silicon-nitride thin film coated article or substrate produced by the process of the present invention. Preferred process conditions evaluates include the RF of 13.56 MHz, 20-80 W Power, power density 0.37 watts/cm 2 to 1.5 watts/cm 2 and a ratio of the silicon-nitrogen source and the hydrogen nitrogen source of between about 0.1/19.9 and 0.6/19.4 percent by volume. When ammonia is used, the aggregate concentration of carbon and oxygen is less than 20 atom percent, preferably less than 10 atomic percent.

Manufacture of semiconductor device

Abstract: PURPOSE:To highly integrate a semiconductor device while preventing a transistor from deteriorating in its characteristics by forming an element separating insulating film of MISFET in plural steps so that at least one of the steps does not include implanting of a channel cut high density impurity CONSTITUTION:A silicon nitride film is grown on an SiO2 film 12 formed on a semiconductor substrate 11, with a mask 23 a nitride film pattern 13 is formed, and P-type impurity is implanted in high density for channel cut Then, the impurity ions 14 are implanted only out of the pattern 13 (a) Then, with the second mask 24 the second nitride film pattern 13a is formed (b) Thereafter, when a field oxide film 15 is formed by thermally oxidizing, a channel cut layer 16 is formed thereunder, but this layer does not affect the other portion of the film 15 Accordingly, the same impurity density as the substrate is obtained over the entire width W (c), the pattern 13a, the oxide film 12 are then removed, a gate oxide film is newly formed, a gate electrode 17 is formed (d), an insulating film, a wiring layer are formed to complete a transistor (e)

Thin-film el device

Abstract: A thin-film EL device of which the surface is coated with a protective film of a two-layer structure consisting of an insulating film (10) and a metallic film (20) in order to obtain good air-tightness and high reliability. The insulating film (10) consists of any one of a silicon oxide film, a silicon nitride film, an aluminum oxide film or a tantalum oxide film, and the metallic film consists of a thin film of either aluminum or tantalum.

Characterization of hot-pressed silicon nitride-based materials by microhardness measurements

Abstract: The microhardness A Si3N4-based materials may be related to their phase and chemical compositions and to microstructural parameters such as porosity, grain size and secondary phases. By reducing the amount of intergranular phase, the microhardness may reach values up toHV 500 = 3000 kg mm−2. Moreover, a comparison among different materials must include the microhardness tests in a wide range of values of the applied load. The relationd n =B 1 +B 2 d 2, obtained from those of Meyer and Kick, gives two constants:B 1 may represent one class of materials andB 2 is specific for each single material.

Rapid thermal nitridized oxide locos process

Abstract: A process for minimizing bird's beak in local oxidation of silicon which is compatible with high density (VLSI) semiconductor devices is disclosed. A pad oxide is nitridized using rapid thermal nitridization, which works quickly with minimal thermal cycling of the wafer. A silicon nitride film is then deposited over the nitridized oxide. Both films are exposed to dry plasma etching which gives more consistent results than wet methods. The field oxide is then grown and finally the masking films of the nitridized oxide and silicon nitride are removed, whereby field oxides are grown with minimal bird's beak, and minimal damage to the wafer with a small number of steps. The pad oxide may be grown in the same rapid thermal annealer used for the rapid thermal nitridization. Both cycles (pad oxide growth and nitridization of the pad oxide) can be integrated to "one" cycle and performed sequentially in the same rapid thermal annealer to increase throughput and improve device quality.

Ion bombardment-induced mechanical stress in plasma-enhanced deposited silicon nitride and silicon oxynitride films

Abstract: We have studied the influence of different deposition conditions on the mechanical stress of silicon nitride and silicon oxynitride layers formed by plasma-enhanced deposition onto silicon substrates. It appears that the mechanical stress of the as-deposited silicon (oxy)nitride layer is a combined effect of the extent of ion bombardment and the deposition temperature on the hydrogen desorption rate. Deposited films show a tensile stress character when the hydrogen desorption rate is thermally controlled, whereas in the case of an ion-bombardement-controlled hydrogen desorption rate the deposited films have a compressive stress. It is also shown that due to annealing at temperatures above the deposition temperature the films are densified as a result of hydrogen desorption and cross-linking.

Thin film transistor

Abstract: PURPOSE:To simplify a manufacturing process by a method wherein a gate electrode or source and drain electrodes provided on the side of a picture element electrode directly above a substrate is (are) composed of a double-layer structure (double-layer structures) of a transparent conductor layer and a metal layer (transparent conductor layers and metal layers) CONSTITUTION:A transparent conductor layer 12 is formed over the whole surface of a transparent substrate 1 and a metal layer 13 is formed on it Then the transparent conductor layer 12 and the metal layer 13 are etched and patterned into the forms of a picture element electrode 3 and a gate electrode 2 Then a silicon nitride layer to be a gate insulating film 4 and an amorphous silicon hydride layer to be a semiconductor layer 5 are successively formed over the whole surface and further a phosphorus-doped amorphous silicon hydride layer to be an n type layer 6 is formed and those layers are etched to be patterned and, at the same time, to form a contact hole 9 Then an aluminum layer to be a source electrode 7 and a drain electrode 8 is formed and then the metal film 13, the silicon nitride film, the amorphous silicon hydride film and the like are removed by etching and a passivation film 10 and a light shield 11 are formed

Method of manufacturing thin-film electroluminescent display panel

Abstract: According to a method of this invention for manufacturing a thin-film electroluminescent display panel of the type having a pair of electrodes sandwiching a three-layer structure composed of a layer covered with dielectric layers on both sides, a silicon nitride or silicon oxynitride film is formed on a layer comprising ZnS by a plasma chemical vapor deposition method with a mixture of silicon and nitrogen gases or of silicon, nitrogen and N2 O gases. Alternatively, this film may be formed in a double-layer structure, the second layer being formed with a mixture of silicon and ammonia gases or of silicon, ammonia and N2 O gases. A dielectric layer thus formed by a method embodying this invention can satisfactorily cover the protrusions and impurities in the layer underneath and thin-film electroluminescent elements manufactured by this method have superior brightness characteristics.

Silicon based mass airflow sensor and its fabrication method

Abstract: A mass airflow sensor is fabricated on a semiconductor substrate and which includes (1) a dielectric diaphragm, (2) p-etch-stopped silicon rim, (3) thin-film heating and temperature sensing elements, and (4) tapered chip edges. The dielectric diaphragm is formed with thin silicon oxide and silicon nitride in a sandwich structure and provides excellent thermal insulation for the sensing and heating elements of the sensor. The diaphragm dimensions, including thickness, are accurately controlled through the use of the heavily-p-doped silicon rim to help ensure uniform and reproducible sensor performance.

Silicon nitride-silicon carbide composite material and process for production thereof

Abstract: A sintered silicon nitride-silicon carbide composite material is provided comprising a matrix phase of silicon nitride and silicon carbide where silicon carbide grains having an average diameter of not more than 1 μm are present at grain boundaries of silicon nitride grains and silicon carbide grains having a diameter of several nanometers to several hundred nanometers, typically not more than about 0.5 micrometers, are dispersed within the silicon nitride grains and a dispersion phase where (a) silicon carbide grains having an average diameter of 2 to 50 μm and/or (b) silicon carbide whiskers having a short axis of 0.05 to 10 μm and an aspect ratio of 5 to 300 are dispersed in the matrix phase. A process for the production of the composite material is also provided.

Electronic processes in silicon nitride

Abstract: Time, electric field, and temperature dependence of the flat‐band voltage shift and steady‐state contact‐current versus contact‐field characteristics in polycrystalline silicon‐oxide‐nitride‐oxide‐silicon structures subjected to high field stress have been studied in detail. Experimental data are compared with exact (numerical) solutions of the Arnett model [P. C. Arnett, J. Appl. Phys. 46, 5236 (1975)] for one‐carrier (electron) transport in silicon nitride. It is shown that a simple field‐assisted thermal ionization (Poole–Frenkel) detrapping mechanism cannot explain the experimental observations, leading to unphysical values for the attempt‐to‐escape frequency. An alternative model is proposed based on a thermally assisted tunneling detrapping mechanism. Trap density, effective capture cross section, ground‐state energy, and an upper limit for the energy of the first excited state of the electron trap are determined.

Structural order in Si–N and Si–N–O films prepared by plasma assisted chemical vapor deposition process

Abstract: Local bonding modes and the nearest‐neighbor environment of the constituent atoms in glow discharge silicon nitride and oxynitride films have been probed with Fourier‐transform infrared spectroscopy. The silicon nitride films prepared under a wide range of (NH3+N2)/SiH4 ratio and rf power levels all show characteristic absorption bands of N–H, Si–H, and Si–N bonds. The Si–H stretch mode absorption peak shifts to higher wave numbers with the increasing number of N–H bonds in the material. This behavior is observed for all power levels and gas flow combinations. The observed universal dependence of the Si–H stretch frequency on the concentration of the N–H bonds, and the sign of the shift indicate that the change in the frequency is caused by the increasing number of nitrogen atoms at the Si site. Arguments advanced on the basis of the electronegativity of the constituents suggest that the formation of N–H and Si–H bonds at the Si–N site leads to opposite shifts in the Si–N frequency. Thermal annealing stud...