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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Issue 3 • Date May 1985

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Displaying Results 1 - 25 of 361
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Static SIMS applications—From silicon single crystal oxidation to DNA sequencing

    Page(s): 451 - 460
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    Static secondary ion mass spectrometry is a hydrogen‐, isotope‐, and compound‐sensitive technique for monolayer analysis. Originally it was applied mainly for the determination of surface composition in surface reaction studies and for the investigation of the secondary ion formation process itself. More recently it has been shown that static SIMS allows high sensitivity detection identification, and structural analysis of large and thermally labile organic molecules such as, e.g., oligopeptides, ‐nucleotides, and ‐saccharides. This opens new fields of applications in the life sciences and many related areas. View full abstract»

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  • The development of photoemission spectroscopy and its application to the study of semiconductor interfaces: Observations on the interplay between basic and applied research

    Page(s): 461 - 470
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    A sketch is given of the development of photoemission electron spectroscopy (PES) with emphasis on the author’s own experience. Emphasis is placed: (1) on the period between 1958–1970; (2) on the various developments which were required for PES to emerge; and (3) on the strong interactions between applied/fundamental and knowledge/empirically based research. A more detailed discussion is given of the recent (1975–present) application of PES to study the interfaces of III–V semiconductors. View full abstract»

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  • History of the modern cryopump

    Page(s): 472 - 475
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    Fast clean pumpdown to 10-7 Torr range from high crossover pressure was a luxury a decade ago. Today the manufacturing/equipment engineer has at hand reliable, economical, and maintainable cryopumps alternative to conventional high vacuum pumps. This paper traces the nonliquid cryogen, mechanical refrigeration supported pump package from its inception to acceptance within IBM. View full abstract»

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  • Pumping of methane by a low power hot‐cathode ion pump/gage

    Page(s): 476 - 478
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    Sealed‐off devices, such as evacuated solar absorbers, with long life spans (about 25 years) frequently require a means of holding down the pressure of gases like methane which are not easily pumped by getters. Required pumping speeds are not high because leak‐up rates are low, but simplicity, low power consumption, together with a means of monitoring the pressure are desirable features. To meet these requirements we have constructed a small hot‐cathode ion pump/gage similar to a small Bayard–Alpert gage and we have subjected it to accelerated life tests in methane. The device consumed less than 1 W of power in operation. After 7×10-2 Torr l of methane had been pumped and with 1 mA of emission current the pumping speed was 2×10-4 l s-1, the equilibrium pressure was 3×10-4 Torr, and the reemission of pumped gas was 6×10-8 Torr l s-1, all quantities being slowly varying functions of the quantity of methane pumped. The sensitivity factor throughout the experiment was 3.3 Torr-1. View full abstract»

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  • High pressure pumping speed measurement on sputter ion pumps

    Page(s): 479 - 482
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    Sputter ion pumps are nowadays available for operating at pressures up to 10-3 Torr. Problems arise when measuring pumping speed in the high pressure range (namely, 10-5–10-3 Torr) where the usual Fisher–Mommsen test dome is inapplicable. As a matter of fact assumptions on which it is based are not verified at such high pressures. In the present work a method is described for measuring pumping speeds in the high pressure range (10-6–10-3 Torr). Examples of application of this method to different pumps are given. Pumping speed plots are compared with the ones obtained with the Fisher–Mommsen test dome. In the 10-6–10-4 Torr range, where these two methods overlap, pumping speeds obtained by both methods are in fairly good agreement. By combining the two methods it is possible to characterize pumping speeds in the whole operating range. View full abstract»

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  • Decreases in deuterium pumping by St707 getter alloy caused by carbon dioxide preexposure

    Page(s): 483 - 486
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    Intentional passivation of the deuterium pumping of the solid getter alloy St707 has been attempted by exposing samples of St707 to carbon dioxide at different pressures, temperatures and exposure times relevant for application to the getter modules in the ALT‐I pump limiter. It was found that one of the most effective treatments examined was a 30 min, 1 Torr exposure at approximately 100 °C. This preexposure kept the getter pumping speed less than 0.001 of its rated value for about 3 min when exposed to deuterium at 1 Torr and 30 °C. After this ‘‘incubation’’ period, the getter speed increases to values greater than ∼1% of fully activated values. If left under high deuterium pressure, the getter eventually flakes off the substrate. Video observations of the flaking process indicate that individual particles leave the constantan getter substrate at velocities of 1 m/s. Attempts at passivating the getter using oxygen and carbon monoxide were found to be no more effective than using carbon dioxide, suggesting that there is no way to completely passivate the getter with these gases at pressures low enough for application to in situ getter arrays used in tokamaks. View full abstract»

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  • Technique for in vacuo passivation of ZrAl alloy bulk getters

    Page(s): 487 - 490
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    We have developed a method for passivating previously activated ZrAl alloy bulk getters. Such passivation is essential for avoiding embrittlement of the getters during discharge cleaning operations in tokamak fusion devices. The method consists of exposing the getters (at room temperature) to a controlled amount of oxygen, followed by pulse discharge cleaning to restore the vacuum vessel walls to clean conditions. We have tested this method on the Tokamak Fusion Test Reactor (TFTR) and present measurements of the decrease in the hydrogen and oxygen pumping speeds as functions of the quantity of oxygen adsorbed. These measurements are in good agreement with previous laboratory results. Using this method followed by 20 h of pulse discharge cleaning, we have reduced the getter pumping speed by more than a factor of 2×103 and have recovered the same clean vacuum conditions as existed prior to the oxygen exposure. View full abstract»

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  • Biplanar source for high rate, large area, reactive sputtering: SiO2

    Page(s): 491 - 494
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    A new type of sputtering source, called a ‘‘biplanar magnetron,’’ is described which permits well controlled, metallic (or ‘‘high rate’’)‐mode deposition of SiO2 for large area industrial applications. Two biplanar magnetrons have been used to fabricate optical multilayer coatings on a 1‐m‐wide web. Clear films of SiO2 have been deposited with optical thickness uniformity equal to ±2% at a deposition rate of 3.6 Å/kW m/min. With one biplanar source operated at 20 kW, this rate corresponds to a line speed of 7.2 cm/min for a 1000‐Å physical thickness of SiO2. The device is equally useful for many other compounds, including AlN, ZnO, Al2O3, ZrO2, and indium tin oxide. View full abstract»

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  • Texturing of poly(ethylene terephthalate) film surfaces by sputter etching

    Page(s): 495 - 498
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    Poly(ethylene terephthalate) surfaces become microtextured during sputter etching due to differences in the etch rates for the crystalline and amorphous regions. Texture development depends on the selectivity and directionality of the etch chemistry used. We report on the etch rate, the selectivity, the directionality of etch, and loading effects for etching of PET in oxygen. Results of etching in argon, nitrogen, and air are also reported. As a result of a higher selectivity and directionality of etch, argon etching generates microtexture features more rapidly than oxygen etching, even though the etch rate in oxygen is four times larger than that in argon. View full abstract»

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  • Electrical characterization of rf glow discharges using an operating impedance bridge

    Page(s): 499 - 503
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    The impedance and its inverse, admittance, of nitrogen rf glow discharge are measured with an operating impedance bridge in two geometrically similar, radial‐flow, parallel‐plate plasma reactors. Separation of these electrical parameters into their constituents, resistance and capacitive reactance for impedance and conductance and susceptance for admittance, permits an evaluation of the electrical behavior of these discharges. At power levels between 0.06 and 0.4 W/cm2 and electrode spacings between 2.5 and 8.2 cm, the discharge conductance generally increases with rf power and electrode spacing. However, the exact trends depend upon the specific reactor. Based upon these results, an electrical similarity criterion is proposed that may assist transfer of plasma etching and deposition processes from one reactor to another. View full abstract»

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  • Multichamber plasma processing system for research laboratory use

    Page(s): 504 - 508
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    A system for reactive ion etching and plasma chemical vapor deposition permits individual processes to be developed using a wide variety of reactants without concern for interference by carryover of tenacious reactants or products such as carbon and halogen compounds. To avoid interference, each investigator has exclusive use of one or more chambers which can be attached easily to a computer controlled console in a matter of minutes. The functions of the console include multiple gas supply and monitoring and control of deposition and etch conditions by means of a dedicated computer. The gas flow within each chamber is conventional but the mechanical design has been simplified so that additional chambers are simple and inexpensive to build and design changes are easily executed. Parameters controlled include pressure, flow rate, temperature, power, and frequency. A unique feature of the chambers is the ability to monitor etch or deposition progress visually. Pressure and power limits for stable plasma operation are presented as are pressure vs flow relationships. View full abstract»

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  • Aluminum plasma etching process using vacuum systems without cold traps

    Page(s): 509 - 511
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    A suitable vacuum pump system used in plasma or RIE‐mode dry etching of Al and Al alloys with CCl4/Cl2 enables to operate without LN2 cold traps. A Roots pump plus rotary vane pump combination, both using inert fluid lubricant, pumps and exhausts all occurring volatile products. Condensing solid AlCl3 is quantitatively removed from the backing pump sealing fluid by means of a high speed, main stream oil purification system via an Al2O3 deep bed filter. Maintenance of the pump system is limited to just changing the Al2O3 filter elements, each time after etching of 4000 4 in. wafers. No decomposition of the sealing fluid could be observed. Any fluid remaining when exchanging the filter elements can practically be recovered by centrifuging. View full abstract»

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  • Metallizing system for coating an astronomical telescope mirror

    Page(s): 512 - 515
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    A vacuum metalizing system developed for coating a 2.12 m astronomical telescope mirror is described. The 3 m diameter chamber, installed at 2800 m altitude at the Mexican National Astronomical Observatory at San Pedro Mártir, Baja California, was developed with uniquely economical equipment and simplicity of design to facilitate ease of operation, safe handling of the mirror, and reliability in this remote location. In order to meet strict performance specifications within a very limited budget, nontraditional equipment suppliers and fabricators were used. The project design and administration philosophy are described. View full abstract»

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  • Glow discharge cleaning of stainless steel accelerator beam tubes

    Page(s): 518 - 522
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    Glow discharge cleaning has been employed successfully in the CERN ISR to eliminate beam induced pressure bumps and had been adopted as a final surface treatment for the beam vacuum system of CBA. A glow discharge cleaning facility for beam tubes up to 5.5 m in length has been constructed and is in operation. To ensure efficient and thorough cleaning of the long tubes, a residual gas analyzer was used to monitor the exhaust during cleaning. Quantitative studies of the glow discharge process were performed on several tubes by using Ar or Ar/O2 mixture (0.1 to 10 Pa) and by varying the discharge density (≤30 μA/cm2). The results of the studies, such as the desorption yields of H2O, CO, and CO2 with respect to the accumulated dosage, the depletion of O2 in Ar/O2 mixture, will be reported here. The effect of venting to air and CO2, as well as plasma deposition of carbon will also be discussed. View full abstract»

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  • A design analysis of intelligent, articulated vacuum processing systems

    Page(s): 523 - 525
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    The current trend toward the use of computers and robotics in vacuum system design is providing practical solutions to increasingly difficult process applications. These systems require a great degree of flexibility for process development and often require high throughput capability. Economical development and reliable performance depends largely upon the proper integration of mechanisms and control devices. This paper focuses upon successfully proven design and programming techniques drawn from the development of fully automated batch and in‐line sputtering systems. In the design analysis, complex processes are divided into a series of basic functions. Each requires a mechanism, sensing device, and hardware/software interface. Functions acting together to perform a specific portion of the process form a module. The module is designed as an independent unit and is controlled by a dedicated program subroutine. The main program accepts operator input and receives data from each module; it then performs necessary calculations, displays information, and controls overall system operation. This approach allows diverse processes to be created, varied, and expanded, resulting in a new generation of highly versatile vacuum systems. View full abstract»

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  • Measurement and calibration techniques used in computer partial pressure analysis

    Page(s): 527 - 532
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    The uses of residual gas analyzers (RGA’s) in computer controlled analytical studies and process monitoring applications are discussed in this paper. The relative merits are compared for the two most commonly used RGA’s, which are the magnetic sector and the quadrupole mass analyzer. Methods of installing RGA’s in vacuum systems and computer interfacing techniques are described. Measurement and calibration methods are outlined for applications where it is desirable to characterize either partial pressures or gas evolution rates. Interpretation of RGA spectra and limitations imposed by analytical errors are also discussed. View full abstract»

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  • Management of vacuum leak‐detection processes, calibration, and standards

    Page(s): 533 - 537
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    Vacuum leak detection requires integrated management action to ensure the successful production of apparatus having required leak tightness. Implementation of properly planned, scheduled, and engineered procedures and test arrangements are an absolute necessity to prevent unexpected, impractical, technically inadequate, or unnecessarily costly incidents in leak‐testing operations. The use of standard procedures, leak standards appropriate to the task, and accurate calibration systems or devices is necessary to validate the integrity of any leak‐test procedure. In this paper, the need for implementing these practices is discussed using case histories of typical examples of large complex vacuum systems. Aggressive management practices are of primary importance throughout a project’s life cycle to ensure the lowest cost; this includes successful leak testing of components. It should be noted that the opinions and conclusions expressed in this paper are those of the author and are not those of the Los Alamos National Laboratory or the Department of Energy. View full abstract»

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  • Depressurization as a means of leak checking large vacuum vessels

    Page(s): 538 - 541
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    A common problem associated with large vacuum vessels used in magnetic confinement fusion experiments is that leak checking is hampered by the inaccessibility to most of the vacuum vessel surface. This inaccessibility is caused by the close proximity of magnetic coils, diagnostics and, for those vessels that are baked, the need to completely surround the vessel with a thermal insulation blanket. These obstructions reduce the effectiveness of the standard leak checking method of using a mass spectrometer and spraying a search gas such as helium on the vessel exterior. Even when the presence of helium is detected, its entry point into the vessel cannot always be pinpointed. This paper will describe a method of overcoming this problem. By slightly depressurizing the vessel, an influx of helium through the leak is created. The leak site can then be identified by personnel within the vessel using standard sniffing procedures. There are two conditions which make this method of leak checking practical. First, the vessel need only be depressurized 2 psi, thus allowing personnel inside to perform the sniffing operation. Second, the sniffing probe used (Leybold–Heraus ‘‘Quick Test’’) could detect a change in helium concentration as small as 100 ppb, which allows for faster scanning of the vessel inferior. Use of this technique to find an elusive 10-3 Torr∙l/s leak in the Doublet III tokamak vacuum vessel will be presented. View full abstract»

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  • Long‐term stability of two types of hot cathode ionization gauges

    Page(s): 542 - 545
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    We have monitored the nitrogen sensitivity of four gauges each of two selected types of hot cathode ion gauges over a 500‐day test period. Gauges of one type, a tungsten filament conventional triode, changed by about 12% during this time, with most of the decrease caused by ‘‘high’’ pressure operation. Gauges of the second type, a twin tungsten filament Bayard–Alpert gauge, changed by no more than 6% and with no obvious correlation between sensitivity changes and ‘‘high’’ pressure operation or exposure to air. There were no significant differences in the sensitivity changes for the two filaments in a given Bayard–Alpert gauge, although their operating times differed by a factor of 10. View full abstract»

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  • Sensitivity of hot cathode ionization gages

    Page(s): 546 - 550
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    As a part of an experimental program of some years duration we have attempted to characterize several hot cathode ionization gage types in the high vacuum range by the uniformity, linearity, and stability of their nitrogen sensitivity. Results for six commonly used types are summarized here. Of the gages tested, the most promising overall performance was obtained from tubulated Bayard–Alpert gages with two tungsten filaments mounted 180° apart about the grid. Conventional triode gages with tungsten filaments came close to this level of performance and have superior high pressure linearity. View full abstract»

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  • Effective hydrogen gas temperature in a cryopumped beam line vessel

    Page(s): 551 - 552
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    Thermal accommodation of hydrogen gas molecules to cold surfaces modifies the effective gas temperature in cryogenically pumped vacuum vessels. In Doublet III neutral beam lines, gas pumping is achieved by liquid‐helium‐cooled panels which are surrounded by liquid‐nitrogen‐cooled thermal shields. By measuring the gas pressure during the injection of a known amount of gas while cooling the thermal shields by liquid nitrogen, we have determined the effective gas temperature according to T/T0=(Pi/Pio)2, where Pi is the pressure monitored by an ionization gauge and the subscript o refers the case of room temperature. The effective gas temperature was determined to be about 150 K when only the thermal shields were cooled down to the liquid nitrogen temperature. Implications of the reduced gas temperature on pressure measurement, pumping speed measurement, and neutral beam reionization loss calculation are discussed. View full abstract»

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  • Plasma assisted physical vapor deposition processes: A review

    Page(s): 553 - 560
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    Increasing use has been made in thin film technology of physical and chemical phenomena occurring in low pressure plasmas which are convenient in situ sources of activated gas and energetic ions to be used as additional process parameters in film growth, structure, and properties. Energetic ions and/or activated species in the vapor phase are now employed in processes for surface treatment (ion nitriding and carburizing), deposition (sputtering, ion plating, activated reactive evaporation, and plasma polymerization) and also for etching (sputtering and plasma etching). In recent years, therefore, considerable efforts have been directed to the analysis of plasma conditions and their correlation with deposited film properties. In this paper, we present a review of plasma‐assisted physical vapor deposition processes (PAPVD) used for the deposition of refractory compounds for the two basic PAPVD processes, (i.e., activated reactive evaporation and reactive sputtering). The film growth mechanism and the role of plasmas in these processes will be compared in terms of three steps in deposition processes; synthesis of the deposition species, transport from source to substrate, and film growth. View full abstract»

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Aims & Scope

The Journal of Vacuum Science and Technology A is devoted to reports of original research, review articles, and Critical Review articles.

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Meet Our Editors

Editor
G. Lucovsky
North Carolina State University