JP5519419B2 - Flat rectangular (Pd) or platinum (Pt) coated copper ribbon for high temperature semiconductor devices - Google Patents

Flat rectangular (Pd) or platinum (Pt) coated copper ribbon for high temperature semiconductor devices Download PDF

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JP5519419B2
JP5519419B2 JP2010135624A JP2010135624A JP5519419B2 JP 5519419 B2 JP5519419 B2 JP 5519419B2 JP 2010135624 A JP2010135624 A JP 2010135624A JP 2010135624 A JP2010135624 A JP 2010135624A JP 5519419 B2 JP5519419 B2 JP 5519419B2
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palladium
platinum
copper
ribbon
purity
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JP2012001746A (en
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道孝 三上
伸一郎 中島
寛 松尾
兼一 宮崎
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Tanaka Denshi Kogyo KK
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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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン、特にアルミパッドのパワー半導体素子とニッケル（Ｎｉ）被覆基板側リード部とを接続するための平角状パラジウムまたは白パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンに関する。 The present invention relates to a flat rectangular palladium (Pd) or platinum (Pt) -coated copper ribbon, particularly an aluminum pad power semiconductor element and nickel for ultrasonic bonding of electronic parts and semiconductor element pads at the same time and connecting them in a loop. (Ni) It relates to a rectangular palladium, white palladium (Pd), or platinum (Pt) -coated copper ribbon for connecting the coated substrate side lead portion.

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）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) having a purity of 0.5 to 1.2 mass% or 0.2 to 0.7 mass%. An aluminum pad made of an alloy such as copper (Cu) or a combination thereof such as Al-Cu-Si is used.
The lead on the nickel (Ni) -coated substrate side is mainly a copper (Cu) alloy or iron (Fe) alloy in which nickel (Ni) is formed by electroplating and sputtering, or a ceramic equipped with a lead made of these. Is 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 to destroy and remove the oxide film naturally formed on the copper ribbon, so that metal atoms such as copper (Cu) are removed from the bottom surface. The 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 that are exposed to each other, and while gradually increasing the new surfaces that are in close contact with each other, It is to bond 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、ボンディングワイヤのウェッジ接合技術を応用することが考えられる。すなわち、銅（Ｃｕ）極細線にパラジウム（Ｐｄ）を０．３μｍ電気めっきしたボンディングワイヤ（実開昭６０-１６０５５４号公報、後述の特許文献１）やパラジウム（Ｐｄ）または白金（Ｐｔ）を０．１μｍ化学蒸着したボンディングワイヤ（特開昭６２-０９７３６０号公報、後述の特許文献２）のウェッジ接合技術を応用することが考えられる。あるいは、パラジウム（Ｐｄ）を０．８μｍ電気めっきした後伸線したボンディングワイヤ（特開２００４-０１４８８４号公報、後述の特許文献３）について、ウェッジ接合技術を応用することが考えられる。こ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パラジウムまたは白金（Ｐｔ）被覆銅リボンの金属面を接合するものとなる。
ところが、この被覆銅リボンは、リボン幅が数百μｍから十数ｍｍあり、リボン厚さが１ｍｍ程度以下とボンディングワイヤよりも幅や厚さが一桁以上も大きくなり、パラジウム（Ｐｄ）被膜または白金（Ｐｔ）被膜が厚くなる。この被覆銅リボンを直接アルミ電極パッドに超音波接合しようとすると、アルミニウムパッドが過度に加熱されるとともに、アルミニウムパッドに対する過大な押圧力によってアルミニウムパッドが割れてしまうという課題があった。一方、パラジウム（Ｐｄ）または白金（Ｐｔ）はニッケル（Ｎｉ）との濡れ性が良いため、リードフレーム側でウェッジ接合すると、ニッケル（Ｎｉ）被覆基板側のリード上を高純度のパラジウム（Ｐｄ）や白金（Ｐｔ）が濡れ拡がり、リボン幅内で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 these solutions, it is conceivable to apply a wedge bonding technique for bonding wires. That is, a bonding wire obtained by electroplating palladium (Pd) on a copper (Cu) fine wire with a thickness of 0.3 μm (Japanese Utility Model Laid-Open No. 60-160554, Patent Document 1 described later), palladium (Pd), or platinum (Pt) is 0. It is conceivable to apply the wedge bonding technique of a bonding wire (Japanese Patent Laid-Open No. 62-097360, Japanese Patent Laid-Open Publication No. 2002-260, later) that is chemically vapor-deposited by 1 μm. Alternatively, it is conceivable to apply a wedge bonding technique to a bonding wire (Japanese Patent Application Laid-Open No. 2004-014884, Patent Document 3 described later) drawn after electroplating of palladium (Pd) with 0.8 μm. When this bonding wire technology is applied to ultrasonic bonding of bonding ribbons, in the case of bonding wires, the electrode on one semiconductor element to be bonded is an aluminum (Al) pad, and the other is a dissimilar metal such as a lead frame. In the case of the bonding ribbon, the metal surface of the palladium or platinum (Pt) -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 clad.
However, this coated copper ribbon has a ribbon width of several hundred μm to several tens of mm, the ribbon thickness is about 1 mm or less, and the width and thickness are larger by one digit or more than the bonding wire, and the palladium (Pd) coating or The platinum (Pt) film becomes thicker. If this coated copper ribbon is to be ultrasonically bonded directly to an aluminum electrode pad, the aluminum pad is excessively heated and the aluminum pad is cracked by an excessive pressing force against the aluminum pad. On the other hand, palladium (Pd) or platinum (Pt) has good wettability with nickel (Ni), so when wedge bonding is performed on the lead frame side, high purity palladium (Pd) is formed on the lead on the nickel (Ni) coated substrate side. Further, platinum (Pt) spreads out and the second bond could not be successfully performed within the ribbon width.

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部の濡れ拡がりを克服するため、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層を薄くすることも考えられうる。
特開２００７−０１２７７６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）を芯材としてパラジウム（Ｐｄ）または白金（Ｐｔ）を電気めっきした後、伸線・熱処理をして外皮層が０．０１６μｍまたは０．００７μｍにしたボンディングワイヤである。この発明によれば、外側のパラジウム（Ｐｄ）等を薄くするため、第二ボンドにおける接合性の濡れ拡がりの課題を解決する可能性がある。また、熱処理による拡散層を設け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。
しかしながら、パラジウム（Ｐｄ）または白金（Ｐｔ）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、外皮層が薄いため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）の加工硬化の影響が直接アルミ電極パッドに伝わるため、アルミパッドにクラック等が入りやすくなる。また、電極パッドの接合界面には銅（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、高温環境下で使用すると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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンの接合強度がなくなり、高温接合信頼性は十分とはいえないものとなる。
なお、パワー半導体等の高温半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンを切断するものである。 For this reason, it is conceivable to reduce the thickness of the palladium (Pd) or platinum (Pt) coating layer in order to overcome the wetting and spreading of the joint portion of the second bond while preventing the oxidation and sulfidation of copper (Cu). sell.
Japanese Patent Laid-Open No. 2007-012776 (Patent Document 3 to be described later) can be regarded as proposed in response to such a demand, and palladium (Pd) or copper (Cu) having high conductivity as a core material is considered. This is a bonding wire obtained by electroplating platinum (Pt) and then drawing and heat treatment to make the outer skin layer 0.016 μm or 0.007 μm. According to this invention, since the outer palladium (Pd) or the like is thinned, there is a possibility of solving the problem of wettability of the bondability in the second bond. Further, it is said that highly reliable joining by ultrasonic bonding can be achieved by providing a diffusion layer by heat treatment.
However, when a large number of palladium (Pd) or platinum (Pt) -coated copper ribbons are simultaneously ultrasonically bonded to an aluminum pad, the outer layer is thin, so the copper (Cu) at the bonded portion is deformed by heat generated during bonding, Since the influence of work hardening of copper (Cu) is directly transmitted to the aluminum electrode pad, cracks and the like are easily generated in the aluminum pad. In addition, an intermetallic compound of copper (Cu) and aluminum (Al) is easily formed at the bonding interface of the electrode pad, and as a result, the bonding strength varies when used in a high temperature environment. If left at a higher temperature, an oxide film of aluminum (Al) develops from voids at the bonding interface, and the bonding strength of the palladium (Pd) or platinum (Pt) -coated copper ribbon at the bonding interface disappears, and high-temperature bonding reliability is sufficient It cannot be said.
Note that ultrasonic bonding using palladium (Pd) or platinum (Pt) -coated copper ribbons for high-temperature semiconductor elements such as power semiconductors forms a loop after the first bond to form a second bond. The plurality of bonds described above are performed, and the palladium (Pd) or platinum (Pt) -coated copper ribbon is cut with a cutter after the final bond.

上記のパラジウム（Ｐｄ）又は白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンの接合表面を安定な皮膜で覆うなどの、パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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。
実開昭６０-１６０５５４号公報 特開昭６２-０９７３６０号公報 特開２００４-０１４８８４号公報 「Aspectroellipsometric investigation of the effect of argon partial pressure onsputtered palladium films」,BrianT. Sullivan et al., 3390, J. Vac. Sci. Techol. A 5(6), Nov/Dec 1987,PP3399-3407 The above-mentioned palladium (Pd) or platinum (Pt) -coated copper ribbon has a problem of bonding reliability because it is a high-temperature semiconductor requiring a heat-resistant temperature of 130 to 175 ° C., particularly an air conditioner, a solar power generation system, a hybrid vehicle, It is a large-capacity palladium (Pd) or platinum (Pt) -coated copper ribbon used for power semiconductors such as electric vehicles. For example, palladium (Pd) or platinum (Pt) -coated copper ribbons used for power semiconductors used in vehicles need 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 ultrasonically bonding a palladium (Pd) or platinum (Pt) -coated copper ribbon is cited as an issue, and bonding of palladium (Pd) or platinum (Pt) -coated copper ribbon is an issue. Improvement in oxidation resistance of palladium (Pd) or platinum (Pt) -coated copper ribbons such as covering the surface with a stable film is required.
In such a mounting environment, it is important to ensure the bonding strength between the palladium (Pd) or platinum (Pt) -coated copper ribbon, the aluminum pad electrode portion, and the nickel (Ni) -coated substrate side lead.
Japanese Utility Model Publication No. 60-160554 JP 62-097360 A JP 2004-014884 A "Aspectroellipsometric investigation of the effect of argon partial pressure onsputtered palladium films", BrianT. Sullivan et al., 3390, J. Vac. Sci. Techol. A 5 (6), Nov / Dec 1987, PP3399-3407

本発明は、上記課題を解決するため、ある程度形状の大きなパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層を設けたパラジウム（Ｐｄ）または白金（Ｐｔ）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リボン幅を超えてぬれ拡がることがなく十分な接合強度を確保することを本発明の課題とする。 In order to solve the above-mentioned problems, the present invention provides a metal or alloy in which palladium (Pd) or platinum (Pt) -coated copper ribbon provided with a palladium (Pd) or platinum (Pt) coating layer having a certain shape is aluminum (Al). Bonding by ultrasonic bonding at multiple locations with the first bond of the semiconductor element pad made of, and bonding by ultrasonic bonding at multiple locations with the second bond of the nickel (Ni) coated substrate by drawing a loop from the first bond It is an object of the present invention to ensure sufficient bonding strength without causing cracks or the like in the aluminum pad at the time of the first bonding and without spreading beyond the ribbon width 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、本発明者らはパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層を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、多数箇所が突出された超硬ツールをパラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンに押し付けてパラジウム（Ｐｄ）または白金（Ｐｔ）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なものであるが、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。本発明者らはパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層を銅（Ｃｕ）芯材と拡散させることなく銅（Ｃｕ）芯材テープ上に微細な粒状結晶を直接積層させた組織構造にすることで、見かけのパラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の粒状組織に吸収させてパラジウム（Ｐｄ）または白金（Ｐｔ））被覆層をバルク組織に戻すことによって、接合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、超硬ツールによりパラジウム（Ｐｄ）または白金（Ｐｔ）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るが、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の厚さは実質的に薄く、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層が濡れ拡がることはない。すなわち、本発明に係るパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の溶け出し量がわずかである。このため、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が、パラジウム（Ｐｄ）または白金（Ｐｔ）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）芯材内部あるいは被覆層のニッケル（Ｎｉ）内部へと拡散してパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層がリボン幅を超えて濡れ広がることはない。 As means for solving the above problems, the present inventors used a fine granular crystal structure for the palladium (Pd) or platinum (Pt) coating layer.
That is, in the first bond with the aluminum pad electrode part, a carbide tool with a large number of protrusions is pressed against a palladium (Pd) or platinum (Pt) -coated copper ribbon to form a palladium (Pd) or platinum (Pt) -coated copper ribbon. It is common to ultrasonically bond a number of locations to an aluminum pad at once, but at this time, the copper (Cu) core tape is deformed to cause work hardening and to cause cracks in the aluminum pad. . The present inventors have a structure in which fine granular crystals are directly laminated on a copper (Cu) core material tape without diffusing the palladium (Pd) or platinum (Pt) coating layer with the copper (Cu) core material. Thus, the apparent palladium (Pd) or platinum (Pt) coating layer is thickened, and the effect of work hardening of the copper (Cu) core tape is weakened by the cushion effect so that cracks and the like do not occur in the aluminum pad. I made it. Also, heat that does not contribute to bonding generated during ultrasonic bonding is absorbed by the granular structure of the palladium (Pd) or platinum (Pt) coating layer, and the palladium (Pd) or platinum (Pt)) coating layer is returned to the bulk structure. Therefore, it was decided to increase the heat generation near the joint and weaken the influence of work hardening of copper (Cu).
Also, even in the second bond, many parts of palladium (Pd) or platinum (Pt) -coated copper ribbon are ultrasonically bonded at once with a carbide tool. In this case, a nickel (Ni) coating layer is used as in the first bond. There are no problems that cause cracks. Therefore, although the heat generation amount of ultrasonic bonding and the pressing force of the carbide tool can be increased, the thickness of the palladium (Pd) or platinum (Pt) coating layer is substantially thin, and the palladium (Pd) or platinum (Pt) ) The coating layer does not spread out. That is, the amount of the palladium (Pd) or platinum (Pt) coating layer according to the present invention is slight. For this reason, copper (Cu) of the copper (Cu) core material and nickel (Ni) of the nickel (Ni) coating layer are directly ultrasonically bonded, but the palladium (Pd) or platinum (Pt) coating layer is bonded. It is destroyed by the load of time and ultrasonic waves, or is diffused into the copper (Cu) core material or nickel (Ni) of the coating layer by the heat at this time, and is coated with palladium (Pd) or platinum (Pt) The layer does not spread wet beyond the ribbon width.

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パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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、前記パラジウム（Ｐｄ）または白金（Ｐｔ）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、室温に保持された前記銅（Ｃｕ）芯材テープ上に、マグネトロンスパッタされた５０〜５００ｎｍ厚の純度９９．９％％以上のパラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) -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 with a second bond by ultrasonic bonding at multiple locations, and a palladium (Pd) or platinum (Pt) coating for connecting the first bond and the second bond in a loop In a flat ribbon composed of a layer and 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, and the palladium (Pd) or platinum (Pt) coating layer is made of argon gas (Ar) or Palladium (Pd) having a purity of 99.9% or more having a thickness of 50 to 500 nm and magnetron sputtered on the copper (Cu) core material tape held at room temperature in a rare gas atmosphere such as neon (Ne) gas. Alternatively, it is characterized by a fine granular crystal structure made of platinum (Pt).

本発明におけるパラジウム（Ｐｄ）または白金（Ｐｔ）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％以上の熱処理したパラジウム（Ｐｄ）または白金（Ｐｔ）バルクの硬さ（１０ｇ加重でいずれも５０Ｈｖ）よりも３倍程度高いもの（１５０Ｈｖ前後）となっている。
これは、本発明のパラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンの表面に直接形成されるパラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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においては、スパッタされるパラジウム（Ｐｄ）または白金（Ｐｔ）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。このパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の硬さは、パラジウム（Ｐｄ）または白金（Ｐｔ）の純度が９９．９５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 palladium (Pd) or platinum (Pt) coating layer according to the present invention is magnetron sputtered while having a high purity of 99.9% or more, and thus has a hardness of a heat-treated palladium (purity of 99.99% or more). Pd) or platinum (Pt) bulk hardness (50Hv at 10g load) is about 3 times higher (around 150Hv).
This is because the palladium (Pd) or platinum (Pt) coating layer formed directly on the surface of the palladium (Pd) or platinum (Pt) coated copper ribbon of the present invention is deposited under a low pressure condition in which a rare gas is interposed. This is probably because a lot of internal strain is accumulated due to the fine polycrystalline structure formed. The cause of this distortion is due to impurities in the source of palladium (Pd) or platinum (Pt), or due to oxygen or moisture remaining in the vacuum apparatus. In particular, in magnetron sputtering, high energy is added to the sputtered palladium (Pd) or platinum (Pt) particles, and the rare gas to be used, such as argon (Ar) or remaining water molecules, is involved. A dense polycrystalline film with small crystal grains is formed under these conditions. The hardness of the palladium (Pd) or platinum (Pt) coating layer tends to decrease as the purity of palladium (Pd) or platinum (Pt) increases from 99.95% by mass to 99.99% by mass.

なお、本発明のパラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンのパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層は、純度９９．９％以上のパラジウム（Ｐｄ）または白金（Ｐｔ）を用いている（好ましくは純度９９．９５％以上、より好ましくは純度９９．９９％以上である）ので、銅（Ｃｕ）芯材の銅（Ｃｕ）との接合性もよく、パラジウム（Ｐｄ）膜または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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。 The palladium (Pd) or platinum (Pt) coating layer of the palladium (Pd) or platinum (Pt) -coated copper ribbon of the present invention uses palladium (Pd) or platinum (Pt) having a purity of 99.9% or more. (Preferably with a purity of 99.95% or more, more preferably with a purity of 99.99% or more), the bonding property of the copper (Cu) core material with copper (Cu) is good, and a palladium (Pd) film or platinum Since the (Pt) film itself is dense and stable, oxygen from inside the copper (Cu) core material enters the interface of the aluminum (Al) pad via the palladium (Pd) or platinum (Pt) coating layer. Is effective in preventing oxidation of aluminum (Al). This is a high temperature storage test after mounting, and even when the palladium (Pd) or platinum (Pt) coating layer diffuses into the copper (Cu) core material and disappears, the aluminum (Al) and copper of the aluminum pad This is supported by the fact that no new aluminum (Al) oxide is formed at the bonding interface with (Cu).

パラジウム（Ｐｄ）または白金（Ｐｔ）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、上記のパラジウム（Ｐｄ）または白金（Ｐｔ）が被覆された銅（Ｃｕ）芯材テープの硬さに対して、前記パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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、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アルミパッド電極を破壊してしまう。 An aluminum pad at the time of the first bond by setting the copper (Cu) core material tape to a Vickers hardness of 70 Hv or less, more preferably 60 Hv or less with respect to the hardness of the palladium (Pd) or platinum (Pt) coating layer. It is possible to suppress chip damage.
The thickness of the palladium (Pd) or platinum (Pt) coating layer is 50 nm or more with respect to the hardness of the copper (Cu) core material tape coated with palladium (Pd) or platinum (Pt). The thickness of the copper (Cu) core material tape is 500 nm or less, preferably in the range of 100 to 400 nm, and the thickness of the magnetron sputtered palladium (Pd) or platinum (Pt) coating layer is in the above range. Hardness is most effective.
In addition, the thickness of the palladium (Pd) or platinum (Pt) coating layer is thin, and the thickness of the palladium (Pd) or platinum (Pt) coating film as the preferred range in the above-mentioned Patent Document 3 The influence of the surface properties of the resulting copper (Cu) core material tape is strong, and the influence of work hardening of the copper (Cu) core material tape is directly transmitted to the aluminum pad to destroy the aluminum pad electrode.

このように、ボンディング時におけるパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層を設けることによって銅（Ｃｕ）芯材テープの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、コスト高の点を除けば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 palladium (Pd) or platinum (Pt) coating layer at the time of bonding, the effect of work hardening of the copper (Cu) core material tape is suppressed, thereby preventing chip damage at the time of the first bond. Ensures stable bonding strength to the chip-side aluminum pad electrode. 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, and it is preferable in high-temperature semiconductor applications except for the high cost. 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パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層および銅（Ｃｕ）芯材テープからなる平角状パラジウム（Ｐｄ）または白金（Ｐｔ）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、前記パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層は、希ガスの低圧雰囲気中で室温の前記銅（Ｃｕ）芯材テープに対して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。 In addition, the palladium (Pd) or platinum (Pt) -coated copper ribbon for high-temperature semiconductor elements of the present invention connects a semiconductor element pad and a nickel (Ni) -coated substrate in a loop shape by ultrasonic bonding at multiple locations. In a rectangular palladium (Pd) or platinum (Pt) -coated copper ribbon comprising a palladium (Pd) or platinum (Pt) coating layer and a copper (Cu) core material tape, the copper (Cu) core material tape is 70 Hv or less Made of copper (Cu) having a Vickers hardness of 99.9% or more, and the palladium (Pd) or platinum (Pt) coating layer is made of the copper (Cu) core material at room temperature in a low pressure atmosphere of a rare gas. It is characterized in that it is formed by magnetron sputtering on a tape and has many strains introduced.

パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン内のパラジウム（Ｐｄ）または白金（Ｐｔ）の銅（Ｃｕ）内部への拡散によるパラジウム（Ｐｄ）皮膜または白金（Ｐｔ）皮膜における歪みの消失を防止するため、室温で直接マグネトロンスパッタ形成することが有効である。また、ループ形成時に急峻なループを描いても、純度９９．９％以上の高純度のパラジウム（Ｐｄ）または白金（Ｐｔ）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／Ｐｄ・Ｐｔ界面が剥がれることもない。 Prevents loss of strain in palladium (Pd) or platinum (Pt) film due to diffusion of palladium (Pd) or platinum (Pt) into copper (Cu) inside a copper ribbon with palladium (Pd) or platinum (Pt) coating Therefore, it is effective to perform direct magnetron sputtering at room temperature. Further, even if a steep loop is drawn at the time of loop formation, adhesion between high-purity palladium (Pd) or platinum (Pt) with a purity of 99.9% or higher and high-purity copper (Cu) with a purity of 99.9% or higher is achieved. The strength is ensured, and the Cu / Pd / Pt interface is not peeled off during ultrasonic bonding.

本発明で得られるパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層は、純度９９．９％以上の高純度でありながら、バルクのパラジウム（Ｐｄ）または白金（Ｐｔ）の硬さよりも２倍以上のビッカース硬さをもち、銅（Ｃｕ）芯材の加工硬化の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パラジウム（Ｐｄ）または白金（Ｐｔ）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）とを直接組み合わせることによって、高温半導体用パラジウム（Ｐｄ）または白金（Ｐｔ）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、パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンをループ状に形成し、その後パラジウム（Ｐｄ）または白金（Ｐｔ）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。
さらに、ボンディングされたパラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンを高温環境に放置しても、パラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) coating layer obtained by the present invention has a high purity of 99.9% or more, and at least twice the hardness of bulk palladium (Pd) or platinum (Pt). It has Vickers hardness and is characterized by reducing the influence of work hardening of the copper (Cu) core material. In the present invention, such a palladium (Pd) or platinum (Pt) coating layer is directly combined with a soft copper (Cu) having a Vickers hardness of 70 Hv or less and a purity of 99.9% or more, thereby forming a palladium for high-temperature semiconductors. The performance as a (Pd) or platinum (Pt) -coated copper ribbon can be exhibited.
That is, many points of palladium (Pd) or platinum (Pt) coated copper ribbon are ultrasonically bonded to an aluminum pad with a carbide tool to form a first bond, and then palladium (Pd) or platinum (Pt) coated with a carbide tool. A copper ribbon is formed in a loop shape, and then a plurality of portions of the palladium (Pd) or platinum (Pt) coated copper ribbon are ultrasonically bonded to a nickel (Ni) coated lead frame or the like with a carbide tool to be connected as a second bond. In a typical ultrasonic bonding process, chip cracking at the time of the first bonding is suppressed, variation in bonding strength at the time of the first bonding and the second bonding is small, and stable bonding can be performed.
Furthermore, even if the bonded palladium (Pd) or platinum (Pt) -coated copper ribbon is left in a high temperature environment, the surface of the palladium (Pd) or platinum (Pt) coating layer is connected to the copper (Cu) core tape interface. It becomes possible to prevent oxygen from entering.

図１は、本発明のパラジウム（Ｐｄ）被覆銅リボンのパラジウム（Ｐｄ）被覆層の上方からみた組織写真である。FIG. 1 is a structural photograph of the palladium (Pd) -coated copper ribbon of the present invention as viewed from above the palladium (Pd) -coated layer. 図２は、比較例のパラジウム（Ｐｄ）層の組織写真である。FIG. 2 is a structural photograph of the palladium (Pd) layer of the comparative example. 図３は、本発明のパラジウム（Ｐｄ）被覆銅リボンのパラジウム（Ｐｄ）被覆層の上方からみた拡大組織写真である(平均粒径：０．０５〜０．３μｍ)。FIG. 3 is an enlarged structure photograph of the palladium (Pd) -coated copper ribbon of the present invention as viewed from above the palladium (Pd) coating layer (average particle diameter: 0.05 to 0.3 μm). 図４は、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボンの断面図であるFIG. 4 is a cross-sectional view of a palladium (Pd) or platinum (Pt) coated copper ribbon. 図５は、従来のパラジウム（Ｐｄ）または白金（Ｐｔ）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. 5 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 palladium (Pd) or platinum (Pt) clad ribbon.

本発明のパラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) -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.

パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の純度は９９．９％よりも９９．９９％であることが好ましい。これは、チップダメージの原因となるパラジウム（Ｐｄ）または白金（Ｐｔ）金属中に含まれる微量元素がマグネトロンスパッタされたパラジウム（Ｐｄ）または白金（Ｐｔ）粒子の表面に析出・凝集してパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層に局部的に硬度の高い箇所が形成されるのを回避するためである。また、長期間高温度で半導体が使用された場合、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層ないし銅（Ｃｕ）芯材と半導体素子のアルミパッドとの接合界面において生じる、微量元素の集積や酸化を防ぎ、接合信頼性を確保するためである。 The purity of the palladium (Pd) or platinum (Pt) coating layer is preferably 99.99% rather than 99.9%. This is because palladium (Pd) or platinum (Pt) metal, which causes chip damage, precipitates and aggregates on the surface of the magnetron sputtered palladium (Pd) or platinum (Pt) particles to form palladium (Pd). This is for avoiding the formation of locally high hardness portions in the Pd) or platinum (Pt) coating layer. In addition, when a semiconductor is used at a high temperature for a long period of time, accumulation of trace elements generated at a bonding interface between a palladium (Pd) or platinum (Pt) coating layer or a copper (Cu) core material and an aluminum pad of a semiconductor element, This is in order to prevent oxidation and ensure bonding reliability.

本発明のパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の硬さは、パラジウム（Ｐｄ）または白金（Ｐｔ）バルクの硬さの２倍以上であることが好ましく、３倍以上であることがより好ましい。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 palladium (Pd) or platinum (Pt) coating layer of the present invention is preferably at least twice the hardness of the palladium (Pd) or platinum (Pt) bulk, more preferably at least three times. preferable. 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％以上のパラジウム（Ｐｄ）または白金（Ｐｔ）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マグネトロンスパッタにより析出されたものであることが好ましい。 Further, the palladium (Pd) or platinum (Pt) coating layer having a purity of 99.9% or more is deposited by magnetron sputtering in a rare gas atmosphere such as argon gas (Ar) or helium (He) gas. Is preferred.

銅（Ｃｕ）芯材テープ上にパラジウム（Ｐｄ）または白金（Ｐｔ）を被覆する場合、析出するパラジウム（Ｐｄ）または白金（Ｐｔ）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、形成されるパラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) on a copper (Cu) core tape, ensuring the purity of the deposited palladium (Pd) or platinum (Pt), and uniformity of film thickness and film quality The chemical vapor deposition method is superior to the magnetron sputtering in terms of the ease of deposition on the corners of the core tape and the throwing power on the back surface of the copper (Cu) core tape. However, when the formed palladium (Pd) or platinum (Pt) coating film, which is a subject of the present invention, is moderately hard and is polycrystallized, it can introduce many strains. Since sputtering is superior, magnetron sputtering is employed in the present invention.

また、パラジウム（Ｐｄ）または白金（Ｐｔ）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）との濡れ拡がりを防止するため、５００ｎｍ以下であることが好ましい。さらに、パラジウム（Ｐｄ）または白金（Ｐｔ）膜厚が５０ｎｍ未満と薄すぎる場合、微細な粒状のパラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) coating layer is determined so that wetting and spreading 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. In order to prevent this, the thickness is preferably 500 nm or less. Furthermore, if the palladium (Pd) or platinum (Pt) film thickness is too thin, less than 50 nm, a fine granular palladium (Pd) or platinum (Pt) crystal structure cannot be formed, causing chip damage of the first bond. Therefore, 50 nm or more is preferable. 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）芯材テープとして実施例試料Ｎｏ．１〜３、４０〜４２、と比較例試料Ｎｏ．１〜３、７〜９、１３〜１５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）平圧延したものをそれぞれ本発明の銅（Ｃｕ）芯材テープとして試料Ｎｏ．４〜６、１６〜１８、２２〜２４、２８〜３０、３４〜３６、４３〜４５、及び試料Ｎｏ．７〜９、４６〜４８に使用し、さらに、純度９９．９９９９質量％の銅（Ｃｕ）平圧延したものを実施例試料Ｎｏ．１０〜１５、１９〜２１、２５〜２７、３１〜３３、３７〜３９、４９〜５４、及び比較例試料Ｎｏ．４〜６、１０〜１２、１６〜１８にそれぞれ使用した。
また、この銅（Ｃｕ）板材に純度９９．９質量％、０．５μｍの白金（Ｐｔ）箔をスパッタにより成膜し、幅２．０ｍｍ、厚さ０．１５ｍｍの銅（Ｃｕ）白金被覆芯材テープを作製した。同様にして、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）パラジウム（Ｐｄ）被覆芯材テープを作製した。
なお、純度９９．９９質量％、９９．９９９９質量％および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の範囲であった。 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 full annealed tape was used as a copper (Cu) core material tape of the present invention. 1 to 3 and 40 to 42, and comparative sample Nos. Used for 1-3, 7-9, 13-15. In addition, samples obtained by subjecting copper (Cu) flat rolled with a purity of 99.99% by mass, a purity of 99.999% by mass, and a purity of 99.9999% by mass as the copper (Cu) core material tape of the present invention were obtained. 4-6, 16-18, 22-24, 28-30, 34-36, 43-45, and sample no. 7-9, 46-48, and copper (Cu) flat-rolled with a purity of 99.9999% by mass were used in Example Sample No. 10-15, 19-21, 25-27, 31-33, 37-39, 49-54, and Comparative Sample No. Used for 4-6, 10-12, 16-18, respectively.
Further, a platinum (Pt) foil having a purity of 99.9% by mass and 0.5 μm was formed on the copper (Cu) plate by sputtering, and a copper (Cu) platinum coated core having a width of 2.0 mm and a thickness of 0.15 mm. A material tape was prepared. Similarly, a palladium (Pd) foil having a purity of 99.9% by mass and 0.5 μm was formed on this copper (Cu) plate by sputtering, and copper (Cu) palladium having a width of 2.0 mm and a thickness of 0.15 mm was formed. (Pd) A coated core tape was produced.
When a copper (Cu) tape having a purity of 99.99 mass%, 99.9999 mass%, and 99.9999 mass% was fully annealed, the Vickers hardness was in the range of 55 to 50 Hv.

〔パラジウム（Ｐｄ）または白金（Ｐｔ）蒸発源の作製〕
純度９９．９質量％のパラジウム（Ｐｄ）または白金（Ｐｔ）をそれぞれ蒸発源として、純度９９．９９質量％のパラジウム（Ｐｄ）または白金（Ｐｔ）をそれぞれ蒸発源として、さらに純度９９．９９５質量％のパラジウム（Ｐｄ）または白金（Ｐｔ）をそれぞれ蒸発源とした。これらの構成を表１〜表３に示す。 [Production of palladium (Pd) or platinum (Pt) evaporation source]
Purity 99.9 mass% palladium (Pd) or platinum (Pt) is used as an evaporation source, purity 99.99 mass% palladium (Pd) or platinum (Pt) is used as an evaporation source, respectively, and purity 99.995 mass is further obtained. % Palladium (Pd) or platinum (Pt) was used as the evaporation source. These configurations are shown in Tables 1 to 3.

〔パラジウム（Ｐｄ）または白金（Ｐｔ）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にしてパラジウム（Ｐｄ）または白金（Ｐｔ）蒸発源を加熱した。蒸発したパラジウム（Ｐｄ）または白金（Ｐｔ）粒子は、直線距離で１００ｍｍ離れた室温の銅（Ｃｕ）芯材テープに、表１〜３に示す所定の膜厚で被着させ、パラジウム（Ｐｄ）または白金（Ｐｔ）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％以上のパラジウム（Ｐｄ）または白金（Ｐｔ）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離れた室温状態の平角状銅（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、同一圧力でパラジウム（Ｐｄ）または白金（Ｐｔ）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。このスパッタ時間は短いので、銅（Ｃｕ）芯材テープの温度上昇は観測されなかった。 [Preparation of palladium (Pd) or platinum (Pt) -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 palladium (Pd) or platinum (Pt) evaporation source was heated at a sputtering power of 1.0 kW. Evaporated palladium (Pd) or platinum (Pt) particles are deposited on a copper (Cu) core tape at room temperature 100 mm apart by a linear distance with a predetermined film thickness shown in Tables 1 to 3, and palladium (Pd) Alternatively, a platinum (Pt) -coated ribbon was produced. The diffusion prevention layer (intermediate layer) was prepared as follows. A target of substance X having a purity of 99.9% by mass or more and a palladium (Pd) or platinum (Pt) target having a purity of 99.9% by mass or more are arranged in the sputtering apparatus, and the sputtering pressure is set to 0.7 Pa. Then, it was filled with argon gas having a purity of 99.99% by mass or more. Thereafter, an intermediate layer was continuously formed on a flat rectangular copper (Cu) core tape in a room temperature state separated by 100 mm by sputtering to form a film having a predetermined shape. Thereafter, a palladium (Pd) or platinum (Pt) coating layer was deposited and formed at the same pressure to form a layer composed of a dense crystal structure having a predetermined thickness. Since the sputtering time was short, no temperature increase of the copper (Cu) core tape was observed.

〔硬さ測定〕
パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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１５０±２０Ｈｖ（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。 [Hardness measurement]
For palladium (Pd) or platinum (Pt) coated copper ribbons, the hardness of the palladium (Pd) or platinum (Pt) coating layer as it was magnetron sputtered with a film thickness of 10, 5, or 3 μm was measured with a micro Vickers hardness meter. However, both values were 150 ± 20 Hv (reading value). 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.

〔内部組織の測定〕
試料番号２の調質処理済のパラジウム（Ｐｄ）被覆銅リボンを薄い硝酸液または王水液にて数秒間浸漬した。そして、浸漬後のパラジウム（Ｐｄ）膜の表面をレーザー顕微鏡で観察した（図１）。
これに対して、比較例として試料番号２のパラジウム（Ｐｄ）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パラジウム（Ｐｄ）被覆銅リボンを同様に浸漬したときのパラジウム（Ｐｄ）膜の表面をレーザー顕微鏡で観察したものを図２に示す。さらに、その試料の膜表面の組織拡大図を図３に示す。
これらの図１および図３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パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）の粒界に析出して区画を形成したものと思われる。 [Measurement of internal structure]
The tempered palladium (Pd) -coated copper ribbon of Sample No. 2 was immersed in a thin nitric acid solution or aqua regia solution for several seconds. And the surface of the palladium (Pd) film | membrane after immersion was observed with the laser microscope (FIG. 1).
On the other hand, as a comparative example, a palladium (Pd) coating obtained by clad rolling a copper (Cu) plate material with a purity of 99.999 mass% with the same composition as palladium (Pd) of sample number 2 and a film thickness of 50 μm. FIG. 2 shows an observation of the surface of the palladium (Pd) film with a laser microscope when the copper ribbon is dipped in the same manner. Furthermore, the structure enlarged view of the film | membrane surface of the sample is shown in FIG.
As is clear from FIG. 1 and FIG. 3, it can be seen that the magnetron sputtered film of the present invention has individual grain boundaries of palladium (Pd) or platinum (Pt) that are divided into spherical shapes and exist independently. This is presumably because a trace amount of elements precipitated at the grain boundaries of palladium (Pd) or platinum (Pt) to form compartments.

〔接合強度試験〕
試料番号１〜１３のパラジウム（Ｐｄ）または白金（Ｐｔ）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２ｍ）上に超音波ボンディングした。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、パラジウム（Ｐｄ）または白金（Ｐｔ）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ｎ＝４０個で超音波ボンディングした場合にボンディング中に発生したワイヤ切断回数を調べた。その判定結果を表１〜３に併記した、接合強度は、パラジウム（Ｐｄ）または白金（Ｐｔ）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。 [Joint strength test]
Purity 99 obtained by subjecting palladium (Pd) or platinum (Pt) -coated copper ribbons of sample numbers 1 to 13 to an aluminum (Al) plate (thickness 2 mm) with a purity of 99.99 mass% and nickel (Ni) electroplating with a thickness of 5 μm. Ultrasonic bonding was performed on a 95% by mass copper (Cu) substrate (thickness 2 m). The apparatus is Orthodyne Electronics (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 crush width is 1.01 to 1.05 times, and the same conditions for all samples. Ultrasonic bonding was performed.
The loop length of the palladium (Pd) or platinum (Pt) -coated copper ribbon is 50 mm, the loop height is 30 mm, and the conditions are set so that the sliding resistance received from the ribbon, path, and tool is greater than normal conditions. did. Each sample was examined for the number of wire cuts that occurred during bonding when ultrasonic bonding was performed with n = 40. The determination results are also shown in Tables 1 to 3. The bonding strength is the share from the side of the joint in the Dage Universal Bond Tester PC4000 type made by Daisy from the side of the palladium (Pd) or platinum (Pt) coated copper ribbon. Intensity measurements were performed.

〔高温接合信頼性試験〕
実施例および比較例のパラジウム（Ｐｄ）または白金（Ｐｔ）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、これらによって評価した。
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１，２および比較例について表３に示す。 [High temperature bonding reliability test]
As a reliability test for the palladium (Pd) or platinum (Pt) -coated copper ribbons of Examples and Comparative Examples, the shear strength after exposing a bonded nickel (Ni) -coated substrate to 175 ° C. × 500 hours was measured. . The 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 based on these values.
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 Tables 1 and 2 for Examples and Table 3 for Comparative Examples.

表１〜表３から明らかなようにパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の組織と厚さが重要であって、本発明範囲の蒸発源９９．９％〜９９．９９９９％の純度の粒状組織であって本発明範囲の厚さの被覆層のものは第一ボンド及び第二ボンドのいずれにおいても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、比較例の試料Ｎｏ．１〜１３に示されているように、それと同等の純度のパラジウム（Ｐｄ）または白金（Ｐｔ）被覆層であっても、被覆層のパラジウム（Ｐｄ）または白金（Ｐｔ）の厚さが本発明範囲を超えて厚いもの(比較例Ｎｏ．７〜９、及びＮｏ．１０〜１２)、或いは、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の厚さが本発明範囲より薄い場合（試料番号１〜３、及びＮｏ．４〜６）、すべて接合強度が劣り、また接合信頼性が不良であることがわかる。
また、パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の厚さが、硬さや被覆層の厚さが本発明範囲であっても（２００ｎｍ、３００ｎｍ）、その被覆層がマグネトロンスパッタによるものではなく、本発明の特徴とする粒状組織を備えていない比較例Ｎｏ．１３〜１８のものは、その、接合強度が低く、接合信頼性も著しく劣ったものとなっている。 As apparent from Tables 1 to 3, the structure and thickness of the palladium (Pd) or platinum (Pt) coating layer is important, and the purity of the evaporation source within the range of the present invention is 99.9% to 99.9999%. A granular structure having a thickness in the range of the present invention has good results in bonding strength and bonding reliability in both the first bond and the second bond.
In contrast, Sample No. 1 to 13, even if the palladium (Pd) or platinum (Pt) coating layer has the same purity, the thickness of the palladium (Pd) or platinum (Pt) of the coating layer is the present invention. Thickness exceeding the range (Comparative Examples No. 7 to 9 and No. 10 to 12), or when the thickness of the palladium (Pd) or platinum (Pt) coating layer is thinner than the range of the present invention (Sample No. 1) -3 and No. 4-6), it can be seen that the bonding strength is inferior and the bonding reliability is poor.
Further, even if the thickness of the palladium (Pd) or platinum (Pt) coating layer is within the scope of the present invention (200 nm, 300 nm), the coating layer is not formed by magnetron sputtering, Comparative Example No. which does not have the granular structure characteristic of the present invention. 13 to 18 have low bonding strength and extremely low bonding reliability.

１３０〜１７５℃の耐熱温度と大容量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ことによって、これらの新たな用途において普及し、当該分野の発展に寄与することが期待される。 By being used in high-temperature semiconductors that require heat-resistant temperatures of 130 to 175 ° C. and high capacity, especially power semiconductors such as air conditioners, solar power generation systems, hybrid cars, and electric cars, they are widely used in these new applications. It is expected to contribute to the development of this field.

１ パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン
２ 金被覆層
３ 銅芯材
４ アルミニウムパッド
５ リード
DESCRIPTION OF SYMBOLS 1 Palladium (Pd) or platinum (Pt) covering copper ribbon 2 Gold coating layer 3 Copper core material 4 Aluminum pad 5 Lead

Claims (8)

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パラジウム（Ｐｄ）または白金（Ｐｔ）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、前記パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層はアルゴンガス（Ａｒ）等の希ガス雰囲気下で、室温に保持された前記銅（Ｃｕ）芯材テープ上に、マグネトロンスパッタされた５０〜５００ｎｍ厚の純度９９．９％以上のパラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）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 palladium (Pd) or platinum (Pt) 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 palladium (Pd) or platinum (Pt) coating layer is argon gas (Ar) or the like. On the copper (Cu) core material tape kept at room temperature in a rare gas atmosphere, the magnetron-sputtered 50-500 nm thick palladium (Pd) or platinum (Pt) having a purity of 99.9% or more A palladium (Pd) or platinum (Pt) -coated copper ribbon for semiconductor elements, characterized by having a fine granular crystal structure. 前記粒状の結晶組織が上方向から見て１μｍあたり１０〜１００個である請求項１に記載の半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン。     2. The palladium (Pd) or platinum (Pt) -coated copper ribbon for a semiconductor device according to claim 1, wherein the granular crystal structure is 10 to 100 per 1 μm as viewed from above. 前記粒状の結晶組織が上方向から見て１μｍあたり１０〜５０個である請求項１に記載の半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン。 2. The palladium (Pd) or platinum (Pt) -coated copper ribbon for a semiconductor device according to claim 1, wherein 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質量％以上である請求項１に記載の半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン。 The palladium (Pd) or platinum (Pt) -coated copper ribbon for semiconductor elements according to claim 1, wherein the purity of the copper (Cu) core material tape is 99.9 % by mass or more. 前記パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の純度が９９．９９質量％以上である請求項１に記載の半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン The palladium (Pd) or platinum (Pt) -coated copper ribbon for a semiconductor device according to claim 1, wherein the purity of the palladium (Pd) or platinum (Pt) coating layer is 99.99 mass% or more. 前記パラジウム（Ｐｄ）または白金（Ｐｔ）被覆層の純度が９９．９９５質量％以上である請求項１に記載の半導体素子用パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン。 The palladium (Pd) or platinum (Pt) -coated copper ribbon for a semiconductor device according to claim 1, wherein the purity of the palladium (Pd) or platinum (Pt) coating layer is 99.995 % by mass or more. 前記パラジウム（Ｐｄ）または白金（Ｐｔ）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パラジウム（Ｐｄ）または白金（Ｐｔ）被覆銅リボン。   The palladium (Pd) or platinum (Pt) for semiconductor element according to claim 1, wherein the palladium (Pd) or platinum (Pt) -coated copper ribbon has a width of 0.5 to 10 mm and a thickness of 0.05 to 1 mm. ) Coated copper ribbon. 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パラジウム（Ｐｄ）または白金（Ｐｔ）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). Palladium (Pd) or platinum (Pt) coated copper ribbon.
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