JP2011236461A - Flat type gold-coated copper ribbon for high temperature semiconductor device - Google Patents

Flat type gold-coated copper ribbon for high temperature semiconductor device Download PDF

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JP2011236461A
JP2011236461A JP2010107778A JP2010107778A JP2011236461A JP 2011236461 A JP2011236461 A JP 2011236461A JP 2010107778 A JP2010107778 A JP 2010107778A JP 2010107778 A JP2010107778 A JP 2010107778A JP 2011236461 A JP2011236461 A JP 2011236461A
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Prior art keywords
gold
copper
coating layer
purity
ribbon
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Michitaka Mikami
道孝 三上
Shinichiro Nakajima
伸一郎 中島
Hiroshi Matsuo
寛 松尾
Kenichi Miyazaki
兼一 宮崎
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Tanaka Denshi Kogyo KK
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Tanaka Denshi Kogyo KK
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Priority to JP2010107778A priority Critical patent/JP2011236461A/en
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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physical Vapour Deposition (AREA)
  • Wire Bonding (AREA)

Abstract

PROBLEM TO BE SOLVED: To improve ultrasonic bondability and high temperature reliability in a bonding ribbon which connects between a semiconductor device pad and a lead on the side of a nickel (Ni)-coated substrate simultaneously at a number of points.SOLUTION: A gold-coated copper ribbon includes a copper core material and a gold coating layer. The copper core material is made of copper (Cu) having a purity of 99.9% or more which has a Vickers hardness of 70 Hv or less to impart conductivity and loop formability. The coating layer is made of gold (Au) having a purity of 99.9% or more having a fine granular crystal structure which is formed by magnetron sputtering of the gold (Au) in a rare gas atmosphere such as argon gas (Ar). Thus, the core material has the same Vickers hardness as the coating layer to prevent the damage of an aluminum pad and improve bondability. The gold fine crystal structure formed by magnetron sputtering in a rare gas atmosphere has a hardness higher than a gold (Au) bulk, and the granular structure suppresses heat broadening during bonding.

Description

本発明は、電子部品および半導体素子パッドを多数箇所同時に超音波接合し、ループ状に接続するための平角状金被覆銅リボン、特に、パワー半導体素子のアルミパッドとニッケル（Ｎｉ）被覆基板側リード部とを接続するための平角状金被覆銅リボンに関する。   The present invention relates to a rectangular gold-coated copper ribbon for ultrasonic bonding of electronic parts and semiconductor element pads at the same time and connecting them in a loop shape, in particular, an aluminum pad of a power semiconductor element and a nickel (Ni) -coated substrate side lead. The present invention relates to a flat gold-coated copper ribbon for connecting parts.

半導体素子に搭載されたボンディングパッドとして、主に純度９９．９９％のアルミニウム（Ａｌ）金属またはそれに０．５〜１．２質量％のシリコン（Ｓｉ）や０．２〜０．７質量％の銅（Cu）または、これらを組み合わせたＡｌ−Ｃｕ−Ｓｉなどの合金からなるアルミパッドが使用される。
また、ニッケル（Ｎｉ）被覆基板側リードには、電気めっきおよびスパッタによりニッケル（Ｎｉ）被覆層が形成された銅（Ｃｕ）合金や鉄（Ｆｅ）合金、あるいは、これらからなるリードを搭載したセラミックスが主に使用されている。このアルミパッドとニッケル（Ｎｉ）被覆リードフレーム等を超音波接合によって接続するのに、平角状銅リボンが使用される。平角状銅リボンのボンディング方法は、銅リボンの上に超硬ツールを押しつけ、その荷重および超音波振動のエネルギーにより接合するものである。超音波印加の効果は、銅リボンの変形を助長するための接合面積の拡大と、銅リボン表面に自然に形成された酸化膜を破壊・除去することにより、銅（Ｃｕ）等の金属原子を下面に露出させ、対抗するアルミニウム（Ａｌ）の第一ボンド面およびニッケル（Ｎｉ）の第二ボンド面と銅リボン面との界面に塑性流動を発生させ、互いに密着する新生面を漸増させながら、両者を原子間結合させることにある。 As a bonding pad mounted on a semiconductor element, mainly aluminum (Al) metal having a purity of 99.99% or silicon (Si) of 0.5 to 1.2% by mass or 0.2 to 0.7% by mass of aluminum (Al) metal. An aluminum pad made of an alloy such as copper (Cu) or a combination thereof such as Al—Cu—Si is used.
In addition, the nickel (Ni) coated substrate side lead has a copper (Cu) alloy or iron (Fe) alloy in which a nickel (Ni) coating layer is formed by electroplating and sputtering, or a ceramic equipped with a lead made of these. Is mainly used. A rectangular copper ribbon is used to connect the aluminum pad to a nickel (Ni) -coated lead frame or the like by ultrasonic bonding. A flat copper ribbon bonding method is a method in which a cemented carbide tool is pressed onto a copper ribbon and bonded by the load and energy of ultrasonic vibration. The effect of applying ultrasonic waves is to increase the bonding area to promote the deformation of the copper ribbon and destroy / remove the oxide film naturally formed on the surface of the copper ribbon, thereby removing metal atoms such as copper (Cu). Both surfaces are exposed to the lower surface, and plastic flow is generated at the interface between the first bond surface of aluminum (Al) and the second bond surface of nickel (Ni) and the copper ribbon surface, and the newly formed surfaces that are in close contact with each other are gradually increased. Is to bond atoms between atoms.

このような半導体素子のアルミ電極パッドおよびこれと接続するニッケル（Ｎｉ）被覆基板側のリードとは、上記したように、それぞれ材質が異なる。このため冶金的な溶融過程を伴わない超音波接合によっても、これらの接合界面では、Ｃｕリボン表面の酸化や硫化による変質層の存在により、必ずしも強固な、信頼性の高い接合は達成できない。
これらの解決策として、銅（Ｃｕ）素材に金（Ａｕ）の電気めっきをし、その後複数回連続伸線して金（Ａｕ）を２．５μｍ及び０．８μｍ被覆した熱圧着ボールによるボンディングワイヤが提案されている（特開昭５９−１５５１６１号公報および特開２００４−００６７４０号公報、後述の特許文献１及び２）。これらのボンディングワイヤの技術をボンディングリボンの超音波接合に適用すると、ボンディングワイヤの場合は接合する一方の半導体素子側の電極がアルミニウム（Ａｌ）パッドであり、他方がリードフレームなどの異種金属であるため、ボンディングリボンの場合も、アルミニウムパッドとニッケル（Ｎｉ）の電気めっきやクラッドが被覆されたコバール等のリードフレームに対して金被覆銅リボンの金属面を接合するものとなる。
しかし、この金（Ａｕ）被膜の厚い金被覆銅リボンは、金（Ａｕ）がニッケル（Ｎｉ）との接合性が悪いため、ニッケル（Ｎｉ）被覆基板側のリードとうまく第二ボンドすることができなかった。 As described above, the material of the aluminum electrode pad of the semiconductor element and the lead on the nickel (Ni) -coated substrate side connected to the aluminum electrode pad are different. For this reason, even by ultrasonic bonding that does not involve a metallurgical melting process, strong and highly reliable bonding cannot always be achieved at these bonding interfaces due to the presence of a deteriorated layer due to oxidation or sulfuration of the Cu ribbon surface.
As a solution to these problems, a bonding wire is formed by thermocompression bonding balls in which gold (Au) is electroplated on a copper (Cu) material, and then continuously drawn a plurality of times to coat gold (Au) with a thickness of 2.5 μm and 0.8 μm. Have been proposed (Japanese Patent Laid-Open Nos. 59-155161 and 2004-006740, and Patent Documents 1 and 2 described later). When these bonding wire technologies are applied to ultrasonic bonding of bonding ribbons, in the case of bonding wires, one of the semiconductor element side electrodes to be bonded is an aluminum (Al) pad, and the other is a dissimilar metal such as a lead frame. Therefore, also in the case of the bonding ribbon, the metal surface of the gold-coated copper ribbon is bonded to a lead frame such as Kovar or the like coated with an aluminum pad and nickel (Ni) electroplating or cladding.
However, this gold-coated copper ribbon with a thick gold (Au) coating has a poor bondability with gold (Au) and nickel (Ni). could not.

このため銅（Ｃｕ）の酸化および硫化を防止しつつ、このような第二ボンドの接合性の悪さを克服するため、金（Ａｕ）被覆層を薄くすることも行われている。
特開２００７−３２４６０３号公報（後述の特許文献３）は、そのような要求に応えて提案されたものとみることもでき、導電性の高い銅（Ｃｕ）を芯材として金（Ａｕ）を被覆して高い導電性とアルミニウムパッドに対する超音波接合性を両立させたものである。
この発明によれば、ワイヤ内側の銅（Ｃｕ）層に対して、外側の金（Ａｕ）で被覆することによって信頼性の高い超音波ボンディングによる接合が達成できるとしている。それによれば、内側の銅（Ｃｕ）によって高い導電性を達成し、それに対して１／１０よりも小さい厚さの金被覆層、実用上厚さ１〜２００nm、有利には約２０〜２５nmの金（Ａｕ）被覆層によって、アルミニウムパッドに対する優れた超音波接合が達成できるとしている。
このような金被覆銅リボンによって1ヶ所で一気に超音波接合する場合、銅（Ｃｕ）が加工硬化をしなければ、銅芯材によって高い導電性は達成しうる。
しかしながら、金被覆銅リボンの多数箇所をアルミパッドへ同時に超音波接合する場合、接合時に発生する熱によって接合箇所における銅（Ｃｕ）は変形し、銅（Ｃｕ）の加工硬化によってアルミパッドにクラック等が入りやすくなる。また、その接合界面には銅（Ｃｕ）とアルミニウム（Ａｌ）との金属間化合物ができやすくなり、結果として接合強度にはバラツキが表れる。さらに高温放置すると、接合界面のボイド等からにアルミニウム（Ａｌ）の酸化膜が発達して接合界面における金被覆銅リボンの接合強度が低下し、高温接合信頼性は十分とはいえないものであった。
なお、パワー半導体等の高温半導体素子用金被覆銅リボンを用いた超音波接合は、第一ボンド後ループを形成して第二ボンドをし、場合によっては更にそれ以上の複数ボンドを行い、最終ボンド後にカッターで金被覆銅リボンを切断するものである。 For this reason, in order to overcome such poor bondability of the second bond while preventing oxidation and sulfidation of copper (Cu), the gold (Au) coating layer is also made thin.
Japanese Unexamined Patent Publication No. 2007-324603 (Patent Document 3 to be described later) can be considered to have been proposed in response to such a request, and gold (Au) is formed using copper (Cu) having high conductivity as a core material. It is coated to achieve both high conductivity and ultrasonic bondability to an aluminum pad.
According to this invention, it is said that highly reliable bonding by ultrasonic bonding can be achieved by covering the copper (Cu) layer inside the wire with the outside gold (Au). According to it, a high conductivity is achieved by the inner copper (Cu), whereas a gold coating layer with a thickness of less than 1/10, practically a thickness of 1 to 200 nm, preferably about 20 to 25 nm. It is said that excellent ultrasonic bonding to an aluminum pad can be achieved by the gold (Au) coating layer.
When ultrasonic bonding is performed at once in a single place with such a gold-coated copper ribbon, high conductivity can be achieved by the copper core material if the copper (Cu) is not work hardened.
However, when a large number of gold-coated copper ribbons are simultaneously ultrasonically bonded to an aluminum pad, the copper (Cu) at the bonded portion is deformed by heat generated during the bonding, and the aluminum pad is cracked by the work hardening of the copper (Cu). Is easier to enter. Further, an intermetallic compound of copper (Cu) and aluminum (Al) is easily formed at the joint interface, and as a result, the joint strength varies. If left at higher temperatures, an aluminum (Al) oxide film develops from voids at the bonding interface and the bonding strength of the gold-coated copper ribbon at the bonding interface decreases, and the high-temperature bonding reliability is not sufficient. It was.
In addition, ultrasonic bonding using a gold-coated copper ribbon for high-temperature semiconductor elements such as power semiconductors forms a loop after the first bond and then a second bond. After bonding, the gold-coated copper ribbon is cut with a cutter.

上記の金被覆銅リボンで接合信頼性が問題となるのは、１３０〜１７５℃の耐熱温度を必要とする高温半導体、特にエアコン、太陽光発電システム、ハイブリッド車や電気自動車などのパワー半導体に採用される大容量の金被覆銅リボンである。例えば、車載用に使用されるパワー半導体に用いられる金被覆銅リボンは、最大で通常１５０〜１７５℃程度の接合部温度に耐える必要がある。このような高温環境下においては、金被覆銅リボンを超音波接合した場合の高温酸化も課題として挙げられ、金被覆銅リボンの接合表面を安定な皮膜で覆うなどの措置により、金被覆銅リボンの耐酸化性向上が求められる。
このような実装環境下では、金被覆銅リボンとアルミパッド電極部およびニッケル（Ｎｉ）被覆基板側リードの接合強度の確保が重要となる。 Bonding reliability becomes a problem with the above gold-coated copper ribbon because it is used for high-temperature semiconductors that require heat resistance of 130 to 175 ° C, especially power semiconductors such as air conditioners, solar power generation systems, hybrid cars, and electric cars. High capacity gold coated copper ribbon. For example, a gold-coated copper ribbon used for a power semiconductor used for in-vehicle needs to withstand a junction temperature of usually about 150 to 175 ° C. at the maximum. In such a high temperature environment, high temperature oxidation when the gold coated copper ribbon is ultrasonically bonded is also an issue, and measures such as covering the bonding surface of the gold coated copper ribbon with a stable film can be used. Improvement in oxidation resistance is required.
In such a mounting environment, it is important to ensure the bonding strength between the gold-coated copper ribbon, the aluminum pad electrode portion, and the nickel (Ni) -coated substrate side lead.

特開昭５９−１５５１６１号公報JP 59-155161 A 特開２００４−００６７４０号公報JP 2004-006740 A 特開２００７−３２４６０３号公報JP 2007-324603 A

本発明は、上記問題を解決するため、ある程度形状の大きな金（Ａｕ）被覆層を設けた金被覆銅リボンがアルミニウム（Ａｌ）の金属または合金からなる半導体素子パッドの第一ボンドで多数箇所の超音波接合によってボンディングし、第一ボンドからループを描いてニッケル（Ｎｉ）被覆基板の第二ボンドで多数箇所の超音波接合によってボンディングしても、第一ボンド時にアルミパッドにクラック等が生じることがなく、第二ボンド時においても十分な接合強度を確保することを課題とする。 In order to solve the above problems, the present invention provides a gold bond copper ribbon provided with a gold (Au) coating layer having a large shape to some extent at the first bond of a semiconductor element pad made of an aluminum (Al) metal or alloy. Even if bonding is performed by ultrasonic bonding, a loop is drawn from the first bond, and bonding is performed by ultrasonic bonding at many locations on the second bond of the nickel (Ni) -coated substrate, cracks or the like occur in the aluminum pad during the first bonding. There is no problem, and it is an object to ensure sufficient bonding strength even at the time of the second bonding.

上記課題を解決するための手段として、本発明者らは金（Ａｕ）被覆層として微細な粒状の結晶組織を利用した。
すなわち、アルミパッド電極部との第一ボンドでは、多数の突出した形状の超硬ツールを金被覆銅リボンに押し付けて金被覆銅リボンの多数箇所をアルミパッドへ一気に超音波接合するのが一般的であるが、この時銅（Ｃｕ）芯材テープが変形されて加工硬化を起こしアルミニウムパッドにクラック等をもたらすものと思われる。本発明者らは金（Ａｕ）被覆層を微細な粒状結晶を積層させた組織構造にすることで、見かけの金（Ａｕ）被覆層の厚さを厚くし、そのクッション効果によって銅（Ｃｕ）芯材テープの加工硬化の影響を弱めてアルミニウムパッドにクラック等が生じないようにした。
また、超音波接合時に発生する接合に寄与しない熱を金（Ａｕ）被覆層の粒状組織に吸収させて金（Ａｕ）被覆層をバルク組織に戻すことによって、接合部近傍の発熱を大きくして銅（Ｃｕ）の加工硬化の影響を弱めることにした。
また、第二ボンドでも、超硬ツールにより金被覆銅リボンの多数箇所を一気に超音波接合するが、この場合は、第一ボンドのようにニッケル（Ｎｉ）被覆層にクラック等が発生するような課題はない。そのため超音波接合の発熱量および超硬ツールの加圧力を大きくすることができ、金（Ａｕ）被覆層の厚さは実質的に薄く無視することができる。すなわち、金（Ａｕ）被覆層はボンディング時の荷重と超音波により破壊されるか、または、このときの熱により銅（Ｃｕ）芯材内部へと拡散するため、銅（Ｃｕ）芯材の銅（Ｃｕ）とニッケル（Ｎｉ）被覆層のニッケル（Ｎｉ）とが直接超音波接合される。 As means for solving the above problems, the present inventors have used a fine granular crystal structure as a gold (Au) coating layer.
In other words, in the first bond with the aluminum pad electrode part, it is common to press a large number of protruding carbide tools against the gold-coated copper ribbon and ultrasonically bond many points of the gold-coated copper ribbon to the aluminum pad at once. However, at this time, the copper (Cu) core material tape is deformed to cause work hardening and to cause cracks in the aluminum pad. The inventors of the present invention have made the gold (Au) coating layer into a structure in which fine granular crystals are laminated, thereby increasing the apparent thickness of the gold (Au) coating layer, and copper (Cu) due to its cushioning effect. The effect of work hardening of the core tape was weakened so that cracks and the like were not generated in the aluminum pad.
In addition, heat that does not contribute to bonding generated during ultrasonic bonding is absorbed by the granular structure of the gold (Au) coating layer, and the gold (Au) coating layer is returned to the bulk structure, thereby increasing heat generation near the bonding portion. We decided to weaken the influence of work hardening of copper (Cu).
In addition, even in the second bond, a large number of gold-coated copper ribbons are ultrasonically bonded at once with a carbide tool. In this case, cracks or the like are generated in the nickel (Ni) coating layer as in the first bond. There are no challenges. Therefore, the calorific value of ultrasonic bonding and the pressurizing force of the carbide tool can be increased, and the thickness of the gold (Au) coating layer is substantially thin and can be ignored. That is, the gold (Au) coating layer is broken by the bonding load and ultrasonic waves, or diffuses into the copper (Cu) core material by the heat at this time, so the copper of the copper (Cu) core material (Cu) and nickel (Ni) of the nickel (Ni) coating layer are directly ultrasonically bonded.

本発明の１３０〜１７５℃の環境下においても使用可能である半導体に使用する金被覆リボンは、アルミニウム（Ａｌ）の金属または合金からなる半導体素子パッドの第一ボンドおよびニッケル（Ｎｉ）被覆基板の第二ボンドを多数箇所の超音波接合によって接合し、第一ボンドと第二ボンドとのあいだをループ状に接続するための金（Ａｕ）被覆層および銅（Ｃｕ）芯材テープからなる平角状リボンにおいて、
前記銅（Ｃｕ）芯材テープは７０Ｈｖ以下のビッカース硬さをもつ純度９９．９％以上の銅（Ｃｕ）からなり、前記金（Ａｕ）被覆層はアルゴンガス（Ａｒ）やネオン（Ｎｅ）ガス等の希ガス雰囲気下でマグネトロンスパッタされた純度９９．９％以上の金（Ａｕ）からなる微細な粒状の結晶組織であることを特徴とする。 The gold-coated ribbon used for a semiconductor that can be used in an environment of 130 to 175 ° C. of the present invention is a first bond of a semiconductor element pad made of an aluminum (Al) metal or alloy and a nickel (Ni) -coated substrate. A rectangular shape composed of a gold (Au) coating layer and a copper (Cu) core tape for joining the second bond by ultrasonic bonding at a number of locations and connecting the first bond and the second bond in a loop shape. In the ribbon,
The copper (Cu) core tape is made of copper (Cu) having a Vickers hardness of 70 Hv or less and a purity of 99.9% or more, and the gold (Au) coating layer is made of argon gas (Ar) or neon (Ne) gas. It is characterized by a fine granular crystal structure made of gold (Au) having a purity of 99.9% or more that is magnetron sputtered under a rare gas atmosphere such as.

本発明における金（Ａｕ）被覆層は、純度９９．９％以上の高純度でありながら、マグネトロンスパッタされているので、硬さは純度９９．９９％以上の熱処理した金（Ａｕ）バルクの硬さ（１０ｇ加重で５０Ｈｖ）よりも２倍以上高いもの（１００〜１５０Ｈｖ）となっている。
これは、本発明の金被覆銅リボンの表面に形成される金（Ａｕ）被覆層が、希ガスが介在する低圧条件下で堆積して形成された微細な多結晶組織からなることにより、多くの内部歪みが蓄積されているためと考えられる。この歪みの原因は、金（Ａｕ）蒸発源の不純物に起因したり、真空装置中に残留する酸素や水分などに起因したりする。特に、マグネトロンスパッタリングの場合には、スパッタされる金（Ａｕ）粒子に高エネルギーが付加されるとともに、使用する希ガス、例えばアルゴン（Ａr）や残留する水分子等が巻き込まれ、特定の条件下で緻密で結晶粒の小さい多結晶膜を形成する。この金（Ａｕ）被覆層の硬さは、金（Ａｕ）の純度が９９．９質量％から９９．９９質量％へと高くなるほど低くなる傾向にある。 The gold (Au) coating layer in the present invention is magnetron sputtered while having a high purity of 99.9% or higher, and thus the hardness of the heat-treated gold (Au) bulk having a purity of 99.99% or higher is high. It is a thing (100-150Hv) higher than twice (10H weight 50Hv).
This is because the gold (Au) coating layer formed on the surface of the gold-coated copper ribbon of the present invention consists of a fine polycrystalline structure formed by depositing under a low pressure condition in which a rare gas is interposed. This is thought to be due to the accumulation of internal distortion. The cause of this distortion is due to impurities in the gold (Au) evaporation source, or due to oxygen or moisture remaining in the vacuum apparatus. In particular, in the case of magnetron sputtering, high energy is added to the gold (Au) particles to be sputtered, and a rare gas to be used, such as argon (Ar) or remaining water molecules, is involved, under specific conditions. A dense polycrystalline film with small crystal grains is formed. The hardness of the gold (Au) coating layer tends to decrease as the purity of gold (Au) increases from 99.9% by mass to 99.99% by mass.

なお、本発明の金被覆銅リボンの金（Ａｕ）被覆層は、純度９９．９％以上の金（Ａｕ）を用いているので、銅（Ｃｕ）芯材の銅（Ｃｕ）との接合性もよく、金（Ａｕ）膜自体も緻密で安定であるため、銅（Ｃｕ）芯材内部からの酸素が金（Ａｕ）被覆層を経由してアルミニウム（Ａｌ）パッドの界面に進入するのを防ぎ、アルミニウム（Ａｌ）の酸化を抑制させる効果がある。このことは実装後の高温放置試験で、金（Ａｕ）被覆層が銅（Ｃｕ）芯材へ拡散して消失した箇所であっても、アルミパッドのアルミニウム（Ａl）と銅（Ｃｕ）との接合界面に新たなアルミニウム（Ａl）酸化物が形成されていないことから裏付けられる。 In addition, since the gold (Au) coating layer of the gold-coated copper ribbon of the present invention uses gold (Au) with a purity of 99.9% or more, the bondability of the copper (Cu) core material with copper (Cu) Since the gold (Au) film itself is dense and stable, oxygen from the copper (Cu) core material enters the interface of the aluminum (Al) pad via the gold (Au) coating layer. It has an effect of preventing and suppressing oxidation of aluminum (Al). This is a high temperature storage test after mounting, even if the gold (Au) coating layer diffuses into the copper (Cu) core material and disappears, the aluminum pad aluminum (Al) and copper (Cu) This is supported by the fact that no new aluminum (Al) oxide is formed at the bonding interface.

金（Ａｕ）被覆層の上記の硬さに対して銅（Ｃｕ）芯材テープを７０Ｈｖ以下、より好ましくは６０Ｈｖ以下のビッカース硬さとすることにより、第一ボンド時におけるアルミパッドのチップダメージを抑制することが可能となる。
また、上記の金（Ａｕ）が被覆された銅（Ｃｕ）芯材テープの硬さに対して、前記金（Ａｕ）被覆層の厚さは、５０ｎｍ以上５００ｎｍ以下であり、好ましくは１００〜４００ｎｍの範囲であり、マグネトロンスパッタされた金（Ａｕ）被覆層の厚さが上記の範囲にあることによって、銅（Ｃｕ）芯材テープの硬さが最も効果を発揮する。
なお、金（Ａｕ）被覆層の厚さが薄く、前記の特許文献３で好適範囲とされているような金（Ａｕ）被膜の厚さでは、下地となる銅（Ｃｕ）芯材テープの表面性状の影響を強く受け、マグネトロンスパッタされた金（Ａｕ）被膜であっても、銅（Ｃｕ）芯材テープの表面性状がそのまま現れて結晶組織を制御することができない。また、このような金（Ａｕ）被膜では、超音波接合の際のエネルギーの集中を受けてその結晶組織を維持できないため、銅（Ｃｕ）芯材テープの加工硬化の影響がそのままアルミパッドに伝わってしまう。 By controlling the Vickers hardness of the copper (Cu) core material tape to 70 Hv or less, more preferably 60 Hv or less with respect to the above-mentioned hardness of the gold (Au) coating layer, the chip damage of the aluminum pad during the first bonding is suppressed. It becomes possible to do.
The thickness of the gold (Au) coating layer is 50 nm or more and 500 nm or less, preferably 100 to 400 nm, relative to the hardness of the copper (Cu) core material tape coated with gold (Au). When the thickness of the magnetron-sputtered gold (Au) coating layer is in the above range, the hardness of the copper (Cu) core tape is most effective.
In addition, the thickness of the gold (Au) coating layer is thin, and the thickness of the gold (Au) coating that is considered to be a suitable range in the above-mentioned Patent Document 3, the surface of the copper (Cu) core tape as a base Even with a gold (Au) film that is strongly influenced by properties and is magnetron sputtered, the surface properties of the copper (Cu) core tape appear as they are, and the crystal structure cannot be controlled. In addition, since such a gold (Au) coating cannot maintain its crystal structure due to energy concentration during ultrasonic bonding, the effect of work hardening of the copper (Cu) core tape is directly transmitted to the aluminum pad. End up.

このように、芯材表面に金（Ａｕ）被覆層を設けることによって銅（Ｃｕ）芯材テープのボンディング時における加工硬化による影響を抑止することで、第一ボンド時におけるチップダメージを防ぐとともに、チップ側のアルミパッド電極に対して安定した接合強度を確保する。また、第二ボンド時における銅（Ｃｕ）芯材がニッケル（Ｎｉ）被覆層と直接超音波接合されることで、第二ボンドの安定した接合強度を確保する。また、銅（Ｃｕ）芯材テープを純度９９．９％以上の銅（Ｃｕ）から純度９９．９９％以上の銅（Ｃｕ）ないし純度９９．９９９％以上の銅（Ｃｕ）へと純度を高めることは、上記効果をさらに向上させる効果がある。銅（Ｃｕ）の純度や微量添加元素の種類は、使用する半導体の目的に応じて適宜選択することができる。なお、純度９９．９９％以上の銅（Ｃｕ）、更には純度９９．９９９％以上の銅（Ｃｕ）のように、より高純度の銅（Ｃｕ）を使用することは、ループ形成時や第一ボンドと第二ボンドの接合時における加工硬化を低減させる効果もあり、高温半導体用途において好ましい。また、このような高純度化により、ループ形成時においては、急峻なループを描いても接合界面からはく離しにくくなる。 In this way, by providing a gold (Au) coating layer on the surface of the core material to suppress the influence of work hardening at the time of bonding of the copper (Cu) core material tape, chip damage at the time of the first bond is prevented, Stable bonding strength is secured to the aluminum pad electrode on the chip side. Moreover, the copper (Cu) core material at the time of the second bond is directly ultrasonically bonded to the nickel (Ni) coating layer, thereby ensuring stable bonding strength of the second bond. Further, the purity of the copper (Cu) core tape is increased from copper (Cu) having a purity of 99.9% or more to copper (Cu) having a purity of 99.99% or more or copper (Cu) having a purity of 99.999% or more. This has the effect of further improving the above effect. The purity of copper (Cu) and the kind of the trace additive element can be appropriately selected according to the purpose of the semiconductor to be used. Note that the use of higher-purity copper (Cu), such as copper (Cu) having a purity of 99.99% or more, and copper (Cu) having a purity of 99.999% or more, is effective at the time of loop formation or There is also an effect of reducing work hardening at the time of joining the first bond and the second bond, which is preferable in high-temperature semiconductor applications. Further, due to such high purity, it becomes difficult to peel off from the bonding interface even when a steep loop is drawn during loop formation.

また、本発明の高温半導体素子用金被覆銅リボンは、半導体の素子パッドとニッケル（Ｎｉ）被覆基板とのあいだを多数箇所の超音波接合によってループ状に接続するための金（Ａｕ）被覆層および銅（Ｃｕ）芯材テープからなる平角状金被覆銅リボンにおいて、前記銅（Ｃｕ）芯材テープは７０Ｈｖ以下のビッカース硬さをもつ純度９９．９％以上の銅（Ｃｕ）からなり、前記金（Ａｕ）被覆層は、希ガスの低圧雰囲気中でマグネトロンスパッタリングによって形成され、多くの歪みが導入されたものからなることを特徴とする。 Further, the gold-coated copper ribbon for high-temperature semiconductor elements of the present invention is a gold (Au) coating layer for connecting a semiconductor element pad and a nickel (Ni) -coated substrate in a loop shape by ultrasonic bonding at many locations. And a rectangular gold-coated copper ribbon made of a copper (Cu) core tape, the copper (Cu) core tape is made of copper (Cu) having a Vickers hardness of 70 Hv or less and a purity of 99.9% or more, The gold (Au) coating layer is formed by magnetron sputtering in a low-pressure atmosphere of a rare gas, and is composed of a material into which many strains are introduced.

金被覆銅リボン内の金（Ａｕ）の銅（Ｃｕ）内部への間の拡散による金皮膜の消失を防止するため、銅（Ｃｕ）芯材と金（Ａｕ）被覆層との間に拡散防止層を形成することは有効であって、拡散防止層は既知のニッケル（Ｎｉ）、亜鉛（Ｚｎ）あるいはチタン（Ｔｉ）、タングステン（Ｗ）、クロム（Ｃｒ）に加え、銅（Ｃｕ）と全率固溶であるパラジウム（Ｐｄ）、白金（Ｐｔ）およびその他白金族金属などをマグネトロンスパッタさせることができる。この拡散防止層は、マグネトロンスパッタによって硬くなっても、金（Ａｕ）被覆層に対してもきわめて薄く、最大でも金（Ａｕ）被覆層に対して数十％オーダー以下の膜厚に過ぎないので、第一ボンド時に拡散防止層の硬さの影響は無視することができる。 Prevention of diffusion between the copper (Cu) core material and the gold (Au) coating layer in order to prevent the disappearance of the gold film due to the diffusion of gold (Au) into the copper (Cu) inside the gold-coated copper ribbon It is effective to form a layer, and the diffusion prevention layer is made of nickel (Ni), zinc (Zn) or titanium (Ti), tungsten (W), chromium (Cr), and copper (Cu). Palladium (Pd), platinum (Pt), other platinum group metals, etc., which are solid solution, can be magnetron sputtered. Even if this diffusion prevention layer is hardened by magnetron sputtering, it is extremely thin with respect to the gold (Au) coating layer, and at most, the film thickness is only several tens of percent or less with respect to the gold (Au) coating layer. The influence of the hardness of the diffusion preventing layer during the first bonding can be ignored.

本発明で得られる金（Ａｕ）被覆層は、純度９９．９％以上の高純度でありながら、バルクの金（Ａｕ）の硬さよりも２倍以上のビッカース硬さをもち、銅（Ｃｕ）芯材の加工硬化による影響を小さくしたことを特徴とする。本発明ではこのような金（Ａｕ）被覆層を軟質の７０Ｈｖ以下のビッカース硬さをもつ純度９９．９％以上の銅（Ｃｕ）とを組み合わせることによって、高温半導体用金被覆銅リボンとしての性能を発揮することができる。
すなわち、金被覆銅リボンの多数箇所を超硬ツールによってアルミパッドと超音波接合して第一ボンドとし、その後超硬ツールによって金被覆銅リボンをループ状に形成し、その後金被覆銅リボンの多数箇所を超硬ツールによってニッケル（Ｎｉ）被覆リードフレーム等と超音波接合して第二ボンドとして接続する、代表的な超音波ボンディング工程において、第一ボンド時のチップ割れを抑制し、第一ボンド時および第二ボンド時の接合強度のバラツキが小さく、安定してボンディングできる。また、ループ形成時に急峻なループを描いても、純度９９．９％以上の高純度の金（Ａｕ）と純度９９．９％以上の高純度の銅（Ｃｕ）との密着強度が確保されており、超音波ボンディング時にそのＣｕ／Ａｕ界面が剥がれることもない。
さらに、ボンディングされた金被覆銅リボンを高温環境に放置しても、金（Ａｕ）被覆層の表面から銅（Ｃｕ）芯材テープ界面への酸素の進入を防ぐことが可能となる。 The gold (Au) coating layer obtained by the present invention has a Vickers hardness of 2 times or more than that of bulk gold (Au) while having a high purity of 99.9% or more, and copper (Cu). It is characterized by reducing the influence of work hardening of the core material. In the present invention, by combining such a gold (Au) coating layer with a soft copper (Cu) having a Vickers hardness of 70 Hv or less and a purity of 99.9% or more, performance as a gold-coated copper ribbon for high-temperature semiconductors is achieved. Can be demonstrated.
That is, many points of the gold-coated copper ribbon are ultrasonically bonded to an aluminum pad with a carbide tool to form a first bond, and then a gold-coated copper ribbon is formed in a loop shape with the carbide tool, and then many of the gold-coated copper ribbons are formed. In a typical ultrasonic bonding process where the part is ultrasonically bonded to a nickel (Ni) coated lead frame etc. with a carbide tool and connected as a second bond, chip cracking during the first bond is suppressed, and the first bond The bonding strength at the time of bonding and second bonding is small and stable bonding can be achieved. Moreover, even if a steep loop is drawn at the time of loop formation, adhesion strength between high-purity gold (Au) with a purity of 99.9% or higher and high-purity copper (Cu) with a purity of 99.9% or higher is ensured. Therefore, the Cu / Au interface is not peeled off during ultrasonic bonding.
Furthermore, even if the bonded gold-coated copper ribbon is left in a high-temperature environment, it is possible to prevent oxygen from entering from the surface of the gold (Au) coating layer to the copper (Cu) core tape interface.

本発明の金被覆銅リボンにおいて、銅（Ｃｕ）芯材テープの純度は９９．９９％以上であることが好ましい。ループ変形時の加工硬化をできるだけ少なくし、ボンディングスピードを速め、単位時間当たりの接続個数を多くするためである。銅（Ｃｕ）芯材テープの純度や種類は使用する半導体やリードフレーム等によって適宜定まるが、ボンディング時における銅（Ｃｕ）芯材テープの加工硬化および不純物の混入を避けるため、純度９９．９９５％以上とできるだけ高純度であることがより望ましい。 In the gold-coated copper ribbon of the present invention, the purity of the copper (Cu) core material tape is preferably 99.99% or more. This is to reduce the work hardening during loop deformation as much as possible, increase the bonding speed, and increase the number of connections per unit time. The purity and type of the copper (Cu) core tape is appropriately determined depending on the semiconductor and lead frame used, but the purity is 99.995% to avoid work hardening of the copper (Cu) core tape and mixing of impurities during bonding. It is more desirable that the purity be as high as possible.

本発明の金（Ａｕ）被覆層の硬さは、金（Ａｕ）バルクの硬さの２倍以上であることが好ましい。接合部における銅（Ｃｕ）芯材テープの銅（Ｃｕ）の加工硬化によるアルミニウム（Ａl）パッドのチップダメージを回避するためである。 The hardness of the gold (Au) coating layer of the present invention is preferably at least twice the hardness of the gold (Au) bulk. This is to avoid chip damage of the aluminum (Al) pad due to the work hardening of copper (Cu) of the copper (Cu) core tape at the joint.

また、純度９９．９％以上の金（Ａｕ）被覆層は、アルゴンガス（Ａr）やヘリウム（Ｈｅ）ガス等の希ガス雰囲気下でスパッタにより析出されたものであることが好ましい。 The gold (Au) coating layer having a purity of 99.9% or more is preferably deposited by sputtering in a rare gas atmosphere such as argon gas (Ar) or helium (He) gas.

銅（Ｃｕ）芯材テープ上に金（Ａｕ）を被覆する場合、析出する金（Ａｕ）の純度を確保すること、並びに、膜厚および膜質の均一性、芯材テープの角部分への析出しやすさ、銅（Ｃｕ）芯材テープの裏面へのつきまわり性などにおいては、マグネトロンスパッタよりも化学蒸着法のほうが優れている。しかし、本発明の課題となる、形成される金（Ａｕ）被覆膜が適度に硬質であり、かつ、多結晶化することにおいては、多くの歪みを導入可能であるマグネトロンスパッタの方が優れているので、本発明においてはマグネトロンスパッタを採用した。 When coating gold (Au) on a copper (Cu) core tape, ensure the purity of the deposited gold (Au), as well as uniformity of film thickness and film quality, deposition on the corners of the core tape The chemical vapor deposition method is superior to the magnetron sputtering in terms of ease of use and throwing power on the back surface of the copper (Cu) core tape. However, in the case where the gold (Au) coating film to be formed, which is the subject of the present invention, is moderately hard and is polycrystallized, magnetron sputtering that can introduce many strains is superior. Therefore, magnetron sputtering is employed in the present invention.

また、金（Ａｕ）被覆層の厚さは、ニッケル（Ｎｉ）被覆リードフレーム等と超音波接合して第二ボンドとして接続する観点から、ニッケル（Ｎｉ）との接合不良を避けるため、５００ｎｍ以下であることが好ましい。さらに、金（Ａｕ）膜厚が５０ｎｍ未満と薄すぎる場合、微細な粒状の金（Ａｕ）結晶組織が形成できず第一ボンドのチップダメージの原因となることから、５０ｎｍ以上が好ましい。より好ましくは１００〜４００ｎｍの領域であり、本領域において、耐チップダメージ性と被覆膜の密着強度のバランスが最も優れている。 In addition, the thickness of the gold (Au) coating layer is 500 nm or less in order to avoid bonding failure with nickel (Ni) from the viewpoint of ultrasonic bonding with a nickel (Ni) coated lead frame or the like to connect as a second bond. It is preferable that Furthermore, if the gold (Au) film thickness is too thin, less than 50 nm, a fine granular gold (Au) crystal structure cannot be formed, causing chip damage of the first bond. More preferably, it is a region of 100 to 400 nm, and in this region, the balance between the chip damage resistance and the adhesion strength of the coating film is most excellent.

以下、本発明の実施例を説明する。
〔銅（Ｃｕ）テープの作製〕
純度９９．９質量％の銅（Ｃｕ）板材を圧延加工して、幅２．０ｍｍ 厚さ０．１５ｍｍの銅（Ｃｕ）テープを作製した。次いで、圧延加工したテープをフル・アニールしたところ、ビッカース硬さが７０Ｈｖから５５Ｈｖになった。このフル・アニールしたテープを本発明の銅（Ｃｕ）芯材テープ「Ｘ１」として実施例と比較例に使用した。また、純度９９．９９質量％、純度９９．９９９質量％、および純度９９．９９９９質量％の銅（Ｃｕ）平圧延したものを本発明の銅（Ｃｕ）芯材テープ「Ｘ２」、「Ｘ３」、「Ｘ４」とした。
また、この銅（Ｃｕ）板材に純度９９．９質量％、０．５μｍのパラジウム（Ｐｄ）箔をスパッタにより成膜し、幅２．０ｍｍ、厚さ０．１５ｍｍの銅（Ｃｕ）芯材テープ「Ｙ」を作製した。
なお、純度９９．９９〜９９．９９９９質量％の銅（Ｃｕ）テープをフル・アニールすると、ビッカース硬さは何れも５５〜５０Ｈｖであった。 Examples of the present invention will be described below.
[Preparation of copper (Cu) tape]
A copper (Cu) plate having a purity of 99.9% by mass was rolled to produce a copper (Cu) tape having a width of 2.0 mm and a thickness of 0.15 mm. Next, when the rolled tape was fully annealed, the Vickers hardness was changed from 70 Hv to 55 Hv. This fully annealed tape was used as the copper (Cu) core tape “X1” of the present invention in the examples and comparative examples. In addition, copper (Cu) core tapes “X2” and “X3” of the present invention obtained by performing copper (Cu) flat rolling with a purity of 99.99% by mass, a purity of 99.999% by mass, and a purity of 99.9999% by mass , “X4”.
Further, a palladium (Pd) foil having a purity of 99.9% by mass and 0.5 μm is formed on the copper (Cu) plate by sputtering, and a copper (Cu) core tape having a width of 2.0 mm and a thickness of 0.15 mm. “Y” was prepared.
When a copper (Cu) tape having a purity of 99.99 to 99.9999% by mass was fully annealed, the Vickers hardness was 55 to 50 Hv.

〔金（Ａｕ）蒸発源の作製〕
純度９９．９質量％の金（Ａｕ）を蒸発源「Ａ」、純度９９．９９質量％の金（Ａｕ）を蒸発源「Ｂ」、純度９９．９９９質量％の金（Ａｕ）を蒸発源「Ｃ」、とした。また、本発明の純度を外れる２Ｎのものを「Ｄ」とした。これらの組成を表１及び表２に示す。

Figure 2011236461
[Production of gold (Au) evaporation source]
Gold (Au) with a purity of 99.9% by mass is the evaporation source “A”, gold (Au) with a purity of 99.99% by mass is the evaporation source “B”, and gold (Au) with a purity of 99.999% by mass is the evaporation source. “C”. Moreover, 2N which deviates from the purity of the present invention was designated as “D”. These compositions are shown in Tables 1 and 2.
Figure 2011236461

Figure 2011236461
Figure 2011236461

〔金被覆銅リボンの作製〕
マグネトロン・スパッタリング装置にアルゴンガスを流入し、真空度０．７Ｐａに保った。次いで、スパッタ電力を１．０kＷにして金（Ａｕ）蒸発源を加熱した。蒸発した金（Ａｕ）粒子は、直線距離で１００ｍｍ離れた室温の銅（Ｃｕ）芯材テープに、表１、および表２に示す所定の膜厚で被着させ、金（Ａｕ）被覆リボンを作製した。また、拡散防止層（中間層）は次のようにして作成した。スパッタリング装置内に中間層となる純度９９．９質量％以上の物質Ｘ のターゲットと純度９９．９質量％以上の金（Ａｕ）ターゲットを配置し、スパッタリング圧力が０．７Ｐａになるように純度９９．９９質量％以上のアルゴンガスで充填した。その後、スパッタリングにより１００mm離れた平角状銅（Ｃｕ）芯材テープへ連続的に中間層の成膜を行い、所定形状の膜厚を形成した。その後、同一圧力で金（Ａｕ）被覆層の堆積・成膜を行い、所定形状の膜厚の緻密な結晶組織からなる層を形成した。
スパッタ時間が短いため、銅（Ｃｕ）芯材テープの表面温度はほぼ室温である。 [Production of gold-coated copper ribbon]
Argon gas was introduced into the magnetron sputtering apparatus, and the degree of vacuum was maintained at 0.7 Pa. Next, the gold (Au) evaporation source was heated at a sputtering power of 1.0 kW. The evaporated gold (Au) particles are deposited on a copper (Cu) core tape at room temperature 100 mm apart at a linear distance with a predetermined film thickness shown in Table 1 and Table 2, and a gold (Au) coated ribbon is applied. Produced. The diffusion prevention layer (intermediate layer) was prepared as follows. In the sputtering apparatus, a target of the substance X 3 having a purity of 99.9% by mass or higher and a gold (Au) target having a purity of 99.9% by mass or higher are disposed in the sputtering apparatus, and the purity of 99 is set so that the sputtering pressure becomes 0.7 Pa. It was filled with 99% by mass or more of argon gas. Thereafter, an intermediate layer was continuously formed on a rectangular copper (Cu) core tape separated by 100 mm by sputtering to form a film having a predetermined shape. Thereafter, a gold (Au) coating layer was deposited and formed at the same pressure to form a layer made of a dense crystal structure having a predetermined thickness.
Since the sputtering time is short, the surface temperature of the copper (Cu) core tape is approximately room temperature.

〔硬さ測定〕
金被覆銅リボンについて、膜厚１０、５、３μｍのマグネトロンスパッタしたままの金（Ａｕ）被覆層の硬さをマイクロビッカース硬さ計で測定したところ、いずれも１００〜１５０Ｈｖ（読取値）であった。このことから、膜厚によらずＨｖ硬度は殆ど変わらないことがわかった。従って、本発明のマグネトロンスパッタにより形成される被膜は著しく硬度が高く、かつ膜厚が小さくても高い値を維持することが解る。
上記で測定した金（Ａｕ）被覆層の厚さは本発明の金（Ａｕ）被覆層の厚さよりも大きいが、Ｈｖ測定には、上記の厚さが必要であり、また、これらの被覆層形成の履歴に差異はないから、本発明範囲の金（Ａｕ）被覆層の厚さにおいても上記測定値が成り立つ。 [Hardness measurement]
With respect to the gold-coated copper ribbon, the hardness of the gold (Au) coating layer as it was magnetron sputtered with a film thickness of 10, 5, 3 μm was measured with a micro Vickers hardness meter, and all were 100 to 150 Hv (reading value). It was. From this, it was found that the Hv hardness hardly changed regardless of the film thickness. Therefore, it can be seen that the film formed by magnetron sputtering of the present invention has extremely high hardness and maintains a high value even when the film thickness is small.
Although the thickness of the gold (Au) coating layer measured above is larger than the thickness of the gold (Au) coating layer of the present invention, the above thickness is necessary for the Hv measurement, and these coating layers are also used. Since there is no difference in the formation history, the above measured value holds even for the thickness of the gold (Au) coating layer in the range of the present invention.

〔内部組織の測定〕
試料番号２の調質処理済の金被覆銅リボンを薄い王水液にて数秒間浸漬した。そして、浸漬後の金（Ａｕ）膜の表面をレーザー顕微鏡で観察した（図１、図２）。さらに、スパッタ表面を拡大（１０，０００倍）したスパッタ面（写真）を図５に示す。
これに対して、比較例として試料番号２の金（Ａｕ）と同一の組成で膜厚が５０μｍのものを純度９９．９９９質量％の銅（Ｃｕ）板材にクラッド圧延加工した、金被覆銅リボンを同様に浸漬したときの金（Ａｕ）膜の表面をレーザー顕微鏡で観察したものを図３及び４に示す。
これらの図１、図２および図５から明らかなとおり、本発明のマグネトロンスパッタ膜は金（Ａｕ）の個々の粒界が球状に区画され、独立して存在していることがわかる。これは微量の元素が金（Ａｕ）の粒界に析出して区画を形成したものと思われる。
これらの金被覆銅リボンの構成について、実施例を表1、比較例を表2に示す。 [Measurement of internal structure]
The tempered gold-coated copper ribbon of Sample No. 2 was immersed in a thin aqua regia solution for several seconds. And the surface of the gold | metal | money (Au) film | membrane after immersion was observed with the laser microscope (FIG. 1, FIG. 2). Furthermore, the sputter surface (photograph) which expanded the sputter | spatter surface (10,000 times) is shown in FIG.
On the other hand, as a comparative example, a gold-coated copper ribbon having a composition equal to that of gold (Au) of sample number 2 and a film thickness of 50 μm was clad-rolled into a copper (Cu) plate having a purity of 99.999 mass%. FIGS. 3 and 4 show the surface of the gold (Au) film observed with a laser microscope when dipped in the same manner.
As is apparent from FIGS. 1, 2 and 5, the magnetron sputtered film of the present invention shows that the individual grain boundaries of gold (Au) are divided into spherical shapes and exist independently. This is probably because a trace amount of elements precipitated at the grain boundaries of gold (Au) to form compartments.
Table 1 shows a configuration of these gold-coated copper ribbons, and Table 2 shows a comparative example.

〔接合強度試験〕
試料番号１〜５４および比較例の試料番号１〜１８の金被覆銅リボンを純度９９．９９質量％のアルミニウム（Ａｌ）板（厚さ２ｍｍ）および５μｍのニッケル（Ｎｉ）電気めっきを施した純度９９．９５質量％の銅（Ｃｕ）基板（厚さ２ｍｍ）上に超音波ボンディングした。ボンディング装置は、オーソダイン社（Ｏｒｔｈｏｄｙｎｅ
Ｅｌｅｃｒｏｎｉｃｓ Ｃｏ.）製全自動リボンボンダー３６００Ｒ型にて、８０ｋＨｚの周波数で、荷重および超音波負荷条件については、潰れ幅が１．０１〜１．０５倍になる条件で、全サンプルについて同一条件で、超音波ボンディングを実施した。
また、金被覆銅リボンのループ長は５０ｍｍで、ループ高さは３０ｍｍとし、通常条件よりもリボンや経路やツールから受ける摺動抵抗が大きくなるような条件に設定した。
そして、各試料とも接合個数：ｎ＝４０個で超音波ボンディングした場合についてボンディング中に発生したワイヤ切断回数を調べたが、これらの条件下ではいずれもワイヤ切断は発生しなかった。 [Joint strength test]
Purity obtained by subjecting the gold-coated copper ribbons of sample numbers 1 to 54 and comparative sample numbers 1 to 18 to 99.99% by mass aluminum (Al) plate (thickness 2 mm) and 5 μm nickel (Ni) electroplating Ultrasonic bonding was performed on a 99.95% by mass copper (Cu) substrate (thickness 2 mm). The bonding apparatus is Orthodyne.
ELECTRONICS CO.) Fully automatic ribbon bonder 3600R type, at a frequency of 80 kHz, with respect to the load and ultrasonic load conditions, the crushing width is 1.01 to 1.05 times, and all samples have the same conditions. Ultrasonic bonding was performed.
Further, the loop length of the gold-coated copper ribbon was 50 mm, the loop height was 30 mm, and the conditions were set such that the sliding resistance received from the ribbon, the path and the tool was larger than the normal conditions.
Each sample was examined for the number of times of wire cutting during bonding when ultrasonic bonding was performed with the number of junctions: n = 40. Under these conditions, no wire cutting occurred.

〔高温接合信頼性試験〕
接合強度は、金被覆銅リボンの側面より、デイジイ社製のＤＡＧＥ万能ボンドテスターＰＣ４０００型にて接合部側面からのシェア強度測定を実施した。
実施例および比較例の金被覆銅リボンについての信頼性試験として、ボンディング済のニッケル（Ｎｉ）被覆基板を１７５℃×５００時間に暴露した後のシェア強度を測定した。そして信頼性試験後の強度を試験実施前のシェア強度で除した値を信頼性試験後の強度比と定義し、これによって評価した。
また、判定は、信頼性試験後の強度比を基にし、信頼性試験後の強度比が０．９以上のものを二重丸（◎）で表記し、０．７以上０．９未満のものを一重丸（○）で表記し、０．７未満のものをバツ（×）印で表記した。これらの結果を実施例について表３および比較例について表４に示す。 [High temperature bonding reliability test]
The joint strength was measured from the side surface of the gold-coated copper ribbon using the DAGE Universal Bond Tester PC4000 type manufactured by Daisy Corporation.
As a reliability test for the gold-coated copper ribbons of Examples and Comparative Examples, the shear strength after the bonded nickel (Ni) -coated substrate was exposed to 175 ° C. × 500 hours was measured. A value obtained by dividing the strength after the reliability test by the shear strength before the test was defined as the strength ratio after the reliability test, and the evaluation was performed.
In addition, the determination is based on the strength ratio after the reliability test, and the strength ratio after the reliability test of 0.9 or more is indicated by a double circle (◎), and is 0.7 or more and less than 0.9. A thing was described with a single circle (O), and a thing less than 0.7 was described with a cross (x) mark. These results are shown in Table 3 for Examples and Table 4 for Comparative Examples.

Figure 2011236461
Figure 2011236461

Figure 2011236461
Figure 2011236461

表３および表４から明らかなように金（Ａｕ）被覆層の純度が重要であって、本発明範囲の蒸発源Ａ〜Ｃの純度の被覆層のものはいずれも接合強度および接合信頼性において良好な結果を得たが、それよりも純度の低い蒸発源Ｄの被覆層を形成した比較例の試料番号１３〜１８のものはすべて信頼性が不良であり、また、接合強度においても劣っていることがわかる。
また、金（Ａｕ）被覆層のマグネトロンスパッタしたままの硬さについても、本発明実施例のものは、Ｈｖ１００〜１５０の範囲にあり、接合強度および接合信頼性において良好な結果を得ている。
これに対して、比較例のものは硬さが本発明範囲にあっても、被覆層の金（Ａｕ）の純度が本発明範囲を外れるもの（比較例１３〜１８）は前記したように接合強度および接合信頼性において劣り、金（Ａｕ）被覆層の厚さが本発明範囲より薄く（試料番号１〜６）ても、あるいは厚くても（試料番号７〜１２）、良い結果が得られない。 As is apparent from Tables 3 and 4, the purity of the gold (Au) coating layer is important, and any of the coating layers having the purity of the evaporation sources A to C within the scope of the present invention is in terms of bonding strength and bonding reliability. Although good results were obtained, all of the comparative sample Nos. 13 to 18 in which the coating layer of the evaporation source D having a lower purity was formed had poor reliability, and the bonding strength was also inferior. I understand that.
Also, the hardness of the gold (Au) coating layer as it is magnetron sputtered is in the range of Hv 100 to 150 in the examples of the present invention, and good results are obtained in bonding strength and bonding reliability.
In contrast, even though the hardness of the comparative example is within the range of the present invention, the case where the purity of the gold (Au) of the coating layer is out of the range of the present invention (Comparative Examples 13 to 18) is bonded as described above. Even if the thickness of the gold (Au) coating layer is thinner than the range of the present invention (sample numbers 1 to 6) or thicker (sample numbers 7 to 12), good results can be obtained. Absent.

本発明のボンディングリボンは、車両搭載用、パワー半導体デバイスなどの急速に発展しつつある領域において高い信頼性を発揮して適用できるものであり、これらの発展分野を中心に産業発展に寄与することが期待される。   The bonding ribbon of the present invention can be applied with high reliability in a rapidly developing area such as for vehicle mounting and power semiconductor devices, and contributes to industrial development mainly in these development fields. There is expected.

図１は、本発明の金被覆銅リボンの金（Ａｕ）被覆層の上からみたレーザ顕微鏡による組織写真（対物レンズ×２０）である。FIG. 1 is a structural photograph (objective lens × 20) of a gold-coated copper ribbon of the present invention as seen from above a gold (Au) coating layer by a laser microscope. 図２は、同じく本発明の金（Ａｕ）被覆層の組織写真（対物レンズ×１５０）である。FIG. 2 is a structure photograph (objective lens × 150) of the gold (Au) coating layer of the present invention. 図３は、比較例の金被覆銅リボンの金（Ａｕ）被覆層の上から見た組織写真（対物レンズ×２０）である。FIG. 3 is a structural photograph (objective lens × 20) as seen from above the gold (Au) coating layer of the gold-coated copper ribbon of the comparative example. 図４は、比較例の金（Ａｕ）被覆層の同じく上から見た組織写真対物レンズ×１５０）である。FIG. 4 is a structure photograph objective lens × 150, similarly viewed from above, of the gold (Au) coating layer of the comparative example. 図５は、本発明の金被覆銅リボンの金（Ａｕ）被覆層の上からみた組織写真（１０、０００倍）である。FIG. 5 is a structural photograph (10,000 times) viewed from above the gold (Au) coating layer of the gold-coated copper ribbon of the present invention. 図６は、本発明の金（Ａｕ）被覆銅リボンの断面図である。FIG. 6 is a cross-sectional view of the gold (Au) -coated copper ribbon of the present invention. 図７は、従来の金（バルク）クラッドリボンにより、半導体素子のパッドとリードフレームを超音波接合によって接続した状態を示す図である。FIG. 7 is a diagram showing a state in which a pad of a semiconductor element and a lead frame are connected by ultrasonic bonding using a conventional gold (bulk) clad ribbon.

Claims (9)

アルミニウム（Ａｌ）の金属または合金からなる半導体素子パッドの第一ボンドおよびニッケル（Ｎｉ）被覆基板の第二ボンドを多数箇所の超音波接合によって接合し、第一ボンドと第二ボンドとのあいだをループ状に接続するための金（Ａｕ）被覆層および銅（Ｃｕ）芯材テープからなる平角状リボンにおいて、
前記銅（Ｃｕ）芯材テープは７０Hv以下のビッカース硬さをもつ純度９９．９％以上の銅（Ｃｕ）からなり、前記金（Ａｕ）被覆層はアルゴンガス（Ａｒ）等の希ガス雰囲気下でマグネトロンスパッタされた純度９９．９％以上の金（Ａｕ）からなる微細な粒状の結晶組織であることを特徴とする半導体素子用金被覆銅リボン。 A first bond of a semiconductor element pad made of an aluminum (Al) metal or an alloy and a second bond of a nickel (Ni) -coated substrate are bonded by ultrasonic bonding at multiple locations, and the gap between the first bond and the second bond is In a rectangular ribbon composed of a gold (Au) coating layer and a copper (Cu) core tape for connecting in a loop shape,
The copper (Cu) core tape is made of copper (Cu) having a Vickers hardness of 70 Hv or less and a purity of 99.9% or more, and the gold (Au) coating layer is in a rare gas atmosphere such as argon gas (Ar). A gold-coated copper ribbon for a semiconductor device, characterized in that it is a fine granular crystal structure made of gold (Au) having a purity of 99.9% or more, which is magnetron sputtered by 1). 前記粒状の結晶組織の結晶粒の線密度が上方向から見て１μｍあたり１０〜１００個である請求項１に記載の半導体素子用金被覆銅リボン。 2. The gold-coated copper ribbon for a semiconductor device according to claim 1, wherein a linear density of crystal grains of the granular crystal structure is 10 to 100 per 1 μm as viewed from above. 前記粒状の結晶組織の結晶粒の線密度が上方向から見て１μｍあたり10〜50個である請求項１に記載の半導体素子用金被覆銅リボン。 2. The gold-coated copper ribbon for a semiconductor device according to claim 1, wherein a linear density of crystal grains of the granular crystal structure is 10 to 50 per 1 μm as viewed from above. 前記銅（Ｃｕ）芯材テープの純度が９９．９以上である請求項１に記載の半導体素子用金被覆銅リボン。 The gold-coated copper ribbon for a semiconductor element according to claim 1, wherein the copper (Cu) core tape has a purity of 99.9 or higher. 前記金（Ａｕ）被覆層の純度が９９．９９以上である請求項１に記載の半導体素子用金被覆銅リボン。 The gold-coated copper ribbon for a semiconductor element according to claim 1, wherein the gold (Au) coating layer has a purity of 99.99 or more. 前記金（Ａｕ）被覆層の純度が９９．９９９以上である請求項１に記載の半導体素子用金被覆銅リボン。 The gold-coated copper ribbon for a semiconductor device according to claim 1, wherein the gold (Au) coating layer has a purity of 99.999 or more. 前記金（Ａｕ）被覆層の厚さが、５０〜５００ｎｍである請求項１に記載の半導体素子用金被覆銅リボン。 The gold-coated copper ribbon for a semiconductor device according to claim 1, wherein the gold (Au) coating layer has a thickness of 50 to 500 nm. 前記金被覆銅リボンの形状が、幅０．５〜１０ｍｍおよび厚さ０．０５〜１ｍｍである請求項１に記載の半導体素子用金被覆銅リボン。 The gold-coated copper ribbon for a semiconductor device according to claim 1, wherein the gold-coated copper ribbon has a width of 0.5 to 10 mm and a thickness of 0.05 to 1 mm. 前記半導体素子パッドが、０．５〜１．５質量％シリコン（Ｓｉ）または０．２〜０．７質量％銅(Cu)を含むアルミニウム(Ａｌ)合金である請求項１に記載の半導体素子用金被覆銅リボン。 2. The semiconductor element according to claim 1, wherein the semiconductor element pad is an aluminum (Al) alloy containing 0.5 to 1.5 mass% silicon (Si) or 0.2 to 0.7 mass% copper (Cu). Gold coated copper ribbon.
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