JP5711511B2 - CaF2-MgF2 binary sintered body and method for producing plasma-resistant fluoride sintered body - Google Patents

Description

本発明は、CaF₂−MgF₂二元系焼結体、及び耐プラズマ性フッ化物焼結体の製造方法に関し、より詳細には、シリコンおよび化合物半導体製造工程などで用いられる耐プラズマ性部材に好適な緻密な構造を有するCaF₂−MgF₂二元系焼結体及びその製造方法に関する。 The present invention relates to a CaF ₂ -MgF ₂ binary sintered body and a method for producing a plasma-resistant fluoride sintered body, and more particularly to a plasma-resistant member used in silicon and compound semiconductor manufacturing processes. The present invention relates to a CaF ₂ —MgF ₂ binary sintered body having a suitable dense structure and a method for producing the same.

シリコン半導体や化合物半導体の製造工程には、ＣＶＤ、ＭＯＣＶＤ、エッチング、クリーニング、アッシングなどの各工程で、フッ素や塩素等のハロゲン系ガスのプラズマを発生させてシリコンまたはガリウムヒ素またはサファイアなどのウエハー（基板）表面の処理を行う各種のプラズマ処理工程がある。プラズマは極めて反応性が高いため、それらプラズマ処理装置のチャンバーや処理用治具等の装置部材には、耐プラズマ性に優れた材料が求められ、厳選して使用される。加えて、シリコンおよび化合物半導体の製造工程では、不純物金属等による汚染およびパーティクル汚染を回避することも極めて重要である。このため、上記プラズマ処理装置においては、優れた耐プラズマ性に加えて、汚染防止性に優れていることも強く要求される。さらには、これら装置部材には、高機械的強度、高耐熱性、高衝撃性、高放熱性、高誘電性など使用部位によってはおのおのに特有の性能（特性）が要求される。当然のことながら、加えて低価格であることも重要な選択要素となっている。   In the manufacturing process of silicon semiconductors and compound semiconductors, wafers of silicon, gallium arsenide, sapphire, etc. are generated by generating plasma of halogen gas such as fluorine or chlorine in each process such as CVD, MOCVD, etching, cleaning, ashing, etc. There are various plasma processing steps for processing the substrate surface. Since plasma is extremely reactive, materials having excellent plasma resistance are required for apparatus members such as chambers and processing jigs of these plasma processing apparatuses, and are carefully selected and used. In addition, in the manufacturing process of silicon and compound semiconductors, it is extremely important to avoid contamination by impurity metals and particle contamination. For this reason, in the said plasma processing apparatus, in addition to the outstanding plasma resistance, it is also requested | required that it is excellent in anti-contamination property. Furthermore, these device members are each required to have specific performance (characteristics) depending on the use site, such as high mechanical strength, high heat resistance, high impact properties, high heat dissipation properties, and high dielectric properties. Of course, the low price is also an important option.

上記のようにプラズマ処理装置の構成部材には耐プラズマ性に優れた材料が求められるが、従来の材料としては、石英ガラス表面に耐プラズマ性に優れたイットリア(酸化イットリウム：Y₂O₃)をイオン化して成膜したり、真空蒸着したりしている。あるいは、耐プラズマ性に優れたアルミナ（Al₂O₃）の焼結体を用いたりしているが、いずれも耐プラズマ性を始めとする諸要求特性を十分満たしているとは言えない。 As described above, a material having excellent plasma resistance is required for the constituent members of the plasma processing apparatus. As a conventional material, yttria (yttrium oxide: Y ₂ O ₃ ) having excellent plasma resistance on the surface of quartz glass is used. Is ionized to form a film, or vacuum deposition is performed. Alternatively, a sintered body of alumina (Al ₂ O ₃ ) having excellent plasma resistance is used, but none of them satisfy the required characteristics including plasma resistance.

ところで、フッ素系または塩素系の所謂ハロゲン系ガスのプラズマに対する耐性を付与するには、一般的には同じハロゲン系元素（フッ素、塩素、臭素、ヨウ素など）を含む化合物が化学的に安定で有利であると推定される。それに加えて上記のプラズマ耐性以外の要求特性を加味すると、フッ化カルシウム（CaF₂）などがこの装置部材の新しい材料の候補と目される。 By the way, in order to impart resistance to the plasma of so-called halogen-based gases such as fluorine-based or chlorine-based compounds, generally compounds containing the same halogen-based elements (fluorine, chlorine, bromine, iodine, etc.) are chemically stable and advantageous. It is estimated that. In addition, considering the required characteristics other than the above-mentioned plasma resistance, calcium fluoride (CaF ₂ ) and the like are regarded as candidates for new materials for this device member.

そのCaF₂は、天然鉱物としては蛍石と称されており、理化学辞典によると融点1418℃、沸点2500℃、密度3.18g/cm³、モース硬度４の立方晶系に属する蛍石構造と称される無色の結晶である。このため、高純度の単結晶体は光透過性に極めて優れ、従来からプリズム、レンズ等の光学部材として用いられてきた。最近ではさらに高純度化、結晶構造の改良などにより真空紫外域における透過率が飛躍的に高められ、真空紫外光を光源とする光学部材として、具体的には波長193nmのArFエキシマレーザーを光源とする縮小投影露光機用レンズ等の高級な光学部品に使用されるようになってきている。 The CaF ₂ is a natural mineral called fluorite. According to the physics and chemistry dictionary, it has a melting point of 1418 ° C, a boiling point of 2500 ° C, a density of 3.18 g / cm ³ and a Mohs hardness of 4 belonging to a cubic system. Colorless crystals. For this reason, high-purity single crystals are extremely excellent in light transmittance, and have been conventionally used as optical members such as prisms and lenses. Recently, the transmittance in the vacuum ultraviolet region has been drastically increased due to higher purity and improved crystal structure, and as an optical member using vacuum ultraviolet light as a light source, specifically, an ArF excimer laser with a wavelength of 193 nm is used as the light source. It has come to be used for high-grade optical parts such as lenses for reduction projection exposure machines.

その一方で、CaF₂は耐プラズマ性に優れた材料であることも知られている。例えば、特許第3017528号公報（下記特許文献１）には、プラズマに曝されるAlまたはステンレス鋼を含む材料から成る電極表面に、イオンプレーティング法と蒸着法の併用によってCaF₂のコーティング膜を形成し、耐プラズマ性を向上させ、電極が汚染源と成らないようにすることで、優れたプラズマ処理装置が得られることが開示されている。しかしながら、例えば、プラズマ処理装置のチャンバー内張り材のように表面積の大きい部材、とくに凹凸の多い複雑な形状の部材や大型品等に、CaF₂を均一にコーティングすることは困難である。仮に、コーティング出来た場合であっても、その膜は剥離し易いという課題を有するものであった。 On the other hand, CaF ₂ is also known to be a material with excellent plasma resistance. For example, in Japanese Patent No. 3017528 (Patent Document 1), a CaF ₂ coating film is formed on an electrode surface made of a material containing Al or stainless steel exposed to plasma by a combination of an ion plating method and a vapor deposition method. It is disclosed that an excellent plasma processing apparatus can be obtained by forming, improving plasma resistance, and preventing the electrode from becoming a contamination source. However, for example, it is difficult to uniformly coat CaF ₂ on a member having a large surface area such as a chamber lining material of a plasma processing apparatus, in particular, a member having a large unevenness or a complicated shape or a large product. Even if it was possible to coat, the film had a problem that it was easy to peel off.

そこで、CaF₂自体を耐プラズマ性部材として利用するため、光学部材に用いられている高純度のCaF₂単結晶体をそのまま耐プラズマ性部材に研削加工することが考えられる。しかしながら、この場合、つぎのような種々の課題を有する。まずは、高純度の単結晶体を製造するには、高度な技術を馳駆し、多大な処理工数を要する原料の高純度化と、数ヶ月に及ぶ高温炉内での単結晶成長をさせねばならず、その結果、膨大な製造費を要し、著しく高価な材料となる。さらに、この材料は、単結晶なるが故に脆性であり、わずかな機械的衝撃でもキズが発生し易く、比較的軽度の衝撃でも割れを生ずる場合がある。また熱的衝撃には極めて弱く割れを生じ易くなるなど、取扱いには高度な知識と熟練の技能を要する。その結果、加工にも高度な技術と多大な工数を要し、著しく高価な加工となる。そのため、本用途への実用化には適さないものであった。 Therefore, in order to use CaF ₂ itself as a plasma-resistant member, it is conceivable to grind the high-purity CaF ₂ single crystal used for the optical member as it is to the plasma-resistant member. However, this case has the following various problems. First, in order to produce a high-purity single crystal, it is necessary to use advanced technology to improve the purity of raw materials that require a large number of processing steps, and to grow single crystals in a high-temperature furnace for several months. As a result, enormous manufacturing costs are required and the material becomes extremely expensive. Furthermore, this material is brittle because it is a single crystal, and is easily scratched even by a slight mechanical impact, and may be cracked even by a relatively mild impact. In addition, it is extremely weak against thermal shock and easily cracks, so it requires advanced knowledge and skill. As a result, the processing requires advanced technology and a great number of man-hours, and the processing becomes extremely expensive. Therefore, it was not suitable for practical use for this application.

光学部材に用いられている高純度のCaF₂単結晶体をそのまま耐プラズマ性部材に用いるには、数々の問題点があることは上記した通りである。これを改良しようとしたのが、例えば特開2003−300777号公報（下記特許文献２）に開示され、光学部材用CaF₂単結晶の切り出し屑など高純度のCaF₂単結晶片を粉砕して得られた粉末を出発原料としてホットプレスによる加熱加圧法で緻密な焼結体とするものが示されている。 As described above, there are a number of problems in using the high-purity CaF ₂ single crystal used for the optical member as it is for the plasma-resistant member. An attempt to improve this is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-300777 (the following Patent Document 2), in which high-purity CaF ₂ single crystal pieces such as cutting scraps of CaF ₂ single crystals for optical members are pulverized. It is shown that the obtained powder is used as a starting material to form a dense sintered body by a hot press method using hot pressing.

しかしながら、この製造方法では以下に示す種々の問題が生ずる。まず、元材料である光学部材用CaF₂単結晶の切り出し屑の粉砕工程で不純物汚染の問題が生ずる。高純度の元材料を不純物汚染を生じさせずに粉砕して高純度のまま焼結用の出発材料とすることは不可能である。焼結用の出発材料とするにはかなり細かな粉状まで微粉砕することが必要であり、まずこの微粉砕の際の容器、粉砕用治具の構成材料が摩耗して出発材料に混入する汚染と、粉砕工程でのハンドリングに起因する環境起因の汚染が考えられる。 However, this manufacturing method has the following various problems. First, the problem of impurity contamination arises in the pulverization process of the cutting material of the CaF ₂ single crystal for optical members, which is the original material. It is impossible to pulverize a high-purity original material without causing impurity contamination and use it as a starting material for sintering while maintaining a high purity. In order to use as a starting material for sintering, it is necessary to finely pulverize it into a fine powder. First, the constituent materials of the container and the jig for grinding are worn out and mixed into the starting material. Contamination and environmental pollution caused by handling in the grinding process are considered.

さらには、その微粉砕した微粉を焼結用の出発材料にするには、一般的には粒度調整工程が必要であり、空気分級とか篩いを用いて粗めの粒子と微細な粒子を除去し、緻密な焼結体に焼結し易い粒度分布に粒度を調整する必要がある。この工程でのハンドリングに起因する環境起因の汚染は避けられない。いずれのハンドリング工程も工程を経れば経るほど不純物汚染は進む。   Furthermore, in order to use the finely pulverized fine powder as a starting material for sintering, a particle size adjustment process is generally required, and coarse particles and fine particles are removed using air classification or sieving. It is necessary to adjust the particle size to a particle size distribution that is easy to sinter into a dense sintered body. Environmental pollution due to handling in this process is inevitable. Impurity contamination progresses as each handling process passes.

また、特開2003−300777号公報（下記特許文献２）の明細書中で、この出来上がった焼結体は粉末X線回折法の解析結果から元材料の単結晶と同等のX線回折ピーク強度およびピーク広がりを持っていると説明されており、単結晶性が高いものである。単結晶体は脆性材料であり、もろく成りやすい。また、ホットプレスによる加熱加圧法ではモールドが必要であり、このモールドと焼結体との熱膨張係数の差異に起因して加熱加圧後の冷却過程で焼結体内部に歪みが発生しやすい。さらに、単結晶体は本来耐衝撃性に劣り、時として割れを生ずることがある。また、ホットプレスによる加熱加圧法はバッチ処理となるため、生産性に劣り、高コストとなりがちである。   Further, in the specification of Japanese Patent Laid-Open No. 2003-300777 (the following Patent Document 2), this finished sintered body has an X-ray diffraction peak intensity equivalent to that of the single crystal of the original material from the analysis result of the powder X-ray diffraction method. In addition, it has been explained that it has a peak broadening, and has high single crystallinity. Single crystals are brittle materials and tend to be brittle. In addition, a mold is required in the hot press method using hot press, and distortion is likely to occur inside the sintered body during the cooling process after heat and pressure due to the difference in thermal expansion coefficient between the mold and the sintered body. . Furthermore, single crystals are inherently inferior in impact resistance and sometimes crack. In addition, since the hot press method using hot press is batch processing, it tends to be inferior in productivity and expensive.

また、特開2004−83362号公報（下記特許文献３）には、Mgを含有する低純度の出発原料に、フッ化水素酸を用いてMg以外の不純物を除去する処理を施し、この後、高純度CaF₂を沈殿させ、これを熱処理し、造粒し、その後成形し、焼結させてMgF₂を含有するCaF₂の焼結体を製造する方法とその焼結体の発明が開示されている。 JP-A-2004-83362 (Patent Document 3 below) performs a treatment for removing impurities other than Mg using hydrofluoric acid on a low-purity starting material containing Mg. precipitated high purity CaF _2, which was heat-treated, granulated, and then molded, the invention of a method and a sintered body thereof for producing a sintered body of CaF ₂ containing MgF ₂ is disclosed by sintering ing.

しかしながらこの発明では、まず出発原料が低純度であり、したがって通常、不純物の種類、濃度が一定しない。そのためその都度分析を行い、その出発原料に合わせてフッ化水素酸を用いた純化処理の条件をその都度変える必要がある。さらには、不純物の種類・その濃度など出発原料中の不純物の状況によっては沈殿処理法では純化が十分行えない場合も生じる。このため、純化処理後の中間生成物は、純度をはじめ物性が不安定となる。この製造方法では、純度を高められる可能性があるのはこの純化処理工程に限られ、結果的に、最終製品である焼結体の物性も不安定なものとなる。言い換えれば、良好な特性を有する焼結体を安定的に得ることは困難な方法と言わざるを得ない。   However, in the present invention, the starting material is first of low purity, and therefore the type and concentration of impurities are usually not constant. Therefore, it is necessary to perform analysis each time, and to change the conditions of the purification treatment using hydrofluoric acid according to the starting material. Furthermore, depending on the state of impurities in the starting material, such as the type and concentration of impurities, the precipitation treatment method may not be able to sufficiently purify. For this reason, the intermediate product after the purification treatment becomes unstable in physical properties including purity. In this manufacturing method, the purity can be increased only in this purification treatment step, and as a result, the physical properties of the sintered product as the final product also become unstable. In other words, it is a difficult method to stably obtain a sintered body having good characteristics.

さらに、この製造方法では、焼結温度が常圧焼結工程、加圧焼結工程ともに高々８００℃と低温であり、後述するようにCaF₂−MgF₂二元系状態図に示すように、固相間反応による固相焼結となる。しかもこの製造方法では、高々８００℃とかなり低温であるため、固相間反応の速度が遅く、粒子同士の結合力が弱く、また粒成長も不十分となり、強度の弱い焼結体となるといった課題がある。
上記したように、従来のCaF₂単一成分の単結晶体、あるいはCaF₂を主成分とする焼結体を耐プラズマ性部材に用いるには種々の問題または解決すべき課題がある。 Furthermore, in this production method, the sintering temperature is as low as 800 ° C. at most in both the normal pressure sintering step and the pressure sintering step, and as shown in the CaF ₂ -MgF ₂ binary phase diagram as described later, It becomes solid phase sintering by reaction between solid phases. Moreover, in this production method, since the temperature is as low as 800 ° C., the reaction speed between the solid phases is slow, the bonding force between the particles is weak, the grain growth is insufficient, and the sintered body is weak. There are challenges.
As described above, there are various problems or problems to be solved in order to use the conventional CaF ₂ single component single crystal body or the sintered body mainly composed of CaF ₂ for the plasma resistant member.

そこで、本発明者らは、既に、特願2009−142911号（平成21年6月16日出願：以下、先願Iと称す）で上記課題を解決すべくCaF₂−MgF₂二元系の耐プラズマ性フッ化物焼結体の製造方法を発明し、出願している。
先願I記載の製造方法では、いずれも固溶体を生ずる高い温度域で加熱・焼結するため、粒成長速度が速く、且つ粒子間の結合強度が大きい焼結体となる。しかしながら、先願Iで開示した高い温度域での焼結は、以下に示すようなマイナス面が出て来る場合もあると考えられた。 Therefore, the present inventors have already disclosed a CaF ₂ -MgF ₂ binary system in order to solve the above problem in Japanese Patent Application No. 2009-142911 (filed on June 16, 2009: hereinafter referred to as Prior Application I). We have invented and filed a method for producing a plasma-resistant fluoride sintered body.
In each of the production methods described in the prior application I, since heating and sintering are performed in a high temperature range where a solid solution is generated, a sintered body having a high grain growth rate and a high bond strength between particles is obtained. However, it was considered that the sintering in the high temperature range disclosed in the previous application I might have the following negative aspects.

第１に、原料がフッ化物のため高温度に加熱するほど気化（蒸発、とも言う）する割合が増加し、焼結体になる割合、すなわち歩留（＝(焼結体質量）×１００÷(原料質量））の低下を招く。また、この気化した物質はフッ素ガスであり、猛毒で強い腐食性をもつ刺激物であり、化学作用が極めて強く、すべての金属元素と直接反応するので、排ガスの十分な処理が必要になる。   First, since the raw material is fluoride, the rate of vaporization (also referred to as evaporation) increases as the raw material is heated to a higher temperature, and the rate of becoming a sintered body, that is, yield (= (sintered body mass) × 100 ÷ (Raw material mass)). In addition, the vaporized substance is fluorine gas, an irritant that is highly toxic and highly corrosive, has a very strong chemical action, and reacts directly with all metal elements, so that sufficient treatment of exhaust gas is required.

第２に、焼結速度が速いため焼結体の部位による緻密化の進行のバラツキが生じ易く、外周に近いほど緻密化が進み、それが過度な場合は外周部の一部が溶けて崩れる虞がある。一方、内部は外周部の緻密化が速過ぎると、内部の気泡や空隙内のガスが外部へ拡散し難くなり、脱泡が進み難くなるため内部側に気泡が残り易くなることがある。気泡が多く残ると緻密化が十分ではなくなり、強度や耐プラズマ性が低下するなどの課題が発現し、耐プラズマ性部材として使用しづらいものとなるなどの課題が残った。   Secondly, since the sintering speed is high, the progress of densification easily varies depending on the portion of the sintered body. Densification progresses as it is closer to the outer periphery, and if it is excessive, a part of the outer periphery melts and collapses. There is a fear. On the other hand, if the inside is too dense at the outer peripheral portion, the bubbles inside and the gas in the gap are difficult to diffuse to the outside, and the bubbles are likely to remain on the inside because defoaming is difficult to proceed. When many bubbles remain, densification is not sufficient, and problems such as reduction in strength and plasma resistance appear, and problems such as difficulty in use as a plasma resistance member remain.

そこで、さらに本発明者らは、既に、特願2009−254436号（平成２１年１１月５日出願：以下、先願IIと称す）で上記課題を解決すべくCaF₂−MgF₂二元系の耐プラズマ性フッ化物焼結体とその製造方法を発明し、出願している。
この先願IIの特徴は、まず第１に焼結温度の低温化により焼結速度が抑制され、焼結体部位毎の焼結進行度の差を低減出来、その結果、その部位毎の脱泡速度の不均一を緩和し、焼結体全体を緻密化することが容易になるところにある。具体的な現象としては、焼結体の外周部はその内部と比べて加熱されやすく焼結速度が速くなり、焼結速度の遅い内部はその内側ほど脱泡が遅くなる。そのため、内側ほど気泡が残留しやすく、低密度となりやすいが、先願IIでは、その内部の低密度化を焼結温度の低温化により低減することが可能となり、焼結体の嵩密度が実用上取扱いに支障のない範囲である３．００g/cm³以上を確保出来るようになった。 Therefore, the present inventors have already made a CaF ₂ -MgF ₂ binary system to solve the above problem in Japanese Patent Application No. 2009-254436 (filed on November 5, 2009: hereinafter referred to as Prior Application II). Have invented and filed a plasma-resistant fluoride sintered body and a method for producing the same.
The feature of this prior application II is that, first, the sintering speed is suppressed by lowering the sintering temperature, and the difference in the degree of sintering progress for each part of the sintered body can be reduced. As a result, defoaming for each part is achieved. It is easy to alleviate the non-uniformity of speed and to densify the entire sintered body. As a specific phenomenon, the outer peripheral portion of the sintered body is easily heated as compared with the inside thereof, and the sintering speed is increased. For this reason, bubbles tend to remain and become lower in density toward the inner side. However, in the prior application II, it is possible to reduce the inner density by lowering the sintering temperature, and the bulk density of the sintered body is practical. It became possible to secure a value of 3.00 g / cm ³ or more, which is a range that does not hinder the handling.

第２に、この焼結体の物理的特性は、優れた耐プラズマ性、誘電特性、熱伝導性などを有し、また良好な機械的強度、耐衝撃性を有するものであり、耐プラズマ性部材のうち機械的強度、耐衝撃性を著しく必要としない部材として使用出来るものであることが分かった。しかしながら先願IIでは、致命的欠陥ではないものの、焼結体の機械的強度のうちで曲げ強度が十分には得られず、そのため耐衝撃性も十分ではなく、耐プラズマ性部材の中での用途を選定する必要があった。
このように、従来の耐プラズマ性部材にはいずれも種々の問題または解決すべき課題がある。 Secondly, the physical properties of this sintered body have excellent plasma resistance, dielectric properties, thermal conductivity, etc., and also have good mechanical strength and impact resistance. It turned out that it can be used as a member which does not require mechanical strength and impact resistance remarkably among members. However, in the prior application II, although it is not a fatal defect, the bending strength cannot be obtained sufficiently among the mechanical strength of the sintered body, and therefore the impact resistance is not sufficient, and among the plasma resistant members, It was necessary to select an application.
Thus, all the conventional plasma-resistant members have various problems or problems to be solved.

特許第3017528号公報Japanese Patent No. 3017528 特開2003−300777号公報Japanese Patent Laid-Open No. 2003-300777 特開2004−83362号公報JP 2004-83362 A

課題を解決するための手段及びその効果Means for solving the problems and their effects

本発明は上記課題に鑑みなされたものであって、シリコン半導体又は化合物半導体の製造工程におけるハロゲン系ガスのプラズマを発生させてウエハー表面の処理を行う各種のプラズマ処理工程に適する高い耐プラズマ性を有し、汚染防止性、耐熱性、放熱性、誘電性などに優れ、なお且つ成形体の大型化と共に高嵩密度化を図ることができると共に、機械的強度、耐衝撃性をより一層向上させることができ、しかも、高純度の単結晶体のような高価格品とはならないCaF₂−MgF₂二元系焼結体、及び耐プラズマ性フッ化物焼結体の製造方法を提供することを目的としている。 The present invention has been made in view of the above-described problems, and has high plasma resistance suitable for various plasma processing processes in which a halogen-based gas plasma is generated in a silicon semiconductor or compound semiconductor manufacturing process to process a wafer surface. It has excellent anti-contamination properties, heat resistance, heat dissipation, dielectric properties, etc., and can increase the bulk density as well as the size of the molded product, and further improve the mechanical strength and impact resistance. And a method for producing a CaF ₂ -MgF ₂ binary sintered body that is not a high-priced product such as a high-purity single crystal, and a plasma-resistant fluoride sintered body. It is aimed.

上記目的を達成するために本発明に係るCaF₂−MgF₂二元系焼結体（１）は、MgF₂を１．５〜１０wt.％含有するCaF₂−MgF₂ 二元系固溶焼結体からなり、該焼結体の嵩密度が３．００g/cm³以上であり、かつ曲げ強度が６０MPa以上であることを特徴としている。 In order to achieve the above object, a CaF ₂ -MgF ₂ binary sintered body (1) according to the present invention is a CaF ₂ -MgF ₂ binary solid solution firing containing 1.5 to 10 wt.% MgF ₂ . consists sintered state, and are a bulk density of 3.00 g / cm ³ or more sintered body, and flexural strength is characterized der Rukoto least 60 MPa.

また、本発明に係るCaF₂−MgF₂二元系焼結体（２）は、上記CaF₂−MgF₂二元系焼結体（１）において、前記焼結体に対するプラズマ波によるエッチング速度が、シリコンウエハー、アルミナ焼結体、及び石英基板にイットリアを成膜したものに対するいずれのエッチング速度より小さいものであることを特徴としている。
本発明に係るCaF₂−MgF₂二元系焼結体によれば、前記焼結体に対するプラズマ波によるエッチング速度が、シリコンウエハー、アルミナ焼結体、及び石英基板にイットリアを成膜したものに対するいずれのエッチング速度より小さく、優れた耐プラズマ性を有している。 Further, the CaF ₂ -MgF ₂ binary sintered body (2) according to the present invention has an etching rate by plasma waves with respect to the sintered body in the CaF ₂ -MgF ₂ binary sintered body (1). It is characterized by being smaller than any etching rate with respect to a silicon wafer, an alumina sintered body, and a quartz substrate on which yttria is formed.
According to the CaF ₂ -MgF ₂ binary sintered body according to the present invention, the etching rate by the plasma wave with respect to the sintered body is that obtained by depositing yttria on a silicon wafer, an alumina sintered body, and a quartz substrate. It is smaller than any of the etching rates and has excellent plasma resistance.

また、本発明に係るCaF₂−MgF₂二元系焼結体（３）は、上記CaF₂−MgF₂二元系焼結体（１）又は（２）において、ビッカース硬度が３００程度、ヤング率が１００ＧＰａ程度、剛性率が４０GPa程度、及び／又はポアソン比が０．３程度の機械的強度を有するものであることを特徴としている。 Further, the CaF ₂ -MgF ₂ binary sintered body (3) according to the present invention has a Vickers hardness of about 300 in the CaF ₂ -MgF ₂ binary sintered body (1) or (2). It has a mechanical strength of about 100 GPa, rigidity of about 40 GPa, and / or Poisson's ratio of about 0.3.

なお、表２に示すように、後述する実施例１及び６のサンプル各１０個、合計２０個について曲げ強度を測定したところ、最小値７０MPa、最大値１２０MPa、平均値９０MPaであった。また、同実施例のサンプル各１０個、合計２０個についてビッカース硬度（kg/mm²）を測定したところ、最小値２３０、最大値４１０、平均値３１３であった。
また、同実施例のサンプル各１０個、合計２０個についてヤング率、剛性率、ポアソン比を測定したところ、各平均値がヤング率（GPa）は１０３、剛性率（GPa）は４０、ポアソン比は０．２９であり、優れた機械的強度を有している。 In addition, as shown in Table 2, when the bending strength was measured for 10 samples in each of Examples 1 and 6 described later, a total of 20 samples, the minimum value was 70 MPa, the maximum value was 120 MPa, and the average value was 90 MPa. Moreover, when Vickers hardness (kg / mm < ² >) was measured about 10 samples of the same Example and a total of 20, it was the minimum value 230, the maximum value 410, and the average value 313.
In addition, when Young's modulus, rigidity, and Poisson's ratio were measured for 10 samples of the same example, a total of 20 samples, the average values were 103 for Young's modulus (GPa), 40 for rigidity (GPa), and Poisson's ratio. Is 0.29 and has excellent mechanical strength.

また“ガラス工学ハンドブック”（山根正之ほか、（１９９９年）株式会社朝倉書店発行、８３頁）の表１．４と本文中に「実用ガラスの大部分のヤング率は５０〜９０、ポアソン比は０．１６〜０．２８の範囲にある。」と記載されており、さらに同書の４９３頁の表５．１には透明石英ガラスのヤング率は７２（室温）、剛性率は３１（同）、ポアソン比は０．１７と記載されており、これらの数値を比較すると、本発明に係るCaF₂−MgF₂二元系焼結体は、実用ガラス及び溶融石英ガラスと比べて弾性的であると言える。 Also, in Table 1.4 of the “Glass Engineering Handbook” (Masayuki Yamane et al., (1999) Asakura Shoten Co., Ltd., page 83) and in the text, “Most Young's modulus of practical glass is 50-90, Poisson's ratio is In addition, in Table 5.1 on page 493 of the same book, the Young's modulus of transparent quartz glass is 72 (room temperature) and the rigidity is 31 (same). The Poisson's ratio is described as 0.17. When these numerical values are compared, the CaF ₂ -MgF ₂ binary sintered body according to the present invention is more elastic than the practical glass and the fused silica glass. It can be said.

また、本発明に係るCaF₂−MgF₂二元系焼結体（４）は、上記CaF₂−MgF₂二元系焼結体（１）〜（３）のいずれかにおいて、熱膨張係数が２．３×１０^−５以下（温度域は２０〜３００℃）、熱伝導率が０．０４Ｗ／（ｃｍ・Ｋ）以上、及び／又は比熱が０．８Ｊ／（ｇ・Ｋ）以上の熱的特性を有するものであることを特徴としている。 Further, the CaF ₂ -MgF ₂ binary sintered body (4) according to the present invention has a thermal expansion coefficient in any of the CaF ₂ -MgF ₂ binary sintered bodies (1) to (3). 2.3 × 10 ⁻⁵ or less (temperature range is 20 to 300 ° C.), heat conductivity is 0.04 W / (cm · K) or more, and / or specific heat is 0.8 J / (g · K) or more. It is characterized by having a characteristic.

本発明に係るCaF₂−MgF₂二元系焼結体によれば、熱膨張係数が２．３×１０^−５以下（温度域は２０〜３００℃）、熱伝導率が０．０４Ｗ／（ｃｍ・Ｋ）以上、及び／又は比熱が０．８Ｊ／（ｇ・Ｋ）以上の優れた熱的特性を有しており、熱による膨張・収縮が少ない熱的に安定なものであり、放熱作用も大きいと言える。 According to the CaF ₂ -MgF ₂ binary sintered body according to the present invention, the thermal expansion coefficient is 2.3 × 10 ⁻⁵ or less (temperature range is 20 to 300 ° C.), and the thermal conductivity is 0.04 W / ( cm · K) and / or excellent thermal characteristics with a specific heat of 0.8 J / (g · K) or more. It can be said that the effect is also great.

また、本発明に係るCaF₂−MgF₂二元系焼結体（５）は、上記CaF₂−MgF₂二元系焼結体（１）〜（４）のいずれかにおいて、誘電率が６．５〜８．５（at １MHz、３００Ｋ）、及び／又は誘電損失が６．５〜８．５×１０^−３（at １MHz、２０℃）の誘電特性を有するものであることを特徴としている。 In addition, the CaF ₂ -MgF ₂ binary sintered body (5) according to the present invention has a dielectric constant of 6 in any one of the CaF ₂ -MgF ₂ binary sintered bodies (1) to (4). .5 to 8.5 (at 1 MHz, 300 K) and / or dielectric loss of 6.5 to 8.5 × 10 ⁻³ (at 1 MHz, 20 ° C.) .

本発明に係るCaF₂−MgF₂二元系焼結体によれば、誘電率が６．５〜８．５（at １MHz、３００Ｋ）、及び／又は誘電損失が６．５〜８．５×１０^−３（at １MHz、２０℃）の優れた誘電特性を有しており、誘電率が小さく自己発熱が抑制され、耐プラズマ性材料として使用し易いものであると言える。 According to the CaF ₂ -MgF ₂ binary sintered body according to the present invention, the dielectric constant is 6.5 to 8.5 (at 1 MHz, 300 K) and / or the dielectric loss is 6.5 to 8.5 ×. It can be said that it has an excellent dielectric property of 10 ⁻³ (at 1 MHz, 20 ° C.), has a small dielectric constant, suppresses self-heating, and is easy to use as a plasma-resistant material.

また、本発明に係る耐プラズマ性フッ化物焼結体の製造方法（１）は、緻密な構造のCaF₂−MgF₂二元系焼結体からなる耐プラズマ性フッ化物焼結体の製造方法であって、高純度CaF₂粉末に高純度MgF₂粉末を１．５〜１０wt.％混合し、さらに焼結助剤を０．１〜１wt.％添加して混合する工程、冷間等方加圧成形（ＣＩＰ）機を用いて成形圧２MPa以上で成形する工程、その成形体を大気雰囲気中で６００〜７００℃で所定時間加熱して仮焼結を行う工程、大気中または不活性ガス雰囲気中で仮焼結体の発泡を抑制し得る８００〜８６０℃の温度範囲で４〜１６時間加熱したあと同雰囲気中で固溶体が生成し始める９００〜１１００℃の温度範囲で０．５〜３時間加熱して緻密な構造のCaF₂−MgF₂二元系焼結体を形成する工程、を含むことを特徴としている。 The method (1) for producing a plasma-resistant fluoride sintered body according to the present invention is a method for producing a plasma-resistant fluoride sintered body comprising a CaF ₂ -MgF ₂ binary sintered body having a dense structure. A process in which high purity MgF ₂ powder is mixed with 1.5 to 10 wt.% Of high purity CaF ₂ powder, and further 0.1 to 1 wt. A step of molding at a molding pressure of 2 MPa or more using a pressure molding (CIP) machine, a step of heating the molded body at 600 to 700 ° C. for a predetermined time in an air atmosphere, and pre-sintering, in the air or an inert gas at a temperature range of presintered body solid solution foamed with 4-16 hours heated after the same atmosphere 800-860 temperature range ° C. capable of suppressing the start to generate 900 to 1100 ° C. in an atmosphere 0.5-3 forming a CaF ₂ MgF ₂ binary sintered body having a dense structure and the heating time, characterized by comprising There.

また、本発明に係る耐プラズマ性フッ化物焼結体の製造方法（２）は、上記耐プラズマ性フッ化物焼結体の製造方法（１）において、前記CaF₂−MgF₂二元系焼結体形成工程において、前記不活性ガスとして、窒素、ヘリウム、アルゴン、ネオンの各ガスの内の１種類または複数の種類を混合したものを使用することを特徴としている。 A method of manufacturing a plasma resistance fluoride sintered body according to the present invention (2) is Oite the production method (1) of the plasma resistance fluoride sintered body, the CaF ₂ MgF ₂ binary system In the sintered body forming step, the inert gas is a mixture of one or more of nitrogen, helium, argon, and neon gases.

まず、本発明者らは、第１の課題である耐プラズマ性を有する物質（化合物）の選定に関する基本的な考察を行った。すなわち、シリコンおよび化合物半導体の製造工程で使用されるプラズマは、主としてフッ素（Ｆ）ガスまたは塩素（Ｃｌ）ガスをプラズマ化している。これらのプラズマに高い耐性を有する化合物としては、同じハロゲン系元素を含む化合物であるフッ化カルシウウム（CaF₂）やフッ化マグネシウム（MgF₂）などのフッ化物または塩化カルシウム（CaCl₂）や塩化マグネシウム（MgCl₂）などの塩化物を想定した。しかしながら、塩化物は加熱時に溶融塩（液相）を造り易く、固相と液相とが混在する固溶体の生成を利用する焼結反応には成りにくく、仮に焼結体が出来たとしても化学的に活性となり安定性を欠く恐れが高い。それに比してフッ化物の焼結体は比較的化学的に安定であるため、フッ化物の方が優位性が見込めるとして選定した。 First, the present inventors performed basic considerations regarding selection of a substance (compound) having plasma resistance, which is the first problem. That is, the plasma used in the manufacturing process of silicon and compound semiconductors is mainly converted from fluorine (F) gas or chlorine (Cl) gas to plasma. Compounds with high resistance to these plasmas include fluorides such as calcium fluoride (CaF ₂ ) and magnesium fluoride (MgF ₂ ), calcium chloride (CaCl ₂ ), and magnesium chloride, which are compounds containing the same halogen-based elements. Chlorides such as (MgCl ₂ ) were assumed. However, chloride is easy to make molten salt (liquid phase) when heated, and it is difficult to make a sintering reaction using the formation of a solid solution in which a solid phase and a liquid phase coexist. There is a high risk of becoming active and lacking stability. Compared to this, the sintered fluoride was relatively chemically stable, so fluoride was selected because it can be expected to be superior.

また、耐プラズマ性以外の要求特性のうち、汚染防止性については、ハンドリング時の損傷やプラズマ波によるプラズマ衝撃、熱衝撃などによる粉塵発生を防止できることが肝要であり、機械的強度、耐熱性、耐衝撃性に優れたものであること、なかでも機械的強度に優れたものが要求されている。   In addition, among the required characteristics other than plasma resistance, regarding pollution prevention, it is essential to be able to prevent dust generation due to damage during handling, plasma shock due to plasma waves, thermal shock, etc., mechanical strength, heat resistance, There is a demand for excellent impact resistance and, in particular, excellent mechanical strength.

焼結体の機械的強度は、粒子間の結合部のミクロ強度と、気泡の大きさ、形状、分布、数などの脱泡状態、換言すると、結合部および元の粒子の結合体（母体）の太さ、長さなどの形状（このことを一般的には焼結体の緻密さと言う）と、さらにはその母体の結晶構造（多結晶または単結晶または非晶質など）とに起因する脆性度によって決まってくる。耐熱性、耐衝撃性、放熱性および誘電性は、上記のように焼結体の緻密さとその母体の結晶構造などによって定まるものと考えられる。   The mechanical strength of the sintered body is the micro-strength of the joint between the particles and the defoamed state such as the size, shape, distribution, number of bubbles, in other words, the joint of the joint and the original particle (matrix). Due to the shape, such as the thickness and length of the material (this is generally referred to as the denseness of the sintered body) and the crystal structure (polycrystalline, single crystal or amorphous) of the matrix It depends on the degree of brittleness. The heat resistance, impact resistance, heat dissipation, and dielectric properties are considered to be determined by the density of the sintered body and the crystal structure of the base as described above.

本発明における基本的な技術的思想は、１）出発原料を二種類混合することによる焼結条件の緩和、すなわち、一種類単味（原料処理技術領域では、単独、と同意語）と比して低温焼結を可能とすること、２）この焼結を、固相間反応による粒成長、またはそれに加えて溶融反応による溶融焼結とを併用し、焼結体を強固な粒子間結合力を有するものとすること、３）このフッ化物系原料は高温で加熱すると、原料の一部が気化する（後述するように、気化し始める温度は約８７０℃であり、約１０００℃からはかなり活発に気化する）。気化によりフッ素ガスが発生し、焼結体中に微細な気泡が生成する。このため比較的低温の加熱で焼結し、この微細気泡の発生（すなわち、発泡）を可能な限り避けて緻密な焼結体とすること、４）前記２）、３）の併用により、耐プラズマ性装置の部材として必要な耐プラズマ性以外の要求特性である機械的強度（形状維持出来る強度を有し、耐衝撃性が良好であること）、熱的特性（耐熱性、放熱性が良好であること）、誘電特性（誘電性が小さいこと）などに優れた特性を有する耐プラズマ性フッ化物焼結体を製造すること、である。   The basic technical idea in the present invention is as follows: 1) Relaxation of sintering conditions by mixing two kinds of starting materials, that is, one kind of simple (in the raw material processing technology field, single and synonymous). 2) This sintering is used in combination with grain growth by solid-phase reaction, or in addition, melt sintering by melting reaction, and the sintered body has strong interparticle bonding strength. 3) When this fluoride-based raw material is heated at a high temperature, a part of the raw material is vaporized (as will be described later, the temperature at which vaporization starts is about 870 ° C., which is considerably higher than about 1000 ° C. Vigorously vaporize). Fluorine gas is generated by vaporization, and fine bubbles are generated in the sintered body. For this reason, sintering should be performed at a relatively low temperature to avoid the generation of fine bubbles (that is, foaming) as much as possible to obtain a dense sintered body. 4) By using the combination of 2) and 3) above, Mechanical strength (having sufficient strength to maintain the shape and good impact resistance) and thermal characteristics (good heat resistance and heat dissipation), which are required characteristics other than plasma resistance necessary for plasma equipment Manufacturing a plasma-resistant fluoride sintered body having excellent characteristics such as dielectric characteristics (small dielectric).

本発明に係るCaF₂−MgF₂二元系焼結体によれば、MgF₂を１．５〜１０wt.％含有するCaF₂−MgF₂焼結体からなり、該焼結体の嵩密度が３．００g/cm³以上の緻密な多結晶構造となっているので、焼結体の組織構造が内外の部位による差が小さく、かつ固溶体生成量を抑制することによる結晶成長を抑え脆性部分の発生を減少させ、焼結体の強度を高めることができ、上記した先願IIを上まわる機械的強度が得られ、これにより高耐プラズマ性、高機械的強度、高耐衝撃性など耐プラズマ性材料に要求される全ての特性に優れている。 According to the CaF ₂ -MgF ₂ binary sintered body according to the present invention, it consists of a CaF ₂ -MgF ₂ sintered body containing 1.5 to 10 wt.% MgF _2, and the bulk density of the sintered body is Since it has a dense polycrystalline structure of 3.00 g / cm ³ or more, the difference in the structure of the sintered body between the inside and outside of the sintered body is small, and the growth of brittle parts is suppressed by suppressing crystal growth by suppressing the amount of solid solution produced. It can reduce the generation and increase the strength of the sintered body, resulting in mechanical strength that exceeds the above-mentioned prior application II, and thus plasma resistance such as high plasma resistance, high mechanical strength, and high impact resistance. Excellent properties for all materials

また、本発明に係る耐プラズマ性フッ化物焼結体の製造方法によれば、高純度CaF₂粉末に高純度MgF₂粉末を１．５〜１０wt.％混合し、さらに焼結助剤を０．１〜１wt.％添加して混合した原料を、冷間等方加圧成形（ＣＩＰ）機を用いて成形圧２MPa以上で成形するので、配合した微粉状の原料を等方に加圧して原料の充填密度をより等方に高めることができる。 Further, according to the method for producing a plasma-resistant fluoride sintered body according to the present invention, high purity MgF ₂ powder is mixed with high purity CaF ₂ powder in an amount of 1.5 to 10 wt. Since the raw material mixed by adding 1 to 1 wt.% Is molded at a molding pressure of 2 MPa or higher using a cold isostatic pressing (CIP) machine, the blended fine powdery raw material is pressurized isotropically The packing density of the raw material can be increased more isotropically.

次に、その成形体を大気雰囲気中で６００〜７００℃程度で所定時間（４〜１０時間）加熱してゆっくりと仮焼結を行い、引き続いて、大気中または不活性ガス雰囲気中で仮焼結体の発泡を抑制し得る第１の温度域（後述する発泡開始温度である８７０℃直下の温度域である８００〜８６０℃）で、比較的長い所定時間（４〜１６時間）ゆっくりと加熱して焼結をより均一に進行させたあと、同雰囲気中で固溶体が生成し始める第２の温度域（図１に示すCaF₂−MgF₂二元系状態図における固溶体を生じ始める温度である９８０℃の前後の温度域である９００〜１１００℃）で比較的短い所定時間（０．５〜３時間）加熱して焼結を促進させる。 Next, the molded body is heated in an air atmosphere at about 600 to 700 ° C. for a predetermined time (4 to 10 hours) and slowly preliminarily sintered, and subsequently calcined in the air or an inert gas atmosphere. Slow heating for a relatively long predetermined time (4 to 16 hours) in a first temperature range (800 to 860 ° C. which is a temperature range immediately below 870 ° C. which is a foaming start temperature described later) that can suppress foaming of the bonded body Then, after the sintering has proceeded more uniformly, the second temperature region where the solid solution starts to form in the same atmosphere (the temperature at which the solid solution in the CaF ₂ -MgF ₂ binary phase diagram shown in FIG. 1 begins to form) Sintering is promoted by heating for a relatively short predetermined time (0.5 to 3 hours) at a temperature range of about 980 ° C. and about 900 to 1100 ° C.

なお、本発明者らは、仮焼結後の焼結条件を選定するにあたり、上記と同じ配合原料を用いた成形体を大気雰囲気中で６００℃で６時間加熱処理した仮焼結体を粉砕したものを示差熱分析計の供試試料とし、加温しつつ試料の重量変化と吸発熱量の変化とを調査した。その結果、おおよそ７５０〜８００℃くらいから極わずかに試料の重量減少が認められた。これは結合性の弱い、例えば仮焼結体の母材に付着したフッ素や母材中に溶解したフッ素がまず先に解離、分解することによる重量減少と考えられた。さらに加温して行くと、８７０℃あたりで重量減少曲線の変曲点となり、その後、重量減少が活発になる現象を発見した。この現象から、８７０℃以上の温度域で加熱すると、MgF₂またはCaF₂中の結合したフッ素の一部が分解し始め、フッ素ガスが発生して微細な気泡が生成する原因になる、と想定した。なお、本願では、上記変曲点の温度である約８７０℃を発泡開始温度と称することにした。 In selecting the sintering conditions after preliminary sintering, the present inventors pulverized the temporary sintered body obtained by heat-treating a molded body using the same blending raw material as described above at 600 ° C. for 6 hours. The sample was used as a test sample for a differential thermal analyzer, and the change in the weight of the sample and the change in the endothermic amount were investigated while heating. As a result, a slight decrease in the weight of the sample was observed from about 750 to 800 ° C. This was considered to be a decrease in weight due to the weak dissociation and decomposition of fluorine that was weakly bonded, for example, fluorine adhering to the base material of the pre-sintered body or fluorine dissolved in the base material. As the temperature further increased, the inflection point of the weight loss curve was found around 870 ° C., and then a phenomenon in which the weight loss became active was discovered. From this phenomenon, it is assumed that when heated in a temperature range of 870 ° C. or higher, a part of the bound fluorine in MgF ₂ or CaF ₂ starts to decompose, causing generation of fluorine gas and generation of fine bubbles. did. In the present application, about 870 ° C., which is the temperature of the inflection point, is referred to as the foaming start temperature.

上記した焼結法によって生成した焼結体は強固な粒子間の結合力を有し、結合部の機械的強度（ミクロ強度）はかなり高いものとなり、課題であった曲げ強度、耐衝撃性は著しく向上し、耐プラズマ性部材として実用上問題なく使用出来るものとなった。また、本発明に係る製造方法によれば、焼結体は、CaF₂−MgF₂の配合比、加熱雰囲気、加熱温度パターンなどの選定により、緻密度の高いものとなり、且つ成形体の大型化と共に高嵩密度化を図ることができた。また、本発明に係る製造方法によれば、母体は焼結体であるため、その結晶構造は多結晶となり、単結晶と比較して脆性度は著しく向上する。 The sintered body produced by the above-mentioned sintering method has a strong bonding force between particles, and the mechanical strength (micro strength) of the bonded portion is considerably high. It has been remarkably improved and can be used as a plasma-resistant member without any practical problems. Further, according to the production method according to the present invention, the sintered body becomes high in density by selecting the compounding ratio of CaF ₂ -MgF ₂ , the heating atmosphere, the heating temperature pattern, etc., and the size of the molded body is increased. In addition, a high bulk density could be achieved. Moreover, according to the manufacturing method according to the present invention, since the base is a sintered body, the crystal structure becomes polycrystalline, and the brittleness is remarkably improved as compared with a single crystal.

CaF₂−MgF₂二元系の状態図である。It is a phase diagram of CaF ₂ -MgF ₂ binary system. 仮焼結工程の加熱条件と仮焼結体の収縮率との関係を示す図である。It is a figure which shows the relationship between the heating conditions of a temporary sintering process, and the shrinkage rate of a temporary sintered compact. 窒素ガス雰囲気中での焼結工程の加熱条件と焼結体の生成状態との関係を示す図である。It is a figure which shows the relationship between the heating conditions of the sintering process in nitrogen gas atmosphere, and the production | generation state of a sintered compact. 窒素ガス雰囲気中での焼結過程の加熱温度、焼結体の嵩密度、質量減（＝（製品質量−原料質量）×１００÷（原料質量）％）の関係を示す図である。It is a figure which shows the relationship of the heating temperature of the sintering process in nitrogen gas atmosphere, the bulk density of a sintered compact, and mass loss (= (product mass-raw material mass) x100 / (raw material mass)%).

以下、本発明に係る耐プラズマ性フッ化物焼結体、より具体的には緻密な構造のCaF₂−MgF₂二元系焼結体、及びその製造方法の実施の形態を図面に基づいて説明する。
本発明に係る耐プラズマ性フッ化物焼結体の製造方法は、高純度（純度99wt.％以上）のCaF₂粉末に高純度（純度99wt.％以上）のMgF₂粉末を１．５〜１０wt.％の割合（内掛け）で混合し、さらに焼結助剤としてたとえばカルボキシメチルセルロース（ＣＭＣ）溶液を前記混合物１００に対し、０．１〜１wt.％添加（外掛け）、混練したものを出発原料とし、冷間等方加圧成形（ＣＩＰ）機を用いて成形圧２MPa以上で成形し、その成形体を大気雰囲気中で６００〜７００℃程度の温度範囲に加熱して仮焼結を行い、その仮焼結体を大気中または不活性ガス雰囲気中で発泡開始温度（示差熱分析計での測定で定めた温度約８７０℃）の直下の第１の温度域、具体的には８００〜８６０℃の温度範囲で４〜１６時間加熱し、焼結をより均一に進行させたあと、固溶体が生成し始める第２の温度域（図１に示すCaF₂−MgF₂二元系状態図における固溶体が生成し始める温度である９８０℃近傍の温度域）、すなわち９００〜１１００℃の温度範囲で０．５〜３時間加熱し、その後冷却して緻密な構造のCaF₂−MgF₂二元系焼結体を製造する。 Hereinafter, embodiments of a plasma-resistant fluoride sintered body according to the present invention, more specifically a CaF ₂ -MgF ₂ binary sintered body having a dense structure, and a manufacturing method thereof will be described with reference to the drawings. To do.
Method for producing a plasma resistance fluoride sintered body according to the present invention, 1.5～10Wt a MgF ₂ powder with high purity (purity 99 wt.% Or higher) CaF ₂ powder with high purity (purity of 99 wt.% Or higher) A mixture of 0.1% to 1% by weight (outer coating), for example, a carboxymethyl cellulose (CMC) solution as a sintering aid is added to the mixture 100 as a sintering aid. The raw material is molded at a molding pressure of 2 MPa or higher using a cold isostatic pressing (CIP) machine, and the molded body is heated to a temperature range of about 600 to 700 ° C. in the atmosphere to perform preliminary sintering. The first sintered body immediately below the foaming start temperature (temperature determined by measurement with a differential thermal analyzer is about 870 ° C.) in the air or in an inert gas atmosphere, specifically 800 to Heating was performed at a temperature range of 860 ° C. for 4 to 16 hours, and the sintering proceeded more uniformly. When the second temperature range where solid solution began to form (a temperature range of 980 ° C. vicinity of the temperature at which solid solution began to form in the CaF ₂ MgF ₂ binary phase diagram shown in FIG. 1), i.e., the 900 to 1100 ° C. Heat in the temperature range for 0.5 to 3 hours, and then cool to produce a CaF ₂ -MgF ₂ binary sintered body having a dense structure.

主原料のCaF₂粉末への副原料であるMgF₂粉末の混合の目的のひとつは、図１に示すように、CaF₂単味では融点（図中では、1410℃と表記）が高く、且つ固溶体生成の温度領域が一部点線表記で不明瞭となっているのを、MgF₂粉末を混合することによって、図１に示す状態図上の固溶体生成領域がより明瞭な範囲での焼結反応とすることにある。 One of the purposes of mixing MgF ₂ powder, which is an auxiliary material, with CaF ₂ powder, which is the main material, is high in melting point (indicated as 1410 ° C in the figure) with CaF ₂ alone, as shown in FIG. The temperature range of solid solution formation is partially obscured by the dotted line notation. By mixing MgF ₂ powder, the sintering reaction in the solid solution formation region on the phase diagram shown in FIG. 1 is clearer. It is to do.

Caとは元素の周期律表の族が同じで周期が隣接し、特性が似通っていると推測されるMgのフッ素化合物であるMgF₂を適量混合することによって、融点の低温化と固溶体の生成温度条件をより明確化することができ（MgF₂の配合により、図１中の固溶体生成開始の温度領域表示線の右端部の点線領域から、左方に位置する中間配合比域の実線領域に近づける）、その結果、焼結温度条件の適正化が容易になる。なお、この混合物としては、Mgのフッ素化合物MgF2のほかにLiがあり、そのフッ素化合物であるLiFを適量混合することによって、同様の効果が得られる。 Ca is the same group of elements in the periodic table, but the periods are adjacent, and MgF ₂ which is a Mg fluorine compound, which is presumed to have similar characteristics, is mixed to lower the melting point and form a solid solution. The temperature conditions can be further clarified (by mixing MgF ₂ , from the dotted line area at the right end of the temperature area display line at the start of solid solution generation in FIG. 1 to the solid line area of the intermediate mixing ratio area located on the left side. As a result, it is easy to optimize the sintering temperature condition. This mixture includes Li in addition to the Mg fluorine compound MgF2, and the same effect can be obtained by mixing an appropriate amount of LiF, which is the fluorine compound.

焼結助剤の選定は、前記のＣＭＣとステアリン酸カルシウムとの２種類を選定し、それぞれの添加割合を変えて、これら焼結助剤の効果について試験を実施した。対比のため、焼結助剤を使わない試験も合わせて行った。   For the selection of the sintering aid, two types of CMC and calcium stearate were selected, and the ratio of each was changed, and the effect of these sintering aids was tested. For comparison, a test without using a sintering aid was also performed.

主原料のCaF₂と副原料のMgF₂との混合は、その混合比を０〜１２．５wt.%の範囲で配合比を種々変化させて行った。ボールミルで半日混練したあと、焼結助剤二種類をおのおの０〜２wt.%の配合比で添加し、ポットミルを用いて一昼夜混練して配合原料とした。使用したボールミルは、内径２８０mm、長さ４００mm、ボールは、φ５：１８００g、φ１０：１７００g、φ２０：３０００g、φ３０：２８００gのアルミナ製ボールを使用した。ポットミルはアルミナ製で内径２００mm、長さ２５０mmのものを使用した。その配合原料を、外径２６５mm、内径１４０mm、高さ８０mmの内容積のＣＩＰ機に充填し、室温で加圧条件を種々変化させて冷間等方加圧成形（ＣＩＰ）を行った。また、後述する実施例の一部では大型化した外径３７０mm、内径２５０mm、高さ６０mmの内容積のＣＩＰ機も使用した。 The mixing of the main raw material CaF ₂ and the auxiliary raw material MgF ₂ was carried out by varying the mixing ratio in the range of 0 to 12.5 wt.%. After kneading for half a day with a ball mill, two kinds of sintering aids were added at a blending ratio of 0 to 2 wt.%, Respectively, and kneaded for a whole day and night using a pot mill to obtain blended raw materials. The ball mill used was an alumina ball having an inner diameter of 280 mm, a length of 400 mm, and a ball of φ5: 1800 g, φ10: 1700 g, φ20: 3000 g, and φ30: 2800 g. The pot mill was made of alumina and had an inner diameter of 200 mm and a length of 250 mm. The blended raw material was filled into a CIP machine having an outer diameter of 265 mm, an inner diameter of 140 mm, and a height of 80 mm, and cold isostatic pressing (CIP) was performed by changing various pressing conditions at room temperature. Also, in some of the examples described later, a CIP machine having an enlarged outer diameter of 370 mm, an inner diameter of 250 mm, and a height of 60 mm was also used.

この成形体を大気雰囲気中で加熱温度５００〜７５０℃、加熱時間３〜１８時間の範囲で加熱条件を種々変化させて仮焼結を実施し、この仮焼結体の外観などを観察した後、事前の予備試験で良好な焼結条件と見込まれた窒素ガス雰囲気中で、室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に８時間保持し、引き続き１０００℃まで２時間掛けて一定速度で昇温させ、同温度に１時間保持し、その後１００℃までの冷却に２０時間を掛けた。取り出した焼結体の外観、内部の緻密化状況などを観察し、適正な原料配合、原料処理条件と仮焼結条件を調査した。   After preliminarily sintering this molded body under various heating conditions in a range of heating temperature 500 to 750 ° C. and heating time 3 to 18 hours in the atmosphere, and observing the appearance of the temporary sintered body In a nitrogen gas atmosphere, which was expected to have good sintering conditions in a preliminary test, the temperature was raised from room temperature to 800 ° C. at a constant rate over 6 hours, held at the same temperature for 8 hours, and then continued to 1000 ° C. for 2 hours. The temperature was raised at a constant rate over time, held at the same temperature for 1 hour, and then cooled to 100 ° C. over 20 hours. The appearance of the sintered body taken out, the state of internal densification, and the like were observed, and the proper raw material composition, raw material processing conditions and pre-sintering conditions were investigated.

その結果、主原料CaF₂への副原料MgF₂の混合比は、１．５wt.%未満では焼結温度の低温化の影響のためか、焼結体の緻密化が不十分となりやすく、一方、１０．１wt.%以上では焼結速度が速過ぎるためか、焼結体の外周部と比べて内部の方に大きい気泡が多く残り緻密化が不十分であった。焼結体の内部と外周部との緻密化の差が小さくなるのは、主原料CaF₂への副原料MgF₂の混合比が１．５〜１０wt.％の場合であり、焼結体の内部と外周部との緻密化の差がさらに小さく優れた均質度となるための望ましい混合比は３〜８wt.％であった。これらのことから、MgF₂の混合比の適正範囲は１．５〜１０wt.%、望ましくは３〜８wt.％とした。 As a result, the mixing ratio of the auxiliary material MgF ₂ in the main raw material CaF _2, either due to the effect of lowering the sintering temperature is less than 1.5 wt.%, Tends to be insufficient densification of the sintered body, whereas If the content is 10.1 wt.% Or more, the sintering speed is too high, so that there are many large bubbles in the interior compared with the outer periphery of the sintered body, and the densification is insufficient. The difference in densification between the inside and the outer periphery of the sintered body is small when the mixing ratio of the auxiliary raw material MgF ₂ to the main raw material CaF ₂ is 1.5 to 10 wt. The desirable mixing ratio for achieving a better uniformity with a smaller difference in densification between the inside and the outer periphery was 3 to 8 wt.%. For these reasons, the appropriate range of the mixing ratio of MgF ₂ is 1.5 to 10 wt.%, Preferably 3 to 8 wt.%.

焼結助剤二種類の効果に大差は無かったが、助剤無しでは成形体の形状維持性能が劣ること、また、配合比が１．１wt.%を超えると仮焼結体あるいは焼結体にその助剤の残留物とみられる着色が認められることがあった。これらのことから、焼結助剤の配合比の適正範囲は０．１〜１wt.%とした。   There was no significant difference in the effect of the two types of sintering aids, but the shape maintenance performance of the molded product was poor without the aid, and when the compounding ratio exceeded 1.1 wt. In some cases, coloration that appears to be a residue of the auxiliaries was observed. For these reasons, the appropriate range of the mixing ratio of the sintering aid is set to 0.1 to 1 wt.

ＣＩＰ機の成形圧が２MPa未満ではハンドリング時に成形体が崩れて壊れ易く、成形圧を２MPaから徐々に増加すると成形体の嵩密度も徐々に増加し、仮焼結体や焼結体の嵩密度もわずかではあるが増加する傾向が認められた。そこで、成形圧を徐々に増やし１５０MPaまで行ったが、成形圧２０MPa以上の場合の仮焼結体、焼結体の性能に顕著な差が認められなかった。これらのことから、成形圧の適正値は２MPa以上、望ましくは２０MPa以上とした。   When the molding pressure of the CIP machine is less than 2 MPa, the molded body collapses and is easily broken during handling. When the molding pressure is gradually increased from 2 MPa, the bulk density of the molded body gradually increases, and the bulk density of the temporary sintered body and the sintered body is increased. However, a slight tendency to increase was observed. Therefore, the molding pressure was gradually increased to 150 MPa, but no significant difference was observed in the performance of the temporary sintered body and the sintered body when the molding pressure was 20 MPa or more. For these reasons, the appropriate value of the molding pressure is set to 2 MPa or more, preferably 20 MPa or more.

成形体の大気雰囲気中の仮焼結条件の調査は図２に示すように、加熱温度が６００℃未満では成形体の寸法と比して収縮がわずかであり、７０１℃以上ではその収縮速度が早く、収縮の制御が困難になることから、仮焼結温度の適正範囲は６００〜７００℃とした。その加熱時間の適正値は図２に示すように、６００℃では収縮速度の評価から８〜９時間が最適であり、４〜１１時間が適正であった。６５０℃では６〜８時間が最適であり、４〜１０時間が適正であった。一方、７００℃では５〜６時間が最適であり、４〜１０時間が適正であった。この結果から、仮焼結の好ましい加熱条件は、大気雰囲気中で６００〜７００℃で４〜１０時間加熱とした。   As shown in FIG. 2, the pre-sintering conditions in the air atmosphere of the molded product showed a slight shrinkage compared to the size of the molded product when the heating temperature was less than 600 ° C., and the shrinkage rate was higher than 701 ° C. Since the shrinkage control becomes difficult quickly, the appropriate range of the pre-sintering temperature was set to 600 to 700 ° C. As shown in FIG. 2, the appropriate heating time was 8 to 9 hours optimum from the evaluation of the shrinkage rate at 600 ° C., and 4 to 11 hours was appropriate. At 650 ° C., 6 to 8 hours was optimum, and 4 to 10 hours were appropriate. On the other hand, 5 to 6 hours were optimum at 700 ° C., and 4 to 10 hours were appropriate. From this result, the preferable heating conditions for pre-sintering were heating at 600 to 700 ° C. for 4 to 10 hours in an air atmosphere.

上記した調査、試験などで焼結工程直前までの適正条件が明らかになった。次の焼結工程は、耐プラズマ性フッ化物焼結体を製造するうえで最後の工程であり、しかも焼結体の性能に最も影響を与える工程である。ここで、耐プラズマ性フッ化物焼結体として望ましいとみられる焼結工程およびその焼結機構について整理してみる。   Appropriate conditions up to just before the sintering process have been clarified by the above investigations and tests. The next sintering step is the last step in producing the plasma-resistant fluoride sintered body, and is the step that most affects the performance of the sintered body. Here, it arranges about the sintering process considered to be desirable as a plasma-resistant fluoride sintered compact and its sintering mechanism.

まず、焼結工程の進行度を表現する用語である「一次凝集過程」、「二次凝集過程」について定義する。「一次凝集過程」とは、焼結の前半段階であり、その初期段階では粒子と粒子の間隔が徐々に狭まり、粒子同士の間の空隙も狭まってくる。さらには、粒子同士の接触部分が太くなり、その間の空隙は更に小さくなる。ただし、その空隙の大多数は開気孔で周りの雰囲気と通じている。この様な段階までを「一次凝集過程」と称する。   First, terms “primary agglomeration process” and “secondary agglomeration process”, which are terms expressing the progress of the sintering process, are defined. The “primary agglomeration process” is the first half stage of sintering, and in the initial stage, the interval between the particles is gradually narrowed, and the voids between the particles are also narrowed. Furthermore, the contact part between particles becomes thick, and the space | gap between them becomes still smaller. However, the majority of the voids are open pores and communicate with the surrounding atmosphere. Such a stage is referred to as “primary aggregation process”.

一方、一次凝集過程を終え更に焼結が進むと、開気孔が徐々に減り閉気孔化して行く。大まかには、この閉気孔化の段階と更にその後の脱泡、緻密化の段階を総称して「二次凝集過程」と称する。   On the other hand, when the primary agglomeration process is completed and the sintering further proceeds, the open pores gradually decrease and become closed pores. Roughly speaking, this stage of closed pore formation and the subsequent defoaming and densification stages are collectively referred to as “secondary aggregation process”.

本発明では、仮焼結工程までの原料混合、粒度調整、混練、成形、仮焼結などで、仮焼結体の粒子間の空隙は小さく、且つ、その空隙は集合せずにほぼ均一に分散しているとみられる（一次凝集過程の前半段階）。次の焼結工程の昇温過程で徐々に加熱温度が上昇し、仮焼結温度域（６００〜７００℃）あたりから粒子同士の集合がはじまり、それに引き続き、固溶体が生成し始める９８０℃よりもかなり低い温度域（一般的には、その温度から１０％程度またはそれ以上低い温度域から始まると言われている）から固相間反応が始まり、それに伴い粒子同士の凝集が進行し、粒子間距離は短くなり空隙は小さくなる。ただし、想定している仮焼結程度の比較的低い温度（６００〜７００℃）で短時間の加熱では、大半の空隙は依然として開気孔状態のままである（一次凝集過程の後半段階）。ここで、注意すべきことは、後述するように約８７０℃以上の温度域で、原料の一部分が気化して発生する微細な気泡（発泡気泡）の挙動である。中でも、約１０００℃以上の加熱をする場合には、この発泡気泡の発生は顕著になるため可能な限り短時間の加熱にすることが重要となる。   In the present invention, by mixing the raw materials up to the preliminary sintering step, adjusting the particle size, kneading, molding, preliminary sintering, etc., the gaps between the particles of the temporary sintered body are small, and the gaps are almost uniform without aggregation. It appears to be dispersed (the first half of the primary aggregation process). The heating temperature gradually rises in the temperature raising process of the next sintering step, the aggregation of particles starts from around the pre-sintering temperature range (600 to 700 ° C.), and subsequently the solid solution starts to form at 980 ° C. The reaction between solid phases starts from a fairly low temperature range (generally, it is said to start from a temperature range that is about 10% or more lower than that temperature). The distance becomes shorter and the gap becomes smaller. However, when heating is performed at a relatively low temperature (600 to 700 ° C.) as short as the pre-sintering as expected, most of the voids still remain in the open pore state (second half stage of the primary aggregation process). What should be noted here is the behavior of fine bubbles (foamed bubbles) generated by vaporization of a part of the raw material in a temperature range of about 870 ° C. or higher as described later. In particular, when heating at about 1000 ° C. or higher, the generation of foamed bubbles becomes significant, and it is important to make the heating as short as possible.

つぎに、原料粒子のミクロな挙動について付記する。副原料であるMgF₂粒子は主原料のCaF₂粒子の周囲に在って、CaF₂粒子との界面反応を進めて行くと推定される。加熱温度が固溶体を生じ始める９８０℃を超えたあたりからは、MgF₂粒子が存在する粒子界面付近から溶融し始め、CaF₂−MgF₂二元系化合物の固溶体が生成し始める。この固溶体が粒子間の空隙を埋めて行き、一部では毛細管現象により微細な空隙も埋まると思われる。一方、加熱温度が９８０℃未満であっても、前述のように約８００℃以上に比較的長時間加熱保持すると、固相間反応が進み易く、時間経過とともに空隙は徐々に減少し、閉気孔化し、それと並行して閉気孔内のガス成分が焼結体のバルク（母体）内に拡散して脱泡が進み、気泡の少ない緻密な焼結体となる（二次凝集過程）。 Next, the micro behavior of the raw material particles will be described. It is presumed that the MgF ₂ particles as the auxiliary material are present around the CaF ₂ particles as the main material, and proceed with the interfacial reaction with the CaF ₂ particles. When the heating temperature exceeds 980 ° C. at which a solid solution starts to form, melting starts from the vicinity of the particle interface where the MgF ₂ particles exist, and a solid solution of CaF ₂ —MgF ₂ binary compound begins to be generated. It seems that this solid solution fills the voids between the particles, and in part, the fine voids are also filled by capillary action. On the other hand, even if the heating temperature is less than 980 ° C., if the heating is maintained at a temperature of about 800 ° C. or higher for a relatively long time as described above, the reaction between the solid phases easily proceeds, and the voids gradually decrease with the passage of time. At the same time, the gas components in the closed pores diffuse into the bulk (matrix) of the sintered body and defoaming proceeds, resulting in a dense sintered body with few bubbles (secondary aggregation process).

ここでも、前述のように、約８７０℃以上の加熱による原料の気化によって発生する微細な気泡（発泡気泡）の存在に注意が必要である。なぜならば、発泡気泡はフッ素ガスが内包されていると想定され、このガスは比較的重い元素であり焼結体のバルク内には拡散しにくいと考えられるからである。この対策としては、気化する温度域での加熱を可能な限り避ける、または極短時間の加熱にとどめることが肝要である。   Here, too, attention must be paid to the presence of fine bubbles (foamed bubbles) generated by vaporization of the raw material by heating at about 870 ° C. or higher as described above. This is because the foamed bubbles are assumed to contain fluorine gas, and this gas is a relatively heavy element and is considered to be difficult to diffuse into the bulk of the sintered body. As a countermeasure against this, it is important to avoid heating in the vaporizing temperature range as much as possible, or to limit the heating to an extremely short time.

なお上記発泡気泡と、焼結工程で閉気孔化し脱泡出来ずに残った気泡（以下、残留気泡と称す）とでは、外観上の差異を有する。すなわち、通常の比較的短時間の加熱で発生した発泡気泡は、サイズがおおよそ直径数〜１０数μm、形状がほぼ真球状であり、一方、残留気泡は、真球状ではなく不定形で、サイズも大中小まちまちであるため、形状の差異からこれらを見分けることが可能である。ただし、１１００℃をはるかに超える高温の加熱や１１００℃を超えて長時間加熱を行った場合には、発泡気泡同士、或は残留気泡と発泡気泡とが集合して大きな不定形の気泡が生成することがあり、この場合は気泡の由来の判別は困難となる。   In addition, there is a difference in appearance between the foamed bubbles and the bubbles that are closed and cannot be degassed in the sintering process (hereinafter referred to as residual bubbles). That is, the foamed bubbles generated by heating for a relatively short period of time are approximately a few tens to several tens of micrometers in diameter and the shape is almost spherical. On the other hand, the residual bubbles are not spherical but are indefinite. Since these are large, medium and small, it is possible to distinguish them from the difference in shape. However, when heating is performed at a temperature much higher than 1100 ° C, or when heating is performed for a long time above 1100 ° C, foamed bubbles or residual bubbles and foamed bubbles gather to form large irregular bubbles. In this case, it is difficult to determine the origin of the bubbles.

上記二次凝集過程の進行に伴い粒子間の空隙は小さくなり、空隙の全部または大半は粒子または焼結体のブリッジ部分などに囲まれ、閉気孔（気泡）となるか、条件によっては空隙（開気孔）を通じて脱ガスし、あるいは粒子や焼結体のブリッジ部分などのバルク（母体）内に気泡内のガスが浸透して脱ガスし、気泡とはならない場合（脱泡現象、と称す）とに分かれる。この粒子間の空隙が閉気孔、すなわち気泡になるか、あるいは脱ガスして気泡が生じないかは、焼結体の緻密化の達成度、ひいては焼結体の特性を決める大きな要素となる。とくに不活性ガスの中でＨｅ、Ｎｅなどの軽元素ガス雰囲気での焼結では、軽元素ほど細孔内とか焼結体のバルク内を拡散し易く毛細管現象と脱泡現象とが促進され、気泡が残り難く、緻密化が容易になるとみられる。この様に全体を緻密化させるためには、前記の一次凝集過程と二次凝集過程とを各々の過程ごとに全体でほぼ同時にほぼ均一に進めることが重要である。   As the secondary agglomeration process proceeds, the voids between the particles become smaller, and all or most of the voids are surrounded by particles or a bridge portion of the sintered body to form closed pores (bubbles) or, depending on conditions, voids ( When degassing through open pores), or when the gas in the bubbles permeates into the bulk (base) such as particles or the bridge portion of the sintered body and does not become bubbles (referred to as defoaming phenomenon) And divided. Whether the voids between the particles become closed pores, that is, bubbles, or bubbles are not generated by degassing is a major factor in determining the degree of densification of the sintered body and, consequently, the characteristics of the sintered body. In particular, sintering in a light element gas atmosphere such as He or Ne in an inert gas facilitates diffusion of the light element into the pores or the bulk of the sintered body, and promotes the capillary phenomenon and the defoaming phenomenon. It seems that bubbles do not remain easily and densification is easy. In order to densify the whole as described above, it is important that the primary agglomeration process and the secondary agglomeration process are almost uniformly advanced almost simultaneously for each process.

本発明では、主として一次凝集過程の前半段階に当たる仮焼結工程と、主として一次凝集過程の後半と二次凝集過程に当たる焼結工程とを分けて行うこととし、二つの凝集過程が焼結体全体をほぼ均一に進みやすくしている。しかしながら、このように仮焼結、焼結と工程を分けたからと言って加熱条件が適正でなければ、例えば、仮焼結工程で適正域を超えた高温で加熱したり、焼結工程の昇温段階で急速に加熱をしたり、同工程の保持温度が適正域を超えた高温であったりすると、焼結体の外周部と内部とで緻密化の程度に著しく差を生じる。このような状態になると、焼結体内部の緻密化過程で脱ガスが困難となり、とくに内部の緻密化が不十分となる。そこで、サイズに即した焼結工程の加熱温度パターンの適正化が重要となる。   In the present invention, the preliminary sintering process corresponding to the first half of the primary agglomeration process and the sintering process corresponding to the second half of the primary agglomeration process and the secondary agglomeration process are performed separately. It is easy to proceed almost uniformly. However, if the heating conditions are not appropriate just because the process is divided into temporary sintering and sintering in this way, for example, heating is performed at a temperature exceeding the appropriate range in the preliminary sintering process, or the temperature of the sintering process is increased. When heating is performed rapidly in the temperature stage, or when the holding temperature in the same process is a high temperature exceeding the appropriate range, the degree of densification is significantly different between the outer peripheral portion and the inside of the sintered body. In such a state, degassing becomes difficult during the densification process inside the sintered body, and the internal densification becomes particularly insufficient. Therefore, it is important to optimize the heating temperature pattern in the sintering process according to the size.

前述のとおり、焼結工程直前までの適正条件が明らかになっており、この焼結工程に供される仮焼結体はその全体が既に一次凝集の前半段階まで進んだ状態になっている。ここで重要なことは、仮焼結体の全体が既にほぼ均一に一次凝集の途中まで進んでいることである。   As described above, appropriate conditions until immediately before the sintering process have been clarified, and the preliminary sintered body provided for this sintering process has already advanced to the first half of the primary aggregation. What is important here is that the entire pre-sintered body has already progressed almost uniformly to the middle of primary aggregation.

本発明者らは、仮焼結後のより適切な焼結条件を見出すため、種々の実験、調査検討を行った。主原料CaF₂にMgF₂を３wt.%混合し、焼結助剤としてＣＭＣを０．２wt．％添加した配合原料を、前述の所定の適正な処理をし、６００℃で６時間仮焼結処理をした仮焼結体を用い、いずれも加熱時間を一定の６時間にして焼結温度を６００℃から１３００℃まで５０℃毎にそれぞれ変更した場合の各焼結体の嵩密度を調査した。その結果、おおよそ８００℃から１１００℃の範囲の場合は３．００ｇ／ｃｍ^３を超える高密度となるが、７５０℃以下の焼結温度の場合と１１５０℃以上の焼結温度の場合はいずれも嵩密度が３．００ｇ／ｃｍ^３を下回った。これらの焼結体の断面を観察すると、７５０℃以下で焼結したものは、わずかではあるが開気孔が認められ、焼結部分のブリッジ幅が細く焼結の進行が不足していた。１１５０℃以上で焼結したものは内部に気泡同士が集合したような大きな気泡が残り、また、焼結体全体に直径数〜１０数μmのほぼ真球状の微細な気泡、すなわち発泡気泡が多数認められた。 The present inventors conducted various experiments and investigations in order to find more appropriate sintering conditions after preliminary sintering. The main raw material CaF ₂ is mixed with 3 wt.% MgF ₂ and CMC is added at 0.2 wt. % Using the pre-sintered body that was pre-sintered at 600 ° C. for 6 hours, and the heating time was set to a constant 6 hours. The bulk density of each sintered body when the temperature was changed from 600 ° C. to 1300 ° C. every 50 ° C. was investigated. As a result, in the range of approximately 800 ° C. to 1100 ° C., the density becomes higher than 3.00 g / cm ³ , but both the sintering temperature of 750 ° C. or lower and the sintering temperature of 1150 ° C. or higher are both used. The bulk density was below 3.00 g / cm ³ . Observing the cross sections of these sintered bodies, those that were sintered at 750 ° C. or lower showed slight open pores, the bridge width of the sintered portion was narrow, and the progress of the sintering was insufficient. When sintered at 1150 ° C. or higher, large bubbles such as bubbles gathered in the interior remain, and there are many almost spherical fine bubbles with a diameter of 10 to several μm in the entire sintered body, that is, many foamed bubbles. Admitted.

一方で、本発明者らの調査によると、このCaF₂−MgF₂二元系の配合原料を示差熱分析計にかけ昇温して行く過程で、温度８７０℃くらいから重量が明確に減少し始め、１０００℃くらいからは急激に減少することが分かった。これは、８７０℃くらいからMgF₂またはCaF₂が分解・気化しフッ素が発生する昇華現象が始まることを意味している。この昇華による焼結体への影響としては、前述したように発泡現象を生じ焼結体全体に微細な気泡が発生することが挙げられる。この発泡により発生した微細な気泡（発泡気泡）は、焼結工程の進行度や、焼結体のどの部位にあるのかにより、脱泡するか、気泡として残るかなどの挙動が決まる。具体的には、例えば一次凝集過程では、焼結体全体がまだ主として開気孔であるため、大半の発泡気泡が開気孔を通じて脱泡出来、気泡として残るものは少ないが、二次凝集過程では、主として閉気孔であるため多くの発泡気泡が脱泡出来ず、気泡として残ると考えられる。したがって、二次凝集過程での焼結を速やかに完了することが気泡を少なくすることにつながる。 On the other hand, according to the investigation by the present inventors, in the process of heating the CaF ₂ -MgF ₂ binary blended raw material through a differential thermal analyzer, the weight begins to decrease clearly from about 870 ° C. It was found that the temperature decreased rapidly from about 1000 ° C. This means that the sublimation phenomenon where MgF ₂ or CaF ₂ decomposes and vaporizes and fluorine is generated starts at about 870 ° C. As an effect of the sublimation on the sintered body, as described above, a foaming phenomenon occurs and fine bubbles are generated in the entire sintered body. The behavior of whether fine bubbles (foamed bubbles) generated by the foaming are defoamed or remain as bubbles is determined depending on the progress of the sintering process and the location of the sintered body. Specifically, for example, in the primary agglomeration process, since the entire sintered body is still mainly open pores, most of the foamed bubbles can be degassed through the open pores, and few remain as bubbles, but in the secondary agglomeration process, Since it is mainly closed pores, it is considered that many foamed bubbles cannot be removed and remain as bubbles. Therefore, promptly completing the sintering in the secondary agglomeration process leads to fewer bubbles.

このことから、一次凝集過程から二次凝集過程への移行は焼結体全体で可能な限り時間差を少なく推移することが望ましい。しかしながら、一次凝集過程から二次凝集過程への移行を焼結体全体で時間差を少なく行うことは容易ではない。   Therefore, it is desirable that the transition from the primary agglomeration process to the secondary agglomeration process changes as little as possible in the entire sintered body. However, it is not easy to perform the transition from the primary aggregation process to the secondary aggregation process with a small time difference in the entire sintered body.

そこで本発明者らは、発泡開始温度（約８７０℃）直下の低めの温度域で加熱を比較的長い時間行って、一次凝集過程と二次凝集過程前半とを完了させ、その後、固溶体が生成し始める温度（９８０℃）域近傍で比較的短時間加熱して二次凝集過程後半を完了させることによって、焼結体全体で焼結進行度を合わせることが可能となり、しかも発泡気泡の生成も少ない優れた焼結方法であることを見出した。   Therefore, the present inventors perform heating for a relatively long time in a lower temperature range just below the foaming start temperature (about 870 ° C.) to complete the primary aggregation process and the first half of the secondary aggregation process, and then a solid solution is formed. By heating for a relatively short time in the vicinity of the temperature (980 ° C.) where heat treatment starts and completing the second half of the secondary agglomeration process, it becomes possible to match the degree of sintering progress throughout the sintered body, and also to generate foamed bubbles. It has been found that there are few excellent sintering methods.

次に、焼結条件の適正範囲について記すことにする。ここで、仮焼結としては大気中で６００℃に６時間保持した。その仮焼結体のサイズは、おおよそ外径２５５〜２６５mm、内径１３５〜１４０mm、厚さ２０〜２１mmのリング形状である。   Next, the appropriate range of sintering conditions will be described. Here, as temporary sintering, it hold | maintained at 600 degreeC in air | atmosphere for 6 hours. The size of the temporary sintered body is a ring shape having an outer diameter of 255 to 265 mm, an inner diameter of 135 to 140 mm, and a thickness of 20 to 21 mm.

加熱雰囲気は窒素ガスとし、加熱パターンのうち、まず昇温、降温条件はおのおの所要時間を４、６、８時間の３ケースで予備試験を行った結果、４時間では焼結体に小さな亀裂が発生し、その他は良好であったので６時間に設定した。   The heating atmosphere is nitrogen gas. Of the heating patterns, first, the temperature rise and fall conditions are preliminarily tested in 3 cases of 4, 6, and 8 hours, respectively. As a result, small cracks were found in the sintered body in 4 hours. It was generated and the others were good, so it was set to 6 hours.

引き続き、加熱雰囲気は窒素ガスとし、まず加熱温度を７００〜１２５０℃の範囲で変化させ、保持時間を３、４、５、６、８、１０、１２、１４、１６、１８時間の１０ケースで実施した。結果は図３に示すように、８００℃未満の場合、保持時間に依らず緻密化が不十分であり、また、保持時間４時間以下の場合、加熱温度に依らず緻密化が不十分であった。一方１１５０℃以上の場合、保持時間に依らず焼結速度が速過ぎるためか気泡が多く発生し、保持時間１８時間以上では焼結体外周の一部が発泡して外観形状が崩れるものが有った。   Subsequently, the heating atmosphere is nitrogen gas. First, the heating temperature is changed in a range of 700 to 1250 ° C., and the holding time is 10 cases of 3, 4, 5, 6, 8, 10, 12, 14, 16, 18 hours. Carried out. As shown in FIG. 3, when the temperature is less than 800 ° C., the densification is insufficient regardless of the holding time, and when the holding time is 4 hours or less, the densification is insufficient regardless of the heating temperature. It was. On the other hand, when the temperature is 1150 ° C. or higher, many bubbles are generated because the sintering speed is too high regardless of the holding time, and when the holding time is 18 hours or more, a part of the outer periphery of the sintered body foams and the appearance shape may be lost. It was.

図３の結果を詳細に見てみると、８００℃の加熱の場合、保持時間が１０、１２時間のときに焼結状態が良好であり、６、８時間ではやや焼結不足、１４時間以上では良否判定不能であった。８３０℃の場合、１０、１２時間が良好であった。８５０℃の場合、８、１０、１２時間が良好であり、５時間ではやや焼結不足であり、１４時間以上では良否判定不能であった。９００℃の場合、５〜１２時間が良好で、４時間ではやや焼結不足、１４時間以上では良否判定不能であった。１０００℃の場合、５〜１２時間が良好で、４時間ではやや焼結不足、１４時間以上では発泡が多く、１０５０℃の場合、５〜１０時間が良好で、４時間ではやや焼結不足、１２時間以上では発泡が多く、１１００℃の場合、５〜８時間が良好で、４時間以下ではやや焼結不足、１０時間以上では発泡が多く見られた。１１５０℃ではいずれも焼結不足か、良否判定不能か、溶け過ぎなどの不良な結果であった。ここで、８００〜８５０℃の比較的低めの加熱温度の場合、保持時間５〜６時間ではやや焼結不足気味であったが、本願の方法では次の加熱焼結工程があるため、この工程での評価は良好と位置付けることにする。   Looking at the results in FIG. 3 in detail, in the case of heating at 800 ° C., the sintered state is good when the holding time is 10 or 12 hours, slightly under-sintered after 6 or 8 hours, 14 hours or more Then it was impossible to judge pass / fail. In the case of 830 degreeC, 10 and 12 hours were favorable. In the case of 850 ° C., 8, 10, and 12 hours were good, the sintering was slightly insufficient in 5 hours, and the good / bad judgment could not be made in 14 hours or more. In the case of 900 ° C., 5 to 12 hours were good, 4 hours was slightly insufficient in sintering, and 14 hours or more was not acceptable. In the case of 1000 ° C., 5 to 12 hours are good, 4 hours are slightly insufficiently sintered, 14 hours or more are foamed a lot, and 1050 ° C., 5 to 10 hours are good, and 4 hours are slightly insufficiently sintered. There were many foams at 12 hours or more, and when the temperature was 1100 ° C., 5 to 8 hours were good, and sintering was slightly insufficient at 4 hours or less, and many foams were seen at 10 hours or more. At 1150 ° C., the results were all poor, such as insufficient sintering, unsatisfactory determination, or excessive melting. Here, in the case of a relatively low heating temperature of 800 to 850 ° C., although the holding time was 5 to 6 hours, it seemed slightly under-sintered. The evaluation in is positioned as good.

つぎに、加熱温度と焼結体の嵩密度、歩留に相当する焼結体の質量減ＴＧとの関係を調べるために、上記と同じ仮焼結体を使用して加熱温度を６００〜１３００℃の範囲で変更（保持時間は６時間一定とし）した。結果は図４に示すように、加熱温度が８００℃で嵩密度はおおよそ３．００g/cm³となり、これ以上の嵩密度の焼結体は図３の結果と同様に後工程での取扱いで崩れる様なトラブルは無く緻密化は十分と判断した。一方、加熱温度が１１５０℃以上では質量減ＴＧは−０．８％以上となり歩留低下が著しい状態となり、またこの温度以上になると焼結体外周の一部が発泡して外観形状が崩れたりするトラブルが発生することがあった。 Next, in order to investigate the relationship between the heating temperature, the bulk density of the sintered body, and the mass loss TG of the sintered body corresponding to the yield, the heating temperature is set to 600 to 1300 using the same temporary sintered body as described above. The temperature was changed in the range of 0 ° C. (the holding time was constant for 6 hours). As shown in FIG. 4, the heating temperature is 800 ° C. and the bulk density is about 3.00 g / cm ^{3. A} sintered body with a bulk density higher than this can be handled in the subsequent process as in the case of FIG. There was no trouble that collapsed and it was judged that densification was sufficient. On the other hand, when the heating temperature is 1150 ° C. or higher, the mass loss TG is −0.8% or higher, and the yield is significantly reduced. When the heating temperature is higher than this temperature, a part of the outer periphery of the sintered body is foamed and the external shape is destroyed. Trouble occurred.

よって、図３、図４の結果から、焼結工程をひとつの加熱工程とした場合の加熱温度は８００〜１１００℃、保持時間５〜１２時間が適正条件であると判断した。ただし、これらの検討中に明らかになったことは、例えば９００℃で１４時間以上、１０００℃で１４時間以上、１１００℃で１０時間以上の比較的長時間加熱をした場合、発泡気泡が多くなり、その一部が集合して大きな気泡に成長し、この様な焼結体は、次の工程である機械加工工程での加工時に大きな気泡部分から亀裂が発生したり、割れの原因になるなどの欠陥を内包するものとなった。   Therefore, from the results of FIG. 3 and FIG. 4, it was determined that the heating temperature when the sintering process was one heating process was 800 to 1100 ° C. and the holding time of 5 to 12 hours were the proper conditions. However, what has become clear during these studies is that, for example, when heated at 900 ° C. for 14 hours or more, 1000 ° C. for 14 hours or more, and 1100 ° C. for 10 hours or more, foam bubbles increase. Part of them gathers and grows into large bubbles, and such a sintered body may cause cracks or cause cracks when processed in the next machining process. It became to contain the defect.

この様な状況から、本願では、焼結工程の基本的な方針として、発泡を極力抑制し、尚且つ焼結反応は十分に進行させ、その後の機械加工工程で良好な加工性を有する焼結体を製造するために、まず、焼結工程の最初の段階では発泡を極力生じさせず、ゆっくりと焼結を進行させ、焼結体内部とその外周部との焼結の進行度に極力差を生じさせないことを基本方針とした。そこで、焼結工程をひとつの加熱工程とした場合の加熱温度域としては上記のとおり８００〜１１００℃の範囲内とし、焼結工程の最初の段階の加熱温度は、発泡開始温度が約８７０℃のため、それを下回る８６０℃以下、すなわち８００〜８６０℃とし、保持時間は５〜１２時間を適正とした。   From this situation, in this application, as a basic policy of the sintering process, the foaming is suppressed as much as possible, the sintering reaction is sufficiently advanced, and the subsequent machining process has good workability. In order to manufacture the body, first, foaming is not generated as much as possible in the first stage of the sintering process, but the sintering is slowly progressed, and the difference in the degree of sintering between the inside of the sintered body and its outer periphery is as much as possible. The basic policy is not to cause Therefore, the heating temperature range when the sintering process is one heating process is within the range of 800 to 1100 ° C. as described above, and the heating temperature in the first stage of the sintering process is a foaming start temperature of about 870 ° C. Therefore, the temperature is set to 860 ° C. or lower, that is, 800 to 860 ° C., and the holding time is appropriately set to 5 to 12 hours.

次の焼結体の焼結反応を高める段階の加熱は、上記の適正条件の内で、固溶体が生成し始める温度９８０℃前後の温度域、すなわち９００〜１１００℃、保持時間については、焼結反応を高めて、且つ発泡を抑えるため極力短時間にすることを目標としており、図３、図４の結果と後述する実施例、比較例の事例などを判断材料にして、０．５時間未満では焼結反応の高まりが乏しく、４時間以上では発泡が多くなり過ぎることから０．５〜３時間の保持が適正とした。   The heating at the stage of enhancing the sintering reaction of the next sintered body is performed within the above-mentioned appropriate conditions at a temperature range around 980 ° C. at which the solid solution starts to be generated, that is, 900 to 1100 ° C. The goal is to shorten the time as much as possible in order to enhance the reaction and suppress foaming. Based on the results of FIGS. 3 and 4 and examples and examples of comparative examples described later, it is less than 0.5 hours. However, since the increase in the sintering reaction is poor, and foaming increases excessively for 4 hours or more, the holding for 0.5 to 3 hours is appropriate.

つぎに、雰囲気ガスをヘリウムに変えた結果は窒素ガスと同じであり、８００℃未満では保持時間に依らず緻密化が不十分であり、また、保持時間４時間以下では加熱温度に依らず緻密化が不十分であった。１１１０℃以上の場合、窒素ガス中と同様に保持時間に依らず焼結速度が速過ぎて気泡が多く発生し、保持時間１６時間以上では発泡して外観形状が崩れることがあった。   Next, the result of changing the atmospheric gas to helium is the same as that of nitrogen gas. Densification is insufficient regardless of the holding time below 800 ° C., and the density is not dependent on the heating temperature below 4 hours. Conversion was insufficient. When the temperature was 1110 ° C. or higher, the sintering speed was too high and many bubbles were generated regardless of the holding time, as in nitrogen gas.

つぎに、加熱温度と焼結体の嵩密度、歩留に相当する焼結体の質量減ＴＧとの関係を調べるために、上記と同じ仮焼結体を使用して加熱温度を６００〜１３００℃の範囲で変更（保持時間は６時間一定とし）した。結果は窒素ガスの場合と同じように、加熱温度８００℃で嵩密度はおおよそ３．００g/cm³となり、これ以上の嵩密度の焼結体は窒素ガスの場合の結果と同様に後工程での取扱いで崩れる様なこともなく緻密化は十分と判断した。一方、加熱温度が１１１０℃以上では質量減ＴＧは−０．８％以上となり歩留低下が著しい状態となり、また、焼結体外周の一部が発泡して外観形状が崩れたりするトラブルが発生したりした。 Next, in order to investigate the relationship between the heating temperature, the bulk density of the sintered body, and the mass loss TG of the sintered body corresponding to the yield, the heating temperature is set to 600 to 1300 using the same temporary sintered body as described above. The temperature was changed in the range of 0 ° C. (the holding time was constant for 6 hours). As in the case of nitrogen gas, the bulk density is approximately 3.00 g / cm ³ at a heating temperature of 800 ° C., and a sintered body having a bulk density higher than this is the same as in the case of nitrogen gas. It was judged that the densification was sufficient without breaking with the handling. On the other hand, when the heating temperature is 1110 ° C. or higher, the mass loss TG is −0.8% or higher, resulting in a significant decrease in yield, and there is a problem that the outer shape of the sintered body is foamed and the appearance shape is destroyed. I did.

よって、雰囲気ガスをヘリウムに変えた場合であっても、加熱温度は８００〜１１００℃、保持時間５〜１２時間が適正条件であると判断した。さらに、加熱温度が８３０〜１０５０℃、保持時間６〜１０時間の場合、機械加工に供す場合に割れ等の欠陥が生じ難く、機械加工性も良好であったことから望ましい加熱温度、保持時間は８３０〜１０５０℃、６〜１０時間であると判断した。よって、ヘリウムガス雰囲気中での本願発明の焼結工程の適正な加熱条件は、前述の窒素ガス雰囲気の場合と同じく、焼結工程の最初の加熱は８００〜８６０℃、５〜１２時間の保持時間、次の工程の加熱は９００〜１１００℃、０．５〜３時間の保持時間が適正条件である。   Therefore, even when the atmospheric gas was changed to helium, it was determined that the heating temperature was 800 to 1100 ° C. and the holding time was 5 to 12 hours. Furthermore, when the heating temperature is 830 to 1050 ° C. and the holding time is 6 to 10 hours, defects such as cracks are not easily generated when subjected to machining, and the machinability is also good, so the desirable heating temperature and holding time are It was judged that the temperature was 830 to 1050 ° C. and 6 to 10 hours. Therefore, the appropriate heating conditions for the sintering process of the present invention in a helium gas atmosphere are the same as in the above-described nitrogen gas atmosphere, and the initial heating in the sintering process is maintained at 800 to 860 ° C. for 5 to 12 hours. The heating for the next step is 900-1100 ° C., and the holding time of 0.5-3 hours is an appropriate condition.

不活性ガスとしては窒素、ヘリウムに限らず、アルゴンでもネオンでも同様の効果が得られる。さらに、ネオンに関しては、本願特許では触れないが、ヘリウムと同様にこの焼結体の母材への溶解度とか拡散性が高いと見込まれるため脱泡現象をより促進し、ヘリウム同等ないしは更なる改善が期待される。   The inert gas is not limited to nitrogen and helium, and the same effect can be obtained with argon or neon. Furthermore, as for neon, which is not mentioned in this patent, it is expected that the sintered body will have high solubility or diffusivity in the same manner as helium. There is expected.

この焼結工程の加熱条件が適正範囲の場合、焼結体の出来上がり状態は常に全体が緻密であり、一般的なセラミックス焼結体などで局部的に見られる大きい空隙とか亀裂などの明らかな欠陥部位は、この焼結体には見られなかった。   When the heating conditions of this sintering process are in the proper range, the final state of the sintered body is always dense, and obvious defects such as large voids and cracks that are found locally in general ceramic sintered bodies The site was not found in this sintered body.

以下、本発明を実施例に基づきさらに具体的に説明するが、本発明は下記の実施例によって制限されるものではない。まず、実施例の中で代表的な焼結体について行う特性評価試験の方法を説明する。   EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example. First, the method of the characteristic evaluation test performed about a typical sintered compact in an Example is demonstrated.

耐プラズマ性は、シリコン半導体製造装置である８インチサイズのエッチング装置を使用し、炉内のシリコン基板置き台上にサンプル（寸法：２０mm×２０mm×ｔ３mm）を置き、CF₄−Ar−O₂混合ガスを流量８５ｃｃ／分で流しながら１０時間プラズマを発生させサンプル厚さの減量（μm／１０hr）、すなわち“エッチング速度”を測定した。 For plasma resistance, an 8-inch etching device, which is a silicon semiconductor manufacturing device, is used, a sample (dimensions: 20 mm × 20 mm × t3 mm) is placed on a silicon substrate stand in the furnace, and CF ₄ —Ar—O ₂ Plasma was generated for 10 hours while flowing the mixed gas at a flow rate of 85 cc / min, and the reduction in thickness of the sample (μm / 10 hr), that is, “etching rate” was measured.

上記の耐プラズマ性試験の比較材としては、シリコンウエハー（Ｓｉ基板）、アルミナ焼結体、イットリア成膜材（石英ガラス基板表面にイットリアを成膜したもの）を用いた。エッチング速度（μm／１０hr）の結果は、表１に示すように、シリコンウエハーは同９３〜１１０、アルミナ焼結体は同４２〜５２、イットリア成膜材は同２１〜３０であり、同２１未満であればこのいずれの比較材よりも優れた耐プラズマ性であると言える。また、この耐プラズマ性は、本発明の緻密な構造のCaF₂−MgF₂二元系焼結体では嵩密度が３．００g/cm³以上のものであれば得られることが分かった。
言い替えれば、このエッチング速度、すなわち耐プラズマ性を得るには、本発明の緻密な構造のCaF₂−MgF₂二元系焼結体では嵩密度が３．００g/cm³以上必要であることが分かった。 As a comparative material for the above plasma resistance test, a silicon wafer (Si substrate), an alumina sintered body, and a yttria film-forming material (a yttria film formed on the surface of a quartz glass substrate) were used. As shown in Table 1, the etching rate (μm / 10 hr) is 93 to 110 for the silicon wafer, 42 to 52 for the alumina sintered body, 21 to 30 for the yttria film forming material, and 21 If it is less than this, it can be said that the plasma resistance is superior to any of these comparative materials. Further, it has been found that this plasma resistance can be obtained if the dense structure of the CaF ₂ -MgF ₂ binary sintered body of the present invention has a bulk density of 3.00 g / cm ³ or more.
In other words, in order to obtain this etching rate, that is, plasma resistance, the CaF ₂ -MgF ₂ binary sintered body having a dense structure according to the present invention needs a bulk density of 3.00 g / cm ³ or more. I understood.

機械的強度としては、曲げ強度、ビッカース硬度およびヤング率の調査を行った。曲げ強度は、試料準備はJIS C2141に準拠して試料寸法４mm×４６mm×ｔ３mmで上下面光学研磨とし、３点曲げ試験JIS R1601に準拠して行った。ビッカース硬度は、島津製作所製の商品名“Micro Hardness Tester”を使用し荷重１００ｇ、荷重時間５秒で圧子を押しつけ、圧痕の対角長を測定し次の硬度換算を行った。
硬度 = 0．18909×Ｐ／ｄ^２
ここで、Ｐ：荷重（Ｎ）、ｄ：圧痕対角線長さ（mm）
ヤング率（Ｅ）、剛性率（Ｇ）、ポアソン比（ν）は、非破壊検査製の商品名“超音波減衰音速測定装置”を使用し、測定試料、寸法Ｗ３０mm×Ｌ３０mm×ｔ２０mmを使い、発信機で発生させた振動波をプローブから試料に伝え試料裏面からの戻り波の時間差を測定する方法で行った。 As the mechanical strength, the bending strength, Vickers hardness and Young's modulus were investigated. Bending strength was prepared according to JIS R1601, a three-point bending test, in which sample preparation was performed with a sample size of 4 mm × 46 mm × t3 mm in accordance with JIS C2141. The Vickers hardness was measured using the trade name “Micro Hardness Tester” manufactured by Shimadzu Corporation, pressing the indenter at a load of 100 g and a load time of 5 seconds, measuring the diagonal length of the indentation, and performing the following hardness conversion.
Hardness = 0.18909 × P / d ²
Where P: Load (N), d: Diagonal diagonal length (mm)
For Young's modulus (E), rigidity modulus (G), and Poisson's ratio (ν), use a product name “ultrasonic attenuation sound velocity measuring device” manufactured by nondestructive inspection, using a measurement sample, dimensions W30 mm × L30 mm × t20 mm, The vibration wave generated by the transmitter was transmitted from the probe to the sample, and the time difference of the return wave from the back of the sample was measured.

熱的特性としては、線膨張係数、熱拡散係数、熱伝導率および比熱の調査を行った。線膨張係数の測定は、マックサイエンス社製“ＴＤ−5000Ｓ”を使用し、測定試料は、寸法Ｗ６．５mm×ｔ３．４mm×Ｌ１５．０mm（蒲鉾形）で行った。測定温度範囲は室温〜３００℃とした。熱拡散係数、熱伝導率および比熱の測定は、アルバック理工社製“ＴＣ−７０００Ｈ”を使用し行った。測定試料は、φ１０mm×ｔ３mm、上下両面光学研磨とした。   As thermal characteristics, the linear expansion coefficient, thermal diffusion coefficient, thermal conductivity and specific heat were investigated. The linear expansion coefficient was measured using “TD-5000S” manufactured by Mac Science Co., Ltd., and the measurement sample was measured with dimensions of W 6.5 mm × t 3.4 mm × L 15.0 mm (saddle shape). The measurement temperature range was room temperature to 300 ° C. The thermal diffusion coefficient, thermal conductivity, and specific heat were measured using “TC-7000H” manufactured by ULVAC-RIKO. The measurement sample was φ10 mm × t3 mm, both upper and lower optical polishing.

電気的特性としては、誘電率、誘電損失の調査を行った。測定装置は、日本ヒューレット・パッカード社製“ＲＦインピーダンス／マテリアルアナライザＨＰ4291”を使用し、測定試料は寸法φ２８mm×ｔ３mmで行った。   As electrical characteristics, dielectric constant and dielectric loss were investigated. As a measuring device, “RF impedance / material analyzer HP4291” manufactured by Hewlett-Packard Japan Co., Ltd. was used, and a measurement sample was measured with a dimension φ28 mm × t3 mm.

高純度のCaF₂粉末（主原料：平均粒径２μm、純度99wt.％以上）に同MgF₂粉末（平均粒径２μm、純度99wt.%以上）を１．５wt.%混合し、ボールミルで１２時間混練した。そのあと、さらに焼結助剤としてカルボキシメチルセルロース（ＣＭＣ）溶液を前記混合物１００に対し、０．２wt.%の割合で添加し、ポットミルで１２時間混合したものを出発原料とし、冷間等方加圧成形（ＣＩＰ）機と外径２６５mm、内径１４０mm、高さ８０mmのリング形状の金型を用いて等方加圧で成形圧２０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６５０℃、６時間仮焼結を行い、外径２６３mm、内径１３４mm、厚さ２０mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８５０℃まで６時間掛けて一定速度で昇温させ、同温度に８時間保持したあと、１０００℃まで２時間掛けて一定速度で昇温させ、同温度に１時間保持し、この後取り出し温度と設定した１００℃までの間加熱を停止してそのまま約２０時間自然冷却（炉冷）し、取り出した。焼結体の概略寸法は、外観の形状と重さから、外径２５５mm、内径１３０mm、厚さ１９mm、嵩密度３．１１g/cm³であり、焼結状態は、はがれ、ひび割れ等の外観上の異常もなく、手に持ったところ適度な重みがあり、内部に粗大な空隙や気泡は極めて少ないと推測される状態であり、良好であった。 Mix 1.5 wt.% Of the same MgF ₂ powder (average particle size 2 μm, purity 99 wt.% Or more) with high purity CaF ₂ powder (main raw material: average particle size 2 μm, purity 99 wt.% Or more). Kneaded for hours. Thereafter, a carboxymethyl cellulose (CMC) solution as a sintering aid was further added to the mixture 100 at a rate of 0.2 wt.%, And the mixture was mixed in a pot mill for 12 hours as a starting material. Using a pressure molding (CIP) machine and a ring-shaped mold having an outer diameter of 265 mm, an inner diameter of 140 mm, and a height of 80 mm, CIP molding was performed at a molding pressure of 20 MPa under isotropic pressure to obtain a molded body. The molded body was pre-sintered at 650 ° C. for 6 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 263 mm, an inner diameter of 134 mm, and a thickness of 20 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 850 ° C. over 6 hours at a constant rate, held at the same temperature for 8 hours, and then heated up to 1000 ° C. over 2 hours at a constant rate. This was held for a period of time, and then the heating was stopped between the take-out temperature and the set temperature of 100 ° C., and the mixture was naturally cooled (furnace cool) for about 20 hours and taken out. The approximate dimensions of the sintered body are, from the appearance and weight, an outer diameter of 255 mm, an inner diameter of 130 mm, a thickness of 19 mm, and a bulk density of 3.11 g / cm ³ , and the sintered state is in terms of appearance such as peeling and cracking. There was no abnormality, and there was an appropriate weight when it was held in the hand, and it was presumed that there were very few coarse voids and bubbles inside, and it was good.

ここで言う“嵩密度”は、焼結体の外観がリング形状であるため、計測したそのリングの内外径と厚さから嵩体積を計算で求め、別に計測した重さを前記嵩体積で除して求める方法を採った。以下、同様に行うこととした。   The “bulk density” here refers to the appearance of the sintered body in a ring shape. Therefore, the bulk volume is calculated from the measured inner and outer diameters and thickness of the ring, and the separately measured weight is divided by the bulk volume. I took the method to ask. Hereinafter, it was decided to carry out similarly.

この焼結体から採取した試料を用いて耐プラズマ性などの特性評価試験を行った結果を表１に示す。以下、実施例、比較例ともに同様とした。なお、耐プラズマ性は、比較材であるシリコンウエハーは９３〜１１０μm／１０Ｈｒ、アルミナ焼結体は同４２〜５２、イットリア成膜材は同２１〜３０であり、比較材中最小のイットリア成膜材より小さいためには同２１未満であることが必要であり、この実施例１の結果である同１０．５は優れた耐プラズマ性である。
また、表２には、この焼結体及び後述する［実施例６］の焼結体から採取した試料を用いて各種の特性評価試験を行った結果を示す。この結果から、機械的強度、熱的特性、誘電特性はともに問題ない良好なものであった。 Table 1 shows the results of a property evaluation test such as plasma resistance using a sample collected from the sintered body. Hereinafter, the examples and comparative examples were the same. The plasma resistance is 93 to 110 μm / 10 Hr for the silicon wafer as a comparative material, 42 to 52 for the alumina sintered body, and 21 to 30 for the yttria film forming material, and the smallest yttria film forming among the comparative materials. In order to be smaller than the material, it is necessary to be less than 21, and 10.5 which is the result of this Example 1 is excellent plasma resistance.
Table 2 shows the results of various property evaluation tests using samples obtained from this sintered body and the sintered body of [Example 6] described later. From these results, the mechanical strength, thermal characteristics, and dielectric characteristics were all good and satisfactory.

上記の実施例１と同じ主原料にMgF₂粉末を７．５wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてステアリン酸カルシウムを０．７wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、冷間等方圧力成形（ＣＩＰ）機と外径３７０mm、内径２５０mm、高さ６０mmのリング形状の金型を用いて成形圧１０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６３０℃、８時間仮焼結を行い、外径３６１mm、内径２４０mm、厚さ１８mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８１０℃まで６時間掛けて一定速度で昇温させ、同温度に９時間保持したあと、９２０℃まで２時間掛けて一定速度で昇温し、同温度に２時間保持し、この後取り出し温度の１００℃まで炉冷し、取り出した。焼結体の概略寸法は、外径３５６mm、内径２３０mm、厚さ１９mm、嵩密度３．０７g/cm³であり、焼結状態は良好であった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 The same main raw material as in Example 1 above was mixed with 7.5 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. Thereafter, 0.7 wt.% Of calcium stearate was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material. A cold isostatic pressing (CIP) machine with an outer diameter of 370 mm, an inner diameter of 250 mm, CIP molding was performed at a molding pressure of 10 MPa using a ring-shaped mold having a height of 60 mm to obtain a molded body. The molded body was pre-sintered at 630 ° C. for 8 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 361 mm, an inner diameter of 240 mm, and a thickness of 18 mm. The temperature was raised from room temperature to 810 ° C. over 6 hours in a nitrogen gas atmosphere at a constant rate, held at the same temperature for 9 hours, then heated up to 920 ° C. over 2 hours at a constant rate, This was held for a period of time and then cooled to the temperature of 100 ° C., which was taken out, and taken out. The approximate dimensions of the sintered body were an outer diameter of 356 mm, an inner diameter of 230 mm, a thickness of 19 mm, and a bulk density of 3.07 g / cm ³ , and the sintered state was good.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を９．８wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を１wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、成形圧３MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６００℃、８時間仮焼結を行い、外径３６３mm、内径２４２mm、厚さ１８．５mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８２０℃まで６時間掛けて一定速度で昇温させ、同温度に６時間保持したあと、９１０℃まで２時間掛けて一定速度で昇温させ、同温度に２．５時間保持し、この後取り出し温度の１００℃まで炉冷し、取り出した。焼結体の概略寸法は、外径３５５mm、内径２３４mm、厚さ１７．５mm、嵩密度３．０１g/cm³であり、焼結状態は良好であった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 9.8 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. Thereafter, 1 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molded at a molding pressure of 3 MPa to obtain a molded body. The molded body was pre-sintered at 600 ° C. for 8 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 363 mm, an inner diameter of 242 mm, and a thickness of 18.5 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 820 ° C. over 6 hours at a constant rate, held at the same temperature for 6 hours, then heated up to 910 ° C. over 2 hours at a constant rate, and the temperature was increased to 2 It was kept for 5 hours, and then cooled to the temperature of 100 ° C., which was taken out, and taken out. The approximate dimensions of the sintered body were an outer diameter of 355 mm, an inner diameter of 234 mm, a thickness of 17.5 mm, and a bulk density of 3.01 g / cm ³ , and the sintered state was good.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を３wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．６wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧１６MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６５０℃、６時間仮焼結を行い、外径２５８mm、内径１３５mm、厚さ２０mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８６０℃まで６時間掛けて一定速度で昇温させ、同温度に５時間保持したあと、１０９０℃まで２時間掛けて一定速度で昇温させ、同温度に０．５時間保持し、この後取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４９mm、１３０mm、厚さ１９mm、嵩密度３．０８g/cm³であり、焼結状態は良好であった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 3 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. Thereafter, 0.6 wt.% Of CMC solution was further added as a sintering aid, and the mixture was mixed for 12 hours in a pot mill as a starting material, and CIP-molded at a molding pressure of 16 MPa in the same manner as in Example 1, did. The molded body was pre-sintered at 650 ° C. for 6 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 258 mm, an inner diameter of 135 mm, and a thickness of 20 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 860 ° C. over 6 hours at a constant rate, held at the same temperature for 5 hours, then heated to 1090 ° C. over 2 hours at a constant rate, and the temperature was reduced to 0 It was held for 5 hours, and then cooled to the temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 249 mm, 130 mm, a thickness of 19 mm, and a bulk density of 3.08 g / cm ³ , and the sintered state was good.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を１．６wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてステアリン酸カルシウムを１．０wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧２５MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で７００℃、６時間仮焼結を行い、外径２５４mm、１３３mm、厚さ２０mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８９０℃まで６時間掛けて一定速度で昇温させ、同温度に５時間保持したあと、１０９０℃まで２時間掛けて一定速度で昇温させ、同温度に０．７５時間保持し、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４９mm、内径１３０mm、厚さ１８.５mm、嵩密度３．１０g/cm³であり、焼結状態は良好であった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 The same main raw material as in Example 1 was mixed with 1.6 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 1.0 wt.% Calcium stearate was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molded at a molding pressure of 25 MPa in the same manner as in Example 1, did. The molded body was pre-sintered at 700 ° C. for 6 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 254 mm, 133 mm, and a thickness of 20 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 890 ° C. over 6 hours at a constant rate, held at the same temperature for 5 hours, then raised to 1090 ° C. over 2 hours at a constant rate, and the temperature was reduced to 0 It was held for 75 hours and cooled in the furnace to a take-off temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 249 mm, an inner diameter of 130 mm, a thickness of 18.5 mm, and a bulk density of 3.10 g / cm ³ , and the sintered state was good.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を３wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．５wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧６０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６６０℃、８時間仮焼結を行い、外径２５２mm、内径１３２mm、厚さ２０.５mmの仮焼結体とした。それをヘルウムガス雰囲気中で室温から８３０℃まで６時間掛けて一定速度で昇温させ、同温度に６時間保持したあと、１０８０℃まで２時間掛けて一定速度で昇温させ、同温度に０．６時間保持し、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４８mm、１３０mm、厚さ１９mm、嵩密度３．１２g/cm³であり、焼結状態は良好であった。
耐プラズマ性および各種特性評価結果は、表１及び表２に示すようにいずれも良好であった。 3 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. After that, 0.5 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molding was performed at a molding pressure of 60 MPa in the same manner as in Example 1. did. The molded body was pre-sintered at 660 ° C. for 8 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 252 mm, an inner diameter of 132 mm, and a thickness of 20.5 mm. The temperature was raised from room temperature to 830 ° C. over 6 hours in a helium gas atmosphere at a constant rate, held at the same temperature for 6 hours, then heated up to 1080 ° C. over 2 hours at a constant rate. It was kept for 6 hours, cooled to the temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 248 mm, 130 mm, a thickness of 19 mm, a bulk density of 3.12 g / cm ³ , and the sintered state was good.
As shown in Tables 1 and 2, the plasma resistance and various characteristics evaluation results were good.

上記実施例１と同じ条件で成形体を作製し、その成形体を大気雰囲気中で６４０℃、６時間仮焼結を行い、外径２５３mm、内径１３３mm、厚さ２１.５mmの仮焼結体とした。それをヘリウムガス雰囲気中で室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に５時間保持したあと、９２０℃まで２時間掛けて一定速度で昇温させ、同温度に１時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外観の形状と重さから、外径２５１mm、１３０mm、厚さ２０mm、嵩密度は３．０２g/cm³でありやや軽めであるが、外観上焼結状態に異常は見られなかった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 A molded body was produced under the same conditions as in Example 1 above, and the molded body was pre-sintered at 640 ° C. for 6 hours in an air atmosphere, and a temporary sintered body having an outer diameter of 253 mm, an inner diameter of 133 mm, and a thickness of 21.5 mm. It was. In a helium gas atmosphere, the temperature is raised from room temperature to 800 ° C. for 6 hours at a constant rate, held at the same temperature for 5 hours, then heated to 920 ° C. for 2 hours at a constant rate, and the temperature is increased to 1 After holding for a time, the furnace was cooled to 100 ° C., and then taken out. Approximate dimensions of the sintered body are slightly light, with an outer diameter of 251 mm, 130 mm, a thickness of 20 mm, and a bulk density of 3.02 g / cm ³ due to the shape and weight of the appearance. Was not seen.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を７．５wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてステアリン酸カルシウムを０．７wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧２０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６１０℃、７時間仮焼結を行い、外径２５６mm、１３４mm、厚さ２０mmの仮焼結体とした。それをヘリウムガス雰囲気中で室温から８２０℃まで６時間掛けて一定速度で昇温させ、同温度に８時間保持したあと、９７０℃まで２時間掛けて一定速度で昇温させ、同温度に１時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４９mm、内径１３０mm、厚さ１９mm、嵩密度は３．０７g/cm³であり幾分軽めであるが、外観上焼結状態に異常は見られなかった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 The same main raw material as in Example 1 above was mixed with 7.5 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. Thereafter, 0.7 wt.% Of calcium stearate was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molded at a molding pressure of 20 MPa in the same manner as in Example 1, did. The molded body was pre-sintered in an air atmosphere at 610 ° C. for 7 hours to obtain a pre-sintered body having an outer diameter of 256 mm, 134 mm, and a thickness of 20 mm. It was heated from room temperature to 820 ° C. at a constant rate for 6 hours in a helium gas atmosphere, held at the same temperature for 8 hours, then heated to 970 ° C. for 2 hours at a constant rate, and the temperature was increased to 1 After holding for a time, the furnace was cooled to 100 ° C., and then taken out. The approximate dimensions of the sintered body were an outer diameter of 249 mm, an inner diameter of 130 mm, a thickness of 19 mm, and a bulk density of 3.07 g / cm ³ , which was somewhat light, but no abnormality was observed in the sintered state in appearance.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

上記の実施例１と同じ主原料にMgF₂粉末を９．８wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を１wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧２０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６００℃、５時間仮焼結を行い、外径２５９mm、内径１３３mm、厚さ２０mmの仮焼結体とした。それをヘリウムガス雰囲気中で室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に８時間保持したあと、９２０℃まで２時間掛けて一定速度で昇温させ、同温度に１時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２５３mm、内径１３１mm、厚さ１９mm、嵩密度は３．０４g/cm³であり幾分軽めであるが、外観上焼結状態に異常は見られなかった。
耐プラズマ性などの特性評価結果は、表１に示すようにいずれも良好であった。 9.8 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. Thereafter, 1 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molding was performed at a molding pressure of 20 MPa in the same manner as in Example 1 to obtain a molded body. The molded body was pre-sintered at 600 ° C. for 5 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 259 mm, an inner diameter of 133 mm, and a thickness of 20 mm. In a helium gas atmosphere, the temperature is raised from room temperature to 800 ° C. over 6 hours at a constant rate, held at the same temperature for 8 hours, then heated up to 920 ° C. over 2 hours at a constant rate, and the temperature is increased to 1 After holding for a time, the furnace was cooled to 100 ° C., and then taken out. The approximate dimensions of the sintered body were an outer diameter of 253 mm, an inner diameter of 131 mm, a thickness of 19 mm, and a bulk density of 3.04 g / cm ³ , which was slightly light, but no abnormality was observed in the sintered state in appearance.
As shown in Table 1, the evaluation results of characteristics such as plasma resistance were all good.

比較例１Comparative Example 1

上記の実施例１と同じ主原料にMgF₂粉末を１２wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．２wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧５MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で７００℃、８時間仮焼結を行い、外径２５１mm、内径１３１mm、厚さ１９.５mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８６０℃まで６時間掛けて一定速度で昇温させ、同温度に６時間保持したあと、１１００℃まで２時間掛けて一定速度で昇温させ、同温度に２時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４８mm、内径１２９mm、厚さはおおよそ１９．５mmであったが、嵩密度は２．９７g/cm³と軽いものであった。焼結体の内部を観察すると、直径０．１mm以上の大きい気泡が無数に存在していた。この大きい気泡は、融点の低いMgF₂粉末を１２wt.%と多く混合したため焼結工程で発泡し易くなり、微細な発泡した気泡（発泡気泡）同士、あるいは同発泡気泡と残留気泡とが集合したものと考えられる。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが散見された。 12 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material. CIP molding was performed at a molding pressure of 5 MPa in the same manner as in Example 1, did. The molded body was pre-sintered at 700 ° C. for 8 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 251 mm, an inner diameter of 131 mm, and a thickness of 19.5 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 860 ° C. over 6 hours at a constant rate, held at the same temperature for 6 hours, and then heated up to 1100 ° C. over 2 hours at a constant rate. After holding for a time, the furnace was cooled to 100 ° C., and then taken out. The approximate dimensions of the sintered body were an outer diameter of 248 mm, an inner diameter of 129 mm, and a thickness of approximately 19.5 mm, but the bulk density was as light as 2.97 g / cm ³ . When the inside of the sintered body was observed, countless large bubbles having a diameter of 0.1 mm or more existed. This large air bubble is easy to foam in the sintering process because MgF ₂ powder with a low melting point of 12 wt.% Is mixed, and fine foamed air bubbles (foamed air bubbles), or the same air bubbles and residual air bubbles gather. It is considered a thing.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength is insufficient in bending strength.

比較例２Comparative Example 2

上記の実施例１と同じ主原料にMgF₂粉末を５wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．２wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧９MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で７００℃、１０時間仮焼結を行い、外径２５２mm、内径１３１mm、厚さ１９mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に１０時間保持したあと、１１６０℃まで２時間掛けて一定速度で昇温させ、同温度に３．５時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２４６〜２４９mm、内径１２５〜１２９mm、厚さはおおよそ１８mm、外周部の一部にはがれたところがあった。このはがれは、発泡した気泡とか残留気泡などが外周部に集合し、外周部の一部が気泡の内圧でひび割れを生じたものと思われる。なお、嵩密度は形状が前述のとおり崩れたところがあり、計測出来ない状態であった。 5 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molded at a molding pressure of 9 MPa in the same manner as in Example 1, did. The molded body was pre-sintered at 700 ° C. for 10 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 252 mm, an inner diameter of 131 mm, and a thickness of 19 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 800 ° C. over 6 hours at a constant rate, held at the same temperature for 10 hours, then raised to 1160 ° C. over 2 hours at a constant rate, After holding for 5 hours, the furnace was cooled to a take-out temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 246 to 249 mm, an inner diameter of 125 to 129 mm, a thickness of about 18 mm, and a part of the outer peripheral portion peeled off. This peeling is thought to be caused by foamed bubbles, residual bubbles, etc. gathering at the outer periphery, and a part of the outer periphery was cracked by the internal pressure of the bubbles. In addition, the bulk density was in a state where the shape could not be measured because the shape collapsed as described above.

比較例３Comparative Example 3

上記の実施例１と同じ主原料粉末に、MgF₂粉末を５wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．２wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧８MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６００℃、４時間仮焼結を行い、外径２５７mm、内径１３５mm、厚さ２０mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に５時間保持したあと８８０℃まで２時間掛けて一定速度で昇温させ、同温度に０．５時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２５１mm、内径１３１mm、厚さはおおよそ１９mmであった。嵩密度は２．９６g/cm³であり軽めである。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが見られた。 The same main raw material powder as in Example 1 was mixed with 5 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP-molded at a molding pressure of 8 MPa as in Example 1, did. The molded body was pre-sintered at 600 ° C. for 4 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 257 mm, an inner diameter of 135 mm, and a thickness of 20 mm. It was heated at a constant rate from room temperature to 800 ° C. in a nitrogen gas atmosphere for 6 hours, held at the same temperature for 5 hours, then heated to 880 ° C. for 2 hours at a constant rate, and the temperature was reduced to 0. After holding for 5 hours, the furnace was cooled to a take-off temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 251 mm, an inner diameter of 131 mm, and a thickness of approximately 19 mm. The bulk density is 2.96 g / cm ³ and is light.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength bending strength was insufficient.

比較例４Comparative Example 4

上記の実施例１と同じ原料粉末を用い、MgF₂粉末を５wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．２wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧７MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で６００℃、３時間仮焼結を行い、外径２５９mm、内径１３６mm、厚さ２０mmの仮焼結体としたが、周辺部の一部、とくに外周のエッジ部分が崩れやすく、外観から仮焼結による収縮が不十分であると判断出来る状態であった。それを窒素ガス雰囲気中で室温から７８０℃まで６時間掛けて一定速度で昇温させ、同温度に４時間保持したあと、９３０℃まで２時間掛けて一定速度で昇温させ、同温度に０．５時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２５６mm、内径１３４mm、厚さ１９.５mmで、一部外周エッジ部に欠けがあるため嵩密度は概算値となるが、約２．９０g/cm³であった。なお、この焼結体をインク液を少量入れ着色した純水に約１時間浸し、引き上げてからその破断面を観察したところ外周部が全体的にこのインク液の色に着色していた。これは、焼結不足で開気孔が多く残っていたものと考えられる。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが認められた。 Using the same raw material powder as in Example 1 above, 5 wt.% Of MgF ₂ powder was mixed and kneaded in a ball mill for 12 hours. Thereafter, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molding was performed at a molding pressure of 7 MPa in the same manner as in Example 1, did. The molded body was pre-sintered at 600 ° C. for 3 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 259 mm, an inner diameter of 136 mm, and a thickness of 20 mm. It was in a state where it was easy to collapse and it could be judged from the appearance that the shrinkage due to pre-sintering was insufficient. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 780 ° C. over 6 hours at a constant rate, held at the same temperature for 4 hours, then heated up to 930 ° C. over 2 hours at a constant rate, and the temperature was reduced to 0 After holding for 5 hours, the furnace was cooled to a take-out temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body are an outer diameter of 256 mm, an inner diameter of 134 mm, and a thickness of 19.5 mm. Some of the outer peripheral edge portions are chipped, so the bulk density is an approximate value, but it is about 2.90 g / cm ^3. It was. The sintered body was dipped in pure water colored with a small amount of ink liquid for about 1 hour, pulled up, and then observed on the fracture surface. As a result, the outer peripheral portion was entirely colored in the color of the ink liquid. This is considered that many open pores remained due to insufficient sintering.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength bending strength was insufficient.

比較例５Comparative Example 5

上記の比較例１と同じ成形体を使用し、大気雰囲気中で６００℃、４時間仮焼結を行い、外径２５８mm、内径１３５mm、厚さ２０mmの仮焼結体とした。それをヘリウムガス雰囲気中で室温から８００℃まで６時間掛けて一定速度で昇温させ、同温度に３時間保持したあと、８９０℃まで２時間掛けて一定速度で昇温させ、同温度に０．３時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の寸法は、外径２５５mm、内径１３４mm、厚さ１９．５mm、嵩密度は２．８９g/cm³とかなり軽いものであった。焼結体内部を観察すると、大きさが中程度の気泡と小さい気泡が無数にあり、また母体の結合部が細めであったこと、また比較例４と同様に破断面の外周部全体にインク液の着色が見られたことから、焼結不足、恐らくは焼結過程の二次凝集が十分には進んでいなかったと推測される。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが認められた。 Using the same molded body as in Comparative Example 1 above, preliminary sintering was performed in an air atmosphere at 600 ° C. for 4 hours to obtain a temporary sintered body having an outer diameter of 258 mm, an inner diameter of 135 mm, and a thickness of 20 mm. In a helium gas atmosphere, the temperature was raised from room temperature to 800 ° C. over 6 hours at a constant rate, held at the same temperature for 3 hours, then heated up to 890 ° C. over 2 hours at a constant rate, and the temperature was reduced to 0 After holding for 3 hours, the furnace was cooled to 100 ° C., and then taken out. The sintered body was as light as possible with an outer diameter of 255 mm, an inner diameter of 134 mm, a thickness of 19.5 mm, and a bulk density of 2.89 g / cm ³ . When the inside of the sintered body was observed, there were innumerable number of medium-sized bubbles and small bubbles, and the joint portion of the base was narrow, and ink was applied to the entire outer peripheral portion of the fracture surface as in Comparative Example 4. Since the liquid was colored, it is presumed that the sintering was insufficient, possibly secondary aggregation in the sintering process was not sufficiently advanced.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength bending strength was insufficient.

比較例６Comparative Example 6

上記の実施例１と同じ主原料にMgF₂粉末を１．３wt.%混合し、ボールミルで同じく１２時間混練した。そのあと、さらに焼結助剤としてＣＭＣ溶液を０．２wt.%添加し、ポットミルで１２時間混合したものを出発原料とし、実施例１と同じように成形圧２０MPaでＣＩＰ成形し、成形体とした。その成形体を大気雰囲気中で７００℃、１０時間仮焼結を行い、外径２５４mm、内径１３１mm、厚さ１９．５mmの仮焼結体とした。それを窒素ガス雰囲気中で室温から８５０℃まで６時間掛けて一定速度で昇温させ、同温度に９時間保持したあと、１１２０℃まで２時間掛けて一定速度で昇温させ、同温度に３時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。焼結体の概略寸法は、外径２５１mm、内径１２９mm、厚さはおおよそ１９mmであったが、嵩密度は２．９７g/cm³とやや軽いものであった。焼結体の内部を観察すると、直径１０μm程度の微細なほぼ真球状の気泡が無数に存在していた。この微細な気泡は、焼結温度の二段階目が発泡開始温度よりもはるかに高い１１２０℃であったため発泡し易くなり、微細な発泡気泡が多数発生したものと考えられる。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが散見された。 The same main raw material as in Example 1 above was mixed with 1.3 wt.% MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, and CIP molded at a molding pressure of 20 MPa as in Example 1, did. The molded body was pre-sintered at 700 ° C. for 10 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 254 mm, an inner diameter of 131 mm, and a thickness of 19.5 mm. In a nitrogen gas atmosphere, the temperature was raised from room temperature to 850 ° C. over 6 hours at a constant rate, held at the same temperature for 9 hours, then raised to 1120 ° C. over 2 hours at a constant rate, After holding for a time, the furnace was cooled to 100 ° C., and then taken out. The approximate dimensions of the sintered body were an outer diameter of 251 mm, an inner diameter of 129 mm, and a thickness of about 19 mm, but the bulk density was slightly light at 2.97 g / cm ³ . When the inside of the sintered body was observed, countless fine spherical particles having a diameter of about 10 μm existed innumerably. These fine bubbles are considered to be easily foamed because the second stage of the sintering temperature is 1120 ° C., which is much higher than the foaming start temperature, and many fine foamed bubbles are generated.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength is insufficient in bending strength.

比較例７Comparative Example 7

上記の比較例６と同じ成形体を使用し、大気雰囲気中で６００℃、４時間仮焼結を行い、外径２５６mm、内径１３５mm、厚さ２０mmの仮焼結体とした。それをヘリウムガス雰囲気中で室温から６００℃まで６時間掛けて一定速度で昇温させ、同温度に４時間保持したあと、９４０℃まで２時間掛けて一定速度で昇温させ、同温度に０．５時間保持したあと、取り出し温度の１００℃まで炉冷し取り出した。 焼結体の概略寸法は、外径２５２mm、内径１３２mm、厚さ１９mmであり、嵩密度は２．９３g/cm³とかなり軽いものであった。焼結体内部を観察すると、真球状の微細な気泡は認めらなかったが、母体の結合部が細めであったこと、また比較例４と同様に破断面の外周部全体にインク液の着色が見られたことから、焼結不足、恐らくは焼結過程の二次凝集が十分には進んでいなかったと推測される。
耐プラズマ性、各種特性評価のうち例えば機械的強度の曲げ強度などに不十分なレベルのものが認められた。 Using the same molded body as in Comparative Example 6 above, preliminary sintering was performed at 600 ° C. for 4 hours in an air atmosphere to obtain a temporary sintered body having an outer diameter of 256 mm, an inner diameter of 135 mm, and a thickness of 20 mm. In a helium gas atmosphere, the temperature was raised from room temperature to 600 ° C. over 6 hours at a constant rate, held at the same temperature for 4 hours, then heated to 940 ° C. over 2 hours at a constant rate, and the temperature was reduced to 0 After holding for 5 hours, the furnace was cooled to a take-out temperature of 100 ° C. and taken out. The approximate dimensions of the sintered body were an outer diameter of 252 mm, an inner diameter of 132 mm, a thickness of 19 mm, and a bulk density of 2.93 g / cm ³ which was quite light. When the inside of the sintered body was observed, no spherical fine bubbles were observed, but the joint portion of the base was narrow, and the entire outer peripheral portion of the fracture surface was colored similarly to Comparative Example 4. From this, it is presumed that the sintering was insufficient, possibly secondary aggregation in the sintering process was not sufficiently advanced.
Among the plasma resistance and various characteristic evaluations, for example, the mechanical strength bending strength was insufficient.

Claims (7)

MgF₂を１．５〜１０wt.％含有するCaF₂−MgF₂ 二元系固溶焼結体からなり、
該焼結体の嵩密度が３．００g/cm³以上であり、
かつ曲げ強度が６０MPa以上であることを特徴とするCaF₂−MgF₂二元系焼結体。 A CaF ₂ -MgF ₂ binary solid solution sintered body containing 1.5 to 10 wt.% MgF ₂
Der bulk density of 3.00 g / cm ³ or more sintered body is,
And CaF flexural strength, characterized in der Rukoto least 60 MPa ₂ MgF ₂ binary sintered body. 前記焼結体に対するプラズマ波によるエッチング速度が、シリコンウエハー、アルミナ焼結体、及び石英基板にイットリアを成膜したものに対するいずれのエッチング速度より小さいものであることを特徴とする請求項１記載のCaF₂−MgF₂二元系焼結体。 The etching rate by the plasma wave with respect to the said sintered compact is a thing smaller than any etching rate with respect to what formed the film | membrane with the yttria on the silicon wafer, the alumina sintered compact, and the quartz substrate. CaF ₂ -MgF ₂ binary sintered body. ビッカース硬度が３００程度、ヤング率が１００ＧＰａ程度、剛性率が４０GPa程度、及び／又はポアソン比が０．３程度の機械的強度を有するものであることを特徴とする請求項１又は請求項２記載のCaF₂−MgF₂二元系焼結体。 3. A mechanical strength having a Vickers hardness of about 300, a Young's modulus of about 100 GPa, a rigidity of about 40 GPa, and / or a Poisson's ratio of about 0.3. CaF ₂ -MgF ₂ binary sintered body. 熱膨張係数が２．３×１０^−５以下（温度域は２０〜３００℃）、熱伝導率が０．０４Ｗ／（ｃｍ・Ｋ）以上、及び／又は比熱が０．８Ｊ／（ｇ・Ｋ）以上の熱的特性を有するものであることを特徴とする請求項１〜３のいずれかの項に記載のCaF₂−MgF₂二元系焼結体。 Thermal expansion coefficient is 2.3 × 10 ⁻⁵ or less (temperature range is 20 to 300 ° C.), thermal conductivity is 0.04 W / (cm · K) or more, and / or specific heat is 0.8 J / (g · K). 4) The CaF ₂ -MgF ₂ binary sintered body according to any one of claims 1 to 3, which has the above-mentioned thermal characteristics. 誘電率が６．５〜８．５（at １MHz、３００Ｋ）、及び／又は誘電損失が６．５〜８．５×１０^−３（at １MHz、２０℃）の誘電特性を有するものであることを特徴とする請求項１〜４のいずれかの項に記載のCaF₂−MgF₂二元系焼結体。 It has a dielectric characteristic of a dielectric constant of 6.5 to 8.5 (at 1 MHz, 300 K) and / or a dielectric loss of 6.5 to 8.5 × 10 ⁻³ (at 1 MHz, 20 ° C.). The CaF ₂ -MgF ₂ binary sintered body according to any one of claims 1 to 4, wherein: 緻密な構造のCaF₂−MgF₂二元系焼結体からなる耐プラズマ性フッ化物焼結体の製造方法であって、
高純度CaF₂粉末に高純度MgF₂粉末を１．５〜１０wt.％混合し、さらに焼結助剤を０．１〜１wt.％添加して混合する工程、
冷間等方加圧成形（ＣＩＰ）機を用いて成形圧２MPa以上で成形する工程、
その成形体を大気雰囲気中で６００〜７００℃で所定時間加熱して仮焼結を行う工程、
大気中または不活性ガス雰囲気中で仮焼結体の発泡を抑制し得る８００〜８６０℃の温度範囲で４〜１６時間加熱したあと同雰囲気中で固溶体が生成し始める９００〜１１００℃の温度範囲で０．５〜３時間加熱して緻密な構造のCaF₂−MgF₂二元系焼結体を形成する工程、を含むことを特徴とする耐プラズマ性フッ化物焼結体の製造方法。 A method for producing a plasma-resistant fluoride sintered body comprising a CaF ₂ -MgF ₂ binary sintered body having a dense structure,
A step of mixing high purity MgF ₂ powder with high purity CaF ₂ powder in an amount of 1.5 to 10 wt.% And further adding 0.1 to 1 wt.% Of a sintering aid;
Forming at a molding pressure of 2 MPa or more using a cold isostatic pressing (CIP) machine;
A step of heating the molded body at 600 to 700 ° C. for a predetermined time in an air atmosphere to perform preliminary sintering;
Temperature range of presintered body solid solution foamed with 4-16 hours heated after the same atmosphere 800-860 temperature range ° C. capable of suppressing the start to generate 900 to 1100 ° C. at or in an inert gas atmosphere the atmosphere And a step of forming a CaF ₂ -MgF ₂ binary sintered body having a dense structure by heating for 0.5 to 3 hours . 前記CaF₂−MgF₂二元系焼結体形成工程において、前記不活性ガスとして、窒素、ヘリウム、アルゴン、ネオンの各ガスの内の１種類または複数の種類を混合したものを使用することを特徴とする請求項６記載の耐プラズマ性フッ化物焼結体の製造方法。 In the CaF ₂ -MgF ₂ binary sintered body forming step, the inert gas may be a mixture of one or more of nitrogen, helium, argon, and neon gases. The method for producing a plasma-resistant fluoride sintered body according to claim 6 .

Images