Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1999-06-04
2002-11-19
Huff, Mark F. (Department: 1756)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S192120, C204S192200
Reexamination Certificate
active
06482301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally related to the fabrication of recording media for use in hard disk drives, and in particular to a collimator system for use in an in-line pass-by sputtering system during the fabrication of recording media to improve the data storage density and read/write performance characteristics of the media.
2. Description of Related Art
Thin film magnetic disks and disk drives are conventionally employed for storing large amounts of data in magnetizable form. Data are written onto and read from a rapidly rotating recording disk by means of a magnetic head transducer assembly that flies closely over the surface of the disk. The escalating requirements for high areal recording density in increasingly smaller disk drives impose increasing demands on thin film magnetic recording media in terms of signal modulation, coercivity (Hr), coercivity squareness (S′), signal-to-medium noise ratio (SMNR), and the sharpness of the output signal of the medium. Considerable effort has been spent in recent years to produce magnetic recording media having higher recording densities and satisfying such demanding requirements, particularly for longitudinal recording.
Sputtering is a common process for depositing thin films onto substrate surfaces. The substrate (e.g., a glass-ceramic material) is typically a planar disk that is positioned in a vertical pallet which passes through a sputtering chamber. This is called in-line pass-by sputtering. A planar target is positioned vertically within the chamber, and spaced apart in a counterfacing relation with the substrate. The target is made of the material that is to be sputtered onto the substrate surface.
Examples of target material that are sputtered onto the substrate to form the recording media include chromium (Cr) or a Cr-containing underlayer, a cobalt (Co) or Co-containing magnetic layer, and a protective carbon (C) overcoat. There also may be a nickel aluminum (NiAl) seed layer between the underlayer and the substrate. The seed layer, underlayer, magnetic layer and overcoat are typically deposited on the substrates in the sputtering system which contains sequential deposition chambers.
Referring to
FIG. 1
, fundamentally, sputtering involves bombarding the surface of a target material
20
to be deposited as the film with electrostatically accelerated argon ions. Generally, magnetic fields are used to trap electrons in a plasma gas, causing a dense concentration of ions to impinge on the target surface. As a result of momentum transfer, atoms (
22
,
24
and
32
) are dislodged from the target surface in an area known as the erosion region. The dislodged particles follow a generally linear trajectory from their point of emission on the target surface to a collision point on the juxtaposed surface of the substrate
26
. Physical adhesion mechanisms cause the target particles to bond to the surface of the substrate, thereby forming a film on the substrate. In addition to achieving high film deposition rates, sputtering offers the ability to tailor film properties to a considerable extent.
It is extremely important in the fabrication of high density/high performance magnetic disks that the process parameters be controlled to ensure the deposited films exhibit the desired properties. However, typical sputtering systems of the type discussed above present certain problems, in that the sputtered layers may show significant crystal anisotropy and/or variations in layer thickness. When the substrate is moving in-line past a target, it is desirable that atoms impact the substrate at or near perpendicular to the surface of the substrate, such as atom
22
. However, it may happen that atoms are emitted that hit the surface of the substrate at oblique angles, such as atom
24
. Atoms which repeatedly hit the substrate at oblique angles may build upon previous atoms so that crystalline structures
28
(shown in
FIG. 2
) are formed that create shadow effects on the substrate that cut off the deposition of atoms near the crystalline structures.
The formation of the crystalline structures, as well as non-uniformity of the deposited layers in general, creates several problems. For example, such crystalline growth can result in anisotropy in the direction of disk travel through the in-line processes. Such anisotropy in the chromium underlayer and/or magnetic layer can significantly reduce storage density and read/write performance of the finished product. Anisotropy in the underlayer can disrupt the subsequent deposition of the magnetic layer in the preferred orientation. Similarly, anisotropy within the magnetic layer, among other things, can lead to a variance and reduction of the coercivity in the magnetic layer. Coercivity is a measure of the magnetic energy necessary to demagnetize a medium from its remanent magnetic state. Moreover, variations in the thickness of the sputtered magnetic layer, as well as variations in coercivity will also lead to signal modulation within the recording media. Signal modulation refers to variations in the signal received by the head during a read cycle.
Poor coercivity resulting from the formation of crystalline structures and non-uniformity of the deposited magnetic layers also adversely effects signal sharpness and signal-to-medium noise ratio. A reversal of polarization between adjacent, oppositely magnetized segments on a medium cannot happen instantaneously. Signal sharpness is a measure of how quickly or sharply this reversal of polarization takes place. Lower coercivities result in a slower and less sharp transition between oppositely magnetized segments, and consequently lower linear densities. Additionally, noise in magnetic recording media is greatest in the transition region between adjacent, oppositely magnetized segments on the media. Therefore, the large transition regions resulting from lower coercivities also increases the noise in the media and degrades the signal-to-media noise ratio.
One conventional method of controlling film deposition on the disk substrate is to locate a shield
30
within the field between the target and the substrates. The shield is preferably formed of a plurality of substantially planar surfaces of minimal thickness in the shape of a rectangular tube. With such an orientation, target atoms in substantially perpendicular paths will reach the substrate without contacting the shield, but target atoms (such as atom
32
) traveling along substantially oblique paths will contact the shield and will be blocked from reaching the substrate. &agr;
1
represents a smallest incident angle possible employing the conventional shield.
Typically, &agr;
1
is approximately 28.5 degrees. It is however a problem with the conventional shield that angles of incidence this low still allow the formation of the crystalline structures, and does not prevent non-uniformity of the deposited layers in general.
It is also possible to enhance the magnetic properties of the media and reduce the modulation by circumferential scratching or employing a high argon pressure in the chamber. However, circumferential scratching can not be used when a glass or glass-ceramic substrate is being used. Furthermore, while reducing the modulation, the high argon pressure also reduces the coercivity.
SUMMARY OF THE INVENTION
It is therefore an advantage of the present invention to provide a magnetic recording medium allowing improved storage density and performance by exhibiting a low signal modulation, a high coercivity, a high coercivity squareness, a high signal-to-medium noise ratio, and a high sharpness of the output signal.
It is a further advantage of the present invention to provide a collimator system for use in a sputter apparatus that prevents atoms from the target from depositing on the substrate at low incident angles.
It is a still further advantage of the present invention to provide a collimator system for improving storage density and performance which may be easily incorporated into existing deposition shields.
These and oth
Chen Qixu
Leu Charles
McLeod Paul Stephen
Ranjan Rajiv Yadav
Shows Mark Anthony
Chacko-Davis Daborah
Fliesler Dubb Meyer & Lovejoy LLP
Huff Mark F.
Seagate Technology Inc.
LandOfFree
Target shields for improved magnetic properties of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Target shields for improved magnetic properties of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Target shields for improved magnetic properties of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2942445