JP3579493B2 - Gold alloy wires for semiconductor devices - Google Patents

Gold alloy wires for semiconductor devices Download PDF

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Publication number
JP3579493B2
JP3579493B2 JP09570295A JP9570295A JP3579493B2 JP 3579493 B2 JP3579493 B2 JP 3579493B2 JP 09570295 A JP09570295 A JP 09570295A JP 9570295 A JP9570295 A JP 9570295A JP 3579493 B2 JP3579493 B2 JP 3579493B2
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Prior art keywords
wire
ppm
weight
addition
gold alloy
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JPH08291348A (en
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智裕 宇野
宏平 巽
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Nippon Steel Corp
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Nippon Steel Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3013—Au as the principal constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/02—Alloys based on gold
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/43—Manufacturing methods
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/4501—Shape
    • H01L2224/45012—Cross-sectional shape
    • H01L2224/45015—Cross-sectional shape being circular
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
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    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/102—Material of the semiconductor or solid state bodies
    • H01L2924/1025—Semiconducting materials
    • H01L2924/10251—Elemental semiconductors, i.e. Group IV
    • H01L2924/10253—Silicon [Si]

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Wire Bonding (AREA)

Description

【０００１】
【産業上の利用分野】
本発明は、半導体素子上の電極と外部リードを電気的接続するためのボンディングに使用される半導体素子用金合金細線に関する。
【０００２】
【従来の技術】
現在半導体素子上の回路配線電極と外部リードとの間の電気的接続としては、ワイヤボンディング方式が主として使用されている。最近、半導体の高集積化、多機能化が進み、さらにＩＣチップの小型化、薄型化の要求も高まる中で、半導体実装の高密度化に対するニーズが高まっている。端子数が増加する多ピン化を実現するためには、インナーリード部がシリコンチップに対して後退するため、ワイヤの接合間（スパン）が長くなる傾向にある。従来のスパンは４ｍｍ以下が主流であったが、近年スパンが５ｍｍ以上のロングスパンが所望され、直線性の確保や、ばらつきの低減などループ形状を厳密に制御することが難しくなっている。
【０００３】
また、多ピン化に伴い、電極間隔が減少する狭ピッチ化が要求され、ワイヤ間の最小ピッチが１００μｍ以下のものまで所望されており、ワイヤも細線化が望まれている。こうした多ピン化、狭ピッチ化を達成するために、ボンディング装置の改善、ルーピング性に優れたワイヤの開発などが進められている。
半導体実装の高密度化において、ワイヤの多ピン化、狭ピッチ化に対応するためには、樹脂封止時のワイヤ流れを抑えることが課題となる。粘性の高いエポキシ樹脂による封止時に、ワイヤが変形して流れることに起因して、隣接ワイヤ間の接触や、ワイヤとチップまたはインナーリード部との接触などに伴う不良が発生するものである。狭ピッチ化の実現のためにワイヤを細線化すると、強度が低下して、封止後のワイヤ流れの問題はより一層深刻となる。
【０００４】
【発明が解決しようとする課題】
スパン長が大きく異なると、ループ形状が変化することはもちろんであるが、さらに樹脂封止時のワイヤの変形挙動に及ぼす影響も大きい。例えば、ループ全体がほぼ均等に変形したとしても、ワイヤ流れ値の絶対値はスパンとともに大きくなる傾向にあり、スパンが５ｍｍ以上のロングスパンになると、ワイヤの樹脂流れの抑制が最大の課題となる。一方、スパンが３ｍｍ程度までの通常の短スパンでは、ループの弛みが少ないことからも、ボール直上のネック部にかかる負担が大きく、このネック部の変形が樹脂流れに及ぼす影響が大きい。また、従来のロングスパン用ワイヤを使用して短スパンを接続した場合の傾向として、ループ高さが低くなることに起因したプル強度の低下も無視できなくなる。
【０００５】
これらの傾向については、ルーピング条件や樹脂封止条件などの装置条件も複雑に関与するため、定量的には整理し難いが、スパン長に合わせた金合金細線の使い分けが要求され、特性を十分把握した上での使い分けが困難である。
本発明は、スパン長の影響を軽減し、ボンディング時のループ曲がりおよび樹脂封止時のワイヤ変形を低減して、高密度実装に適した金合金細線を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者等は、以上の点に鑑み、ループ形状および樹脂流れ性とスパン長との関係について調査し、特性発現のための元素添加効果について研究した結果、Ｃａの添加、ＹまたはＳｃの添加、Ｃｅ族希土類の添加、Ｉｎの添加による複合効果が有効であること、さらに後述するように接合性をより向上する元素添加の効果、およびループ高さに関する元素添加の効果を見出した。
【０００７】
すなわち、本発明の要旨とするところは下記のとおりである。
（１）Ｃａを１０〜６０重量ｐｐｍ、ＹまたはＳｃの１種または２種を総計で５〜７０重量ｐｐｍ、ＬａまたはＣｅの１種または２種を総計で６〜８０重量ｐｐｍ、Ｉｎを６〜１００重量ｐｐｍ含有し、残部は金とその不可避不純物からなることを特徴とする半導体素子用金合金細線。
【０００８】
（２）前項１記載の成分に加えて、Ａｌ、Ｃｕ、Ｐｔ、Ｐｄの１種または２種以上を総計で５〜１００重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。
（３）前項１記載の成分に加えて、Ｓｉ、Ｇｅの１種または２種を総計で５〜５０重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。
【０００９】
（４）前項２記載の成分に加えて、Ｓｉ、Ｇｅの１種または２種を総計で５〜５０重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。
【００１０】
【作用】
以下に、本発明の金合金細線の構成についてさらに説明する。
さまざまなスパン長を考慮して樹脂流れ性（封止後のワイヤ流れ）を低減するワイヤとしては、Ａｕ中にＣａを１０〜６０重量ｐｐｍ、ＹまたはＳｃの１種または２種を総計で５〜７０重量ｐｐｍ、ＬａまたはＣｅの１種または２種を総計で６〜８０重量ｐｐｍ、Ｉｎを６〜１００重量ｐｐｍの範囲で添加することが有効である。
【００１１】
高温特性の向上には希土類元素の添加が有効であることを見出し、その特性発現をさらに細かく分類した結果、ＹまたはＳｃは高温域での破断強度の上昇をもたらし、ＬａまたはＣｅの添加は金型の加熱温度付近の温度域における弾性率の向上が認められた。耐流れ性の点では、ＬａまたはＣｅの添加は母線部の弾性変形を抑制し、ＹまたはＳｃは主に降伏力が上昇して、弾性変形域を拡げて塑性域を抑制し、さらに塑性域での変形抵抗が増加することが判明した。ここで、ＹとＳｃの両者とも含有しないと、弾性域を超えて荷重が負荷されたワイヤでは変形抵抗が十分でないため、樹脂の注入方向とワイヤの位置関係によっては樹脂流れのばらつきが大きくなる。他方で、ＬａとＣｅのどちらも含有しない場合は、弾性域でのワイヤ流れが増大するため、スパン長が長くなるほど問題となる。すなわち、耐流れ性を向上させるには、ＬａまたはＣｅの添加と、ＹまたはＳｃの添加を併用することが必要である。
【００１２】
Ｌａ、Ｃｅの総含有量を上記範囲と設定したのは、６重量ｐｐｍ未満では上記効果が小さく、８０重量ｐｐｍ超では、ボールの真球性が低下するため、小ボールの形成などの不良が発生するためである。また、Ｙ、Ｓｃの総含有量を上記範囲と設定したのは、５重量ｐｐｍ未満では上記効果が小さく、７０重量ｐｐｍ超では、ボールの真球性の低下、さらに引け巣の発生が認められるためである。
【００１３】
Ｃｅ、Ｌａ、Ｃａを添加した金合金細線が、例えば特公平２−１２０２２号公報に開示されているが、ロングスパン用途においては、前述したように、Ｌａ、Ｃｅの添加に加えて、Ｙ、Ｓｃの添加を併用することにより耐流れ性の効果を高めるものであり、またＣａのみでなく、Ｙ、Ｓｃを添加することにより、後述するような複合効果が得られる。
【００１４】
Ｃａ添加は、主としてネック部の再結晶挙動を抑制することから、ループ高さの制御に有効であり、さらに強度の確保も期待される。短スパンでの樹脂流れでは、ネック部分の強度が高い方が樹脂流れも少なく、また、プル強度を上昇させるためには、スパン長に関係なく破断箇所であるネック部の強度増加が望まれ、これにはＣａ添加と、ＹまたはＳｃの添加の組み合わせが有効である。Ｃａは再結晶の粒成長を抑制することによる強度増加であり、加えてＹまたはＳｃの添加は、粒成長抑制は観察されないものの、Ｃａ単独添加よりも強度をさらに増加させる。これはＹまたはＳｃの添加が、Ｃａにより微細化された結晶粒内での強度増加の作用があるものと考えられる。一方、ＹまたはＳｃの添加だけでは、結晶粒が大きいことから、強度が弱い粒界近傍での変形が助長されてしまい、ネック部の強化効果は小さい。
【００１５】
ここで、Ｃａの添加量を上記範囲と定めたのは、１０重量ｐｐｍ未満では上記の再結晶抑制の効果が小さく、一方６０重量ｐｐｍ超では、ボール形成時の表面酸化に関連すると思われる、ボールの最頂部に引け巣が生成し、接合性の低下が懸念されるためである。
ロングスパンにおける樹脂流れを低減するためには、封止前のループ曲がりを抑え、直線性を高めることも重要である。Ｉｎの添加は、高温特性への寄与は小さいものの、常温程度での強度上昇には有効であり、特にＣａ、Ｌａ、Ｃｅとの共存により、常温での弾性率を増加させ、ループ曲がりのばらつきを低減する効果が高い。ＩｎはＡｕ中の最大固溶度が１０重量％程度あり、単独添加では効果が小さいが、Ｃａ、Ｌａ、Ｃｅをさらに含有せしめることにより、Ａｕ中に固溶しているＩｎと何らかの相互作用を及ぼし合うことにより、ループの直線性を高めているものと考えられる。Ｉｎの含有量が６重量ｐｐｍ未満では上記効果が小さく、１００重量ｐｐｍ超では、ボールの真球性の低下、さらに収縮孔の発生が認められるためである。
【００１６】
狭ピッチ化のためにはボール径も小さくする要求が高く、ボール部の接合性を確保することが課題であり、その方策として、Ａｌ、Ｃｕ、Ｐｔ、Ｐｄの１種または２種以上を総計で５〜１００重量ｐｐｍの範囲で含有すると、接合強度が上昇する。これは、接合時のＡｕボール部とＡｌ電極部との界面において金属間化合物の成長が助長されているためと推察される。添加量が５重量ｐｐｍ未満では効果は小さく、１００重量ｐｐｍ超ではボール表面に酸化膜が形成されて逆に接合性が低下するため、含有量は上記範囲と設定した。
【００１７】
最近、ＩＣパッケージの薄型化を実現するために、ワイヤの低ループ化が所望されており、上記の元素の中でも、Ｃａ、Ｌａ、Ｃｅ、Ｙ、Ｓｃはループ高さを低くする傾向にある。一方で、ボンディングの高速化や操作性の向上を目的として、ループ垂れを低減するために、ネック近傍の直立部を十分確保するという要求には対応できない。その場合でも、ＳｉまたはＧｅの１種以上を総計で５〜５０重量ｐｐｍの範囲で含有することにより、ネック部の再結晶制御により、ループ高さを高くすることが出来ることを見出した。ここで添加量を上記範囲と定めたのは、総含有量が５重量ｐｐｍ未満では上記効果が小さく、５０重量ｐｐｍ超では、ネック強度が弱くなるためである。
【００１８】
【実施例】
以下、実施例について説明する。
金純度が約９９．９９５重量％以上の電解金を用いて、表１〜３に示す化学成分の金合金を溶解炉で溶解鋳造し、その鋳塊を圧延および伸線により、最終線径が２７μｍの金合金細線とした後に、大気中で連続焼鈍して伸びを調整した。
【００１９】
ワイヤボンディングに使用される高速自動ボンダーを使用して、アーク放電によりワイヤ先端に作製した金合金ボールを走査型電子顕微鏡で観察し、ボール形状が異常なもの、ボール先端部において収縮孔の発生が認められるもの等半導体素子上の電極に良好な接合ができないものを△印、良好なものを○印にて表記した。
【００２０】
ネック部の強度は、ワイヤ両端の接合距離（スパン）が３ｍｍとなるようボンディングしたリードフレームと測定する半導体素子を冶具で固定した後に、ループの中央部を引張り、その細線破断時の引張強度を６０本測定したプル強度の平均値で評価した。また、ボール部の接合強度については、アルミ電極の２μｍ上方で冶具を平行移動させて剪断破断を読みとるシェアテスト法で測定し、５０本の破断荷重の平均値を測定した。
【００２１】
ループ高さは、半導体素子上の電極と外部リードとの間を接合した後に、形成される各ループの頂高と当該半導体素子の電極面とを光学顕微鏡で１００本測定し、その両者の高さの差であるループ高さとそのばらつきで評価した。
ワイヤ曲がりは、スパンが５ｍｍとなるようボンディングしたものを準備し、半導体素子とほぼ垂直上方向から観察し、ワイヤ中心部からワイヤの両端接合部を結ぶ直線と、ワイヤの曲がりが最大の部分との垂線の距離を、投影機を用いて４０本測定した平均値で示した。
【００２２】
樹脂封止後のワイヤ流れの測定に関しては、ワイヤのスパンとして４．５ｍｍが得られるようボンディングした半導体素子をそれぞれ準備し、モールディング装置を用いてエポキシ樹脂で封止した後に、軟Ｘ線検査装置を用いて樹脂封止された素子内部をＸ線投影し、前述したワイヤ曲がりと同等の手順によりワイヤ流れが最大の部分の流れ量を３０本測定し、その平均値をワイヤのスパン長さで除算した値（百分率）を封止後のワイヤ流れと定義した。
【００２３】
表１において、実施例１〜１２は本発明の請求項１記載の発明に係わるものであり、表２において実施例１３〜１６は請求項２記載の発明、実施例１７〜２０は請求項３記載の発明、実施例２１、２２は請求項４記載の発明に係わるものである。
樹脂封止後のワイヤ流れについては、本発明金合金線に関しては、いづれも４％以下に抑えられているが、特に、ＣｅとＬａの１種以上、且つＹまたはＳｃの１種以上の組み合わせにより、３％以下まで低減しているものが確認された。また、Ｉｎの添加量が多い実施例１２などで、ワイヤ曲がりの低減が顕著である。
【００２４】
表３に比較例を示す。プル強度が低くなるときは、比較例１、２におけるＣａの添加量が本発明の範囲より少ないとき、あるいは比較例７においてＹまたはＳｃが少ないときにに限られている。
Ａｌ、Ｃｕ、Ｐｔ、Ｐｄの１種以上の添加量が請求項２の範囲であれば、シェア強度も６０ｇｆ以上の高い値が得られ、また、ＳｉまたはＧｅの添加量が請求項３の範囲であれば、ループ高さも２００μｍ以上まで高くすることが可能であることが確認された。
【００２５】
【表１】

Figure 0003579493
【００２６】
【表２】
Figure 0003579493
【００２７】
【表３】
Figure 0003579493
【００２８】
【発明の効果】
以上述べたように、本発明に係わる金合金細線は、樹脂封止時のワイヤ流れが低減され、しかもループの直線性が向上し、また接合性も向上しているので、半導体の高密度実装に対応できるものであるから、本発明の産業上の有用性はきわめて大きい。[0001]
[Industrial applications]
The present invention relates to a gold alloy thin wire for a semiconductor element used for bonding for electrically connecting an electrode on a semiconductor element to an external lead.
[0002]
[Prior art]
At present, as an electrical connection between a circuit wiring electrode on a semiconductor element and an external lead, a wire bonding method is mainly used. In recent years, as semiconductors have become more highly integrated and multifunctional, and the demand for smaller and thinner IC chips has been increasing, the need for higher density of semiconductor mounting has increased. In order to increase the number of terminals and increase the number of pins, the inner lead portion is retracted with respect to the silicon chip, so that the wire bonding interval (span) tends to be longer. Conventionally, the main span is 4 mm or less, but in recent years, a long span of 5 mm or more is desired, and it is difficult to strictly control the loop shape such as securing linearity and reducing variation.
[0003]
In addition, with the increase in the number of pins, a narrow pitch in which the electrode interval is reduced is required, and a minimum pitch between wires of 100 μm or less is desired, and a thin wire is also desired. In order to achieve the increase in the number of pins and the reduction in the pitch, improvement of a bonding apparatus, development of a wire having excellent looping properties, and the like have been advanced.
In order to cope with the increase in the number of pins and the narrowing of the wires in the high-density semiconductor mounting, it is necessary to suppress the flow of wires during resin sealing. When the wire is deformed and flows at the time of sealing with a highly viscous epoxy resin, defects due to contact between adjacent wires or contact between the wire and the chip or the inner lead portion occur. If the wire is made thinner to achieve a narrower pitch, the strength is reduced, and the problem of wire flow after sealing becomes even more serious.
[0004]
[Problems to be solved by the invention]
If the span length is largely different, the loop shape is changed, but the influence on the deformation behavior of the wire during resin sealing is also great. For example, even if the entire loop is deformed almost evenly, the absolute value of the wire flow value tends to increase with the span, and when the span becomes a long span of 5 mm or more, suppression of the resin flow of the wire becomes the biggest problem. . On the other hand, in a normal short span having a span of about 3 mm, since the slack of the loop is small, the load on the neck portion immediately above the ball is large, and the deformation of the neck portion has a large effect on the resin flow. Further, as a tendency when a short span is connected using a conventional long span wire, a decrease in pull strength due to a decrease in loop height cannot be ignored.
[0005]
Regarding these trends, equipment conditions such as looping conditions and resin encapsulation conditions are involved in a complicated manner, so it is difficult to organize them quantitatively.However, it is required to use gold alloy fine wires properly according to the span length, and sufficient characteristics are required. It is difficult to use properly after grasping.
An object of the present invention is to provide a gold alloy thin wire suitable for high-density mounting by reducing the influence of span length, reducing loop bending during bonding and wire deformation during resin sealing.
[0006]
[Means for Solving the Problems]
In view of the above points, the present inventors have investigated the relationship between the loop shape and the resin flowability and the span length, and studied the effect of adding elements for developing characteristics. As a result, the addition of Ca, the addition of Y or Sc It has been found that the addition of the rare earth elements of Ce and the combination of In and the addition of In are effective, and that the effect of the addition of an element for further improving the bonding property and the effect of the addition of the element relating to the loop height, as described later.
[0007]
That is, the gist of the present invention is as follows.
(1) 10 to 60 ppm by weight of Ca, 5 to 70 ppm by weight of one or two of Y or Sc, 6 to 80 ppm by weight of one or two of La or Ce, and 6 to 80 ppm by weight of In. 1 to 100 ppm by weight, with the balance being gold and its unavoidable impurities.
[0008]
(2) A gold alloy thin wire for a semiconductor element, comprising a total of 5 to 100 ppm by weight of one or more of Al, Cu, Pt, and Pd in addition to the components described in 1 above.
(3) A gold alloy thin wire for a semiconductor element, characterized by containing one or two of Si and Ge in total of 5 to 50 ppm by weight in addition to the components described in the above (1).
[0009]
(4) A gold alloy thin wire for a semiconductor element, characterized by containing one or two of Si and Ge in total of 5 to 50 ppm by weight in addition to the components described in (2) above.
[0010]
[Action]
Hereinafter, the configuration of the gold alloy thin wire of the present invention will be further described.
As a wire for reducing the resin flowability (wire flow after encapsulation) in consideration of various span lengths, 10 to 60 ppm by weight of Ca in Au and one or two types of Y or Sc in a total of 5 are used. It is effective to add up to 70 wt ppm, one or two kinds of La or Ce in a total range of 6 to 80 wt ppm, and In of 6 to 100 wt ppm.
[0011]
It has been found that the addition of rare earth elements is effective in improving the high-temperature properties, and as a result of further categorizing the development of the properties, Y or Sc results in an increase in the breaking strength in a high-temperature range, and the addition of La or Ce does not An improvement in the elastic modulus in the temperature range near the heating temperature of the mold was observed. In terms of flow resistance, the addition of La or Ce suppresses elastic deformation of the bus bar, and Y or Sc mainly increases the yield force, expands the elastic deformation region, suppresses the plastic region, and further suppresses the plastic region. It was found that the deformation resistance in the steel increased. Here, if neither Y nor Sc is contained, the deformation resistance of the wire subjected to a load exceeding the elastic range is not sufficient, so that the resin flow varies greatly depending on the resin injection direction and the positional relationship of the wire. . On the other hand, when neither La nor Ce is contained, the wire flow in the elastic region increases, so that the longer the span length, the more the problem becomes. That is, in order to improve the flow resistance, it is necessary to use the addition of La or Ce together with the addition of Y or Sc.
[0012]
When the total content of La and Ce is set in the above range, the effect is small when the content is less than 6 ppm by weight, and when the content is more than 80 ppm by weight, the sphericity of the ball is reduced. Because it happens. When the total content of Y and Sc is set to the above range, the above effect is small when the content is less than 5 ppm by weight, and when the content is more than 70 ppm by weight, a decrease in the sphericity of the ball and generation of a shrinkage cavity are observed. That's why.
[0013]
A gold alloy fine wire to which Ce, La, and Ca are added is disclosed in, for example, Japanese Patent Publication No. 2-1022, but in long-span applications, as described above, in addition to the addition of La and Ce, Y, The combined use of Sc enhances the flow resistance, and the addition of not only Ca but also Y and Sc provides a composite effect as described below.
[0014]
Since Ca addition mainly suppresses the recrystallization behavior of the neck portion, it is effective for controlling the loop height, and is also expected to ensure strength. In the resin flow in a short span, the higher the strength of the neck portion is less resin flow, and in order to increase the pull strength, it is desired to increase the strength of the neck portion which is a break point regardless of the span length, For this purpose, a combination of addition of Ca and addition of Y or Sc is effective. Ca is an increase in strength by suppressing the grain growth of recrystallization. In addition, the addition of Y or Sc further increases the strength as compared with the addition of Ca alone, although no grain growth suppression is observed. This is presumably because the addition of Y or Sc has the effect of increasing the strength within the crystal grains refined by Ca. On the other hand, if only Y or Sc is added, since the crystal grains are large, the deformation near the grain boundaries having low strength is promoted, and the effect of strengthening the neck portion is small.
[0015]
Here, the addition amount of Ca is defined as the above range, the effect of suppressing the recrystallization is less than 10 ppm by weight, while if more than 60 ppm by weight, it is considered to be related to surface oxidation during ball formation. This is because shrinkage cavities are formed at the top of the ball, and there is a concern that the bonding property may decrease.
In order to reduce the resin flow in a long span, it is also important to suppress loop bending before sealing and to improve linearity. Although the addition of In has a small contribution to the high-temperature characteristics, it is effective for increasing the strength at about room temperature. In particular, the coexistence of Ca, La, and Ce increases the elastic modulus at room temperature, and the variation of the loop bend. The effect of reducing is high. In has a maximum solid solubility of about 10% by weight in Au, and has little effect when added alone. However, by further adding Ca, La, and Ce, some interaction with In that is dissolved in Au is made. It is considered that the linearity of the loop is improved by exerting the influence. If the In content is less than 6 ppm by weight, the above effect is small. If the In content is more than 100 ppm by weight, a decrease in the sphericity of the ball and generation of shrinkage holes are observed.
[0016]
To narrow the pitch, there is a high demand to reduce the ball diameter, and it is an issue to secure the bonding property of the ball portion. As a measure, one or more of Al, Cu, Pt, and Pd are used in total. If the content is in the range of 5 to 100 ppm by weight, the joining strength increases. This is presumably because the growth of the intermetallic compound was promoted at the interface between the Au ball portion and the Al electrode portion during bonding. If the addition amount is less than 5 ppm by weight, the effect is small, and if it exceeds 100 ppm by weight, an oxide film is formed on the ball surface, and conversely, the bonding property is lowered. Therefore, the content is set in the above range.
[0017]
Recently, it has been desired to reduce the loop of the wire in order to realize a thin IC package. Among these elements, Ca, La, Ce, Y, and Sc tend to reduce the loop height. On the other hand, in order to reduce the loop droop for the purpose of speeding up the bonding and improving the operability, it is not possible to cope with a demand to secure a sufficient upright portion near the neck. Even in such a case, it has been found that the loop height can be increased by controlling the recrystallization of the neck by containing at least one of Si and Ge in a total range of 5 to 50 ppm by weight. Here, the addition amount is defined as the above range because the effect is small when the total content is less than 5 ppm by weight, and when the total content exceeds 50 ppm by weight, the neck strength is weakened.
[0018]
【Example】
Hereinafter, examples will be described.
Using electrolytic gold having a gold purity of about 99.995% by weight or more, a gold alloy having a chemical composition shown in Tables 1 to 3 is melt-cast in a melting furnace, and the ingot is rolled and drawn to have a final wire diameter. After forming a 27 μm thin gold alloy wire, continuous elongation was performed in the air to adjust elongation.
[0019]
Using a high-speed automatic bonder used for wire bonding, observe the gold alloy ball produced at the wire tip by arc discharge with a scanning electron microscope, and if the ball shape is abnormal, shrinkage holes are generated at the ball tip. Those that could not be bonded to the electrodes on the semiconductor element, such as those that were recognized, were marked with △, and those that were good were marked with ○.
[0020]
The strength of the neck is determined by fixing the semiconductor device to be measured with the lead frame bonded to the wire end so that the bonding distance (span) at both ends of the wire is 3 mm, and then pulling the center of the loop to determine the tensile strength when the thin wire breaks. Evaluation was made based on the average value of the pull strengths measured for 60 pieces. The joint strength of the ball portion was measured by a shear test method in which a jig was moved in parallel 2 μm above the aluminum electrode and a shear fracture was read, and an average value of 50 fracture loads was measured.
[0021]
After joining the electrode on the semiconductor element and the external lead, the loop height is measured by measuring the height of each loop formed and the electrode surface of the semiconductor element by 100 using an optical microscope. The evaluation was made based on the difference in loop height and its variation.
The wire bend was prepared by bonding so that the span was 5 mm. Observation was performed almost vertically above the semiconductor element, and a straight line connecting the center of the wire to the joint at both ends of the wire, and a portion where the wire bend was the largest. Are shown as an average value of 40 lines measured using a projector.
[0022]
Regarding the measurement of the wire flow after resin sealing, semiconductor devices bonded to each other so as to obtain a wire span of 4.5 mm are prepared, and sealed with an epoxy resin using a molding device. The inside of the element sealed with resin is projected by X-ray, and the flow amount of the portion where the wire flow is maximum is measured by the same procedure as the wire bending described above, and the average value is measured by the span length of the wire. The divided value (percentage) was defined as the wire flow after sealing.
[0023]
In Table 1, Examples 1 to 12 relate to the invention described in claim 1 of the present invention. In Table 2, Examples 13 to 16 correspond to the invention described in claim 2, and Examples 17 to 20 correspond to claim 3 in the present invention. The described inventions and Embodiments 21 and 22 relate to the invention described in claim 4.
Regarding the wire flow after resin encapsulation, any of the gold alloy wires of the present invention is suppressed to 4% or less. As a result, it was confirmed that the content was reduced to 3% or less. In Example 12 in which the amount of In added is large, the reduction of wire bending is remarkable.
[0024]
Table 3 shows a comparative example. When the pull strength is low, the amount of Ca in Comparative Examples 1 and 2 is limited to when the time less than the range of the present invention, or Comparative Example 7 in Oite Y or Sc is small.
If the amount of addition of at least one of Al, Cu, Pt, and Pd is in the range of claim 2, a high shear strength of 60 gf or more can be obtained, and the amount of addition of Si or Ge is in the range of claim 3. Then, it was confirmed that the loop height can be increased to 200 μm or more.
[0025]
[Table 1]
Figure 0003579493
[0026]
[Table 2]
Figure 0003579493
[0027]
[Table 3]
Figure 0003579493
[0028]
【The invention's effect】
As described above, the gold alloy thin wire according to the present invention reduces the wire flow during resin encapsulation, improves the linearity of the loop, and improves the bonding property. Therefore, the industrial utility of the present invention is extremely large.

Claims (4)

Ｃａを１０〜６０重量ｐｐｍ、ＹまたはＳｃの１種または２種を総計で５〜７０重量ｐｐｍ、ＬａまたはＣｅの１種または２種を総計で６〜８０重量ｐｐｍ、Ｉｎを６〜１００重量ｐｐｍ含有し、残部は金とその不可避不純物からなることを特徴とする半導体素子用金合金細線。10 to 60 ppm by weight of Ca, 5 to 70 ppm by weight of one or two of Y or Sc, 6 to 80 ppm by weight of one or two of La or Ce, 6 to 100% by weight of In 1. A fine gold alloy wire for a semiconductor element, which contains ppm and the balance consists of gold and its unavoidable impurities. 請求項１記載の成分に加えて、Ａｌ、Ｃｕ、Ｐｔ、Ｐｄの１種または２種以上を総計で５〜１００重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。2. A gold alloy thin wire for a semiconductor element, comprising a total of 5 to 100 ppm by weight of one or more of Al, Cu, Pt, and Pd in addition to the components described in claim 1. 請求項１記載の成分に加えて、Ｓｉ、Ｇｅの１種または２種を総計で５〜５０重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。2. A gold alloy thin wire for a semiconductor device, comprising a total of 5 to 50 ppm by weight of one or two of Si and Ge in addition to the components described in claim 1. 請求項２記載の成分に加えて、Ｓｉ、Ｇｅの１種または２種を総計で５〜５０重量ｐｐｍ含有することを特徴とする半導体素子用金合金細線。3. A gold alloy thin wire for a semiconductor element, comprising a total of 5 to 50 ppm by weight of one or two of Si and Ge in addition to the components described in claim 2.
JP09570295A 1995-04-20 1995-04-20 Gold alloy wires for semiconductor devices Expired - Lifetime JP3579493B2 (en)

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JP09570295A JP3579493B2 (en) 1995-04-20 1995-04-20 Gold alloy wires for semiconductor devices

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JP3579493B2 true JP3579493B2 (en) 2004-10-20

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JP3426473B2 (en) * 1997-07-01 2003-07-14 新日本製鐵株式会社 Gold alloy wires for semiconductor devices
EP0890987B1 (en) * 1997-07-07 2003-03-05 W.C. Heraeus GmbH & Co. KG Fine wire of a gold alloy, method of making the same and its use
JP4513440B2 (en) * 2004-07-15 2010-07-28 住友ベークライト株式会社 Semiconductor device
JP4130843B1 (en) * 2007-04-17 2008-08-06 田中電子工業株式会社 High reliability gold alloy bonding wire and semiconductor device
JP4150752B1 (en) * 2007-11-06 2008-09-17 田中電子工業株式会社 Bonding wire
KR20220153015A (en) * 2020-03-13 2022-11-17 닛데쓰마이크로메탈가부시키가이샤 Al bonding wire
CN111485131B (en) * 2020-04-17 2021-12-24 烟台招金励福贵金属股份有限公司 Gold bonding wire and preparation method thereof

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