Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Patent
2000-01-05
2000-10-17
McDonald, Rodney
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
20429806, 20429817, 20429819, 335209, 335296, 335302, 335306, C23C 1435
Patent
active
061325767
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a vacuum sputtering apparatus.
Vacuum sputtering is a technique whereby very thin films of material can be deposited upon a substrate. The technique involves projecting charged particles, usually positive ions generated in a plasma under near perfect vacuum conditions, at a target so as to eject atoms of the target material therefrom. Typical operating conditions involve use of pressures of at most a few Pa. Such atoms of target material will then deposit upon a substrate at an appropriate potential which is placed in their path and will then build up as a thin layer on the substrate. The technique is widely used in the microelectronics and computer industries for production of semiconductor devices and other thin film devices, for example, magnetic read heads for computer disk drives or integrated circuit devices.
Generation of a plasma is effected by admission of one or more plasma generating gases at a controlled rate to the plasma chamber under high vacuum conditions and then applying d.c. or r.f. power thereto so as to strip electrons off the atoms of gas to form positive ions. When using d.c. power it is expedient to apply a magnetic field within the vacuum chamber so as to trap electrons in the plasma region, thereby to increase the chance of collisions between electrons and neutral atoms of the plasma in the main body of the vacuum chamber and consequent ionisation thereof. This technique is used in the magnetron electrode.
Plasma generation can be carried out using d.c. power and a magnetron electrode so long as the target electrode is electrically conductive. R.f. power can be used, with or without magnetic enchancement, when the target electrode is made of a dielectric material.
Typical gases used for plasma generation include Ar, O.sub.2, Cl.sub.2, N.sub.2, CO.sub.2, SF.sub.6, C.sub.2 F.sub.6 or a C.sub.2 F.sub.6 /CHF.sub.3 mixture.
In order to improve the uniformity of the film deposited upon the substrate, particularly when depositing thin films upon a large semiconductor wafer having, for example, a diameter of about 8 inches (about 200 mm), one proposal has been to mount a rotatable magnet device behind the target which is arranged for rotation about an axis substantially orthogonal to the target face of the target electrode. The rotatable magnet device is arranged so that a magnetic field of appropriate configuration extends over the face of the target electrode and sweeps thereover as the magnet device is rotated. In such an arrangement the rotatable magnet means typically comprises a circular, but non-axisymmetric, permanent magnet assembly; upon rotation thereof about its axis, its magnetic field sweeps over the target face and causes the plasma also to sweep thereover with a view to improving the uniformity of the sputtered film and/or the uniformity of target utilisation. However, although the results can be better when using this arrangement than in sputtering apparatus with stationary magnets, the uniformity of the deposited film still leaves something to be desired.
If a magnetic film is to be deposited on a substrate it is necessary to provide a magnetic orienting field in order to impart the desired magnetic properties to the deposited film. Distortion of the plasma can be caused by application of such a magnetic field, leading in turn to production of a non-uniform sputtered film deposit upon the substrate, besides leading to operational problems.
It has been found that the uniformity of the sputtered film is improved by increasing the size of the target with respect to the substrate upon which the sputtered film is to be deposited. it is also improved by reducing the distance between the target and the substrate.
Although the uniformity of sputtering can be improved using such a device, the geometry of the target electrode and its material of construction can affect the uniformity of the magnetic field across the target face. Accordingly it may be necessary to provide a different magnet device for different geometries of, or different materials of cons
REFERENCES:
patent: 4631106 (1986-12-01), Nakazato et al.
patent: 4746417 (1988-05-01), Ferenbach et al.
patent: 5262030 (1993-11-01), Potter
McDonald Rodney
Nordiko Limited
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