Vacu u m news
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Important Notice to Readers For further information on any matter mentioned in Vacuum News, tear out and post one of the reader enquiry service cards. Readers in the USA should use the cards addressed to New York; all other readers are requested to use the cards addressed to London. Contents Technical and industrial developments
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PlasmaVac sputtering unit - - electron-beam evaporator ultra-high-vacuum c h a m b e r - ultra-high-vacuum bakeable flanges-- high-vacuum p u m p s - - new production process for s e m i c o n d u c t o r s - pedal bin for vacuum insulated containers
Commercial news
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National Research Development Corporation
International meeting
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European Standard of Nuclear Electronics Committee
Technical and industrial developments PlasmaVae sputtering unit for thin-tilm deposition A n economic breakthrough of major importance is forecast for the micro-electronics, optical and other thin-film industries as a result of the introduction of a new vacuum coating technique. The technique involves the use of a commercial low-energy sputtering unit, known as PlasmaVac, which is being introduced into the U K by the Consolidated Vacuum Corporation (a division of Bell & Howell Limited). PlasmaVac is claimed by its manufacturers to offer the thin-film industries the first real chance to increase product yields to a level that will make the films available for large-scale use in conventional products such as household appliances, radio and TV, and electrical systems of cars. It is basically a triode sputtering system offering many advantages over deposition equipment in which diode sputtering or conventional evaporation is utilised. It may be operated at pressures as low as 10 -~ torr and guarantees precision control over factors most affecting yields and costs, deposition rate, thickness uniformity and compositional control. A broad range of materials are claimed to be successfully deposited. A m o n g these are: beryllium- copper and aluminium for use as conductors; tantalum, tungsten and nichrome for resistor applications; permalloy for inductors can be sputtered directly; and silicon and germanium semiconductors. The deposition rate is said to be constant throughout the fabrication period and the thickness uniformity can be controlled to within 1 per cent over a 1 × 1-in substrate. Reactive sputtering in atmospheres other than argon is possible. Unique features that contribute to improved film quality and reproducibility are claimed for the PlasmaVac. Its arrangement of filament, anode, and target elements (see Figure 1), combined with controlled gas flow, offer a completely controllable and repeatable method of sputtering. The PlasmaVac unit has separated the conventional diode sputtering plasma formation and sputtering functions to permit greater control of film thickness t h a n that achieved with diode sputtering. The sputtering rate is determined by the material, the voltage of the target a n d the current, which are individually
fe and (furnished )mer)
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Figure 1. Schematic diagram of installed bell-jar components of the PlasmaVac system. controlled and monitored. A greater uniformity of film thickness is also said to be obtained. Film contamination by residual gases is lower in the PlasmaVac sputtering unit because of the lower normal operating pressure (10 -3 torr). The PlasmaVac has two target power supplies. Two materials may be sputtered simultaneously, and, if required, one source can be a material such as titanium, which is sputtered only for its gettering action during the deposition process. Sequential sputtering is also possible. 371
Vacuum news The PlasmaVac unit is an accessory package designed for use with most standard evaporators. Figure 3 shows the unit installed in CVC's type CV-18 system. The PlasmaVac is easy to install and the package contains all the necessary components except for special fixtures. Consolidated Vacuum Corporation (a division o f Bell • Howell), Rochester, N Y, U S A Ch'cle number 64 on Reader Enquh'y Service card
Figure 2. Source material (at right) can be placed within three inches of the substrate and mask with the new PlasmaVac. Because of the separation of the plasma formation and sputtering operations, substrates can be cleaned by the plasma, before sputtering takes place, in order to improve adherence further. Metal or semiconductor substrates can he cleaned by applying a potential and sputtering the surface for more effective cleaning. Since material is sputtered from the entire surface of the target and follows cosine distribution, through-hole coating may be obtained by simultaneously sputtering two sources on opposite sides of a thin substrate. Cylinders can also be coated by sputtering, from a rod placed along the central axis for the inside and from a hollow cylinder with the required diameter for the outside. Other curved surfaces may also be coated. The low power input of the unit permits attainment of a given deposition rate with minimum heating of the target and substrate.
Figure 3. PlasmaVac low-energy sputtering unit installed in a CV-18 system. 372
Electron-beam evaporator A new electron gun for evaporating materials under vacuum is Consolidated Vacuum Corporation's Electron Beam Evaporator, type AEB-2. This gun is a triode type with a tungsten filament serving as the source of electrons. The grid acts as a lens to combine and direct the electrons; the anode, held at ground potential, accelerates the electrons t o increase their kinetic energy. An electromagnetic coil focuses the beam at a specific distance from the exit aperture of the gun. The distance to the point of focus can be altered by adjusting the current to the coil. Thus the size of the spot where the focused electron beam strikes the stationary evaporant material can be increased or decreased. The AEB-2 package is claimed to satisfy a wide spectrum of electron beam evaporation requirements. It consists of an electronbeam gun, a control package, and a power supply package, all designed and produced by CVC to provide a matched system that has the greatest possible utility. The gun can be installed inside or outside the vacuum chamber and can be located above or below the substrate. The same gun can perform multiple evaporations of the same material or different materials (including refractory metals, dielectrics and oxides) during a single vacuum cycle. CVC's electron beam gun is claimed to offer flexibility of operation. Power density, spot size and spot position are individually controlled by the operator; each is adjustable throughout a broad range. The deposition rate is variable, and extremely high rates are possible with most materials. When evaporations are made with the AEB-2 the evaporant can be loaded in an amount sufficient to form its own crucible. There are normally no filaments, boats, crucibles, etc, which might serve as a source of contamination in the production of high-purity films. The possibility of contamination is further reduced by using only the highest grade material in the construction of the electron-beam gun. The low operating voltage (10 kV) of the AEB-2 system eliminates the X-ray hazard. Additional protection is provided by a safety switch installed in the vacuum chamber; which disconnects the gun from the power supply when the chamber is at atmospheric pressure, and by interlocks which cut off the power when the cover is removed from either of the power-supply cabinets. The AEB-2 electron-beam gun requires no water cooling and has a standard CVC high-vacuum flange attachment. It is supplied with all the fasteners required to connect it to a matching flange on a metal chamber or feed-through ring. It can be easily installed in any position in a vacuum chamber. The long-life filament can be quickly and easily replaced. Consolidated Vacuum Corporation, Rochester, N Y , USA Circle number 65 on Reader Enquiry Service card
Ultra-high-vacuum chamber A new ultra-high-vacuum chamber, CVU-18, manufactured by the Consolidated Vacuum Corporation is claimed to be a complete, integrated unit that operates in the 4 × 10 -l° to 1 x 10-3 torr range. It has an initial pump down to 1 × 10 -9 torr from atmosphere in 21 hours and cycles from atmosphere down to 1 × 10 -9 torr in 3~: hours after the initial pump down. It has an ultimate pressure in the low 10 -1° torr region (after overnight bakeout). The unit has been designed expressly for ultra-high-vacuum applications and incorporates time-proven CVC components and the accumulated knowledge of 25 years in the vacuum field. The CVU-18, it is claimed, is especially useful for space simulation, vapour deposition, materials analysis, solid-state research and various similar applications.