Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2001-06-25
2002-09-24
Diamond, Alan (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298190, C204S298210, C204S298140, C204S298080, C204S298070, C204S298260, C204S298200, C204S298160, C204S298090, C204S298180, C204S298220
Reexamination Certificate
active
06454920
ABSTRACT:
SUMMARY OF THE INVENTION
This invention relates to a magnetron sputtering source, a vacuum chamber and for such source and a vacuum coating system.
In essence the present invention is based on the need for depositing on large-surface, in particular rectangular substrates with an area of at least 900 cm
2
, a film having a homogenous thickness distribution, by means of sputter coating, in particular also reactive sputter coating. Such substrates are in particular used in the manufacture of flat panels, normally on glass substrates thinner than 1 mm, such as for TFT panels or plasma display panels (PDP).
When magnetron sputter coating large surfaces, even larger sputter surfaces and consequently larger targets are normally required unless the sputtering source and the substrate are moved relative to each other. However, this results in problems with respect to
(a) uniformity of the process conditions on the large-surface target, with particular severity in reactive sputter coating
(b) erosion profile
(c) cooling
(d) strain on the large targets, in particular through atmospheric pressure and coolant pressure.
In order to solve the mechanical strain problem (d) relatively thick target plates have to be used which in turn reduces the magnetic penetration and consequently the electron trap effect for a given electrical input power. If the power is increased this results in cooling problems (c), in particular because elaborate methods are needed for achieving good contact between the target and the cooling medium, and also because of the obstruction resulting from the installations on the back for accommodating the magnets. It is also known that in magnetron sputtering, be it reactive or non-reactive, the target arrangement normally consisting of a sputtering area defining target plate made of the material to be sputtered and a bonded mounting plate, the target is sputter eroded along so-called “race tracks”. On the sputter surface one or several circular erosion furrows are created due to the tunnel-shaped magnet fields applied to the target along specific courses, which produce circular zones with elevated plasma density. These occur due to the high electron density in the area of the tunnel-shaped circular magnetron fields (electron traps). Due to these “race tracks” an inhomogenous film thickness distribution occurs already on relatively small-surface coating substrates arranged in front of the magnetron sputtering source. In addition the target material is inefficiently utilized because the sputter erosion along the “race tracks” removes little material from target areas outside these tracks which results in a wave-shaped or furrow-shaped erosion profile. Because of these “race tracks” the actually sputtered surface even of a large target is small relative to the substrate surface. For eliminating the effect of said “race tracks” on the coating it would be possible to move the sputtering source and the substrate to be coated relative to each other, as mentioned above, however, this results in a lower deposition rate per unit of time. If locally higher sputtering power is used, cooling problems are incurred in systems using relative motion.
In trying to achieve the desired goal basically four complexes of problems (a), (b), and (c), (d) are encountered whose individual solutions aggravate the situation with respect to the others; the solutions are mutually contradictory.
The objective of the present invention is to create a magnetron sputtering source through which said problems can be remedied, that can be implemented in practically any size, and that is capable of economically achieving a homogenous coating thickness distribution on at least one large-surface substrate that is stationary relative to the source. In addition to maintaining highly uniform process conditions the source shall be suitable for sensitive reactive processes with high deposition or coating rates. In reactive processes, inhomogenous “race track” effects lead to known, severe problems due to the large plasma density gradients.
This is achieved by the magnetron sputtering source according to the present invention in which at least two, preferably more than two, electrically isolated long target arrangements are placed parallel to each other at a distance that is significantly smaller than the width of the target arrangement, where each target arrangement has its own electrical connections, and where in addition an anode arrangement is provided. The targets of the target arrangements have preferably rounded corners, following the “race track” paths.
On such a magnetron sputtering source according to the invention with independently controllable electrical power input to the individual target arrangements, the film thickness distribution deposited on the substrate located above can already be significantly improved. The source according to the invention can be modularly adapted to any substrate size to be coated.
With respect to the overall arrangement the anode arrangement can—unless it is temporarily formed by the target arrangements themselves—be located outside the overall arrangement but preferably comprises anodes that are installed longitudinally between the target arrangements and/or on the face of the target arrangement, but particularly preferred longitudinally.
Also preferred is a stationary magnetron arrangement on the source; the latter is preferably formed by a magnet frame that encircles all the target arrangements, or is preferably implemented with one frame each encircling each target arrangement. Although it may be feasible and reasonable to implement the magnets on the frame(s), or on the stationary magnet arrangement at least partially by means of controllable electric magnets, the magnets of the arrangement or the frame are preferably implemented with permanent magnets.
Through a corresponding design of said stationary magnet arrangement, preferably the permanent-magnet frames with respect to the magnet field they generate on the immediately adjacent target arrangement, the aforementioned film thickness distribution on the substrate and the utilization efficiency of the long targets can be further enhanced through specific shaping of “race tracks”.
Magnet arrangements are provided preferably below each of the at least two target arrangements. These may be locally stationary and be fixed over time in order to create the tunnel shaped magnet field on each of the target arrangements. Preferably they are designed in such a way that they cause a time-dependent variation of the magnet field pattern on the target arrangements. With respect to the design and the generation of the magnet field pattern on each of the target arrangements according to the invention, we refer to EP-A-0 603 587 or U.S. Pat. No. 5,399,253 of the same application, whose respective disclosure content is declared to be an integral part of the present description.
According to
FIG. 2
of EPO-A-0 603 587 the location of the magnet pattern and consequently the zones of high plasma density can be changed as a whole, but preferably it is not changed, or changed only insignificantly, whereas according to
FIGS. 2 and 3
of said application the location of the apex—the point of maximum plasma density—is changed.
For changing the location of the zones or the apex on the magnet arrangements, selectively controlled electric magnets—stationary or movable—can be provided below each of the target arrangements, but far preferably this magnet arrangement is implemented with driven movable permanent magnets.
A preferred, moving magnet arrangement is implemented with at least two magnet drums arranged longitudinally below the driven and pivot bearing mounted target arrangements, again preferably with permanent magnets as illustrated, for an individual target, in
FIGS. 3 and 4
of EP-A-0 603 587.
The magnet drums are driven with pendulum motion with a pendulum amplitude of preferably ≦&tgr;/4. With respect to this technique and its effect we again refer fully to said EP-A-0 603 587 or U.S. Pat. No. 5,399,253 respectively which also in
Grunenfelder Pius
Haag Walter
Krassnitzer Siegfried
Schlegel Markus
Schwendener Urs
Diamond Alan
Notaro & Michalos P.C.
Unaxis Trading AG
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