U.S. patent application number 12/997043 was filed with the patent office on 2011-05-05 for cylindrical sputtering target and process for producing the same.
This patent application is currently assigned to Tosoh Corporation. Invention is credited to Kenichi Itoh, Tetsuo Shibutami, Kimiaki Tamano, Shigehisa Todoko.
Application Number | 20110100808 12/997043 |
Document ID | / |
Family ID | 41416766 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110100808 |
Kind Code |
A1 |
Todoko; Shigehisa ; et
al. |
May 5, 2011 |
CYLINDRICAL SPUTTERING TARGET AND PROCESS FOR PRODUCING THE
SAME
Abstract
Provided is a cylindrical ceramic sputtering target, which
significantly reduces the occurrence of a crack, a chip,
extraordinary discharge and a nodule. By filling a molten bonding
material in a cavity defined by a cylindrical ceramic target
material and a cylindrical base material, starting cooling the
molten bonding material from its one end toward its other end in a
cylindrical axial direction in sequence, and further filling the
molten bonding material in the cavity during cooling, a cylindrical
ceramic sputtering target is manufactured so as to be characterized
in that as observed by an X-ray radiograph of the bonding material,
the total area of portions where no bonding material exists is 10
cm.sup.2 or less per 50 cm.sup.2 of X-ray radiograph area, and the
maximum area of the portions where no bonding material exists is 9
cm.sup.2 or less.
Inventors: |
Todoko; Shigehisa;
(Minato-ku, JP) ; Tamano; Kimiaki; (Ayase-shi,
JP) ; Itoh; Kenichi; (Ayase-shi, JP) ;
Shibutami; Tetsuo; (Ayase-shi, JP) |
Assignee: |
Tosoh Corporation
|
Family ID: |
41416766 |
Appl. No.: |
12/997043 |
Filed: |
June 9, 2009 |
PCT Filed: |
June 9, 2009 |
PCT NO: |
PCT/JP2009/060553 |
371 Date: |
December 9, 2010 |
Current U.S.
Class: |
204/298.13 ;
264/237 |
Current CPC
Class: |
C23C 14/086 20130101;
C23C 14/3407 20130101; H01J 37/3426 20130101; H01J 37/3491
20130101; C23C 14/081 20130101; C23C 14/3414 20130101 |
Class at
Publication: |
204/298.13 ;
264/237 |
International
Class: |
C23C 14/06 20060101
C23C014/06; C23C 14/34 20060101 C23C014/34; B29C 71/00 20060101
B29C071/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2008 |
JP |
2008-152061 |
Claims
1. A cylindrical ceramic sputtering target comprising a bonding
material filled in a cavity defined by a cylindrical ceramic target
material and a cylindrical base material, wherein as observed by an
X-ray radiograph of the bonding material, the total area of
portions where no bonding material exists is 10 cm.sup.2 or less
per 50 cm.sup.2 of X-ray radiograph area, and the maximum area of
the portions where no bonding material exists is 9 cm.sup.2 or less
and wherein the volume ratio of the bonding material at 25.degree.
C. that is filled in the cavity is at least 96.8% with respect to
the volume of the cavity at the melting point of the bonding
material.
2. (canceled)
3. The target according to claim 2, wherein the volume ratio is at
least 98%.
4. The target according to claim 2, wherein the volume ratio is at
least 100%.
5. The target according to claim 1, wherein the bonding material is
In, an In alloy, Sn or a Sn alloy.
6. The target according to claim 1, wherein the cylindrical ceramic
target material comprises ITO or AZO.
7. A process for producing the target recited in claim 1,
comprising filling a molten bonding material in a cavity, starting
cooling the molten bonding material from its one end toward its
other end in a cylindrical axial direction in sequence, and further
filling the molten bonding material in the cavity during
cooling.
8. The method according to claim 7, further comprising supplying
the molten boding material from an end opposite the one end in the
cylindrical axial direction where cooling starts.
9. The method according to claim 7, further comprising filling the
molten bonding material by supplying, during cooling, the molten
bonding material from a bonding material supply portion to store
the molten bonding material.
10. The method according to claim 7, further comprising vibrating
the molten bonding material filled in the cavity when or after
filling the boding material in the cavity.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cylindrical sputtering
target used in a magnetron rotary cathode sputtering apparatus etc,
and a process for producing the same.
BACKGROUND ART
[0002] A magnetron rotary cathode sputtering apparatus has a
magnetic field-generating device on the inside of a cylindrical
sputtering target and is designed to carry out sputtering while
cooling from the inside of the target and rotating the target, and
the entire surface of the target material undergoes erosion and is
uniformly shaved off, whereby it is possible to obtain a remarkably
high target utilization ratio (at least 60%) as compared with the
utilization ratio (from 20 to 30%) of a conventional planar
magnetron sputtering apparatus. Further, by rotating the target, it
is possible to input a large power per unit area as compared with a
conventional planar magnetron sputtering apparatus, whereby a high
film deposition rate can be obtained (see Patent Document 1).
[0003] As the process for producing a ceramic target used in a
magnetron rotary cathode sputtering apparatus, there have known,
e.g. a process for forming a target layer on an outer peripheral
side of an cylindrical base material by a plasma spray method (see
Patent Document 2), and a process for filling powder in an outer
peripheral side of an cylindrical base material, and forming and
bonding a target by a hot isostatic press (HIP) (see Patent
Document 3).
[0004] However, an arc spray method and an HIP method not only
require an expensive apparatus to carry out these methods and a
large operating cost, but also are uneconomical since a cylindrical
base material is made integrally with a cylindrical target
material, making it difficult to reuse the cylindrical base
material. Further, these methods are likely to be subjected to
peeling or cracking attributable to the difference in the thermal
expansion coefficient between both materials.
[0005] As the process for producing a ceramic target at a low cost,
it has been strongly desired to develop a process for bonding a
separately produced cylindrical target material made of a ceramic
sintered body by means of a bonding material, such as a solder
material. Such a desired process has advantages of, e.g. being
capable of obtaining a quality film and a high production yield
since a ceramic sintered body having a high density is usable in
comparison with an arc spray method and an HIP method. As the
process for producing a cylindrical ceramic sputtering target by
means of a solder material, there has been known a process for
sealing one end of each of a cylindrical target material and a
cylindrical base material and introducing the cylindrical base
material into the cylindrical target material with a solder
material in a molten state being put therein (see Patent Document
4).
[0006] However, this method has caused a decrease in volume
attributable to a phase change of the solder material from a liquid
state to a solid state, and a decrease in volume attributable to
cooling from the melting point of the solder material to normal
temperature, whereby the occurrence of bonding layer defect
attributable to such a decrease in volume has made thermal
conduction poor, has caused a crack and a chip, or has generated
extraordinary discharge due to poor electrical conduction in some
cases. Further, this method has produced a needle-like protrusion
called a nodule during sputtering, whereby extraordinary discharge
is generated or particles are produced in some cases. For example,
in a case where the solder material is made of generally used In,
the volume decreases by 2.7% when the solder material is solidified
at 156.6.degree. C., the volume decreases by 1.2% when the solder
material is cooled from 156.6.degree. C. to 25.degree. C., and the
volume finally decreases by 3.9%. It should be noted that such a
cylindrical ceramic target material generally has a smaller thermal
expansion coefficient than a cylindrical base material. For this
reason, when a bonding material is cooled from its melting point to
normal temperature, the volume of a cavity defined by a cylindrical
ceramic target material and a cylindrical base material is
increased to causes bonding defects beyond expectation based on
such a decrease in volume of the above-mentioned solder material
made of In. These phenomena are not problematic in a conventional
planar sputtering target since even if the volume of the bonding
material is deceased, the distance between the planar target
material and the planar base material is made narrower accordingly.
These phenomena have a problem inherent to a cylindrical sputtering
target because of being caused only in such a cylindrical
sputtering target. Such a cylindrical sputtering target has been
liable to cause a problem of a crack, a chip, extraordinary
discharge and a nodule attributable to bonding layer defect since a
larger power per unit area is input as compared with such a planar
sputtering target.
[0007] As a method for inspecting the bonded state of a ceramic
material or a metal material when such a material is bonded by
means of a bonding material, there has been known a method for
applying an X-ray to one side of an object to be measured,
detecting a transmitted X-ray on the other side and determining the
presence and absence of a bonding material based on a difference in
X-ray absorption in respective parts of the object to be measured.
No review has been made on whether the above-mentioned problem
inherent to a cylindrical sputtering target, i.e. the occurrence of
a crack, a chip, extraordinary discharge and a nodule is relevant
to the state of a bonding layer in the cylindrical sputtering
target, which is assumed not to be identified by the other
methods.
PRIOR ART REFERENCE
[0008] Patent Document
[0009] Patent Document 1: JP-A-58-500174
[0010] Patent Document 2: JP-A-05-222527
[0011] Patent Document 3: JP-A-05-230645
[0012] Patent Document 4: Japanese Patent No. 3618005
SUMMARY OF THE INVENTION
Object to be Accomplished by the Invention
[0013] It is an object of the present invention to provide a
cylindrical ceramic sputtering target, which significantly reduces
the occurrence of a crack, a chip, extraordinary discharge and a
nodule, and a process for producing the same.
Means to Accomplish the Object
[0014] The present inventors have conducted an extensive study to
accomplish the above-mentioned object. As a result, they have
accomplished the present invention based on the finding that it is
possible to significantly reduce the occurrence of bonding layer
defect by filling a molten bonding material in a cavity defined by
a cylindrical ceramic target material and a cylindrical base
material, starting cooling the molten bonding material from its one
end toward its other end in a cylindrical axial direction in
sequence, and further filling the molten bonding material in the
cavity.
[0015] Further, the inventors have conducted an extensive study,
focusing attention on the relationship between the occurrence of a
crack, a chip, extraordinary discharge and a nodule, and the state
of a bonding layer in a cylindrical sputtering target, which is
identified by means of an X-ray radiograph. As a result, they have
accomplished the present invention based on the finding that it is
possible to significantly reduces the occurrence of a crack, a
chip, extraordinary discharge and a nodule by controlling, in a
sputtering target including a bonding layer formed by solidifying a
molten bonding material, the total area of portions where no
bonding material exists and the maximum area of the portions where
no bonding material exists, the total area and the maximum area
being observable by an X-ray radiograph.
[0016] The present invention provides a cylindrical ceramic
sputtering target, which has a bonding material filled in a cavity
defined by a cylindrical ceramic target material and a cylindrical
base material, characterized in that as observed by an X-ray
radiograph of the bonding material, the total area of portions
where no bonding material exists is 10 cm.sup.2 or less per 50
cm.sup.2 of X-ray radiograph area, and the maximum area of the
portions where no bonding material exists is 9 cm.sup.2 or
less.
[0017] The present invention also provides a process for producing
a cylindrical ceramic sputtering target, which has a bonding
material filled in a cavity defined by a cylindrical ceramic target
material and a cylindrical base material, characterized in that the
process includes filling a molten bonding material in the cavity,
starting cooling the molten bonding material from its one end
toward its other end in a cylindrical axial direction in sequence,
and further filling the molten bonding material in the cavity
during cooling.
EFFECTS OF THE INVENTION
[0018] In accordance with the present invention, it is possible to
provide a cylindrical sputtering target, which significantly
reduces the occurrence of a crack, a chip, extraordinary discharge
and a nodule. By employing the target according to the present
invention, it is possible to attain film deposition in a
transparent conductive film etc. with a high target utilization
ratio and with a high film deposition rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view of a cylindrical sputtering
target according to the present invention, taken along a plane
containing the central axis thereof.
MODE FOR CARRYING OUT THE INVENTION
[0020] Now, the present invention will be described in detail.
[0021] In the target according to the present invention, the cavity
defined by a cylindrical ceramic target material and a cylindrical
base material means a portion indicated by reference numeral 3 in
FIG. 1, where a bonding material is filled therein.
[0022] The X-ray radiograph of the bonding material according to
the present invention is taken for the purpose of inspecting defect
in the bonding material. For example, the X-ray radiograph may be
taken by applying an X-ray from outside a cylindrical sputtering
target by means of an X-ray irradiation system, and recording an
image on a radiographic film affixed on an inner side of the
cylindrical base material. A plurality of radiographic films may be
used to record images, taking into account the curvature of the
cylindrical sputtering target.
[0023] In an X-ray radiograph of the bonding material, the total
area of portions where no bonding material exists may be found by
various kinds of methods. In particular, it is preferred in terms
of simplicity and accuracy that a taken X-ray radiograph be
recorded in a digital format, and a commercially available image
analysis software be employed for image analysis.
[0024] The cylindrical ceramic sputtering target according to the
present invention is characterized in that the total area of
portions where no bonding material exists is 10 cm.sup.2 or less
per 50 cm.sup.2 of X-ray radiograph area. By reducing the defect in
a bonding layer to such a value, it is possible to reduce the
occurrence of a crack, a chip and extraordinary discharge etc.
attributable to poor thermal conduction or poor electrical
conduction. The total area is preferably 2 cm.sup.2 or less per 50
cm.sup.2 of X-ray radiograph area, more preferably 1 cm.sup.2 or
less per 50 cm.sup.2 of X-ray radiograph area.
[0025] In the X-ray radiograph of the bonding material, the maximum
area of the portions where no bonding material exists may be
measured in a similar way by the above-mentioned method. The
cylindering sputtering target according to the present invention is
characterized in that the maximum area of the portions where no
bonding material exists is 9 cm.sup.2 or less as observed by an
X-ray radiograph. By reducing the maximum area of the defect in the
bonding layer to such a value, it is possible to reduce the
occurrence of a crack, a chip, extraordinary discharge etc. due to
poor thermal conduction or poor electrical conduction attributable
to the defect. The maximum area of the portions where no bonding
material exists is preferably 1 cm.sup.2 or less. In the present
invention, when a single cylindrical sputtering target contains a
plurality of portions where no bonding material exists, the maximum
area means the maximum value among the area values obtained by
finding the areas of the respective portions.
[0026] The volume of the cavity at the melting point of the bonding
material means a volume in such a state that the bonding material
can be filled therein in a molten state at the melting point. The
value of the volume of the cavity may be found based on the melting
point of the bonding material, and the thermal expansion
coefficient and the dimensions of each of the cylindrical target
material and a cylindrical base material. When the cylindrical
target material is made of a plurality of parts, and when an
intermediate member etc. is inserted between adjacent divided
parts, the value of the cavity is found, regarding the entire
volume containing such an intermediate member as a single
cylindrical target.
[0027] On the other hand, the volume of the bonding material that
has been filled in the cavity and has a temperature of 25.degree.
C. may be found by dividing an increased weight attributable to the
filling of the bonding material by the density of the bonding
material at 25.degree. C.
[0028] In other words, the proportion of both volumes may be
calculated according to the following formula:
Volume proportion (%)=(the volume of the bonding material that has
been filled in the cavity and has a temperature of 25.degree.
C)/(the volume of the cavity at the melting point of the bonding
material).times.100
[0029] Heretofore, even if the bonding material is ideally filled
without containing foams, the proportion of both volumes has had a
value of from 94 to 96% at most because of a density difference
between the bonding material in a liquid phase (molten) state and
the bonding material in a cooled solid state, and thermal
expansion, although the proportion varies according to what the
bonding material is made of. The proportion has been actually a
lower value than the above-mentioned values since foams are
involved during filling.
[0030] However, the cylindrical sputtering target according to the
present invention is characterized in that the proportion of both
volumes is at least 96%. It is possible to reduce the occurrence of
a crack, a chip, extraordinary discharge, a nodule etc. caused by
poor thermal conduction or poor electrical conduction attributable
to defect in the bonding layer by reducing the occurrence of the
defect in the bonding layer up to a high volume proportion that has
not been attained heretofore as described above. The proportion of
both volumes is preferably at least 98%, more preferably at least
100%.
[0031] In the target according to the present invention, both of
the total area and the maximum area of the portions where no
bonding material exists as observed by an X-ray radiograph satisfy
the above-mentioned conditions as described above. The target
according to the present invention preferably satisfies the
above-mentioned volume proportion as well. Such a cylindrical
sputtering target can further reduce the occurrence of a crack, a
chip, extraordinary discharge and a nodule.
[0032] As the bonding material, materials generally employed as a
solder material are applicable. The bonding material is preferably
made of a solder material having a low melting point. Specific
examples of the material include In, an In alloy, Sn and a Sn
alloy. The bonding material is preferably made of In and an In
alloy.
[0033] As the cylindrical ceramic target material, various ceramic
materials are applicable. The target material may be, for example,
an oxide, which contains as main component at least one selected
from the group consisting of In, Sn, Zn, Al, Ta, Nb and Ti.
Specific examples include ITO (indium tin oxide), AZO (aluminum
zinc oxide), IZO (indium zinc oxide), Ta.sub.2O.sub.5,
Nb.sub.2O.sub.5 and TiO.sub.2. In particular, ITO and AZO are
preferred as the cylindrical ceramic target material according to
the present invention since such materials are susceptible to the
occurrence a crack and a chip and since the target is employed for
the purpose of producing a flat panel display having a problem of
occurrence of a nodule.
[0034] Examples of the cylindrical base material include Cu, Ti,
Al, Mo, an alloy containing at least one of these metals, and SUS.
The cylindrical base material preferably has a proper thermal
conduction, electric conduction and strength. Among them, Ti and
SUS are preferred as the cylindrical base material.
[0035] The cylindrical ceramic sputtering target according to the
present invention may be produced by the method according to the
present invention.
[0036] As the method for filing a molten bonding material in the
cavity defined by the cylindrical base material and the cylindrical
target material, there are following method. Examples include a
method for disposing a cylindrical target material outside a
cylindrical base material, followed by sealing a lower portion of
the gap between the cylindrical base material and the cylindrical
target material and pouring a molten bonding material in the gap
from an upper portion of the gap, and a method for sealing one end
each of a cylindrical target material and a cylindrical base
material, and putting the cylindrical base material in the
cylindrical target material where a molten bonding material has
been introduced.
[0037] When filling a molten bonding material or after filling a
molten bonding material, it is preferred to vibrate the molten
bonding material. In this way, the bonding material sufficiently
spreads in the cavity defined by the cylindrical base material and
the cylindrical target material without containing foams, whereby
the bonding material can be filled with a higher proportion. The
given vibration has an acceleration of 0.05 G or more, preferably
at least 0.1 G, more preferably at least 1 G. The vibration has an
amplitude of at least 0.01 mm, preferably at least 0.03 mm.
Although there are no upper limits to the vibration acceleration
and the vibration amplitude from the point of view of the purpose
for filing the bonding material with a high proportion, the
vibration acceleration and the vibration amplitude are preferably
200 G or less and 1 mm or less, respectively, since it is likely
that strong vibration subjects the cylindrical target material to
positional shift or the bonding material leaks from the sealed
portion.
[0038] Although there is no limitation to the method for vibrating
the bonding material, a vibration table or a vibrator may be
employed for example. In order to prevent the cylindrical target
material from positionally shifting and to prevent the bonding
material from leaking, it is preferred to vibrate the cylindrical
base material to vibrate the bonding material rather than to
vibrate the cylindrical target material.
[0039] As the method wherein the molten bonding material, which has
been filled in the cavity defined by the cylindrical target
material and the cylindrical base material, starts to be cooled
from one end toward the other end in a cylindrical axis direction
in sequence, there is the following method. For example, the method
may be conducted such that a plurality of heaters are disposed on
an outer peripheral side of the cylindrical target material so as
to be independently temperature-controlled, and the entire
cylindrical target material is heated by the heaters, followed by
starting cooling the bonding material by reducing the intensity of
heating or stopping heating from one end toward the other end in a
cylindrical axial direction in sequence. In this way, the bonding
material is sequentially cooled from the one end toward the other
end, being solidified. Although there is no limitation to the
cooling rate, the cooling rate is preferably about 0.05 to
3.degree. C./min, more preferably 0.5 to 1.5.degree. C./min since
too low a cooling rate lowers productivity while it is likely that
too high a cooling rate causes the cylindrical target material to
be subjected to a crack due to thermal shock. Although there is no
limitation to the temperature gradient when cooling is sequentially
conducted from the one end toward the other end, the temperature
gradient is preferably about 0.1 to 3.degree. C./cm, more
preferably 0.4 to 1.degree. C./cm since too small a temperature
gradient makes the temperature control different while too high a
temperature gradient is likely to cause the cylindrical target
material to be subjected to a crack due to thermal shock. It should
be noted that the temperature control is conducted so as to avoid a
case where the bonding material is once cooled to its melting point
or less, followed by being heated beyond the melting point again.
In this way, it is possible to further reduce the occurrence of the
bonding layer defect.
[0040] Examples of the method for further supplying a molten
bonding material during cooling the molten bonding material filled
in the cavity defined by the cylindrical ceramic target material
and the cylindrical base material include a method for arbitrarily
replenishing the molten bonding material and a method for disposing
a bonding material supply portion on a top portion of the cavity to
store the molten bonding material and supplying the molten bonding
material from the supply portion. In order to disposes such a
bonding material supply portion, a cylindrical jig, which has a
slightly larger inner diameter than the outer diameter of the
cylindrical base material may be coupled to a top portion of the
cylindrical target material so as to store the molten bonding
material in a space defined by the cylindrical jig and the
cylindrical base material for example. By adopting this
arrangement, it is possible to reduce the bonding layer defect
caused during cooling the molten bonding material filled in the
cavity defined by the cylindrical ceramic target material and the
cylindrical base material. When the molten bonding material is
supplied to the cavity during cooling, it is preferred to supply
the molten bonding material from the end opposite the one end in
the cylindrical axial direction, where cooling starts.
EXAMPLES
[0041] Now, the present invention will be described in further
detail in reference to examples, but it should be understood that
the present invention is by no means thereby restricted.
Example 1
[0042] Two cylindrical target materials, which were made of ITO and
had an outer diameter of 98 mm, an inner diameter of 78 mm and a
length of 175 mm, and one cylindrical base material, which was made
of SUS 304 and had an outer diameter of 76 mm, an inner diameter of
70 mm and a length of 470 mm, were prepared. One of the cylindrical
target materials and the cylindrical base material were held by a
jig such that the bottom end of a lower cylindrical target material
was located at a position of 60 mm lower than the bottom end of the
cylindrical base material. A sheet made of Teflon (trademark), the
other cylindrical target material, a sheet made of Teflon
(trademark) and an aluminum jig (having an outer diameter of 98 mm,
an inner diameter of 78 mm and a length of 40 mm) were stacked on
the one cylindrical target material in this order. An O-ring having
a heat resistance (O-ring made of a silicone resin) was disposed on
the bottom end of the lower cylindrical target material, and a load
of 50 kgf was applied in a cylindrical axial direction from a top
portion of the aluminum jig. Four ribbon heaters were wound on
outer sides of the cylindrical target materials, and one ribbon
heater was wound on the aluminum jig, followed by heating the
heaters to 180.degree. C. Then, molten In was poured into from the
top of the gap between the aluminum jig and the cylindrical base
material. During pouring, an electric vibrator was employed to
vibrate the cylindrical base material such that the molten In
sufficiently spread into every corner. The vibration acceleration
and the vibration amplitude were from 50 to 100 G and from 0.1 to
0.2 mm, respectively. After the molten In was filled up to the top
end of the aluminum jig, the temperature given by the four ribbon
hearers attached to the cylindrical target materials were lowered
by 0.42.degree. C./min at intervals of 30 minutes from a lower
portion toward an upper portion of the cylindrical target
materials, whereby the temperatures of each cylindrical target
material was lowered to 130.degree. C. During lowering the
temperature, the aluminum jig was heated so as to be kept at
180.degree. C., whereby the In material filled in between the
aluminum jig and the cylindrical base material made of SUS 304 kept
a molten state. The aluminum jig corresponds to the bonding
material supply portion to store the molten bonding material.
[0043] After each cylindrical target material was entirely cooled
down to 130.degree. C., the aluminum jig was also cooled down
130.degree. C., followed by cooling down all these members to
25.degree. C. Then, all these members were heated to 50.degree. C.
again, and the sheets made of Teflon (trademark) inserted between
the cylindrical target materials and between the upper cylindrical
target material and the aluminum jig were removed. After that, all
these members were cooled down to 25.degree. C., and the aluminum
jig and the In material filled in between the aluminum jig and the
cylindrical base material made of SUS304 were removed, whereby a
cylindrical sputtering target was obtained. The volume ratio of the
In material at 25.degree. C. that was filled in the cavity was
100.3% with respect to the volume of the cavity that was defined by
each cylindrical target material and the cylindrical base material
and had a temperature equal to the melting point of In. An X-ray
radiograph was taken by applying an X-ray from outside the
cylindrical sputtering target by means of an X-ray irradiation
system, and recording an image on a radiographic film affixed on an
inner side of the cylindrical base material. It was revealed that
the maximum area of portions where no bonding material existed was
0.4 cm.sup.2 and that the total area of the portions where no
bonding material existed was 0.9 cm.sup.2 per 50 cm.sup.2 of X-ray
radiograph area. A discharge test was carried out for the
cylindrical sputtering target under the conditions of a rotation
number of 6 rpm, a sputtering pressure of 0.4 Pa and a power
density of 4.0 W/ cm.sup.2. The test results showed that neither a
nodule nor extraordinary discharge was generated and that neither a
crack nor a chip was observed until the life end.
Example 2
[0044] An ITO cylindrical sputtering target was fabricated in the
same manner as in Example 1 except that the bonding material was
made of InSn, the bonding material had a temperature of 160.degree.
C. when being poured, and the first dropping temperature was set at
100.degree. C. The volume ratio of the InSn material at 25.degree.
C. that was filled in the cavity was 98.3% with respect to the
volume of the cavity that was defined by each cylindrical target
material and the cylindrical base material and had a temperature
equal to the melting point of InSn. An X-ray radiograph was taken
in the same manner as in Example 1. It was revealed that the
maximum area of portions where no bonding material existed was 1.0
cm.sup.2 and that the total area of the portions where no bonding
material existed was 1.9 cm.sup.2 per 50 cm.sup.2 of X-ray
radiograph area. A discharge test was carried out for this ITO
cylindrical sputtering target under the same conditions as in
Example 1. The test results showed that neither a nodule nor
extraordinary discharge was generated and that neither a crack nor
a chip was observed until the life end.
Example 3
[0045] An AZO cylindrical sputtering target was fabricated in the
same manner as in Example 1 for that a cylindrical target material
was made of AZO. The volume ratio of the In material at 25.degree.
C. that was filled in the cavity was 100.2% with respect to the
volume of the cavity that was defined by each cylindrical target
material and the cylindrical base material and had a temperature
equal to the melting point of In. An X-ray radiograph was taken in
the same manner as in Example 1. It was revealed that the maximum
area of portions where no bonding material existed was 0.5 cm.sup.2
and that the total area of the portions where no bonding material
existed was 1.2 cm.sup.2 per 50 cm.sup.2 of X-ray radiograph area.
A discharge test was carried out for this AZO cylindrical
sputtering target under the same conditions as in Example 1. The
test results showed that neither a nodule nor extraordinary
discharge was generated and that neither a crack nor a chip was
observed until the life end.
Example 4
[0046] An ITO cylindrical sputtering target was fabricated in the
same manner as in Example 1 except that weak vibration was given
when pouring the bonding material. In this Example, the vibration
acceleration and the vibration amplitude were from 0.1 to 6 G and
from 0.01 to 0.03 mm, respectively. The volume ratio of the In
material at 25.degree. C. that was filled in the cavity was 96.8%
with respect to the volume of the cavity that was defined by each
cylindrical target material and the cylindrical base material and
had a temperature equal to the melting point of In. An X-ray
radiograph was taken in the same manner as in Example 1. It was
revealed that the maximum area of portions where no bonding
material existed was 1.5 cm.sup.2 and that the total area of the
portions where no bonding material existed was 3.1 cm.sup.2 per 50
cm.sup.2 of X-ray radiograph area. A discharge test was carried out
for this ITO cylindrical sputtering target under the same
conditions as in Example 1. The test results showed that neither a
nodule nor extraordinary discharge was generated and that neither a
crack nor a chip was observed until the life end.
Example 5
[0047] An ITO cylindrical sputtering target was fabricated in the
same manner as in Example 1 except that no aluminum jig was
employed. The volume ratio of the In material at 25.degree. C. that
was filled in the cavity was 93.2% with respect to the volume of
the cavity that was defined by each cylindrical target material and
the cylindrical base material and had a temperature equal to the
melting point of In. An X-ray radiograph was taken in the same
manner as in Example 1. It was revealed that the maximum area of
portions where no bonding material existed was 7.0 cm.sup.2 and
that the total area of the portions where no bonding material
existed was 7.5 cm.sup.2 per 50 cm.sup.2 of X-ray radiograph area.
A discharge test was carried out for this ITO cylindrical
sputtering target under the same conditions as in Example 1. The
test results showed that although a quite small number of nodules
were produced, such a quite small number of nodules had no adverse
effect to use, and that neither a crack nor a chip was observed
until the life end.
Comparative Example 1
[0048] An ITO cylindrical sputtering target was fabricated in the
same manner as in Example 1 except that no aluminum jig was
employed and the temperatures of the four ribbon heaters on the
cylindrical target materials were simultaneously dropped by
0.42.degree. C./min to uniformly cool down each ITO cylindrical
target material in its entirety. The volume ratio of the In
material at 25.degree. C. that was filled in the cavity was 87.6%
with respect to the volume of the cavity that was defined by each
cylindrical target material and the cylindrical base material and
had a temperature equal to the melting point of In. An X-ray
radiograph was taken in the same manner as in Example 1. It was
revealed that the maximum area of portions where no bonding
material existed was 5.8 cm.sup.2 and that the total area of the
portions where no bonding material existed was 10.6 cm.sup.2 per 50
cm.sup.2 of X-ray radiograph area. A discharge test was carried out
for this ITO cylindrical sputtering target in the same manner as in
Example 1. The test results showed that nodules were produced
during discharge, that extraordinary discharge was generated and
that a crack occurred in use.
Comparative Example 2
[0049] An ITO cylindrical sputtering target was fabricated in the
same manner as in Comparative Example 1 except that no vibration
was given when pouring molten In. The volume ratio of the In
material at 25.degree. C. that was filled in the cavity was 82.1%
with respect to the volume of the cavity that was defined by each
cylindrical target material and the cylindrical base material and
had a temperature equal to the melting point of In. An X-ray
radiograph was taken in the same manner as in Example 1. It was
revealed that the maximum area of portions where no bonding
material existed was 9.7 cm.sup.2 and that the total area of the
portions where no bonding material existed was 12.5 cm.sup.2 per 50
cm.sup.2 of X-ray radiograph area. A discharge test was carried out
for this ITO cylindrical sputtering target in the same manner as in
Example 1. The test results showed that nodules were produced
during discharge, that extraordinary discharge was generated and
that a crack occurred in use.
INDUSTRIAL APPLICABILITY
[0050] The cylindrical ceramic sputtering target produced according
to the production method of the present invention can minimize the
occurrence of a crack, a chip, extraordinary discharge and a nodule
in use, and obtain a high target utilization ratio and a high film
deposition rate, being appropriately applied to flat panel
displays.
[0051] The entire disclosure of Japanese Patent Application No.
2008-152061 filed on Jun. 10, 2008 including specification, claims,
drawings and summary is incorporated herein by reference in its
entirety.
EXPLANATION OF REFERENCE NUMERALS
[0052] 1: Cylindrical target material [0053] 2: Cylindrical base
material [0054] 3: Cavity defined by the cylindrical target
material and the cylindrical base material
* * * * *