JP5109881B2 - Copper bonding wire - Google Patents

Copper bonding wire Download PDF

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Publication number
JP5109881B2
JP5109881B2 JP2008227625A JP2008227625A JP5109881B2 JP 5109881 B2 JP5109881 B2 JP 5109881B2 JP 2008227625 A JP2008227625 A JP 2008227625A JP 2008227625 A JP2008227625 A JP 2008227625A JP 5109881 B2 JP5109881 B2 JP 5109881B2
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Prior art keywords
copper
wire
bonding
coating
ppm
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JP2008227625A
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Japanese (ja)
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JP2010062395A (en
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亮 富樫
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Sumitomo Metal Mining Co Ltd
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Sumitomo Metal Mining Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive copper bonding wire that has a Pd coating stably formed on a copper surface, is drawn up to a final wire diameter without being heated after the coating formation, and has high stitch bondability, and to provide a copper bonding wire that prevents an electric short circuit due to contacting of wires with each other during resin sealing. <P>SOLUTION: The copper bonding wire is formed in such a way that a copper ultra-thin wire of oxygen-free copper consisting of &le;1 ppm of Cl, 10 to 200 ppm of P, Cu as the rest and inevitable impurities as the rest is used as a core, the Pd coating is provided on a surface of the core and a thermosetting copolymerization type polyimide resin coating is formed on a surface of the Pd coating. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

本発明は、半導体素子上の電極と外部電極とを接続するために用いる銅ボンディングワイヤに関するものである。   The present invention relates to a copper bonding wire used for connecting an electrode on a semiconductor element and an external electrode.

一般に半導体素子上の電極と外部電極との結線に用いられるボンディングワイヤの直径は１５〜７５μｍと非常に細く、また、化学的な安定性や大気中での取り扱いやすさから、従来は金線が用いられていた。
しかし、Ａｕ線の組成は、９９ｍａｓｓ％から９９．９９ｍａｓｓ％がＡｕであるため非常に高価であることから、金線使用量のＩＯピン数が非常に多いプラスチックボールグリッドアレイパッケージ（Ｐｌａｓｔｉｃ Ｂａｌｌ Ｇｒｉｄ Ａｌｌｅｙ Ｐａｃｋａｇｅ、以下ＰＢＧＡと記す。）や製品価格が安いメモリパッケージでは、細い線径の金線を用いることで、Ａｕの使用量を減らし、そのコストを下げたいとの要望があった。 In general, the diameter of a bonding wire used for connection between an electrode on a semiconductor element and an external electrode is very thin, 15 to 75 μm. In addition, because of chemical stability and ease of handling in the air, a gold wire has been conventionally used. It was used.
However, since the composition of Au wire is very expensive because 99 mass% to 99.99 mass% is Au, a plastic ball grid array package (Plastic Ball Grid Array) with a very large number of IO pins for gold wire usage is used. In a memory package having a low package price and package (hereinafter referred to as PBGA), there is a demand to reduce the amount of Au used and to reduce the cost by using a thin wire diameter gold wire.

一方、Ａｕの電気比抵抗は約２．３μΩｃｍであるが、線径を細くすることで、その電気抵抗も上昇するため、電流値を変化させたくない半導体パッケージでは細線化には限界があり、更にパッケージの高密度化における発熱の低減などの観点から、電気比抵抗が約１．７μΩｃｍとＡｕより低く、安価なＣｕに代替したいとの要望があった。   On the other hand, the electrical specific resistance of Au is about 2.3 μΩcm, but by reducing the wire diameter, the electrical resistance also increases, so there is a limit to thinning the semiconductor package that does not want to change the current value. Further, from the viewpoint of reducing heat generation in increasing the density of the package, there has been a demand to replace Cu with an inexpensive electrical specific resistance of about 1.7 μΩcm, which is lower than Au.

このような状況から銅ボンディングワイヤが開発、製品化されてきている。
しかしながら、銅ボンディングワイヤを最新の高集積度半導体パッケージに適用するためには、シリコンチップ上の脆弱なアルミ電極パッドへのダメージを回避する初期銅ボールの軟らかさと、銅ボールとアルミニウム電極との接合界面の腐食を阻止するための銅組成、更には銅ボールとアルミニウム電極との接合界面に生成するアルミニウム銅合金層の酸化を阻止するための初期銅ボールの無酸素化、高集積化により狭まった隣接ワイヤループが樹脂封止時の樹脂流れによって起こる電気的短絡などを解消しなければならなかった。 Under such circumstances, copper bonding wires have been developed and commercialized.
However, in order to apply the copper bonding wire to the latest highly integrated semiconductor package, the softness of the initial copper ball that avoids damage to the fragile aluminum electrode pad on the silicon chip and the bonding of the copper ball and the aluminum electrode Copper composition to prevent corrosion at the interface, and further narrowed by oxygen-free and high integration of the initial copper ball to prevent oxidation of the aluminum copper alloy layer formed at the bonding interface between the copper ball and the aluminum electrode It was necessary to eliminate the electrical short circuit caused by the resin flow when the adjacent wire loop was sealed with resin.

ボールボンディングにおける接合界面の信頼性に最も強く影響する不純物元素は塩素であることが知られているが、特許文献１には、グロー放電質量分析法によって検出される塩素量が１質量ｐｐｍ以下の無酸素銅を使用することで銅ボールとアルミニウム電極との接合界面の腐食を阻止できることが開示されており、こうした銅ボンディングワイヤを使用することでＰＢＧＡの組立も金線から銅線への置き換えも可能となっている。   Although it is known that the impurity element that most strongly affects the reliability of the bonding interface in ball bonding is chlorine, Patent Document 1 discloses that the amount of chlorine detected by glow discharge mass spectrometry is 1 mass ppm or less. It has been disclosed that the use of oxygen-free copper can prevent the corrosion of the bonding interface between the copper ball and the aluminum electrode. By using such a copper bonding wire, it is possible to assemble PBGA and replace gold wire with copper wire. It is possible.

一方、銅ボンディングワイヤは表面が酸化しやすいため、酸化によってステッチボンディングの接合性が低下するという問題があり、特許文献２には、高純度銅極細線の表面にＰｄ被膜を形成して銅表面の酸化を防止する方法が開示されている。
更に、特許文献３には、Ｐｄ被覆銅ボンディングワイヤ表面のＰｄ被覆層と銅芯材との界面での剥離を防止するための方法が開示されており、被膜形成後に熱処理を施して銅パラジウム界面に濃度勾配を設けることが示されている。
又、最終線径まで伸線した後に銅芯材表面へパラジウム被膜を形成し、最終熱処理で拡散層を形成して界面の接合強度を高める方法も提案されている。 On the other hand, since the surface of a copper bonding wire is easily oxidized, there is a problem that the bonding property of stitch bonding is reduced by oxidation. Patent Document 2 discloses that a copper surface is formed by forming a Pd film on the surface of a high purity copper fine wire. A method for preventing the oxidation of is disclosed.
Further, Patent Document 3 discloses a method for preventing peeling at the interface between the Pd coating layer on the surface of the Pd-coated copper bonding wire and the copper core material, and heat treatment is performed after the coating is formed to provide a copper palladium interface. Is shown to provide a concentration gradient.
A method has also been proposed in which a palladium coating is formed on the surface of a copper core after drawing to the final wire diameter, and a diffusion layer is formed by final heat treatment to increase the bonding strength at the interface.

樹脂流れ性の向上については、銅ボール硬度の低減やステッチボンディング性向上のためにＰＢＧＡやメモリパッケージ向けの銅ボンディングワイヤは軟化処理によって弾性率は５２〜７０ＧＰａ程度と一般的な高強度金線の８０〜９０ＧＰａよりも低く、樹脂封止時のループへの流動応力に耐えずループが撓み、隣接するループと接触して電気的短絡を起こすことが問題となっていた。
このような樹脂封止時のループの接触による電気的短絡防止アイデアとしては、特許文献４及び特許文献５に、ワイヤ表面を電気絶縁性の物質で覆い、仮にループが接触してもワイヤ表面の絶縁性被膜が電気的短絡を回避するいわゆる絶縁ボンディングワイヤが提案されている。 Regarding the improvement of resin flowability, the copper bond wires for PBGA and memory packages are softened to reduce the hardness of the copper balls and improve the stitch bondability, and the elastic modulus is about 52 to 70 GPa due to softening treatment. It is lower than 80 to 90 GPa, and the loop is not able to withstand the flow stress to the loop at the time of resin sealing.
As an idea of preventing an electrical short circuit due to the contact of the loop at the time of resin sealing, Patent Document 4 and Patent Document 5 cover the surface of the wire with an electrically insulating material, and even if the loop contacts, So-called insulating bonding wires have been proposed in which the insulating coating avoids electrical shorts.

ところで、絶縁ボンディングワイヤの芯材が金線である場合には、Ａｕは化学的に安定な金属であるため、例えば熱可塑性であるナイロンやアクリルといった樹脂を直接塗布する方法を用いることが可能であるが、芯材が銅線の場合には、延性がＡｕよりも低いＣｕではステッチボンディングでの銅ボールとアルミニウム電極との接合面積が小さくなり、ワイヤとリード電極との接合界面に延びた絶縁性被膜が残留し、金属接合を阻害するためにステッチボンディングが不十分となり、連続ボンディング性の低下による生産性の低下やボンドプル強度の低下の原因となっている。   By the way, when the core of the insulating bonding wire is a gold wire, since Au is a chemically stable metal, it is possible to use a method of directly applying a thermoplastic resin such as nylon or acrylic. However, when the core material is copper wire, Cu having lower ductility than Au reduces the bonding area between the copper ball and the aluminum electrode in stitch bonding, and the insulation extends to the bonding interface between the wire and the lead electrode. Since the conductive film remains and inhibits metal bonding, stitch bonding becomes insufficient, which causes a decrease in productivity and a decrease in bond pull strength due to a decrease in continuous bonding performance.

又、絶縁性被膜として熱可塑性のナイロンやアクリル系の樹脂、あるいは熱硬化性のポリウレタンは、ボール形成時の熱影響部での樹脂の溶け上がり量が多く、ボール直上部のワイヤがむき出しになってしまうため、チップを多数積層させた最新のスタックドパッケージで要求される低ループでのクロス配線における電気的短絡回避を解決できないでいる。   In addition, thermoplastic nylon, acrylic resin, or thermosetting polyurethane as the insulating coating has a large amount of resin melting at the heat affected zone during ball formation, and the wire immediately above the ball is exposed. For this reason, it is not possible to solve the electrical short circuit avoidance in the cross wiring in the low loop, which is required in the latest stacked package in which a large number of chips are stacked.

更に、絶縁性確保のためには、所定の厚みの絶縁性被膜を設ける必要があるが、絶縁性被膜が厚くなるとステッチボンディング性が低下するというトレードオフの関係があるなか、高密度化を実現するためにワイヤの線径を細くしていくと、ステッチボンディングの接合面積は減少していくが、接合面積が小さくなっても高い接合強度を得るためには被膜樹脂が接合界面に残留しにくいことが重要であり、ポリイミド樹脂などの熱硬化性樹脂がこのような効果を示すことが知られている。
特願２００６−３１４８０５号 特開昭６２−９７３６０号公報 特開２００６−２１６９２９号公報 特許２７０５９７８号公報 特開２０００−１９５８９２号公報 Furthermore, in order to ensure insulation, it is necessary to provide an insulation film with a predetermined thickness. However, as the insulation film becomes thicker, there is a trade-off relationship that the stitch bonding property is reduced. Therefore, as the wire diameter is reduced, the bonding area of stitch bonding decreases. However, in order to obtain high bonding strength even if the bonding area is reduced, the coating resin does not remain at the bonding interface. It is important that thermosetting resins such as polyimide resins exhibit such effects.
Japanese Patent Application No. 2006-314805 JP-A-62-97360 JP 2006-216929 A Japanese Patent No. 2705978 JP 2000-195892 A

しかしながら、Ｐｄの被膜形成速度は蒸着法にしてもメッキ法にしても遅く、又拡散層の形成に要する加熱工程も必要になるため、生産性の点からＰｄ被膜の形成は、ある程度の太線で行い、加熱無しに最終線径までの伸線を行うことでＰｄ被膜の形成を行ないたいが、無酸素銅、より高純度の銅にＰｄ被膜を設けて加熱せずに伸線を行うと、Ｐｄ被膜が剥がれ易くなって、芯材の銅線が剥き出しになりやすい問題がある。   However, the Pd film formation rate is slow both in the vapor deposition method and in the plating method, and the heating process necessary for forming the diffusion layer is also necessary. Therefore, the Pd film is formed with a certain amount of thick lines from the viewpoint of productivity. I want to form a Pd film by drawing up to the final wire diameter without heating, but when oxygen-free copper, higher purity copper is provided with a Pd film and drawn without heating, There is a problem that the Pd film is easily peeled off, and the copper wire of the core material is easily exposed.

又、絶縁性被膜に用いる熱硬化性樹脂は、ステッチボンディング性が良好となることは知られていたが、例えば絶縁性被膜として厚さ５０ｎｍと極めて薄いポリイミド被膜を用いた場合であっても、この極薄のポリイミド被膜中に存在する、ポリイミドなどの熱硬化性樹脂の溶媒として極めて一般的に用いられるＮ−メチルピロリジノンとＣｕとが直接反応して銅線表面を黒く変色し、変色層が異物となってプラズマ放電によって得られるワイヤ先端のボール形状が真球になりにくい、或いはステッチボンディング強度が低いといった問題が生じていた。   In addition, the thermosetting resin used for the insulating coating was known to have good stitch bonding properties. For example, even when a very thin polyimide coating with a thickness of 50 nm is used as the insulating coating, In this ultra-thin polyimide coating, N-methylpyrrolidinone, which is very commonly used as a solvent for thermosetting resins such as polyimide, reacts directly with Cu to discolor the surface of the copper wire black, and the discoloration layer There has been a problem that the ball shape at the tip of the wire obtained by plasma discharge as a foreign substance is difficult to become a perfect sphere or the stitch bonding strength is low.

即ち、本発明は係る課題に対して、銅表面にＰｄ被膜を安定して形成し、被膜形成後に加熱せずに最終線径まで伸線でき、ステッチ接合性の高い安価な銅ボンディングワイヤ、並びに樹脂封止時のワイヤ同士の接触による電気的短絡を防止する銅ボンディングワイヤの提供を目的とするものである。   That is, the present invention addresses the problem by stably forming a Pd film on the copper surface, drawing the film to the final wire diameter without heating after the film formation, and an inexpensive copper bonding wire with high stitch bondability, and An object of the present invention is to provide a copper bonding wire that prevents an electrical short circuit due to contact between wires during resin sealing.

上記課題を解決するために、本発明による銅ボンディングワイヤは、Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上、２００ｐｐｍ以下含み、残部Ｃｕと不可避不純物とからなる無酸素銅の銅極細線を芯材とし、前記芯材の表面にＰｄ被膜が形成されていることを特徴とするものである。   In order to solve the above-mentioned problems, a copper bonding wire according to the present invention includes, as a core, an oxygen-free copper extra-fine copper wire that contains Cl at 1 ppm or less, P at 10 ppm or more and 200 ppm or less, and the balance Cu and inevitable impurities, A Pd film is formed on the surface of the core material.

更に、Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上、２００ｐｐｍ以下含み、残部Ｃｕと残部不可避不純物とからなる無酸素銅の銅極細線を芯材とし、前記芯材の表面にＰｄ被膜を設け、前記Ｐｄ被膜の表面に熱硬化性共重合型ポリイミド樹脂被膜が形成されていることを特徴とする銅ボンディングワイヤである。   Furthermore, Cl is 1 ppm or less, P is 10 ppm or more and 200 ppm or less, a copper fine wire of oxygen-free copper consisting of the remainder Cu and the remainder inevitable impurities is used as a core material, a Pd coating is provided on the surface of the core material, and the Pd A copper bonding wire characterized in that a thermosetting copolymer polyimide resin coating is formed on the surface of the coating.

本発明に係る銅ボンディングワイヤによれば、芯材がＣｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上、２００ｐｐｍ以下の範囲で含み、残部Ｃｕ及び不可避不純物からなる無酸素銅の銅極細線であるため、アルミニウム電極とのボール接合界面での腐食が発生しにくく、Ｐｄ被膜とＣｕとの界面の接合強度も良好で、加熱を行わなくとも伸線によってボンディングに十分な強度が得られるために剥離の発生が無く、無酸素銅であるために、高温評価時に、Ｐｄが吸収する水素と銅中に存在する酸素とが反応して水蒸気を形成し、この水蒸気に起因するボール粒界での割れも発生しない。   According to the copper bonding wire according to the present invention, the core material is an oxygen-free copper copper fine wire containing Cl in the range of 1 ppm or less, P in the range of 10 ppm or more and 200 ppm or less, and the balance Cu and inevitable impurities. Corrosion hardly occurs at the ball bonding interface with the electrode, the bonding strength at the interface between the Pd coating and Cu is good, and sufficient strength for bonding can be obtained by wire drawing without heating. Since it is oxygen-free copper, the hydrogen absorbed by Pd reacts with oxygen present in the copper to form water vapor at the time of high temperature evaluation, and there is no crack at the ball grain boundary caused by this water vapor. .

更に、この銅極細線の表面にＰｄ被膜が設けられることで、絶縁性樹脂被膜の形成が銅と反応しやすいＮ−メチルピロリジノンなどの有機溶媒を使用した可溶性ポリイミドインクを用いた場合でも、この有機溶媒は、銅線とは直接には接触しないことから、可溶性ポリイミドインクをＰｄ被膜表面に塗布した後に、加熱によってポリイミド被膜となって接合信頼性が高く、絶縁性を有する銅ボンディングワイヤを容易に形成することが可能となる。   Furthermore, even when a soluble polyimide ink using an organic solvent such as N-methylpyrrolidinone, in which the formation of the insulating resin film easily reacts with copper, is provided by providing a Pd film on the surface of the copper fine wire. Since the organic solvent does not come into direct contact with the copper wire, after applying the soluble polyimide ink to the surface of the Pd coating, it becomes a polyimide coating by heating and has high bonding reliability, making it easy to produce an insulating copper bonding wire. Can be formed.

本発明の芯材となる銅極細線が、Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上２００ｐｐｍ以下含み、残部Ｃｕと不可避不純物とからなる無酸素銅であることで、形成される銅ボールの初期硬さをより柔らかくする効果を示すと共に、Ｐｄ被膜が吸収する水素との反応によるボール粒界での割れの発生を大きく抑制するものである。
尚、この不可避不純物は、純度９９．９９％の銅の不可避不純物レベル以下であることが望ましい。又、この銅極細線の製造においては、純度９９．９９％以上の銅原料を用いて、所定成分組成に溶解鋳造することが好ましく、特には酸素濃度は１０ｐｐｍ以下であると良い。 The initial hardness of the formed copper ball is that the copper fine wire as the core material of the present invention is oxygen-free copper containing 1 ppm or less of Cl, 10 ppm or more and 200 ppm or less of P, and the balance Cu and inevitable impurities. In addition to the softening effect, cracking at the ball grain boundary due to the reaction with hydrogen absorbed by the Pd coating is greatly suppressed.
The inevitable impurities are desirably below the inevitable impurity level of copper having a purity of 99.99%. Further, in the production of the copper fine wire, it is preferable to use a copper raw material having a purity of 99.99% or more and melt and cast to a predetermined component composition, and the oxygen concentration is particularly preferably 10 ppm or less.

Ｃｌ含有量が１ｐｐｍ以下であると、銅ボールとアルミニウム電極との接合界面の腐食が防止されるもので、一方Ｐは、芯材の銅極細線とＰｄ被膜との接合強度を保ち、銅ボール形成時の銅ボールの酸化を防ぎ、又脱酸作用により銅ボールの表面硬さを硬くしないためにパッドダメージを発生させない働きを示すもので、そのＰ含有量が１０ｐｐｍ以上２００ｐｐｍ以下の範囲において良好な効果を有する。   When the Cl content is 1 ppm or less, corrosion of the bonding interface between the copper ball and the aluminum electrode is prevented. On the other hand, P maintains the bonding strength between the copper fine wire of the core material and the Pd coating, Prevents oxidation of copper balls during formation and does not increase the surface hardness of the copper balls due to deoxidation, and does not cause pad damage. Its P content is good in the range of 10 ppm to 200 ppm. It has a great effect.

銅極細線の表面にＰｄ被膜を設けることは、絶縁性被膜を形成するときの絶縁性被膜成分による銅極細線の表面汚染や変色を防止する効果や銅ボール形成時のボールの真球度を悪化させない予防効果が得られるものである。
そのＰｄ被膜の厚みは、５ｎｍから１００ｎｍが望ましく、この範囲内では、銅線表面の変色を抑え、ワイヤ先端に溶融形成される銅ボール表面に濃縮するＰｄ層の厚みも薄くなり、チップダメージの損傷を抑えたボールボンディングが可能である。５ｎｍ未満では効果がなく、１００ｎｍを超える厚みのＰｄ被膜では、銅ボールを形成したときの真球度が低下するためで、望ましくは、１０ｎｍから３０ｎｍが良く、更に望ましくは１０ｎｍから１５ｎｍである。 Providing a Pd film on the surface of the copper fine wire has the effect of preventing the surface contamination and discoloration of the copper fine wire due to the insulating film component when forming the insulating film, and the sphericity of the ball when forming the copper ball. A preventive effect that does not deteriorate is obtained.
The thickness of the Pd film is desirably 5 nm to 100 nm. Within this range, the discoloration of the copper wire surface is suppressed, and the thickness of the Pd layer concentrated on the surface of the copper ball melt-formed at the tip of the wire is also thinned. Ball bonding with reduced damage is possible. If the thickness is less than 5 nm, there is no effect, and the Pd film having a thickness exceeding 100 nm has a reduced sphericity when a copper ball is formed, so that it is preferably 10 nm to 30 nm, and more preferably 10 nm to 15 nm.

本発明において、熱硬化性共重合型ポリイミド樹脂を絶縁性被膜に用いるのは、塗布回数による被膜の厚み調整が容易で、又溶剤中にポリシランを混合してガラス転位温度や延性の調整も可能となるため、絶縁性が高くかつボンダビリティの高い絶縁性被膜を容易に形成するためである。
更に、熱硬化性共重合型ポリイミド樹脂に対して、１０ｍａｓｓ％以下の範囲でポリシロキサンを添加しても良く、この添加された絶縁性被膜は、より高い絶縁性を示すが、１０ｍａｓｓ％を超えての含有は、ステッチボンディング強度を弱め、銅ボール形成時の真球度が悪化する。 In the present invention, the thermosetting copolymer polyimide resin is used for the insulating coating because the coating thickness can be easily adjusted by the number of coatings, and the glass transition temperature and ductility can be adjusted by mixing polysilane in the solvent. Therefore, an insulating film having high insulation and high bondability is easily formed.
Furthermore, polysiloxane may be added in the range of 10 mass% or less with respect to the thermosetting copolymer polyimide resin, and the added insulating film exhibits higher insulation properties, but exceeds 10 mass%. If the content is too low, the stitch bonding strength is weakened, and the sphericity at the time of copper ball formation deteriorates.

その絶縁性被膜の厚みが、５０ｎｍから２００ｎｍであれば、連続ボンディング性を維持しつつ、良好な絶縁性も得られる。５０ｎｍ未満では、必要とする絶縁性が得られず、２００ｎｍを超える厚みでは、ステッチボンディング強度が必要とする強度より低下してしまう。より望ましくは、５０ｎｍから１００ｎｍにすると更に諸特性が良好となる。   If the thickness of the insulating coating is 50 nm to 200 nm, good insulating properties can be obtained while maintaining continuous bonding. If it is less than 50 nm, the required insulation cannot be obtained, and if it exceeds 200 nm, the stitch bonding strength is lower than the required strength. More desirably, when the thickness is 50 nm to 100 nm, various characteristics are further improved.

以下、実施例を用いて本発明を説明する。
表１に示す芯材成分組成、Ｐｄ被膜、絶縁性被膜の組み合わせで被覆した実施例１〜１４、比較例１〜２５の銅ボンディングワイヤを以下の製造法で作製した。 Hereinafter, the present invention will be described using examples.
Copper bonding wires of Examples 1 to 14 and Comparative Examples 1 to 25 coated with a combination of the core material component composition, Pd film, and insulating film shown in Table 1 were produced by the following production method.

実施例１〜７及び比較例１〜１０は、Ｐｄ被膜を有する銅ボンディングワイヤで、純度９９．９９９９％の電気銅（以下６Ｎ銅と記す）又は純度９９．９９％の電気銅（以下４Ｎ銅と記す）を使用して表１に示すＣｌ含有量、Ｐ含有量になるように溶解鋳造し、ダイスによる冷間伸線により線径１ｍｍまで縮径した後、アルカリ脱脂、水洗、電解脱脂、水洗、酸活性、水洗を行い、０．１μｍ厚のＰｄストライクメッキを行い、さらに水洗し、所定厚みでＰｄメッキを行い、引き続き水洗、湯洗を行い、エアブロウして水分を除去した後、ダイスによる冷間伸線によって直径２５μｍまで縮径した。次いで、５％Ｈ２−９５％Ｎ２雰囲気の４００℃以上６００℃以下の温度に保たれた長さ５０ｃｍの炉中を線速５０ｍ／分以上の速度で連続的に焼鈍して加工歪みを除去した。
図１（ａ）にその断面形状を示す。１０ａはＰｄ被膜付きの銅ボンディングワイヤ、１は銅極細線、２はＰｄ被膜である。 Examples 1 to 7 and Comparative Examples 1 to 10 are copper bonding wires having a Pd coating, which are 99.9999% pure copper (hereinafter referred to as 6N copper) or 99.99% pure copper (hereinafter 4N copper). Are used to melt and cast so as to have the Cl content and P content shown in Table 1, and after the wire diameter is reduced to 1 mm by cold drawing with a die, alkali degreasing, water washing, electrolytic degreasing, After washing with water, acid activity, washing with water, 0.1 μm thick Pd strike plating, further washing with water, Pd plating with a predetermined thickness, followed by washing with water and hot water, air blowing to remove moisture, The diameter was reduced to 25 μm by cold drawing. Subsequently, a processing strain is reduced by continuously annealing in a 50 cm long furnace maintained at a temperature of 400 ° C. or more and 600 ° C. or less in a 5% H 2 -95% N 2 atmosphere at a linear speed of 50 m / min or more. Removed.
FIG. 1A shows the cross-sectional shape. 10a is a copper bonding wire with a Pd film, 1 is a copper fine wire, and 2 is a Pd film.

実施例８〜１４及び比較例１１〜２５は、Ｐｄ被膜上に絶縁性被膜を施した銅ボンディングワイヤで、６Ｎ銅又は４Ｎ銅を使用してＣｌ含有量、Ｐ含有量になるように溶解鋳造し、ダイスによる冷間伸線により線径１ｍｍまで縮径した後、アルカリ脱脂、水洗、電解脱脂、水洗、酸活性、水洗を行い、０．１μｍ厚のＰｄストライクメッキを行い、更に水洗し、所定厚みでＰｄメッキを行い、その後水洗、湯洗を行い、ダイスによる冷間伸線を経て直径２５μｍまで縮径した。次いで、５％Ｈ２−９５％Ｎ２雰囲気の４００℃以上６００℃以下の温度に保たれた長さ５０ｃｍの炉中を線速５０ｍ／分以上の速度で連続的に焼鈍して加工歪みを除去した後、ワイヤ表面に可溶性ポリイミドインクを塗布し、直後に３００℃以上４００℃以下の温度に加熱し、硬化させてポリイミド樹脂被膜を形成する工程を、複数回行い、表１に示す所定の厚みのポリイミド樹脂被膜を形成した。
その断面形状を図１（ｂ）に示す。１０ｂはポリイミド樹脂被覆の銅ボンディングワイヤ、１は銅極細線、２はＰｄ被膜、３は熱硬化性共重合型ポリイミド樹脂被膜である。 Examples 8 to 14 and Comparative Examples 11 to 25 are copper bonding wires in which an insulating film is applied on a Pd film, and are melt cast so as to have a Cl content and a P content using 6N copper or 4N copper. Then, after reducing the wire diameter to 1 mm by cold drawing with a die, alkali degreasing, water washing, electrolytic degreasing, water washing, acid activity, water washing, 0.1 μm thick Pd strike plating, and further water washing, Pd plating was performed at a predetermined thickness, followed by washing with water and hot water, and then reducing the diameter to 25 μm through cold drawing with a die. Subsequently, a processing strain is reduced by continuously annealing in a 50 cm long furnace maintained at a temperature of 400 ° C. or more and 600 ° C. or less in a 5% H 2 -95% N 2 atmosphere at a linear speed of 50 m / min or more. After the removal, a soluble polyimide ink is applied to the surface of the wire, and immediately after heating to a temperature of 300 ° C. to 400 ° C. and cured, a step of forming a polyimide resin film is performed a plurality of times. A polyimide resin film having a thickness was formed.
The cross-sectional shape is shown in FIG. 10b is a polyimide bonding copper bonding wire, 1 is a copper fine wire, 2 is a Pd film, and 3 is a thermosetting copolymer polyimide resin film.

Ｐｄ被膜を形成するＰｄメッキは、市販の高純度パラジウムメッキ液を用いて電気メッキ法で行った。
ポリイミド樹脂被膜の形成は、熱硬化性共重合型ポリイミド樹脂被膜では、テトラカルボン酸ジ無水物とジアミンとを環化反応させたブロック共重合型ポリイミドを、Ｎ−メチルピロリジノンを主とする溶媒に溶解した可溶性ポリイミドインクを用いて行い、熱硬化性変性型ポリイミド樹脂被膜では、ポリイミド分子中にフッ素を含有させて耐熱性を共重合型よりも向上させたポリイミドを、Ｎ−メチルピロリジノンを主とする溶媒に溶解した可溶性ポリイミドインクを用いて形成し、熱硬化性共縮合型ポリイミド樹脂被膜では、テトラカルボン酸ジ無水物とジアミンとを脱水縮合反応させて得るポリアミック酸を加熱し形成したポリイミドを、Ｎ−メチルピロリジノンを主とする溶媒に溶解した可溶性ポリイミドインクを用いて形成した。 Pd plating for forming a Pd film was performed by electroplating using a commercially available high-purity palladium plating solution.
The polyimide resin film is formed by using a block copolymer polyimide obtained by cyclization reaction of tetracarboxylic dianhydride and diamine with a solvent mainly composed of N-methylpyrrolidinone in a thermosetting copolymer polyimide resin film. In the thermosetting modified polyimide resin coating, a polyimide having a fluorine molecule contained in the polyimide molecule to improve the heat resistance as compared with the copolymer type is mainly composed of N-methylpyrrolidinone. In the thermosetting co-condensation type polyimide resin coating, the polyimide formed by heating polyamic acid obtained by dehydration condensation reaction of tetracarboxylic dianhydride and diamine is formed. , And a soluble polyimide ink dissolved in a solvent mainly containing N-methylpyrrolidinone.

Figure 0005109881
Figure 0005109881

この作製した銅ボンディングワイヤを用いて、各界面の接続強度、銅ボール形成能、ステッチ接合性、絶縁性の各特性を以下に示す方法で評価し、その結果を表２に示す。   Using this prepared copper bonding wire, the connection strength at each interface, copper ball forming ability, stitch bondability, and insulating properties were evaluated by the following methods, and the results are shown in Table 2.

Ｐｄ被膜と芯材の銅極細線との界面の接合強度については、ダイス伸線後のワイヤを２インチスプールへクロス巻で２００ｍ巻き取り、表面を実体顕微鏡観察して、銅表面が露出している場合を界面の接合強度が弱いと判断して「×」とし、露出が見られない場合を強いと判断して「○」とした。   As for the bonding strength at the interface between the Pd coating and the copper fine wire of the core material, the wire after die drawing was wound up to 200 inches by cross winding onto a 2-inch spool, the surface was observed with a stereoscopic microscope, and the copper surface was exposed. The case where the bonding strength at the interface was weak was judged as “x”, and the case where no exposure was observed was judged as strong, and was marked as “◯”.

Ｐｄ被膜と絶縁性被膜との界面の接合強度については、絶縁性被膜を形成後に、ワイヤを２インチスプールへクロス巻で２００ｍ巻き取り、表面を実体顕微鏡観察して、チョコレート色に変色している場合を「×」、変色が見られない場合を「○」と判断した。   Regarding the bonding strength at the interface between the Pd coating and the insulating coating, after forming the insulating coating, the wire was wound into a 2-inch spool in a cross-winding manner by 200 m, and the surface was observed with a stereomicroscope, and the color changed to a chocolate color. The case was judged as “X”, and the case where no discoloration was observed was judged as “◯”.

ボール形成能は、新川社製ワイヤボンダＵＴＣ１０００を用いて、５％Ｈ２−９５％Ｎ２雰囲気下で直径５０μｍの初期銅ボールを５０個作成して評価した。
ボールの変形については、ボールの真球度（真円度と偏芯性）が目視観察で明らかに劣るものが１つでも発生した場合を「×」と判断し、発生しない場合を「○」として変形性を記した。
ボールの酸化については、ＳＥＭ観察によってボール表面に細かい凹凸が形成された場合は「×」と判断し、平滑な表面である場合には「○」と評価した。 The ball forming ability was evaluated by preparing 50 initial copper balls having a diameter of 50 μm in a 5% H 2 -95% N 2 atmosphere using a wire bonder UTC 1000 manufactured by Shinkawa.
Regarding the deformation of the ball, if any one of the sphericity (roundness and eccentricity) of the ball is clearly inferior by visual observation occurs, it is judged as “x”, and if it does not occur, “○”. Described as deformability.
Regarding the oxidation of the ball, it was judged as “X” when fine irregularities were formed on the ball surface by SEM observation, and “◯” was evaluated when the surface was smooth.

パッドダメージについては、シリコンチップの酸化シリコン上に酸化チタン薄膜を形成し、さらに０．８μｍ厚のアルミニウム薄膜を形成したテストチップを用い、１００個のボールボンディングを１００回行い、試料を作製した。水酸化カリウム水溶液でテストチップの表層のアルミニウム薄膜を除去した後、実体顕微鏡でパッドを観察し、酸化チタンに割れ欠けといった損傷が確認された場合を「×」と判定し、損傷のない場合を「○」とした。   Regarding the pad damage, a sample was prepared by performing 100 ball bondings 100 times using a test chip in which a titanium oxide thin film was formed on silicon oxide of a silicon chip and an aluminum thin film having a thickness of 0.8 μm was formed. After removing the aluminum thin film on the surface of the test chip with an aqueous potassium hydroxide solution, observe the pad with a stereomicroscope, and if the titanium oxide is confirmed to be damaged, such as a chipped crack, it is judged as “x”. “○”.

ステッチ接合性は、プラスチック基板上のＡｕメッキ面と、プラスチック基板にダイボンディンされたアルミニウム蒸着チップとの間でボールボンディングを行った後、ボンドプル強度を測定し、センタープル強度で３９ｍＮ未満となるワイヤが観察された場合を「×」と判定し、３９ｍＮ以上の場合を「○」とした。   The stitch bondability is determined by measuring the bond pull strength after ball bonding between the Au plated surface on the plastic substrate and the aluminum vapor-deposited chip bonded to the plastic substrate, and the center pull strength is less than 39 mN. Was observed as “×”, and the case of 39 mN or more was determined as “◯”.

絶縁性については、図２及び図３に示す、プラスチック基板２０上にダイボンディングされたアルミニウムパッド７を有するテストチップ６と、基板上のＡｕメッキリード８との間でワイヤボンディングを行なう際に、２本毎に外側ループワイヤ５を内側ループワイヤ４上で接触するように交差するクロスボンディングを行い一対とし、２本のリード間での電気抵抗を抵抗測定器９を用いて導通の有無を測定する絶縁性試験装置を用い、その導通が観察された場合を「×」とし、絶縁状態の場合を「○」判定した。   As for insulation, when performing wire bonding between the test chip 6 having the aluminum pad 7 die-bonded on the plastic substrate 20 and the Au plating lead 8 on the substrate, as shown in FIGS. Cross bonding is performed so that the outer loop wires 5 come into contact with each other on the inner loop wire 4 every two wires, and the electrical resistance between the two leads is measured using a resistance measuring device 9 to measure the presence or absence of conduction. Using the insulation test apparatus, the case where the continuity was observed was determined as “X”, and the case of the insulation state was determined as “◯”.

含まれるＣｌによる信頼性評価に関しては、Ｆｅ−４２％ＮｉリードフレームのＡｇメッキ面上にダイボンディングされた０．８μｍ厚のアルミニウム電極と、Ａｇメッキリード電極間をワイヤボンディングによって接続し、その後温度８５℃湿度８５％の環境で２１６時間放置してシア強度測定を行い、ボールが剥がれた後のパッド面に塩素による腐食変色が確認された場合をＮＧと判断した。   Regarding the reliability evaluation by the contained Cl, the 0.8 μm thick aluminum electrode die-bonded on the Ag-plated surface of the Fe-42% Ni lead frame and the Ag-plated lead electrode are connected by wire bonding, and then the temperature is increased. Shear strength measurement was performed by leaving it in an environment of 85 ° C. and 85% humidity for 216 hours, and when the discoloration due to chlorine was confirmed on the pad surface after the ball was peeled off, it was judged as NG.

Figure 0005109881
Figure 0005109881

表２から明らかなように、本発明に係る実施例１から１４は、各界面の接合強度、銅ボール形成能、ステッチ接合性、絶縁性共に優れている。   As is apparent from Table 2, Examples 1 to 14 according to the present invention are excellent in bond strength, copper ball forming ability, stitch bondability, and insulation at each interface.

実施例１〜７は、Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上２００ｐｐｍ以下含み、残部Ｃｕと不可避不純物の成分組成からなる銅極細線の表面にＰｄ被膜が形成されるために、銅極細線とＰｄ被膜との接合強度が強く、伸線前に焼鈍によってＰｄとＣｕとの界面で拡散接合を行わなくとも伸線後にＰｄが剥離して銅表面が露出することはない。
又、Ｐｄ被膜が剥離せずに芯材の銅極細線を覆っているために、銅ボール形成後の銅ボールの変形や芯ずれも発生せず、その酸化もなく、含まれるＰにより銅ボールの表面硬さが硬くならないためにパッドダメージも発生せず、ステッチ接合性も良好で、Ｃｌ含有量が１ｐｐｍ以下であるため湿度を含む信頼性評価においても、銅ボール接合界面の塩素濃化による銅ボール剥がれの発生が無いことがわかる。 In Examples 1 to 7, since the Pd film is formed on the surface of the copper fine wire containing Cl at 1 ppm or less, P at 10 ppm or more and 200 ppm or less and the remaining Cu and the inevitable impurities, the copper fine wire and Pd Bonding strength with the coating is strong, and Pd is not peeled after drawing and the copper surface is not exposed even if diffusion bonding is not performed at the interface between Pd and Cu by annealing before drawing.
In addition, since the Pd coating does not peel off and covers the copper fine wire of the core material, the copper ball is not deformed or misaligned after the formation of the copper ball, and there is no oxidation of the copper ball due to the contained P. Since the surface hardness of the steel does not become hard, pad damage does not occur, stitch jointability is good, and Cl content is 1 ppm or less, so even in reliability evaluation including humidity, due to chlorine concentration at the copper ball joint interface It can be seen that there is no copper ball peeling.

実施例８〜１４は、銅極細線とＰｄ被膜との接合強度が強いために伸線前に焼鈍によってＰｄとＣｕとの界面で拡散接合を行わなくとも伸線後にＰｄが剥離して銅表面が露出することがないので、銅の変色を起こすことなくＮ−メチルピロリジノンを溶媒とした熱硬化性共重合型ポリイミドインク溶液を均一にＰｄ被膜上へ塗布し、加熱硬化させることでポリイミド被膜が容易に形成されている。   In Examples 8 to 14, since the bonding strength between the copper fine wire and the Pd film is strong, the Pd peels off after the wire drawing without performing diffusion bonding at the interface between Pd and Cu by annealing before wire drawing. Is not exposed, so that a polyimide coating is obtained by uniformly applying a thermosetting copolymer type polyimide ink solution using N-methylpyrrolidinone as a solvent on a Pd coating without causing copper discoloration, and then curing by heating. It is easily formed.

このＰｄ被膜上にポリイミド樹脂が被覆された銅ボンディングワイヤは、Ｐｄ被膜が剥離せずに芯材の銅極細線を覆っているために、銅ボール形成後の銅ボールの変形や芯ずれも発生せず、その酸化もなく、含まれるＰにより銅ボールの表面硬さが硬くならないためにパッドダメージも発生せず、ステッチ接合性も良好で、Ｃｌ含有量が１質量ｐｐｍ以下であるため湿度を含む信頼性評価においても、銅ボール接合界面の塩素濃化による銅ボール剥がれの発生が無いと共に、絶縁性を付与する被膜が熱硬化性共重合型ポリイミド樹脂であるためステッチボンディング中に樹脂が微細に粉砕されて剥離するためにステッチ接合性も良好であり、熱硬化性樹脂であるため高温のクロスボンディングにおいてもワイヤが被膜樹脂にめり込んで芯材同士が接触する、電気的な短絡現象を起こすこともない。   The copper bonding wire with the polyimide resin coated on this Pd film covers the copper fine wire of the core material without peeling off the Pd film, so deformation and misalignment of the copper ball after forming the copper ball also occur No oxidation, no surface damage of the copper balls due to the contained P, so pad damage does not occur, stitch bondability is good, and the Cl content is 1 mass ppm or less, so the humidity is low. In the reliability evaluation, the copper ball does not peel off due to chlorine concentration at the copper ball joint interface, and the coating that provides insulation is a thermosetting copolymer polyimide resin, so the resin is fine during stitch bonding. Because it is pulverized and peeled off, the stitch bondability is good. There is contact, it is not even cause an electrical short circuit phenomenon.

一方、本発明の範囲を逸脱した比較例１〜２５では、何らかの特性が劣っていることがわかる。
Ｐの含有量が１０ｐｐｍ未満である比較例１、３、６、８、１１、１２、１３、１８、１９、２０及び２４は、いずれの場合もＰｄ被膜形成後の伸線工程でＰｄが剥離して芯材の地肌が露出してしまい、ボールの芯ズレも多発し、ステッチボンディング性も低下している。
一方、Ｐを２００ｐｐｍを超えて含有する比較例２、５、７、１０、１６及び２３では、いずれの場合もパッドダメージが観察されている。 On the other hand, in Comparative Examples 1 to 25 that depart from the scope of the present invention, it can be seen that some characteristics are inferior.
In any of Comparative Examples 1, 3, 6, 8, 11, 12, 13, 18, 19, 20, and 24 in which the P content is less than 10 ppm, Pd is peeled off in the wire drawing step after the Pd film is formed. As a result, the background of the core material is exposed, the core misalignment of the ball occurs frequently, and the stitch bonding property is also deteriorated.
On the other hand, in Comparative Examples 2, 5, 7, 10, 16, and 23 containing P in excess of 200 ppm, pad damage is observed in any case.

Ｃｌが１ｐｐｍを超えて含有する比較例３、４、５、８、９、１０、１７、２４及び２５では、いずれの場合にも湿度を含む信頼性評価にて銅ボール接合界面での塩素濃化による腐食によって生じるボール剥離が観察されている。   In Comparative Examples 3, 4, 5, 8, 9, 10, 17, 24, and 25 containing Cl in excess of 1 ppm, the chlorine concentration at the copper ball joint interface was evaluated by reliability evaluation including humidity in any case. Ball separation caused by corrosion due to crystallization has been observed.

又、絶縁被膜に熱硬化性共重合型ポリイミド樹脂とは異なる熱硬化性縮合型ポリイミド樹脂や熱硬化性変性型ポリイミド樹脂を使用した比較例１２、１３、１４、１５、
１９、２０、２１及び２２では、ステッチボンディング性が大きく低下したり、ワイヤボンディングを完全に行ったクロスワイヤー対を用いた絶縁性の評価において、ボンディングワイヤが樹脂被膜にめり込んで発生する絶縁不良が観察されたりしている。 Further, Comparative Examples 12, 13, 14, 15 using a thermosetting condensation type polyimide resin or a thermosetting modified polyimide resin different from the thermosetting copolymer type polyimide resin for the insulating coating
19, 20, 21, and 22, the stitch bonding property is greatly deteriorated, or in the insulation evaluation using the cross wire pair in which the wire bonding is completely performed, the insulation failure caused by the bonding wire being embedded in the resin film is caused. It has been observed.

本発明に係る銅ボンディングワイヤの断面図で、（ａ）はＰｄ被覆銅ボンディングワイヤ、（ｂ）樹脂被覆の銅ボンディングワイヤである。It is sectional drawing of the copper bonding wire which concerns on this invention, (a) is a Pd covering copper bonding wire, (b) is a resin covering copper bonding wire. 絶縁性試験装置の模式平面図である。It is a model top view of an insulation test apparatus. 図２の絶縁性試験装置のボンディングループを表す側面図である。It is a side view showing the bonding loop of the insulation test apparatus of FIG.

符号の説明Explanation of symbols

１ 銅極細線
２ Ｐｄ被膜
３ 絶縁性被膜（熱硬化性共重合型ポリイミド樹脂被膜）
４ 内側ループワイヤ
５ 外側ループワイヤ
６ テストチップ
７ アルミニウムパッド
８ Ａｕメッキリード
９ 抵抗測定器
１０ａ 銅ボンディングワイヤ
１０ｂ 銅ボンディングワイヤ（絶縁性樹脂被覆）
２０ プラスチック基板 1 Copper fine wire 2 Pd coating 3 Insulating coating (thermosetting copolymer type polyimide resin coating)
4 inner loop wire 5 outer loop wire 6 test chip 7 aluminum pad 8 Au plating lead 9 resistance measuring instrument 10a copper bonding wire 10b copper bonding wire (insulating resin coating)
20 Plastic substrate

Claims (2)

Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上、２００ｐｐｍ以下含み、残部Ｃｕと不可避不純物とからなる無酸素銅の銅極細線を芯材とし、前記芯材の表面にＰｄ被膜が形成されていることを特徴とする銅ボンディングワイヤ。   Cl is 1 ppm or less, P is 10 ppm or more and 200 ppm or less, a copper fine wire of oxygen-free copper composed of the remainder Cu and inevitable impurities is used as a core material, and a Pd film is formed on the surface of the core material And copper bonding wire. Ｃｌを１ｐｐｍ以下、Ｐを１０ｐｐｍ以上、２００ｐｐｍ以下含み、残部Ｃｕと残部不可避不純物とからなる無酸素銅の銅極細線を芯材とし、前記芯材の表面にＰｄ被膜を設け、前記Ｐｄ被膜の表面に熱硬化性共重合型ポリイミド樹脂被膜が形成されていることを特徴とする銅ボンディングワイヤ。   Cl is 1 ppm or less, P is 10 ppm or more and 200 ppm or less, a copper fine wire of oxygen-free copper composed of the remainder Cu and the remainder unavoidable impurities is used as a core material, a Pd film is provided on the surface of the core material, A copper bonding wire, wherein a thermosetting copolymer polyimide resin film is formed on a surface.
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