WO2014025017A1 - Sputtering target for forming transparent oxide film and method for producing same - Google Patents

Abstract

Provided is a sputtering target for forming a zinc oxide-based transparent oxide film, which is capable of forming a transparent oxide film by direct current sputtering, while being free from the occurrence of abnormal discharge. This sputtering target for forming a transparent oxide film is characterized by being a fired body of a composition that contains 0.6-8.0 at% of Al and/or Ga and 0.1 at% or more of Si so that the total of Al, Ga and Si is 33.0 at% or less relative to the total amount of all the metal elements, with the balance made up of Zn and unavoidable impurities. This sputtering target for forming a transparent oxide film is also characterized in that complex oxide particles of Zn and Si, which have particle diameters of 5 μm or less, are present in the fired body.

Description

Sputtering target for forming transparent oxide film and method for producing the same

In particular, the present invention is a light barrier protective film suitable for an optical disc, a touch panel element, a liquid crystal display element, an electroluminescence display element, an electrophoretic display element, a gas barrier layer used for electronic paper such as a toner display element, a solar cell, etc. The present invention relates to a zinc oxide-based sputtering target for forming a transparent oxide film and a method for producing the same.
This application claims priority based on Japanese Patent Application No. 2012-178802 filed in Japan on August 10, 2012 and Japanese Patent Application No. 2013-150310 filed on July 19, 2013 in Japan. , The contents of which are incorporated herein.

Conventionally, as a light transmission protective film suitable for an optical disk, and further as a gas barrier layer used for electronic paper such as a touch panel element, a liquid crystal display element, an electroluminescence display element, an electrophoretic display element, a toner display element, and a solar cell. A technique for producing a zinc oxide-based transparent oxide film by a sputtering method is known.

For example, Patent Document 1 contains tin oxide and at least one additive element selected from the group consisting of Si, Ge, and Al. The additive element is based on the total content of the additive element and Sn. The composition of the crystal phase includes at least one of a metal phase of the additive element, an oxide phase of the additive element, and a composite oxide phase of the additive element and Sn. Using the oxide sintered body in which the oxide phase of the additive element and the composite oxide phase of the additive element and Sn are dispersed with an average particle size of 50 μm or less as a sputtering target, A method of forming a transparent oxide film on the surface of a resin film substrate by a sputtering method using a pulsing method has been proposed.

The transparent oxide film obtained by this method is a transparent oxide film containing tin oxide and at least one additional element selected from the group consisting of Si, Ge, and Al. It is included at a ratio of 15 atomic% to 63 atomic% with respect to the total of the additive element and Sn, is an amorphous film, and has a refractive index of 1.90 or less at a wavelength of 633 nm.

Patent Document 2 describes forming a light transmission film used as a protective film for a phase change optical disk. Here, 0.01 to 20% by weight of one or more glass-forming oxides selected from Nb ₂ O ₅ , V ₂ O ₅ , B ₂ O ₃ , SiO ₂ , and P ₂ O ₅ , Al ₂ O ₃ or Ga ₂ O _{3 in an amount} of 0.01 to 20% by weight, and using a sputtering target containing a balance of one or more oxides selected from In ₂ O ₃ , SnO ₂ and ZnO, by a sputtering method, 0.01 to 20% by weight of one or more glass-forming oxides selected from Nb ₂ O ₅ , V ₂ O ₅ , B ₂ O ₃ , SiO ₂ and P ₂ O ₅ , Al ₂ O ₃ or Ga the ₂ O ₃ and 0.01 to 20 wt%, the balance _in 2 _{O 3,} SnO 2, a method of forming a light transmitting film is one or more oxides selected from ZnO has been proposed .

Japanese Unexamined Patent Publication No. 2007-290916 (A) Japanese Unexamined Patent Publication No. 2000-119062 (A)

In the conventional technique, for example, when an oxide film is formed using the target described in Patent Document 1, many nodules are generated during sputtering of the film formation, and it takes time to clean the apparatus. Therefore, there has been a demand for a transparent oxide film that is not tin oxide-based but has an excellent gas barrier property of another composition system. However, since the transparent oxide film described in Patent Document 2 has a high refractive index, the refractive index of the resin film base material can be used for the gas barrier layer on the resin film base material used in the electronic paper and solar cell described above. In order to approach (for example, the refractive index n: 1.5 to 1.7 at a wavelength of 633 nm), the refractive index of the film needs to be lowered.

For this reason, it can be considered that the zinc oxide-based transparent oxide film contains more SiO ₂ to lower the refractive index. However, when SiO ₂ is added to the sputtering target, since the SiO ₂ itself is insulative, high-frequency (RF) sputtering must be employed for forming the oxide film. However, since this high-frequency sputtering has a low film formation rate, it is expected that high-productivity direct current (DC) sputtering will be adopted when forming an oxide film. Therefore, as described in Patent Document 2, it has been proposed to reduce the resistance of the target so that DC sputtering can be employed.
In order to reduce the resistance, Al ₂ O ₃ or Ga ₂ O ₃ is contained in the sputtering target, but in order to achieve transparency close to the refractive index of glass, a large amount of SiO ₂ is added. Must. On the contrary, the addition of a large amount of SiO ₂ makes it difficult to employ DC sputtering.

Here, in order to produce a zinc oxide-based sputtering target that satisfies the above-described requirements, mixing is performed by mixing and mixing an appropriate amount of ZnO powder, SiO ₂ powder, and Al ₂ O ₃ powder or Ga ₂ O ₃ powder. It is necessary to obtain a sintered body obtained by firing the powder under predetermined firing conditions. At this time, depending on the firing method, ZnO and SiO ₂ react with each other in the sintered body, and large particles of a composite oxide of Zn and Si (composition formula: Zn ₂ SiO ₄ ) are present. It is formed. However, when a sputtering target containing such complex oxide particles is used, if a film is formed by direct current sputtering, plasma is not generated and sputtering cannot be performed due to abnormal discharge. Alternatively, there has been a problem that abnormal discharge frequently occurs and this affects film formation. Furthermore, even when Al ₂ O ₃ powder or Ga ₂ O ₃ is used as a raw material powder in a large amount of powder, direct current (DC) sputtering is performed using the manufactured zinc oxide-based sputtering target. There was a problem that abnormal discharge occurred frequently.

Therefore, the present invention has been made in view of the above-mentioned problems, and by adjusting the generation of a composite oxide of Zn and Si in a sputtering target, a transparent oxide film can be formed by DC sputtering, An object of the present invention is to provide a zinc oxide-based sputtering target for forming a transparent oxide film that hardly causes abnormal discharge during sputtering and a method for producing the same.

The inventors of the present invention used a zinc oxide-based sputtering target containing SiO ₂ , Al ₂ O ₃ and / or Ga ₂ O ₃ to dc-sputter an A1 (and / or Ga) —Zn—Si—O film. Research was conducted to form a film.

As described above, in manufacturing this zinc oxide-based sputtering target, a sintered powder is obtained by firing a mixed powder of ZnO powder, SiO ₂ powder, Al ₂ O ₃ powder and / or Ga ₂ O ₃ powder. As a result, composite oxide particles of Zn ₂ Si ₄ of Zn ₂ SiO ₄ having a large particle size are formed in the substrate of the sintered body. Moreover, the adjustment to the formation of the composite oxide particles is difficult even if various baking conditions are devised.

Therefore, the inventors do not obtain a sintered body by firing a mixed powder of ZnO powder, SiO ₂ powder, Al ₂ O ₃ powder or Ga ₂ O ₃ powder, but first, ZnO powder and After calcining the mixed powder of SiO ₂ powder to obtain a calcined body in which a composite oxide of Zn and Si of Zn ₂ SiO ₄ is formed, this calcined body is made into a fine pulverized powder, The pulverized powder is used as a raw material powder, and the composition of the A1 (and / or Ga) -Zn-Si-O film, which is a film-forming purpose, is composed of ZnO powder and Al ₂ O ₃ powder or Ga ₂ O ₃ powder. It is easy to adjust the presence of composite oxide particles of Zn and Si in the produced sputtering target by firing the mixed powder weighed and mixed so as to obtain a fired body. This complex acid of Zn and Si Things particles was also obtained knowledge that is finely formed.

Then, the present inventors tried manufacture of a zinc oxide type sputtering target as one test example. First, ZnO, each raw material powder of _{SiO 2 ZnO: SiO 2 = 2} : 1 were weighed so that the molar ratio, wet mixing the raw material powder this weighed. The obtained mixed powder was dried, granulated, and fired in the atmosphere at 1200 ° C. for 5 hours to obtain a calcined powder. This calcined powder is a complex oxide of Zn and Si of Zn ₂ SiO ₄ . The calcined powder was pulverized and granulated. Next, the calcined powder is used as a raw material powder, each raw material powder of ZnO and Al ₂ O ₃ is weighed so as to have a predetermined ratio, and the weighed raw material powders are mixed. The obtained mixed powder was fired in a nitrogen gas atmosphere at 1400 ° C. for 3 hours to obtain a sintered body. The sintered body was machined into a predetermined shape to produce a sputtering target for forming a transparent oxide film. The composition component in the manufactured sputtering target was analyzed. The analysis result is shown in FIG.

The photograph in FIG. 1 is an element distribution image obtained by EPMA (field emission electron probe) for the manufactured sputtering target. From the four photographs in the figure, Zn, Si, A1, and O The state of composition distribution of each element can be observed individually.
Note that the element distribution image by EPMA is originally a color image, but in the photograph of FIG. 1, it is converted into a black and white image. Therefore, the whiter in the photograph, the higher the concentration of the element. ing. Specifically, in the distribution image related to Al, the Al element is distributed in white spots (relatively white portions), and in the distribution image related to Zn, the Zn element exists as a whole, and among them, the concentration is high. The white parts to be observed are distributed, and in the distribution image relating to O, it is observed that the O element is present at a certain concentration as a whole. In the distribution image relating to Si, it can be observed that the Si element is present at a certain concentration, but is not present in the portion where the Zn element concentration is high. From these, and ZnO, composite oxides of Si and Zn and _(Zn 2 SiO _4), but is presumed to exist separately.

On the other hand, the graph of FIG. 2 has shown the analysis result by X-ray diffraction (XRD) of the sputtering target for transparent oxide film formation manufactured as mentioned above. The upper graph in FIG. 2 shows the entire peak, the middle graph shows the peak related to Zn ₂ SiO ₄ , and the lower graph shows the peak related to ZnO. . Considering the distribution image shown in FIG. 1 and the peak appearing in the graph of FIG. 2 together, ZnO and / or AZO (Al-doped ZnO) and the composite oxide of Zn and Si are separated. It can be seen that there is no SiO ₂ crystal phase. If SiO ₂ is present alone and crystal phase is precipitated, a corresponding peak should appear in the XRD diffraction result. In the diffraction result graph of FIG. No peak appeared and no SiO ₂ crystal phase was detected.

To sum up the above, in the manufactured sputtering target, Si is present as a composite oxide of Zn and Si in the substrate of the fired body made of the Al—Zn—Si—O quaternary element, It was confirmed that no SiO ₂ crystal phase was present. Therefore, when manufacturing a sputtering target for forming an A1 (and / or Ga) —Zn—Si—O transparent oxide film, a pre-fired Zn ₂ SiO ₄ composite oxide of Zn and Si is used. Prepared as a raw material powder, and using this raw material powder, ZnO powder, Al ₂ O ₃ powder and / or Ga ₂ O ₃ powder, A1 (and / or Ga) -Zn— It was confirmed that the procedure of firing the mixed powder weighed so as to have the component composition of the Si—O film is effective in adjusting the presence of complex oxide particles of Zn and Si in the sputtering target. It was. By adopting this procedure, it was found that, during sputtering, abnormal discharge and generation of particles can be reduced, and a transparent oxide film can be formed by DC sputtering. Note that the same was true for a fired body made of a Ga—Zn—Si—O quaternary element in which Al was replaced with Ga.

Therefore, the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems.
(1) The sputtering target for forming a transparent oxide film according to the present invention includes one or two of Al and Ga: 0.6 to 8.0 at%, Si: 0.0. 1 at% or more, and a total of 33.0 at% or less of Al, Ga and Si, and the balance is a fired body having a composition composed of Zn and inevitable impurities, and the fired body has a particle size of 5 μm or less. The composite oxide of Zn and Si is present, the bending strength of the fired body is 90 MPa or more, the relative density of the fired body is 90% or more, The heat conductivity of the fired body is 7.5 W / m · k or more.

(2) A method of manufacturing a transparent oxide film forming sputtering target of the present invention is a method for producing a transparent oxide film-forming sputtering target of (1), a ZnO powder and SiO ₂ powder The raw material powder blended and mixed at a molar ratio of 2: 1 is fired and then pulverized to obtain a composite oxide powder, and any one or two of the composite oxide powder, Al ₂ O ₃ powder and Ga ₂ O ₃ powder And a mixed powder obtained by mixing and mixing ZnO powder to obtain a fired body, and in the manufacturing method, the mixed powder is non-oxidized at a temperature of 1100 to 1450 ° C. It is characterized in that it is fired in a neutral atmosphere for 1 to 10 hours, and the fired body is cooled at a cooling rate of 30 to 150 ° C./h. Alternatively, the manufacturing method of the sputtering target for forming the transparent oxide film includes ZnO powder having an average particle diameter of 0.1 to 3.0 μm, SiO ₂ powder having an average particle diameter of 0.2 to 4.0 μm, and Al _2. One or two of O ₃ powder and Ga ₂ O ₃ powder are blended and mixed, and the temperature is 1150 to 1300 ° C., the pressure is 100 to 400 kgf / cm ² , and the non-oxidizing atmosphere is 1 to 10 hours. And is fired under pressure to obtain a fired body.

The reasons for limiting each element in the sputtering target for forming a transparent oxide film of the present invention will be described below.
1) Si: 0.1 at% or more:
The content of Si in the sputtering target, with respect to the total metal component amount is less than 0.01 at%, since the effect of suppressing crystallization is small no effect of addition, whereas, if too great, SiO ₂ Therefore, the Si content is preferably 0.1 at% or more and the total of Al and Ga is preferably 33 at% or less, which effectively suppresses crystallization. be able to.
2) Any one or two of Al and Ga: 0.6 to 8.0 at%:
If the total content of any one or two of Al and Ga in the sputtering target is less than 0.6 at%, sufficient conductivity for direct current sputtering cannot be obtained. On the other hand, if it exceeds 8.0 at%, ZnAl ₂ O ₄ and ZnGa ₂ O ₄ which are complex oxides of Al or Ga and Zn are likely to be generated, and abnormal discharge occurs due to this. Therefore, direct current sputtering cannot be performed. In order to suppress the occurrence of abnormal discharge, it is desirable that the (311) diffraction peak of these composite oxides is not more than the (101) diffraction peak of ZnO.
3) Si + Al + Ga: 33 at% or less:
If the total content of Al, Ga and Si in the sputtering target exceeds 33 at%, the specific resistance of the sputtering target itself increases, abnormal discharge is likely to occur, and stable direct current sputtering becomes difficult. The total content of Al, Ga, and Si was 33 at% or less.
4) Particle size of complex oxide of Zn and Si:
The reason why the average particle size (D50) of the composite oxide of Zn and Si (Zn ₂ SiO ₄ ) present in the sputtering target is 5 μm or less is that when this particle size exceeds 5 μm, This is because abnormal discharge occurs frequently, and the occurrence of abnormal discharge was suppressed by setting the thickness to 5 μm or less. The particle size of the composite oxide of Zn and Si is more preferably 4.5 μm or less, and most preferably 4.1 μm or less.
5) Folding strength, relative density and thermal conductivity of the fired body:
The bending strength of the fired body was 90 MPa or more, the relative density of the fired body was 90% or more, and the thermal conductivity of the fired body was 7.5 W / m · k or more. The reason for this limitation is that the generation of target cracks can be suppressed.

Further, in the transparent oxide film-forming sputtering target producing process of the present invention, prior to making a sintered body which is a material of the sputtering target, in advance, ZnO each raw material powder of ZnO and SiO _2: SiO _{2 = 2} The powder mixture weighed so as to be 1 (molar ratio) was fired to obtain a calcined body of a complex oxide of Zn and Si (Zn ₂ SiO ₄ ). Using this calcined body, it can be pulverized to produce a fine Zn ₂ SiO ₄ powder having an average particle diameter (D50). This powder was used as a raw material powder for obtaining the sintered body. The calcining conditions for obtaining this calcined body can be calcined in the air or in an oxygen atmosphere at a temperature of 1000 to 1500 ° C., preferably 1100 to 1200 ° C. for 2 to 9 hours. If the particle diameter of the Zn ₂ SiO ₄ powder is 30 μm or less, the average particle diameter (D50) of the mixed powder obtained by pulverizing and mixing this powder, the Al ₂ O ₃ powder, and the ZnO powder is 5 μm. It is easy to: If the particle size exceeds 30 μm, it takes too much time to ball mill and make the average particle size (D50) of the mixed powder 5 μm or less, which is not preferable.

Next, the calcined powder obtained by pulverizing the calcined body, that is, a fine Zn ₂ SiO ₄ powder is used as one raw material powder for obtaining a fired body, and ZnO powder, Al ₂ O ₃ powder and Ga ₂ O are obtained. Any one or two raw material powders of the _three powders are adjusted to a predetermined ratio so as to have a component composition of the A1 (or Ga) —Zn—Si—O quaternary oxide film for film formation. Weighing and mixing the weighed raw material powders to obtain a mixed powder. After this mixed powder is formed by cold isostatic pressing (CIP), an inert gas atmosphere such as nitrogen is applied at a temperature of 1200 to 1450 ° C., preferably at a temperature of 1350 to 1400 ° C. for 2 to 9 hours. Bake in. This baking may be performed by hot pressing (HP) or hot isostatic pressing (HIP). The fired body is machined into a predetermined shape to produce a sputtering target having a predetermined shape.

In the method for producing a sputtering target for forming a transparent oxide film of the present invention, the mixed powder is heated to 1100 to 1450 ° C. in a non-oxidizing atmosphere (N ₂ gas, Ar gas, vacuum), and 1 to 10 The fired body can be fired while maintaining time, and the fired body can be cooled at a cooling rate of 30 to 150 ° C./h.
When the mixed powder is fired, if the firing holding time is too short and the cooling rate is too low, all of the bending strength, relative density, and thermal conductivity are lowered, and abnormal discharge occurs frequently.
On the other hand, if the firing holding time is too long and the cooling rate is too high, target cracks occur, which is not preferable. By producing a sputtering target according to these conditions, it is possible to adjust the bending strength, relative density, and thermal conductivity of the fired body to appropriate ranges, and it is possible to reduce abnormal discharge and suppress the generation of target cracks. .

In the method for producing a sputtering target for forming a transparent oxide according to the present invention, a ZnO powder having an average particle size of 0.1 to 3.0 μm, and an SiO ₂ powder having an average particle size of 0.2 to 4.0 μm One or two of Al ₂ O ₃ powder and Ga ₂ O ₃ powder are blended and mixed, and 1 to 1 at a temperature of 1150 to 1300 ° C., a pressure of 100 to 400 kgf / cm ² and a non-oxidizing atmosphere. A fired body can be obtained by pressure firing while holding for 10 hours.
By using ZnO powder having an average particle diameter of 0.1 to 3.0 μm and SiO ₂ powder having an average particle diameter of 0.2 to 4.0 μm as the raw material powder, the manufacturing process of the calcined body is omitted. It is possible.
In addition, the mixed powder can be fired in a temperature of 1150 to 1300 ° C., 100 to 400 kgf / cm ² , and a non-oxidizing atmosphere (N ₂ gas, Ar gas, vacuum) for 1 to 10 hours. . As the firing method, for example, hot press or HIP can be used.

If the average particle size of the ZnO powder and the SiO ₂ powder is too small, handling during mixing becomes difficult. On the other hand, if it is too large, the particle size of the complex oxide of Zn and Si (Zn ₂ SiO ₄ ) during firing Is larger than 5 μm, and abnormal discharge occurs frequently. When the mixed powder is fired, if the firing holding time is too short and the cooling rate is too low, all of the bending strength, relative density, and thermal conductivity are lowered, and abnormal discharge occurs frequently. On the other hand, if the firing holding time is too long and the cooling rate is too high, target cracks occur, which is not preferable. By producing a sputtering target according to these conditions, it is possible to adjust the bending strength, relative density, and thermal conductivity of the fired body to appropriate ranges, and it is possible to reduce abnormal discharge and suppress the generation of target cracks. .

In addition, in the manufacturing method of the sputtering target for transparent oxide film formation of this invention, it is preferable to bake in the atmosphere whose oxygen content is less than air | atmosphere. This is because if the sintering is performed in an atmosphere having a lower oxygen content than the air, the specific resistance of the sputtering target tends to be low, and abnormal discharge of direct current sputtering tends to be low.

As described above, the sputtering target for forming a transparent oxide film of the present invention can be used for the formation of a transparent oxide film having a low refractive index by direct current sputtering, and is suitable for a light transmission protective film, a touch panel element, and a liquid crystal display suitable for optical disks. It is suitable for use in forming a film such as a gas barrier layer used in electronic paper such as an element, an electroluminescence display element, an electrophoretic display element, and a toner display element, and a solar cell.

According to the sputtering target for forming a transparent oxide film of the present invention, since a fine composite oxide of Zn and Si having a particle size (D50) of 5 μm or less is present in the fired body, direct current sputtering is used. When forming the film, the occurrence of abnormal discharge can be eliminated or reduced, and the transparent oxide film can be formed efficiently by direct current sputtering. Then, in the production of the transparent oxide film-forming sputtering target, advance to create a composite oxide of a previously tentatively calcined Zn ₂ SiO ₄ and Zn and Si as raw material powder, and the raw material powder, and ZnO powder , Al ₂ O ₃ powder and / or Ga ₂ O ₃ powder, mixed powder weighed to have a component composition of A1 (and / or Ga) —Zn—Si—O film for film formation By adopting the procedure of firing, it becomes easy to refine the composite oxide of Zn and Si of Zn ₂ SiO ₄ existing in the sputtering target, and the amount thereof can be easily adjusted. be able to.

It is an element distribution image of each element which measured the structure | tissue of the sputtering target by EPMA about one specific example of the sputtering target for transparent oxide film formation which concerns on this invention. It is a graph which shows the analysis result of the X-ray diffraction (XRD) of the sputtering target for transparent oxide film formation which concerns on this invention.

Next, the target for forming a transparent oxide film and the method for producing the same of the present invention will be specifically described below with reference to examples.

[First embodiment]
In the first embodiment, in producing a sputtering target for forming a transparent oxide film, first, a calcined body made of a composite oxide of Zn and Si, obtained by firing a raw material powder of zinc oxide powder and silicon oxide powder. The calcined body was prepared and pulverized to obtain a composite oxide powder of Zn and Si. Next, the obtained composite oxide powder of Zn and Si, zinc oxide powder, and mixed powder of one or two of aluminum oxide powder and gallium oxide powder are fired after molding to obtain a fired body. This was machined to produce a sputtering target. This production will be described in detail below.

1) A case where a mixed powder of a composite oxide powder of Zn and Si, a zinc oxide powder, and an aluminum oxide powder is used will be described.
First, each raw material powder of zinc oxide (chemical formula: ZnO, D ₅₀ = 1 μm) and silicon oxide (chemical formula: SiO ₂ , D ₅₀ = 2.0 μm) becomes ZnO: SiO ₂ = 2: 1 (molar ratio). Weigh as follows. Each of the weighed raw material powders and three times the weight (weight ratio) of zirconia balls (diameters 5 mm and 10 mm are the same weight) are placed in a plastic container and wet-mixed for 16 hours in a ball mill apparatus to obtain a mixed powder. . In addition, alcohol is used for the solvent in this case, for example.

Next, the obtained mixed powder is dried, granulated, and fired in the atmosphere at 1200 ° C. for 5 hours to obtain a calcined body (complex oxide of Zn and Si: Zn ₂ SiO ₄ ). This calcined body and a zirconia ball of 5 times the weight (weight ratio) (diameters of 5 mm and 10 mm are the same weight) are put in a plastic container and wet pulverized in a ball mill apparatus for 24 hours. In addition, alcohol is used for the solvent in this case, for example. After pulverized, dried and granulated calcined powder (composite oxide powder of Zn and Si) (chemical formula: Zn ₂ SiO ₄ , D ₅₀ = 12 μm) and zinc oxide (chemical formula: ZnO, D ₅₀ = 1 μm) Each raw material powder with aluminum oxide (chemical formula: Al ₂ O ₃ , D ₅₀ = 0.2 μm) is weighed to a predetermined ratio. These blending ratios are shown in Table 1.

Each of the weighed raw material powders and zirconia balls of 5 times the weight (weight ratio) (diameters 5 mm and 10 mm are the same weight) are put in a plastic container and wet-mixed for 24 hours in a ball mill apparatus. In addition, alcohol is used for the solvent in this case, for example. Next, the obtained mixed powder was dried, granulated, molded by cold isostatic pressing (CIP), and then fired in a nitrogen gas atmosphere at 1400 ° C. for 3 hours to obtain a fired body. Note that this baking can also be performed by hot pressing (HP) under a load of 200 kgf · cm ⁻² at 1200 ° C. for 3 hours in a vacuum or an inert atmosphere. The fired body was machined to obtain a sputtering target having a diameter of 125 mm and a thickness of 5 mm. Thus, the sputtering targets of Examples 1 to 8 and Comparative Examples 1 to 4 shown in Table 1 were manufactured. In addition, the calcined body in the case of the comparative example 4 was baked at the temperature of 950 degreeC.

2) The case of using a mixed powder of a composite oxide powder of Zn and Si, zinc oxide powder (ZnO), and gallium oxide powder (Ga ₂ O ₃ ) will be described.
Also in this case, the sputtering target was manufactured in the same procedure as the case of using the mixed oxide powder of Zn and Si, the zinc oxide powder, and the aluminum oxide powder described above. That is, gallium oxide powder was used in place of the aluminum oxide powder, and a mixed powder was obtained according to the blending ratio shown in Table 1. Thus, the sputtering targets of Examples 9 to 12 and Comparative Examples 5 and 6 shown in Table 1 were manufactured.

3) A case where a mixed powder of a composite oxide powder of Zn and Si, zinc oxide powder (ZnO), aluminum oxide powder (Al ₂ O ₃ ), and gallium oxide powder (Ga ₂ O ₃ ) is used will be described. .
Also in this case, the sputtering target was manufactured in the same procedure as the case of using the mixed oxide powder of Zn and Si, the zinc oxide powder, and the aluminum oxide powder described above. That is, in addition to the aluminum oxide powder, gallium oxide powder was also used, and a mixed powder was obtained according to the blending ratio shown in Table 1. Thus, the sputtering targets of Example 13 and Comparative Example 7 shown in Table 1 were manufactured.

In the production of the sputtering target described so far, a composite oxide powder of Zn and Si is used as a raw material powder, and a mixed powder containing this powder and other raw material powders is fired to obtain a fired body. Here, for comparison, a composite oxide powder of Zn and Si is not obtained as a raw material powder by calcination of zinc oxide (ZnO) and silicon oxide (SiO ₂ ). Thus, the raw material powder of zinc oxide (ZnO) and silicon oxide (SiO ₂ ) was mixed so as to have a predetermined ratio, and fired under the same conditions as described above to prepare a fired body. In this case, during this firing, a composite oxide of Zn and Si (Zn ₂ SiO ₄ ) is formed in the fired body from zinc oxide (ZnO) and silicon oxide (SiO ₂ ). Table 1 shows the sputtering target of Comparative Example 8.

Next, Table 2 shows the metal compositions of the sputtering targets of Examples 1 to 13 and Comparative Examples 1 to 8.

Next, the sputtering targets of Examples 1 to 13 and Comparative Examples 1 to 8 shown in Tables 1 and 2 were subjected to XRD analysis, analysis by EPMA, and specific resistance measurement.

<XRD analysis>
The XRD analysis was performed by the same method as the XRD analysis shown in FIG. The presence or absence of an XRD peak was confirmed by XRD analysis on the sputtering target. This XRD analysis was performed under the following conditions.
Preparation of sample: The sample was wet-polished with SiC-Paper (grit 180) and dried, and then used as a measurement sample.
Equipment: Rigaku Electric Co., Ltd. (RINT-Ultima / PC)
Tube: Cu
Tube voltage: 40 kV
Tube current: 40 mA
Scanning range (2θ): 5 ° -80 °
Slit size: Divergence (DS) 2/3 degree, Scattering (SS) 2/3 degree, Light reception (RS) 0.8mm
Measurement step width: 0.02 degrees at 2θ Scan speed: 2 degrees per minute Sample stage rotation speed: 30 rpm

<EPMA analysis>
The distribution of Zn, Si, Al, Ga, and O in the structure of the sputtering target was confirmed from the element distribution image obtained by EPMA.

<EBSD analysis>
The size of the composite oxide (Zn ₂ SiO ₄ ) particles of Zn and Si in the structure of the sputtering target was confirmed from the IQ map obtained by EBSD. In addition, the IQ map measured the particle size quantitatively by observing a cross-sectional area of 95 μm × 33 μm.
In addition, EBSD collected the pattern using OIM Data Collection of TSL Solutions, Inc., and calculated the particle size using OIM Analysis 5.31 manufactured by the company.

<Specific resistance measurement>
The specific resistance of the sputtering target was measured using a resistance measuring instrument Loresta GP manufactured by Mitsubishi Chemical Corporation.

Next, using the sputtering targets of Examples 1 to 13 and Comparative Examples 1 to 8 described above, a film formation test was performed under the following film formation conditions.
<Film formation conditions>
Power supply: DC1000W or RF1000W
Total pressure: 0.4Pa
Sputtering gas: Ar = 45 sccm, O ₂ : 5 sccm
Target-substrate (TS) distance: 70mm

The number of abnormal discharges was measured by a film formation test according to the above film formation conditions. Based on the measurement results, the possibility of direct current (DC) sputtering of the sputtering targets of Examples 1 to 13 and Comparative Examples 1 to 8 was evaluated. The results of the measurement / evaluation are shown in Table 3.

<Measurement of abnormal discharge times>
Sputtering was performed for 12 hours under the above conditions, and the number of abnormal discharges was measured. Thereafter, the sputtering chamber was opened, and particles in the chamber were confirmed.

In Table 3, when plasma is not generated and sputtering is impossible, “sputtering impossible” is indicated.
The above results are shown in Table 3.

As shown in Table 3, in any of the sputtering targets of Examples 1 to 13, ZnO and Zn ₂ SiO ₄ were formed in the target structure in the XRD analysis and EPMA analysis described above. It could be confirmed.

According to Table 3, as a result of direct current sputtering using the sputtering targets of Examples 1 to 13, it was confirmed that in all cases, the number of abnormal discharges was extremely small (0 to 3 times per hour). In any of the examples, it was proved that direct current sputtering can be performed, and generation of particles could not be confirmed. On the other hand, when the sputtering targets of Comparative Examples 1, 3, and 5 are to be formed by direct current sputtering, plasma is not generated and sputtering becomes impossible, or Comparative Examples 2, 4, 6, 7, and 8 In the case of, continuous sputtering for 10 seconds or more could not be performed due to frequent abnormal discharge (10,000 times or more per hour). In each comparative example, the film could be formed by high frequency sputtering.

Further, in the case of Comparative Example 4, when the mixed powder of ZnO powder and SiO ₂ powder was calcined, the calcining temperature was low, so that a complex oxide of Zn and Si was sufficient in the calcined body. When a sintered body is obtained by firing a mixed powder of the pulverized powder of this calcined body, ZnO powder, and Al ₂ O ₃ powder, a large composite oxide particle of Zn and Si It is thought that was formed. Furthermore, in the case of Comparative Example 8, since a sintered body is obtained by firing a mixed powder of ZnO powder and SiO ₂ powder from the beginning, at that time, a large-sized composite oxide of Zn and Si Particles are formed.

[Second Embodiment]
In the first embodiment described above, in manufacturing a sputtering target for forming a transparent oxide film, first, a raw material in which zinc oxide (ZnO) powder and silicon oxide (SiO ₂ ) powder are mixed and mixed in a molar ratio of 2: 1. A calcined body made of a complex oxide of Zn and Si (Zn ₂ SiO ₄ ), pulverized and fired after firing the powder, and the calcined body is ground to a composite oxide of Zn and Si (Zn ₂ SiO ₄ ) powder is obtained. Next, the obtained mixed powder of Zn ₂ SiO ₄ powder, ZnO powder, and one or two of aluminum oxide (Al ₂ O ₃ ) powder and gallium oxide (Ga ₂ O ₃ ) powder is fired after molding. By doing this, a fired body was obtained and machined to produce a sputtering target.

In the second embodiment, in the method for producing the sputtering target for forming a transparent oxide film, firing holding that affects the bending strength, thermal conductivity, and relative density of the fired body obtained by firing the above-mentioned mixed powder compact. The time and the cooling rate after firing were adjusted as shown in Table 4, and the transparent oxide film forming sputtering targets of Examples 101 to 127 were produced. In Examples 101 to 109, when a mixed powder of Zn ₂ SiO ₄ powder: 50.0 mol%, Al ₂ O ₃ powder: 3.0 mol%, and ZnO powder: remainder is used, Examples 110 to 118 are used. In the case of using a mixed powder of Zn ₂ SiO ₄ powder: 80.0 mol%, Al ₂ O ₃ powder: 1.0 mol%, and ZnO powder: balance, Examples 119 to 127 are Zn ₂ SiO ₄ powder: 22.0 mol%, Al ₂ O ₃ powder: 0.6 mol%, and a mixed powder of ZnO powder: remainder are shown representatively.

Therefore, the bending strength, thermal conductivity, and relative speed of the produced sputtering targets for forming a transparent oxide film of Examples 101 to 127 were measured. The measurement results are shown in Table 4.

<Measurement of bending strength>
A plate having dimensions of width: 4 mm, length: 40 mm, thickness: 3 mm was cut out from the fired body obtained above to produce a bending test piece.
Using this test piece, a three-point bending test was performed by the method specified in JIS R-1601 to determine the bending strength (MPa).

<Measurement of thermal conductivity>
The sample obtained from the fired body obtained above was measured for thermal conductivity (W / m · k) by a laser flash method.
Analytical apparatus: NETZSCH-Geratebau GmbH, Xe flash analyzer, sample size: 10 mm × 10 mm, thickness: 2 mm, measurement temperature: 25 ° C., standard comparison sample: SUS310, pulse width: 0.2 ms, charge level: 270 V Measurements were made. This measurement was performed three times on the same sample, and the average value of the measured values was obtained.

<Measurement of relative density>
The relative density ratio (%) was calculated by machining the fired body to a predetermined size, measuring the weight, obtaining the bulk density, and dividing by the theoretical density ρ _fn . The theoretical density ρ _fn was determined by the following formula based on the weight of the raw material. Since this formula shows a case where both Al ₂ O ₃ powder and Ga ₂ O ₃ powder are mixed, in the second embodiment, only Al ₂ O ₃ powder is mixed, so C4: Ga ₂ It is determined that there is no term relating to O ₃ .

Next, XRD analysis, analysis by EPMA, and specific resistance measurement were performed on the sputtering targets of Examples 101 to 127 shown in Table 4. XRD analysis, analysis by EPMA, and specific resistance measurement were performed under the same conditions as those for the sputtering target of the first example. The results are shown in Table 5.
Further, using the sputtering targets of Examples 101 to 127, a film formation test was performed under the same film formation conditions as in the first example.
The number of abnormal discharges was measured by a film formation test according to the above film formation conditions. Based on the measurement results, the possibility of direct current (DC) sputtering of the sputtering targets of Examples 101 to 127 was evaluated. The results of the measurement / evaluation are shown in Table 5.

As shown in Table 5, in any of the sputtering targets of Examples 101 to 127, ZnO and Zn ₂ SiO ₄ were formed in the target structure in the XRD analysis and EPMA analysis described above. It can be confirmed that the Zn ₂ SiO ₄ particle size is 5 μm or less. Further, as a result of performing direct current sputtering using the sputtering targets of Examples 101 to 127, in all cases, the number of occurrences of abnormal discharge was small, and it was proved that direct current sputtering can be performed in any of the Examples. The generation of particles could not be confirmed. And by adjusting the firing holding time and the cooling rate after firing, it is confirmed that a sputtering target having an appropriate bending strength, thermal conductivity and relative density can be obtained, the occurrence of abnormal discharge can be reduced, Target cracking could be suppressed. Incidentally, instead of _Al 2 _{O 3} powder, only _Ga 2 _{O 3} powder, or in the case of mixing of both _Al 2 _{O 3} powder and _Ga 2 _{O 3} powder is also similar to the above results were obtained .

[Third embodiment]
Above the transparent oxide film for forming a sputtering target manufacturing method of the first embodiment, a composite oxide of Zn and Si was calcined and ZnO powder and SiO ₂ powder _(Zn 2 SiO ₄₎ as a raw material powder, Table Although the mixed powder having the raw material composition shown in FIG. 1 was fired, in the third example, the manufacturing process of the calcined body was omitted, and instead of using the Zn ₂ SiO ₄ powder, a considerable amount of ZnO powder and SiO ₂ were used. _Two powders were used as raw powders. In the third embodiment a transparent oxide film-forming sputtering target manufacturing method of according to, SiO ₂ powder, the _Al 2 _{O 3} powder and ZnO powder as the raw material powder. Of the raw material powder, for ZnO powder and SiO ₂ powder were used ZnO powder and SiO ₂ powder having a particle diameter shown in Table 6. Further, the firing temperature and firing retention time affecting the bending strength, thermal conductivity and relative density of the fired body were adjusted as shown in Table 6, and the transparent oxides of Examples 201 to 227 were used. A sputtering target for film formation was produced. Examples 201 to 209 use a mixed powder of SiO ₂ powder: 25.4 mol%, Al ₂ O ₃ powder: 1.6 mol%, and ZnO powder: the balance. Examples 210 to 218 When using a mixed powder of SiO ₂ powder: 30.6 mol%, Al ₂ O ₃ powder: 0.4 mol%, and ZnO powder: balance, Examples 219 to 227 are SiO ₂ powder: 15 The case where a mixed powder of .3 mol%, Al ₂ O ₃ powder: 0.4 mol%, and ZnO powder: remainder is used is representatively shown.

Accordingly, the bending strength, thermal conductivity, and relative velocity of the produced sputtering targets for forming transparent oxide films of Examples 201 to 227 were measured in the same manner as in the second example. The measurement results are shown in Table 6.

Next, XRD analysis, analysis by EPMA, and specific resistance measurement were performed on the sputtering targets of Examples 201 to 227 shown in Table 6. XRD analysis, analysis by EPMA, and specific resistance measurement were performed under the same conditions as those for the sputtering target of the first example. The results are shown in Table 7.
In addition, a film formation test was performed using the sputtering targets of Examples 201 to 227 under the same film formation conditions as in the first example.
The number of abnormal discharges was measured by a film formation test according to the above film formation conditions. Based on the measurement results, the possibility of direct current (DC) sputtering of the sputtering targets of Examples 201 to 227 was evaluated. The results of the measurement / evaluation are shown in Table 7.

As shown in Table 7, in any of the sputtering targets of Examples 201 to 227, ZnO and Zn ₂ SiO ₄ were formed in the target structure in the XRD analysis and EPMA analysis described above. It can be confirmed that the Zn ₂ SiO ₄ particle size is 5 μm or less. Furthermore, as a result of performing direct current sputtering using the sputtering targets of Examples 201 to 227, the number of occurrences of abnormal discharge was small in any case, and it was proved that direct current sputtering can be performed in any of the Examples. The generation of particles could not be confirmed. And by adjusting the firing temperature and firing holding time, it is confirmed that a sputtering target having an appropriate bending strength, thermal conductivity and relative density can be obtained, the occurrence of abnormal discharge can be reduced, and target cracking can be reduced. I was able to suppress it. Incidentally, instead of _Al 2 _{O 3} powder, only _Ga 2 _{O 3} powder, or in the case of mixing of both _Al 2 _{O 3} powder and _Ga 2 _{O 3} powder is also similar to the above results were obtained .

As described above, according to the method for manufacturing a sputtering target for forming a transparent oxide film according to the present invention, a mixed powder of ZnO powder and SiO ₂ powder is temporarily fired to obtain Zn and Si having a composition of Zn ₂ SiO ₄ . A calcined body is obtained by forming a composite oxide, and the calcined body is made into a fine pulverized powder. Then, the pulverized powder is used as a raw material powder, ZnO powder, Al ₂ O ₃ powder, and Ga. _{Since a} fired body is obtained by firing a mixed powder obtained by mixing one or two kinds of ₂ O ₃ powder, a fine complex oxide of Zn and Si (Zn _{2) is} contained in the fired body. The presence of SiO ₄ ) was confirmed, and the sputtering target was able to reduce the specific resistance and enable direct current (DC) sputtering. Furthermore, since a sputtering target having appropriate bending strength, thermal conductivity and relative density can be obtained, occurrence of abnormal discharge can be reduced and target cracking can be suppressed.

By adjusting the production of complex oxides of Zn and Si in the sputtering target, it becomes possible to form a transparent oxide film by direct current sputtering. Further, it is possible to provide a zinc oxide-based sputtering target for forming a transparent oxide film that hardly causes abnormal discharge during sputtering and a method for manufacturing the same.

Claims (7)

1. One or two of Al and Ga: 0.6 to 8.0 at% and Si: 0.1 at% or more with respect to the total metal component amount, and a total of 33 of Al, Ga and Si. 0.0 at% or less, and the balance is a fired body having a composition consisting of Zn and inevitable impurities,
   A sputtering target for forming a transparent oxide film, wherein a particle size of a complex oxide of Zn and Si is 5 μm or less in the fired body.
2. 2. The sputtering target for forming a transparent oxide film according to claim 1, wherein the bending strength of the fired body is 90 MPa or more.
3. 2. The sputtering target for forming a transparent oxide film according to claim 1, wherein a relative density of the fired body is 90% or more.
4. 2. The sputtering target for forming a transparent oxide film according to claim 1, wherein the fired body has a thermal conductivity of 7.5 W / m · k or more.
5. It is a manufacturing method of the sputtering target for transparent oxide film formation according to any one of claims 1 to 4,
   A raw material powder prepared by mixing and mixing ZnO powder and SiO ₂ powder at a molar ratio of 2: 1 is fired and then pulverized to obtain a composite oxide powder.
   A mixed powder obtained by blending and mixing any one or two of the composite oxide powder, Al ₂ O ₃ powder and Ga ₂ O ₃ powder, and ZnO powder is fired to obtain a fired body. A method for producing a sputtering target for forming a transparent oxide film, comprising:
6. The mixed powder is fired at a temperature of 1100 to 1450 ° C. in a non-oxidizing atmosphere for 1 to 10 hours,
   The method for producing a sputtering target for forming a transparent oxide film according to claim 5, wherein the fired body is cooled at a cooling rate of 30 to 150 ° C / h.
7. It is a manufacturing method of the sputtering target for transparent oxide film formation according to any one of claims 1 to 4,
   ZnO powder having an average particle diameter of 0.1 to 3.0 μm, SiO ₂ powder having an average particle diameter of 0.2 to 4.0 μm, any one of Al ₂ O ₃ powder and Ga ₂ O ₃ powder, or 2 It is characterized by blending seeds and mixing them to obtain a fired body by pressurizing and firing at a temperature of 1150 to 1300 ° C., a pressure of 100 to 400 kgf / cm ² and a non-oxidizing atmosphere for 1 to 10 hours. A method for producing a sputtering target for forming a transparent oxide film.

Images