Search

The historical background and current use of getter sputtering are reviewed and it is shown that the process often occured in early apparatus because of fortuitous layout of the chamber components. Getter systems are classified into “static” and “ynamic” according to the gas flow and pumping conditions. In conclusion mass spectra are given of the gas atmospheres in an r.f. getter sputtering plant when depositing tantalum. It is shown that gettering reduces the gaseous impurities. However, provision of the extra getter target requires use of increased power input. Otherwise the deposition rate can fall (from an overall reduction in ion current density) which increases in the desired coating the proportion of sorbed impurity from gas released in the substrate coating vessel.

A method for the powder-metallurgy fabrication of tool-steel bar stock has been developed that requires neither isostatic compaction nor low-oxygen powders. The powder is heated in sealed steel tubes and directly step-forged to 99·5% density. Further reduction by rolling raises the density to 100%. A reducing agent and an oxygen getter are enclosed in the container, together with the powder for in situ reduction of particle surface oxides. This makes initial evacuation of the containers unnecessary and allows powders with high oxygen contents to be used. Mechanical properties compare well with those of material rolled from ingot.

Silicon p+n junctions heat treated at high temperatures (1200°C) for a long time (2–20 hr) and then quenched to room temperatures or below shows two deep donor levels (EC−264meV andEC−542meV) in the n-type side of the junction depletion layer which appear to originate from the same imperfection center. The concentration of these levels ranges from 1013 to 1014 cm−3. The junction leakage current comes from carrier generation at the deeper level in the depletion region. Phosphorus gettering was found ineffective in reducing the concentration of these quenched-in levels, but they are annealed out by very slow cooling (25°C/hr to 650°C then quench to room temperatures). The thermal emission and capture rates of electrons and holes at these levels are measured as a function of temperature and electric field by the junction high frequency capacitance and d.c. leakage current transient techniques. It is demonstrated that the detailed balance relationship does not hold. The origin of this double donor center is yet to be identified.

The rate of removal of oxygen from inert gas by metallic getter is measured continuously, and the dilution model is adopted for explaining the rate of purification. The rate of removal of oxygen increases with flow rate. It is found that hydrogen and water vapor present in the inert gas contributes very effectively to reducing the oxygen partial pressure. The rate of removal of oxygen with a titanium getter increases with temperature below about 800°C, but levels off above about 800°C.

In an extension of earlier studies on vinyltrimethylsilane (VTMS) containing reactive plasma [1, 3], the reactor was modified so as to allow less elapsed reaction time before sampling. This resulted in only a modest increase in the detection of primary electron impact produced species. The relative amounts of ionic and neutral species were mapped as a function of axial distance between the electrodes, and this showed that the discharge has a definite structure. The concentration of VTMS is somewhat greater near the driving electrode, making it appear as if the electrode behaves as a getter. The mass spectra of VTMS—helium and VTMS—argon discharges differ: low pressure VTMS—helium discharges resemble the 26 eV electron impact spectrum of VTMS while VTMS—argon discharges are relatively more abundant in mass 43 and 45 fragment ions. In both cases, the mass 73 fragment ion is overabundant relative to the electron impact results. From the present studies, argon ion and metastable energy exchange processes are believed to be less important than previously suggested [1], while low energy successive electron impact is believed to be responsible for the results obtained. Only those processes have been observed which involve species that are not incorporated into polymer at the electrode surfaces, although polymer formation is an extremely efficient pathway for utilizing VTMS molecules.

A recently developed 14-kW 240 ° electron beam gun was installed in an 18-in. glass belljar pumped by a liquid-helium cryopumping system made by Air Liquide, a French supplier of cryogenic pumps. The cryogenic pump has a speed of 6000 liter/sec for air. Pumping of hydrogen and helium is accomplished by bleeding in a small amount of argon which freezes on the helium reservoir and has a gettering effect on these gases. Experiments were conducted to determine the operating characteristics of this type of system when evaporating various materials such as aluminum, copper, and tantalum. Data taken during the evaporation runs consisted of major gases evolved, time for belljar pressure to recover to 10−7 Torr range, pressure during evaporation, effectiveness of argon sublimator in reducing pressure, and pumpdown curves. It was found that using a liquid-helium cryopumping system in conjunction with an electron beam gun gives exceptional results. It would be particularly advantageous in the fabrication of MOS devi...

1. A study was made of the compressibility and sinterability of KhN55VMTFKYu-alloy powders produced by: 1) processing waste machining swarf, 2) simultaneously reducing a mixture of oxides and metal powders with calcium hydride, and 3) atomizing an alloy melt and subsequently reducing the powder with calcium hydride, 2. The KhN55VMTFKYu-alloy powder obtained from swarf was found to have the poorest compressibility; thanks to its well-developed particle surfaces, however, it had the best compactibility. 3. The most effective protective atmosphere for the sintering of KhN55VMTFKYu-alloy powders is hydrogen with a dew point of between −30 and −40‡C, used in conjunction with Koreks packing material and a titanium sponge getter. 4. The KhN55VMTFKYu-alloy powder obtained from swarf was found to be superior in sinterability to the other two types of powder studied. 5. Virtually nonporous compacts from the KhN55VMTFKYu-alloy powders were produced by hydrostatic pressing under pressures in excess of 90 kg/mm2 and sintering at 1300‡C.

The recently developed large-area field-emission photocathode is described. It consists of a finely spaced array of point emitters fabricated by etching of p-type silicon or other semiconductor. Uniform emission over areas of 6-7 cm2have been obtained. For Si, the spectral response extends from 0.4 to 1.1 µm. Quantum yields of 25 percent at 0.86 µm have been measured, which is about five times the value reported for the extended S-20 photocathode and comparable to the best III-V photoemitters. Calculations indicate that quantum yields of up to 40 percent at 0.86 µm and 28 percent at 0.9 µm are attainable with the present photocathode structures. For low dark current densities, photocathode cooling to temperatures approaching 77 K must be employed at present. The dark current is shown to be dominated by surface-generated electrons in the space-chargeregion of the emitters. Effects of phosphorus gettering and annealing treatments on dark current are discussed, and the spatial frequency response of the device is determined. The results of a computer study show that the field intensification factor of p-semiconductor field emitters behaves quite differently from that of metallic emitters.

Current-voltage measurements have been carried out at room temperature on anodized tantalum thin films ranging in thickness from 120 to 400 nm. The tantalum was prepared by getter sputtering in such a way as to reduce the possibility of impurities and defects being present as was found in tantalum foil. The films were found to be rectifying, the forward direction of current flow being with the aluminium counter-electrode positive with respect to the base tantalum. The conduction mechanism is believed to be space-charge-limited in the forward direction and Schottky-controlled emission in the reverse direction. The current in the forward direction was on average two orders of magnitude higher than that in the reverse direction, and the mobility of the electrons in the space-charge-limited mode, as obtained from steady-state and transient measurements, is very low, being of the order of 10−17 m2 V−1 s−1. The results in general support those of Aris and Lewis (1973) and show that localized conduction does not play an important part in the conduction process.

Amorphous Sb films ranging in thickness between 170 and 14 000 \AA{} were prepared at 77\ifmmode^\circ\else\textdegree\fi{}K in three different ways: getter sputtering, evaporation from Sb, and evaporation from PtSb. The electrical resistivity of these various films is well fitted between 30 and 160 \ifmmode^\circ\else\textdegree\fi{}K by the relation $\ensuremath{\rho}={\ensuremath{\rho}}_{0}\mathrm{exp}[{(\frac{{T}_{0}}{T})}^{\frac{1}{4}}]$ with ${T}_{0}\ensuremath{\simeq}{10}^{7}$ \ifmmode^\circ\else\textdegree\fi{}K.

Several related problems involving the recovery of tritium from the breeding blanket in fusion power reactors are considered. They include the use of stagnant lithium blankets, the use of lithium as a regenerable getter pump, and the use of breeder materials that are lithium intermetallic alloys. Transient tritium recovery rates during startup are also estimated. Keeping the tritium inventory low and providing an economical recovery cycle are conflicting goals. These topics may provide a scheme by which both might be accomplished. (auth)

It has previously been demonstrated2 that the growth conditions of thermal SiO 2 can be optimized to give acceptable operating performance for P-MOS devices and circuits after ionizing radiation dose levels of 107 rads and above. Further work has since been done to apply this hardening technology to CMOS circuits, with very promising results. Also studied were the effects of adding HCl gettering, chrome doping, and aluminum ion implantation to the hardened SiO 2 . Each of these additions, when properly employed, was found to give improved hardening. The nature of these improvements is described in this paper, along with their applicability to the fabrication of CMOS circuits with improved hardness but which retain all the other advantages of the SiO 2 gate insulator. Since all process variations were performed in the same laboratory under otherwise identical conditions, the results presented here represent a true comparison of the various hardening techniques.

A method of continuously monitoring and controlling the firing of commercial barium/aluminium alloy getters has been developed for use in opaque vacuum tubes or tubes in which rf heating is not possible. The getters are fired by a unit providing a series of short incrementally increasing voltage pulses, alternating with stabilising period at a lower reference voltage, V ref , at which no evaporation takes place. The change of / ref is shown to be correlated with the degree of barium evaporation from the getter. This fact is applied to a system of continuously monitoring and controlling the firing of getters, which is capable of automation and which could form part of a tube mass production process. Tests on a large number of getters resulted in correct firing of all, with a margin of safety in hand. The implicit getter resistance increase is shown to be mainly due to inter-diffusion between the aluminum from the getter alloy and the iron of the getter sheath.

A new type of high vacuum pump has been developed which makes possible the elimination of organic vapors and high vapor pressure materials from vacuum systems, without using coolant traps or baffles. This pump utilizes the gettering action of continuously evaporated titanium in conjunction with ion pumping. Some pumping speeds achieved are: 7000–8000 liters/sec at 3×10−6 mm of Hg for hydrogen, 6500–7500 liters/sec at 1.5×10−6 mm for nitrogen and oxygen, approximately 9 liters/sec at 4×10−6 mm for argon, and approximately 4 liters/sec at 3×10−5 mm for helium. The lowest pressure obtainable is about 2×10−7 mm of Hg. Dependence of pumping speeds on the temperature of the gettering surface, the pressure and the rate of evaporation of titanium is given.

Small‐angle double‐Bragg x‐ray scattering has been used for the study of recrystallization kinetics and angular misorientation of the mosaic structure in cold‐worked nickel and iron foil. The scattering measurements showed that short time recrystallization in nickel took place by growth of initial blocks with an activation energy of 2.2 ev. The use of a getter during the vacuum anneal increased the growth rate by a factor of 1000. Angular misorientation was found to be associated with work hardening in both nickel and iron.