JP6894886B2 - Sputtering target material and its manufacturing method, and sputtering target - Google Patents

Description

The present invention relates to a sputtering target material and a method for producing the same. The present invention also relates to a sputtering target provided with the sputtering target material.

The sputtering method is extremely effective as a manufacturing method for forming a thin film with a large area and high accuracy, and in recent years, the sputtering method has been utilized in display devices such as liquid crystal display devices.

By the way, in the recent technical field of semiconductor devices such as thin film transistors (hereinafter, also referred to as "TFT"), oxidation represented by In-Ga-Zn composite oxide (hereinafter, also referred to as "IGZO") is used instead of amorphous silicon. Physical semiconductors are attracting attention, and the sputtering method is also used for forming IGZO thin films. It is known that when a specific transition metal such as Fe or Cu is mixed in an oxide semiconductor thin film typified by IGZO, deterioration of TFT characteristics occurs. Even if the amount of Fe and Cu mixed in the thin film is at the level of several ppm, the effect is extremely large on the oxide semiconductor. For example, a thin-film semiconductor device in which Fe or Cu is mixed tends to have a lower field effect mobility among various characteristics of the TFT than a thin-film semiconductor device in which they are not mixed, and the ON / OFF ratio is also high. It tends to decrease. Such defects have been pointed out as a major obstacle to the recent increase in the area of display panels, and urgent technical improvement is required.

Therefore, in Patent Document 1, in the split sputtering target obtained by joining a plurality of target members, a ceramic material or the like is filled in the gap between the joined members to prevent Cu from being mixed from the base material. Technology has been proposed.

Patent Document 2 discloses a technique of lengthening the target member itself to minimize the number of gaps between the joining members. As in the same document, the effect of preventing the mixing of Cu and Fe derived from the base material can be obtained by lengthening the target member.

International Publication No. 2012/063523 Japanese Unexamined Patent Publication No. 2013-147368

However, in all of the techniques described in Patent Documents 1 and 2 described above, in terms of preventing impurities from being mixed into the target material itself, only a method of using a high-purity product as a raw material is adopted. No treatment has been carried out to remove impurities of several ppm originally contained in the raw material and impurities mixed in the manufacturing process. Among these impurities, iron in particular is used as a material for equipment and appliances such as stainless steel, and may be mixed at various stages in the actual manufacturing process of the target material. It can be a serious problem in the technical field of oxide semiconductors.

Further, in recent years, in addition to the conventional flat plate magnetron sputtering apparatus, a rotary magnetron cathode sputtering apparatus has become widespread. The rotary magnetron cathode sputtering device is a device that has a magnetic field generator inside a cylindrical target and performs sputtering while rotating the target while cooling the target from the inside. In the rotary magnetron cathode sputtering device, the entire surface of the target material becomes erosion and is uniformly scraped. Due to this, the utilization efficiency of the target material is usually 20 to 30% in the flat plate magnetron sputtering apparatus, whereas the utilization efficiency of the target material can be 70% or more in the rotary magnetron cathode sputtering apparatus. It can be used, and extremely high usage efficiency can be obtained. In such a cylindrical target, since most of the target material is used for sputtering, the influence of impurities mixed in is greater than that of the flat plate type.

Therefore, an object of the present invention is to provide a sputtering target material, a method for producing the same, and a sputtering target that can eliminate various drawbacks of the above-mentioned prior art.

The present invention provides a sputtering target material containing at least one oxide selected from the group consisting of In, Ga, Zn, Sn and Al. The sputtering target material is derived from iron, or no to the surface area 1000 .mu.m ² or more discoloration, or from iron, if having an area 1000 .mu.m ² or more discoloration on the surface, is the ratio 0.02 pieces / 1200 cm ² or less.

The present invention also provides a sputtering target including the above-mentioned sputtering target material and a base material.

Furthermore, the present invention provides a suitable method for producing the above-mentioned sputtering target material. This manufacturing method includes at least one magnetic separation step in the manufacturing step of the sputtering target material.

Detailed description of the invention

Hereinafter, the present invention will be described based on its preferred embodiment. The sputtering target material of the present invention contains at least one oxide selected from the group consisting of In, Ga, Zn, Sn and Al. This oxide may be any one of indium oxide, gallium oxide, zinc oxide, tin oxide and aluminum oxide. Alternatively, the oxide can be a composite oxide of any two or more elements selected from the group consisting of In, Ga, Zn, Sn and Al. Specific examples of the composite oxide include In-Ga oxide, In-Zn oxide, Zn-Sn oxide, In-Ga-Zn oxide, In-Zn-Sn oxide, and In-Al-Zn. Oxides, In-Ga-Zn-Sn oxides, In-Al-Zn-Sn oxides and the like can be mentioned, but the present invention is not limited thereto. The sputtering target material of the present invention contains at least one oxide selected from the group consisting of In, Ga, Zn, Sn and Al, and does not contain a transition metal element other than these elements. Is preferable.

The sputtering target material of the present invention is composed of a sintered body containing the above-mentioned oxide. The shapes of the sintered body and the sputtering target material are not particularly limited, and conventionally known shapes such as a flat plate type and a cylindrical shape can be adopted, but in the following description, a shape having a particularly large effect in the present invention. Examples thereof include an oxide cylindrical sintered body and an oxide cylindrical sputtering target material. The following description applies similarly to shapes other than cylinders.

<Oxide cylindrical sintered body>
The oxide cylindrical sintered body is a sintered body containing at least one oxide selected from the group consisting of In, Ga, Zn, Sn and Al. The relative density of the oxide cylindrical sintered body is not particularly limited, but the higher the relative density, the smaller the influence on the vacuum system of the sputtering apparatus, which is advantageous for forming a good thin film. From this viewpoint, the relative density is preferably 90% or more, more preferably 95% or more, still more preferably 98.0% or more. The relative density is measured by the method described in Examples described later.

<Oxide Cylindrical Sputtering Target Material>
The oxide cylindrical sputtering target material comprises the above-mentioned oxide cylindrical sintered body. The oxide cylindrical sputtering target material is produced by appropriately processing the oxide cylindrical sintered body. For example, it is manufactured by performing cutting or the like. The size of the oxide cylindrical sputtering target material is not particularly limited, but the outer diameter is preferably 140 mm or more and 170 mm or less, the inner diameter is preferably 110 mm or more and 140 mm or less, and the length is 50 mm or more. It is preferable to have. The length is appropriately determined according to the application.

One of the features of the oxide cylindrical sputtering target material of the present invention is that the amount of iron, which is an impurity contained therein, is suppressed. Specifically, the sputtering target material of the present invention preferably does not have a discolored portion having ^{an area of 1000 μm 2 or more derived from iron on the surface.} Alternatively, when the sputtering target material of the present invention has ^{a discolored portion having an area of 1000 μm 2} or more derived from iron on the surface, the ratio thereof is preferably 0.02 pieces / 1200 cm ² or less. When iron is mixed in the sputtering target material of the present invention, the mixed portion exhibits a different color from the portion where iron is not mixed. Therefore, in the present invention, the iron mixed portion is referred to as a discolored portion. When the iron mixed portion is present on the surface of the sputtering target material, the discolored portion can be confirmed by observing the appearance. In that sense, the discolored portion observed on the surface of the sputtering target material is also referred to as "surface discolored portion". The discolored portion is composed of iron oxides such as Fe ₂ O ₃ and Fe ₃ O ₄ , and has any chemical structure of the TFT produced from the sputtering target material of the present invention. It has a negative effect on performance. Therefore, what kind of chemical structure the iron constituting the discolored portion has is not an essential problem in the present invention, but the existence of the discolored portion containing iron is a problem. The term "iron" in the present invention also includes iron contained as a component in alloys, oxides and the like.

If iron is not mixed in the sputtering target material of the present invention, or even if iron is mixed, the amount of iron mixed is less than a specific value, the TFT manufactured by using the sputtering target material of the present invention. For the first time, the present inventor has found that the performance deterioration of the above can be effectively prevented. In this respect, the sputtering target material, when having derived from iron, or no to the surface area 1000 .mu.m ² or more discoloration, or from iron, an area 1000 .mu.m ² or more discoloration on the surface, The ratio is preferably 0.02 pieces / 1200 cm ² or less, and more preferably 0.01 pieces / 1200 cm ² or less. Reason for the minimum area of discoloration was 1000 .mu.m ² may be any area of discoloration is 1000 .mu.m ² or less, even if the iron is mixed into the film by sputtering, the influence its amount is the degradation of the TFT characteristics This is because it does not. Even if the surface has a discolored part with an area of 1000 μm ² or more, if the ratio is 0.02 pieces / 1200 cm ² or less, the amount of iron mixed in the sputtering target material may be present. Even if the amount of iron is sufficiently small and iron is mixed into the film by sputtering, the amount does not affect the performance deterioration of the TFT characteristics.

The discolored part of the sputtering target material is specified and the number of discolored parts is measured by visually observing the outer surface, and the area thereof is measured using a microscope such as a microscope capable of measuring the scale. A means for preventing the sputtering target material from having a discolored portion, or a means for suppressing the amount of the sputtered target material to a specific value or less even if it has a discolored portion will be described later.

<Oxide Cylindrical Sputtering Target>
An oxide cylindrical sputtering target can be obtained by joining the oxide cylindrical sputtering target material to a base material with a bonding material. The substrate usually has a cylindrical shape to which a cylindrical sputtering target material can be bonded. The type of the base material is not particularly limited, and a conventionally used base material can be appropriately selected and used. Examples of the material of the base material include stainless steel, titanium, copper and the like. The type of the joining material is not particularly limited, and a conventionally used joining material can be appropriately selected and used. Examples of the bonding material include indium solder and the like.

One oxide cylindrical sputtering target material may be bonded to the outside of one substrate, or two or more of them may be bonded side by side on the same axis. When two or more are joined side by side, the gap between each oxide cylindrical sputtering target material, that is, the length of the divided portion is usually 0.05 mm or more and 0.5 mm or less. The shorter the length of the split portion, the less likely it is that arcing will occur during sputtering, but if it is less than 0.05 mm, the target materials may collide with each other and crack due to thermal expansion during the joining process or sputtering. The method of joining the base material and the oxide cylindrical sputtering target material is not particularly limited, and a method similar to a conventionally known method can be adopted.

<Manufacturing method of oxide cylindrical sintered body>
The oxide cylindrical sintered body is preferably produced by a method including steps of pulverizing, classifying and mixing the raw material powder. Iron, which is an impurity, may be mixed in at any stage of this step. Specifically, iron is mixed in at least one of the grinding, classifying and mixing steps, or is originally included in the raw material powder. Regardless of the reason, it is advantageous to perform magnetic separation to attract and remove iron to the magnet. In the present invention, "magnetic separation" refers to a step of removing impurities adhering to a magnet such as iron. By performing magnetic separation, not only iron but also other impurities adhering to magnets such as Ni and its alloys and oxides, Co and its alloys and oxides can be naturally removed.

The present production method may include a step of producing a slurry containing the raw material powder and the organic additive. Alternatively, the present production method may include a step of producing a slurry containing the raw material powder and organic additives after magnetic separation. In any case, it is advantageous to perform magnetic separation to attract and remove the iron contained in the slurry to the magnet. Further, the present production method may include a step of producing granulated powder from the slurry before magnetic separation or from the slurry after magnetic separation. In that case, the produced granulated powder is magnetically selected to produce iron. It is advantageous to attract and remove the magnet.

In the present production method, it is preferable to carry out magnetic separation by magnetic force at least once between the step of preparing the raw material powder and the step of forming the oxide cylinder-formed body. Specifically, for example, (A) magnetic separation of raw material powder,
(B) If the process of crushing, classifying, mixing, etc. of the raw material powder is included, magnetic separation of the processed powder,
(C) If a step of producing a slurry containing a raw material powder and an organic additive is included, magnetic separation of the slurry,
(D) When the step of producing granulated powder from the slurry is included, magnetic separation of the granulated powder,
And so on. Among the above, it is particularly preferable to perform magnetic separation of (C) slurry. It is advantageous to carry out magnetic separation in a state of being dispersed in a solvent like a slurry because the iron contained therein easily approaches the magnet and the magnetic separation efficiency becomes high. When the slurry is magnetically separated, the viscosity of the slurry is preferably 200 mPa · s or less at the temperature at the time of magnetic separation. If the viscosity of the slurry exceeds 200 mPa · s, it may be difficult for the slurry to pass through the magnetic separator, and iron contained in the slurry tends to be difficult to approach the magnet. For the above reasons, the viscosity of the slurry is more preferably 100 mPa · s or less, and particularly preferably 80 mPa · s or less. The lower limit of the viscosity of the slurry is not particularly specified, but is usually 1 mPa · s or more.
Further, the number of magnetic separations in each process is not limited to one. For example, it is advantageous because the magnetic separation efficiency can be increased by performing magnetic separation a plurality of times, for example, by further magnetically separating the slurry that has been subjected to magnetic separation.

The oxide cylindrical sintered body can be efficiently produced according to the method described below. However, the method for producing the oxide cylindrical sintered body is not particularly limited except for the above-mentioned production conditions for magnetic separation, and is not limited to the production method described below. A preferred embodiment of the method for producing an oxide cylindrical sintered body is a step of producing a granulated powder from a slurry containing a raw material powder and an organic additive, and a CIP molding of the granulated powder to form a cylindrical molded body. 2. Is included, a step 3 of degreasing the molded body, and a step 4 of firing the degreased molded body. Hereinafter, each step will be described.

<Step 1>
In step 1, granulated powder is produced from a slurry containing a raw material powder and an organic additive. As the raw material powder, for example, _{a mixed powder of any one of In 2} O ₃ powder, Ga ₂ O ₃ powder, Zn _{O powder, SnO 2} powder, and Al ₂ O ₃ powder or any two or more kinds of powder can be used. Can be used. When a mixed powder is used, the mixing ratio of each powder is appropriately determined by the content of the constituent elements in the present oxide cylindrical sintered body. For example, when the finally obtained sintered body has an atomic ratio of In: Ga: Zn: O = 1: 1: 1: 4, the content of In, Ga, Zn, and O in the sintered body is high. The ratio of each raw material powder contained in the raw material powder is determined so that the atomic ratio is 1: 1: 1: 4. Further, the powder that has been reacted and solid-dissolved in advance can be used alone. In that case, for example, the finally obtained sintered body has an atomic ratio of In: Ga: Zn: O = 1: 1: 1: When it is 4, the IGZO powder having an atomic ratio of In: Ga: Zn: O = 1: 1: 1: 4 can be used alone. In this production method, the ratio of each element in the raw material powder can be equated with the ratio of each element in the finally obtained sintered body and the target material.

In the present invention, the mixed powder of the oxide powder used for producing the granulated powder is also referred to as "raw material powder". Alternatively, when the oxide powder is used alone, the single powder is also referred to as "raw material powder". In ₂ O ₃ powder, _Ga 2 _{O 3} powder, ZnO powder, mixed powder composed of any two or more combinations of the SnO ₂ powder and _Al 2 _{O 3} powder, and single powders, BET (Brunauer-Emmett- The specific surface area measured by the Teller) method is usually 1 m ² / g or more and 40 m ² / g or less, respectively.

When the mixed powder is used as the raw material powder, the mixing method of each oxide powder is not particularly limited, and for example, each oxide powder and zirconia balls can be put in a pot and mixed by a ball mill. After mixing in a ball mill, the zirconia balls and the mixed powder are separated by a sieve.

The raw material powder can be subjected to a magnetic separation process using a dry magnetic separator (for example, CG-150HHH manufactured by Nippon Magnetics Co., Ltd.). The stronger the magnetic force of the magnetic separator, the more effectively iron can be removed. Since stainless steel used in devices and appliances, which is one of the causes of iron contamination, generally has a weak magnetic force, it is desirable to set the magnetic force of the magnetic separator to be strong, specifically 3000 G or more, and more. Iron can be removed more effectively when the amount is preferably 7,000 G or more, more preferably 10,000 G or more.

The organic additive added to the raw material powder before or after magnetic separation is a substance used for appropriately adjusting the properties of the slurry or molded product. Examples of the organic additive include a binder, a dispersant, a plasticizer and the like. The binder is added to bind the raw material powder in the molded product and increase the strength of the molded product. As the binder, a binder usually used when obtaining a molded product by a known powder sintering method can be used. Examples of the binder include polyvinyl alcohol. The dispersant is added to enhance the dispersibility of the raw material powder in the slurry. Examples of the dispersant include ammonium polycarboxylic acid and ammonium polyacrylate. The plasticizer is added to increase the plasticity of the molded product. Examples of the plasticizer include polyethylene glycol (PEG) and ethylene glycol (EG).

The dispersion medium used when producing the slurry containing the raw material powder and the organic additive is not particularly limited, and may be appropriately selected from water and a water-soluble organic solvent such as alcohol depending on the purpose. it can. The method for producing a slurry containing the raw material powder and the organic additive is not particularly limited, and for example, a method in which the raw material powder, the organic additive, the dispersion medium and the zirconia balls are placed in a pot and mixed by a ball mill can be used.

The produced slurry can be subjected to a magnetic separation process using a wet magnetic separator (for example, a magnet strainer manufactured by Nippon Magnetics Co., Ltd.). Regarding the magnetic force, the same conditions as those for magnetic separation of the raw material powder by the dry magnetic separator described above can be adopted.

There is no particular limitation on the method for producing the granulated powder using the slurry before or after the magnetic separation. For example, a spray-drying method, a rolling granulation method, an extrusion granulation method, or the like can be used. Of these, the spray-drying method is preferable because the granulated powder has high fluidity and it is easy to produce granulated powder that is easily crushed during molding. The conditions of the spray-drying method are not particularly limited, and the conditions usually used for granulating the raw material powder can be appropriately selected and carried out.

The granulated powder obtained by granulation can be subjected to a magnetic separation process using a dry magnetic separator (for example, CG-150HHH manufactured by Nippon Magnetics Co., Ltd.). Regarding the magnetic force, the same conditions as those for magnetic separation of the raw material powder by the dry magnetic separator and magnetic separation of the slurry by the wet magnetic separator can be adopted.

<Process 2>
In step 2, the granules obtained in step 1 are CIP-molded (cold isotropic molding) to produce a cylindrical molded body. The pressure during CIP molding is usually 800 kgf / cm ² or more. The higher the pressure, the denser the molded product can be obtained, whereby the density and strength of the molded product can be increased.

<Step 3>
In step 3, the molded product produced in step 2 is degreased. Solventing is generally performed by heating the molded product. The degreasing temperature is usually preferably 600 ° C. or higher and 800 ° C. or lower, more preferably 700 ° C. or higher and 800 ° C. or lower, and further preferably 750 ° C. or higher and 800 ° C. or lower. The higher the degreasing temperature, the higher the strength of the molded product. However, if the temperature exceeds 800 ° C., the molded product may shrink, so degreasing is preferably performed at 800 ° C. or lower.

<Step 4>
In step 4, that is, in the firing step, the molded product degreased in step 3 is fired. The firing furnace used for firing is not particularly limited, and a firing furnace conventionally used for producing an oxide sintered body can be used. The firing temperature is usually preferably 1300 ° C. or higher and 1700 ° C. or lower. The firing time is usually 3 hours or more and 30 hours or less, provided that the firing temperature is within this range. The firing atmosphere is usually an air or oxygen atmosphere.

A sputtering target material can be obtained by subjecting the oxide cylindrical sintered body produced by the above steps to cutting or the like. A sputtering target can be obtained by joining this sputtering target material to a base material. The sputtering target thus obtained is suitably used for producing an oxide semiconductor. Since the mixing of iron is suppressed in this sputtering target, the characteristics of the oxide semiconductor manufactured by using the sputtering target are not easily impaired due to this. Therefore, by using this sputtering target, the manufacturing yield of the oxide semiconductor device can be improved.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples.
The evaluation method of the oxide sintered body obtained in the examples and comparative examples described below is as follows.

1. 1. Relative Density The relative density of the oxide sintered body was measured based on the Archimedes method. Specifically, the aerial mass of the oxide sintered body is divided by the volume (mass of the oxide sintered body in water / water specific gravity at the measured temperature), and the theoretical density ρ (g / cm) based on the following formula (1) is used. ^{The value of the percentage with respect to 3} ) was defined as the relative density (unit:%).
Constituents in the formula _(1), C 1 -C _i represents the content in terms of oxide constituents of each sintered body (% by mass), the ρ ₁ ~ρ _i corresponding to _C 1 -C _i The density of oxides (g / cm ³ ) is shown.

2. Slurry Viscosity The slurry was sampled before it was passed through a magnetic separator and the viscosity of the slurry was measured. The viscosity of the slurry was measured using a spiral viscometer (manufactured by Malcolm Co., Ltd., PC-10C).

3. 3. Surface discoloration due to iron When iron is mixed in the oxide sintered body and iron is exposed on the target surface, the iron-containing part is oxidized and discolored red. Not all iron is deposited on the oxide surface, but in the present invention, the ratio of the discolored portion appearing on the surface is used as a scale to make a relative evaluation of the amount of mixed iron. As for the discolored part, it was visually confirmed how many discolored parts having an area of 1000 μm ^{2 or more were generated on the target surface 1 m 2.}

<Example 1>
_{In 2} O ₃ powder, Ga ₂ O ₃ ^{powder, and Zn O powder having a specific surface area of 5 m 2} / g measured by the BET method, and having an atomic ratio of In: Ga: Zn: O of 1: 1: 1: A mixed powder was obtained by blending so as to be 4. This mixed powder was ball-mill mixed with zirconia balls in a pot to prepare an IGZO raw material powder.

After mixing in a ball mill, the zirconia balls and the raw material powder were separated by a sieve, and the raw material powder was subjected to a magnetic separation process (12000 G) using a dry magnetic separator. The raw material powder after being subjected to the magnetic separation treatment contains 0.3% by mass of polyvinyl alcohol (binder), 0.5% by mass of ammonium polycarboxylic acid (dispersant), and 0.3% by mass with respect to the raw material powder. Polyethylene glycol (plasticizer) and 50% by mass of water (dispersion medium) were added and mixed by a ball mill to prepare a slurry. The viscosity of the slurry was 200 mPa · s or less.

This slurry was subjected to a magnetic separation process using a wet magnetic separator (10000 G). Then, the slurry was supplied to a spray-drying apparatus, and spray-dried under the conditions of an atomizing rotation speed of 14,000 rpm, an inlet temperature of 200 ° C., and an outlet temperature of 80 ° C. to produce granulated powder. The produced granulated powder was subjected to a magnetic separation process using a dry magnetic separator (12000 G).

The granulated powder after the magnetic separation treatment was filled into a cylindrical urethane rubber mold while being tapped. The urethane rubber mold had an inner diameter of 225 mm (thickness of 10 mm), a length of 400 mm, and a columnar core (mandrel) having an outer diameter of 150 mm arranged inside. After sealing the urethane rubber mold, CIP molding was performed at a pressure of ^{800 kgf / cm 2 to produce a cylindrical molded body.}

The molded product was then heat degreased. The degreasing temperature was 600 ° C., the degreasing time was 10 hours, and the heating rate was 20 ° C./h. The degreased molded product was fired under the conditions of a firing temperature of 1500 ° C., a firing time of 12 hours, and a heating rate of 300 ° C./h. The atmosphere was the atmosphere. After the completion of firing, the obtained fired product was cooled at a temperature lowering rate of 50 ° C./h.

The relative density of the sintered body thus obtained was 99.7%. The obtained sintered body was cut to obtain an IGZO cylindrical sputtering target material having an outer diameter of 153 mm, an inner diameter of 135 mm, and a length of 250 mm. The cutting process was performed by processing the outer diameter using a grindstone, holding the outer diameter with a jig to process the inner diameter, and then holding the inner diameter with a jig to finish the outer diameter. In this way, 100 IGZO cylindrical sputtering target materials were produced, and when the outer surface was visually observed, the number of surface discolored portions having an ^{area of 1000 μm 2} or more was ^{0/1200 cm 2.} The results of the manufacturing conditions and the incidence of surface discoloration are shown in Table 1 below.
The produced IGZO cylindrical sputtering target material was bonded to a titanium base material using indium as a bonding material to obtain an IGZO cylindrical sputtering target having no surface discoloration portion of ^{1000 μm 2 or more.}

<Example 2>
An IGZO cylindrical sputtering target material was produced in the same manner as in Example 1 except that the raw material powder was not subjected to the magnetic separation treatment. The same evaluation as in Example 1 was performed on this sputtering target material. The results are shown in Table 1.

<Example 3>
An IGZO cylindrical sputtering target material was produced in the same manner as in Example 1 except that the raw material powder and the slurry were not subjected to the magnetic separation treatment. The same evaluation as in Example 1 was performed on this sputtering target material. The results are shown in Table 1.
Among the manufactured IGZO cylindrical sputtering target materials, a target material ^{having no surface discoloration portion of 1000 μm 2} or more is bonded to a titanium base material using indium as a bonding material, and a surface discoloration portion of ^{1000 μm 2 or more is formed.} A non-existent IGZO cylindrical sputtering target was obtained.

<Example 4>
An IGZO cylindrical sputtering target material was produced in the same manner as in Example 1 except that the raw material powder and the granulated powder were not subjected to the magnetic separation treatment. The same evaluation as in Example 1 was performed on this sputtering target material. The results are shown in Table 1.

<Example 5>
An IGZO cylindrical sputtering target material was produced in the same manner as in Example 1 except that the slurry and the granulated powder were not subjected to the magnetic separation treatment. The same evaluation as in Example 1 was performed on this sputtering target material. The results are shown in Table 1.

<Comparative example 1>
An IGZO cylindrical sputtering target material was produced in the same manner as in Example 1 except that no magnetic separation treatment was performed. The same evaluation as in Example 1 was performed on this sputtering target material. The results are shown in Table 1.

As is clear from the results shown in Table 1, the sputtering target material of each example subjected to the magnetic separation treatment had a very small amount of surface discoloration due to iron, whereas it was obtained without magnetic separation. In the sputtering target material of Comparative Example 1 obtained, more surface discoloration due to iron was observed than in each example.

According to the present invention, it is possible to prevent iron from being mixed into the thin film and improve the manufacturing yield of the oxide semiconductor device.

Claims (3)

A method for producing a sputtering target material containing at least one oxide selected from the group consisting of In, Ga, Zn, Sn and Al.
A step of preparing a slurry containing the oxide and a step of magnetically separating the slurry are included.
A method for producing a sputtering target, which magnetically separates the slurry having a viscosity of 80 mPa · s or less with a magnetic force of 3000 G or more. The method for producing a sputtering target material according to claim 1 , further comprising a step of magnetically separating the raw material powder of the sputtering target material with a magnetic force of 3000 G or more. The sputtering target according to claim 1 or 2 , further comprising a step of producing a slurry containing the oxide, a step of producing granulated powder from the slurry, and a step of magnetically separating the granulated powder with a magnetic force of 3000 G or more. Material manufacturing method.