JP5293728B2 - Bonding wire - Google Patents

Bonding wire Download PDF

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JP5293728B2
JP5293728B2 JP2010278076A JP2010278076A JP5293728B2 JP 5293728 B2 JP5293728 B2 JP 5293728B2 JP 2010278076 A JP2010278076 A JP 2010278076A JP 2010278076 A JP2010278076 A JP 2010278076A JP 5293728 B2 JP5293728 B2 JP 5293728B2
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wire
palladium
ball
copper
bonding
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JP2012129301A (en
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亮 富樫
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Nippon Micrometal Corp
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Nippon Micrometal Corp
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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、またはワイヤ先端にボールを形成し、電極パッドあるいは外部電極にスタッドバンプを形成する銅バンプワイヤなどに用いられる半導体装置の接続用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, or a semiconductor used for a copper bump wire in which a ball is formed at the tip of a wire and a stud bump is formed on an electrode pad or an external electrode. The present invention relates to a connecting wire for the apparatus.

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、従来は金線をボンディングワイヤとして用いていた。
しかし、金線の組成は、９９ｍａｓｓ％から９９．９９ｍａｓｓ％が金であり、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）や製品価格が安いメモリパッケージでは、より細い線径の金線を用いることで、金の使用量を減らし、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 connecting an electrode on a semiconductor element and an external electrode is very thin, 15 to 75 μm, and it has been conventionally a gold wire because of its chemical stability and ease of handling in the atmosphere. Was used as a bonding wire.
However, the composition of the gold wire is gold from 99 mass% to 99.99 mass%, which is very expensive. Therefore, the plastic ball grid array package (Plastic Ball Grid Array) with a very large number of IO pins used for the gold wire is used. In the case of a memory package having a low package price or a product price, there is a demand to reduce the amount of gold used and to reduce the cost by using a gold wire having a thinner wire diameter.

一方、金の電気比抵抗は約２．３μΩｃｍで低いものであるが、その線径を細くすることは、その電気抵抗の上昇を招くため、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と金より低く、安価な銅に代替したいとの要望があった。
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。 On the other hand, the electrical resistivity of gold is as low as about 2.3 μΩcm. However, reducing the wire diameter leads to an increase in the electrical resistance, so that the semiconductor package that does not want to change the current value is thinned. There is a limit, and from the viewpoint of reducing heat generation in increasing the density of the package, there has been a demand for replacement with inexpensive copper, which has an electrical specific resistance of about 1.7 μΩcm, which is lower than gold.
Under such circumstances, copper bonding wires have been developed and commercialized.

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酸化、などの問題を解消しなければならなかった。   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 Problems such as copper composition to prevent corrosion at the interface and oxidation 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 must be solved. did not become.

さらに、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１には、高純度銅極細線の表面にパラジウム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２や特許文献３には、パラジウム被覆銅ボンディングワイヤ表面のパラジウム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。 Furthermore, since the surface of the copper bonding wire is easily oxidized, there is a problem that the bonding property of the stitch bonding is lowered due to the oxidation. Patent Document 1 discloses that the surface of the copper is formed by forming a palladium coating on the surface of the high-purity copper fine wire. A method for preventing the oxidation of is disclosed.
Further, Patent Document 2 and Patent Document 3 disclose a method for preventing peeling at the interface between the palladium coating layer and the copper core material on the surface of the palladium-coated copper bonding wire, and heat treatment is performed after the coating is formed. It is shown that a concentration gradient is provided at the copper palladium interface.
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.

特許文献２では、メッキで被覆する際の被覆材と芯材との拡散を課題とし、芯材をワイヤ表面に露出させない薄膜被覆の状態を述べている。オージェ電子分光法を用いて深さ方向にスパッタしたときの時間をＳｉＯ２の厚みで換算して得られるパラジウムと銅の強度スペクトルから、深さによる両元素の存在比率すなわち原子分率が計算される。
この方法から、例えばパラジウムの存在比率が１０〜９０ａｔ％となる領域の厚み、いわゆる拡散層の厚みが算出されるが、拡散層の厚みに関わらずめっきが銅芯材表面から剥がれやすい場合があり、めっき後の伸線加工中に局部的にめっきが剥がれてパラジウム層の厚みが薄くなってしまったり、はがれたパラジウムが伸線ダイスとワイヤとの間に噛み込んで伸線キズを発生させたり、あるいは半導体素子組み立て中にボール形状の真球性が低いボールが発生したり、ボンディング後のボールが均一な色を呈せずに一部に銅色の強い、すなわちパラジウム濃度の低い部分が発生したりした。 Patent Document 2 describes the state of thin film coating in which the core material is not exposed on the wire surface, with the problem of diffusion between the coating material and the core material when coating with plating. From the intensity spectrum of palladium and copper obtained by converting the time when sputtered in the depth direction using Auger electron spectroscopy into the thickness of SiO 2 , the abundance ratio of both elements, that is, the atomic fraction, is calculated. The
From this method, for example, the thickness of a region where the abundance ratio of palladium is 10 to 90 at%, that is, the thickness of a so-called diffusion layer is calculated, but the plating may be easily peeled off from the copper core material surface regardless of the thickness of the diffusion layer. During the wire drawing after plating, the plating is peeled off locally and the thickness of the palladium layer is reduced, or the peeled palladium is caught between the wire drawing die and the wire to cause wire drawing flaws. Or, ball-shaped balls with low sphericity are generated during the assembly of semiconductor elements, or the bonded balls do not exhibit a uniform color and some of them have a strong copper color, that is, a low palladium concentration. I did.

特許文献２や特許文献３では、被覆層を形成した後に熱処理を施すことが好ましいとして、めっき後に熱処理を施し、銅をある程度パラジウム側に拡散させ、パラジウム層と銅との界面に濃度勾配を設けたり、金属間化合物層を形成したりする方法が提案されている。しかし、メッキ直後に銅がパラジウムへ拡散するほどの熱処理を行うと、パラジウム被覆膜の表面粗さが大きくなり、伸線中にパラジウム被覆膜が剥がれたり割れたりしやすくなることが観察された。   In Patent Document 2 and Patent Document 3, it is preferable to perform a heat treatment after forming a coating layer. A heat treatment is performed after plating, copper is diffused to the palladium side to some extent, and a concentration gradient is provided at the interface between the palladium layer and copper. Or a method of forming an intermetallic compound layer has been proposed. However, it is observed that if the heat treatment is performed so that copper diffuses into palladium immediately after plating, the surface roughness of the palladium-coated film increases, and the palladium-coated film tends to peel or crack during wire drawing. It was.

さらに、特許文献２あるいは特許文献３では、ワイヤの先端に形成されるボールの表面が一様にパラジウム色になりにくく、パラジウム色がボール全体の５０％を下回る場合にはボール接合性が不安定になったり、あるいはバンプワイヤとして使用する場合にはボール上面がパラジウムに十分覆われずに、銅色を呈する部分が発生して酸化し、形成されたバンプ上部の接合性が悪化してしまうためにバンプワイヤとして連続ボンディングができなくなるという不具合も発生した。   Furthermore, in Patent Document 2 or Patent Document 3, the surface of the ball formed at the tip of the wire does not easily become palladium-colored, and the ball bondability is unstable when the palladium color is less than 50% of the entire ball. Or when it is used as a bump wire, the upper surface of the ball is not sufficiently covered with palladium, and a copper-colored portion is generated and oxidized, which deteriorates the bondability of the formed bump upper portion. There was also a problem that continuous bonding was not possible as a bump wire.

特許文献４のようにパラジウム層と銅芯材との間に金層を設けることによって、銅とパラジウムとの密着性を高める方法も提案されているが、ボールの真球度は高まるものの、ボール表面にパラジウムと金が濃縮して、パラジウムと金と銅との合金が形成されやすく、そのため合金化による加工硬化の上昇が著しく、ボールボンディング後のパッドダメージの発生がパラジウム層のみの場合に比べて高いという問題があり、その適用は、パッドが堅牢な素子に限られていた。   Although a method for improving the adhesion between copper and palladium by providing a gold layer between a palladium layer and a copper core as in Patent Document 4 has also been proposed, although the sphericity of the ball increases, the ball Palladium and gold are concentrated on the surface, and an alloy of palladium, gold, and copper is likely to be formed. Therefore, the work hardening due to alloying is significantly increased, and the occurrence of pad damage after ball bonding is compared to the case of only the palladium layer. And its application has been limited to devices with robust pads.

特開昭６２−９７３６０号公報JP-A-62-97360 特開２００６−１００７７７号公報Japanese Patent Laid-Open No. 2006-100777 特開２００６−２１６９２９号公報JP 2006-216929 A 特開２００４−００６７４０号公報JP 2004-006740 A

銅芯材をパラジウムで被覆するボンディングワイヤ、あるいはバンプワイヤの問題点は、ボール形成後にボール表面が合金化によって硬化してしまい、ボールボンディング時にパッドダメージが出来やすくなることと、ボール表面にパラジウムに覆われない部分が発生して酸化し、バンプ形成後のバンプ上へのスティッチ接合性が悪化することである。   The problem with bonding wires or bump wires that cover the copper core material with palladium is that the ball surface hardens due to alloying after ball formation, making it easier to cause pad damage during ball bonding, and covering the ball surface with palladium. A part which is not broken is generated and oxidized, and the stitch bondability on the bump after the bump formation is deteriorated.

本発明に係る課題であるボール表面の合金化による硬度上昇の防止と、ボール表面のパラジウム被膜形成性を向上させ、パッドダメージの発生しないボール、接合性の良いバンプを形成する半導体装置用ボンディングワイヤあるいはバンプワイヤの提供を目的とするものであり、パッドダメージのために発生する高温放置後プル試験におけるボールリフトの問題を解消することにある。   Bonding wire for a semiconductor device which prevents the increase in hardness due to alloying of the ball surface, which is a problem related to the present invention, and improves the formation of a palladium film on the ball surface to form a ball free from pad damage and a bump having good bondability Alternatively, it is intended to provide a bump wire and to solve the problem of ball lift in a pull test after standing at a high temperature due to pad damage.

上記課題に鑑み、本発明の第１の発明は、半導体装置用のボンディングワイヤ、およびバンプワイヤに好適な銅を主成分とする芯材にパラジウムを被覆した半導体装置の接続用ワイヤであって、５０ａｔ％以上のパラジウムを含むパラジウム被覆層と、銅成分が５０ａｔ％以上である芯材との間に、５ａｔ％以上、４０ａｔ％以下の炭素を含む中間層を備えることを特徴とするものである。   In view of the above problems, a first invention of the present invention is a bonding wire for a semiconductor device, and a connecting wire for a semiconductor device in which a core material mainly composed of copper suitable for a bump wire is coated with palladium, and has 50 at. An intermediate layer containing carbon of 5 at% or more and 40 at% or less is provided between a palladium coating layer containing palladium of at least% and a core material having a copper component of 50 at% or more.

本発明の第２の発明は、第１の発明における中間層が、５ａｔ％以上、２０ａｔ％以下の炭素を含むことを特徴とするものである。
さらに、本発明の第３の発明は、第１および第２の発明において、芯材へのめっきによるパラジウム被覆後に、引き抜き伸線加工を行うことを特徴とするものである。
また、本発明の第４の発明は、第１から第３の発明における芯材へのパラジウム被覆前に、芯材を大気中で加熱処理することを特徴とするものである。 A second invention of the present invention is characterized in that the intermediate layer in the first invention contains 5 at% or more and 20 at% or less of carbon.
Furthermore, the third invention of the present invention is characterized in that in the first and second inventions, the drawing and drawing are performed after the palladium coating by plating on the core material.
The fourth invention of the present invention is characterized in that the core material is heat-treated in the atmosphere before the palladium coating on the core material in the first to third inventions.

本発明の第５の発明は、第１の発明から第４の発明のいずれかの発明による半導体装置の接続用ワイヤを用いた半導体装置用ボンディングワイヤである。
また、本発明の第６の発明は、第１の発明から第４の発明のいずれかの発明による半導体装置の接続用ワイヤを用いた半導体装置用バンプワイヤである。 According to a fifth aspect of the present invention, there is provided a bonding wire for a semiconductor device using the connection wire for a semiconductor device according to any one of the first to fourth aspects of the invention.
According to a sixth aspect of the present invention, there is provided a bump wire for a semiconductor device using a connection wire for a semiconductor device according to any one of the first to fourth aspects of the invention.

本発明のパラジウム被覆銅ボンディングワイヤは、その材料費が安価で、且つ製造が容易であり、従って製造コストも安価である。
また、このパラジウム被覆銅ボンディングワイヤの表面は、酸化しにくく、ボールボンディングにおける半導体素子の損傷も回避し、ボール真球性や接合性が高く、スティッチ接合性も良好な、幅広い半導体素子に使用することが可能となるボンディングワイヤである。さらに、半導体素子上に形成されたバンプとリードを結ぶバンプワイヤとしても有用である。 The palladium-coated copper bonding wire of the present invention has a low material cost and is easy to manufacture, and thus the manufacturing cost is also low.
Also, the surface of this palladium-coated copper bonding wire is difficult to oxidize, avoids damage to the semiconductor element in ball bonding, is used for a wide range of semiconductor elements that have high ball sphericity and bondability and good stitch bondability. This is a bonding wire that can be used. Furthermore, it is also useful as a bump wire that connects a bump formed on a semiconductor element and a lead.

本発明の半導体装置の接続用ワイヤのオージェ電子分光分析法による深さ方向でのパラジウム、銅、炭素の深さ方向の半定量値プロファイルを示す図である。It is a figure which shows the semi-quantitative value profile of the depth direction of the depth direction by the Auger electron spectroscopy analysis method of the connection wire of the semiconductor device of this invention. 潰しボールの外観例を示す図で、（ａ）はボール上部がほぼパラジウムで覆われている例、（ｂ）は明らかに銅が露出している場合の例を示す図である。It is a figure which shows the example of an external appearance of a crushing ball, (a) is a figure which shows the example in which the upper part of a ball is substantially covered with palladium, and (b) is an example in case copper is exposed. 接続用ワイヤの特性評価における「キャピラリ詰まり」の評価方法を示す説明図である。It is explanatory drawing which shows the evaluation method of "capillary clogging" in the characteristic evaluation of a connecting wire.

本発明に係るボンディングワイヤ、およびバンプワイヤは、銅を主成分とする芯材に、パラジウムを被覆したワイヤであって、オージェ電子分光法による深さ方向分析において、パラジウムが５０ａｔ％以上であるパラジウム被覆層と、銅が５０ａｔ％以上である芯材との間に、５ａｔ％以上４０ａｔ％以下の炭素を含む中間層を有するものである。   The bonding wire and the bump wire according to the present invention are wires in which a core mainly composed of copper is coated with palladium, and in a depth direction analysis by Auger electron spectroscopy, palladium is coated with 50 at% or more of palladium. An intermediate layer containing carbon of 5 at% or more and 40 at% or less is provided between the layer and the core material in which copper is 50 at% or more.

中間層における炭素量を、５ａｔ％以上とするのは、ワイヤ端にフォーミングガス中で形成されたボールの表面で、パラジウムと銅との合金を形成し難くするためであり、４０ａｔ％以下とするのはワイヤボンディング中にパラジウムがワイヤから剥離したり、窒素ガス中で形成されたボールの上部において、銅を露出しにくくするためである。
特に、炭素含有量が５ａｔ％以上、２０ａｔ％以下では、ボールボンディング後の１７５℃で１４４時間での高温放置試験プル破断試験における破断モードにおいて、ボールリフトの発生率がないという極めて優れた利点があり、最も高信頼性が要求される小ボール接合が不可欠なファインピッチＰＢＧＡへの適用が可能となる。 The reason why the carbon amount in the intermediate layer is 5 at% or more is to make it difficult to form an alloy of palladium and copper on the surface of the ball formed in the forming gas at the wire end, and is 40 at% or less. This is because palladium is peeled off from the wire during wire bonding or copper is hardly exposed at the upper part of the ball formed in nitrogen gas.
In particular, when the carbon content is 5 at% or more and 20 at% or less, there is an extremely excellent advantage that there is no occurrence of ball lift in the break mode in the high temperature standing test pull break test at 175 ° C. for 144 hours after ball bonding. In addition, it can be applied to a fine pitch PBGA in which small ball bonding requiring the highest reliability is indispensable.

ところで、各層（芯材、パラジウム被覆層、中間層）の各成分、芯材では銅成分、パラジウム被覆層ではパラジウム成分、中間層では炭素成分の値は、オージェ電子分光法による深さ方向の分析により求めることが良く、以下に示す方法で行うことが簡易である。
先ず、試料線径よりも小さいビーム径で照射し、スパッタリングによって深さ方向でのワイドスキャンスペクトルから各検出元素の半定量値を算出し、続いてパラジウム、銅、炭素の半定量プロファイルを作成し、パラジウムが５０％以上である被覆層となる深さ位置と、銅が５０％以上の芯材となる深さ位置を同定し、その両者の間での炭素の半定量値の最大値を読み取る。
その分析例として図１に示すパラジウム、銅、炭素の深さ方向の半定量値プロファイルからは、この試料はパラジウム被覆層と芯材層との間の中間層の炭素量が、約１３ａｔ％から約１０ａｔ％程度であることがわかる。 By the way, values of each component (core material, palladium coating layer, intermediate layer), copper component in the core material, palladium component in the palladium coating layer, and carbon component in the intermediate layer are analyzed in the depth direction by Auger electron spectroscopy. It is easy to obtain by the following method.
First, irradiate with a beam diameter smaller than the sample wire diameter, calculate the semi-quantitative value of each detection element from the wide scan spectrum in the depth direction by sputtering, then create a semi-quantitative profile of palladium, copper, and carbon. The depth position where the coating layer is 50% or more of palladium and the depth position where the core material is 50% or more of copper are identified, and the maximum value of the semi-quantitative value of carbon between them is read. .
As an analysis example, from the semi-quantitative profile in the depth direction of palladium, copper, and carbon shown in FIG. 1, this sample has a carbon content of about 13 at% in the intermediate layer between the palladium coating layer and the core material layer. It turns out that it is about 10 at%.

次に、芯材にパラジウムを被覆する方法としては、スパッタリング、イオンプレーティング、真空蒸着に代表される物理蒸着方法、プラズマＣＶＤに代表される化学蒸着方法、めっき等が考えられるが、安価な設備で簡易に、かつワイヤ長手方向に連続的に大量生産する手法としては、真空設備が不要で、短時間で被膜を形成でき、かつプロセス中でパラジウムの重量バランス管理が安易で重量ロスも少ないめっき法が好ましい。   Next, as a method for coating palladium on the core material, sputtering, ion plating, physical vapor deposition method represented by vacuum vapor deposition, chemical vapor deposition method represented by plasma CVD, plating, etc. can be considered. A simple and easy method for mass production in the longitudinal direction of the wire is a plating process that does not require vacuum equipment, can form a coating in a short time, and is easy to manage the weight balance of palladium in the process with little weight loss. The method is preferred.

さらに、パラジウム被覆層の形成前に、芯材を大気中で加熱処理すると、ワイヤ全面に炭素量が５ａｔ％以上２０ａｔ％以下の層が形成されやすくなるため好ましい。   Furthermore, it is preferable to heat-treat the core material in the air before forming the palladium coating layer because a layer having a carbon content of 5 at% or more and 20 at% or less is easily formed on the entire surface of the wire.

以下、実施例を用いて本発明を説明する。
表１に実施例の芯材の組成、パラジウム被覆厚み、製造条件を纏めて示す。
実施例１〜９、及び比較例１〜９は、Ｐｄ被膜を有する半導体用接続ワイヤで、純度９９．９９９９％の電気銅に、表１に示すＰ含有量になるようにリン銅地金を添加して連続熔解鋳造を行い、ダイスによる引き抜き伸線加工を加えて、線径０．２ｍｍまで縮径した後、線速１０ｍ／ｍｉｎで連続加熱処理（加熱処理１）を行った。さらに、めっき前処理となる脱脂、化学研摩、酸活性を施し、銅素地を露出させて膜厚０．１μｍのパラジウムストライクメッキを施し、次に、所定厚みのパラジウムメッキを行い、次いで加熱処理２を行い、ダイスによる引き抜き伸線加工を経て、直径２０μｍまで縮径し、伸び率が１０％となるように窒素ガス雰囲気中で線速５０ｍ／ｍｉｎで連続焼鈍した。なお、メッキ厚はメッキの時間を変えることで調整した。 Hereinafter, the present invention will be described using examples.
Table 1 summarizes the composition of the core material, the palladium coating thickness, and the manufacturing conditions of the examples.
Examples 1-9 and Comparative Examples 1-9 are connecting wires for semiconductors having a Pd coating, and phosphorous copper ingots are made to have a P content shown in Table 1 on electrolytic copper having a purity of 99.9999%. After adding and performing continuous melt casting, drawing wire drawing with a die was performed to reduce the wire diameter to 0.2 mm, continuous heat treatment (heat treatment 1) was performed at a wire speed of 10 m / min. Further, degreasing, chemical polishing, and acid activation, which are pretreatments for plating, are performed, the copper base is exposed, and palladium strike plating with a film thickness of 0.1 μm is performed, then palladium plating with a predetermined thickness is performed, and then heat treatment 2 After drawing and drawing with a die, the diameter was reduced to 20 μm, and continuous annealing was performed at a linear speed of 50 m / min in a nitrogen gas atmosphere so that the elongation rate was 10%. The plating thickness was adjusted by changing the plating time.

実施例１〜３は、炭素量が５〜２０ａｔ％、実施例４〜９は炭素量が２１〜４０ａｔ％、比較例１〜６は、炭素量５ａｔ％未満、比較例７〜９は炭素量が４０ａｔ％を超えるものである。
この炭素量は、加熱処理１または加熱処理２の温度、および雰囲気ガスの種類で調整した。ここで、温度の低温とは再結晶温度未満の温度であり、中温とは再結晶温度近傍、高温とは結晶粒が粗大化する程度の高温を示すものである。加熱処理１では大気中、もしくは５％水素を含む窒素ガス（表１ではＦＧと示す）を用いた連続加熱処理を行い、加熱処理２では窒素ガスを用いて雰囲気焼鈍を行った。 Examples 1 to 3 have a carbon content of 5 to 20 at%, Examples 4 to 9 have a carbon content of 21 to 40 at%, Comparative Examples 1 to 6 have a carbon content of less than 5 at%, and Comparative Examples 7 to 9 have a carbon content. Is over 40 at%.
The amount of carbon was adjusted by the temperature of heat treatment 1 or heat treatment 2 and the type of atmospheric gas. Here, the low temperature is a temperature lower than the recrystallization temperature, the intermediate temperature is near the recrystallization temperature, and the high temperature is a high temperature at which the crystal grains become coarse. In heat treatment 1, continuous heat treatment was performed in the air or using nitrogen gas containing 5% hydrogen (shown as FG in Table 1), and in heat treatment 2, atmosphere annealing was performed using nitrogen gas.

作製した接続用ワイヤを「ボンディングワイヤ」、「バンプワイヤ」として用いるためにボンディングテストを実施して、その特性評価を行った。
ボンディングテストは、ワイヤボンダ（キューリック＆ソファ社製の「ＩＣｏｎｎ」）を使用し、ボール形成に用いたガスは、５％水素−９５％窒素のフォーミングガス（表２において、「ＦＧ」と表記）と、１００％窒素ガス（表２において、「窒素」と表記）の２種類を用いた。 In order to use the produced connection wires as “bonding wires” and “bump wires”, a bonding test was performed and the characteristics were evaluated.
For the bonding test, a wire bonder (“ICon” manufactured by Curik & Sofa) was used, and the gas used for ball formation was 5% hydrogen-95% nitrogen forming gas (indicated as “FG” in Table 2). And 100% nitrogen gas (shown as “nitrogen” in Table 2).

なお、この使用したワイヤボンダは、ボール形成に用いるガスをボンディングサイトへも吹き付ける機能があり、顧客の使用条件と同条件での評価とするため、今回の特性評価でもガスのボンディングサイトへの吹き付けを採用して行った。
ボールボンディング評価用の半導体素子としてはパッドの材質が、Ａｌ−０．５％Ｃｕでアルミニウム膜厚が０．６μｍの市販のテストウエハを用い、リードフレームに３μｍ厚の銀めっき品を用いた。 The wire bonder used has a function to blow the gas used for ball formation to the bonding site, and the evaluation is performed under the same conditions as the customer's use conditions. Adopted.
As a semiconductor element for ball bonding evaluation, a commercially available test wafer having a pad material of Al-0.5% Cu and an aluminum film thickness of 0.6 μm was used, and a 3 μm-thick silver plating product was used for the lead frame.

シア強度およびプル強度は、デイジ社のボンドテスター５０００を用いて、ワイヤボンダのトランスデューサの振動方向であるＹ方向にボンディングされたワイヤのシア強度と、ループの中央にフックを掛けて引っ張って行うセンタープル強度で測定した。
Ｙ方向にはボールボンディング時にボールによるアルミニウム押出しが発生しやすく、接合性評価時の接合部破壊のきっかけになりやすい。また、Ｙ方向でのボンディング時にはワイヤが銀メッキ上で滑りやすくなるため、いずれの接合もＸ方向に比べて不十分な接合になりやすく、接合性の比較評価は、主にＹ方向にボンディングされたワイヤで行った。 The shear strength and pull strength are determined by using a bond tester 5000 from Daisy, and the center strength of the wire bonded in the Y direction, which is the vibration direction of the transducer of the wire bonder, and the center pull of the loop. Measured by strength.
In the Y direction, aluminum is likely to be extruded by the ball at the time of ball bonding, and it is likely to cause the joint to be broken at the time of evaluation of bondability. In addition, since the wire becomes slippery on the silver plating during bonding in the Y direction, all the joints are likely to be insufficient in comparison with the X direction, and the comparative evaluation of the bondability is mainly performed in the Y direction. Made with a wire.

接合性評価としては、線径の１．７倍の直径となるように形成したボールの水平方向から観察したボール形状、潰しボールの直径が線径の２倍となるようにボールボンディングされたＹ方向でのシア強度、さらにはＹ方向でのプル強度測定における破壊モードのうちパッドダメージが原因と判断されるアルミニウムパッドの下層からの金属膜の剥離、すなわちメタルピーリングの有無を測定し、表２に「０時間放置パッドダメージ」として評価した。   For the evaluation of bondability, the ball shape observed from the horizontal direction of the ball formed so as to have a diameter 1.7 times the wire diameter, and the ball-bonded Y so that the diameter of the crushed ball becomes twice the wire diameter. Table 2 shows the presence or absence of metal peeling from the lower layer of the aluminum pad, which is determined to be caused by pad damage, among the failure modes in the measurement of shear strength in the direction and pull strength in the Y direction. Was evaluated as "pad damage left for 0 hours".

ボンディング直後には観察されないパッドダメージについては、近年海外の半導体装置組立メーカーが採用している１７５℃高温放置後のプル破断試験における破断モードであるボールリフトモードの発生状態の有無で評価した。
わずかでもパッドダメージがあれば高温放置後のプル試験ではボールリフトが発生するが、１００本中１本でもボールリフトモードが発生した場合を「×」、発生しない場合を「○」とした。 The pad damage that is not observed immediately after bonding was evaluated by the presence or absence of the occurrence of a ball lift mode, which is a break mode in a pull break test after being left at a high temperature of 175 ° C., which has recently been adopted by overseas semiconductor device assembly manufacturers.
If there is even a slight pad damage, a ball lift occurs in the pull test after being left at a high temperature. However, a ball lift mode occurs even if one out of 100 is “x”, and a case where it does not occurs is “◯”.

ボール形状については、ボール１００個を水平方向から観察し、ワイヤの軸中心とボールの軸中心が一致しない、いわゆる芯ずれ、あるいは鏃状ボールが発生したり、ボールの底部が尖ったりした形状の場合を「×」、いずれの異常も発生していない場合を「○」とした。   Regarding the ball shape, 100 balls are observed from the horizontal direction, so that the center of the wire and the center of the ball do not coincide with each other, a so-called misalignment or a bowl-shaped ball is generated, or the bottom of the ball is pointed. The case was “X”, and the case where no abnormality occurred was “◯”.

潰しボール外観については、ボンディングされたボール５０個を上方から観察し、銅の明らかな露出が１個でも見られた場合を「×」とした。
図２に、潰しボールの外観例を示す。図２（ａ）はボール上部がほぼパラジウムで覆われている例を示し、図２（ｂ）は明らかに銅が露出している場合の例を示すものである。 With respect to the appearance of the crushed ball, 50 bonded balls were observed from above, and the case where even one clear exposure of copper was seen was marked as “x”.
FIG. 2 shows an example of the appearance of a crushed ball. 2A shows an example in which the upper part of the ball is almost covered with palladium, and FIG. 2B shows an example in which copper is clearly exposed.

シア強度については、形成したボンディング部２４個についてプル破断試験を行い、シア強度を測定した。次に、Ｘ方向での平均潰れ径とＹ方向での平均潰れ径から計算される平均つぶれ径を、直径として計算される円の面積を接合面積とみなし、測定したシア強度（単位はｇｆ）を接合面積（単位は平方ｍｍ）で除した、単位面積あたり強度（単位はｋｇｆ／ｍｍ２）で判断し、９ｋｇｆ／ｍｍ２未満のボールが発生した場合を「×」、９以上１０．５ｋｇｆ／ｍｍ２未満のボールが発生した場合を「△」、全てのボールが１０．５ｋｇｆ／ｍｍ２以上となった場合を「○」とした。 Regarding the shear strength, a pull fracture test was performed on 24 formed bonding portions, and the shear strength was measured. Next, the average crushing diameter calculated from the average crushing diameter in the X direction and the average crushing diameter in the Y direction is regarded as the joint area, and the measured shear strength (unit is gf). Is determined by the strength per unit area (unit is kgf / mm 2 ) divided by the bonding area (unit is square mm), and a case where a ball of less than 9 kgf / mm 2 is generated is indicated by “x”, 9 or more and 10.5 kgf The case where a ball of less than / mm 2 is generated is indicated by “Δ”, and the case where all the balls are 10.5 kgf / mm 2 or more is indicated by “◯”.

キャピラリ詰まりについては、図３に示すように大気中でワイヤをキャピラリと７０度をなす方向へ強制的に毎分３ｍの速度で３分間引き出し、５０倍の顕微鏡でキャピラリ内に光を通し、透過光が円状の場合を「○」とし、パラジウム片によって一部が欠けた円状となった場合を「×」とした。なお、１はキャピラリ、２はワイヤ、３はキャピラリとワイヤのなす角度を示す。   For capillary clogging, as shown in Fig. 3, the wire is forcibly pulled in the direction of 70 degrees with the capillary in the atmosphere for 3 minutes at a speed of 3m / min, and light is transmitted through the capillary with a 50x microscope. The case where the light was circular was indicated as “◯”, and the case where the light was circular due to a piece of palladium was indicated as “X”. Note that 1 is a capillary, 2 is a wire, and 3 is an angle formed by the capillary and the wire.

パッドダメージについては、０時間放置、９６時間放置、１４４時間放置における１７５℃高温放置後のプル破断試験を行い、各２４個の破断モードを観察した。
０時間放置においては、「シリコン部の亀裂や破壊」、あるいは「メタルピーリングのモード」が発生した場合を「×」、ボールがアルミニウムパッドから剥がれてしまう「ボールリフトのモード」が発生した場合を「△」、すべてのモードが「スティッチ切れ」、あるいは「ワイヤ切れ」で「メタルピーリングのモード」や「ボールリフトのモード」の発生が無い場合を良好として「○」と記した。
また、９６時間および１４４時間放置においては、ボールがアルミニウムパッドから剥がれてしまう「ボールリフトのモード」が発生した場合を「×」、すべてのモードが「スティッチ切れ」、あるいは「ワイヤ切れ」で、「メタルピーリングのモード」や「ボールリフトのモード」の発生が無い場合を良好として「○」と記した。
表２に特性評価の結果をまとめて示す。 For pad damage, a pull break test was performed after leaving at 175 ° C. for 0 hours, 96 hours, and 144 hours, and 24 break modes were observed.
In the case of leaving for 0 hour, “X” indicates the case of “cracking or breaking of the silicon part” or “Metal peeling mode”, and “Ball lift mode” in which the ball is peeled off the aluminum pad. A case where “△”, all modes were “stitch cut”, or “wire cut” and “metal peeling mode” or “ball lift mode” did not occur was marked as “good”.
In addition, in 96 hours and 144 hours, when “ball lift mode” in which the ball is peeled off from the aluminum pad occurs, “×”, all modes are “stitch cut”, or “wire cut”. A case where there was no occurrence of “metal peeling mode” or “ball lift mode” was marked as “Good”.
Table 2 summarizes the results of the characteristic evaluation.

表１及び表２から明らかなように、本発明に係る実施例１から実施例９の接続用ワイヤは、９６時間の高温放置後のプル破断試験において、パッドダメージによるボールリフトモードの発生がない（表２では、「○」と表記。）という点で優れている。
また、実施例３と実施例９では、ボンディング直後のプル強度試験においてメタルピーリングを示しているものの、ボール形成時のガスをフォーミングガスではなく不活性の窒素ガス（表２の「ボール形成ガス」の項における「窒素」）に変えることによって、メタルピーリングを防止して使用することが可能で、高温放置後のボールリフトの発生解消を享受できる。
実施例１〜３（実施例３は「ボール形成ガスが、窒素の場合」は、１４４時間高温放置後もボールリフトの発生は、見られず（表２では「○」と表記。）、パッドダメージの無い極めて良好な接合状態であると推察され、今後の高密度実装に不可欠なＬｏｗ−ｋ誘電体を利用した脆弱なシリコンチップが搭載されるファインピッチＰＢＧＡへの利用が可能である。 As is clear from Tables 1 and 2, the connection wires of Examples 1 to 9 according to the present invention do not generate a ball lift mode due to pad damage in a pull break test after being left at a high temperature for 96 hours. (In Table 2, it is expressed as “◯”).
In Example 3 and Example 9, metal peeling was shown in the pull strength test immediately after bonding, but the gas at the time of ball formation was not an forming nitrogen gas but an inert nitrogen gas ("Ball forming gas" in Table 2). By changing to “nitrogen” in the section, it is possible to prevent the use of metal peeling and to eliminate the occurrence of ball lift after being left at a high temperature.
In Examples 1 to 3 (in Example 3, “when the ball forming gas is nitrogen”), no ball lift was observed even after standing at high temperature for 144 hours (indicated as “◯” in Table 2), and the pad. It is presumed that it is a very good bonded state without damage, and can be used for a fine pitch PBGA on which a fragile silicon chip using a low-k dielectric that is indispensable for high-density mounting in the future is mounted.

１ キャピラリ
２ ワイヤ
３ キャピラリとワイヤのなす角度 1 Capillary 2 Wire 3 Angle between capillary and wire

Claims (6)

銅を主成分とする芯材に、パラジウムを被覆したワイヤであって、
５０ａｔ％以上のパラジウムを含むパラジウム被覆層と、銅成分が５０ａｔ％以上であり、残部がパラジウム、炭素及び１２０質量ｐｐｍ以下のリンである芯材との間に、
５ａｔ％以上、４０ａｔ％以下の炭素を含み、残部が５０ａｔ％未満のパラジウム及び５０ａｔ％未満の銅である中間層が設けられていることを特徴とする半導体装置の接続用ワイヤ。 It is a wire coated with palladium on a core material mainly composed of copper,
Palladium coating layer containing 50at% or more palladium state, and are copper component is more than 50at%, the balance being palladium, between the core material is phosphorus the following carbon and 120 mass ppm,
A connecting wire for a semiconductor device, characterized in that an intermediate layer containing carbon of 5 at% or more and 40 at% or less and the balance of palladium of less than 50 at% and copper of less than 50 at% is provided. 前記中間層が、５ａｔ％以上、２０ａｔ％以下の炭素を含む層であることを特徴とする請求項１記載の半導体装置の接続用ワイヤ。   2. The wire for connecting a semiconductor device according to claim 1, wherein the intermediate layer is a layer containing carbon of 5 at% or more and 20 at% or less. 前記芯材にパラジウムめっきを施した後に、引き抜き伸線加工して製造されたことを特徴とする請求項１又は２に記載の接続用ワイヤ。   The connection wire according to claim 1 or 2, wherein the core material is manufactured by drawing and drawing after palladium plating. 前記パラジウムの被覆前に、前記芯材を大気中で加熱処理することを特徴とする請求項１〜３のいずれか１項に記載の半導体装置の接続用ワイヤ。   The wire for connecting a semiconductor device according to claim 1, wherein the core material is heat-treated in the atmosphere before the palladium coating. 請求項１から４のいずれかに記載の半導体装置の接続用ワイヤを用いた半導体装置用ボンディングワイヤ。   A bonding wire for a semiconductor device using the connection wire for a semiconductor device according to claim 1. 請求項１から４のいずれかに記載の半導体装置の接続用ワイヤを用いた半導体装置用バンプワイヤ。

A bump wire for a semiconductor device using the connection wire for a semiconductor device according to claim 1.

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