High substrate bias sputtering underlayer for longitudinal...

Details High substrate bias sputtering underlayer for longitudinal... High substrate bias sputtering underlayer for longitudinal...

1998-11-09

2001-03-27

Kiliman, Leszek (Department: 1773)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C428S428000, C428S336000, C428S690000, C428S690000, C428S900000, C204S192200, C427S128000, C427S129000, C427S130000, C427S131000

Reexamination Certificate

active

06207269

ABSTRACT:

This application contains subject matter related to subject matter disclosed in copending U.S. patent application Ser. No. 09/188,678, filed on Nov. 10, 1998, now pending.
TECHNICAL FIELD
The present invention relates to magnetic recording media, such as thin film magnetic recording disks, and to a method of manufacturing the media. The present invention has particular applicability to high areal density magnetic recording media exhibiting low noise, high remanent coercivity and high coercivity squareness.
BACKGROUND ART
The requirements for increasingly high areal recording density impose increasingly greater demands on thin film magnetic recording media in terms of remanent coercivity (Hr) , magnetic remanance (Mr) , Mr times thickness (Mrt), coercivity squareness (S*) , medium noise, i.e., signal-to-noise ratio (SNR), and narrow track recording performance. It is extremely difficult to produce a magnetic recording medium satisfying such demanding requirements.
The linear recording density can be increased by increasing the coercivity of the magnetic recording medium. However, this objective can only be accomplished by decreasing the medium noise, as by maintaining very fine magnetically non-coupled grains. Medium noise is a dominant factor restricting increased recording density of high density magnetic hard disk drives. Medium noise in thin films is attributed primarily to inhomogeneous grain size and intergranular exchange coupling. Accordingly, in order to increase linear density, medium noise must be minimized by suitable microstructure control.
A conventional longitudinal recording disk medium is depicted in FIG.
1
and comprises a substrate
10
, typically an aluminum (Al) or an (Al)-alloy, such as an Al-magnesium (AlMg) alloy, plated with a layer of amorphous nickel-phosphorous (NiP). Alternative substrates include glass, ceramic, silicon, plastics, glass-ceramic materials, as well as graphite. There are typically sequentially sputter deposited on each side of substrate
10
an adhesion enhancement layer
11
,
11
′, e.g., chromium (Cr) or a Cr alloy, a seedlayer
12
,
12
′, such as NiP, an underlayer
13
,
13
′, such as Cr or a Cr alloy, a magnetic layer
14
,
14
′, such as a cobalt (Co)-based alloy, and a protective overcoat
15
,
15
′, such as a carbon-containing overcoat. Typically, although not shown for illustrative convenience, a lubricant topcoat is applied on the protective overcoat
15
,
15
′.
It is recognized that the magnetic properties, such as Hr, Mr, S* and SNR, which are critical to the performance of a magnetic alloy film, depend primarily upon the microstructure of the magnetic layer which, in turn, is influenced by the underlying layers, such as the underlayer. It is recognized that underlayers having a fine grain structure are highly desirable, particular for growing fine grains of hexagonal close packed (HCP) Co alloys deposited thereon.
As the requirements for high areal recording density escalate it becomes increasingly more important to provide high recording signals and low medium noise. Consequently, it is necessary to develop thin film structure fabrication techniques which favorably affect the microstructure, surface orientation and grain structure of the deposited films. Previously, efforts have been made to obtain suitable thin film media with advantageous magnetic performance and recording performance by varying the materials employed for the seedlayer, underlayer or buffer layer for longitudinal magnetic recording media. The epitaxial growth of a magnetic material on such layers imparts a certain crystallographic structure which results in certain magnetic properties.
Different sputtering conditions also impact the resulting magnetic proprieties, including substrate heating, varying the film thickness, and altering the re-sputtering gas and pressure. Such sputtering conditions alter the energies of the sputtered atoms and, hence, alter the growth mechanism of the films, as by thermal diffusion, crystallization and lattice matching or expansion. A substrate bias of about 100 to about 250 volts has been applied during thin film deposition. The application of a substrate bias would also increase sputtering on the grown films, further altering the surface morphology as well as crystallographic structure, thereby influencing the magnetic performance of the resulting media.
There exists a continuing need for simplified methodology enabling the fabrication of high areal recording density magnetic recording media exhibiting a high Hr, high S* and high SNR.
DISCLOSURE OF THE INVENTION
An object of the present invention is a magnetic recording medium for high areal recording density exhibiting low noise, high Hr and S*.
Another object of the present invention is a method of manufacturing a magnetic recording medium for high areal recording density exhibiting low noise, high Hr and high S*.
Additional objects, advantages and other features of the present invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following only to be learned from the practice of the present invention. The objects and advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the foregoing and other objects are achieved by a magnetic recording medium comprising a non-magnetic substrate; a chromium manganese (CrMn) underlayer on the substrate; and a magnetic layer on the underlayer.
Another aspect of the present invention is a magnetic recording medium, the method comprising: sputter depositing an underlayer on a non-magnetic substrate while applying a substrate bias greater than about 300 volts; and depositing a magnetic layer on the underlayer.
Additional objects and advantages of the present invention will become readily apparent to those having ordinary skill in the art from the following detailed description, wherein the embodiments of the present invention are described, simply by way of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various other respects without departing from the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.


REFERENCES:
patent: 5800931 (1998-09-01), Lee
patent: 5851628 (1998-12-01), Ohkubo
patent: 5922456 (1999-07-01), Tonahashi
patent: 5968679 (1999-10-01), Kobayashi
patent: 5993956 (1999-11-01), Lambeth
patent: 6010795 (2000-01-01), Chen
patent: 6022609 (2000-02-01), Gao
patent: 6077603 (2000-06-01), Zhang

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