JP7269361B2 - Wire bonding structure, bonding wire and semiconductor device used therefor - Google Patents

Wire bonding structure, bonding wire and semiconductor device used therefor Download PDF

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Publication number
JP7269361B2
JP7269361B2 JP2021551112A JP2021551112A JP7269361B2 JP 7269361 B2 JP7269361 B2 JP 7269361B2 JP 2021551112 A JP2021551112 A JP 2021551112A JP 2021551112 A JP2021551112 A JP 2021551112A JP 7269361 B2 JP7269361 B2 JP 7269361B2
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gold
bonding
wire
silver
electrode
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JPWO2021065036A1 (en
JPWO2021065036A5 (en
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優希 安徳
雄祐 ▲崎▼田
将太 川野
▲祐▼佳 平井
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Tanaka Denshi Kogyo KK
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Tanaka Denshi Kogyo KK
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    • H01L2924/181—Encapsulation

Description

本発明は、ワイヤ接合構造とそれに用いられるボンディングワイヤ及び半導体装置に関する。 TECHNICAL FIELD The present invention relates to a wire bonding structure, a bonding wire used therein, and a semiconductor device.

半導体チップの電極とリードフレームや回路基板等の回路基材の外部電極とは、例えばボンディングワイヤにより接続される。ボンディングワイヤでは、例えばボール接合と呼ばれる方式により半導体チップの電極にボンディングワイヤの一端を接合（第１接合）し、ウェッジ接合と呼ばれる方式によりボンディングワイヤの他端を回路基材の外部電極に接合（第２接合）することが一般的である。ボール接合においては、ボンディングワイヤの一端を放電等により溶融させ、表面張力等により球形状に凝固させてボールを形成する。凝固したボールはフリーエアーボール（Ｆｒｅｅ Ａｉｒ Ｂａｌｌ：ＦＡＢ）と呼ばれ、超音波併用熱圧着ボンディング法等により半導体チップの電極に接続されてワイヤ接合構造が形成される。ここで、ボンディングワイヤに設けられたＦＡＢを電極に接合した構造を、ここではワイヤ接合構造と呼び。さらに、ボンディングワイヤが接続された半導体チップを、ボンディングワイヤや回路基材の一部と共に樹脂封止することによって、半導体装置が構成される。 Electrodes of a semiconductor chip and external electrodes of a circuit substrate such as a lead frame or a circuit board are connected by bonding wires, for example. For bonding wires, for example, one end of the bonding wire is bonded (first bonding) to an electrode of a semiconductor chip by a method called ball bonding, and the other end of the bonding wire is bonded (first bonding) to an external electrode of a circuit board by a method called wedge bonding. second bonding). In ball bonding, one end of a bonding wire is melted by electric discharge or the like, and solidified into a spherical shape by surface tension or the like to form a ball. The solidified ball is called a free air ball (FAB), and is connected to the electrode of the semiconductor chip by a thermocompression bonding method combined with ultrasonic waves to form a wire bonding structure. Here, the structure in which the FAB provided on the bonding wire is bonded to the electrode is called a wire bonding structure. Furthermore, a semiconductor device is configured by resin-sealing the semiconductor chip to which the bonding wires are connected together with the bonding wires and part of the circuit board.

近年、半導体装置には低消費電力化及び信号処理速度の高速化が求められており、そのような半導体装置に使用されるボンディングワイヤは電気抵抗（比抵抗）が低く（例えば、純度９９．９９質量％の４ＮＡｕワイヤ以下）、かつ、過酷な環境でも長時間にわたり比抵抗が低いまま保持されること、すなわち、高信頼性であることが求められる。高信頼性とは、高温多湿な環境下においても腐食（硫化や酸化）されず、長期間電気抵抗が上昇しないことを意味する。しかし、従来から一般的に用いられている金ワイヤは材料コストが高く、また銅ワイヤや被覆銅ワイヤは材料が硬く、半導体チップにダメージを与えてしまうという課題がある。また、銀ワイヤはコストが安く、柔らかいため、ボンディングワイヤとして好適であるものの、純銀ワイヤは大気中に長期間放置されると表面が硫化するという課題を有する。硫化対策として製品化されている銀合金ボンディングワイヤは純銀にパラジウムや金等の金属元素を添加しているため、銀の含有量は９０質量％から９７質量％となる。硫化対策はやや改善されたものの、銀合金ボンディングワイヤは、添加元素の含有量の影響で比抵抗が高くなるという難点があり、近年の半導体装置の要求に十分には適合しない。貴金属の含有量を低下させ、金ワイヤと同等の比抵抗を有する銀合金ワイヤが提案されているが、今度は耐腐食性の問題があることから半導体装置を構成するモールド樹脂、すなわち高信頼性に影響を及ぼす元素が入っていない樹脂の選定等が必要になる点やボンディングワイヤと電極の界面で生成される金属間化合物のため高信頼性評価基準を満たすことが困難であるというような課題もある。 In recent years, semiconductor devices are required to have low power consumption and high signal processing speed, and bonding wires used in such semiconductor devices have low electrical resistance (specific resistance) (for example, purity 99.99 % by mass of 4NAu wire or less) and to maintain low specific resistance for a long time even in a harsh environment, that is, to be highly reliable. High reliability means that it does not corrode (sulfurize or oxidize) even in a hot and humid environment and does not increase electrical resistance for a long period of time. However, the gold wire, which has been generally used in the past, has a high material cost, and the copper wire and the coated copper wire are hard materials, and have the problem of damaging the semiconductor chip. In addition, although silver wires are inexpensive and soft, they are suitable as bonding wires, but pure silver wires have the problem of sulfidation on the surface if left in the atmosphere for a long period of time. A silver alloy bonding wire commercialized as a countermeasure against sulfurization has a metal element such as palladium or gold added to pure silver, so the silver content is 90% by mass to 97% by mass. Although the countermeasures against sulfurization have been somewhat improved, the silver alloy bonding wire has the disadvantage that the specific resistance increases due to the influence of the content of the additive element, and it does not fully meet the requirements of recent semiconductor devices. Silver alloy wires have been proposed that have a lower content of precious metals and have a resistivity equivalent to that of gold wires. It is necessary to select a resin that does not contain elements that affect There is also

上記したような課題を解決するために、銀ワイヤの表面に耐腐食性の高いパラジウム等の白金族元素や金等の被覆層を形成することが提案されている。白金族元素や金等の被覆層は、溶融しない固体のままの状態であれば銀ワイヤ表面の硫化を抑制し得る。よって、ウェッジボンディング（第２接合）のように溶融しないで接合する場合には効果を発揮する。ところが、半導体チップ上にある電極と接合する（第１接合）際に問題が生じる。ボンディングワイヤは先に説明した通り、ワイヤの一端を放電等により溶融させ、表面張力等により球形状に凝固させてボールを形成する。凝固したボールはフリーエアーボール（ＦＡＢ）といい、ＦＡＢを超音波併用熱圧着ボンディング法等により半導体チップの電極に接続されてワイヤ接合構造が形成される。ボールを形成しないで接合するウェッジ接合だと接合面積が小さくなり接合強度が弱まるため、一般的にボール状にして接合面積を広くすることで接合力を高める方法が用いられている。ＦＡＢ形成時に白金族元素や金を被覆したワイヤ全体を溶融するため、被覆されている白金族元素や金も融点差等の理由により時間差はあるものの、ほぼ同時に溶かされボール内部に白金族元素や金が入り込み、ボール表面の白金族元素や金の濃度が相対的に低くなる。ＦＡＢ表面の耐腐食性のある白金族元素や金の濃度が低くなり、銀の濃度が相対的に高くなったＦＡＢを半導体チップのアルミニウム電極に接合した場合、ＦＡＢと電極との接合界面近傍に、相対的に多くなった銀と電極を構成するアルミニウムとで銀とアルミニウムの金属間化合物が形成されやすくなる。銀とアルミニウムの金属間化合物はハロゲン元素や水分等に腐食されやすく、比抵抗の上昇を招き通電不良を起こす原因となる。特に、自動車等の高温多湿の環境下で使用する場合、ボンディングワイヤと電極との接合界面に形成された金属間化合物がより腐食されやすくなる。これらの現象は電気抵抗（比抵抗）の上昇を招き、通電不良の原因となる。よって、ボンディングワイヤと電極との界面において高温多湿のような過酷な環境下でも長時間にわたり比抵抗が上昇しない接合構造の形成が求められている。 In order to solve the above-described problems, it has been proposed to form a coating layer of a platinum group element such as palladium or gold, which has high corrosion resistance, on the surface of the silver wire. A coating layer of a platinum group element, gold, or the like can suppress sulfidation of the silver wire surface if it remains in a solid state without being melted. Therefore, it is effective when bonding without melting like wedge bonding (second bonding). However, a problem arises when bonding to the electrodes on the semiconductor chip (first bonding). As described above, the bonding wire is formed by melting one end of the wire by electric discharge or the like and solidifying it into a spherical shape by surface tension or the like to form a ball. The solidified ball is called a free air ball (FAB), and the FAB is connected to the electrode of the semiconductor chip by a thermocompression bonding method combined with ultrasonic wave, etc. to form a wire bonding structure. Wedge bonding, in which bonding is performed without forming a ball, reduces the bonding area and weakens the bonding strength. Therefore, generally, a method of increasing the bonding strength by forming a ball shape to increase the bonding area is used. Since the entire wire coated with platinum group elements and gold is melted during FAB formation, the coated platinum group elements and gold are also melted almost at the same time, although there is a time difference due to differences in melting points, etc., and the platinum group elements and gold are melted inside the ball. Gold enters and the concentrations of platinum group elements and gold on the surface of the ball become relatively low. When bonding an FAB with a relatively high concentration of silver and a relatively high concentration of platinum group elements and gold on the surface of the FAB to an aluminum electrode of a semiconductor chip, there is a , an intermetallic compound of silver and aluminum is likely to be formed by relatively increased silver and aluminum constituting the electrode. Intermetallic compounds of silver and aluminum are easily corroded by halogen elements, moisture, and the like, which causes an increase in specific resistance and causes poor conduction. In particular, when used in automobiles or the like in a hot and humid environment, the intermetallic compound formed at the bonding interface between the bonding wire and the electrode is more likely to corrode. These phenomena lead to an increase in electrical resistance (specific resistance), which causes poor conduction. Therefore, there is a demand for a bonding structure in which the resistivity does not increase over a long period of time even in a harsh environment such as high temperature and high humidity at the interface between the bonding wire and the electrode.

例えば、特開平１０－３２６８０３号公報（特許文献１）は、Ａｇを１１～１８．５質量％の範囲で含有し、残部が金及び不可避不純物からなる金銀合金ワイヤ、さらにＣｕ、Ｐｄ、Ｐｔの少なくとも１種を総計で０．０１～４質量％、Ｃａ、Ｉｎ、希土類元素の少なくとも１種を総計で０．０００５～０．０５質量％、又はＭｎ、Ｃｒの少なくとも１種を総計で０．０１～０．２質量％の範囲で含有させた金銀合金ワイヤを開示している。特許文献１は特定量の銀を含有させることによって、銀によるアルミニウム電極との接合信頼性を改善しつつ低コスト化を図った金銀合金ワイヤを提供している。しかしながら、依然として主成分は金であることから、銀ワイヤ、銀合金ワイヤ、被覆銀ワイヤ等に比べて高価であり、材料コストが高いという課題が解決されていない。また、コストの問題だけではなく比抵抗が上昇するという懸念もある。 For example, Japanese Patent Laying-Open No. 10-326803 (Patent Document 1) describes a gold-silver alloy wire containing Ag in a range of 11 to 18.5% by mass, the balance being gold and inevitable impurities, and Cu, Pd, and Pt. 0.01 to 4% by mass of at least one in total, 0.0005 to 0.05% by mass in total of at least one of Ca, In and rare earth elements, or 0.005 to 0.05% in total of at least one of Mn and Cr A gold-silver alloy wire containing 01 to 0.2% by mass is disclosed. Patent Literature 1 provides a gold-silver alloy wire in which a specific amount of silver is contained, thereby improving the reliability of bonding with an aluminum electrode by silver and reducing the cost. However, since the main component is still gold, it is more expensive than silver wire, silver alloy wire, coated silver wire, etc., and the problem of high material costs has not been solved. In addition to the problem of cost, there is also the concern that the resistivity will increase.

また、従来の被覆銀ボンディングワイヤに関して、例えば国際公開２０１３／１２９２５３号（特許文献２）は、Ａｇ又はＡｇ合金ワイヤの表面にＰｄ、Ａｕ、Ｚｎ、Ｐｔ、Ｎｉ、Ｓｎの１種以上又はこれらの合金もしくはこれら金属の酸化物又は窒化物を有するワイヤ被覆層を有するボンディングワイヤを開示している。特許文献２には、パワー半導体装置内の接続に被覆層を有するＡｇ又はＡｇ合金ワイヤを用いると共に、ボール接合ではなくウェッジ接合を用いることによって、Ａｌ電極とＡｇワイヤとの接合界面における金属間化合物の形成を抑制して接合信頼性を高めることが開示されている。しかしながら、特許文献２は上記したようにＡｇワイヤのウェッジ接合を前提としているため、被覆ワイヤを溶融凝固しなければならないＦＡＢを形成しないため、被覆層の構成元素が芯材であるＡｇワイヤ中に入り込むことを考慮していない。従って、特許文献２はＦＡＢを電極に接合した際の接合界面の構成元素を考慮しておらず、接合界面の構成元素に基づいて信頼性を向上させることを考慮していない。さらになお構成元素のＡｇワイヤ中への入り込みを抑制するための構成も開示していない。 Further, regarding conventional coated silver bonding wires, for example, International Publication No. WO 2013/129253 (Patent Document 2) discloses that one or more of Pd, Au, Zn, Pt, Ni, and Sn or one or more of these is added to the surface of Ag or Ag alloy wire. Bonding wires are disclosed having wire coating layers comprising alloys or oxides or nitrides of these metals. In Patent Document 2, an Ag or Ag alloy wire having a coating layer is used for connection in a power semiconductor device, and by using wedge bonding instead of ball bonding, an intermetallic compound at the bonding interface between an Al electrode and an Ag wire is used. It is disclosed to suppress the formation of . However, since Patent Document 2 is based on the premise of wedge bonding of Ag wires as described above, FAB, which must melt and solidify the coated wire, is not formed. I haven't considered getting in. Therefore, Patent Document 2 does not consider the constituent elements of the bonding interface when the FAB is bonded to the electrode, and does not consider improving the reliability based on the constituent elements of the bonding interface. Furthermore, it does not disclose a configuration for suppressing the intrusion of the constituent elements into the Ag wire.

さらに、特開２００１－１９６４１１号公報（特許文献３）は、Ａｇ線と、Ａｇ線を被覆するＡｕ膜とを有し、Ａｕ膜はＮａ、Ｓｅ、Ｃａ、Ｓｉ、Ｎｉ、Ｂｅ、Ｋ、Ｃ、Ａｌ、Ｔｉ、Ｒｂ、Ｃｓ、Ｍｇ、Ｓｒ、Ｂａ、Ｌａ、Ｙ、Ｃｅの少なくとも１つの元素を含むボンディングワイヤを開示している。特許文献３は、Ａｕ被覆したＡｇワイヤではＦＡＢの形状が軸対称にならないことから、Ａｕ膜に上記した元素を含有させてアーク放電が一点に集中することを抑制し、表面全体からアークを生じさせてＦＡＢの形状を安定化させることを開示している。しかし、特許文献３もまたＦＡＢ形成時に被覆層のＡｕがＡｇ線中に入り込むことを考慮しておらず、またＡｕのＡｇ線への入り込みを抑制するための構成を開示していない。従って、特許文献３は金被覆銀ワイヤを用いた際にＡｌ電極とＡｇワイヤとの接合界面に金属間化合物が形成されて接合信頼性が低下することを示唆していないだけでなく、さらにＡｌ電極とＡｇワイヤとの接合信頼性を高めるための構成も開示していない。また、上記したような添加元素は、その含有量によってはワイヤ自体の特性や被覆層の形成性等に悪影響を及ぼすおそれがある。このため、ワイヤ自体の特性や被覆層の形成性等に悪影響を及ぼすことなく、ＡｕのＡｇ線への入り込みを抑制してワイヤ接合構造の信頼性を高める技術が求められている。 Furthermore, Japanese Patent Application Laid-Open No. 2001-196411 (Patent Document 3) has an Ag wire and an Au film covering the Ag wire, and the Au film is Na, Se, Ca, Si, Ni, Be, K, C , Al, Ti, Rb, Cs, Mg, Sr, Ba, La, Y, Ce. In Patent Document 3, since the shape of the FAB is not axially symmetrical with the Au-coated Ag wire, the Au film contains the above-described element to suppress the arc discharge from concentrating on one point, and the arc is generated from the entire surface. It is disclosed to stabilize the shape of the FAB by allowing the However, Patent Literature 3 also does not take into account that the Au of the coating layer enters the Ag wire during FAB formation, and does not disclose a configuration for suppressing the entry of Au into the Ag wire. Therefore, Patent Document 3 does not suggest that when a gold-coated silver wire is used, an intermetallic compound is formed at the bonding interface between the Al electrode and the Ag wire to reduce the bonding reliability. Nor does it disclose a configuration for improving the reliability of bonding between the electrode and the Ag wire. Moreover, the additive elements described above may adversely affect the properties of the wire itself, the formability of the coating layer, etc., depending on the content thereof. Therefore, there is a demand for a technique that suppresses the penetration of Au into the Ag wire and enhances the reliability of the wire bonding structure without adversely affecting the properties of the wire itself, the formability of the coating layer, and the like.

特開平１０－３２６８０３号公報JP-A-10-326803 国際公開２０１３／１２９２５３号WO2013/129253 特開２００１－１９６４１１号公報Japanese Patent Application Laid-Open No. 2001-196411

本発明が解決しようとする課題は、材料コストを抑えたボンディングワイヤとアルミニウム電極とを接合しても比抵抗の上昇を抑制しつつ、過酷な環境下においても長期間ボンディングワイヤとアルミニウム電極との接合信頼性を保つことを可能にしたワイヤ接合構造と、それに用いられるボンディングワイヤ及び半導体装置を提供することにある。 The problem to be solved by the present invention is to suppress an increase in specific resistance even when bonding a bonding wire and an aluminum electrode with reduced material cost, and to maintain a long-term bond between the bonding wire and the aluminum electrode even in a harsh environment. An object of the present invention is to provide a wire bonding structure capable of maintaining bonding reliability, a bonding wire used therein, and a semiconductor device.

本発明のワイヤ接合構造は、アルミニウムを主成分として含む電極と、ボンディングワイヤと、前記ボンディングワイヤの一端に設けられ、前記電極に接合されたボール圧縮部とを具備する。本発明のワイヤ接合構造において、前記ボンディングワイヤは、銀を主成分とする芯材と、前記芯材の表面に設けられ、金を主成分とする被覆層とを有し、硫黄、テルル、セレン、ヒ素、及びアンチモンから選ばれる少なくとも１つの第１５及び１６族元素を含有する金被覆銀ボンディングワイヤであって、ワイヤ全体に対して、金濃度が２．０質量％以上７．０質量％以下であり、第１５及び１６族元素濃度が合計で４質量ｐｐｍ以上８０質量ｐｐｍ以下であり、前記電極と前記ボール圧縮部との接合界面近傍に、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域を設けることで課題が解決される。 A wire bonding structure of the present invention includes an electrode containing aluminum as a main component, a bonding wire, and a ball compressing portion provided at one end of the bonding wire and bonded to the electrode. In the wire bonding structure of the present invention, the bonding wire has a core material mainly composed of silver and a coating layer mainly composed of gold provided on the surface of the core material, and contains sulfur, tellurium and selenium. , arsenic and antimony. and the total concentration of Group 15 and 16 elements is 4 ppm by mass or more and 80 ppm by mass or less, and the concentration of gold is the total amount of gold, silver, and aluminum in the vicinity of the bonding interface between the electrode and the ball compression portion. The problem is solved by providing a gold-enriched junction region of 5 atomic % or more with respect to .

本発明の金被覆銀ボンディングワイヤは、本発明のワイヤ接続構造に用いられる金被覆ボンディングワイヤであって、前記金被覆ボンディングワイヤは、銀を主成分として含む芯材と、前記芯材の表面に設けられ、金を主成分として含む被覆層とを有し、前記金被覆銀ボンディングワイヤは、硫黄、テルル、セレン、ヒ素、及びアンチモンから選ばれる少なくとも１つの第１５及び１６族元素を含有し、前記金被覆銀ボンディングワイヤにおいて、ワイヤ全体に対して、金の濃度が２．０質量％以上７．０質量％以下であり、第１５及び１６族元素の濃度が４質量ｐｐｍ以上８０質量ｐｐｍ以下であり、前記金被覆銀ボンディングワイヤは、アルミニウムを主成分とする電極にボールボンディングで接合することによりボール圧縮部を形成したとき、前記電極と前記ボール圧縮部との接合界面近傍に、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域が形成される、金被覆銀ボンディングワイヤである。 The gold-coated silver bonding wire of the present invention is a gold-coated bonding wire used in the wire connection structure of the present invention, wherein the gold-coated bonding wire comprises a core material containing silver as a main component and a a coating layer containing gold as a main component, wherein the gold-coated silver bonding wire contains at least one group 15 and 16 element selected from sulfur, tellurium, selenium, arsenic, and antimony; In the gold-coated silver bonding wire, the concentration of gold is 2.0% by mass or more and 7.0% by mass or less, and the concentration of Group 15 and 16 elements is 4 ppm by mass or more and 80 mass ppm or less with respect to the entire wire. When the gold-coated silver bonding wire is bonded to an electrode containing aluminum as a main component by ball bonding to form a ball compressed portion, gold is present near the bonding interface between the electrode and the ball compressed portion. A gold-coated silver bonding wire in which a gold-enriched bonding region having a concentration of 5 atomic percent or more based on the total amount of gold, silver, and aluminum is formed.

本発明の半導体装置は、少なくとも１つの電極を有する１つ又は複数の半導体チップと、リードフレーム又は基板と、前記半導体チップの電極と前記リードフレームとの間、前記半導体チップの電極と前記基板の電極との間、及び前記複数の半導体チップの電極間から選ばれる少なくとも１つを、銀を主成分として含む芯材と、前記芯材の表面に設けられ、金を主成分として含む被覆層とを有するボンディングワイヤで接続した半導体装置であって、前記電極と前記ボンディングワイヤとの接続構造は、前記電極に前記ボンディングワイヤの一端を接合するように設けられたボール圧縮部を備え、前記電極と前記ボール圧縮部との接合界面近傍に、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域が設けられている。 The semiconductor device of the present invention comprises one or more semiconductor chips having at least one electrode, a lead frame or a substrate, between the electrode of the semiconductor chip and the lead frame, and between the electrode of the semiconductor chip and the substrate. a core material containing silver as a main component and at least one selected from between the electrodes and between the electrodes of the plurality of semiconductor chips; and a coating layer containing gold as a main component provided on the surface of the core material. wherein the connection structure between the electrode and the bonding wire includes a ball compressing portion provided to join one end of the bonding wire to the electrode, the electrode and A gold-enriched bonding region having a gold concentration of 5 atomic % or more with respect to the total amount of gold, silver, and aluminum is provided in the vicinity of the bonding interface with the ball compression portion.

本発明のワイヤ接合構造及びそれに用いられるボンディングワイヤによれば、ボンディングワイヤの比抵抗の上昇を抑えた上で、電極とボール圧縮部との接合界面近傍に金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域を設けることができる。このような金濃化接合領域を設けることによって、電極とボール圧縮部との接合信頼性を高めることができる。また、そのようなワイヤ接合構造を適用した本発明の半導体装置によれば、金濃化接合領域による電極とボール圧縮部との接合信頼性、ひいては半導体装置自体の信頼性を向上させることが可能になる。 According to the wire bonding structure of the present invention and the bonding wire used therein, the increase in the specific resistance of the bonding wire is suppressed, and the concentration of gold in the vicinity of the bonding interface between the electrode and the ball compression portion is the concentration of gold, silver, and aluminum. A gold-enriched junction region of 5 atomic percent or more can be provided with respect to the total amount. By providing such a gold-enriched bonding region, the bonding reliability between the electrode and the ball compression portion can be enhanced. Further, according to the semiconductor device of the present invention to which such a wire bonding structure is applied, it is possible to improve the reliability of bonding between the electrode and the ball compression portion by means of the gold-enriched bonding region, and thus the reliability of the semiconductor device itself. become.

実施形態のワイヤ接合構造を示す断面図である。It is a sectional view showing wire joint structure of an embodiment. 実施形態のワイヤ接合構造におけるボール圧縮部から電極に向けて実施したライン分析の濃度プロファイルの一例を示す図である。It is a figure which shows an example of the concentration profile of the line analysis performed toward the electrode from the ball|bowl compression part in the wire joint structure of embodiment. 実施形態のワイヤ接合構造における金濃化接合領域の形成位置の一例を示す断面図である。FIG. 4 is a cross-sectional view showing an example of a formation position of a gold-enriched bonding region in the wire bonding structure of the embodiment; 実施形態のワイヤ接合構造に用いられる金被覆銀ボンディングワイヤの一端にＦＡＢを形成した状態を示す断面図である。FIG. 4 is a cross-sectional view showing a state in which an FAB is formed at one end of the gold-coated silver bonding wire used in the wire bonding structure of the embodiment; 実施形態の半導体装置の樹脂封止する前の状態を示す断面図である。1 is a cross-sectional view showing a state before resin sealing of a semiconductor device according to an embodiment; FIG. 実施形態の半導体装置の樹脂封止した状態を示す断面図である。1 is a cross-sectional view showing a resin-sealed state of a semiconductor device according to an embodiment; FIG. 実施形態の半導体装置における半導体チップの電極とボンディングワイヤとの接合構造を拡大して示す断面図である。2 is an enlarged cross-sectional view showing a bonding structure between electrodes of a semiconductor chip and bonding wires in the semiconductor device of the embodiment; FIG.

以下、本発明の実施形態のワイヤ接合構造とそれに用いるボンディングワイヤ及び半導体装置について、図面を参照して説明する。各実施形態において、実質的に同一の構成部位には同一の符号を付し、その説明を一部省略する場合がある。図面は模式的なものであり、厚さと平面寸法との関係、各部の厚さの比率や縮尺、縦寸法と横寸法との比率や縮尺等は現実のものとは異なる場合がある。 DESCRIPTION OF THE PREFERRED EMBODIMENTS A wire bonding structure, a bonding wire used therein, and a semiconductor device according to embodiments of the present invention will be described below with reference to the drawings. In each embodiment, the same code|symbol may be attached|subjected to the substantially same component part, and the description may be partially abbreviate|omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the ratio and scale of thickness of each part, the ratio and scale of vertical and horizontal dimensions, and the like may differ from the actual ones.

（ワイヤ接合構造とそれに用いられるボンディングワイヤ）
図１は実施形態のワイヤ接合構造を示す断面図である。実施形態のワイヤ接合構造１は、アルミニウム（Ａｌ）を主成分として含む電極２と、電極２に一端が接合されたボンディングワイヤ３とを備えている。ボンディングワイヤ３は、銀（Ａｇ）を主成分とする芯材（銀芯材とも記す）４と、芯材４の表面に設けられ、金（Ａｕ）を主成分として含む被覆層５とを有する金被覆銀ボンディングワイヤである。(Wire bonding structure and bonding wire used for it)
FIG. 1 is a cross-sectional view showing the wire bonding structure of the embodiment. A wire bonding structure 1 of the embodiment includes an electrode 2 containing aluminum (Al) as a main component and a bonding wire 3 having one end bonded to the electrode 2 . The bonding wire 3 has a core material (also referred to as a silver core material) 4 containing silver (Ag) as a main component, and a coating layer 5 provided on the surface of the core material 4 and containing gold (Au) as a main component. Gold coated silver bonding wire.

電極２は、アルミニウムを主成分として含んでいる。電極２の構成例としては、半導体チップに設けられた電極が挙げられるが、これに限定されるものではない。電極２は、純アルミニウムにより構成してもよいし、またアルミニウムに添加元素を加えたアルミニウム合金により構成してもよい。ただし、アルミニウム電極２としての機能を損なわないように、電極２はアルミニウムを主成分として含むものとする。一般的に、電極２はＡｌ‐０．５％銅（Ｃｕ）、Ａｌ－１．０％シリコン（Ｓｉ）‐銅（Ｃｕ）で構成されているが、これらに限定されるものではない。 The electrode 2 contains aluminum as a main component. A configuration example of the electrode 2 includes an electrode provided on a semiconductor chip, but is not limited to this. The electrode 2 may be composed of pure aluminum, or may be composed of an aluminum alloy obtained by adding additive elements to aluminum. However, the electrode 2 shall contain aluminum as a main component so as not to impair the function as the aluminum electrode 2 . Generally, the electrode 2 is composed of Al-0.5% copper (Cu), Al-1.0% silicon (Si)-copper (Cu), but is not limited thereto.

実施形態のワイヤ接合構造１は、電極２に金被覆銀ボンディングワイヤ３の一端を接合するように設けられたボール圧縮部６を備えている。ボール圧縮部６は、後に詳述するように、ボールボンディングする際にワイヤをキャピラリーと呼ばれる貫通した治具に通してボンディングするが、電極に押し付けて接合する際にキャピラリー内部の形状にボールが変形加工されて形作られる部分を言う。ボンディングワイヤ３の一端を放電等により溶融し、表面張力等により球状に凝固させて形成したＦＡＢを、超音波併用熱圧着ボンディング法等により電極２に押し付けてボンディングすることにより形成される。電極２とボール圧縮部６との接合界面近傍には、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域７が設けられている。 The wire bonding structure 1 of the embodiment includes a ball compressing portion 6 provided to bond one end of the gold-coated silver bonding wire 3 to the electrode 2 . As will be described in detail later, the ball compressing portion 6 passes the wire through a penetrating jig called a capillary when performing ball bonding. Refers to the part that is processed and shaped. One end of the bonding wire 3 is melted by electric discharge or the like, and the FAB is formed by solidifying into a spherical shape by surface tension or the like. In the vicinity of the bonding interface between the electrode 2 and the ball compression portion 6, there is provided a gold-enriched bonding region 7 having a gold concentration of 5 atomic % or more with respect to the total amount of gold, silver and aluminum.

接合界面近傍に金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域７を設けることによって、接合界面近傍における金濃度を高め、相対的に銀濃度を低く抑えることができる。従って、電極２とボール圧縮部６との接合信頼性を向上させることが可能になる。すなわち、銀純度が９８質量％以上となる銀合金ボンディングワイヤ（以下、高純度銀合金ワイヤと記す）を用いてボール圧縮部６を形成すると、接合界面近傍の銀濃度が高くなり、腐食されやすい銀とアルミニウムとの金属間化合物（銀とアルミニウムの比率が３対１となるＡｇ３Ａｌ等）が形成されやすくなる。高純度銀合金ワイヤには金やパラジウムのような貴金属等が最大で２質量％含まれるものの、Ａｇ３Ａｌのような耐食性の低い銀とアルミニウムとの金属間化合物が生成されるため、モールド樹脂に含まれる塩素（Ｃｌ）等のハロゲンやモールド樹脂に吸湿された水分によって金属間化合物が腐食され、電極２とボール圧縮部６との間に通電不良が生じやすくなる。これに対して、接合界面近傍における金濃度を高めて、銀の純度を相対的に低下させることにより、Ａｇ３Ａｌ金属間化合物が抑制されることにより、銀とアルミニウムの比率が２対１となるＡｇ２Ａｌ金属間化合物が生成されやすくなる。Ａｇ２Ａｌ金属間化合物は、Ａｇ３Ａｌ金属間化合物に比べて耐食性に優れていることから、電極２とボール圧縮部６との接合信頼性を向上させることができる。加えて、金濃化接合領域７に存在する金が過酷な環境下における経時変化、例えば、銀のマイグレーションや拡散等に対してバリアー的な役割を果たし、耐食性のあるＡｇ２Ａｌ金属間化合物を維持することができる。さらに、金はアルミニウムと、より耐食性に優れた金とアルミニウムの金属間化合物（例えばＡｕ４Ａｌ金属間化合物）が生成されると考えられ、より一層の接合信頼性の向上に寄与していると推察される。このように、電極２とボール圧縮部６との接合界面近傍に金濃化接合領域７を形成することによって、特に自動車等の高温多湿の過酷な環境下で使用される半導体装置の信頼性を高めことができる。By providing a gold-enriched bonding region 7 having a gold concentration of 5 atomic % or more with respect to the total amount of gold, silver, and aluminum in the vicinity of the bonding interface, the gold concentration in the vicinity of the bonding interface is increased, and the silver concentration is relatively increased. can be kept low. Therefore, it is possible to improve the joint reliability between the electrode 2 and the ball compression portion 6 . That is, when the ball compression portion 6 is formed using a silver alloy bonding wire having a silver purity of 98% by mass or more (hereinafter referred to as a high-purity silver alloy wire), the concentration of silver in the vicinity of the bonding interface increases and is easily corroded. Intermetallic compounds of silver and aluminum (such as Ag 3 Al in which the ratio of silver to aluminum is 3:1) are likely to be formed. Although high-purity silver alloy wires contain up to 2% by mass of precious metals such as gold and palladium, intermetallic compounds of silver and aluminum with low corrosion resistance such as Ag 3 Al are generated, so the mold resin The intermetallic compound is corroded by halogens such as chlorine (Cl) contained in the mold resin and moisture absorbed by the molding resin, and the conduction failure between the electrode 2 and the ball compression portion 6 is likely to occur. On the other hand, by increasing the gold concentration in the vicinity of the bonding interface and relatively lowering the purity of silver, the Ag 3 Al intermetallic compound is suppressed, so that the ratio of silver to aluminum is 2:1. An Ag 2 Al intermetallic compound is likely to be generated. Since the Ag 2 Al intermetallic compound is superior in corrosion resistance to the Ag 3 Al intermetallic compound, it is possible to improve the joint reliability between the electrode 2 and the ball compression portion 6 . In addition, the gold present in the gold-enriched bonding region 7 plays a role of a barrier against changes over time in a harsh environment, such as migration and diffusion of silver, and forms a corrosion-resistant Ag 2 Al intermetallic compound. can be maintained. Furthermore, it is thought that gold forms an intermetallic compound of gold and aluminum (for example, an Au4Al intermetallic compound) with better corrosion resistance than aluminum, which contributes to further improvement in bonding reliability. guessed. By forming the gold-enriched junction region 7 in the vicinity of the junction interface between the electrode 2 and the ball compression portion 6 in this manner, the reliability of the semiconductor device used in a severe environment of high temperature and humidity, such as in automobiles, is improved. can be raised.

電極２とボール圧縮部６との接合界面近傍に形成される金濃化接合領域７において、金濃度は金と銀とアルミニウムの合計量に対して５原子％以上とする。金濃化接合領域７における金の濃度が金と銀とアルミニウムの合計量に対して５原子％未満であると、金による腐食（硫化や酸化）を抑制する効果を十分に得ることができないと共に、相対的に銀濃度が増加するため、Ａｇ３Ａｌ金属間化合物が形成されやすくなり、電極２とボール圧縮部６との接合信頼性が低下する。金濃化接合領域７における金と銀とアルミニウムの合計量に対する金濃度は５原子％以上がより好ましく、さらに１０原子％以上が望ましい。銀芯材４の直径に対する被覆層５の厚さの比により決定されるものである。In the gold-enriched bonding region 7 formed in the vicinity of the bonding interface between the electrode 2 and the ball compression portion 6, the gold concentration is set to 5 atomic % or more with respect to the total amount of gold, silver and aluminum. If the concentration of gold in the gold-enriched bonding region 7 is less than 5 atomic percent with respect to the total amount of gold, silver, and aluminum, the effect of suppressing corrosion (sulfidation and oxidation) due to gold cannot be sufficiently obtained. , Ag 3 Al intermetallic compound is likely to be formed because the silver concentration is relatively increased, and the reliability of bonding between the electrode 2 and the ball compression portion 6 is lowered. The gold concentration with respect to the total amount of gold, silver and aluminum in the gold-enriched junction region 7 is more preferably 5 atomic % or more, and more preferably 10 atomic % or more. It is determined by the ratio of the thickness of the coating layer 5 to the diameter of the silver core material 4 .

上述した金濃化接合領域７は、さらにパラジウム（Ｐｄ）、白金（Ｐｔ）、ゲルマニウム（Ｇｅ）、インジウム（Ｉｎ）、銅（Ｃｕ）、及びニッケル（Ｎｉ）から選ばれる少なくとも１つ元素（以下、Ｍ元素と呼び）を含んでいることが好ましい。金濃化接合領域７が上記したようなＭ元素を含むことによって、電極２とボール圧縮部６との接合信頼性をさらに向上させることができる。Ｍ元素は、例えば銀芯材４に含有させておくことができる。Ｍ元素はその含有量がワイヤ全体に対して０．２原子％以上２．０原子％以下となるように含まれることが好ましい。０．２原子％未満であると、Ｍ元素による接合信頼性のさらなる向上効果を十分に得ることができず、また２．０原子％を超えると銀芯材４の比抵抗を上昇させるおそれがある。 The gold-enriched junction region 7 described above further includes at least one element selected from palladium (Pd), platinum (Pt), germanium (Ge), indium (In), copper (Cu), and nickel (Ni) (hereinafter , called the M element). By including the M element as described above in the gold-enriched bonding region 7, the bonding reliability between the electrode 2 and the ball compression portion 6 can be further improved. The M element can be contained in the silver core material 4, for example. It is preferable that the content of M element is 0.2 atomic % or more and 2.0 atomic % or less with respect to the whole wire. If it is less than 0.2 atomic %, the effect of further improving the bonding reliability by the M element cannot be sufficiently obtained, and if it exceeds 2.0 atomic %, the specific resistance of the silver core material 4 may be increased. be.

金濃化接合領域の分析方法を、接合対象としてアルミニウム電極を採用した場合を例に、詳細に説明する。アルミニウムとアルミニウム以外の元素を含む電極を用いる場合も同様である。金被覆銀ボンディングワイヤを用いてフリーエアーボールを形成し、アルミニウム電極上にボールボンディングする。アルミニウム電極に接合されたボール圧縮部をワイヤ長手方向の中心線に平行な面が露出するように切断する。この切断面を、ワイヤ側の所定箇所から接合面に略垂直方向（深さ方向）にライン分析する。ライン分析としては、電解放出形走査型電子顕微鏡／エネルギー分散型Ｘ線分光分析（ＦＥ－ＳＥＭ／ＥＤＸ）が好適である。なお、当該分析に係る切断面はワイヤ長手方向の中心線を含むか、中心線にできるだけ近づけるように形成することが好ましい。 A method for analyzing the gold-enriched bonding area will be described in detail, taking as an example a case where an aluminum electrode is adopted as a bonding object. The same is true when using electrodes containing aluminum and elements other than aluminum. A free air ball is formed using a gold coated silver bonding wire and ball bonded onto an aluminum electrode. The ball compressed portion joined to the aluminum electrode is cut so that a plane parallel to the center line in the longitudinal direction of the wire is exposed. This cut surface is subjected to line analysis from a predetermined position on the wire side in a substantially vertical direction (depth direction) to the joint surface. Field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDX) is suitable for line analysis. In addition, it is preferable that the cut surface for the analysis includes the center line in the longitudinal direction of the wire or is formed so as to be as close to the center line as possible.

ボール接合部の切断面は次のようにして作製することができる。リードフレームとして、例えばＰＢＧＡ３２ＰＩＮフレームを用い、このフレーム中央部に略正方形の半導体チップを接合する。半導体チップ上のアルミニウム電極とフレーム上の外部電極を、金被覆銀ボンディングワイヤによってワイボンディングして測定サンプルを作製する。この半導体チップ上にあるアルミニウム電極に金被覆銀ボンディングワイヤワイヤをボール接合（第１接合）し、リードフレームにウェッジ接合（第２接合）する。通常チップには、多くの電極が複数列に列設されているので、例えばそのうちの一列（４個）の電極にボンディングワイヤを等間隔で接合し、他の３列（３辺）も同様に接合する。合計で１６個のアルミニウム電極にボール接合する。リードフレームへのウェッジ接合を含めると合計で３２組のワイヤボンディングとなる。 A cut surface of the ball joint can be produced as follows. A PBGA32PIN frame, for example, is used as the lead frame, and a substantially square semiconductor chip is bonded to the center of the frame. An aluminum electrode on the semiconductor chip and an external electrode on the frame are wire-bonded with a gold-coated silver bonding wire to prepare a measurement sample. A gold coated silver bonding wire is ball bonded (first bond) to an aluminum electrode on the semiconductor chip and wedge bonded (second bond) to a lead frame. Since many electrodes are usually arranged in multiple rows on a chip, for example, bonding wires are joined to the electrodes of one row (four electrodes) at equal intervals, and the other three rows (three sides) are similarly connected. Join. A total of 16 aluminum electrodes are ball-bonded. Including the wedge bond to the lead frame, there are a total of 32 pairs of wire bonds.

フリーエアーボールの形成条件は、例えば、金被覆銀ボンディングワイヤの線径が１０～３０μｍである場合に、放電電流値が３０～９０ｍＡ、フリーエアーボール径がワイヤ線径の１．５～２．３倍となるようにアーク放電条件を設定する。ボンダー装置は、例えば、ケー・アンド・エス社製のボンダー装置（全自動ボンダー：ＩＣｏｎｎ ＰｒｏＣｕ ＰＬＵＳ）等の市販品を使用することができる。当該ボンダー装置を使用する場合、装置の設定として放電時間が５０～１０００μｓ、ＥＦＯ－Ｇａｐが２５～４５ｍｉｌ（約６３５～１１４３μｍ）、テール長さが６～１２ｍｉｌ（約１５２～３０５μｍ）であることが好ましい。当該ボンダー装置以外のその他のボンダー装置を用いる場合、上記と同等の条件、例えばフリーエアーボール径が上記と同等の大きさになる条件であればよい。 The conditions for forming the free air balls are, for example, when the diameter of the gold-coated silver bonding wire is 10 to 30 μm, the discharge current value is 30 to 90 mA, and the diameter of the free air balls is 1.5 to 2.5 μm of the wire diameter. Arc discharge conditions are set so as to be three times as large. As the bonder, for example, a commercially available product such as a K&S bonder (fully automatic bonder: IConn ProCu PLUS) can be used. When using the bonder device, the setting of the device should be a discharge time of 50 to 1000 μs, an EFO-Gap of 25 to 45 mil (about 635 to 1143 μm), and a tail length of 6 to 12 mil (about 152 to 305 μm). preferable. When a bonder other than the bonder concerned is used, conditions equivalent to those described above, such as conditions under which the free air ball diameter is equivalent to the above, may be used.

また、ボール接合条件（第１接合の条件）は、例えばワイヤ線径φが２０μｍでボール径が３６μｍのフリーエアーボールを形成したものについては、ボール圧縮部のくびれ部から接合界面側の高さが略１０μｍ、接合面に略平行方向の最大幅が略４５μｍとなるように、また、ボールシェア強度が１５ｇｆ以上となるようにボンダー装置にて調節することができる。また、第２接合の条件は、例えば、圧着力６０ｇｆ、超音波出力９０ｍＡｍｐｓ、超音波出力時間１５ｍｓである。なお、第１接合部から第２接合部までのループ長さは２．０ｍｍにてボンディングすることができる。 In addition, the ball bonding conditions (conditions for the first bonding) are, for example, in the case of forming a free air ball having a wire diameter φ of 20 μm and a ball diameter of 36 μm, the height from the constricted portion of the ball compressed portion to the bonding interface side is about 10 μm, the maximum width in the direction substantially parallel to the bonding surface is about 45 μm, and the ball shear strength is adjusted to 15 gf or more. The conditions for the second bonding are, for example, a crimping force of 60 gf, an ultrasonic output of 90 mAmps, and an ultrasonic output time of 15 ms. Bonding can be performed with a loop length of 2.0 mm from the first joint to the second joint.

次に、上記で形成された合計１６組の接合部を含む半導体チップを封止樹脂によってモールド機でモールドする。モールドが固まったらモールドした部分をフレームからカットし、さらに、モールド部分の中にあるボール接合部の一列（一辺）の近傍を切断する。切断したモールドは円筒状の型（かた）にボール接合部の断面が研磨できる方向に置き、埋め込み樹脂を流し込み硬化剤を添加して硬化させる。そのあと、この半導体チップ入の硬化させた円筒状の樹脂をなるべくボール接合部の中心付近が露出するように研磨器にて粗研磨する。おおよそボール接合部の中心断面近くまで研磨したら、最終研磨仕上げおよびボール中心部を含む面（ワイヤ部の中心線を通り、中心線に平行な面）がちょうど露出して分析面の位置になるようにイオンミリング装置にて微調整する。ワイヤ部断面のワイヤ幅がワイヤ直径の長さになれば切断面がボール中心部を含む面になっている目安となる。切断面を分析する面として、その所望の箇所を、ＦＥ－ＳＥＭ／ＥＤＸによって、ボール側から電極側に向けてライン分析する。ライン分析条件は、例えば、加速電圧６ｋｅＶ、測定領域φ０．１８μｍ、測定間隔０．０２μｍである。 Next, a semiconductor chip including a total of 16 joints formed as described above is molded with a sealing resin by a molding machine. After the mold has hardened, the molded portion is cut from the frame, and the area near one row (one side) of the ball joints in the molded portion is cut. The cut mold is placed in a cylindrical mold in a direction where the cross section of the ball joint can be polished, and the embedding resin is poured in and a hardening agent is added to harden it. After that, the hardened cylindrical resin containing the semiconductor chip is roughly ground with a grinder so that the vicinity of the center of the ball joint portion is exposed as much as possible. After polishing to near the center cross section of the ball joint, the surface including the final polishing finish and the center of the ball (the surface that passes through the center line of the wire part and is parallel to the center line) is just exposed and positioned at the analysis surface. finely adjusted with an ion milling device. If the wire width in the cross section of the wire portion is equal to the length of the wire diameter, it is an indication that the cut surface includes the center of the ball. As a surface to be analyzed, the cut surface is subjected to line analysis from the ball side to the electrode side by FE-SEM/EDX at a desired portion. Line analysis conditions are, for example, an acceleration voltage of 6 keV, a measurement area of 0.18 μm, and a measurement interval of 0.02 μm.

金濃化接合領域７の有無を定量的に測定するには、上記した測定試料の分析面（研磨断面）において、ボール圧縮部６側から接合界面を介して電極２側に向けて、電界放出型走査電子顕微鏡（ＦＥ－ＳＥＭ：Ｆｉｅｌｄ Ｅｍｉｓｓｉｏｎ－Ｓｃａｎｎｉｎｇ Ｅｌｅｃｔｒｏｎ Ｍｉｃｒｏｓｃｏｐｅ）付属のエネルギー分散型Ｘ線分析（ＥＤＸ：Ｅｎｅｒｇｙ Ｄｉｓｐｅｒｓｉｖｅ Ｘ－ｒａｙ Ｓｐｅｃｔｒｏｍｅｔｒｙ）によりライン分析することで金濃化接合領域７を確認できる。ライン分析条件は、日立ハイテクノロジーズ社製のＦＥ－ＳＥＭ ＳＵ８２２０とブルカー社製のＸＦｌａｓｈ（Ｒ）５０６０ＦＱを用いて、加速電圧６ｋｅＶ、測定長さ２μｍ、測定間隔０．０３μｍ、測定時間６０秒とする。ライン分析の濃度プロファイルにて、金濃度が銀と金及びアルミニウムの合計量に対して５原子％以上の箇所が存在していれば、金濃化接合領域７が形成されていると判断できる。 In order to quantitatively measure the presence or absence of the gold-enriched bonding region 7, field emission The gold-enriched junction region 7 can be confirmed by line analysis using energy dispersive X-ray spectrometry (EDX) attached to a field emission-scanning electron microscope (FE-SEM). The line analysis conditions are an acceleration voltage of 6 keV, a measurement length of 2 μm, a measurement interval of 0.03 μm, and a measurement time of 60 seconds using FE-SEM SU8220 manufactured by Hitachi High-Technologies Corporation and XFlash (R) 5060FQ manufactured by Bruker. . In the concentration profile of the line analysis, if there is a portion where the gold concentration is 5 atomic % or more with respect to the total amount of silver, gold and aluminum, it can be judged that the gold-enriched junction region 7 is formed.

金濃化接合領域は、フリーエアーボールと電極とが接触して接合された接合面近傍、すなわち、アルミニウムと銀と金が共存する領域において、金、銀、及びアルミニウムの合計に対する金の割合が５．０原子％以上、好ましくは１０．０原子％以上となる所定の範囲として評価することができる。具体的には、上記ボール接合部の断面の所定の箇所を、ボール接合部の任意の面からアルミニウム電極の面に向けてワイヤ長手方向に平行にＦＥ－ＳＥＭ／ＥＤＸによってライン分析したときに、アルミニウムが５．０原子％を超え９５．０原子％以下の範囲内の各測定点で、金、銀、及びアルミニウムの合計に対する金の割合が５．０原子％以上、好ましくは１０．０原子％以上となる所定の範囲を金濃化接合領域として評価することができる。ここで、アルミニウム濃度が５．０原子％を超え９５．０原子％以下の範囲で測定する理由は、分析におけるノイズ等の影響でアルミニウムが存在しない箇所の分析値が０原子％にならないことや、アルミニウムのみの箇所の分析値が１００原子％にならないことがあるからである。 In the gold-enriched bonding region, the ratio of gold to the total of gold, silver, and aluminum is in the vicinity of the bonding surface where the free air ball and the electrode are in contact and bonded, that is, in the region where aluminum, silver, and gold coexist. It can be evaluated as a predetermined range of 5.0 atomic % or more, preferably 10.0 atomic % or more. Specifically, when a predetermined portion of the cross section of the ball joint is line-analyzed by FE-SEM/EDX parallel to the longitudinal direction of the wire from any surface of the ball joint toward the surface of the aluminum electrode, The ratio of gold to the total of gold, silver, and aluminum is 5.0 atomic % or more, preferably 10.0 atoms, at each measurement point within the range of aluminum exceeding 5.0 atomic % and 95.0 atomic % or less % or more can be evaluated as a gold-enriched junction region. Here, the reason why the aluminum concentration is measured in the range of more than 5.0 atomic % and 95.0 atomic % or less is that the analytical value of the place where aluminum does not exist does not become 0 atomic % due to the influence of noise etc. in the analysis. , and the analytical value of only aluminum may not be 100 atomic %.

図２はＥＤＸによるライン分析結果の一例を示している。図２において、縦軸は各元素の濃度（原子％）であり、横軸は測定試料における測定距離（μｍ）である。図２の横軸の測定距離が約２．２μｍの箇所から約２．６μｍの箇所までが接合界面近傍の領域となり、そのような領域に金濃度が５．０原子％以上の領域、すなわち金接合濃化領域が存在している。ここでは金のピーク濃度が約１５．０原子％を示している。従って、図２に示す濃度プロファイルを有するワイヤ接合構造１は、電極２とボール圧縮部６との接合界面近傍に金濃化接合領域７が存在していると判断することができる。また、図２において接合界面近傍に金濃度が低い領域（横軸２．４μｍ付近）があるが、その付近の銀とアルミニウムの濃度比から耐食性の強いＡｇ２Ａｌ金属間化合物が生成されていると推測される。FIG. 2 shows an example of line analysis results by EDX. In FIG. 2, the vertical axis is the concentration (atomic %) of each element, and the horizontal axis is the measurement distance (μm) in the measurement sample. The region near the bonding interface is the region where the measurement distance on the horizontal axis of FIG. 2 is approximately 2.2 μm to approximately 2.6 μm. Junction thickening regions are present. Here, the peak concentration of gold is about 15.0 atomic percent. Therefore, it can be determined that the wire bonding structure 1 having the concentration profile shown in FIG. In FIG. 2, there is a region with a low gold concentration (near 2.4 μm on the horizontal axis) in the vicinity of the joint interface, and an Ag 2 Al intermetallic compound with strong corrosion resistance is generated from the concentration ratio of silver and aluminum in the vicinity of that region. It is speculated that

上述した金濃化接合領域７の形成範囲は、電極２とボール圧縮部６との接合界面の全域であることが好ましいが、それに限られるものではない。すなわち、金濃化接合領域７は電極２とボール圧縮部６との接合信頼性を高める上で、図３に示すように、ボール圧縮部６の最大幅Ｙに対して、金濃化接合領域７が少なくともボール圧縮部６の両外周部から１／８の位置（線Ｘ１及び線Ｘ２で示す）までの間にそれぞれ形成されていればよい。ここで、ボール圧縮部６の最大幅Ｙとは、図３に示す電極２とボール圧縮部６との接合構造をワイヤ３の長手方向に切断した断面図において、長手方向に直交する水平方向におけるボール圧縮部６の両最外端部（線Ｘで示す）間の幅を示す。このような両最外端部（線Ｘ）から、ボール圧縮部６の最大幅（線Ｙ）を８等分したうちの両最外端部から１／８の位置（線Ｘ１及び線Ｘ２）までの間に、少なくとも金濃化接合領域７が形成されていればよい。このような位置に金濃化接合領域７を形成することによって、接合界面に侵入する大気や水分等による電極２とボール圧縮部６との接合信頼性の低下を抑制することができる。なぜなら、封止樹脂等からのハロゲン元素や水分は、ボール接合面近傍の両端、すなわち、ボールと電極の接合部の際付近のわずかな隙間等から浸入してくる可能性が高いため、両端付近に耐腐食性の高い金濃化接合領域があることがハロゲン等の浸入を阻止するという意味で非常に重要な役割を果たすからである。 The formation range of the gold-enriched bonding region 7 described above is preferably the entire bonding interface between the electrode 2 and the ball compression portion 6, but is not limited thereto. In other words, the gold-enriched bonding region 7 increases the bonding reliability between the electrode 2 and the ball compression portion 6, and as shown in FIG. 7 should be formed at least between both outer peripheral portions of the ball compression portion 6 and 1/8 positions (indicated by lines X1 and X2). Here, the maximum width Y of the ball compression portion 6 is defined as the width in the horizontal direction orthogonal to the longitudinal direction in the cross-sectional view of the joint structure between the electrode 2 and the ball compression portion 6 shown in FIG. The width between the two outermost ends (indicated by line X) of the ball compression portion 6 is shown. 1/8 position (line X1 and line X2) from both outermost ends of the maximum width (line Y) of the ball compression portion 6 divided into 8 equal parts from such both outermost ends (line X) It suffices that at least the gold-enriched junction region 7 is formed during the period. By forming the gold-enriched bonding region 7 at such a position, it is possible to suppress deterioration in bonding reliability between the electrode 2 and the ball compression portion 6 due to air, moisture, etc. entering the bonding interface. This is because there is a high possibility that halogen elements and moisture from the sealing resin, etc., will enter through both ends near the ball joint surface, that is, through a small gap near the joint between the ball and the electrode. This is because the presence of the gold-enriched junction region with high corrosion resistance in the junction plays a very important role in terms of preventing penetration of halogen and the like.

さらに、発明者らが鋭意研究した結果、金濃化接合領域７の形成範囲は、上記したボール圧縮部６の最大幅Ｙに対して、占有率が合計で２５％以上となるように形成されていることが好ましいことが分かった。ここで言う金濃化接合領域７の占有率とは、図３に示す電極２とボール圧縮部６との接合構造の断面図において、金濃化接合領域７の形成領域を分析した際に、ボール圧縮部６の最大幅Ｙに対して金濃化接合領域７の形成領域が２５％以上であることを意味する。このように、ボール圧縮部６の最大幅Ｙに対して金濃化接合領域７の占有率が少なくとも２５％となるように形成することによって、接合界面に侵入する大気や水分等による電極２とボール圧縮部６との接合信頼性の低下を抑制することができる。なお、ボール圧縮部６の最大幅Ｙに対する金濃化接合領域７の占有率は少なくとも２５％であればよいが、さらに４０％以上であることがより好ましく、５０％以上であることがさらに好ましい。 Furthermore, as a result of the inventors' intensive research, the formation range of the gold-enriched joint region 7 is formed so that the total occupation ratio of the maximum width Y of the ball compression portion 6 is 25% or more. It has been found that it is preferable to The occupancy rate of the gold-enriched junction region 7 referred to here is the cross-sectional view of the junction structure between the electrode 2 and the ball compression portion 6 shown in FIG. It means that the formation area of the gold-enriched bonding area 7 is 25% or more of the maximum width Y of the ball compressed portion 6 . In this way, by forming the gold-enriched bonding region 7 so that the occupation ratio of the gold-enriched bonding region 7 is at least 25% with respect to the maximum width Y of the ball compression portion 6, the electrode 2 is prevented from being affected by air, moisture, etc. that enter the bonding interface. Decrease in joint reliability with the ball compression portion 6 can be suppressed. The gold-enriched bonding region 7 occupies at least 25% of the maximum width Y of the ball compression portion 6, preferably 40% or more, and even more preferably 50% or more. .

金濃化接合領域の測定方法について説明する。例えば、ＥＰＭＡ測定（面分析）では、通常、測定対象の元素の存在率を、測定対象に電子線を照射したときに当該元素から発せられるＸ線強度として測定し、その強度をＥＰＭＡ画像上で色彩に反映させたカラーマッピングで表示するのが一般的である。つまり、測定対象の元素が存在しない点は真っ黒に表示され、元素の存在確率が高い順に一例として「白、赤、黄、緑、青、黒」等のグラデーションで表示される。このようなＥＰＭＡ画像の接合面近傍において、最も金強度が小さい点、すなわち、ＥＰＭＡ画像上に真っ黒ではないが金による強度が観測される箇所のなかで一番暗い箇所（黒に近い青色の箇所）において、金濃度が５．０原子％以上あれば、それ以外に表示される上記の箇所よりも強度の強い色彩で表示される領域を金濃化接合領域として特定することができる。また、ライン分析とＥＰＭＡ画像（面分析）の結果を重ね合わせて、ライン分析で金濃度が５．０原子％あるいはこれ以上に観測された、ＥＰＭＡ上の測定点と強度が同等かそれ以上の箇所を、強度差（画像上での色彩）として識別できる設定にするか、目視で判定する。これにより、金濃化接合領域の有無および占有率が算出できる。なお、金濃化接合領域の占有率を算出する場合において、ＥＰＭＡのカラーマッピング画像を用いるが、画像を拡大すればするほど金濃化接合領域が「疎」な状態に見えてしまうことがあるので、少なくともボール圧縮部が１枚の画像（枠）に収まる程度の倍率で占有率を算出するのが好ましい。 A method for measuring the gold-enriched junction area will be described. For example, in EPMA measurement (surface analysis), the abundance of an element to be measured is usually measured as the X-ray intensity emitted from the element when the object to be measured is irradiated with an electron beam, and the intensity is displayed on the EPMA image. It is common to display by color mapping that is reflected in colors. That is, the points where the element to be measured does not exist are displayed in black, and the points are displayed in gradation such as "white, red, yellow, green, blue, black" in descending order of the existence probability of the element. In the vicinity of the joint surface of such an EPMA image, the point where the gold intensity is the lowest, that is, the darkest point among the points where gold intensity is observed although it is not completely black on the EPMA image (blue area close to black) ), if the gold concentration is 5.0 atomic % or more, the area displayed in a stronger color than the above-described other displayed areas can be specified as the gold-enriched bonding area. In addition, by superimposing the results of the line analysis and the EPMA image (area analysis), the line analysis showed that the gold concentration was 5.0 atomic % or more, and the intensity was equal to or higher than the measurement points on the EPMA. It is visually determined whether the location is set to be identifiable as an intensity difference (color on the image). Thereby, the presence or absence of the gold-enriched junction region and the occupancy can be calculated. In addition, when calculating the occupancy of the gold-enriched bonding area, an EPMA color mapping image is used, but the more the image is enlarged, the more the gold-enriched bonding area may appear to be in a "sparse" state. Therefore, it is preferable to calculate the occupancy rate at a magnification that allows at least the ball compression portion to fit within one image (frame).

実施形態のワイヤ接合構造１において、銀を主成分とする芯材（銀芯材）４は、ボンディングワイヤ３を主として構成するものであり、ボンディングワイヤ３の機能を担うものである。このような芯材４は、純銀により構成することが好ましいが、場合によっては銀に添加元素を加えた銀合金により構成してもよい。ただし、銀ボンディングワイヤとしての機能を損なわないように、芯材４は銀を主成分として含むものとする。ここで、銀を主成分として含むとは、芯材４が少なくとも５０質量％以上の銀を含むことを意味する。芯材４を銀合金で構成する場合、パラジウム（Ｐｄ）、白金（Ｐｔ）、リン（Ｐ）、金（Ａｕ）、ニッケル（Ｎｉ）、銅（Ｃｕ）、鉄（Ｆｅ）、カルシウム（Ｃａ）、ロジウム（Ｒｈ）、ゲルマニウム（Ｇｅ）、ガリウム（Ｇａ）及びインジウム（Ｉｎ）から選ばれる少なくとも１つ以上の元素を含む銀合金を適用することが好ましいが、これらに限定されるものではない。 In the wire bonding structure 1 of the embodiment, the core material (silver core material) 4 containing silver as a main component mainly constitutes the bonding wire 3 and functions as the bonding wire 3 . Such a core material 4 is preferably made of pure silver, but may be made of a silver alloy in which additive elements are added to silver in some cases. However, the core material 4 contains silver as a main component so as not to impair the function as a silver bonding wire. Here, containing silver as a main component means that the core material 4 contains at least 50% by mass or more of silver. When the core material 4 is composed of a silver alloy, palladium (Pd), platinum (Pt), phosphorus (P), gold (Au), nickel (Ni), copper (Cu), iron (Fe), calcium (Ca) , rhodium (Rh), germanium (Ge), gallium (Ga) and indium (In).

芯材４を構成する銀合金における添加元素は、電極との接合性や接合信頼性、機械的強度の向上等に効果を示す。ただし、添加元素の含有量が多すぎると芯材４の比抵抗が増加し、銀ボンディングワイヤとしての機能が低下するおそれがある。このため、金被覆銀ボンディングワイヤ３は金ワイヤ（純度９９．９９質量％（４Ｎ））の比抵抗以下、例えば２．３μΩ・ｃｍ以下の範囲となるように添加元素の含有量を設定することが好ましい。純銀及び銀合金のいずれで芯材４を構成する場合においても、不可避な不純物を含んでいてもよいが、金被覆銀ボンディングワイヤ３の比抵抗が２．３μΩ・ｃｍ以下の範囲となる不純物量であることが好ましい。このような銀芯材４を適用することによって、ボンディングワイヤ３に求められる比抵抗の値を満足させることができる。金よりも比抵抗の低い銀が多く含有している銀合金のほうが比抵抗は低いと考えられがちであるが、純金（４Ｎ）よりも銀合金の方が合金化によって比抵抗が高くなることが多い。なお、ワイヤの比抵抗は四端子法で測定することが好ましく、例えば、ミリオームメーター（横河ヒューレット・パッカード株式会社製 型番４３２８Ａ）等を用いて測定する。 The additive elements in the silver alloy that constitutes the core material 4 are effective in improving the bondability with the electrode, the bonding reliability, the mechanical strength, and the like. However, if the content of the additive element is too high, the specific resistance of the core material 4 may increase and the function as a silver bonding wire may deteriorate. Therefore, the content of the additive element in the gold-coated silver bonding wire 3 should be set so that the resistivity of the gold wire (purity 99.99% by mass (4N)) or less, for example, 2.3 μΩ·cm or less. is preferred. Regardless of whether the core material 4 is composed of pure silver or a silver alloy, it may contain unavoidable impurities, but the amount of impurities is such that the specific resistance of the gold-coated silver bonding wire 3 is in the range of 2.3 μΩ·cm or less. is preferably By applying such a silver core material 4, the specific resistance value required for the bonding wire 3 can be satisfied. It is often thought that silver alloys containing more silver, which has a lower resistivity than gold, have lower resistivity, but silver alloys tend to have higher resistivity than pure gold (4N) due to alloying. There are many. The specific resistance of the wire is preferably measured by the four-terminal method, for example, using a milliohmmeter (model number 4328A manufactured by Yokogawa Hewlett-Packard Co., Ltd.).

実施形態の金被覆銀ボンディングワイヤ３において、被覆層５は金を主成分として含んでいる。ここで、金を主成分として含むとは、被覆層５が５０質量％以上の金を含むことを意味する。被覆層５における金含有量は、多ければ多いほどよく、少なくとも金が被覆層５中に５０質量％以上含まれていればよく、さらに金含有量は８０％質量以上が好ましく、９９質量％以上がより好ましい。被覆層５の金含有量は、ボンディングワイヤ３の表面からオージェ電子分光（ＡＥＳ：Ａｕｇｅｒ Ｅｌｅｃｔｒｏｎ Ｓｐｅｃｔｒｏｓｃｏｐｙ）等によるワイヤ最表面の定量分析にて測定できる。なお、ここでいう金含有量は、検出される金属元素の合計量に対する値であり、表面に吸着等で存在している炭素や酸素等は含めない。 In the gold-coated silver bonding wire 3 of the embodiment, the coating layer 5 contains gold as a main component. Here, containing gold as a main component means that the coating layer 5 contains 50% by mass or more of gold. The gold content in the coating layer 5 is preferably as high as possible, and at least gold should be contained in the coating layer 5 in an amount of 50% by mass or more, and the gold content is preferably 80% by mass or more, and 99% by mass or more. is more preferred. The gold content of the coating layer 5 can be measured from the surface of the bonding wire 3 by quantitative analysis of the wire outermost surface by Auger Electron Spectroscopy (AES) or the like. The gold content referred to here is a value for the total amount of metal elements detected, and does not include carbon, oxygen, etc. present on the surface due to adsorption or the like.

上述した金被覆銀ボンディングワイヤ３は、１３μｍ以上３０μｍ以下の線径を有することが好ましい。ワイヤ３の線径が１３μｍ未満であると、半導体装置の製造時にボンディングワイヤ３を用いてワイヤボンディングを行った際に、強度や導電性等が低下してワイヤボンディングの信頼性等が低下するおそれがある。ワイヤ３の線径が３０μｍを超えると、ボンディング本数が稼げないことと、隣接するボンディングワイヤとの接触（ショート）する可能性が高くなる。 The gold-coated silver bonding wire 3 described above preferably has a wire diameter of 13 μm or more and 30 μm or less. If the wire diameter of the wire 3 is less than 13 μm, there is a risk that the strength, conductivity, etc., will decrease and the reliability, etc. of wire bonding will decrease when wire bonding is performed using the bonding wire 3 during the manufacture of a semiconductor device. There is If the wire diameter of the wire 3 exceeds 30 μm, the number of bonding wires cannot be increased and the possibility of contact (short circuit) with adjacent bonding wires increases.

上記した線径を有する金被覆銀ボンディングワイヤ３において、線径に応じて被覆層５の厚さは５０ｎｍ以上２６０ｎｍ以下であることが好ましい。被覆層５の厚さは、金を主成分とする領域のワイヤ３の表面から垂直方向に対して芯材４に向かう深さ方向の厚さを示すものである。被覆層５の厚さが５０ｎｍ未満であると、金被覆銀ボンディングワイヤ３と電極２との接合信頼性を、金を主成分とする被覆層５により十分に高めることができないおそれがある。被覆層５の厚さが２６０ｎｍを超えると、被覆層５の形成性が低下するおそれがある。なお、被覆層５の厚さは金被覆銀ボンディングワイヤ３の線径に応じて設定することが好ましい。 In the gold-coated silver bonding wire 3 having the wire diameter described above, the thickness of the coating layer 5 is preferably 50 nm or more and 260 nm or less depending on the wire diameter. The thickness of the coating layer 5 indicates the thickness in the depth direction from the surface of the wire 3 in the region containing gold as the main component toward the core material 4 in the vertical direction. If the thickness of the coating layer 5 is less than 50 nm, the bonding reliability between the gold-coated silver bonding wire 3 and the electrode 2 may not be sufficiently improved by the coating layer 5 mainly composed of gold. If the thickness of the coating layer 5 exceeds 260 nm, the formability of the coating layer 5 may deteriorate. The thickness of the coating layer 5 is preferably set according to the wire diameter of the gold-coated silver bonding wire 3 .

被覆層５の厚さは、以下のようにして測定するものとする。すなわち、金被覆銀ボンディングワイヤ３において、その表面からＡＥＳにより深さ方向に元素濃度分析を実施して、表面近傍に存在する金の含有量の最大値を１００％としたときの５０％に位置する箇所を境界部とし、その境界部から表面までの領域を被覆層５の厚さとして求める。金被覆銀ボンディングワイヤ３の表面から深さ方向への元素分布は、ＡＥＳ分析によって測定することができる。例えば、ワイヤ１の表面から銀芯材４に向かって被覆層５の各元素濃度を分析する手段として、ＡＥＳ分析による濃度測定が有効である。ここでは一例として日本電子製のオージェ電子分光装置（商品名：ＪＡＭＰ－９５００Ｆ）を用いて、一次電子線の加速電圧１０ｋＶ、照射電流５０ｎＡ、ビーム径約４μｍφに設定し、Ａｒイオンスパッタ速度をＳｉＯ２換算値で約３．０ｎｍ／ｍｉｎの条件により実施した。 The thickness of the coating layer 5 shall be measured as follows. That is, in the gold-coated silver bonding wire 3, the element concentration analysis is performed from the surface in the depth direction by AES, and the maximum value of the gold content existing in the vicinity of the surface is 50% when the maximum value is 100%. A boundary portion is defined as a portion where the contact point is formed, and the thickness of the coating layer 5 is obtained from the area from the boundary portion to the surface. The element distribution in the depth direction from the surface of the gold-coated silver bonding wire 3 can be measured by AES analysis. For example, concentration measurement by AES analysis is effective as means for analyzing the concentration of each element in the coating layer 5 from the surface of the wire 1 toward the silver core material 4 . Here, as an example, using an Auger electron spectrometer (trade name: JAMP-9500F) manufactured by JEOL Ltd., the acceleration voltage of the primary electron beam is set to 10 kV, the irradiation current is 50 nA, and the beam diameter is set to about 4 μmφ, and the Ar ion sputtering speed is SiO It was carried out under the conditions of about 3.0 nm/min in terms of converted value.

実施形態のワイヤ接合構造１において、電極２とボール圧縮部６との接合界面近傍における金濃化接合領域７の形成方法は、特に限定されるものではない。金濃化接合領域７の形成方法としては、例えば金被覆銀ボンディングワイヤ３の一端にＦＡＢを形成する際に、ＦＡＢの表面に金が濃化した領域（表面金濃化領域）を形成することによって達成できる。表面に金濃化領域を形成したＦＡＢを電極２に接合してボール圧縮部６を形成することによって、電極２とボール圧縮部６との接合界面近傍に金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域７を形成することができる。詳しい形成方法については後述する。 In the wire bonding structure 1 of the embodiment, the method of forming the gold-enriched bonding region 7 near the bonding interface between the electrode 2 and the ball compression portion 6 is not particularly limited. As a method for forming the gold-enriched bonding area 7, for example, when forming the FAB on one end of the gold-coated silver bonding wire 3, a gold-enriched area (surface gold-enriched area) is formed on the surface of the FAB. can be achieved by By bonding FAB having a gold-enriched region formed on the surface to the electrode 2 to form the ball compression portion 6, the concentration of gold in the vicinity of the bonding interface between the electrode 2 and the ball compression portion 6 is equal to that of gold, silver, and aluminum. A gold-enriched junction region 7 of 5 atomic % or more can be formed with respect to the total amount. A detailed forming method will be described later.

金濃化接合領域７の形成方法の一例として、ボンディングワイヤを制御して形成する方法について説明する。すなわち、表面に金濃化領域を形成したＦＡＢを電極２に接合してボール圧縮部６を形成する方法について述べる。金被覆銀ボンディングワイヤ３を電極２に接合するにあたって、まず図４に示すように、金被覆銀ボンディングワイヤ３の一端にＦＡＢ８を形成する。ＦＡＢ８の形成条件としては、例えば金被覆銀ボンディングワイヤ３の線径が１３μｍ以上３０μｍ以下である場合に、線径に応じて放電電流値が３０ｍＡ以上１２０ｍＡ以下、ＦＡＢ８の直径がワイヤ線径の１．５倍以上２．０倍以下となるようにアーク放電条件を設定する。ボンダー装置は、例えばキューリック・アンド・ソッファ社製のボンダー装置（全自動ボンダー：ＩＣｏｎｎ ＰＬＵＳ）などの市販品を使用することができる。当該ボンダー装置を使用する場合、装置の設定として放電時間が５０μｓ以上１０００μｓ以下、ＥＦＯ－Ｇａｐが２０ｍｉｌ以上４０ｍｉｌ以下（約６３５μｍ以上１１４３μｍ以下）、テール長さが６ｍｉｌ以上１２ｍｉｌ以下（約１５２μｍ以上３０５μｍ以下）を適用することが好ましい。また、当該ボンダー装置以外のボンダー装置を用いる場合には、当該ボンダー装置と同等の条件、例えばＦＡＢ８の直径が当該ボンダー装置と同等の大きさになる条件であればよい。 As an example of the method of forming the gold-enriched bonding region 7, a method of forming a bonding wire under control will be described. That is, a method of forming the ball compression portion 6 by bonding the FAB having the gold-enriched region on the surface thereof to the electrode 2 will be described. When bonding the gold-coated silver bonding wire 3 to the electrode 2, first, as shown in FIG. The conditions for forming the FAB 8 are, for example, when the wire diameter of the gold-coated silver bonding wire 3 is 13 μm or more and 30 μm or less, the discharge current value is 30 mA or more and 120 mA or less depending on the wire diameter, and the diameter of the FAB 8 is 1 of the wire diameter. Arc discharge conditions are set so as to be 5 times or more and 2.0 times or less. As the bonder, a commercial product such as a bonder manufactured by Curic & Soffa (fully automatic bonder: IConn PLUS) can be used. When using the bonder, the discharge time is 50 μs or more and 1000 μs or less, the EFO-Gap is 20 mil or more and 40 mil or less (approximately 635 μm or more and 1143 μm or less), and the tail length is 6 mil or more and 12 mil or less (approximately 152 μm or more and 305 μm or less). ) is preferably applied. If a bonder other than the bonder is used, the same conditions as those of the bonder, for example, the diameter of the FAB 8 may be the same as that of the bonder.

このとき、銀ボンディングワイヤ表面に被覆した金被覆層５を溶融凝固してＦＡＢを作製するとき、表面の金がボール内部へ入り込んで結果的にボール表面の金濃度が下がり、相対的に銀濃度が上がり、アルミニウムを主成分とする電極に接合したときに腐食されやすいＡｇ３Ａｌ金属間化合物が生成してしまうという課題に対して、発明者らはボールを形成したときでも、固体ワイヤと同様にボール表面にも金を留めさせて相対的に銀濃度を減らしアルミニウム電極に接合したときに腐食に強いＡｇ２Ａｌ金属間化合物の生成、ならびに、非常に化学反応に対して安定している「貴」な金をワイヤ接合界面近傍に留まらせることができないか鋭意研究を重ねた。特に金被覆層に何らかの元素を添加すれば溶融したときでも金が表面に留まるのではないかと考え、金めっき時に数多くの種類の元素を添加してＦＡＢを作り表面の金濃度を分析するという実験を繰り返し行った。その結果、第１５及び１６族元素を添加するとＦＡＢ表面に金が留まることをついに発見した。At this time, when the gold coating layer 5 coated on the surface of the silver bonding wire is melted and solidified to produce an FAB, the gold on the surface enters the inside of the ball, resulting in a decrease in the gold concentration on the surface of the ball. In order to solve the problem that Ag 3 Al intermetallic compound, which is easily corroded when it is joined to an electrode whose main component is aluminum, is generated, the inventors have found that even when a ball is formed, it is similar to a solid wire. Gold is also retained on the ball surface to relatively reduce the silver concentration, and when bonded to an aluminum electrode, the formation of an Ag 2 Al intermetallic compound that is resistant to corrosion and is extremely stable against chemical reactions. We conducted extensive research to find out if precious gold could be retained in the vicinity of the wire bonding interface. In particular, I thought that if some element was added to the gold coating layer, the gold would remain on the surface even when it melted, so I added many kinds of elements during the gold plating process to create an FAB and analyze the gold concentration on the surface. was repeated. As a result, it was finally discovered that the addition of Group 15 and 16 elements retained gold on the FAB surface.

通常、特別な元素を添加しない金で形成した場合、金被覆銀ボンディングワイヤ３の一端を溶融・凝固させてＦＡＢ８を形成する際に、被覆層５を構成する金が銀芯材４中に入り込んでしまう。よって、ＦＡＢ８の表面に金が濃化した領域（表面金濃化領域）を形成することができない。言い換えると、金被覆層はＦＡＢ８の形成前までは効果を発揮するものの、ＦＡＢ８の形成後には表面金濃化領域を存在させることができない。すなわち、ウェッジボンディングでは効果を発揮するが、ボールボンディングでは高信頼性の効果を十分には発揮できない。そのようなＦＡＢ８を電極２に接合しても、電極２とボール圧縮部６との接合界面近傍に金濃化接合領域７を再現性よく形成することができない。ここで、金層の厚さを単に厚くしても、銀芯材の直径と比較した場合、金層の厚さの比率は小さいため、金が銀芯材中に入り込むことを抑制できない。また、金層の厚さのみに基づいて、ＦＡＢの形成後の表面における金濃度を高めた場合、金被覆銀ワイヤというより金ワイヤに近い状態となり、材料コストが大幅に上がってしまう。また、金層の厚さをワイヤ全体における金濃度に換算して７質量％を超えるとＦＡＢのボール形成性、すなわちボールの偏芯等が生じる可能性が高くなる。 Normally, when gold is used to which no special elements are added, the gold constituting the coating layer 5 enters the silver core material 4 when one end of the gold-coated silver bonding wire 3 is melted and solidified to form the FAB 8. I'll put it away. Therefore, a gold-enriched region (surface gold-enriched region) cannot be formed on the surface of the FAB 8 . In other words, the gold coating layer is effective before the formation of FAB8, but the surface gold-enriched region cannot exist after the formation of FAB8. In other words, wedge bonding is effective, but ball bonding cannot sufficiently achieve high reliability. Even if such a FAB 8 is bonded to the electrode 2, the gold-enriched bonding region 7 cannot be formed in the vicinity of the bonding interface between the electrode 2 and the ball compression portion 6 with good reproducibility. Here, even if the thickness of the gold layer is simply increased, since the ratio of the thickness of the gold layer to the diameter of the silver core is small, the penetration of gold into the silver core cannot be suppressed. Further, if the gold concentration on the surface after FAB formation is increased based only on the thickness of the gold layer, the state becomes closer to that of a gold wire rather than a gold-coated silver wire, resulting in a significant increase in material cost. Further, if the thickness of the gold layer exceeds 7% by mass in terms of the gold concentration in the entire wire, the ball formability of the FAB, that is, the eccentricity of the ball, etc., will likely occur.

発明者らは前述の通り鋭意研究の結果、ＦＡＢ８の形成時における金の銀芯材４中への入り込みを抑制する解決手段を解明した。金の銀芯材４中への入り込みの抑制は、被覆層５を構成する金中に、硫黄（Ｓ）、セレン（Ｓｅ）、テルル（Ｔｅ）、ヒ素（Ａｓ）、及びアンチモン（Ｓｂ）から選ばれる少なくとも１つ以上の第１５及び１６族元素を含有させることにより得られることを見出した。さらに、量的にはワイヤ全体に対して第１５及び１６族元素の合計量は４質量ｐｐｍ以上８０質量ｐｐｍ以下が好適であることを見出した。 As a result of intensive research as described above, the inventors have elucidated a solution for suppressing the intrusion of gold into the silver core material 4 during the formation of the FAB 8 . Intrusion of gold into the silver core material 4 is suppressed by adding sulfur (S), selenium (Se), tellurium (Te), arsenic (As), and antimony (Sb) to the gold constituting the coating layer 5. It has been found that it can be obtained by containing at least one or more selected group 15 and 16 elements. Furthermore, it was found that the total amount of Group 15 and 16 elements in the entire wire is preferably 4 mass ppm or more and 80 mass ppm or less.

第１５及び１６族元素による金の銀芯材４中への入り込みの抑制メカニズムは完全に解明されていないが、ＦＡＢ８が形成される過程において、被覆層５中の第１５及び１６族元素は溶融状態の被覆層５の表面張力に作用し、金が濃化した領域の形成に寄与すると推測される。従来の金被覆銀ボンディングワイヤの場合、溶融銀の表面張力は溶融金の表面張力よりも小さく、表面張力の違いにより発生する流れ（マランゴニ対流）が表面張力の小さい方から大きい方へ、つまり溶融銀（溶融ボール）から溶融金（溶融状態の被覆された金）に向かって発生するため、溶融金はボール内部へ移動する。一方、第１５及び１６族元素が被覆層５に存在する場合、溶融した被覆層５の表面張力は溶融銀よりも小さくなり、マランゴニ対流の向きが溶融金から溶融銀の方向へと反転するため、溶融金はＦＡＢ８の内部に入り込まない。従って、ＦＡＢ８の表面に表面金濃化領域９を形成することができると推測した。 Although the mechanism by which the elements of Groups 15 and 16 suppress the entry of gold into the silver core material 4 has not been completely elucidated, the elements of Groups 15 and 16 in the coating layer 5 are melted in the process of forming the FAB 8. It is speculated that it acts on the surface tension of the underlying coating layer 5 and contributes to the formation of gold-enriched regions. In the case of conventional gold-coated silver bonding wires, the surface tension of molten silver is smaller than the surface tension of molten gold, and the flow (Marangoni convection) generated by the difference in surface tension flows from the lower surface tension to the higher surface tension, that is, the melting Molten gold moves inside the ball because it is generated from silver (molten ball) to molten gold (molten coated gold). On the other hand, when the group 15 and 16 elements are present in the coating layer 5, the surface tension of the molten coating layer 5 becomes smaller than that of the molten silver, and the direction of the Marangoni convection is reversed from the molten gold to the molten silver. , molten gold does not enter the interior of FAB8. Therefore, it was surmised that the surface gold-enriched region 9 could be formed on the surface of the FAB 8 .

上述した被覆層５中の第１５及び１６族元素の効果が発揮されるタイミング及び表面金濃化領域が形成される過程について、ＦＡＢ８の形成過程に沿って説明する。ＦＡＢ８は金被覆銀ボンディングワイヤ３をリード又はバンプ上に第２接合した後、所定長さのワイヤが繰り出され、切断されたボンディングワイヤ３の先端と放電トーチの間にアーク放電を生じさせ、ワイヤ先端を溶融することにより形成される。ボンディングワイヤ３は第２接合の際キャピラリーで押し潰されることにより変形するため、ボンディングワイヤ３とキャピラリーが接触する領域は被覆層５が存在せず、芯材４が露出した状態となる。溶融ボールの形成初期段階では、この芯材４が露出したワイヤ先端のみ溶融されたボールは被覆層５が存在していない箇所が存在するため、金濃化領域は形成されてない。アーク放電により初期溶融ボールの溶融が進むにつれて、芯材４が露出していないワイヤ部分が溶融され始めると、被覆層５中の第１５及び１６族元素が溶融時の表面張力に作用し、溶融金はＦＡＢ８の内部へ入り込むことなくＦＡＢ８の表面領域に存在する。やがて、小さいボールから大きいボールへと成長してゆくが、金はボンディングワイヤ３から連続的に供給される。溶融金はアーク放電の熱により溶融した芯材４と合金化される。 The timing at which the effects of the group 15 and 16 elements in the coating layer 5 are exhibited and the process of forming the surface gold-enriched region will be described along with the process of forming the FAB 8 . After the FAB 8 secondly bonds the gold-coated silver bonding wire 3 onto the lead or bump, a wire of a predetermined length is drawn out, and an arc discharge is generated between the tip of the cut bonding wire 3 and the discharge torch, and the wire It is formed by melting the tip. Since the bonding wire 3 is deformed by being crushed by the capillary during the second bonding, the coating layer 5 does not exist in the region where the bonding wire 3 contacts the capillary, and the core material 4 is exposed. At the initial stage of formation of the molten ball, only the tip of the wire where the core material 4 is exposed has a portion where the coating layer 5 does not exist in the molten ball, so a gold-enriched region is not formed. As the arc discharge progresses the melting of the initially melted ball, when the wire portion where the core material 4 is not exposed begins to melt, the group 15 and 16 elements in the coating layer 5 act on the surface tension during melting, and melting Gold resides in the surface area of FAB8 without penetrating into the interior of FAB8. The gold is continuously supplied from the bonding wire 3 while the ball grows from a small ball to a large ball in due time. The molten gold is alloyed with the molten core material 4 by the heat of the arc discharge.

被覆層５を有する金被覆銀ボンディングワイヤ３において、金はワイヤ３の全体量に対して、２質量％以上７質量％以下の範囲で含まれることが好ましい。ワイヤ３の全体量に対する金の含有量が２質量％未満であると、銀芯材４を主体とする金被覆銀ボンディングワイヤ３に形成されたＦＡＢ８を用いて形成したボール圧縮部６と電極２との間の接合信頼性を十分に高めることができないおそれがある。ワイヤ３の全体量に対する金の含有量が７質量％を超えると、溶融時のボール形状、ひいてはＦＡＢ８の形状が偏芯等により低下し、ボール圧縮部６の形状や信頼性が損なわれると共に、金被覆銀ボンディングワイヤ３の材料コストが上昇する。ワイヤ３の直径や被覆層５の厚さにもよるが、ワイヤ３の全体量に対する金の含有量は３．５質量％以上がより好ましい。 In the gold-coated silver bonding wire 3 having the coating layer 5 , gold is preferably contained in the range of 2% by mass or more and 7% by mass or less with respect to the total amount of the wire 3 . When the content of gold with respect to the total amount of the wire 3 is less than 2% by mass, the ball compression part 6 and the electrode 2 formed using the FAB 8 formed on the gold-coated silver bonding wire 3 mainly composed of the silver core material 4 It may not be possible to sufficiently improve the bonding reliability between the If the gold content exceeds 7% by mass with respect to the total amount of the wire 3, the ball shape at the time of melting and the shape of the FAB 8 are deteriorated due to eccentricity, etc., and the shape and reliability of the ball compression part 6 are impaired. The material cost of the gold-coated silver bonding wire 3 increases. Although it depends on the diameter of the wire 3 and the thickness of the coating layer 5, the content of gold with respect to the total amount of the wire 3 is more preferably 3.5% by mass or more.

被覆層５中に第１５及び１６族元素を存在させる場合、第１５及び１６族元素は上記した金被覆銀ボンディングワイヤ３の全体量に対して、４質量ｐｐｍ以上８０質量ｐｐｍ以下の範囲で含まれることが好ましい。ワイヤ３の全体量に対する第１５及び１６族元素の含有量が４質量ｐｐｍ未満であると、ＦＡＢ８の形成時における金の濃化効果、それによる表面金濃化領域の形成性を十分に得ることができない。ワイヤ３の全体量に対する第１５及び１６族元素の含有量が８０質量ｐｐｍを超えると、被覆層５にクラックや割れ等が生じやすくなり、伸線加工時に断線等の加工性、生産性が低下し、所望の線径の金被覆銀ボンディングワイヤ３が得られにくくなる。なお、第１５及び１６族元素は２種類以上を混合して適用してもよく、その場合には第１５及び１６族元素の合計量が上記した含有範囲となるように調整する。 When group 15 and group 16 elements are present in the coating layer 5, the group 15 and group 16 elements are included in the range of 4 mass ppm or more and 80 mass ppm or less with respect to the total amount of the gold-coated silver bonding wire 3. preferably If the content of the group 15 and 16 elements with respect to the total amount of the wire 3 is less than 4 ppm by mass, the effect of gold enrichment during the formation of FAB 8, thereby sufficiently obtaining the formation of the surface gold enriched region can't If the content of the group 15 and 16 elements with respect to the total amount of the wire 3 exceeds 80 ppm by mass, the coating layer 5 is likely to crack or fracture, and workability such as wire breakage during wire drawing and productivity are reduced. As a result, it becomes difficult to obtain a gold-coated silver bonding wire 3 having a desired wire diameter. Two or more Group 15 and 16 elements may be mixed and applied, in which case the total amount of the Group 15 and 16 elements is adjusted so as to fall within the above-described content range.

上記した第１５及び１６族元素を含む被覆層５を有する被覆銀ボンディングワイヤ１を用いた場合、被覆層５に含有させた第１５及び１６族元素により、ＦＡＢ８の表面領域、例えば形成されるＦＡＢ８の直径にもよるが表面から深さ方向に対して１０μｍ以下（あるいはＦＡＢ８の直径に対して１０％以下）の範囲に表面金濃化領域９が形成される。この表面金濃化領域９はＦＡＢ８と電極２との接合後も維持されるため、電極２とボール圧縮部６との接合界面近傍に金濃化接合領域７を形成することができる。すなわち、金濃化接合領域７を有するワイヤ接合構造１を得ることが可能になる。なお、上記した金濃化接合領域７の形成方法及び形成過程は一例であり、それに限定されるものではない。 When the coated silver bonding wire 1 having the coating layer 5 containing the group 15 and 16 elements described above is used, the surface region of the FAB 8, for example, the FAB 8 formed by the group 15 and 16 elements contained in the coating layer 5 A surface gold-enriched region 9 is formed in a range of 10 μm or less (or 10% or less of the diameter of FAB 8 ) from the surface in the depth direction, depending on the diameter of the FAB 8 . Since the surface gold-enriched region 9 is maintained even after the FAB 8 and the electrode 2 are joined, the gold-enriched joining region 7 can be formed in the vicinity of the joining interface between the electrode 2 and the ball compression portion 6 . That is, it becomes possible to obtain a wire bond structure 1 having a gold-enriched bond region 7 . It should be noted that the method and process of forming the gold-enriched junction region 7 described above are merely examples, and are not limited thereto.

例えば、ＦＡＢと電極２との接合条件について、以下のような条件でも金濃化接合領域７を形成することができる。具体的には、アルミニウム電極表面に金を蒸着する等でも金濃化接合領域７を形成するこができる。しかしながら、電極への金被覆は材料コスト、製造コストの面から非常にコスト高になってしまうため推奨しない。実施形態のワイヤ接合構造１は、電極２とボール圧縮部６との接合界面近傍に金濃化接合領域７を設けることによって、上述した電極２とボール圧縮部６との接合信頼性を高めるものであるため、金濃化接合領域７の形成方法は特に限定されるものではない。 For example, the gold-enriched bonding region 7 can be formed even under the following conditions for bonding the FAB and the electrode 2 . Specifically, the gold-enriched junction region 7 can be formed by vapor-depositing gold on the surface of the aluminum electrode. However, it is not recommended to coat the electrodes with gold because the material cost and manufacturing cost are very high. The wire bonding structure 1 of the embodiment improves the bonding reliability between the electrode 2 and the ball compression portion 6 by providing the gold-enriched bonding region 7 in the vicinity of the bonding interface between the electrode 2 and the ball compression portion 6. Therefore, the method of forming the gold-enriched junction region 7 is not particularly limited.

以下に、金被覆銀ボンディングワイヤ３の全体量における金の含有量及び第１５及び１６族元素の含有量の算出方法について述べる。まず、金の含有量を算出する。ボンディングワイヤ３を希硝酸に入れ、芯材４を溶解した後、溶解液を採取する。この溶解液に塩酸を加え、超純水で定容液とする。被覆層５は希王水で溶解し、超純水で定容液とする。これらの定容液中の金の定量分析をＩＣＰ発光分光分析法（ＩＣＰ－ＡＥＳ：Ｉｎｄｕｃｔｉｖｅｌｙ Ｃｏｕｐｌｅｄ Ｐｌａｓｍａ Ａｔｏｍｉｃ Ｅｍｉｓｓｉｏｎ Ｓｐｅｃｔｒｏｓｃｏｐｙ）で行うことにより、金含有量を測定する。 A method for calculating the content of gold and the content of group 15 and group 16 elements in the entire gold-coated silver bonding wire 3 will be described below. First, the gold content is calculated. After the bonding wire 3 is placed in dilute nitric acid to dissolve the core material 4, the solution is sampled. Hydrochloric acid is added to this solution, and ultrapure water is added to make a constant volume solution. The coating layer 5 is dissolved in dilute aqua regia and made into a constant volume solution with ultrapure water. The gold content is determined by quantitative analysis of gold in these constant volumes by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).

次に、第１５及び１６族元素の含有量を算出する。被覆層５のセレン及びテルルの含有量は、ボンディングワイヤ３を希硝酸に入れ、芯材４を溶融した後に被覆層５を抽出する。さらに、被覆層５を希王水で加熱分解した後、超純水で定容した溶液を用いて測定する。この定容液中のセレン、テルル、ヒ素、及びアンチモンの定量分析をＩＣＰ質量分析法（ＩＣＰ－ＭＳ：Ｉｎｄｕｃｔｉｖｅｌｙ Ｃｏｕｐｌｅｄ Ｐｌａｓｍａ Ｍａｓｓ Ｓｐｅｃｔｒｏｍｅｔｒｙ）を用いて測定する。一方、芯材４のセレン、テルル、ヒ素、及びアンチモンの含有量は、ボンディングワイヤ３を希硝酸に入れ、芯材４を溶融した液を用いてＩＣＰ－ＭＳまたはＩＣＰ－ＡＥＳにより測定する。その後、被覆層５及び芯材４の金の含有量とセレン、テルル、ヒ素、及びアンチモンの含有量からボンディングワイヤ３全体における金含有量とセレン、テルル、ヒ素、及びアンチモンの含有量を算出する。また、上記以外にもＩＣＰ－ＡＥＳに水素化物発生装置を取り付けて、セレン、テルル、ヒ素、及びアンチモンの水素化物を生成することによって分析する方法もある。また、芯材４及び被覆層５の硫黄（Ｓ）の含有量は、ボンディングワイヤ３に対して燃焼赤外線吸収法を用いて測定する。測定１回あたりのボンディングワイヤ３の重量は０．５ｇ以上とすることが好ましい。試料が溶けにくい場合、必要に応じて助燃材を使用してもよい。 Next, the contents of Group 15 and 16 elements are calculated. The content of selenium and tellurium in the coating layer 5 is determined by extracting the coating layer 5 after the bonding wire 3 is put into dilute nitric acid and the core material 4 is melted. Furthermore, after the coating layer 5 is thermally decomposed with dilute aqua regia, the measurement is performed using a solution whose volume is constant with ultrapure water. Quantitative analysis of selenium, tellurium, arsenic, and antimony in this constant volume liquid is measured using ICP mass spectrometry (ICP-MS: Inductively Coupled Plasma Mass Spectrometry). On the other hand, the content of selenium, tellurium, arsenic, and antimony in the core material 4 is measured by ICP-MS or ICP-AES using a liquid in which the bonding wire 3 is placed in dilute nitric acid and the core material 4 is melted. Thereafter, the gold content and the selenium, tellurium, arsenic and antimony content in the entire bonding wire 3 are calculated from the gold content and the selenium, tellurium, arsenic and antimony content of the coating layer 5 and the core material 4. . In addition to the above, there is also a method of analyzing by attaching a hydride generator to the ICP-AES to generate hydrides of selenium, tellurium, arsenic and antimony. Also, the sulfur (S) content of the core material 4 and the coating layer 5 is measured with respect to the bonding wire 3 using a combustion infrared absorption method. The weight of the bonding wire 3 per measurement is preferably 0.5 g or more. If the sample is difficult to dissolve, a combustion improver may be used as necessary.

次に、ボンディングワイヤの製造方法について説明する。芯材４として銀を用いる場合には、所定の純度の銀を溶解させ、また銀合金を用いる場合には、所定の純度の銀を添加元素と共に溶解させることによって、銀芯材材料又は銀合金芯材材料が得られる。溶解には、アーク加熱炉、高周波加熱炉、抵抗加熱炉、連続鋳造炉等の加熱炉が用いられる。大気中からの酸素や水素の混入を防止する目的で、加熱炉の銀溶湯の上部は真空あるいはアルゴン、窒素等の不活性ガス雰囲気に保持することが好ましい。溶解させた芯材材料は、加熱炉から所定の線径となるように鋳造凝固させるか、溶融した芯材材料を鋳型に鋳造してインゴットを作り、そのインゴットをロール圧延した後、所定の線径まで伸線して銀線材（純銀線材及び銀合金線材を含む）が得られる。 Next, a method for manufacturing a bonding wire will be described. When silver is used as the core material 4, silver of a predetermined purity is dissolved, and when a silver alloy is used, silver of a predetermined purity is dissolved together with an additive element to form a silver core material or a silver alloy. A core material is obtained. A heating furnace such as an arc heating furnace, a high-frequency heating furnace, a resistance heating furnace, or a continuous casting furnace is used for melting. For the purpose of preventing contamination of oxygen and hydrogen from the air, the upper portion of the molten silver in the heating furnace is preferably maintained in a vacuum or an atmosphere of an inert gas such as argon or nitrogen. The melted core material is cast and solidified from a heating furnace so as to have a predetermined wire diameter, or the melted core material is cast into a mold to make an ingot. A silver wire (including a pure silver wire and a silver alloy wire) is obtained by drawing to a diameter.

銀線材の表面に金層を形成する方法としては、例えばめっき法（湿式法）や蒸着法（乾式法）が用いられる。めっき法は電解めっき法と無電解めっき法のいずれの方法であってもよい。ストライクめっきやフラッシュめっき等の電解めっきでは、めっき速度が速く、また金めっきに適用すると、金層の銀線材への密着性が良好であるために好ましい。めっき法で金層内に硫黄族元素を含有させるためには、例えば上記電解めっきにおいて、金めっき液に硫黄、セレン、テルル、ヒ素、及びアンチモンから選ばれる少なくとも１つを含むめっき添加剤を含有させためっき液を使用する。この際、めっき添加剤の種類や量を調整することによって、被覆層５中の第１５及び１６族元素含有量を調整することができ、さらにワイヤ３中の第１５及び１６族元素含有量を調整することができる。 As a method for forming a gold layer on the surface of the silver wire, for example, a plating method (wet method) or a vapor deposition method (dry method) is used. The plating method may be either an electrolytic plating method or an electroless plating method. Electrolytic plating such as strike plating and flash plating is preferable because the plating speed is high, and when applied to gold plating, the adhesion of the gold layer to the silver wire is good. In order to contain a sulfur group element in the gold layer by plating, for example, in the electroplating, the gold plating solution contains a plating additive containing at least one selected from sulfur, selenium, tellurium, arsenic, and antimony. Use a plating solution that has been At this time, by adjusting the type and amount of the plating additive, the content of Group 15 and 16 elements in the coating layer 5 can be adjusted, and the content of Group 15 and 16 elements in the wire 3 can be adjusted. can be adjusted.

蒸着法としては、スパッタ法、イオンプレーティング法、真空蒸着法等の物理蒸着（ＰＶＤ）や、熱ＣＶＤ、プラズマＣＶＤ、有機金属気相成長法（ＭＯＣＶＤ）等の化学蒸着（ＣＶＤ）を利用することができる。これらの方法によれば、形成後の金被覆層の洗浄が不要であり、洗浄時の表面汚染等の懸念がない。蒸着法によって金層内に第１５及び１６族元素を含有させる手法としては、第１５及び１６族元素を含有させた金ターゲットを用いて、マグネトロンスパッタリング等によって金層を形成する手法がある。それ以外の方法を適用する場合も、金材料に第１５及び１６族元素を含有させた原料を用いればよい。 As the vapor deposition method, physical vapor deposition (PVD) such as sputtering method, ion plating method and vacuum deposition method, and chemical vapor deposition (CVD) such as thermal CVD, plasma CVD and metal organic chemical vapor deposition (MOCVD) are used. be able to. According to these methods, it is not necessary to wash the gold coating layer after formation, and there is no concern about surface contamination during washing. As a technique for incorporating the elements of Groups 15 and 16 into the gold layer by vapor deposition, there is a technique of forming the gold layer by magnetron sputtering or the like using a gold target containing the elements of Groups 15 and 16. Also when applying other methods, it is sufficient to use a raw material in which an element of Groups 15 and 16 is contained in a gold material.

金層を形成するタイミングは特に限定されない。金層を被覆した銀線材を最終線径まで伸線し、必要に応じて熱処理することによって、銀芯材４の表面に被覆層５を設けた金被覆銀ボンディングワイヤ３が製造される。伸線加工は銀線材の段階で実施してもよいし、またある程度の線径まで銀線材に伸線加工を施し、金層を形成した後に最終線径まで伸線加工してもよい。伸線加工と熱処理は、段階的に行われてもよい。伸線加工の加工率は、製造される金被覆銀ボンディングワイヤ３の最終線径や用途等に応じて決定される。伸線加工の加工率は、一般的には銀線材を最終線径に加工するまでの加工率として９０％以上であることが好ましい。この加工率は、ワイヤ断面積の減少率として算出することができる。伸線加工は、複数のダイヤモンドダイスを用いて、段階的に線径を縮小するように行うことが好ましい。この場合、ダイヤモンドダイス１つあたりの減面率（加工率）は５％以上１５％以下が好ましい。 The timing of forming the gold layer is not particularly limited. A gold-coated silver bonding wire 3 having a coating layer 5 on the surface of a silver core 4 is manufactured by drawing a silver wire coated with a gold layer to a final wire diameter and heat-treating it as necessary. The wire drawing may be performed at the stage of the silver wire, or the silver wire may be drawn to a certain wire diameter, and after forming a gold layer, the wire may be drawn to the final wire diameter. Wire drawing and heat treatment may be performed in stages. The processing rate of wire drawing is determined according to the final wire diameter of the gold-coated silver bonding wire 3 to be manufactured, the application, and the like. Generally, it is preferable that the processing rate of wire drawing is 90% or more as a processing rate until the silver wire is processed to the final wire diameter. This processing rate can be calculated as a reduction rate of the wire cross-sectional area. Wire drawing is preferably performed using a plurality of diamond dies so as to reduce the wire diameter in stages. In this case, the area reduction rate (processing rate) per diamond die is preferably 5% or more and 15% or less.

金層を被覆した銀線材を最終線径まで伸線した後に、最終熱処理を実施することが好ましい。最終熱処理は、最終線径において、ワイヤ３の内部に残留する金属組織の歪みを除去する歪み取り熱処理や必要とされるワイヤ特性を考慮して実行される。歪み取り熱処理は、必要とされるワイヤ特性を考慮して、温度及び時間を決定することが好ましい。その他、ワイヤ製造の任意の段階で、目的に応じた熱処理を施してもよい。このような熱処理としては、ワイヤの伸線過程での歪み取り熱処理、金層を形成した後に接合強度を上げるための拡散熱処理等がある。拡散熱処理を行うことで、芯材４と被覆層５との接合強度を向上させることができる。熱処理は、所定の温度に加熱された加熱雰囲気内にワイヤを通過させて熱処理を行う走間熱処理が、熱処理条件を調節しやすいために好ましい。走間熱処理の場合、熱処理時間はワイヤの通過速度と加熱容器内のワイヤの通過距離によって算出することができる。加熱容器としては電気炉等が使用される。 It is preferable to perform the final heat treatment after drawing the silver wire coated with the gold layer to the final wire diameter. The final heat treatment is performed in consideration of the strain relief heat treatment that removes the distortion of the metal structure remaining inside the wire 3 and the required wire characteristics at the final wire diameter. It is preferable to determine the temperature and time for the strain relief heat treatment in consideration of the required wire properties. In addition, heat treatment may be applied according to the purpose at any stage of wire production. Examples of such heat treatment include strain relief heat treatment in the process of wire drawing, diffusion heat treatment for increasing the bonding strength after forming a gold layer, and the like. By performing the diffusion heat treatment, the bonding strength between the core material 4 and the coating layer 5 can be improved. The heat treatment is preferably a heat treatment while running, in which the wire is passed through a heating atmosphere heated to a predetermined temperature, because the heat treatment conditions can be easily adjusted. In the case of heat treatment while running, the heat treatment time can be calculated from the passing speed of the wire and the passing distance of the wire in the heating container. An electric furnace or the like is used as the heating container.

次に、上述した金被覆銀ボンディングワイヤ３の一端にＦＡＢ８を形成する。ＦＡＢ８は、ワイヤ３の先端と放電トーチの間にアーク放電を生じさせ、ワイヤ３の先端を溶融することにより形成される。金被覆銀ボンディングワイヤ３の一端に形成されたＦＡＢ８を、超音波併用熱圧着ボンディング法等により電極２に接合する。電極２に接触したＦＡＢ８を、超音波併用熱圧着時の圧力により変形させつつ、超音波及び熱により電極２に接合することによって、電極２に接合されたボール圧縮部６を形成することができる。 Next, a FAB 8 is formed at one end of the gold-coated silver bonding wire 3 described above. The FAB 8 is formed by causing an arc discharge between the tip of the wire 3 and the discharge torch to melt the tip of the wire 3 . The FAB 8 formed at one end of the gold-coated silver bonding wire 3 is bonded to the electrode 2 by a thermocompression bonding method combined with ultrasonic wave or the like. The ball compression part 6 joined to the electrode 2 can be formed by joining the FAB 8 in contact with the electrode 2 to the electrode 2 by ultrasonic waves and heat while deforming the FAB 8 in contact with the electrode 2 by pressure during thermocompression bonding with ultrasonic waves. .

（半導体装置）
次に、実施形態のワイヤ接合構造を適用した半導体装置について、図５ないし図７を参照して説明する。なお、図５は実施形態の半導体装置の樹脂封止する前の段階を示す断面図、図６は実施形態の半導体装置の樹脂封止した段階を示す断面図、図７は実施形態の半導体装置における半導体チップの電極とボンディングワイヤとの接合部を拡大して示す断面図である。(semiconductor device)
Next, a semiconductor device to which the wire bonding structure of the embodiment is applied will be described with reference to FIGS. 5 to 7. FIG. 5 is a sectional view showing a stage before resin sealing of the semiconductor device of the embodiment, FIG. 6 is a sectional view showing the stage of resin sealing of the semiconductor device of the embodiment, and FIG. 7 is a semiconductor device of the embodiment. 1 is an enlarged cross-sectional view showing a joint portion between an electrode of a semiconductor chip and a bonding wire in FIG.

実施形態の半導体装置１０（樹脂封止する前の半導体装置１０Ｘ）は、図５及び図６に示すように、外部電極１１を有する回路基板１２と、回路基板１２上に配置され、少なくとも１つの電極（チップ電極）１３をそれぞれ有する複数の半導体チップ１４（１４Ａ、１４Ｂ、１４Ｃ）と、回路基板１２の外部電極１１と半導体チップ１４の電極１３、及び複数の半導体チップ１４の電極１３間を接続するボンディングワイヤ１５とを備えている。回路基板１２には、例えば樹脂材やセラミックス材等の絶縁基材の表面や内部に配線網を設けたプリント配線板やセラミックス回路基板等が用いられる。 As shown in FIGS. 5 and 6, the semiconductor device 10 (semiconductor device 10X before being resin-sealed) of the embodiment includes a circuit board 12 having external electrodes 11, and is arranged on the circuit board 12 and has at least one Connection between a plurality of semiconductor chips 14 (14A, 14B, 14C) each having an electrode (chip electrode) 13, the external electrodes 11 of the circuit board 12, the electrodes 13 of the semiconductor chip 14, and the electrodes 13 of the plurality of semiconductor chips 14 and a bonding wire 15 for connecting. For the circuit board 12, a printed wiring board, a ceramic circuit board, or the like, in which a wiring network is provided on the surface or inside of an insulating base material such as a resin material or a ceramic material, is used.

なお、図５及び図６は回路基板１２上に複数の半導体チップ１４を実装した半導体装置１０を示しているが、半導体装置１０の構成はこれに限られるものではない。例えば、半導体チップはリードフレーム上に実装されていてもよく、その場合には半導体チップの電極はリードフレームの外部電極として機能するアウターリードにボンディングワイヤ１５を介して接続される。半導体チップの回路基板やリードフレームに対する搭載数は、１つ及び複数のいずれであってもよい。ボンディングワイヤ１５は、回路基板１２の外部電極１１と半導体チップ１４の電極１３、リードフレームと半導体チップの電極、及び複数の半導体チップ１４の電極１３間の少なくとも１つに適用される。 Although FIGS. 5 and 6 show the semiconductor device 10 having a plurality of semiconductor chips 14 mounted on the circuit board 12, the configuration of the semiconductor device 10 is not limited to this. For example, the semiconductor chip may be mounted on a lead frame, in which case electrodes of the semiconductor chip are connected via bonding wires 15 to outer leads functioning as external electrodes of the lead frame. The number of semiconductor chips mounted on a circuit board or lead frame may be either one or a plurality. The bonding wires 15 are applied to at least one of the external electrodes 11 of the circuit board 12 and the electrodes 13 of the semiconductor chip 14 , the electrodes of the lead frame and the semiconductor chip, and the electrodes 13 of the plurality of semiconductor chips 14 .

図５及び図６に示す半導体装置１０の複数の半導体チップ１４のうち、半導体チップ１４Ａ、１４Ｃは回路基板１２のチップ実装領域にダイボンディング材１６を介して実装されている。半導体チップ１４Ｂは半導体チップ１４Ａ上にダイボンディング材１６を介して実装されている。半導体チップ１４Ａの１つの電極１３はボンディングワイヤ１５を介して回路基板１２の外部電極１１と接続されており、他の１つの電極１３はボンディングワイヤ１５を介して半導体チップ１４Ｂの電極１３と接続されており、さらに他の１つの電極１３はボンディングワイヤ１５を介して半導体チップ１４Ｃの電極１３と接続されている。半導体チップ１４Ｂの他の１つの電極１３は、ボンディングワイヤ１５を介して回路基板１２の外部電極１１と接続されている。半導体チップ１４Ｃの他の１つの電極１３は、ボンディングワイヤ１５を介して回路基板１２の外部電極１１と接続されている。 Of the plurality of semiconductor chips 14 of the semiconductor device 10 shown in FIGS. 5 and 6, the semiconductor chips 14A and 14C are mounted on the chip mounting area of the circuit board 12 with the die bonding material 16 interposed therebetween. The semiconductor chip 14B is mounted on the semiconductor chip 14A with a die bonding material 16 interposed therebetween. One electrode 13 of the semiconductor chip 14A is connected via a bonding wire 15 to the external electrode 11 of the circuit board 12, and the other electrode 13 is connected via a bonding wire 15 to the electrode 13 of the semiconductor chip 14B. , and the other electrode 13 is connected via a bonding wire 15 to the electrode 13 of the semiconductor chip 14C. Another electrode 13 of the semiconductor chip 14B is connected to the external electrode 11 of the circuit board 12 via a bonding wire 15. As shown in FIG. Another electrode 13 of the semiconductor chip 14C is connected to the external electrode 11 of the circuit board 12 via a bonding wire 15. As shown in FIG.

半導体チップ１４は、シリコン（Ｓｉ）半導体や化合物半導体等からなる集積回路（ＩＣ）を備えている。チップ電極１３は、例えば、少なくとも最表面にアルミニウム（Ａｌ）層、ＡｌＳｉＣｕ、ＡｌＣｕ等のアルミニウム合金層を有するアルミニウム電極からなる。アルミニウム電極は、例えばシリコン（Ｓｉ）基板の表面に、内部配線と電気的に接続するようにＡｌやＡｌ合金等の電極材料を被覆することにより形成される。半導体チップ１４は、外部電極１１及びボンディングワイヤ１５を介して、外部デバイスとの間でデータ通信をしたり、また外部デバイスから電力を供給したりする。 The semiconductor chip 14 includes an integrated circuit (IC) made of silicon (Si) semiconductor, compound semiconductor, or the like. The tip electrode 13 is composed of, for example, an aluminum electrode having an aluminum (Al) layer, an aluminum alloy layer such as AlSiCu, AlCu, etc. on at least the outermost surface. The aluminum electrode is formed, for example, by coating the surface of a silicon (Si) substrate with an electrode material such as Al or an Al alloy so as to be electrically connected to the internal wiring. The semiconductor chip 14 communicates data with an external device through the external electrodes 11 and the bonding wires 15 and supplies power from the external device.

回路基板１２の外部電極１１は、回路基板１２に実装された半導体チップ１４の電極１３とボンディングワイヤ１５を介して電気的に接続されている。実施形態の半導体装置１０において、ボンディングワイヤ１５の一端は、チップ電極１３にボール接合（第１接合）されており、他端は外部電極１１にウェッジ接合（第２接合）されている。複数の半導体チップ１４の電極１３間をボンディングワイヤ１５で接続する場合も同様であり、ボンディングワイヤ１５の一端は、半導体チップ１４のチップ電極１３にボール接合（第１接合）され、他端は他の半導体チップ１４のチップ電極１３にウェッジ接合（第２接合）される。なお、半導体チップ１４の電極１３とは、半導体チップ１４上にある電極パッドにあらかじめバンプを接合した形態も含むものとする（図示しない）。 External electrodes 11 of circuit board 12 are electrically connected to electrodes 13 of semiconductor chip 14 mounted on circuit board 12 via bonding wires 15 . In the semiconductor device 10 of the embodiment, one end of the bonding wire 15 is ball-bonded (first bonding) to the chip electrode 13 and the other end is wedge-bonded (second bonding) to the external electrode 11 . The same applies to connecting the electrodes 13 of a plurality of semiconductor chips 14 with bonding wires 15. One end of the bonding wire 15 is ball-joined (first joint) to the chip electrode 13 of the semiconductor chip 14, and the other end are wedge-bonded (second bonded) to the chip electrode 13 of the semiconductor chip 14 . Note that the electrodes 13 of the semiconductor chip 14 also include a form in which bumps are bonded in advance to electrode pads on the semiconductor chip 14 (not shown).

ボンディングワイヤ１５の一端をチップ電極１３にボール接合するにあたって、ボンディングワイヤ１５の一端を放電等により溶融し、表面張力等により球状に凝固させることによって、図４に示したようなＦＡＢ８を形成する。このようなＦＡＢ８を、超音波併用熱圧着ボンディング法等によりチップ電極１３にボンディングすることによって、図１に示したワイヤ接合構造１が形成される。すなわち、図７に示すように、ボンディングワイヤ１５とチップ電極１３とチップ電極１３に接合されたボール圧縮部６とを有するワイヤ接合構造１が形成される。この後、複数の半導体チップ１４及びボンディングワイヤ１５を樹脂封止するように、回路基材１２上に封止樹脂層１７を形成することによって、半導体装置１０が製造される。半導体装置１０の具体例としては、ロジックＩＣ、アナログＩＣ、ディスクリート半導体、半導体メモリ、光半導体等が挙げられる。 When one end of the bonding wire 15 is ball-bonded to the chip electrode 13, one end of the bonding wire 15 is melted by electric discharge or the like and solidified into a spherical shape by surface tension or the like to form the FAB 8 shown in FIG. The wire bonding structure 1 shown in FIG. 1 is formed by bonding such FAB 8 to the chip electrode 13 by a thermocompression bonding method combined with ultrasonic wave or the like. That is, as shown in FIG. 7, the wire bonding structure 1 having the bonding wires 15, the chip electrodes 13, and the ball compression portions 6 bonded to the chip electrodes 13 is formed. Thereafter, the semiconductor device 10 is manufactured by forming a sealing resin layer 17 on the circuit board 12 so as to resin-seal the plurality of semiconductor chips 14 and the bonding wires 15 . Specific examples of the semiconductor device 10 include logic ICs, analog ICs, discrete semiconductors, semiconductor memories, optical semiconductors, and the like.

半導体装置１０におけるワイヤ接合構造１には、前述した実施形態のワイヤ接合構造１が適用される。すなわち、ボンディングワイヤ１５の一端に設けられたボール圧縮部６とチップ電極１３との接合界面近傍には、図１に示したように、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域７が設けられている。このような金濃化接合領域７を存在させ、接合界面近傍における金濃度を高めることによって、非常に脆く、腐食されやすいＡｇ３Ａｌ金属間化合物の形成を抑制し、耐食性に優れて安定なＡｇ２Ａｌ金属間化合物を形成することによって、電極２とボール圧縮部６との接合信頼性を向上させることができ、ひいては半導体装置１の信頼性を高めることが可能になる。The wire bonding structure 1 of the above-described embodiment is applied to the wire bonding structure 1 in the semiconductor device 10 . That is, in the vicinity of the bonding interface between the ball compression portion 6 provided at one end of the bonding wire 15 and the chip electrode 13, as shown in FIG. A gold-enriched junction region 7 of 5 atomic % or more is provided. By allowing such a gold-enriched bonding region 7 to exist and increasing the gold concentration in the vicinity of the bonding interface, the formation of an Ag 3 Al intermetallic compound, which is very brittle and susceptible to corrosion, is suppressed, and corrosion-resistant and stable Ag By forming the 2Al intermetallic compound, the reliability of bonding between the electrode 2 and the ball compression portion 6 can be improved, and thus the reliability of the semiconductor device 1 can be improved.

次に、本発明の実施例について説明する。本発明は以下の実施例に限定されない。例１～２６は実施例であり、例２７～３２は比較例である。 Next, examples of the present invention will be described. The invention is not limited to the following examples. Examples 1-26 are working examples, and examples 27-32 are comparative examples.

（実施例１～２６）
芯材として、連続鋳造で作製した銀もしくは銀合金の芯材を用意し、連続伸線を行って中間線径０．０５ｍｍ～１．０ｍｍまで加工した。さらに、中間線径の銀線材に、硫黄、セレン、テルル、ヒ素、及びアンチモンの各々の添加剤を適量添加した金電解めっき浴を使用し、銀線材を連続的に送線しながら浸漬した状態で、銀線材に電流密度０．２０Ａ／ｄｍ２以上２．０Ａ／ｄｍ２以下で電流を流し、金被覆層を形成した。この後、最終線径のφ２０μｍまで伸線加工したワイヤに最終熱処理を施し、実施例１から実施例２６の金被覆銀ボンディングワイヤを作製した。(Examples 1 to 26)
As a core material, a core material of silver or a silver alloy produced by continuous casting was prepared and subjected to continuous wire drawing to process to an intermediate wire diameter of 0.05 mm to 1.0 mm. Furthermore, a gold electroplating bath in which appropriate amounts of additives of sulfur, selenium, tellurium, arsenic, and antimony are added to a silver wire with an intermediate wire diameter is used, and the silver wire is continuously immersed while being fed. A current was passed through the silver wire at a current density of 0.20 A/dm 2 or more and 2.0 A/dm 2 or less to form a gold coating layer. Thereafter, the wire drawn to a final wire diameter of φ20 μm was subjected to a final heat treatment to produce gold-coated silver bonding wires of Examples 1 to 26.

（比較例２７～３２）
実施例と同様にして、金被覆銀ボンディングワイヤを作製した。ボンディングワイヤの組成については表１にまとめて示す。(Comparative Examples 27-32)
A gold-coated silver bonding wire was produced in the same manner as in the example. The compositions of the bonding wires are summarized in Table 1.

（含有量測定）
金被覆銀ボンディングワイヤ中の金含有量（金は被覆層由来であり銀芯材には含まれていない）、銀芯材への添加元素であるパラジウム、インジウム、及び第１５及び１６族元素含有量は、前述した方法前述した方法（(Content measurement)
Gold content in the gold-coated silver bonding wire (gold is derived from the coating layer and is not contained in the silver core material), palladium, indium, and group 15 and 16 elements contained in the silver core material The amount is determined by the method described above (

、 ,

参照）にしたがって測定した。その結果を表１に示す。 reference). Table 1 shows the results.

（ワイヤ表面割れ観察）
中間線径及び最終線径の金被覆銀ボンディングワイヤの外観をキーエンス社製のレーザー顕微鏡（商品名：ＶＫ－Ｘ２００）を用いて、高倍率による金被膜の割れ（亀裂）の有無を確認した。サンプリング本数は合計１０本で、主に伸線加工時に発生する引張応力により、金被膜に亀裂が発生して銀芯材の露出が１本でも見られた場合を不合格（X）、１本も見られなかった場合を合格（○）とした。その結果を表１に示す。なお、表面割れのあったサンプルについては、これ以降のボール形成性やＨＡＳＴ評価等を実施しなかったので表中には未実施（－）と示した。(Observation of wire surface cracks)
The appearance of the gold-coated silver bonding wires with intermediate wire diameter and final wire diameter was checked for cracks (cracks) in the gold coating at high magnification using a laser microscope (trade name: VK-X200) manufactured by Keyence Corporation. A total of 10 samples were sampled, and if even one wire was found to have a crack in the gold film and the silver core was exposed due to the tensile stress that occurs mainly during wire drawing, it was rejected (X), and one wire was rejected. A case in which neither was observed was regarded as a pass (○). Table 1 shows the results. The samples with surface cracks were not subjected to subsequent ball forming properties, HAST evaluation, etc., and are indicated as untested (-) in the table.

（ＦＡＢ作製条件）
上述の条件によりＦＡＢを作製し、上述の接合条件で電極に接合した（［００２４］、［００４０］参照）。(FAB production conditions)
The FAB was produced under the conditions described above and bonded to the electrodes under the bonding conditions described above (see [0024] and [0040]).

（ボール形成性）
ボール形成性はボール圧着後の真円性にて評価することができる。３０本の第１接合について、接合されたボールを上部から観察し、圧着ボールの最大幅とこれに直交する幅を測定し、最大幅とこれに直交する幅の比（最大幅／直交する幅）を求めた。この比の値の、上記３０本の平均値が１．００以上１．１５未満であれば良好（○）、１．１５以上であれば問題ありで不良（Ｘ）とした(ball formability)
The ball formability can be evaluated by the roundness after the ball is press-bonded. For the 30 first bonds, the bonded balls were observed from above, the maximum width of the crimped ball and the width perpendicular thereto were measured, and the ratio of the maximum width and the width perpendicular thereto (maximum width / width perpendicular to this) ). If the average value of the above 30 values of this ratio is 1.00 or more and less than 1.15, it is good (○), and if it is 1.15 or more, there is a problem and it is bad (X).

（金濃化接合領域等の測定）
次に、上述した方法で作製したサンプルの接合界面近傍について金濃化接合領域の有無（金濃度分析値）、及び、ボール圧縮部の全長に対して８分の１の箇所とボール圧縮部の端との間に金濃化接合領域が存在するか、また、接合界面近傍における占有率が２５％以上あるかを測定した。１サンプルにつき電極とボール接合との接合構造が４組できる。その４組について上記３つの評価を行なった。金濃化接合領域の金濃度についてはパラジウムやインジウム、及び第１５及び１６族元素等の添加元素を考慮せずに求めた。すなわち、分母に入れずに求めた。表１の金濃化接合領域の金の分析値は４組の接合構造のうち１番金濃度が高かった組の値を採用し、その組の接合界面近傍におけるライン分析の測定点で金濃度が高い順から３点選び、その３点の平均値を記載した。圧縮部の両端から上記８分の１の箇所までの間に金濃化接合領域があるかないかの評価は、４組のボールすべてであった場合は合格（○）で、１組でも無ければ不合格（Ｘ）とした。同様に金濃化接合領域の占有率に関しても４組の接合構造すべて２５％以上あった場合には合格（○）、１組でも２５％未満だった場合は不合格（Ｘ）と記載した。（各評価方法の詳細については［００２７］から［００３２］を参照）。(Measurement of gold-enriched junction area, etc.)
Next, the presence or absence of a gold-enriched bonding region (analysis value of gold concentration) in the vicinity of the bonding interface of the sample prepared by the above method, and the location of 1/8 of the total length of the ball compression portion and the ball compression portion. It was measured whether there was a gold-enriched bonding region between the edge and whether the occupancy rate in the vicinity of the bonding interface was 25% or more. Four pairs of joint structures of electrodes and ball joints are produced for each sample. The above three evaluations were performed on the four sets. The gold concentration in the gold-enriched junction region was determined without considering additional elements such as palladium, indium, and group 15 and 16 elements. That is, it was obtained without putting it in the denominator. For the analytical value of gold in the gold-enriched joint region in Table 1, the value of the group with the highest gold concentration among the four joint structures was adopted. 3 points were selected from the highest order, and the average value of the 3 points was recorded. The evaluation of whether or not there is a gold-enriched joint area between both ends of the compressed part to the above 1/8 point was passed (○) if there were all four sets of balls, and if there was not even one set. It was set as failure (X). Similarly, regarding the occupancy rate of the gold-enriched bonding region, when all four bonding structures were 25% or more, it was described as a pass (○), and when even one of the bonding structures was less than 25%, it was described as a failure (X). (See [0027] to [0032] for details of each evaluation method).

（ＨＡＳＴ試験用サンプルの作製）
各例で得られた金被覆銀ボンディングワイヤについて、市販のボンダー装置（Ｋ＆Ｓ ＩＣＯＮＮ）にて、ＢＧＡ（Ｂａｌｌ Ｇｒｉｄ Ａｒｒａｙ）基板上の厚さ３００μｍのＳｉチップ上の厚さ０．８μｍのＡｌ－０．５質量％Ｃｕ合金電極上に、それぞれ上記フリーエアーボール、ボール接合及び第二接合と同様の条件でワイヤボンディングを行なった。つまり、フリーエアーボールの形成は、全自動ボンダーを用いて、ボール径が線径の１．５～２．３倍の範囲の所定の大きさになるように、エレクトロン・フレーム・オフ（ＥＦＯ）電流を３０～９０ｍＡの範囲、放電時間を５０～１０００μｓの範囲でそれぞれ所定の値に調節し、ＥＦＯ－Ｇａｐが２５～４５ｍｉｌ（約６３５～１１４３μｍ）、テール長さが６～１２ｍｉｌ（約１５２～３０５μｍ）で行なった。(Preparation of sample for HAST test)
For the gold-coated silver bonding wires obtained in each example, Al-0 with a thickness of 0.8 μm on a Si chip with a thickness of 300 μm on a BGA (Ball Grid Array) substrate with a commercial bonder (K&S ICONN). Wire bonding was performed on the 5% by mass Cu alloy electrode under the same conditions as the above free air ball, ball bonding and second bonding, respectively. That is, the formation of free-air balls is carried out using a fully automatic bonder so that the ball diameter has a predetermined size in the range of 1.5 to 2.3 times the wire diameter, using electron flame off (EFO). The current was adjusted to a predetermined value in the range of 30 to 90 mA, and the discharge time was adjusted to a predetermined value in the range of 50 to 1000 μs. 305 μm).

第１接合の条件は、例えば、ワイヤ線径φが２０μｍの実施例１については、ボール径が３６μｍのフリーエアーボールを形成し、ボール圧縮部の高さが１０μｍ、ボール圧縮部の接合面に平行方向の最大幅が４５μｍ、ボールシェア強度１５ｇｆ以上となるようにボンディング条件を調整した。この際、チップ上のＡｌ－０．５質量％Ｃｕ合金電極は隣り合うボンド部のみが電気的に接続されて、隣り合う２本のワイヤ同士で電気的に１つの回路を形成しており、計３２０回路が形成する。その後、このＢＧＡ基板上のＳｉチップを市販のトランズファーモールド機（第一精工製株式会社、ＧＰＧＰ－ＰＲＯ－ＬＡＢ８０）を使って樹脂封止して試験片を得た。なお、封止した樹脂は市販されているハロゲンフリーの樹脂（塩素濃度１５ｐｐｍ以下、ｐｈ６以上７以下）を使用した。また、実施例の試験片についてはボール圧縮部の高さが７～１３μｍ、ボール圧縮部の接合面に平行方向の最大幅は形成されたフリーエアーボールの１．２倍となるようにボール接合した。 For example, in Example 1 where the wire diameter φ is 20 μm, a free air ball with a ball diameter of 36 μm is formed, the height of the ball compression portion is 10 μm, and the joint surface of the ball compression portion is The bonding conditions were adjusted so that the maximum width in the parallel direction was 45 μm and the ball shear strength was 15 gf or more. At this time, the Al-0.5 mass % Cu alloy electrodes on the chip are electrically connected only at the adjacent bond portions, and two adjacent wires electrically form one circuit. A total of 320 circuits are formed. Thereafter, the Si chip on the BGA substrate was resin-sealed using a commercially available transfer molding machine (Daiichi Seiko Co., Ltd., GPGP-PRO-LAB80) to obtain a test piece. A commercially available halogen-free resin (chlorine concentration: 15 ppm or less, pH: 6 or more and 7 or less) was used as the sealing resin. The test pieces of the examples were ball-bonded so that the height of the ball-compressed portion was 7 to 13 μm, and the maximum width in the direction parallel to the joint surface of the ball-compressed portion was 1.2 times that of the formed free-air ball. bottom.

＜ＨＡＳＴ（Ｈｉｇｈｌｙ Ａｃｃｅｌｅｒａｔｅｄ Ｔｅｍｐｅｒａｔｕｒｅ ａｎｄＨｕｍｉｄｉｔｙ Ｓｔｒｅｓｓ Ｔｅｓｔ（高温高湿環境暴露試験））＞
この試験片についてＨＡＳＴ装置（株式会社平山製作所、ＰＣＲ８Ｄ）を用いて、１３０℃、８５．０％ＲＨ（相対湿度）、２．２気圧で２００時間保持した。保持前後に上記３２０回路の電気抵抗値を測定し、保持後の電気抵抗値が保持前の電気抵抗値に比べすべての回路で上昇率が８％以下であった場合を（Ｓ）、１回路でも８％を超えそれ以外の回路が１０％以下である場合を（Ａ）、１回路でも１０％を超えそれ以外の回路が１５％以下である場合を（Ｂ）、１回路でも１５％を超えそれ以外の回路が２０％以下である場合を（Ｃ）、２０％超えた回路が一つでもあった場合を不良（×）とした。２０％以下はＳからＣのランクを付けたが製品上問題ないレベルなので合格とした。<HAST (Highly Accelerated Temperature and Humidity Stress Test)>
This test piece was held at 130° C., 85.0% RH (relative humidity), and 2.2 atm for 200 hours using a HAST device (Hirayama Seisakusho Co., Ltd., PCR8D). The electrical resistance values of the above 320 circuits were measured before and after holding, and if the rate of increase in the electrical resistance value after holding was 8% or less in all circuits compared to the electrical resistance value before holding (S), 1 circuit. However, if it exceeds 8% and the other circuits are 10% or less (A), if even one circuit exceeds 10% and the other circuits are 15% or less (B), even one circuit is 15% A case where the other circuits exceeded 20% or less was rated as (C), and a case where even one circuit exceeded 20% was rated as defective (x). If it was 20% or less, it was ranked from S to C, and since it is a level that does not pose any problem in terms of the product, it was accepted.

Figure 0007269361000001
Figure 0007269361000001

表１に示すように、実施例１～２６の金被覆銀ボンディングワイヤによれば、アルミニウムを含む電極とボール圧縮部との接合界面近傍に金濃度がアルミニウムと銀と金の合計に対して５．０原子％以上となる金濃化接合領域が形成できる。そのような接合構造があることにより、ＨＡＳＴ評価が良好となり、高温高湿等の厳しい環境下に長時間さらされても、接続部の比抵抗が上昇しない高い信頼性のある半導体装置を提供できる。表１からの傾向として、金濃化接合領域が接合界面の両端付近にあることが好ましく、また、接合界面において金濃化接合領域がボール圧縮部の幅に対して２５％以上占めることでＨＡＳＴ評価が良好なことが分かる。さらに、ワイヤの芯材にパラジウムやインジウムの添加元素を添加することもＨＡＳＴ評価が良好になる要素のひとつとなる。金濃化接合領域の金濃度に関しても、金濃度が高いほどＨＡＳＴ評価が良くなる傾向にある。どちらかというと金濃度が高いほうが、芯材にパラジウム等を添加するよりもＨＡＳＴ評価に良い影響を与えていると考えられる。 As shown in Table 1, according to the gold-coated silver bonding wires of Examples 1 to 26, the concentration of gold in the vicinity of the bonding interface between the electrode containing aluminum and the ball compression portion is 5 with respect to the total of aluminum, silver, and gold. A gold-enriched junction region having a concentration of 0.0 atomic % or more can be formed. With such a junction structure, the HAST evaluation is good, and a highly reliable semiconductor device can be provided in which the resistivity of the junction does not increase even when exposed to severe environments such as high temperature and high humidity for a long time. . As a tendency from Table 1, it is preferable that the gold-enriched bonding regions are located near both ends of the bonding interface, and the gold-enriched bonding region occupies 25% or more of the width of the ball compression portion at the bonding interface, so that HAST It can be seen that the evaluation is favorable. Furthermore, adding an additive element such as palladium or indium to the core material of the wire is one of the factors that improve the HAST evaluation. Regarding the gold concentration in the gold-enriched junction region, the higher the gold concentration, the better the HAST evaluation. If anything, the higher gold concentration is considered to have a better effect on the HAST evaluation than the addition of palladium or the like to the core material.

一方、比較例に示す通り、ワイヤに被覆している金層（表１では濃度換算した値）が２．０質量％未満だと、金濃化接合領域の金濃度が５原子％未満となりＨＡＳＴ評価では不合格となり、反対にワイヤに被覆する金層を厚くしすぎると（ここでは濃度換算して７質量％を超えると）、ＦＡＢ形成時に偏芯等が生じ、ボール形成性が悪くなることが分かる。第１５族元素及び第１６族元素の添加量も重要になる。４質量ｐｐｍ未満だと金濃化接合領域の金濃度が５原子％未満となって、ＨＡＳＴ評価も不合格となり、８０質量ｐｐｍを超えると、今度はワイヤ表面に割れ不良が発生してしまう。もちろん、第１５族及び第１６族元素を添加しない場合も金濃化接合領域が５原子％未満となりＨＡＳＴ評価も不合格となる。 On the other hand, as shown in the comparative example, when the gold layer covering the wire (concentration-converted value in Table 1) is less than 2.0% by mass, the gold concentration in the gold-enriched junction region is less than 5 atomic%, resulting in HAST. On the contrary, if the gold layer coated on the wire is too thick (exceeding 7% by mass in terms of concentration), eccentricity etc. will occur during FAB formation, resulting in poor ball formability. I understand. The addition amounts of group 15 elements and group 16 elements are also important. If it is less than 4 ppm by mass, the gold concentration in the gold-enriched bonding region becomes less than 5 atomic %, and the HAST evaluation fails. Of course, even when the group 15 and group 16 elements are not added, the gold-enriched junction region becomes less than 5 atomic % and the HAST evaluation fails.

以上の通り、本発明のワイヤ接合構造及びそれに用いられるボンディングワイヤによれば、ボンディングワイヤの比抵抗の上昇を抑えた上で、電極とボール圧縮部との接合界面近傍に金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域を設けることによって、電極とボール圧縮部との接合信頼性を高めることができる。また、そのようなワイヤ接合構造を適用した本発明の半導体装置によれば、金濃化接合領域による電極とボール圧縮部との接合信頼性、ひいては半導体装置自体の信頼性を向上させることが可能になる。 As described above, according to the wire bonding structure of the present invention and the bonding wire used therein, the increase in the specific resistance of the bonding wire is suppressed, and the concentration of gold in the vicinity of the bonding interface between the electrode and the ball compression portion is reduced to that of gold. By providing a gold-enriched bonding area of 5 atomic % or more with respect to the total amount of silver and aluminum, the bonding reliability between the electrode and the ball compression portion can be enhanced. Further, according to the semiconductor device of the present invention to which such a wire bonding structure is applied, it is possible to improve the reliability of bonding between the electrode and the ball compression portion by means of the gold-enriched bonding region, and thus the reliability of the semiconductor device itself. become.

１…ワイヤ接合構造、２…電極、３…金被覆銀ボンディングワイヤ、４…芯材（銀芯材）、５…被覆層、６…ボール圧縮部、７…金濃化接合領域、８…ＦＡＢ（ボール）、９…表面金濃化領域、１０…半導体装置、１１…外部電極、１２…回路基板、１３…チップ電極、１４…半導体チップ、１５…ボンディングワイヤ、１６…ダイボンディング材、１８…封止樹脂層。 REFERENCE SIGNS LIST 1 wire bonding structure, 2 electrode, 3 gold-coated silver bonding wire, 4 core material (silver core material), 5 coating layer, 6 ball compressed portion, 7 gold-enriched bonding region, 8 FAB (Ball) 9 Surface gold-enriched region 10 Semiconductor device 11 External electrode 12 Circuit board 13 Chip electrode 14 Semiconductor chip 15 Bonding wire 16 Die bonding material 18 Sealing resin layer.

Claims (7)

アルミニウムを含む電極と、ボンディングワイヤと、前記ボンディングワイヤの一端に設けられ、前記電極に接合されたボール圧縮部とを有するワイヤ接合構造であって、
前記ボンディングワイヤは、銀を主成分とする芯材と、前記芯材の表面に設けられ、金を主成分とする被覆層とを有し、硫黄、テルル、セレン、ヒ素、及びアンチモンから選ばれる少なくとも１つの第１５及び１６族元素を含有する金被覆銀ボンディングワイヤであって、ワイヤ全体に対して、金濃度が２．０質量％以上７．０質量％以下であり、第１５及び１６族元素濃度が合計で４質量ｐｐｍ以上８０質量ｐｐｍ以下であり、
前記電極と前記ボール圧縮部との接合界面近傍に、金濃度が、アルミニウムと銀と金の合計に対して５．０原子％以上となる金濃化接合領域を有する、ワイヤ接合構造。 A wire bonding structure having an electrode containing aluminum, a bonding wire, and a ball compressing portion provided at one end of the bonding wire and bonded to the electrode,
The bonding wire has a core material mainly composed of silver and a coating layer mainly composed of gold provided on the surface of the core material, and is selected from sulfur, tellurium, selenium, arsenic, and antimony. A gold-coated silver bonding wire containing at least one group 15 and 16 element, having a gold concentration of 2.0% or more and 7.0% or less by weight of the total wire and containing groups 15 and 16 The total element concentration is 4 ppm by mass or more and 80 ppm by mass or less,
A wire bonding structure comprising a gold-enriched bonding region having a gold concentration of 5.0 atomic % or more with respect to a total of aluminum, silver, and gold in the vicinity of the bonding interface between the electrode and the ball compression portion. 前記接合界面近傍の金濃化接合領域が、前記ボール圧縮部の最大幅に対して、少なくとも前記ボール圧縮部の両端から１／８の位置の間に各々形成されている、請求項１に記載のワイヤ接合構造。 2. The gold-enriched bonding region near the bonding interface is formed between at least ⅛ positions from both ends of the ball compressing portion with respect to the maximum width of the ball compressing portion. wire-bonded structure. 前記接合界面近傍の金濃化接合領域の占有率が、前記ボール圧縮部の最大幅に対して、合計で２５％以上である、請求項１又は２に記載のワイヤ接合構造。 3. The wire bonding structure according to claim 1, wherein the gold-enriched bonding area near the bonding interface has a total occupation ratio of 25% or more with respect to the maximum width of the ball compressed portion. 請求項１ないし請求項３のいずれか１項に記載のワイヤ接続構造に用いられる金被覆銀ボンディングワイヤであって、前記金被覆銀ボンディングワイヤは、銀を主成分として含む芯材と、前記芯材の表面に設けられ、金を主成分として含む被覆層とを有し、
前記金被覆銀ボンディングワイヤは、硫黄、テルル、セレン、ヒ素、及びアンチモンから選ばれる少なくとも１つの第１５及び１６族元素を含有し、
前記金被覆銀ボンディングワイヤにおいて、ワイヤ全体に対して、金濃度が２．０質量％以上７．０質量％以下であり、第１５及び１６族元素濃度が合計で４質量ｐｐｍ以上８０質量ｐｐｍ以下であり、
前記金被覆銀ボンディングワイヤは、アルミニウムを含む電極上にボール接合してボール圧縮部を形成したとき、前記電極と前記ボール圧縮部との接合界面近傍に、金濃度が、アルミニウムと金と銀の合計に対して５．０原子％以上となる金濃化接合領域が形成される、金被覆銀ボンディングワイヤ。 4. A gold-coated silver bonding wire used in the wire connection structure according to any one of claims 1 to 3, wherein said gold-coated silver bonding wire comprises a core material containing silver as a main component and said core A coating layer provided on the surface of the material and containing gold as a main component,
the gold-coated silver bonding wire contains at least one Group 15 and 16 element selected from sulfur, tellurium, selenium, arsenic, and antimony;
In the gold-coated silver bonding wire, the gold concentration is 2.0% by mass or more and 7.0% by mass or less, and the total concentration of Group 15 and 16 elements is 4 mass ppm or more and 80 mass ppm or less. and
When the gold-coated silver bonding wire is ball-bonded to an electrode containing aluminum to form a ball-compressed portion, the concentration of gold in the vicinity of the bonding interface between the electrode and the ball-compressed portion is that of aluminum, gold, and silver. A gold-coated silver bonding wire with a gold-enriched bonding area of 5.0 atomic percent or greater for the total. 前記金被覆銀ボンディングワイヤの比抵抗が２．３μΩ・ｃｍ以下である、請求項４に記載の金被覆銀ボンディングワイヤ。 5. The gold-coated silver bonding wire according to claim 4, wherein the gold-coated silver bonding wire has a specific resistance of 2.3 μΩ·cm or less. 前記金被覆銀ボンディングワイヤは、パラジウム（Ｐｄ）、白金（Ｐｔ）、金（Ａｕ）、ニッケル（Ｎｉ）、銅（Ｃｕ）、鉄（Ｆｅ）、カルシウム（Ｃａ）、ロジウム（Ｒｈ）、ゲルマニウム（Ｇｅ）、ガリウム（Ｇａ）、及びインジウム（Ｉｎ）から選ばれる少なくとも１つの元素を含む、請求項４又は請求項５に記載の金被覆銀ボンディングワイヤ。 The gold-coated silver bonding wire includes palladium (Pd), platinum (Pt), gold (Au), nickel (Ni), copper (Cu), iron (Fe), calcium (Ca), rhodium (Rh), germanium ( 6. The gold-coated silver bonding wire according to claim 4 or claim 5, comprising at least one element selected from Ge), gallium (Ga), and indium (In). 少なくとも１つのアルミニウムを含む電極を有する１つ又は複数の半導体チップと、
リードフレーム又は基板と、
前記半導体チップの電極と前記リードフレームとの間、前記半導体チップの電極と前記基板の電極との間、及び前記複数の半導体チップの電極間から選ばれる少なくとも１つを、銀を主成分として含む芯材と、前記芯材の表面に設けられ、金を主成分として含む被覆層とを有するボンディングワイヤで接続した半導体装置であって、
前記ボンディングワイヤは、銀を主成分とする芯材と、前記芯材の表面に設けられ、金を主成分とする被覆層とを有し、硫黄、テルル、セレン、ヒ素、及びアンチモンから選ばれる少なくとも１つの第１５及び１６族元素を含有する金被覆銀ボンディングワイヤであって、ワイヤ全体に対して、金濃度が２．０質量％以上７．０質量％以下であり、第１５及び１６族元素濃度が合計で４質量ｐｐｍ以上８０質量ｐｐｍ以下であり、
前記電極と前記ボンディングワイヤとの接続構造は、前記電極に前記ボンディングワイヤの一端を接合するように設けられたボール圧縮部を備え、前記電極と前記ボール圧縮部との接合界面近傍に、金の濃度が金と銀とアルミニウムの合計量に対して５原子％以上の金濃化接合領域が設けられている、半導体装置。 one or more semiconductor chips having at least one electrode comprising aluminum;
a lead frame or substrate;
At least one selected from between the electrodes of the semiconductor chip and the lead frame, between the electrodes of the semiconductor chip and the electrodes of the substrate, and between the electrodes of the plurality of semiconductor chips contains silver as a main component. A semiconductor device connected by a bonding wire having a core material and a coating layer provided on the surface of the core material and containing gold as a main component,
The bonding wire has a core material mainly composed of silver and a coating layer mainly composed of gold provided on the surface of the core material, and is selected from sulfur, tellurium, selenium, arsenic, and antimony. A gold-coated silver bonding wire containing at least one group 15 and 16 element, having a gold concentration of 2.0% or more and 7.0% or less by weight of the total wire and containing groups 15 and 16 The total element concentration is 4 ppm by mass or more and 80 ppm by mass or less,
The connection structure between the electrode and the bonding wire includes a ball compression portion provided to bond one end of the bonding wire to the electrode, and gold is placed near the bonding interface between the electrode and the ball compression portion. A semiconductor device provided with a gold-enriched junction region having a concentration of 5 atomic % or more with respect to the total amount of gold, silver, and aluminum.
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