JPH11302016A - Ito sputtering target suitable for film formation at low temperature, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ITO sputtering target capable of forming a low resistance thin ITO film having excellent crystallinity even at a low substrate temp. SOLUTION: When an ITO target is produced by casting, a polysaccharide binder is used as a binder to obtain the objective uniform ITO sputtering target capable of forming a low resistance thin ITO film having excellent crystallinity even at a low substrate temp. When the half-width of (222) peak is represented by Ws and the half-width of (222) peak obtd. by the X-ray diffraction of a cross section of the target is represented by Wc, the relations of 0<= |Ws-Wc|/ Wc}×100<=25 and 0<= |Ws-Wc|/Ws}×100<=40 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a transparent conductive film forming method.
The present invention relates to a TO sputtering target, which is a film formed at a low substrate temperature of 200 ° C. or less, particularly an ITO target for forming a low-resistance transparent conductive film having good crystallinity even at 120 ° C. to 150 ° C.

[0002]

2. Description of the Related Art A transparent conductive film applied to a liquid crystal device or the like has a low specific resistance and a high transmittance.
A tin oxide (ITO) film is used. As a method for obtaining an ITO film, a mixed powder of indium oxide and tin oxide
The mainstream is a sputtering method using a material molded from P or the like and sintered. It is known that an ITO thin film formed on a substrate heated to about 300 ° C. by a sputtering method has a specific resistance of about 1.2 × 10 ⁻⁴ Ω · cm.

[0003]

In recent years, however, with the development of color liquid crystals, it has become necessary to form a low-resistance ITO film on a substrate made of an organic material having a low heat-resistant temperature. At present, 2.0 at substrate temperature 200 ° C
Although an ITO thin film having a specific resistance of less than × 10 ⁻⁴ Ω · cm has been obtained, an IT thin film having a low specific resistance at a lower temperature is obtained.
It is desired to form an O thin film. However,
It has been difficult to produce an ITO target for forming a transparent conductive film that can obtain a low-resistance ITO film even by low-temperature film formation.

[0004] Here, as a method of manufacturing an ITO sputtering target, for example, a casting method is known as disclosed in Japanese Patent Application Laid-Open No. 9-188564.

[0005]

The present inventors have studied a method of forming a low-resistance ITO thin film at a low substrate temperature by sputtering an ITO target, and found that there is a correlation between the crystallinity of the target and the specific resistance of the film. Then, when sputtering film formation is performed using an ITO target in which the sintered structure of the target is uniform in any direction, the crystallinity is excellent at a low substrate temperature, particularly at 120 ° C. to 150 ° C.,
It has been found that an ITO thin film having a specific resistance of 2.0 × 10 ⁻⁴ Ω · cm or less can be produced, and further, in performing a casting method as a known production method, when a polysaccharide-based binder is used as a binder, It has been found that an ITO target in which the sintered structure of the target is uniform in any direction can be obtained, and the present invention has been completed. The reason that the ITO target, which has a uniform sintered structure in any direction, has good film-forming properties because the sintered body has high crystallinity and uniform crystallinity. This is considered to be because an ITO thin film having high crystallinity was formed even at a low substrate temperature.
Also, the reason for using a polysaccharide-based binder to obtain an ITO target in which the sintered structure of such a target is uniform in any direction is that the polysaccharide-based binder decomposes compared to other binders. This is considered to be due to the fact that carbon particles are less likely to remain after the degreasing step and uniform grain growth is likely to occur.

Usually, the crystallite size calculated by X-ray diffraction of an ITO thin film formed by sputtering at a low substrate temperature of 200 ° C. or less is at most about 300 to 500 °, and when the substrate temperature during the film formation is lowered, Then, the crystallinity decreases, and the crystallite size gradually decreases, and the structure changes to an amorphous structure. However, the ITO thin film formed using the target of the present invention maintains high crystallinity even at 120 ° C. to 150 ° C., shows a sharp X-ray diffraction peak, and has a crystallite size calculated from the half value width of X-ray diffraction and the peak position. Is 50
It has a considerably large value of 0 ° or more. For this reason, carrier electrons are hardly scattered at crystal grain boundaries, and a low specific resistance is realized.

The specific determination of the uniformity of the target structure can be made by using the (222) peak obtained by X-ray diffraction of the sputtering surface of the target. That is,
The half width of the (222) peak determined by X-ray diffraction on the sputtering surface of the target is Ws, and the X
The half width of the (222) peak determined by X-ray diffraction
When c, 0 ≦ {| Ws−Wc | / Wc} × 100
≦ 25 and 0 ≦ ｛| Ws−Wc | / Ws｝ ×
If the film is formed using an ITO sputtering target satisfying 100 ≦ 40, scattering of carrier electrons at crystal grain boundaries hardly occurs, and a low specific resistance is realized. That is, the present invention is as follows.

(1) When the half width of the (222) peak determined by X-ray diffraction of the sputtering surface of the target is Ws, and the half width of the (222) peak determined by X-ray diffraction of the cross section of the target is Wc, 0 ≤ ｛│Ws-Wc│
/ Wc｝ × 100 ≦ 25 and 0 ≦ ｛| Ws−
An ITO sputtering target with Wc│ / Ws｝ × 100 ≦ 40. (2) A slurry containing 80 to 98 parts by weight of indium oxide powder, 2 to 20 parts by weight of tin oxide, a slurry containing a dispersant and a polysaccharide-based binder is cast and then molded under an atmosphere containing oxygen. The method for producing an ITO sputtering target according to (1), wherein the target is sintered. (3) After casting a slurry containing 80 to 98 parts by weight of indium oxide powder, 2 to 20 parts by weight of tin oxide, and a dispersant and a polysaccharide-based binder in terms of oxides The method for producing an ITO sputtering target according to (1), wherein the sintering is performed in an atmosphere containing oxygen.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The indium oxide powder used in the present invention can be obtained by, for example, calcining indium hydroxide obtained by dissolving metal indium in acid and neutralizing with alkali. Can be obtained by, for example, baking tin hydroxide obtained by dissolving metal tin in acid and neutralizing with alkali.

[0010] The ITO composite oxide powder is, for example,
After mixing the indium oxide powder and the tin oxide powder, they can be calcined in the air to obtain the powder.

The polysaccharide-based binder used in the present invention includes, for example, cellulose, xylan, dextran, pullulan and the like. Name: Pullulan PF-20, manufactured by Hayashibara Chemical Co., Ltd.).

As the dispersant used in the present invention, for example, acrylic acid, acrylate, acrylate, methacrylic acid, methacrylate, methacrylate, or the like may be used alone or in combination. Can be used. Further, those copolymers may be used.

In the present invention, indium oxide powder 80 to 9
An ITO mixed powder or an ITO composite oxide powder composed of 8 parts by weight and 2 to 20 parts by weight of tin oxide is used, but preferably 85 to 95 parts by weight of indium oxide powder and 5 parts by weight of tin oxide.
To 15 parts by weight, more preferably 88 to 93 parts by weight of indium oxide powder and 7 to 12 parts by weight of tin oxide.

The indium oxide powder has an average secondary particle diameter of 0.3 to 3.0 μm and a specific surface area of 1.0 to 5.0 m ^2.
/ G is preferable, and the average particle size of the secondary particles is 0.5 to 2.5 μm, and the specific surface area is 2.0 to 4.0 m ² / g.
Are more preferred.

On the other hand, tin oxide powder has an average secondary particle diameter of 0.3 to 3.0 μm and a specific surface area of 1.0 to 5.0 m ² /
g is preferable, and the average particle size of the secondary particles is 0.4 to 2.5 μm, and the specific surface area is 2.0 to 4.0 m ² / g.
Are more preferred.

The ITO composite oxide powder has an average secondary particle diameter of 0.3 to 3.5 μm and a specific surface area of 1.0 to 3.5 μm.
The average particle diameter of the secondary particles is preferably from 0.5 to 2.5 μm, and the specific surface area is preferably from 2.0 to 4.0 m ² / g.
Those having 0 m ² / g are more preferred. Such an ITO composite oxide powder can be obtained, for example, by mixing tin oxide or tin hydroxide with indium oxide or indium hydroxide so as to have a mixing ratio as described above and firing the mixture.

As the dispersion medium used for the slurry, for example, water or alcohols such as ethanol, butanol, and propanol can be used, but water is preferably used from the viewpoint of low cost.

The slurry can be formed by a ball mill method such as a rotary ball mill method or an attritor method, or a mixing method of rotary blades such as a slasher.

The oxygen-containing atmosphere, which is one of the sintering conditions of the present invention, is 0 to 40 l / min using an atmospheric furnace or the like.
Is preferably performed in an oxygen flow atmosphere, and more preferably, the oxygen flow rate is 10 to 20 l / min.

The sintering temperature and sintering time in the sintering of the present invention are preferably 1400 to 1650 ° C. and 2 to 5 hours, respectively, and more preferably 1500 to 1600 ° C. and 3.5 to 4.5.
Time is more preferred.

In the ITO sputtering target of the present invention, the half width of the (222) peak determined by X-ray diffraction of the sputtering surface of the target is Ws, and the half width of the (222) peak determined by X-ray diffraction of the cross section of the target is Wc. 0 ≦ {| Ws−Wc | / Wc} × 10
0 ≦ 25 and 0 ≦ {| Ws−Wc | / Ws} × 1
An ITO sputtering target with 00 ≦ 40, where 0 ≦ {| Ws−Wc | / Wc} × 100 ≦ 22,
And 0 ≦ {(| Ws−Wc | / Ws} × 100 ≦ 30
0 ≦ {| Ws−Wc | / Wc} × 1
00 ≦ 19 and 0 ≦ {| Ws−Wc | / Ws} ×
More preferably, 100 ≦ 25.

The target of the present invention can be manufactured by the method according to the second or third aspect. However, even with a target manufactured by another method, half of the (222) peak determined by X-ray diffraction of the sputtering surface of the target is used. Assuming that the value width is Ws and the half value width of the (222) peak determined by X-ray diffraction of the target cross section is Wc, 0 ≦ Ｗ | Ws−Wc | /
Wc｝ × 100 ≦ 25, and 0 ≦ ｛| Ws−W
If c│ / Ws｝ × 100 ≦ 40, the effect is obtained.

Hereinafter, embodiments of the present invention will be described. Of course,
The present invention is not limited to the embodiments.

Example 1 The amounts, average particle diameters,
Table 1 shows indium oxide powder and tin oxide powder having a specific surface area.
The dispersion medium, the dispersant, and the binder under the conditions shown in Table 1 were cast using the slurry prepared by the slurry preparation method shown in Table 1, and sintered under the sintering conditions shown in Table 1 to form an ITO.
A sintered body was prepared and then bonded to a backing plate to obtain an ITO sputtering target. X-ray diffraction measurement of the target using MAC Science Co. X-ray diffraction apparatus M18XHF ^32, tube voltage 40 kV, tube current 300
A Cu-Kα1 line was generated at mA, and the area around the target peak was measured by the FT method (step scan). At this time, the step width is 0.01 °, and the counting time is 1 second. Thereafter, under the film forming conditions shown in Table 2, a film was formed by a DC magnetron sputtering method. The specific resistance of the obtained film was measured by a four-point terminal method. Table 2 also shows the results.

[0025]

[Table 1]

[0026]

[Table 2]

Example 2 An indium hydroxide powder having an average particle size of 0.02 μm and a tin hydroxide powder having an average particle size of 0.03 μm were mixed by a rotary ball mill method. A composite oxide powder was obtained. Casting was performed using the slurry prepared by the slurry preparation method shown in Table 3 using the ITO composite oxide powder, dispersion medium, dispersant, and binder under the conditions shown in Table 3, and under the sintering conditions shown in Table 3. Sintering was performed to produce an ITO sintered body, which was then joined to a backing plate to obtain an ITO sputtering target. X-ray diffraction measurement of the target was performed in the same manner as in Example 1. Thereafter, under the film forming conditions shown in Table 4, a film was formed by a DC magnetron sputtering method. The specific resistance of the obtained film was measured by a four-point terminal method. Table 4 also shows the results.

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

As is clear from the above examples, the ITO sputtering target of the present invention has uniform crystallinity, so that the manner of scattering of sputtered particles is uniform and has excellent crystallinity even at a low substrate temperature. A low-resistance ITO thin film can be formed.

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[Procedure amendment]

[Submission date] October 6, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

[0029]

[Table 4]

Claims (3)

[Claims] When the half width of the (222) peak determined by X-ray diffraction on the sputtering surface of the target is Ws, and the half width of the (222) peak determined by X-ray diffraction on the cross section of the target is Wc, 0 ≦ ｛(│Ws-Wc│ /
Wc｝ × 100 ≦ 25, and 0 ≦ ｛| Ws−W
An ITO sputtering target in which c│ / WsＩＴ × 100 ≦ 40. 2. A cast containing a slurry containing 80 to 98 parts by weight of indium oxide powder, 2 to 20 parts by weight of tin oxide, a dispersant and a saccharide-based binder, and then under an atmosphere containing oxygen. The method for producing an ITO sputtering target according to claim 1, wherein the target is sintered. 3. Indium oxide powder 80 in terms of oxide
IT consisting of up to 98 parts by weight and 2 to 20 parts by weight of tin oxide
The method for producing an ITO sputtering target according to claim 1, wherein a slurry containing the O composite oxide powder, the dispersant, and the saccharide-based binder is cast and then sintered in an atmosphere containing oxygen.