Apparatus for coating a substrate

Details Apparatus for coating a substrate Apparatus for coating a substrate

1996-10-22

2001-01-02

McDonald, Rodney G. (Department: 1753)

Chemistry: electrical and wave energy

Apparatus

Coating, forming or etching by sputtering

C204S298230, C204S298240, C204S298260, C204S298070, C204S298080, C204S298190, C204S298110, C204S192120

Utility Patent

active

06168698

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention pertains to an AC sputtering apparatus for a pair of targets mounted on respective magnetron cathodes.
DD 252205 discloses a sputtering apparatus for the production of thin layers including a system of magnets and at least two electrodes carrying the material to be sputtered above the magnets. These electrodes are arranged electrically to alternate between being the cathode and the anode of a gas discharge. For this purpose, the electrodes are connected to a source of alternating, sine-wave voltage of preferably 50 Hz.
This known sputtering apparatus is said to be especially suitable for the deposition of dielectric layers by reactive sputtering. The goal of operating the apparatus at about 50 Hz is to prevent formation of tinsel at the anode and also to prevent electrical short-circuits (so-called arcs) when coating is being carried out with metal.
U.S. Pat. No. 4,943,363 discloses an apparatus for depositing a thin film by sputtering, in which the rate at which the layers of different materials are deposited can be controlled so that extremely thin layer packages can be produced, by providing at least two different types of counterelectrodes on the cathode side.
DE 35 41 621 discloses apparatus for the deposition of a metal alloy by means of HF sputtering in which two targets are driven in alternation. The targets contain the metal components of the metal alloy to be deposited but in different proportions. The substrates are for this purpose mounted on a substrate carrier, which is rotated by a drive unit during the sputtering process.
DE 38 02 852 discloses an apparatus for the coating of a substrate with two electrodes and at least one material to be sputtered, in which the substrate to be coated is mounted between and a certain distance away from the two electrodes, and in which the alternating current half-waves are selected to have essentially the same amplitudes.
DE 41 06 770 discloses a method and an apparatus for the reactive coating of a substrate with an electrically insulating material such as silicon dioxide (SiO
2
). The apparatus includes a source of alternating current, which is connected to cathodes. The cathodes enclose magnets and are mounted in a coating chamber. The cathodes work together with targets, and each of the two ungrounded outputs of the a.c. power source is connected to one of the cathodes carrying one of the targets. The two cathodes are installed next to each other in the coating chamber in a plasma space, and each of them is approximately the same distance away from the substrate facing it. The effective value of the discharge voltage is measured by an effective voltage value measuring device connected by a line to the cathode, and the signal is sent as a direct voltage over a line to a controller. The controller drives a control valve in such a way as to adjust the flow rate of reactive gas from the tank into the distribution line so that the measured voltage agrees with the nominal voltage.
Finally, DE 42 04 999 discloses an apparatus for coating a substrate especially with nonconductive layers from electrically conductive targets in a reactive atmosphere, in which a power source is connected to the cathodes. The cathodes enclose magnets and are installed in an evacuatable coating chamber. The cathodes interact electrically with the targets. Two anodes, separated electrically from each other and from the sputtering chamber, are installed on a plane between the cathodes and the substrate. Each of the two outputs of the secondary winding of a transformer connected to a medium-frequency generator is connected to one of the cathodes by way of a power supply line. The first and second supply lines are connected to each other by a branch line, into which an oscillatory circuit, preferably a coil and a capacitor, is inserted. Each of the two supply lines is connected to the coating chamber by way of a first electric element, which adjusts the direct voltage potential with respect to ground; to the associated anode by way of a corresponding second electric element; and also to the coating chamber by way of a branch line with an inserted capacitor. A choke coil is inserted into the section of the first supply line which connects the oscillatory circuit to the second terminal of the secondary.
SUMMARY OF THE INVENTION
Whereas the known apparatuses deal with the problem of “arcing”, that is, with the problem of preventing the formation of undesirable arcs and of protecting the surface of the target from the formation of insulating layers, the object of the present invention is not only to increase the stability of the sputtering process but also to make it possible to control the uniformity of the layer thicknesses. In addition, the apparatus according to a specific embodiment is also be designed in such a way that it can be conditioned extremely quickly, which means that any water which may be wetting the inside surfaces of the chambers, inserts, and targets can be efficiently removed.
According to the present invention, each of the two outputs of the a.c. power source is connected to a cathode by a power supply line, and each of the two cathodes is installed in its own, separate compartment, included among a plurality of adjacent compartments, which together form a vacuum chamber and which are connected to each other by a passageway. The two compartments holding the cathodes are either immediately adjacent to each other or are separated from each other by one or more additional compartments.
In a particular embodiment, one of the poles of the alternating current source is connected to one of the cathodes, while the other pole is connected to the other cathode, in both cases by way of power supply lines. Each of the two cathodes, furthermore, is installed in its own compartment, which is included among a plurality of adjacent compartments, which together form a vacuum chamber and which are connected to each other by a passageway. The two compartments holding the cathodes connected to the a.c. power source are separated from each other by one or more compartments, at least some of which are equipped with their own sputter cathodes.


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