JP4232088B2 - Manufacturing method of high purity electrolytic copper - Google Patents
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- JP4232088B2 JP4232088B2 JP2003107777A JP2003107777A JP4232088B2 JP 4232088 B2 JP4232088 B2 JP 4232088B2 JP 2003107777 A JP2003107777 A JP 2003107777A JP 2003107777 A JP2003107777 A JP 2003107777A JP 4232088 B2 JP4232088 B2 JP 4232088B2
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Description
【０００１】
【産業上の利用分野】
この発明は、電気銅を再電解して純度：９９.９９９９質量％以上の高純度電気銅を製造する方法に関するものであり、尿素を含有する電解液を使用することにより特に硫黄含有量の極めて少ない純度：９９.９９９９質量％以上の高純度電気銅を製造する方法に関するものである。
【０００２】
【従来の技術】
一般に、高純度銅は、電解精製することにより製造されることは知られており、この銅の電解精製では、銅濃度：４０〜５０ｇ／Ｌ、遊離硫酸濃度：１５０〜２２０ｇ／Ｌにさらに添加剤として膠を電気銅１トン当り３０〜１３０ｇ、チオ尿素を電気銅１トン当り１５〜８０ｇを添加し、さらに銀の含有量を低下させるためにＨＣｌ：５０〜１００ｍｇ／Ｌを添加した電解液中を用い、アノードとして純度：９９質量％前後の粗銅を使用し、カソードとしてステンレス鋼板、チタン板などを使用して浴温：５０〜７０℃、電流密度：１００〜３００Ａ／ｍ2で電解し、カソードに銅を析出させることにより行われることは知られている。
このようにして得られた電気銅は、その純度が９９.９９質量％程度の純銅であるが、近年、純銅は半導体装置のボンディングワイヤーや半導体デバイスの配線に使用されるようになり、かかる用途には純度が９９.９９質量％程度の純銅では純度が不十分であった。そのために、さらなる高純度の電気銅を製造すべく研究が重ねられ、それによって純度：９９．９９９質量％以上の電気銅が製造されるようになり市販されている。この９９.９９９質量％以上の高純度電気銅を製造する方法として、遊離硫酸銅：９０〜２２０ｇ／Ｌ、温度：４０℃以下で有機質添加剤を添加することなのない電解液を使用し、電流密度：２５０Ａ／ｍ2以下で電解浴に有機質添加剤を添加することなく電気銅を再電解精製する方法（特許文献１参照）、浴電解温度：３０〜５０℃、電流密度：５０〜１５０Ａ／ｍ2で、電解浴に膠を添加して電気銅を再電解精製する方法（特許文献２参照）などが知られている。
しかし、近年の半導体デバイスの小型化、高密度化などに伴って、半導体デバイスの配線に使用される高純度銅は、９９.９９９９質量％以上の高純度であることが求められており、かかる純度：９９.９９９９質量％以上の高純度電気銅を製造する方法として、粗銅または通常の電気銅の硫酸銅浴での電解精製において、アノードとカソードを隔膜で仕切り、アノード室から排出される電解液を濾過するかまたは予め調整した純度の高い銅溶液をカソード室に給液し、電解浴中の硫酸濃度を１０〜１５０ｇ／Ｌ、電流密度：３０〜１５０Ａ／ｍ2とし、カソードにチタン板を用いて再電解する方法（特許文献３参照）、
電気銅または電気銅相当の純銅を有する金属銅をアノードとし、銅濃度：２０〜４５ｇ／Ｌ、遊離硫酸濃度：４０〜８０ｇ／Ｌ、浴温度：１０〜４０℃の硫酸酸性電解液を用い、電流密度２００〜５００Ａ／ｍ2で電解する第１工程と、第１の工程より得られた電着銅をアノードとし、電流密度１００〜２００Ａ／ｍ2で電解する第２工程を含む再電解方法（特許文献４参照）などが提案されている。
【０００３】
【特許文献１】
特開昭６１−８４３８９号公報
【特許文献２】
特公平５−５９０３号公報
【特許文献３】
特公平５−２５９５６号公報
【特許文献４】
特公平７−６８６２７号公報
【０００４】
【発明が解決しようとする課題】
しかし、前記特許文献３記載の純度：９９.９９９９質量％以上の高純度電気銅を製造する方法では硫黄（以下、Ｓと記す）の十分な減少を果たすことができず、またカソードにチタン板を使用しなければならないのでコストがかるなどの課題があり、さらに、前記特許文献４記載の純度：９９.９９９９質量％以上の高純度電気銅を製造する方法ではＳの含有量の減少は達成できるものの、電解を２工程で行なう必要があり、量産する場合は２つの特殊な装置を必要とするのでコストがかるなどの課題があった。
【０００５】
【課題を解決するための手段】
そこで、本発明者らは、かかる観点から、通常の装置を用いて純度：９９.９９９９質量％以上の高純度電気銅の製造方法を得るべく研究を行った。その結果、（イ）従来の高純度電気銅の製造方法で使用する電解液に含まれるチオ尿素に代えて尿素を含有する電解液を使用すると、得られた電気銅に含まれるＳ含有量を極めて低く低減させることができる、
（ロ）この時、電解液に含まれる尿素は１〜２０ｍｇ／Ｌである、
（ハ）したがって、この発明の高純度電気銅の製造方法で使用する電解液は、Ｃｕ：２０〜５０ｇ／Ｌ、遊離硫酸：１００〜１５０ｇ／Ｌを含む硫酸酸性電解液に、添加剤としてＨＣｌ：１０〜１００ｍｇ／Ｌ、膠：１０〜５０ｍｇ／Ｌ、尿素：１〜２０ｍｇ／Ｌを添加した電解液であることが好ましい、などの知見を得たのである。
【０００６】
この発明は、かかる知見にもとづいてなされたものであって、
（１）硫酸酸性の電解液を用い、電気銅をアノードとして再電解することにより純度：９９．９９９９質量％以上の高純度銅を製造する方法において、前記電解液は尿素を含む電解液である高純度電気銅の製造方法、
（２）硫酸酸性の電解液を用い、電気銅をアノードとして再電解することにより純度：９９．９９９９質量％以上の高純度銅を製造する方法において、前記電解液は尿素：１〜２０ｍｇ／Ｌを含む電解液である高純度電気銅の製造方法、
（３）電解液を用いて電気銅を再電解することにより純度：９９．９９９９質量％以上の高純度銅を製造する方法において、前記電解液は、Ｃｕ：２０〜５０ｇ／Ｌ、遊離硫酸：１００〜１５０ｇ／Ｌ、添加剤としてＨＣｌ：１０〜１００ｍｇ／Ｌ、膠：１０〜５０ｍｇ／Ｌ、尿素：１〜２０ｍｇ／Ｌを含む電解液である高純度電気銅の製造方法、に特徴を有するものである。
【０００７】
この発明の高純度電気銅の製造方法において、電解液の温度は１７〜２５℃の範囲内に保持されていることが好ましい。したがって、この発明は、
（４）電解液の温度を１７〜２５℃の範囲内に保持されている前記（１）、（２）または（３）記載の高純度電気銅の製造方法、に特徴を有するものである。
【０００８】
この発明の高純度電気銅の製造方法において、電解液は循環供給して使用されるが、電解液をマイクロポアフィルターを通して循環させることにより一層高純度の電気銅を製造することができる。また、電解液に供給する電流密度は５０〜１００Ａ／ｍ2であることが好ましい。したがって、この発明は、
（５）電流密度が５０〜１００Ａ／ｍ2である前記（１）、（２）、（３）または（４）記載の高純度電気銅の製造方法、に特徴を有するものである。
【０００９】
この発明の尿素を含む電解液を用いて高純度電気銅を製造すると、カソード母板に電着する高純度電気銅は、純度が９９．９９９９質量％を有し、表面が平滑で、しかもカソード母板表面から厚さ方向に柱状晶が成長した金属組織を有する。一般に、電解液を用いて電気銅を再電解することにより純度：９．９９９９質量％以上の高純度銅を製造する方法において、カノード母板としてステンレス鋼板を用いると結晶粒が微細化し、硫酸中の硫黄および電解液中の固形物であるＡｇが結晶粒内に巻き込まれ、得られた電気銅中のＡｇやＳが増加するところからステンレス鋼板では十分な高純度の高純度電気銅は得られないと言われており、一方、チタン板をカソード母板として用いると得られる電気銅の結晶粒が大きくなり、表面が平滑でかつ硫酸中の硫黄および電解液中の固形物である銀が結晶粒内に巻き込まれることが少なく、したがってＡｇやＳなどの含有量が少なくなると言われている。
しかし、この発明ではカノード母板としてステンレス鋼板を用いても同様に高純度電気銅が得られる。その理由として、尿素を含有する電解液を用い、ステンレス鋼板をカノード母板として電解することにより得られた電着銅は、電着初期に生成した結晶粒が微細であっても、ステンレス鋼板製カソードに電着した電気銅はカソード母板表面から厚さ方向に平行に柱状晶として著しく成長するところから、不純物が柱状晶の成長に伴ってＳなどの不純物が電解液側に排出され、それによって高純度の電気銅が得られるものと考えられる。この発明で得られたカソード母板に電着した電気銅は、電着した電気銅の厚さの１／２の厚さ位置で電解面に平行に切断した切断面における柱状晶の平均太さが５０〜３００μｍの範囲内にある。
【００１０】
次ぎに、この発明の高純度電気銅の製造方法における電解液の組成、温度および電流密度について前述のごとく限定した理由を説明する。
（Ａ）電解液組成：
尿素
電解液中に含まれる尿素は添加物として電解液に含有させることによりカソードに電着した電気銅の結晶を欠陥なく柱状晶状に成長させる成分であるが、その含有量が１ｍｇ／Ｌ未満では、電着した電気銅表面に細かなブツが発生したり、電着不良が発生したりするので好ましくなく、一方、２０ｍｇ／Ｌを越えて含有すると、電着した電気銅表面に比較的大きなブツが発生したり、柱状晶に亀裂が入ったりして不純物を巻きこむので好ましくない。したがって、電解液中に含まれる尿素の含有量は１〜２０ｍｇ／Ｌ（一層好ましくは、１．５〜５ｍｇ／Ｌ）に定めた。
【００１１】
膠
電解液中に含まれる膠はカソードに電着した電気銅表面を緻密かつ平滑にさせる成分であるが、その含有量が１０ｍｇ／Ｌ未満では所望の効果が得られず、一方、５０ｍｇ／Ｌを越えて含有すると、電解液の抵抗が大きくなって電解効率が悪くなるので好ましくない。したがって、膠の含有量は１０〜５０ｍｇ／Ｌに定めた。電解液中に含まれる膠の含有量の一層好ましい範囲は１５〜３０ｍｇ／Ｌである。
【００１２】
塩素イオン濃度
電解液中に含まれる塩素イオンは、ＨＣｌとして添加され、電着した電気銅に含まれるＡｇを少なくし、また電気銅の表面を平滑にするなどの作用を有するが、その含有量が１０ｍｇ／Ｌ未満では所望の効果が得られず、一方、１００ｍｇ／Ｌを越えて含有すると、得られたカソード表面が平滑でなく、表面に微細な孔が発生するので好ましくない。したがって、電解液中に含まれる塩素イオンは１０〜１００ｍｇ／Ｌに定めた。電解液中に含まれる塩素イオンの含有量の一層好ましい範囲は２０〜６０ｍｇ／Ｌである。
【００１３】
銅濃度
電解液中に含まれる銅は低い方が電着した電解銅の緻密性を高くし、さらに平滑性をよくする作用を有するが、２０ｇ／Ｌ未満では生産性が低くなるので好ましくなく、一方、５０ｇ／Ｌを越えると、緻密性が悪くなるので好ましくない。したがって、電解液中に含まれる銅濃度は、２０〜５０ｇ／Ｌ（一層好ましくは、３５〜４５ｇ／Ｌ）に定めた。
【００１４】
遊離硫酸濃度
電解液中に含まれる遊離硫酸は、電着した電解銅の緻密性を高くし、さらに平滑性をよくする作用を有するが、１００ｇ／Ｌ未満では秘密性、平滑性が悪くなるので好ましくなく、一方、１５０ｇ／Ｌを越えると、硫酸銅の溶解度が減少して緻密性が悪くなるので好ましくない。したがって、電解液中に含まれる銅濃度は、１００〜１５０ｇ／Ｌ（一層好ましくは、１１５〜１４０ｇ／Ｌ）に定めた。
【００１５】
（Ｂ）電解条件
電解液温度
尿素を含む電解液の温度は、１７℃未満では電解液の硫酸銅が結晶化して電解液の濃度が変化するので好ましくなく、一方、２５℃を越えると電着した電気銅の緻密性および平滑性がそこなわれるようになるので好ましくない。したがって、尿素を含む電解液の温度は１７〜２５℃に定めた。
【００１６】
電流密度
尿素を含む電解液を使用して電解する際の電流密度は、５０Ａ／ｍ2未満では電流密度が低くなりすぎて生産性が悪くなるので好ましくなく、一方、１００Ａ／ｍ2を越えると電着した電解銅の緻密性および平滑性を阻害するので好ましくない。したがって、電流密度は５０〜１００Ａ／ｍ2に定めた。電流密度の一層好ましい範囲は６０〜８０Ａ／ｍ2である。
【００１７】
【発明の実施の形態】
実施例１〜６、比較例１〜２および従来例
純度：９９．９９質量％の市販の電気銅を用意し、この電気銅をアノードとしてこれをポリプロピレン製布袋に収納することによりアノードバックを作製した。さらに、ＳＵＳ３０４製板からなるカソード母板を用意した。さらに、表１に示される尿素、膠、ＨＣｌ、銅、遊離硫酸を含む電解液を用意した。さらにチオ尿素を含む電解液も用意した。前記アノードバックおよびＳＵＳ３０４製カソード母板を用い、表１に示される電解液を使用し、この電解液をマイクロポアフィルターを通しながら循環させることにより表１に示される条件で電解することにより実施例１〜６、比較例１〜２および従来例を実施した。この実施例１〜６、比較例１〜２および従来例でカソードに電着した電気銅に含まれる不純物を測定し、その結果を表２に示した。さらに、実施例１〜６で得られたカソードに電着した電気銅の断面を切断し、その組織を測定したところ、銅カソード板の厚さ方向に柱状晶が成長した組織を有することが分かり、電気銅の厚さの１／２の厚さ位置で電解面に平行に切断した切断面（すなわち、図１におけるＡ−Ａ位置で切断した切断面）における柱状晶の平均太さを測定し、その結果を表１に示した。一例として、実施例１で作製した電着した高純度電気銅の断面組織を図１に金属組織写真として示し、図２に従来例で作製した電着した高純度電気銅の断面組織を図２に金属組織写真として示す。図１および図２において、金属組織写真の上部はカソードに電着した電気銅の表面を示し、下方は電着した電気銅のカソードに接する面を示す。図１と図２を比較すると、実施例１において電着した電気銅は、従来例において電着した電気銅に比べて柱状晶が著しく発達していることが分かる。
【００１８】
【表１】
【表２】
表１〜２に示される結果から、尿素を含む電解液を用いて電解する実施例１〜６により得られた高純度電気銅は、チオ尿素を含む電解液を用いて電解する従来例で得られた高純度電気銅に比べて特にＳ含有量が少ないことが分かる。また、この発明の条件から外れた値の尿素を含む電解液を用いて電解する比較例１〜２で得られた高純度電気銅は、Ｓ濃度およびＡｇ濃度も高くなるなどの好ましくない性質が現れることが分かった。
【００２１】
【発明の効果】
上述のように、この発明の方法によると、低コストで純度：９９．９９９９質量％以上のＳ含有量の極めて少ない高純度銅が得られ、特に半導体デバイスなどの産業分野で優れた効果をもたらすものである。
【図面の簡単な説明】
【図１】実施例１で得られた電着電気銅の断面の金属組織写真である。
【図２】従来例で得られた電着電気銅の断面の金属組織写真である。[0001]
[Industrial application fields]
The present invention relates to a method for producing high-purity electrolytic copper having a purity of 99.9999% by mass by re-electrolysis of electrolytic copper, and particularly by using an electrolytic solution containing urea, the sulfur content is extremely high. Low purity: The present invention relates to a method for producing high-purity electrolytic copper of 99.9999% by mass or more.
[0002]
[Prior art]
In general, it is known that high-purity copper is produced by electrolytic purification. In this copper electrolytic purification, copper concentration: 40 to 50 g / L and free sulfuric acid concentration: 150 to 220 g / L are further added. Electrolyte containing 30 to 130 g of glue per ton of electrolytic copper, 15 to 80 g of thiourea per ton of electrolytic copper as agents, and further adding HCl: 50 to 100 mg / L to reduce the silver content Electrolyzed at a bath temperature of 50 to 70 ° C. and a current density of 100 to 300 A / m 2 using crude copper having a purity of about 99% by mass as an anode and a stainless steel plate or titanium plate as a cathode. It is known to be performed by depositing copper on the cathode.
The electrolytic copper thus obtained is pure copper having a purity of about 99.99% by mass. Recently, pure copper has been used for bonding wires of semiconductor devices and wiring of semiconductor devices. However, pure copper having a purity of about 99.99% by mass was insufficient in purity. Therefore, research is repeated to produce higher-purity electrolytic copper, and thereby, electrolytic copper having a purity of 99.999% by mass or more is produced and is commercially available. As a method for producing high-purity electrolytic copper of 99.999% by mass or more, an electrolytic solution containing free copper sulfate: 90 to 220 g / L, temperature: 40 ° C. or less and without adding an organic additive is used. Density: 250 A / m 2 or less, a method for re-electrolytic purification of electrolytic copper without adding an organic additive to the electrolytic bath (see Patent Document 1), bath electrolysis temperature: 30-50 ° C., current density: 50-150 A / A method of refining electrolytic copper by adding glue to the electrolytic bath at m 2 (see Patent Document 2) is known.
However, with recent miniaturization and higher density of semiconductor devices, high-purity copper used for wiring of semiconductor devices is required to have a high purity of 99.9999% by mass or more. Purity: As a method for producing high-purity electrolytic copper of 99.9999% by mass or more, in electrolytic refining of crude copper or ordinary electrolytic copper in a copper sulfate bath, the anode and the cathode are separated by a diaphragm, and the electrolysis discharged from the anode chamber The solution is filtered or a preliminarily prepared high purity copper solution is supplied to the cathode chamber, the sulfuric acid concentration in the electrolytic bath is 10 to 150 g / L, and the current density is 30 to 150 A / m 2. (Refer to Patent Document 3)
Metal copper having pure copper or copper equivalent to pure copper is used as an anode, and a sulfuric acid electrolytic solution having a copper concentration of 20 to 45 g / L, a free sulfuric acid concentration of 40 to 80 g / L, and a bath temperature of 10 to 40 ° C. is used. a first step of electrolysis at a
[0003]
[Patent Document 1]
JP 61-84389 A [Patent Document 2]
Japanese Patent Publication No. 5-5903 [Patent Document 3]
Japanese Patent Publication No. 5-25956 [Patent Document 4]
Japanese Examined Patent Publication No. 7-68627 [0004]
[Problems to be solved by the invention]
However, the method of producing high-purity electrolytic copper having a purity of 99.9999% by mass or more described in Patent Document 3 cannot sufficiently reduce sulfur (hereinafter referred to as S), and a titanium plate is used as a cathode. However, the method of producing high purity electrolytic copper with a purity of 99.9999% by mass or more described in Patent Document 4 can achieve a reduction in the S content. However, it is necessary to perform electrolysis in two steps, and in the case of mass production, there are problems such as high costs because two special devices are required.
[0005]
[Means for Solving the Problems]
Therefore, the present inventors have studied from such a viewpoint to obtain a method for producing high-purity electrolytic copper having a purity of 99.9999% by mass or more using a normal apparatus. As a result, (a) when using an electrolyte containing urea instead of thiourea contained in the electrolyte used in the conventional method for producing high purity electrolytic copper, the S content contained in the obtained electrolytic copper is reduced. Can be reduced very low,
(B) At this time, urea contained in the electrolyte is 1 to 20 mg / L.
(C) Therefore, the electrolytic solution used in the method for producing high-purity electrolytic copper according to the present invention is a sulfuric acid electrolytic solution containing Cu: 20 to 50 g / L and free sulfuric acid: 100 to 150 g / L, and HCl as an additive. : 10 to 100 mg / L, glue: 10 to 50 mg / L, urea: 1 to 20 mg / L of electrolyte solution is preferable.
[0006]
This invention was made based on such knowledge,
(1) In a method for producing high-purity copper having a purity of 99.9999% by mass or more by re-electrolyzing with electrolytic copper as an anode using a sulfuric acid electrolyte, the electrolyte is an electrolyte containing urea. Production method of high purity electrolytic copper,
(2) In a method for producing high-purity copper having a purity of 99.9999% by mass or more by re-electrolyzing with electrolytic copper as an anode using a sulfuric acid electrolyte, the electrolyte contains urea: 1 to 20 mg / L A method for producing high-purity electrolytic copper, which is an electrolytic solution containing
(3) In a method for producing high purity copper having a purity of 99.9999% by mass or more by re-electrolyzing electrolytic copper using an electrolytic solution, the electrolytic solution contains Cu: 20 to 50 g / L, free sulfuric acid: It is characterized by a method for producing high-purity electrolytic copper that is an electrolytic solution containing 100 to 150 g / L, HCl: 10 to 100 mg / L, glue: 10 to 50 mg / L, and urea: 1 to 20 mg / L as additives. Is.
[0007]
In the method for producing high-purity electrolytic copper according to the present invention, the temperature of the electrolytic solution is preferably maintained within a range of 17 to 25 ° C. Therefore, the present invention
(4) It has the characteristics in the manufacturing method of the high purity electrolytic copper as described in said (1), (2) or (3) by which the temperature of electrolyte solution is hold | maintained in the range of 17-25 degreeC.
[0008]
In the method for producing high-purity electrolytic copper according to the present invention, the electrolytic solution is circulated and used, but higher-purity electrolytic copper can be produced by circulating the electrolytic solution through a micropore filter. Moreover, it is preferable that the current density supplied to electrolyte solution is 50-100 A / m < 2 >. Therefore, the present invention
(5) It has the characteristics in the manufacturing method of the high purity electrolytic copper as described in said (1), (2), (3) or (4) whose current density is 50-100 A / m < 2 >.
[0009]
When high-purity electrolytic copper is produced using the electrolytic solution containing urea of the present invention, the high-purity electrolytic copper electrodeposited on the cathode base plate has a purity of 99.9999% by mass, a smooth surface, and a cathode. It has a metal structure in which columnar crystals grow in the thickness direction from the surface of the base plate. In general, in a method for producing high-purity copper having a purity of 9.9999% by mass or more by re-electrolyzing electrolytic copper using an electrolytic solution, when a stainless steel plate is used as a canode base plate, crystal grains are refined and sulfuric acid is added. Since stainless steel and Ag, which is a solid substance in the electrolyte, are entrained in the crystal grains, and Ag and S in the obtained electrolytic copper increase, high-purity electrolytic copper with sufficient purity can be obtained with a stainless steel plate. On the other hand, when a titanium plate is used as a cathode base plate, the crystal grain of the obtained electrolytic copper becomes large, the surface is smooth, sulfur in sulfuric acid and silver which is a solid substance in the electrolyte are crystallized. It is said that it is less likely to be caught in the grains, and therefore the content of Ag, S, etc. is reduced.
However, in this invention, even if a stainless steel plate is used as the canode mother plate, high-purity electrolytic copper can be obtained similarly. The reason for this is that electrodeposited copper obtained by electrolyzing a stainless steel plate as a canode base plate using an electrolyte containing urea is made of a stainless steel plate, even if the crystal grains produced in the initial electrodeposition are fine. The electrolytic copper electrodeposited on the cathode grows remarkably as columnar crystals parallel to the thickness direction from the cathode base plate surface, and impurities such as S are discharged to the electrolyte side as the columnar crystals grow. It is considered that high purity electrolytic copper can be obtained. The electrolytic copper electrodeposited on the cathode base plate obtained in the present invention has an average thickness of columnar crystals in the cut surface cut in parallel to the electrolytic surface at a thickness position that is 1/2 the thickness of the electrodeposited electrolytic copper. Is in the range of 50 to 300 μm.
[0010]
Next, the reason why the composition, temperature and current density of the electrolytic solution in the method for producing high purity electrolytic copper of the present invention are limited as described above will be described.
(A) Electrolyte composition:
Urea contained in the urea electrolyte is a component that allows the electrolytic copper electrodeposited on the cathode to grow into a columnar crystal without defects by being contained in the electrolyte as an additive, but its content is less than 1 mg / L In this case, it is not preferable because fine flaws or poor electrodeposition occurs on the electrodeposited electrolytic copper surface. On the other hand, when the content exceeds 20 mg / L, the electrodeposited electrolytic copper surface is relatively large. It is not preferable because it generates impurities or cracks in the columnar crystal and entraps impurities. Therefore, the content of urea contained in the electrolytic solution is set to 1 to 20 mg / L (more preferably, 1.5 to 5 mg / L).
[0011]
The glue contained in the glue electrolyte is a component that makes the surface of electrolytic copper electrodeposited on the cathode dense and smooth, but if its content is less than 10 mg / L, the desired effect cannot be obtained, while 50 mg / L If the content exceeds V, the resistance of the electrolytic solution increases and the electrolysis efficiency deteriorates. Therefore, the glue content was set to 10 to 50 mg / L. A more preferable range of the content of glue contained in the electrolytic solution is 15 to 30 mg / L.
[0012]
Chloride ion concentration Chloride ions added as HCl have the effect of reducing the Ag contained in the electrodeposited electrolytic copper and smoothing the surface of the electrolytic copper. If it is less than 10 mg / L, the desired effect cannot be obtained. On the other hand, if it exceeds 100 mg / L, the obtained cathode surface is not smooth and fine pores are generated on the surface, which is not preferable. Therefore, the chlorine ion contained in electrolyte solution was set to 10-100 mg / L. A more preferable range of the content of chlorine ions contained in the electrolytic solution is 20 to 60 mg / L.
[0013]
The copper contained in the copper concentration electrolytic solution has the effect of increasing the denseness of the electrodeposited electrolytic copper and further improving the smoothness, but less than 20 g / L is not preferable because the productivity is reduced, On the other hand, if it exceeds 50 g / L, the denseness deteriorates, which is not preferable. Therefore, the copper concentration contained in the electrolytic solution is set to 20 to 50 g / L (more preferably 35 to 45 g / L).
[0014]
Free sulfuric acid concentration Free sulfuric acid contained in the electrolytic solution increases the density of the electrodeposited electrolytic copper and further improves the smoothness. However, if it is less than 100 g / L, the confidentiality and smoothness deteriorate. On the other hand, if it exceeds 150 g / L, the solubility of copper sulfate decreases and the denseness deteriorates. Therefore, the copper concentration contained in the electrolytic solution is set to 100 to 150 g / L (more preferably, 115 to 140 g / L).
[0015]
(B) Electrolytic conditions Electrolyte temperature If the temperature of the electrolyte solution containing urea is less than 17 ° C, copper sulfate in the electrolyte solution is crystallized and the concentration of the electrolyte solution changes. On the other hand, if it exceeds 25 ° C, electrodeposition is performed. This is not preferable because the denseness and smoothness of the electro-copper are deteriorated. Therefore, the temperature of the electrolyte containing urea was set to 17 to 25 ° C.
[0016]
Current density when electrolyzing using an electrolyte containing urea is less than 50 A / m 2, which is not preferable because the current density becomes too low and the productivity deteriorates. On the other hand, when the current density exceeds 100 A / m 2 , This is not preferable because the denseness and smoothness of the electrodeposited electrolytic copper are hindered. Therefore, the current density was set to 50~100A / m 2. A more preferable range of the current density is 60 to 80 A / m 2 .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Examples 1 to 6, Comparative Examples 1 to 2 and Conventional Example Purity: 99.99 mass% of commercially available electrolytic copper was prepared, and this electrolytic copper was used as an anode, and this was stored in a polypropylene cloth bag to produce an anode bag. did. Further, a cathode base plate made of SUS304 plate was prepared. Furthermore, an electrolyte solution containing urea, glue, HCl, copper, and free sulfuric acid shown in Table 1 was prepared. An electrolyte containing thiourea was also prepared. Example using the anode bag and the cathode mother plate made of SUS304, using the electrolytic solution shown in Table 1, and circulating the electrolytic solution through a micropore filter under the conditions shown in Table 1. 1-6, Comparative Examples 1-2, and the prior art example were implemented. Impurities contained in electrolytic copper electrodeposited on the cathodes in Examples 1 to 6, Comparative Examples 1 and 2 and the conventional example were measured, and the results are shown in Table 2. Furthermore, when the cross section of the electrolytic copper electrodeposited on the cathode obtained in Examples 1 to 6 was cut and the structure was measured, it was found that it had a structure in which columnar crystals grew in the thickness direction of the copper cathode plate. Measure the average thickness of the columnar crystals on the cut surface (that is, the cut surface cut at the position AA in FIG. 1) cut in parallel with the electrolytic surface at a thickness position that is 1/2 the thickness of the electrolytic copper. The results are shown in Table 1. As an example, the cross-sectional structure of the electrodeposited high-purity electrolytic copper produced in Example 1 is shown in FIG. 1 as a metal structure photograph, and FIG. 2 shows the cross-sectional structure of the electrodeposited high-purity electrolytic copper produced in the conventional example. Is shown as a metallographic photograph. In FIG. 1 and FIG. 2, the upper part of the metallographic photograph shows the surface of electrolytic copper electrodeposited on the cathode, and the lower part shows the surface in contact with the electrodeposited electrolytic copper cathode. When FIG. 1 and FIG. 2 are compared, it can be seen that the electrodeposited electrode in Example 1 has remarkably developed columnar crystals compared to the electrodeposited electrodeposited electrode in the conventional example.
[0018]
[Table 1]
[Table 2]
From the results shown in Tables 1 and 2, the high-purity electrolytic copper obtained in Examples 1 to 6 that are electrolyzed using an electrolytic solution containing urea is obtained in a conventional example in which electrolysis is performed using an electrolytic solution containing thiourea. It can be seen that the S content is particularly small compared to the obtained high-purity electrolytic copper. Moreover, the high purity electrolytic copper obtained in Comparative Examples 1 and 2 that electrolyze using an electrolytic solution containing urea with a value outside the conditions of the present invention has undesirable properties such as an increase in S concentration and Ag concentration. I knew it would appear.
[0021]
【The invention's effect】
As described above, according to the method of the present invention, high-purity copper having an extremely low S content with a purity of 99.9999% by mass or more can be obtained at a low cost, and particularly has an excellent effect in industrial fields such as semiconductor devices. Is.
[Brief description of the drawings]
1 is a metallographic photograph of a cross section of electrodeposited electrolytic copper obtained in Example 1. FIG.
FIG. 2 is a metallographic photograph of a cross section of electrodeposited electrolytic copper obtained in a conventional example.
Claims (7)
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| JP2006253345A (en) * | 2005-03-10 | 2006-09-21 | Furukawa Circuit Foil Kk | High purity electrolytic copper foil and manufacturing method thereof |
| CN102534658B (en) * | 2012-03-01 | 2014-07-23 | 崔海林 | Method for preparing electrolytic copper fast with copper ore |
| CN104047021A (en) * | 2013-03-13 | 2014-09-17 | 江苏瑞崚新材料科技有限公司 | Method for preparing 6N-Cu by electrolysis technology |
| WO2018221724A1 (en) * | 2017-06-01 | 2018-12-06 | 三菱マテリアル株式会社 | High-purity electrolytic copper |
| EP3636803A4 (en) | 2017-06-01 | 2021-02-24 | Mitsubishi Materials Corporation | Method for producing high-purity electrolytic copper |
| CN107974695B (en) * | 2017-11-17 | 2020-01-10 | 金川集团股份有限公司 | Method for producing ultra-high pure copper by one-step electrolysis method |
| KR102237348B1 (en) * | 2018-11-29 | 2021-04-07 | 에스지금속 주식회사 | Recovery method of copper and precious metal by electrolysis of crude copper containing precious metal using copper chloride solution |
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| JP7454329B2 (en) | 2017-06-01 | 2024-03-22 | 三菱マテリアル株式会社 | High purity electrical copper plate |
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