JP5205696B2 - Gallium oxide based sintered body and method for producing the same - Google Patents
Gallium oxide based sintered body and method for producing the same Download PDFInfo
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本発明は、スパッタリング法による酸化ガリウム系透明薄膜の成膜に用いられるスパッタリングターゲット、および、該スパッタリングターゲットに用いられる酸化ガリウム系焼結体とその製造方法に関する。 The present invention relates to a sputtering target used for forming a gallium oxide based transparent thin film by a sputtering method, a gallium oxide based sintered body used for the sputtering target, and a method for producing the same.
液晶ディスプレイ、プラズマディスプレイ、太陽電池においては、透明導電性薄膜が必要とされており、低い比抵抗を有するＩｎ2Ｏ3−ＳｎＯ2（ＩＴＯ）膜およびＺｎＯ−Ａｌ2Ｏ3（ＡＺＯ）膜が使用されている。これらの薄膜は、その組成を有する焼結体により形成されたスパッタリングターゲットを用いて、スパッタリング法によって成膜されている。 In a liquid crystal display, a plasma display, and a solar cell, a transparent conductive thin film is required, and an In 2 O 3 —SnO 2 (ITO) film and a ZnO—Al 2 O 3 (AZO) film having a low specific resistance are used. It is used. These thin films are formed by a sputtering method using a sputtering target formed of a sintered body having the composition.
一方、低い比抵抗のほかに、透過率などの特性を重視したＧａＩｎＯ3型結晶系からなる透明導電膜（特許文献１）、ＧａＩｎＺｎＯ4からなる自然超格子ホモロガス単結晶薄膜（特許文献２）など、様々な透明薄膜がデバイスの用途に応じて開発されている。 On the other hand, in addition to low specific resistance, a transparent conductive film made of a GaInO 3 type crystal system that emphasizes characteristics such as transmittance (Patent Document 1), a natural superlattice homologous single crystal thin film made of GaInZnO 4 (Patent Document 2), etc. Various transparent thin films have been developed according to the device application.
これらの透明薄膜は、導電膜以外の用途、すなわち、光デバイス、電子デバイス、Ｘ線光学デバイスにおいて利用されることが期待されている。 These transparent thin films are expected to be used in applications other than conductive films, that is, optical devices, electronic devices, and X-ray optical devices.
これらの透明薄膜は、スパッタリング法のほか、分子線エピタキシー（ＭＢＥ）法、化学気相蒸着（ＣＶＤ）法、パルスレーザーデポジション（ＰＬＤ）法が広く知られている。 For these transparent thin films, in addition to sputtering, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and pulsed laser deposition (PLD) are widely known.
しかしながら、これらの成膜に用いられる、ＧａＩｎＭxＯy（Ｍは正２価以上の金属元素）焼結体を含む酸化ガリウム系焼結体に関する報告は、ほとんどなされていない。 However, there have been almost no reports on gallium oxide-based sintered bodies including GaInM x O y (M is a positive divalent or higher-valent metal element) sintered body used for film formation.
一般的に、透明薄膜を形成する手段として、ＣＶＤ法あるいはスパッタリング法が用いられている。このうち、スパッタリング法では、薄膜の組成に対応する組成からなる焼結体により形成されるスパッタリングターゲットを用いる。 Generally, a CVD method or a sputtering method is used as a means for forming a transparent thin film. Among these, the sputtering method uses a sputtering target formed of a sintered body having a composition corresponding to the composition of the thin film.
スパッタリング法により成膜を行う際に、異常放電が生じる場合がある。異常放電が頻繁に起きると、プラズマ放電状態が不安定となり、安定した成膜が行われず、膜特性に悪影響を及ぼす。 When film formation is performed by a sputtering method, abnormal discharge may occur. If abnormal discharge frequently occurs, the plasma discharge state becomes unstable, and stable film formation is not performed, which adversely affects the film characteristics.
また、スパッタリングターゲットにノジュールという黒化物が発生する場合がある。ノジュールが存在すると、スパッタリングにおいて異常放電の発生原因となり、さらに、成膜速度の低下やアーキングの発生により、パーティクルが薄膜に付着するなどして、薄膜の透過率などの膜特性に悪影響を及ぼす。 Further, a blackened product called nodule may be generated on the sputtering target. The presence of nodules causes abnormal discharge in sputtering, and further, the film deposition rate decreases and arcing causes particles to adhere to the thin film, which adversely affects the film characteristics such as the transmittance of the thin film.
さらに、スパッタリング中に、スパッタリングターゲットにクラックや割れが生ずる場合がある。かかるクラックや割れからアーキングやノジュールが発生し、成膜の歩留まりを下げるという問題がある。 Furthermore, a crack and a crack may arise in a sputtering target during sputtering. There is a problem that arcing and nodules are generated from such cracks and cracks, and the yield of film formation is lowered.
本発明は、酸化ガリウム系薄膜の成膜において、スパッタリング中における、かかる異常放電の発生、ノジュールやアーキングの発生、クラックや割れの発生を抑制しうるスパッタリングターゲット、およびその原料となる酸化ガリウム系焼結体を提供することを目的とする。 The present invention provides a sputtering target capable of suppressing the occurrence of such abnormal discharge, nodule and arcing, cracking and cracking during sputtering in the formation of a gallium oxide-based thin film, and a gallium oxide-based firing as a raw material thereof. The purpose is to provide ligation.
本発明に係る酸化ガリウム系焼結体は、ＧａＩｎＭxＯy（Ｍは正２価以上の金属元素、ｘは整数で１〜３、ｙは整数で４〜８）の式で表され、焼結体密度が相対密度で９５％以上であり、Ｇａ2Ｏ3の絶縁相が存在せず、平均結晶粒径が１０μｍ以下であることを特徴とする。 The gallium oxide based sintered body according to the present invention is represented by the formula GaInM x O y (M is a positive divalent or higher metal element, x is an integer from 1 to 3, and y is an integer from 4 to 8). The aggregate density is 95% or more in relative density, there is no Ga 2 O 3 insulating phase, and the average crystal grain size is 10 μm or less.
その比抵抗は０．１Ω・ｃｍ以下であることが好ましい。 The specific resistance is preferably 0.1 Ω · cm or less.
かかる酸化ガリウム系焼結体は、比表面積が３〜１５ｍ2／ｇの酸化インジウム粉、酸化ガリウム粉、および、金属酸化物粉からなる原料粉をビーズミルによりスラリー中の粒度分布がすべて１μｍ以下と均一になるまで混合、粉砕した後に、スプレードライヤなどを用いて急速乾燥造粒を行い、得られた造粒物を冷間静水圧プレス（ＣＩＰ）により成形した後、得られた成形体を、導入する酸素流量を２〜２０ｍＬ／ｍｉｎとし、６００〜１４００℃の温度範囲における昇温速度を１〜１０℃／ｍｉｎとして昇温し、１２００〜１４００℃にて１０〜３０ｈ焼成することにより得られる。 Such a gallium oxide-based sintered body has a particle size distribution of 1 μm or less in a slurry using a bead mill made of indium oxide powder, gallium oxide powder, and metal oxide powder each having a specific surface area of 3 to 15 m 2 / g. After mixing and pulverizing until uniform, rapid dry granulation is performed using a spray dryer, etc., and the resulting granulated product is molded by cold isostatic pressing (CIP) , The oxygen flow rate to be introduced is set to 2 to 20 mL / min, the temperature rising rate in the temperature range of 600 to 1400 ° C. is set to 1 to 10 ° C./min, and the temperature is obtained by baking at 1200 to 1400 ° C. for 10 to 30 hours. .
得られた焼結体を所定形状に加工することにより、スパッタリングターゲットを作製する。 A sputtering target is produced by processing the obtained sintered body into a predetermined shape.
本発明に係る酸化ガリウム系焼結体を用いると、ＤＣスパッタリング中において、スパッタリングターゲットにクラックおよびノジュールが発生することが抑制され、また、異常放電の発生も少ないため、高品質の透明薄膜を、効率的に、安価に、省エネルギーで成膜することが可能となる。 When the gallium oxide-based sintered body according to the present invention is used, the generation of cracks and nodules in the sputtering target is suppressed during DC sputtering, and the occurrence of abnormal discharge is small. It becomes possible to form a film efficiently, inexpensively and with energy saving.
本発明に係る酸化ガリウム系焼結体は、ＧａＩｎＭxＯy（Ｍは正２価以上の金属元素、ｘは整数で１〜３、ｙは整数で４〜８）の式で表される。かかる焼結体を得るためには、酸化ガリウム（Ｇａ2Ｏ3）粉と酸化インジウム（Ｉｎ2Ｏ3）粉と金属酸化物（ＭＯ）粉からなる原料粉末を、混合、粉砕した後に、造粒を行い、得られた造粒物を成形した後、得られた成形体を所定温度で所定時間焼成することにより焼結させる。ここで、ＭＯとしては、酸化亜鉛のほか、酸化マグネシウム、酸化マンガン、酸化鉄、酸化コバルト、酸化ニッケル、酸化銅などが挙げられる。 The gallium oxide-based sintered body according to the present invention is represented by the formula GaInM x O y (M is a positive divalent or higher metal element, x is an integer of 1 to 3, and y is an integer of 4 to 8). In order to obtain such a sintered body, a raw material powder composed of gallium oxide (Ga 2 O 3 ) powder, indium oxide (In 2 O 3 ) powder, and metal oxide (MO) powder is mixed and pulverized, and then manufactured. After granulating and molding the obtained granulated product, the obtained molded body is sintered by firing at a predetermined temperature for a predetermined time. Here, as MO, magnesium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, etc. other than zinc oxide are mentioned.
本発明者は、上記課題を解決するために、酸化ガリウム系焼結体について解析を行い、鋭意検討を行った結果、酸化ガリウム系焼結体をスパッタリングターゲットとして利用可能とするためには、以下の事項が必要とされるとの知見を得た。 In order to solve the above-mentioned problems, the present inventor has analyzed the gallium oxide-based sintered body and intensively studied. As a result, in order to make the gallium oxide-based sintered body usable as a sputtering target, The knowledge that this matter is needed was obtained.
（１）焼結体密度が相対密度で９５％以上であること、
（２）焼結体の比抵抗が０．１Ωｃｍ以下であること、
（３）平均結晶粒径が１０μｍ以下であること、
（４）実質的に酸化ガリウム（Ｇａ2Ｏ3）の絶縁相が存在しないこと。
(1) The sintered body density is 95% or more by relative density,
(2) The specific resistance of the sintered body is 0.1 Ωcm or less,
(3) The average crystal grain size is 10 μm or less,
(4) The insulating phase of gallium oxide (Ga 2 O 3 ) is substantially absent.
これらについて、具体的に説明する。 These will be specifically described.
（焼結体密度）
焼結体の焼結体密度は、相対密度で９５％以上であることが好ましい。ここでは、真密度を式１で計算し、実際に作製した焼結体密度の実測値から相対密度を算出している。なお、焼結体密度の実測値は、アルキメデス法による。
(Sintered body density)
The sintered body density of the sintered body is preferably 95% or more in terms of relative density. Here, the true density is calculated by Equation 1, and the relative density is calculated from the actually measured sintered body density. In addition, the measured value of a sintered compact density is based on the Archimedes method.
計算真密度＝１００／（Ｇａ2Ｏ3の配合比（質量％）／Ｇａ2Ｏ3の密度＋Ｉｎ2Ｏ3の配合比（質量％）／Ｉｎ2Ｏ3の密度＋ＭＯの配合比（質量％）／ＭＯの密度）・・・式１
焼結体密度が高いほど、ノジュールと呼ばれる黒化物の発生が少なくなる。このノジュールは、低級酸化物であり、薄膜に対して透過率などの悪影響を及ぼす。
Calculated true density = 100 / (Ga 2 O 3 blending ratio (mass%) / Ga 2 O 3 density + In 2 O 3 blending ratio (mass%) / In 2 O 3 density + MO blending ratio (mass%) ) / MO density) Equation 1
The higher the density of the sintered body, the less blackened product called nodules. This nodule is a lower oxide and has an adverse effect on the thin film such as transmittance.
相対密度を９５％以上とするためには、各原料の比表面積を制御する必要がある。比表面積が低すぎる場合、原料の粒径が大きくなり、粉末の充填密度が高くなるが、粒径が大きく表面エネルギーが小さいため、焼結駆動力が小さくなり、高密度化が達成できない。逆に、比表面積が高すぎる場合、原料の充填密度は低くなり、そこで生じた空孔が低密度の原因となる。したがって、いずれの場合も、焼結体密度は高くならず、ノジュール発生の起因となる。 In order to make the relative density 95% or more, it is necessary to control the specific surface area of each raw material. If the specific surface area is too low, the particle size of the raw material becomes large and the packing density of the powder becomes high. However, since the particle size is large and the surface energy is small, the sintering driving force becomes small and high density cannot be achieved. On the contrary, when the specific surface area is too high, the packing density of the raw material becomes low, and the voids generated there cause low density. Therefore, in any case, the density of the sintered body is not increased, which causes generation of nodules.
また、焼成温度が１２００℃未満であると焼結体の相対密度が低くなり、ノジュール発生の原因となる。一方、１４００℃を超えた温度で焼成すると、焼結体と炉の間で反応が発生し、生産上好ましくない。 On the other hand, if the firing temperature is less than 1200 ° C., the relative density of the sintered body becomes low, causing nodule generation. On the other hand, when firing at a temperature exceeding 1400 ° C., a reaction occurs between the sintered body and the furnace, which is not preferable for production.
さらに、焼成時間を１０ｈ以上とすれば、９５％以上の相対密度を達成できるが、焼成時間を１０〜３０ｈとすることが好ましい。１０ｈより短い時間では成形体が十分に焼結せず、焼結体の相対密度は９５％を下回ってしまう。一方、３０ｈよりも長時間焼成を施すと、焼結体の平均結晶粒径が大きくなり、後述するように焼結体強度が低くなってしまう。 Furthermore, if the firing time is 10 hours or more, a relative density of 95% or more can be achieved, but the firing time is preferably 10 to 30 hours. If the time is shorter than 10 hours, the molded body does not sinter sufficiently, and the relative density of the sintered body falls below 95%. On the other hand, if firing is performed for longer than 30 hours, the average crystal grain size of the sintered body increases, and the strength of the sintered body decreases as described later.
（平均結晶粒径）
焼結体中の平均結晶粒径が大きいと焼結体強度は低くなり、スパッタリング中におけるスパッタリングターゲットのクラックの原因となる。したがって、平均結晶粒径は１０μｍ以下とすることが好ましい。所望の焼結体密度を達成し、かつ、平均結晶粒径を１０μｍ以下とするためには、焼成温度、焼成時間の調整も必要となる。なお、平均結晶粒径は、焼結体破断面を鏡面研磨した後、熱腐食によって粒界を析出させ、ＳＥＭ観察にて測定する。
(Average crystal grain size)
When the average crystal grain size in the sintered body is large, the strength of the sintered body is lowered, which causes cracks in the sputtering target during sputtering. Therefore, the average crystal grain size is preferably 10 μm or less. In order to achieve a desired sintered body density and to make the average crystal grain size 10 μm or less, it is necessary to adjust the firing temperature and firing time. The average crystal grain size is measured by SEM observation after the fracture surface of the sintered body is mirror-polished and then grain boundaries are precipitated by thermal corrosion.
一般的に、平均結晶粒径は、焼成温度、焼成時間に依存する。成形体の焼結温度が低く、焼成時間が短い方が、得られる焼結体の平均結晶粒径は小さくなる。酸化ガリウム系焼結体の場合、焼結体の相対密度を９５％以上とするために好ましい焼成条件は、焼成温度：１２００〜１４００℃で、焼成時間：１０ｈ以上である。この焼成条件において、焼結体密度を相対密度で９５％以上、平均結晶粒径を１０μｍ以下とするためには、焼成時間を１０〜３０ｈにする必要がある。１０ｈよりも短いと、平均結晶粒径は１０μｍ以下となるが、焼結体密度が相対密度で９５％を下回ってしまう。一方、３０ｈを超えて焼成を行うと、焼結体密度が相対密度で９５％を超えるが、平均結晶粒径が１０μｍを超えてしまう。 In general, the average crystal grain size depends on the firing temperature and firing time. The lower the sintering temperature of the molded body and the shorter the firing time, the smaller the average crystal grain size of the obtained sintered body. In the case of a gallium oxide-based sintered body, preferable firing conditions for setting the relative density of the sintered body to 95% or more are a firing temperature: 1200 to 1400 ° C., and a firing time: 10 hours or more. Under these firing conditions, in order to set the sintered body density to 95% or more in terms of relative density and the average crystal grain size to 10 μm or less, the firing time needs to be 10 to 30 hours. If it is shorter than 10 h, the average crystal grain size is 10 μm or less, but the sintered compact density is less than 95% in terms of relative density. On the other hand, when firing is performed for more than 30 hours, the sintered body density exceeds 95% in terms of relative density, but the average crystal grain size exceeds 10 μm.
（焼結体比抵抗）
スパッタリングターゲットにおいて、比抵抗は重要である。スパッタリングターゲットの比抵抗が高いと熱伝導が悪くなるため、スパッタリングターゲットに熱応力が発生し、クラックが発生しやすくなる。このため、スパッタリングターゲットに用いる焼結体は、その比抵抗が小さい方が好ましい。また、比抵抗が小さい焼結体をスパッタリングターゲットとして使用することで、成膜時の電流、電圧が小さくなり、膜へのダメージの減少、省エネも期待される。比抵抗は０．１Ω・ｃｍ以下とすることが好ましい。なお、焼結体の比抵抗は、４端針法で測定する。
(Sintered body resistivity)
In the sputtering target, the specific resistance is important. When the specific resistance of the sputtering target is high, the heat conduction is deteriorated, so that thermal stress is generated in the sputtering target and cracks are likely to occur. For this reason, the one where the specific resistance of the sintered compact used for a sputtering target is small is preferable. In addition, by using a sintered body having a small specific resistance as a sputtering target, the current and voltage during film formation are reduced, and a reduction in damage to the film and energy saving are also expected. The specific resistance is preferably 0.1 Ω · cm or less. The specific resistance of the sintered body is measured by a four-end needle method.
焼結体密度が低いと焼結体の比抵抗は高くなり、相対密度を９５％以上にすることで、焼結体の比抵抗は０．１Ω・ｃｍ以下となる。 When the sintered body density is low, the specific resistance of the sintered body is high, and by setting the relative density to 95% or more, the specific resistance of the sintered body is 0.1 Ω · cm or less.
（絶縁相の有無）
焼結体中に酸化ガリウム（Ｇａ2Ｏ3）の絶縁相が存在すると、スパッタリングにおける異常放電の原因となるので存在しない方が好ましい。Ｇａ2Ｏ3の絶縁層の有無は、原料の粉砕条件、造粒方法に起因する。この相が存在しない焼結体を作製するためには、原料の比表面積の調整、スプレードライヤなどの急速乾燥を用いた造粒方法が必要になる。
(With or without insulation phase)
If an insulating phase of gallium oxide (Ga 2 O 3 ) is present in the sintered body, it will cause abnormal discharge in sputtering, so it is preferable that it does not exist. The presence or absence of the Ga 2 O 3 insulating layer is caused by the raw material grinding conditions and the granulation method. In order to produce a sintered body in which this phase does not exist, it is necessary to adjust the specific surface area of the raw material, and to perform a granulation method using rapid drying such as a spray dryer.
すなわち、原料粉をボールミル混合・粉砕した後、自然乾燥で乾燥させ、粉砕、成形、焼結を行うと、数１０〜１００μｍ程度のＧａ2Ｏ3が偏折した相が発生し、これが異常放電の発生の原因となる。なお、酸化ガリウム（Ｇａ2Ｏ3）の絶縁相の存在は、Ｘ線回折で判断する。 That is, after the raw material powder is mixed and pulverized in a ball mill, dried by natural drying, and pulverized, molded, and sintered, a phase in which Ga 2 O 3 of several tens to 100 μm is bent is generated, which is an abnormal discharge. Cause the occurrence of Note that the presence of an insulating phase of gallium oxide (Ga 2 O 3 ) is determined by X-ray diffraction.
焼結体がこれらの条件を具備することによって、長期的にクラック、異常放電の発生が少ないスパッタリングターゲットを得ることができる。 By providing the sintered body with these conditions, it is possible to obtain a sputtering target with less generation of cracks and abnormal discharge over the long term.
次に、酸化ガリウム系焼結体の製造工程における、酸化ガリウム系焼結体に影響する各因子について、以下に説明する。 Next, each factor affecting the gallium oxide-based sintered body in the manufacturing process of the gallium oxide-based sintered body will be described below.
［原料粉末］
本願発明の酸化ガリウム系焼結体を得るための原料であるＧａ2Ｏ3粉末、Ｉｎ2Ｏ3粉末、ＭＯ粉末としては、比表面積が３〜１５ｍ2／ｇの粉末を用いる。比表面積が３ｍ2／ｇ未満であると、粉末の充填密度が高くなるが、粒径が大きく表面エネルギーが小さいため焼結駆動力が小さくなり、焼結体を高密度とすることはできない。一方、１５ｍ2／ｇよりも大きいと、原料の充填密度は低くなり、そこで生じた空孔が焼結体の低密度化の原因となる。
[Raw material powder]
As the Ga 2 O 3 powder, In 2 O 3 powder, and MO powder, which are raw materials for obtaining the gallium oxide sintered body of the present invention, a powder having a specific surface area of 3 to 15 m 2 / g is used. When the specific surface area is less than 3 m 2 / g, the packing density of the powder becomes high, but since the particle size is large and the surface energy is small, the sintering driving force becomes small and the sintered body cannot be made high density. On the other hand, if it is larger than 15 m 2 / g, the packing density of the raw material becomes low, and the voids generated there cause a reduction in the density of the sintered body.
［混合］
最初に原料粉末を混合する。混合については、湿式または乾式によるボールミル、振動ミル、ビーズミル等を用いることができる。均一で微細な結晶粒および空孔を得るには、短時間で凝集体の解砕効率が高く、添加物の分散状態も良好となるビーズミル混合法が最も好ましい。
[mixture]
First, the raw material powder is mixed. For mixing, a wet or dry ball mill, vibration mill, bead mill, or the like can be used. In order to obtain uniform and fine crystal grains and vacancies, a bead mill mixing method is most preferable because the crushing efficiency of the aggregates is high in a short time and the additive is well dispersed.
ビーズミルによる粉砕、混合時間は、装置の大きさ、処理するスラリー量によって異なるが、スラリー中の粒度分布がすべて１μｍ以下と均一になるように調整する。 The pulverization and mixing time by the bead mill varies depending on the size of the apparatus and the amount of slurry to be processed, but is adjusted so that the particle size distribution in the slurry is uniform to 1 μm or less.
処理時間が短いと、原料粉末を均一に混合、粉砕できないため、焼結体に空孔が生じ、相対密度の低下につながる。一方、１μｍ以下に調整しても、長時間の粉砕、混合を行うと微粒子が存在するようになり、原料の充填密度が低くなって、焼結体の相対密度の低下を招く。 When the treatment time is short, the raw material powder cannot be uniformly mixed and pulverized, so that voids are generated in the sintered body, leading to a decrease in relative density. On the other hand, even if the thickness is adjusted to 1 μm or less, fine particles are present when pulverized and mixed for a long period of time, the raw material packing density is lowered, and the relative density of the sintered body is lowered.
また、混合する際にはバインダーを任意量だけ添加し、同時に混合を行う。バインダーには、ポリビニルアルコール、酢酸ビニル等を用いることができる。 When mixing, an arbitrary amount of binder is added and mixed at the same time. As the binder, polyvinyl alcohol, vinyl acetate, or the like can be used.
［急速乾燥造粒］
次に、原料粉末スラリーから造粒粉を得る。造粒に際しては、急速乾燥造粒を行うことが好ましい。急速乾燥造粒するための装置としては、スプレードライヤが広く用いられている。具体的な乾燥条件は、乾燥するスラリーのスラリー濃度、乾燥に用いる熱風温度、風量等の諸条件により決定されるため、実施に際しては、予め最適条件を求めておくことが必要となる。自然乾燥を行うと、原料粉末の比重差によって沈降速度が異なるため、Ｇａ2Ｏ3粉末、Ｉｎ2Ｏ3粉末、ＺｎＯ粉末の分離が起こり、均一な造粒粉が得られなくなる。この不均一な造粒粉を用いて焼結体を作製すると、絶縁相であるＧａ3Ｏ3相が存在して、スパッタリングにおける異常放電の原因となる。
[Quick drying granulation]
Next, granulated powder is obtained from the raw material powder slurry. In granulation, it is preferable to perform rapid drying granulation. As an apparatus for rapid drying granulation, a spray dryer is widely used. The specific drying conditions are determined by various conditions such as the slurry concentration of the slurry to be dried, the temperature of hot air used for drying, the air volume, etc., and therefore, it is necessary to obtain optimum conditions in advance. When natural drying is performed, the sedimentation rate varies depending on the difference in specific gravity of the raw material powder, so that separation of Ga 2 O 3 powder, In 2 O 3 powder, and ZnO powder occurs, and uniform granulated powder cannot be obtained. When a sintered body is produced using this non-uniform granulated powder, a Ga 3 O 3 phase that is an insulating phase is present, which causes abnormal discharge in sputtering.
［成形］
造粒粉に対して、金型プレスまたは冷間静水圧プレス（ＣＩＰ）により、１ｔｏｎ／ｃｍ2以上の圧力で成形を施し、成型体を得る。
[Molding]
The granulated powder is molded at a pressure of 1 ton / cm 2 or more by a die press or cold isostatic press (CIP) to obtain a molded body.
［焼成方法］
本発明の酸化ガリウム系焼結体を得るための焼結方法としては、常圧焼結法のほか、ホットプレス、酸素加圧、熱間静水圧等の加圧焼結法も採用することができる。ただし、製造コストの低減、大量生産の可能性、容易に大型の焼結体を製造できるといった観点から、常圧焼結法を採用することが好ましい。
[Baking method]
As a sintering method for obtaining the gallium oxide-based sintered body of the present invention, a pressure sintering method such as hot pressing, oxygen pressing, hot isostatic pressing, etc. can be adopted in addition to the atmospheric pressure sintering method. it can. However, it is preferable to employ a normal pressure sintering method from the viewpoints of reducing manufacturing costs, possibility of mass production, and easy production of large sintered bodies.
［焼成雰囲気］
常圧焼結法では、通常、成形体を大気中にて焼成して焼結させる。焼結体密度を一層高くする場合には、昇温過程で酸素を導入して焼結させる。しかし、酸素の導入により酸素欠損が抑制され、焼結体の比抵抗が高くなるおそれがある。したがって、酸素を導入する場合の酸素流量としては、２〜２０Ｌ／ｍｉｎが好ましい。焼結体に添加される金属酸化物（ＭＯ）が蒸発しやすい酸化物である場合、たとえばＺｎＯである場合、焼結中の酸素流量が２Ｌ／ｍｉｎ未満であると、金属酸化物の蒸発抑制（密度増大）効果が薄れて、焼結体密度が低くなってしまう。一方、２０Ｌ／ｍｉｎを超えると、その流量によって焼結炉内が冷却され、均熱性が低下してしまう。
[Baking atmosphere]
In the atmospheric pressure sintering method, the compact is usually fired and sintered in the atmosphere. In order to further increase the density of the sintered body, oxygen is introduced and sintered in the temperature raising process. However, oxygen deficiency is suppressed by introduction of oxygen, and the specific resistance of the sintered body may be increased. Therefore, the oxygen flow rate when introducing oxygen is preferably 2 to 20 L / min. When the metal oxide (MO) added to the sintered body is an easily evaporated oxide, for example, when it is ZnO, if the oxygen flow rate during sintering is less than 2 L / min, the evaporation suppression of the metal oxide is performed. (Density increase) The effect is reduced, and the density of the sintered body is lowered. On the other hand, if it exceeds 20 L / min, the inside of the sintering furnace is cooled by the flow rate, and soaking is reduced.
［焼成温度］
焼成温度は、１２００〜１４００℃とする。また、焼成時間は、１０〜３０ｈとする。焼成温度が１２００℃未満であると、焼結体の相対密度を９５％以上とすることができない。一方、焼成温度が１４００℃を超えるか、または、焼成時間が３０ｈを超えると、著しい結晶粒成長により平均結晶粒径の増大、粗大空孔の発生を来たし、焼結体強度の低下や異常放電の原因となる。
[Baking temperature]
A baking temperature shall be 1200-1400 degreeC. The firing time is 10 to 30 hours. When the firing temperature is less than 1200 ° C., the relative density of the sintered body cannot be 95% or more. On the other hand, when the firing temperature exceeds 1400 ° C. or the firing time exceeds 30 hours, the average crystal grain size increases due to remarkable crystal grain growth, and coarse pores are generated, resulting in a decrease in sintered body strength and abnormal discharge. Cause.
さらに、焼結に際しての昇温速度は、６００〜１４００℃の温度範囲における昇温速度を１〜１０℃／ｍｉｎとする必要がある。６００〜１４００℃の温度範囲は、焼結が最も進行する範囲であり、この温度範囲での昇温速度が１℃／分より遅くなると、結晶粒成長が著しくなって、高密度化を達成することができない。一方、昇温速度が１０℃／ｍｉｎより速くなると、焼結炉内の均熱性が低下し、その結果、焼結中の収縮量に分布が生じて、焼結体が割れてしまうことがある。 Furthermore, the temperature rising rate during sintering needs to be 1 to 10 ° C./min in the temperature range of 600 to 1400 ° C. The temperature range of 600 to 1400 ° C. is the range in which the sintering proceeds most. When the rate of temperature increase in this temperature range is slower than 1 ° C./min, the crystal grain growth becomes remarkable and high density is achieved. I can't. On the other hand, when the rate of temperature rise is faster than 10 ° C./min, the heat uniformity in the sintering furnace is lowered, and as a result, the amount of shrinkage during sintering occurs and the sintered body may be cracked. .
焼結体の製造工程における諸条件を上記の通りに制御することにより、焼結体密度が相対密度で９５％以上であり、比抵抗が０．１Ωｃｍ以下であり、平均結晶粒径が１０μｍ以下であり、かつ、実質的に酸化ガリウム（Ｇａ2Ｏ3）相が存在しない、酸化ガリウム系焼結体を得ることができる。 By controlling the various conditions in the production process of the sintered body as described above, the sintered body density is 95% or more in relative density, the specific resistance is 0.1 Ωcm or less, and the average crystal grain size is 10 μm or less. And a gallium oxide-based sintered body substantially free of a gallium oxide (Ga 2 O 3 ) phase can be obtained.
かかる酸化ガリウム系焼結体を所定形状に加工することにより、酸化ガリウム系透明薄膜の成膜に用いることができ、ノジュールや異常放電、さらにはクラックの発生が生じない、スパッタリングターゲットを得ることができる。 By processing such a gallium oxide-based sintered body into a predetermined shape, it is possible to obtain a sputtering target that can be used for film formation of a gallium oxide-based transparent thin film and that does not generate nodules, abnormal discharge, and cracks. it can.
［実施例１］
比表面積１０．５ｍ2／ｇのＩｎ2Ｏ3粉および比表面積１１．２ｍ2／ｇのＧａ2Ｏ3粉をそれぞれ２５ｍｏｌ％、比表面積８．５ｍ2／ｇのＺｎＯ粉末を５０ｍｏｌ％となるように配合し、ビーズミルにて各原料粉末の粒度分布が１μｍ以下になるまで混合、粉砕を行った。なお、混合、粉砕を行う際に、バインダーとしてポリビニルアルコールを１質量％添加した。
[Example 1]
The In 2 O 3 powder having a specific surface area of 10.5 m 2 / g and the Ga 2 O 3 powder having a specific surface area of 11.2 m 2 / g are each 25 mol%, and the ZnO powder having a specific surface area of 8.5 m 2 / g is 50 mol%. And mixed and pulverized with a bead mill until the particle size distribution of each raw material powder became 1 μm or less. When mixing and pulverizing, 1% by mass of polyvinyl alcohol was added as a binder.
なお、比表面積の測定は（株）マウンテック社製、Macsorb HM model-1208で行った。 The specific surface area was measured with Macsorb HM model-1208 manufactured by Mountec Co., Ltd.
こうして作製したスラリーを取り出して、スラリー供給速度１４０ｍｌ／ｍｉｎ、熱風温度１４０℃、熱風量８Ｎｍ3／ｍｉｎの条件で、スプレードライヤを用いて急速乾燥造粒し、造粒物を冷間静水圧プレスにて３ｔｏｎ／ｃｍ2の圧力で成形し、直径１００ｍｍ、厚さ８ｍｍの円盤状の成形体を得た。 The slurry thus produced was taken out and rapidly dried and granulated using a spray dryer under conditions of a slurry supply rate of 140 ml / min, a hot air temperature of 140 ° C. and a hot air volume of 8 Nm 3 / min, and the granulated product was subjected to cold isostatic pressing. Was molded at a pressure of 3 ton / cm 2 to obtain a disk-shaped molded body having a diameter of 100 mm and a thickness of 8 mm.
次に、この成形体を大気中にて、６００℃までは０．５℃／ｍｉｎの速度で昇温し、酸素ガスを１０Ｌ／ｍｉｎの流速で導入しながら、６００〜８００℃までは１℃／ｍｉｎの速度で、さらに８００〜１３００℃の温度範囲では３℃／ｍｉｎの速度で昇温した。その後、１３００℃にて２０ｈの保持を行い、焼結体を得た。 Next, this molded body is heated in the atmosphere at a rate of 0.5 ° C./min up to 600 ° C., and oxygen gas is introduced at a flow rate of 10 L / min, while 1 ° C. up to 600-800 ° C. The temperature was increased at a rate of 3 ° C./min at a rate of 3 ° C./min. Thereafter, holding was performed at 1300 ° C. for 20 hours to obtain a sintered body.
得られた焼結体の密度を、焼結体の重量と幾何学的な寸法より算出後、焼結体の一部を切断して、切断部を鏡面研磨後、熱腐食して、ＳＥＭ観察（（株）日立ハイテクノロジーズ社製、S-800を使用）によって平均結晶粒径を測定した。Ｘ線回折結果（（株）リガク社製、rad-RVBを使用）からこの焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からはＧａ2Ｏ3に起因する回折ピークは検出されなかった。 After calculating the density of the obtained sintered body from the weight and geometric dimensions of the sintered body, a part of the sintered body is cut, the cut portion is mirror-polished, and then thermally corroded, and observed by SEM. The average crystal grain size was measured by (manufactured by Hitachi High-Technologies Corporation, using S-800). From the X-ray diffraction results (manufactured by Rigaku Corporation, using rad-RVB), it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected.
また、得られた焼結体を直径７５ｍｍ、厚さ６ｍｍの円盤状に加工して、スパッタリングターゲットを作製した。このターゲットを用いてＤＣマグネトロンスパッタリング中の異常放電回数、クラックの発生有無を調べた。スパッタリング条件は、投入電力２００Ｗ、Ａｒガス圧０．３Ｐａに固定した。そして実験開始から１０時間経過後の１０分間あたりに発生する異常放電回数を測定した。得られた結果を表１に示す。 Further, the obtained sintered body was processed into a disk shape having a diameter of 75 mm and a thickness of 6 mm to produce a sputtering target. Using this target, the number of abnormal discharges during DC magnetron sputtering and the presence or absence of cracks were examined. The sputtering conditions were fixed at an input power of 200 W and an Ar gas pressure of 0.3 Pa. And the frequency | count of abnormal discharge which generate | occur | produces per 10 minutes after 10-hour progress from the start of experiment was measured. The obtained results are shown in Table 1.
［実施例２］
比表面積を３．５ｍ2／ｇのＩｎ2Ｏ3粉、比表面積４．０ｍ2／ｇのＧａ2Ｏ3粉、比表面積３．１ｍ2／ｇのＺｎＯ粉末を用いたこと以外は、実施例１と同様の測定および試験を行った。その結果を表１に示す。
[Example 2]
In 2 O 3 powder with a specific surface area of 3.5m 2 / g, Ga 2 O 3 powder having a specific surface area of 4.0 m 2 / g, except for using ZnO powder having a specific surface area of 3.1m 2 / g, carried Measurements and tests similar to Example 1 were performed. The results are shown in Table 1.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例３］
比表面積１４．５ｍ2／ｇのＩｎ2Ｏ3粉、比表面積１４．６ｍ2／ｇのＧａ2Ｏ3粉、比表面積１４．９ｍ2／ｇのＺｎＯ粉末を用いたこと以外は、実施例１と同様にして焼結体を得た。
[Example 3]
In 2 O 3 powder having a specific surface area of 14.5m 2 / g, Ga 2 O 3 powder having a specific surface area of 14.6 m 2 / g, except for using ZnO powder having a specific surface area of 14.9m 2 / g, Example In the same manner as in No. 1, a sintered body was obtained.
得られた焼結体のＸ線回折結果からこの焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例４］
焼結温度を１２００℃、焼結時間を１０ｈにしたこと以外は、実施例１と同様にして焼結体を得た。
[Example 4]
A sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was 1200 ° C. and the sintering time was 10 h.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例５］
焼結温度を１４００℃、焼結時間を３０ｈにしたこと以外は、実施例１と同様にして焼結体を得た。
[Example 5]
A sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was 1400 ° C. and the sintering time was 30 h.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例６］
焼結時の酸素流量を２０Ｌ／ｍｉｎにしたこと以外は、実施例１と同様にして焼結体を得た。
[Example 6]
A sintered body was obtained in the same manner as in Example 1 except that the oxygen flow rate during sintering was 20 L / min.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例７］
焼結時の酸素流量を２Ｌ／ｍｉｎにしたこと以外は、実施例１と同様にして焼結体を得た。
[Example 7]
A sintered body was obtained in the same manner as in Example 1 except that the oxygen flow rate during sintering was 2 L / min.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例８］
６００〜１３００℃の温度範囲で１℃／ｍｉｎで昇温を行った以外は、実施例１と同様にして焼結体を得た。
[Example 8]
A sintered body was obtained in the same manner as in Example 1 except that the temperature was raised at 1 ° C./min in the temperature range of 600 to 1300 ° C.
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［実施例９］
６００〜８００℃までは１℃／ｍｉｎの速度で、さらに８００〜１３００℃の温度範囲では１０℃／ｍｉｎの速度で昇温したこと以外は、実施例１と同様にして焼結体を得た。
[Example 9]
A sintered body was obtained in the same manner as in Example 1 except that the temperature was increased at a rate of 1 ° C./min from 600 to 800 ° C., and further at a rate of 10 ° C./min in the temperature range of 800 to 1300 ° C. .
得られた焼結体のＸ線回折結果から、この焼結体の結晶構造はＩｎＧａＺｎＯ4であることがわかった。Ｘ線回折結果からＧａ2Ｏ3に起因する回折ピークは検出されなかった。また、得られた焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 From the X-ray diffraction result of the obtained sintered body, it was found that the crystal structure of this sintered body was InGaZnO 4 . From the X-ray diffraction results, no diffraction peak due to Ga 2 O 3 was detected. Moreover, the same measurement and test as Example 1 were performed about the obtained sintered compact. The results are shown in Table 1.
［比較例１］
比表面積２．５ｍ2／ｇのＩｎ2Ｏ3粉、比表面積０．９ｍ2／ｇのＧａ2Ｏ3粉、比表面積２．２ｍ2／ｇのＺｎＯ粉末を用いたこと以外は実施例１と同様にして焼結体を得た。
[Comparative Example 1]
In 2 O 3 powder having a specific surface area of 2.5m 2 / g, Ga 2 O 3 powder having a specific surface area of 0.9 m 2 / g, except for using ZnO powder having a specific surface area of 2.2 m 2 / g Example 1 In the same manner, a sintered body was obtained.
なお、ビーズミルによる混合、粉砕後のスラリーの粒度分布を測定してみると、ビーズミルにおける回転数および混合・粉砕時間を実施例１と同じにしたにも関わらず、スラリーの粒度分布は最大で１０μｍであった。 When the particle size distribution of the slurry after mixing and pulverization by the bead mill was measured, the particle size distribution of the slurry was 10 μm at the maximum even though the rotation speed and mixing / pulverization time in the bead mill were the same as in Example 1. Met.
得られた焼結体の密度を測定した後、焼結体の一部を切断して、切断面を鏡面研磨後、熱腐食して、ＳＥＭ観察によって平均結晶粒径を測定した。Ｘ線回折結果からこの焼結体は、ＩｎＧａＺｎＯ4相とＧａ2Ｏ3相で構成されることがわかった。 After measuring the density of the obtained sintered body, a part of the sintered body was cut, and the cut surface was mirror-polished and thermally corroded, and the average crystal grain size was measured by SEM observation. From the X-ray diffraction results, it was found that this sintered body was composed of an InGaZnO 4 phase and a Ga 2 O 3 phase.
また、得られた焼結体を直径７５ｍｍ、厚さ６ｍｍの円盤状に加工して、スパッタリングターゲットを作製した。このターゲットを用いてＤＣマグネトロンスパッタリング中の異常放電回数、クラックの発生有無を調べた。スパッタリング条件は、投入電力２００Ｗ、Ａｒガス圧０．３Ｐａに固定した。そして実験開始から１０時間経過後の１０分間あたりに発生する異常放電回数を測定した。得られた結果を表１に示す。 Further, the obtained sintered body was processed into a disk shape having a diameter of 75 mm and a thickness of 6 mm to produce a sputtering target. Using this target, the number of abnormal discharges during DC magnetron sputtering and the presence or absence of cracks were examined. The sputtering conditions were fixed at an input power of 200 W and an Ar gas pressure of 0.3 Pa. And the frequency | count of abnormal discharge which generate | occur | produces per 10 minutes after 10-hour progress from the start of experiment was measured. The obtained results are shown in Table 1.
［比較例２］
比表面積１５．５ｍ2／ｇのＩｎ2Ｏ3粉、比表面積１６．３ｍ2／ｇのＧａ2Ｏ3粉、比表面積１５．８ｍ2／ｇのＺｎＯ粉末を用いたこと以外は実施例１と同様にして焼結体を得た。
[Comparative Example 2]
In 2 O 3 powder having a specific surface area of 15.5m 2 / g, Ga 2 O 3 powder having a specific surface area of 16.3 m 2 / g, except for using ZnO powder having a specific surface area of 15.8 m 2 / g Example 1 In the same manner, a sintered body was obtained.
得られた焼結体の密度を測定した後、焼結体の一部を切断して、切断面を鏡面研磨後、熱腐食して、ＳＥＭ観察によって平均結晶粒径を測定した。Ｘ線回折結果からこの焼結体は、ＩｎＧａＺｎＯ4相のみで構成されることが分かった。 After measuring the density of the obtained sintered body, a part of the sintered body was cut, and the cut surface was mirror-polished and thermally corroded, and the average crystal grain size was measured by SEM observation. From the X-ray diffraction results, it was found that this sintered body was composed only of InGaZnO 4 phase.
また、得られた焼結体の密度を測定した後、焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 Moreover, after measuring the density of the obtained sintered compact, the same measurement and test as Example 1 were performed about the sintered compact. The results are shown in Table 1.
［比較例３］
焼結温度を１２００℃、焼結時間を５ｈにしたこと、以外は実施例１と同様に焼結体を得た。
[Comparative Example 3]
A sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was 1200 ° C. and the sintering time was 5 h.
得られた焼結体の密度を測定した後、焼結体の一部を切断して、切断面を鏡面研磨後、熱腐食して、ＳＥＭ観察によって平均結晶粒径を測定した。Ｘ線回折結果からこの焼結体は、ＩｎＧａＺｎＯ4相のみで構成されることが分かった。 After measuring the density of the obtained sintered body, a part of the sintered body was cut, and the cut surface was mirror-polished and thermally corroded, and the average crystal grain size was measured by SEM observation. From the X-ray diffraction results, it was found that this sintered body was composed only of InGaZnO 4 phase.
また、得られた焼結体の密度を測定した後、焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 Moreover, after measuring the density of the obtained sintered compact, the same measurement and test as Example 1 were performed about the sintered compact. The results are shown in Table 1.
［比較例４］
焼結温度を１４００℃、焼結時間を３５ｈにしたこと、以外は実施例１と同様に焼結体を得た。
[Comparative Example 4]
A sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was 1400 ° C. and the sintering time was 35 h.
得られた焼結体の密度を測定した後、焼結体の一部を切断して、切断面を鏡面研磨後、熱腐食して、ＳＥＭ観察によって平均結晶粒径を測定した。Ｘ線回折結果からこの焼結体は、ＩｎＧａＺｎＯ4相のみで構成されることが分かった。 After measuring the density of the obtained sintered body, a part of the sintered body was cut, and the cut surface was mirror-polished and thermally corroded, and the average crystal grain size was measured by SEM observation. From the X-ray diffraction results, it was found that this sintered body was composed only of InGaZnO 4 phase.
また、得られた焼結体の密度を測定した後、焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 Moreover, after measuring the density of the obtained sintered compact, the same measurement and test as Example 1 were performed about the sintered compact. The results are shown in Table 1.
［比較例５］
比表面積を１０．５ｍ2／ｇのＩｎ2Ｏ3粉、比表面積１１．２ｍ2／ｇのＧａ2Ｏ3粉をそれぞれ２５ｍｏｌ％、比表面積８．５ｍ2／ｇのＺｎＯ粉末を５０ｍｏｌ％となるように配合し、ビーズミルにて各原材料粉末の粒度分布が１μｍ以下になるまで混合、粉砕を行った。この際に、バインダーとしてポリビニルアルコールを１質量％添加した。
[Comparative Example 5]
The specific surface area was 10.5 m 2 / g In 2 O 3 powder, the specific surface area 11.2 m 2 / g Ga 2 O 3 powder was 25 mol%, and the specific surface area 8.5 m 2 / g ZnO powder was 50 mol%. The mixture was mixed and pulverized with a bead mill until the particle size distribution of each raw material powder became 1 μm or less. At this time, 1% by mass of polyvinyl alcohol was added as a binder.
こうして作製したスラリーを取り出して、高温槽で自然乾燥し、３００μｍ以下に粉砕した。この造粒物を冷間静水圧プレスにて３ｔｏｎ／ｃｍ2の圧力で成形し、直径１００ｍｍ、厚さ８ｍｍの円盤状の成形体を得た。 The slurry thus prepared was taken out, naturally dried in a high-temperature bath, and pulverized to 300 μm or less. This granulated product was molded by a cold isostatic press at a pressure of 3 ton / cm 2 to obtain a disk-shaped molded body having a diameter of 100 mm and a thickness of 8 mm.
次に、この成形体を実施例１と同様に焼結し、焼結体を得た。 Next, this molded body was sintered in the same manner as in Example 1 to obtain a sintered body.
得られた焼結体の密度を測定した後、焼結体の一部を切断して、切断面を鏡面研磨後、熱腐食して、ＳＥＭ観察によって平均結晶粒径を測定した。Ｘ線回折結果からこの焼結体は、ＩｎＧａＺｎＯ4相とＧａ2Ｏ3で構成されることが分かった。 After measuring the density of the obtained sintered body, a part of the sintered body was cut, and the cut surface was mirror-polished and thermally corroded, and the average crystal grain size was measured by SEM observation. From the X-ray diffraction results, it was found that this sintered body was composed of an InGaZnO 4 phase and Ga 2 O 3 .
また、得られた焼結体の密度を測定した後、焼結体について実施例１と同様の測定および試験を行った。その結果を表１に示す。 Moreover, after measuring the density of the obtained sintered compact, the same measurement and test as Example 1 were performed about the sintered compact. The results are shown in Table 1.
［比較例６］
６００〜８００℃までは１℃／ｍｉｎの速度で、さらに８００〜１３００℃の温度範囲では１２℃／ｍｉｎの速度で昇温したこと以外は、実施例１と同様にして焼結を実施したところ、焼結中に焼結体の割れが発生した。
[Comparative Example 6]
Sintering was performed in the same manner as in Example 1 except that the temperature was increased from 600 to 800 ° C. at a rate of 1 ° C./min, and further in the temperature range of 800 to 1300 ° C., at a rate of 12 ° C./min. During the sintering, cracks occurred in the sintered body.
焼結温度近傍における昇温速度が１０℃／ｍｉｎより速くなると、必ず焼結体が割れる訳ではないが、割れが発生し易い。 If the heating rate in the vicinity of the sintering temperature is faster than 10 ° C./min, the sintered body is not necessarily broken, but cracks are likely to occur.
実施例１〜９は、Ｇａ2Ｏ3、Ｉｎ2Ｏ3、ＺｎＯの比表面積が、本発明の範囲にある例である。表１からわかるように、得られた酸化ガリウム系焼結体の焼結体密度が相対密度で９５〜９８％以上である。また、焼結体の比抵抗においても最大で０．０８Ω・ｃｍである。さらに、得られた焼結体には、酸化ガリウム（Ｇａ2Ｏ3）が存在していない。 Examples 1 to 9 are examples in which the specific surface areas of Ga 2 O 3 , In 2 O 3 , and ZnO are within the scope of the present invention. As can be seen from Table 1, the sintered body density of the obtained gallium oxide-based sintered body is 95 to 98% or more in relative density. In addition, the maximum resistivity of the sintered body is 0.08 Ω · cm. Furthermore, gallium oxide (Ga 2 O 3 ) does not exist in the obtained sintered body.
これに対して、比較例１および比較例２は、Ｇａ2Ｏ3、Ｉｎ2Ｏ3、ＺｎＯの比表面積が、本発明の範囲外にある例である。したがって、比較例１では、焼結体の焼結体密度、平均結晶粒径、比抵抗の値すべてについて要件を満たさず、さらにＧａ2Ｏ3相も見られた。このため、クラック、異常放電が発生した。また、比較例２も、焼結体の焼結体密度、比抵抗の値について要件を満たさず、クラック、異常放電が発生した。 On the other hand, Comparative Example 1 and Comparative Example 2 are examples in which the specific surface areas of Ga 2 O 3 , In 2 O 3 and ZnO are outside the scope of the present invention. Therefore, in Comparative Example 1, all the sintered body density, average crystal grain size, and specific resistance values of the sintered body did not satisfy the requirements, and a Ga 2 O 3 phase was also observed. For this reason, cracks and abnormal discharge occurred. In Comparative Example 2, the sintered body density and specific resistance of the sintered body did not satisfy the requirements, and cracks and abnormal discharge occurred.
比較例３および比較例４は、焼結条件が本発明の範囲外にある例である。したがって、比較例３では、焼結体密度および比抵抗について要件を満たさず、異常放電が発生しており、比較例４では、結晶粒径について要件を満たさず、にかかる酸化ガリウム系焼結体についての要件を満たさず、クラックの発生、異常放電の発生が見られた。 Comparative Example 3 and Comparative Example 4 are examples in which the sintering conditions are outside the scope of the present invention. Therefore, in Comparative Example 3, the sintered body density and specific resistance do not satisfy the requirements and abnormal discharge occurs, and in Comparative Example 4, the crystal grain size does not satisfy the requirements and the gallium oxide-based sintered body is applied. The above-mentioned requirements were not met, and cracks and abnormal discharges were observed.
比較例５は、造粒を自然乾燥で行ったため、焼結体密度、比抵抗について要件を満たしておらず、さらにＧａ2Ｏ3相も存在していた。したがって、クラック、異常放電の発生が見られた。 In Comparative Example 5, since granulation was performed by natural drying, the sintered body density and specific resistance were not satisfied, and a Ga 2 O 3 phase was also present. Accordingly, cracks and abnormal discharge were observed.
Claims (4)
ＧａＩｎＭxＯｙ（Ｍは２価以上の金属元素、ｘは整数で１〜３、ｙは整数で４〜８）の式で表され、焼結体密度が相対密度で９５％以上であり、Ｇａ2Ｏ3の絶縁相が存在せず、平均結晶粒径が１０μｍ以下であることを特徴とする酸化ガリウム系焼結体。 After mixing and pulverizing raw material powder consisting of indium oxide powder, gallium oxide powder, and metal oxide powder having a specific surface area of 3 to 15 m 2 / g until the particle size distribution in the slurry is all uniform at 1 μm or less by a bead mill. Then, after rapid drying granulation, the obtained granulated product was molded by cold isostatic pressing, and the resulting molded product was subjected to 600 at a normal pressure sintering method with an oxygen flow rate of 2 to 20 mL / min. It is obtained by heating at a rate of temperature rise in the temperature range of ˜1400 ° C. as 1 to 10 ° C./min and firing at 1200 to 1400 ° C. for 10 to 30 hours,
GaInM x O y (M is a divalent or higher-valent metal element, x is an integer of 1 to 3, y is an integer of 4 to 8), and the sintered body density is 95% or more in terms of relative density, A gallium oxide-based sintered body having no Ga 2 O 3 insulating phase and an average crystal grain size of 10 μm or less.
After mixing and pulverizing raw material powder consisting of indium oxide powder, gallium oxide powder, and metal oxide powder having a specific surface area of 3 to 15 m 2 / g until the particle size distribution in the slurry is all uniform at 1 μm or less by a bead mill. Then, after rapid drying granulation, the obtained granulated product was molded by cold isostatic pressing, and the resulting molded product was subjected to 600 at a normal pressure sintering method with an oxygen flow rate of 2 to 20 mL / min. The temperature rise rate in a temperature range of ˜1400 ° C. is raised as 1 to 10 ° C./min, and sintered at 1200 to 1400 ° C. for 10 to 30 hours to obtain a sintered body. Of manufacturing a gallium oxide sintered body.
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