JP3786324B2 - Bonding wire - Google Patents

Bonding wire Download PDF

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Publication number
JP3786324B2
JP3786324B2 JP33745597A JP33745597A JP3786324B2 JP 3786324 B2 JP3786324 B2 JP 3786324B2 JP 33745597 A JP33745597 A JP 33745597A JP 33745597 A JP33745597 A JP 33745597A JP 3786324 B2 JP3786324 B2 JP 3786324B2
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Japan
Prior art keywords
weight
wire
bonding
amount
bonding wire
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Expired - Fee Related
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JP33745597A
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JPH11176867A (en
Inventor
秀人 吉田
寿一 清水
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Sumitomo Metal Mining Co Ltd
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Sumitomo Metal Mining Co Ltd
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Priority to JP33745597A priority Critical patent/JP3786324B2/en
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    • 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
    • H01L2224/44—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
    • H—ELECTRICITY
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    • 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
    • H01L2224/44—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
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    • 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
    • H01L2224/45117—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 400°C and less than 950°C
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
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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
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    • 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
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Description

【０００１】
【発明の属する技術分野】
本発明は、半導体素子上の電極と外部リードとを接続するために用いるボンディングワイヤに関する。
【０００２】
【従来の技術】
ＩＣ，ＬＳＩなどの半導体素子（チップ）の電極と外部リードとを接続するため、０．０２〜０．１ｍｍの範囲の直径を有するボンディングワイヤが用いられている。ボンディングワイヤには良好な導電性、チップや外部リードとの接合性、使用雰囲気中での耐環境性が要求され、そのためボンディングワイヤとしては、Ａｌ、Ａｕ、Ｃｕ等の純金属もしくはその合金が用いられてきた。近年では低コスト化という観点から樹脂を用いた半導体パッケージが多用されてきており、そのため耐環境性に優れるＡｕ系ワイヤが最も多く用いられている。
【０００３】
最近の半導体デバイスの発展はパッケージの多ピン化をもたらし、その結果として、より細いワイヤを狭いピッチや長い距離でワイヤボンディングを行う必要性が増してきた。しかしながら、従来のＡｕ系ボンディングワイヤはワイヤ強度が弱いために、より細いワイヤを狭いピッチや長い距離でワイヤボンディングを行った場合には、樹脂封入を始めとする半導体デバイス組み立て工程中においてワイヤの変形不良が頻発化し、半導体デバイスの組み立て収率が大幅に低下するという問題があった。
【０００４】
こうした問題を解決する手段として、例えば特公昭６２―２２４５０号公報、特公昭６２―２２４５１号公報等で示されているように、多量のＡｇを添加してワイヤ強度を高めるという方法があった。
【０００５】
しかし、Ａｇを多量に添加したワイヤはボールボンディング時に形成されるボールの硬度が高いために、ボールボンディング時にチップの電極部を損傷する確率が高いという問題があった。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、かかる点に鑑み、Ａｇを多量に含むＡｕ系ワイヤのボール硬度を低下させ、多ピン半導体デバイス用として好適な高強度ボンディングワイヤを提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、本発明のボンディングワイヤは、
（１）Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、さらにＳｎを０．０００１〜０．０１重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とする。
【０００８】
（２）Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、さらにＣｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒの内の１種以上を合計で０．１〜５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とする。
【０００９】
（３）Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、さらにＢｅ、Ｇｅ、Ｉｎの内の１種以上を０．０００１〜０．００５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とする。
【００１０】
（４）Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒの内の１種以上を合計で０．１〜５重量％含み、さらにＢｅ、Ｇｅ、Ｉｎの内の１種以上を０．０００１〜０．００５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とする。
【００１１】
【発明の実施の形態】
Ａｇは金に固溶することによりワイヤ強度を向上させる元素である。本発明において、Ａｇの濃度を１〜４０重量％としたのは、１重量％未満では強度向上の効果が不十分であり、逆に４０重量％を超すと強度向上の効果が飽和するだけでなく、耐食性が低下してプラスチックパッケージ中で使用するのが難しくなるからである。
【００１２】
Ｃａは、Ａｇとともにワイヤ強度を向上させるとともにボンディングワイヤに必要な耐熱性を付加する元素である。Ｃａの濃度を０．０００１〜０．０１重量％としたのは、０．０００１重量％未満では添加効果が不十分であり、逆に０．０１重量％を超すと添加効果が飽和するからである。
【００１３】
Ｓｎは、その機構は不明であるが、ＡｇとＣａを含むＡｕ系ワイヤのボール硬度を低下させる効果を有する元素である。Ｓｎの濃度を０．０００１〜０．０１重量％としたのは、０．０００１重量％未満では添加効果が不充分だからであり、逆に０．０１重量％を超えると添加効果が飽和するからである。
【００１４】
第２、４の発明におけるＣｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒは、ワイヤ強度をさらに向上させる元素である。Ｃｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒの内の１種以上を０．１〜５重量％としたのは、０．１重量％未満では添加効果が不十分であり、逆に５重量％を超えるとボール硬度が向上してチップ電極部を損傷する確率が高くなるからである。
【００１５】
また、第３、４の発明におけるＢｅ、Ｇｅ、Ｉｎは、ワイヤのルーピング性を向上するための元素である。Ｂｅ、Ｇｅ、Ｉｎの１種以上を１種以上を０．０００１〜０．００５重量％としたのは、０．０００１重量％未満では添加効果が不十分であり、逆に０．００５重量％を超えると添加効果が講和するからである。
【００１６】
【実施例】
純度９９．９９９重量％の金、９９．９９重量％のＡｇ、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒ、及び所定の添加元素を１重量％含む金母合金を用いて、表１に示す組成の金合金を溶解鋳造した。得られた鋳塊は溝ロール加工を施した後に、ダイヤモンドダイスを用いた伸線加工を行って直径０．０２５ｍｍの合金線を得た。得られた合金線は熱処理を施すことによって特性を調整して試料とした。
【００１７】
【表１】

Figure 0003786324
【００１８】
このように作製された試料の評価として、ワイヤ強度は引張り試験により求めた。ボール硬度については、市販のワイヤボンダーによって約６０μｍφのボールを形成し、そのボールを荷重５０ｇで潰した状態において、超微小ヴィッカース硬度計（荷重１ｇ）を用いて測定した。
【００１９】
ボンディング接合性すなわちボンディングワイヤとチップ電極及び外部リードとの接合性は、ステージ温度２５０℃で市販のワイヤボンダーを用い超音波熱圧着方式によりボンディングしたワイヤについて、フックを引っかけて引張り試験を実施した場合に、破断がワイヤの部分で起こった場合を良、接合部で破断した場合を不良と評価した。
【００２０】
ワイヤボンディング時のチップ電極の損傷については、ボンディング接合性の評価に用いたのと同一料について、電極部を水酸化ナトリウム水溶液によって除去した後に、電極部下のクラック発生の有無を光学顕微鏡を用いて観察することによって行った。
【００２１】
接合部の耐環境性については、上記と同様な方法でワイヤボンディングした試料について、２００℃で１００時間保持した後のボンディング接合性を評価することにより行った。
【００２２】
封入抵抗によるワイヤ変形については、上記と同様な方法で５ｍｍの間隔にワイヤボンディングした試料について、モールド機（トランスファーモールド型）によりエポキシ樹脂（住友ベークライト製、ＥＭＥ−６３００）を金型温度１８０℃、射出圧１００ｋｇ／ｃｍ2の条件でモールドした時のワイヤの流れ量をＸ線透過装置により撮影したＸ線写真から求め、その値で評価した。
【００２３】
なお、ワイヤ流れ量は、エポキシ樹脂を封入した時のワイヤの変形量で示した。
【００２４】
表１に、上記評価の結果を市販材及び比較材の評価結果とともに示した。
【００２５】
表１において明らかなように、Ｓｎを添加した本発明のボンディングワイヤは比較材と比べてボール硬度が低くチップ電極部の損傷が起こりにくいことがわかる。また、市販品に比較して強度が高くてワイヤ流れ量が小さく、ボンディング接合性にも問題のないことがわかる。
【００２６】
【発明の効果】
以上から明らかなように、本発明により、半導体デバイス組み立て時におけるワイヤの変形不良が起こりにくく、かつワイヤボンディング時のチップ電極の損傷が小さい多ピン半導体デバイス用として好適なボンディングワイヤを提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bonding wire used for connecting an electrode on a semiconductor element and an external lead.
[0002]
[Prior art]
Bonding wires having a diameter in the range of 0.02 to 0.1 mm are used to connect electrodes of semiconductor elements (chips) such as ICs and LSIs and external leads. Bonding wires are required to have good conductivity, bondability with chips and external leads, and environmental resistance in the operating atmosphere. Therefore, pure metals such as Al, Au, Cu, or alloys thereof are used as bonding wires. Has been. In recent years, semiconductor packages using a resin have been frequently used from the viewpoint of cost reduction, and therefore Au-based wires having excellent environmental resistance are most often used.
[0003]
Recent development of semiconductor devices has led to an increase in the number of pins in the package, and as a result, the need for wire bonding of thinner wires at narrow pitches and long distances has increased. However, since conventional Au-based bonding wires have weak wire strength, when wire bonding is performed on narrower wires at a narrow pitch or a long distance, deformation of the wire during the semiconductor device assembly process including resin encapsulation There has been a problem that defects frequently occur and the assembly yield of the semiconductor device is greatly reduced.
[0004]
As a means for solving such a problem, there has been a method of increasing the wire strength by adding a large amount of Ag as disclosed in, for example, Japanese Patent Publication No. 62-22450 and Japanese Patent Publication No. 62-22451.
[0005]
However, since a wire added with a large amount of Ag has a high hardness of a ball formed at the time of ball bonding, there is a problem that the probability of damaging the electrode portion of the chip at the time of ball bonding is high.
[0006]
[Problems to be solved by the invention]
In view of this point, an object of the present invention is to provide a high-strength bonding wire suitable for a multi-pin semiconductor device by reducing the ball hardness of an Au-based wire containing a large amount of Ag.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the bonding wire of the present invention comprises:
(1) 1 to 40% by weight of Ag, 0.0001 to 0.01% by weight of Ca, 0.0001 to 0.01% by weight of Sn, and the balance consisting of Au and inevitable impurities And
[0008]
(2) 1-40 wt% Ag, 0.0001-0.01 wt% Ca, 0.0001-0.01 wt% Sn, and Cu, Pt, Pd, Ru, Os, Rh In addition, it is characterized in that one or more of Ir are contained in a total amount of 0.1 to 5% by weight, with the balance being Au and inevitable impurities.
[0009]
(3) 1 to 40% by weight of Ag, 0.0001 to 0.01% by weight of Ca, 0.0001 to 0.01% by weight of Sn, and one or more of Be, Ge, and In Is 0.0001 to 0.005% by weight, and the balance is made of Au and inevitable impurities.
[0010]
(4) 1-40 wt% Ag, 0.0001-0.01 wt% Ca, 0.0001-0.01 wt% Sn, Cu, Pt, Pd, Ru, Os, Rh, Including one or more of Ir in a total amount of 0.1 to 5% by weight, further including one or more of Be, Ge, and In in an amount of 0.0001 to 0.005% by weight, with the balance being Au and inevitable impurities It is characterized by becoming.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Ag is an element that improves the wire strength by dissolving in gold. In the present invention, the concentration of Ag is set to 1 to 40% by weight. If it is less than 1% by weight, the effect of improving the strength is insufficient. Conversely, if the concentration exceeds 40% by weight, the effect of improving the strength is only saturated. This is because the corrosion resistance is lowered and it is difficult to use in a plastic package.
[0012]
Ca is an element that improves the wire strength together with Ag and adds heat resistance necessary for the bonding wire. The reason why the Ca concentration is 0.0001 to 0.01% by weight is that the addition effect is insufficient if it is less than 0.0001% by weight, and conversely, if the content exceeds 0.01% by weight, the addition effect is saturated. is there.
[0013]
Sn is an element having an effect of reducing the ball hardness of an Au-based wire containing Ag and Ca, although the mechanism is unknown. The reason why the Sn concentration is 0.0001 to 0.01% by weight is that if less than 0.0001% by weight, the effect of addition is insufficient, and conversely if it exceeds 0.01% by weight, the effect of addition is saturated. It is.
[0014]
Cu, Pt, Pd, Ru, Os, Rh, and Ir in the second and fourth inventions are elements that further improve the wire strength. The reason why one or more of Cu, Pt, Pd, Ru, Os, Rh, and Ir is 0.1 to 5% by weight is that the effect of addition is insufficient when the content is less than 0.1% by weight. This is because if it exceeds wt%, the ball hardness is improved and the probability of damaging the chip electrode portion is increased.
[0015]
In the third and fourth inventions, Be, Ge, and In are elements for improving the looping property of the wire. The reason why one or more of Be, Ge and In is 0.0001 to 0.005% by weight is that the addition effect is insufficient if it is less than 0.0001% by weight, and conversely 0.005% by weight. This is because the additive effect is moderated if the amount exceeds.
[0016]
【Example】
Using a gold mother alloy containing 99% by weight of gold, 99.99% by weight of Ag, Cu, Pt, Pd, Ru, Os, Rh, Ir, and 1% by weight of a predetermined additive element, Table 1 A gold alloy having the composition shown below was melt cast. The obtained ingot was subjected to groove roll processing, followed by wire drawing using a diamond die to obtain an alloy wire having a diameter of 0.025 mm. The obtained alloy wire was subjected to heat treatment to adjust the characteristics to obtain a sample.
[0017]
[Table 1]
Figure 0003786324
[0018]
As an evaluation of the sample thus prepared, the wire strength was obtained by a tensile test. The ball hardness was measured using an ultrafine Vickers hardness meter (load 1 g) in a state where a ball of about 60 μmφ was formed by a commercially available wire bonder and the ball was crushed with a load of 50 g.
[0019]
Bonding bondability, that is, bondability between bonding wire and chip electrode and external lead is based on the case where a tensile test is performed by hooking a hook on a wire bonded by an ultrasonic thermocompression bonding method using a commercially available wire bonder at a stage temperature of 250 ° C. In addition, the case where the break occurred at the wire portion was evaluated as good, and the case where the break occurred at the joint portion was evaluated as defective.
[0020]
Regarding the damage of the chip electrode during wire bonding, the same material used for the evaluation of the bondability was removed by using an optical microscope to check for cracks under the electrode after removing the electrode with a sodium hydroxide aqueous solution. This was done by observing.
[0021]
About the environmental resistance of a junction part, about the sample wire-bonded by the method similar to the above, it performed by evaluating the bonding bondability after hold | maintaining at 200 degreeC for 100 hours.
[0022]
For wire deformation due to encapsulated resistance, an epoxy resin (EME-6300, manufactured by Sumitomo Bakelite Co., Ltd.) was used at a mold temperature of 180 ° C. by a molding machine (transfer mold type) for a sample wire-bonded at an interval of 5 mm by the same method as above. The flow rate of the wire when molded under the condition of an injection pressure of 100 kg / cm 2 was obtained from an X-ray photograph taken with an X-ray transmission device, and evaluated by that value.
[0023]
In addition, the wire flow amount was shown by the deformation amount of the wire when the epoxy resin was sealed.
[0024]
In Table 1, the result of the said evaluation was shown with the evaluation result of a commercial material and a comparative material.
[0025]
As is apparent from Table 1, it can be seen that the bonding wire of the present invention to which Sn is added has a lower ball hardness than the comparative material, and the chip electrode portion is hardly damaged. Moreover, it turns out that strength is high compared with a commercial item, the amount of wire flows is small, and there is no problem also in bonding bondability.
[0026]
【The invention's effect】
As is apparent from the above, according to the present invention, it is possible to provide a bonding wire that is suitable for a multi-pin semiconductor device that is less likely to cause deformation of the wire during assembly of the semiconductor device and that causes little damage to the chip electrode during wire bonding. it can.

Claims (4)

Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、さらにＳｎを０．０００１〜０．０１重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とするボンディングワイヤ。Bonding characterized in that it contains 1 to 40% by weight of Ag, 0.0001 to 0.01% by weight of Ca, 0.0001 to 0.01% by weight of Sn, and the balance is made of Au and inevitable impurities. Wire. Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、さらにＣｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒの内の１種以上を合計で０．１〜５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とするボンディングワイヤ。1 to 40% by weight of Ag, 0.0001 to 0.01% by weight of Ca, 0.0001 to 0.01% by weight of Sn, and Cu, Pt, Pd, Ru, Os, Rh, Ir 1 to 5% by weight in total, and the balance consists of Au and inevitable impurities. Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、さらにＢｅ、Ｇｅ、Ｉｎの内の１種以上を０．０００１〜０．００５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とするボンディングワイヤ。Ag is contained in an amount of 1 to 40% by weight, Ca is contained in an amount of 0.0001 to 0.01% by weight, Sn is contained in an amount of 0.0001 to 0.01% by weight, and at least one of Be, Ge, and In is added in an amount of 0. A bonding wire comprising 0001 to 0.005% by weight, the balance being made of Au and inevitable impurities. Ａｇを１〜４０重量％含み、Ｃａを０．０００１〜０．０１重量％含み、Ｓｎを０．０００１〜０．０１重量％含み、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｕ、Ｏｓ、Ｒｈ、Ｉｒの内の１種以上を合計で０．１〜５重量％含み、さらにＢｅ、Ｇｅ、Ｉｎの内の１種以上を０．０００１〜０．００５重量％含み、残部がＡｕ及び不可避不純物からなることを特徴とするボンディングワイヤ。1 to 40% by weight of Ag, 0.0001 to 0.01% by weight of Ca, 0.0001 to 0.01% by weight of Sn, Cu, Pt, Pd, Ru, Os, Rh, Ir 1 to 5% in total, further including 0.0001 to 0.005% by weight of one or more of Be, Ge, and In, with the balance being Au and inevitable impurities A characteristic bonding wire.
JP33745597A 1997-12-08 1997-12-08 Bonding wire Expired - Fee Related JP3786324B2 (en)

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