U.S. patent application number 10/886943 was filed with the patent office on 2005-03-03 for vacuum arc evaporation apparatus and method, and magnetic recording medium formed thereby.
Invention is credited to Nagata, Naruhisa.
Application Number | 20050045472 10/886943 |
Document ID | / |
Family ID | 34209736 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050045472 |
Kind Code |
A1 |
Nagata, Naruhisa |
March 3, 2005 |
Vacuum arc evaporation apparatus and method, and magnetic recording
medium formed thereby
Abstract
In a vacuum arc evaporation apparatus, to stably maintain vacuum
arc discharge at an arc source when depositing a cathode material
on a substrate, namely a magnetic recording medium, an ungrounded
anode of a coil-type tube is placed inside an arc source discharge
vacuum chamber. A DC arc power supply is connected between the
cathode and the anode to cause an arc current to flow in the anode
to generate a first magnetic field in one direction, from the
cathode toward the anode. A second magnetic field is generated in
the opposite direction, from the anode to the cathode by feeding a
specified current to an external coil positioned around the
discharge chamber. The external coil includes an around-cathode
coil and an around-anode coil. The arc discharge can be started by
operating a striker to carry out the deposition.
Inventors: |
Nagata, Naruhisa; (Nagano,
JP) |
Correspondence
Address: |
ROSSI & ASSOCIATES
P.O. Box 826
Ashburn
VA
20146-0826
US
|
Family ID: |
34209736 |
Appl. No.: |
10/886943 |
Filed: |
July 8, 2004 |
Current U.S.
Class: |
204/192.38 ;
204/298.41 |
Current CPC
Class: |
H01J 37/3266 20130101;
H01J 37/32055 20130101 |
Class at
Publication: |
204/192.38 ;
204/298.41 |
International
Class: |
C23C 014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2003 |
JP |
2003-272059 |
Claims
What is claimed is:
1. A vacuum arc evaporation apparatus comprising: a deposition
vacuum chamber; a discharge unit that discharges an arc of an
ungrounded cathode target to form a cathode-material plasma; and a
plasma guiding unit disposed between the deposition vacuum chamber
and the discharge unit for guiding the cathode-material plasma to
the deposition vacuum chamber by an induced magnetic field to
deposit the cathode target on the substrate, wherein the discharge
unit comprises an electrically grounded discharge vacuum chamber, a
first generating unit provided inside the discharge vacuum chamber
to generate a first magnetic field, and a second generating unit
provided around the discharge vacuum chamber to generate a second
magnetic field, wherein the ungrounded cathode target is located in
the discharge vacuum chamber.
2. The vacuum arc evaporation apparatus according to claim 1,
wherein the ungrounded cathode target is positioned away from the
plasma guiding unit and the first generating unit is positioned
between the plasma guiding unit and the cathode target.
3. The vacuum arc evaporating apparatus according to claim 2,
wherein the first magnetic field extends substantially along a
first direction, and the second magnetic field extends
substantially along a second direction, which is substantially
opposite to the first direction.
4. The vacuum arc evaporation apparatus according to claim 2,
wherein the first direction extends substantially along a direction
extending substantially from the cathode target toward the first
generating unit, and the second direction extends substantially
along a direction extending substantially from the first generating
unit toward the cathode target.
5. The vacuum arc evaporation apparatus according to claim 1,
wherein the first generating unit is an electrically ungrounded
coil-type anode provided along the inside of the discharge vacuum
chamber, and the direction of the center axis of the coil-type
anode is substantially parallel with the direction from the cathode
target to the first generating unit.
6. The vacuum arc evaporation apparatus according to claim 1,
wherein the second generating unit is a coil provided along the
outside of the discharge vacuum chamber, and the direction of the
center axis of the coil is substantially parallel with the
direction from the cathode target to the first generating unit.
7. The vacuum arc evaporation apparatus according to claim 1,
wherein the discharge vacuum chamber has a tubular shape and is
provided with an insulating material between the inner surface of
the discharge vacuum chamber and the first generating unit.
8. The vacuum arc evaporation apparatus according to claim 1,
further including a cooling unit for preventing the cathode target,
the first generating unit, and the discharge vacuum chamber from
being overheated by the arc discharge.
9. The vacuum arc evaporation apparatus according to claim 1,
wherein the deposition material is carbon.
10. The vacuum arc evaporation apparatus according to claim 1,
wherein the substrate has a magnetic recording layer.
11. The vacuum arc evaporation apparatus according to claim 10,
wherein the carbon is deposited on the magnetic recording layer to
form an overcoat layer having a tetrahedral amorphous carbon
structure with a high hardness.
12. A method of depositing a film on to substrate, with a vacuum
arc evaporation apparatus comprising: a deposition vacuum chamber;
a discharge unit that discharges an arc of an ungrounded cathode
target to form a cathode-material plasma; and a plasma guiding unit
disposed between the deposition vacuum chamber and the discharge
unit for guiding the cathode-material plasma to the deposition
vacuum chamber by an induced magnetic field to deposit the cathode
target on the substrate, wherein the discharge unit comprises an
electrically grounded discharge vacuum chamber, a first generating
unit provided inside the discharge vacuum chamber to generate a
first magnetic field, and a second generating unit provided around
the discharge vacuum chamber to generate a second magnetic field,
wherein the ungrounded cathode target is located in the discharge
vacuum chamber, the method comprising steps of: evacuating the
deposition vacuum chamber containing a substrate; generating the
cathode material plasma by arc discharging the cathode target with
the discharge unit; and depositing the cathode target on the
substrate by guiding the cathode material plasma to the deposition
vacuum chamber with the plasma guiding unit.
13. The method according to claim 12, wherein the deposition
material is carbon.
14. The method according to claim 12, wherein the substrate has a
magnetic recording layer and the cathode material is deposited on
the magnetic layer as an overcoat layer.
15. The method according to claim 14, wherein the deposition
material is carbon to form the overcoat layer having a tetrahedral
amorphous carbon structure with a high hardness.
16. A magnetic recording medium formed by depositing the overcoat
layer on the substrate with the magnetic layer according to the
method of claim 14.
17. A magnetic recording medium formed by depositing the carbon on
the substrate with the magnetic layer according to the method of
claim 15.
18. A magnetic recording medium formed by the apparatus of claim
10.
19. A magnetic recording medium formed by the apparatus of claim
11.
Description
BACKGROUND
[0001] A diamond-like carbon (DLC) film, formed of carbon, is
suitable for a wear or abrasive resistant layer of a magnetic
recording medium because it has an excellent surface smoothness and
a high hardness. Such a hard coating has been typically formed via
a sputtering method, a plasma CVD method, or a vacuum arc
evaporation method. FIG. 1 illustrates an example of an arrangement
of a filtered cathodic arc (FCA) evaporation apparatus currently
used in a vacuum arc evaporation method.
[0002] In the example of the arrangement in FIG. 1, a cathode
material plasma P is generated at an arc source Sa. With the use of
a magnetic filter 10, the plasma P is guided as a cathode material
plasma beam Pb to a substrate 13, which is held in a deposition
vacuum chamber 14 having a shutter 19. The magnetic filter 10 has a
stainless steel pipe 11 bent in a quarter circular-arc-shape as a
core, on which an electromagnet coil 12 is provided. Between the
magnetic filter 10 and the deposition vacuum chamber 14, a raster
coil 18 is provided. With this arrangement, a film of cathode
material ions can be formed on the substrate 13. When carbon
(graphite) is used as the cathode material or target in the vacuum
arc evaporation apparatus, the formed film has a tetrahedral
amorphous carbon (ta-C) structure, containing no hydrogen, but rich
in sp.sup.3 bond carbon, with a high hardness.
[0003] At the arc source Sa in the above arrangement, with the
deposition material taken as a cathode target 16, a vacuum arc
discharge is induced between the cathode target 16 and an anode 17
by contacting a striker 15 with the surface of the cathode target
16 to thereby generate the cathode material plasma P. However, with
this arrangement, it is difficult to stably maintain the arc
discharge. Moreover, another problem is that a cathode spot of the
discharge circumvents the cathode target 16, making it difficult to
discharge the cathode material plasma beam Pb toward the desired
direction.
[0004] Examples of an arrangement of the arc source Sa are
disclosed in JP-A-2002-32907 and JP-A-2002-88466. To stably
maintain arc discharge in the above arrangements, specialized
arrangement of the arc source and the method of generating the arc
discharge must be considered. Furthermore, in the arrangement
disclosed in the latter reference, it is difficult to provide a
cooling mechanism for the magnetic material.
[0005] Accordingly, there is a need for a vacuum arc evaporation
apparatus or method provided with a vacuum arc discharge unit that
can stably maintain vacuum arc discharge at an arc source. The
present invention addresses this need.
SUMMARY OF THE INVENTION
[0006] The present invention relates to a vacuum arc evaporation
apparatus, a vacuum arc evaporation method, and a magnetic
recording medium formed thereby. In particular, to a vacuum arc
evaporation apparatus and a vacuum arc evaporation method that can
be used for forming a hard coating of a wear resistant material or
an abrasive resistant material on a magnetic recording medium as an
overcoat layer.
[0007] One aspect of the present invention is the vacuum arc
evaporation apparatus. It can include a deposition vacuum chamber,
a discharge unit, and a plasma unit. The discharge unit discharges
an arc of an ungrounded cathode material or target to form a
cathode-material plasma. The plasma guiding unit is disposed
between the deposition vacuum chamber and the discharge unit and
guides the cathode-material plasma to the deposition vacuum chamber
by an induced magnetic field to deposit the cathode target on the
substrate. The discharge unit can include an electrically grounded
discharge vacuum chamber, which contains the ungrounded cathode
target therein, a first generating unit provided inside the
discharge vacuum chamber to generate a first magnetic field, and a
second generating unit provided around the discharge vacuum chamber
to generate a second magnetic field.
[0008] The ungrounded cathode target is positioned away from the
plasma guiding unit and the first generating unit is positioned
between the plasma guiding unit and the cathode target. The first
magnetic field can extend substantially along a first direction,
and the second magnetic field can extend substantially along a
second direction, which is substantially opposite to the first
direction. The first direction can extend substantially in a
direction from the cathode target toward the first generating unit,
and the second direction can extend substantially in the opposite
direction of the first direction, namely from the first generating
unit toward the cathode target.
[0009] The first generating unit can be an electrically ungrounded
coiled or coil-type anode disposed along the inside of the
discharge vacuum chamber, and the direction of the center axis of
the coil-type anode can be substantially parallel with the
direction from the cathode target to the first generating unit. The
second generating unit can be a coil provided along the outside of
the discharge vacuum chamber, and the direction of the center axis
of the coil can be substantially parallel with the direction from
the cathode target to the first generating unit.
[0010] The discharge vacuum chamber can have a tubular shape and
can be provided with an insulating material between the inner
surface of the discharge vacuum chamber and the first generating
unit. The apparatus can include a cooling unit for preventing the
cathode target, the first generating unit, and the discharge vacuum
chamber from being overheated by the arc discharge.
[0011] The deposition material can be carbon. The substrate can
include a magnetic recording layer. When the carbon is deposited on
the magnetic recording layer, it forms an overcoat layer having a
tetrahedral amorphous carbon structure with a high hardness.
[0012] Another aspect of the present invention is the method of
depositing a film on to a substrate, with the above-described
vacuum arc evaporation apparatus. The method comprises the steps of
evacuating the deposition vacuum chamber containing the substrate,
generating the cathode material plasma by arc discharging the
cathode target with the discharge unit, and depositing the cathode
target on the substrate by guiding the cathode material plasma to
the deposition vacuum chamber with the plasma guiding unit.
[0013] Another aspect of the present invention is a magnetic
recording medium formed by depositing the overcoat layer on the
substrate with the magnetic layer according to the above-described
method.
[0014] Another aspect of the present invention is a magnetic
recording medium formed by the above-described apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates an example of an arrangement of a
currently used vacuum arc evaporation apparatus.
[0016] FIG. 2 illustrates a principal part of an embodiment of a
vacuum arc evaporation apparatus according to the present
invention.
DETAILED DESCRIPTION
[0017] The present vacuum arc evaporation apparatus can include a
deposition vacuum chamber 14, a discharge unit Sa for discharging
arc from a cathode target 2, which is made of a deposition material
for depositing on a substrate disposed in the deposition vacuum
chamber, and a plasma guiding unit 10 disposed between the
deposition vacuum chamber and the discharge unit for guiding the
cathode material plasma generated by the arc discharge to the
deposition vacuum chamber by an induced magnetic field, which can
be generated by feeding a current to a coil of the plasma guiding
unit, to deposit the cathode target on the substrate.
[0018] Referring to FIG. 2, the discharge unit can include an arc
source discharge vacuum chamber 1 containing the cathode target 2.
The discharge vacuum chamber is electrically grounded while the
cathode target 2 is electrically ungrounded and made of the
deposition material. An anode 3, which is also electrically
ungrounded, can be provided as a first generating unit, which can
be arranged between the cathode target 2 and the plasma guiding
unit 10 to generate a first magnetic field by feeding a current for
the arc discharge. The discharge unit can include a unit or means
for supplying power for the arc discharge, a unit or means for
starting the arc discharge, and a unit or means for generating a
second magnetic field as a second generating unit provided around
the discharge vacuum chamber. The unit for generating a magnetic
field generates the second magnetic field in the discharge vacuum
chamber in the direction substantially opposite to the direction of
the first magnetic field generated by the anode. This stably
maintains the vacuum arc discharge at the arc source when carrying
out deposition.
[0019] Note that FIG. 2 illustrates an arrangement of a principal
part of an embodiment of a vacuum arc evaporation apparatus
according to the present invention. The other part (the part on the
left side of a magnetic filter 10 shown in phantom) of the vacuum
arc evaporation apparatus can have the same arrangement as that
shown in FIG. 1. According to the present apparatus, the arc source
Sa can be a cylindrical stainless pipe with an outer diameter of 76
mm and an inner diameter of 70 mm as a main body of the discharge
vacuum chamber 1, which is electrically grounded. The cathode
target 2 of the arc source Sa can be a cylindrical graphite
(carbon) at a purity of 99.999% with a diameter of 30 mm and a
length of 30 mm, disposed inside the discharge vacuum chamber 1,
while being isolated (not electrically grounded). The cathode
target or cathode 2 can be connected to a DC arc power supply Es2.
An anode 3 can be a copper tube in having a diameter of 4 mm formed
in a coil configuration with a length 1 of a winding portion being
60 mm and the number of winding of 9 turns, disposed inside the
discharge vacuum chamber 1, while being isolated (not electrically
grounded). The anode 3 is connected to a DC arc power supply Es2.
An arc current flowing in the coil-type anode 3 generates a
magnetic field substantially in the direction A toward the anode 3
from the cathode 2.
[0020] Still referring to FIG. 2, a striker 4 is provided together
with a striker power supply Es1. The striker 4 is in the ground
potential and is provided for starting the arc discharge by
contacting the surface of the cathode 2. The cathode 2, the anode
3, and the discharge vacuum chamber 1 can be cooled, such as with a
cooling fluid or liquid, i.e., water, to prevent overheating when
the arc discharge is carried out. For example, copper tubes 5a, 5b
can be used to circulate water to cool the anode 3. The copper tube
5a also can be used to connect the anode 3 to the DC arc power
supply Es2. Cooling liquid also can be circulated through cooling
spaces 6a and 6b for cooling the arc source vacuum chamber 1.
Around the arc source vacuum chamber 1, a Helmholtz-coil-type
external coil, which includes an around-cathode coil 7 and an
around-anode coil 8, for generating a magnetic field in the
discharge vacuum chamber 1 is formed. Furthermore, between the
inner peripheral surface of the arc source vacuum chamber 1 and the
anode 3, an insulator 9, such as quartz glass, is disposed.
[0021] The magnetic filter 10 (similarly arranged to that shown in
FIG. 1) can be an electromagnetic coil with a quarter circular-arc
stainless steel pipe, having an outer diameter of 76 mm, an inner
diameter of 70 mm and a radius of curvature of 300 mm, taken as a
core, on which a polyester covered copper wire having a diameter of
2 mm is wound. The number of turns per unit length of the winding
of the electromagnetic coil can be 1000 turns/m.
[0022] The vacuum arc deposition apparatus according to the present
invention has the magnetic filter 10 and the arc source Sa provided
independently of each other. Therefore, the magnetic field
generated by the magnetic filter 10 exerts no adverse effect on the
maintenance of the arc discharge. In other word, enhancement of
transport efficiency of the plasma and maintenance of the plasma
discharge can be independently controlled to make it possible to
stably maintain the vacuum arc discharge at the arc source for
carrying out excellent deposition.
[0023] Examples of the vacuum arc evaporation method, carried out
by using the vacuum arc evaporation apparatus with the above
arrangement, will be explained below.
[0024] In the first Example, a magnetic field along a first
direction (in the direction of A) is generated at the coil-type
anode 3 at about 0.02 T, and an arc discharge was started by
operating the striker 4 with a magnetic field of about 0.002 T
generated between the cathode 2 and the anode 3 in the direction
toward the cathode 2 from the anode 3 (opposite to the first
direction A) by feeding a specified current to both the
around-cathode coil 7 and the around-anode coil 8 of the
Helmholtz-coil-type external coil. The arc voltage and current were
30V and 120 A, respectively. After the arc discharge was started by
operating the striker 4, even though the voltage of the striker
power supply Es1 was then turned off, the arc discharge was stably
maintained between the cathode 2 and the anode 3. Furthermore, no
cathode spot of the discharge went around the cathode target 2 to
allow the carbon plasma to be guided by the magnetic filter 10 to
the deposition chamber 14. Thus, a tetrahedral amorphous carbon
film can be deposited for a desired time on a substrate to be
coated (not shown) in the deposition chamber.
[0025] In the second Example, with the apparatus shown in FIG. 2, a
test was carried out with a magnetic field of about 0.001 T
generated between the cathode 2 and the anode 3 in the direction
toward the cathode 2 from the anode 3 (opposite to the direction A)
by feeding a current only to the around-cathode coil 7 or to the
around-anode coil 8 included in the Helmholtz-coil-type external
coil. The other conditions were the same as those in the first
Example. In all of the cases, after the arc discharge was started
by operating the striker 4, even though the voltage of the striker
power supply Es1 was then turned off, the arc discharge was stably
maintained between the cathode 2 and the anode 3. Furthermore, no
cathode spot of the discharge went around the cathode target 2 to
allow the carbon material plasma to be guided by the magnetic
filter 10 to the deposition chamber (not shown). Thus, the
tetrahedral amorphous carbon film can be deposited for a desired
time on the substrate to be coated (not shown) in the deposition
chamber.
[0026] In the first Comparative Example, in the apparatus shown in
FIG. 2, a test was carried out with no current fed to any of the
around-cathode coil 7 and the around-anode coil 8 of the
Helmholtz-coil-type external coil. The other conditions were the
same as those in the first Example. Here, although arc discharge
was started by operating the striker 4, however, when the voltage
of the striker power supply Es1 was turned off, the arc discharge
stopped.
[0027] In the second Comparative Example, in the apparatus of FIG.
2, a test was carried out with current fed to both and one of the
around-cathode coil 7 and the around-anode coil 8 of the
Helmholtz-coil-type external coil, but with the magnetic field
generated in the direction toward the anode 3 from the cathode 2
(in the direction A). The other conditions were the same as those
in the first Example. Here, in all of the respective cases of
feeding current to both of the around-cathode coil 7 and the
around-anode coil 8, to only the around-cathode coil 7, and to only
the around-anode coil 8, even the starting of the arc discharge was
not possible by operating the striker 4.
[0028] In the third Comparative Example, in the apparatus of FIG.
2, a test was carried out with the magnetic field generated by
feeding current to the Helmholtz-coil-type external coil so that
the magnetic field generated by the around-cathode coil 7 and the
magnetic field generated by the around-anode coil 8 are in the
opposite directions, namely toward each other or away from each
other. The other conditions were the same as those in the first
Example. Here, in all of the cases, although arc discharge was
started by operating the striker 4, however, when the voltage of
the striker power supply Es1 was turned off, the arc discharge
stopped.
[0029] In the third Example, with a vacuum arc deposition method of
the first or second Example a disk with a magnetic recording layer
was disposed in the deposition vacuum chamber, and an overcoat
layer was formed on the disk, by which a magnetic recording medium
can be manufactured. The overcoat layer formed this way used
graphite (carbon) as the cathode material to therefore permit a
formation of a film of a tetrahedral amorphous carbon containing no
hydrogen, but rich in sp.sup.3 bond carbon and having a high
hardness.
[0030] Given the disclosure of the present invention, one versed in
the art would appreciate that there may be other embodiments and
modifications within the scope and spirit of the present invention.
Accordingly, all modifications and equivalents attainable by one
versed in the art from the present disclosure within the scope and
spirit of the present invention are to be included as further
embodiments of the present invention. The scope of the present
invention accordingly is to be defined as set forth in the appended
claims.
[0031] The disclosure of the priority application, JP 2003-272059,
in its entirety, including the drawings, claims, and the
specification thereof, is incorporated herein by reference.
* * * * *