TWI565679B - Oxide sintered body and sputtering target - Google Patents

Description

Oxide sintered body and sputtering target

The present invention relates to an oxide sintered body and a sputtering target which can be used for forming an oxide semiconductor film of a thin film transistor (TFT: Thin Film Transistor) used for a display device such as a liquid crystal display or an organic EL display by sputtering. .

An amorphous (amorphous) oxide semiconductor used for a TFT has a high carrier mobility and a large optical band gap as compared with a general-purpose amorphous germanium (a-Si), and can be formed at a low temperature. Therefore, expecting a large size for the request. High resolution. The next generation display with high speed drive or a resin substrate with low heat resistance is applicable. As a composition of an oxide semiconductor suitable for such applications, an amorphous oxide semiconductor containing In is proposed. For example, an In—Ga—Zn-based oxide semiconductor, an In—Ga—Zn—Sn-based oxide semiconductor, an In—Ga—Sn-based oxide semiconductor, and the like are attracting attention.

In the formation of the above oxide semiconductor thin film, a sputtering method in which a sputtering target (hereinafter also referred to as "target material") of the same material as the thin film is sputtered can be suitably used. The sputtering target is used in a state in which the oxide sintered body is bonded to the back sheet, but the oxide sintered body is bonded to the back sheet. In the step, the oxide sintered body is broken.

For example, Patent Document 1 discloses an oxide semiconductor film suitable for the patterning step in the production of a semiconductor element, and an oxide sintered body in which the semiconductor film can be formed, which is 0.10 Å In/(In+ Ga+Sn) ≦0.60, 0.10≦Ga/(In+Ga+Sn)≦0.55, 0.0001<Sn/(In+Ga+Sn)≦0.60 atomic ratio including indium element (In), gallium element (Ga), and A tin element (Sn) and an oxide sintered body containing Ga _3-x In _5+x Sn ₂ O ₁₆ .

Patent Document 2 discloses a technique for reducing abnormal discharge during sputtering, which includes indium element (In), gallium element (Ga), zinc element (Zn), and tin element (Sn), and includes Ga ₂ In ₆ Sn _{2 .} O ₁₆ or (Ga, In) ₂ O ₃ compound, the specific resistance value is 200mΩ. An oxide sintered body of cm.

Further, Patent Document 3 discloses that the sputtering operation is excellent in the increase in the sputtering rate, the prevention of the occurrence of nodules, the prevention of cracking, and the like, and the sputtering of the transparent conductive film having a particularly low resistance can be formed in the low-temperature substrate. The ITO sintered body used for the target and the target material is a high-density ITO sintered body having a sintered density of 90% or more and 100% or less and a sintered particle diameter of 1 μm or more and 20 μm or less.

Prior technical literature Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-174134

Patent Document 2: Japanese Laid-Open Patent Publication No. 2008-280216

Patent Document 3: Japanese Laid-Open Patent Publication No. 05-311428

With the improvement of the performance of display devices in recent years, the characteristics of the oxide semiconductor film are required to be improved or the characteristics are stabilized, and the production of the display device is required to be more efficient. In addition, in consideration of the productivity, the manufacturing cost, and the like, the sputtering target used for the production of the oxide semiconductor thin film for a display device and the oxide sintered body of the material thereof are of course suppressed from being cracked by the sputtering target in the sputtering step. Further, it is further required to suppress the cracking of the oxide sintered body in the joining step.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an oxide sintered body capable of suppressing occurrence of cracking during joining and a sputtering target using the oxide sintered body.

The oxide sintered body of the present invention which is obtained by sintering indium oxide, gallium oxide and tin oxide is characterized in that the relative density of the oxide sintered body is 90% or more. The average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase of the oxide sintered body is 3 μm or less, and the ratio of the coarse crystal grains having a crystal grain size of 10 μm or more in the oxide sintered body is less than 10%. When the ratio (atomic %) of the content of indium, gallium, and tin is set to [In], [Ga], and [Sn] for all the metal elements other than the oxygen contained in the oxide sintered body, the following formula (1) is satisfied. When (3), while the oxide sintered body is X-rayed, the Ga ₃ InSn ₅ O ₁₆ phase satisfies the following formula (4); 35 atomic % ≦ [In] ≦ 50 atom%. . . (1)

20 atom% ≦ [Ga] ≦ 35 atom%. . . (2)

20 atom%<[Sn]≦40 atom%. . . (3)

0.02 ≦ [Ga ₃ InSn ₅ O ₁₆ ] ≦ 0.2. . . (4)

However, [Ga ₃ InSn ₅ O ₁₆ ]=I(Ga ₃ InSn ₅ O ₁₆ )/(I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ))

Wherein I(Ga ₃ InSn ₅ O ₁₆ ), I(Ga ₂ In ₆ Sn ₂ O ₁₆ ), and I(SnO ₂ ) are each a Ga ₃ InSn ₅ O ₁₆ phase, Ga ₂ defined by X-ray diffraction. The diffraction peak intensity of the In ₆ Sn ₂ O ₁₆ phase and the SnO ₂ phase.

In a preferred embodiment of the present invention, when the oxide sintered body is X-ray-diffracted, the Ga ₂ In ₆ Sn ₂ O ₁₆ phase satisfies the following formula (5); 0.8 ≦ [Ga ₂ In ₆ Sn ₂ O ₁₆ ]≦0.98. . . (5)

However, [Ga ₂ In ₆ Sn ₂ O ₁₆ ]=I(Ga ₂ In ₆ Sn ₂ O ₁₆ )/I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ))

Wherein I(Ga ₂ In ₆ Sn ₂ O ₁₆ ), I(Ga ₃ InSn ₅ O ₁₆ ), and I(SnO ₂ ) are each a Ga ₂ In ₆ Sn ₂ O ₁₆ phase defined by X-ray diffraction, The diffraction peak intensity of the Ga ₃ InSn ₅ O ₁₆ phase and the SnO ₂ phase.

Further, the sputtering target of the present invention which solves the above problems is a sputtering target obtained by using the oxide sintered body described in any of the above, and has a specific resistance of 1 Ω. Below cm.

According to the present invention, it is possible to provide an oxide sintered body capable of suppressing occurrence of cracking at the time of joining, and a sputtering target using the oxide sintered body.

Fig. 1A is a photograph showing the presence or absence of black deposits of No. 1 of Example 2.

Fig. 1B is a photograph showing the presence or absence of black deposit of No. 2 of Example 2.

Form of implementing the invention

The present inventors have invented an In-Ga-Sn-based oxide semiconductor thin film (IGTO) having a specific ratio of a metal element to be described later, which is compared with a conventional In-Ga-Zn-based oxide semiconductor thin film (IGZO). An oxide semiconductor thin film having a high carrier mobility and excellent evaluation of the mobility of a TFT has been proposed.

However, in the oxide sintered body of the material of the sputtering target used for the production of the In-Ga-Sn-based oxide semiconductor thin film (IGTO), the oxide sintered body of the bonding step is further suppressed in consideration of productivity, manufacturing cost, and the like. The cracker is also important, so it is necessary to improve the oxide sintered body.

Therefore, the present inventors burned an oxide of a material of an In-Ga-Sn-based sputtering target suitable for forming the above oxide semiconductor thin film. The knot is repeatedly reviewed in order to suppress cracking at the time of joining.

As a result, an oxide sintered body obtained by mixing and sintering indium oxide, gallium oxide, and tin oxide having a ratio of a specific metal element satisfying the following formulas (1) to (3) is found, and (a) an oxide sintered body is obtained. When X-ray diffraction is performed, the ratio of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is preferably controlled by controlling the Ga ₃ InSn ₅ O ₁₆ phase, and the effect of suppressing cracking of the oxide sintered body at the time of bonding is obtained (b) By increasing the relative density of the oxide sintered body, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is refined to suppress the ratio of the coarse crystal grains, and the suppression effect of the crack of the oxide sintered body can be further improved. The invention is achieved.

First, the configuration of the oxide sintered body of the present invention will be described in detail.

In order to form an oxide semiconductor thin film having an effect excellent in TFT characteristics, it is necessary to appropriately control the content of the metal element contained in the oxide sintered body.

Specifically, the ratio (atomic %) of the content of each metal element such as indium, gallium, and tin is set to [In], [Ga], [Sn] for all metal elements other than oxygen contained in the oxide sintered body. At the time, it is controlled so as to satisfy the following formulas (1) to (3).

35 atom% ≦ [In] ≦ 50 atom%. . . (1)

20 atom% ≦ [Ga] ≦ 35 atom%. . . (2)

20 atom%<[Sn]≦40 atom%. . . (3)

The above formula (1) defines the In ratio ([In] = In / (In + Ga + Sn)) in all the metal elements. When [In] is too low, oxygen cannot be reached. The relative density improvement effect of the sintered body or the specific resistance of the sputtering target is reduced, and the carrier mobility of the oxide semiconductor thin film after film formation is also lowered. On the other hand, when [In] is too high, the carrier is formed in addition to the excessive amount of the carrier, and the stability to stress is lowered. Therefore, [In] is 35 atom% or more, preferably 37 atom% or more, more preferably 40 atom% or more, and 50 atom% or less, preferably 47 atom% or less, more preferably 45 atom% or less.

The above formula (2) defines the Ga ratio ([Ga] = Ga / (In + Ga + Sn)) in all the metal elements. [Ga] is an effect of improving the stress resistance, particularly the resistance to light + negative bias stress, in addition to reducing the oxygen deficiency and making the amorphous structure of the oxide semiconductor film stable. On the other hand, when [Ga] is too high, the mobility is lowered. Therefore, [Ga] is 20 atom% or more, preferably 22 atom% or more, more preferably 24 atom% or more, and is 35 atom% or less, preferably 32 atom% or less, and more preferably 29 atom% or less.

The above formula (3) defines the Sn ratio ([Sn] = Sn / (In + Ga + Sn)) in all the metal elements. [Sn] has an effect of improving the chemical resistance of the oxide semiconductor thin film such as wet etching property. However, since the etching rate is slowed as the chemical liquid resistance is improved, if [Sn] is too high, the etching workability is lowered. Therefore, [Sn] is more than 20 atom%, preferably 23 atom% or more, more preferably 25 atom% or more, and 40 atom% or less, preferably 35 atom% or less, more preferably 31 atom% or less.

In the oxide sintered body of the present invention, the metal element is composed of the above ratios of In and Ga and Sn, and does not contain Zn. Implemented as described later As shown in the example, when a film is formed using a conventional IGZO target containing In and Ga and Zn, the composition deviation is increased between the IGZO target and the IGZO film, and Zn and O are formed on the surface of the IGZO target. Black deposits. The black deposit is peeled off from the target surface during sputtering to form particles, which causes arcing or the like, and causes a large problem in film formation.

Here, when the target of IGZO is used, the main reason for the above problem is considered to be because the vapor pressure of Zn is higher than Ga and In. For example, when a film is formed by using a target, in consideration of cost, it is recommended to perform sputtering under an inert atmosphere containing oxygen of a specified partial pressure after performing pre-sputtering only with an inert gas such as argon without oxygen. However, in the above-described pre-sputtering, when Zn is reduced, since the vapor pressure of Zn is high, it is likely to evaporate and adhere to the surface of the target to form a black deposit. As a result, the composition of the target and the film are deviated, and the atomic ratio of Zn in the film is greatly reduced as compared with the target.

The oxide sintered body of the present invention is preferably composed of indium oxide, gallium oxide and tin oxide which satisfy the above-mentioned specified metal element content, and the remainder is an impurity which is inevitably formed in the production of oxides.

Next, a Ga ₃ InSn ₅ O ₁₆ phase detected when the oxide sintered body is X-rayd is described. The Ga ₃ InSn ₅ O ₁₆ phase is an oxide formed by bonding In, Ga, and Sn constituting the oxide sintered body of the present invention. In the oxide sintered body of the present invention, the Ga ₃ InSn ₅ O ₁₆ phase has an effect of suppressing grain growth of Ga ₂ In ₆ Sn ₂ O ₁₆ and suppressing cracking due to stress at the time of bonding.

In order to be an oxide sintered body having such an effect, the peak intensity of the Ga ₃ InSn ₅ O ₁₆ phase defined by the X-ray diffraction must satisfy the following formula (4).

0.02 ≦ [Ga ₃ InSn ₅ O ₁₆ ] ≦ 0.2. . . (4)

However, [Ga ₃ InSn ₅ O ₁₆ ]=I(Ga ₃ InSn ₅ O ₁₆ )/(I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ))

Wherein I(Ga ₃ InSn ₅ O ₁₆ ), I(Ga ₂ In ₆ Sn ₂ O ₁₆ ) and I(SnO ₂ ) are each a Ga ₃ InSn ₅ O ₁₆ phase defined by X-ray diffraction, Ga ₂ The diffraction peak intensity of the In ₆ Sn ₂ O ₁₆ phase and the SnO ₂ phase.

The compound phase is a diffraction peak obtained by X-ray diffraction of an oxide sintered body, and has a crystal structure described in ICDD (International Center for Diffraction Data) card 51-0214, 89-7011, and 41-1445. (each corresponds to a Ga ₃ InSn ₅ O ₁₆ phase, a Ga ₂ In ₆ Sn ₂ O ₁₆ phase, and a SnO ₂ phase).

The present invention is characterized in that when the oxide sintered body is X-ray-diffracted, the Ga ₃ InSn ₅ O ₁₆ phase is contained in a predetermined ratio. When the peak intensity ratio ([Ga ₃ InSn ₅ O ₁₆ ]) of the Ga ₃ InSn ₅ O ₁₆ phase is small, the grain growth suppressing effect of Ga ₂ In ₆ Sn ₂ O ₁₆ is weak, so it is necessary to be 0.02 or more. It is preferably 0.05 or more, more preferably 0.08 or more, and still more preferably 0.1 or more. On the other hand, in the upper limit, since the pinning effect is saturated and the cost is high, it is 0.2 or less, preferably 0.18 or less, and more preferably 0.16 or less.

Further, in the invention of the present invention, when the oxide sintered body is X-ray-diffracted, the Ga ₂ In ₆ Sn ₂ O ₁₆ phase preferably satisfies the following formula (5).

0.8≦[Ga ₂ In ₆ Sn ₂ O ₁₆ ]≦0.98. . . (5)

However, [Ga ₂ In ₆ Sn ₂ O ₁₆ ]=I(Ga ₂ In ₆ Sn ₂ O ₁₆ )/I(Ga ₃ InSn ₅ O ₁₆ )+ I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ))

Wherein I(Ga ₂ In ₆ Sn ₂ O ₁₆ ), I(Ga ₃ InSn ₅ O ₁₆ ), and I(SnO ₂ ) are each a Ga ₂ In ₆ Sn ₂ O ₁₆ phase defined by X-ray diffraction, The diffraction peak intensity of the Ga ₃ InSn ₅ O ₁₆ phase and the SnO ₂ phase.

When the peak intensity ratio ([Ga ₂ In ₆ Sn ₂ O ₁₆ ]) of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is small, cracking of the oxide sintered body at the time of bonding is likely to occur, so it is preferably 0.8 or more. More preferably, it is 0.82 or more, and particularly preferably 0.84 or more. On the other hand, the upper limit is preferably as high as possible from the above viewpoint. However, considering the pinching effect by Ga ₂ In ₆ Sn ₂ O ₁₆ , it is preferably 0.98 or less, more preferably 0.95 or less. Preferably, it is 0.92 or less, and particularly preferably 0.9 or less.

The oxide sintered body of the present invention has a relative density of 90% or more. By increasing the relative density of the oxide sintered body, the crack suppressing effect at the time of joining can be further improved. In order to obtain such an effect, the oxide sintered body of the present invention must have a relative density of at least 90% or more, preferably 95% or more, more preferably 98% or more. The upper limit is not particularly limited and may be 100%, but it is preferably 99% in consideration of the manufacturing cost.

Moreover, in order to further improve the crack suppression effect at the time of joining, it is necessary to refine the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase of the oxide sintered body. Specifically, the oxide sintered body is cut at an arbitrary position in the thickness direction at the fracture surface of the oxide sintered body, and is observed at a position on the surface of the cut surface by a scanning electron microscope (SEM: Scanning Electron Microscope). The average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is 3 μm or less, and the cracking of the oxide sintered body can be further suppressed. The average crystal grain size is preferably 2.8 μm or less, more preferably 2.5 μm or less. On the other hand, the lower limit of the average crystal grain size is not particularly limited. However, from the viewpoint of the balance between the average crystal grain size and the production cost, the preferred lower limit of the average crystal grain size is about 0.1 μm.

Further, in the present invention, it is necessary to appropriately control the particle size distribution. Specifically, since coarse crystal grains having a crystal grain size of 10 μm or more are caused by cracking of the oxide sintered body at the time of joining, it is preferably as small as possible, and the coarse crystal grain system is less than 10%, preferably 8% or less. More preferably, it is 6% or less, and particularly preferably 4% or less, and most preferably 0%.

Next, a suitable production method of the oxide sintered body of the present invention will be described.

The oxide sintering system of the present invention is obtained by mixing and sintering indium oxide, gallium oxide and tin oxide. Further, the sputtering target of the present invention can be produced by processing the above oxide sintered body. Basically, the oxide powder is mixed via (a). Crush → (b) dry. Granulation → (c) preliminary forming → (d) degreasing → (e) an oxide sintered body obtained by atmospheric sintering, and (f) processing → (g) bonding to obtain a sputtering target. Among the above steps, the present invention is characterized in that the (e) sintering conditions are appropriately controlled as described in detail below, and the other steps are not particularly limited, and a commonly used step can be appropriately selected. Hereinafter, each step will be described, but the present invention is not limited thereto.

1. First, indium oxide powder, gallium oxide powder and tin oxide powder are blended and mixed in a specified ratio. Smash. The purity of each of the raw material powders used is preferably about 99.99% or more. This is because if trace impurities The presence of an element may impair the semiconductor characteristics of the oxide semiconductor thin film. The blending ratio of each raw material powder is preferably controlled within the above range.

(a) Mixing. The pulverization is preferably carried out by using a ball mill or a bead mill to feed the raw material powder together with water. For the balls or beads used in these steps, for example, a material such as nylon, alumina, zirconia or the like is preferably used. At this time, the binder may be mixed for the purpose of uniform mixing, or the binder may be mixed in order to ensure the ease of the subsequent molding step. The mixing time is preferably 2 hours or longer, more preferably 10 hours or longer, and particularly preferably 20 hours or longer.

Next, for the mixed powder obtained in the above step, for example, it is preferably dried by a spray dryer or the like (b). Granulation.

For drying. After granulation, (c) preliminary forming is performed. When forming, it will dry. The granulated powder is filled in a mold of a predetermined size, and pre-formed by pressurization of the mold. This preliminary molding is performed for the purpose of improving the handleability, and a molded body may be formed by applying a pressing force of about 49 to 98 MPa. The obtained preliminary forming system was formally formed by cold hydrostatic pressurization (CIP: Cold Isostatic Pressing). In order to increase the relative density of the sintered body, the pressure at the time of forming is preferably controlled to be 98 to 490 MPa.

Further, when a dispersant or a binder is added to the mixed powder, in order to remove the dispersant or the binder, the formed body is preferably heated to perform (d) degreasing. The heating condition is not particularly limited as long as it can achieve the purpose of degreasing, and for example, it can be kept at about 500 ° C for about 5 hours in the air.

After degreasing, the formed body is fixed to a molding die in such a manner as to obtain a desired shape, and (e) sintered under atmospheric sintering. In the present invention, after the molded body is heated to a sintering temperature of 1400 to 1550 ° C, the temperature is maintained for 1 to 50 hours. By sintering in the temperature range and the holding time, the compound phase satisfying the above formulas (1) to (3) is obtained, and the Ga ₃ InSn ₅ O ₁₆ phase satisfying the above formula (4) is preferably satisfied. A ratio of a Ga ₂ In ₆ Sn ₂ O ₁₆ phase of the formula (5) to a sintered body having a suitable particle diameter. When the sintering temperature is low, a Ga ₃ InSn ₅ O ₁₆ phase satisfying the above formula (4) and a Ga ₂ In ₆ Sn ₂ O ₁₆ phase satisfying the above formula (5) cannot be produced. Further, the oxide sintered body cannot be sufficiently densified, and the desired relative density cannot be achieved. On the other hand, when the sintering temperature is too high, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase or the crystal grains of the oxide sintered body is coarsened, and the Ga ₂ In ₆ Sn ₂ O ₁₆ phase cannot be obtained. The average crystal grain size or the average crystal grain size of the crystal grains of the oxide sintered body is controlled within a specified range. Therefore, the sintering temperature is preferably 1400 ° C or higher, more preferably 1425 ° C or higher, particularly preferably 1450 ° C or higher, and preferably 1550 ° C or lower, more preferably 1525 ° C or lower.

In addition, when the holding time of the sintering temperature is too long, the crystal grains grow and coarsen, and the average crystal grain size of the crystal grains cannot be controlled within a predetermined range. On the other hand, if the holding time is too short, the above-mentioned Ga ₃ InSn ₅ O ₁₆ phase cannot be formed within the above ratio, and the above Ga ₂ In ₆ Sn ₂ O ₁₆ phase is preferable, and the density cannot be sufficiently densified. Therefore, the holding time is preferably 0.1 hour or longer, more preferably 0.5 hour or longer, and is preferably 5 hours or shorter.

Further, in the present invention, after the forming, the above sintering temperature is The average temperature increase rate before is preferably 100 ° C / hour or less. When the average temperature increase rate exceeds 100 ° C / hour, abnormal growth of crystal grains occurs, and the ratio of coarse crystal grains becomes high. Also, the relative density cannot be sufficiently increased. A more preferable average temperature increase rate is 75 ° C / hour or less, and particularly preferably 50 ° C / hour or less. On the other hand, the lower limit of the average temperature increase rate is not particularly limited, but from the viewpoint of productivity, it is preferably 10 ° C /hr or more, more preferably 20 ° C / h or more.

Furthermore, in the present invention, it is recommended to temporarily hold it during the process of raising the temperature to the above-mentioned sintering temperature at the above average temperature increase rate. Specifically, it is preferably maintained in a temperature range of 1100 ° C to 1300 ° C for 1 hour or more and 10 hours or less. By maintaining the specified time in this temperature range, the formation of the above Ga ₃ InSn ₅ O ₁₆ phase can be promoted to form the above ratio. Moreover, by temporarily holding, the growth of the crystal grains of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase can be suppressed. The lower limit of the temperature at the time of temporary holding (pre-sintering temperature) is more preferably 1120 ° C or more, and particularly preferably 1140 ° C or more. Further, the upper limit of the above temperature is more preferably 1270 ° C or lower, particularly preferably 1250 ° C or lower, and more preferably 1200 ° C or lower.

In the sintering step, the sintering environment is preferably an oxygen atmosphere such as an atmospheric environment or an oxygen-pressurized environment. Further, the pressure of the ambient gas is preferably atmospheric pressure. The oxide sintered system obtained as described above has a relative density of 90% or more.

After the oxide sintered body is obtained as described above, the sputtering target of the present invention is obtained by (f) processing → (g) bonding by a usual method. The processing method of the oxide sintered body is not particularly limited and can be Well known methods are processed into shapes that conform to various uses.

A sputtering target can be manufactured by bonding a processed oxide sintered body to a backing plate by a bonding material. The material type of the back sheet is not particularly limited, but is preferably pure copper or a copper alloy excellent in thermal conductivity. The type of the bonding material is not particularly limited, and various well-known bonding materials having conductivity can be used. For example, an In-based welding material, a Sn-based welding material, or the like can be exemplified. The bonding method is not particularly limited. For example, the oxide sintered body and/or the back sheet may be heated to a temperature at which the bonding material is dissolved, for example, dissolved at about 140 to 220 ° C, and the dissolved bonding material may be applied to the bonding of the back sheet. The surfaces are bonded to the respective joint faces, and the two are pressed together to be cooled.

The sputtering target obtained by using the oxide sintered body of the present invention is not broken by the stress or the like generated during the bonding operation, and the specific resistance is also very good, preferably 1 Ω. Below cm, more preferably 10 ^-1 Ω. Below cm, especially preferably 10 ^-2 Ω. Below cm. When the sputtering target of the present invention is used, the abnormal discharge during sputtering and the cracking of the sputtering target can be further suppressed by the film formation system, and the physical use of the sputtering target can be efficiently performed in the production line of the display device. Evaporation. Further, the obtained oxide semiconductor film also showed good TFT characteristics.

Example

The present invention will be more specifically described by the following examples, but the present invention is not limited by the following examples, and may be appropriately modified and implemented in the scope of the invention. Within the technical scope of the invention.

Example 1 (production of sputtering target)

Indium oxide powder (InO _1.5 ) having a purity of 99.99%, gallium oxide powder (GaO _1.5 ) having a purity of 99.99%, and tin oxide powder (SnO ₂ ) having a purity of 99.99% were blended at a mass ratio and an atomic ratio shown in Table 1, Water and a dispersing agent (ammonium polycarboxylate) were added and mixed in a nylon ball mill for 24 hours. Next, the mixed powder obtained in the above step is dried and granulated.

The powder thus obtained was pressurized with a mold, and after preliminary molding under the following conditions, it was subjected to formal molding by a CIP at a molding pressure of 294 MPa.

(conditions for preparation)

Forming pressure: 98MPa

When the thickness is set to t, the size of the formed body is Φ110mm×t13mm

The molded body thus obtained was fixed in a sintering furnace and sintered under the conditions shown in Table 2. The obtained oxide sintered body was machined and processed into Φ100 mm×t5 mm. After the oxide sintered body and the Cu back sheet were heated to 180 ° C for 20 minutes, the oxide sintered body was bonded to the back sheet using a bonding material (indium) to prepare a sputtering target.

(Measurement of relative density)

The relative density is a fracture surface of the oxide sintered body, that is, the oxide sintered body is cut at an arbitrary position in the thickness direction, and the surface of the cut surface is mirror-polished, and is measured by a scanning electron microscope (SEM). The porosity is obtained. Take 1000 times photography, at 50μm square The area ratio of the pores is measured as the porosity. The average of 20 pieces was taken as the average porosity of the sample, and [100-average porosity] was taken as the average relative density. A relative density of 90% or more was evaluated as acceptable. The results are shown in the column "Relative density (%)" in Table 4.

(average crystal grain size of Ga ₂ In ₆ Sn ₂ O ₁₆ phase)

The average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is obtained by mirror-polishing the fracture surface of the oxide sintered body, and photographing the structure by a scanning electron microscope (SEM) at a magnification of 400 times, and drawing 100 μm in any direction. The straight line of the length, the sum (L) and the number (N) of the lengths of the crystal grains of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase contained in the straight line are obtained, and the value calculated from [L/N] is This "average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase on a straight line" was made. In the same manner, 20 straight lines are formed at intervals (at least 20 μm or more) in which the coarse crystal grains are not repeated, and the average particle diameter on each straight line is calculated, and the total average crystal grain size on each straight line is calculated. The value calculated by /20] is taken as "the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase". The Ga ₂ In ₆ Sn ₂ O ₁₆ phase system was identified by energy dispersive X-ray spectrometry (EDS: Energy dispersive X-ray spectrometry) based on data of elemental ratio and X-ray diffraction, and Ga ₂ In was determined. ₆ Sn ₂ O ₁₆ phase average crystal grain size. In the present embodiment, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase was 3 μm or less, which was evaluated as acceptable. The results are shown in the column of "Ga ₂ In ₆ Sn ₂ O ₁₆ average particle diameter (μm)" in Table 4.

(ratio of coarse crystal grains)

The ratio of the coarse crystal grains is the same as the average crystal grain size of the above Ga ₂ In ₆ Sn ₂ O ₁₆ phase, and the fracture surface of the oxide sintered body is observed by SEM, and a straight line of a length of 100 μm is drawn in an arbitrary direction. Crystal grains having a length of 10 μm or more cut on the straight line are regarded as coarse crystal grains. The length L of the coarse crystal grains on the straight line (the sum of the complex crystals: μm) is obtained, and the value calculated from [L/100] is taken as the "ratio of the coarse crystal grains on the straight line" (%) ). Further, 20 lines are formed at intervals (at least 20 μm or more) in which coarse crystal grains are not repeated, and the ratio of coarse crystal grains on each straight line is calculated, and at the same time, the coarse crystal grains on each straight line are The calculated value of the total of the ratios is regarded as "the ratio of the coarse crystal grains of the oxide sintered body" (%). The ratio of the coarse crystal grains of the oxide sintered body to less than 10% was evaluated as acceptable. The results are shown in the column "Proportion (%) of coarse crystal grains" in Table 4.

(ratio of Ga ₃ InSn ₅ O ₁₆ phase and Ga ₂ In ₆ Sn ₂ O ₁₆ phase)

The ratio of the crystal phase was after the sputtering, the sputtering target was removed from the back sheet, and a test piece of 10 mm square was cut out, and the intensity (diffraction peak) of the ray was measured by X-ray diffraction under the following conditions.

Analysis device: "X-ray diffraction device RINT-1500" manufactured by Rigaku Motor Co., Ltd.

Analysis conditions:

Target: Cu

Monochromatization: using a monochromator (Kα)

Target output: 40kV-200mA

(continuous burning measurement) θ/2θ scanning

Slit: divergence 1/2°, scattering 1/2°, light receiving 0.15 mm

Monochromator light receiving slit: 0.6mm

Scanning speed: 2°/min

Sampling width: 0.02°

Measuring angle (2θ): 5~90°

For the diffraction peak obtained by this measurement, the peak of each crystal phase was identified based on the ICDD card, and the height of the diffraction peak was measured. The peaks of these crystals are selected such that the diffraction intensity of the phase of the crystal is sufficiently high, and the peaks of the other crystal phases are as small as possible. The measured values of the peak heights of the designated peaks of the respective crystal phases are respectively regarded as I (Ga ₃ InSn ₅ O ₁₆ ), I (Ga ₂ In ₆ Sn ₂ O ₁₆ ), and I (SnO ₂ ) ([I] means X The peak intensity ratio of [Ga ₃ InSn ₅ O ₁₆ ] and [Ga ₂ In ₆ Sn ₂ O ₁₆ ] was determined by the following formula.

[Ga ₃ InSn ₅ O ₁₆ ]=I(Ga ₃ InSn ₅ O ₁₆ )/(I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ))

[Ga ₂ In ₆ Sn ₂ O ₁₆ ]=I(Ga ₂ In ₆ Sn ₂ O ₁₆ )/I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO ₂ ) )

When [Ga ₃ InSn ₅ O ₁₆ ] was 0.02 or more and 0.2 or less, it was evaluated as a pass. Further, it was evaluated that [Ga ₂ In ₆ Sn ₂ O ₁₆ ] was 0.8 or more and 0.98 or less. The results are shown in the column of "Ga ₃ InSn ₅ O ₁₆ intensity ratio" and "Ga ₂ In ₆ Sn ₂ O ₁₆ intensity ratio" in Table 4.

(rupture at the time of joining)

After the above-described mechanically sintered oxide sintered body was heated and joined to the back sheet, it was visually confirmed whether or not the surface of the oxide sintered body was cracked. When a crack of more than 1 mm was observed on the surface of the oxide sintered body, it was judged that "crack" occurred. The bonding operation was performed 10 times, and it was evaluated as a failure when it was once broken ("Yes"), and it was evaluated as "No" when there was no one failure. The results are shown in the column "Broken at the time of joining" in Table 4.

(specific resistance)

The specific resistance value was measured by a four-probe method using a resistivity meter of Loresta GP (MCP-T610 type manufactured by Mitsubishi Chemical Corporation) using Φ100 mm × t5 mm after machining. The specific resistance is 1Ω. Below cm is considered qualified. The results are shown in the column of "specific resistance value (Ω.cm)" in Table 4.

The results of these are collectively shown in Table 4. In the far right column of Table 4, the column of comprehensive evaluation is set, and all the above-mentioned evaluation items are marked as OK, and any one of the unqualified ones is attached with NG.

Sample Nos. 1 to 7 satisfying the preferred composition and production conditions of the present invention were not required to be sputtered, and the target was not broken at the time of bonding. Moreover, the relative density and specific resistance of the sputtering target thus obtained also gave good results.

On the other hand, samples No. 8 to 9 which did not satisfy the composition of the present invention and samples No. 10 to 12 which did not satisfy the manufacturing conditions were broken at the sputtering target at the time of bonding. Therefore, in these examples, bonding is performed under bonding conditions in which the sputtering target does not break, and the specific resistance is measured using a sputtering target that does not cause cracking.

Sample No. 8 is an example in which the steel composition f of Table 1 which is low in [Sn] and does not satisfy the requirements of the present invention is used for the composition of the oxide sintered body. As a result, in this example, the relative density was low, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase was large, and the ratio of the coarse crystal grains was high, and the Ga ₃ InSn ₅ O ₁₆ phase was not formed. In this example, cracking occurred in the oxide sintered body at the time of joining. Moreover, the specific resistance is also high.

Sample No. 9 is an example in which the composition of the oxide sintered body is a steel type g of Table 1 which is low in [In] and does not satisfy the requirements of the present invention. As a result, in this example, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is large, and the ratio of the coarse crystal grains is high, and the peak intensity ratio of the Ga ₃ InSn ₅ O ₁₆ phase is too high. In this example, cracking occurred in the oxide sintered body at the time of joining. Moreover, the specific resistance is also high.

The composition of the sample No. 10 oxide sintered body was an example in which the steel type a of Table 1 which satisfies the requirements of the present invention was used, but the holding temperature at the time of sintering was high. In this example, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is large. In this example, cracking occurred in the oxide sintered body at the time of joining.

The composition of the sample No. 11 oxide sintered body was an example in which the steel type a of Table 1 which satisfies the requirements of the present invention was used, but the holding temperature at the time of sintering was low. In this example, the relative density is low, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is large, and the ratio of the coarse crystal grains is high. In this example, cracking occurred in the oxide sintered body at the time of joining. Moreover, the specific resistance is also high.

The composition of the sample No. 12-based oxide sintered body was an example in which the steel type a of Table 1 which satisfies the requirements of the present invention was used, but the temperature was raised before the sintering temperature without being temporarily held. In this example, the average crystal grain size of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase is large, and the ratio of the coarse crystal grains is high, and the peak intensity ratio of the Ga ₃ InSn ₅ O ₁₆ phase is too low. In this example, cracking occurred in the oxide sintered body at the time of joining.

Example 2

In the present example, in order to confirm the usefulness of the In-Ga-Sn oxide sintered body (IGTO) defined by the present invention, the following experiment was carried out in comparison with the conventional In-Ga-Zn oxide sintered body (IGZO). .

First, the target of No. 1 of Table 4 of the above-mentioned Example 1 was used, and pre-sputtering and sputtering of the main film before the film formation were performed under the following conditions, and the oxide semiconductor film was applied to the glass substrate. Film formation. For reference, in the No. 1 of Table 5, the composition of the target of No. 1 of the above Table 4 (the same as the component No. a of Table 1) is described together.

Sputtering device: ULVAC system "CS-200"

DC (direct current) magnetron sputtering

Substrate temperature: room temperature

(1) Pre-sputtering

Air pressure: 1mTorr

Oxygen partial pressure: 100 × O ₂ / (Ar + O ₂ ) = 0% by volume

Film forming power density: 2.5W/cm ²

Pre-sputter time: 10 minutes

(2) Formal film formation

Air pressure: 1mTorr

Oxygen partial pressure: 100 × O ₂ / (Ar + O ₂ ) = 4 vol%

Film forming power density: 2.5W/cm ²

Film thickness: 40nm

For comparison, an oxide semiconductor thin film was formed under the same conditions as described above using the IGZO target described in No. 2 of Table 5. The atomic ratio of In to Ga and Zn in the target of No. 2 described above was 1:1:1. The method for producing the above IGZO target is as follows.

(production of IGZO sputtering target)

Indium oxide powder (In ₂ O ₃ ) having a purity of 99.99%, gallium oxide powder (Ga ₂ O ₃ ) having a purity of 99.99%, and zinc oxide powder having a purity of 99.99% were blended at a mass ratio and an atomic ratio shown in Table 1. ZnO ₂ ), water and a dispersing agent (agglomerated ammonium acid) and a binder were added and mixed in a ball mill for 20 hours. Next, the mixed powder obtained in the above step is dried and granulated.

The powder thus obtained is pressurized with a mold under the following conditions After preliminary molding, it was raised to a temperature of 500 ° C under normal pressure in an atmosphere, and was kept at this temperature for 5 hours to be degreased.

(conditions for preparation)

Forming pressure: 1.0 ton / cm ²

When the thickness is set to t, the size of the formed body is Φ110mm×t13mm

The obtained molded body was fixed to a graphite mold, and hot pressed under the condition G shown in Table 2. At this time, N ₂ gas was introduced into the hot press furnace and sintered in an N ₂ atmosphere.

The obtained oxide sintered body was machined and processed into Φ100 mm×t5 mm. After the oxide sintered body and the Cu back sheet were heated to 180 ° C for 10 minutes, the oxide sintered body was bonded to the back sheet using a bonding material (indium) to prepare a sputtering target.

With respect to each of the oxide semiconductor thin films thus obtained, the ratio (atomic %) of each metal element in each film was measured by a high-frequency inductively coupled plasma (ICP) method. The results of these are described in Table 6.

Comparing the composition of the target (atomic %) shown in Table 5 with the constituent atoms (%) of the film shown in Table 6, in the IGTO target of No. 1 which satisfies the composition of the present invention, the target and the target were not observed at all. The composition between the films deviates.

With respect to this, in the IGZO target of No. 2 containing no Sn and not containing Sn of the composition of the present invention, the compositional deviation between the target and the film becomes large. In detail, in No. 2, the Zn ratio in the film = 36.5 at%, and the Zn ratio in the film was also reduced to 6.8 at%, depending on the Zn ratio in the target = 33.3 at%.

Therefore, it was confirmed that when the target of the present invention is used, a film having no compositional deviation from the composition of the target can be formed into a film.

Further, the surface state of each of the targets obtained by filming each of the above-mentioned respective targets was visually observed, and the presence or absence of black deposits was evaluated. For reference, such photographs are shown in Figures 1A and 1B.

As a result, when the IGTO target of No. 1 of the present invention example was used, black deposits were not observed on the target surface after film formation as shown in Fig. 1A, whereas No. 2 of the conventional example was used. In the case of the IGZO target, black deposits were observed on the surface of the target after film formation as shown in Fig. 1B. When a black deposit exists on the surface of the target as described above, it is peeled off from the target surface during sputtering to become particles, which may cause arcing. Therefore, if the target of the present invention is used, not only a film having no composition deviation but also sputtering can be prevented. The arcing, etc., proved very useful.

The present invention has been described with reference to the specific embodiments thereof, and various modifications and changes can be made without departing from the spirit and scope of the invention.

This application is based on the Japanese invention patent application filed on February 14, 2014 (Japanese Patent Application No. 2014-026835) and the Japanese invention patent application filed on December 26, 2014 (Japanese Patent Application No. 2014-266399). The content is incorporated herein by reference.

Industrial utilization possibility

The oxide sintering system of the present invention is suitable as a sputtering target for an oxide semiconductor thin film of a TFT used in a display device such as a liquid crystal display or an organic EL display, and has no crack at the time of bonding.

Claims (3)

An oxide sintered body obtained by sintering indium oxide, gallium oxide, and tin oxide, wherein the oxide sintered body has a relative density of 90% or more, and the oxide sintered body is Ga. ₂ In ₆ Sn ₂ O The average crystal grain size of the _16- phase is 3 μm or less, and the ratio of the coarse crystal grains having a crystal grain size of 10 μm or more in the oxide sintered body is less than 10%, and is in comparison with the oxide sintered body. When the ratio (atomic %) of the content of indium, gallium, and tin is set to [In], [Ga], and [Sn] for all the metal elements other than oxygen, the following formulas (1) to (3) are satisfied. When the oxide sintered body is X-rayed at the same time, the Ga ₃ InSn ₅ O ₁₆ phase satisfies the following formula (4); 35 atomic % ≦ [In] ≦ 50 atom%. . . (1) 20 atom% ≦ [Ga] ≦ 35 atom%. . . (2) 20 atom%<<Sn]≦40 atom%. . . (3) 0.02 ≦ [Ga ₃ InSn ₅ O ₁₆ ] ≦ 0.2. . . (4) However, [Ga ₃ InSn ₅ O ₁₆ ]=I(Ga ₃ InSn ₅ O ₁₆ )/(I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ )+I(SnO _{In the} formula ₂ ), I(Ga ₃ InSn ₅ O ₁₆ ), I(Ga ₂ In ₆ Sn ₂ O ₁₆ ), and I(SnO ₂ ) are each a Ga ₃ InSn ₅ O ₁₆ phase defined by X-ray diffraction. The diffraction peak intensity of the Ga ₂ In ₆ Sn ₂ O ₁₆ phase and the SnO ₂ phase. The oxide sintered body of claim 1, wherein the oxide sintered body is X-ray-diffracted, the Ga ₂ In ₆ Sn ₂ O ₁₆ phase satisfies the following formula (5); 0.8 ≦ [Ga ₂ In ₆ Sn ₂ O ₁₆ ]≦0.98. . . (5) However, [Ga ₂ In ₆ Sn ₂ O ₁₆ ]=I(Ga ₂ In ₆ Sn ₂ O ₁₆ )/(I(Ga ₃ InSn ₅ O ₁₆ )+I(Ga ₂ In ₆ Sn ₂ O ₁₆ ) +I(SnO ₂ )) wherein I(Ga ₂ In ₆ Sn ₂ O ₁₆ ), I(Ga ₃ InSn ₅ O ₁₆ ), and I(SnO ₂ ) are each Ga ₂ In defined by X-ray diffraction The diffraction peak intensity of ₆ Sn ₂ O ₁₆ phase, Ga ₃ InSn ₅ O ₁₆ phase and SnO ₂ phase. A sputtering target using a sputtering target obtained by the oxide sintered body of claim 1 or 2, characterized in that the specific resistance is 1 Ω. Below cm.