JP2007246315A - Ito sintered compact, sputtering target material, sputtering target, and manufacturing method of sputtering target material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ITO sputtering target material having high usage efficiency, a long life, and a small aging change of a sputtering condition, and to provide an ITO sputtering target and an ITO sintered compact that is suited for using to obtain them. <P>SOLUTION: The ITO sintered compact satisfies the relationship of formular -30≤100×(Av1-Av2)/Av1≤30, wherein Av1 expresses an average value (nm) of the maximum diameter of fine particles in the In<SB>2</SB>O<SB>3</SB>host phase particles that exist in the center part of the sintered compact and Av2 expresses an average value (nm) of the maximum diameter of fine particles in the In<SB>2</SB>O<SB>3</SB>host phase particles that exist in the end part of the sintered compact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an ITO sintered body, a sputtering target material using the same, and a sputtering target. More specifically, the present invention relates to an ITO sintered body in which variation in the form of fine particles existing in the In ₂ O ₃ parent phase grains of each part of the ITO sintered body is reduced, an ITO sputtering target material using the ITO sintered body, and an ITO sputtering target.

  The present invention also relates to a method for producing a sputtering target material. In more detail, it is related with the manufacturing method suitable for manufacture of the said ITO sputtering target material.

  In general, in sputtering using an ITO sputtering target, a portion called an erosion portion of a sputtering surface (surface to be used for sputtering) of the ITO target material is consumed while performing sputtering continuously or intermittently. Go away. The life of the ITO sputtering target ends when consumption of this erosion part advances and a suitable ITO thin film cannot be formed due to frequent arcing, generation of particles and yellow powder, and the like.

  Conventionally, various attempts have been made to prevent the occurrence of arcing and particles during sputtering. However, when a simple flat-plate-shaped ITO target material is used, the consumption of the ITO target material by sputtering is still It remains at 30% or less of the total weight of the target material, and there remains a problem that usage efficiency is low and life is short.

  Furthermore, the oxygen partial pressure dependency and the voltage dependency at the time of sputtering of the ITO target material change over time while the sputtering is continuously or intermittently performed, and a suitable ITO thin film is formed. For this purpose, the sputtering conditions must be adjusted each time, and there is also a problem that the condition setting operation is complicated and hinders the improvement of the film formation yield.

By the way, when an ITO sintered body used as an ITO sputtering target material is cut horizontally in the thickness direction, the obtained cut surface is etched, and the microstructure is observed, In ₂ O _{3 as} main crystal grains and In addition to the grain boundary, a compound phase existing in a state along the grain boundary and fine particles present in the In ₂ O ₃ matrix may be seen. However, as far as the present inventors know, conventionally, the microstructure of such an ITO sintered body, the use efficiency of ITO target material, the lifetime, the oxygen partial pressure dependency over time during sputtering, and the voltage dependency over time Whether or not there is an association with changes has not been studied.

For example, conventionally, with respect to Al target materials and Al alloy target materials, a technique for reducing the variation in crystal grain size by performing a rolling process and a recrystallization process has been reported (see Patent Document 1). However, in this report, there is no disclosure of the fine particles inside the crystal grains of the target material, that is, the fine particles in the parent phase grains, including the presence thereof. In addition, this technology targets metal target materials or alloy target materials, but ceramic target materials such as ITO are brittle materials, so plastic processing such as rolling cannot be performed, and this technology cannot be applied. Can not.
JP-A-6-299342

  An object of the present invention is to provide an ITO sputtering target material and an ITO sputtering target that have high use efficiency, a long life, and a small change with time in sputtering conditions, and an ITO sintered body suitable for use in these materials.

  Moreover, this invention also makes it the subject to provide the manufacturing method of a sputtering target material, especially the manufacturing method of the sputtering target material suitable for manufacture of the said ITO sputtering target material.

The present inventors examined the relationship between the microstructure of the ITO sintered body and the use efficiency of the target material, the lifetime, the oxygen partial pressure dependence change over time, and the voltage dependence change over time. According to the ITO sintered body in which the variation due to the difference in the part of the ITO sintered body is controlled with respect to the form of fine particles present in the In ₂ O ₃ parent phase grains which are the main crystal grains of the sintered body, the use efficiency It is possible to provide an ITO sputtering target material and an ITO sputtering target that are high in life, have a long life, and have little change over time in sputtering conditions, and that the variation in the form of the fine particles is due to firing during the production of the target material (sintered body). In the processing, the present invention is completed by finding that it can be controlled by cooling so that both ends thereof have a temperature gradient for each object to be fired after heating. It led to.

That is, the present invention relates to the following matters.
The ITO sintered body according to the present invention is characterized by satisfying the relationship of the following formula.
−30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30
In the formula, Av1 is the average value (nm) of the maximum diameter of fine particles in the In ₂ O ₃ matrix phase grains present in the center of the sintered body, and Av2 is In ₂ O present at the end of the sintered body. The average value (nm) of the maximum diameter of the fine particles in the _three parent phase grains is represented. In the present specification, ITO usually means a material obtained by adding 1 to 35% by weight of tin oxide (SnO ₂ ) to indium oxide (In ₂ O ₃ ).

In one preferred embodiment of the ITO sintered body of the present invention, it is further desirable that both Av1 and Av2 are 120 nm or less.
In one preferred embodiment of the ITO sintered body of the present invention, it is further desirable that both Av1 and Av2 are larger than 120 nm.

The ITO sintered body of the present invention can be suitably used as a sputtering target material.
In addition, an ITO sputtering target according to the present invention includes the ITO sintered body and a backing plate.

  Moreover, the manufacturing method of the sputtering target material which concerns on this invention is a method of manufacturing a sputtering target material by a powder metallurgy method, Comprising: The heating process which heats the to-be-fired body after shaping | molding, and to-be-fired after passing through a heating process It is characterized by performing a baking process including a cooling step of cooling at a temperature lowering rate of 50 ° C./hour or more or less than 50 ° C./hour so that both ends of each body have a temperature gradient.

  Furthermore, in the manufacturing method of this sputtering target material, it is preferable that the said sputtering target material consists of ceramics, it is more preferable that it contains indium oxide, and it is further more preferable that it consists of ITO.

In the ITO sintered body of the present invention, the variation in the form of fine particles existing in the In ₂ O ₃ matrix phase grains is controlled regardless of the difference in the parts of the sintered body, and the entire structure including the fine structure is controlled. Since the ITO sintered body is used as a sputtering target material, it is possible to obtain an ITO sputtering target material and an ITO sputtering target that have high use efficiency, long life, and little change over time in sputtering conditions. be able to.

  Since the ITO sputtering target material and the ITO sputtering target of the present invention have high use efficiency, long life, and small change with time in sputtering conditions, an ITO thin film having excellent physical properties can be easily and stably formed with a high yield.

  Moreover, according to the manufacturing method of the sputtering target material of this invention, the sputtering target material in which the whole structure | tissue including a fine structure was made uniform can be obtained. The manufacturing method of this sputtering target material is suitable for manufacture of the said ITO sputtering target material.

Hereinafter, the present invention will be specifically described.
<ITO sintered body, sputtering target material, sputtering target>
The ITO sintered body of the present invention satisfies the relationship of the following formula.

−30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30
In the above formula, Av1 is the average value (nm) of the maximum diameter of fine particles in the In ₂ O ₃ matrix phase grains present in the center of the sintered body, and Av2 is In ₂ present at the end of the sintered body. The average value (nm) of the maximum diameter of the fine particles in the O ₃ matrix phase is expressed.

Here, the average value of the maximum diameter of the fine particles present in the In ₂ O ₃ matrix grains is a cut surface obtained by horizontally cutting the ITO sintered body in the thickness direction using a diamond cutter. Polishing step by step using emery paper # 170, # 320, # 800, # 1500, # 2000, and finally buffing to finish to a mirror surface, followed by 40 ° C etching solution (nitric acid (60-61% Aqueous solution, manufactured by Kanto Chemical Co., Ltd., nitric acid 1.38 deer first grade product number 28161-03), hydrochloric acid (35.0-37.0% aqueous solution, manufactured by Kanto Chemical Co., Ltd., deer hydrochloric acid first grade product number 18078-01) and water in volume Etching is carried out by dipping in HCl: H ₂ O: HNO ₃ = 1: 1: 0.08 in a ratio for 9 minutes and etching, and an arbitrary 2 μm × 2 μm region of the appearing surface (however, along grain boundaries and grain boundaries) Of the fine particles observed in the compound phase existing in the wet state and in the region not including any of the free zones defined later) The average value of the maximum diameter.

The maximum diameter of the fine particles refers to the largest of the straight lines (diameters) connecting any two points on the observed cross section of the fine particles. Observation of fine particles is performed by SEM (scanning electron microscope) (magnification 30,000 times). The fine particles present in the In ₂ O ₃ matrix are considered to be a compound different from In ₂ O ₃ from the SEM image, and presumably to be In ₄ Sn ₃ O ₁₂ . The fine particle free zone is a region in the In ₂ O ₃ matrix in which fine particles are not observed when SEM observation is performed at a magnification of 3,000 in the above observation method (however, in a state along the grain boundary). Does not include the region of the compound phase present).

Usually, the maximum diameter of a plurality of In ₂ O ₃ parent phase grains observed from each part (for example, the central part and the end part of the ITO sintered body) of the cut surface of the ITO sintered body is the same by the observation method described above. Even so, the form (size, shape) and dispersion state of the fine particles present in these In ₂ O ₃ matrix grains vary depending on each part of the ITO sintered body and vary.

However, according to the study by the present inventors, even if the form and dispersion state of the fine particles present in the In ₂ O ₃ parent phase grains in each part of the ITO sintered body are different, the variation is within a specific range. If it fits within, there is no hindrance to sputtering, rather it can be said that the microstructure is made uniform throughout the entire ITO sintered body, and when this is used as a target material for sputtering, It has been clarified that since the entire sputtering surface is sputtered uniformly, the use efficiency is improved, the target life is extended, and the oxygen partial pressure dependency change over time and the voltage dependency change over time during sputtering can be suppressed.

That is, the ITO sintered body satisfies the relationship of the above formula, and the variation in the average value (nm) of the maximum diameter of the fine particles in the In ₂ O ₃ parent phase grains at the center and the end of the sintered body is ± More preferably within the range of 30%, the relationship of the following formula −10 ≦ 100 × (Av1−Av2) / Av1 ≦ 10 (where Av1 and Av2 have the same meaning as described above) is satisfied, When the variation of the average value (nm) of the maximum diameter of the fine particles in the In ₂ O ₃ matrix particles at the center and the end of the sintered body is within a range of ± 10%, the portion of the sintered body Regardless of the difference in size, the microstructure is made uniform throughout the entire sintered body, and not only the dispersion of the size of the fine particles but also the dispersion state is made uniform to the extent that there is no problem with sputtering. Has been. In the ITO sintered body having the uniform microstructure as described above, it is expected that the generation of arcing and particles is also reduced.

On the other hand, if the variation of the morphology of individual fine particles present in each In ₂ O ₃ matrix phase is large and does not satisfy the relationship of the above formula, the microstructure structure is different due to the difference in the part of the target material. Since the ITO sintered body is used as a sputtering target material and is sputtered because it is greatly different, the sputtering rate changes according to the structure of the site of the target material, and the erosion part is not sputtered uniformly. In addition, the use efficiency of the target material is poor and the life is shortened. In addition, arcing and particles are expected to occur frequently. In this case, not only the variation in the size of the fine particles, but also the variation in the dispersion state becomes large, and the microstructure of the exposed structure greatly changes as the consumption of the target material by sputtering proceeds. It is considered that the time-dependent change in the oxygen partial pressure dependency and voltage dependency of sputtering is large.

  The ITO sintered body of the present invention that satisfies the relationship of the above formula includes two preferred embodiments. Specifically, (1) in addition to satisfying the relationship of the above formula, and further, an aspect in which both Av1 and Av2 are 120 nm or less, and (2) in addition to satisfying the relationship of the above formula, further, the Av1 and Av2 Are both larger than 120 nm.

Hereinafter, the ITO sintered bodies (1) and (2) will be described in detail.
The ITO sintered body (1) which is one of the preferred embodiments of the present invention, in addition to satisfying the relationship of the above formula, ITO further has both Av1 and Av2 of 120 nm or less, more preferably in the range of 10 to 100 nm. It is a sintered body. In the case where both Av1 and Av2 satisfy the relationship of the above formula and both are 120 nm or less, more preferably within the specified range, In ₂ O ₃ Since the fine particles present in the mother phase grains are small and the dispersion state is uniform, the entire sputtering surface is sputtered uniformly, and the use efficiency as a target material can be expected to be improved.

1 schematically shows a part of the structure of the ITO sintered body (1) (however, FIG. 1 schematically shows the structure of the ITO sintered body in an exaggerated manner for the sake of explanation). The dimensions and ratios of each component are different from the actual product). In FIG. 1, 10 indicates the ITO sintered body (1) as a whole, and fine particles 12 are present in the In ₂ O ₃ parent phase grains 11 which are the main crystals of the ITO sintered body (1). Furthermore, the compound phase 14 exists along the grain boundary 13. There is also a fine particle free zone 15 which is a region in the In ₂ O ₃ matrix 11 where the fine particles 12 are not observed.

In addition, the ITO sintered body (2), which is one of the preferred embodiments of the present invention, satisfies the relationship of the above formula, and further, both Av1 and Av2 are larger than 120 nm, preferably in the range of 150 to 1000 nm. It is a certain ITO sintered body. In the case where both Av1 and Av2 satisfy the relationship of the above formula and both are larger than 120 nm, and more preferably within the specific range, the In ₂ O ₃ matrix is compared with those not satisfying the above condition. Since the number of fine particles present in the grains increases, the number thereof decreases, and it becomes difficult to become the starting point of the generation of yellow powder and particles, so that the generation of these can be expected.

FIG. 2 schematically shows a part of the structure of the ITO sintered body (2) (however, FIG. 2 schematically shows the structure of the ITO sintered body in an exaggerated manner for the sake of explanation). The dimensions and ratios of each component are different from the actual product). In FIG. 2, 10 indicates the ITO sintered body (2) as a whole, and fine particles 12 are present in the In ₂ O ₃ parent phase grains 11 which are the main crystals of the ITO sintered body (2). Furthermore, the compound phase 14 exists along the grain boundary 13. There is also a fine particle free zone 15 which is a region in the In ₂ O ₃ matrix 1 where the fine particles 12 are not observed.

  These ITO sintered bodies are so-called powders that are compression-molded by adding a binder to the raw material powder as necessary, and after the obtained molded body is degreased as necessary, the molded body is fired to obtain a sintered body. According to the metallurgical method, it can manufacture by performing a baking process on specific conditions. More specifically, the sputtering target material manufacturing method described later can be suitably applied, and details thereof will be described in the description of the sputtering target material manufacturing method below.

  The ITO sintered body can be preferably used as an ITO sputtering target material after being cut into a desired shape by known means, ground, etc., if necessary. Furthermore, an ITO sputtering target can be obtained by cutting the ITO sintered body into a desired shape as necessary, grinding, etc., and then joining with a backing plate that is a cooling plate.

  The backing plate is not particularly limited as long as it is normally used as a backing plate for a sputtering target, but a copper or copper alloy backing plate is preferable because of its good thermal conductivity. Moreover, the shape may be a known one and is not particularly limited.

  It should be noted that the ITO sintered body and the backing plate can be appropriately joined by a known method and is not particularly limited, but from the viewpoint of cost and productivity, a method of joining via a bonding agent such as In solder. Is preferred. Specifically, the ITO sintered body is cut into a desired shape as necessary, ground as necessary, and then heated to a temperature equal to or higher than the melting point of In. The bonded In solder can be bonded by a method such as applying molten In solder to the surface to be bonded to the backing plate, bonding it to the backing plate, allowing to cool while being pressurized, and cooling to room temperature.

<Method for producing sputtering target material>
The method for producing a sputtering target material according to the present invention is a method for producing a sputtering target material by powder metallurgy, and includes a heating process for heating a fired body after molding, and a fired body after passing through the heating process. A firing process including a cooling step of cooling at a temperature lowering rate of 50 ° C./hour or less or less than 50 ° C./hour is performed so that both ends have a temperature gradient.

The material of the sputtering target material that can be produced by the production method of the present invention is not particularly limited as long as the powder metallurgy method can be applied, and examples thereof include sintered alloys and ceramics. From the viewpoint that the effects of the present invention can be more effectively exhibited, those that cannot be subjected to plastic working such as rolling treatment, for example, ceramics are preferably mentioned. Among them, those containing indium oxide are preferable, and ITO is more preferable. This is because the size and dispersion state of the fine particles present in the In ₂ O ₃ matrix particles of the ITO sintered body are considered to be influenced by the manufacturing method of the ITO sintered body, particularly the firing conditions. For example, when the fired body after being molded in a conventionally known batch-type furnace (hereinafter also referred to as a batch furnace), uneven distribution of heat is generated in the furnace. Even if it is set, the entire body to be fired cannot be uniformly heated or cooled at that temperature, and the final heat history is different between the center and the end of the obtained ITO sintered body. . This difference in thermal history affects the growth of fine particles existing in the In ₂ O ₃ matrix phase grains of the obtained ITO sintered body. This is thought to increase the dispersion of the dispersion state.

Operations other than the above-mentioned firing treatment of the production method of the present invention can be performed according to known means and conditions usually performed in powder metallurgy. For example, raw material powder (for example, in the case of ITO, indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ )) are mixed in a desired ratio, and a binder is added if necessary, followed by compression molding. Thus, an operation from obtaining a molded body (hereinafter also referred to as a fired body) to degreasing the obtained molded body as necessary can be performed by commonly known means and conditions.

  Specifically, the raw material powder may be subjected to calcination and classification as required, and the subsequent mixing of the raw material powder can be performed by, for example, a ball mill. Thereafter, the mixed raw material powder is filled into a mold and compression-molded to produce a molded body, which may be degreased in an air atmosphere or an oxygen atmosphere, or a slurry described in JP-A-11-228220 Slurry consisting of mixed raw material powder, ion-exchanged water, and organic additives in a filtration mold made of a water-insoluble material for draining water from a ceramic raw material slurry under reduced pressure as in the casting method The molded body may be produced by draining water in the slurry under reduced pressure, and the molded body may be dried and degreased. In addition, you may perform degreasing | defatting of a molded object in the continuous furnace mentioned later.

  Next, the thus obtained molded body (sintered body) is subjected to a firing treatment including the specific cooling step. This baking process has a heating process, a cooling process, and a heat retention process as needed. Hereinafter, each step will be described in this order.

  First, the to-be-fired body (molded body) after the molding is heated by a process of heating in the furnace so that both ends have a temperature gradient for each to-be-fired body. More specifically, the object to be fired is heated while being conveyed so that the object to be fired passes through two or more adjacent regions set at different temperatures provided in the furnace. A process is mentioned preferably. When heated in this way, the sintered body can be heated and sintered sequentially from the end on the conveyance direction side, and shrinkage due to sintering is sequentially performed from the end. Therefore, problems such as cracking are unlikely to occur. Furthermore, since the unevenness of the heat distribution is extremely small as compared with the batch furnace, the thermal history of each part in the heating process can be made to the same degree regardless of the difference in the parts of the body to be fired. The conveying means may be a known means, and is not particularly limited. However, depending on the type of furnace to be used, the object to be fired is placed on a plurality of rollers, and these rollers are rotated in one direction and conveyed. And a means for placing the object to be fired on a belt and moving and transporting the belt.

  In addition, when the surface shape viewed from above of the object to be fired has a different aspect ratio such as a rectangle, it is placed so that the longer side of the surface shape of the object to be fired is parallel to the transport direction. To transport. Moreover, from the point which makes a heat history more uniform, you may use for a heating process, the cooling process mentioned later, or all of a heat retention process in the state which mounted the to-be-fired body on the well-known baking board.

  The length in the conveying direction of each region in the furnace (length in the longitudinal direction) may be the same as or different from other regions for each region, and the size of the body to be fired, the size of the furnace to be used, It can be determined appropriately depending on the number of regions to be arranged. The number of regions to be arranged can be appropriately determined according to the size of the body to be fired and the firing program.

  In addition, the temperature of each of the two or more adjacent regions in the heating step is sequentially in the range of 10 to 500 ° C. as compared with the temperature of the regions adjacent to each other in the heating direction. The conveyance speed of the object to be fired that is set to be high and passes through these two or more regions is usually in the range of 1 to 50 mm / min. In the heating step, the temperature in the lowest temperature region is usually room temperature to 800 ° C, and the temperature in the highest temperature region is usually 1400 to 1600 ° C.

  The set temperature of each region in the heating step is determined by a temperature detection device such as a thermocouple installed at a substantially middle point with respect to the length in the longitudinal direction for each region. At this time, it is desirable that the temperature between the temperature detecting devices installed in the regions adjacent to each other is normally adjusted to increase at a rate of 0.02 to 1.11 ° C./mm.

In addition, when the sputtering target material to be obtained is made of an ITO sintered body, from the viewpoint of improving the density of the obtained ITO sintered body, oxygen is introduced into the furnace and the heating step is performed in an oxygen atmosphere. It is desirable to do so. The flow rate of oxygen introduced into the furnace is usually in the range of 0.1 to 500 m ³ / hour per 1 m ^{3 in} the furnace. When oxygen is introduced in the heating step, oxygen may be continuously introduced in an amount within the above range in the cooling step and the heat retention step described later, or the introduction of oxygen is stopped and the atmosphere in the furnace is kept in the atmosphere. Or nitrogen.

  Subsequently, the to-be-baked body after passing through the said heating process is cooled by the cooling process cooled so that the both ends may have a temperature gradient about the one. More specifically, the fired body is cooled while being transported so that the fired body passes through two or more adjacent regions set in the furnace and set at different temperatures. A process is mentioned preferably. The conveying means is the same as the heating process described above.

  When cooled in this way, the sintered body can be sequentially cooled from the end on the conveyance direction side per one sintered body, and the deviation in heat distribution is extremely small as compared with a batch furnace. For this reason, the final thermal history of each part can be made to the same degree regardless of the difference in the part of the body to be fired. Therefore, the growth of fine particles existing in the crystal grains (parent phase grains) of the obtained sintered body becomes the same level, and variations in the form and dispersion state in each part can be kept within the specific range. It is considered a thing.

  The length of the transport direction side of each region in the cooling step (length in the longitudinal direction) may be the same as or different from other regions for each region, the size of the body to be fired, the size of the furnace to be used, It can be determined appropriately depending on the number of regions to be arranged. The number of regions to be arranged can be appropriately determined according to the size of the body to be fired and the firing program.

  In the cooling step, the temperature of each of the two or more adjacent regions is usually in the range of 10 to 500 ° C. as compared to the temperature of the adjacent region among them, and sequentially. It is set so that it may become low, respectively, and the conveyance speed of the molded object which passes through these two or more area | regions is the range of 1-50 mm / min normally. Furthermore, in the cooling step, the temperature in the highest temperature region is usually 1400 to 1600 ° C., and the temperature in the lowest temperature region is usually room temperature to 400 ° C.

  The set temperature of each region in the cooling step is determined for each region by a temperature detection device such as a thermocouple installed at a substantially middle point with respect to the length in the longitudinal direction of each region. At this time, it is desirable that the temperature between the temperature detecting devices installed in the mutually adjacent regions is normally set to drop at a rate of 0.02 to 1.11 ° C./mm.

In addition, when the sputtering target material to be obtained is made of an ITO sintered body, the viewpoint of controlling the average value of the maximum diameters of the fine particles existing in the main crystal grains of In ₂ O ₃ mother phase grains From the above cooling process, it is desirable to adjust the rate of temperature decrease in the cooling process by adjusting the conveyance speed of the object to be fired when passing through the region set to the temperature from the maximum temperature to 400 ° C.

Specifically, the cooling rate in the temperature range from the maximum temperature to 400 ° C. in the cooling process is adjusted to 50 ° C./hour or more, preferably 100 to 300 ° C./hour, more preferably 150 to 300 ° C./hour. then, the object to be fired rapidly cooling after a heating step, the growth of the in ₂ O ₃ matrix grains of the fine particles is prevented, in ₂ O ₃ matrix phase present in the sintered body central portion The average value Av1 (nm) of the maximum diameter of the fine particles in the grain and the average value Av2 (nm) of the maximum diameter of the fine particles in the In ₂ O ₃ parent phase grains existing at the end of the sintered body are both 120 nm or less. In addition, it is possible to obtain an ITO sintered body in which these values satisfy the following relationship: −30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30. In addition, when the said temperature fall rate exceeds 300 degreeC / hour, the probability that the sintered compact will generate | occur | produce will become high and it is unpreferable on production efficiency.

On the other hand, when the cooling rate in the temperature range from the maximum temperature to 400 ° C in the cooling step is adjusted to less than 50 ° C / hour, preferably 20 to 40 ° C / hour, more preferably 25 to 35 ° C / hour. The sintered body after the heating process is slowly cooled, so that the growth of fine particles in the In ₂ O ₃ matrix phase is promoted and coarsened, and both Av1 (nm) and Av2 (nm) from 120 nm In addition to being largely controllable, it is possible to obtain an ITO sintered body in which these values satisfy the relationship of the following formula −30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30.

In the cooling step, the temperature drop rate in the region set to a temperature from less than 400 ° C. to room temperature is not particularly limited. This is because in such a temperature region, the fine particles within the In ₂ O ₃ matrix phase do not substantially grow. Specifically, the temperature lowering rate in these regions may be set as appropriate, and in particular, the temperature may be allowed to cool without adjusting the temperature lowering rate and may be naturally cooled to room temperature.

  Further, in the present invention, if necessary, between the heating step and the cooling step, when the heating step is performed a plurality of times stepwise, the cooling step is performed a plurality of steps stepwise during each heating step. In some cases, a heat retaining step can be provided between the cooling steps. In the heat retaining process, the temperature of the immediately preceding heating process area or cooling process area is maintained. The length and number of regions in the heat retaining step can be appropriately determined depending on the size of the object to be fired, the size of the furnace to be used, the total number of regions to be disposed, and the like.

  In addition, it is preferable that the heating process and the cooling process (including a heat retaining process when a heat retaining process is included) are performed in a continuous furnace in order to easily control the temperature rising and temperature lowering conditions. Here, the continuous furnace means a furnace that can continuously heat and cool the object to be fired, or a furnace that can continuously heat, cool, and keep the object to be fired. Examples include roller hearth kiln, pusher furnace, and mesh belt furnace.

Further, from the viewpoint of reducing the uneven temperature distribution in the width direction in the furnace and achieving uniform heating of the width direction portion of the body to be fired, the continuous furnace is vertically moved with the conveyance path of the body to be fired as a boundary. A heating means is preferably provided in the direction, and a roller hearth kiln is more preferable. A roller hearth kiln is a kind of continuous furnace that can provide a preheating region, a heating region, a heat retaining region, a cooling region, and the like depending on the set temperature, and can execute a specific temperature profile. In addition, when a heating means is provided in the vertical direction with the conveyance path of the body to be fired as the boundary, thermocouples may be similarly provided in the vertical direction and temperature detection and temperature control may be performed in the vertical direction.

  The sintered body obtained through the above-described firing treatment can be preferably used as a sputtering target material after being cut into a desired shape and ground by a known means, if necessary.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
<Manufacture of ITO sputtering target>
A specific surface area of 8.07m ² / g tin oxide powder 100g of the indium oxide powder 900g and specific surface area of 2.2 m ² / g of zirconia balls of deionized water 30g and a diameter of 5mm for 20 hours ball milling put in a resin pot It was. Next, 178.3 g of ion-exchanged water and 7.9 g of a polycarboxylic acid dispersant were added and ball mill mixed for 1 hour. One hour later, 9.9 g of a wax-based binder was added, and ball mill mixing was performed for 19 hours to obtain a slurry.

  Next, 0.2 g of an amide-based antifoaming agent was added to the resulting slurry and vacuum deaeration was performed. The solid content concentration of this slurry was 83% by weight. The molding mold 2 is loaded on the molding mold having the structure shown in FIG. 3, specifically, on the lower molding mold 3 having the drainage hole 6 through the filter 4 and the seal material 5. Slurry 1 was cast into a concave part of a molding die having the above structure and drained from the drain hole 6 under reduced pressure to 760 mmHg to obtain a molded body of 350 mm × 400 mm × 12 mm.

After drying the obtained molded body at 25 ° C., it was introduced into a roller hearth kiln (24 regions, total length 10,800 mm), and oxygen gas with an oxygen concentration of 100% was introduced into the furnace at a flow rate of 0 per 1 m ³ in the furnace. The baking treatment was performed under the conditions shown in Table 1 while flowing at 2 m ³ / hour. After the firing treatment, the fired molded body was taken out from the roller hearth kiln outlet and cooled to room temperature to obtain an ITO sintered body. The size of the obtained ITO sintered body was about 300 mm × 348 mm × 10 mm.

  When introducing the molded body into the roller hearth kiln, the molded body is gradually brought closer to the entrance of the roller hearth kiln so that the temperature of the green body to be fired does not rise rapidly. When taking out from the hearth kiln, the green body was gradually moved away from the take-out port of the roller hearth kiln so that the temperature of the fired green body did not drop rapidly.

Moreover, the average temperature-fall rate of the temperature range from the highest temperature to 400 degreeC among the cooling processes of the said baking processing was 200 degreeC / hour. The temperature profile at this time is shown in FIG.
Based on the four-probe method, the specific resistance of the obtained ITO sintered body was measured using a constant-current voltage measuring device (Caseley; SMU236), a measurement stand (Kyowa Riken; K-504RS), and a four-probe probe (Kyowa Riken). Measured using K89PS150μ), it was 1.7 × 10 ⁻⁴ (Ω · cm).

Subsequently, the cut surface obtained by cutting the obtained ITO sintered body horizontally with a diamond cutter at a position 5 mm from the upper surface at the time of sintering with a diamond cutter is used as an emery paper # 170, # 320, # Using 800, # 1500, and # 2000, each of them is polished stepwise by rotating 90 degrees, and finally buffed to give a mirror finish. Then, an etching solution of 40 ° C. (nitric acid (60-61% aqueous solution, Kanto) Chemical Co., Nitric acid 1.38 Deer grade 1, product number 28161-03), HCl (35.0-37.0% aqueous solution, Kanto Chemical Co., Ltd., Deer grade 1, product number 18078-01) and water in HCl by volume : H ₂ O:
HNO ₃ = 1: 1: 0.08) and dipped for 9 minutes to etch, (i) the center position of the appearing surface, (ii) the position 30 mm in the longitudinal direction + 30 mm in the width direction from the corner, respectively SEM observation (JSM-6380A; manufactured by JEOL) was performed at magnifications of 3,000 and 30,000, and the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix at each site was determined.

As a result, (i) the average value (Av1) of the maximum diameter of the fine particles in the In ₂ O ₃ matrix phase particles present in the central portion of the ITO sintered body is 70 nm, and (ii) is present at the end of the sintered body. The average value (Av2) of the maximum diameter of the fine particles in the In ₂ O ₃ matrix phase is 65 nm, and (iii) the variation of the fine particles is 7.1% (= 100 × (Av1−Av2) / Av1) there were. The In ₂ O ₃ matrix particle size at the center and end of the ITO sintered body was uniform within a range of ± 1 μm.

Next, the ITO sintered body was cut out to an appropriate size, and both surfaces were ground with a surface grinder to obtain an ITO sputtering target material having a diameter of 152.4 mm and a thickness of 6 mm. The obtained ITO sputtering target material was joined to a copper backing plate via In solder to produce an ITO sputtering target.
<Performance evaluation of ITO sputtering target>
Using the obtained ITO sputtering target, the usage efficiency and lifetime of the target material, the change with time in oxygen partial pressure dependency during sputtering and the change with time in voltage dependency were evaluated by the following methods.

These results are summarized in Table 3.
((Evaluation of target material usage efficiency and life))
After the weight of the obtained ITO sputtering target was measured, the ITO sputtering target was sputtered under the following conditions, and an arc detection voltage of 100 V and an on / off arc energy boundary using a μ arcing monitor (manufactured by Landmark Technology). The cumulative number of arcs from the start of sputtering was measured under the conditions of 50 mJ and medium and small arc energy boundaries of 10 mJ. The input electric energy (Wh / cm ² ) except for the arc) was determined, and this was evaluated as the lifetime of the ITO sputtering target material.

  Moreover, the weight (M2) of the ITO sputtering target after sputtering is measured, and applied to the following formula together with the weight (M1) of the ITO sputtering target before starting sputtering measured in advance, and the usage efficiency (%) of the ITO sputtering target material Was evaluated.

Use efficiency of target material (%) = 100 × (M1-M2) / M1
((Evaluation of oxygen partial pressure dependence time-dependent change during sputtering))
Using the obtained ITO sputtering target, pre-sputtering and sputtering were performed under the following conditions, and the specific resistance (a) (Ω · cm) of the ITO film formed immediately after the start of sputtering and the cumulative input power 40 Wh / cm ² The specific resistance (b) (Ω · cm) of the ITO film sometimes formed was measured with ResiTest 8308 (manufactured by Toyo Technica) based on the van der Pauw method (however, in order to eliminate the influence of the initial arc, 15 Sputtering was started after a minute pre-sputtering).

The obtained specific resistance measurement value was applied to the following formula, and the oxygen partial pressure dependency change during sputtering was determined as a film specific resistance change rate (%), and evaluated according to the following criteria.
Film resistivity change rate (%) = 100 × | (a−b) / a |
Evaluation Criteria; Large: Membrane resistivity change rate exceeds 20%
Middle: Film resistivity change rate is over 15% to 20%
Small: Rate of change in film resistivity is 15% or less ((Evaluation of voltage-dependent temporal change during sputtering))
Similarly, sputtering is performed after pre-sputtering for 15 minutes, and the time required to form an ITO film having a thickness of 1200 mm on the substrate is set immediately after the start of sputtering (c), and the cumulative input power is 40 Wh / cm ^2. Each measurement was performed under the conditions of time (d), and the obtained measurement values were applied to the following formulas, and the voltage dependency change during sputtering was determined as the rate of decrease in sputtering rate (%) and evaluated according to the following criteria.

Sputter rate reduction rate (%) = 100 × | (cd) / c |
Evaluation criteria: Large: Sputter rate reduction rate exceeds 20%
Medium: Sputter rate reduction rate is over 10% to 20%
Small: Sputter rate reduction rate is 10% or less <Sputtering conditions>
Deposition conditions:
Equipment: DC magnetron sputtering equipment, exhaust system; cryopump, rotary pump Ultimate vacuum: 3.0 × 10 ⁻⁶ Pa
Sputtering pressure: 0.4 Pa (nitrogen conversion value, Ar pressure),
Oxygen partial pressure: 5 × 10 ⁻³ Pa
Input power: 600 W (1.85 W / cm ² )
Substrate temperature: 250 ° C
Substrate: Glass substrate (Corning # 1737) Thickness 0.8mm
Film thickness: 1200mm

[Example 2]
Example 1 according to the conditions shown in Table 2 and the temperature profile shown in FIG. 5 except that the average temperature drop rate in the temperature range from the highest temperature to 400 ° C. was 30 ° C./hour in the cooling process of the firing process. In the same manner, an ITO sintered body was obtained.

When the specific resistance of the obtained ITO sintered body was measured in the same manner as in Example 1, it was 2.0 × 10 ⁻⁴ (Ω · cm). Further, the microstructure of the obtained ITO sintered body was observed in the same manner as in Example 1. As a result, (i) Av1 was 300 nm, (ii) Av2 was 280 nm, and (iii) the variation in fine particles was 6 0.7%. The In ₂ O ₃ matrix particle size at the center and end of the ITO sintered body was uniform within a range of ± 1 μm.

  Next, an ITO sputtering target was prepared in the same manner as in Example 1, and the usage efficiency and life of the target material, the oxygen partial pressure dependency with time and the voltage dependency with time during sputtering were evaluated.

  The results are shown in Table 3.

[Comparative Example 1]
An ITO sintered body was obtained in the same manner as in Example 1 except that the firing process was performed in a batch furnace set to the following temperature conditions without using a roller hearth kiln.

200 ℃ → (100 ℃ / hr) → 800 ℃ × 2hr → (200 ℃ / hr) → 1600 ℃ × 8hr → (-200 ℃ / hr) → 400
℃
When the specific resistance of the obtained ITO sintered body was measured in the same manner as in Example 1, it was 1.8 × 10 ⁻⁴ (Ω · cm). Further, when the microstructure of the obtained ITO sintered body was observed in the same manner as in Example 1, it was found that (i) Av1 was 70 nm, (ii) Av2 was 30 nm, and (iii) dispersion of fine particles was 57. It was 1%. The In ₂ O ₃ matrix particle size at the center and end of the ITO sintered body was uniform within a range of ± 1 μm.

  Next, an ITO sputtering target was prepared in the same manner as in Example 1, and the usage efficiency and life of the target material, the oxygen partial pressure dependency with time and the voltage dependency with time during sputtering were evaluated.

The results are shown in Table 3.
[Comparative Example 2]
An ITO sintered body was obtained in the same manner as in Example 1 except that the firing process was performed in a batch furnace set to the following temperature conditions without using a roller hearth kiln.

200 ℃ → (100 ℃ / hr) → 800 ℃ × 2hr → (200 ℃ / hr) → 1600 ℃ × 8hr → (-30 ℃ / hr) → 400 ℃
When the specific resistance of the obtained ITO sintered body was measured in the same manner as in Example 1, it was 2.2 × 10 ⁻⁴ (Ω · cm). Further, when the microstructure of the obtained ITO sintered body was observed in the same manner as in Example 1, it was found that (i) Av1 was 300 nm, (ii) Av2 was 200 nm, and (iii) dispersion of fine particles was 33. 3%. In addition, the In ₂ O ₃ matrix particle size of the ITO sintered body central portion and the end portion was both uniform within a range of ± 1 μm. Next, in the same manner as in Example 1, an ITO sputtering target was prepared, The use efficiency and life of the target material, the time-dependent change in oxygen partial pressure during sputtering and the time-dependent change in voltage dependence were evaluated.

  The results are shown in Table 3.

From Table 3, the ITO sputtering target material and the ITO sputtering target obtained from the ITO sintered bodies of Examples 1 and 2 satisfying the relationship of the formula −30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30 have high use efficiency. It can be seen that the change in the sputtering conditions over time is small with a long life. On the other hand, the ITO sputtering target material and the ITO sputtering target obtained from the ITO sintered bodies of Comparative Examples 1 and 2 that do not satisfy the relationship of the above formula have low usage efficiency, short life, and large change in sputtering conditions over time. I understand. This is presumably because, in Comparative Examples 1 and 2, unlike Examples 1 and ₂ , there are large variations in the form of fine particles in the In ₂ O ₃ parent phase grains at both ends of the ITO sputtering target material.

FIG. 1 is a schematic diagram of the microstructure of the ITO sintered body (1). FIG. 2 is a schematic diagram of the microstructure of the ITO sintered body (2). FIG. 3 is a schematic cross-sectional view showing the structure of the molding die of Example 1. FIG. 4 is a temperature profile diagram of the baking treatment of Example 1. FIG. 5 is a temperature profile diagram of the baking treatment of Example 2.

Explanation of symbols

1: Slurry 2: Molding for molding 3: Lower mold for molding 4: Filter 5: Sealing material 6: Drainage hole 10: ITO sintered body 11: In ₂ O ₃ parent phase grain 12: Fine particle 13: Grain boundary 14: Compound phase 15: Fine particle free zone

Claims (10)

ITO (Indium-Tin-Oxide) sintered body characterized by satisfying the relationship of the following formula;
−30 ≦ 100 × (Av1−Av2) / Av1 ≦ 30
In the formula, Av1 is the average value (nm) of the maximum diameter of fine particles in the In ₂ O ₃ matrix phase grains present in the center of the sintered body, and Av2 is In ₂ O present at the end of the sintered body. The average value (nm) of the maximum diameter of the fine particles in the _three parent phase grains is represented.   Furthermore, both said Av1 and Av2 are 120 nm or less, The ITO sintered compact of Claim 1 characterized by the above-mentioned.   Furthermore, both said Av1 and Av2 are larger than 120 nm, The ITO sintered compact of Claim 1 characterized by the above-mentioned.   It is a sputtering target material, The ITO sintered compact in any one of Claims 1-3 characterized by the above-mentioned.   An ITO sputtering target comprising the ITO sintered body according to any one of claims 1 to 3 and a backing plate.   A method for producing a sputtering target material by a powder metallurgy method, wherein a heating step for heating a fired body after molding and a temperature gradient at both ends of each fired body after the heating step are performed. A method for producing a sputtering target material, comprising performing a firing process including a cooling step of cooling at a temperature lowering rate of 50 ° C./hour or more.   A method for producing a sputtering target material by a powder metallurgy method, wherein a heating step for heating a fired body after molding and a temperature gradient at both ends of each fired body after the heating step are performed. A method for producing a sputtering target material, comprising performing a baking treatment including a cooling step of cooling at a temperature lowering rate of less than 50 ° C./hour.   The said sputtering target material consists of ceramics, The manufacturing method of the sputtering target material of Claim 6 or 7 characterized by the above-mentioned.   The said sputtering target material contains indium oxide, The manufacturing method of the sputtering target material of Claim 6 or 7 characterized by the above-mentioned.   The said sputtering target material consists of ITO, The manufacturing method of the sputtering target material of Claim 6 or 7 characterized by the above-mentioned.

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