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Optimized Planar Magnetron Sputter Deposition Source for Highly Magnetic Materials

IP.com Disclosure Number: IPCOM000043025D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 4 page(s) / 66K

Publishing Venue

IBM

Related People

Guarnieri, CR: AUTHOR [+4]

Abstract

Background Magnetron sputter deposition is used for depositing thin film coatings. Currently available commercial equipment is relatively impractical in terms of its capacity to deposit highly magnetic coatings. There are severe limitations on target shape and thickness, awkward erosion patterns or complicated design. None is of the planar magnetron configuration. The planar magnetron configuration is desirable because of its simplicity, convenience, target design, and economic advantages. Nevertheless, none of the planar magnetron sources presently available is adequate for depositing highly magnetic material, which is useful in magnetic recording and bubble memory devices.

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Optimized Planar Magnetron Sputter Deposition Source for Highly Magnetic Materials

Background Magnetron sputter deposition is used for depositing thin film coatings. Currently available commercial equipment is relatively impractical in terms of its capacity to deposit highly magnetic coatings. There are severe limitations on target shape and thickness, awkward erosion patterns or complicated design. None is of the planar magnetron configuration. The planar magnetron configuration is desirable because of its simplicity, convenience, target design, and economic advantages. Nevertheless, none of the planar magnetron sources presently available is adequate for depositing highly magnetic material, which is useful in magnetic recording and bubble memory devices. Planar Magnetron Sources It is known that in order to deposit magnetic material from a planar magnetic source, it is necessary to saturate the target that high flux permanent magnets, such as Sm-Co, are desirable, and that a permanent magnet rather than soft iron pole pieces should be placed close to the target. This is correct for non-magnetic or weakly magnetic targets, but one purpose of this article is to point out that this is wrong for the deposition of highly magnetic material. The logic embodied in the present art is that, with soft iron pole pieces, flux will "jump the gap" behind the target and not be available for magnetron action; but, with permanent magnet pole tips, the anisotropy of the permanent magnet will prevent this. See Fig. 1 for an illustration of this point. The problem with this logic is that it has overlooked the fact that for a magnetic target, the target itself is a key part of the magnetic circuit. Thus if we add the magnetic target to Fig. 1, we have the result in Fig. 2, i.e., the flux is trapped within the target in either case. Thus in order to produce magnetron action, it is necessary to supply sufficient flux to saturate the target. Clearly, one can use a sufficiently thin target to saturate the target. With conventional design, resulting targets are impractically thin. Just as clearly the two magnet arrangements are nearly equivalent. This article shows that to supply the maximum flux to saturate the target, it is necessary to have the iron pole pieces rather than the permanent magnets in contact with the target. Design Optimization Consider Figs. 1 and 2 to be cross sections of a circular planar magnetron. In order to supply sufficient flux to saturate the target out to a diameter d (creating an effective source of diameter
d) requires:

(Image Omitted)

where t is target thickness and the subscripts t and p refer to "target" and "center pole". The maximum target thickness that can be saturated is when d=do or

(Image Omitted)

Clearly, to maximize the target thickness or target area requires the ratio (4fMp/4fMt) to be maximized. Consider an approximate worst case where one desires an Fe target of maximum thickness. 4fMt = 21,000 gauss. If the c...