Vacuum Chamber

Fig. 3 A schematic diagram of a low-energy IAD system (5).

states, and a poor vacuum because of the gas flow through the ion gun.

A representative of the second configuration built by Kant et. al. (6) is shown schematically in Fig. 4. This system uses the high energy (25200 keV) ion beam from an implanter to bombard the growing film at a 45° angle to the normal to the substrate. Film growth rate is again measured with a quartz crystal thickness monitor and the evaporator power supply is computer controlled. Advantages of this system are a mass analyzed beam of well defined charge state and energy, a much better vacuum, and the ability to obtain ions of both gaseous elements and metals. Disadvantages are a low ion current and relatively high cost if an implanter is not available.

The dual ion gun system has been used extensively because it is the lowest cost of the three configurations. A typical system is described in the work of Cuomo et. al. (7). This system has the same advantage and disadvantages as the first system described plus it is more difficult to obtain a large uniform area of treated film.

All the above systems have the ability to independently control the ion flux, atom flux, ion energy and background pressure. By contrast it should be noted that processes which use a glow discharge to produce a plasma and then extract ions from the plasma cannot independently change the ion current, ion energy and gas pressure (8). In addition, entrapment of gas atoms and impurities in the growing film is a problem. However, film growth rates can be high and the high pressures are conducive to high "throwing power" for non-line-of-sight conditions.

Fig. 4 A schematic diagram of a high-energy IAD system (6).
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