U.S. patent application number 10/230009 was filed with the patent office on 2003-01-02 for method for producing sputtering target with lowered oxygen content.
This patent application is currently assigned to Mitsui Mining & Smelting Co., Ltd.. Invention is credited to Ikeda, Norioki, Imamura, Masato, Kobayashi, Satoru, Sakai, Hiroyuki, Sera, Yoshihiro, Shihara, Shuji.
Application Number | 20030000068 10/230009 |
Document ID | / |
Family ID | 26584281 |
Filed Date | 2003-01-02 |
United States Patent
Application |
20030000068 |
Kind Code |
A1 |
Kobayashi, Satoru ; et
al. |
January 2, 2003 |
Method for producing sputtering target with lowered oxygen
content
Abstract
Method for producing a sputtering target with a lowered oxygen
content by providing an alloy selected from the group consisting of
NiFe, CoCrPt, CoCrPtB, CoPt, PtMn, FeAlSi, FeCo, and FeMn; adding
an oxygen scavenger element to the molten alloy selected from the
group consisting of Group 4A, 3B and 4B elements; melting the alloy
and the oxygen scavenger; reacting the oxygen scavenger element
with oxygen in the melt to reduce the oxygen content of the alloy
to a level of not more than 50 ppm and achieving a residual oxygen
scavenger element content of not more than 100 ppm.
Inventors: |
Kobayashi, Satoru;
(Tokyo-To, JP) ; Sera, Yoshihiro; (Tokyo-To,
JP) ; Ikeda, Norioki; (Tokyo-To, JP) ;
Imamura, Masato; (Tokyo-To, JP) ; Shihara, Shuji;
(Tokyo-To, JP) ; Sakai, Hiroyuki; (Tokyo-To,
JP) |
Correspondence
Address: |
Richard L. Byrne
Webb Ziesenheim Logsdon Orkin & Hanson
700 Koppers Building
436 Seventh Avenue
Pittsburgh
PA
15219-1818
US
|
Assignee: |
Mitsui Mining & Smelting Co.,
Ltd.
|
Family ID: |
26584281 |
Appl. No.: |
10/230009 |
Filed: |
August 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10230009 |
Aug 28, 2002 |
|
|
|
09768702 |
Jan 24, 2001 |
|
|
|
Current U.S.
Class: |
29/592.1 ;
423/479; 423/608; 75/392 |
Current CPC
Class: |
Y10T 29/49002 20150115;
C23C 14/3414 20130101 |
Class at
Publication: |
29/592.1 ;
423/479; 423/608; 75/392 |
International
Class: |
C22B 009/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2000 |
JP |
2000-18520 |
Sep 1, 2000 |
JP |
2000-265607 |
Claims
What is claimed is:
1. A sputtering target with a lowered oxygen content, said
sputtering target containing an oxygen scavenger comprising an
element capable of reducing metal components constituting the
sputtering target, the lowered oxygen content of the sputtering
target having been achieved by the oxygen scavenger.
2. The sputtering target with a lowered oxygen content according to
claim 1, which has an oxygen content of not more than 500 ppm,
preferably not more than 300 ppm, more preferably not more than 200
ppm, still more preferably not more than 50 ppm, still more
preferably not more than 10 ppm.
3. The sputtering target with a lowered oxygen content according to
claim 1, wherein the oxygen scavenger is at least one member
selected from the group consisting of group 4A, 3B, and 4B
elements.
4. The sputtering target with a lowered oxygen content according to
claim 1, wherein melting a starting material for a sputtering
target and/or casting the melt involving the addition of the oxygen
scavenger is carried out in a CaO crucible.
5. The sputtering target with a lowered oxygen content according to
claim 1, wherein the oxygen scavenger is at least one member
selected from the group consisting of group 4A elements.
6. The sputtering target with a lowered oxygen content according to
claim 1, wherein the oxygen scavenger is at least one member
selected from the group consisting of titanium, aluminum, boron,
and carbon.
7. The sputtering target with a lowered oxygen content according to
claim 1, wherein the oxygen scavenger is titanium.
8. The sputtering target with a lowered oxygen content according to
claim 1, wherein the sputtering target is an NiFe-base,
CoCrPt-base, CoCrPtB-base, CoPt-base, PtMn-base, FeAlSi-base,
FeCo-base, or FeMn-base target.
9. The sputtering target with a lowered oxygen content according to
claim 1, wherein the sputtering target is an NiFe-base, Co-base, or
Fe-base target with an oxygen content of not more than 10 ppm,
preferably not more than 5 ppm.
10. The sputtering target with a lowered oxygen content according
to claim 1, wherein the concentration of the residual oxygen
scavenger in the sputtering target is not more than 200 ppm,
preferably not more than 100 ppm, more preferably not more than 50
ppm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sputtering target for use
in the formation of a thin film by sputtering, and more
particularly to a sputtering target with a lowered oxygen
content.
BACKGROUND ART
[0002] A target material composed of a Co--Cr-base, Co--Ni-base, or
Co--Ni--C-base alloy has hitherto been industrially used as a
sputtering target for the formation of a thin film, such as a
magnetic film, by sputtering.
[0003] All of the Co--Cr-base, Co--Ni-base, and Co--Ni--Cr-base
alloys are rollable, and, thus, a cast ingot produced by melting
and casting can be relatively easily rolled to a predetermined
thickness.
[0004] In the sputtering targets of alloy systems as described
above, oxygen is unavoidably included in the step of the
preparation of the starting material or in the step of the
production of the target. Up to now, attention has not been always
fully paid to the presence of oxygen unavoidably included in the
alloy system and the regulation of the content of oxygen in the
alloy system.
[0005] The present inventor has found that, in the above-described
sputtering target materials for the formation of thin films, such
as magnetic films, the properties of the magnetic films,
particularly magnetic properties, are deteriorated by oxygen
unavoidably included in the alloy material system.
DISCLOSURE OF THE INVENTION
[0006] The present invention has been made with a view to solving
the above problems of the prior art, and it is an object of the
present invention to provide a sputtering target with a
significantly lowered content of included oxygen causative of a
deterioration in the properties of magnetic films.
[0007] In order to attain the above object of the present
invention, there is provided a sputtering target with a lowered
oxygen content, said sputtering target containing an oxygen
scavenger comprising an element capable of reducing metal
components constituting the sputtering target, the lowered oxygen
content of the sputtering target having been achieved by the oxygen
scavenger.
[0008] According to a preferred embodiment of the present
invention, the content of oxygen in the sputtering target is not
more than 500 ppm, more preferably not more than 300 ppm,
particularly preferably not more than 10 ppm.
[0009] According to the present invention, the oxygen scavenger is
preferably at least one member selected from the group consisting
of group 4A, 3B, and 4B elements, more preferably at least one
member selected from the group consisting of group 4A elements,
particularly preferably at least one member selected from the group
consisting of titanium, aluminum, boron, and carbon, most
preferably titanium.
[0010] According to a preferred embodiment of the present
invention, melting a starting material for a sputtering target
and/or casting the melt involving the addition of the oxygen
scavenger is carried out in a CaO crucible. In this case, the
oxygen scavenger is most preferably titanium.
[0011] The sputtering target with a lowered oxygen content
according to the present invention is applicable to an NiFe-base,
CoCrPt-base, CoCrPtB-base, CoPt-base, PtMn-base, FeAlSi-base,
FeCo-base, or FeMn-base sputtering target.
[0012] According to a preferred embodiment of the present
invention, the sputtering target is an NiFe-base, Co-base, or
Fe-base target with an oxygen content of not more than 10 ppm, more
preferably not more than 5 ppm.
[0013] According to a preferred embodiment of the present
invention, the concentration of the residual oxygen scavenger in
the sputtering target is not more than 200 ppm, preferably not more
than 100 ppm, more preferably not more than 50 ppm.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] The sputtering target with a lowered oxygen content
according to the present invention contains an oxygen scavenger
comprising an element capable of reducing metal components
constituting the sputtering target, the lowered oxygen content of
the sputtering target having been achieved by the oxygen
scavenger.
[0015] In the sputtering target with a lowered oxygen content
according to a preferred embodiment of the present invention, the
content of oxygen in the sputtering target is not more than 500
ppm, more preferably not more than 300 ppm, particularly preferably
not more than 10 ppm.
[0016] The oxygen scavenger according to the present invention is
preferably at least one member selected from the group consisting
of group 4A, 3B, and 4B elements, more preferably at least one
member selected from the group consisting of group 4A elements,
particularly preferably at least one member selected from the group
consisting of titanium, aluminum, boron, and carbon.
[0017] The sputtering target with a lowered oxygen content
according to the present invention is applicable to an NiFe-base,
CoCrPt-base, CoCrPtB-base, CoPt-base, PtMn-base, FeAlSi-base,
FeCo-base, or FeMn-base sputtering target.
[0018] According to a preferred embodiment of the present
invention, the sputtering target is an NiFe-base, Co-base, or
Fe-base target with an oxygen content of not more than 10 ppm, more
preferably not more than 5 ppm.
[0019] According to a preferred embodiment of the present
invention, the concentration of the residual oxygen scavenger in
the sputtering target is not more than 200 ppm, preferably not more
than 100 ppm, more preferably not more than 50 ppm.
[0020] The present invention will be described in more detail with
reference to the production process of the present invention.
[0021] In, the production process according to the present
invention, in vacuo, constituent metal materials for constituting a
sputtering target are melted, and the melt is then cast. The
melting-casting process per se may be carried out by a conventional
process. After casting, the cast ingot thus obtained is optionally
rolled, followed by machining (for example, cutting) to provide a
predetermined sputtering target.
[0022] The sputtering target with a lowered oxygen content
according to the present invention is applicable to an NiFe-base,
CoCrPt-base, CoCrPtB-base, CoPt-base, PtMn-base, FeAlSi-base,
FeCo-base, or FeMn-base sputtering target. According to a preferred
embodiment of the present invention, the sputtering target is an
NiFe-base, Co-base, or Fe-base target.
[0023] Preferred production processes will be described for each
type of the alloy system.
[0024] In the case of an NiFe-base alloy system, the step of
melting and casting is carried out, for example, under a vacuum of
not more than 3.times.10.sup.-4 Torr. The resultant cast ingot is
rolled at a temperature of about 1,100.degree. C. to provide a
rolled plate which is then cut to a product size, followed by
machining such as lathing or milling. Thus, a sputtering target is
produced.
[0025] In the case of a CoCrPt-base alloy system, the step of
melting and casting is carried out, for example, under a vacuum of
not more than 3.times.10.sup.-2 Torr. The resultant cast ingot is
rolled at a temperature of about 1,100 to 1,200.degree. C. to
provide a rolled plate which is then cut to a product size,
followed by machining such as lathing or milling. Thus, a
sputtering target is produced.
[0026] In the case of a PtMn-base alloy system, the step of melting
and casting is carried out, for example, under a vacuum of not more
than 3.times.10.sup.-2 Torr. The resultant cast ingot is subjected
to machining, such as lathing or milling, to produce a sputtering
target. This sputtering target is generally joined to a
predetermined backing plate.
[0027] In the sputtering target according to the present invention,
an oxygen scavenger comprising an element capable of reducing metal
components for constituting the sputtering target is added in the
step of melting and casting. A lowering in oxygen content has been
achieved by this oxygen scavenger.
[0028] The oxygen scavenger added is preferably at least one member
selected from the group consisting of group 4A, 3B, and 4B
elements, more preferably at least one member selected from the
group consisting of group 4A elements, particularly preferably at
least one member selected from the group consisting of titanium,
aluminum, boron, and carbon. According to the present invention,
the oxygen scavenger is most preferably titanium.
[0029] According to the present invention, in the step of melting
and casting, in particular, when the base metal in the melting is
iron, it is considered that the presence of an oxygen scavenger,
for example, titanium, permits the following reaction to proceed in
the molten metal: 2/3Fe.sub.2O.sub.3+Ti=TiO.sub.2+4/3Fe. TiO.sub.2
floats, on the surface of a molten metal, as dross (a scum
component of oxides) which, therefore, can be effectively
removed.
[0030] The present inventor has found that the oxygen content can
be further lowered by carrying out the step of melting
(dissolution) and/or casting in a CaO crucible. The present
inventor has further found that the use of a combination of the CaO
crucible with titanium among the above-described oxygen scavengers
can offer improved oxygen scavenging effect surpassing the expected
effect, and, at the same time, can offer desulfurization effect.
The development of this advantageous cooperative function and
effect attained by the above combination is particularly
significant in a PtMn-base sputtering target. It has hitherto been
relatively difficult to scavenge oxygen from the PtMn-base
sputtering target.
[0031] The reason why the above advantageous cooperative function
and effect can be developed has not been fully elucidated yet.
However, the reason is believed to be as follows, although the
present invention is not limited to any theory. Specifically,
TiO.sub.2 as a deoxidation product in the molten metal is absorbed
in the CaO crucible according to the following reaction
formula:
CaO+TiO.sub.2=CaO.multidot.TiO.sub.2
[0032] At that time, on the wall surface of the crucible, CaO
effectively functions to simultaneously cause a desulfurization
reaction according to the following reaction formula:
Ti+2CaO+2S=2CaS+TiO.sub.2
[0033] The amount of the oxygen scavenger added in the step of
melting and casting is properly selected according to the estimated
content of dissolved oxygen. In general, however, the amount of the
oxygen scavenger added is suitably in the range of 0.001 to 1.0% by
weight, preferably in the range of 0.001 to 0.5% by weight, more
preferably in the range of 0.001 to 0.5% by weight.
[0034] In particular, in the PtMn-base sputtering target, in
melting platinum and manganese in the CaO crucible, the addition of
titanium preferably in an amount of 0.001 to 3% by weight, more
preferably 0.01 to 0.5% by weight, based on the amount of manganese
can lower the oxygen content, for example, to not more than 50 ppm.
Further, in this case, the amount of residual titanium can be
reduced to not more than 200 ppm.
[0035] According to the present invention, the Addition of the
oxygen scavenger in the above amount range permits the content of
oxygen in the sputtering target to be regulated to not more than
500 ppm, more preferably not more than 300 ppm, particularly
preferably not more than 10 ppm. Further, in particular, in the
case of an NiFe-base, Co-base, or Fe-base sputtering target, the
oxygen content can be regulated to not more than 10 ppm, more
preferably not more than 5 ppm.
[0036] According to the present invention, the concentration of the
residual oxygen scavenger in the sputtering target after the
removal of oxygen is not more than 200 ppm, preferably not more
than 100 ppm, more preferably not more than 50 ppm. The present
inventor has found that a concentration of the residual oxygen
scavenger of not more than 100 ppm does not adversely affect the
properties of the sputtering target.
EXAMPLES
[0037] The following examples further illustrate the present
invention, but should not be construed as limiting the present
invention.
Example 1
Production of NiFe-base Sputtering Target with Lowered Oxygen
Content
[0038] Amass of nickel (5,000.0 g, 20.times.20.times.5 mm, 3N5), a
mass of iron (1,110.0 g, 15.times.15.times.5 mm, 3N5), and a piece
of titanium (1.8 g, 5.times.5.times.1 mm, 4N) (total weight 6,111.8
g; amount of titanium added 0.05% by weight) were placed in an MgO
crucible, and were then melted in a vacuum melting furnace by high
frequency melting.
[0039] The melting temperature was up to 1450.degree. C., and the
system was evacuated to not more than 3.times.10.sup.-4 Torr. About
two hr after the initiation of melting, the melt was cast in a mold
which had been previously provided (casting temperature
1360.degree. C.) to prepare an ingot having a size of
150.times.150.times.20 t.
[0040] This ingot was heated at 1100.degree. C. for one hr, and
then rolled. The rolling was carried out by four passes for one
heating, and this was repeated several times to prepare a rolled
plate having a predetermined thickness (5 to 7 mm).
[0041] A sample having a size of about 5 mm square was taken off
from the rolled plate by wire cutting, and applied to gas analysis
(non-dispersive infrared absorption analysis with dissolution in
inert gas).
[0042] As a result, for a sample on melting without the addition of
titanium, the oxygen content was 35 ppm, whereas, for the sample on
melting with the addition of titanium, the oxygen content was 2.8
ppm. The amount of titanium remaining in the sample was 60 ppm.
Example 2
Production of PtMn-base Sputtering Target
[0043] A piece of platinum (7,282.0 g, 40.times.20.times.1 mm,
3N5), a mass of manganese (2,718.0 g, 15.times.15.times.5 mm, 3N),
and a piece of titanium (5.0 g, 5.times.5.times.1 mm, 3N5) (total
weight 10,005.0 g; amount of titanium added 0.05% by weight) were
placed in an MgO crucible, and were then melted in a vacuum melting
furnace by high frequency melting.
[0044] After the evacuation of the furnace, the furnace was filled
with argon gas, and raising the temperature was initiated. The
furnace was then evacuated in argon atmosphere to not more than
3.times.10.sup.-2 Torr. About two hr after the initiation of
melting, the melt was cast in a mold which had been previously
provided (casting temperature 1430.degree. C.) to prepare an ingot
having a size of 150 .phi..times.20 t.
[0045] A sample having a size of about 5 mm square was taken off
from the ingot by wire cutting, and applied to gas analysis
(non-dispersive infrared absorption analysis with dissolution in
inert gas).
[0046] As a result, for a sample on melting without the addition of
titanium, the oxygen content was 900 ppm, whereas, for the sample
on melting with the addition of titanium, the oxygen content was
250 ppm. The amount of titanium remaining in the sample was 70
ppm.
Example 3
Production of CoCrPtTa-base Sputtering Target
[0047] A mass of cobalt (866.4 g, 20.times.20.times.5 mm, 3N5), a
mass of chromium (186.6 g, 30.times.30.times.8 mm, 3N5), a piece of
platinum (235.8 g, 40.times.20.times.1 mm, 3N5), tantalum particles
(109.2 g, 5 .times.7'6 mm, 3N5), and a piece of titanium (0.7 g,
5.times.5.times.1 mm, 3N5) (total weight 1,398.7 g; amount of
titanium added 0.05% by weight) were placed in an MgO crucible, and
were then melted in a vacuum melting furnace by high frequency
melting.
[0048] The melting temperature was up to 1450.degree. C., and the
system was evacuated to not more than 3.times.10.sup.-4 Torr. About
two hr after the initiation of melting, the melt was cast in a mold
which had been previously provided (casting temperature
1360.degree. C.) to prepare an ingot having a size of
100.times.150.times.15 t.
[0049] This ingot was heated at 1100.degree. C. for one hr, and
then rolled. The rolling was carried out by two passes for one
heating, and this was repeated several times to prepare a rolled
plate having a predetermined thickness (5 to 7 mm).
[0050] A sample having a size of about 5 mm square was taken off
from the rolled plate by wire cutting, and applied to gas analysis
(non-dispersive infrared absorption analysis with dissolution in
inert gas).
[0051] As a result, for a sample on melting without the addition of
titanium, the oxygen content was 35 ppm, whereas, for the sample on
melting with the addition of titanium, the oxygen content was 9
ppm. The amount of titanium remaining in the sample was 70 ppm.
Example 4
[0052] Sputtering targets were produced in the same manner as in
Examples 1 to 3, except that a CaO crucible was used instead of the
MgO crucible.
[0053] For the sputtering targets thus obtained, the oxygen content
was as follows, and, for all the targets, the results were
satisfactorily good.
[0054] NiFe-base target: oxygen content 3 ppm
[0055] PtMn-base target: oxygen content 40 ppm
[0056] CoCrPtTa-base target: oxygen content 5 ppm
[0057] As is apparent also from the results of the examples, the
sputtering target according to the present invention contains an
oxygen scavenger comprising an element capable of reducing metal
components constituting the sputtering target, the lowered oxygen
content of the sputtering target having been achieved by the oxygen
scavenger. Thus, the present invention can provide a sputtering
target with a lowered oxygen content which can prevent a
deterioration in properties of magnetic films caused by unavoidably
included oxygen present in an alloy material system, and, hence, is
very useful from the viewpoint of industry.
* * * * *