Showing papers on "Substrate (electronics) published in 1988"

Electrical and Optical Properties of Stannite-Type Quaternary Semiconductor Thin Films

Abstract: Quaternary stannite-type semiconductor films of Cu2CdSnS4 and Cu2ZnSnS4 with (112) orientation were deposited on heated glass substrates using atom beam sputtering. These p-type films showed resistivities which were decreasing functions of the substrate temperature up to 240°C. The films had an absorption coefficient larger than 1 × 104 cm-1 in the visible wavelength range. The direct optical band gaps of the (112) oriented polycrystalline films were estimated as 1.06 eV and 1.45 eV for Cu2CdSnS4 and Cu2ZnSnS4, respectively.

Silicon carbide semiconductor device

Abstract: PURPOSE: To prevent leakage currents even under severe conditions such as a high temperature, large power, etc., by forming a first electrode onto the surface of an silicon carbide semiconductor layer shaped onto one surface of a substrate, a second electrode onto the other surface of the substrate and a third electrode onto the side face of the silicon carbide semiconductor layer. CONSTITUTION: A nickel film formed onto the rear of an silicon substrate 1 is used as a drain electrode 7, and a titanium-aluminum film shaped onto the projecting end face of an silicon carbide growth layer 2 having mesa structure is employed as a source electrode 6. Currents flowing between the source electrode 6 and the drain electrode 7 are controlled by fluctuating voltage applied to gate electrodes 8 and changing the width of depletion layers 9 spreading in the silicon carbide growth layer 2. Accordingly, an silicon carbide semiconductor device, in which leakage currents are not generated even under severe conditions such as a high temperature, large power, etc., and which has excellent characteristics, can be acquired. COPYRIGHT: (C)1989,JPO&Japio

Quantum size effects on the optical band gap of microcrystalline Si:H.

Abstract: We have succeeded in fabricating the mostly crystallized Si:H materials having a wide optical band gap of up to 2.4 eV by means of a reactive sputtering technique with a low substrate temperature of \ensuremath{\sim}100 K. The structural analysis showed that the materials consist of small crystalline silicon particles surrounded by hydrogen atoms, whose diameters are 20--30 A\r{}. The widening of the optical band gap can be explained by a three-dimensional quantum-well effect in the small particles.

Cooperative growth phenomena in silicon/germanium low-temperature epitaxy

Abstract: A series of Si:Ge alloys and structures has been prepared by ultrahigh‐vacuum chemical vapor deposition. Alloys of composition 0≤Ge/Si≤0.20 are readily deposited at T=550 °C. Commensurate, defect‐free strained layers are deposited up to a critical thickness, whereupon the accumulated stress in the films is accommodated by the formation of dislocation networks in the substrate wafers. A cooperative growth phenomenon is observed where the addition of 10% germane to the gaseous deposition source accelerates silane’s heterogeneous reaction rate by a factor of 25. A model is proposed where Ge acts as a desorption center for mobile hydrogen adatoms on the Si[100] surface, accelerating heterogeneous silane pyrolysis by the enhanced availability of chemisorption sites.

Single-Crystal YBa2Cu3O7-x Thin Films by Activated Reactive Evaporation

Abstract: By means of the activated reactive evaporation, YBa2Cu3O7-x single-crystal thin films with the c axis perpendicular to the substrate plane have been directly and epitaxially grown on the (100) surface of SrTiO3. The substrate temperature was kept below 600°C and the oxidation treatment was performed at below 500°C. The ac-resistive measurement for a film with 2000 A thickness gave a sharp superconducting transition, where the endpoint was 90.2 K and ΔTc(10–90%)=1.7 K. From the complex susceptibility measurement we confirmed the Meissner effect as well as the structural uniformity of the specimen.

Migration-Enhanced Epitaxy of GaAs and AlGaAs

Abstract: Surface migration is effectively enhanced by evaporating Ga or Al atoms onto a clean GaAs surface under an As-free or low As pressure atmosphere. This characteristic was utilized by alternately supplying Ga and/or Al and AS4 to the substrate surface for growing atomically-flat GaAs-AlGaAs heterointerfaces, and also for growing high-quality GaAs and AlGaAs layers at very low substrate temperatures. The migration characteristics of surface adatoms have been investigated through reflection high-energy electron diffraction measurements. It was found that different growth mechanisms are operative in this method at both high and low temperatures. Both these mechanisms are expected to yield flat heterojunction interfaces. By applying this method, GaAs layers and GaAs-AlGaAs single quantum-well structures with excellent photoluminescence were grown at substrate temperatures of 200 and 300degC, respectively.

High‐resolution electron‐beam induced deposition

Abstract: A finely focused electron beam is used as a source of energy to decompose molecules, e.g., organometallics or hydrocarbons, adsorbed on the surface of a substrate. Films deposited by these means can be used as etch mask for reactive ion etching, as an absorber for various types of radiation, or directly as part of a device structure. A vector scan electron beam system with a LaB6 cathode has been equipped with a temperature controlled reservoir to supply vapors into a differentially pumped sample chamber. The substrate is mounted on a stage which can be cooled or heated in the range of −40 to +110 °C. The ability to utilize backscattered electron micro‐ scopy is maintained. Area, line, and spot deposition rates have been measured for tungsten hexacarbonyl [W(CO)6] and dimethyl–gold–trifluoro–acetylacetonate [Me2Au(tfac)] at various fluxes, sample temperatures, and current densities. Three‐dimensional buildup of tips and free standing lines across holes in membranes and resolution better than 0.25 μm have ...

Chemical vapor deposition and characterization of 6H‐SiC thin films on off‐axis 6H‐SiC substrates

Abstract: High‐quality, monocrystalline 6H‐SiC thin films have been epitaxially grown on 6H‐SiC {0001} substrates which were prepared 3° off‐axis from 〈0001〉 towards 〈1120〉 at 1773 K via chemical vapor deposition (CVD). Essentially, no defects were generated from the epilayer/substrate interface as determined by cross‐sectional transmission electron microscopy (XTEM). Double positioning boundaries which were observed in β‐SiC grown on 6H‐SiC substrates were eliminated as confirmed by plan‐view TEM. A strong dependence of the surface morphology of the as‐grown thin films on the tilting orientation of the substrates was observed and reasons for this phenomenon are discussed. The unintentionally doped 6H‐SiC thin films always exhibit n‐type conduction with a carrier concentration on the order of 1016 cm−3. Au‐6H‐SiC Schottky barrier diodes were fabricated on the CVD 6H‐SiC thin films and it was found that the leakage current at a reverse bias of 55 V was only 3.2×10−5 A/cm2. This is compared to SiC films grown on oth...

Electrically-programmable low-impedance anti-fuse element

Abstract: Electrically-programmable low-impedance anti-fuses are disclosed having capacitor-like structure with very low leakage before programming and a low resistance after programming. The electrically-programmable low-impedance antifuses of the present invention include a first conductive electrode which may be formed as a diffusion region in a semiconductor substrate or may be formed from a semiconductor material, such as polysilicon, located above and insulated from the substrate. A dielectric layer, which, in a preferred embodiment includes a first layer of silicon dioxide, a second layer of silicon nitride and a third layer of silicon dioxide, is disposed over the first electrode. A second electrode is formed over the dielectric layer from a semiconductor material such as polysilicon, or a metal having a barrier metal underneath. At least one of the two electrodes of each anti-fuse is highly-doped or implanted with arsenic such that high concentrations of arsenic exist at the interface between the electrode and the dielectric layer. This arsenic will combine with other material and flow into the anti-fuse filament after programmed to form a low resistance controllable anti-fuse link. Circuitry is provided which allows the anti-fuse of the present invention to be programmed by application of a suitable programming voltage to input-output pins of the integrated circuit containing the antifuse. Where more than one anti-fuse is to be programmed using the programming voltage applied at the input-output terminals, other additional input-output terminals may serve as address inputs to specify the anti-fuse to be programmed.

Method of fabricating back surface point contact solar cells

Abstract: A back surface point contact silicon solar cell having improved characteristics is fabricated by hydrogenating a silicon-silicon oxide interface where hydrogen atoms are diffused through silicon nitride and silicon oxide passivating layers on the surface of a silicon substrate. In carrying out the hydrogenation, the substrate and passivation layers are placed in a hydrogen atomsphere at an elevated temperature of at least 900° C. whereby hydrogen atoms diffuse through the two passivation layers. Self-alignment techniques are employed in forming small-geometry doped regions in the surface of the silicon substrate for the p-n junctions of the solar cell. Openings are formed through the passivation layers to expose first surface areas on the substrate, and a doped silicon oxide layer is then formed over the passivation layers and on the exposed surface areas. Portions of the first doped layer on the two passivation layers are removed and then second portions of the two passivation layers are removed, thereby exposing second surface areas. A second doped silicon oxide layer is then formed over the passivation layers and on the second exposed surface areas. Dopants from the two doped silicon oxide layers are then diffused into the first and second surface layers to form p and n diffused regions in the surface of the substrate. Thereafter, the first and second doped silicon oxide layers are removed by a preferential etchant which does not remove the silicon nitride layer, thereby exposing the first and second surface areas. A two-level metal interconnect structure is then formed for separately contacting the first surface areas and the second surface areas.

Magnetic recording medium

Abstract: PURPOSE:To prevent the exfoliation of a metallic underlying layer and to improve durability by interposing an intermediate layer consisting of a specific metal oxide between a nonmagnetic and nonmetallic substrate and the metallic underlying layer so that the metallic underlying layer is securely laminated and deposited on the nonmetallic substrate CONSTITUTION:The intermediate layer 2 consisting of the oxide of >=1 kinds of metals including at least 1 kind of element among Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Mn is deposited and formed on the memory medium consisting of nonmagnetic and nonmetallic material such as ceramics and glass. The metallic underlying layer 3 consisting of, for example, Cr or 'Permalloy(R)' selected according to the compsn. of the magnetic layer is laminated and deposited on the intermediate layer 2 and in succession, the required magnetic layer 4 consisting of Co-Ni or further a protective film layer 5 according to need are deposited thereon. The metallic underlying layer 3 is securely bonded via the intermediate layer 2 to the nonmetallic substrate 1 and is stabilized in strength by which the exfoliation by mechanical and/or thermal impact is obviated and the durability is exhibited for a long period of time.

In situ preparation of Y‐Ba‐Cu‐O superconducting thin films by magnetron sputtering

Abstract: Thin superconducting films of YBa2 Cu3 O7 have been prepared by magnetron sputtering from targets of sintered material in an oxygen‐argon atmosphere. The compositional and structural properties were studied by Rutherford backscattering and x‐ray diffraction. The films were deposited at substrate temperatures between 580 and 800 °C. It was found that the material grows in the oxygen deficient tetragonal phase. In situ heat treatment at 430 °C in pure O2 atmosphere generates the orthorhombic structure and the films on sapphire and SrTiO3 coated sapphire substrates show the full superconducting transition at 83 K.

Substrate-polarity dependence of metal-organic vapor-phase epitaxy-grown GaN on SiC

Abstract: Single‐crystal gallium nitride was grown on each of the two polar {0001} planes of 6H‐silicon carbide substrates utilizing metal‐organic vapor‐phase epitaxy. The substrate polarity is clearly shown to strongly influence the surface morphology and the photoluminescence property of the layer. The examination of the layer surfaces using x‐ray photoelectron spectroscopy revealed that {0001} GaN grown on the basal planes of SiC changes its polarity in accordance with the substrate polarity.

Method of and apparatus for sputtering

Abstract: A thin film forming method and apparatus is provided, wherein a negative voltage is applied alternate­ly to a target (6) and a substrate (8) to perform film formation and reverse sputter alternately. Further, a coil (5) is mounted between the target and the substrate and a high frequency current (3) is made to flow there­through to generate plasma. A negative base voltage smaller in absolute value than that during sputter may be applied to the substrate to make a fraction of Ar ions to flow into the substrate while it is subjected to reverse sputter. Thus, a film whose step coverage is 0.3 or more is possible. It becomes also possible to hole stable discharge and reverse sputter at high vacuum region. The pressure of an Ar atmosphere may be lowered to 10⁻³ Torr or less. A film whose peak value of x-ray diffraction strength in (111) plane is 150 Xcps or more is possible. Also, a barrier layer with a layered structure of granular and columnar crystals or a mixed structure thereof and hence with an efficient barrier effect and a large specific resistance is possible.

Electron‐spin‐resonance study of radiation‐induced paramagnetic defects in oxides grown on (100) silicon substrates

Abstract: We have used electron‐spin resonance to investigate radiation‐induced point defects in Si/SiO2 structures with (100) silicon substrates. We find that the radiation‐induced point defects are quite similar to defects generated in Si/SiO2 structures grown on (111) silicon substrates. In both cases, an oxygen‐deficient silicon center, the E’ defect, appears to be responsible for trapped positive charge. In both cases trivalent silicon (Pb centers) defects are primarily responsible for radiation‐induced interface states. In earlier electron‐spin‐resonance studies of unirradiated (100) substrate capacitors two types of Pb centers were observed; in oxides prepared in three different ways only one of these centers, the Pb0 defect, is generated in large numbers by ionizing radiation.

Method for lifting-off epitaxial films

Abstract: A method for removing epitaxial films from a single crystal substrate upon which it is grown comprising (a) providing a thin release layer (≦1000A) between the film to be grown and the substrate; (b) growing the epitaxial film(s); (c) applying a polymeric support layer which is under tension over the film; and (d) selectively etching the release layer, the tension in the support layer causing the edges of the film to curve upwardly as the release layer is etched away.

An investigation of hardness and adhesion of sputter-deposited aluminum on silicon by utilizing a continuous indentation test

Abstract: The hardness of aluminum films on silicon are measured as functions of depth of the indenter. The films have thicknesses of 0.25,0.5, and 1.0μm. The adhesion between one film and the substrate has been reduced through the prior deposition of a 10 nm layer of carbon. In each case the hardness is found to increase as the indenter approaches the film-substrate interface, but the rate of increase is greater for a film with good adhesion than for one with poor adhesion. It is suggested that this increase results from the constraint on deformation of the film by the substrate. A physical model is proposed whereby the yield stress of the film, σo, and an average effective shear strength τ of the indenter-film and film-substrate interfaces, may be determined from the data.

Thermal conductivity of heavily doped low‐pressure chemical vapor deposited polycrystalline silicon films

Abstract: The lateral thermal conductivity of heavily doped low‐pressure chemical vapor deposited polycrystalline silicon films is measured using polycrystalline silicon microbridges elevated three micrometers above a silicon substrate. The bridges, lightly doped in their central regions and heavily doped elsewhere, are fabricated using a sacrificial silicon‐dioxide layer and phosphorus out‐diffusion from doped oxide. Voltage‐current characteristics measured on the bridges both under high vacuum and in silicone oil are used to calculate lateral thermal conductivity in the polycrystalline silicon. The experimental values for the thermal conductivity of heavily doped polycrystalline silicon range from 0.29 to 0.34 W cm−1 K−1 and average 0.32 W cm−1 K−1. These values agree closely with results obtained by a second method that employs uniformly doped polycrystalline silicon bridges. In the second method, high‐vacuum, voltage‐current characteristics are measured and the indicated thermal conductivities for two samples a...

Process for making thin film solar cell

Abstract: A method of making group I-III-VI compound semiconductors such as copper indium diselenide for use in thin film heterojunction photovoltaic devices. A composite film of copper, indium, and possibly other group IIIA elements, is deposited upon a substrate. A separate film of selenium is deposited on the composite film. The substrate is then heated in a chamber in the presence of a gas containing hydrogen to form the compound semiconductor material.

Three-Dimensional Quantum Well Effects in Ultrafine Silicon Particles

Abstract: The mostly crystallized Si:H having a wide optical band gap and showing a visible photoluminescence at room temperature, has been fabricated by means of a planar magnetron rf sputtering technique in hydrogen gas onto a low temperature (about 100 K) substrate. The materials consist of very small crystalline silicon particles (average diameters: 2–5 nm) surrounded by =SiH2 groups. The observed macroscopic physical properties are explained by the three-dimensional quantum size effects in the ultrafine silicon particles.

Direct measurement of surface forces between sapphire crystals in aqueous solutions

Abstract: Measurements are presented of the electrical double layer and van der Waals forces between the (0001) surfaces of two single-crystal sapphire platelets immersed in an aqueous solution of NaCl at pH values from 6.7 to 11. The results fit the standard Deryaguin-Landau-Verwey-Overbeek (DLVO) theory, with a Hamaker constant of 6.7 × 10−20 J. These are the first measurements made using the Israelachvili surface forces apparatus without mica as a substrate material, and they demonstrate the possibility of using this technique to explore the surface chemistry of a wider range of materials.

Semiconductor substrate heater and reactor process and apparatus

Abstract: A reaction system and process for uniformly heating semiconductor substrates and a device for supporting the same and direct conductive heating of IC wafers within a reactor are described. The substrate is held in direct contact with the heating source positioned within the reactor. The heat source is a thermal delivery module made of material such as solid silicon carbide, or high temperature material containing resistive heating elements. The heat is uniformly transferred to the walls of the module by a molten metal having a low melting point and high boiling point such as essentially indium or bismuth or a eutectic or indium and bismuth.

Dual ion beam ballistic alloying process

Abstract: The invention discloses a dual ion beam ballistic alloying process for forming a film such as diamond onto a substrate, which comprises the steps of: (a) cleaning the surface of the substrate with a first energy beam of inert atoms; (b) depositing a layer of a desired non-hydrocarbon substance on the substrate with a low energy, sputtered atomic beam; (c) simultaneously exposing the substrate to said first energy beam of inert atoms with a high energy to grow a ballistically alloyed layer having a thickness of about 10-2000 Å; and (d) reducing the energy level of the first, high energy beam to cause the growth of the layer of said substance on said substrate to a final desired thickness.

Method and product for fabricating a resonant-bridge microaccelerometer

Abstract: A resonant bridge microaccelerometer is formed using patterned Silicon-on-Insulator (SOI) material. A buried layer is formed in the silicon substrate using preferably oxygen ion implanting techniques. A predetermined proof mass is subsequently formed by selective deposition of an appropriate material on an epitaxially grown layer of silicon generally over the buried layer. The buried layer is subsequently removed by a hydrofluoric acid etch, thereby forming a gap generally everywhere therebetween the proof mass and the supporting silicon substrate, and delineating the resonant microbridges within the microaccelerometer.

Method of making high speed semiconductor device having a silicon-on-insulator structure

Abstract: A CMOS silicon-on-insulation structure is fabricated by first forming an insulating SiO 2 layer on a silicon substrate having a (110) plane. Openings are then formed in the SiO 2 layer to expose a part of the substrate, and a polycrystalline or an amorphous silicon layer is deposited on the SiO 2 layer and in the openings. The deposited silicon layer is divided into islands so that a first island includes one of the openings and a second island does not include any openings. A laser beam is then irradiated onto the islands so as to melt the islands, and when the laser light irradiation is discontinued, the melted islands recrystallize so that the first island forms a (110) plane and the second island forms a (100) plane. A p-channel MOSFET is fabricated on the first island, and an n-channel MOSFET is fabricated on the second island. The thus paired CMOS operates at high speeds, because the p-channel MOSFET using positive holes as the carrier is fast in a (110) crystal, and the n-channel MOSFET using electrons as the carrier is fast in a (100) crystal.

Process for growing III-V compound semiconductors on sapphire using a buffer layer

Abstract: In organometallic vapor phase hetero-epitaxial processes for growing Al x Ga 1-x N films on a sapphire substrate, the substrate is subjected to a preheat treatment of brief duration, such as less than 2 minutes, at relatively low temperatures in an atmosphere comprising Al-containing organometallic compound, NH 3 and H 2 gases, prior to the hetero epitaxial growth of Al x Ga 1-x N films. Thus, single crystalline Al x Ga 1-x N layers of high uniformity and high quality having smooth, flat surfaces are provided. Multi-layers grown according to the process of the invention are free from cracks and have preferable UV or blue light emission properties.

Passivation coating for flexible substrate mirrors

Abstract: A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention

Method of plasma enhanced silicon oxide deposition

Abstract: A method of depositing a hard silicon oxide based film is provided by controllably flowing a gas stream including an organosilicon compound into a plasma and depositing a silicon oxide onto a substrate while maintaining a pressure of less than about 100 microns during the depositing. The organosilicon compound is preferably combined with oxygen and helium and at least a portion of the plasma is preferably magnetically confined adjacent to a substrate during the depositing, most preferably by an unbalanced magnetron. These silicon oxide based films may be reproducibly deposited on small or large substrates, such as glass, plastic, mineral or metal, with preselected properties.

A superconducting thin film and a method for preparing the same

Abstract: An outer surface of a superconducting thin film of compound oxide such as YBa2Cu3O7-.delta. is protected with a protective layer which is composed of any one of (i) oxide of metal such as SiO2 and TiO2, (ii) carbide such as SiC, (iii) nitride such as BN or (iv) the same material as the substrate such as SrTiO3.