GB1010456A - Means for measuring and/or controlling the evaporation rate in vacuum evaporation processes - Google Patents

Abstract

<PICT:1010456/C6-C7/1> <PICT:1010456/C6-C7/2> <PICT:1010456/C6-C7/3> In a vapour deposition process using an electron beam emitter to evaporate the source material, the rate of evaporation is controlled by regulating the current through the emitter according to the ionization current resulting from the evaporation, the ionization current being registered by a vapour ion electrode exposed to part of the evaporant stream. A residual ion electrode outside the path of the evaporant stream registers the background ionization current and the electrodes are mounted in an assembly comprising an earthed shielding electrode 1, residual ion electrode 2 and a vapour ion electrode 3 insulated by spacers 4, 5 and 6. A collimator tube 7 passes through electrodes 1 and 2 and shields the residual ion electrode from the evaporant. The electrode assembly is mounted on pillars 10 in a vacuum chamber between the source material and the substrate and an electron beam emitter 25 vaporizes the source material, the vapour material passing through the tube 7 and aperture 18 in the vapour ion electrode 3 which thus acquires a positive charge. As shown in Fg. 4 the difference in the outputs of the vapour ion and residual ion electrodes is amplified at 21 and fed to a controller meter 22 which indicates the rate of evaporation and/or opertes pre-set relays to actuate motor 23 of transformer 24 which controls the current input to the emitter 25. Alternatively (Fig. 5, not shown) the output from 21 may be applied to a saturable reactor which controls the source temperture at constant high tension. Timing mechanisms may also be incorporated in the control gear. An alternative arrangement of the electrode assembly is also described (Fig. 6, not shown).