JP4042095B2 - High purity metal powder manufacturing method and high purity metal powder manufacturing apparatus - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、スパッタリングターゲット等に用いられる高純度金属粉の製造方法に関するものである。
【０００２】
【従来の技術】
RFプラズマを利用した金属粉製造方法は、例えば高純度のスパッタリングターゲットに用いる高純度球状粉末に応用されている。この手法では、原材料粉末を投入するRFプラズマ炎を発生させるプラズマ動作ガスに水素ガスを導入する。このように動作ガス中に水素を導入するのは、プラズマ炎中で水素が活性種として作用し、プラズマ炎に精錬効果を付与するためであり、この技術は例えば特開2001-20065号公報に記載されている。
この水素ガスが活性種として作用することによる精錬メカニズムについては明確となっていないが、水素ガスの導入により蒸気圧の高い不純物金属の含有量が低減し、加えて非処理金属粉中の不純物ガスの含有量が低減することが知られている。
【０００３】
プラズマ炎中に投入された粉末は瞬時に融解した後、上述のように精錬されながら表面張力によって球状化する。このようにしてできた粉末は、精錬により不純物が低減されることに加えて、溶解炉を用いないため、炉材からの不純物混入が原理的になく、また、水溶液内での析出反応などを利用していないため酸などの残留がない。したがって、本精錬法によって得られた粉末は他の手法によるものよりも高純度の粉末を得ることができる。
【０００４】
【発明が解決しようとする課題】
上述のようにプラズマ炎中に導入された水素は活性種として作用し、プラズマ炎中で溶融した金属粉に対する精錬効果が期待される。しかしながら、動作ガスに水素を添加したプラズマではエネルギ密度が高くなり、またプラズマ炎の領域が狭くなる。エネルギ密度が高いとプラズマ炎の単位体積当りの精錬効果が高くなるが、同時に金属粉の蒸発量も著しく増大するため、原料の歩留まりが悪くなる。また、プラズマ炎の領域が狭くなると、プラズマ炎中の原料の滞留時間が短くなるため、プラズマ炎全体としての精錬効果は低くなる。したがって、動作ガス中に水素を添加した場合では、十分な精錬効果と歩留まりを同時に得られないという問題を生じる。
【０００５】
本発明の目的はRFプラズマを利用した高純度金属粉の製造における量産性の低さを解消し、高純度化と量産性を同時に達成することである。
【０００６】
【課題を解決するための手段】
本発明者らは、上記知見に基づき鋭意研究開発を行った結果、動作ガス中の水素量を制限し、プラズマ炎の尾部から精錬ガスを導入することにより、高純度の金属粉を歩留まりよく製造することを見出した。
すなわち、本発明はRFプラズマ炎中に原料を供給して金属粉を製造する方法において、プラズマ炎の尾部に水素を含む精錬ガスを導入し、プラズマ炎を発生する動作ガス中の水素量が5vol％以下、動作ガスと精錬ガスを含む混合ガスの水素量が10vol％以上であることを特徴とする高純度金属粉の製造方法である。
【０００７】
本発明では原料の供給位置が精錬ガスの供給位置に対してプラズマ炎の上流側であることが好ましい。
また、前記高純度金属粉の酸素含有量は500ppm以下であることが好ましい。
また、原料は高融点金属を主とすることが好ましい。
【０００８】
また本発明は、動作ガス供給装置を具備しプラズマ炎を発生するRFプラズマトーチと、プラズマ炎中に金属粉の原料を供給する原料供給装置と、プラズマ炎に精錬ガスを供給する精錬ガス供給装置と、プラズマ炎により加熱された金属粉を冷却するチャンバを具備する高純度金属粉の製造装置であって、精錬ガス供給装置の精錬ガス供給位置はプラズマ炎の尾部に位置し、原料供給装置の原料供給位置は精錬ガス供給位置に対してプラズマ炎の上流側に位置しており、動作ガス供給装置と精錬ガス供給装置はそれぞれ、動作ガス中の水素量が5vol％以下、動作ガスと精錬ガスを含む混合ガスの水素量が10vol％以上となる動作ガス、精錬ガスを供給する高純度金属粉の製造装置である。
【０００９】
【発明の実施の形態】
上述のように本発明では、RFプラズマ炎中に原料を供給して金属粉を製造する方法において、プラズマ炎の尾部に水素を含む精錬ガスを導入し、プラズマ炎を発生する動作ガス中の水素量が5vol％以下、動作ガスと精錬ガスを含む混合ガスの水素量が10vol％以上とすることにより、プラズマ内での被処理金属粉の蒸発を抑制し、同時に水素ガスによる十分な精錬効果を得る。以下にこれらの規定の理由を説明する。
【００１０】
なお、本発明で動作ガスとはプラズマを発生させることを目的としてプラズマトーチの電極の上流側から供給するガスでありアルゴン、ヘリウムなどの不活性ガス、もしくはこれらと水素などの活性ガスとを混合したガスを用いることが出来る。
また、精錬ガスとはプラズマ動作ガスとは別に、プラズマ炎の精錬効果の向上を目的として導入するガスで、水素、もしくは水素とアルゴンなどの不活性ガスを混合したガスである。
また、RFプラズマとはRF（高周波）エネルギによりプラズマ状態としたものであるが、本発明でRFプラズマを用いるのは、無極性のプラズマであるため電極からの不純物混入が原理的になく高純度化に適しているからである。
【００１１】
本発明で動作ガス中の水素量を5vol％以下とするのは、5vol％より多いと原料の材料歩留まりが低くなり、またプラズマ炎が不安定となるからである。
既述のようにプラズマ中で水素は活性種として働き精錬効果を促進するため、動作ガス中の水素量を増加するほどプラズマ炎の精錬効果が向上し、金属粉の高純度化を達成することができる。したがって、プラズマ炎の精錬効果を向上する点からは動作ガス中の水素量を多くすることが望ましい。しかしながら、動作ガス中の水素量を増加すると、プラズマ炎のエネルギ密度が過度に高くなる。これによりプラズマ内でのマトリックス金属（被処理金属粉）の蒸発量も増加し、原料の歩留まりの低下をもたらす。さらに、プラズマ動作ガスへ過度に水素を添加すると、プラズマ炎の発生自体に影響し、添加の量や増加に伴いプラズマの状態が変化する。その結果、プラズマ領域が減少し、原料がプラズマ炎を通過する時間が短くなり、精錬効果の低下を招く場合がある。加えて、プラズマ炎自体が不安定となり、場合によってはプラズマ炎の形成自体が困難となる。
よって、本発明では動作ガス中の水素量を5vol％以下とする。好ましくは2vol％以下である。
【００１２】
一方、動作ガス中の水素量を制限すると、本来の目的であるプラズマ炎と水素ガスによる精錬効果が不十分となり、マトリックス金属の高純度化を達成することが出来ない。そこで本発明では、水素を含む精錬ガスをプラズマ炎の尾部から導入する。本発明でプラズマ炎の尾部とは、高周波によって発生したプラズマが動作ガスの流れにより伸長されたプラズマ部分で、高周波コイルよりプラズマ下流部分を示す。
【００１３】
プラズマ炎の尾部はプラズマ発生部以降に位置するため、ここから水素を含有する精錬ガスを導入しても、プラズマトーチの高周波コイルの上流側から導入するのと比べてプラズマ炎のエネルギ密度が過度に高くなることがなく、またプラズマ炎の安定性も保たれる。従って、既述の動作ガスの水素量を増加した場合に生ずる不都合を抑えたまま、プラズマ中の水素量の増加が可能となる。
これによりプラズマ炎は十分な精錬効果を有するものとなり、原料の歩留まりの低下を抑え、マトリックス金属の高純度化を達成することができる。この際、動作ガスと精錬ガスを含む混合ガスの水素量が10vol%未満では、水素による精錬効果が十分に得られず、高純度化が達成されない。よって、本発明では動作ガスと精錬ガスを含む混合ガスの水素量は10vol％以上と規定する。好ましくは15vol％以上とする。
【００１４】
なお、本発明で動作ガスと精錬ガスを含む混合ガスの水素量とは、プラズマ炎に導入される全てのガスの水素濃度、流量から、標準状態でのトータルの水素濃度を算出し、これを体積百分率で表した値である。プラズマ炎内に導入されるガスが、動作ガス、精錬ガスのみである場合には、動作ガス、精錬ガスそれぞれのガスの水素濃度と、流量から算出する水素量であり、動作ガスと精錬ガスの濃度、流量を変えることで所望の混合ガスの水素量を得る。具体的には、例えば、水素量が3vol％、流量が50l/secの動作ガスと、水素量が50vol％、流量が20l/secの動作ガスを用いた場合の動作ガスと精錬ガスを含む混合ガスの水素量は16.4vol％となる。
【００１５】
本発明では、原料の供給位置は精錬ガスの供給位置に対してプラズマ炎の上流側であることが好ましい。
水素を含むプラズマ中では原料が高温に加熱されているほど精錬効果が高くなる。従って本発明では、原料が十分加熱された状態でプラズマ炎の尾部に供給される事が望ましい。高周波コイル付近のプラズマ発生部はもっとも高温であるので、原料を精錬ガスの供給位置に対してプラズマ炎の上流側より供給することにより、原料はより高温部で加熱された後、精錬ガスを多く含んだ精錬効果の高いプラズマ炎中へ供給することが可能になる。
【００１６】
原料の供給位置を精錬ガスの供給位置に対してプラズマ炎の上流側から行う方法として、具体的には、動作ガスをキャリアガスとして用いて動作ガスと同経路で原料をプラズマ炎中に供給する方法と、精錬ガス、動作ガスの供給位置の間に別の原料供給位置を設けて行う方法がある。
本発明では、動作ガスの供給経路とは別に原料供給位置を設けてプラズマ炎中に原料を供給することが好ましい。動作ガスと同経路で原料を供給する場合、すべての原料が温度の高いプラズマ炎中を通下するのではなく、プラズマ炎の外周部も通過する。このようにプラズマ炎中を通過しない原料は十分に精錬されないまま凝固し、処理後の金属粉の不純物含有量を増加する。したがって、全ての原料についてプラズマ炎中を通過させることが必要であり、そのためには原料をプラズマ炎中に直接供給することが望ましい。これにより、原料がプラズマ炎中に効率よく投入され、原料の精錬効果をより高めることが出来る。
【００１７】
なお、別の原料供給位置を設ける場合には、動作ガス、精錬ガスに加え原料を移動させるためのキャリアガスも別に必要となる。この場合には混合ガスの水素量は、動作ガス、精錬ガス、キャリアガスの水素濃度、流量で調整する。
【００１８】
本発明の高純度金属粉の製造方法は酸素含有量が500ppm以下の、高純度金属粉を製造するのに特に好適である。
半導体メモリ、LSIなどの高集積化が著しい電子部品の製造において用いられるターゲットでは、ターゲット中に含有される不純物の低減が重要な課題である。特にガス成分の不純物については、スパッタ膜の電気特性向上の観点から、酸素含有量を低減することが要求される。
ターゲット中の不純物含有量を低減するには、ターゲットの原料である金属粉を高純度化することが必要であるが、本発明の高純度粉末の製造方法によれば酸素含有量が500ppm以下の高純度金属粉を効率的に製造することが可能となる。
【００１９】
また本発明の製造方法では、熱源としてエネルギ密度の高いRF熱プラズマを用いるため、高融点金属粉の製造に好適である。本発明に適する高融点金属粉としては具体的には例えば、W、Pt、Ta、Ru等やそれらの合金の金属粉が挙げられる。
従来、これらの高融点金属粉はEB溶解、凝固、インゴット粉砕等の工程により製造されることが多く、この製造方法では工数が多くかかり、また不純物酸素の含有量も500ppmより多いものであったが、本発明の製造方法によれば高純度な金属粉を効率的に製造することが可能となる。
【００２０】
また別の本発明は、上述の製造方法を実施する製造装置であって、動作ガス供給装置を具備しプラズマ炎を発生するRFプラズマトーチと、プラズマ炎中に金属粉の原料を供給する原料供給装置と、プラズマ炎に精錬ガスを供給する精錬ガス供給装置と、プラズマ炎により加熱された金属粉を冷却するチャンバを具備する高純度金属粉の製造装置であって、精錬ガス供給装置の精錬ガス供給位置はプラズマ炎の尾部に位置し、原料供給装置の原料供給位置は精錬ガス供給位置に対してプラズマ炎の上流側に位置しており、動作ガス供給装置と精錬ガス供給装置はそれぞれ、動作ガス中の水素量が5vol％以下、動作ガスと精錬ガスを含む混合ガスの水素量が10vol％以上となる動作ガス、精錬ガスを供給する高純度金属粉の製造装置である。
【００２１】
以下に図１に一例を示す本発明の製造装置に基づいて、本発明の高純度金属粉の製造方法および製造装置を説明する。
RFプラズマトーチ１３は、動作ガス供給装置１１により動作ガス供給位置６から供給される水素量が5vol%以下の動作ガスとコイル７から発生する高周波エネルギによりプラズマ炎３を発生する。
原料供給装置１（例えば電磁振動原料供給装置）に投入された原料は、キャリアガスと共に原料供給位置２よりプラズマ炎３内部の高温部（５０００〜１０００００℃）に投入する。プラズマ炎中に投入された原料は瞬時に溶融し、表面張力により球状となる。
【００２２】
本発明では、精錬ガス供給装置１２において動作ガスと精錬ガスとキャリアガスを含む混合ガスの水素量が10vol％以上となるよう調整された精錬ガスが、高周波エネルギを発生するコイル７に対してプラズマ炎の下流側、すなわちプラズマ炎の尾部に設けられた精錬ガス供給位置８から供給されており、精錬ガス供給位置８より下流側では水素量が多く、かつ安定したプラズマを形成している。
精錬ガス供給位置８に対してプラズマ炎の上流側に位置する原料供給位置２から供給された原料は、十分に加熱、溶融された状態で精錬効果の高いプラズマ部分を通過し、不純物ガス等が低減される。
プラズマ炎内で処理された金属粉はチャンバ４中を落下しながら凝固し、凝固金属粉９として下部の粉末回収部５に集められ、回収される。
以上のようにして、高純度金属粉を歩留まり良く効率的に製造することができる。
【００２３】
（実施例１）
図1に示した装置にてルテニウム粉末の処理をおこなった。市販の純度99.9mass％のルテニウム原料粉末をボールミル粉砕により平均粒径１０μｍとした。本粉末をプラズマ炎中に投入し精錬を実施した。
プラズマ発生条件及び処理結果を表1に纏める。ルテニウム粉末の組成の決定はGDMS（グロー放電質量分析）、ガス成分は赤外線吸収法および熱伝導度法にて測定した。
【００２４】
【表１】
動作ガス中の水素量が5vol%以下、混合ガスの水素量が5vol%未満である比較例１では、金属粉の回収率は96%と高いものの、十分な精錬効果が得られていない。また、動作ガス中の水素量が5vol%より多く、混合ガスの水素量が5vol%以上である比較例２では、比較例１と比べて混合ガス水素濃度が高いにも関わらず十分な精錬効果が得られていない。これは比較例２では動作ガス中の水素濃度が高いことに起因して、プラズマ領域が狭いためと考えられる。また低い金属粉の回収率となった。これも動作ガス中の水素濃度が高いことに起因してプラズマの温度が過度に高いためと考えられる。
これに対し、本発明例１、２では十分な高純度化効果を得ることが出来た上に、回収率も高く、高純度と量産性の向上を同時に得ることができた。
【００２６】
（実施例２）
市販の純度99.9mass%のタンタル粉末（平均粒径50μm）を原料として、プラズマ炎に投入し精錬を実施した。プラズマ発生条件及び処理結果を表２に纏める。実施例１と同様に分析をおこなった。
【００２７】
【表２】
タンタルは実施例１で用いたルテニウムと比べて酸素との親和力が高いため全体的に酸素含有量が高いものの、表２に示すように処理前後の純度の比較では実施例１と同様の結果となり、本発明例３、４では十分な高純度化効果を得ることが出来た上に、回収率も高く、高純度と量産性の向上を同時に得ることができた。
【００２９】
（実施例３）
市販の純度99.9mass%のモリブデン粉末（平均粒径10μm）を原料として、プラズマ炎に投入し精錬を実施した。プラズマ発生条件及び処理結果を表３に纏める。実施例１と同様に分析をおこなった。
【００３０】
【表３】
モリブデンは実施例１で用いたルテニウムと比べて酸素との親和力が高いため全体的に酸素含有量が高いものの、表２に示すように処理前後の純度の比較では実施例１と同様の結果となり、本発明例５、６では十分な高純度化効果を得ることが出来た上に、回収率も高く、高純度と量産性の向上を同時に得ることができた。
【００３２】
【発明の効果】
本発明によれば、RFプラズマを用いた高純度金属粉の製造において、原料の歩留まりが高く、高純度化と量産性を同時に達成することが可能となる。
【図面の簡単な説明】
【図１】本発明の製造方法を実施する装置の一例を示す図である。
【符号の説明】
１．原料供給装置、２．原料供給位置、３．プラズマ炎、４．チャンバ、５．粉末回収部、６．動作ガス供給位置、７．コイル、８．精錬ガス供給位置、９．凝固金属粉、１０．水冷管、１１．動作ガス供給装置、１２．精錬ガス供給装置、１３．RFプラズマトーチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a high-purity metal powder used for a sputtering target or the like.
[0002]
[Prior art]
A metal powder manufacturing method using RF plasma is applied to, for example, a high-purity spherical powder used for a high-purity sputtering target. In this method, hydrogen gas is introduced into a plasma working gas that generates an RF plasma flame into which raw material powder is introduced. The reason why hydrogen is introduced into the working gas in this way is that hydrogen acts as an active species in the plasma flame and gives a refining effect to the plasma flame. This technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-20065. Are listed.
Although the refining mechanism by this hydrogen gas acting as an active species is not clear, the introduction of hydrogen gas reduces the content of impurity metal with high vapor pressure, and in addition, impurity gas in untreated metal powder It is known that the content of is reduced.
[0003]
The powder thrown into the plasma flame is melted instantly and then spheroidized by surface tension while being refined as described above. In addition to impurities being reduced by refining, the powder thus produced does not use a melting furnace, so there is no principle of impurity contamination from the furnace material, and precipitation reactions in aqueous solutions, etc. There is no acid residue because it is not used. Therefore, the powder obtained by this refining method can obtain a powder of higher purity than that obtained by other methods.
[0004]
[Problems to be solved by the invention]
As described above, hydrogen introduced into the plasma flame acts as an active species, and a refining effect on the metal powder melted in the plasma flame is expected. However, in the plasma in which hydrogen is added to the working gas, the energy density is high and the region of the plasma flame is narrowed. When the energy density is high, the refining effect per unit volume of the plasma flame is increased, but at the same time, the evaporation amount of the metal powder is remarkably increased, so that the yield of the raw material is deteriorated. Further, when the region of the plasma flame is narrowed, the residence time of the raw material in the plasma flame is shortened, so that the refining effect as the whole plasma flame is lowered. Therefore, when hydrogen is added to the working gas, there arises a problem that a sufficient refining effect and yield cannot be obtained at the same time.
[0005]
An object of the present invention is to eliminate the low mass productivity in the production of high purity metal powder using RF plasma, and to achieve high purity and mass productivity at the same time.
[0006]
[Means for Solving the Problems]
As a result of diligent research and development based on the above findings, the present inventors limited the amount of hydrogen in the working gas and introduced refining gas from the tail of the plasma flame to produce high-purity metal powder with high yield. I found out.
That is, the present invention is a method for producing metal powder by supplying raw materials into an RF plasma flame, introducing a refining gas containing hydrogen into the tail of the plasma flame, and the amount of hydrogen in the working gas generating the plasma flame is 5 vol. % or less, a process for producing a high-purity metal powder, wherein the amount of hydrogen mixed gas containing working gas and refining gas is not less than 10 vol%.
[0007]
In the present invention, the raw material supply position is preferably upstream of the plasma flame with respect to the refining gas supply position.
The oxygen content of the high purity metal powder is preferably 500 ppm or less.
Moreover, it is preferable that a raw material is mainly a refractory metal.
[0008]
The present invention also includes an RF plasma torch that includes a working gas supply device and generates a plasma flame, a raw material supply device that supplies a raw material of metal powder in the plasma flame, and a refining gas supply device that supplies a refining gas to the plasma flame And a high-purity metal powder production apparatus comprising a chamber for cooling the metal powder heated by the plasma flame, wherein the refining gas supply position of the refining gas supply apparatus is located at the tail of the plasma flame, The raw material supply position is located on the upstream side of the plasma flame with respect to the refining gas supply position. The operating gas supply device and the refining gas supply device each have a hydrogen content of 5 vol% or less, and the operating gas and refining gas. Is an apparatus for producing high-purity metal powder that supplies working gas and refining gas in which the hydrogen content of the mixed gas containing 10 vol% or more.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As described above, in the present invention, in a method for producing a metal powder by supplying raw materials into an RF plasma flame, a refining gas containing hydrogen is introduced into the tail of the plasma flame to generate hydrogen in the working gas that generates the plasma flame. The amount of hydrogen is 5 vol% or less, and the amount of hydrogen in the mixed gas containing working gas and refining gas is 10 vol% or more, so that evaporation of metal powder to be treated in the plasma is suppressed and at the same time sufficient refining effect by hydrogen gas is achieved obtain. The reasons for these provisions are explained below.
[0010]
In the present invention, the working gas is a gas supplied from the upstream side of the electrode of the plasma torch for the purpose of generating plasma, and an inert gas such as argon or helium or a mixture of these with an active gas such as hydrogen. Gas can be used.
Further, the refining gas is a gas introduced for the purpose of improving the refining effect of the plasma flame separately from the plasma working gas, and is a gas obtained by mixing hydrogen or an inert gas such as hydrogen and argon.
In addition, RF plasma is a plasma state by RF (high frequency) energy. However, RF plasma is used in the present invention because it is non-polar plasma, so it does not contain impurities from the electrode in principle and has high purity. It is because it is suitable for conversion.
[0011]
The reason why the amount of hydrogen in the working gas is set to 5 vol% or less in the present invention is that if it exceeds 5 vol%, the material yield of the raw material becomes low and the plasma flame becomes unstable.
As described above, hydrogen acts as an active species in the plasma and promotes the refining effect. Therefore, as the amount of hydrogen in the working gas increases, the refining effect of the plasma flame improves and high purity of the metal powder is achieved. Can do. Therefore, it is desirable to increase the amount of hydrogen in the working gas in order to improve the refining effect of the plasma flame. However, when the amount of hydrogen in the working gas is increased, the energy density of the plasma flame becomes excessively high. As a result, the evaporation amount of the matrix metal (metal powder to be processed) in the plasma also increases, resulting in a decrease in the yield of the raw material. Furthermore, excessive addition of hydrogen to the plasma working gas affects the generation of the plasma flame itself, and the plasma state changes with the amount and increase of the addition. As a result, the plasma region is reduced, the time for the raw material to pass through the plasma flame is shortened, and the refining effect may be reduced. In addition, the plasma flame itself becomes unstable, and in some cases, the formation of the plasma flame itself becomes difficult.
Therefore, in the present invention, the amount of hydrogen in the working gas is set to 5 vol% or less. Preferably it is 2 vol% or less.
[0012]
On the other hand, when the amount of hydrogen in the working gas is limited, the refining effect by the plasma flame and hydrogen gas, which are the original purposes, becomes insufficient, and the high purity of the matrix metal cannot be achieved. Therefore, in the present invention, a refining gas containing hydrogen is introduced from the tail of the plasma flame. In the present invention, the tail portion of the plasma flame is a plasma portion where the plasma generated by the high frequency is expanded by the flow of the working gas, and indicates the downstream portion of the plasma from the high frequency coil.
[0013]
Since the tail of the plasma flame is located after the plasma generation part, even if a refining gas containing hydrogen is introduced from here, the energy density of the plasma flame is excessive compared to that introduced from the upstream side of the high frequency coil of the plasma torch. And the stability of the plasma flame is maintained. Therefore, it is possible to increase the amount of hydrogen in the plasma while suppressing the disadvantages that occur when the amount of hydrogen in the operating gas described above is increased.
As a result, the plasma flame has a sufficient refining effect, suppresses a decrease in the yield of the raw material, and can achieve high purity of the matrix metal. At this time, if the amount of hydrogen in the mixed gas including the working gas and the refining gas is less than 10 vol%, the refining effect by hydrogen cannot be sufficiently obtained, and high purity cannot be achieved. Therefore, in the present invention, the hydrogen amount of the mixed gas containing the working gas and the refining gas is defined as 10 vol% or more. Preferably it is 15 vol% or more.
[0014]
In the present invention, the hydrogen amount of the mixed gas including the working gas and the refining gas is calculated from the hydrogen concentration and flow rate of all gases introduced into the plasma flame, and the total hydrogen concentration in the standard state is calculated. It is a value expressed in volume percentage. When the gas introduced into the plasma flame is only the working gas and the refining gas, it is the hydrogen amount calculated from the hydrogen concentration and flow rate of the working gas and the refining gas. The desired amount of hydrogen in the mixed gas is obtained by changing the concentration and flow rate. Specifically, for example, a mixture containing a working gas and a refining gas when a working gas having a hydrogen amount of 3 vol% and a flow rate of 50 l / sec and a working gas having a hydrogen amount of 50 vol% and a flow rate of 20 l / sec are used. The amount of hydrogen in the gas is 16.4vol%.
[0015]
In the present invention, the raw material supply position is preferably upstream of the plasma flame with respect to the refining gas supply position.
In the plasma containing hydrogen, the refining effect becomes higher as the raw material is heated to a higher temperature. Therefore, in the present invention, it is desirable that the raw material is supplied to the tail of the plasma flame in a sufficiently heated state. Since the plasma generating part near the high frequency coil is the hottest, by supplying the raw material from the upstream side of the plasma flame to the refining gas supply position, the raw material is heated at a higher temperature part and then the refining gas is increased. It becomes possible to supply into a plasma flame with high refining effect.
[0016]
As a method of performing the raw material supply position from the upstream side of the plasma flame with respect to the refining gas supply position, specifically, using the operating gas as a carrier gas, the raw material is supplied into the plasma flame through the same path as the operating gas. And a method in which another raw material supply position is provided between the refining gas and working gas supply positions.
In the present invention, it is preferable to provide a raw material supply position separately from the working gas supply path to supply the raw material into the plasma flame. When the raw material is supplied through the same path as the working gas, not all the raw material passes through the plasma flame having a high temperature, but also passes through the outer periphery of the plasma flame. In this way, the raw material that does not pass through the plasma flame solidifies without being sufficiently refined, increasing the impurity content of the metal powder after treatment. Therefore, it is necessary to pass all the raw materials through the plasma flame. For this purpose, it is desirable to supply the raw materials directly into the plasma flame. As a result, the raw material is efficiently put into the plasma flame, and the refining effect of the raw material can be further enhanced.
[0017]
In addition, when providing another raw material supply position, the carrier gas for moving a raw material in addition to working gas and refining gas is needed separately. In this case, the hydrogen amount of the mixed gas is adjusted by the hydrogen concentration and flow rate of the working gas, the refining gas, and the carrier gas.
[0018]
The method for producing a high purity metal powder of the present invention is particularly suitable for producing a high purity metal powder having an oxygen content of 500 ppm or less.
In a target used in the manufacture of electronic parts that are remarkably highly integrated such as semiconductor memories and LSIs, reduction of impurities contained in the target is an important issue. In particular, with respect to impurities as gas components, it is required to reduce the oxygen content from the viewpoint of improving the electrical characteristics of the sputtered film.
In order to reduce the impurity content in the target, it is necessary to highly purify the metal powder that is the raw material of the target. According to the method for producing a high-purity powder of the present invention, the oxygen content is 500 ppm or less. High-purity metal powder can be efficiently produced.
[0019]
Moreover, since the manufacturing method of the present invention uses RF thermal plasma having a high energy density as a heat source, it is suitable for manufacturing refractory metal powder . Specific examples of refractory metal powders suitable for the present invention include metal powders of W, Pt, Ta, Ru, etc. and their alloys.
Conventionally, these refractory metal powders are often produced by processes such as EB melting, coagulation, and ingot crushing, and this production method requires a lot of man-hours and the content of impurity oxygen is more than 500 ppm. However, according to the production method of the present invention, it is possible to efficiently produce high-purity metal powder.
[0020]
Another embodiment of the present invention is a manufacturing apparatus for performing the above-described manufacturing method, comprising an RF plasma torch that includes a working gas supply device and generates a plasma flame, and a raw material supply that supplies a raw material of metal powder in the plasma flame A refining gas supply device for supplying a refining gas to a plasma flame, and a high purity metal powder production device comprising a chamber for cooling the metal powder heated by the plasma flame, the refining gas of the refining gas supply device The supply position is located at the tail of the plasma flame, the raw material supply position of the raw material supply device is located upstream of the refining gas supply position, and the operating gas supply device and the refining gas supply device are each operated. This is an apparatus for producing high-purity metal powder that supplies working gas and refining gas in which the amount of hydrogen in the gas is 5 vol% or less, and the amount of hydrogen in the mixed gas containing working gas and refining gas is 10 vol% or more.
[0021]
Based on the manufacturing apparatus of the present invention shown in FIG. 1 as an example, the manufacturing method and manufacturing apparatus of the high-purity metal powder of the present invention will be described below.
The
The raw material charged into the raw material supply device 1 (for example, the electromagnetic vibration raw material supply device) is supplied together with the carrier gas from the raw material supply position 2 to the high temperature part (5000 to 100,000 ° C.) inside the plasma flame 3. The raw material thrown into the plasma flame melts instantly and becomes spherical due to surface tension.
[0022]
In the present invention, the refining gas adjusted so that the amount of hydrogen of the mixed gas including the working gas, the refining gas, and the carrier gas in the refining gas supply device 12 is 10 vol% or more is plasma to the coil 7 that generates high-frequency energy. The gas is supplied from the refining gas supply position 8 provided on the downstream side of the flame, that is, at the tail of the plasma flame, and the downstream side of the refining gas supply position 8 has a large amount of hydrogen and forms stable plasma.
The raw material supplied from the raw material supply position 2 located on the upstream side of the plasma flame with respect to the refining gas supply position 8 passes through a plasma portion having a high refining effect in a sufficiently heated and melted state, so that impurity gas or the like is generated. Reduced.
The metal powder treated in the plasma flame is solidified while falling in the chamber 4, and is collected and recovered as a solidified metal powder 9 in the lower powder recovery unit 5.
As described above, high-purity metal powder can be efficiently produced with a high yield.
[0023]
Example 1
The ruthenium powder was processed with the apparatus shown in FIG. A commercially available ruthenium raw material powder having a purity of 99.9 mass% was adjusted to an average particle size of 10 μm by ball milling. This powder was put into a plasma flame and refined.
Table 1 summarizes plasma generation conditions and processing results. The composition of the ruthenium powder was determined by GDMS (glow discharge mass spectrometry), and the gas component was measured by an infrared absorption method and a thermal conductivity method.
[0024]
[Table 1]
In Comparative Example 1 where the amount of hydrogen in the working gas is 5 vol% or less and the amount of hydrogen in the mixed gas is less than 5 vol%, the metal powder recovery rate is as high as 96%, but a sufficient refining effect is not obtained. In Comparative Example 2 where the amount of hydrogen in the working gas is greater than 5 vol% and the amount of hydrogen in the mixed gas is 5 vol% or more, a sufficient refining effect is achieved even though the mixed gas hydrogen concentration is higher than in Comparative Example 1. Is not obtained. This is probably because the plasma region is narrow in Comparative Example 2 due to the high hydrogen concentration in the working gas. In addition, the metal powder recovery rate was low. This is also because the plasma temperature is excessively high due to the high hydrogen concentration in the working gas.
On the other hand, in Examples 1 and 2 of the present invention, it was possible to obtain a sufficiently high purification effect and a high recovery rate, and it was possible to simultaneously obtain high purity and mass productivity.
[0026]
(Example 2)
A commercially available tantalum powder with a purity of 99.9 mass% (average particle size 50 μm) was used as a raw material, and it was put into a plasma flame for refining. Table 2 summarizes plasma generation conditions and processing results. Analysis was performed in the same manner as in Example 1.
[0027]
[Table 2]
Although tantalum has a higher affinity for oxygen than ruthenium used in Example 1, the overall oxygen content is high. However, as shown in Table 2, the purity results before and after treatment are similar to those in Example 1. In Invention Examples 3 and 4, it was possible to obtain a sufficiently high purification effect and a high recovery rate, and it was possible to simultaneously obtain high purity and mass productivity.
[0029]
(Example 3)
A commercially available molybdenum powder with a purity of 99.9 mass% (average particle size 10 μm) was used as a raw material and put into a plasma flame for refining. Table 3 summarizes plasma generation conditions and processing results. Analysis was performed in the same manner as in Example 1.
[0030]
[Table 3]
Molybdenum has a higher affinity for oxygen than ruthenium used in Example 1, so that the overall oxygen content is high. However, as shown in Table 2, the purity results before and after treatment are similar to those in Example 1. In Invention Examples 5 and 6, it was possible to obtain a sufficiently high purification effect and a high recovery rate, and it was possible to obtain high purity and mass productivity at the same time.
[0032]
【The invention's effect】
According to the present invention, in the production of high-purity metal powder using RF plasma, the yield of raw materials is high, and it is possible to achieve high purity and mass productivity at the same time.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an apparatus for carrying out a manufacturing method of the present invention.
[Explanation of symbols]
1. 1. Raw material supply device, 2. Raw material supply position; 3. Plasma flame, Chamber, 5. Powder recovery section, 6. 6. working gas supply position; Coil, 8. Refining gas supply position, 9. Solidified metal powder, 10. Water-cooled tubes, 11. Working gas supply device, 12. 12. Refining gas supply device, RF plasma torch
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| KR100584570B1 (en) | 2006-02-28 | 2006-05-30 | 한국기계연구원 | Apparatus for plasma reaction |
| EP1942202A3 (en) * | 2007-01-08 | 2010-09-29 | Heraeus, Inc. | High density, low oxygen Re and Re-based consolidated powder materials for use as deposition sources & methods of making the same |
| WO2009119196A1 (en) * | 2008-03-28 | 2009-10-01 | 日鉱金属株式会社 | Platinum powder for magnetic material target, method for producing the powder, method for producing magnetic material target composed of platinum sintered compact, and the sintered magnetic material target |
| CN103736435B (en) * | 2013-12-27 | 2015-11-18 | 中国神华能源股份有限公司 | A kind of equipment and system utilizing ac plasma nodularization powder |
| KR102273282B1 (en) * | 2020-01-30 | 2021-07-06 | 주식회사 나노코리아 | Method for producing metal powder |
| KR102467741B1 (en) * | 2021-08-05 | 2022-11-16 | 한국핵융합에너지연구원 | Atomizing system and atomizing method using plasma |
| KR102491080B1 (en) * | 2021-08-05 | 2023-01-19 | 한국핵융합에너지연구원 | Powder spheronization device using plasma |
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| KR102020314B1 (en) * | 2017-12-07 | 2019-09-11 | 한국생산기술연구원 | Method for manufacturing spherical high purity metal powder |
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