Substrate Temperature Rise Research Articles

Plasma cleaning of metals: Lubricant oil removal

Preliminary experiments have shown that oxygen plasmas can be effectively used for lubricant oil removal from metal surfaces in a roll-to-roll process. A linear multichannel hollow cathode plasma source for oxygen plasma cleaning (etching) and surface modification has been developed. The source is a linear set of plasma torches coming out from all holes. The discharge is magnetically enhanced and directed toward the substrates. Using a set of such cathodes should allow oil removal from both sides of a metal roll in production. Hollow cathode plasma cleaning of metal strip can provide an economical, practical solution for in situ metal strip cleaning in vacuum when accompanied by a subsequent deposition or corrosion-inhibiting process. Multiple banks of hollow cathodes can be used for higher line speeds, and depending on allowable substrate temperature rise, these may be on both sides simultaneously in free span material.

Deposition of boron doped a-Si:H films by a novel combination of rf glow discharge technique and filament heating: Enhancement of doping efficiency

A novel variation of plasma enhanced chemical vapour deposition in the form of insertion of a heated filament in the plasma was applied to a SiH 4+1% B 2H 6(in H 2)+H 2 gas mixture for the deposition of boron doped hydrogenated amorphous silicon thin films. Current levels giving filament temperatures below and above the thermionic emission level of the filament material were used to separate the effect of thermal dissociation of B 2H 6 from that of the production of atomic hydrogen in combination with B 2H 6 dissociation. Control runs without filament heating but accounting for rise in substrate temperature because of the heated coil were also carried out. The films were characterised by electrical and optical measurements, infrared vibrational spectroscopy and secondary ion mass spectroscopy. A significant enhancement in the doping efficiency of boron was obtained by this technique and thus was found not to be an artifact of increase in substrate temperature. Nor could it be attributed to the effect of atomic hydrogen only.

Effect of substrate temperature and heat treatment on the microstructure of diamondlike carbon films

Nonhydrogenated diamondlike carbon films prepared at a substrate temperature (ST) of 100, 300, and 500 °C by the laser ablation of graphite on a single-crystal silicon substrate have been characterized by scanning tunneling microscopy for the surface structure and Raman spectroscopy for the microstructure. Distorted pentagonal and hexagonal rings are observed on the surface of the film grown at 100 °C while only hexagonal rings are observable for the one grown at 500 °C. The rise in ST is found to increase the surface roughness. To assign the various coexisting carbonaceous species formed at different growth temperatures and to check their thermal stability, heat treatment was performed at up to 1300 °C in vacuum and 600 °C in air. The changes occurring on heat treatment in vacuum in these films around 600 °C have been correlated with the release of defects from the threefold network. Likewise, 950 °C temperature has been associated with the conversion of disordered tetrahedral bonding to a distorted trigonal one. The heat treatment in air shows that the microstructure induced due to lower ST is thermally more stable.

Two Stages High Rate Reactive Sputtering, Divided Sputter Process and Oxidation Process.

For optical thin film production by a sputtering method, it is common to use RF or DC reactive sputtering. Since during deposition sputtering and reactive processes are operated simultaneously, a substrate temperature rise is caused. Also the deposition rate is very low because metal atoms sputtered need enough time for sufficient oxidation. For solving these problems, we separated the deposition process into two stages, i.e., sputtering and reactive processes. As result of these two successively separated processes, the deposition rate for metal oxides can be as similar to that of pure metals with no substrate temperature rise. This is completely different from that during RF sputtering. This new type DC reactive sputtering method is called Two Stages High Rate Sputtering, Divided Sputtering Prosess and Reactive process (TSH Sputtering Method). This paper describes the deposition principle and reports the improvements of refractive index, deposition rate and substrate temperature rise. Finally the antireflection coatings produced by the TSH sputtering method as an example of multilayer, and their spectral characteristics and reproducibility are represented.

Perturbation of the substrate temperature by the impingement of laser ablated particles

During the process of pulsed laser deposition of thin film materials, the impingement of the laser ablated particles onto the substrate increases the substrate temperature. In this work, the energy exchange between the ablated particles and the substrate is analyzed. The substrate temperature rise is studied via a transient two dimensional heat transfer model. In particular, the temperature evolution of silicon and quartz substrates induced by the deposition of carbon and copper films are examined. The effects of experimental conditions on the maximum substrate temperature rise are discussed.

Vacuum metallizing—Quality and productivity enhancements through in-line technology

Preliminary experiments have shown that oxygen plasmas can be effectively used for lubricant oil removal from metal surfaces in a roll-to-roll process. A linear multichannel hollow cathode plasma source for oxygen plasma cleaning (etching) and surface modification has been developed. The source is a linear set of plasma torches coming out from all holes. The discharge is magnetically enhanced and directed toward the substrates. Using a set of such cathodes should allow oil removal from both sides of a metal roll in production.Hollow cathode plasma cleaning of metal strip can provide an economical, practical solution for in situ metal strip cleaning in vacuum when accompanied by a subsequent deposition or corrosion-inhibiting process. Multiple banks of hollow cathodes can be used for higher line speeds, and depending on allowable substrate temperature rise, these may be on both sides simultaneously in free span material.

Properties of Laser-Deposited Yttria Films on CdTe and Silicon Substrates

Yttria (Y2O3) films have been used for a variety of applications including MIS diodes, capacitors, insulators in transistor gates and electro-luminescent devices, and as optical AR coatings. Several conventional Physical Vapor Deposition (PVD) techniques have been used to deposit Y2O3 films such as evaporationl,2,3,4, ion beam, RF and DC magnetron sputtering5,6,7,8. Here we report on the growth of Y2O3 films using excimer-based Pulsed-Laser Deposition (PLD). This study was motivated by the need to deposit high-quality yttria films onto the backsides of CdTe and CdZnTe substrates to act as an Infra-Red (IR) Anti-Reflective (AR) coating. AR coatings can theoretically increase the efficiency of back-side illuminated HgCdTe photo-voltaic IR detectors from about 65% to 80% over the 3 to 5 μm and 8 to 12 μm bands. For detector fabrication Y2O3 is deposited onto the substrate backside, after HgCdTe diodes have been formed. Low deposition temperatures (T< 75°C) are thus essential in order to reduce Hg diffusion and minimize the creation of vacancies in the HgCdTe lattice. Unfortunately, conventional PVD techniques inadvertently heat uncooled substrates to temperatures above 100°C, even at modest deposition rates (1 Å /sec). Effective cooling of the CdTe or CdZnTe is not practical since these substrates are very fragile and cannot be clamped with significant pressure to cooled backing plates. Furthermore, the fact that the HgCdTe diode array has already been formed on the front-side of the substrate precludes the use of thermal grease or epoxy to improve contact with a water cooled stage. PLD on the other hand, has the ability to deposit Y2O3 fims at relatively high deposition rates when compared to sputtering, with only a small rise in substrate temperature.

Enhanced radiative absorption of thin, heavily beryllium-doped GaAs films

Beryllium-doped GaAs layers have been grown by molecular beam epitaxy with doping concentrations up to 1.2 × 1020 cm−3. Upon initiation of doping, an unintentional substrate temperature rise is observed pyrometrically that is caused by various radiant sources used in the growth process. The heating effect is correlated with the doping concentration and dependent upon machine configuration and geometry. Electrical and secondary ion mass spectrometry measurements indicate that the temperature rise can cause significant beryllium diffusion. Since most of the temperature rise occurs during the first 1000A of growth, degradation of thin device layers is possible. Transmission and reflection measurements on the beryllium-doped samples indicate strong sub-bandgap absorption that correlates with the doping concentration. The absorption is due to intervalence band transitions as well as free carrier absorption.

Optimization studies on magnetic field geometry for planar magnetron sputtering targets

The present study deals with the design aspects of planar magnetron sputtering targets. A permanent ring magnet with modified pole piece geometry has been used for maximum ionization efficiency. The efficiency of electron containment on the target surface has been evaluated in terms of current at the electrically isolated substrates. The details of the relation between the magnetic field strength and field geometry on the ionization currents and operating pressure have been discussed. The best among the designs studied, when operated at a pressure of $8A—10^-^3$ Torr resulted in a deposition rate of about 2000 A/min at a current density of 4 mA/cm2. The substrate temperature rise was about 20°C under these conditions. The design details of the magnetrons, experimentation for evaluating the electron containment have been discussed in this article.

Clarification of the effect of bias in the hot filament process

The effect of applying d.c. and a.c. bias in the hot-filament process was investigated using in situ rate determination. Biasing the substrate 150 V positive relative to the filament caused a rise in substrate temperature. Adjusting the filament power to maintain a constant substrate temperature when applying the bias did not increase the deposition rate. A bias of less than 120 V did not affect the deposition rate. The positive substrate bias resulted in a slightly higher nucleation density and shortened the incubation time to reach steady state growth but also decreased the diamond quality.

Structure and optical properties of CuGaSe 2 thin films

Thin films of CuGaSe 2 were prepared by electron beam evaporation of pre-reacted material onto Corning glass substrates maintained at 350 to 450°C. The structure of the films were examined by XRD, Scanning and Transmission electron microscopy. The measured grain sizes were 1–2 μm. At T s < 400°C, XRD data showed secondary phase formation due to excess copper, where as at T s ⩾ 400°C the films were always chalcopyrite with strong (112) preferred orientation. The optical absorption data showed three characteristic energy gaps at 1.66, 1.76 and 2.45 eV, which correspond to fundamental, band splitting and copper 3d level transitions, respectively. The absorption coefficient was found to decrease with the rise of substrate temperature.

Effect of the detailed growth conditions on the injection efficiency of (N)AlGaAs-(p+)GaAs heterojunctions produced by molecular-beam epitaxy

Abrupt (N)AlGaAs-(p+ )GaAs heterojunction diodes were grown by molecular-beam epitaxy. It was found that the position with respect to the heterointerface at which the substrate temperature was changed from that for the growth of (p+ )GaAs to that for the growth of (N)AlGaAs had a significant effect on the injection efficiency of the devices. By initiating the substrate temperature rise right at the start of the (N)AlGaAs growth, heterojunction bipolar transistors with an abrupt (N)Al0.18 Ga0.82 As-(p+ )GaAs emitter-base junction having current gains of between 60 and 70 were fabricated. These relatively high-current gains are argued to be due to the effects of hot-electron injection into the base.

イオンアシスト蒸着窒化鉄薄膜の磁気特性に及ぼす基板温度の影響

The structure and magnetic properties of iron nitride thin films were examined with substrate temperature as a parameter. The coercivity and squareness ratio decreased with the rise in substrate temperature, while the saturation magnetization remained constant. SEM observation showed that the columnar growth deteriorated at high substrate temperature. Mossbauer measurements indicated that the films consisted of γ'-Fe4N, e-Fe2∼3N and ζ-Fe2N and that their concentrations were nearly independent of the substrate temperature. The domain replacement was found to be more dominant at higher substrate temperature, which implies the change of paramagnetic distribution. These results suggest that the decrease in coercivity could be attributed to a reduction in the shape anisotropy due to the disordered growth of the columns and a decrease in magnetic separation effect by paramagnetic phases in each column.

High-performance heat sinking for VLSI

The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.

高速スパッタによるガスタービン用超合金保護膜の形成

The life and performances of gas turbine engines are greatly damaged by the oxidation, sulphidation, and hot corrosion of the surface layer of the blades. Recently, protective coatings of superalloys on the blades have been frequently attempted to improve them. We have designed and constructed a sputtering apparatus with two targets facing each other to deposit magnetic films on the blade alloy at a very high rate with no extreme rise in substrate temperature. Protective coatings of superalloys of the (Co, Ni)-Cr-Al-Y system of ferromagnetic properties at high rates have been made under various sputtering conditions. Films of above 4μm in thickness were deposited at a rate of about 3000Å/min with the two circular targets of the same composition and of 58mm in diameter. This deposition rate is about 30 times as high as the rate observed in conventional diode sputtering techniques. The films deposited in the argon atmosphere of the pressure below 5×10-3 Torr were adherent to the substrate and crack-free even after annealing at 900°C. In addition, the films exhibited neither any structural imperfections such as spits, flake and linear defects nor any columnar structure. These results show that this sputtering method can be practically used to deposit the superalloy films on the blades of gas turbine engine for protective coating purposes.

Application of High Current Arsenic Ion Implantation to Dynamic MOS Memory LSI's

Application of high current arsenic ion implantation technology to the fabrication of MOS LSI's is investigated. Substrate temperature rise during ion implantation, carrier profile and residual defect profile after high temperature annealing are measured to solve the fundamental problems involved in high current ion implantation. MOS FET's, junction diodes and 4 K-bit dynamic MOS memory LSI's are fabricated using high current arsenic ion implantation technology. MOS FET characteristics are improved by this implantation technology, when compared with the characteristics of devices fabricated by conventional ampule diffusion technology. The generation-recombination center concentrations derived from junction leakage current measurements are below 1011 cm-3, and are in good agreement with the results for dynamic MOS memory refreshtime.

Substrate Temperature Measurement during Ion Implantation

A quantitative estimation of the substrate temperature rise in situ during ion implantation is performed using a wide range infrared thermometer. The accuracy of the measurement is within ±3°C. The ion implantation is carried out on a silica glass wafer and the temperature rise is measured for He+, B+, N+, N+2, P+ and BF+2 ion species. The higher the implant power is, the higher becomes the substrate temperature, and an implant power of 6 W/cm2 raises the substrate temperature to 730°C. The mass dependence of the temperature rise is observed, and is explained by the electrical and nuclear stopping power of the substrate.

A New Cold Sputtering System Using a Trapping Electrode

The temperature rise of the substrate during sputtering is considered to be mainly due to the secondary electron bombardment and thermal radiation from the target. In this study, a new coaxial type cold sputtering system with a trapping electrode and a magnetic field is attempted in order to reduce the temperature rise of the substrate. Experimental results obtained for chromium deposition show that the substrate temperature rise is about 10°C in 10 minutes after switch-on at a deposition rate of 70 Å/min. The incident power density to the substrate estimated from this temperature rise is 3.4 mW/cm2, which is less than one fiftieth in magnitude in the case of r-f planer diode. Bright and shiny films of aluminum, chromium, copper, platinum can be deposited on nylon, ABS, polycarbonate and other plastics without any deformation.

Photochemical Reactions of Uranyl Ions with Organic Compounds. V. Effects of Temperature and Solvent on the Photooxidation of Alcohols

Abstract A comparative study of the photokinetic behaviors of aliphatic alcohols and related substrates was made for the photooxidation with uranyl ions. Ethylene glycol, glucose, sucrose and some other substrates showed abnormal results compared to a series of simple aliphatic alcohols: the photoredox quantum yields φ for the former substrates decreased with substrate concentration (at their higher concentrations) and temperature rise, in contrast to simple aliphatic alcohols. In aqueous acetone solution φ increased with the increase in acetone content, the reaction constant ρ* being more negative than in aqueous solution. In 40% aqueous acetone solution the φ values for simple aliphatic alcohols varied in a complicated way with temperature. The abnormal results were interpreted in terms of the relative importance of physical quenching competing with the primary chemical process.

Transient Surface Temperature Response of Liquid Crystal Films

Abstract Various commercially available microencapsulated cholesteric liquid crystal films and coatings were tested to determine their response to rapid heating. The rapid response data are required for the diagnostic devices to be used to measure the spatial energy distribution in lasers and electron beams. These films, which reversibly change color at discrete temperatures, were placed on tapered stainless steel strips that were pulse heated to a predetermined level in 30 μsec by discharging through the steel strip the stored charge from a high-voltage low-inductance capacitor bank. The taper introduced a temperature gradient along the length of the strip with the higher temperature at the narrow end. A high-speed movie camera and time fiducial system recorded the color change movement along the length of the bar as a function of time. The response time is the time required for the material to achieve its event temperature when the ratio of event temperature less initial temperature to substrate temperature rise is 0.9. These data are reported in tabular form for each material tested. In general, the response is inversely proportional to the film thickness squared since this is one of the limiting factors for heat diffusion. Various techniques to reduce film and coating thickness and enhance response were demonstrated and are discussed in the paper.