U.S. patent number RE32,464 [Application Number 06/854,657] was granted by the patent office on 1987-07-28 for thin film recording and method of making.
Invention is credited to Harry E. Aine.
United States Patent |
RE32,464 |
Aine |
July 28, 1987 |
Thin film recording and method of making
Abstract
A thin film of magnetic recording material is sputter deposited
over a base layer of gold and tantalum on a polished substrate. A
protective layer of gold and tantalum is deposited overlaying the
magnetic recording film. A solid lubricant layer such as carbon,
preferably in the form of graphite, gold, silver, tin, molybdenum
disulfide, and tungsten disulfide is sputter deposited or ion
plated over the protective layer to reduce wear. The recording
contacting portion of the recording head is similarly coated with a
solid lubricant material. Other suitable protective materials
include tantalum, niobium, tungsten and nitrides and carbides of
such metals. In a preferred method for making such recording
members, the layers are successively sputter deposited in an
evacuated sputter chamber, whereby the recording layers and
protective coatings are formed in a continuous process requiring
only one pump down.
Inventors: |
Aine; Harry E. (Los Altos,
CA) |
Family
ID: |
27385411 |
Appl.
No.: |
06/854,657 |
Filed: |
April 16, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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691285 |
Jan 4, 1985 |
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280844 |
Jul 6, 1981 |
4411963 |
Oct 25, 1983 |
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736814 |
Oct 29, 1976 |
4277540 |
Jul 7, 1981 |
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139887 |
May 3, 1971 |
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Reissue of: |
280844 |
Jul 6, 1981 |
04411963 |
Oct 25, 1983 |
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Current U.S.
Class: |
428/622;
204/192.15; 204/192.2; 205/159; 205/162; 205/188; 205/189; 205/922;
427/131; 427/132; 427/523; 428/457; 428/627; 428/630; 428/634;
428/656; 428/661; 428/662; 428/667; 428/672; 428/827; 428/900;
428/928 |
Current CPC
Class: |
G11B
5/725 (20130101); Y10T 428/31678 (20150401); Y10T
428/12576 (20150115); Y10T 428/12812 (20150115); Y10T
428/12778 (20150115); Y10T 428/12597 (20150115); Y10T
428/12625 (20150115); Y10T 428/12889 (20150115); Y10T
428/12854 (20150115); Y10T 428/12542 (20150115); Y10T
428/12819 (20150115) |
Current International
Class: |
G11B
5/72 (20060101); G11B 5/725 (20060101); B21D
039/00 () |
Field of
Search: |
;428/622,457,627,630,634,656,661,662,667,672,694,695,900,928
;204/56R,192C,192M,192N ;427/38,131,132,127-130 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Friedman, et al, vol. 9, No. 7, Dec. 66, IBM Tech. Dis. Bull., Lub
for Mag. Record. Medium, p. 779..
|
Primary Examiner: Pianalto; Bernard D.
Attorney, Agent or Firm: Aine; Harry E.
Parent Case Text
RELATED CASES
.[.This is a division, of application Ser. No. 736,814, filed Oct.
29, 1976, U.S. Pat. No. 4,277,540 which in-turn was a
continuation-in-part of parent application Ser. No. 139,887 filed
May 3, 1971, abandoned..].
.Iadd.This is a reissue file wrapper continuation of reissue
application Ser. No. 691,285, filed Jan. 14, 1985 (now abandoned in
favor of the present application) for reissue of U.S. Pat. No.
4,411,963 issued Oct. 25, 1983 and filed July 6, 1981 as a
divisional application Ser. No. 280,844 of application Ser. No.
736,814, filed Oct. 29, 1976 and issued as U.S. Pat. No. 4,277,540
on July 7, 1981, which in turn was a continuation-in-part of a
parent application Ser. No. 139,887 filed May 3, 1971, now
abandoned. .Iaddend.
Claims
What is claimed is:
1. In a magnetic recording medium, a substrate member, a film of
magnetic recording material overlaying said substrate, and a
protective layer of gold and tantalum overlaying said film of
magnetic recording material.
2. The recording medium of claim 1 including a lubricant layer of
carbon overlaying said protective layer.
3. The recording medium of claim 2 wherein said layer of carbon is
in the form of graphite.
4. The recording medium of claim 2 wherein said layer of carbon is
bonded to the adjacent sublayer on said substrate member.
5. The recording medium of claim 1 wherein said substrate is made
of a material selected from the class consisting of ceramic,
aluminum, and glass, said substrate having a polished surface, and
wherein said magnetic film is deposited to a thickness between 2
and 15 microinches overlaying said polished surface of said
substrate.
6. In a method for making a magnetic recording medium, depositing a
film of magnetic recording material onto a substrate member, and
depositing a layer of gold and tantalum over said film of magnetic
recording material.
7. The method of claim 6 wherein said layer of gold and tantalum is
deposited by sputtering gold and tantalum over said magnetic film
in a gaseous atmosphere at subatmospheric pressure.
8. The method of claim 6 including the step of, depositing a layer
of carbon over said layer of gold and tantalum.
9. The method of claim 8 wherein said layer of carbon is deposited
by sputtering carbon over said gold and tantalum in a gaseous
atmosphere at subatmospheric pressure.
10. The method of claim 9 wherein said carbon is sputtered from a
graphite target by ion bombardment to form a graphite layer of
carbon over said gold and tantalum.
11. The method of claim 8 wherein said layer of carbon is deposited
by ion plating carbon over said gold and tantalum layer from a glow
discharge in a gaseous atmosphere at subatmospheric pressure.
12. In a method for making a magnetic recording medium the steps
of, depositing at subatmospheric pressure a base layer of a metal
selected from the group consisting of molybdenum, titanium,
chromium, niobium, tantalum, vanadium, and tungsten overlaying a
substrate member, said substrate member comprising a material
selected from the class consisting of ceramic, aluminum and glass,
depositing at subatmospheric pressure a film of magnetic recording
material over said first layer, and depositing at subatmospheric
pressure a protective layer of material selected from the class
consisting of niobium, tantalum, and tungsten over said magnetic
recording film.
13. The method of claim 12 including the step of forming a solid
lubricating layer selected from the class consisting of carbon,
graphite, molybdenum disulfide, tin, gold, silver, and tungsten
disulfide over said protective layer.
14. The method of claim 13 wherein said base, magnetic, protective,
and lubricating layers are all deposited by sputtering said
respective materials onto said substrate from respective targets in
a gaseous atmosphere at subatmospheric pressure.
15. The method of claim 12 wherein said base, magnetic, and
protective layers are all deposited by sputtering said respective
materials onto said substrate from respective targets in a gaseous
atmosphere at subatmospheric pressure.
16. The method of claim 12 wherein said step of depositing a
protective layer comprises the step of depositing a layer of gold
and tantalum over said magnetic recording layer with the proportion
of gold in the layer increasing in a direction taken away from the
direction of the magnetic recording layer, whereby the proportion
of gold increases at the outer surface to form a lubricating
coating over a wear resistant and corrosion resistant protective
layer.
17. The method of claim 12 wherein each of said base and protective
layers comprises a layer of gold and tantalum.
18. In a method for making a recording medium, the steps of,
growing a film of recording material onto a substrate member, and
growing a protective layer of material over said film of recording
material, such protective layer being selected from the class
consisting of niobium, tantalum, tungsten, refractory carbides and
refractory nitrides.
19. The method of claim 18 including the step of anodizing the
protective layer.
20. The method of claim 18 wherein the step of growing the
protective layer comprises the step of sputter depositing said
protective layer.
21. The product made by the method of claim 18.
22. The method of claim 18 wherein said protective layer is
selected from the group consisting of silicon nitride and silicon
carbide. .Iadd.
23. In a method for protecting a magnetic recording disc of the
type having a disc-shaped substrate coated with a continuous,
non-particulate film of magnetic recording medium, the steps
of:
exciting a gaseous atmosphere at subatmospheric pressure with an
electrical discharge;
sputtering carbon within said excited gaseous atmosphere at
subatmospheric pressure; and
depositing a film of the sputtered carbon onto the coated substrate
and tightly adhering the sputtered carbon film to the coated
substrate in overlaying relationship with the film of magnetic
recording medium to form a tightly adherent wear-resistant carbon
film on the coated substrate for causing the magnetic recording
disc to be wear-resistant. .Iaddend.
.Iadd.24. The product made by the method of claim 23. .Iaddend.
.Iadd.25. The method of claim 23 wherein said wear resistant film
of carbon is deposited by sputtering carbon from a carbon target,
disposed within said gaseous atmosphere at subatmospheric pressure,
onto the substrate in overlaying relationship with said film of
magnetic recording medium. .Iaddend. .Iadd.26. The method of claim
23 including the step of adhering the carbon film directly onto a
layer of a carbide former material on the disc. .Iaddend. .Iadd.27.
In a method for protecting a magnetic recording disc of the type
having a disc-shaped substrate coated with a continuous
non-particulate film of magnetic recording medium, the steps
of:
exciting a gaseous atmosphere at subatmospheric pressure with an
electrical discharge; and
ionizing carbon within said excited gaseous atmosphere at
subatmospheric pressure; and
plating a film of the ionized carbon onto the coated substrate in
overlaying relationship with the film of magnetic recording medium
to form a tightly adherent wear-resistant carbon layer on the
coated substrate for causing the resultant magnetic recording disc
to be wear-resistant.
.Iaddend. .Iadd.28. The product made by the method of claim 27.
.Iaddend. .Iadd.29. In a method for making a magnetic recording
disc of the type having a disc-shaped, polished, aluminum
substrate, the steps of:
sputter depositing a film of chromium overlaying the substrate,
sputter depositing a film of cobalt alloy as the magnetic recording
layer and adhering the cobalt film directly to said chromium film;
and
sputter depositing a tightly adherent wear resistant film of carbon
onto the substrate in overlaying relationship with the cobalt alloy
film for causing the resultant magnetic recording disc to be wear
resistant. .Iaddend.
Description
DESCRIPTION OF THE PRIOR ART
Heretofore, thin film magnetic recording media, such as discs,
drums, tapes and the like have been manufactured by plating
extremely thin metallic films of magnetic recording material onto a
suitable substrate member. Generally speaking, the metallic
magnetic recording materials, such as iron, nickel, cobalt or
nickel-cobalt alloys are deposited to a thickness between two and
ten microinches. Such thin films are subject to corrosion in
storage and use and, thus, corrosion resistant overcoatings have
been applied to a thickness of between two and five microinches.
Corrosion resistant materials for the coatings have included
rhodium, C.sub.r O and SiO.
Such thin magnetic films have typically been deposited by a number
of different methods, such as by electrochemical deposition, auto
catalytic deposition, or vacuum deposition by evaporating the
magnetic material in an evacuated chamber and condensing the
evaporated material on the substrate. Various magnetic materials
and methods for applying same are disclosed and discussed in an
article entitled "A Critical Review of Magnetic Recording
Materials" appearing in the IEEE Transactions on Magnetics, Volume
MAG-5, #4, of December 1969, pages 821-839. And in an article
entitled "An Analysis of High-Coercivity Thin Film Fabrication
Techniques and Their Associated Properties" appearing in the
November-December 1968 issue of Electrochemical Technology, pages
419-427.
Briefly, the greatest problem in utilizing thin film magnetic
recording media is the susceptibility of magnetic recording media
to wear. The transducer normally skims between a few microns and
several microinches above the magnetic media supported by a thin
film of compressed air. Periodically the transducer sinks into
contact with the recording media resulting in a high speed impact
of the transducer with the recording media. Collisions of this
nature cause extreme wear and actual breakdown and destruction of
portions of the recording media. Wear of most thin films is usually
attributed to the breakdown of adhesion between the metal film and
the substrate.
Protective layers deposited over the recording media must be well
adhered to the media and have a greater cohesion than the metal
film on which they are deposited or they will compound the problem.
In addition, the overcoated protective layers are preferably
conductive to prevent the build up of statis electricity. The use
of lubricants to minimize the problems of wear and impact has not
been satisfactory. Such lubricants often tend to accumulate dust
and loose magnetic material on the disc or tape. Debris collected
on the transducer can cause severe damage to the magnetic material
in an avalanching effect.
The protective overcoating layers should be corrosion resistive and
electrically conductive to prevent build-up of static electric
charge. Evaporated films exhibit by far the worse wear
characteristic compared to electroless and electro plated films,
probably due to their porosity and generally poor adhesion to the
substrate.
Vacuum deposition is the least complex of the fabrication
techniques in that it is truly a one step process. However, vacuum
deposited films heretofore have had excess porosity leading to poor
wear and corrosion resistance.
Others have attempted to sputter deposit thin films of magnetic
recording material onto suitably polished substrates of glass and
fused quartz. However, as reported in U.S. Pat. No. 3,148,079
issued Sept. 8, 1964, such prior attempts at sputter depositing
magnetic films has not been successful.
SUMMARY OF THE PRESENT INVENTION
The principal object of the present invention is the provision of
an improved thin film magnetic recording medium and method of
making same.
In one feature of the present invention, the magnetic recording
film is covered with a protective coating of gold and tantalum,
whereby a protective coating is formed on the magnetic recording
film.
In another feature of the present invention, a wear resistant layer
of carbon is deposited as by sputtering .[.on.]. .Iadd.or
.Iaddend.ion plating, preferably in the form of graphite, over the
thin film of magnetic recording material to protect it from
excessive wear.
In another feature of the present invention, the surface portion of
the magnetic transducer which occasionally contacts the recording
medium is coated with an adherent solid lubricant layer of carbon
preferably in the form of graphite.
In another feature of the present invention, one or more of the
layers of the recording medium such as the magnetic recording
material, or one or more of its protective coatings, is deposited
overlaying a polished surface of the substrate by sputter
depositing the respective material over the substrate in a gaseous
atmosphere at subatmospheric pressure.
Other features and advantages of the present invention will become
apparent upon a perusal of the following specification.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A suitable substrate material such as mylar, in the case of
recording tape, or aluminum, alumina, beryllia, or glass such as
pyroceram, pyrex or the like, is lapped and polished to provide an
extremely smooth surface onto which the recording medium is to be
deposited. The substrate member is disposed in a chamber which is
evacuated to a relatively low pressure, as of 5.times.10.sup.-5
torr. Suitable diffusion pumps and/or getter ion pumps together
with liquid nitrogen forepumps and traps are utilized for the pump
down of the chamber to assure a clean vacuum and to prevent back
streaming of oil from the diffusion pumps. A quartz heating element
is placed within the chamber to provide a mild bakeout of the
substrate during pump down. After the pressure reaches
5.times.10.sup.-5 torr the quartz heaters are turned off and argon
is leaked into the chamber through an automatic leak valve to
obtain a pressure of 7.times.10.sup.-3 torr.
The evacuated chamber contains any one of a number of different rf
induced plasma sputtering electrode arrangements, such as any one
or more of those disclosed in an article entitled "Advances In
RF-Induced Plasma Sputtering" appearing in SCP and Solid-State
Technology, December, 1967, pages 45-49 and 75. In a preferred
embodiment, a plasma coil configuration of the electrodes is
employed. Such configuration of electrodes includes a pair of
target electrodes made of a material which is to be sputtered onto
the substrate. A dc bias potential is applied to the target
electrodes. Radio frequency energy is applied to a coil interposed
between the target electrodes and the substrate. The dc power
supply is used to establish a target potential which is negative
with respect to the glow discharge.
In the glow discharge, argon ions are created and they are
attracted from the plasma to bombard the target electrodes. The ion
bombardment of the target electrodes causes the target material to
be sputtered therefrom and to be collected or deposited upon the
substrate which is to be coated. The sputtered target material
arrives at the substrate with energies between 30 and 300 electron
volts. By causing the target material to be driven onto the
substrate, improved density of the deposited layer and improved
adhesion between the deposited layer and the substrate or sublayer
is obtained. Both of these characteristics, namely the improvement
in density of the layer and of the improved adhesion of the layer
to the substrate improves the wear resistance of the resultant
recording medium.
A base layer of material (primary coat) which is compatible with
the substrate is deposited up to 40 microinches in thickness,
preferably in the range of 2 to 10 microinches in thickness. The
base metal is selected from the group consisting of molybdenum,
titanium, chromium, niobium, tantalum, vanadium and tungsten, and
is preferably sputter deposited onto the polished surface of the
substrate member. During deposition, relative movement between the
substrate and the targets is obtained, as by combined rotation and
rectilinear translation of the substrate, to assure uniform
deposition of the sputtered material onto the substrate layer. The
substrate is preferably first cleaned before depositing the base
layer by sputter etching the surface, i.e. reversing the d.c. bias
potential such that the substrate becomes the target.
The magnetic recording layer is deposited over the base layer. In a
preferred embodiment, target electrodes of magnetic material are
substituted for the original targets, as by flipping over the
targets or by using other targets, for depositing a thin film of
magnetic recording material onto the base layer. For example, a
suitable magnetic material is selected from the class consisting of
iron, nickel, cobalt or alloys thereof. In a preferred embodiment a
nickel-cobalt alloy consisting of 30% nickel and 70% cobalt is
sputter deposited onto the base layer to a thickness of between 2
and 15 microinches and preferably to a thickness of approximately 5
microinches. Relative movement between the target and the substrate
is produced, as aforedescribed, to obtain uniform thickness of the
deposited layer over the surface to be coated. Alternatively, the
magnetic layer is deposited by the conventional electroless
process.
A corrosion resistant protective layer is deposited, preferably by
sputtering, over the magnetic layer to a thickness between 2 and 10
microinches and preferably approximately 5 microinches. Suitable
corrosion resistant materials include gold, tantalum, niobium,
platinum, chromium, tungsten and rhodium.
However, a corrosion resistant layer of gold and tantalum,
preferably obtained by co-sputter deposition, is especially
effective in preventing corrosion products from permeating the gold
and tantalum layer into the magnetic material. The precise
mechanism of how gold and tantalum serves to especially inhibit
corrosion and corrosion products from diffusion through the layer
to the substrate is not understood. The tantalum forms a very hard
tightly adherent wear resistant and corrosion resistant layer on
the magnetic layer. Gold infiltrates into the grain boundaries to
inhibit permeation by corrosion products, such as hydrogen. Gold
also serves as a solid lubricant on the outer surface of the gold
and tantalum layer. Sputter deposited gold, as a solid lubricant,
has increased adhesion to the tantalum and magnetic layers, thereby
reducing the tendency for the gold to agglomerate on the surface of
the recording medium.
A tantalum or tantalum and gold base layer (primary coat) is
especially advantageous with use of a tantalum or tantalum and gold
protective coating since such a base layer protects the magnetic
layer from corrosion products diffusing from the substrate into the
magnetic layer.
Alternatively, a corrosion resistant and wear resistant protective
coating is obtained by reactively sputter depositing refractory
nitrides or refractory carbides, such as nitrides or carbides of
Si, Zr, Hf, Ti, Ta, W and Nb to a thickness of between two and ten
microinches, preferably four microinches, onto the sputter etched
or cleaned magnetic layer and then stabilizing the protective layer
by growing an anodic oxide layer thereon to a thickness of
approximately one to two microinches and annealing same at
250.degree.-400.degree. C. for five hours. Such carbide and nitride
tantalum and niobium layers are anodized by an aqueous solution of
0.1% H.sub.3 PO.sub.4. Such refractory nitrides and carbides are
obtained by introducing N.sub.2 or ethane or methane into the argon
glow discharge used to sputter deposit the other constituents of
the nitride or carbide. See Electrochemical Technology,
July-August, 1968 issue, pages 269 et seq. Tungsten carbide
reactively sputter deposited, as abovedescribed, also provides a
wear resistant coating.
As aforementioned, gold provides a solid lubricant for reducing
friction and thus wear. Other solid lubricants include silver,
carbon (especially in the form of graphite), M.sub.o S.sub.2, Sn
and WS.sub.2. Such lubricants are preferably sputter deposited to a
thickness of one to five microinches over the aforedescribed
protective layer. Sputter deposition of the lubricants serves to
improve the adhesion of the lubricant to the sublayer, thereby
increasing the wear resistance of the protective coatings. Of the
solid lubricants, gold and graphite are particularly desirable.
Graphite and carbon are particularly suitable for deposition on
sublayers comprised of carbide formers such as Si, Zr, Hf, Ti, Ta,
Nb and W.
The magnetic transducer head portion which occasionally sinks into
contact with the recording medium is preferably formed of or coated
with carbon, preferably in the form of graphite, to provide a low
friction wear resistant contacting surface with the recording
medium.
As an alternative to sputter depositing the carbon onto the
sublayer, the low friction carbon layer may be formed by ion
plating according to the method disclosed in U.S. Pat. Nos.
3,329,601 or 3,386,909. The use of sputter deposition or ion
plating of the carbon coating results in a tightly adherent coating
of the carbon on the surface coated.
The advantage to the use of sputter deposition for depositing the
successive layers of materials onto the substrate member of the
recording medium is that such layers may be deposited in a one-step
method where the recording medium need only be subjected to one
pump down within the evacuated chamber. In addition, use of sputter
deposition aparatus allows the substrate surfaces and the surfaces
of subsequent layers which are to be coated to be cleaned first by
bombarding the surface to be coated with ions for cleaning away
contaminants that may be present on the surface to be coated. In
this manner tightly adherent wear resistant and relatively non
porous coatings are obtained.
* * * * *