Title: Sputtering target and transparent conductive film
Abstract: A sputtering target containing a hexagonal laminar compound formed of indium oxide and zinc oxide and represented by In2O3(ZnO)m wherein m is an integer of 2 to 7 and further contains 0.01 to 1 at % of an oxide of a third element having a normal valence of 4 or more, and a transparent electrically conductive film formed therefrom. The sputtering target has a low volume resistivity and permits stable sputtering. The transparent electrically conductive film is excellent in etchability.
Patent Number: 6,998,070 Issued on 02/14/2006 to Inoue, et al.
| Inventors:
|
Inoue; Kazuyoshi (Sodegaura, JP);
Matsuzaki; Shigeo (Sodegaura, JP)
|
| Assignee:
|
Idemitsu Kosan Co., Ltd. (JP)
|
| Appl. No.:
|
483614 |
| Filed:
|
May 24, 2002 |
| PCT Filed:
|
May 24, 2002
|
| PCT NO:
|
PCT/JP02/05058
|
| 371 Date:
|
January 14, 2004
|
| 102(e) Date:
|
January 14, 2004
|
| PCT PUB.NO.:
|
WO03/008661 |
| PCT PUB. Date:
|
January 30, 2003 |
Foreign Application Priority Data
| Jul 17, 2001[JP] | 2001-216618 |
| Current U.S. Class: |
252/519.51; 428/922 |
| Current Intern'l Class: |
H01B 1/08 (20060101) |
| Field of Search: |
252/51951
428/432,918,922
204/192.21
|
References Cited [Referenced By]
U.S. Patent Documents
| 5972527 | Oct., 1999 | Kaijou et al.
| |
| 6534183 | Mar., 2003 | Inoue.
| |
| 6669830 | Dec., 2003 | Inoue et al.
| |
| Foreign Patent Documents |
| 0 677 593 | Oct., 1995 | EP.
| |
| 1 033 355 | Sep., 2000 | EP.
| |
| 6-234565 | Aug., 1994 | JP.
| |
| 6-318406 | Nov., 1994 | JP.
| |
| 7-235219 | Sep., 1995 | JP.
| |
| 7-335046 | Dec., 1995 | JP.
| |
| 9-071860 | Mar., 1997 | JP.
| |
Other References
English translation of JP 7-235219A.
|
Primary Examiner: Kopec; Mark
Attorney, Agent or Firm: Steptoe & Johnson LLP
Claims
The invention claimed is:
1. A sputtering target containing a hexagonal laminar compound formed of indium
oxide and zinc oxide and represented by In
2O
3(ZnO)
m
wherein m is an integer of 2 to 7, and 0.02 to 0.2 at % of an oxide of a third
element having a normal valence of 4 or more.
2. A sputtering target as recited in claim 1, wherein the atomic ratio of indium
atom to the total of indium atom and zinc atom [In/(In+Zn)] is from 0.7 to 0.95.
3. A sputtering target as recited in claim 1, wherein the third element having
a normal valence of 4 or more is one or more elements selected from the group consisting
of titanium, zirconium, hafnium, vanadium, niobium, tantalum, ruthenium, rhodium,
iridium, germanium, tin, antimony and lead.
4. A sputtering target as recited in claim 1, wherein the third element having
a normal valence of 4 or more is cerium.
5. A sputtering target as recited in claim 1, which has a relative density of
0.95 or more.
6. A transparent electrically conductive film formed from the sputtering target
as recited in claim 1 by a sputtering method.
Description
TECHNICAL FIELD
The present invention relates to a sputtering target to be used for forming a
transparent electrically conductive film by a sputtering method, and a transparent
electrically conductive film formed using the target.
TECHNICAL BACKGROUND
Owing to excellent display performances and low power consumption, thin film
liquid crystal displays have come to prevail as display devices for portable personal
computers and television. Any liquid crystal display has a sandwich structure in
which a liquid crystal display device is interposed between transparent electrically
conductive films.
Transparent electrically conductive films for use in these display devices
are generally formed by a sputtering method using a sintered body target. As a
material for the target, conventionally, an indium-tin oxide (to be abbreviated
as "ITO" hereinafter) has been used. That is because a transparent electrically
conductive film formed from the ITO target has high light transmittance and further
has excellent electrical conductivity. However, the transparent electrically conductive
film formed from the ITO target has a problem that since the etching thereof requires
a strong acid such as aqua regia, hydrochloric acid or hydrobromic acid, a wiring
material in a thin film liquid crystal display may be ultimately also etched.
For overcoming the above problem, therefore, JP-A-6-234565 and JP-A-6-318406
propose a method in which a film is formed from a sputtering target formed of a
zinc-oxide-indium-oxide-containing material. When a transparent electrically conductive
film formed from the above sputtering target formed of a zinc-oxide-indium-oxide-containing
material is used, a weak acid such as oxalic acid can be used, so that the wiring
material in a thin film liquid crystal display is no longer likely to be ultimately
etched. Since, however, the above sputtering target formed of a zinc-oxide-indium-oxide-containing
material has a high volume resistivity itself, there is caused a problem that the
target breaks or causes abnormal discharge during sputtering.
Further, for decreasing the volume resistivity of the above sputtering target
formed of a zinc-oxide-indium-oxide-containing material, JP-A-9-71860 proposes
a sputtering target formed by adding an oxide of a metal having a normal valence
of 3 or more to a zinc-oxide-indium-oxide-containing material. However, there is
a problem that a transparent electrically conductive film formed from the above
target has no sufficient etching property, although the volume resistivity of the
target can be decreased by adding an oxide of a metal having a normal valence of
3 or more.
It is an object of the present invention to provide a sputtering target that
has
a low volume resistivity and permits stable sputtering, and a transparent electrically
conductive film that is formed from the target and is excellent in etchability.
The present inventors have made diligent studies, and as a result, it has been
found that the above object can be achieved by a sputtering target containing a
hexagonal laminar compound formed of indium oxide and zinc oxide and further containing
an oxide of a third element having a normal valence of 4 or more. On the basis
of the above finding, the present invention has been completed.
DISCLOSURE OF THE INVENTION
That is, the subject matters of the present invention are as follows.
(1) A sputtering target containing a hexagonal laminar compound formed of indium
oxide and zinc oxide and represented by In
2O
3(ZnO) wherein
m is an integer of 2 to 7 and further containing 0.01 to 1 at % of an oxide of
a third element having a normal valence of 4 or more.
(2) A sputtering target as recited in the above (1), wherein the atomic ratio
of indium atom to the total of indium atom and zinc atom [In/(In+Zn)] is from 0.7
to 0.95.
(3) A sputtering target as recited in the above (1) or (2), wherein the third
element having a normal valence of 4 or more is one or more elements selected from
the group consisting of titanium, zirconium, hafnium, cerium, vanadium, niobium,
tantalum, ruthenium, rhodium, iridium, germanium, tin, antimony and lead.
(4) A sputtering target as recited in any one of the above (1) to (3), which
has a relative density of 0.95 or more.
(5) A transparent electrically conductive film formed from the sputtering target
as recited in any one of the above (1) to (4) by a sputtering method.
BEST MODE FOR CARRYING OUT THE INVENTION
The sputtering target of the present invention is a sputtering target containing
a hexagonal laminar compound formed of indium oxide and zinc oxide and represented
by In
2O
3(ZnO)
m wherein m is an integer of 2 to
7 and further containing 0.01 to 1 at % of an oxide of a third element having a
normal valence of 4 or more.
The hexagonal laminar compound formed of indium oxide and zinc oxide, contained
in the above sputtering target, is a compound that exhibits an X-ray diffraction
pattern assigned to a hexagonal laminar compound in a measurement based on an X-ray
diffraction method, and the hexagonal laminar compound contained in the sputtering
target of the present invention is a compound represented by In
2O
3(ZnO)
m.
In the above formula, m is an integer of 2 to 7, preferably 3 to 5. That is because
a compound of the formula in which m is 1 has no hexagonal laminar structure, and
because a compound of the formula in which m exceeds 7 has a high volume resistivity
although it has a hexagonal laminar structure. The above hexagonal laminar compound
is formed by sintering a mixture of indium oxide and zinc oxide. In this case,
indium oxide and zinc oxide form a hexagonal laminar compound in an amount ratio
corresponding to their stoichiometric ratio. Indium oxide or zinc oxide present
in an amount over the stoichiometric ratio is present as a crystalline material
in the sintered body.
Concerning the content ratio of indium oxide and zinc oxide contained
in the sputtering target, the atomic ratio of the indium atom to the total of the
indium atom and the zinc atom, [In/(In+Zn)] is preferably 0.7 to 0.95. When the
atomic ratio of the indium atom is less than 0.7, the specific resistance of a
transparent electrically conductive film formed from such a sputtering target can
increase. When the atomic ratio of the indium atom exceeds 0.95, a transparent
electrically conductive film formed from the target can be crystallized to decrease
light transmittance, or its specific resistance can be caused to increase. The
above atomic ratio of the indium atom is more preferably 0.8-0.95, since such a
sputtering target also has excellent durability.
Further, the third element having a normal valence or 4 or more, contained
in the sputtering target of the present invention, preferably is one or more elements
selected from the group consisting of titanium, zirconium, hafnium, cerium, vanadium,
niobium, tantalum, ruthenium, rhodium, iridium, germanium, tin, antimony and lead.
Of these, cerium, tin, antimony, lead, zirconium, hafnium, germanium and ruthenium
are particularly preferred.
The content of an oxide of the third element having a normal valence of 4 or
more in the sputtering target is 0.01 to 1 at %. By bringing the content of an
oxide of the third element into the above range, the volume resistivity of the
sputtering target can be fully decreased. That is, the volume resistivity can be
decreased to 7 mΩcm or less, preferably 5 mΩcm or less at which abnormal
discharge does not occur or the target does not break during the formation of a
film from the target. The above target gives a transparent electrically conductive
film that can be easily etched with a weak acid such as oxalic acid. When the content
of the above oxide of the third element is less than 0.01 at %, the volume resistivity
of the sputtering target cannot be controlled so as to be a fully low value. When
the content of the above oxide of the third element exceeds 1 at %, it may be difficult
to etch a transparent electrically conductive film formed from the target, with
a weak acid such as oxalic acid. The content of the oxide of the third element
is more preferably 0.02 to 0.2 at %, still more preferably 0.03 to 0.1 at %.
The above sputtering target has a relative density of 95% or more, preferably
96% or more. Such a target has high mechanical strength and excellent electrical
conductivity, so that the target can have improved stability during sputtering
with the target fixed to an RF magnetron sputtering apparatus or a DC magnetron
sputtering apparatus. The above relative density refers to a percentage of an actually
measured density of a sputtering target based on a theoretical density calculated
from densities inherent to indium oxide and zinc oxide and their compositional ratio.
Concerning the method of producing the above sputtering target, the sputtering
target can be produced by the steps of mixing indium oxide, zinc oxide and an oxide
of the third element having a normal valence of 4 or more as raw materials, shaping
a mixture of the raw materials into a shaped body, sintering the shaped body and
annealing a sintered body.
The indium oxide, zinc oxide and the oxide of the third element are desirably
selected from raw materials having high purity, and the raw materials have a purity
of at least 99%. The purity thereof is preferably at least 99.9%, more preferably
at least 99.99%. The reason therefor is that when raw materials having high purity
are used, a sintered body having a dense system is obtained, and a sputtering target
formed of the sintered body comes to have a low volume resistivity. Further, the
above metal oxides as raw materials suitably have an average particle diameter
of 0.01 to 10 μm, preferably 0.05 to 5 μm, more preferably 0.1 to 5
μm. When the average particle diameter of these metal oxides is less than
0.01 μm, the metal oxides are liable to aggregate. When it exceeds 10 μm,
they have an insufficient mixing property, and a sintered body having a dense system
may not be obtained. These metal oxides as raw materials can be mixed with a general
mixing device such as a ball mill, a jet mill or a roll mill.
While the thus-obtained mixture may be directly shaped into a shaped body,
it is preferred to carry out preliminary firing treatment thereof before the shaping.
Concerning preliminary firing treatment conditions, the preliminary firing temperature
is 800 to 1,500° C., preferably 900 to 1,400° C., more preferably 1,000
to 1,300° C., and the firing time period is 1 to 100 hours, preferably 2 to
50 hours, more preferably 3 to 30 hours. When the metal oxide powder as raw materials
is subjected to the preliminary firing under the above conditions, the formation
of a hexagonal laminar compound formed of indium oxide and zinc oxide is promoted.
The above preliminary firing treatment may be carried out once, or may be repeated
twice or more times. Further, when granulated, the metal oxide powder subjected
to the above preliminary firing treatment comes to be improved in flowability and
filling property in the shaping step later. The above granulation treatment can
be carried out with a spray dryer, or the like. Preferably, the above granulation
treatment is carried out by a method using an aqueous solution or alcohol solution
of the above metal oxide powder and a binder such as polyvinyl alcohol. The granulation
product formed by the above granulation treatment has a particle diameter of 1
to 100 μm, preferably 5 to 100 μm, more preferably 10 to 100 μm.
Then, in the shaping step, the powder or granulation product of the metal oxides
is shaped by a method such as press-molding, cast molding, injection molding, or
the like. For obtaining a sintered body having a high sintering density as a sputtering
target, the above shaping step is preferably carried out by a method in which a
preliminary shaping is performed by press-molding and then a preliminary-shaped
product is further compacted under pressure by a method of cold hydrostatic-pressure
press-molding or the like. In the above shaping step, various shaping aids can
be used, and it is preferred to use polyvinyl alcohol, methyl cellulose, polywax
or oleic acid. The shaping pressure is 1 MPa to 10 GPa, preferably 10 MPa to 10
GPa. Further, the shaping time period can be determined to be 10 minutes to 10
hours. The above shaped body preferably has a form having dimensions corresponding
to the dimensions of a transparent electrically conductive film to be formed by
sputtering for easily finishing the sputtering target by adjusting the form after sintering.
In the step of sintering the thus-obtained shaped body, the shaped body can be
sintered by a generally employed sintering method such as atmospheric-pressure
sintering, hot press sintering or hot hydrostatic-press sintering. Concerning the
condition for the above sintering, the sintering temperature is 1,200 to 1,600°
C., preferably 1,250 to 1,550° C., more preferably 1,300 to 1,500° C.
When the above sintering temperature is lower than 1,200° C., a hexagonal
laminar compound of indium oxide and zinc oxide may not be fully formed in a sintered
boy obtained. Further, when the sintering temperature exceeds 1,600° C., the
composition of the metal oxides in a sintered body obtained may vary due to the
sublimation of indium oxide and zinc oxide, and the value of m in the formula In
2O
3(ZnO)
m
in the hexagonal laminar compound formed may exceed 7, so that a sintered body
has a high volume resistivity. Although differing depending upon the sintering
temperature, the sintering time period is 1 to 50 hours, preferably 2 to 30 hours,
more preferably 3 to 20 hours. The atmosphere during the above sintering may be
air, a reducing gas such as hydrogen gas, methane gas or carbon monoxide, or an
inert gas such as argon gas or nitrogen gas.
Then, in the annealing step, the thus-obtained sintered body is annealed in
a sintering furnace or a hot press reducing furnace at an annealing temperature
of 200 to 1,000° C., preferably 300 to 1,000° C., more preferably 400
to 1,000° C., for an annealing time period of 1 to 50 hours, preferably 2
to 30 hours, more preferably 3 to 20 hours. When the annealing treatment is carried
out under the above conditions, the volume resistivity of the sintered body can
be decreased. The annealing treatment may be carried out in vacuum, or it may be
carried out in the atmosphere of a reducing gas such as hydrogen gas, methane gas
or carbon oxide gas or in the atmosphere of an inert gas such as argon gas or nitrogen gas.
For forming a sputtering target from the thus-obtained sintered body, the sintered
body can be grounded so as to have a form suitable for mounting it to a sputtering
apparatus and an attaching tool is fixed thereto.
When the above sputtering target is used to form a transparent electrically
conductive film, the transparent electrically conductive film is formed on a substrate.
The substrate is preferably selected from transparent substrates, and a conventionally
used glass substrate, or a film or sheet made of a highly transparent synthetic
resin can be used. The above synthetic resin includes polycarbonate resins, polymethyl
methacrylate resins, polyester resins, polyether sulfone resins and polyallylate resins.
When the above sputtering target is used to form a transparent electrically
conductive film on the transparent substrate by a sputtering method, a magnetron
sputtering apparatus is preferred. Concerning the condition of film formation by
sputtering using the above apparatus, the output of plasma varies depending upon
the surface area of the target or the thickness of the transparent electrically
conductive film. Generally, however, the plasma output is set in a range of 0.3
to 4 W per cm
2 of the target surface area, and the film formation time
period is determined to be 5 to 120 minutes, whereby a transparent electrically
conductive film having an intended thickness can be obtained. While the thickness
of the above transparent electrically conductive film changes depending upon displays
in kind, the thickness is generally 200 to 6,000 angstroms, preferably 300 to 2,000 angstroms.
The thus-obtained transparent electrically conductive film has such transparency
that its light transmittance to light having a wavelength of 500 nm is at least
80%. The above transparent electrically conductive film is therefore suitable for
use as a transparent electrode in various display devices such as a liquid crystal
display device and an organic electroluminescence display device that is required
to have high transparency and electrical conductivity.
EXAMPLES
The present invention will be explained in detail with reference to Examples
and Comparative Examples hereinafter.
Example 1
(1) Preparation of Sputtering Target
280 Grams of an indium oxide powder (average particle diameter 1 μm) having
a purity of 99.99% and 19.7 g of a zinc oxide powder (average particle diameter
1 μm) having a purity of 99.9% and 0.3 g of a tin oxide powder (average particle
diameter 1 μm) having a purity of 99.99% as an oxide of a third element having
a normal valence of 4 or more were placed as raw materials in a pot made of polyimide
together with ethyl alcohol and zirconia balls, and these materials were mixed
by means of a planetary ball mill for 2 hours.
Then, the obtained powder mixture was placed in a mold of a press-molding machine
and preliminarily shaped under a pressure of 10 MPa. A shaped body obtained by
the preliminary shaping was compacted with a cold hydrostatic-pressure press-molding
machine under a pressure of 400 MPa, then charged into a sintering furnace and
fired in an air atmosphere at 1,450° C. for 8 hours.
The thus-obtained sintered body was evaluated for its crystal structure with
an X-ray diffraction measuring apparatus supplied by Rigakusha, to show that a
hexagonal laminar compound formed of indium oxide and zinc oxide and represented
by In
2O
3(ZnO)
3 and indium oxide represented by
In
2O
3 were present. Further, the sintered body was composition-analyzed
with inductive coupling plasma emission spectroscopy (ICP analysis) using SPS-1500VR
supplied by Seiko Instruments Inc. As a result, it was found that the atomic ratio
of indium oxide to the total of indium oxide and zinc oxide, [In/(In+Zn)] in the
sintered body was 0.89, and that the atomic % of tin oxide to the total of indium
oxide, zinc oxide and tin oxide, [Sn/(In+Zn+Sn)]×100, was 0.088%.
The above sintered body had a relative density of 96.5%. Further, a 20 mm×40
mm×5 mm test piece was prepared from the above sintered body, and the test
piece was measured for a volume resistivity by a four-probe method to show 0.1 mΩ·cm.
(2) Lifetime Test of Sputtering Target
The sintered body obtained in the above (1) was ground to prepare a sputtering
target having a diameter of about 10 cm and a thickness of about 5 mm. The sputtering
target was mounted to a DC magnetron sputtering apparatus, and a transparent electrically
conductive film was formed on a glass substrate at room temperature. Concerning
sputtering conditions, a mixture prepared by mixing argon gas with a proper amount
of oxygen gas was used as an atmosphere, and a lifetime test for 100 hours was
carried out under a sputtering pressure of 3×10
-1 Pa at an ultimate
pressure of 5×10
-4 Pa, at a substrate temperature of 25° C.
and at an input voltage of 5 W/cm
2. As a result, no abnormal discharge
was observed, and the sputtering target caused no breaking.
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
Part of the transparent electrically conductive film formed on the glass substrate
in the above (2) was etched with an oxalic acid aqueous solution having an oxalic
acid concentration of 3.4 mass % at 30° C. As a result, the transparent electrically
conductive film showed an etching rate of 860 Å/min. and it was found that
the transparent electrically conductive film had excellent etchability.
Table 1 shows the composition, properties and evaluation results of the sputtering
target prepared in this Example.
Example 2
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the amount of zinc oxide was changed to 19.9 g and the amount of tin oxide was
changed to 0.1 g as raw materials.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Example 3
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the tin oxide powder was replaced with 0.2 g a cerium oxide powder (an average
particle diameter of 3 μm) having a purity of 99.99% as an oxide of a third
element having a normal valence of 4 or more as a raw material.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Example 4
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the tin oxide powder was replaced with 0.2 g a zirconium oxide powder (an average
particle diameter of 4 μm) having a purity of 99.99% as an oxide of a third
element having a normal valence of 4 or more as a raw material.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Example 5
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the tin oxide powder was replaced with 0.2 g a germanium oxide powder (an average
particle diameter of 3 μm) having a purity of 99.999% as an oxide of a third
element having a normal valence of 4 or more as a raw material.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Example 6
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the tin oxide powder was replaced with 0.2 g a ruthenium oxide powder (an average
particle diameter of 4 μm) having a purity of 99.9% as an oxide of a third
element having a normal valence of 4 or more as a raw material.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Comparative Example 1
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the amount of indium oxide as a raw material was changed to 260 g, that the amount
of zinc oxide as a raw material was changed to 20 g and that the amount of tin
oxide was changed to 20 g.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
(3) Evaluation of Transparent Electrically Conductive Film for Etchability
The transparent electrically conductive film formed in the above (2) was evaluated
for etchability in the same manner as in (3) of Example 1.
Table 1 shows the results.
Comparative Example 2
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the amount of indium oxide as a raw material was changed to 294 g, that the amount
of zinc oxide as a raw material was changed to 3.4 g and that the oxide of the
third element having a normal valence of 4 or more was not added.
In the evaluation of the above sputtering target for a crystal structure by the
X-ray diffraction method, the presence of indium oxide was found, while the presence
of a hexagonal laminar compound was not found.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
As a result, abnormal discharge was observed 25 hours after the formation of a
transparent electrically conductive film was started. Then, the sputtering target
underwent breaking 30 hours after, so that the film formation was discontinued.
Table 1 shows the results.
Comparative Example 3
(1) Preparation of Sputtering Target
A sputtering target was obtained in the same manner as in Example 1 except that
the amount of indium oxide as a raw material was changed to 240 g, that the amount
of zinc oxide as a raw material was changed to 60 g and that the oxide of the third
element having a normal valence of 4 or more was not added.
In the evaluation of the above sputtering target for a crystal structure by the
X-ray diffraction method, it was found that a compound represented by In
2O
3(ZnO)
5
was formed as a hexagonal laminar compound.
(2) Lifetime Test of Sputtering Target
A lifetime test was carried out in the same manner as in (2) of Example 1 except
that the sputtering target was replaced with the sputtering target obtained in
the above (1).
As a result, abnormal discharge was found 50 hours after the formation of a transparent
electrically conductive film was started, and at the same time, the sputtering
target underwent breaking, so that the film formation was discontinued.
Table 1 shows the results.
| Sputtering target |
|
|
|
|
|
|
|
|
|
| In/(In + Zn) |
0.89 |
0.89 |
0.89 |
0.89 |
0.89 |
0.89 |
0.81 |
0.97 |
0.70 |
| Third element |
SnO2 |
SnO2 |
CeO2 |
ZrO2 |
GeO2 |
RuO2 |
SnO2 |
— |
— |
| [oxide] |
| Content of third |
0.088 |
0.029 |
0.051 |
0.072 |
0.085 |
0.066 |
6.6 |
— |
— |
| element (at %) |
| Relative |
96.5 |
96.4 |
96.1 |
96.3 |
96.6 |
96.4 |
93.2 |
93.8 |
92.8 |
| density(%) |
| Volume |
0.1 |
0.2 |
0.1 |
0.3 |
0.2 |
0.1 |
0.9 |
680 |
34.5 |
| resistivity |
| (mΩcm) |
| Abnormal |
No |
No |
No |
No |
No |
No |
No |
Yes*2 |
Yes*4 |
| discharge during |
| film formation |
| Breaking during |
No |
No |
No |
No |
No |
No |
No |
Yes*3 |
Yes*5 |
| film formation |
| Etchability of |
860 |
870 |
850 |
850 |
840 |
820 |
280 |
— |
— |
| transparent |
| electrically |
| conductive film*1 |
|
| (CEx) = (Comparative Example) |
| *1Unit: Å/min. |
| *225 hours after start of film formation |
| *330 hours after start of film formation |
| *450 hours after start of film formation |
| *550 hours after start of film formation |
INDUSTRIAL UTILITY
The sputtering target of the present invention has a low volume resistivity,
so that there is no abnormal discharge or breaking during film formation. Further,
a transparent electrically conductive film formed therefrom has excellent etchability.
*
