TWI836009B - Oxide sintered body, sputtering target and method for manufacturing sputtering target - Google Patents

Abstract

The present invention is an oxide sintered body. The surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm.

Description

Oxide sintered body, sputtering target and method for manufacturing sputtering target

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

Previously, in display devices such as liquid crystal displays or organic EL (Electroluminescence) displays driven by thin film transistors (hereinafter referred to as "TFT (Thin Film Transistor)"), the channel layer of the TFT mainly used amorphous Quality silicon film or crystalline silicon film.

On the other hand, in recent years, with the demand for higher-precision displays, oxide semiconductors have attracted attention as materials used in the channel layer of TFTs.

Among oxide semiconductors, amorphous oxide semiconductors including indium, gallium, zinc and oxygen (In-Ga-Zn-O, hereinafter referred to as "IGZO") are preferably used because of their high carrier mobility. However, IGZO has the disadvantage of high raw material cost because it uses In and Ga as raw materials.

From the viewpoint of reducing the raw material cost, Zn-Sn-O (hereinafter abbreviated as "ZTO") or In-Sn-Zn-O (hereinafter abbreviated as "ITZO") in which Sn is added instead of Ga in IGZO has been proposed.

Since ITZO exhibits a very high mobility compared to IGZO, ITZO is highly anticipated as a next-generation oxide semiconductor material that is advantageous for miniaturization of TFTs and narrow edges of panels.

However, due to its large thermal expansion coefficient and low thermal conductivity, ITZO is prone to cracking due to thermal stress during bonding to a Cu or Ti backing plate or during sputter plating.

In recent studies, it is reported that reliability, the biggest problem of oxide semiconductor materials, can be improved by making the films denser.

High-power film formation is effective in order to densify the film. However, in large-scale mass production equipment, breakage at the end of the target where plasma is concentrated becomes a problem. In particular, targets made of ITZO materials tend to break easily.

For example, Document 1 (International Publication No. 2017/158928) describes that in an oxide sintered body essentially containing indium, tin, magnesium, and oxygen, by appropriately adjusting the composition and sintering conditions of the sintered body, it is possible to Achieve higher flexural strength. Furthermore, Document 1 describes that since the oxide sintered body has a high flexural strength and the generation of particles during sputtering is small, stable sputtering can be performed.

Examples of causes of cracks in the sputtering target include uneven density, uneven particle size, micropores, and microcracks.

The causes of the occurrence of cracks can also be cited as grinding lines generated in the surface grinding process of the sputtering target. If a sputtering target with grinding lines is used for sputtering, arcing will be generated, or the tensile stress on the surface generated by the thermal contraction of the target after the sputtering discharge will easily cause cracks.

On the other hand, it is known that the grinding streaks generated during the grinding process of the sputtering target are reduced by reducing the particle size of the abrasive grains embedded in the grindstone and making the cutting depth of the abrasive grains shallower.

For example, document 1 describes that a sintered body including oxides of indium, tin, magnesium, and oxygen was ground with a #80 grindstone and then ground with a #400 grindstone to obtain a sintered body having a surface roughness Ra of 0.46 μm.

However, even if the surface of the oxide sintered body is polished with a #80 grindstone and then polished with a #400 grindstone as described in Document 1, there are also sputtering targets including the oxide sintered body. Insufficient crack resistance.

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

[1A]. An oxide sintered body, The surface roughness Rz of the surface of the above-mentioned oxide sintered body is less than 2.0 μm.

[2A]. A sputtering target material including the oxide sintered body of [1A].

[1]. A sputtering target material, which is a sputtering target material including an oxide sintered body, and The surface roughness Rz of the surface of the above-mentioned oxide sintered body is less than 2.0 μm.

[2]. Sputtering target material such as [1] or [2A], where The above-mentioned oxide sintered body contains indium element, tin element and zinc element.

[3]. The sputtering target material is as in [2], where The above-mentioned oxide sintered body further contains X element, The X element is at least one element selected from the group consisting of germanium element, silicon element, yttrium element, zirconium element, aluminum element, magnesium element, ytterbium element and gallium element.

[4]. Sputtering target material such as [2] or [3], where The oxide sintered body satisfies the range of atomic composition ratio represented by 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)

[5]. The sputtering target material according to any one of [2] to [4], wherein the above-mentioned oxide sintered body contains a hexagonal crystal layer represented by In ₂ O ₃ (ZnO)m [m=2~7] -like compounds and spinel structure compounds represented by Zn ₂ SnO ₄ .

[5A]. The sputtering target material according to any one of [2] to [4], wherein the above-mentioned oxide sintered body includes a hexagonal crystal layer represented by In ₂ O ₃ (ZnO)m [m=2~7] -like compounds and spinel structure compounds represented by Zn _{2 - x} Sn _{1 - y} In _{x + y} O ₄ [0≦x<2, 0≦y<1].

[6A]. The sputtering target material according to any one of [2] to [5], [2A] and [5A], wherein among the grinding scars of the above-mentioned oxide sintered body, the depth is the largest and the width is the smallest. The ratio H/L of depth (H) to width (L) does not reach 0.2.

[6]. A method of manufacturing a sputtering target, which is used to manufacture a sputtering target as any one of [1] to [5], [2A], [5A] and [6A].

[7]. The manufacturing method of a sputtering target as in [6], which includes the step of grinding the surface of the above-mentioned oxide sintered body, and The abrasive grain size of the first grinding stone used for initial grinding is 100 μm or less.

[8]. A method for manufacturing a sputtering target material as described in [7], wherein After grinding with the first grindstone, a second grindstone having a smaller grinding particle size than the first grindstone is used to grind the surface of the oxide sintered body, and After grinding with the second grindstone, a third grindstone having a smaller grinding particle size than the second grindstone is used to grind the surface of the oxide sintered body.

[9]. A method for manufacturing a sputtering target material as described in [7] or [8], wherein the feed speed v (m/min) of the object to be ground, the peripheral speed V (m/min) of the first grinding stone, the cutting depth t (μm) and the abrasive grain diameter d (μm) of the first grinding stone satisfy the following relationship (4). (v/V) ^1/3 × (t) ^1/6 × d＜50 (4)

According to one aspect of the present invention, an oxide sintered body and a sputtering target having improved crack resistance can be provided. In addition, according to one aspect of the present invention, a method for manufacturing the sputtering target can be provided.

The following describes the implementation forms with reference to the drawings and the like. However, it is easy for practitioners to understand that the implementation forms can be implemented in many different forms, and various changes can be made to the forms and details without departing from the gist and scope. Therefore, the present invention is not limited to the following description of the implementation forms.

In the drawings, the size, thickness of layers, and regions are exaggerated for the sake of clarity. Therefore, the present invention is not limited to the size, thickness of layers, and regions shown in the drawings. Furthermore, the drawings are schematic diagrams of 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 this manual are used to avoid confusion among constituent elements. For constituent elements that are not specified according to numerical rules, the numerical rules are not followed. Make restrictions.

In this specification, etc., the term "film" or "thin film" and the term "layer" can be used interchangeably as appropriate.

In the sintered body and oxide semiconductor thin film in this specification, etc., the term "compound" and the term "crystalline phase" can be used interchangeably as appropriate.

In this specification, the "oxide sintered body" may be simply referred to as "sintered body".

In this specification, the "sputtering target" may be simply referred to as the "target".

[Sputtering target] Cracks in sputtering targets originate from the weaker parts of the target.

Therefore, the inventors of the present invention considered reducing the strength variation within the surface of the sputtering target, and in particular, increasing the minimum strength, as a measure for improving the crack resistance.

Previously, the grinding stripes in the sputtering target were evaluated using the surface roughness Ra (sometimes called arithmetic mean roughness). In Document 1, the bending strength, which is one of the indicators indicating the strength of the target, is also sufficient. Thus, previously, it was considered that Ra was sufficient for evaluation of grinding streaks on the surface of an oxide sintered body, and that the difference between surface roughness Ra and surface roughness Rz (sometimes referred to as the maximum height) was small.

However, the inventor conducted a detailed investigation of the grinding damage of ITZO and found that ITZO is brittle compared to previous target materials. Generally, except for the grinding damage observed on the surface of the oxide sintered body after surface grinding In addition to stripes, crystalline structures are also found as parts (holes) where larger pieces are peeled off. It can be seen that the depth of the peeled part is one level deeper than the depth of the normal grinding stripe.

The inventor of the present invention conducted intensive research on grinding processing methods, and as a result obtained the following knowledge. In order to reduce the peeling parts as described above, the grinding process was started with a grinding stone with a medium particle size as a grinding stone. By gradually replacing the grinding with a grindstone with a smaller particle size, large holes are not left (that is, the surface roughness Rz can be reduced), and the peeling parts can be reduced. As a result, the sputtering target material Crack resistance is also greatly improved.

The inventors invented the present invention based on these knowledge and insights.

A sputtering target according to an embodiment of the present invention (hereinafter sometimes referred to as the sputtering target according to the embodiment) includes an oxide sintered body.

The sputtering target of the present embodiment is obtained by, for example, cutting and grinding an oxide sintered body into a shape suitable as a sputtering target.

Furthermore, the sputtering target of the present embodiment can also be obtained by grinding a bulk of an oxide sintered body and bonding the sputtering target material obtained by grinding to a backing plate.

Moreover, as another aspect of the sputtering target material of this embodiment, a target material consisting only of an oxide sintered body can also be mentioned.

The shape of the oxide sintered body is not particularly limited.

It may also be a plate-shaped oxide sintered body as shown by symbol 1 in FIG. 1 .

It may also be a cylindrical oxide sintered body as shown by symbol 1A in Figure 2 .

When the oxide sintered body has a plate shape, the planar shape of the oxide sintered body may be a rectangle as shown by symbol 1 in Figure 1 or a circle as shown by symbol 1B in Figure 3 .

The oxide sintered body may be a one-piece molded body or may be divided into a plurality of pieces as shown in FIG4 . Each of the oxide sintered bodies (symbol 1C) divided into a plurality of pieces may be fixed to a backing plate 3. In this way, there is a case where a sputtering target obtained by joining a plurality of oxide sintered bodies 1C to a backing plate 3 is called a multi-split sputtering target. The backing plate 3 is a component 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, and SUS is used.

(Surface roughness Rz) In the target material of this embodiment, the surface roughness Rz (maximum height) of the oxide sintered body is less than 2.0 μm. In this specification, the surface roughness Rz is measured using a confocal laser microscope (LSM) ("OPTELICS H1200" manufactured by Lasertec Co., Ltd.) based on the cross-sectional distribution observed at an objective magnification of ×100 (approximately 2000 times) in accordance with JIS B 0601:2001 and JIS B 0610:2001. The measurement site of the surface roughness Rz is the surface of a test piece for measurement cut out of the central part of the ground oxide sintered body plate with a size of 4 cm ² (2 cm×2 cm).

If the surface roughness Rz of the oxide sintered body is less than 2.0 μm, the sputtering target has improved crack resistance. It is believed that the reason for such improved crack resistance is that the crystal structure is not peeled off as a large block, and the surface smoothness of the oxide sintered body is higher.

The surface roughness Rz of the oxide sintered body is preferably 1.5 μm or less, more preferably 1.0 μm or less.

Furthermore, the oxide sintered body in the sputtering target has a bonding surface bonded to the backing plate and a sputtering surface opposite to the bonding surface and is sputtered. In this embodiment, the surface roughness Rz of the surface corresponding to the sputtered surface only needs to be less than 2.0 μm. The surface roughness Rz of the joint surface is also preferably smaller. However, if it is too small, the wettability of indium (In) used as a wax agent during the joint process will deteriorate and the joint rate will decrease. Therefore, it is appropriately selected to ensure the wettability. conditions.

In addition, in the target material, the thermal stress generated on the sputtering surface after sputtering discharge is tensile stress. Thermal stress generated on the sputtering surface will be the main cause of cracks. However, in the joint surface on the back side of the target, the so-called thermal stress generates opposite compressive stress, so cracks are less likely to occur on the sputtering surface. The influence of thermal stress is small.

(Surface roughness Ra) In the target material of this 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 is less likely to occur during sputtering, and discharge stability is excellent. That is, when a new target material is used in a normal manufacturing process, low-power pre-sputtering is performed in order to improve the surface roughness. When the surface roughness Ra is small, the pre-sputtering time can be shortened and it can be converted to high-power sputtering discharge in a short time.

(Composition of oxide sintered body) The oxide sintered body of this embodiment preferably contains indium element (In), tin element (Sn) and zinc element (Zn).

The oxide sintered body of this embodiment may contain metal elements other than In, Sn, and Zn within a range that does not impair the effects of the present invention, may contain substantially only In, Sn, and Zn, or may contain only In, Sn, and Zn. Composed of In, Sn and Zn. Here, "substantially" means that 95 mass % or more and 100 mass % or less (preferably 98 mass % or more and 100 mass % or less) of the metal elements in the oxide sintered body are indium element (In), tin element ( Sn) and zinc element (Zn). The oxide sintered body of this embodiment may contain unavoidable impurities in addition to In, Sn, Zn, and oxygen (O) within a range that does not impair the effects of the present invention. The unavoidable impurities mentioned here refer to elements that are not intentionally added, but are mixed in raw materials or manufacturing steps.

The oxide sintered body of this embodiment also preferably contains indium element (In), tin element (Sn), zinc element (Zn) and X element.

The oxide sintered body of this embodiment may contain metal elements other than In, Sn, Zn, and X elements within the range that does not impair the effects of the present invention, or may contain substantially only In, Sn, Zn, and X elements. , or may be composed only of In, Sn, Zn and X elements. Here, "substantially" means that 95 mass % or more and 100 mass % or less (preferably 98 mass % or more and 100 mass % or less) of the metal elements in the oxide sintered body are In, Sn, Zn, and X elements. The oxide sintered body of this embodiment may contain unavoidable impurities in addition to In, Sn, Zn, X element, and oxygen element (O) within a range that does not impair the effects of the present invention. The unavoidable impurities mentioned here refer to elements that are not intentionally added, but are mixed in raw materials or manufacturing steps.

The X element is at least one element selected from the group consisting of germanium (Ge), silicon (Si), yttrium (Y), zirconium (Zr), aluminum (Al), magnesium (Mg), ytterbium (Yb) and gallium (Ga).

Examples of unavoidable impurities include alkali metals (Li, Na, K, Rb, etc.), alkali earth metals (Ca, Sr, Ba, etc.), hydrogen (H), boron (B), carbon (C), nitrogen (N), fluorine (F), and chlorine (Cl).

The impurity concentration can be measured by ICP (Inductively Coupled Plasma) or SIMS (secondary ion mass spectrometry).

<Measurement of impurity concentration (H, C, N, F, Si, Cl)> The impurity concentration (H, C, N, F, Si, Cl) in the obtained sintered body can be determined by SIMS analysis using a sector-type dynamic secondary ion mass spectrometer (IMS 7f-Auto, manufactured by AMETEK CAMECA Corporation) Quantitative evaluation.

Specifically, the primary ion Cs ⁺ was first used to perform sputtering at an accelerating voltage of 14.5 kV until the depth of 20 μm from the surface of the sintered body to be measured was reached. Then, the mass spectrum intensity of impurities (H, C, N, F, Si, Cl) was integrated while sputtering was performed using the primary ion on a grating 100 μm square (100 μm×100 μm size), a measurement area 30 μm square (30 μm×30 μm size), and a depth of 1 μm.

Furthermore, the absolute value of the impurity concentration is calculated from the mass spectrum, and each impurity is controlled by ion implantation and injected into the sintered body to produce a standard sample with a known impurity concentration. The mass spectrum intensity of the impurities (H, C, N, F, Si, Cl) of the standard sample is obtained by SIMS analysis, and the relationship between the absolute value of the impurity concentration and the mass spectrum intensity is made into a calibration curve.

Finally, the impurity concentration of the object to be measured is calculated using the mass spectrum intensity of the sintered body of the object to be measured and the calibration curve, and this value is set 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 mass spectrum of each impurity is measured by setting the primary ion to O ₂ ⁺ and the primary ion accelerating voltage to 5.5 kV. In addition, the absolute value of the impurity concentration of the measurement object (atom・cm ^-3 ) can be obtained by the same evaluation as the measurement of H, C, N, F, Si, and Cl.

In the oxide sintered body of 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 respectively represent the contents of indium element, zinc element and tin element in the oxide sintered body.

If Zn/(In+Sn+Zn) is 0.40 or more, a spinel phase is easily generated in the oxide sintered body, and semiconductor characteristics are easily obtained.

If Zn/(In+Sn+Zn) is 0.80 or less, the decrease in strength due to abnormal grain growth of the spinel phase in the oxide sintered body can be suppressed. Furthermore, 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.

If Sn/(Sn+Zn) is 0.15 or more, the decrease in strength due to abnormal grain growth of the spinel phase in the oxide sintered body can be suppressed.

If Sn/(Sn+Zn) is 0.40 or less, the aggregation of tin oxide that causes abnormal discharge during sputtering can be suppressed in the oxide sintered body. Also, if Sn/(Sn+Zn) is 0.40 or less, the oxide semiconductor thin film formed using the sputtering target can be easily etched using weak acids such as oxalic acid. If Sn/(Sn+Zn) is 0.15 or more, the etching speed can be suppressed 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 reduced. Also, when In/(In+Sn+Zn) is 0.10 or more, the mobility of the oxide semiconductor thin film can be suppressed from becoming extremely low.

If In/(In+Sn+Zn) is 0.35 or less, the film can be prevented from becoming a conductor during sputtering film formation, making it easier to obtain semiconductor properties.

In/(In+Sn+Zn) is more preferably at least 0.10 and at most 0.30.

When the oxide sintered body of the present embodiment contains the element X, it is preferred that the atomic ratio of each element satisfies the following formula (1X). 0.001≦X/(In＋Sn＋Zn＋X)≦0.05              (1X) (In formula (1X), In, Zn, Sn and X represent the contents of indium element, zinc element, tin element and X element in the oxide sintered body, respectively.)

If it is within the range of the above formula (1X), the crack resistance of the oxide sintered body of this embodiment can be made sufficiently high.

The X element is preferably at least one selected from the group consisting of silicon element (Si), aluminum element (Al), magnesium element (Mg), ytterbium element (Yb) and gallium element (Ga).

More preferably, the X element is at least one selected from the group consisting of silicon (Si), aluminum (Al) and gallium (Ga).

Aluminum (Al) and gallium (Ga) are more preferable because the composition of the oxides as raw materials is stable and the effect of improving the turtle crack resistance is higher.

If X/(In+Sn+Zn+X) is 0.001 or more, the strength reduction of the sputtering target can be suppressed. If X/(In+Sn+Zn+X) is 0.05 or less, the oxide semiconductor thin film formed using the sputtering target including the oxide sintered body can be easily etched using weak acids such as oxalic acid. Furthermore, if X/(In+Sn+Zn+X) is 0.05 or less, the reduction of TFT characteristics, especially mobility, can be suppressed.

X/(In + Sn + Zn +

When the oxide sintered body of the present embodiment contains an X element, the X element may be only one or two or more. When two or more X elements are contained, X in the formula (1X) is the total atomic ratio of the X elements.

The existing form of the element X in the oxide sintered body is not particularly specified. Examples of the existing form of the element X in the oxide sintered body include the form of the element X existing as an oxide, the form of the element X existing as a solid solution, and the form of the element X existing as a grain boundary.

The atomic ratio of each metal element in the oxide sintered body can be controlled by adjusting the amount of raw materials. In addition, the atomic ratio of each element can be determined by quantitatively analyzing the contained elements using an inductively coupled plasma emission spectrometer (ICP-AES).

The oxide sintered body of this 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 this specification, a spinel structure compound may be called 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 of this embodiment preferably contains a hexagonal crystal layered compound represented by In ₂ O ₃ (ZnO) _m . In this embodiment, in the formula represented by In ₂ O ₃ (ZnO) _m , m is an integer of 2 to 7, preferably an integer of 3 to 5. If m is 2 or more, the compound adopts a hexagonal crystal layered structure. When m is 7 or less, the volume resistivity of the oxide sintered body becomes low.

The oxide sintered body of this embodiment more preferably contains a hexagonal crystal 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, 0≦y＜1] represents a spinel structure compound.

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

The oxide sintered body of this embodiment may also contain 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 represents the bixbyite structure compound.

(Volume resistance) When the oxide sintered body of the present embodiment contains the element X, if the content ratio of the element X is within the range of the above formula (1X), the volume resistance of the sputtering target can be sufficiently low.

The bulk resistance of the sputtering target of this embodiment is preferably 50 mΩcm or less, more preferably 25 mΩcm or less, further preferably 10 mΩcm or less, further preferably 5 mΩcm or less, and particularly preferably 3 mΩcm or less. If the bulk resistance is 50 mΩcm or less, stable film formation can be performed by direct current sputtering.

The bulk resistance value can be measured using a known resistivity meter based on the four-probe method (JIS R 1637: 1998). Preferably, the measurement points are about 9 points, and the average value of the values measured at the 9 points is set as the bulk resistance value.

When the planar shape of the oxide sintered body is a quadrilateral when the measurement part is located, it is preferable to divide the surface into nine parts of 3×3 and set the center points of each quadrilateral at nine parts.

Furthermore, when the planar shape of the oxide sintered body is a circle, it is preferable to divide the square inscribed in the circle into 9 parts of 3×3 and set the 9 locations as the center points of the squares.

(average crystal grain size) From the viewpoint of preventing abnormal discharge and ease of production, the average crystal grain size of the oxide sintered body of this embodiment is preferably 10 μm or less, more preferably 8 μm or less.

If 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 from the viewpoint of ease of production, it is preferably 1 μm or more.

The average crystal grain size can be adjusted by selecting raw materials and changing manufacturing conditions. Specifically, it is better to use raw materials with a smaller average grain size, and it is more preferable to use raw materials with an average grain size of less than 1 μm. Furthermore, during sintering, there is a tendency that the higher the sintering temperature or the longer the sintering time, the larger the average crystal grain size.

The average grain size can be measured in the following manner.

When the surface of an oxide sintered body is ground and the planar shape is a quadrilateral, the surface is divided into 16 parts with equal area, and the measurement is performed at 16 parts at the center point of each quadrilateral at a magnification of 1000 times (80 μm × 125 μm), the average particle size of the particles in the frame at 16 locations was calculated, and finally the average value of the 16 measured values was set as the average crystal particle size.

When the surface of the oxide sintered body is ground and the plane shape is a circle, a square inscribed in the circle is divided into 16 parts with equal area. The particle size observed in the frame with a magnification of 1000 times (80 μm×125 μm) is measured at the 16 locations at the center of each square, and the average particle size of the particles in the frame of the 16 locations is calculated.

Regarding the particle size, for particles with an aspect ratio of less than 2, the particle size of the crystal grains is measured as the equivalent circular diameter based on JIS R 1670:2006. Specifically, as the measurement procedure of the equivalent circular diameter, the target crystal grains of the microstructure photograph are measured with a compass and the diameter equivalent to the area of the target crystal grains is read. For particles with an aspect ratio of more than 2, the average value of the longest diameter and the shortest diameter is set as the particle size of the particle. The crystal grains can be observed by a scanning electron microscope (SEM). Hexagonal layered compounds, spinel compounds and ferromanganese structure compounds can be confirmed by the methods described in the following examples.

When the oxide sintered body of this embodiment contains a hexagonal crystal layered compound and a spinel compound, the difference between the average crystal grain size of the hexagonal crystal layered compound and the average crystal grain size of the spinel compound is preferably 1 Below μm. By setting the average crystal grain size within this range, the strength of the oxide sintered body can be improved.

More preferably, the average crystal grain size of the oxide sintered body of this embodiment is 10 μm or less, and the difference between the average crystal grain size of the hexagonal crystal layered compound and the spinel compound is 1 μm or less.

Furthermore, when the oxide sintered body of the present embodiment contains a bixbyite structural compound and a spinel compound, it is preferable that the average crystal grain size of the bixbyite structural compound and the average crystal grain size of the spinel compound are The difference is less than 1 μm. By setting the average crystal grain size within this range, the strength of the oxide sintered body can be improved.

More preferably, the average crystal grain size of the oxide sintered body of this embodiment is 10 μm or less, and the difference between the average crystal grain size of the bixbyite 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 of this embodiment is preferably 95% or more, and more preferably 96% or more.

If the relative density of the oxide sintered body of the present embodiment is 95% or more, the mechanical strength of the sputtering target of the present embodiment is high and the electrical conductivity is excellent. Therefore, the stability of plasma discharge when the sputtering target of the present embodiment is installed in an RF (radio frequency) magnetron sputtering device or a DC (direct current) magnetron sputtering device for sputtering can be further improved. The relative density of the oxide sintered body is the density of the oxide sintered body actually measured relative to the theoretical density calculated based on the inherent density of each oxide in the sintered body and the composition ratio, expressed as a percentage. The relative density of the oxide sintered body is, for example, the density of the oxide sintered body actually measured relative to the theoretical density, which is calculated based on the intrinsic densities of the oxides of indium oxide, zinc oxide, tin oxide, and the X element contained as required, and the composition ratio thereof, and is expressed as a percentage.

The relative density of the oxide sintered body can be measured based on Archimedes' method. Specifically, the relative density (unit: %) is the air weight of the oxide sintered body divided by the volume (=weight of the sintered body in water/specific gravity of water at the measurement temperature), and is set as the relative density based on the following formula (Equation 5) The value as a percentage of the theoretical density ρ (g/cm ³ ). 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 (number 5)

Furthermore, in Formula (5), C ₁ to C _n represent the contents (mass %) of the oxide sintered body or the constituents of the oxide sintered body, respectively, and ρ ₁ to ρ _n represent the densities (g/cm ³ ) of the constituents corresponding to C ₁ to C _n .

Furthermore, since density and specific gravity are approximately the same, the density of each constituent substance can be determined by using the specific gravity value of the oxide described in the Basics of Chemistry, Volume I, Chemical Society of Japan, revised 2nd edition (Maruzen Co., Ltd.).

(Ratio of depth (H) to width (L) of grinding scar of surface roughness H/L) In the present invention, the so-called "grinding scar" refers to the scar produced in the grinding step when manufacturing the sputtering plating target material from the oxide sintered body.

In the grinding scars of the oxide sintered body of the present embodiment, the ratio H/L of the depth (H) to the width (L) of the grinding scar with the largest depth and the smallest width is preferably less than 0.2, and more preferably less than 0.19.

In the oxide sintered body of this embodiment, if the ratio H/L of the depth (H) and width (L) of the grinding scars is less than 0.2, the grinding scars will be gentle, preventing the grinding scars from becoming the starting point of breakage and oxidation. The tensile strength of the sintered body increases.

In the oxide sintered body of the present embodiment, the ratio H/L of the depth (H) to the width (L) of the grinding scar is preferably greater than 0.01, more preferably greater than 0.05.

By taking countermeasures against grinding scars such as reducing the feed rate of the grinding target part and reducing the cutting depth of the grindstone, the depth of the grinding scars and the difference between the grinding scars and the base can be reduced.

If the ratio H/L of the depth (H) to the width (L) of the grinding scars in the oxide sintered body of this embodiment is 0.01 or more, it is possible to efficiently manufacture sputters on the production line after taking the above-mentioned countermeasures against the grinding scars. Plating target material.

[Production method of oxide sintered body] The method of manufacturing an oxide sintered body according to this embodiment includes mixing, pulverizing, granulating, molding, and sintering. The method of manufacturing the oxide sintered body may also include other steps. As other steps, an annealing step can be cited.

Hereinafter, a case of manufacturing an ITZO-based oxide sintered body is taken as an example and each step is explained in detail.

The oxide sintered body of the present embodiment can be manufactured by mixing and pulverizing an indium raw material, a zinc raw material, a tin raw material and an X element raw material, a pulverizing step, a granulating step of granulating the raw material mixture, a forming step of forming the raw material granulated powder, a sintering step of sintering the formed body, and an annealing step of annealing the sintered body as needed.

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

In the mixing and grinding steps, first, raw materials for the oxide sintered body are prepared.

The raw materials used when 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 a sintered body of an oxide containing the element X are as follows.

The raw material of the X element is not particularly limited as long as it is a compound or metal containing the X element.

The In raw material, Zn raw material, Sn raw material and X element raw material are preferably oxides.

The raw materials such as indium oxide, zinc oxide, tin oxide and X element oxide are preferably of high purity. The purity of the raw materials of the oxide sintered body is preferably 99 mass % or more, more preferably 99.9 mass % or more, and further preferably 99.99 mass % or more. If high-purity raw materials are used, a sintered body with a dense structure is obtained, and the volume resistivity of the sputtering target including the sintered body becomes low.

The average particle size of the primary particles of the metal oxide used as a raw material is preferably 0.01 μm to 10 μm, more preferably 0.05 μm to 5 μm, and further preferably 0.1 μm to 5 μm.

If the average particle diameter of the primary particles of the metal oxide used as the raw material is 0.01 μm or more, aggregation is difficult, and if the average particle diameter is 10 μm or less, the mixability is sufficient and a sintered body with a dense structure is obtained. The average particle size adopts the median particle size D50. The average particle diameter (median particle diameter D50) was measured using a laser diffraction particle size distribution measuring device SALD-300V (manufactured by Shimadzu Corporation).

A dispersant for deagglomeration and a thickener for adjusting the viscosity suitable for granulation using a spray dryer are added to the raw material of the oxide sintered body, and the mixture is mixed and crushed using a bead mill or the like. Examples of the dispersant include ammonia neutralized products of acrylic acid and methacrylic acid copolymers, and examples of the thickener include polyvinyl alcohol, etc.

(2) Calcination treatment step The raw material mixture obtained in the mixing and grinding steps can be directly granulated, but it can also be calcined before granulation. In the calcining treatment, the raw material mixture is usually calcined at a temperature of 700°C or more and 900°C or less for 1 hour or more and 5 hours or less.

(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 properties in the forming step (4) described below.

In this specification, the step of granulating the raw material of the oxide sintered body to obtain the raw material granulated powder is sometimes referred to as the granulation step.

The granulation treatment can be performed using a spray dryer, etc. The shape of the granulated powder obtained in the granulation step is not particularly limited, but in order to uniformly fill the mold in the molding step, it is preferably a true spherical shape.

The granulation conditions are appropriately selected by adjusting the concentration of the introduced raw material slurry, the rotation speed of the spray dryer, the hot air temperature, etc.

Regarding the preparation of the slurry solution, when using a raw material mixture that has not been calcined, the slurry solution obtained in the mixing and grinding steps is directly used. When using a raw material mixture that has been calcined, the slurry solution is mixed again. , crushing step, prepare the slurry solution before use.

In the method for producing an oxide sintered body of the present embodiment, the particle size of the raw material granulated powder formed by the granulation treatment is not particularly limited, but is preferably controlled within the range of 25 μm to 150 μm.

If the particle size of the raw material granulated powder is 25 μm or more, the slipperiness of the raw material granulated powder relative to the surface of the mold used in the molding step (4) below is improved, and the raw material granulated powder can be fully filled in the mold.

If the particle size of the raw material granulated powder is 150 μm or less, the filling rate in the mold can be reduced due to the particle size being too large.

The particle size of the raw material granulated powder is preferably 25 μm or more and 75 μm or less.

The method of obtaining raw material granulated powder having a particle size within a specific range is not particularly limited. For example, the following method can be cited: putting the granulated raw material mixture (raw material granulated powder) into a sieve, and screening the raw material granulated powder falling into a desired particle size range. The screen used in this method is preferably a screen having an opening of a size that allows the raw material granulated powder of a desired particle size to pass. It is preferable to use a first screen and a second screen. The first screen is used to screen the raw granulated powder based on the lower limit of the particle size range, and the second screen is used to screen the raw granulated powder based on the lower limit of the particle size range. The limit value is used as a basis to screen raw material granulation powder. For example, when the particle size of the raw material granulated powder is controlled to be within the range of 25 μm or more and 150 μm or less, first, the raw material granulated powder with a diameter of less than 25 μm can pass through, but the raw material granulated powder with a size of 25 μm or more is not allowed to pass. The sieve (first sieve) with an opening of a size through which the granulated powder passes, sifts the raw material granulated powder having a particle size of 25 μm or more. Next, for the screened raw material granulated powder, use a sieve (second screen) with an opening having a size that can pass raw material granulated powder of 150 μm or less but does not allow raw material granulated powder exceeding 150 μm to pass. , screening raw material granulation powder within the range of 25 μm and below 150 μm. It is also possible to use the second sieve first, then the first sieve.

The method of controlling the particle size range of the raw material granulated powder is not limited to the above-mentioned method of using a screen, as long as the raw material granulated powder used in the forming step (4) below can be controlled within the desired range.

Furthermore, in the raw material mixture that has been subjected to a calcination treatment, particles are bound together, and therefore, when a granulation treatment is performed, it is preferred to perform a pulverization treatment before the granulation treatment.

(4) Forming steps In this specification, the step of filling the raw material granulated powder obtained in the granulation step into a mold, and shaping the raw material granulated powder filled in the mold to obtain a shaped body may be called a forming step.

Examples of the molding method in the molding step include die press molding.

As a sputtering target, when obtaining a sintered body with a high sintering density, it is preferable to pre-form it by mold pressure molding or the like in the molding step, and then use cold isostatic pressing (CIP; Cold Isostatic Pressing) ), etc. and then compacted.

(5) Sintering step In this specification, the step of sintering the formed body obtained in the forming step within a specific temperature range is sometimes referred to as the sintering step.

In the sintering step, commonly used sintering methods such as normal pressure sintering, hot press sintering, or hot isostatic pressing (HIP; Hot Isostatic Pressing) sintering can be used.

The sintering temperature is not particularly limited, but is preferably 1310° C. to 1440° C., more preferably 1320° C. to 1430° C.

If the sintering temperature is 1310°C or above, sufficient sintering density can be obtained and the volume resistance of the sputtering target can also be reduced.

If the sintering temperature is 1440°C or lower, sublimation of zinc oxide during sintering can be suppressed.

In the sintering step, the heating rate from room temperature to the sintering temperature is not particularly limited, but is preferably 0.1°C/min to 3°C/min.

In addition, during the heating process, the temperature may be maintained at 700°C or more and 800°C or less for 1 hour or more and 10 hours or less, and after the temperature is maintained at a specific temperature for a specific time, the temperature may be raised to the sintering temperature.

The sintering time varies depending on the sintering temperature, but is preferably from 1 hour to 50 hours, more preferably from 2 hours to 30 hours, and still more preferably from 3 hours to 20 hours.

Examples of the sintering environment include an air or oxygen environment, an air or oxygen environment and a reducing gas, or an air or oxygen environment and an inert gas environment. Examples of the reducing gas include hydrogen, methane, and carbon monoxide. Examples of the inert gas include argon and nitrogen.

(6) Annealing step In the method for manufacturing the oxide sintered body of the present embodiment, the annealing step is not essential. When the annealing step is performed, the temperature is usually maintained at 700°C to 1100°C for 1 hour to 5 hours.

The annealing step may be performed by temporarily cooling the sintered body and then heating it again for annealing, or by cooling it down from the sintering temperature.

Examples of the environment during annealing include an environment of air or oxygen, an environment containing air or oxygen and a reducing gas, or an environment containing air, oxygen 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, nitrogen gas, and the like.

Furthermore, when manufacturing an oxide sintered body of a system different from the ITZO system, it can also be manufactured by the same steps as above.

[Manufacturing method of sputtering target] The sputtering target of this 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 also referred to as a target material) is obtained by cutting an oxide sintered body into a shape suitable for installation in a sputtering device. The sputtering target is obtained by bonding the target material to the backing plate.

The surface roughness Rz of the oxide sintered body of this embodiment used as the target material is less than 2.0 μm, preferably 1.5 μm or less, and more preferably 1.0 μm or less.

As a method of adjusting the surface roughness Rz of the oxide sintered body, for example, there is a method of grinding the surface using a grindstone having a specific grain size or more.

(7) Surface grinding step In this specification, the step of grinding the surface of the oxide sintered body used as the target material is sometimes referred to as the surface grinding step.

The manufacturing method of the sputtering target material of this embodiment includes a surface grinding step.

The abrasive grain size of the grindstone (first grindstone) used to initially grind the surface of the oxide sintered body is preferably 100 μm or less, more preferably 80 μm or less. The abrasive particle size is a value that converts the expression of the grindstone's particle size number into an expression of particle size.

If the abrasive grain size of the first grindstone is less than 100 μm, it is not easy to peel off as a block with a larger crystal structure. On the other hand, when the abrasive grain size of the first grindstone is less than 100 μm, the grinding time may become longer, but by adjusting the feed speed v (m/min) of the grinding object, the peripheral speed V (m/min) of the first grindstone, the cutting depth t (μm), and the abrasive grain size d (μm) of the first grindstone to the range where the relationship (4) is established, the grinding time can be prevented from becoming longer, and the improvement of the crack resistance and the manufacturing efficiency of the spatter plating target can be achieved at the same time.

(v/V) ^1/3 ×(t) ^1/6 ×d<50 (4)

The feed speed v (m/min) of the object to be ground, the peripheral speed V (m/min) of the first grinding stone, the cutting depth t (μm), and the abrasive grain diameter d (μm) of the first grinding stone preferably satisfy the following relationship (4A), and further preferably satisfy the following relationship (4B).

(v/V) ^1/3 ×(t) ^1/6 ×d<30 (4A)

(v/V) ^1/3 ×(t) ^1/6 ×d<20 (4B)

Regarding the grinding conditions used in the second and subsequent stages of grinding such as the second grinding stone and the third grinding stone, it is preferable to satisfy the above-mentioned relational expression (4), more preferably to satisfy the above-mentioned relational expression (4A), and still more preferably Satisfies the above relationship (4B).

In this manual, the grit number of the grinding stone is sometimes referred to as the grit size.

Furthermore, in the surface grinding step of this embodiment, it is preferred to use a grinding stone with a grain size of 100 μm or less as the first grinding stone. If a grinding stone with a grain size of 100 μm or less is used as the first grinding stone, it is possible to prevent the crystalline structure from being peeled off as a larger block. Even if a grinding stone with a smaller grain size is used for a long time to grind the part (hole) where the crystalline structure is peeled off as a larger block, the peeled peripheral part will become brittle, the hole cannot be removed, and the crack resistance cannot be improved.

The surface grinding step of this embodiment is preferably to grind the surface of the oxide sintered body using grindstones of multiple particle sizes. In this case, it is preferable that, in addition to performing the grinding process using the first grindstone, the grinding process is also performed using a grinding stone having a smaller abrasive grain size than that of the first grindstone.

For example, there is an aspect in which, after grinding with the first grindstone, the surface of the oxide sintered body is further ground using a grindstone (second grindstone) having a smaller abrasive grain size than that of the first grindstone. After grinding with the second grindstone, the surface of the oxide sintered body is further ground using a grindstone (third grindstone) having a smaller abrasive grain size than that of the second grindstone. The surface grinding step of this embodiment is also preferably performed in three or more stages as in this aspect.

When a grinding process is performed in multiple stages, the combination of the abrasive grain diameters of the grindstones used in each stage may be, for example, the following combinations (P1) to (P4).

＜3-stage grinding process: Stage 1 ⇒ Stage 2 ⇒ Stage 3 ＞ (P1)80 μm⇒40 μm⇒20 μm

＜4 stages of grinding: Stage 1⇒ Stage 2⇒ Stage 3⇒ Stage 4＞ (P2)100 μm⇒80 μm⇒40 μm⇒20 μm

<5-stage grinding: Stage 1⇒Stage 2⇒Stage 3⇒Stage 4⇒Stage 5> (P3)100 μm⇒80 μm⇒60 μm⇒40 μm⇒20 μm

<6 stages of grinding: Stage 1 ⇒ Stage 2 ⇒ Stage 3 ⇒ Stage 4 ⇒ Stage 5 ⇒ Stage 6 > (P4)100 μm⇒80 μm⇒60 μm⇒40 μm⇒30 μm⇒20 μm

The abrasive grain size of the grindstone used in the surface grinding step in this embodiment is preferably 100 μm or less. If the abrasive grain size of the grindstone is 100 μm or less, breakage of the sputtering target material can be prevented.

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

The surface roughness Ra of the oxide sintered body after the surface grinding step of this embodiment is preferably 0.5 μm or less.

Preferably, the surface roughness Ra of the sputtering target material is less than 0.5 μm and has a non-directional grinding surface. If the surface roughness Ra of the sputtering target material is less than 0.5 μm and has a non-directional grinding surface, abnormal discharge and particle generation can be prevented.

As a method for adjusting the surface roughness Ra of the sintered body, for example, there is a method of grinding the sintered body using a flat grinding disc.

Finally, the obtained sputtering target material is cleaned. As a method of cleaning, for example, any method such as a blower and running water cleaning can be listed. When using a blower to remove foreign matter, it is more effective to remove foreign matter by using a dust collector to suck air from the side where the blower nozzle is facing.

Furthermore, in addition to the above-mentioned cleaning treatments of blower or running water cleaning, ultrasonic cleaning can also be further performed. As ultrasonic cleaning, a method of multiple vibrations between a frequency of 25 kHz or more and 300 kHz or less is more effective. For example, the following method is preferred: between a frequency of 25 kHz or more and 300 kHz or less, 12 frequencies are multiple-vibrated every 25 kHz to perform ultrasonic cleaning.

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.

By joining the sputtering target material obtained through the above steps and treatments to a backing plate, a sputtering target can be manufactured. Alternatively, a plurality of sputtering target materials can be mounted on one backing plate to substantially manufacture one sputtering target (multi-split sputtering target).

The oxide sintered body as a sputtering target material has a bonding surface bonded to a backing plate and a sputtering surface to be sputtered on the opposite side of the bonding surface. In this embodiment, it is preferred to set the surface with a surface roughness Rz less than 2.0 μm as the sputtering surface, and set the surface opposite to the sputtering surface as the bonding surface. Therefore, in the manufacturing method of the sputtering target of this embodiment, the bonding surface side of the oxide sintered body is bonded to the backing plate.

The sputtering target of this embodiment includes an oxide sintered body, and the surface roughness Rz of the surface of the oxide sintered body is less than 2.0 μm, so it is a sputtering target with improved crack resistance.

If the sputtering target of this embodiment is used for sputtering film formation, crack resistance is improved, so that an oxide semiconductor thin film can be stably produced. Example

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

(Manufacturing of sputtering targets) Manufacturing of sputtering targets containing ITZO-based oxide sintered bodies.

(Example 1) First, as raw materials, the following powders were weighed in such a way that the atomic ratio (In: 25 atomic%, Sn: 15 atomic%, Zn: 60 atomic%) was obtained. ・In raw material: Indium oxide powder with a purity of 99.99 mass% (Average particle size: 0.3 μm) ・Sn raw material: Tin oxide powder with a purity of 99.99 mass% (Average particle size: 1.0 μm) ・Zn raw material: Zinc oxide powder with a purity of 99.99 mass% (Average particle size: 3 μm)

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

Next, acrylic methacrylic acid copolymer ammonia neutralized product (manufactured by Sanming Chemical Co., Ltd., Bangster After mixing and grinding for 2 hours, a slurry solution for granulation with a solid content concentration of 70% by mass was obtained. The obtained slurry solution was supplied to a spray dryer, rotated at 12,000 rpm, and granulated at a hot air temperature of 150°C to obtain raw material granulated powder.

The raw material granulated powder is passed through a 200-mesh screen to remove granulated powder with a particle size exceeding 75 μm, and secondly, by passing through a 500-mesh screen to remove granulated powder less than 25 μm. The particle size of the granulated powder is adjusted to the range of 25 μm to 75 μm.

Next, the raw material granulated powder is uniformly filled into a mold with an inner diameter of 300 mm×600 mm×9 mm and press-formed using a cold press. After press-forming, a cold isostatic press device (CIP device) is used to form the molded body at a pressure of 294 MPa.

The three molded bodies thus obtained were heated to 780°C in an oxygen environment in a sintering furnace, maintained at 780°C for 5 hours, further heated to 1400°C, and maintained at the sintering temperature (1400°C) for 20 hours, and then the furnace was Internal cooling is performed to obtain an oxide sintered body. Furthermore, it was carried out at a temperature rising rate of 2°C/min.

The three obtained oxide sintered bodies were cut separately and plane ground to obtain three oxide sintered body plates of 142 mm×305 mm×5 mmt. One piece was used for characteristic evaluation, and two pieces were used for the G1 target [142 mm × 610 mm (divided into 2 parts) × 5 mmt].

Surface grinding uses a surface grinding disc and a diamond grindstone with a grindstone particle size of 80 μm for surface grinding of the oxide sintered body. The surface grinding processing conditions are as follows.

Surface grinding processing conditions: Grinding object feed speed v: 1 m/min Grinding stone peripheral speed V: 500 m/min Grinding stone cutting depth (cutting depth t): 5 μm Grinding stone abrasive particle diameter d: 80 μm Grinding stone type: diamond grinding stone

After grinding under the above-mentioned plane grinding conditions, grinding is performed under the above-mentioned plane grinding conditions using a diamond grindstone with an abrasive grain size of 40 μm, a diamond grindstone with an abrasive grain size of 20 μm, and a grindstone with a finer abrasive grain size.

(Manufacturing of target materials) The G1 target material was manufactured by using two of the obtained oxide sintered body plates (142 mm × 305 mm × 5 mmt) and joining them to a Cu backing plate. The joining method is to set the plane-ground surface as the sputtering surface, and set the surface opposite to the sputtering surface (the surface after rough grinding with a grindstone with abrasive grain size of 130 μm) as the joining surface, and sinter the oxide The joint surface side of the body panel is joined to the backing panel. Among all target materials, the bonding rate is over 98%. When the oxide sintered body plate is joined to the backing plate, no cracks occur in the oxide sintered body plate, and the sputtering target material can be manufactured satisfactorily. The bonding rate was confirmed by X-ray CT.

(Examples 2~6)

The oxide sintered bodies of Examples 2 to 6 were produced in the same manner as in Example 1, except that the grinding conditions in Example 1 were changed to those described in Table 1.

The sputtering targets of Examples 2 to 6 were produced in the same manner as in Example 1 using the oxide sintered body plates of Examples 2 to 6.

(Comparative Examples 1~2)

The oxide sintered bodies of Comparative Examples 1 and 2 were produced in the same manner as in Example 1, except that the grinding processing conditions and the abrasive grain size of the grindstone in Example 1 were changed to those described in Table 1.

(Comparative example 3)

The oxide sintered body of Comparative Example 3 was manufactured in the same manner as Example 1 except that the grinding processing conditions and the abrasive grain size of the grinding stone in Example 1 were changed to those listed in Table 1.

The sputtering targets of Comparative Examples 1 to 3 were produced in the same manner as in Example 1 using the oxide sintered body plates of Comparative Examples 1 to 3.

Furthermore, the following properties were measured for the obtained oxide sintered body and 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 the size of the 2cm square (2cm x 2cm) central part of an oxide sintered body plate (142mm×305mm×5mmt) cut out for grinding processing other than target manufacturing. ), using a confocal laser microscope (LSM) ("OPTELICS H1200" manufactured by Lasertec Co., Ltd.), the surface roughness Rz was evaluated based on the cross-sectional distribution when observed at an objective lens magnification of ×100 (approximately 2000 times). The data of surface roughness Rz is calculated using the software attached to the confocal laser microscope. Data calculation is based on JIS B 0601:2001 and JIS B 0610:2001. The surface roughness Rz can also be evaluated using a sample cut out from the center of the oxide sintered body plate.

The observation position of the oxide sintered body of each embodiment and comparative example was set at the center, and the measurement direction was made so that the grinding direction was consistent with the lead vertical direction of the grinding line and was set to be perpendicular to the lead vertical direction.

(2) Ratio of depth (H) to width (L) of grinding scars in oxide sintered bodies In the cross-sectional distribution data calculated from the surface roughness above, the minimum height of the surface roughness identified as the oxide sintered body is set to 30% of the surface roughness Rz. The adjacent apex points of the identified roughness are defined as one grinding scar. The apex point of the roughness is defined as the point where the inclination of the tangent line of the roughness (the angle between the tangent line drawn from the roughness profile curve and the base flat surface) is 0 degrees.

Here, the grinding flaw consistent with the surface roughness Rz with the largest depth (H) is specified. Among them, the depth (H) and width (L) of the grinding flaw with the smallest width (L) relative to the surface length direction are calculated. Ratio.

5 to 12 and 23 show observation images of the planes of the oxide sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 after plane grinding. In addition, the dotted lines in the images of Figures 5 to 12 and 23 indicate the positions where the surface roughness was measured. Furthermore, FIGS. 25 to 33 also show the cross-sectional distribution of the surface roughness measurement positions of the oxide sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 after plane grinding. The thick frame in the cross-sectional distribution indicates the measurement range used to calculate the depth (H) and width (L) of the grinding scars in the ratio H/L. Table 2 shows the starting point, end point and measurement results in surface roughness measurement.

13 to 20 and 24 show 3D observation images of the oxide sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3 after plane grinding.

(3) XRD measurement The crystalline structure was investigated by X-ray diffraction measurement (XRD) using the oxide sintered body plate used for surface roughness measurement. As a result, in the oxide sintered bodies of Examples 1 to 6 and Comparative Examples 1 to 3, the presence of a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (where m = an integer from 2 to 7) and a spinel compound represented by Zn _2-x Sn _1-y In _x+y O ₄ [0≦x<2, 0≦y<1] was confirmed. FIG. 21 shows the XRD pattern of the oxide sintered body of Example 1.・Equipment: Smartlab manufactured by RIGAKU Co., Ltd. ・X-ray: Cu-Kα ray (wavelength 1.5418×10 ^-10 m) ・Parallel beam, 2θ-θ reflection method, continuous scanning (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

Using the remaining oxide sintered body plate used for surface roughness and XRD, the atomic ratio of the oxide sintered body was analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES, manufactured by Agilent). 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 using the G1 sputtering device with the ambient gas being 100% Ar and the sputtering power being 1 kW. Here, the so-called G1 sputtering equipment refers to the first generation sputtering equipment for mass production with a substrate size of approximately 300 mm × 400 mm. After pre-sputtering, perform continuous discharge for 2 hours at each power under the film forming conditions shown in Table 3. After the discharge at each power is completed, open the chamber, visually confirm whether there are cracks, increase the power, and repeat the discharge. Test, whereby the maximum power without cracking is evaluated as crack resistance.

Crack resistance refers to the maximum sputtering power that can prevent cracking of the sputtering target. Table 1 shows the evaluation results of the crack resistance of each sputtering target material. Moreover, the relationship between surface roughness Rz and crack resistance is shown in the graph of FIG. 22 .

[Table 1] Feed speed of grinding object: v(m/min) Grinding stone peripheral speed: V(m/min) Grinding stone cutting depth: t(μm) Abrasive particle size of grindstone: d (μm) (v/V) ^1/3 (t) ^1/6 (d) R _a (μm) R _z (μm) H/L Crack resistance (kW) Stage 1: d1 Stage 2 Stage 3 Stage 4 Example 1 1 500 5 80 40 20 - 13.18 0.24 1.344 0.11 3.0 Example 2 1 500 10 80 40 20 - 14.79 0.25 1.486 0.15 2.9 Example 3 1 2,500 5 80 40 20 - 7.71 0.05 0.298 0.07 3.1 Example 4 1 2,500 10 80 40 20 - 8.65 0.06 0.319 0.06 3.1 Example 5 10 2,500 5 80 40 20 - 16.61 0.30 1.614 0.13 2.8 Example 6 10 2,500 10 80 40 20 - 18.64 0.39 1.713 0.17 2.7 Comparative example 1 10 500 5 160 80 40 20 56.79 0.74 3.474 0.28 2.5 Comparative example 2 10 500 10 160 80 40 20 63.75 0.77 4.216 0.28 2.5 Comparative example 3 10 500 10 80 40 20 - 28.40 0.35 2.100 0.21 2.5

[Table 2] Starting point End Test results approximation X Y Z X Y Z Height Difference Plane distance Spatial distance angle Center X Center Y Center Z Radius [μm] [μm] [μm] [μm] [μm] [μm] [μm] [μm] [μm] [deg] Embodiment 1 0.000 87.886 5.665 179.814 87.886 4.321 1.344 179.814 179.819 -0.428 ----- ----- ----- ----- Embodiment 2 0.000 76.636 5.140 179.814 76.636 3.654 1.486 179.814 179.820 -0.473 ----- ----- ----- ----- Embodiment 3 0.000 87.886 5.009 179.814 87.886 4.711 0.298 179.814 179.814 -0.095 ----- ----- ----- ----- Embodiment 4 0.000 89.995 5.439 179.814 89.995 5.120 0.319 179.814 179.814 -0.102 ----- ----- ----- ----- Embodiment 5 0.000 106.166 5.633 179.814 106.166 4.019 1.614 179.814 179.820 -0.514 ----- ----- ----- ----- Embodiment 6 0.000 80.152 5.933 179.814 80.152 4.220 1.713 179.814 179.822 -0.546 ----- ----- ----- ----- Comparison Example 1 0.000 75.933 6.242 179.814 75.933 2.768 3.474 179.814 179.847 -1.107 ----- ----- ----- ----- Comparison Example 2 0.000 75.933 7.263 179.814 75.933 3.047 4.216 179.814 179.863 -1.343 ----- ----- ----- ----- Comparison Example 3 0.000 89.995 4.350 179.814 89.995 6.450 2.100 179.814 179.826 0.669 ----- ----- ----- -----

[table 3] Continuous discharge test conditions Ambient gases Ar+O ₂ Back pressure before film formation (Pa) 2×10 ^{- 4} Splash plating pressure during film formation (Pa) 0.5 Oxygen partial pressure during film formation (%) 20

It is found that the sputtering targets using the oxide sintered bodies of Examples 1 to 6 have excellent resistance to gouging cracks. It is considered that the surface roughness Rz of the oxide sintered bodies is less than 2 μm and the surface roughness is sufficiently small, so the resistance to gouging cracks is improved.

It is found that the sputtering target using the oxide sintered bodies of Comparative Examples 1 to 2 has poorer crack resistance during sputtering than Examples 1 to 6. It is considered that since the surface roughness Rz of the oxide sintered bodies of Comparative Examples 1 to 2 exceeds 3 μm, the crack resistance is reduced at the sites where the crystal structure is peeled off during the grinding step.

It can be seen that the crack resistance during sputtering of the sputtering target using the oxide sintered body of Comparative Example 3 is worse than that of Examples 1 to 6. It is considered that since the surface roughness Rz of the oxide sintered body of Comparative Example 3 exceeds 2 μm, a portion where the crystal structure is peeled off occurs during the grinding step, and the crack resistance is reduced.

1: Plate-shaped oxide sintered body 1A: Cylindrical oxide sintered body 1B: Round oxide sintered body 1C: Divided into plural oxide sintered bodies 3: Backing board

FIG. 1 is a perspective view showing the shape of a target material in one embodiment of the present invention. FIG. 2 is a perspective view showing the shape of a target material in one embodiment of the present invention. FIG. 3 is a perspective view showing the shape of a target material in one embodiment of the present invention. FIG. 4 is a perspective view showing the shape of a target material in one embodiment of the present invention. FIG. 5 is a plane observation image of the oxide sintered body (after surface grinding) of Example 1 under a confocal laser microscope. FIG. 6 is a plane observation image of the oxide sintered body (after surface grinding) of Example 2 under a confocal laser microscope. FIG. 7 is a plane observation image of the oxide sintered body (after surface grinding) of Example 3 under a confocal laser microscope. FIG8 is a plane observation image of the oxide sintered body (after surface grinding) of Example 4 under a confocal laser microscope. FIG9 is a plane observation image of the oxide sintered body (after surface grinding) of Example 5 under a confocal laser microscope. FIG10 is a plane observation image of the oxide sintered body (after surface grinding) of Example 6 under a confocal laser microscope. FIG11 is a plane observation image of the oxide sintered body (after surface grinding) of Comparative Example 1 under a confocal laser microscope. FIG12 is a plane observation image of the oxide sintered body (after surface grinding) of Comparative Example 2 under a confocal laser microscope. FIG13 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 1 under a confocal laser microscope. FIG. 14 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 2 using a confocal laser microscope. FIG. 15 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 3 using a confocal laser microscope. FIG. 16 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 4 using a confocal laser microscope. FIG. 17 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 5 using a confocal laser microscope. FIG. 18 is a 3D observation image of the oxide sintered body (after surface grinding) of Example 6 using a confocal laser microscope. FIG. 19 is a 3D observation image of the oxide sintered body (after surface grinding) of Comparative Example 1 using a confocal laser microscope. FIG. 20 is a 3D observation image of the oxide sintered body (after surface grinding) of Comparative Example 2 using a confocal laser microscope. FIG. 21 is an XRD (X ray diffraction) diagram of the oxide sintered body of Example 1. FIG. 22 is a graph showing the relationship between surface roughness Rz and crack resistance. FIG. 23 is a planar observation image of the oxide sintered body (after surface grinding) of Comparative Example 3 using a confocal laser microscope. FIG. 24 is a 3D observation image of the oxide sintered body (after surface grinding) of Comparative Example 3 using a confocal laser microscope. FIG. 25 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 1 after plane grinding. FIG. 26 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 2 after plane grinding. FIG. 27 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 3 after plane grinding. FIG. 28 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 4 after plane grinding. FIG. 29 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 5 after plane grinding. FIG. 30 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Example 6 after plane grinding. FIG. 31 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Comparative Example 1 after plane grinding. FIG. 32 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Comparative Example 2 after plane grinding. FIG. 33 is a diagram showing the cross-sectional distribution of the surface roughness measurement position of the oxide sintered body of Comparative Example 3 after plane grinding.

Claims (9)

An oxide sintered body contains indium element, tin element and zinc element, and the surface roughness Rz of the surface of the above-mentioned oxide sintered body does not reach 2.0 μm. A sputtering target material, comprising an oxide sintered body as claimed in claim 1. As in the sputtering target of claim 2, the above-mentioned oxide sintered body further contains element X, and element X is at least one element selected from the group consisting of germanium, silicon, yttrium, zirconium, aluminum, magnesium, ferroxene and gallium. The sputtering target of claim 2, wherein the oxide sintered body satisfies the atomic composition ratio range represented by 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). The sputtering target of claim 2, wherein the _oxide sintered body comprises a hexagonal layered compound represented by _In2O3 (ZnO)m[m=2-7] and a spinel structure compound represented by Zn2 _{- xSn1-yInx + yO4} [0≦x<2, 0≦y<1]. The sputtering target material according to any one of claims 2 to 5, wherein among the grinding scars of the above-mentioned oxide sintered body, the ratio of the depth (H) to the width (L) of the grinding scar with the largest depth and the smallest width is H/ L is less than 0.2. A method for manufacturing a sputtering target material, which is used to manufacture a sputtering target material as described in any one of claims 2 to 6, and includes a step of grinding the surface of the above-mentioned oxide sintered body, wherein the abrasive grain diameter of the first grinding stone used for the initial grinding is less than 100μm. A method for manufacturing a sputtering target material as claimed in claim 7, wherein after grinding with the first grindstone, a second grindstone having a smaller grinding particle size than the first grindstone is used to grind the surface of the oxide sintered body, and after grinding with the second grindstone, a third grindstone having a smaller grinding particle size than the second grindstone is used to grind the surface of the oxide sintered body. A method for manufacturing a sputtering target material as claimed in claim 7 or 8, wherein the feed speed v (m/min) of the grinding object, the peripheral speed V (m/min) of the above-mentioned first grinding stone, the cutting depth t (μm) and the abrasive grain size d (μm) of the above-mentioned first grinding stone satisfy the following relationship (4), (v/V) ^1/3 × (t) ^1/6 × d<50 (4).