CN118159686A

CN118159686A - Sputtering target

Info

Publication number: CN118159686A
Application number: CN202380014136.5A
Authority: CN
Inventors: 寺村享祐; 广藤贤太郎
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 2022-01-31
Filing date: 2023-01-16
Publication date: 2024-06-07
Also published as: TW202342791A; JP7403718B1; WO2023145499A1; JPWO2023145499A1

Abstract

The sputtering target of the present invention is a sputtering target formed by bonding a plurality of sputtering targets to a substrate with a bonding material, wherein the sputtering target is made of an oxide containing indium (In) element, zinc (Zn) element, and an additive element (X) containing at least 1 element selected from tantalum (Ta) and niobium (Nb), and the atomic ratio of each element satisfies a predetermined relational expression, and the sputtering target has a substrate protection member disposed In a gap formed between the plurality of sputtering targets.

Description

Sputtering target

Technical Field

The present invention relates to a sputtering target.

Background

In the field of thin film transistors (hereinafter also referred to as "TFTs") used In flat panel displays (hereinafter also referred to as "FPDs"), oxide semiconductors typified by In-Ga-Zn composite oxides (hereinafter also referred to as "IGZO") have been attracting attention In place of conventional amorphous silicon as FPDs are being increasingly used In practice. IGZO has the advantage of exhibiting high field effect mobility and low leakage current. In recent years, with the progress of further higher functionality of FPDs, materials exhibiting field effect mobility higher than that exhibited by IGZO have been desired.

For example, patent documents 1 and 2 propose oxide semiconductors for TFTs, which are obtained from In-Zn-X composite oxides containing indium (In) element, zinc (Zn) element, and optional element X. According to the above-mentioned document, the oxide semiconductor is formed by sputtering using a target material containing an in—zn—x composite oxide.

In addition, in a sputtering target of an oxide semiconductor used for sputtering, since the material is ceramic, it is difficult to construct a large-area target with one target. Thus, a large-area oxide semiconductor sputtering target is manufactured by preparing a plurality of targets having a certain size and bonding the targets to a substrate having a desired area (for example, refer to patent document 3).

As a base material of the sputtering target, cu, ti, SUS or the like is generally used, and a bonding material having excellent heat conduction, for example, a metal such as In is used for bonding these base materials and the target. For example, in the case of manufacturing a large-sized oxide semiconductor sputtering target, a large-sized Cu flat substrate and a Ti cylindrical substrate are prepared, and a plurality of targets bonded to the substrates are prepared. Then, a plurality of targets are disposed on the substrate, and the targets are bonded to the substrate by using a bonding material of In-based or Sn-based metal. In this bonding, adjacent targets are arranged so that a gap of 0.1mm to 1.0mm is generated at room temperature, taking into account the difference in thermal expansion between the base material and the targets.

Prior art literature

Patent literature

Patent document 1: US2013/270109 publication

Patent document 2: US2014/102892 publication

Patent document 3: WO 2012/063238

Disclosure of Invention

In the case of using such a sputtering target formed by bonding a plurality of targets and a semiconductor element having a thin film formed by sputtering, cu and Ti, which are constituent materials of a base material, are sputtered from gaps between the targets during sputtering, and there is a concern that the Cu and Ti may be mixed into the thin film. Although the mixing of Cu and Ti in the thin film is at a level of several ppm, the effect thereof is extremely large ON the oxide semiconductor, and for example, when comparing a semiconductor element formed in the vicinity of the gap of the target material and mixed with Cu and Ti with a semiconductor element other than the semiconductor element, the field effect mobility of the TFT element tends to be low, and the ON/OFF ratio also tends to be low. Such a problem is also to be solved in order to promote the large area of the sputtering target.

The purpose of the present invention is to provide a sputtering target which can effectively prevent the mixing of the constituent materials of a base material into a thin film formed even in a large-area sputtering target obtained by bonding a plurality of targets.

As a result of intensive studies to solve the above problems, the present inventors have found that by disposing a base material protection member in a gap formed between a plurality of sputtering targets, the constituent materials of the base material are not sputtered, and the constituent materials can be effectively prevented from being mixed into the thin film to be formed.

Specifically, the present invention provides a sputtering target formed by bonding a plurality of sputtering targets made of an oxide containing indium (In) element, zinc (Zn) element and an additive element (X) to a base material by a bonding material,

The additive element (X) contains at least 1 element selected from tantalum (Ta) and niobium (Nb),

The atomic ratio of each element satisfies all of the formulae (1) to (3) (wherein X is the sum of the content ratios of the above-mentioned additional elements),

0.4≤(In+X)/(In+Zn+X)＜0.75 (1)

0.25＜Zn/(In+Zn+X)≤0.6 (2)

0.001≤X/(In+Zn+X)≤0.015 (3)

The sputtering target has a substrate protection member disposed in a gap formed between the plurality of sputtering targets.

Drawings

Fig. 1 is a schematic diagram schematically showing a cross section of one embodiment of a sputtering target according to the present invention.

Fig. 2 is a schematic diagram schematically showing a cross section of another embodiment of the sputtering target of the present invention.

Fig. 3 is a schematic diagram schematically showing a cross section of a sputtering target according to still another embodiment of the present invention.

Fig. 4 is a schematic view schematically showing a cross section of a sputtering target according to still another embodiment of the present invention.

Fig. 5 is a schematic view schematically showing a cross section of a sputtering target according to still another embodiment of the present invention.

Fig. 6 is a schematic diagram schematically showing a cross section of a sputtering target according to still another embodiment of the present invention.

Fig. 7 is a schematic diagram showing the structure of an embodiment of a TFT element manufactured using the sputtering target of the present invention.

Fig. 8 is a graph showing XRD measurement results of the target material obtained in example 1.

Detailed Description

The present invention will be described below based on preferred embodiments thereof. The terms "to" representing the numerical range are used in the meaning of including the numerical values before and after the term "to" as the lower limit value and the upper limit value, and unless otherwise specified, the terms "to" below "are used in the same meaning.

The present invention relates to a sputtering target (hereinafter also referred to as "target"). The sputtering target (hereinafter also referred to as "target") used In the target of the present invention is made of an oxide containing indium (In) element, zinc (Zn) element, and additive element (X). The additive element (X) contains at least 1 element selected from tantalum (Ta) and niobium (Nb). The target of the present invention contains In, zn, and an additive element (X) as metal elements constituting it, but trace elements may be intentionally or inevitably contained In addition to these elements within a range that does not impair the effects of the present invention. Examples of the trace elements include elements contained in an organic additive described later, and medium materials such as a ball mill mixed in the process of producing a target material. Examples of trace elements in the target material of the present invention include Fe, cr, ni, al, si, W, zr, na, mg, K, ca, ti, Y, ga, sn, ba, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, nb, sr and Pb. The content of these is usually 100 mass ppm (hereinafter also referred to as "ppm") or less, more preferably 80ppm or less, and still more preferably 50ppm or less, relative to the total mass of the oxides containing In, zn, and X contained In the target material of the present invention. The total amount of these trace elements is preferably 500ppm or less, more preferably 300ppm or less, and still more preferably 100ppm or less. When the target material of the present invention contains trace elements, the total mass also contains trace elements.

The target of the present invention can be suitably made of a sintered body containing the above-mentioned oxide. The shape of the sintered body and the sputtering target is not particularly limited, and conventionally known shapes, for example, flat plate shape, cylindrical shape, and the like can be used.

In the target of the present invention, it is preferable that the atomic ratio of the metal elements constituting the target, i.e., in, zn, and X, be within a specific range, in order to improve the performance of the oxide semiconductor element formed from the target.

Specifically, in and X preferably satisfy an atomic ratio represented by the following formula (1) (X In the formula is the sum of the content ratios of the above-mentioned additional elements, and hereinafter, the same applies to the formulas (2) and (3).

0.4≤(In+X)/(In+Zn+X)＜0.75 (1)

The atomic ratio of Zn is preferably satisfied as shown in the following formula (2).

0.25＜Zn/(In+Zn+X)≤0.6 (2)

X is preferably an atomic ratio represented by the following formula (3).

0.001≤X/(In+Zn+X)≤0.015 (3)

By making the atomic ratios of In, zn, and X satisfy all of the above-described formulas (1) to (3), a semiconductor element having an oxide thin film formed by sputtering using the target of the present invention exhibits high field-effect mobility, low leakage current, and a threshold voltage close to 0V. From the viewpoint of making these advantages more remarkable, it is more preferable that the following formulas (1-2) to (1-5) are satisfied for In and X.

0.43≤(In+X)/(In+Zn+X)≤0.74 (1-2)

0.48≤(In+X)/(In+Zn+X)≤0.73 (1-3)

0.53≤(In+X)/(In+Zn+X)≤0.72 (1-4)

0.58≤(In+X)/(In+Zn+X)≤0.70 (1-5)

From the same viewpoints as described above, the formulae (2-2) to (2-5) below are more preferably satisfied for Zn, and the formulae (3-2) to (3-5) below are more preferably satisfied for X.

0.26≤Zn/(In+Zn+X)≤0.57 (2-2)

0.27≤Zn/(In+Zn+X)≤0.52 (2-3)

0.28≤Zn/(In+Zn+X)≤0.47 (2-4)

0.30≤Zn/(In+Zn+X)≤0.42 (2-5)

0.0015≤X/(In+Zn+X)≤0.013 (3-2)

0.002＜X/(In+Zn+X)≤0.012 (3-3)

0.0025≤X/(In+Zn+X)≤0.010 (3-4)

0.003≤X/(In+Zn+X)≤0.009 (3-5)

As described above, 1 or more selected from Ta and Nb is used as the additive element (X). These elements may be used each alone or 2 kinds may be used in combination. In particular, ta is preferably used as the additive element (X) from the viewpoint of the overall performance of the oxide semiconductor element manufactured from the target of the present invention and from the viewpoint of economy in manufacturing the target.

From the viewpoint of further improving the field-effect mobility of the oxide semiconductor element formed from the target of the present invention and the viewpoint of exhibiting a threshold voltage close to 0V, it is preferable that the target of the present invention satisfies the following formula (4) In terms of the atomic ratio of In and X In addition to satisfying the above-described relationships (1) to (3).

0.970≤In/(In+X)≤0.999 (4)

As is clear from the formula (4), in the target of the present invention, by using a very small amount of X relative to the amount of In, the field-effect mobility of the oxide semiconductor element formed from the target becomes high. This is the result of the first discovery by the inventors. In the heretofore known prior art (for example, the prior art described In patent documents 1 and 2), the amount of X used with respect to the amount of In is larger than that of the present invention.

From the standpoint of further improving the field-effect mobility of the oxide semiconductor formed from the target and from the standpoint of exhibiting a threshold voltage close to 0V, it is more preferable that the atomic ratio of In and X satisfies the following formulas (4-2) to (4-4).

0.980≤In/(In+X)≤0.997 (4-2)

0.990≤In/(In+X)≤0.995 (4-3)

0.990＜In/(In+X)≤0.993 (4-4)

In view of the high functionality of the FPD due to the good transfer characteristics of the TFT element as the oxide semiconductor element, it is preferable that the value of the field-effect mobility of the oxide semiconductor element formed of the target material is large. Specifically, the field effect mobility (cm ²/Vs) of the TFT including the oxide semiconductor element formed from the target is preferably 45cm ²/Vs or more, more preferably 50cm ²/Vs or more, further preferably 60cm ²/Vs or more, further preferably 70cm ²/Vs or more, further preferably 80cm ²/Vs or more, further preferably 90cm ²/Vs or more, and particularly preferably 100cm ²/Vs or more. The larger the value of the field-effect mobility is, the more preferable from the viewpoint of the high functionality of the FPD, but if the field-effect mobility is as high as about 200cm ²/Vs, a sufficiently satisfactory degree of performance can be obtained.

The ratio of each metal contained in the target material of the present invention can be measured by ICP emission spectrometry, for example.

The term "substrate protection member disposed in a gap formed between a plurality of sputtering targets" in the present invention refers to a member that covers the surface of a substrate exposed from the gap between a plurality of targets bonded to the substrate and has a function of preventing a substance from adversely affecting a thin film formed in the gap during sputtering. As such a base material protecting member, a band-shaped base material protecting member may be disposed on the surface of a base material, or a substance to be used as a base material protecting member may be provided in a film-like or sheet-like or band-like form by coating, plating, sputtering, plating, or the like. The substrate protection member may be disposed so as to fill the gap. Further, a part of the planar member may be protruded, and the convex portion may be embedded in the gap. In the present invention, a belt-shaped member is particularly preferably disposed as the base material protection member.

As a material of such a base material protective member, a material which does not adversely affect even if mixed into the formed thin film, for example, all or a part of elements constituting the composition of the target, an alloy containing these elements, an oxide, or the like can be used.

The material of the substrate protection member is a material having a chemical composition substantially different from that of a bonding material used for bonding to a substrate. For example, in the case of using metallic indium as the bonding material, this means that the base material protection member at this time is not metallic indium. In addition, metallic indium as a bonding material may remain in a gap between targets, but when indium remaining in the gap is solidified, oxidation may occur on the surface thereof. In the case where the metal indium used as the joining material is solidified in the gap as described above, it is difficult to form a uniform oxide film on the indium surface, and therefore the above-described effect as the base material protective member of the present invention cannot be exerted.

The sputtering target of the present invention is, for example, a plate-like or cylindrical sputtering target. The plate-like sputtering target is formed by disposing and bonding a plurality of plate-like targets on a plate-like substrate surface. The cylindrical sputtering target is formed by inserting or inserting a plurality of cylindrical targets into or through a cylindrical base material, disposing and bonding the targets in a multistage manner in the cylindrical axial direction of the cylindrical base material, or bonding a plurality of curved targets, in which hollow cylinders are vertically cut in the cylindrical axial direction, to the outer side surface of the cylindrical base material in a parallel manner in the circumferential direction. The plate-like or cylindrical sputtering target is often used in a large-area sputtering apparatus. The present invention is not limited to the sputtering target having another shape, and the target is not limited to this shape.

The base material protection member of the present invention is preferably any one metal of Zn, ta, and Nb, or an alloy containing any two or more of In, zn, ta, and Nb, or a ceramic containing any one or more of In, zn, ta, and Nb. When such a metal or ceramic is used as the base material protective member, even if a small amount of the metal or ceramic is mixed into the oxide semiconductor thin film to be formed, the influence on the characteristics of the TFT element can be reduced as compared with Cu, ti, or the like. The material of the ceramic may be an oxide, nitride, oxynitride, or the like containing one or more of In, zn, ta, and Nb, but since the target is an oxide, the ceramic material is preferably also an oxide. Specifically, examples of the ceramic material include In ₂O₃、ZnO、Ta₂O₅、Nb₂O₅, in-Zn oxide, in-Ta oxide, in-Nb oxide, zn-Ta oxide, zn-Nb oxide, zn-Ta-Nb oxide, in-Zn-Ta oxide, in-Zn-Nb oxide, in-Zn-Ta-Nb oxide, and the like, inN, zn ₃N₂, taN, nbN, in-Zn nitride, in-Ta nitride, in-Nb nitride, zn-Ta nitride, zn-Nb nitride, zn-Ta-Nb nitride, in-Zn-Ta nitride, in-Zn-Nb nitride, in-Zn-Ta-Nb nitride, and the like, but are not limited thereto.

When the base material protection member is made of the above-described metal, alloy, or ceramic, the base material protection member is preferably contained in a proportion of 90 mass% or more, more preferably 95 mass% or more, still more preferably 99 mass% or more, still more preferably 99.5 mass% or more, particularly preferably 99.9 mass% or more, and most preferably 99.95 mass% or more, based on the main material.

When the metal or ceramic constituting the base material protecting member is formed into the film-like, sheet-like or strip-like shape as described above, the thickness of the base material protecting member is preferably 0.0001mm to 1.0mm. The width of the base material protecting member is preferably the same as or wider than the gap formed between the target members, and is preferably 5.0mm to 30 mm. In the case where the substrate protection member having the above-described shape is disposed on the substrate, the bonding material of the target material, the conductive double-sided tape, or the like may be used for bonding.

The base material protecting member of the present invention may have a structure in which the 1 st base material protecting member and the 2 nd base material protecting member are laminated. In the case of such a structure in which the base material protective members are laminated, the sputtering target of the present invention can be easily manufactured, and the materials of the 1 st base material protective member and the 2 nd base material protective member can be appropriately selected to match the materials of the target and the base material. The 1 st base material protecting member and the 2 nd base material protecting member may have the same width or may have different widths. The substrate protection member of the laminated structure is disposed along the gap formed between the targets in a state where the 1 st substrate protection member is the target side and the 2 nd substrate protection member is the substrate side.

In the case where the base material protection member of the present invention is provided by using a laminated structure, the following structure may be set: a1 st base material protecting member of a small width and a2 nd base material protecting member of a large width are laminated, and the 2 nd base material protecting member is exposed at both end sides of the 1 st base material protecting member. In this structure, the 1 st base material protective member having a small width is laminated on the 2 nd base material protective member having a large width.

When the substrate protection member of the present invention is formed in a laminated structure in a film-like, sheet-like or strip-like shape, the 1 st substrate protection member preferably has a thickness of 0.0001 to 0.3mm, and the 2 nd substrate protection member preferably has a thickness of 0.1 to 0.7mm. The total thickness of the 1 st base material protecting member and the 2 nd base material protecting member is preferably set to 0.3mm to 1.0mm. When the 1 st base material protection member and the 2 nd base material protection member having the same width are laminated, the widths of these base material protection members are preferably set to 5mm to 30mm. Moreover, the method is also applicable to the field of the present invention. When the 1 st base material protection member having a small width and the 2 nd base material protection member having a large width are laminated, the 1 st base material protection member preferably has the same width as or a width greater than the gap formed between the target members, and is preferably 5mm to 20mm in view of operability and the like. The width of the 2 nd base material protecting member having a large width is preferably 3mm to 10mm larger than the width of the 1 st base material protecting member.

In the case where the base material protecting member of the present invention is configured as the above-described laminated structure, it is preferable that the 2 nd base material protecting member is configured as any one metal of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta or an alloy containing any two or more of these metals. The 1 st base material protective member is preferably formed of any one of Zn, ta, and Nb, or an alloy containing any two or more of In, zn, ta, and Nb, or a ceramic containing any one or more of In, zn, ta, and Nb.

When the base material protective member of the present invention has the above-described laminated structure, the 1 st base material protective member is preferably formed of a ceramic containing at least one of In, zn, ta, and Nb. This is because, in the case of these ceramics, the same composition as the target member or the same composition as the target material is partially used, and therefore, even if the ceramics are mixed into the film at the time of film formation, the influence on the TFT element characteristics is reduced. The ceramics include oxides, nitrides, oxynitrides, and the like containing at least one of In, zn, ta, and Nb, but the ceramics are preferably oxides because the target is an oxide. Specifically, examples of the ceramics include In ₂O₃、ZnO、Ta₂O₅、Nb₂O₅, in-Zn oxide, in-Ta oxide, in-Nb oxide, zn-Ta oxide, zn-Nb oxide, zn-Ta-Nb oxide, in-Zn-Ta oxide, in-Zn-Nb oxide, in-Zn-Ta-Nb oxide, and the like, inN, zn ₃N₂, taN, nbN, in-Zn nitride, in-Ta nitride, in-Nb nitride, zn-Ta nitride, zn-Nb nitride, zn-Ta-Nb nitride, in-Zn-Ta nitride, in-Zn-Nb nitride, in-Zn-Ta-Nb nitride, and the like, but are not limited thereto.

When the 2 nd base material protecting member is made of the metal or alloy as described above, it is preferable that the base material protecting member is contained in a proportion of 90 mass% or more, more preferably 95 mass% or more, still more preferably 99 mass% or more, still more preferably 99.5 mass% or more, particularly preferably 99.9 mass% or more, and most preferably 99.95 mass% or more, based on the main material. In the case where the 1 st base material protection member is made of the above-described metal, alloy, or ceramic, the base material protection member is preferably contained in a proportion of 90 mass% or more, more preferably 95 mass% or more, still more preferably 99 mass% or more, still more preferably 99.5 mass% or more, particularly preferably 99.9 mass% or more, and most preferably 99.95 mass% or more, based on the main material.

In the case where ceramics are used as the 1 st base material protective member, these ceramics may be formed as the 1 st base material protective member by vapor deposition, sputtering, plasma spraying, cold spraying, aerosol deposition, coating, or the like, and thus may be applied to the present invention.

The target of the present invention is characterized by a high relative density In addition to the atomic ratios of In, zn and X. In detail, the target material of the present invention preferably has a relative density of 95% or more. Such a high relative density is preferable because generation of particles can be suppressed in the case of sputtering using the target of the present invention. From this viewpoint, the target material of the present invention has a relative density of more preferably 97% or more, still more preferably 98% or more, still more preferably 99% or more, particularly preferably 100% or more, and particularly preferably more than 100%. The target of the present invention having such a relative density can be suitably produced by a method described later. The relative density was determined according to archimedes method. Specific measurement methods are described in detail in examples described later.

The target of the present invention is made of an oxide containing In, zn, and X as described above. The oxide may be an oxide of In, an oxide of Zn or an oxide of X. Or the oxide may be a composite oxide of any two or more elements selected from In, zn, and X. Specific examples of the composite oxide include, but are not limited to, in-Zn composite oxide, zn-Ta composite oxide, in-Nb composite oxide, zn-Nb composite oxide, in-Zn-Ta composite oxide, in-Zn-Nb composite oxide, and the like.

In the target material of the present invention, it is particularly preferable that the target material contains an In ₂O₃ phase which is an oxide of In and a Zn ₃In₂O₆ phase which is a composite oxide of In and Zn, from the viewpoints of increasing the density and strength of the target material and reducing the electric resistance. The fact that the target of the present invention contains In ₂O₃ phase and Zn ₃In₂O₆ phase can be determined by measuring by X-ray diffraction (hereinafter also referred to as "XRD") of the target of the present invention based on whether In ₂O₃ phase and Zn ₃In₂O₆ phase are observed. The In ₂O₃ phase of the present invention may contain a trace amount of Zn element.

Specifically, in XRD measurement using cukα rays as an X-ray source, the main peak is observed In the In ₂O₃ phase In the range of 2θ=30.38 ° or more and 30.78 ° or less. The Zn ₃In₂O₆ phase observed a main peak in the range of 2θ=34.00 ° or more and 34.40 ° or less.

When the In ₂O₃ phase is observed In the target of the present invention by XRD measurement, it is preferable that the grain size of the In ₂O₃ phase satisfies a specific range In terms of increasing the density and strength of the target of the present invention and reducing the resistance. Specifically, the grain size of the In ₂O₃ phase is preferably 3.0 μm or less, more preferably 2.7 μm or less, and even more preferably 2.5 μm or less. The smaller the crystal grain size, the more preferable, the lower limit is not particularly specified, but is usually 0.1 μm or more.

When the Zn ₃In₂O₆ phase is observed in the target of the present invention by XRD measurement, the Zn ₃In₂O₆ phase is preferably a crystal grain size satisfying a specific range from the viewpoint of increasing the density and strength of the target of the present invention and reducing the electric resistance. Specifically, the size of the crystal grains of the Zn ₃In₂O₆ phase is preferably 3.9 μm or less, more preferably 3.5 μm or less, still more preferably 3.0 μm or less, still more preferably 2.5 μm or less, still more preferably 2.3 μm or less, particularly preferably 2.0 μm or less, and particularly preferably 1.9 μm or less. The smaller the crystal grain size, the more preferable, the lower limit is not particularly specified, but is usually 0.1 μm or more.

In order to set the grain size of the In ₂O₃ phase and the grain size of the Zn ₃In₂O₆ phase to the above-described ranges, a target material may be manufactured by a method described below, for example.

The size of the crystal grains of the In ₂O₃ phase and the size of the crystal grains of the Zn ₃In₂O₆ phase were measured by observing the target material of the present invention by a scanning electron microscope (hereinafter also referred to as "SEM"). Specific measurement methods are described in detail in examples described later.

Next, a suitable method for producing the target material of the present invention will be described. In the present manufacturing method, an oxide powder serving as a raw material of a target is molded into a predetermined shape to obtain a molded body, and the molded body is fired to obtain a target made of a sintered body. For obtaining the shaped body, methods known to date in the art can be employed. In particular, in view of the capability of producing a dense target, a casting molding method or a CIP molding method is preferably used.

The casting process is also known as slip casting. For carrying out the cast molding method, a slurry containing a raw material powder and an organic additive is first prepared using a dispersion medium.

As the raw material powder, an oxide powder or a hydroxide powder is suitably used. As the oxide powder, an In oxide powder, a Zn oxide powder, and an X oxide powder are used. As the In oxide, for example, in ₂O₃ can be used. As the Zn oxide, znO may be used, for example. As the powder of the X oxide, for example, ta ₂O₅ and Nb ₂O₅ can be used.

In the present production method, these raw material powders are all mixed and then fired. In contrast to this, in the prior art, for example, the technology described In patent document 2, in ₂O₃ powder and Ta ₂O₅ powder are mixed and then fired, and then the obtained fired powder and ZnO powder are mixed and then fired again. In this method, the particles constituting the powder are coarsened by firing in advance, so that a target having a high relative density is not easily obtained. In contrast, in the present production method, it is preferable that all of the In oxide powder, the Zn oxide powder, and the X oxide powder are mixed and molded at normal temperature, and then fired, so that a dense target having a high relative density can be easily obtained.

The amounts of In oxide powder, zn oxide powder, and X oxide powder used are preferably adjusted so that the atomic ratios of In, zn, and X In the target to be targeted satisfy the above ranges.

The particle diameter of the raw material powder is preferably 0.1 μm or more and 1.5 μm or less, as represented by a volume cumulative particle diameter D ₅₀ when the cumulative volume obtained by the laser diffraction scattering particle size distribution measurement method is 50% by volume. By using the raw material powder having the particle diameter in this range, a target having a high relative density can be easily obtained.

The organic additive is used to appropriately adjust properties of the slurry and the molded article. Examples of the organic additive include a binder, a dispersant, and a plasticizer. The binder is added to improve the strength of the molded article. As the binder, a binder generally used for obtaining a molded body by a known powder sintering method can be used. As the binder, for example, polyvinyl alcohol is mentioned. The dispersant is added to improve dispersibility of the raw material powder in the slurry. Examples of the dispersant include polycarboxylic acid dispersants and polyacrylic acid dispersants. The plasticizer is added to improve the plasticity of the molded article. Examples of the plasticizer include polyethylene glycol (PEG) and Ethylene Glycol (EG).

The dispersion medium used for producing the slurry containing the raw material powder and the organic additive is not particularly limited, and may be appropriately selected from water, alcohol and other water-soluble organic solvents according to the purpose. The method for producing the slurry containing the raw material powder and the organic additive is not particularly limited, and for example, a method in which the raw material powder, the organic additive, the dispersion medium, and the zirconia balls are charged into a tank and mixed by a ball mill may be used.

After the slurry was obtained in the above-described manner, the slurry was poured into a mold, and the dispersion medium was removed to prepare a molded article. Examples of the usable mold include a metal mold, a plaster mold, and a resin mold that is pressurized to remove the dispersion medium.

On the other hand, in the CIP molding method, the same slurry as that used in the casting molding method is spray-dried to obtain a dry powder. The obtained dry powder was filled into a mold, and CIP molding was performed.

The molded article is obtained by the above-described procedure, and then fired. The firing of the molded article can be usually performed in an oxygen-containing atmosphere. In particular, firing in an atmosphere is simple and convenient. The firing temperature is preferably 1200 ℃ to 1600 ℃, more preferably 1300 ℃ to 1500 ℃, still more preferably 1350 ℃ to 1450 ℃. The firing time is preferably 1 hour or more and 100 hours or less, more preferably 2 hours or more and 50 hours or less, and still more preferably 3 hours or more and 30 hours or less. The temperature rise rate is preferably 5 to 500 ℃/hr, more preferably 10 to 200 ℃/hr, still more preferably 20 to 100 ℃/hr.

In the firing of the compact, it is preferable to maintain the temperature of the phase that generates the composite oxide of In and Zn, for example Zn ₅In₂O₈, for a certain period of time during the firing from the viewpoint of promoting the firing and the formation of a dense target. Specifically, when the raw material powder contains In ₂O₃ powder and ZnO powder, the In ₂O₃ powder and ZnO powder react with each other as the temperature increases to form a Zn ₅In₂O₈ phase, and thereafter the Zn ₄In₂O₇ phase becomes a Zn ₃In₂O₆ phase. In particular, since volume diffusion is advanced and densification is promoted at the time of phase formation of Zn ₅In₂O₈, it is preferable to reliably form a phase of Zn ₅In₂O₈. From such a viewpoint, the temperature is preferably maintained in the range of 1000 ℃ to 1250 ℃ for a certain period of time, and more preferably in the range of 1050 ℃ to 1200 ℃ during the temperature rising process of the firing. The temperature to be maintained is not necessarily limited to a specific point, and may be a temperature range having a certain width. Specifically, when a specific temperature selected from the range of 1000 ℃ to 1250 ℃ inclusive is T (°c), the temperature may be, for example, t±10 ℃, preferably t±5 ℃, more preferably t±3 ℃, and even more preferably t±1 ℃ if the temperature is included in the range of 1000 ℃ to 1250 ℃. The time for maintaining this temperature range is preferably 1 hour or more and 40 hours or less, more preferably 2 hours or more and 20 hours or less.

The target material obtained in the above-described manner can be processed into a predetermined size by grinding or the like. By bonding it to a substrate, a sputtering target is obtained. The sputtering target obtained by operating as described herein can be suitably used for the production of an oxide semiconductor. For example, in the manufacture of TFTs, the target of the present invention may be used.

The sputtering target of the present invention can be formed by disposing and bonding a plurality of targets 20 on a Cu base material 10 as shown in fig. 1, for example. Between these targets, a gap 30 of 0.1mm to 1.0mm is formed.

As shown in fig. 2, a substrate protection member 50 is attached to the surface of the substrate 10 at a position corresponding to the gap formed between the targets. The substrate protection member may be attached to the surface of the substrate 10 using a bonding material, a conductive double-sided tape, or the like.

The plurality of target members are arranged as shown In fig. 1, for example, and bonded using bonding materials of In and Sn. The bonding is performed by the steps of: the surface of the substrate is coated with a molten bonding material, and the target is placed on the bonding material and cooled to room temperature.

Fig. 3 shows a schematic cross-sectional view of a substrate protection member using a single layer. The thickness of the single-layer base material protection member 50 is 0.0001mm to 1.0mm, and the base material protection member is formed of any one metal of Zn, ta, and Nb, an alloy containing any two or more of In, zn, ta, and Nb, or a ceramic containing any one or more of In, zn, ta, and Nb. The bonding material 60 having In is present at both end sides of the single-layer base material protection member 50.

Fig. 4 is a schematic cross-sectional view of a two-layer structure of a substrate protection member formed by stacking substrate protection members having the same width. The substrate protection member 50 of the two-layer structure is made of a 1 st substrate protection member 51 and a 2 nd substrate protection member 52. In view of operability, the widths of the 1 st base material protecting member 51 and the 2 nd base material protecting member are preferably 5mm to 20mm. In addition, the bonding material 60 having In is present at both end sides of the 1 st base material protection member 51 and the 2 nd base material protection member 52. Although a two-layer structure is shown in fig. 4, the base material protecting member may have a three-layer structure or more. For example, considering the difference in linear expansion coefficient between the material of the 1 st base material protecting member and the material of the 2 nd base material protecting member, the intermediate layer may be provided using a material having a linear expansion coefficient intermediate between the material of the 1 st base material protecting member and the material of the 2 nd base material protecting member.

Fig. 5 is a schematic cross-sectional view of a two-layer structure of a base material protection member formed by stacking base material protection members having different widths. The substrate protection member 50 of the two-layer structure is made of a 1 st substrate protection member 51 and a2 nd substrate protection member 52. In view of operability, the 1 st base material protecting member 51 has a width of 5mm to 20mm, and the 2 nd base material protecting member 52 has a width of 8mm to 30mm, and the 2 nd base material protecting member has a larger width than the 1 st base material protecting member. Then, the 1 st base material protection member 51 is disposed at the substantially center of the 2 nd base material protection member, and thereby the 2 nd base material protection member 52 is exposed at both end sides of the 1 st base material protection member. The width of the exposed portion is 1.5mm to 5mm on each of both end sides. In addition, the bonding material 60 having In is present at both end sides of the 1 st base material protection member 51 and the 2 nd base material protection member 52. Although a two-layer structure is shown in fig. 5, the base material protecting member may have a three-layer structure or more. For example, considering the difference in linear expansion coefficient between the material of the 1 st base material protecting member and the material of the 2 nd base material protecting member, the intermediate layer may be provided using a material having a linear expansion coefficient intermediate between the material of the 1 st base material protecting member and the material of the 2 nd base material protecting member.

The 2 nd base material protecting member 52 shown in fig. 4 and 5 has a thickness of 0.1mm to 0.7mm and is made of any one of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta or an alloy containing any one of them. The 1 st base material protection member 51 shown in fig. 4 and 5 has a thickness of 0.0001 to 0.3mm and is formed of any one metal selected from Zn, ta, and Nb, an alloy containing In, zn, ta, nb or a ceramic containing In, zn, ta, nb or more.

The two-layer structure base material protection member shown in fig. 4 and 5 can be produced by, for example, blowing a powder of Ta ₂O₅、Nb₂O₅ onto a Cu metal sheet of 0.3mm thickness by plasma spraying.

Fig. 6 is a schematic cross-sectional view showing a modification of the substrate protection member using a single layer. In fig. 6, a single-layer substrate protection member 50 is filled in the gap 30 between the targets 20. In this case, the thickness of the base material protection member 50 is set to 0.0001mm to 1.0mm so that the target 20 and the base material protection member 50 are not flush. Thereby, sputtering of the base material protection member 50 can be suppressed. In the present modification, the bonding material 60 In which In is present between the target 20 and the base material protection member 50 and the base material 10 is present.

An example of the TFT element 100 is schematically shown in fig. 7. The TFT element 100 shown in the figure is formed on one surface of a glass substrate 110. A gate electrode 120 is disposed on one surface of the glass substrate 110, and a gate insulating film 130 is formed so as to cover the gate electrode. On the gate insulating film 130, a source electrode 160, a drain electrode 161, and a channel layer 140 are disposed. An etch stop layer 150 is disposed on the channel layer 140. And a protective layer 170 is disposed at the uppermost portion. In the TFT element 100 having this structure, the channel layer 140 can be formed using the target material of the present invention, for example. In this case, the channel layer 140 is made of an oxide containing indium (In) element, zinc (Zn) element, and additive element (X), and the atomic ratio of the indium (In) element, the zinc (Zn) element, and the additive element (X) satisfies the above formula (1). The above formulas (2) and (3) are satisfied.

The oxide semiconductor element formed from the target material of the present invention preferably has an amorphous structure in terms of improving the performance of the element.

The present invention also includes the following inventions in view of the above embodiments.

A sputtering target comprising a substrate and, bonded thereto by a bonding material, a plurality of sputtering targets each comprising an oxide containing an indium (In) element, a zinc (Zn) element and an additive element (X) containing at least 1 element selected from tantalum (Ta) and niobium (Nb), wherein the atomic ratio of each element satisfies all of the formulae (1) to (3) (wherein X In the formulae is the sum of the content ratios of the additive elements)

0.4≤(In+X)/(In+Zn+X)＜0.75 (1)

0.25＜Zn/(In+Zn+X)≤0.6 (2)

0.001≤X/(In+Zn+X)≤0.015 (3)

The sputtering target according to item [ 2], wherein the base material protecting member comprises any one metal of Zn, ta and Nb or an alloy containing any two or more of In, zn, ta and Nb.

The sputtering target according to item [ 3 ], wherein the base material protecting member comprises a ceramic containing at least one of In, zn, ta and Nb.

The sputtering target according to item [4 ], wherein the ceramic contains an oxide, nitride or oxynitride containing at least one of In, zn, ta and Nb.

The sputtering target according to [ 3] or [ 4 ], wherein the ceramic contains an oxide containing at least one of In, zn, ta and Nb.

The sputtering target according to any one of [1] to [ 5 ], wherein the base material protecting member has a structure in which a1 st base material protecting member on the sputtering target side and a2 nd base material protecting member on the base material side are laminated.

The sputtering target according to item [ 7 ], wherein the 2 nd base material protecting member comprises any one metal of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta or an alloy containing any two or more of these metals, and the 1 st base material protecting member comprises any one metal of Zn, ta and Nb or an alloy containing any two or more of In, zn, ta and Nb.

The sputtering target according to item [ 8 ], wherein the 2 nd base material protecting member comprises any one metal of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta or an alloy containing any two or more of these metals, and the 1 st base material protecting member comprises a ceramic containing any one or more of In, zn, ta and Nb.

The sputtering target according to item [ 9 ], wherein the 1 st base material protecting member comprises an oxide, nitride or oxynitride containing at least one of In, zn, ta and Nb.

The sputtering target according to [ 8 ] or [ 9], wherein the 1 st base material protecting member comprises an oxide containing at least one of In, zn, ta and Nb.

The sputtering target according to any one of [ 1 ] to [ 10 ], wherein the additive element (X) is tantalum (Ta).

The sputtering target according to any one of [ 1 ] to [ 11 ], wherein the sputtering target material contains an In ₂O₃ phase and a Zn ₃In₂O₆ phase.

The sputtering target according to [ 12 ], wherein the size of the crystal grains of the In ₂O₃ phase is 0.1 μm or more and 3.0 μm or less, and the size of the crystal grains of the Zn ₃In₂O₆ phase is 0.1 μm or more and 3.9 μm or less.

The sputtering target according to any one of [ 1] to [ 13 ], which further satisfies the formula (4), wherein 0.970.ltoreq.in/(In+X). Ltoreq.0.999 (4).

Examples

The present invention will be described in further detail with reference to examples. The scope of the invention is not limited by this example.

[ Example 1 (examples 1-1 to 1-6) ]

In ₂O₃ powder having an average particle diameter D ₅₀ of 0.6 μm, znO powder having an average particle diameter D ₅₀ of 0.8 μm, and Ta ₂O₅ powder having an average particle diameter D ₅₀ of 0.6 μm were dry-mixed by a ball mill using zirconia balls to prepare a mixed raw material powder. The average particle diameter D ₅₀ of each powder was measured using a particle size distribution measuring apparatus MT3300EXII manufactured by Microtrac BEL corporation. In the measurement, the solvent was measured using water to measure the refractive index of the substance at 2.20. The mixing ratio of each powder was set so that the atomic ratio of In, zn, and Ta became the values shown In table 4 below.

A slurry was prepared by adding 0.2 mass% of a binder to the mixed raw material powder, 0.6 mass% of a dispersant to the mixed raw material powder, and 20 mass% of water to the mixed raw material powder to a tank in which the mixed raw material powder was prepared, and mixing the mixture with zirconia balls by a ball mill.

The prepared slurry was poured into a metal mold having a filter sandwiched therebetween, and water in the slurry was discharged to obtain a molded article. The molded body is fired to produce a sintered body. The firing was performed in an atmosphere having an oxygen concentration of 20% by volume at a firing temperature of 1400 ℃ for 8 hours at a heating rate of 50 ℃/hour and a cooling rate of 50 ℃/hour. During the firing, the temperature was maintained at 1100℃for 6 hours to promote the production of Zn ₅In₂O₈.

The sintered body obtained in the above-described manner was subjected to cutting to obtain an oxide sintered body (target material) having a width of 210mm×a length of 710mm×a thickness of 6 mm. A grinding stone of #170 was used in the cutting process.

The phi 8 inch target was cut out of the target and bisected at the center. These targets were bonded to a Cu backing plate (base material) with In solder so that the gap formed between the targets was 0.5mm, to obtain a sputtering target. At this time, a base material protection member is disposed between the Cu backing plate and the target along a gap formed between the targets.

[ Examples 1 to 1]

In the sputtering target, as a single-layer base material protection member, a Ta metal sheet having a thickness of 0.3mm and a width of 20mm was disposed.

[ Examples 1-2 ]

As a single-layer base material protection member, zn metal sheet having a thickness of 0.3mm and a width of 20mm was disposed.

[ Examples 1 to 3]

As a single-layer base material protection member, a ceramic sheet having the same composition as the target material and a thickness of 0.3mm and a width of 20mm was disposed.

[ Examples 1 to 4]

As the base material protection member of the laminated structure, a member obtained in the following manner was arranged: a Ta film having a thickness of 0.0001mm and a width of 20mm was formed as a1 st base material protective member by sputtering on a 2 nd base material protective member of a Cu metal sheet having a thickness of 0.3mm and a width of 20 mm.

[ Examples 1 to 5]

As the base material protection member of the laminated structure, a member obtained in the following manner was arranged: a Ta ₂O₅ film having a thickness of 0.1mm and a width of 20mm was formed as a1 st base material protective member by plasma spraying on a2 nd base material protective member of a Cu metal sheet having a thickness of 0.3mm and a width of 20 mm.

[ Examples 1 to 6 ]

As the base material protection member of the laminated structure, a member obtained in the following manner was arranged: a film having the same composition as the target material and having a thickness of 0.1mm and a width of 20mm was formed as the 1 st base material protective member on the 2 nd base material protective member of the Cu metal sheet having a thickness of 0.3mm and a width of 20mm by plasma spraying.

Comparative example 1

The base material protection member is not disposed at the gap portion and bonded.

[ Examples 2 to 7]

In example 1, the raw material powders were mixed so that the atomic ratios of In, zn, and Ta became the values shown In table 4 below. A sputtering target was obtained in the same manner as in example 1 except for this. The arrangement of the base material protection member was the same as that of examples 1 to 5.

[ Examples 8-1 to 8-6 ]

In example 1, instead of Ta ₂O₅ powder, nb ₂O₅ powder having an average particle diameter D ₅₀ of 0.7 μm was used. The raw material powders were mixed so that the atomic ratios of In, zn, and Nb were set to values shown In table 1 below. A sputtering target was obtained in the same manner as in example 1 except for this.

[ Example 8-1 ]

In the sputtering target, nb metal sheets having a thickness of 0.3mm and a width of 20mm were arranged as a single-layer base material protection member.

[ Examples 8-2 ]

[ Examples 8 to 3]

[ Examples 8 to 4]

As the base material protection member of the laminated structure, a member obtained in the following manner was arranged: on the 2 nd base material protecting member of the Cu metal sheet having a thickness of 0.3mm and a width of 20mm, an Nb film having a thickness of 0.0001mm and a width of 20mm was formed as the 1 st base material protecting member by sputtering.

[ Examples 8 to 5]

As the base material protection member of the laminated structure, a member obtained in the following manner was arranged: a Nb ₂O₅ film having a thickness of 0.1mm and a width of 20mm was formed as a1 st base material protective member by plasma spraying on a2 nd base material protective member of a Cu metal plate having a thickness of 0.3mm and a width of 20 mm.

[ Examples 8 to 6 ]

Comparative example 2

[ Example 9 (examples 9-1 to 9-9) ]

In example 1, ta ₂O₅ powder and Nb ₂O₅ powder were mixed so that the atomic ratios of In, zn, ta, and Nb were set to values shown In table 2 below, instead of Ta ₂O₅ powder. The molar ratio of Ta and Nb was set to Ta: nb=3: 2. a sputtering target was obtained in the same manner as in example 1 except for this.

[ Example 9-1 ]

[ Examples 9-2 ]

As a single-layer base material protection member, nb metal pieces having a thickness of 0.3mm and a width of 20mm were arranged.

[ Examples 9 to 3]

[ Examples 9 to 4]

[ Examples 9 to 5]

[ Examples 9 to 6 ]

[ Examples 9 to 7]

[ Examples 9 to 8 ]

[ Examples 9 to 9 ]

[ Comparative example 3]

The proportions of the metals contained in the targets obtained in the examples and comparative examples were measured by ICP emission spectrometry. It was confirmed that the atomic ratios of In, zn, ta and Nb were the same as the raw material ratios shown In table 4.

[ Evaluation 1]

The relative densities of the targets obtained in the examples were measured by the following methods. XRD measurements were performed on the targets obtained In examples 1 to 9 under the following conditions, and the presence or absence of the In ₂O₃ phase and the Zn ₃In₂O₆ phase was confirmed. The targets obtained In examples 1 to 9 were subjected to SEM observation, and the sizes of the crystal grains of the In ₂O₃ phase and the crystal grains of the Zn ₃In₂O₆ phase were measured by the following methods. The results are shown in table 4 below.

[ Relative Density ]

The value of the percentage relative to the theoretical density ρ (g/cm ³) based on the following formula (i) is set as the relative density (unit:%) by dividing the air mass of the target by the volume (mass in water of the target/specific gravity of water at measured temperature).

(Wherein Ci represents the content (mass%) of constituent substances of the target material, ρi represents the density (g/cm ³) of each constituent substance corresponding to Ci.)

In the case of the present invention, the target constituent material is considered to be In ₂O₃、ZnO、Ta₂O₅、Nb₂O₅, and the theoretical density ρ can be calculated by applying the following conditions to the formula (i),

C1: mass% of In ₂O₃ of target material

Ρ1: density of In ₂O₃ (7.18 g/cm ³)

C2: znO of target material mass%

Ρ2: density of ZnO (5.60 g/cm ³)

And C3: ta ₂O₅ mass% of target material

Ρ3: ta ₂O₅ Density (8.73 g/cm ³)

And C4: mass% of Nb ₂O₅ in target material

Ρ4: the density of Nb ₂O₅ (4.60 g/cm ³).

The mass% of In ₂O₃, the mass% of ZnO, the mass% of Ta ₂O₅, and the mass% of Nb ₂O₅ can be obtained from the analysis results of the respective elements of the target material obtained by ICP emission spectrometry.

[ XRD measurement conditions ]

SmartLab (registered trademark) of Rigaku, inc. was used. The measurement conditions are as follows. The results of XRD measurement on the target material obtained in example 1 are shown in fig. 8.

Ray source: cuK alpha rays

Guan Dianya: 40kV (kilovolt)

Guan Dianliu: 30mA

Scanning speed: 5 degree/min

Step size: 0.02 degree

Scan range: 2θ=5 to 80 degrees

[ Size of crystal grains of In ₂O₃ phase, size of crystal grains of Zn ₃In₂O₆ phase ]

SEM observation was performed on the surface of the target material using a scanning electron microscope SU3500 manufactured by HITACHI HIGH-Technologies, and evaluation of the structural phase and crystal shape of the crystal was performed.

Specifically, the cut surfaces obtained by cutting the target material were polished in stages using sandpaper #180, #400, #800, #1000, #2000, and finally polished to a mirror surface. SEM observation was performed on the mirror finished surface. For evaluation of the crystal shape, 10 fields of view were randomly photographed for BSE-COMP images in a range of 87.5 μm×125 μm at a magnification of 1000 times, and SEM images were obtained.

The resulting SEM image was subjected to image processing software: the analysis was performed by ImageJ 1.51k (http:// ImageJ.nih.gov/ij/, provider: national institute of health (NIH: national Institutes of Health)). The specific steps are as follows.

The sample used in the SEM image photographing was subjected to thermal etching at 1100 ℃ for 1 hour, and SEM observation was performed, whereby an image showing grain boundaries was obtained. The resulting image was first depicted along the grain boundaries of the In ₂O₃ phase. After all the drawing was completed, particle analysis (analysis. Fwdarw. Analyze Particles) was performed to obtain the area of each particle. Thereafter, the area equivalent circle diameter was calculated from the area of each particle obtained. The arithmetic average of the area equivalent circle diameters of all the particles calculated In the 10 fields of view was set as the size of the crystal grains of the In ₂O₃ phase. Then, drawing was performed along the grain boundary of the Zn ₃In₂O₆ phase, and analysis was performed in the same manner, and the area equivalent circle diameter was calculated from the area of each particle thus obtained. The arithmetic average of the area equivalent circle diameters of all the particles calculated in the 10 fields of view was set as the size of the crystal grains of Zn ₃In₂O₆ phase.

[ Evaluation 2]

The amounts of Cu mixed in the sputtering targets of examples 1-1 to 1-6, examples 8-1 to 8-6, examples 9-1 to 9-6 and comparative examples 1 to 3 by Cu backing plates (substrates) of the sputtered films were evaluated. Specifically, a film having a thickness of 14 μm was formed on a glass substrate (OA-10 manufactured by Nitro Corp.) using a sputtering apparatus (SML-464 manufactured by Tokki Co., ltd.). Then, the substrate on which the film is formed is cut out to a portion corresponding to a portion directly above the gap formed between the targets. The cut substrates were evaluated by measuring the Cu content in each film by ICP-OES using ICP-OES (ICP-OES spectrometry) device 720 manufactured by Agilent Technologies.

The results are shown in tables 1 to 3.

TABLE 1

TABLE 2

Table 3

As shown in tables 1 to 3, in the case where the base material protection member is disposed, the Cu content of the sputtered film is less than 2ppm. In contrast, in the case where the base material protection member is not disposed, the Cu content of the sputtered film is 21 to 23ppm. From the results, it was found that the inclusion of Cu into the sputtered film can be prevented by disposing the base material protective member.

[ Evaluation 3]

The TFT element 1 shown in fig. 6 was fabricated by photolithography using the sputtering targets of examples 1 to 5, examples 2 to 7, examples 8 to 5, examples 9 to 6, and comparative examples 1 to 3.

In the production of the TFT element 1, an M omic thin film was first formed as the gate electrode 20 on the glass substrate (OA-10 manufactured by japan electric nitrate co.) 10 using a DC sputtering apparatus. Then, a SiOx thin film was formed as the gate insulating film 30 under the following conditions.

Film forming apparatus: PD-2202L manufactured by Samco Co., ltd

Film forming gas: siH ₄/N₂O/N₂ mixed gas

Film formation pressure: 110Pa

Substrate temperature: 250-400 DEG C

Then, the channel layer 40 was formed into a thin film having a thickness of 30nm by sputtering using the sputtering targets obtained in examples 1 to 5, examples 2 to 7, examples 8 to 5, examples 9 to 6 and comparative examples 1 to 3 under the following conditions. In forming the channel layer 40, film formation is performed directly above the gap formed between the targets.

Film forming apparatus: SML-464 manufactured by DC sputtering apparatus Tokki Co., ltd

Extreme vacuum: less than 1X 10 ^-4 Pa

Sputtering gas: ar/O ₂ mixed gas

Sputtering gas pressure: 0.4Pa

O ₂ gas partial pressure: 50 percent of

Substrate temperature: room temperature

Sputtering power: 3W/cm ²

Subsequently, as the etching stopper layer 50, a SiOx thin film was formed using the plasma CVD apparatus described above. Then, mo thin films were formed as the source electrode 60 and the drain electrode 61 using the above DC sputtering apparatus. As the protective layer 70, a SiOx film was formed using the above-described plasma CVD apparatus. Finally, a heat treatment is carried out at 350 ℃.

The transfer characteristics of the TFT element 1 thus obtained were measured when the drain voltage vd=5v. The transfer characteristics measured were field effect mobility μ (cm ²/Vs), SS (subthreshold swing; subthreshold Swing) value (V/dec) and threshold voltage Vth (V). The transfer characteristics were measured by a semiconductor device parameter analyzer B1500A manufactured by Agilent Technologies co. The measurement results are shown in tables 1 and 2. Although not shown in the table, the present inventors confirmed by XRD measurement that: the channel layer 40 of the TFT element 1 obtained in each example has an amorphous structure.

The field effect mobility is a channel mobility obtained from a change in drain current with respect to a gate voltage when a drain voltage is made constant in a saturation region of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) operation, and the larger the value, the better the transfer characteristic.

The SS value is a gate voltage required to raise the leakage current by 1 bit around the threshold voltage, and the smaller the value, the better the transfer characteristic.

The threshold voltage is a voltage at which a leakage current flows and reaches 1nA when a positive voltage is applied to the drain and a negative voltage is applied to the gate, and is preferably approximately 0V. More specifically, the threshold voltage is more preferably-2V or more, still more preferably-1V or more, still more preferably 0V or more. The threshold voltage is more preferably 3V or less, still more preferably 2V or less, and still more preferably 1V or less.

As is clear from the results shown in table 4, the TFT element manufactured using the target material obtained in each example was excellent in transfer characteristics.

The target material obtained In example 1 includes an In ₂O₃ phase and a Zn ₃In₂O₆ phase. The same results were obtained for the targets obtained in examples 2 to 9.

Industrial applicability

According to the present invention, a sputtering target can be provided in which a constituent material of a base material can be effectively prevented from being mixed into a thin film to be formed even in a large-area sputtering target obtained by joining a plurality of targets.

The sputtering target of the present invention can be suitably used in the technical field of Thin Film Transistors (TFTs) used in Flat Panel Displays (FPDs). In addition, by disposing the base material protection member in the gap formed between the plurality of sputtering targets, the constituent material of the base material is not sputtered as compared with the conventional sputtering targets, and the constituent material can be effectively prevented from being mixed into the thin film formed. This suppresses the production of a sputtered film outside the target containing a large amount of impurities, thereby realizing sustainable management of natural resources, efficient use, and decarburization (carbon neutralization).

Claims

1. A sputtering target formed by bonding a plurality of sputtering targets to a base material with a bonding material,

The sputtering target is made of an oxide containing indium, i.e., in element, zinc, i.e., zn element, and an additive element X containing at least 1 element selected from tantalum, i.e., ta, and niobium, i.e., nb, the atomic ratio of each element satisfying all of the formulas (1) to (3), wherein X is set as the sum of the content ratios of the additive elements,

0.4≤(In+X)/(In+Zn+X)＜0.75 (1)

0.25＜Zn/(In+Zn+X)≤0.6 (2)

0.001≤X/(In+Zn+X)≤0.015 (3)

2. The sputtering target of claim 1, wherein,

The base material protection member includes any one metal of Zn, ta, and Nb, or an alloy containing any two or more of In, zn, ta, and Nb.

3. The sputtering target of claim 1, wherein,

The base material protection member includes a ceramic containing at least one of In, zn, ta, and Nb.

4. The sputtering target according to claim 3, wherein,

The ceramic contains an oxide, nitride or oxynitride containing at least one of In, zn, ta and Nb.

5. The sputtering target according to claim 3 or 4, wherein,

The ceramic contains an oxide containing at least one of In, zn, ta, and Nb.

6. The sputtering target according to any one of claims 1 to 4, wherein,

The substrate protection member has a structure in which a1 st substrate protection member on the sputtering target side and a2 nd substrate protection member on the substrate side are laminated.

7. The sputtering target of claim 6, wherein,

The 2 nd base material protecting member includes any one metal of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta, or an alloy containing any two or more of these metals, and the 1 st base material protecting member includes any one metal of Zn, ta and Nb, or an alloy containing any two or more of In, zn, ta and Nb.

8. The sputtering target of claim 6, wherein,

The 2 nd base material protection member includes any one metal of Ti, V, cr, mn, fe, co, ni, cu, zn, nb, mo, ag and Ta, or an alloy containing any two or more of these metals, and the 1 st base material protection member includes a ceramic containing any one or more of In, zn, ta, and Nb.

9. The sputtering target of claim 8, wherein,

The 1 st base material protection member includes an oxide, nitride, or oxynitride containing any one or more of In, zn, ta, and Nb.

10. The sputter target according to claim 8 or 9, wherein,

The 1 st base material protection member includes an oxide containing at least one of In, zn, ta, and Nb.

11. The sputtering target according to any one of claims 1 to 4, wherein,

The additive element X is tantalum, namely Ta.

12. The sputtering target according to any one of claims 1 to 4, wherein,

The sputtering target comprises an In ₂O₃ phase and a Zn ₃In₂O₆ phase.

13. The sputter target of claim 12, wherein,

The grain size of the In ₂O₃ phase is 0.1 μm or more and 3.0 μm or less,

The size of the crystal grains of Zn ₃In₂O₆ phase is 0.1 μm or more and 3.9 μm or less.

14. The sputtering target according to any one of claim 1 to 4, which further satisfies the formula (4),

0.970≤In/(In+X)≤0.999 (4)。