GB736512A - Improvements in or relating to cathode sputtering apparatus - Google Patents

Abstract

736,512. Coating by sputtering. EDWARDS & CO. (LONDON), Ltd., W. Jan. 15, 1954 [Aug. 25, 1952], No. 21340/52. Class 82 (2). A cathode sputtering apparatus comprises a vacuum chamber, which may be cylindrical, a support for the work, an anode, which may be the housing, a first cathode comprising the material to be applied as a coating, a second cathode in the same general plane as the work support and shaped to surround, partially or wholly, the periphery thereof, and means providing a magnetic field the lines of force of which extend between the cathodes. As shown, a hollow cylinder 1 of copper has its lower end resting on a vacuum seal ring gasket 2 in a mild steel base-plate 4, said base-plate forming one polepiece of an electromagnet 5, the opposite polepiece comprising a mild steel annulus 6 placed on the upper end of said cylinder 1 with similar vacuum sealing. A mild steel plate 8 spans the annulus 6 and rests upon a further vacuum seal ring 9 in the upper face of the annulus, the plate 8 thus completing the second polepiece and forming a door providing access to the chamber formed by the cylinder 1, the base 4 and the annulus 6. A disc cathode 11, composed of the material to be sputtered, is secured to the door 8 by means of insulators 1 and engages, by means of a spring-metal strip 12, the upper end of a terminal rod 13, which is shielded for the greater part of its length, by a tube 15, from the anode formed by the cylinder 1. An annular cathode 16, which may be made from the same material as the disc cathode if uniformity of the deposit is not important, or from a metal which has a low intrinsic sputtering rate, e.g. aluminium, if uniformity is desired, is supported upon insulators 17 and a circular glass plate 18, forming a work-table, is supported within the annular cathode on insulators 19 carried by a stand 20 which rests on the baseplate 4. A terminal post 21 connected to the cathode 16 is supported by an insulating bushing 22 in the base-plate 4, the latter being apertured to receive an exhaust pipe 24 for connection to a vacuum pump. In operation of the apparatus, a field of 200 gauss is supplied by the magnet, the cylinder 1 is connected to the positive terminal of a D.C. source providing 1500 volts and the cathodes 11 and 16 are connected to the negative terminal, the total current being about 150 mA. and the current density 0.25 mA. per square cm. The pressure within the chamber is reduced to 0.08 mm. Hg by pumping, it being further reduced to 3.5 X 10<SP>-3</SP> mm. Hg. when the magnetic field is applied.