JPWO2020170950A1 - Oxide sintered body, sputtering target and manufacturing method of sputtering target - Google Patents

Abstract

An oxide sintered body having a surface roughness Rz of less than 2.0 μm on the surface of the oxide sintered body.

Description

The present invention relates to an oxide sintered body, a sputtering target, and a method for manufacturing the sputtering target.

Conventionally, in a display device such as a liquid crystal display or an organic EL display driven by a thin film transistor (hereinafter referred to as "TFT"), an amorphous silicon film or a crystalline silicon film is mainly adopted for the channel layer of the TFT. rice field.
On the other hand, in recent years, with the demand for higher definition of displays, oxide semiconductors have been attracting attention as materials used for the channel layer of TFTs.

Among the oxide semiconductors, an amorphous oxide semiconductor composed of indium, gallium, zinc and oxygen (In-Ga-Zn-O, hereinafter abbreviated as "IGZO") is preferable because it has high carrier mobility. It is used. However, IGZO has a drawback that the raw material cost is high because In and Ga are used as raw materials.

From the viewpoint of reducing the raw material cost, it is abbreviated as Zn-Sn-O (hereinafter abbreviated as "ZTO") or In-Sn-Zn-O (hereinafter abbreviated as "ITZO") in which Sn is added instead of Ga of IGZO. ) Has been proposed.
Since ITZO exhibits extremely high mobility as compared with IGZO, it is expected as a next-generation oxide semiconductor material which is advantageous for miniaturization of TFTs and narrowing of the frame of panels.

However, since ITZO has a large coefficient of thermal expansion and low thermal conductivity, there is a problem that cracks are likely to occur due to thermal stress during bonding to a backing plate made of Cu or Ti and during sputtering.
Recent studies have reported that reliability, which is the greatest challenge for oxide semiconductor materials, can be improved by densifying the film.
High-power film formation is effective for densifying the film. However, in large-scale mass production equipment, cracking of the end portion of the target where plasma is concentrated becomes a problem, and in particular, the target of ITZO-based material tends to be easily cracked.

For example, in Patent Document 1, in an oxide sintered body substantially composed of indium, tin, magnesium and oxygen, high bending strength is achieved by appropriately adjusting the composition and sintering conditions of the sintered body. It is stated that it can be done. Further, Patent Document 1 describes that since the oxide sintered body has a high bending strength, less particles are generated during sputtering, and stable sputtering becomes possible.

International Publication No. 2017/158928

Examples of the causes of cracks generated in the sputtering target include various causes such as density variation, particle size variation, pores and microcracks.

As a cause of crack generation, there is also a grinding streak generated in the surface grinding process of the sputtering target. When sputtering is performed using a sputtering target having a grinding streak, arcing is likely to occur, and cracks are likely to occur due to the tensile stress on the surface caused by the thermal shrinkage of the target after the sputter discharge.

On the other hand, it is known that the grinding streaks generated in the grinding process of the sputtering target are reduced by making the cutting depth of the abrasive grains shallow, such as by reducing the particle size of the abrasive grains embedded in the grindstone.
For example, in Patent Document 1, an oxide sintered body composed of indium, tin, magnesium and oxygen is polished with a # 80 grindstone and then polished with a # 400 grindstone to obtain a surface roughness Ra of 0. It is described that a 46 μm sintered body was obtained.

However, as described in Patent Document 1, even if the surface of the oxide sintered body is polished with a # 80 grindstone and then polished with a # 400 grindstone, the sputtering target containing the oxide sintered body is still available. Crack resistance may not be sufficient.

It is an object of the present invention to provide an oxide sintered body and a sputtering target having improved crack resistance, and to provide a method for manufacturing the sputtering target.

[1A]. It is an oxide sintered body
The surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm.
Oxide sintered body.

[2A]. A sputtering target containing the oxide sintered body according to [1A].

[1]. A sputtering target containing an oxide sintered body.
The surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm.
Sputtering target.

[2]. In the sputtering target according to [1] or [2A].
The oxide sintered body contains an indium element, a tin element and a zinc element.
Sputtering target.

[3]. In the sputtering target described in [2],
The oxide sintered body further contains element X and contains.
Element X is at least one element selected from the group consisting of germanium element, silicon element, ittrium element, zirconium element, aluminum element, magnesium element, itterbium element and gallium element.
Sputtering target.

[4]. In the sputtering target according to [2] or [3].
The oxide sintered body satisfies the range of the atomic composition ratio represented by the following formulas (1), (2) and (3).
Sputtering target.
0.40 ≤ Zn / (In + Sn + Zn) ≤ 0.80 ... (1)
0.15 ≤ Sn / (Sn + Zn) ≤ 0.40 ... (2)
0.10 ≤ In / (In + Sn + Zn) ≤ 0.35 ... (3)

[5]. In the sputtering target according to any one of [2] to [4].
The oxide sintered body is a _{sputtering target containing a hexagonal layered compound represented by In 2} O ₃ (ZnO) m [m = 2 to 7] and a spinel structure compound represented by _{Zn 2} SnO _4.

[5A]. In the sputtering target according to any one of [2] to [4].
The oxide sintered body includes _{a hexagonal layered compound represented by In 2} O ₃ (ZnO) m [m = 2 to 7] and Zn _2-x Sn _1-y In _{x + y} O ₄ [0 ≦ x <2. A sputtering target containing a spinel-structured compound represented by 0 ≦ y <1].

[6A]. In the grinding scratches of the oxide sintered body, the ratio H / L between the depth (H) and the width (L) of the grinding scratches having the maximum depth and the minimum width is less than 0.2. The sputtering target according to any one of [2] to [5], [2A] and [5A].

[6]. The method for manufacturing a sputtering target for manufacturing the sputtering target according to any one of [1] to [5], [2A], [5A] and [6A].

[7]. In the method for manufacturing a sputtering target according to [6],
Including the step of grinding the surface of the oxide sintered body.
The grain size of the first grindstone used for the first grinding is 100 μm or less.
Manufacturing method of sputtering target.

[8]. In the method for manufacturing a sputtering target according to [7],
After grinding with the first grindstone, the surface of the oxide sintered body is further ground with a second grindstone having an abrasive grain size smaller than that of the first grindstone.
After grinding with the second grindstone, the surface of the oxide sintered body is further ground using a third grindstone having an abrasive grain size smaller than that of the second grindstone.
Manufacturing method of sputtering target.

[9]. In the method for manufacturing a sputtering target according to [7] or [8], the feed rate v (m / min) of the object to be ground, the grindstone peripheral speed V (m / min) of the first grindstone, and the cutting depth t ( A method for manufacturing a sputtering target, wherein the grain size d (μm) of the first grindstone and the first grindstone satisfies the following relational expression (4).
(V / V) ^1/3 x (t) ^1/6 x d <50 ... (4)

According to one aspect of the present invention, it is possible to provide an oxide sintered body and a sputtering target having improved crack resistance. Further, according to one aspect of the present invention, it is possible to provide a method for manufacturing the sputtering target.

It is a perspective view which shows the shape of the target which concerns on one Embodiment of this invention. It is a perspective view which shows the shape of the target which concerns on one Embodiment of this invention. It is a perspective view which shows the shape of the target which concerns on one Embodiment of this invention. It is a perspective view which shows the shape of the target which concerns on one Embodiment of this invention. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 1. FIG. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 2. FIG. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 3. FIG. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 4. FIG. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 5. FIG. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 6. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Comparative Example 1. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Comparative Example 2. It is a 3D observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 1. FIG. It is a 3D observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 2. FIG. It is a 3D observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 3. FIG. It is a 3D observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Example 4. FIG. 6 is a 3D observation image of the oxide sintered body (after surface grinding) according to Example 5 by a confocal laser scanning microscope. 6 is a 3D observation image of the oxide sintered body (after surface grinding) according to Example 6 by a confocal laser scanning microscope. 6 is a 3D observation image of the oxide sintered body (after surface grinding) according to Comparative Example 1 by a confocal laser scanning microscope. 3D observation image of the oxide sintered body (after surface grinding) according to Comparative Example 2 by a confocal laser scanning microscope. It is an XRD chart of the oxide sintered body which concerns on Example 1. FIG. It is a graph which shows the relationship between the surface roughness Rz and the crack resistance. It is a plane observation image by the confocal laser scanning microscope of the oxide sintered body (after surface grinding) which concerns on Comparative Example 3. 3D observation image of the oxide sintered body (after surface grinding) according to Comparative Example 3 by a confocal laser scanning microscope. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 1 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 2 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 3 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 4 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 5 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Example 6 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Comparative Example 1 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on Comparative Example 2 after surface grinding. It is a figure which shows the cross-sectional profile of the surface roughness measurement position of the oxide sintered body which concerns on the comparative example 3 after surface grinding.

Hereinafter, embodiments will be described with reference to drawings and the like. However, it is easily understood by those skilled in the art that the embodiments can be implemented in many different embodiments, and the embodiments and details can be variously changed without departing from the spirit and scope thereof. .. Therefore, the present invention is not construed as being limited to the description of the following embodiments.

In the drawings, the size, layer thickness, area, etc. may be exaggerated for clarity. Therefore, the present invention is not limited to the illustrated size, layer thickness, region, and the like. The drawings schematically show ideal examples, and the present invention is not limited to the shapes and values shown in the drawings.

The ordinal numbers "1st", "2nd", and "3rd" used in the present specification are added to avoid confusion of the components, and the components are not described to be numerically specified. Is not limited in number.

In the present specification and the like, the terms "film" or "thin film" and the term "layer" can be interchanged with each other in some cases.

In the sintered body and the oxide semiconductor thin film of the present specification and the like, the term "compound" and the term "crystal phase" can be interchanged with each other in some cases.

In the present specification, the "oxide sintered body" may be simply referred to as a "sintered body".
In the present specification, the "sputtering target" may be simply referred to as a "target".

[Sputtering target]
Cracks in the sputtering target occur starting from a portion of the target where the strength is weak.
Therefore, as a measure for improving the crack resistance, the present inventor has considered reducing the variation in the strength in the sputtering target surface, particularly improving the minimum strength.
Conventionally, the grinding streaks in a sputtering target have been evaluated by the surface roughness Ra (sometimes referred to as arithmetic mean roughness), and also in Patent Document 1, the bending strength, which is one of the indexes indicating the strength of the target. However, it was said to be sufficient. As described above, conventionally, Ra is sufficient for the evaluation of the grinding streaks on the surface of the oxide sintered body, and the difference between the surface roughness Ra and the surface roughness Rz (sometimes referred to as the maximum height) is small. It was being considered.
However, as a result of scrutinizing the grinding damage of ITZO, the present inventor found that ITZO is more brittle than the conventional target material, and in addition to the grinding streaks normally observed on the surface of the oxide sintered body after surface grinding. , I found a place (hole) where the crystal structure was peeled off as a large mass. It was found that the depth of the peeled portion was more than an order of magnitude deeper than the depth of a normal grinding streak.
As a result of diligent studies on the grinding method, the present inventor has started grinding with a grindstone having a medium grain size as a grindstone for grinding in order to reduce the peeling points as described above. By gradually switching to a grindstone with a smaller grain size and grinding, no large holes remain (that is, the surface roughness Rz can be reduced), and the number of peeling points can be reduced, resulting in a sputtering target. It was found that the crack resistance of the grindstone is also greatly improved.
The present inventor invented the present invention based on these findings.

The sputtering target according to one embodiment of the present invention (hereinafter, may be simply referred to as a sputtering target according to the present embodiment) includes an oxide sintered body.
The sputtering target according to the present embodiment is obtained by cutting and grinding an oxide sintered body into a shape suitable as a sputtering target, for example.
Further, the sputtering target according to the present embodiment can also be obtained by grinding the bulk of the oxide sintered body and bonding the sputtering target material obtained by grinding to the backing plate.
Further, as the sputtering target of the present embodiment according to another aspect, a target made of only an oxide sintered body can be mentioned.

The shape of the oxide sintered body is not particularly limited.
A plate-shaped oxide sintered body as shown by reference numeral 1 in FIG. 1 may be used.
A cylindrical oxide sintered body as shown by reference numeral 1A in FIG. 2 may be used.
When the oxide sintered body has a plate shape, the planar shape of the oxide sintered body may be a rectangle as shown by reference numeral 1 in FIG. 1 or a circle as shown by reference numeral 1B in FIG.

The oxide sintered body may be an integrally molded product, or may be divided into a plurality of parts as shown in FIG. Each of the oxide sintered bodies (reference numeral 1C) divided into a plurality of parts may be fixed to the backing plate 3. A sputtering target obtained by bonding a plurality of oxide sintered bodies 1C to one backing plate 3 in this way may be referred to as a multi-division type sputtering target. The backing plate 3 is a member for holding and cooling the oxide sintered body. The material of the backing plate 3 is not particularly limited. As the material of the backing plate 3, for example, at least one material selected from the group consisting of Cu, Ti, SUS and the like is used.

(Surface roughness Rz)
In the target according to the present embodiment, the surface roughness Rz (maximum height) of the oxide sintered body is less than 2.0 μm. In the present specification, the surface roughness Rz is measured when observed with a confocal laser scanning microscope (LSM) (manufactured by Laser Tech Co., Ltd., “OPTELICS H1200”) at an objective lens magnification of × 100 (about 2000 times). It is carried out in accordance with JIS B 0601: 2001 and JIS B 0610: 2001 based on the cross-sectional profile of. The measurement point of the surface roughness Rz is the surface of the test piece for measurement obtained by cutting out ^{the central portion 4 cm 2 (2 cm × 2 cm) of the oxide sintered body plate after the grinding process.}
When the surface roughness Rz of the oxide sintered body is less than 2.0 μm, the crack resistance of the sputtering target is improved. It is considered that the reason why the crack resistance is improved in this way is that the crystal structure is not peeled off as a large mass and the surface smoothness of the oxide sintered body is high.
The surface roughness Rz of the oxide sintered body is preferably 1.5 μm or less, and more preferably 1.0 μm or less.
The oxide sintered body in the sputtering target has a bonding surface bonded to the backing plate and a surface opposite to the bonding surface and sputtered. In the present embodiment, the surface roughness Rz of the surface corresponding to the sputtering surface may be less than 2.0 μm. It is preferable that the surface roughness Rz of the bonding surface is also small, but if it is too small, the wettability of indium (In), which is a wax agent in the bonding process, deteriorates and the bonding rate decreases, so that the wettability can be ensured. Will be selected as appropriate.
Further, in the target, the thermal stress generated on the sputtering surface after the sputtering discharge is the tensile stress. The thermal stress generated on the sputtering surface can be a main cause of crack generation, but on the bonding surface behind the target, a compressive stress opposite to the thermal stress is generated, so that cracks are less likely to occur and occur on the sputtering surface. The effect of thermal stress is small.

(Surface roughness Ra)
In the target according to the present embodiment, the surface roughness Ra (arithmetic mean roughness) of the oxide sintered body is preferably less than 0.5 μm, more preferably 0.25 μm or less.
If the surface roughness Ra is less than 0.5 μm, arcing or the like is unlikely to occur during sputtering, and the discharge stability is excellent. That is, when a new target is used in a normal process, low power pre-sputtering is performed to improve the surface roughness. When the surface roughness Ra is small, the pre-sputtering time can be shortened, and the sputtering discharge with high power can be performed in a short time.

(Composition of oxide sintered body)
The oxide sintered body according to the present embodiment preferably contains an indium element (In), a tin element (Sn) and a zinc element (Zn).
The oxide sintered body according to the present embodiment may contain a metal element other than In, Sn and Zn as long as the effect of the present invention is not impaired, and substantially In, Sn and Zn. It may be contained only, or it may be composed only of In, Sn and Zn. Here, "substantially" means that 95% by mass or more and 100% by mass or less (preferably 98% by mass or more and 100% by mass or less) of the metal element of the oxide sintered body are indium element (In) and tin element (Sn). ) And zinc element (Zn). The oxide sintered body according to the present embodiment may contain unavoidable impurities in addition to In, Sn, Zn and the oxygen element (O) as long as the effects of the present invention are not impaired. The unavoidable impurities referred to here are elements that are not intentionally added and are mixed with raw materials or manufacturing processes.

The oxide sintered body according to the present embodiment preferably contains an indium element (In), a tin element (Sn), a zinc element (Zn) and an X element.
The oxide sintered body according to the present embodiment may contain a metal element other than In, Sn, Zn and X element as long as the effect of the present invention is not impaired, and substantially In, It may contain only Sn, Zn and X elements, or may contain only In, Sn, Zn and X elements. Here, "substantially" means In, Sn, Zn and X elements in an amount of 95% by mass or more and 100% by mass or less (preferably 98% by mass or more and 100% by mass or less) of the metal element of the oxide sintered body. Means that. The oxide sintered body according to the present embodiment may contain unavoidable impurities in addition to In, Sn, Zn, X element and oxygen element (O) as long as the effect of the present invention is not impaired. The unavoidable impurities referred to here are elements that are not intentionally added and are mixed with raw materials or manufacturing processes.
The X element is germanium element (Ge), silicon element (Si), ittrium element (Y), zirconium element (Zr), aluminum element (Al), magnesium element (Mg), itterbium element (Yb) and gallium element (Ga). ) Is at least one element selected from the group consisting of.

Examples of unavoidable impurities are alkali metals (Li, Na, K, Rb, etc.), alkaline earth metals (Ca, Sr, Ba, etc.), hydrogen (H) elements, boron (B) elements, carbon (C) elements. , Nitrogen (N) element, Fluorine (F) element and Chlorine (Cl) element.

Impurity concentration can be measured by ICP or SIMS.

<Measurement of impurity concentration (H, C, N, F, Si, Cl)>
Impurity concentration (H, C, N, F, Si, Cl) in the obtained sintered body is determined by SIMS analysis using a sector type dynamic secondary ion mass spectrometer (IMS 7f-Auto, manufactured by AMETEK CAMECA). Can be quantitatively evaluated by.
Specifically, first, the primary ion Cs ⁺ is used to perform sputtering at an acceleration voltage of 14.5 kV to a depth of 20 μm from the surface of the sintered body to be measured. After that, impurities (H, C, N, F, Si, Cl) are sputtered with a raster of 100 μm □ (size of 100 μm × 100 μm), a measurement area of 30 μm □ (size of 30 μm × 30 μm), and a depth of 1 μm with primary ions. Integrate the mass spectral intensities of.

Further, in order to calculate the absolute value of the impurity concentration from the mass spectrum, each impurity is implanted into the sintered body by controlling the dose amount by ion implantation to prepare a standard sample having a known impurity concentration. The mass spectral intensity of impurities (H, C, N, F, Si, Cl) is obtained from the standard sample by SIMS analysis, and the relational expression between the absolute value of the impurity concentration and the mass spectral intensity is used as a calibration curve.
Finally, the impurity concentration of the measurement target is calculated using the mass spectral intensity of the sintered body to be measured and the calibration curve, and this is taken as the absolute value of the impurity concentration (atom · cm ^-3 ).

<Measurement of impurity concentration (B, Na)>
The impurity concentration (B, Na) of the obtained sintered body can also be quantitatively evaluated by SIMS analysis using a sector type dynamic secondary ion mass spectrometer (IMS 7f-Auto, manufactured by AMETEK CAMECA). The primary ions _O ^{2 +,} 5.5 kV accelerating voltage of primary ion, except that the measurement of the mass spectrum of each impurity, measurement H, C, N, F, Si, by measuring the same evaluation Cl The absolute value of the target impurity concentration (atom · cm ^-3 ) can be obtained.

In the oxide sintered body according to the present embodiment, it is more preferable that the atomic composition ratio of each element satisfies at least one of the following formulas (1), (2) and (3).
0.40 ≤ Zn / (In + Sn + Zn) ≤ 0.80 ... (1)
0.15 ≤ Sn / (Sn + Zn) ≤ 0.40 ... (2)
0.10 ≤ In / (In + Sn + Zn) ≤ 0.35 ... (3)

In formulas (1) to (3), In, Zn and Sn represent the contents of indium element, zinc element and tin element in the oxide sintered body, respectively.

When Zn / (In + Sn + Zn) is 0.40 or more, a spinel phase is likely to be generated in the oxide sintered body, and semiconductor characteristics can be easily obtained.
When Zn / (In + Sn + Zn) is 0.80 or less, it is possible to suppress a decrease in strength due to abnormal grain growth of the spinel phase in the oxide sintered body. Further, when Zn / (In + Sn + Zn) is 0.80 or less, the decrease in mobility of the oxide semiconductor thin film can be suppressed.
Zn / (In + Sn + Zn) is more preferably 0.50 or more and 0.70 or less.

When Sn / (Sn + Zn) is 0.15 or more, it is possible to suppress a decrease in strength due to abnormal grain growth of the spinel phase in the oxide sintered body.
When Sn / (Sn + Zn) is 0.40 or less, aggregation of tin oxide that causes abnormal discharge during sputtering can be suppressed in the oxide sintered body. Further, when Sn / (Sn + Zn) is 0.40 or less, the oxide semiconductor thin film formed by using the sputtering target can be easily etched with a weak acid such as oxalic acid. When Sn / (Sn + Zn) is 0.15 or more, it is possible to suppress the etching rate from becoming too fast and the etching control becomes easy.
Sn / (Sn + Zn) is more preferably 0.15 or more and 0.35 or less.

When In / (In + Sn + Zn) is 0.10 or more, the bulk resistance of the obtained sputtering target can be lowered. Further, when In / (In + Sn + Zn) is 0.10 or more, it is possible to suppress the mobility of the oxide semiconductor thin film from becoming extremely low.
When In / (In + Sn + Zn) is 0.35 or less, it is possible to suppress the film from becoming a conductor when a sputtering film is formed, and it becomes easy to obtain the characteristics as a semiconductor.
In / (In + Sn + Zn) is more preferably 0.10 or more and 0.30 or less.

When the oxide sintered body according to the present embodiment contains an element X, the atomic ratio of each element preferably satisfies the following formula (1X).
0.001 ≤ X / (In + Sn + Zn + X) ≤ 0.05 ... (1X)
(In the formula (1X), In, Zn, Sn and X represent the contents of the indium element, the zinc element, the tin element and the X element in the oxide sintered body, respectively.)

Within the range of the above formula (1X), the crack resistance of the oxide sintered body according to the present embodiment can be sufficiently increased.
The element X is preferably at least one selected from the group consisting of element silicon (Si), element aluminum (Al), element magnesium (Mg), element itterbium (Yb) and element gallium (Ga).
It is more preferable that the element X is at least one selected from the group consisting of element silicon (Si), element aluminum (Al) and element gallium (Ga).
The aluminum element (Al) and the gallium element (Ga) are more preferable because the composition of the oxide as a raw material is stable and the effect of improving the crack resistance is high.

When X / (In + Sn + Zn + X) is 0.001 or more, the decrease in the strength of the sputtering target can be suppressed. When X / (In + Sn + Zn + X) is 0.05 or less, the oxide semiconductor thin film formed by using the sputtering target containing the oxide sintered body can be easily etched with a weak acid such as oxalic acid. become. Further, when X / (In + Sn + Zn + X) is 0.05 or less, it is possible to suppress a decrease in TFT characteristics, particularly mobility.
X / (In + Sn + Zn + X) is preferably 0.001 or more and 0.05 or less, more preferably 0.003 or more and 0.03 or less, and 0.005 or more and 0.01 or less. Is more preferable, and 0.005 or more and less than 0.01 are even more preferable.
When the oxide sintered body according to the present embodiment contains an element X, the element X may be only one kind or two or more kinds. When two or more kinds of X elements are contained, X in the formula (1X) is the total atomic ratio of the X elements.
The existence form of the X element in the oxide sintered body is not particularly specified. Examples of the existing form of the X element in the oxide sintered body include a form existing as an oxide, a form in which it is solid-solved, and a form in which it is segregated at the grain boundaries.

The atomic ratio of each metal element in the oxide sintered body can be controlled by the blending amount of the raw materials. Further, the atomic ratio of each element can be obtained by quantitatively analyzing the contained elements with an inductively coupled plasma emission spectrophotometer (ICP-AES).

The oxide sintered body according to the present embodiment _{preferably contains a spinel structure compound represented by Zn 2-x} Sn _1-y In _{x + y} O ₄ [0 ≦ x <2, 0 ≦ y <1]. .. In the present specification, a spinel structure compound may be referred to as a spinel compound. In Zn _2-x Sn _1-y In _{x + y} O ₄ , when x is 0 and y is 0, it is represented by _{Zn 2} SnO _4.

The oxide sintered body according to the present embodiment preferably contains a hexagonal layered compound represented by _{In 2} O ₃ (ZnO) _m. In the present embodiment, in the _{formula represented by In 2} O ₃ (ZnO) _m , m is an integer of 2 to 7, and preferably an integer of 3 to 5. If m is 2 or more, the compound has a hexagonal layered structure. When m is 7 or less, the volume resistivity of the oxide sintered body becomes low.

The oxide sintered body according to the present embodiment includes _{a hexagonal layered compound represented by In 2} O ₃ (ZnO) _m [m = 2 to 7] and Zn _2-x Sn _1-y In _{x + y} O ₄ [0 ≦]. It is more preferable to contain a spinel structure compound represented by x <2,0 ≦ y <1].

The hexagonal layered compound composed of indium oxide and zinc oxide is a compound showing an X-ray diffraction pattern attributed to the hexagonal layered compound in the measurement by the X-ray diffraction method. The hexagonal layered compound contained in the oxide sintered body is a compound represented by In ₂ O ₃ (ZnO) _m .

The oxide sintered body according to the present embodiment _{is a spinel structure compound represented by Zn 2-x} Sn _1-y In _{x + y} O ₄ [0 ≦ x <2, 0 ≦ y <1] and In ₂ O ₃ . It may contain the represented big bite structure compound.

(Bulk resistance)
When the oxide sintered body according to the present embodiment contains an element X, the bulk resistance of the sputtering target can be sufficiently lowered if the content ratio of the element X is within the range of the above formula (1X).

The bulk resistance of the sputtering target according to the present embodiment is preferably 50 mΩcm or less, more preferably 25 mΩ cm or less, further preferably 10 mΩ cm or less, still more preferably 5 mΩ cm or less, and 3 mΩ cm or less. Is particularly preferable. When the bulk resistance is 50 mΩcm or less, stable film formation can be performed by direct current sputtering.
The bulk resistivity value can be measured based on the four-probe method (JIS R 1637: 1998) using a known resistivity meter. The number of measurement points is about 9, and it is preferable that the average value of the measured 9 points is the bulk resistance value.
When the plane shape of the oxide sintered body is a quadrangle, it is preferable that the surface is divided into 9 parts of 3 × 3 and the center points of each quadrangle are 9 points.
When the planar shape of the oxide sintered body is circular, it is preferable to divide the square inscribed in the circle into 9 parts of 3 × 3 so that the center points of each square are 9 points.

(Average crystal grain size)
The average crystal grain size of the oxide sintered body according to the present embodiment is preferably 10 μm or less, more preferably 8 μm or less, from the viewpoint of prevention of abnormal discharge and ease of manufacture.
When the average crystal grain size is 10 μm or less, abnormal discharge caused by grain boundaries can be prevented. The lower limit of the average crystal grain size of the oxide sintered body is not particularly specified, but is preferably 1 μm or more from the viewpoint of ease of production.
The average crystal grain size can be adjusted by selecting raw materials and changing manufacturing conditions. Specifically, it is preferable to use a raw material having a small average particle size, and it is more preferable to use a raw material having an average particle size of 1 μm or less. Further, at the time of sintering, the higher the sintering temperature or the longer the sintering time, the larger the average crystal grain size tends to be.

The average crystal grain size can be measured as follows.
The surface of the oxide sintered body is ground, and if the plane shape is a quadrangle, the surface is divided into 16 equal areas, and at 16 center points of each quadrangle, the inside of the frame has a magnification of 1000 times (80 μm × 125 μm). The particle size observed in is measured, the average value of the particle size of the particles in the frame at 16 places is obtained, and finally the average value of the measured values at 16 places is taken as the average crystal grain size.
When the surface of the oxide sintered body is ground and the plane shape is circular, the square inscribed in the circle is divided into 16 equal areas, and the magnification is 1000 times (80 μm × 125 μm) at the center points of each square. The particle size of the particles observed in the frame is measured, and the average value of the particle size of the particles in the 16 frames is obtained.
For particles with an aspect ratio of less than 2, the particle size is measured based on JIS R 1670: 2006, with the particle size of the crystal grains as the equivalent circle diameter. Specifically, as a procedure for measuring the diameter equivalent to a circle, a circle ruler is applied to the grain to be measured in the microstructure photograph, and the diameter corresponding to the area of the target grain is read. For particles with an aspect ratio of 2 or more, the average value of the longest diameter and the shortest diameter is taken as the particle size of the particles. Crystal grains can be observed with a scanning electron microscope (SEM). The hexagonal layered compound, the spinel compound, and the bigvite structure compound can be confirmed by the method described in Examples described later.

When the oxide sintered body according to the present embodiment contains a hexagonal layered compound and a spinel compound, the difference between the average crystal grain size of the hexagonal layered compound and the average crystal grain size of the spinel compound is 1 μm or less. It is preferable to have. By setting the average crystal grain size in such a range, the strength of the oxide sintered body can be improved.
It is more preferable that the average crystal grain size of the oxide sintered body according to the present embodiment is 10 μm or less, and the difference between the average crystal grain size of the hexagonal layered compound and the average crystal grain size of the spinel compound is 1 μm or less. ..

When the oxide sintered body according to the present embodiment contains a bigvite structure compound and a spinel compound, the difference between the average crystal grain size of the bigbite structure compound and the average crystal grain size of the spinel compound is 1 μm. The following is preferable. By setting the average crystal grain size in such a range, the strength of the oxide sintered body can be improved.
It is more preferable that the average crystal grain size of the oxide sintered body according to the present embodiment is 10 μm or less, and the difference between the average crystal grain size of the big bite structure compound and the average crystal grain size of the spinel compound is 1 μm or less. ..

(Relative density)
The relative density of the oxide sintered body according to the present embodiment is preferably 95% or more, more preferably 96% or more.
When the relative density of the oxide sintered body according to the present embodiment is 95% or more, the mechanical strength of the sputtering target according to the present embodiment is high and the conductivity is excellent. Therefore, when the sputtering target according to the present embodiment is attached to an RF magnetron sputtering apparatus or a DC magnetron sputtering apparatus to perform sputtering, the stability of plasma discharge can be further improved. The relative density of the oxide sintered body indicates the actually measured density of the oxide sintered body with respect to the theoretical density calculated from the inherent density of each oxide in the sintered body and the composition ratio thereof, as a percentage. It is a thing. The relative density of the oxide sintered body is calculated from, for example, the inherent densities of indium oxide, zinc oxide and tin oxide, and the oxides of element X contained as necessary, and their composition ratios. The actual measured density of the oxide sintered body is shown as a percentage.

The relative density of the oxide sintered body can be measured based on the Archimedes method. The relative density (unit:%) is specifically calculated by dividing the aerial weight of the oxide sintered body by the volume (= the weight of the sintered body in water / the specific gravity of water at the measured temperature) by the following formula (Equation 5). It is the value of the percentage with respect to the theoretical density ρ (g / cm ^{3) based on.}
Relative density = {(air weight / volume of oxide sintered body) / theoretical density ρ} × 100

_{ρ = (C 1/100 /} ρ 1 + C 2/100 / ρ 2 ··· + C n / 100 / ρ n) -1 ... ( 5)
In the formula (Equation 5), C _{1 to} C _n indicate the content (mass%) of the oxide sintered body or the constituent substance of the oxide sintered body, respectively, and ρ _{1 to ρ n} are The density (g / cm ³ ) of each constituent substance corresponding to C _{1 to} C _n is shown.
Since the density and the specific gravity are almost the same, the density of each constituent substance uses the value of the specific gravity of the oxide described in the Chemical Society of Japan, Revised 2nd Edition (Maruzen Co., Ltd.). be able to.

(Ratio H / L of surface roughness grinding scratch depth (H) and width (L))
In the present invention, the "grinding scratch" refers to a scratch formed in the grinding process when a sputtering target is manufactured from an oxide sintered body.
In the grinding scratches of the oxide sintered body according to the present embodiment, the ratio H / L between the depth (H) and the width (L) of the grinding scratches having the maximum depth and the minimum width is 0. It is preferably less than .2, more preferably 0.19 or less.
In the oxide sintered body according to the present embodiment, if the ratio H / L of the depth (H) and the width (L) of the grinding scratch is less than 0.2, the grinding scratch is gentle and the grinding scratch. Is prevented from becoming the starting point of fracture, and the tensile strength of the oxide sintered body is increased.
In the oxide sintered body according to the present embodiment, the ratio H / L of the depth (H) and the width (L) of the grinding scratch is preferably 0.01 or more, and is preferably 0.05 or more. Is more preferable.
By taking measures against grinding scratches such as reducing the feed rate of the grinding target portion and reducing the depth of cut of the grindstone, the depth of the grinding scratches and the difference between the grinding scratches and the background can be reduced.
If the ratio H / L of the depth (H) to the width (L) of the oxide sintered body according to the present embodiment is 0.01 or more, the above-mentioned measures against grinding scratches are taken. In addition, the sputtering target can be efficiently manufactured on the production line.

[Manufacturing method of oxide sintered body]
The method for producing an oxide sintered body according to the present embodiment includes a mixing / crushing step, a granulation step, a molding step, and a sintering step. The method for producing the oxide sintered body may include other steps. Other steps include an annealing step.
Hereinafter, each step will be specifically described with reference to the case of producing an ITZO-based oxide sintered body as an example.

The oxide sintered body according to the present embodiment has a mixing / crushing step of mixing and crushing an indium raw material, a zinc raw material, a tin raw material and an X element raw material, a granulation step of granulating a raw material mixture, and molding of a raw material granulated powder. It can be manufactured through a molding step of performing, a sintering step of sintering a molded body, and an annealing step of annealing the sintered body as needed.

(1) Mixing / crushing step The mixing / crushing step is a step of mixing and crushing the raw materials of the oxide sintered body to obtain a raw material mixture. The raw material mixture is preferably in the form of powder, for example.
In the mixing / crushing step, first, the raw material of the oxide sintered body is prepared.

The raw materials for producing an oxide sintered body containing In, Zn and Sn are as follows.
The indium raw material (In raw material) is not particularly limited as long as it is a compound or metal containing In.
The zinc raw material (Zn raw material) is not particularly limited as long as it is a compound or metal containing Zn.
The tin raw material (Sn raw material) is not particularly limited as long as it is a compound or metal containing Sn.

The raw materials for producing an oxide sintered body containing the X element are as follows.
The raw material of the element X is not particularly limited as long as it is a compound or a metal containing the element X.

The In raw material, Zn raw material, Sn raw material and X element raw material are preferably oxides.
Raw materials such as indium oxide, zinc oxide, tin oxide and element X oxide are preferably of high purity. The purity of the raw material of the oxide sintered body is preferably 99% by mass or more, more preferably 99.9% by mass or more, and further preferably 99.99% by mass or more. When a high-purity raw material is used, a sintered body having a fine structure can be obtained, and the volume resistivity of the sputtering target made of the sintered body is lowered.

The average particle size of the primary particles of the metal oxide as a raw material is preferably 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 5 μm or less, and 0.1 μm or more and 5 μm or less. Is more preferable.
If the average particle size of the primary particles of the metal oxide as a raw material is 0.01 μm or more, it is difficult to aggregate, and if the average particle size is 10 μm or less, the mixing property is sufficient and the sintered body has a fine structure. Is obtained. For the average particle size, the median diameter D50 is adopted. The average particle size (median diameter D50) is measured by a laser diffraction type particle size distribution measuring device SALD-300V (manufactured by Shimadzu Corporation).

A dispersant for breaking agglomeration and a thickener for adjusting the viscosity suitable for granulation with a spray dryer are added to the raw material of the oxide sintered body, and the mixture is mixed and pulverized with a bead mill or the like. .. Examples of the dispersant include an acrylic acid methacrylic acid copolymer ammonia neutralized product and the like, and examples of the thickener include polyvinyl alcohol and the like.

(2) Temporary baking treatment step The raw material mixture obtained in the mixing / crushing step may be immediately granulated, or may be subjected to a calcining treatment before granulation. The calcining treatment is usually performed by firing the raw material mixture at 700 ° C. or higher and 900 ° C. or lower for 1 hour or longer and 5 hours or shorter.

(3) Granulation step The raw material mixture that has not been calcined or the raw material mixture that has been calcined can be granulated to improve the fluidity and filling property in the molding step of (4) below. ..
In the present specification, the step of granulating the raw material of the oxide sintered body to obtain the raw material granulated powder may be referred to as a granulation step.
The granulation treatment can be performed using a spray dryer or the like. The shape of the granulated powder obtained in the granulation step is not particularly limited, but is preferably a true sphere for uniform filling into the mold in the molding step.
The granulation conditions are appropriately selected by adjusting the concentration of the raw material slurry to be introduced, the rotation speed of the spray dryer, the hot air temperature, and the like.
For the preparation of the slurry solution, when using the raw material mixture not subjected to the calcining treatment, the slurry solution obtained in the mixing / crushing step is used as it is, and when using the raw material mixture subjected to the calcining treatment, the mixture is mixed again. -Used after being prepared into a slurry solution through a crushing step.

In the method for producing an oxide sintered body according to the present embodiment, the particle size of the raw material granulated powder formed by the granulation treatment is not particularly limited, but may be controlled within the range of 25 μm or more and 150 μm or less. preferable.
When the particle size of the raw material granulated powder is 25 μm or more, the slipperiness of the raw material granulated powder on the surface of the mold used in the molding step (4) below is improved, and the raw material granulated powder is sufficiently placed in the mold. Can be filled in.
When the particle size of the raw material granulated powder is 150 μm or less, it is possible to prevent the particle size from being too large and the filling rate in the mold being low.
The particle size of the raw material granulated powder is more preferably 25 μm or more and 75 μm or less.

The method for obtaining the raw material granulated powder having a particle size within a predetermined range is not particularly limited. For example, a method of sieving a raw material mixture (raw material granulated powder) that has been subjected to a granulation treatment to select a raw material granulated powder belonging to a desired particle size range can be mentioned. The sieve used in this method is preferably a sieve having an opening having a size through which the raw material granulated powder having a desired particle size can pass. It is preferable to use a first sieve for selecting the raw material granulated powder based on the lower limit of the particle size range and a second sieve for selecting the raw material granulated powder based on the upper limit of the particle size range. For example, when the particle size of the raw material granulated powder is controlled within the range of 25 μm or more and 150 μm or less, first, the raw material granulated powder of less than 25 μm can pass through, and the size of the raw material granulated powder of 25 μm or more does not pass through. Using a sieve having an opening (first sieve), raw material granulated powder having a particle size of 25 μm or more is selected. Next, a sieve (second sieve) having an opening having a size that allows the raw material granulation powder of 150 μm or less to pass through the raw material granulated powder after this sorting and does not allow the raw material granulated powder exceeding 150 μm to pass through is used. Then, the raw material granulated powder within the range of 25 μm or more and 150 μm or less is selected. The order may be such that the second sieve is used first and then the first sieve is used.
The method for controlling the particle size range of the raw material granulated powder is not limited to the method using a sieve as described above, and it is sufficient that the raw material granulated powder used for the molding step of the following (4) can be controlled within a desired range.

In the raw material mixture that has been subjected to the calcining treatment, the particles are bonded to each other. Therefore, when the granulation treatment is performed, it is preferable to perform the pulverization treatment before the granulation treatment.

(4) Molding Step In the present specification, a step of filling a mold with the raw material granulated powder obtained in the granulation step and molding the raw material granulated powder filled in the mold to obtain a molded product. Sometimes referred to as a molding process.
Examples of the molding method in the molding step include mold press molding.
When a sintered body having a high sintering density is obtained as a sputtering target, it is preformed by die press molding or the like in the molding process, and then further consolidated by cold hydrostatic pressing (CIP) molding or the like. It is preferable to do so.

(5) Sintering Step In the present specification, a step of sintering a molded body obtained in a molding step within a predetermined temperature range may be referred to as a sintering step.
In the sintering step, a commonly used sintering method such as normal pressure sintering, hot press sintering, or hot isostatic pressing (HIP) sintering can be used.

The sintering temperature is not particularly limited, but is preferably 1310 ° C. or higher and 1440 ° C. or lower, and more preferably 1320 ° C. or higher and 1430 ° C. or lower.
When the sintering temperature is 1310 ° C. or higher, a sufficient sintering density can be obtained, and the bulk resistance of the sputtering target can be lowered.
When the sintering temperature is 1440 ° C. or lower, sublimation of zinc oxide during sintering can be suppressed.

In the sintering step, the rate of temperature rise from room temperature to reaching the sintering temperature is not particularly limited, but is preferably 0.1 ° C./min or more and 3 ° C./min or less.
Further, in the process of raising the temperature, the temperature may be maintained at 700 ° C. or higher and 800 ° C. or lower for 1 hour or longer and 10 hours or lower, held at a predetermined temperature for a predetermined time, and then raised to the sintering temperature.

The sintering time varies depending on the sintering temperature, but is preferably 1 hour or more and 50 hours or less, more preferably 2 hours or more and 30 hours or less, and preferably 3 hours or more and 20 hours or less. More preferred.
Examples of the atmosphere at the time of sintering include an atmosphere of air or oxygen gas, an atmosphere containing air or oxygen gas and a reducing gas, or an atmosphere containing air or oxygen gas and an inert gas. Examples of the reducing gas include hydrogen gas, methane gas, carbon monoxide gas and the like. Examples of the inert gas include argon gas and nitrogen gas.

(6) Annealing Step In the method for producing an oxide sintered body according to the present embodiment, the annealing step is not essential. When the annealing step is carried out, the temperature is usually maintained at 700 ° C. or higher and 1100 ° C. or lower for 1 hour or longer and 5 hours or lower.
In the annealing step, the sintered body may be cooled once and then heated again to be annealed, or may be annealed when the temperature is lowered from the sintering temperature.
Examples of the atmosphere at the time of annealing include an atmosphere of air or oxygen gas, an atmosphere containing air or oxygen gas and a reducing gas, or an atmosphere containing air or oxygen gas and an inert gas. Examples of the reducing gas include hydrogen gas, methane gas, carbon monoxide gas and the like. Examples of the inert gas include argon gas and nitrogen gas.

Even when an oxide sintered body having a system different from that of the ITZO system is produced, it can be produced by the same process as described above.

[Manufacturing method of sputtering target]
The sputtering target according to the present embodiment can be manufactured by cutting the oxide sintered body obtained by the above-mentioned manufacturing method into an appropriate shape and grinding the surface of the oxide sintered body.
Specifically, a sputtering target material (sometimes referred to as a target material) is obtained by cutting the oxide sintered body into a shape suitable for mounting on a sputtering apparatus. By adhering this target material to the backing plate, a sputtering target can be obtained.

The oxide sintered body according to the present embodiment used as the target material has a surface roughness Rz of less than 2.0 μm, preferably 1.5 μm or less, and more preferably 1.0 μm or less.
Examples of the method for adjusting the surface roughness Rz of the oxide sintered body include a method of grinding the surface using a grindstone having a predetermined count or higher.

(7) Surface Grinding Process In the present specification, the process of grinding the surface of the oxide sintered body used as the target material may be referred to as a surface grinding process.
The method for manufacturing a sputtering target according to the present embodiment includes a surface grinding step.
The grain size of the grindstone (first grindstone) that first grinds the surface of the oxide sintered body is preferably 100 μm or less, and more preferably 80 μm or less. The grain size of the grindstone is a value obtained by converting the number notation of the grindstone into the notation of the grain size.
When the grain size of the first grindstone is 100 μm or less, the crystal structure becomes a large lump and is difficult to peel off. On the other hand, when the grain size of the first grindstone is 100 μm or less, the grinding time may be long, but the feed speed v (m / min) of the object to be ground and the peripheral speed V (m / m /) of the first grindstone. By adjusting the depth of cut t (μm) and the grain size d (μm) of the first grindstone to the range where the relational expression (4) holds, it is possible to prevent the grinding time from becoming long and crack resistance. It is possible to achieve both the improvement of the grinding wheel and the manufacturing efficiency of the sputtering target.
(V / V) ^1/3 x (t) ^1/6 x d <50 ... (4)

The feed rate v (m / min) of the object to be ground, the peripheral speed V (m / min) of the first grindstone, the cutting depth t (μm), and the grain size d (μm) of the first grindstone have the following relationships. It is more preferable to satisfy the formula (4A), and it is further preferable to satisfy the following relational expression (4B).
(V / V) ^1/3 × (t) ^1/6 × d <30… (4A)
(V / V) ^1/3 x (t) ^1/6 x d <20 ... (4B)

Regarding the grinding conditions used for grinding the second and subsequent stages of the second grindstone and the third grindstone, it is preferable that the above relational expression (4) is satisfied, more preferably the above relational expression (4A) is satisfied, and the above relational expression is satisfied. It is more preferable to satisfy (4B).

In the present specification, the number of grindstones may be referred to as particle size.

In the surface grinding step of the present embodiment, it is preferable to use a grindstone having an abrasive grain size of 100 μm or less as the first grindstone. When a grindstone having a grain size of 100 μm or less is used as the first grindstone, it is possible to prevent the crystal structure from peeling off as a large lump. Even if the portion (hole) where the crystal structure is peeled off as a large mass is subsequently ground for a long time using a grindstone with a smaller count, the peeled peripheral portion becomes brittle, the hole cannot be removed, and the crack resistance is not improved.

In the surface grinding step according to the present embodiment, it is preferable to grind the surface of the oxide sintered body using a grindstone of a plurality of types. In this case, in addition to the grinding process by the first grindstone, it is preferable to perform the grinding process by using a grindstone having an abrasive grain size smaller than that of the first grindstone.
For example, after grinding with the first grindstone, the surface of the oxide sintered body is further ground with a grindstone (second grindstone) smaller than the grain size of the first grindstone, and after grinding with the second grindstone, the second grindstone is used. 2. An embodiment in which the surface of the oxide sintered body is further ground by using a grindstone (third grindstone) smaller than the grindstone grain size of the grindstone can be mentioned. In the surface grinding process according to the present embodiment, it is also preferable to carry out three or more stages of grinding as in this embodiment.

Examples of the combination of the grain size of the grindstone used in each step when performing the grinding process in a plurality of steps include the following combinations (P1) to (P4).

<3-stage grinding: 1st stage ⇒ 2nd stage ⇒ 3rd stage>
(P1) 80 μm ⇒ 40 μm ⇒ 20 μm

<4 stage grinding: 1st stage ⇒ 2nd stage ⇒ 3rd stage ⇒ 4th stage>
(P2) 100 μm ⇒ 80 μm ⇒ 40 μm ⇒ 20 μm

<Five-stage grinding: 1st stage ⇒ 2nd stage ⇒ 3rd stage ⇒ 4th stage ⇒ 5th stage>
(P3) 100 μm ⇒ 80 μm ⇒ 60 μm ⇒ 40 μm ⇒ 20 μm

<6th stage grinding: 1st stage ⇒ 2nd stage ⇒ 3rd stage ⇒ 4th stage ⇒ 5th stage ⇒ 6th stage>
(P4) 100 μm ⇒ 80 μm ⇒ 60 μm ⇒ 40 μm ⇒ 30 μm ⇒ 20 μm

The grain size of the grindstone used in the surface grinding step of the present embodiment is preferably 100 μm or less. When the grain size of the grindstone is 100 μm or less, cracking of the sputtering target material can be prevented.

The grindstone used in the surface grinding step in the present embodiment is preferably a diamond grindstone.

The surface roughness Ra of the oxide sintered body after the surface grinding step according to the present embodiment is preferably 0.5 μm or less.
It is preferable that the surface roughness Ra of the sputtering target material is 0.5 μm or less and the ground surface has no directionality. If the surface roughness Ra of the sputtering target material is 0.5 μm or less and a non-directional grinding surface is provided, abnormal discharge and generation of particles can be prevented.
Examples of the method for adjusting the surface roughness Ra of the sintered body include a method of grinding the sintered body with a surface grinding machine.

Finally, the obtained sputtering target material is cleaned. Examples of the cleaning treatment method include any method such as air blow and running water cleaning. When removing foreign matter with an air blow, foreign matter can be removed more effectively by sucking air with a dust collector from the opposite side of the nozzle of the air blow.
In addition to the above cleaning treatment by air blow or running water cleaning, ultrasonic cleaning or the like may be further performed. As the ultrasonic cleaning, a method of oscillating multiple times between a frequency of 25 kHz or more and 300 kHz or less is effective. For example, a method of performing ultrasonic cleaning by oscillating 12 kinds of frequencies in 25 kHz increments between frequencies of 25 kHz or more and 300 kHz or less is preferable.

The thickness of the sputtering target material is usually 2 mm or more and 20 mm or less, preferably 3 mm or more and 12 mm or less, more preferably 4 mm or more and 9 mm or less, and further preferably 4 mm or more and 6 mm or less. preferable.

A sputtering target can be manufactured by bonding the sputtering target material obtained through the above steps and treatments to a backing plate. Further, a plurality of sputtering target materials may be attached to one backing plate to substantially manufacture one sputtering target (multi-division type sputtering target).
The oxide sintered body as the sputtering target material has a bonding surface bonded to the backing plate and a surface opposite to the bonding surface and sputtered. In the present embodiment, it is preferable that the surface having a surface roughness Rz of less than 2.0 μm is the sputtering surface, and the surface opposite to the sputtering surface is the bonding surface. Therefore, in the method for manufacturing a sputtering target according to the present embodiment, the bonding surface side of the oxide sintered body is bonded to the backing plate.

The sputtering target according to the present embodiment is a sputtering target having an improved crack resistance because it contains an oxide sintered body and the surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm.

If a sputtering film is formed using the sputtering target according to the present embodiment, the crack resistance is improved, so that an oxide semiconductor thin film can be stably produced.

Hereinafter, the present invention will be specifically described based on examples. The present invention is not limited to the examples.

(Manufacturing of sputtering target)
A sputtering target made of an ITZO-based oxide sintered body was produced.

(Example 1)
First, the following powders were weighed so as to have an atomic ratio (In: 25 atomic%, Sn: 15 atomic%, Zn: 60 atomic%) as a raw material.
-In raw material: Indium oxide powder with a purity of 99.99% by mass
(Average particle size: 0.3 μm)
-Sn raw material: tin oxide powder with a purity of 99.99% by mass
(Average particle size: 1.0 μm)
Zn raw material: Zinc oxide powder with a purity of 99.99% by mass
(Average particle size: 3 μm)

A median diameter D50 was adopted as the average particle size of the oxide powder used as a raw material. The average particle size (median diameter D50) was measured with a laser diffraction type particle size distribution measuring device SALD-300V (manufactured by Shimadzu Corporation).

Next, acrylic acid methacrylic acid copolymer ammonia neutralized product (manufactured by Sanmei Kasei Co., Ltd., Banstar X754B) as a dispersant, polyvinyl alcohol as a thickener, and water were added to these raw materials, and the mixture was subjected to a bead mill. The mixture was mixed and pulverized for 2 hours to obtain a slurry solution for granulation having a solid content concentration of 70% by mass. The obtained slurry solution was supplied to a spray dryer and granulated under the conditions of a rotation speed of 12,000 rpm and a hot air temperature of 150 ° C. to obtain a raw material granulated powder.
The raw material granulated powder is passed through a 200 mesh sieve to remove granulated powder having a particle size of more than 75 μm, and then passed through a 500 mesh sieve to remove granulated powder having a particle size of less than 25 μm. The particle size of the above was adjusted to the range of 25 μm or more and 75 μm or less.

Next, this raw material granulated powder was uniformly filled in a mold having an inner diameter of 300 mm × 600 mm × 9 mm, and pressure-molded by a cold press machine. After pressure molding, molding was performed at a pressure of 294 MPa with a cold isotropic pressure pressurizing device (CIP device) to obtain a molded product.
The three molded bodies thus obtained were heated to 780 ° C. in an oxygen atmosphere in a sintering furnace, held at 780 ° C. for 5 hours, and further heated to 1400 ° C. to this sintering temperature (1400). It was held at ° C.) for 20 hours and then cooled in a furnace to obtain an oxide sintered body. The rate of temperature rise was 2 ° C./min.
The three obtained oxide sintered bodies were cut and surface-ground, respectively, to obtain three oxide sintered body plates having a size of 142 mm × 305 mm × 5 mmt. Of these, one was used for characterization and two were used for the G1 target [142 mm x 610 mm (divided into two) x 5 mmt].
In the surface grinding, the oxide sintered body was surface-ground using a diamond grindstone having a grindstone particle size of 80 μm using a surface grinding machine. The surface grinding conditions are as follows.
Surface grinding conditions:
Feed rate of the object to be ground v: 1m / min
Grindstone peripheral speed V: 500m / min
Grindstone depth of cut (cutting depth t): 5 μm
Grindstone grain size d: 80 μm
Whetstone type: Diamond whetstone

After grinding under the above-mentioned surface grinding conditions, a diamond grindstone having an abrasive grain size of 40 μm, then a diamond grindstone having an abrasive grain size of 20 μm, and a grindstone having a fine abrasive grain size are used in order under the above-mentioned surface grinding conditions. Grinded in.

(Manufacturing of target)
A G1 target was manufactured by bonding two obtained oxide sintered body plates (142 mm × 305 mm × 5 mmt) to a backing plate made of Cu. For bonding, the surface ground on the surface is used as the sputtering surface, and the surface opposite to the sputtering surface (the surface subjected to rough polishing with a grindstone having an abrasive grain size of 130 μm) is used as the bonding surface, and the bonding of the oxide sintered body plate is performed. The surface side was bonded to the backing plate. For all targets, the bonding rate was 98% or higher. When the oxide sintered body plate was bonded to the backing plate, cracks did not occur in the oxide sintered body plate, and the sputtering target could be manufactured satisfactorily. The bonding rate (bonding rate) was confirmed by X-ray CT.

(Examples 2 to 6)
The oxide sintered body according to Examples 2 to 6 was manufactured in the same manner as in Example 1 except that the grinding conditions in Example 1 were changed to the conditions shown in Table 1.
The sputtering target according to Examples 2 to 6 was manufactured in the same manner as in Example 1 using the oxide sintered body plate according to Examples 2 to 6.

(Comparative Examples 1 and 2)
The oxide sintered body according to Comparative Examples 1 and 2 was manufactured in the same manner as in Example 1 except that the grinding conditions and the grain size of the grindstone in Example 1 were changed to the contents shown in Table 1. ..

(Comparative Example 3)
The oxide sintered body according to Comparative Example 3 was manufactured in the same manner as in Example 1 except that the grinding conditions and the grain size of the grindstone in Example 1 were changed to the contents shown in Table 1.
The sputtering targets according to Comparative Examples 1 to 3 were manufactured in the same manner as in Example 1 using the oxide sintered body plates according to Comparative Examples 1 to 3.

Furthermore, the following characteristics were measured for the obtained oxide sintered body and the sputtering target. The measurement results are shown in Table 1.

(1) Surface roughness Rz
The surface roughness Rz of the surface of the oxide sintered body is 2 cm □ (2 cm × 2 cm) at the center of one oxide sintered body plate (142 mm × 305 mm × 5 mmt) after grinding other than that used for target manufacturing. Surface roughness based on the cross-sectional profile when observed with a confocal laser scanning microscope (LSM) (“OPTELICS H1200” manufactured by Lasertech Co., Ltd.) at an objective lens magnification of × 100 (about 2000 times). Rz was evaluated. The surface roughness Rz data was calculated by the software attached to the confocal laser scanning microscope. The data calculation was based on JIS B 0601: 2001 and JIS B 0610: 2001. The surface roughness Rz may be evaluated using a sample cut out from the central portion of the oxide sintered body plate.
The observation position of the oxide sintered body according to each Example and Comparative Example was set to the central portion, and the measurement direction was set to be perpendicular to the vertical direction by aligning the grinding direction with the vertical direction of the grinding streaks.

(2) Ratio of Grinding Scratch Depth (H) and Width (L) in Oxide Sintered Body The minimum height that distinguishes it from the unevenness of the surface of the oxide sintered body in the cross-sectional profile data for calculating the surface roughness. Is 30% of the surface roughness Rz. Of the identified irregularities, the area between the convex vertices adjacent to each other is defined as one grinding scratch. The convex apex of the unevenness is defined as a point where the slope of the uneven tangent line (the angle formed by the tangent line drawn on the uneven contour curve and the flat surface of the base) is 0 degree.
Here, a grinding scratch having a depth (H) corresponding to the maximum surface roughness Rz is identified, and the depth (H) and the width (L) are identified in the grinding scratch having the smallest width (L) with respect to the surface longitudinal direction. ) Was calculated.

Observation images of the plane of the oxide sintered body according to Examples 1 to 6 and Comparative Examples 1 to 3 after surface grinding are shown in FIGS. 5 to 12 and 23. The broken lines in the images of FIGS. 5 to 12 and 23 represent the positions where the surface roughness is measured. Further, FIGS. 25 to 33 also show a cross-sectional profile of the surface roughness measurement position of the oxide sintered body according to each of Examples 1 to 6 and Comparative Examples 1 to 3 after surface grinding. The thick frame in the cross-sectional profile indicates the measurement range of the depth (H) and width (L) of the grinding scratch for calculating the ratio H / L. Table 2 shows the start point, the end point, and the measurement result in the surface roughness measurement.

3D observation images of the oxide sintered body according to Examples 1 to 6 and Comparative Examples 1 to 3 after surface grinding are shown in FIGS. 13 to 20 and 24.

(3) XRD measurement Using the oxide sintered body plate used for surface roughness measurement, the crystal structure was examined by an X-ray diffraction measuring device (XRD). As a result, in the oxide sintered bodies according to Examples 1 to 6 and Comparative Examples 1 to 3, _{hexagonal crystals represented by In 2} O ₃ (ZnO) _m (in the formula, an integer of m = 2 to 7). It was confirmed that the layered compound and the _{spinel compound represented by Zn 2-x} Sn _1-y In _{x + y} O ₄ [0 ≦ x <2, 0 ≦ y <1] existed. FIG. 21 shows an XRD chart of the oxide sintered body according to the first embodiment.
・ Equipment: Smartlab manufactured by Rigaku Co., Ltd.
· X-ray: Cu-K [alpha line (wavelength 1.5418 × ^{10 -10} m)
・ Parallel beam, 2θ-θ reflection method, continuous scan (2.0 ° / min)
・ Sampling interval: 0.02 °
・ Divergence Slit (DS): 1.0 mm
-Scattering Slit (SS): 1.0 mm
-Receiving Slit (RS): 1.0 mm

The atomic ratio of the oxide sintered body was analyzed by an inductively coupled plasma emission spectrophotometer (ICP-OES, manufactured by Agilent) using the surface roughness and the remaining oxide sintered body plate used for XRD. The results are as follows.
Zn / (In + Sn + Zn) = 0.60
Sn / (Sn + Zn) = 0.20
In / (In + Sn + Zn) = 0.25

(4) Crack resistance during sputtering Using the prepared sputtering target, pre-sputtering was performed for 1 hour in a G1 sputtering apparatus under the conditions that the atmospheric gas was 100% Ar and the sputtering power was 1 kW. Here, the G1 sputtering apparatus refers to a first-generation mass production sputtering apparatus having a substrate size of about 300 mm × 400 mm. After pre-sputtering, continuous discharge is performed for 2 hours at each power under the film formation conditions shown in Table 3, and after the discharge at each power is completed, the chamber is opened, the presence or absence of cracks is visually checked, the power is increased, and the discharge is performed. By repeating the test, the maximum power at which cracks did not occur was evaluated as crack resistance.
Crack resistance is the maximum sputtering power that does not cause cracks in the sputtering target. Table 1 shows the evaluation results of the crack resistance of each sputtering target. Further, the relationship between the surface roughness Rz and the crack resistance is shown in the graph of FIG.

According to the sputtering target using the oxide sintered body according to Examples 1 to 6, it was found that the crack resistance was excellent. It is considered that the crack resistance was improved because the surface roughness Rz of the oxide sintered body was less than 2 μm and the surface roughness was sufficiently small.
It was found that the sputtering target using the oxide sintered body according to Comparative Examples 1 and 2 was inferior to Examples 1 and 6 in crack resistance during sputtering. Since the surface roughness Rz of the oxide sintered body according to Comparative Examples 1 and 2 exceeds 3 μm, it is considered that the crystal structure is peeled off in the grinding step and the crack resistance is lowered.
It was found that the sputtering target using the oxide sintered body according to Comparative Example 3 was inferior in crack resistance during sputtering to Examples 1 to 6. Since the surface roughness Rz of the oxide sintered body according to Comparative Example 3 exceeds 2 μm, it is considered that the crystal structure is peeled off in the grinding step and the crack resistance is lowered.

1, 1A, 1B, 1C ... Oxide sintered body, 3 ... Backing plate.

Claims (11)

It is an oxide sintered body
The surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm.
Oxide sintered body. A sputtering target comprising the oxide sintered body according to claim 1. The oxide sintered body contains an indium element, a tin element and a zinc element.
The sputtering target according to claim 2. The oxide sintered body further contains element X and contains.
Element X is at least one element selected from the group consisting of germanium element, silicon element, ittrium element, zirconium element, aluminum element, magnesium element, itterbium element and gallium element.
The sputtering target according to claim 3. The oxide sintered body satisfies the range of the atomic composition ratio represented by the following formulas (1), (2) and (3).
The sputtering target according to claim 3 or 4.
0.40 ≤ Zn / (In + Sn + Zn) ≤ 0.80 ... (1)
0.15 ≤ Sn / (Sn + Zn) ≤ 0.40 ... (2)
0.10 ≤ In / (In + Sn + Zn) ≤ 0.35 ... (3) The oxide sintered body includes _{a hexagonal layered compound represented by In 2} O ₃ (ZnO) m [m = 2 to 7] and Zn _2-x Sn _1-y In _{x + y} O ₄ [0 ≦ x <2. Includes a spinel-structured compound represented by 0 ≦ y <1].
The sputtering target according to any one of claims 3 to 5. In the grinding scratches of the oxide sintered body, the ratio H / L between the depth (H) and the width (L) of the grinding scratches having the maximum depth and the minimum width is less than 0.2. be,
The sputtering target according to any one of claims 2 to 6. The method for manufacturing a sputtering target for manufacturing the sputtering target according to any one of claims 2 to 7. In the method for manufacturing a sputtering target according to claim 8.
Including the step of grinding the surface of the oxide sintered body.
The grain size of the first grindstone used for the first grinding is 100 μm or less.
Manufacturing method of sputtering target. In the method for manufacturing a sputtering target according to claim 9.
After grinding with the first grindstone, the surface of the oxide sintered body is further ground with a second grindstone having an abrasive grain size smaller than that of the first grindstone.
After grinding with the second grindstone, the surface of the oxide sintered body is further ground using a third grindstone having an abrasive grain size smaller than that of the second grindstone.
Manufacturing method of sputtering target. In the method for manufacturing a sputtering target according to claim 9 or 10.
The feed rate v (m / min) of the object to be ground, the peripheral speed V (m / min) of the grindstone of the first grindstone, the cutting depth t (μm), and the grain size d (μm) of the first grindstone Satisfy the following relational expression (4),
Manufacturing method of sputtering target.
(V / V) ^1/3 x (t) ^1/6 x d <50 ... (4)

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