Showing papers on "Substrate (electronics) published in 1990"

Oxidation of metastable single‐phase polycrystalline Ti0.5Al0.5N films: Kinetics and mechanisms

Abstract: Metastable single‐phase, NaCl‐structure, polycrystalline Ti0.5Al0.5N alloy films have been shown to exhibit much better high‐temperature (750–900 °C) oxidation resistance than polycrystalline TiN films grown under similar conditions. The Ti0.5Al0.5N alloys, ≂3 μm thick, were deposited at temperatures between 400 and 500 °C on stainless‐steel substrates by dc magnetron sputter deposition in mixed Ar+N2 discharges with an applied negative substrate bias Vs of either 0 or 150 V. Oxidation in pure O2 initially occurred at a rate that varied parabolically with time. The oxide overlayers consisted of two partially crystalline sublayers, the upper one Al‐rich and the lower one Ti‐rich, with no measurable N concentrations in either. Inert‐marker transport experiments showed that oxidation proceeded by the simultaneous outward diffusion of Al to the oxide/vapor interface and inward diffusion of O to the oxide/nitride interface. The oxidation rate constant K increased with oxidation temperature Tox at a rate much h...

Van der Waals bonding of GaAs epitaxial liftoff films onto arbitrary substrates

Abstract: Epitaxial liftoff is an alternative to lattice‐mismatched heteroepitaxial growth. Multilayer AlxGa1−xAs epitaxial films are separated from their growth substrates by undercutting an AlAs release layer in HF acid (selectivity ≳108 for x≤0.4). The resulting AlxGa1−xAs films tend to bond by natural intermolecular surface forces to any smooth substrate (Van der Waals bonding). We have demonstrated GaAs thin‐film bonding by surface tension forces onto Si, glass, sapphire, LiNbO3, InP, and diamond substrates, as well as self‐bonding onto GaAs substrates. In transmission electron microscopy the substrate and thin‐film atomic lattices can be simultaneously imaged, showing only a thin (20–100 A) amorphous layer in between.

Formation of arsenic precipitates in GaAs buffer layers grown by molecular beam epitaxy at low substrate temperatures

Abstract: We have grown film structures by molecular beam epitaxy which include GaAs buffer layers grown at low substrate temperatures (250 °C). The film structures have been examined using transmission electron microscopy. The layers grown at normal temperatures (600 °C) were free of defects or clusters. In contrast, the layer which was grown at low substrate temperatures contained precipitates which have been identified as hexagonal arsenic. The density of the arsenic precipitates is found to be very sensitive to the substrate temperature during growth.

Low resistivity indium–tin oxide transparent conductive films. II. Effect of sputtering voltage on electrical property of films

Abstract: A low resistivity and high transmittance Sn doped In2O3 (ITO) film was formed on a glass substrate by dc magnetron sputtering and lower sputtering voltage gave a lower resistivity film. At a sputtering voltage of −250 V, the resistivity obtained was 5.0×10−4Ω cm for room temperature substrate, 2.0×10−4Ω cm for 160 °C substrate, 1.9×10−4Ω cm for 200 °C substrate, and 1.2×10−4Ω cm for 460 °C substrate. At a sputtering voltage of −80 V, the resistivity was 1.3×10−4Ω cm for 200 °C substrate. A measurement of Hall effect shows that the decreased resistivity by lower sputtering voltage is not caused by the Hall mobility but by an increased carrier concentration.

Silicon dioxide deposition method using a magnetic field and both sputter deposition and plasma-enhanced cvd

Abstract: In plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide on a substrate, voids and discontinuities are reduced by first depositing silicon dioxide in a sputter each chamber (22) in which a magnetic field is produced within the rf plasma for depositing the silicon dioxide. Simultaneous sputter etch and deposition occurs which inhibits net deposition at the corners of metal conductors over which the silicon dioxide is deposited. The substrate is then removed and transferred through a load lock (27) to a conventional PECVD deposition chamber (23).

Method and apparatus for measuring thickness of thin films

Abstract: An apparatus (20) for measuring the thickness of a thin film layer (32) on substrate (28) includes a probe beam of radiation (24) focused substantially normal to the surface of the sample using a high numerical aperture lens (30). The high numerical aperture lens (30) provides a large spread of angles of incidence of the rays within the incident focused beam. A detector (50) measures the intensity across the reflected probe beam as a function of the angle of incidence with respect to the surface of the substrate (28) of various rays within the focused incident probe beam. A processor (52) functions to derive the thickness of the thin film layer based on these angular dependent intensity measurements. This result is achieved by using the angular dependent intensity measurements to solve the layer thickness using variations of the Fresnel equations. The invention is particularly suitable for measuring thin films, such as oxide layers, on silicon semiconductor samples.

Lifetime of an adsorbate-substrate vibration: H on Si(111).

Abstract: We present the measurement of the lifetime of the adsorbate-substrate vibration for hydrogen on silicon (111) by Sum-Frequency Generation. The lifetime is 0.8 ns.

Early formation of chemical vapor deposition diamond films

Abstract: Nanometer‐size diamond particles formed on a silicon substrate by the hot‐filament chemical vapor deposition method were examined by a high‐resolution electron microscope. The particles developed well‐faceted cuboctahedral habits. Examination of their morphologies and microstructures provides a wealth of information on their crystal growth mechanism. The effect of the pretreatment of the substrate by diamond powder, which has been known to enhance thin‐film growth, was found to be due to seeding by ‘‘diamond dust’’ on the substrate surface.

The application of fine-grained, tensile polysilicon to mechanicaly resonant transducers

Abstract: Resonant force sensors are devices which convert axially applied forces to changes in resonant frequency. These structures are fundamentally wires or beams or more complicated structures which are in a vacuum envelope. They become interesting and useful if they can be miniaturized, can be fabricated from a single material in a cost effective manner and can be excited and read via simple techniques. The devices which are reported here satisfy most of the above criteria. The construction material involves a silicon substrate, tensile strain polysilicon films and strain-compensated silicon nitride deposits. Clamped-clamped beams of polysilicon, typically 400,μm long, 40,μm wide and 2μm thick are fabricated with an isoplanar process over an oxide filled tub. Low-pressure chemical-vapor-deposited (LPCVD) nitride is used as a second sacrificial layer which also serves to support a second polysilicon layer which is part of the vacuum envelope. Internal surface adhesion problems are avoided by freeze-sublimation procedures which remove surface tension-induced beam deflections. Passivation and sealing is accomplished via LPCVD nitride and reactive sealing. Excitation and sensing is accomplished via ion implanted resistors. Experimental results always produce quality factors, Q , above 35 000. Resonant frequencies to 750 kHz have been achieved. It is estimated that these devices can measure axially applied forces below 0.1 dyne with standard electronic interfaces.

A transmission electron microscopy study of low‐temperature reaction at the Co‐Si interface

Abstract: An efficient preparation method, which provides wedge‐shaped cross‐section transmission electron microscopy samples, has been developed. It was then used to investigate the structure of as‐deposited cobalt multilayers on silicon substrates by rf plasma sputtering. It was found that an extended reaction takes place between Co and Si probably during the deposition. The cobalt atoms react with the silicon substrate to form an amorphous silicide layer. When the deposited layer is <3 nm thick, it entirely reacts with the substrate and can form an amorphous silicide as large as 5 nm. Above 4–5 nm thickness, growth of Co crystallites comes in competition with the formation of the amorphous silicide and limits it to 2 nm. The composition of this amorphous silicide is estimated to be Co2Si. In Co/C multilayers, the reactivity between the two materials is negligible, and the coalescence thickness of cobalt is 2–3 nm. At 2 nm, the cobalt layers are noncontinuous and very rough, whereas at 3 nm the critical thickness...

Formation of cubic boron nitride films by arc‐like plasma‐enhanced ion plating method

Abstract: Thin cubic boron nitride (cBN) films were synthesized at 350 °C on various substrates such as silicon, stainless steel, TiN‐coated WC–Co and WC–Co by means of an arc‐like plasma‐enhanced ion plating process. In this process, polycrystalline cBN films were obtained at deposition rates of 0.004 to 0.03 μm/min. The infrared spectra showed strong absorption at 1050 cm−1, indicating cubic structure of the deposited film. The electron diffraction patterns also showed the cubic structure, with a lattice parameter of 3.63 A. It is inferred that ion bombardment during film growth plays a important role in the formation of cBN films. The cBN films deposited in this process had a high compressive stress of 4×1010dyn/cm2, which is significantly greater than the value of hard amorphous boron nitride (iBN) films, 1.6×1010dyn/cm2. The internal stress of cBN films was greatly reduced if iBN was used as a buffer layer between cBN and substrate.

Substrate for growing gallium nitride compound-semiconductor device and light emitting diode

Abstract: A substrate for producing a gallium nitride compound-semiconductor (Al.su Ga1-x N; X=0 inclusive) device in vapor phase on a sapphire substrate using gaseous organometallic compound, and a also blue light emitting diode produced by using the substrate. The buffer layer comprising aluminium nitride (AlN) and having a crystal structure where microcrystal or polycrystal is mixed in amorphous state, is formed on the sapphire substrate. The buffer layer is formed at a growth temperature of 380° to 800° C. to have a thickness of 100 to 500 Å. Further, on the buffer layer is formed the layer of gallium nitride compound-semiconductor (Alx Ga1-x N; X=0 inclusive). The layer of gallium nitride compound-semiconductor (Alx Ga1-x N; X=0 inclusive) comprising at least two layers having different conductive types and being sequentially layered on the buffer layer, functions as a light emitting layer. The existence of the buffer layer having the aforementioned structure greatly contributes on the improved high-quality single crystal of the gallium nitride compound-semiconductor. On the other hand, the blue light emitting property is also improved due to the increase of the quality.

The synthesis of high-quality diamond in combustion flames

Abstract: High‐quality diamond with good crystallinity has been successfully synthesized on a substrate using an oxy‐acetylene combustion flame in the atmosphere. The crystal grains under some conditions have good optical transparency. The deposition rate of transparent diamond depended strongly on substrate temperatures and the O2/C2H2 ratio and averaged ∼30 μm/h. The substrate temperature for the growth of optically transparent crystals was 500–750 °C, which is relatively low compared with other chemical vapor deposition methods. The optical transparency is attributed to the low defect densities in the crystals, as determined by transmission electron microscope, which results from the low substrate temperatures and moderate growth rates. Raman spectroscopy and x‐ray diffraction data on the synthesized crystals were comparable with that of natural diamond. The synthesis conditions and corresponding diamond quality as well as emission spectrum analysis of the combustion flame during diamond synthesis are described.

Light emitting diode device and method for producing same

Abstract: A light emitting diode device comprises an n type silicon carbide substrate having first and second major surfaces opposite to each other at least inclined at a predetermined angle not less than 3° from a {0001} plane, an n type silicon carbide layer grown on the first major surface, a p type silicon carbide layer grown on the n type silicon carbide layer, a p type ohmic electrode formed on a partial area of the p type silicon carbide layer, and an n type ohmic electrode formed on a partial area of the second major surface. The diode element has a substantially trapezoidal form in a cross section orthogonal to the first major surface. The diode element has the side of the p type silicon carbide layer broader than the side of the second major surface and is supported at the side of the type silicon carbide layer fixed to a supporting stem.

The nucleation and morphology of diamond crystals and films synthesized by the combustion flame technique

Abstract: The nucleation and morphology of diamond crystals and films synthesized by the use of a combustion flame have been investigated By operating an oxy-acetylene torch in a fuel-rich mode, diamond crystals and films have been deposited on mechanically abraded molybdenum, on in situ created molybdenum carbide, and on thin diamond-like carbon (DLC) layers synthesized on molybdenum Scanning electron microscopy, Auger and Raman spectroscopy have been used to characterize the films and crystals Diamond is found to be uniformly deposited in the region of the substrate that intersects the inner, acetylene-rich region of the flame The nucleation density, the growth rate, and the morphology of the diamond crystals and films are found to be strongly influenced by the surface condition of the substrate On mechanically abraded molybdenum, abraded with 600 mesh silicon carbide, and on molybdenum carbide, well-formed cubo-octahedrons of diamond, up to 45 µm in diameter, are formed for deposition times of 90 min Film formation is seldom observed under these conditions To enhance nucleation, thin layers of DLC were formed on molybdenum substrates by reducing the O2/C2H2 ratio in the gas mix to ~ 075 for short periods of time under 30 s This was followed by increasing the O2/C2H2 ratio to conditions that produce diamond (an O2/C2H2 ratio of ~ 09) Under these conditions the nucleation density of diamond was increased by an order of magnitude and the growth rates by about 60%, as compared to diamond deposited on abraded molybdenum and molybdenum carbide In addition, the morphology of the diamond crystals and films was substantially affected with indications of dendritic growth The DLC layer is effective in promoting diamond nucleation due to the high surface defect density and the high hydrogen concentration of these films The combination of surface defects, in the form of dangling bonds, and the evolution of hydrogen from the DLC layer during the diamond deposition process, which is characterized by higher temperatures, result in a high concentration of active surface sites for diamond nucleation The nucleation density, the distribution on the substrate, and the morphology of diamond crystals and films are not driven by the transport of reactive specie in the flame to the substrate, but rather by nucleation processes, temperature distribution across the surface, and attendant surface phenomena

Epitaxy of Y-Ba-Cu-O thin films grown on single-crystal MgO

Abstract: The epitaxy of a thin‐film Y‐Ba‐Cu‐O (YBCO) superconductor deposited on a single‐crystal [001] MgO substrate was examined by transmission electron microscopy. The large lattice mismatch (8–10%) in the basal plane of YBCO and MgO is accommodated mainly by the formation of a polycrystalline, mosaic structure. The grain boundaries correspond to unique crystallographic interfaces, determined by the crystal symmetry of the substrate and the thin film.

Ferroelectric thin film material, method of deposition, and devices using same

Abstract: A ferroelectric device that comprises a polarizing thin film of BaMF4 deposited on a substrate. Ba is barium, M is one of the metals of the group consisting of iron (FE), manganese (Mn), cobolt (Co), nickel (Ni), magnesium (Mg), and zinc (Zn). The substrate is silicon, sapphire, or gallium arsenide. A non-volatile NDRO and DRO memory cell and methods for depositing the thin film. A method of depositing bismuth titanate on a substrate are described.

A substrate for thin-film gas sensors in microelectronic technology

Abstract: A laboratory model of a substrate for a gas sensor based on semiconducting tin oxide and produced in microelectronic technology is described. The paper discusses not only the problems of miniaturization of these gas sensors but also important production processes, with the exception of the gas-sensitive layer. The whole chip has a size of 2.7 by 2.7 mm and an active area of only 0.45 by 0.45 mm. The power consumption at the operating temperature of 300°C is below 75 mW. The active area is supported by a thin (10 μm) membrane of silicon oxide and nitride; an outer silicon frame provides mechanical stability. The heater is made from a NiFe alloy. The tested samples are stable and prove that a miniaturized low-cost gas sensor is feasible.

Method and apparatus for semiconductor circuit chip cooling

Abstract: In a semiconductor device, a thin, synthetic diamond film (i.e. a man made film) enhances the transfer of heat from a semiconductor circuit chip to a cooling medium. The heat generating semiconductor circuit chip is located in efficient thermal transfer engagement with one surface of a synthetically deposited diamond film. The opposite surface of the diamond film forms the bottom wall of a cavity that contains a cooling medium. In one embodiment of the invention, the cavity is formed by depositing the diamond film on the surface of a silicon substrate, and then etching the silicon substrate to form an open-top cavity having side walls that comprise the silicon substrate, and having a bottom wall that comprises the diamond film. In a second embodiment of the invention, the open-top cavity is formed by an apertured silicon preform that is bonded to the diamond film. A capping member closes the top of the cavity. A cooling medium is placed within the cavity. A fluid cooling medium may be circulated through the cavity by the use of an inlet and an outlet that are located in the capping member.

Diffusion barrier properties of Ti/TiN investigated by transmission electron microscopy

Abstract: Detailed analytical transmission electron microscopy investigations were performed on a well‐known diffusion barrier system for very‐large‐scale integration metallization. It will be demonstrated that interfacial reactions are of great importance for the barrier mechanism. Both Ti and TiN act as diffusion barrier for the semiconductor and the metallization, respectively. For an aluminum‐based metallization, TiN has a ‘‘spongelike’’ function due to its ability to absorb several amounts of aluminum at elevated temperatures and therefore inhibits diffusion towards the substrate. Ti acts for silicon as a compound forming barrier according to Nicolet’s classification [in Tungsten and Other Refractory Metals for Very Large Scale Integration Applications II, edited by E. K. Broadbent (Materials Research Society, Pittsburgh, 1987); pp. 19–26].

Y1Ba2Cu3O7−x thin films grown on sapphire with epitaxial MgO buffer layers

Abstract: We have developed a process for growing as‐deposited Y1Ba2Cu3O7−x (YBCO) thin films on R‐plane sapphire substrates with an intermediate layer of epitaxial MgO. The orientation of the layers has YBCO (001) parallel to MgO (100) which is parallel to the substrate normal. These films are superconducting by 88.5 K and exhibit Jc=1×106 A/cm2 at 77 K and 2.5×107 A/cm2 at 4.2 K. The MgO layers may be grown at temperatures as low as 370 °C and are very stable in air. Little or no diffusion occurs between the substrate and the two layers as measured by Auger profiling.

Process for forming refractory metal silicide layers of different thicknesses in an integrated circuit

Abstract: A method for forming reactive metal silicide layers at two spaced locations on a silicon substrate, which layers can be of different thicknesses and/or of different reactive metals is provided. A sililcon substrate has a silicon dioxide layer formed thereon followed by the formation of a polysilicon layer on the silicon dioxide layer, followed by forming a layer of refractory metal, e.g. titanium on the polysilicon. A non-reflecting material, e.g. titanium nitride is formed on the refractory metal. Conventional photoresist techniques are used to pattern the titanium nitride, the titanium and polysilicon, and the titanium is reacted with the contacted polysilicon to form a titanium silicide. The portion of silicon dioxide overlying the silicon substrate is then removed and the exposed substrate is ion implanted to form source/drain regions. A second layer of refractory metal, either titanium or some other refractory metal, is deposited over the source/drain region, and either over the titanium nitride, or over the first formed silicide by first removing the titanium nitride. The second layer of refractory metal is reacted with the substrate at the source/drain region to form a refractory metal silicide, after which the unreacted refractory metal is removed.

The structure and properties of phthalocyanine films grown by the molecular beam epitaxy technique. I. Preparation and characterization

Abstract: Ultrathin films of the cofacially stacked F‐bridged Al‐phthalocyanine polymer, (AlPcF)n , have been grown using the highly controlled technique of molecular beam epitaxy. A parallel orientation of the polymer backbone to the substrate surface occurs in films on silicon and quartz, but epitaxy is not apparent. On single‐crystal alkali halide substrates, the backbone is perpendicular to the substrate surface, and an epitaxial relationship exists that is influenced by the interaction between the substrate and phthalocyanine molecule. The transmission electron microscopy studies indicate that the most highly ordered films are produced on KBr(100) and have good continuity and unidirectional crystallite orientation.

Process for creating an etch mask suitable for deep plasma etches employing self-aligned silicidation of a metal layer masked with a silicon dioxide template

Abstract: A process, compatible with reduced-pitch masking technology, for creating a metal etch mask that will not erode in a halogenated-plasma etch environment. The process begins by creating an isolation layer (preferably of silicon dioxide) on top of the layer to be etched (typically a silicon substrate). A thin layer of a metal selected from a group consisting of cobalt, nickel, palladium, iron, and copper is then deposited on top of the isolation layer. A hard-material mask (preferably of silicon dioxide) is then created on top of the metal layer as though it were to be the final etch mask. A layer of polysilicon is then blanket deposited on the surface of the in-process wafer. The polysilicon layer must be sufficiently thick to entirely convert exposed regions of the underlying metal layer to silicide during a subsequent elevated temperature step. Only metal in regions not covered by the hard-material mask is converted to silicide. Unreacted polysilicon is then removed with a wet polysilicon etch, followed by the removal of the hard-material mask with a wet etch selective for silicon dioxide over the existent metal silicide, followed by removal of the metal silicide with a wet etch selective for silicide over silicon dioxide to avoid undercutting the oxide isolation layer beneath the metal layer remnants. The metal layer remnants constitute a metal mask which precisely duplicates the pattern of the hard-material mask.