JP7201595B2 - Sputtering target, method for forming oxide semiconductor film, and backing plate - Google Patents

Description

The present invention relates to a sputtering target, a method for forming an oxide semiconductor film, and a backing plate.

Conventionally, in display devices such as liquid crystal displays and organic EL displays driven by thin film transistors (hereinafter referred to as "TFTs"), the majority of display devices employ an amorphous silicon film or a crystalline silicon film for the channel layer of the TFT. is. On the other hand, with the demand for lower power consumption and higher definition of displays, oxide semiconductors are attracting attention as a material used for the channel layer of TFTs.

Among oxide semiconductors, in particular, an amorphous oxide semiconductor (In—Ga—Zn—O, hereinafter abbreviated as “IGZO”) composed of indium, gallium, zinc, and oxygen disclosed in Patent Document 1 has a high carrier Since it has mobility, it is preferably used. However, since IGZO uses In and Ga as raw materials, it has the drawback of high raw material costs.

From the viewpoint of reducing raw material costs, Zn—Sn—O (hereinafter abbreviated as “ZTO”) (Patent Document 2) and In—Sn—Zn—O (hereinafter “ITZO”) added with Sn instead of Ga in IGZO ) (Patent Document 3) has been proposed. Among them, ITZO is attracting attention as a next-generation material next to IGZO because of its extremely high mobility compared to IGZO.

When a high-mobility oxide semiconductor is used for the channel layer of a TFT, the film is generally formed by magnetron sputtering using a sputtering target of the oxide semiconductor.

Since the sputtering target is consumed as the film formation progresses, the thicker the target, the better from the viewpoint of life.
On the other hand, in the case of magnetron sputtering, the consumption rate of the sputtering target depends on the density of the plasma, the strength and shape of the magnetic field that confines the plasma, and the method of moving the magnet. Thus, the consumption rate of a sputtering target is not uniform across the target.

Therefore, as in Patent Documents 4 to 6, structures have been proposed in which portions of the sputtering target that are rapidly consumed are thickened.

In addition, ensuring reliability is also an issue in high-mobility oxide semiconductors. The reliability here means, for example, cycle stability of the threshold voltage _Vth when an oxide semiconductor film is used for a channel layer of a transistor.
It is said that the cyclic stability of the threshold voltage _Vth can be improved by densifying the film.
In order to make the film denser, it is effective to perform high-power film formation by increasing the sputtering power during film formation.
However, when high-power film formation is performed, a region of the target where the plasma is concentrated becomes hotter than other regions, and cracking of the target due to thermal stress becomes a problem.
In particular, in the case of planar oscillating magnetron sputtering, the plasma always concentrates on the edge of the target parallel to the oscillating direction of the magnetic field, so it is necessary to prevent the edge of the target from cracking.

In Patent Documents 7 and 8, as a structure for preventing cracking of the sputtering target, the sputtering target is divided into a region (erosion region) where plasma consumption progresses greatly and other regions, and a gap is provided between the regions. A structure has been proposed in which deformation due to thermal stress is released to the gap.

The thermal stress referred to here is a value determined by the following formulas (A) and (B). The same applies to the following description.
Thermal stress (σ) = -E x α x ΔT (A)
ΔT=[Q×d/A]/λ (B)
The symbols in the formulas (A) and (B) are explained below.
E: elastic modulus of the sputtering target α: linear expansion coefficient of the sputtering target ΔT: temperature difference between the front and back sides of the sputtering target in the plate thickness direction Q: heat quantity passing from the front to the back of the sputtering target in the plate thickness direction d: the plate of the sputtering target Thickness A: Area of sputtering target viewed from plate thickness direction λ: Thermal conductivity of sputtering target

Further, Patent Documents 9 to 11 describe sputtering targets having inclined portions on the sputtering surface.

WO2012/067036 JP 2017-36497 A WO2013/179676 Japanese Utility Model Laid-Open No. 63-131755 JP-A-01-290764 JP-A-06-172991 JP-A-03-287763 JP-A-05-287522 JP-A-2000-204468 JP-A-2004-83985 JP-A-2008-38229

However, the techniques described in Patent Documents 4 to 8 have the following problems.
In the techniques described in Patent Documents 4 to 6, there is a problem that increasing the thickness of the target increases the thermal stress, making the sputtering target more likely to crack.
In particular, ITZO has a large coefficient of linear expansion and a small thermal conductivity. Therefore, in magnetron sputtering, there is a problem that cracks are likely to occur in the sputtering target due to thermal stress.

When the techniques described in Patent Documents 7 and 8 are applied to planar type oscillating magnetron sputtering, thermal stress also occurs in the erosion region. was inadequate.

As described above, when an oxide semiconductor film is formed by magnetron sputtering, there is a problem that cracks are likely to occur in the sputtering target when an attempt is made to improve the life and film density of the sputtering target.

In addition, in the targets described in Patent Documents 9 to 11, the sputtering surface has both an inclined portion and a flat portion, and the height and direction of the sputtering surface are not uniform. There is a problem that the discharge during sputtering becomes unstable, and a problem that redeposition (redeposition) tends to accumulate on the surface of the target.
In addition, in the target described in Patent Document 11, since both end portions of the target are inclined, a gap is generated between the ground shield and the target, and there is a problem that particles that cause a short tend to accumulate in the gap. be.

The present invention provides a sputtering target capable of preventing cracking during film formation and stably discharging without extremely shortening the target life, a method for forming an oxide semiconductor film using the sputtering target, and a backing plate. intended to provide
Another object of the present invention is to provide a sputtering target capable of preventing cracking during film formation and allowing stable discharge without extremely shortening the target life, and forming an oxide semiconductor film using the sputtering target. A method and a backing plate are provided.

According to the present invention, the following sputtering target, method for forming an oxide semiconductor film, and backing plate are provided.

[1]. Equipped with a plate-shaped oxide sintered body,
The oxide sintered body has a plurality of regions arranged in a first direction,
The plurality of regions are end regions that are regions including ends in the first direction;
an inner region that is the second region on the inner side counting from the end in the first direction;
has
When the plate thickness of the end region is t ₁ , the width of the end region in the first direction is L ₁ , and the plate thickness of the inner region is t ₂ , t ₁ , L ₁ , and t ₂ are , a sputtering target that satisfies the following formulas (1) to (4).
t ₂ > t ₁ (1)
t ₁ (mm)>L ₁ (mm)×0.1+4 (2)
t ₁ (mm) < 9 (3)
₁₀ <L1 (mm)<35 (4)

[2]. Furthermore, the sputtering target according to [ ₁ ], wherein t1 and t2 satisfy the following formula ( ₅ ).
0.6<t1 _/ t2<0.8 ( ₅ )

[3]. The plurality of regions are
An intermediate region that is the third region on the inner side counting from the end in the first direction,
The sputtering target according to [1] or [2], wherein t ₁ , t ₂ , and t ₃ satisfy the following formula (6), where t ₃ is the thickness of the intermediate region.
t2> _t1 >t3 _{( 6} )

[4]. The sputtering target according to any one of [1] to [3], wherein the plurality of regions of the oxide sintered body are arranged separately from each other.

[5]. The sputtering target according to any one of [1] to [4], wherein the oxide sintered body has a rectangular planar shape and the first direction is the long side direction of the rectangle. .

[6]. The oxide sintered body has a rectangular long side of 2300 mm or more and 3800 mm or less, a short side of ₂₀₀ mm or more and 300 mm or less, a plate thickness t2 of the inner region of 9 mm or more and 15 mm or less, and L1 of more than ₁₀ mm and 35 mm. The sputtering target according to [5], wherein the width of the inner region in the first direction is 170 mm or more and 300 mm or less.

[7]. a plate-shaped oxide sintered body;
a backing plate holding the oxide sintered body;
a spacer provided between the oxide sintered body and the backing plate,
The oxide sintered body has a plurality of regions arranged in a first direction,
The plurality of regions include an end region that is a region including the end in the first direction, an inner region that is the second region on the inner side counting from the end in the first direction, has
the backing plate has a retaining surface that retains the end region and the inner region;
the spacer is provided on the holding surface and holds the end region;
The end region has a back surface facing the holding surface,
a rear surface of the end region is inclined with respect to the holding surface;
The slope of the back surface of the end region is a downward slope from the end of the oxide sintered body toward the inside,
Let _t11 be the maximum value of the plate thickness of the end region,
When the width of the end region in the first direction is _L11 ,
t ₁₁ and L ₁₁ satisfy the following formula (12),
sputtering target.
t ₁₁ (mm)>L ₁₁ (mm)×0.1+4 (12)

[8]. The sputtering target according to [7], wherein the angle formed by the back surface of the end region and the holding surface is 4 degrees or more and 15 degrees or less.

[9]. The inner region has a back surface facing the holding surface,
a portion of the back surface of the inner region is inclined with respect to the holding surface;
The slope of the back surface of the inner region is a downward slope from the end of the oxide sintered body toward the inside,
Let _t15 be the minimum value of the plate thickness of the end region,
Let t12 be the plate thickness of the inner region in a region that is not inclined _on the back surface of the inner region, and
When L13 is the width of the inner region and the width _in the first direction of the region inclined on the back surface of the inner region,
t ₁₁ , t ₁₂ , t ₁₅ , L ₁₁ , and L ₁₃ satisfy the following equations (11), (13), (14), (15) and (16),
The sputtering target according to [7] or [8].
t12> _t11 >t15 _{( 11} )
t ₁₁ (mm) < 9 (13)
₁₀ <L11 (mm)<35 (14)
t15 (mm)>3 ( ₁₅ )
3<L13 ₍ mm)<35 (16)

[10]. The sputtering target according to any one of [7] to [9], wherein the oxide sintered body has a rectangular planar shape and the first direction is the long side direction of the rectangle. .

[11]. The oxide sintered body has a rectangular long side of 2300 mm or more and 3800 mm or less, a short side of 200 mm or more and 300 mm or less, and a plate thickness of the inner region, and the back surface of the inner region is not inclined. The sputtering target according to [10], wherein the plate thickness t12 is ₉ mm or more and 15 mm or less, L11 is more than ₁₀ mm and less than 35 mm, and the width of the inner region in the first direction is 170 mm or more and 300 mm or less.

[12]. The sputtering target according to any one of [1] to [11], wherein the end region and the inner region are provided at both ends in the first direction.

[13]. The oxide sintered body has a plate shape having two main surfaces, the height difference in the plate thickness direction of one main surface of the plurality of regions is within 100 μm, and the arithmetic mean roughness Ra is smaller than the other main surfaces, [1] to [12].

[14]. The sputtering target according to any one of [1] to [13], wherein the oxide sintered body has an average bending strength of 320 MPa or less at 30 points.

[15]. The sputtering target according to [14], wherein the oxide sintered body has a minimum bending strength of 200 MPa or less at 30 points.

[16]. The sputtering target according to any one of [1] to [15], wherein the oxide sintered body has a linear expansion coefficient of 7.50×10 ⁻⁶ /K or more.

[17]. The sputtering target according to any one of [1] to [7], wherein the oxide sintered body has an elastic modulus of 150 GPa or more.

[18]. The oxide sintered body has a thermal conductivity of 6.5 (W / m / K) or less,
The sputtering target according to any one of [1] to [17].

[19]. The sputtering target according to any one of [1] to [18], wherein the oxide sintered body has (linear expansion coefficient x elastic modulus)/thermal conductivity of 200 Pa/W or more.

[20]. The sputtering according to any one of [1] to [19], wherein the oxide sintered body is made of an oxide containing indium element (In), tin element (Sn), and zinc element (Zn). target.

[21]. The oxide sintered body is
The sputtering target according to [20], comprising a _spinel structure compound represented by _Zn2SnO4 .

[22]. The oxide sintered body is
The sputtering target of [20] or [21], comprising a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m [m=2-7].

[23]. Furthermore, the sputtering target according to any one of [20] to [22], wherein the oxide sintered body satisfies the following formula (7).
0.40≦Zn/(In+Sn+Zn)≦0.80 (7)

[24]. Furthermore, the sputtering target according to any one of [20] to [23], wherein the oxide sintered body satisfies the following formula (8).
0.15≦Sn/(Sn+Zn)≦0.40 (8)

[25]. Furthermore, the sputtering target according to any one of [20] to [24], wherein the oxide sintered body satisfies the following formula (9).
0.10≦In/(In+Sn+Zn)≦0.35 (9)

[26]. a holding surface that holds the oxide sintered body; a backing plate that has a convex portion that protrudes from the holding surface and holds the intermediate region;
a spacer provided between the retaining surface and the end region;
The sputtering target according to [3], comprising:

[27]. Using the sputtering target according to any one of [1] to [26] as a target, using a magnetic field oscillation type magnetron sputtering apparatus as a film forming apparatus, and setting the oscillation direction of the magnetic field to the first direction and the plate A method of forming an oxide semiconductor film, wherein a second direction perpendicular to a thickness direction is formed, and the end portion of the magnetic field in the first direction is positioned in the inner region.

[28]. a holding surface for holding the oxide sintered body according to [3]; a convex portion protruding from the holding surface and holding the intermediate region;
a spacer provided between the holding surface and the end region;
a backing plate.

[29]. The backing plate according to [28], wherein the height of the protrusion is higher than that of the spacer.

According to one aspect of the present invention, a sputtering target that can prevent cracking during film formation without extremely shortening the target life, a method for forming an oxide semiconductor film using the sputtering target, and a backing plate are provided. can provide.
Further, according to one aspect of the present invention, there is provided a sputtering target capable of preventing cracking during film formation without extremely shortening the target life and allowing stable discharge, and an oxide semiconductor film using the sputtering target. and a backing plate.

1 is a perspective view of a sputtering target according to an embodiment of the invention; FIG. 2 is a side view of FIG. 1; FIG. FIG. 2 is a plan view of FIG. 1; FIG. 4 is a perspective view of a backing plate; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4B is a side view showing another aspect of the sputtering target according to the embodiment of the present invention; FIG. 4 is a diagram showing the stress distribution of the sputtering target when a simulation of magnetron sputtering is performed using the sputtering target according to the preliminary test, (A) is a plan view, (B) is a side view, and (C) is ( It is an enlarged view near the end of A). FIG. 10 is a diagram showing measurement of the depth of wear of a sputtering target in an example.

Hereinafter, embodiments will be described with reference to the drawings and the like. Those skilled in the art will readily appreciate, however, that the embodiments can be embodied in many different forms and that various changes in form and detail can be made therein without departing from the spirit and scope thereof. . Therefore, the present invention should not be construed as being limited to the description of the following embodiments.

Also, in the drawings, sizes, layer thicknesses, or regions may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale. The drawings schematically show an ideal example, and are not limited to the shapes or values shown in the drawings.

In addition, the ordinal numbers "first", "second", and "third" used in this specification are added to avoid confusion of constituent elements, and are not numerically limited. Add a note.

In this specification and the like, the terms “film” or “thin film” and the term “layer” can be interchanged depending on the case.
In addition, in the sintered body and the oxide semiconductor thin film in this specification and the like, the terms “compound” and “crystalline phase” can be interchanged depending on the case.

In the present specification, the numerical range represented using "to" means a range including the numerical value described before "to" as the lower limit and the numerical value described after "to" as the upper limit. do.

An example of a preferred embodiment of the present invention will be described in detail below with reference to the drawings.
First, with reference to FIGS. 1 to 3, the structure of a sputtering target according to one embodiment of the present invention (sometimes referred to as a sputtering target according to the first aspect) will be described. Here, as a sputtering target, a target used as a film raw material in a magnetic field oscillation type magnetron sputtering apparatus for forming an oxide semiconductor film is exemplified.

As shown in FIG. 1 , a sputtering target 1 includes an oxide sintered body 3 .
In FIG. 1 the sputtering target 1 also comprises a backing plate 5 .

The oxide sintered body 3 is a film raw material used when forming an oxide semiconductor film by sputtering, and has a plate shape.
In FIGS. 1 to 3, the oxide sintered body 3 has a rectangular planar shape. In the following description, the long side direction of the rectangle is the Y direction (first direction), the plate thickness direction is the Z direction, and the short side direction is the X direction (the direction perpendicular to the first direction and the plate thickness direction, the second direction). direction). Further, in the following description, the rectangular plane of the oxide sintered body 3 is described as the main surface, the main surface on the side in contact with the backing plate 5 is the "back surface", and the main surface on the side not in contact with the backing plate 5 is the ""Frontsurface" is described. The "front surface" may also be referred to as the sputtering surface.
The X direction is the direction in which the magnetic field oscillates in a magnetic field oscillation type magnetron sputtering apparatus. As shown in FIG. 3, the magnetic field M has a doughnut-shaped loop. A plurality of loop shapes may be formed in the X direction, and the number is not limited (in the case of a plurality of loop shapes, the length in the Y direction is the same and the width in the X direction is narrow). The width _LM in the _X direction is shorter than the width Lx in the X direction of the oxide sintered body 3 .
Therefore, during film formation, the magnetic field M oscillates (reciprocates) in the X direction so that the entire surface of the oxide sintered body 3 in the X direction is brought into contact with the plasma.

The oxide sintered body 3 has end regions 7A and 7B, inner regions 9A and 9B, and an intermediate region 11 as a plurality of regions arranged in the Y direction.
The end regions 7A and 7B are regions including end portions of the oxide sintered body 3 in the Y direction (also referred to as sintered body end portions). In FIG. 2, the end regions 7A and 7B are provided at both ends in the Y direction.
The inner regions 9A and 9B are the second inner regions counted in the Y direction from the ends. In FIG. 1, the inner regions 9A and 9B are provided on both end sides in the Y direction.
The intermediate region 11 is the third region on the inner side as counted from the end in the Y direction.
1 to 3, from the left end to the right end of the sputtering target 1, the regions are arranged in the order of end region 7A, inner region 9A, intermediate region 11, inner region 9B, and end region 7B. It is Each of the end region 7A, the inner region 9A, the inner region 9B, and the end region 7B has a rectangular planar shape, two opposing sides are parallel to the X direction, and the other two sides are perpendicular to the corresponding side. is parallel to the Y direction.

1 to 3, the end regions 7A, 7B, the inner regions 9A, 9B, and the intermediate region 11 are arranged separately from each other, and the oxide sintered body 3 is multi-divided. . 1 to 3, the intermediate region 11 is also divided into three regions 11A, 11B, 11C along the Y direction. This is because, when each region is deformed by thermal stress generated during sputtering, the deformed portion is released to the gap between the regions. The regions 11A, 11B, and 11C are arranged in order of the regions 11A, 11B, and 11C from the left side in FIGS. Each of the regions 11A, 11B, and 11C has a rectangular planar shape, two opposing sides parallel to the X direction, and two other sides orthogonal to the corresponding side parallel to the Y direction. However, the planar shapes of the end regions 7A, 7B, the inner regions 9A, 9B, and the intermediate region 11 are not limited to rectangles.
_The dimension of the gap G1 between the end regions 7A, 7B and the inner regions 9A, 9B is not particularly limited. _The dimension of the gap G1 is, for example, about 0.1 mm to 0.5 mm. _The dimension of the gap G2 between the inner regions 9A, 9B and the intermediate region 11 is also not particularly limited. _The dimension of the gap G2 is, for example, about 0.1 mm to 0.5 mm.

When the plate thickness of the end regions 7A and 7B is t ₁ , the Y-direction width of the end regions 7A and 7B is L ₁ , and the plate thickness of the inner regions 9A and 9B is t ₂ , t ₁ , L ₁ , and t2 satisfies the following formulas ( ₁ ) to (4).
t ₂ > t ₁ (1)
t ₁ (mm)>L ₁ (mm)×0.1+4 (2)
t ₁ (mm) < 9 (3)
₁₀ <L1 (mm)<35 (4)
If the plate thickness is not uniform within the end regions 7A and 7B, the minimum value of the plate thickness within the end regions 7A and 7B is taken as the plate thickness _t1 . _If the width in the Y direction is not constant in the end regions 7A and 7B, the maximum value of the width in the Y direction in the region is set to L1. If the plate thickness is not constant within the inner regions 9A and 9B, the minimum value of the plate thickness within the inner regions 9A and 9B is taken as the plate thickness _t2 .

The reason for defining formula (1) is as follows.
In a magnetic field swing type magnetron sputtering apparatus, the magnetic field M swings in the X direction during film formation. It hardly swings in the Y direction. Therefore, the inner regions 9A, 9B and the end regions 7A, 7B are regions where the ends of the magnetic field M are always located in the vicinity, and the upper surfaces of the inner regions 9A, 9B and the end regions 7A, 7B are the other regions. The plasma confined by the magnetic field M tends to be hotter than the upper surface of the .

In addition, since the end surfaces 8 in the Y direction of the end regions 7A and 7B are not close to other regions, the lower surfaces of the end regions 7A and 7B are cooled by the backing plate 5 more than the lower surfaces of the other regions. Efficient and low temperature.
Therefore, the end regions 7A and 7B have a larger temperature difference (ΔT in the formula (B)) in the plate thickness direction than other regions, and cracks due to thermal stress are likely to occur.
Therefore, it is preferable that the plate thickness _t1 of the end regions 7A and 7B is small.

Also, since the sputtering target 1 is a magnetic field oscillation type device target, the inner regions 9A and 9B are regions where the magnetic field M and the plasma confined by the magnetic field M are always located during film formation. Therefore, in order to prolong the life of the sputtering target ₁ , it is preferable that the plate thickness t2 is large.
On the other hand, the inner regions 9A, 9B are sandwiched between the end regions 7A, 7B and the intermediate region 11, and heat is less likely to escape from the end surfaces. not as large as Therefore, the inner regions 9A and 9B are less likely to crack than the end regions 7A and 7B even if the plate thickness is increased.
Therefore, the plate thickness t1 of the end regions 7A, 7B must be thinner _than the plate thickness _t2 of the inner regions 9A, 9B.

A target with a thicker plasma concentration region, such as the sputtering target 1, is also called an EP (erosion pattern) target.

The reason for defining the formulas (2) to (4) is as follows.
_The longer L1 is, the closer the end regions 7A and 7B are to the ends of the magnetic field M (see FIG. 3), and the more likely they are to be worn during film formation. Therefore, the longer L1 is, the thicker _t1 is required (equation ( ₂ )).
Formula (2) is preferably the following formula (2A), more preferably the following formula (2B), still more preferably the following formula (2C), and particularly preferably the following formula (2D) is.
t ₁ (mm)≧L ₁ (mm)×0.1+4.25 (2A)
t ₁ (mm)≧L ₁ (mm)×0.1+4.5 (2B)
t ₁ (mm)≧L ₁ (mm)×0.1+4.75 (2C)
t ₁ (mm)≧L ₁ (mm)×0.1+5 (2D)
However, if t1 is too thick, cracking due to thermal stress is likely to occur, so there is _an upper limit to the thickness (equation (3)).
Furthermore, if L ₁ is made too long, the end regions 7A and 7B will approach the ends of the magnetic field M, so L ₁ also has an upper limit (equation (4)). _If L1 is too short, the end regions 7A and 7B become too narrow, and cracks due to thermal stress tend to occur, so there is also _a lower limit to L1 (equation (4)).
More preferably, t ₁ and L ₁ satisfy the conditions shown in formulas (3A) and (4A) below.
t ₁ (mm) < 8.5 (3A)
12.5≦L ₁ (mm)≦32.5 (4A)
More preferably, t ₁ and L ₁ satisfy the conditions shown in formulas (3B) and (4B) below.
t ₁ (mm) ≤ 8 (3B)
15≦L ₁ (mm)≦30 (4B)

In order to prolong the life of the sputtering target ₁ , it is more preferable that t1 and t2 satisfy the following formula ( ₅ ).
0.6<t1 _/ t2<0.8 ( ₅ )

When the plate thickness of the intermediate region 11 is t3, it is _more preferable that t1 _, t2 _, and t3 satisfy the following _formula (6).
t2> _t1 >t3 _{( 6} )
This is because during film formation, depending on the position of the magnetic field M in the X direction, there is a time zone in which the plasma does not come into contact with the intermediate region 11, and the intermediate region 11 is consumed less than the end regions 7A and 7B and the inner regions 9A and 9B. This is because the plate thickness t3 of the intermediate region ₁₁ does not necessarily need to be increased because it is slow. Also, it is advantageous in terms of cost to reduce the plate thickness t3 of the intermediate region ₁₁ .
When the plate thickness is not constant within the intermediate region 11 _, the minimum value of the plate thickness within the region is set to the plate thickness t3.

Specific dimensions of the oxide sintered body 3 are not particularly limited as long as the formulas (1) to (4) are satisfied. For example, the following range is suitable as a target for a magnetic field oscillation type magnetron sputtering apparatus, which is used as a standard in a large-sized sputtering apparatus.

The long side of the rectangle (L _Y in FIG. 3) is preferably 2300 mm or more and 3800 mm or less. The long side of the rectangle (L _Y in FIG. 3) is more preferably 2500 mm or more and 3600 mm or less, still more preferably 2500 mm or more and 3400 mm or less.

A short side of the rectangle (L _x in FIG. 3) is preferably 200 mm or more and 300 mm or less. The short side of the rectangle (L _x in FIG. 3) is more preferably 230 mm or more and 300 mm or less, still more preferably 250 mm or more and 300 mm or less.

The plate thickness t2 is preferably 9 mm or _more and 15 mm or less. The plate thickness t2 is _more preferably 9 mm or more and 12 mm or less, and still more preferably 9 mm or more and 10 mm or less.

L ₁ is preferably more than 10 mm and less than 35 mm, more preferably 12.5 mm or more and 32.5 mm or less, still more preferably 15 mm or more and 30 mm or less, and particularly preferably 15 mm or more and 20 mm or less.

A width L2 of the inner regions 9A and 9B in the Y direction ( _first direction) is preferably 170 mm or more and 300 mm or less. The width L2 of the inner regions 9A and 9B in the Y direction ( _first direction) is more preferably 180 mm or more and 300 mm or less, and even more preferably 185 mm or more and 300 mm or less.

The width L ₃ (see FIG. 2) of the intermediate region 11 is preferably 1700 mm or more and 3500 mm or less. The width L ₃ (see FIG. 2) of the intermediate region 11 is more preferably 1900 mm or more and 3200 mm or less, and still more preferably 2000 mm or more and 3000 mm or less.

Since the number of divisions of the intermediate region 11 is not specified, the width L ₄ (see FIG. ₂ ) of 11A, 11B, and 11C is also not specified. The following are preferred. The width L ₄ (see FIG. 2) of the regions 11A, 11B, and 11C is more preferably 500 mm or more and 1200 mm or less, still more preferably 600 mm or more and 1000 mm or less.

When the sputtering target 1 is used for magnetic field oscillation type magnetron sputtering, L ₁ , the end region 7A, It is also possible to define the inner end of 7B (X-direction position P in FIG. 2). Here, the position where the consumption during film formation is greatest is referred to as the maximum erosion position. The wear depth at the maximum erosion position is called the maximum erosion depth.
The position of P is preferably a position where the wear depth is 50% or more and 75% or less of the maximum erosion depth. The sputtering target 1 is less likely to crack by setting it to the position where the wear depth is 50% or more. The target life can be maintained by setting the position where the wear depth is 75% or less.

The position of P is preferably 5 mm or more and 10 mm or less from the maximum erosion position toward the end in the X direction. By setting the position to 5 mm or more, the target life can be maintained. The position of 10 mm or less makes the sputtering target 1 less likely to crack.

The oxide sintered body 3 is plate-shaped. Oxide sintered body 3 has two main surfaces. It is preferable that the height difference (step) in the thickness direction of the main surface is as small as possible and the arithmetic mean roughness is smaller than that of the other main surfaces. Specifically, it is desirable that the height difference (step) in the thickness direction of the front surfaces 21A, 23A, and 25A (one main surface) is as small as possible. It is desirable that the front surfaces 21A, 23A, and 25A have a smaller arithmetic mean roughness Ra than the back surfaces 21B, 23B, and 25B (other main surfaces).
This is for the following reasons.

Since the front surfaces 21A, 23A, and 25A are surfaces that are consumed by plasma during film formation, steps (unevennesses) should be present as much as possible between the front surfaces 21A, 23A, and 25A in order to prevent abnormal discharge. preferably not. On the other hand, since the back surfaces 21B, 23B, and 25B are fixed to the backing plate 5 with a brazing material or the like, the step (unevenness) is not much of a problem. It is advantageous in terms of cost not to smooth the back surface by polishing or the like.

Ideally, the steps between the front surfaces 21A, 23A, and 25A are zero. Specifically, as shown in FIG. 2, it is preferable that the front surfaces 21A, 23A, and 25A are positioned on a virtual plane 27 parallel to the XY plane. This state is also called "face-to-face". However, if the difference in height in the Z direction between the front surfaces 21A, 23A, and 25A is 100 μm or less, problems such as abnormal discharge can be prevented as in the case of flush.

The backing plate 5 is a member that holds and cools the oxide sintered body 3 . As shown in FIG. 4, the backing plate 5 includes a body 13 and spacers 17A and 17B.

The main body 13 is a plate-like member provided with a flow path (not shown) through which cooling water or the like flows. The main body 13 has a holding surface 13A and a convex portion 15 . The material of the main body 13 is preferably a material with high thermal conductivity from the viewpoint of cooling efficiency. Copper, for example, is used as the material of the main body 13 .

The holding surface 13A is a portion that contacts and holds the protrusion 15, the end regions 7A and 7B, and the spacers 17A and 17B.
The convex portion 15 is a member that protrudes from the holding surface 13A. The convex portion 15 is a member that contacts the intermediate region 11 and holds the intermediate region 11 . The convex portion 15 may be integrated with the main body 13 or may be a separate plate member. The planar shape of the convex portion 15 is preferably a shape corresponding to the planar shape of the intermediate region 11, and is preferably rectangular in this embodiment. The thickness t ₄ (see FIG. 2) of the convex portion 15 is such that t ₃ +t ₄ =t ₂ (the sum of the thickness of the convex portion 15 and the thickness of the intermediate region 11 is equal to the thickness of the inner regions 9A and 9B). to the same extent) is preferred. This is to minimize the difference in level between the front surfaces of the inner regions 9A and 9B and the front surface of the intermediate region 11 .

The spacers 17A, 17B are members that hold the end regions 7A, 7B. As the spacers 17A and 17B, a thin plate made of the same material as that of the main body 13, a metal wire, or the like is used. The spacers 17A and 17B are provided on both ends of the protrusion 15 in the Y direction, respectively, while being spaced apart from the protrusion 15 . The positions of the spacers 17A, 17B are positions corresponding to the end regions 7A, 7B. The planar shape of the spacers 17A, 17B is preferably a shape corresponding to the end regions 7A, 7B. The thickness t ₅ (see FIG. 2) of the spacers 17A and 17B is such that t ₁ +t ₅ =t ₂ (the sum of the thickness of the spacers 17A and 17B and the thickness of the end regions 7A and 7B is the inner region 9A, 9B) is preferred. This is to make the inner regions 9A, 9B and the end regions 7A, 7B flush. In addition, when the expression (6) is satisfied, the Z-direction height of the convex portion 15 is higher than the spacers 17A and 17B.

The oxide sintered body 3 is fixed to the backing plate 5 by brazing or the like. When metal wires are used for the spacers 17A and 17B, the thickness of the metal wires and the thickness of the brazing material may be made the same and used by brazing.
The above is the description of the structure of the sputtering target 1 (sputtering target according to the first aspect) according to one embodiment of the present invention.

Next, structures of sputtering targets according to other aspects will be briefly described. In the present specification and the drawings, constituent elements having substantially the same functions and configurations are denoted by the same reference numerals, and descriptions thereof are omitted.

(Sputtering target according to the second aspect)
Although the intermediate region 11 is divided into three regions 11A, 11B, and 11C in FIGS. 1 to 3, the number of divided regions is not limited to three. The number of regions forming the intermediate region 11 may be two, or may be four or more.
An example of the sputtering target according to the second aspect is a sputtering target 101 having an intermediate region 11 divided into four regions 11D, 11E, 11F and 11G as shown in FIG.

As another example of the sputtering target according to the second aspect, there is a sputtering target 102 in which the intermediate region 11 is one region as shown in FIG. 6 without dividing the intermediate region 11 .

1 to 3, the thickness t ₃ of the intermediate region 11 is thinner than the plate thickness t ₂ of the inner regions 9A and 9B, but another example of the sputtering target according to the second aspect is shown in FIG. As shown, there is a sputtering target 103 in which the thickness _t3 of the intermediate region ₁₁ is the same as the plate thickness t2. In this case, the backing plate 5 is not provided with the projections 15 shown in FIG.

1-3, the end regions 7A, 7B, the inner regions 9A, 9B, and the intermediate region 11 are separate, but may be partly or wholly integrated.
For example, as another example of the sputtering target according to the second aspect, as shown in FIG. A target 104 may be mentioned.
Another example of the sputtering target according to the second aspect is a sputtering target 105 having a structure in which the inner regions 9A and 9B and the intermediate region 11 are integrated as shown in FIG.

Further, FIG. 10 shows another example of the sputtering target according to the second aspect, which has a structure in which the end region 7A and the inner region 9A are integrated, and the end region 7B and the inner region 9B are integrated. A target 106 is shown.
Further, as another example of the sputtering target according to the second aspect, as shown in FIG. 11, the end region 7A and the inner region 9A are integrated, and the end region 7B and the inner region 9B are integrated, A sputtering target 107 having a structure in which the backing plate 5 is not provided with the projections 15 is exemplified.

(Sputtering target according to the third aspect)
Moreover, unlike the sputtering targets shown in FIGS. An aspect (referred to as a third aspect) in which the back surface of the body 3 is an inclined surface is also available.
More specifically, in the oxide sintered body according to the third aspect, the back surface of the end region is inclined with respect to the holding surface, and the inclination of the back surface of the end region is the same as that of the oxide sintered body. It slopes down from the edge towards the inside.
When the back surface of the end region thus has a downward slope toward the inside from the end of the oxide sintered body, the maximum value of the plate thickness of the end region is _t11 , and the above-mentioned When the width in the first direction is L ₁₁ , t ₁₁ and L ₁₁ preferably satisfy the following formula (12).
t ₁₁ (mm)>L ₁₁ (mm)×0.1+4 (12)

According to the sputtering target according to the third aspect, since the back surface of the oxide sintered body is inclined, thickness reduction processing for stress reduction can be performed without dividing the oxide sintered body. Further, in the sputtering target according to the third aspect, it is sufficient to provide a slope on the back surface of the oxide sintered body, and the surface height of the oxide sintered body is uniform without providing a slope on the surface. Therefore, there is no gap between the ground shield and the sputtering target, and particles that cause short circuits can be prevented from entering the gap.

FIG. 12 shows a side view of a sputtering target 108 according to one example of a sputtering target according to the third aspect.
Although the sputtering target 108 has an inclined back surface, the shape of the front surface is the same shape as the sputtering target 1, and the shape represented by the plan view of the sputtering target 1 shown in FIG. 108 can be similarly applied.

In sputtering target 108 , oxide sintered body 3 has end regions 7A, 7B, inner regions 9A, 9B, and middle region 11 . The end region 7A and the inner region 9A are integrated, the end region 7B and the inner region 9B are integrated, and the inner regions 9A, 9B and the intermediate region 11 are separated from each other.

The back surface 21B of the end region 7A of the sputtering target 108 is inclined in the Y direction. The rear surface of the end region 7B is also inclined in the same manner as the rear surface 21B. Since the back surfaces of the end regions 7A and 7B are inclined, the thickness of the end regions 7A and 7B gradually increases from the outside to the inside of the oxide sintered body 3 in the Y direction. Therefore, the effect of "easy to achieve both power resistance and life" is achieved.

_The inclination angle of the back surface 21B is the angle θ ₁ formed by the holding surface 13A of the main body 13 of the backing plate 5 and the back surface 21B. The following are more preferable. It is preferable that the end region 7B has the same inclination angle as the end region 7A.

In the sputtering target 108, it is preferable that part or all of the back surfaces of the inner regions 9A and 9B are inclined. In the embodiment shown in FIG. 12, part of the back surface of the inner regions 9A and 9B is inclined, more specifically, part of the back surface of the inner region 9A on the side of the end region 7A is inclined, and the end of the inner region 9B is inclined. A portion of the rear surface on the side of the partial region 7B is inclined. In the sputtering target 108, the back surfaces of the inner regions 9A, 9B include a back surface 23B substantially parallel to the holding surface 13A of the main body 13 of the backing plate 5 and an inclined back surface 23C. _The inclination angle of the inclined back surface 23C of the inner region 9A is the angle θ2 formed by the holding surface 13A of the main body 13 of the backing plate ₅ and the inclined back surface 23C of the inner region 9A. It is preferably 5 degrees or more and 12 degrees or less. The inner region 9B also preferably has the same inclination angle as the inner region 9A.
In the sputtering target 108, the inclination of the back surface of the end region 7A and the inclination of the back surface of the inner region 9A are continuously inclined from the outside to the inside of the oxide sintered body 3 (the inclination angle is constant). ) is preferred. Regarding the inclination of the back surface of the end region 7B and the inclination of the back surface of the inner region 9B, the inclination of the back surface of the end region 7B and the inclination of the back surface of the inner region 9B are also changed from the outside to the inside of the oxide sintered body 3. is continuously inclined (the inclination angle is constant).

In the sputtering target 108, the surfaces of the spacers 17A and 17B (end spacers) corresponding to the end regions 7A and 7B, which are in contact with the oxide sintered body 3, have inclinations corresponding to the back surfaces of the end regions 7A and 7B. preferably. In addition, since the inner regions 9A and 9B also have a sloped back surface, it is preferable to provide the holding surface 13A with a spacer (inner spacer) having a slope corresponding to the slope of the back surface of the inner regions 9A and 9B. The end spacers and inner spacers may be integral or separate.

Also in the sputtering target 108, as shown in FIG. 12, it is preferable that the front surfaces 21A, 23A, and 25A are positioned on a virtual plane 27 parallel to the XY plane ("flush"). However, in the sputtering target 108 as well, if the difference in height in the Z direction is 100 μm or less, problems such as abnormal discharge can be prevented as in the case of flush.

In the sputtering target 108,
The maximum thickness of the end regions 7A and 7B is _t11 ,
The minimum thickness of the end regions 7A and 7B is _t15 ,
_L11 is the width of the end regions 7A and 7B in the Y direction,
The plate thickness of the inner regions 9A and 9B, and the plate thickness in the region where the back surface of the inner regions 9A and 9B is not inclined is _t12 ,
When L13 is the width of the inner region and the width _in the first direction of the region inclined on the back surface of the inner region,
Preferably, t ₁₁ , t ₁₂ , t ₁₅ , L ₁₁ and L ₁₃ satisfy the following formulas (11), (13), (14), (15) and (16), and t More preferably, ₁₁ , t ₁₂ , t ₁₅ , L ₁₁ and L ₁₃ satisfy formulas (11) to (16).
t12> _t11 >t15 _{( 11} )
t ₁₁ (mm) < 9 (13)
₁₀ <L11 (mm)<35 (14)
t15 (mm)>3 ( ₁₅ )
3<L13 ₍ mm)<35 (16)

In addition, if the plate thickness of the inner regions 9A and 9B and the plate thickness in the non-slanted back surface of the inner regions 9A and 9B are not constant, the minimum value of the plate thickness in the non-slanted back surface is The plate thickness is _t12 .

Note that, like the sputtering target 108, when the back surfaces of the end regions 7A and 7B are continuously inclined from the outside to the inside of the oxide sintered body 3 in the Y direction (the inclination angle is constant case), the thickness of the end regions 7A, 7B at the outer end surface ₁₈ of the end regions 7A, 7B corresponds to t15, and the thickness of the end regions 7A, 7B at the inner end surface 28 of the end regions 7A, 7B corresponds to _t11 .

A sputtering target that satisfies Equation (15) is less likely to crack during sputtering discharge.

The sputtering target can achieve both power resistance and target life (TG life) by satisfying formula (16).
Formula (16) is preferably the following formula (16A).
5≦L ₁₃ (mm)<35 (16A)

The sputtering target can achieve both power resistance and target life (TG life) by satisfying the formula (11).

Moreover, the reason for defining the formula (11) is as follows.
In a magnetic field swing type magnetron sputtering apparatus, the magnetic field M swings in the X direction during film formation. It hardly swings in the Y direction. Therefore, the inner regions 9A, 9B and the end regions 7A, 7B are regions in which the ends of the magnetic field M are always located in the vicinity, and the upper surfaces (front surfaces) of the inner regions 9A, 9B and the end regions 7A, 7B ) tends to reach a higher temperature due to the plasma confined by the magnetic field M than the upper surface (front surface) of other regions.

In addition, since the outer end surfaces 18 of the end regions 7A and 7B in the Y direction are not close to other regions, the lower surfaces of the end regions 7A and 7B are more likely to be affected by the backing plate 5 than the lower surfaces of the other regions. Good cooling efficiency, easy to low temperature.
Therefore, the end regions 7A and 7B have a larger temperature difference (ΔT in the formula (B)) in the plate thickness direction than other regions, and cracks due to thermal stress are likely to occur.
Therefore, it is preferable that _t11 of the end regions 7A and 7B be thin.

Also, since the sputtering target 108 is a magnetic field oscillation type device target, the inner regions 9A and 9B are regions where the magnetic field M and the plasma confined by the magnetic field M are always located during film formation. Therefore, in order to prolong the life of the sputtering target 108, it is preferable that the plate thickness _t12 is large.
On the other hand, the inner regions 9A, 9B are sandwiched between the end regions 7A, 7B and the intermediate region 11, and heat is less likely to escape from the end surfaces. not as large as Therefore, the inner regions 9A and 9B are less likely to crack than the end regions 7A and 7B even if the plate thickness is increased.
Therefore, the plate thickness _t11 of the end regions 7A, 7B is preferably thinner than the plate thickness _t12 of the inner regions 9A, 9B.

It should be noted that a target with a thick plasma-concentrating region, such as the sputtering target 108, is also called an EP (erosion pattern) target.

The reason for defining the formulas (12) to (14) is as follows.
The longer L ₁₁ , the closer the end regions 7A, 7B are to the ends of the magnetic field M (see FIG. 3, where L ₁ in FIG. 3 corresponds to L ₁₁ in the sputtering target 108). Therefore, the end regions 7A and 7B are likely to be worn during film formation. Therefore, the longer _L11 is, the thicker t11 is required (equation ( ₁₂ )).
Formula (12) is preferably the following formula (12A), more preferably the following formula (12B), still more preferably the following formula (12C), and particularly preferably the following formula (12D) is.
_t11 (mm)≧ _L11 (mm)×0.1+4.25 (12A)
_t11 (mm)≧ _L11 (mm)×0.1+4.5 (12B)
_t11 (mm)≧ _L11 (mm)×0.1+4.75 (12C)
_t11 (mm)≧ _L11 (mm)×0.1+5 (12D)
However, if _t11 is too thick, cracking due to thermal stress is likely to occur, so there is an upper limit to the thickness (equation (13)).
Furthermore, L ₁₁ also has an upper limit because if L ₁₁ is too long, the edge regions 7A, 7B will approach the edges of the magnetic field M (equation (14)). If L ₁₁ is too short, the end regions 7A and 7B become too narrow, and cracks due to thermal stress tend to occur, so there is also a lower limit for L ₁₁ (equation (14)).

More preferably, t ₁₁ and L ₁₁ satisfy the conditions shown in formulas (13A) and (14A) below.
t ₁₁ (mm) < 8.5 (13A)
12.5≦ _L11 (mm)≦32.5 (14A)

More preferably, t ₁₁ and L ₁₁ satisfy the conditions shown in formulas (13B) and (14B) below.
t ₁₁ (mm) ≤ 8 (13B)
15≦L ₁₁ (mm)≦30 (14B)

_In order to prolong the life of the sputtering target 108, it is more preferable that t11 and t12 satisfy the following equation ( ₁₇ ).
0.6< _t11 /t12<0.8 ( ₁₇ )

Assuming that the plate thickness of the intermediate region ₁₁ is t13, it is more preferable that _t11 , _t12 , and t13 satisfy the following formula ₍ 18).
t12> _t11 >t13 _{( 18} )
This is because during film formation, depending on the position of the magnetic field M in the X direction, the plasma does not come into contact with the intermediate region 11, and the intermediate region 11 wears slower than the end regions 7A and 7B and the inner regions 9A and 9B. Therefore, it is not always necessary to increase the thickness. Further, it is advantageous in terms of cost to reduce the plate thickness of the intermediate region 11 .
If the plate thickness is not constant within the intermediate region ₁₁ , the minimum value of the plate thickness within the region is set to the plate thickness t13.

The specific dimensions of the oxide sintered body 3 according to the third aspect are not particularly limited as long as the formula (12) is satisfied. For example, the following range is suitable as a target for a magnetic field oscillation type magnetron sputtering apparatus that is standardly used in a large-sized sputtering apparatus.

In the sputtering target 108, the long side of the rectangle (corresponding to _LY in FIG. 3) is preferably 2300 mm or more and 3800 mm or less. In the sputtering target 108, the long side of the rectangle (corresponding to _LY in FIG. 3) is more preferably 2500 mm or more and 3600 mm or less, still more preferably 2500 mm or more and 3400 mm or less.

In the sputtering target 108, the rectangular short side (corresponding to _Lx in FIG. 3) is preferably 200 mm or more and 300 mm or less. In the sputtering target 108, the short side of the rectangle (corresponding to _Lx in FIG. 3) is more preferably 230 mm or more and 300 mm or less, still more preferably 250 mm or more and 300 mm or less.

The plate thickness t12 is preferably ₉ mm or more and 15 mm or less. The plate thickness t12 is more preferably 9 mm or more and ₁₂ mm or less, and still more preferably 9 mm or more and 10 mm or less.

L ₁₁ is preferably more than 10 mm and less than 35 mm, more preferably 12.5 mm or more and 32.5 mm or less, still more preferably 15 mm or more and 30 mm or less, and particularly preferably 15 mm or more and 20 mm or less.

A width _L12 in the Y direction (first direction) of the inner regions 9A and 9B is preferably 170 mm or more and 300 mm or less. The width _L12 of the inner regions 9A and 9B in the Y direction (first direction) is more preferably 180 mm or more and 300 mm or less, and even more preferably 185 mm or more and 300 mm or less. The width L ₁₃ and the width L ₁₂ preferably satisfy the relationship of L ₁₂ ≧L ₁₃ and the relationship of L ₁₂ >L ₁₃ .

The width L ₁₄ (see FIG. 12) of the intermediate region 11 is preferably 1700 mm or more and 3500 mm or less. The width L ₁₄ (see FIG. 12) of the intermediate region 11 is more preferably 1900 mm or more and 3200 mm or less, and still more preferably 2000 mm or more and 3000 mm or less.

The width L ₁₅ (see FIG. 12) of the regions 11A, 11B, and 11C is preferably 250 mm or more and 1700 mm or less. The width L ₁₅ (see FIG. 12) of the regions 11A, 11B, and 11C is more preferably 500 mm or more and 1200 mm or less, still more preferably 600 mm or more and 1000 mm or less.

When the sputtering target 108 is used for magnetic field swing magnetron sputtering, L ₁₁ , the end region 7A, It is also possible to define the inner end of 7B (X-direction position P in FIG. 12). Here, the position where the consumption during film formation is greatest is referred to as the maximum erosion position. The wear depth at the maximum erosion position is called the maximum erosion depth.
The position of P is preferably a position where the wear depth is 50% or more and 75% or less of the maximum erosion depth. The sputtering target 108 is less likely to crack by setting the position to a depth of consumption of 50% or more. The target life can be maintained by setting the position where the wear depth is 75% or less.

The position of P is preferably 10 mm or more and 30 mm or less from the maximum erosion position toward the end in the X direction. By setting the position to 10 mm or more, the target life can be maintained. By setting the position to 30 mm or less, the sputtering target 108 is less likely to crack.

_The dimension of the gap G2 between the inner regions 9A, 9B and the intermediate region 11 in the sputtering target 108 is also not particularly limited. _The dimension of the gap G2 is, for example, about 0.1 mm to 0.5 mm.

The above is a description of various aspects of the sputtering target.

(Composition, crystal structure and physical properties of sputtering target)
Next, the composition and crystal structure of the sputtering target 1 according to the embodiment of the present invention will be described.
The composition and crystal structure of the sputtering target 1 are not particularly limited. However, as the sputtering target 1 according to the present embodiment, an oxidation target with a large linear expansion coefficient and a small thermal conductivity that causes cracking problems during film formation using a magnetic field oscillation type magnetron sputtering apparatus. Sputtering targets comprising sintered bodies are preferred. The oxide sintered body is made of an oxide containing indium element (In), tin element (Sn), and zinc element (Zn), and is sintered containing a spinel structure compound represented by Zn ₂ SnO ₄ body is effective. Further, as the oxide sintered body, In ₂ O ₃ (ZnO) _m [wherein m is an integer of 2-7. ] is more effective.
The crystal structure of the sputtering target can be confirmed by an X-ray diffraction measurement device (XRD).

A hexagonal layered compound composed of indium oxide and zinc oxide is a compound that exhibits an X-ray diffraction pattern attributed to a hexagonal layered compound as measured by an X-ray diffraction method. Specifically, it is a compound represented by In ₂ O ₃ (ZnO) _m . m in the formula is an integer of 2-7, preferably 3-5. When m is 2 or more, the compound has a hexagonal layered structure, and when m is 7 or less, the volume resistivity can be lowered.
In the oxide sintered body, the atomic ratio of each element preferably satisfies the following formula (7).
0.40≦Zn/(In+Sn+Zn)≦0.80 (7)

When Zn/(In+Sn+Zn) is 0.4 or more, a spinel phase is likely to occur in the oxide sintered body when the film is formed by sputtering, and the characteristics as a semiconductor can be easily obtained. If 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, a decrease in mobility of the oxide semiconductor film can be suppressed. Zn/(In+Sn+Zn) is more preferably 0.50 or more and 0.70 or less.
In the oxide sintered body, the atomic ratio of each element preferably satisfies the following formula (8).
0.15≦Sn/(Sn+Zn)≦0.40 (8)

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, which causes abnormal discharge during sputtering, can be suppressed in the oxide sintered body. Further, when Sn/(Sn+Zn) is 0.40 or less, an oxide semiconductor film formed using a sputtering target can be easily etched with a weak acid such as oxalic acid. When Sn/(Sn+Zn) is 0.15 or more, the etching rate can be prevented from becoming too fast, and the etching can be easily controlled. Sn/(Sn+Zn) is more preferably 0.15 or more and 0.35 or less.

In the oxide sintered body, the atomic ratio of each element preferably satisfies the following formula (9).
0.10≦In/(In+Sn+Zn)≦0.35 (9)
By setting In/(In+Sn+Zn) to be 0.10 or more, the bulk resistance of the obtained sputtering target can be lowered. In addition, the mobility of the oxide semiconductor film can be prevented from being extremely low. If In/(In+Sn+Zn) is 0.35 or less, it is possible to suppress the film from becoming a conductor when the film is formed by sputtering, and it becomes easy to obtain characteristics as a semiconductor. In/(In+Sn+Zn) is more preferably 0.10 or more and 0.30 or less.

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

Next, physical properties of the oxide sintered body contained in the sputtering target will be described.

The oxide sintered body preferably has an average value of 30 bending strengths of 320 MPa or less, more preferably 300 MPa or less.
The oxide sintered body preferably has a minimum bending strength of 200 MPa or less, more preferably 180 MPa or less, at 30 points.
The bending strength of the oxide sintered body is measured by uniformly cutting out test pieces of 3 mm × 4 mm × 40 mm from one tile of the oxide sintered body and performing a three-point bending test in accordance with JIS R 1601. can. The bending strength was measured for 30 test pieces, and the average and minimum values were calculated.

The oxide sintered body preferably has a coefficient of linear expansion of 7.50×10 ⁻⁶ /K or more, more preferably 7.7×10 ⁻⁶ /K or more.
The linear expansion coefficient of the oxide sintered body can be measured according to the JIS R 1618 method at a measurement temperature of 30° C. to 500° C., a heating rate of 10 K/min, and an atmospheric atmosphere.

The oxide sintered body preferably has an elastic modulus of 150 GPa or more, more preferably 155 GPa.
The elastic modulus of the oxide sintered body can be measured in accordance with JIS R 1602 using an ultrasonic flaw detector at room temperature in the air.

The oxide sintered body preferably has a thermal conductivity of 6.5 (W/m/K) or less, more preferably 6.0 (W/m/K) or less.
Regarding the thermal conductivity of the oxide sintered body, the specific heat capacity is measured by the laser flash method (room temperature, in a vacuum), and the thermal diffusivity is measured by the laser flash method (room temperature, in the air) in accordance with the JIS R 1611 method. The thermal conductivity was calculated from the following formula.
λ (thermal conductivity) = Cp (specific heat capacity) x ρ (density) x α (thermal diffusivity)
ρ is the density of the oxide sintered body.

The density of the oxide sintered body was calculated from the dimensions and weight of the thermal conductivity measurement sample.
In the oxide sintered body, (linear expansion coefficient×elastic modulus)/thermal conductivity is preferably 200 Pa/W or more, more preferably 220 Pa/W or more.

The above is the description of the composition, crystal structure and physical properties of the sputtering target 1 according to the embodiment of the present invention.
The descriptions of the composition, crystal structure and physical properties of the sputtering target 1 are also applicable to the sputtering targets according to the second and third aspects.

(Method for Forming Oxide Semiconductor Film)
Next, a method for forming an oxide semiconductor film using the sputtering target 1 according to this embodiment will be briefly described.
A film forming method is not particularly limited. However, the sputtering target 1 is suitable for film formation using a magnetic field oscillation type magnetron sputtering device as a film formation device.
Specifically, film formation is performed so that the oscillation direction of the magnetic field M is the X direction, and the ends of the magnetic field M in the Y direction are positioned from the inner region 9A to the end region 7A and from the inner region 9B to the end region 7B. conduct. According to this method, since the plasma is concentrated in the inner regions 9A and 9B where the plate thickness _t2 is the thickest, the target life can be ensured. Furthermore, according to this method, since the thermal stress is highest in the end regions 7A and 7B, which are thinner than the inner regions 9A and 9B, cracking can also be prevented.
The above is the description of the method for forming an oxide semiconductor film using the sputtering target 1 according to the present embodiment.
The description of the method for forming an oxide semiconductor film using the sputtering target 1 can also be applied to the sputtering targets according to the second and third aspects.

Thus, according to this embodiment, the plate-like oxide sintered body 3 having the end regions 7A, 7B and the inner regions 9A, 9B arranged in the Y direction is provided, and t ₁ , L ₁ , and t ₂ satisfies equations (1) to (4).
Therefore, cracks during film formation can be prevented without extremely shortening the target life.

The present invention will be described in detail below based on examples. However, the present invention is not limited to the examples.

(Preliminary test)
First, as a preliminary test, a case where a known ITZO-based sputtering target was used for magnetron sputtering was simulated, and the relationship between the stress distribution and the erosion region was calculated. The specific procedure is as follows.

First, as a sputtering target, a known ITZO-based sputtering target 1A shown in FIG. 13 was assumed. This sputtering target 1A differs from the sputtering target 1 shown in FIG. 1 in that it has comparative end regions 31 at its ends corresponding to the combined regions of the end regions 7A, 7B and the inner regions 9A, 9B. The sputtering target 1A has a density of 6.39 g/cm ³ , a Poisson's ratio of 0.28, an elastic modulus (E) of 158 GPa, a linear expansion coefficient (α) of 7.7×10 ⁻⁶ /K, and a thermal conductivity (λ ) was 4.87 W/m/K, and the specific heat was 416 J/kg/°C.

As the dimensions of the sputtering target 1A, the total length L _x in the X direction is 272 mm, the total length LY in the _Y direction is 2525 mm, the plate thickness t ₂ of the comparison end region 31 is 9 mm, and the length in the Y direction of the comparison end region 31 is 200 mm, and the plate thickness t3 of the intermediate region 11 was ₆ mm.

Assuming a magnetic field M that forms a loop with a maximum length in the X direction of 232 mm and a maximum length in the Y direction of 2576 mm for this sputtering target 1A, the magnetic field M is 0.1 mm / s between both ends in the X direction. was reciprocated (oscillated).

The sputtering power was 16 kW, and the heat transfer coefficient was 5800 W/m ² /K.

After holding for 2000 seconds under these conditions, the temperature difference in the plate thickness direction of the sputtering target 1A is calculated by the finite element method, the thermal stress is obtained using the formulas (A) and (B), and the relative distribution is calculated. bottom.
Thermal stress (σ) = -E x α x ΔT (A)
ΔT=[Q×d/A]/λ (B)
The symbols in the formulas (A) and (B) are explained below.
E: Elastic modulus of sputtering target (GPa)
α: Linear expansion coefficient of the sputtering target (10 ^-6 /K)
ΔT: temperature difference (K) between the front and back sides of the sputtering target in the plate thickness direction
Q: Amount of heat (W) that passes from the front to the back of the sputtering target in the plate thickness direction
d: Plate thickness of sputtering target (mm)
A: Area of sputtering target viewed from plate thickness direction (mm ² )
λ: Thermal conductivity of sputtering target (W/m/K)

Preliminary test results are shown in FIG.
As shown in FIG. 13, the regions with the highest thermal stress were the ends in the Y direction.

(Power resistance and life test 1)
From the results of preliminary tests, the present inventors found that if the plate thickness of the Y-direction end where the thermal stress is highest is reduced, the thermal stress can be reduced, and cracking can be prevented without extremely shortening the target life. I thought it might be.

Therefore, as shown in FIG. 1, a sputtering target 1 having a plate thickness t ₁ smaller than the plate thickness t ₂ and having the same other dimensions as those in the preliminary test was prepared (sample number 2), and was used in an actual magnetron sputtering apparatus. , power resistance and target life were measured under the same conditions as the preliminary test. L1 was _{15 mm} and L2 was 185 mm.

Power tolerance is the maximum sputtering power that does not crack the sputtering target. It was determined that a crack occurred when arcing occurred in the sputtering target.
The life is obtained by multiplying the power resistance by the time required for the remaining thickness of the sputtering target to reach 1 mm (here, the unit is [hr]), and the life of the sputtering target under the same conditions as in the preliminary test is It was set as a ratio when it is set to 100%.
Table 1 shows the results. Table 1 also shows, as a comparative example, the case where the thickness of the sputtering target was made uniform to 6 mm (Sample No. 3). The preliminary test sputtering target is shown in Table 1 as Sample No. 1.

As shown in Table 1, it was found that the examples can improve the power resistance more than the preliminary test without shortening the life. From this result, it was suggested that thinning the plate thickness at the end in the Y direction enables high-density film formation without shortening the life.

(Erosion depth distribution measurement)
Next, 100 hours after the start of the test of "Sample No. 2" in order to investigate whether the depth and position of wear of the sputtering target are affected by reducing the plate thickness of the end in the Y direction. The distribution of the erosion depth in the Y direction was measured for the samples after the passage of time.
The measurement area is three locations parallel to the Y direction (50 mm, 136 mm, and 222 mm in the X direction from the upper end of FIG. 13, and the X direction positions are described as 4, 5, and 6 in FIG. 14), and the actual measurement is performed at three locations. values, and average values.
The results are shown in FIG. The “Y-direction position” on the horizontal axis of FIG. 14 means the position in the Y-direction when the left end in the Y-direction is 0.
As shown in FIG. 14, the region with the deepest erosion depth was the inner region of more than 15 mm and 30 mm or less from the end in the Y direction. This is within the inner regions 9A, 9B. In addition, the region of 15 mm or less from the end in the Y direction had a wear depth of 75% or less of the maximum erosion depth, and most of them were 50% or less.

From this result, it was found that the region with the highest thermal stress is different from the region with the highest erosion depth. Therefore, as described in Patent Documents 7 and 8, even if the region with the deepest erosion depth is divided, it has been found that the prevention of cracks due to thermal stress is insufficient.
Further, from this result, it can be seen that while the end regions 7A and 7B have the highest thermal stress, the erosion depth is shallower _than that of the inner regions 9A and 9B. I found it difficult.

(Optimization of L ₁ , t ₁ and t ₂ )
Next, in order to specify the range of L ₁ , t ₁ and t ₂ that can improve the power resistance without extremely shortening the life, L ₁ , t ₁ and t ₂ in sample number 2 A changed sputtering target was produced, and the other conditions were the same as those of sample number 2, and the power durability and life were evaluated. A life of 80% or more was regarded as passing. A power tolerance of 10 kW or more was considered acceptable. Table 2 shows the results. In Table 2, "A" indicates the case where the formulas (1) to (4) are satisfied, and "B" indicates the case where the formulas (1) to (4) are not satisfied.

As shown in Table 2, power resistance and life were acceptable when all of formulas (1) to (4) were satisfied.
In addition, among the sputtering targets with acceptable power resistance and life, the sputtering targets satisfying the range of 0.6<t ₁ /t ₂ <0.8 (sample numbers 8, 9, and 13) had power resistance of was higher.

(Power resistance and life test 2)
As shown in FIG. 12, an ITZO-based sputtering target having slopes on the rear surfaces of the end regions 7A and 7B and the inner regions 9A and 9B and satisfying the dimensions shown in Table 3 was produced. The tilt angle and dimensions other than those shown in Table 3 were prepared in the same manner as in the preliminary test described above.
The power durability and target life (life) of the produced sputtering targets were measured using an actual magnetron sputtering apparatus under the same conditions as in the preliminary test.

The power resistance and target life (life) of the sputtering targets of the sample numbers shown in Table 3 were evaluated using the same evaluation criteria as in "Power Resistance and Life Test 1" described above. Evaluation results are shown in Tables 3 and 4. As sample number 28, a sample having an inclination angle of 0° and the back surface of the end region not being inclined was used.
In Table 3, "A" indicates the case where the formulas (11) to (16) are satisfied, and "B" indicates the case where the formulas (11) to (16) are not satisfied.

As shown in Tables 3 and 4, as in sample numbers 23 to 27, the back surface of the end region has a downward slope toward the inside from the end of the oxide sintered body, and the formula (12) By satisfying the relationship, the power resistance and target life (life) were passed. Furthermore, as in Sample Nos. 26 and 27, the inclination angle of the end region was 10 degrees or more and 12 degrees or less, so that the target life was improved.

DESCRIPTION OF SYMBOLS 1... Sputtering target 3... Oxide sintered compact 5... Backing plate 7A, 7B... End area 9A, 9B... Inner area 11... Intermediate area 13... Main body 13A... Holding surface 15... Convex Parts 17A, 17B... Spacers 21A, 23A, 25A... Front surfaces 21B, 23B, 25B... Back surfaces.

Claims (27)

comprising a plate-shaped oxide sintered body , a backing plate, and a spacer ,
The oxide sintered body has a plurality of regions arranged in a first direction,
The plurality of regions are
an end region that is a region including the end in the first direction;
an inner region that is the second region on the inner side counting from the end in the first direction;
an intermediate region that is the third region on the inner side counting from the end in the first direction;
has
The backing plate has a holding surface that holds the oxide sintered body, and a convex portion that protrudes from the holding surface and holds the intermediate region,
the spacer is provided between the holding surface and the end region;
When the plate thickness of the end region is t1, the width of the end region in the _first direction is _L1 , the plate thickness of the inner region is t2 _, and the thickness of the intermediate region is t3 , _{t 1} , L ₁ , and t ₂ satisfy the following equations (1), (2), (3A), and (4A), and t ₁ , t ₂ , and t ₃ satisfy the following equations (6 ),
sputtering target.
t ₂ > t ₁ (1)
t ₁ (mm)>L ₁ (mm)×0.1+4 (2)
t1 ( _mm ) < 8.5 (3A)
12.5≦L ₁ (mm)≦32.5 (4A)
t2 >t1 _> t3 _{( 6} ) Furthermore, t ₁ and t ₂ satisfy the following equation (5),
A sputtering target according to claim 1 .
0.6<t1 _/ t2<0.8 ( ₅ ) In the oxide sintered body, the plurality of regions are arranged separately from each other,
A sputtering target according to claim 1 or 2 . The oxide sintered body has a rectangular planar shape, and the first direction is the long side direction of the rectangle,
A sputtering target according to any one of claims 1 to 3 . The oxide sintered body has a rectangular long side of 2300 mm or more and 3800 mm or less, a short side of ₂₀₀ mm or more and 300 mm or less, a plate thickness t2 of the inner region of 9 mm or more and 15 mm or less, and L1 of more than ₁₀ mm and 35 mm. less than, the width of the inner region in the first direction is 170 mm or more and 300 mm or less,
A sputtering target according to claim 4 . a plate-shaped oxide sintered body;
a backing plate holding the oxide sintered body;
a spacer provided between the oxide sintered body and the backing plate,
The oxide sintered body has a plurality of regions arranged in a first direction,
The plurality of regions are
an end region that is a region including the end in the first direction;
an inner region that is the second region on the inner side counting from the end in the first direction;
an intermediate region that is the third region on the inner side counting from the end in the first direction ;
The backing plate has a holding surface that holds the end region and the inner region, and a convex portion that protrudes from the holding surface and holds the intermediate region ,
the spacer is provided between the holding surface and the end region to hold the end region;
The end region has a back surface facing the holding surface,
a rear surface of the end region is inclined with respect to the holding surface;
The slope of the back surface of the end region is a downward slope inward from the end of the oxide sintered body,
The inner region has a back surface facing the holding surface,
a portion of the back surface of the inner region is inclined with respect to the holding surface;
The inclination of the back surface of the inner region is downward from the end of the oxide sintered body toward the inside,
Let _t11 be the maximum value of the plate thickness of the end regions, t12 be the plate thickness of the inner region where the plate thickness is not inclined on the back surface of the inner region, and t12 be the plate thickness of _the intermediate region. is t ₁₃ and the width of the end region in the first direction is L ₁₁ , t ₁₁ and L ₁₁ satisfy the following equation (12), and t ₁₁ , t ₁₂ and t ₁₃ satisfies the following equation (18):
sputtering target.
t ₁₁ (mm)>L ₁₁ (mm)×0.1+4 (12)
t12 > _t11 > t13 _{( 18} ) The angle formed by the back surface of the end region and the holding surface is 4 degrees or more and 15 degrees or less.
A sputtering target according to claim 6 . Let _t15 be the minimum value of the plate thickness of the end region ,
When L13 is the width of the inner region and the width _in the first direction of the region inclined on the back surface of the inner region,
t ₁₁ , t ₁₂ , t ₁₅ , L ₁₁ , and L ₁₃ satisfy the following equations (11), (13), (14), (15) and (16),
A sputtering target according to claim 6 or 7 .
t12> _t11 >t15 _{( 11} )
t ₁₁ (mm) < 9 (13)
₁₀ <L11 (mm)<35 (14)
t15 (mm)>3 ( ₁₅ )
3<L13 ₍ mm)<35 (16) The sputtering target according to any one of claims 6 to 8 , wherein the oxide sintered body has a rectangular planar shape, and the first direction is a long side direction of the rectangle. The oxide sintered body has a rectangular long side of 2300 mm or more and 3800 mm or less, a short side of 200 mm or more and 300 mm or less, and a plate thickness of the inner region, and the back surface of the inner region is not inclined. The sputtering target according to claim 9 , wherein the plate thickness t12 is ₉ mm or more and 15 mm or less, L11 is more than ₁₀ mm and less than 35 mm, and the width of the inner region in the first direction is 170 mm or more and 300 mm or less. The end region and the inner region are provided at both ends in the first direction,
A sputtering target according to any one of claims 1-10 . The oxide sintered body has a plate shape having two main surfaces, the height difference in the plate thickness direction of one main surface of the plurality of regions is within 100 μm, and the arithmetic mean roughness Ra is smaller than the other major surfaces,
A sputtering target according to any one of claims 1-11 . The oxide sintered body has an average value of 30 bending strengths of 320 MPa or less.
A sputtering target according to any one of claims 1-12 . The oxide sintered body has a minimum bending strength of 200 MPa or less at 30 points.
14. A sputtering target according to claim 13 . The oxide sintered body has a linear expansion coefficient of 7.50 × 10 ^-6 /K or more,
A sputtering target according to any one of claims 1-14 . The oxide sintered body has an elastic modulus of 150 GPa or more,
A sputtering target according to any one of claims 1-15 . The oxide sintered body has a thermal conductivity of 6.5 (W / m / K) or less,
A sputtering target according to any one of claims 1-16 . The sputtering target according to any one of claims 1 to 17 , wherein the oxide sintered body has (linear expansion coefficient x elastic modulus)/thermal conductivity of 200 Pa/W or more. The oxide sintered body is made of an oxide containing indium element (In), tin element (Sn), and zinc element (Zn).
A sputtering target according to any one of claims 1-18 . The oxide sintered body is
including a spinel structure compound represented by Zn ₂ SnO ₄ ,
20. A sputtering target according to claim 19 . The oxide sintered body is
including a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m [m = 2 to 7],
Sputtering target according to claim 19 or 20 . Furthermore, the oxide sintered body satisfies the following formula (7),
A sputtering target according to any one of claims 19-21 .
0.40≦Zn/(In+Sn+Zn)≦0.80 (7) Furthermore, the oxide sintered body satisfies the following formula (8),
A sputtering target according to any one of claims 19-22 .
0.15≦Sn/(Sn+Zn)≦0.40 (8) Furthermore, the oxide sintered body satisfies the following formula (9),
A sputtering target according to any one of claims 19-23 .
0.10≦In/(In+Sn+Zn)≦0.35 (9) Using the sputtering target according to any one of claims 1 to 24 as a target, using a magnetic field oscillation type magnetron sputtering apparatus as a film forming apparatus, and using the magnetic field oscillation direction as the first direction and the plate thickness direction and a second direction perpendicular to the first direction, and the end of the magnetic field in the first direction is positioned in the inner region;
A method for forming an oxide semiconductor film. A backing plate for holding a plate-shaped oxide sintered body,
The oxide sintered body has a plurality of regions arranged in a first direction,
The plurality of regions are
an end region that is a region including the end in the first direction;
an inner region that is the second region on the inner side counting from the end in the first direction;
an intermediate region that is the third region on the inner side counting from the end in the first direction;
has
When the plate thickness of the end region is t1 , the width of the end region in the first direction is L1 _{, the} plate thickness of the inner region is t2 _, and the thickness of the intermediate region is t3 , _{t 1} , L ₁ , and t ₂ satisfy Equations (1), (2), (3A), and (4A) below, and t ₁ , t ₂ , and t ₃ satisfy Equation (6) below The filling,
The backing plate includes a holding surface, a protrusion projecting from the holding surface and holding the intermediate region, and a spacer provided between the holding surface and the end region.
backing plate.
t ₂ > t ₁ (1)
t ₁ (mm)>L ₁ (mm)×0.1+4 (2)
t ₁ (mm) < 8.5 (3A)
12.5≦L ₁ (mm)≦32.5 (4A)
t2 >t1 _> t3 _{( 6} ) the height of the protrusion is higher than the spacer;
27. The backing plate of Claim 26 .

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