Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2001-01-30
2002-09-03
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192120, C204S192150, C204S298120, C204S298130, C204S298190
Reexamination Certificate
active
06444100
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for performing high-rate cathode sputtering utilizing a hollow cathode sputter source for depositing high purity thin film layers of desired physical, chemical, and/or mechanical properties. The invention has particular utility in the manufacture of magnetic or magneto-optical (“MO”) recording media comprising a layer stack or laminate of a plurality of layers on a suitable substrate, e.g., a disk-shaped substrate, wherein the layer stack or laminate includes an upper, carbon-based protective layer.
BACKGROUND OF THE INVENTION
Magnetic and MO media are widely employed in various applications, particularly in the computer industry for data/information storage and retrieval purposes. A magnetic medium in e.g., disk form, such as utilized in computer-related applications, comprises a non-magnetic substrate, e.g., of glass, ceramic, glass-ceramic composite, polymer, metal, or metal alloy, typically an aluminum (Al)-based alloy such as aluminum-magnesium (Al—Mg), having at least one major surface on which a layer stack comprising a plurality of thin film layers constituting the medium are sequentially deposited. Such layers may include, in sequence from the workpiece (substrate) deposition surface, a plating layer, e.g., of amorphous nickel-phosphorus (Ni—P), a polycrystalline underlayer, typically of chromium (Cr) or a Cr-based alloy such as chromium-vanadium (Cr—V), a magnetic layer, e.g., of a cobalt (Co)-based alloy, and a protective overcoat layer, typically of a carbon-based material having good mechanical (i.e., tribological) properties. A similar situation exists with MO media, wherein a layer stack is formed which comprises a reflective layer, typically of a metal or metal alloy, one or more rare-earth thermo-magnetic (RE-TM) alloy layers, one or more dielectric layers, and a protective overcoat layer, for functioning as reflective, transparent, writing, writing assist, and read-out layers, etc.
According to conventional manufacturing methodology, a majority of the above-described layers constituting magnetic and/or MO recording media are deposited by cathode sputtering, typically by means of multi-cathode and/or multi-chamber sputtering apparatus wherein a separate cathode comprising a selected target material is provided for deposition of each component layer of the stack and the sputtering conditions are optimized for the particular component layer to be deposited. Each cathode comprising a selected target material can be positioned within a separate, independent process chamber, in a respective process chamber located within a larger chamber, or in one of a plurality of separate, interconnected process chambers each dedicated for deposition of a particular layer. According to such conventional manufacturing technology, media substrates, typically in disk form, are serially transported, in linear or circular fashion, depending upon the physical configuration of the particular apparatus utilized, from one sputtering target and/or process chamber to another for sputter deposition of a selected layer thereon. In some instances, again depending upon the particular apparatus utilized, sputter deposition of the selected layer commences only when the substrate (e.g., disk) deposition surface is positioned in complete opposition to the sputtering target, e.g., after the disk has fully entered the respective process chamber or area in its transit from a preceding process chamber or area, and is at rest. Stated somewhat differently, sputter deposition commences and continues for a predetermined interval only when the substrate is not in motion, i.e., deposition occurs onto static substrates. In other instances, however, substrate transport, hence motion, between adjoining process chambers or areas is continuous, and sputter deposition of each selected target material occurs in a “pass-by” mode onto moving substrates as the latter pass by each cathode/target assembly.
Regardless of which type of sputtering apparatus is employed for forming the thin layer stacks constituting the magnetic recording medium, it is essential for obtaining high recording density, high quality media that each of the component layers be deposited in a highly pure form and with desired physical, chemical, and/or mechanical properties. Film purity depends, inter alia, upon the purity of the atmosphere in which the film is grown; hence films are grown in as low a vacuum as is practicable. However, in order to maintain the rate of sputtering of the various target materials at levels consistent with the throughput requirements of cost-effective, large-scale media manufacture, the amount of sputtering gas in the process chamber(s), typically argon (Ar), must be maintained at levels which generate and sustain plasmas containing an adequate amount of ions for providing sufficient bombardment and sputtering of the respective target material. The requirement for maintaining an adequate amount of Ar sputtering gas for sustaining the plasma at an industrially viable level, however, is antithetical to the common practice of applying a negative voltage bias to the substrates during sputter deposition thereon for achieving optimum film properties, such as, for example, the formation of carbon-based protective films containing a greater proportion of desirable sp
3
bonds (as in diamond), for use as protective overcoat layers in the manufacture of disk media. Contamination of the bias-sputtered films with Ar atoms occurs because the plasmas almost always contain a large number of Ar
+
ions, relative to the number of ions of the sputtered target species, which Ar
+
ions are accelerated towards the negatively biased substrate surfaces and implanted in the growing films along with the sputtered target species.
Accordingly, there exists a need for improved means and methodology for depositing, by sputtering techniques and at deposition rates consistent with the throughput requirements of automated manufacturing processing, thin films of high purity and of desired physical, chemical, and/or mechanical properties, which means and methodology overcomes the drawback associated with the apparent competing factors of the presence of a large number of ions of the sputtering gas (e.g., Ar) in the plasma and the usual application of a negative polarity substrate bias during film deposition, as described supra. More specifically, there exists a need for improved means and methodology for sputtering high purity, high quality, thin film layer stacks or laminates having optimal physical, chemical, and/or mechanical properties for use in the manufacture of single- and/or dual-sided magnetic and/or MO media, e.g., in the form of disks, which means and methodology provide rapid simple, and cost-effective formation of such media, as well as various other products and manufactures comprising at least one thin film layer.
The present invention addresses and solves compositional, throughput, and film property problems attendant upon the deposition of thin film layers by sputtering of target materials in plasmas comprising a sputter gas, which thin film deposition is utilized, inter alia, in the manufacture of high quality, thin film magnetic and/or MO recording media, while maintaining full compatibility with all aspects of conventional automated manufacturing technology therefor. Further, the means and methodology afforded by the present invention enjoy diverse utility in the manufacture of various devices and articles requiring high purity, high quality thin films with optimal physical, chemical, and/or mechanical properties.
DISCLOSURE OF THE INVENTION
An advantage of the present invention is an improved hollow cathode sputter source.
Another advantage of the present invention is an improved apparatus for sputter coating of a workpiece surface, comprising a hollow cathode sputter source.
Yet another advantage of the present invention is an improved method of coating over a workpiece, utilizing a hollow cathode sputter source.
Still another advantage
Seagate Technology LLC
VerSteeg Steven H.
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