Showing papers on "Substrate (electronics) published in 1975"

Vibrating reed internal friction apparatus for films and foils

Abstract: An apparatus is described which permits for the first time the resolution of anelastic relaxation effects in evaporated metallic thin films and ion-implanted surface layers of silicon. The composite samples consist of the film or layer of interest on a carrier substrate having the form of a thin cantilevered reed. Low external losses and an exceptionally good span of operating frequencies are obtained by integrally bonding the substrate to a supporting pedestal and by using electrostatic drive and detection for the transverse modes of vibration. The internal friction can be measured with relatively simply instrumentation, at pressures below 10-5 (1.33 × 10-3 Pa) and over the temperature range -190°C to 550°C. The apparatus has considerable versatility for work in a number of areas, including the investigation of metallic foils prepared by splat-cooling.

GaAs planar technology by molecular beam epitaxy (MBE)

Abstract: GaAs integrated circuits require planar growth of isolated devices on an insulating substrate. A new approach to achieve planar growth has been demonstrated by molecular beam epitaxy (MBE). In the MBE process polycrystalline and monocrystalline GaAs are selectively grown producing a pattern which consists of areas of device−quality single−crystal material isolated by semi−insulating polycrystalline material. The active device positions were defined by windows in SiO2 layers which covered the Cr−doped semi−insulating GaAs substrate.

Photoelectrolysis of water by solar radiation

Abstract: Photoelectrolysis of water by solar radiation to produce hydrogen is achieved using semiconducting thin film electrodes. The cell comprises (a) an anodic electrode comprising at least one thin n-type semiconducting layer which has a bandgap ranging from about 0.5 to 4.0 eV and which is disposed on a supporting conductive substrate; (b) a cathodic counter-electrode comprising at least one thin p-type semiconducting layer which has a bandgap ranging from about 0.5 to 4.0 eV and which is supported on a supporting conductive substrate, the p-type layer adjacent the n-type layer being such that incident solar radiation impinges substantially simultaneously on both the n- and p-type electrodes; (c) means for retaining an electrolyte in contact with the exposed surfaces of the n- and p-type semiconducting electrodes; (d) external bias means between the electrode and the counter-electrode for biasing the cell with from 0 to about 1 V; and (e) means for collecting hydrogen and any oxidation products produced.

Ionized cluster beam deposition

Abstract: We describe a form of deposition in which material is vaporized in a crucible and the vapor then ejected through a fine nozzle at the focus of an electron beam in a high vacuum. The vapor, on emerging from the nozzle, is partially condensed into clusters that are ionized by electron bombardment and then accelerated onto the substrate. The deposited films show good adhesion and large crystallite size. Examples include the deposition of Cu onto glass, Si onto Si, and ZnS onto NaCl.

High‐contrast optical storage in VO2 films

Abstract: When vanadium dioxide, VO2, undergoes its semiconductor‐to‐metal transition at 68 °C its reflectivity decreases by about a factor of 2 throughout the visible range. By using a thin VO2 film on a vanadium substrate we were able to achieve a much higher contrast between the reflectivities of the two VO2 phases. The VO2 film was grown as an antireflecting coating for one of the phases and thus the film thickness was used to determine the light wavelength at which the contrast will reach its maximum value. For example, with an 800‐A‐thick film a contrast of 16 (rather than 2) was obtained at a light wavelength of 7000 A. In utilizing the present system for optical storage the high contrast obtained yielded an order of magnitude higher read‐out efficiency than the efficiency reported for VO2 films sputtered on glass. To demonstrate information recording in the present system, both a pulsed laser and a cw laser were used for spatially selective’’writing’’ in the film. It was found that the present system has hi...

Glass-sealed GaAs-AlGaAs transmission photocathode

Abstract: A GaAs/GaAlAs/GaAs/GaAlAs heterostructure has been prepared on a GaAs susbtrate, bonded to 7056 Corning glass, and the substrate and first AlGaAs removed chemically, utilizing the differential etching characteristics of GaAs and AlGaAs in NH4OH−H2O2 and HF solutions. The resulting structure of GaAs/AlGaAs/glass has excellent layer morphology, uniform thickness, and good transmission photocathode performance.

Cross‐sectional electron microscopy of silicon on sapphire

Abstract: Cross sections of (100)Si/(012)sapphire were examined by transmission electron microscopy. The foil plane was (011)Si and contained the [100]Si growth direction. The number of faults (i.e., microtwins and isolated stacking faults) per cm measured in the [022]Si direction, FD, decreases with increasing distance d from the silicon/substrate growth interface according to the equations FD= (3.1×107)/d0.63 (440⩽d⩽2400 A), and FD= (1.3×1011)/d1.7 (2400?d?4.3×104 A). Misfit dislocations were not observed, and no evidence for the presence of an Al‐bearing phase was seen in the proximity of the interface.

A study of electron traps in vapour-phase epitaxial GaAs

Abstract: The occurence and physical properties of electron traps in device-quality VPEn-GaAs are studied using transient capacitance and DLTS (deep level transient spectroscopy). Four traps labeled A, B, C, and F are seen. Trap A is identified to be the same as the often reported one, commonly attributed to oxygen in substrate material; this trap is also dominant in the VPE layers. The other traps are (to our knowledge) reported here for the first time. No correlation appears to exist between the concentrations of the various traps. The emission rate vs. temperature dependence, a characteristic physical property, is obtained for each of these traps.

Studies of the optimum conditions for growth of rf‐sputtered ZnO films

Abstract: A technique for deposition of highly oriented rf‐sputtered zinc oxide films on (111) gold, (111) silicon, (0001) sapphire, and fused quartz is described. The major parameters that were controlled during deposition are substrate temperature, input rf power, deposition pressure, and the deposition atmosphere. It was found that the best results were obtained with an rf power of 160 W, a deposition at 4 μ pressure in an 80 : 20 argon : oxygen mixture, and with the substrate temperature varied between 225 and 400 °C depending on the substrate. The deposition rate varied slightly around 120 A/min, with very small variation for different substrates. The quality of the ZnO films was determined by reflection electron diffraction and scanning electron microscopy. Acoustic‐bulk‐wave and acoustic‐surface‐wave delay lines were made by this technique. In all cases, high coupling coefficients were obtained.

Liquid‐phase‐epitaxial growth of single‐crystal LiNbO3 thin film

Abstract: The phase equilibrium of the LiVO3‐LiNbO3 pseudobinary system has been investigated, and a LiNbO3 single‐crystal thin film has been grown epitaxially onto the substrate by dipping a c‐plate LiTaO3 substrate into a LiVO3 flux solution. An x‐ray rocking curve indicated that the film had a high single crystallinity with good epitaxy. The composition ratio Li/Nb of the film was estimated to be close to the stoichiometric value Li/Nb≈1.0.

The Preparation and Properties of Aluminum Nitride Films

Abstract: Aluminum nitride films have been deposited on silicon substrates at 800-1200 C by the pyrolysis of an aluminum trichloride-ammonia complex, AlCl3.3NH3, in a gas flow system. The deposit was transparent, tightly adherent to the substrate, and was confirmed to be aluminum nitride by X-ray and electron diffraction techniques. The deposited aluminum nitride films were found to be polycrystalline with the crystallite size increasing with increasing temperature of deposition. Other properties of aluminum nitride films relevant to device applications, including density, refractive index, dissolution rate, dielectric constant, and masking ability, have been determined. These properties indicate that aluminum nitride films have potential as a dielectric in electronic devices.

Growth, environmental, and electrical properties of ultrathin metal films

Abstract: The conduction mechanisms of ultrathin (10−100 A) metal films are investigated. The electrical conductivity and activation energy of discontinuous Au films grown in UHV are correlated with island size and separation and average film thickness. The relationship between film conductivity and deposition rate and substrate temperature is presented. Film temperature data indicate the validity of the proposed model. Some anomalous conductivity effects are reported for films deposited below the UHV range. The results are explained in terms of substrate and film surface contamination. Data are presented indicating the sensitivity of the conductivity of discontinuous films to ambient gas concentration. Reversible and irreversible situations are discussed.

Bonds between metal and a non-metallic substrate

Abstract: A direct bond between metallic members and non-metallic members is achieved at elevated temperatures in a controlled reactive atmosphere without resorting to the use of electroless plating, vacuum deposition or intermediate metals. A metal member such as copper, for example, is placed in contact with a non-metallic substrate, such as alumina, the metal member and the substrate are heated to a temperature slightly below the melting of the metal, e.g., between approximately 1065° and 1080° C. for copper, with the heating being performed in a reactive atmosphere, such as an oxidizing atmosphere, for a sufficient time to create a copper-copper oxide eutectic melt which, upon cooling, bonds the copper to the substrate. Various metals, non-metals and reactive gases are described for direct bonding.

Method of manufacture of an epitaxial semiconductor layer on an insulating substrate

Abstract: A thin epitaxial layer of silicon is disposed on a supporting silicon substrate and a silicon oxide layer or other suitable layer is formed on the epitaxial layer. The substrate, epitaxial layer and oxide layer sandwich is bonded by the simultaneous application of heat and voltaic pressure to another oxidized substrate such that the epitaxial layer is sandwiched between the two substrates with the oxide layer at the sandwich interface. Alternatively, the substrates may be joined by bonding without the use of voltaic pressure by placing the substrates (parent and supporting) at approximately 900° C. The substrates with the epitaxial layer is processed to remove a substantial portion of the silicon substrate with the final portion being removed by etching. When the final portion of the silicon substrate is removed by etching, exposing the epitaxial silicon layer, the etching rate changes dramatically and this is reflected in the byproduct concentration in the etchant solution. The etching process is immediately terminated when the epitaxial layer is fully exposed. After further finishing steps, the resulting product of this method is an epitaxial monocrystalline silicon layer of high crystalline perfection, separated by a silicon oxide layer from a supporting silicon substrate.

Device design considerations for ion implanted n-channel MOSFETs

Abstract: Device design considerations are presented for ion implanted, n-channel, polysilicon gate, enhancement-mode MOSFETs for dynamic switching applications. A shallow channel implant is used to raise the magnitude of the gate threshold voltage while also maintaining a low substrate sensitivity (i.e., without substantially increasing the dependence of the threshold voltage on the source-to-substrate "backgate" bias). Design trade-offs between channel implantation energy and dose and substrate bias were examined using both computer analyses and experimental devices. The design objective was to identify the combination of these three parameter values that gives both a low substrate sensitivitya nd a steep subthreshold conduction characteristic under the conditions of a gate threshold voltage of 1 V and a substrate bias range of 0 to -1 V. One-dimensional and two-dimensional computer analyses were performed to predict the effect of the device parameters on the electrical characteristics. MOSFETs were then fabricated to investigate the extremes of the design parameter range, and the experimental and predicted device characteristics were compared. An enclosed device structure proved particularly useful in evaluating the subthreshold characteristic at very low values of drain current.

X-ray study of AlxGa1-xAs epitaxial layers

Abstract: Lattice deformation and strain are studied in double-hetero-structure epitaxial layers of AlxGa1−xAs. The lattices of all three epitaxial layers are found to be tetragonally deformed under the stress due to lattice mismatch amounting to 108 dyn/cm2 at room temperature. The strains in the epitaxial layers are measured up to 800°C. The influence of the crystalline quality of the substrates on that of epitaxial layers is studied. It is observed that the density of dark spot defects in the epitaxial layers is always greater than the dislocation density in the substrates. Es werden Gittterverzerrungen und Spannungen in epitaktischen Doppelheterostrukturschichten von AlxGa1−xAs untersucht. Es wird gefunden, das die Gitter aller drei epitaktischen Schichten unter Spannung tetragonal verformt sind infolge der Gitterfehlanpassung von etwa 108 dyn/cm2 bei Zimmertemperatur. Die Spannungen in den Epitaxieschichten werden bis zu 800°C gemessen. Der Einflus der Kristallqualitat der Substrate auf die Qualitat der Epitaxieschichten wird untersucht. Es wird beobachtet, das die Dichte der Dunkelpunktdefekte in den Epitaxieschichten stets groser als die Versetzungsdichte in den Substraten ist.

Plasma spraying process for preparing polycrystalline solar cells

Abstract: Polycrystalline silicon films useful in preparing solar cells primarily for terrestrial application are prepared by a plasma spraying process. A doped silicon powder is injected into a high temperature ionized gas (plasma) to become molten and to be sprayed onto a low-cost substrate. Upon cooling, a dense polycrystalline silicon film is obtained. A p-n junction is formed on the sprayed film by spray deposition, diffusion or ion implantation. A sprayed junction is produced by plasma spraying a thin layer of silicon of opposite polarity or type over the initially deposited doped film. In forming a diffused junction, dopant is applied over the surface of the initial plasma-sprayed film usually from the vapor phase and heat is used to cause the dopant to diffuse into the film to form a shallow layer of opposite polarity to that in the original film. A junction is also formed by implanting dopant ions in the surface of the originally deposited film by the use of electrical fields. When used in conjunction with ohmic contacts and electrical conductors, the p-n junctions produced using plasma-sprayed polycrystalline silicon films are formed into solar cells which are useful for directly converting sunlight into electricity by means of the photovoltaic effect.

Conduction system for thin film and hybrid integrated circuits

Abstract: A metallization scheme for interconnection of elements in thin film and hybrid circuits is described. A thin layer of titanium is first formed, preferably by evaporation or sputtering, on the surface of the insulating substrate. A thin layer of copper is then formed in the same manner over the titanium layer. This is followed by electroplating of copper to a desired thickness onto selected portions of the Ti-Cu multilayer. Successive layers of nickel and gold are then selectively electroplated onto the plated copper regions. An additional layer of palladium may also be included between the titanium and copper layers for improved adhesion. The Ti-Cu-Ni-Au metallization system has been found unusually compatible with the major processing requirements of thin film circuits, for example, thermocompression bonding, soldering, via-hole coverage and resistor stabilization.

Methods and apparatus for producing unsupported monocrystalline films of silicon and of other materials

Abstract: This invention deals with methods and apparatus for producing unsupported monocrystalline films of silicon, germanium, gallium aresenide, and many other semiconductors and other materials. Said methods comprise: (a) repetitively using a monocrystalline substrate S having a crystal structure closely matching that of the desired films; (b) epitaxially depositing on substrate S first an intermediate monocrystalline layer I and next an outer monocrystalline layer 0 so as to form a three-layer S-I-O configuration, said three layers having closely matching crystal structures; and (c) at least partly disintegrating said intermediate layer I so as to free said outer layer 0 and make substrate S available to repeat the same cycle.

Bulk superconductivity above 20 K in Nb 3 Ge

Abstract: The superconducting properties of bulk films(0.02- 0.06 mm thick) of Nb 3 Ge deposited on Cu substrates by chemical vapor deposition have been studied along with physical parameters characterizing these deposits. Results of susceptibility measurements showing superconducting onsets greater than 21 K and resistivity measurements showing onset greater than 22 K are presented along with heat capacity measurements. Data are also presented defining a relationship between superconducting transition temperature and lattice spacing throughout the range of 4 - 21 K. In addition, the effects of substrate temperature and substrate material, as well as mechanical properties such as substrate adherence are described.

Reactive ion etching of aluminum

Abstract: A process for etching aluminum wherein a masked layer of aluminum, supported on a substrate, is exposed to a plasma formed by imposing an RF voltage across at least two spaced electrodes in an ambient including a gas selected from the group consisting of CCl4, Cl2, Br2, HCl. The resultant conditions provide a reactive environment where the aluminum is bombarded with chlorine or bromine ions. The aluminum reacts with chlorine or bromine ions to form an aluminum chloride or bromide compound, which is volatile at the temperature of the sputtered substrate.

Method of forming silicon dioxide

Abstract: A method of depositing a layer comprising SiO2 on a surface of a substrate at a rate which is temperature independent is disclosed. The method includes combining dichlorosilane (SiH2 Cl2) with an oxidizing gas, such as O2, CO2, N2 O, H2 O, to form SiO2.

Measurement of thin films by polarized light

Abstract: In order to measure the thickness and refractive index of a thin film on a substrate, such as a film of silicon dioxide on a substrate of silicon, a beam of substantially monochromatic polarized light is directed on the film. The reflected light is transmitted through an optical compensator and an optical analyzer both of which are rotating at different angular speeds, ωA and ωC, respectively; and the transmitted optical intensity is measured as a function of time. A Fourier analysis, for example, of the profile of this optical intensity vs. time can then be used for determining the Stokes parameters of the light reflected by the thin film and thereby also the thickness and refractive index of the film.

Chromium-silicon oxide thin film resistors

Abstract: An arrangement of thin film resistive layers for hybrid microcircuits thatliminates electrical contact problems and provides a means for obtaining high precision by trimming. A thin resistive film is deposited on an insulating substrate over a mask. Without breaking vacuum, a second resistive film which is not subject to oxidation is deposited over the first resistive film. The second resistive film is then etched away from portions which are not used as contact points. Since the second resistive material has a different resistivity, it is also used for low value resistive portions in multiple resistor networks.

Self-aligned integrated circuits

Abstract: Semiconductor integrated circuits, including, e.g., field effect transistors and memory cells employing field effect transistors, are formed by providing at a surface of semiconductor substrate a pair of isolation mediums and a plurality of spaced apart conductive lines extending between the isolation mediums. The conductive lines, such as polycrystalline silicon or polysilicon lines, are preferably thermally, chemically or anodically self insulatable in an unmasked batch process step and are made of a material suitable for defining a barrier to a dopant for the semiconductor substrate. Signal or bias voltages are applied to selected or predetermined conductive lines to provide control electrodes or field shields for the transistors. When the substrate has deposited on its surface an insulating medium made of a dual dielectric, such as silicon dioxide-silicon nitride, the dopant may be ion implanted through the insulating medium to form, e.g., the source and drain electrodes of the transistors as defined by the isolation mediums and the conductive lines. Other elements may be added to the structure to form, e.g., a memory cell. By depositing a conductive medium over the insulated conductive lines, the medium may be appropriately etched to provide desired access lines, capacitor electrodes, ground planes or additional field shields for the cells.

Method for forming recessed dielectric isolation with a minimized "bird's beak" problem

Abstract: In the fabrication of integrated circuits, a method is provided for forming recessed silicon dioxide isolation in integrated circuits in which the "bird's beak" problems associated with conventional silicon dioxide-silicon nitride composite masking structures is minimized. A conventional composite mask comprising a bottom layer of silicon dioxide and an upper layer of silicon nitride having a plurality of openings defining the regions in the silicon substrate which are to be thermally oxidized is formed on a silicon substrate. Recesses are then etched in the silicon substrate in registration with the openings in the composite mask. Then, the silicon dioxide layer is, in effect, over-etched to extend the openings in the silicon dioxide to greater lateral dimensions than the openings in the silicon nitride layer whereby the silicon nitride at the periphery of the openings is undercut. A layer of silicon is then deposited in the recesses covering the undercut portions of said silicon nitride layer. Then, the structure subjected to thermal oxidation whereby the silicon in and abutting the recesses is oxidized to form regions of recessed silicon dioxide substantially coplanar with the unrecessed portions of the silicon substrate. Because of the undercutting and the deposition of silicon in the recesses, the "bird's beak" effect is minimized.