JP2011104680A - Polishing liquid containing cerium oxide particle and polishing method using the same - Google Patents
Polishing liquid containing cerium oxide particle and polishing method using the same Download PDFInfo
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本発明は、半導体平坦化用研磨液に適した酸化セリウム粒子を含む研磨液及びこれを用いた研磨法に関する。 The present invention relates to a polishing liquid containing cerium oxide particles suitable for a semiconductor flattening polishing liquid and a polishing method using the same.
素材表面を精密に研磨加工することが必要な用例として、光ディスク基板、磁気ディスク、フラットパネルディスプレイ用ガラス基板、時計板、カメラレンズ、光学部品用の各種レンズに用いられるガラス素材やフィルタ類等の結晶素材、半導体用のシリコンウエハ等の基板、半導体デバイス製造の各工程において形成された絶縁膜、金属層、バリア層等がある。 Examples of applications that require precise polishing of the material surface include optical disks, magnetic disks, glass substrates for flat panel displays, watch plates, camera lenses, glass materials used in various lenses for optical components, filters, etc. There are crystal materials, substrates such as semiconductor silicon wafers, insulating films, metal layers, barrier layers and the like formed in each process of semiconductor device manufacturing.
これらの素材表面は、高精度に研磨することが要求される。半導体デバイス製造における研磨加工の工程としては、例えば、酸化珪素膜等の層間絶縁膜の平坦化や、集積回路内の素子を分離するため基板上に埋め込んだ余分な酸化珪素膜を除くシャロー・トレンチ素子分離膜等がある。 The surface of these materials is required to be polished with high accuracy. As a polishing process in semiconductor device manufacturing, for example, planarization of an interlayer insulating film such as a silicon oxide film, or a shallow trench excluding an extra silicon oxide film embedded on a substrate to isolate an element in an integrated circuit There are element isolation films and the like.
これらの半導体デバイス製造における精密研磨用研磨液として、特に、シリカ微粒子を研磨粒子として用いたシリカ研磨液は、被研磨面の研磨傷発生等が少ないことから広く普及しているが、研磨速度が遅いため、近年、研磨速度が速い酸化セリウムを含む研磨液が注目されている。
しかし、このような研磨液はシリカ粒子と比較して研磨傷が多いという課題がある。
As a polishing liquid for precision polishing in manufacturing these semiconductor devices, in particular, a silica polishing liquid using silica fine particles as polishing particles is widespread because there are few occurrences of polishing scratches on the surface to be polished. In recent years, a polishing liquid containing cerium oxide, which has a high polishing rate, has attracted attention.
However, there is a problem that such a polishing liquid has more polishing scratches than silica particles.
酸化セリウムを含む研磨液は、古くからガラス研磨用に用いられてきたが、半導体平坦化に適用するためには不純物混入を極力避ける必要があった。そこで、希土類原料を一旦精製し、セリウム塩を経由して焼成することにより、高純度の酸化セリウムを得ている。 Polishing liquids containing cerium oxide have been used for glass polishing for a long time, but it was necessary to avoid contamination with impurities as much as possible in order to apply them to semiconductor planarization. Therefore, high-purity cerium oxide is obtained by once refining the rare earth material and firing it via a cerium salt.
セリウム塩としては炭酸セリウム、シュウ酸セリウム、硝酸セリウム等が用いられる。これらのセリウム塩を仮焼、粉砕した酸化セリウムを分散して、半導体平坦化用研磨液が製造されている。 Examples of cerium salts include cerium carbonate, cerium oxalate, and cerium nitrate. A polishing liquid for semiconductor planarization is produced by dispersing cerium oxide obtained by calcining and grinding these cerium salts.
研磨の過程で生じる研磨傷は、研磨液中の大粒径粒子の含有率を低くすることで低減する傾向がある。
しかし、従来酸化セリウムの製造に用いられている炭酸セリウム等のセリウム化合物を焼成粉砕する方法では、粉砕に長時間を要する上、粉砕機の部品が磨耗して磨耗粉が研磨液中に混入する可能性が高まる。研磨液に混入した磨耗粉は研磨傷の原因となるため好ましくない。
Polishing flaws that occur during the polishing process tend to be reduced by lowering the content of large-diameter particles in the polishing liquid.
However, in the method of firing and pulverizing cerium compounds such as cerium carbonate conventionally used in the production of cerium oxide, it takes a long time for pulverization, and the parts of the pulverizer are worn and wear powder is mixed into the polishing liquid. The possibility increases. Abrasion powder mixed in the polishing liquid is not preferable because it causes polishing scratches.
また、短時間の粉砕では大粒子径粒子が粉砕されずに残り、研磨液中に混入するため、大粒径粒子の含有率を低くすることは困難である（例えば、特許文献１参照）。 Moreover, since the large particle diameter particles are not pulverized and mixed in the polishing liquid in a short pulverization, it is difficult to reduce the content of the large particle diameter particles (see, for example, Patent Document 1).
一方で半導体の高集積化が進行し、配線等の加工寸法は１００ｎｍまで微細化している。それに伴い研磨傷等の欠陥低減要求はますます強く、研磨速度、平坦性、研磨傷低減の全てを満たす研磨液が要求されている。 On the other hand, higher integration of semiconductors has progressed, and the processing dimensions of wiring and the like have been reduced to 100 nm. Accordingly, there is an increasing demand for reducing defects such as polishing scratches, and a polishing liquid that satisfies all of the polishing rate, flatness, and polishing scratch reduction is required.
研磨液による研磨傷低減を目的として、炭酸セリウムとシュウ酸等の酸を混合後、焼成して得られた酸化セリウム粉体を粉砕して酸化セリウム粒子とし研磨液として用いることで、研磨傷を低減した半導体平坦化用研磨液の製造方法が提案されている。（例えば、特許文献２参照） For the purpose of reducing polishing scratches by the polishing liquid, cerium carbonate and acid such as oxalic acid are mixed and then baked to pulverize the cerium oxide powder and use it as cerium oxide particles as a polishing liquid. A method for manufacturing a reduced semiconductor planarization polishing liquid has been proposed. (For example, see Patent Document 2)
炭酸セリウムと酸を混合した後に焼成して得た酸化セリウム粉体は、炭酸セリウムをそのまま焼成して得た酸化セリウム粉体と形状が異なり、粉砕性が向上するため、粉砕時間を短縮し粉砕機からの設備磨耗粉の混入を防ぐと同時に大粒子径粒子の含有率を低減できるため、研磨傷を低減することができる。 The cerium oxide powder obtained by firing after mixing cerium carbonate and acid is different in shape from the cerium oxide powder obtained by firing cerium carbonate as it is, and the grindability is improved. Since it is possible to prevent the mixing of equipment wear powder from the machine and at the same time to reduce the content of large particles, polishing flaws can be reduced.
しかしながら、上記の製造方法では、製造ロットによって、焼成後に得られる酸化セリウム粉体の粉砕性がばらつく傾向があり、粉砕性のよい酸化セリウム粉体を安定的に得ることが困難である。 However, in the above production method, the pulverizability of the cerium oxide powder obtained after firing tends to vary depending on the production lot, and it is difficult to stably obtain a cerium oxide powder with good pulverizability.
また、焼成を、量産性に優れるロータリーキルンやトンネル炉等の連続運転式の焼成炉により行うと、得られる酸化セリウム粉体の結晶性が高まりやすい傾向がある。酸化セリウム粉体の結晶性が高くなると、酸化セリウム粉体を粉砕処理する際に、粉砕機の部品が磨耗しやすくなる。そうすると、粉砕機の磨耗粉が酸化セリウム粒子中に混入してしまい、得られた酸化セリウム粒子を含有する研磨液中にも混入するため好ましくない。 In addition, when firing is performed by a continuous operation firing furnace such as a rotary kiln or a tunnel furnace excellent in mass productivity, the crystallinity of the obtained cerium oxide powder tends to increase. When the crystallinity of the cerium oxide powder becomes high, the parts of the pulverizer are easily worn when the cerium oxide powder is pulverized. If it does so, the abrasion powder of a grinder will mix in the cerium oxide particle, and since it mixes also in the polishing liquid containing the obtained cerium oxide particle, it is not preferable.
そこで、結晶性を高めないように焼成温度及び昇温速度を調整する方法が考えられるが一方で、結晶性を低くすると、得られる酸化セリウム粒子の粉砕性が悪いという問題がある。 Therefore, a method of adjusting the firing temperature and the temperature rising rate so as not to increase the crystallinity is conceivable. On the other hand, if the crystallinity is lowered, there is a problem that the cerium oxide particles to be obtained have poor grindability.
本発明は、上記に鑑みて、酸化セリウム粒子粉砕工程において生じうる、粉砕機の摩耗粉等の異物の混入を防ぎつつ、粉砕性に優れた酸化セリウム粒子を、より安定的に効率良く得ることにより、研磨傷を低減させることが可能な酸化セリウム粒子を含有する研磨液を提供することを目的とする。 In view of the above, the present invention is capable of more stably and efficiently obtaining cerium oxide particles having excellent pulverizability while preventing contamination of foreign substances such as pulverizer wear powder that may occur in the cerium oxide particle pulverization step. Thus, an object of the present invention is to provide a polishing liquid containing cerium oxide particles capable of reducing polishing scratches.
上記課題を解決する為、本発明者等は鋭意検討した結果、以下のことを見出した。
粉末の炭酸セリウムと有機酸は、お互いが含有している水分を媒体として、混合状態中、反応が緩やかに逐次進行している。炭酸セリウムと有機酸との反応が完了していない場合、混合してから焼成するまでの間も反応が進行してしまう。このため、混合してから焼成するまでの時間を一定にしなければ、製造ロットごとに酸化セリウム粉体の粉砕性にバラツキが発生してしまうと考えた。
In order to solve the above-mentioned problems, the present inventors have intensively studied and found the following.
The reaction of powdered cerium carbonate and organic acid proceeds gradually and gradually in a mixed state using moisture contained in each other as a medium. When the reaction between cerium carbonate and the organic acid is not completed, the reaction proceeds from mixing to firing. For this reason, if the time from mixing to baking is not constant, it was considered that the pulverizability of the cerium oxide powder would vary among production lots.
そこで、本発明者等は、高粉砕性酸化セリウム粉体を安定的に得るためには、炭酸セリウムと有機酸の反応を途中で停止させる必要があると予測し、加熱混合により反応系内の水分を蒸発させ、反応を停止させることで、高粉砕性酸化セリウム粉体を安定的に得られる条件を見出した。 Therefore, the present inventors predicted that it is necessary to stop the reaction between cerium carbonate and the organic acid in the middle in order to stably obtain a highly pulverizable cerium oxide powder, and by heating mixing in the reaction system The present inventors have found conditions under which high pulverizable cerium oxide powder can be stably obtained by evaporating water and stopping the reaction.
より具体的には、一定条件の加熱混合により反応系内の水分を蒸発させ、反応を停止させることで、混合してから焼成するまでの時間によらず、同程度の粉砕性及び同程度の結晶性を有する酸化セリウム粉体を安定的に製造でき、それにより異なる製造ロットにおいても、研磨傷低減を可能とした酸化セリウム粒子を安定的に効率よく得られることを見出した。 More specifically, by evaporating the water in the reaction system by heating and mixing under certain conditions and stopping the reaction, the same degree of pulverization and the same degree can be obtained regardless of the time from mixing to firing. It has been found that cerium oxide powder having crystallinity can be stably produced, and thereby cerium oxide particles capable of reducing polishing scratches can be stably and efficiently obtained even in different production lots.
また、炭酸セリウムと有機酸を混合した後、焼成及び粉砕工程を経て酸化セリウム粒子を得る従来の製造方法では、酸化セリウム粉体の結晶性は昇温速度の影響を受ける。例えば、ロータリーキルンやトンネル炉等の連続運転式の焼成炉を用い急加熱して焼成温度まで昇温して焼成する場合、バッチ式炉で緩やかに加熱を行い焼成温度まで昇温し焼成した場合と比べ、得られる酸化セリウム粉体の結晶性が高まる傾向がある。
しかし、本発明においては、加熱混合することで、連続運転式の焼成炉で急加熱しても結晶性を高めずに粉砕性のよい酸化セリウム粉体が得られ、それにより研磨傷低減を可能とした酸化セリウム粒子を安定的に効率よく得られることを見出し、本発明を完成するに至った。
In the conventional manufacturing method in which cerium oxide particles are obtained by mixing cerium carbonate and an organic acid, followed by firing and pulverization processes, the crystallinity of the cerium oxide powder is affected by the rate of temperature rise. For example, when using a continuous kiln, such as a rotary kiln or a tunnel furnace, rapidly heating and raising the temperature to the firing temperature, when heating it gently in a batch furnace and raising the temperature to the firing temperature and firing In comparison, the crystallinity of the obtained cerium oxide powder tends to increase.
However, in the present invention, cerium oxide powder with good grindability can be obtained without increasing crystallinity even by rapid heating in a continuous operation type firing furnace by heating and mixing, thereby reducing polishing scratches. The present inventors have found that the cerium oxide particles obtained can be obtained stably and efficiently, and have completed the present invention.
すなわち、本発明は、以下の通りである。
（１） 酸化セリウム粒子及び水を含む研磨液において、研磨液１ｍｌ中の粒子径０．７５μｍ以上の粒子数が３×１０６個以下である、研磨液。
（２） 酸化セリウム粒子が、（Ｉ）炭酸セリウムと有機酸とを加熱混合し加熱混合粉体を得る工程、（ＩＩ）該加熱混合粉体を焼成して酸化セリウム粉体を得る工程、（ＩＩＩ）該酸化セリウム粉体を粉砕して、酸化セリウム粒子を得る工程、を有することを特徴とする製造方法により作製された酸化セリウム粒子である前記の研磨液。
（３） （Ｉ）工程直後の加熱混合粉体の質量と、該加熱混合粉体を温度２５℃で２４時間放置した後の加熱混合粉体の質量とを比較したとき、質量減少量が、０〜０．１質量％である前記の研磨液。
（４） （Ｉ）工程の加熱が、４０〜２００℃の範囲で行われる前記の研磨液。
（５） （Ｉ）工程の加熱混合の時間が、１．５〜４時間である前記の研磨液。
（６） 加熱混合粉体を焼成して得られた酸化セリウム粉体が、線源をＣｕＫα線とする粉末Ｘ線回折パターンから求められる酸化セリウム結晶の（１１１）面による回折ピークの半値幅が０．２７〜０．５０°であり、粉砕した後の酸化セリウム粉砕物の９９体積％以上が粒子径０．１〜１μｍである前記の研磨液。
（７） （ＩＩ）工程の焼成が、４００〜９００℃の範囲で行われる前記の研磨液。
（８） 研磨液中の酸化セリウム粒子の粒子径の中央値が０．１〜１μｍである前記の研磨液。
（９） 研磨液中の、粒子径３μｍ以上の酸化セリウム粒子含有量が固体中の５００ｐｐｍ以下である前記の研磨液。
（１０） さらに分散剤を含む前記の研磨液。
（１１） 研磨液中の酸化セリウム粒子全体の９９体積％以上が粒子径１μｍ以下である前記の研磨液。
（１２） 前記の研磨液で所定の基板を研磨することを特徴とする基板の研磨法。
（１３） 所定の基板が、少なくともＳｉＯ２膜が形成された半導体チップである前記の基板の研磨法。
That is, the present invention is as follows.
(1) A polishing liquid comprising a cerium oxide particle and water, wherein the number of particles having a particle diameter of 0.75 μm or more in 1 ml of the polishing liquid is 3 × 10 6 or less.
(2) The cerium oxide particles are (I) a step of heating and mixing cerium carbonate and an organic acid to obtain a heated mixed powder, and (II) a step of firing the heated mixed powder to obtain a cerium oxide powder. III) The above polishing liquid, which is a cerium oxide particle produced by a production method comprising the step of pulverizing the cerium oxide powder to obtain cerium oxide particles.
(3) When the mass of the heated mixed powder immediately after the step (I) and the mass of the heated mixed powder after leaving the heated mixed powder at a temperature of 25 ° C. for 24 hours are compared, The said polishing liquid which is 0-0.1 mass%.
(4) The said polishing liquid in which the heating of (I) process is performed in the range of 40-200 degreeC.
(5) The said polishing liquid whose time of the heat mixing of a process (I) is 1.5 to 4 hours.
(6) The cerium oxide powder obtained by firing the heated mixed powder has a half-value width of the diffraction peak due to the (111) plane of the cerium oxide crystal obtained from a powder X-ray diffraction pattern using CuKα rays as a radiation source. The said polishing liquid which is 0.27-0.50 degree and 99 volume% or more of the cerium oxide ground material after grind | pulverizing is a particle diameter of 0.1-1 micrometer.
(7) The said polishing liquid with which baking of a process (II) is performed in 400-900 degreeC.
(8) The said polishing liquid whose median value of the particle diameter of the cerium oxide particle in polishing liquid is 0.1-1 micrometer.
(9) The above polishing liquid, wherein the content of cerium oxide particles having a particle diameter of 3 μm or more in the polishing liquid is 500 ppm or less in the solid.
(10) The polishing liquid further containing a dispersant.
(11) The said polishing liquid whose 99 volume% or more of the whole cerium oxide particle | grains in polishing liquid are 1 micrometer or less in particle diameter.
(12) A method for polishing a substrate, comprising polishing a predetermined substrate with the polishing liquid.
(13) The method for polishing a substrate, wherein the predetermined substrate is a semiconductor chip on which at least a SiO 2 film is formed.
本発明によれば、配線形成工程における半導体表面を高速で研磨でき、且つ平坦性良好で研磨傷を低減することが可能な酸化セリウム粒子を、効率よく安定的に得ることが可能であり、この酸化セリウム粒子を含む研磨液及びこれを用いた研磨法を提供することができる。 According to the present invention, it is possible to efficiently and stably obtain cerium oxide particles capable of polishing a semiconductor surface in a wiring formation process at high speed and having good flatness and capable of reducing polishing scratches. A polishing liquid containing cerium oxide particles and a polishing method using the same can be provided.
以下、発明を実施するための最良の形態について詳細に説明する。
本発明の研磨液は、酸化セリウム粒子及び水を含む研磨液において、研磨液１ｍｌ中の粒子径０．７５μｍ以上の粒子数が３×１０６個以下であることを特徴とする。
Hereinafter, the best mode for carrying out the invention will be described in detail.
The polishing liquid of the present invention is characterized in that, in a polishing liquid containing cerium oxide particles and water, the number of particles having a particle diameter of 0.75 μm or more in 1 ml of the polishing liquid is 3 × 10 6 or less.
＜酸化セリウム粒子の製造方法及びそれより得られる酸化セリウム粒子＞
本発明に使用される酸化セリウム粒子の製造方法は、下記の工程を有することが好ましい。
（Ｉ）炭酸セリウムと有機酸とを加熱混合し加熱混合粉体を得る工程、
（ＩＩ）該加熱混合粉体を焼成して酸化セリウム粉体を得る工程、
（ＩＩＩ）該酸化セリウム粉体を粉砕して、酸化セリウム粒子を得る工程。
なお、本発明において、加熱混合とは、混合してから加熱する方法と加熱しながら混合する方法を意味するが、均一に加熱する点で加熱しながら混合する方が好ましい。
<Method for producing cerium oxide particles and cerium oxide particles obtained therefrom>
The method for producing cerium oxide particles used in the present invention preferably has the following steps.
(I) a step of heating and mixing cerium carbonate and an organic acid to obtain a heated mixed powder;
(II) firing the heated mixed powder to obtain a cerium oxide powder;
(III) A step of pulverizing the cerium oxide powder to obtain cerium oxide particles.
In the present invention, heat mixing means a method of mixing and heating and a method of mixing while heating, but it is preferable to mix while heating in terms of heating uniformly.
また、本発明において、「加熱混合粉体」とは、炭酸セリウムと有機酸とを加熱混合して得られた粉体のことであり、焼成工程の前の粉体である。「酸化セリウム粉体」とは、前記加熱混合粉体を焼成した粉体のことであり、粉砕工程の前の粉体である。「酸化セリウム粒子」とは、前記酸化セリウム粉体を粉砕したものであり、粉砕後に必要により沈降分級、ろ過等で処理することが好ましく、処理された粒子も「酸化セリウム粒子」に相当する。さらに、後述の「酸化セリウム粉砕物」とは、酸化セリウム粉体を特定の条件（詳細は後述するが、粉砕条件（ａ））で粉砕した後の粉砕物をいう。 In the present invention, “heat mixed powder” refers to a powder obtained by heating and mixing cerium carbonate and an organic acid, and is a powder before the firing step. The “cerium oxide powder” is a powder obtained by firing the heated mixed powder, and is a powder before the pulverization step. The “cerium oxide particles” are those obtained by pulverizing the cerium oxide powder, and it is preferable that the cerium oxide particles be treated by sedimentation classification, filtration or the like after pulverization, and the treated particles also correspond to “cerium oxide particles”. Furthermore, “cerium oxide pulverized product” described later refers to a pulverized product obtained by pulverizing cerium oxide powder under specific conditions (details will be described later, pulverization conditions (a)).
従来酸化セリウムの製造に用いられていた、炭酸セリウムやシュウ酸セリウム等のセリウム塩を焼成する方法では、セリウム塩が熱分解し、酸化セリウム粉体が得られる。その際、セリウム塩と酸化セリウム粉体の形状に大きな違いは無いことが多い。
しかし、炭酸セリウムと有機酸を混合して焼成を行うと、炭酸セリウムと有機酸との化学反応が起こり、炭酸イオンが置換され、セリウムの有機酸塩の生成を経て熱分解し、酸化セリウム粉体が得られる。この酸化セリウム粉体は、炭酸セリウムと形状が大きく異なり、また、市販のセリウム塩をそのまま焼成して得られる酸化セリウム粉体とも形状が大きく異なり、微細な粒子の集合体となる。この酸化セリウム粉体は微細な粒子の集合体であるために容易に短時間で粉砕され、酸化セリウム微粒子となる。
In the conventional method of firing cerium salts such as cerium carbonate and cerium oxalate, which has been used in the production of cerium oxide, the cerium salt is thermally decomposed to obtain cerium oxide powder. In that case, there is often no significant difference between the shapes of the cerium salt and the cerium oxide powder.
However, when cerium carbonate and organic acid are mixed and baked, a chemical reaction between cerium carbonate and organic acid takes place, carbonate ions are replaced, and thermal decomposition occurs through the formation of an organic acid salt of cerium. The body is obtained. This cerium oxide powder is greatly different in shape from cerium carbonate, and also different in shape from cerium oxide powder obtained by firing a commercially available cerium salt as it is, and becomes an aggregate of fine particles. Since this cerium oxide powder is an aggregate of fine particles, it is easily pulverized in a short time to become cerium oxide fine particles.
炭酸セリウムと有機酸との反応は、お互いが含有する水分を媒体として混合状態中に反応が逐次進行している。固体同士の反応であるため、反応を完了させるには長時間を要する。反応が完了していない場合は、焼成までの時間を一定としなければ、すなわち、反応進行度を一定としなければ、異なる製造ロットにおいて同程度の粉砕性を有する酸化セリウム粉体を製造することが困難である。そこで、本発明においては、反応が完了していない場合でも、同一条件の加熱混合により反応系内から媒体となる水分を蒸発させ、加熱混合終了時点で反応が進行しなくなるようにすることで、反応進行度を一定とすることができ、それにより、焼成までの時間によらず同程度の粉砕性を有する酸化セリウム粉体を安定的に製造することが可能となった。それにより、平坦性良好で研磨傷を低減することが可能な酸化セリウム粒子を、効率よく安定的に得ることができる。 The reaction between cerium carbonate and the organic acid proceeds sequentially in a mixed state using moisture contained in each other as a medium. Since it is a reaction between solids, it takes a long time to complete the reaction. If the reaction is not completed, the cerium oxide powder having the same degree of grindability can be produced in different production lots unless the time until firing is constant, that is, the reaction progress is constant. Have difficulty. Therefore, in the present invention, even when the reaction is not completed, by evaporating the moisture as a medium from the reaction system by heating and mixing under the same conditions, the reaction does not proceed at the end of heating and mixing. The degree of progress of the reaction can be made constant, which makes it possible to stably produce a cerium oxide powder having the same degree of grindability regardless of the time until firing. Thereby, cerium oxide particles having good flatness and capable of reducing polishing scratches can be obtained efficiently and stably.
下記に酸化セリウム粉体の粉砕性について具体的に説明する。
従来は、炭酸セリウムと有機酸を混合後、焼成、粉砕して酸化セリウム粒子を得る製造方法において、粉砕性は、酸化セリウム粉体の形状と結晶性で決まる。
酸化セリウム粉体の形状は、炭酸セリウムと有機酸を混合してセリウムの有機酸塩が生成し、焼成によりセリウムの有機酸塩が熱分解するときの形状により決まる。セリウムの有機酸塩の形状は、混合後、熱分解温度に達するまでの時間や、温度、水分等の雰囲気の状態によって決まる。また、セリウムの有機酸塩が生成する反応の進行度の影響も受ける。
The grindability of the cerium oxide powder will be specifically described below.
Conventionally, in a production method in which cerium carbonate and an organic acid are mixed and then fired and pulverized to obtain cerium oxide particles, the pulverizability is determined by the shape and crystallinity of the cerium oxide powder.
The shape of the cerium oxide powder is determined by the shape when cerium carbonate and an organic acid are mixed to produce an organic acid salt of cerium, and the organic acid salt of cerium is thermally decomposed by firing. The shape of the organic acid salt of cerium is determined by the time until it reaches the thermal decomposition temperature after mixing, and the state of the atmosphere such as temperature and moisture. It is also affected by the degree of progress of the reaction produced by the cerium organic acid salt.
一方、酸化セリウム粉体の結晶性は、熱分解時の形状と焼成温度で決まる。従って、従来は、熱分解温度に達するまでの昇温速度の影響を受け、ロータリーキルンやトンネル炉等を用い急加熱して焼成温度まで昇温し焼成すると、バッチ式炉で緩やかに加熱を行い焼成温度まで昇温し焼成した場合と比べ、得られる酸化セリウム粉体の結晶性が高まってしまう問題がある。 On the other hand, the crystallinity of the cerium oxide powder is determined by the shape during pyrolysis and the firing temperature. Therefore, conventionally, affected by the rate of temperature rise until reaching the thermal decomposition temperature, when heated rapidly using a rotary kiln, tunnel furnace, etc., raised to the firing temperature and fired, the batch furnace is heated gently and fired There is a problem that the crystallinity of the obtained cerium oxide powder is increased as compared with the case where the temperature is raised to a temperature and firing.
しかし、本発明において、焼成前の炭酸セリウムと有機酸との加熱混合により、セリウムの有機酸塩が生成する反応の進行度と形状を制御でき、急加熱しても結晶性を高めずに、粉砕性のよい酸化セリウム粉体を製造することが可能となった。 However, in the present invention, by the heating and mixing of cerium carbonate and organic acid before firing, the progress and shape of the reaction that the organic acid salt of cerium is generated can be controlled without increasing the crystallinity even by rapid heating. It became possible to produce cerium oxide powder with good grindability.
本発明における有機酸は、２５℃で固体であることが好ましい。有機酸が気体であると酸の取り扱いや、炭酸セリウムとの混合が困難であり好ましくない。また、有機酸が液体または溶液状態であると、炭酸セリウムとの混合物が液状になり、加熱混合工程に長時間を要する。
さらに、本発明における有機酸は粉末状であることが、炭酸セリウムと混合しやすいことから好ましい。粉末の大きさは特に限定されるものではない。
The organic acid in the present invention is preferably a solid at 25 ° C. If the organic acid is a gas, handling of the acid and mixing with cerium carbonate is difficult, which is not preferable. Further, when the organic acid is in a liquid or solution state, the mixture with cerium carbonate becomes liquid, and the heating and mixing step takes a long time.
Furthermore, the organic acid in the present invention is preferably in the form of a powder because it is easy to mix with cerium carbonate. The size of the powder is not particularly limited.
本発明における有機酸は、炭素原子、酸素原子及び水素原子から構成されることが好ましい。この他に窒素原子や硫黄原子を含んでいても良いが、焼成時に硝酸イオンや硫酸イオンとなり、焼成温度が低い場合は脱離せず酸化セリウム粉体中に残存する可能性がある。 The organic acid in the present invention is preferably composed of a carbon atom, an oxygen atom and a hydrogen atom. In addition to this, it may contain nitrogen atoms or sulfur atoms, but it becomes nitrate ions or sulfate ions at the time of firing, and if the firing temperature is low, it may not be detached and remain in the cerium oxide powder.
本発明における有機酸は、その酸解離定数ｐＫａは、炭酸の一段目の酸解離定数ｐＫａ１より小さい、つまり炭酸よりも強酸の有機酸が好ましい。有機酸のｐＫａが６以下であるのがさらに好ましい。なお、有機酸が多段解離する場合は、一段目の酸解離定数ｐＫａ１と炭酸のｐＫａ１とを比較する。酸解離定数ｐＫａが炭酸の酸解離定数ｐＫａ１より小さい有機酸を炭酸セリウムと混合すると、セリウムの有機塩が生成する反応が起こりやすいため好ましい。なお、本発明において酸解離定数は、実際の酸解離定数Ｋａの逆数の常用対数値ｐＫａで示すものとする。また、有機酸が多段解離する場合は、一段目の酸解離定数ｐＫａ１の値で示すものとする。 The organic acid in the present invention has an acid dissociation constant pKa smaller than the acid dissociation constant pKa 1 of the first stage of carbonic acid, that is, an organic acid that is a stronger acid than carbonic acid. More preferably, the pKa of the organic acid is 6 or less. In the case where the organic acid is multistage dissociation compares the pKa 1 of the first stage of the acid dissociation constant pKa 1 and carbonate. It is preferable to mix an organic acid having an acid dissociation constant pKa smaller than the acid dissociation constant pKa 1 of carbonic acid with cerium carbonate because a reaction of forming an organic salt of cerium easily occurs. In the present invention, the acid dissociation constant is represented by a common logarithmic value pKa that is the reciprocal of the actual acid dissociation constant Ka. Further, if the organic acid is multistage dissociation, it shall indicate the value of the acid dissociation constant pKa 1 of the first stage.
本発明における有機酸は、コハク酸、マロン酸、クエン酸、酒石酸、リンゴ酸、シュウ酸、マレイン酸、アジピン酸、サリチル酸、安息香酸、フタル酸、グリコール酸、アスコルビン酸、これらの異性体、重合体もしくは共重合体、ポリアクリル酸、ポリメタクリル酸から選ばれる少なくとも１種以上であることが好ましい。これらの有機酸は室温（２５℃）で固体であり、粉末が容易に入手可能である。 The organic acid in the present invention is succinic acid, malonic acid, citric acid, tartaric acid, malic acid, oxalic acid, maleic acid, adipic acid, salicylic acid, benzoic acid, phthalic acid, glycolic acid, ascorbic acid, isomers thereof, heavy acid It is preferably at least one selected from a coalescence or copolymer, polyacrylic acid, and polymethacrylic acid. These organic acids are solid at room temperature (25 ° C.) and powders are readily available.
本発明においては、反応系内から水分除去することが重要である。なお、水分の除去は、系内から完全に除去することが好ましいが、加熱混合において反応が停止し、且つ炭酸セリウムと有機酸との加熱混合後から焼成までの間に反応が進行しなければ、水分が残存していても本発明の効果は得られる。すなわち、加熱混合した後の粉体（加熱混合粉体）をすぐに焼成する場合は、反応が停止する程度に水分を除去すれば問題はない。また、加熱混合した後すぐに焼成せずに、保管しておくことも可能である。その場合は、反応系内から水分を完全除去した場合は、保管中に水分が混入しないようにすれば反応は進行しない。反応系内に水分が残存している場合は、加熱混合における加熱温度、水分の残存量と、保管条件（温度）が保管中の反応停止の有無の重要パラメータとなる。詳細は後述する。また、水分が残存する場合も保管中は、水分が混入しないように保管しておくことが重要である。 In the present invention, it is important to remove water from the reaction system. The removal of moisture is preferably completely removed from the system, but the reaction must be stopped in the heating and mixing, and the reaction should not proceed between the heating and mixing of cerium carbonate and organic acid until the firing. Even if moisture remains, the effect of the present invention can be obtained. That is, when the powder after heating and mixing (heated mixed powder) is immediately fired, there is no problem if the water is removed to such an extent that the reaction stops. Moreover, it is also possible to store without heating immediately after mixing. In that case, when moisture is completely removed from the reaction system, the reaction does not proceed if moisture is not mixed during storage. When moisture remains in the reaction system, the heating temperature in the heating and mixing, the amount of moisture remaining, and the storage conditions (temperature) are important parameters for whether or not the reaction is stopped during storage. Details will be described later. Also, even when moisture remains, it is important to keep the moisture from entering during storage.
反応を停止させるためには反応系内から水分を除去することが重要であるが、異なるロットで同程度の粉砕性を有する酸化セリウム粉体を得るためには、炭酸セリウムと有機酸との加熱混合の条件を同一条件とすることが重要である。以下、本発明における加熱混合の好ましい条件を示す。
酸化セリウム粒子の製造方法において、前記（Ｉ）工程の加熱は、４０〜２００℃の範囲で行われることが好ましい。
In order to stop the reaction, it is important to remove water from the reaction system, but in order to obtain cerium oxide powder having the same degree of grindability in different lots, heating with cerium carbonate and an organic acid is required. It is important that the mixing conditions are the same. Hereinafter, preferable conditions for heating and mixing in the present invention will be shown.
In the method for producing cerium oxide particles, the heating in the step (I) is preferably performed in the range of 40 to 200 ° C.
本発明において、「加熱温度」とは反応に用いる加熱混合装置設定温度を表す。但し、加熱混合装置が大きかったり、仕込み量が多かったり等の理由で内部温度が設定温度の±２０％を超えて異なる場合は、内部の温度を実測して加熱温度とする。加熱における加熱温度としては、加熱混合装置の大きさや伝熱面積、設備材質の伝熱効率、混合方式、装置の密閉性といった外部要因を考慮して決定することができるが、具体的には、例えば、４０〜２００℃の範囲が好ましい。水分が容易に蒸発するようにする点では、加熱温度は５０℃以上であることが好ましく、８０℃以上であることがより好ましい。一方、加熱温度が高いと有機酸が分解する可能性もあるので、加熱温度の上限としては、１８０℃以下が好ましく、１５０℃以下がより好ましい。 In the present invention, “heating temperature” represents a set temperature of a heating and mixing apparatus used for the reaction. However, if the internal temperature differs by more than ± 20% of the set temperature because the heating and mixing device is large or the preparation amount is large, the internal temperature is measured and used as the heating temperature. The heating temperature in heating can be determined in consideration of external factors such as the size and heat transfer area of the heating and mixing device, the heat transfer efficiency of the equipment material, the mixing method, and the sealing property of the device. The range of 40-200 degreeC is preferable. The heating temperature is preferably 50 ° C. or higher and more preferably 80 ° C. or higher from the viewpoint of easily evaporating moisture. On the other hand, since the organic acid may be decomposed when the heating temperature is high, the upper limit of the heating temperature is preferably 180 ° C. or less, and more preferably 150 ° C. or less.
また、本発明において、加熱時に反応系を減圧することが好ましい。具体的には、例えば、５０℃未満の加熱である場合、水分が蒸発しにくくなるため、−９０ｋＰａ以下に減圧することが好ましい。また、５０℃以上での加熱であっても適宜減圧を組み合わせることにより、より効率的に水分除去が進むこともある。 In the present invention, the reaction system is preferably decompressed during heating. Specifically, for example, in the case of heating at less than 50 ° C., it is preferable to reduce the pressure to −90 kPa or less because moisture hardly evaporates. Moreover, even when heating at 50 ° C. or higher, moisture removal may proceed more efficiently by appropriately combining reduced pressure.
加熱混合における時間としては、加熱温度とも関係するが、１．５〜４時間が好ましく、２〜３時間がより好ましい。なお、本発明において、加熱混合時間とは、炭酸セリウムと有機酸とを加熱混合装置内に仕込み、混合と装置の加熱を開始してから、装置の混合と加熱を停止するまでの時間をいう。 The time for heating and mixing is also related to the heating temperature, but is preferably 1.5 to 4 hours, more preferably 2 to 3 hours. In the present invention, the heating and mixing time refers to the time from when cerium carbonate and an organic acid are charged into a heating and mixing apparatus and the mixing and heating of the apparatus are started until the mixing and heating of the apparatus are stopped. .
加熱混合方式については特に制限はないが、加熱混合により二酸化炭素と水蒸気が発生するため、密閉されていない加熱混合装置又は密閉されており排気機能を持つ加熱混合装置が好ましい。具体的には、例えば、図１に示すように、反応容器３の内部に攪拌羽根２を備え、容器外周に加熱手段４を有する、密閉されていない加熱混合攪拌装置１等が挙げられる。なお、反応容器３や攪拌羽根２の形状は特に限定されない。
Although there is no restriction | limiting in particular about a heating mixing system, Since a carbon dioxide and water vapor | steam generate | occur | produce by heating mixing, the heating mixing apparatus which is not sealed or the heating mixing apparatus which is sealed and has an exhaust function is preferable. Specifically, as shown in FIG. 1, for example, a non-sealed heated mixing and stirring apparatus 1 having a
また、加熱混合装置１は、装置と原料の有機酸が接する部分は、有機酸による金属腐食が起因となり、腐食した金属が混合粉に混入し金属異物となる可能性があるため、有機酸による金属腐食性を考慮して、攪拌羽根２や反応容器３の内壁等の接粉部を耐腐食性のある樹脂や金属仕様とすることが好ましい。
Further, in the heating and mixing apparatus 1, the portion where the apparatus and the organic acid of the raw material are in contact is caused by metal corrosion due to the organic acid, and the corroded metal may be mixed into the mixed powder and become a metal foreign matter. In consideration of metal corrosivity, it is preferable that the contact portion such as the
炭酸セリウムは水分を含有しており、粉体流動性が良くなく、加熱混合装置に対する付着性が強い。そのため加熱混合装置の接粉部に対して、表面のすべりが向上し平坦性の良いポリフッ化エチレン系樹脂コーティング処理を行うと、有機酸に対する耐腐食性も兼ね備えているため好ましい。 Cerium carbonate contains moisture, has poor powder flowability, and has strong adhesion to a heating and mixing apparatus. Therefore, it is preferable to apply a polyfluorinated ethylene resin coating treatment with improved surface slip and good flatness to the powder contact portion of the heating and mixing apparatus because it also has corrosion resistance against organic acids.
密閉されていない加熱混合装置で加熱混合する場合、原料としての炭酸セリウムと有機酸とに含有される水分を蒸発させて除去するため、十分な蒸気排出口を持つ容器が好ましい。十分な蒸気排出口がなければ加熱混合装置内に蒸気が滞留し、水分除去を速やかに行うことができない又は滞留した蒸気が原料と接することで、原料がドロドロとした粘土のような状態となってしまう場合がある。 In the case of heating and mixing with a non-sealed heating and mixing apparatus, a vessel having a sufficient vapor outlet is preferable in order to evaporate and remove moisture contained in the cerium carbonate and organic acid as raw materials. If there is not enough steam outlets, steam will stay in the heating and mixing device and moisture removal cannot be performed quickly, or if the staying steam comes into contact with the raw material, the raw material will become a clay-like state. May end up.
密閉されており排気機能を持つ加熱混合装置を使用する場合、十分な排気能力を備えている装置が好ましい。排気能力が十分でなければ加熱混合装置内に蒸気が滞留し、水分除去を速やかに行うことができない又は滞留した蒸気が原料と接することで、原料がドロドロとした粘土のような状態となってしまう場合がある。 When using a heating and mixing apparatus that is hermetically sealed and has an exhaust function, an apparatus having sufficient exhaust capability is preferable. If the exhaust capacity is not sufficient, steam will remain in the heating and mixing device, moisture removal cannot be performed quickly, or the staying steam comes into contact with the raw material, and the raw material becomes a clay-like state. May end up.
密閉されており排気機能を持つ加熱混合装置を使用する場合、排気と同時に減圧することで、より水分を除去しやすい条件とすることができる。減圧する際の真空度に関して制限はないが、加熱温度、加熱混合時間、混合方式、加熱混合装置への原料仕込み量、加熱混合装置の粉に対する伝熱面積等のパラメータが関係する。これらのパラメータに留意し、蒸気を十分に排出させて水分を除去することが好ましい。 When using a heating and mixing apparatus that is sealed and has an exhaust function, it is possible to make it easier to remove moisture by reducing the pressure simultaneously with exhaust. Although there is no restriction | limiting regarding the vacuum degree at the time of pressure reduction, Parameters, such as heating temperature, heating mixing time, a mixing system, the raw material preparation amount to a heating mixing apparatus, and the heat transfer area with respect to the powder of a heating mixing apparatus, are related. Taking these parameters into consideration, it is preferable to remove moisture by sufficiently discharging steam.
加熱混合により水分を除去し、炭酸セリウムと有機酸との反応が停止したことを確認する方法として、加熱混合粉体の経時による質量減少の有無を確認する方法がある。反応が進行すると二酸化炭素が発生するため、その分の質量が減少するため、質量が減少していなければ反応が進行していないと判断できる。 As a method for confirming that the reaction between cerium carbonate and the organic acid has been stopped by removing moisture by heat mixing, there is a method for confirming the presence or absence of mass reduction of the heat mixed powder over time. Since carbon dioxide is generated as the reaction proceeds, the corresponding mass decreases. Therefore, if the mass does not decrease, it can be determined that the reaction does not proceed.
質量減少の有無の判断方法として、加熱混合終了直後の粉体（加熱混合粉体）の質量と、焼成を行う直前の粉体の質量を測定し、その間の質量減少量を測定することで判断できる。本発明においては、加熱混合粉体を温度２５℃で２４時間放置した後の質量減少量が０〜０．１質量％であるとき、反応が停止していると判断できる。なお、本発明において「加熱混合終了直後の粉体の質量」とは、具体的には、加熱及び混合を終了して３０分以内に、５〜４０℃の範囲で測定した質量とする。 As a method of determining the presence or absence of mass reduction, the mass of the powder immediately after the end of heating and mixing (heated mixed powder) and the mass of the powder immediately before firing are measured, and the amount of mass reduction between them is measured. it can. In the present invention, it can be determined that the reaction has stopped when the mass loss after the heated mixed powder is left at a temperature of 25 ° C. for 24 hours is 0 to 0.1 mass%. In the present invention, “the mass of the powder immediately after completion of heating and mixing” is specifically the mass measured in the range of 5 to 40 ° C. within 30 minutes after the completion of heating and mixing.
具体的な測定方法としては次のようなものが挙げられる。すなわち、炭酸セリウムと有機酸とを加熱混合し、加熱混合装置を停止して加熱混合粉体を得た後（３０分以内）に、１〜１００ｇ程度、加熱混合粉体を量りとる。次に、その加熱混合粉体サンプルを温度２５℃で２４時間放置し、再度質量を測定する。そして、加熱混合終了直後の加熱混合粉体の質量と２４時間放置後の粉体の質量から、質量減少量を計算で求める。このようにして求めた２４時間放置後の加熱混合粉体の質量減少量は、加熱混合粉体の質量に対して０〜０．１質量％であることが好ましく、０〜０．０５質量％がより好ましく、０〜０．０２質量％であればさらに好ましい。少なくとも質量減少量が０．１質量％以下であれば、質量減少は無く反応が停止していると判断することができる。 Specific measurement methods include the following. That is, cerium carbonate and an organic acid are heated and mixed, and the heating and mixing apparatus is stopped to obtain a heated mixed powder (within 30 minutes), and then about 1 to 100 g of the heated mixed powder is weighed. Next, the heated mixed powder sample is left at a temperature of 25 ° C. for 24 hours, and the mass is measured again. Then, a mass reduction amount is obtained by calculation from the mass of the heat-mixed powder immediately after completion of the heat-mixing and the mass of the powder after being left for 24 hours. The mass reduction amount of the heated mixed powder after standing for 24 hours determined in this manner is preferably 0 to 0.1% by mass, and 0 to 0.05% by mass with respect to the mass of the heated mixed powder. Is more preferably 0 to 0.02% by mass. If the amount of mass reduction is at least 0.1% by mass, it can be determined that there is no mass reduction and the reaction is stopped.
反応系内から水分を完全に除去しない場合、加熱混合粉体を保管する環境によって、炭酸セリウムと有機酸との反応が停止する場合と停止しない場合がある。保管する環境が高温である方が反応は停止しにくい。例えば、保管を室温下で行う場合、夏季と冬季のように大気温度で約３０℃差がある環境では、夏季の温度条件を考慮して加熱温度を設定する必要がある。加熱混合工程において、反応系内から水分を完全除去する場合は、保管温度と加熱温度を考慮しなくてもよい。いずれにしても、本発明においては、加熱混合粉体を温度２５℃で２４時間放置した後の質量減少量が０〜０．１質量％であるとき、反応が停止していると判断できる。 When moisture is not completely removed from the reaction system, the reaction between cerium carbonate and organic acid may or may not stop depending on the environment in which the heated mixed powder is stored. The reaction is more difficult to stop if the storage environment is hot. For example, when storage is performed at room temperature, it is necessary to set the heating temperature in consideration of summer temperature conditions in an environment where there is a difference of about 30 ° C. in the atmospheric temperature, such as in summer and winter. In the heating and mixing step, when moisture is completely removed from the reaction system, the storage temperature and heating temperature need not be taken into consideration. In any case, in the present invention, it can be determined that the reaction is stopped when the mass loss after the heated mixed powder is left at a temperature of 25 ° C. for 24 hours is 0 to 0.1 mass%.
また、質量減少の有無の別の判断方法として、加熱混合粉体を少量サンプリングし、保管環境よりも高温に加熱し質量変化が起きないか加速試験を行うことでも、判断可能である。具体的には例えば、保管環境が１０〜２５℃である場合、水分を蒸発させた加熱後のサンプルの質量を測定し、そのサンプルを温度４０℃の環境にある高温槽又はオーブン内に２時間放置し、再度質量を測定する等の方法を挙げることができる。これにより、簡易に質量減少の有無を判断できる。
つまり、「４０℃２時間放置後の質量減少量」が０〜０．１質量％であれば、「２５℃で２４時間放置した後の質量減少量」も０〜０．１質量％と判断でき、すなわち反応が停止していると判断できる。しかし、「４０℃２時間放置後の質量減少量」が０．１質量％を超える場合は、２５℃で２４時間放置した後の質量減少量の確認が必要である。
Further, as another determination method for determining whether there is a decrease in mass, it is also possible to determine by sampling a small amount of the heated mixed powder, heating it to a temperature higher than the storage environment, and performing an accelerated test for mass change. Specifically, for example, when the storage environment is 10 to 25 ° C., the mass of the heated sample after evaporating moisture is measured, and the sample is placed in a high-temperature bath or oven in an environment of 40 ° C. for 2 hours. Examples of the method include leaving it alone and measuring the mass again. Thereby, the presence or absence of mass reduction can be judged easily.
That is, if the “mass loss after standing at 40 ° C. for 2 hours” is 0 to 0.1% by mass, the “mass loss after 24 hours at 25 ° C.” is also determined to be 0 to 0.1% by mass. That is, it can be judged that the reaction has stopped. However, when the “mass loss after standing at 40 ° C. for 2 hours” exceeds 0.1% by mass, it is necessary to confirm the mass reduction after leaving at 25 ° C. for 24 hours.
次に、上記のようにして得た加熱混合粉体を、バッチ式炉、ロータリーキルン、トンネル炉等の従来公知装置を用いて焼成し、酸化セリウム粉体を得る。本発明における焼成温度は、セリウム化合物の酸化温度が３００℃であることから、３５０℃以上が好ましく、より好ましくは４００℃以上９００℃以下、さらに好ましくは、６００℃以上８００℃以下である。
なお、本発明において、焼成の昇温速度は特に制限はない。
Next, the heated mixed powder obtained as described above is fired by using a conventionally known apparatus such as a batch furnace, a rotary kiln, a tunnel furnace, etc., to obtain a cerium oxide powder. The firing temperature in the present invention is preferably 350 ° C. or higher, more preferably 400 ° C. or higher and 900 ° C. or lower, and still more preferably 600 ° C. or higher and 800 ° C. or lower because the oxidation temperature of the cerium compound is 300 ° C.
In the present invention, there is no particular limitation on the heating rate of firing.
上記方法により作製された酸化セリウム粉体は、線源をＣｕＫα線とする粉末Ｘ線回折パターンから求められる主ピークである酸化セリウム結晶の（１１１）面による回折ピークの半値幅が０．２７〜０．５０°であることが好ましい。半値幅が０．２７°以上である場合は、粉砕機の部品を磨耗させることもなく、磨耗粉が研磨液中に混入する可能性が高まり、研磨傷の原因となることもなく好ましい。半値幅が０．５０°以下の場合は粉砕性が低下することもなく、大粒径粒子が粉砕されずに残り、研磨液中に混入して研磨傷の原因となることもなく好ましい。 The cerium oxide powder produced by the above method has a half-value width of the diffraction peak due to the (111) plane of the cerium oxide crystal, which is the main peak obtained from a powder X-ray diffraction pattern using a CuKα ray as a radiation source. It is preferably 0.50 °. When the full width at half maximum is 0.27 ° or more, the parts of the pulverizer are not worn, and the possibility that the abrasion powder is mixed into the polishing liquid is increased, which is preferable without causing a polishing flaw. When the full width at half maximum is 0.50 ° or less, the pulverizability is not lowered, and the large particle size remains without being pulverized and is preferably mixed into the polishing liquid without causing polishing scratches.
線源をＣｕＫα線とする粉末Ｘ線回折パターン（以下、「ＣｕＫα粉末Ｘ線回折パターン」ともいう）は、Ｘ線回折装置（株式会社リガク製、製品名：ＲＩＮＴ２１００）で測定できる。
測定条件は、発散スリット１°、散乱スリット１°、受光スリット０．３０ｍｍ、ステップ幅０．０２°、計数時間５．０ｓｅｃ、管電圧４０ｋＶ、管電流２０ｍＡとする。回折角（２θ）を横軸に、回折Ｘ線強度（ｃｐｓ）を縦軸にとり、得られたデータをプロットし、研磨液中の酸化セリウム粒子の主ピークである酸化セリウム結晶の（１１１）面による回折ピークの半値幅を求める。半値幅はピーク高さの半分のところのピーク幅である。図２に半値幅の測定例を示す。
A powder X-ray diffraction pattern (hereinafter also referred to as “CuKα powder X-ray diffraction pattern”) using CuKα rays as a radiation source can be measured with an X-ray diffractometer (product name: RINT2100, manufactured by Rigaku Corporation).
The measurement conditions are a diverging slit 1 °, a scattering slit 1 °, a light receiving slit 0.30 mm, a step width 0.02 °, a counting time 5.0 sec, a tube voltage 40 kV, and a tube current 20 mA. The diffraction angle (2θ) is taken on the horizontal axis and the diffraction X-ray intensity (cps) is taken on the vertical axis, and the obtained data is plotted, and the (111) plane of the cerium oxide crystal that is the main peak of the cerium oxide particles in the polishing liquid. Find the half-width of the diffraction peak. The full width at half maximum is the peak width at half the peak height. FIG. 2 shows an example of measuring the half width.
上記方法により作製された酸化セリウム粉体は、下記粉砕条件（ａ）で粉砕した後の酸化セリウム粉砕物の全体の９９体積％（以下、「Ｄ９９」という。）が粒子径０．１〜１μｍが好ましく、より好ましくは０．１〜０．８μｍである。下記粉砕条件（ａ）後の酸化セリウム粉砕物のＤ９９は、本発明で用いる酸化セリウム粒子の製造方法の粉砕工程における粉砕性の指標とできる。
粉砕条件（ａ）後の酸化セリウム粉砕物のＤ９９が１μｍを超える場合は、使用に問題はないが、粉砕性が悪く、以下に記述する粉砕工程で大粒子径粒子が粉砕されずに残り、研磨液中に混入し、研磨傷の原因となる傾向があるため好ましくない。粉砕条件（ａ）で粉砕した後の酸化セリウム粉砕物のＤ９９が０．１μｍ未満の場合は、使用に問題はないが、ＳｉＯ２膜あるいは窒化珪素膜を高速に研磨することが困難となる傾向があるため好ましくない。
The cerium oxide powder produced by the above method has a particle size of 0.1 to 1 μm with 99 volume% (hereinafter referred to as “D99”) of the pulverized cerium oxide after pulverization under the following pulverization conditions (a). Is more preferable, and 0.1 to 0.8 μm is more preferable. D99 of the cerium oxide pulverized product after the following pulverization condition (a) can be used as an index of pulverization in the pulverization step of the method for producing cerium oxide particles used in the present invention.
When D99 of the cerium oxide pulverized product after the pulverization condition (a) exceeds 1 μm, there is no problem in use, but the pulverization property is poor, and the large particle size particles remain without being pulverized in the pulverization step described below, It is not preferable because it tends to be mixed into the polishing liquid and cause polishing scratches. When D99 of the cerium oxide pulverized product after pulverization under the pulverization condition (a) is less than 0.1 μm, there is no problem in use, but it tends to be difficult to polish the SiO 2 film or the silicon nitride film at high speed. This is not preferable.
粉砕条件（ａ）：酸化セリウム粉体に対して、湿式粉砕機マイクロ分散チャンバー内のオリフィスで高圧で加速させて粉砕する方式の湿式粉砕機を用い、圧力１００ＭＰａでオリフィス径０．１ｍｍの分散チャンバーを１５回通過させて湿式粉砕処理を行う。
より具体的には、酸化セリウム粉体２７ｇとポリアクリル酸アンモニウム塩水溶液（４０質量％）６．８ｇと脱イオン水１５２ｇとを混合した後、湿式粉砕機（Ｍｉｃｒｏｆｌｕｉｄｉｃｓ社製、製品名：マイクロフルイダイザーＭ−１１０ＥＨ、粉砕チャンバー型式：Ｈ１０Ｚ−１、オリフィス径：０．１ｍｍ）を、粉砕圧力１００ＭＰａ、液温５〜２０℃にて１５回通過させ湿式粉砕処理を行い、酸化セリウム粉砕物を得る。湿式粉砕処理後のスラリ中の酸化セリウム粉砕物の粒子径をレーザ回折式粒度分布計（株式会社堀場製作所社製、商品名：ＬＡ−９２０）を用い、屈折率１．９３、透過度８５％の条件で測定して、Ｄ９９を求める。
Pulverization condition (a): Dispersion chamber having a pressure of 100 MPa and an orifice diameter of 0.1 mm using a wet pulverizer of a type in which cerium oxide powder is pulverized by accelerating at a high pressure with an orifice in a micro dispersion chamber of a wet pulverizer. Is passed 15 times to perform wet grinding.
More specifically, 27 g of cerium oxide powder, 6.8 g of an ammonium polyacrylate aqueous solution (40% by mass) and 152 g of deionized water were mixed, and then a wet pulverizer (manufactured by Microfluidics, product name: Microfluidic). Dicer M-110EH, crushing chamber type: H10Z-1, orifice diameter: 0.1 mm) is passed 15 times at a crushing pressure of 100 MPa and a liquid temperature of 5 to 20 ° C., and wet crushing is performed to obtain a cerium oxide pulverized product. . The particle diameter of the cerium oxide pulverized product in the slurry after the wet pulverization treatment was measured using a laser diffraction particle size distribution meter (manufactured by Horiba, Ltd., trade name: LA-920), with a refractive index of 1.93 and a transmittance of 85%. D99 is obtained by measuring under the following conditions.
また、半導体素子研磨に使用することから、アルカリ金属及びハロゲン類の含有率は酸化セリウム粒子中１０ｐｐｍ以下に抑えることが好ましい。 Moreover, since it uses for semiconductor element grinding | polishing, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium oxide particle.
上記の方法により製造された酸化セリウム粉体を、粉砕することにより、本発明に使用される酸化セリウム粒子が得られる。本発明における粉砕方法は、特に制限はないが、ジェットミル等による乾式粉砕、遊星ビーズミル等による湿式粉砕が挙げられる。なかでも湿式粉砕で粉砕する場合は、粉砕設備に対する酸化セリウム粒子中の微粒子の付着が少ないという点で好ましい。乾式粉砕で粉砕する場合は、粉砕設備機内の温度上昇が発生しにくいという点で好ましい。ジェットミルとしては、例えば、化学工業論文集、第６巻、第５号、（１９８０）、５２７〜５３２頁に説明されている。 The cerium oxide particles used in the present invention can be obtained by pulverizing the cerium oxide powder produced by the above method. The pulverization method in the present invention is not particularly limited, and examples thereof include dry pulverization using a jet mill or the like, and wet pulverization using a planetary bead mill or the like. In particular, when the pulverization is performed by wet pulverization, it is preferable in that the adhesion of the fine particles in the cerium oxide particles to the pulverization equipment is small. In the case of pulverization by dry pulverization, it is preferable in that the temperature rise in the pulverization equipment is less likely to occur. The jet mill is described, for example, in Chemical Industrial Papers, Vol. 6, No. 5, (1980), pages 527-532.
＜研磨液及びこれを用いた研磨法＞
本発明の研磨液は、少なくとも酸化セリウム粒子及び水を含む研磨液を言う。
上記のように製造された本発明の酸化セリウム粒子は、研磨液、特に、半導体平坦化用研磨液として好適に用いられる。
<Polishing liquid and polishing method using the same>
The polishing liquid of the present invention refers to a polishing liquid containing at least cerium oxide particles and water.
The cerium oxide particles of the present invention produced as described above are suitably used as a polishing liquid, particularly as a polishing liquid for semiconductor planarization.
本発明の研磨液は、上記製造方法で得られた酸化セリウム粒子及び水を含み、例えば、酸化セリウム粒子を水に分散することによって得られる。 The polishing liquid of the present invention contains cerium oxide particles and water obtained by the above production method, and is obtained, for example, by dispersing cerium oxide particles in water.
本発明の研磨液は、さらに分散剤を含むことが好ましく、例えば、本発明の研磨液は、上記製造方法で作製した酸化セリウム粒子、分散剤を含んだ組成物を水に分散させることによって得られる。
酸化セリウム粒子の濃度に制限はないが、分散液状の研磨液の取り扱いやすさから、０．１質量％以上、２０質量％以下の範囲が好ましい。
The polishing liquid of the present invention preferably further contains a dispersant. For example, the polishing liquid of the present invention is obtained by dispersing a composition containing cerium oxide particles and a dispersant prepared by the above-described production method in water. It is done.
Although there is no restriction | limiting in the density | concentration of a cerium oxide particle, From the ease of handling of a dispersion | distribution liquid polishing liquid, the range of 0.1 mass% or more and 20 mass% or less is preferable.
分散剤としては、例えば、アクリル酸系のモノマを重合させたポリマ又はその塩が好ましい。アクリル酸モノマとしては、例えば、アクリル酸、メタクリル酸、マレイン酸、フマル酸等が挙げられ、これらのホモポリマ又はコポリマであってもよい。半導体素子研磨に使用することからナトリウムイオン、カリウムイオン等のアルカリ金属及びハロゲンの含有率を１０ｐｐｍ以下に抑えることが好ましい。より具体的には、例えば、ポリアクリル酸の塩、アクリル酸とメタクリル酸の共重合体の塩等が好ましく、塩としてはアンモニウム塩であることが好ましい。 As the dispersant, for example, a polymer obtained by polymerizing an acrylic acid monomer or a salt thereof is preferable. Examples of the acrylic acid monomer include acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and these homopolymers or copolymers may be used. Since it is used for semiconductor element polishing, it is preferable to suppress the content of alkali metals such as sodium ions and potassium ions and halogens to 10 ppm or less. More specifically, for example, a salt of polyacrylic acid, a salt of a copolymer of acrylic acid and methacrylic acid, and the like are preferable, and the salt is preferably an ammonium salt.
分散剤添加量は、研磨液中の粒子の分散性及び沈降防止、さらに研磨傷と分散剤添加量との関係から酸化セリウム粒子１００質量部に対して、０．０１質量部以上５．０質量部以下の範囲が好ましい。 The added amount of the dispersant is 0.01 parts by mass or more and 5.0 parts by mass with respect to 100 parts by mass of the cerium oxide particles from the relationship between the dispersibility of the particles in the polishing liquid and settling prevention, and the relationship between the polishing scratches and the added amount of the dispersant. A range of parts or less is preferred.
分散剤の重量平均分子量は、１００〜５０，０００が好ましく、１，０００〜１０，０００がより好ましい。分散剤の分子量が１００以上であると、ＳｉＯ２膜又は窒化珪素膜を研磨するときに、十分な研磨速度を得やすく、分散剤の分子量が５０，０００以下であれば、粘度が高くなることもなく、研磨液の保存安定性が低下することもない。
なお、本発明において、重量平均分子量は、ゲルパーミエーションクロマトグラフィーで測定し、標準ポリスチレン換算した値である。
The weight average molecular weight of the dispersant is preferably from 100 to 50,000, and more preferably from 1,000 to 10,000. When the molecular weight of the dispersant is 100 or more, it is easy to obtain a sufficient polishing rate when polishing the SiO 2 film or the silicon nitride film, and when the molecular weight of the dispersant is 50,000 or less, the viscosity becomes high. In addition, the storage stability of the polishing liquid is not lowered.
In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography and converted to standard polystyrene.
これらの酸化セリウム粒子を水中に分散させる方法としては、通常の攪拌機による分散処理の他にホモジナイザー、超音波分散機、湿式ボールミル等を用いることができる。 As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill or the like can be used in addition to a dispersion treatment using a normal stirrer.
本発明の研磨液中に含まれる粒子径０．７５μｍ以上の粒子数は、１ｍｌ中に３×１０６個以下である。これにより研磨傷低減効果が向上する。１ｍｌ中の粒子数が、３×１０６個を超えると研磨液による研磨傷が増加するおそれがある。
具体的な測定方法としては、研磨液１ｍｌ中の粒子径０．７５μｍ以上の粒子数は、ベックマンコールター社製のマルチサイザー３を用い、ＩＳＯＴＯＮ ＩＩ（ベックマンコールター社製：測定用電解液）９０ｍｌに酸化セリウム濃度４質量％の研磨液を６００μｌ投入し、径３０μｍのアパーチャーを使用して、分析体積５０μｌとし測定する方法が挙げられる。
The number of particles having a particle diameter of 0.75 μm or more contained in the polishing liquid of the present invention is 3 × 10 6 or less in 1 ml. This improves the effect of reducing polishing scratches. If the number of particles in 1 ml exceeds 3 × 10 6, there is a possibility that polishing scratches due to the polishing liquid increase.
As a specific measurement method, the number of particles having a particle size of 0.75 μm or more in 1 ml of polishing liquid is 90 ml of ISOTON II (manufactured by Beckman Coulter, Inc .: electrolyte for measurement) using Multisizer 3 made by Beckman Coulter. An example is a method in which 600 μl of a polishing liquid having a cerium oxide concentration of 4% by mass is introduced and an analysis volume of 50 μl is measured using an aperture having a diameter of 30 μm.
本発明の研磨液中の固体全体に占める粒子径３μｍ以上の酸化セリウム粒子の粗大粒子含有量は少ないことが好ましい。前記３μｍ以上の粗大粒子とは、本発明では孔径３μｍのフィルタでろ過することで捕捉される粒子をいう。本発明では、研磨液中の固体全体に占める粒子径３μｍ以上の粒子含有量が質量比で５００ｐｐｍ以下であることが好ましく、これにより研磨傷低減効果が明らかである。固体全体に占める３μｍ以上の粒子含有量が２００ｐｐｍ以下の場合研磨傷低減効果が大きく、より好ましい。固体全体に占める３μｍ以上の粒子含有量が１００ｐｐｍ以下の場合には研磨傷低減効果が最も大きく、さらに好ましい。 The coarse particle content of cerium oxide particles having a particle diameter of 3 μm or more in the entire solid in the polishing liquid of the present invention is preferably small. In the present invention, the coarse particles of 3 μm or more mean particles captured by filtering with a filter having a pore diameter of 3 μm. In the present invention, the content of particles having a particle diameter of 3 μm or more in the entire solid in the polishing liquid is preferably 500 ppm or less in terms of mass ratio. When the content of particles of 3 μm or more occupying the whole solid is 200 ppm or less, the effect of reducing polishing scratches is large, which is more preferable. When the content of particles of 3 μm or more occupying the whole solid is 100 ppm or less, the effect of reducing polishing scratches is the largest and more preferable.
３μｍ以上の粗大粒子含有量は、孔径３μｍのフィルタでろ過することで捕捉される粒子を質量測定で求めることができる。研磨液中の固体全体の含有量は、別途、研磨液を乾燥させて測定しておく。例えば、１０ｇの研磨液を１５０℃で１時間乾燥させた残りを質量測定して固体濃度を得る。そして、孔径３μｍのフィルタでのろ過に用いる研磨液の質量に前記固体濃度を乗じて、固体全体の含有量を得ることができる。
粗大粒子含有量を低減する手段としては、ろ過、分級が可能であるが、これに限定されるものではない。
The coarse particle content of 3 μm or more can be obtained by mass measurement of particles captured by filtering with a filter having a pore diameter of 3 μm. The content of the entire solid in the polishing liquid is measured by separately drying the polishing liquid. For example, 10 g of the polishing liquid is dried at 150 ° C. for 1 hour, and the mass of the remainder is measured to obtain the solid concentration. And the content of the whole solid can be obtained by multiplying the mass of the polishing liquid used for filtration with a filter having a pore diameter of 3 μm by the solid concentration.
Filtration and classification are possible as means for reducing the coarse particle content, but are not limited thereto.
本発明の研磨液中の酸化セリウム粒子の粒子径の中央値（以下、「Ｄ５０」ともいう）は、０．１〜１μｍが好ましく、より好ましくは０．１〜０．５μｍ、さらに好ましくは０．１〜０．３μｍである。粒子径の中央値が０．１μｍ以上であるとＳｉＯ２膜あるいは窒化珪素膜の研磨速度が低くなることもなく、１μｍ以下であれば被研磨膜表面に研磨傷が生じることもないからである。 The median particle diameter of the cerium oxide particles in the polishing liquid of the present invention (hereinafter also referred to as “D50”) is preferably 0.1 to 1 μm, more preferably 0.1 to 0.5 μm, and still more preferably 0. .1 to 0.3 μm. This is because if the median particle diameter is 0.1 μm or more, the polishing rate of the SiO 2 film or silicon nitride film does not decrease, and if it is 1 μm or less, polishing scratches do not occur on the surface of the film to be polished. .
本発明の研磨液中の前記酸化セリウム粒子のＤ９９は、粒子径１μｍ以下であることが好ましい。Ｄ９９が１μｍを超えると研磨傷発生が多くなる。Ｄ９９が０．７μｍ以下の場合、研磨傷を少なくできるため、さらに好ましい。
研磨液中の酸化セリウム粒子の中央値（Ｄ５０）及びＤ９９は、レーザ回折式粒度分布計（例えば、堀場製作所製、ＬＡ−９２０）を用い、屈折率１．９３、透過度７４％の条件で測定する。
また、研磨液中の酸化セリウム粒子の中央値（Ｄ５０）及びＤ９９を上記範囲とするために、粉砕後に、沈降分級、ろ過等により調製することが好ましい。
The D99 of the cerium oxide particles in the polishing liquid of the present invention is preferably 1 μm or less. When D99 exceeds 1 μm, the generation of polishing scratches increases. When D99 is 0.7 μm or less, polishing scratches can be reduced, which is more preferable.
The median value (D50) and D99 of the cerium oxide particles in the polishing liquid are determined using a laser diffraction particle size distribution analyzer (for example, LA-920, manufactured by HORIBA, Ltd.) under the conditions of a refractive index of 1.93 and a transmittance of 74%. taking measurement.
Moreover, in order to make the median value (D50) and D99 of the cerium oxide particles in the polishing liquid fall within the above range, it is preferable to prepare the particles by pulverization, sedimentation, filtration, or the like.
また、研磨液には、平坦性、分散性を更に向上させる高分子添加剤を加えることができる。以下に限定されるわけではないが、例えばアクリル酸エステル誘導体、アクリル酸、アクリル酸塩等のポリマーを加えることができる。高分子添加剤の添加量は、特に限定されないが、酸化セリウム粒子１００質量部に対して、５質量部以上３０質量部以下が好ましい。
なお、アクリル酸は上記分散剤としても用いられるが、高分子添加剤にアクリル酸を用いる場合は、アクリル酸の添加量は高分子添加剤の添加量を基準とすればよい。
In addition, a polymer additive that further improves the flatness and dispersibility can be added to the polishing liquid. Although not necessarily limited to the following, for example, a polymer such as an acrylate derivative, acrylic acid, acrylate, or the like can be added. The addition amount of the polymer additive is not particularly limited, but is preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the cerium oxide particles.
Acrylic acid is also used as the dispersant, but when acrylic acid is used as the polymer additive, the amount of acrylic acid added may be based on the amount of polymer additive added.
高分子添加剤の重量平均分子量は１００〜５０，０００が好ましく、１，０００〜１０，０００がより好ましい。重量平均分子量が１００以上であれば、ＳｉＯ２膜あるいは窒化珪素膜を研磨するときに、十分な研磨速度を得ることができ、重量平均分子量が５０，０００以下であれば、粘度が高くなり、研磨液の保存安定性が低下することもないためである。 The weight average molecular weight of the polymer additive is preferably 100 to 50,000, more preferably 1,000 to 10,000. When the weight average molecular weight is 100 or more, a sufficient polishing rate can be obtained when polishing the SiO 2 film or the silicon nitride film, and when the weight average molecular weight is 50,000 or less, the viscosity becomes high, This is because the storage stability of the polishing liquid is not lowered.
本発明の研磨液は、ｐＨが、３以上９以下であることが好ましく、５以上８以下であることがより好ましい。ｐＨが３以上であれば化学的作用力が小さすぎることもなく、研磨速度が低下することもない。ｐＨが９以下であれば化学的作用が強すぎて被研磨面が皿状に窪む（ディッシング）こともない。
ｐＨは、ｐＨメータ（例えば、横河電機株式会社製のＭｏｄｅｌ ｐＨ８１）で測定することができる。具体的には、標準緩衝液（フタル酸塩ｐＨ緩衝液ｐＨ：４．２１（２５℃）、中性りん酸塩ｐＨ緩衝液ｐＨ６．８６（２５℃））を用いて、２点校正した後、電極を研磨液に入れて、２分以上経過して安定した後の値を測定する。
The polishing liquid of the present invention preferably has a pH of 3 or more and 9 or less, and more preferably 5 or more and 8 or less. If the pH is 3 or more, the chemical action force is not too small, and the polishing rate is not reduced. If the pH is 9 or less, the chemical action is too strong and the surface to be polished is not dished (dishing).
The pH can be measured with a pH meter (for example, Model pH81 manufactured by Yokogawa Electric Corporation). Specifically, after two-point calibration using a standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)) The value after the electrode is put into the polishing liquid and stabilized for 2 minutes or more is measured.
本発明の研磨液は、例えば、酸化セリウム粒子、分散剤、高分子添加剤及び水から構成される一液式研磨液としても調整することができ、また酸化セリウム粒子、分散剤及び水からなる酸化セリウムスラリーと、高分子添加剤及び水からなる添加剤とを分けた二液式研磨液として調整することもできる。いずれの場合においても、安定した特性を得ることができる。 The polishing liquid of the present invention can be prepared as a one-part polishing liquid composed of, for example, cerium oxide particles, a dispersant, a polymer additive, and water, and is also composed of cerium oxide particles, a dispersant, and water. It can also be prepared as a two-part polishing liquid in which the cerium oxide slurry is separated from an additive composed of a polymer additive and water. In either case, stable characteristics can be obtained.
酸化セリウムスラリーと添加剤とを分けた二液式研磨液として保存する場合、これら二液の配合を任意に変えられることにより平坦化特性と研磨速度の調整が可能となる。二液式の場合、添加剤と酸化セリウムスラリーとを別々の配管で任意の流量で送液し、これらの配管を合流させて、すなわち供給配管出口の直前で両者を混合して、研磨定盤上に供給する方法か、予め任意の割合で両者を容器内で混合してから供給する方法（事前混合方式）がとられる。 In the case of storing as a two-component polishing liquid in which the cerium oxide slurry and the additive are separated, the flattening characteristics and the polishing rate can be adjusted by arbitrarily changing the composition of these two liquids. In the case of the two-pack type, the additive and the cerium oxide slurry are sent at different flow rates through separate pipes, and these pipes are merged, that is, both are mixed just before the supply pipe outlet, and the polishing surface plate Either a method of supplying the above or a method of supplying them after mixing them in a container in an arbitrary ratio in advance (pre-mixing method) is used.
本発明の研磨液は、基板に形成されている被研磨膜と、研磨布との間に研磨液を供給しながら、被研磨膜が研磨布に接するよう基板を研磨布に押し当て加圧し、被研磨膜と研磨布とを相対的に動かして被研磨膜の平坦化研磨に使用される。 The polishing liquid of the present invention is to press and press the substrate against the polishing cloth so that the polishing film is in contact with the polishing cloth while supplying the polishing liquid between the polishing film formed on the substrate and the polishing cloth. The film to be polished and the polishing cloth are relatively moved to be used for planarization polishing of the film to be polished.
被研磨膜が形成されている基板としては、例えば、半導体装置の形成工程に関する基板、具体的には回路素子が形成された段階の半導体基板上に無機絶縁層が形成された基板、シャロー・トレンチ素子分離形成工程において基板上に無機絶縁層が埋込まれた基板等が挙げられる。そして、被研磨膜である前記無機絶縁層としては、少なくとも酸化珪素膜からなる絶縁層が挙げられる。 As the substrate on which the film to be polished is formed, for example, a substrate relating to a semiconductor device formation process, specifically, a substrate in which an inorganic insulating layer is formed on a semiconductor substrate at a stage where a circuit element is formed, or a shallow trench Examples include a substrate in which an inorganic insulating layer is embedded on a substrate in the element isolation formation step. And as the said inorganic insulating layer which is a to-be-polished film | membrane, the insulating layer which consists of a silicon oxide film at least is mentioned.
以下、本発明の実施例及びその比較例により、本発明をさらに具体的に説明するが、本発明はこれらの実施例に制限されるものではない。
（実施例１）
＜研磨液の製造＞
加熱混合装置として、円筒状回転羽根式混合装置（ｍａｚｅｌａｒ製、製品名：ＰＭＴ−１８、オプション：ヒータを円筒外部に巻付け間接加熱を設置、装置内の接粉部をポリフッ化エチレン系繊維コーティングでシュウ酸の金属腐食防止処理）を用い、該装置内に市販の炭酸セリウム２．８ｋｇ及びシュウ酸２．３ｋｇを投入した。
Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples.
Example 1
<Manufacture of polishing liquid>
Cylindrical rotary blade type mixing device (product name: PMT-18, option: Indirect heating is installed by winding a heater around the outside of the cylinder, and the powder contact part inside the device is coated with a polyfluorinated ethylene fiber. In this apparatus, 2.8 kg of commercially available cerium carbonate and 2.3 kg of oxalic acid were put into the apparatus.
その後、混合羽根の回転と装置の加熱を同時に開始して、ヒータ設定温度１１０℃で２．５時間加熱混合を行った。その後、混合羽根の回転と加熱を停止し、加熱混合粉体を回収した。回収直後と回収から１時間後の加熱混合粉体の質量を測定したところ、その間の質量減少は０質量％であった。また、２５℃で２４時間後の加熱混合粉体の質量を測定したところ、その質量減少は０質量％であった。
回収から１時間後に質量測定した後、加熱混合粉をロータリーキルン（炉径２５０ｍｍ、炉長４０００ｍｍ）に毎時８ｋｇの速度で投入し、空気を吹き込みながら７３０℃で１時間焼成し（投入された加熱混合粉が焼成温度７３０℃まで昇温する昇温速度は毎分５３℃）、黄白色の粉末を１．４ｋｇ得た。この粉末をＸ線回折法で相同定を行ったところ酸化セリウム粉体であることを確認した。また、ＣｕＫα粉末Ｘ線回折パターンの酸化セリウム結晶の（１１１）面による回折ピークの半値幅は０．２７３°であった。
Thereafter, rotation of the mixing blade and heating of the apparatus were started simultaneously, and heating and mixing were performed at a heater set temperature of 110 ° C. for 2.5 hours. Thereafter, the rotation and heating of the mixing blade were stopped, and the heated mixed powder was recovered. When the mass of the heated mixed powder was measured immediately after collection and 1 hour after collection, the mass reduction during the measurement was 0% by mass. Moreover, when the mass of the heat-mixed powder 24 hours after 25 degreeC was measured, the mass reduction | decrease was 0 mass%.
After measuring the mass one hour after the recovery, the heated mixed powder was put into a rotary kiln (furnace diameter 250 mm, furnace length 4000 mm) at a rate of 8 kg / hour and fired at 730 ° C. for 1 hour while blowing air (heated and mixed heat-in). The heating rate at which the powder was heated to a calcination temperature of 730 ° C. was 53 ° C. per minute), and 1.4 kg of yellowish white powder was obtained. When this powder was phase-identified by X-ray diffraction, it was confirmed to be a cerium oxide powder. Further, the half width of the diffraction peak due to the (111) plane of the cerium oxide crystal in the CuKα powder X-ray diffraction pattern was 0.273 °.
粉砕性を確認するため、酸化セリウム粉砕物のＤ９９を下記のように測定した。上記作製した酸化セリウム粉体２７ｇとポリアクリル酸アンモニウム塩水溶液（４０質量％）６．８ｇと脱イオン水１５２ｇとを混合した後、湿式粉砕機（Ｍｉｃｒｏｆｌｕｉｄｉｃｓ社製、製品名：マイクロフルイダイザーＭ−１１０ＥＨ、粉砕チャンバー型式：Ｈ１０Ｚ−１、オリフィス径：０．１ｍｍ）を、粉砕圧力１００ＭＰａ、液温５〜２０℃にて１５回通過させ湿式粉砕処理を行った。湿式粉砕処理後のスラリ中の酸化セリウム粉砕物の粒子径をレーザ回折式粒度分布計（株式会社堀場製作所社製、商品名：ＬＡ−９２０）を用い、屈折率１．９３、透過度８５％の条件で測定したところ、酸化セリウム粉砕物のＤ９９は０．８０μｍであった。 In order to confirm the grindability, D99 of the ground cerium oxide was measured as follows. 27 g of the prepared cerium oxide powder, 6.8 g of an ammonium polyacrylate aqueous solution (40% by mass) and 152 g of deionized water were mixed, and then a wet pulverizer (manufactured by Microfluidics, product name: Microfluidizer M- 110EH, crushing chamber type: H10Z-1, orifice diameter: 0.1 mm) was passed 15 times at a crushing pressure of 100 MPa and a liquid temperature of 5 to 20 ° C. to perform wet crushing treatment. The particle diameter of the cerium oxide pulverized product in the slurry after the wet pulverization treatment was measured using a laser diffraction particle size distribution meter (manufactured by Horiba, Ltd., trade name: LA-920), with a refractive index of 1.93 and a transmittance of 85%. As a result, the D99 of the cerium oxide ground product was 0.80 μm.
また、上記作製した酸化セリウム粉体１０００ｇとポリアクリル酸アンモニウム塩水溶液（４０質量％）２５ｇと脱イオン水５６００ｇとを混合し、１０分間撹拌した後、湿式粉砕機（Ｍｉｃｒｏｆｌｕｉｄｉｃｓ社製、製品名：マイクロフルイダイザーＭ−１１０ＥＨ）を粉砕圧力１００ＭＰａ、液温５〜２０℃にて６回通過させ湿式粉砕処理を行った。得られた分散液を室温（２５℃）で１００時間静置沈降させ、上澄みを採取した。この上澄み液を孔径０．７μｍのフィルタでろ過した後、再び０．７μｍのフィルタでろ過し、脱イオン水を加えて固形分濃度を５質量％に調整して、半導体平坦化用研磨液を作製した。 Further, 1000 g of the prepared cerium oxide powder, 25 g of an aqueous solution of ammonium polyacrylate (40% by mass) and 5600 g of deionized water were mixed and stirred for 10 minutes, and then a wet pulverizer (manufactured by Microfluidics, product name: Microfluidizer M-110EH) was passed 6 times at a pulverization pressure of 100 MPa and a liquid temperature of 5 to 20 ° C. to perform wet pulverization. The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. This supernatant liquid is filtered through a filter having a pore size of 0.7 μm, then filtered again through a 0.7 μm filter, deionized water is added to adjust the solid content concentration to 5% by mass, and a polishing liquid for semiconductor planarization is prepared. Produced.
得られた半導体平坦化用研磨液中の酸化セリウム粒子の粒子径を、レーザ回折式粒度分布計（株式会社堀場製作所社製、商品名：ＬＡ−９２０）を用い、屈折率１．９３、透過度７４％の条件で測定した結果、粒子径の中央値（Ｄ５０）は０．１６μｍ、Ｄ９９は０．５μｍであった。
また、原子吸光光度計（株式会社島津製作所製、型番：ＡＡ−６６５０）を用いて測定した酸化セリウム粒子含有のスラリー中の不純物（Ｆｅ）は、質量比で０．２ｐｐｍ以下であった。なお、不純物（Ｆｅ）は、湿式粉砕時の粉砕機の摩耗による混入と考えられる。
The particle diameter of the cerium oxide particles in the obtained polishing liquid for semiconductor flattening was measured using a laser diffraction particle size distribution meter (manufactured by Horiba, Ltd., trade name: LA-920) with a refractive index of 1.93 and transmission. As a result of measurement under the condition of a degree of 74%, the median particle diameter (D50) was 0.16 μm and D99 was 0.5 μm.
Moreover, the impurity (Fe) in the slurry containing cerium oxide particles measured using an atomic absorption photometer (manufactured by Shimadzu Corporation, model number: AA-6650) was 0.2 ppm or less in mass ratio. Impurities (Fe) are considered to be mixed due to wear of the pulverizer during wet pulverization.
研磨液中の粒子径０．７５μｍ以上の粒子数を下記のように測定した。上記半導体平坦化用研磨液を脱イオン水で４分の５倍に希釈し、酸化セリウム濃度を４質量％に調整した。ベックマンコールター社製のマルチサイザー３を用い、希釈した研磨液６００μｌをＩＳＯＴＯＮ ＩＩ（ベックマンコールター社製：測定用電解液）９０ｍｌに投入し、径３０μｍのアパーチャーを使用して、分析体積５０μｌの条件で測定した。その結果、測定サンプル５０μｌ中の粒子径０．７５μｍ以上の粒子数は７００個であった。これを研磨液１ｍｌ中の値に換算すると、７００÷５０μｌ×（９０ｍｌ÷６００μｌ）＝２．１×１０６個／ｍｌであった。 The number of particles having a particle diameter of 0.75 μm or more in the polishing liquid was measured as follows. The polishing liquid for semiconductor planarization was diluted 5 times with deionized water to adjust the cerium oxide concentration to 4% by mass. Using a multisizer 3 manufactured by Beckman Coulter, 600 μl of the diluted polishing solution was put into 90 ml of ISOTON II (manufactured by Beckman Coulter, Inc .: measurement electrolyte), and an aperture with a diameter of 30 μm was used and the analysis volume was 50 μl. It was measured. As a result, the number of particles having a particle size of 0.75 μm or more in 50 μl of the measurement sample was 700. When this was converted into a value in 1 ml of polishing liquid, it was 700 ÷ 50 μl × (90 ml ÷ 600 μl) = 2.1 × 10 6 pieces / ml.
研磨液中の粒子径３μｍ以上の粗大粒子含有量を調べるために、得られた半導体平坦化用研磨液を１５倍に希釈し、３μｍフィルタ（ワットマン社製のサイクロポア トラック エッチ メンブランフィルタ）で３０ｇろ過した。ろ過後、フィルタを室温（２５℃）で乾燥させて、フィルタの質量を測定し、ろ過前後の質量増加分から３μｍ以上の粗大粒子量を求めた。別途、この研磨液１０ｇを１５０℃で１時間乾燥させて研磨液中の固体濃度を算出した。その結果、３μｍ以上の粗大粒子量（質量比）は、研磨液の固体中２０ｐｐｍであった。 In order to examine the content of coarse particles having a particle diameter of 3 μm or more in the polishing liquid, the obtained polishing liquid for planarizing the semiconductor was diluted 15 times, and 30 g was filtered with a 3 μm filter (a cyclopore track etch membrane filter manufactured by Whatman). did. After filtration, the filter was dried at room temperature (25 ° C.), the mass of the filter was measured, and the amount of coarse particles of 3 μm or more was determined from the mass increase before and after filtration. Separately, 10 g of this polishing liquid was dried at 150 ° C. for 1 hour, and the solid concentration in the polishing liquid was calculated. As a result, the amount of coarse particles (mass ratio) of 3 μm or more was 20 ppm in the solid of the polishing liquid.
＜研磨液の評価＞
また、上記半導体平坦化用研磨液を脱イオン水で５倍に希釈し、以下の方法で研磨を行った。研磨速度は３５０ｎｍ／ｍｉｎ、光学顕微鏡でウエハ表面を観察したところ、２００ｍｍウエハ全面に研磨傷は５個観察された。
<Evaluation of polishing liquid>
Further, the polishing liquid for semiconductor flattening was diluted 5 times with deionized water and polished by the following method. When the polishing speed was 350 nm / min and the wafer surface was observed with an optical microscope, five polishing scratches were observed on the entire surface of the 200 mm wafer.
［研磨試験方法］
研磨荷重：３０ｋＰａ
研磨パッド：ロデール社製発泡ポリウレタン樹脂（ＩＣ−１０００）
回転数：定盤７５ｒｐｍ、パッド７５ｒｐｍ
研磨液供給速度：２００ｍＬ／ｍｉｎ
研磨対象物：Ｐ−ＴＥＯＳ成膜Ｓｉウェハ（２００ｍｍ）
[Polishing test method]
Polishing load: 30 kPa
Polishing pad: Rodel foam polyurethane resin (IC-1000)
Rotation speed: surface plate 75rpm, pad 75rpm
Polishing liquid supply rate: 200 mL / min
Polishing object: Si wafer with P-TEOS film (200mm)
（比較例１）
市販の炭酸セリウム２．８ｋｇをアルミナ製容器に入れ、バッチ式炉にて、空気雰囲気下、昇温速度毎分６．５℃で８００℃まで昇温し、その後８００℃で１時間保持し焼成することにより黄白色の粉末を１．４ｋｇ得た。この粉末をＸ線回折法で相同定を行ったところ酸化セリウム粉体であることを確認した。また、ＣｕＫα粉末Ｘ線回折パターンの酸化セリウム結晶の（１１１）面による回折ピークの半値幅は０．２７４°であった。
(Comparative Example 1)
2.8 kg of commercially available cerium carbonate is put in an alumina container, heated in a batch furnace to 800 ° C. at a heating rate of 6.5 ° C./min in an air atmosphere, and then held at 800 ° C. for 1 hour for firing. As a result, 1.4 kg of a yellowish white powder was obtained. When this powder was phase-identified by X-ray diffraction, it was confirmed to be a cerium oxide powder. Moreover, the half width of the diffraction peak due to the (111) plane of the cerium oxide crystal in the CuKα powder X-ray diffraction pattern was 0.274 °.
上記作製した酸化セリウム粉体を、粉砕性を確認するために、実施例１と同様に湿式粉砕処理を行い、酸化セリウム粉砕物の粒子径を測定したところ、酸化セリウム粉砕物のＤ９９は１．５５μｍであった。 In order to confirm the pulverizability of the prepared cerium oxide powder, wet pulverization treatment was performed in the same manner as in Example 1, and the particle diameter of the cerium oxide pulverized product was measured. It was 55 μm.
また、上記作製した酸化セリウム粉体を用い、実施例１と同様の方法で半導体平坦化用研磨液を作製した。 Also, a semiconductor planarization polishing liquid was prepared in the same manner as in Example 1 using the cerium oxide powder prepared above.
得られた半導体平坦化用研磨液中の酸化セリウム粒子の粒子径を、実施例１と同様にして測定した結果、酸化セリウム粒子の粒子径の中央値は０．１６μｍ、Ｄ９９は０．５０μｍであった。また、実施例１と同様にして測定した酸化セリウムスラリー中の不純物（Ｆｅ）は、質量比で０．２ｐｐｍ以下であった。
研磨液１ｍｌ中の粒子径０．７５μｍ以上の粒子数を、実施例１と同様にして測定すると、６．０×１０７個／ｍｌであった。
研磨液中の粒子径３μｍ以上の粗大粒子含有量を調べるために、得られた半導体平坦化用研磨液を実施例１と同様にしてろ過前後の質量増加分から３μｍ以上の粗大粒子量を求めた。その結果、粒子径３μｍ以上の粗大粒子量は固体中６０ｐｐｍであった。
As a result of measuring the particle diameter of the cerium oxide particles in the obtained polishing liquid for semiconductor flattening in the same manner as in Example 1, the median particle diameter of the cerium oxide particles was 0.16 μm, and D99 was 0.50 μm. there were. Moreover, the impurity (Fe) in the cerium oxide slurry measured in the same manner as in Example 1 was 0.2 ppm or less by mass ratio.
When the number of particles having a particle diameter of 0.75 μm or more in 1 ml of the polishing liquid was measured in the same manner as in Example 1, it was 6.0 × 10 7 particles / ml.
In order to examine the content of coarse particles having a particle diameter of 3 μm or more in the polishing liquid, the amount of coarse particles of 3 μm or more was determined from the increase in mass before and after filtration of the obtained semiconductor flattening polishing liquid in the same manner as in Example 1. . As a result, the amount of coarse particles having a particle diameter of 3 μm or more was 60 ppm in the solid.
また、上記半導体平坦化用研磨液を脱イオン水で５倍に希釈し、実施例１と同じ研磨試験方法で研磨を行った。研磨速度は３５０ｎｍ／ｍｉｎ、光学顕微鏡でウエハ表面を観察したところ、２００ｍｍウエハ全面に研磨傷は３０個観察された。 Further, the polishing liquid for semiconductor flattening was diluted 5 times with deionized water, and polishing was performed by the same polishing test method as in Example 1. When the polishing speed was 350 nm / min and the wafer surface was observed with an optical microscope, 30 polishing scratches were observed on the entire surface of the 200 mm wafer.
前記のように、粒子径０．７５μｍ以上の粒子数が２．１×１０６個／ｍｌ（３×１０６個／ｍｌ以下）である実施例１は、比較例１と比べて、ウエハ面の研磨傷が非常に少なく、本発明の研磨液及び研磨法は、配線形成工程における半導体表面を高速で研磨でき、且つ平坦性良好で研磨傷を低減することが可能な、研磨液及びこれを用いた研磨法であることがわかった。 As described above, Example 1 in which the number of particles having a particle diameter of 0.75 μm or more is 2.1 × 10 6 particles / ml (3 × 10 6 particles / ml or less) is larger than that of Comparative Example 1 on the wafer surface. The polishing liquid and the polishing method of the present invention can polish the semiconductor surface at a high speed in the wiring formation process, and have a good flatness and can reduce the polishing scratches. It was found that this was the polishing method used.
１ 加熱混合装置（加熱混合攪拌装置）
２ 攪拌羽根
３ 反応容器
４ 加熱手段
1 Heating and mixing equipment
2 Stirring blade 3 Reaction vessel 4 Heating means
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| WO2015182756A1 (en) * | 2014-05-30 | 2015-12-03 | 日立化成株式会社 | Polishing liquid for cmp, polishing liquid set for cmp, and polishing method |
| JPWO2015182756A1 (en) * | 2014-05-30 | 2017-05-25 | 日立化成株式会社 | Polishing liquid for CMP, polishing liquid set for CMP, and polishing method |
| US9966269B2 (en) | 2014-05-30 | 2018-05-08 | Hitachi Chemical Company, Ltd. | Polishing liquid for CMP, polishing liquid set for CMP, and polishing method |
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