Processing Equipment

Laboratory. Most of the IBAD systems that exist in government, industry, and university laboratories are designed for sample sizes with diameters less than 30 mm (1.2 in.). These facilities are able to perform depositions on a small scale for limited batch sizes.

One common means of fabricating an IBAD system is to utilize commercially available electron-beam-source "box coaters" that are capable of large-area, high-volume coating applications and then modify them to accept commercially available low-energy, high-current ion guns of various designs. Deposition rates are determined by the electron-beam-source evaporation rate and the required arrival ratio of ions to atoms for a particular coating. When the required arrival ratios are between 0.1 and 1.0, the maximum current of a Kaufman-type ion gun (~1 mA/cm2) translates into deposition rates of about 40 to 4 pm/h (100 A/s to 10 A/s), respectively, for a system based on an electron beam source.

Production. Many applications require large areas to be coated. Linear ion guns are made with lengths up to 1000 mm (40 in.) and widths of 20 mm (0.8 in.), whereas circular-aperture ion guns have diameters ranging from 10 to 380 mm (0.4 to 15 in.). Systems that can handle workpieces with a 1 m (40 in.) diameter have been built. In nonoptical applications, where film uniformity is not as strict a requirement, very large areas could be coated using existing equipment by the routine manipulation of the workpieces.

Even larger surface areas can be handled by using continuous coating schemes. The primary obstacle to scale-up is the requirement of line-of-sight processing, especially for odd-shape parts. Cylinders can easily be coated, but it is not yet clear whether complex shapes, like gear teeth, can be uniformly and reliably coated. Figure 3(a) shows a scheme developed for the large-area, high-volume deposition of optical films, which could be adapted easily for sheet-metal applications (Ref 13). Figure 3(b) depicts a prototype large-area, high-volume system used for sheet steel (Ref 14), which will be discussed later.

Fig. 3 Two methods used for large-area, high-volume implementation of ion-beam-assisted-deposition. (a) For optical films. (b) For steel sheet

Dual-ion-beam-assisted deposition (DIBS) systems, which utilize ion-beam sputter deposition, are also commercially available for use on substrates that are up to 120 mm (4.7 in.) in diameter. Some of these units are used for semiconductor applications, as well as for nonelectronic applications, such as the deposition of molybdenum disulfide films for friction reduction. In the case of sputter deposition, maximum deposition rates depend on the material to be deposited and are considerably less than for systems based on an electron beam. Ion-beam-sputtering systems are particularly suited to highly controlled, thin-film, multilayer coating applications, where up to six different sputtering targets can be sequentially moved into the sputter target position. High-quality, multilayer x-ray mirrors; laser mirrors; metallic multilayers; and other products have been manufactured using this method.

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