JP5765323B2 - Copper bonding wire and manufacturing method thereof - Google Patents

Copper bonding wire and manufacturing method thereof Download PDF

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JP5765323B2
JP5765323B2 JP2012268363A JP2012268363A JP5765323B2 JP 5765323 B2 JP5765323 B2 JP 5765323B2 JP 2012268363 A JP2012268363 A JP 2012268363A JP 2012268363 A JP2012268363 A JP 2012268363A JP 5765323 B2 JP5765323 B2 JP 5765323B2
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copper
bonding wire
layer
oxygen
core material
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JP2014116405A (en
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英之 佐川
英之 佐川
青山　正義
正義 青山
亨 鷲見
亨 鷲見
啓輔 藤戸
啓輔 藤戸
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Hitachi Metals Ltd
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Hitachi Metals Ltd
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    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • H01B1/026—Alloys based on copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
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Description

本発明は、銅ボンディングワイヤ及びその製造方法に関する。   The present invention relates to a copper bonding wire and a manufacturing method thereof.

従来、半導体素子の電極パッドと回路基板の配線パッドとを接続するボンディングワイヤには、金（Ａｕ）線が使用されており、特に樹脂モールドタイプの半導体素子では接続信頼性の観点から直径０．０２〜０．０３ｍｍ程度のＡｕ線が多く使用されてきた。   Conventionally, gold (Au) wire has been used as a bonding wire for connecting an electrode pad of a semiconductor element and a wiring pad of a circuit board. In particular, a resin mold type semiconductor element has a diameter of 0. Au wires of about 02 to 0.03 mm have been used a lot.

近年、Ａｕ価格の高騰を背景として、自動車等の車両のパワーモジュール用のワイヤボンディングには、Ａｕ線よりも材料コストが大幅に低い直径０．１〜０．３ｍｍ程度のアルミニウム線が用いられるようになっている。   In recent years, with the rising price of Au, aluminum wires with a diameter of about 0.1 to 0.3 mm are used for wire bonding for power modules of vehicles such as automobiles, which has a material cost much lower than that of Au wires. It has become.

しかし、自動車などのパワーモジュールでは、装置の小型化や電流密度の増大の面から、アルミニウム線よりも熱伝導率、電気伝導率（導電率）の高い素材が求められている。   However, in power modules such as automobiles, a material having higher thermal conductivity and electrical conductivity (conductivity) than aluminum wires is required from the viewpoints of downsizing the device and increasing current density.

このため、銅（Ｃｕ）又はＣｕ合金を心材とし、この外周に直接又は中間層を介してパラジウム（Ｐｄ）又はＰｄ合金を被覆したボンディングワイヤが提案されている（特許文献１参照）。このボンディングワイヤには、表面酸化が防止でき、材料保管時の耐酸化性に優れるメリットがある反面、以下の技術的課題がある。   For this reason, a bonding wire has been proposed in which copper (Cu) or a Cu alloy is used as a core material and the outer periphery thereof is covered with palladium (Pd) or a Pd alloy directly or via an intermediate layer (see Patent Document 1). While this bonding wire has the merit of preventing surface oxidation and excellent oxidation resistance during material storage, it has the following technical problems.

すなわち、Ｐｄ被覆したボンディングワイヤは、ボールボンディング時にワイヤ先端にボールを形成する際にＰｄがＣｕ中へ固溶した場合、ごく微量であってもボールの硬さがＣｕよりも硬くなるため、また、固溶せずに表層に残ったＰｄ自体も硬いため、ボールボンディング時にシリコンチップ上の脆弱なアルミパッドにダメージを与えてしまうという問題がある。また、被覆材として用いるＰｄ自体の材料コストも高いという問題がある。   That is, a bonding wire coated with Pd has a ball hardness that is higher than that of Cu even when the amount of Pd is dissolved in Cu when forming a ball at the wire tip during ball bonding. However, since Pd itself that remains on the surface layer without being dissolved is hard, there is a problem that a fragile aluminum pad on the silicon chip is damaged during ball bonding. In addition, there is a problem that the material cost of Pd itself used as a coating material is high.

一方、Ｃｕ又はＣｕ合金からなる心材の表面にＺｎなどからなる被覆層を形成したボンディングワイヤが提案されている（特許文献２、３参照）。   On the other hand, a bonding wire has been proposed in which a coating layer made of Zn or the like is formed on the surface of a core material made of Cu or Cu alloy (see Patent Documents 2 and 3).

実開昭６０−１６０５５４号公報Japanese Utility Model Publication No. 60-160554 特開昭６０−２０７３５７号公報JP 60-207357 A 特開昭６２−２８７６３４号公報JP 62-287634 A

Ｃｕ又はＣｕ合金からなる心材の表面にＺｎからなる被覆層を形成した従来のボンディングワイヤは、ＺｎがＰｄよりも材料費が安く、また、Ｃｕ中にＺｎ成分が固溶した場合にも、Ｐｄを使用する場合に比してボールが硬くなりにくい傾向にある点で有利である。   A conventional bonding wire in which a coating layer made of Zn is formed on the surface of a core material made of Cu or a Cu alloy has a material cost lower than that of Pd, and even when a Zn component is dissolved in Cu, Pd This is advantageous in that the ball tends to be harder than the use of.

しかし、ボンディングワイヤの保管時にボンディングワイヤ表面に心材中のＣｕが拡散し、その拡散したＣｕと酸素が結合して酸化膜が成長し、また、Ｚｎからなる被覆層が厚く形成された場合、Ｚｎ自体が酸素と結びつき、Ｚｎの酸化膜を厚く成長させてしまうことがあり、その結果、ボンディング時にアルミパッドとの接続不良を招くという問題を生じている。   However, when the bonding wire is stored, Cu in the core material diffuses on the surface of the bonding wire, the diffused Cu and oxygen are combined to grow an oxide film, and a Zn coating layer is formed thick. As a result, the Zn oxide film itself may be connected to oxygen and grow a thick oxide film. As a result, there arises a problem that connection failure with the aluminum pad is caused at the time of bonding.

そこで、本発明の目的は、ボンディングワイヤの保管時にボンディングワイヤ表面に酸化膜が成長するのを抑制し、ボンディング時の接続信頼性を向上させることができる銅ボンディングワイヤを提供することにある。   Therefore, an object of the present invention is to provide a copper bonding wire that can suppress the growth of an oxide film on the surface of the bonding wire during storage of the bonding wire and improve the connection reliability during bonding.

本発明は、上記目的を達成するために、下記［１］〜［６］の銅ボンディングワイヤ及びその製造方法を提供する。
In order to achieve the above object, the present invention provides the following copper bonding wires [1] to [ 6 ] and a method for producing the same.

［１］銅を主成分とする心材と、前記心材の表面に形成された、銅よりも酸素との親和性が高い金属である亜鉛及び酸素を含有するアモルファス層を有する表面処理層と、を備えた銅ボンディングワイヤ。
［２］前記アモルファス層は、前記心材から拡散した銅をさらに含有する前記［１］に記載の銅ボンディングワイヤ。
［３］前記表面処理層は、前記アモルファス層の下に、さらに、銅及び銅よりも酸素との親和性が高い金属である亜鉛、又は、銅、銅よりも酸素との親和性が高い金属である亜鉛及び酸素を含有する拡散層を有する前記［１］又は前記［２］に記載の銅ボンディングワイヤ。
［４］前記表面処理層の厚さは、３ｎｍ以上０．６μｍ以下である前記［１］〜［３］の何れか１つに記載の銅ボンディングワイヤ。
［５］銅を主成分とする心材の表面に、銅よりも酸素との親和性が高い金属である亜鉛からなる被覆層を形成し、形成された前記被覆層を、５０℃以上１５０℃以下の温度で、３０秒以上６０分以下の時間で加熱処理することによって、表面処理層を形成する銅ボンディングワイヤの製造方法。
［６］前記表面処理層の厚さは、３ｎｍ以上０．６μｍ以下である前記［５］に記載の銅ボンディングワイヤの製造方法。
[1] A core material mainly composed of copper, and a surface treatment layer formed on the surface of the core material and having an amorphous layer containing zinc and oxygen, which is a metal having higher affinity with oxygen than copper. Copper bonding wire provided.
[2] The copper bonding wire according to [1], wherein the amorphous layer further contains copper diffused from the core material.
[3] The surface treatment layer is a metal having a higher affinity for oxygen than copper and copper, or a metal having a higher affinity for oxygen than copper and copper under the amorphous layer. The copper bonding wire according to [1] or [2], including a diffusion layer containing zinc and oxygen.
[ 4 ] The copper bonding wire according to any one of [1] to [ 3 ], wherein the thickness of the surface treatment layer is 3 nm or more and 0.6 μm or less.
[ 5 ] A coating layer made of zinc, which is a metal having a higher affinity with oxygen than copper, is formed on the surface of the core material mainly composed of copper, and the formed coating layer is formed at 50 ° C or higher and 150 ° C or lower. The manufacturing method of the copper bonding wire which forms a surface treatment layer by heat-processing at the temperature of 30 seconds or more and 60 minutes or less.
[ 6 ] The method for producing a copper bonding wire according to [ 5], wherein the thickness of the surface treatment layer is 3 nm or more and 0.6 μm or less.

本発明によれば、ボンディングワイヤの保管時にボンディングワイヤ表面に酸化膜が成長するのを抑制し、ボンディング時の接続信頼性を向上させることができる銅ボンディングワイヤを提供することができる。   ADVANTAGE OF THE INVENTION According to this invention, it can suppress that an oxide film grows on the bonding wire surface at the time of storage of a bonding wire, and can provide the copper bonding wire which can improve the connection reliability at the time of bonding.

本発明の一の実施の形態に係る銅ボンディングワイヤを模式的に示す断面図である。It is sectional drawing which shows typically the copper bonding wire which concerns on one embodiment of this invention. 本発明の他の実施の形態に係る銅ボンディングワイヤを模式的に示す断面図である。It is sectional drawing which shows typically the copper bonding wire which concerns on other embodiment of this invention. 本発明の実施例３に係る銅ボンディングワイヤの恒温（１００℃）保持試験における３６００時間試験品の、表層からスパッタを繰り返しながら深さ方向のオージェ元素分析を行った結果を示すグラフである。It is a graph which shows the result of having performed the Auger elemental analysis of the depth direction, repeating a sputter | spatter from a surface layer of the 3600 hour test item in the constant temperature (100 degreeC) holding | maintenance test of the copper bonding wire which concerns on Example 3 of this invention. 本発明の実施例３、比較例１、及び従来例１に係る銅ボンディングワイヤの恒温（１００℃）保持試験における、表層からの酸素侵入深さ（酸化膜厚さ）の時間変化を示すグラフ図である。The graph which shows the time change of the oxygen penetration depth (oxide film thickness) from a surface layer in the constant temperature (100 degreeC) holding | maintenance test of the copper bonding wire which concerns on Example 3, Comparative example 1, and the prior art example 1 of this invention. It is. 本発明の実施例３に係る銅ボンディングワイヤのＲＨＥＥＤ分析結果を示す電子線の回折像である。It is an electron beam diffraction image which shows the RHEED analysis result of the copper bonding wire which concerns on Example 3 of this invention.

（銅ボンディングワイヤの構成）
図１は、本発明の一の実施の形態に係る銅ボンディングワイヤを模式的に示す断面図である。また、図２は、本発明の他の実施の形態に係る銅ボンディングワイヤを模式的に示す断面図である。 (Composition of copper bonding wire)
FIG. 1 is a cross-sectional view schematically showing a copper bonding wire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a copper bonding wire according to another embodiment of the present invention.

図１に示される本発明の一の実施の形態に係る銅ボンディングワイヤ１は、銅を主成分とする心材２と、心材２の表面に形成された表面処理層３と、を備える。   A copper bonding wire 1 according to an embodiment of the present invention shown in FIG. 1 includes a core material 2 mainly composed of copper and a surface treatment layer 3 formed on the surface of the core material 2.

心材２を構成する、銅を主成分とする材料としては、例えば、無酸素銅、タフピッチ銅等を使用することができる。また、必ずしも純銅である必要はなく、本発明の効果を奏する限りにおいては、銅合金を使用することも可能であり、具体的には、３〜１５質量ｐｐｍの硫黄と、２〜３０質量ｐｐｍの酸素と、５〜５５質量ｐｐｍのＴｉとを含む希薄銅合金等を使用することができる。   For example, oxygen-free copper, tough pitch copper, or the like can be used as the material mainly comprising copper that constitutes the core material 2. Moreover, it is not necessarily pure copper, and as long as the effect of the present invention is exhibited, it is possible to use a copper alloy, specifically, 3 to 15 mass ppm of sulfur and 2 to 30 mass ppm. A dilute copper alloy containing 5 to 55 ppm by mass of oxygen can be used.

表面処理層３は、銅よりも酸素との親和性が高い金属及び酸素を含有するアモルファス層を有する。或いは、表面処理層３は、銅よりも酸素との親和性が高い金属、酸素、及び心材２から拡散した銅を含有するアモルファス層を有する。   The surface treatment layer 3 has a metal having higher affinity with oxygen than copper and an amorphous layer containing oxygen. Alternatively, the surface treatment layer 3 has an amorphous layer containing a metal having higher affinity with oxygen than copper, oxygen, and copper diffused from the core material 2.

なお、図２に示すように、本発明の他の実施の形態に係る銅ボンディングワイヤ４として、表面処理層５は、アモルファス層７と、アモルファス層７の下に形成された、銅及び銅よりも酸素との親和性が高い金属、又は、銅、銅よりも酸素との親和性が高い金属及び酸素を含有する拡散層６を有するものであってもよい。銅、銅よりも酸素との親和性が高い金属及び酸素からなる拡散層６であることが好ましい。   As shown in FIG. 2, as the copper bonding wire 4 according to another embodiment of the present invention, the surface treatment layer 5 includes an amorphous layer 7 and copper and copper formed under the amorphous layer 7. Alternatively, a metal having a high affinity with oxygen, or a diffusion layer 6 containing oxygen and a metal having a higher affinity with oxygen than copper or copper may be used. The diffusion layer 6 is preferably made of copper, a metal having higher affinity with oxygen than copper, and oxygen.

アモルファス層（表面処理層３）、及び拡散層６を有する場合はアモルファス層７を構成する、銅よりも酸素との親和性が高い金属としては、亜鉛が好ましい。亜鉛以外には、例えば、Ｔｉ，Ｍｇ，Ｚｒ，Ａｌ，Ｆｅ，Ｓｎ，Ｍｎ等を挙げることができる。とりわけ、リサイクルの観点から、銅の製造時に酸化除去し易いＴｉ、Ｍｇ及びＺｒが好ましい。拡散層６を構成する、銅よりも酸素との親和性が高い金属についても、アモルファス層を構成する、銅よりも酸素との親和性が高い金属の場合と同様であり、同じ金属を使用することが好ましい。   In the case where the amorphous layer (surface treatment layer 3) and the diffusion layer 6 are provided, zinc is preferable as the metal constituting the amorphous layer 7 and having higher affinity with oxygen than copper. In addition to zinc, for example, Ti, Mg, Zr, Al, Fe, Sn, Mn and the like can be mentioned. In particular, from the viewpoint of recycling, Ti, Mg, and Zr, which are easily oxidized and removed during copper production, are preferable. The metal constituting the diffusion layer 6 and having higher affinity with oxygen than copper is the same as that of the metal constituting the amorphous layer and having higher affinity with oxygen than copper, and the same metal is used. It is preferable.

元素がランダムに配置されるアモルファス層は、元素が規則正しく配列した結晶質層と比較して緻密な構造と考えられるため、このアモルファス層が、銅素材の酸化の原因である表面処理層の表面への銅の拡散、及び銅素材中への酸素の侵入を抑制ないし低減させる。その結果、アモルファス層は、銅及び酸素が結合することを阻止するバリア層として機能すると考えられる。   The amorphous layer in which the elements are randomly arranged is considered to have a dense structure compared to the crystalline layer in which the elements are regularly arranged. Therefore, the amorphous layer is transferred to the surface of the surface treatment layer that causes oxidation of the copper material. This suppresses or reduces copper diffusion and oxygen intrusion into the copper material. As a result, the amorphous layer is considered to function as a barrier layer that prevents copper and oxygen from being combined.

このアモルファス層を形成するためには、酸素と銅以外の他の金属とが優先的に結合することが必要であり、そのアモルファス層の形成を促進するためには、心材２である銅よりも酸素との親和性が高い金属（例えば、亜鉛）が心材の表面に配置されていることが好ましい。   In order to form this amorphous layer, it is necessary that oxygen and other metals other than copper be preferentially bonded. In order to promote the formation of the amorphous layer, it is more preferable than copper as the core material 2. It is preferable that a metal (for example, zinc) having a high affinity with oxygen is disposed on the surface of the core material.

表面処理層３及び５は、異種元素が界面で接するため、異種元素界面で、通常なだらかな濃度変化を示すものであり、表面処理層の厚さの定義が難しい。そこで、本発明においては、表面処理層の厚さを、「銅よりも酸素との親和性が高い金属及び酸素、並びに場合に応じて銅を含有する層の厚さであり、かつ、その層を構成する元素のいずれをも元素含有比率としての原子濃度（ａｔ％）として２ａｔ％以上含有する層の厚さ」と定義する。   Since the surface treatment layers 3 and 5 are in contact with different elements at the interface, the surface treatment layers usually show a gentle concentration change at the interface between the different elements, and it is difficult to define the thickness of the surface treatment layer. Therefore, in the present invention, the thickness of the surface treatment layer is “the thickness of the metal and oxygen having higher affinity with oxygen than copper, and optionally the layer containing copper, and the layer. Is defined as “the thickness of the layer containing at least 2 at% as an atomic concentration (at%) as an element content ratio”.

本実施の形態に係る銅ボンディングワイヤ１に用いられる表面処理層３（拡散層６を有する銅ボンディングワイヤ４の場合は表面処理層５）の厚さは、拡散層６の厚さ及び加熱処理条件にもよるが、３ｎｍ以上０．６μｍ以下が好ましい。より好ましくは、６ｎｍ以上０．６μｍ以下である。   The thickness of the surface treatment layer 3 (surface treatment layer 5 in the case of the copper bonding wire 4 having the diffusion layer 6) used for the copper bonding wire 1 according to the present embodiment is the thickness of the diffusion layer 6 and the heat treatment conditions. However, it is preferably 3 nm or more and 0.6 μm or less. More preferably, it is 6 nm or more and 0.6 μm or less.

拡散層６を有する場合、拡散層６の厚さは、その下限値としては特に制限はなく、心材としての銅が被覆されていればよく、実用上、下限の被覆厚さは３ｎｍ程度であることが好ましい。また、拡散層６の厚さの上限値は、０．５μｍ以下が好ましい。０．５μｍを超えると、高い耐食性の発現に寄与するアモルファス層７が安定して形成されにくくなることがある。アモルファス層７の厚さとしては、特に制限はないが、３ｎｍ以上が好ましい。   When the diffusion layer 6 is provided, the lower limit value of the thickness of the diffusion layer 6 is not particularly limited, and it is sufficient that copper as a core material is coated. In practice, the lower limit coating thickness is about 3 nm. It is preferable. The upper limit value of the thickness of the diffusion layer 6 is preferably 0.5 μm or less. If it exceeds 0.5 μm, the amorphous layer 7 that contributes to the development of high corrosion resistance may not be stably formed. Although there is no restriction | limiting in particular as thickness of the amorphous layer 7, 3 nm or more is preferable.

（銅ボンディングワイヤの製造方法）
本実施の形態に係る銅ボンディングワイヤは、銅よりも酸素との親和性が高い金属が、例えば、亜鉛である場合には、最終製品のサイズ及び形状にて、銅系導体の表面に電解めっきでＺｎ層（厚さが２０μｍ以下が好ましく、１７μｍ以下がより好ましく、１５μｍ以下がさらに好ましい）を形成した後、そのまま５０℃以上１５０℃以下の温度で３０秒以上６０分以下の時間の条件で大気中にて加熱することで製造することができる。これにより、少なくとも亜鉛及び酸素を含有するアモルファス層を有する表面処理層を備えた銅ボンディングワイヤが得られる。つまり、銅を主成分とする心材の表面に、亜鉛を被覆して所定の加熱処理を施すだけの簡易な手法によりアモルファス層を形成することができる。 (Copper bonding wire manufacturing method)
In the copper bonding wire according to the present embodiment, when the metal having higher affinity with oxygen than copper is, for example, zinc, the surface of the copper-based conductor is electrolytically plated in the size and shape of the final product. After forming a Zn layer (thickness is preferably 20 μm or less, more preferably 17 μm or less, more preferably 15 μm or less), the temperature is 50 ° C. or more and 150 ° C. or less as it is for 30 seconds or more and 60 minutes or less. It can be manufactured by heating in the atmosphere. Thereby, the copper bonding wire provided with the surface treatment layer which has an amorphous layer containing at least zinc and oxygen is obtained. That is, the amorphous layer can be formed on the surface of the core material mainly composed of copper by a simple method of covering the surface with zinc and performing a predetermined heat treatment.

本発明の銅ボンディングワイヤの製造方法では、上述のように、被覆層を、５０℃以上１５０℃以下の温度で、３０秒以上６０分以下の時間で加熱処理することが好ましい。また、Ｚｎ層の形成は、めっき法を好ましく用いることができる。めっき法のほか、スパッタ法、真空蒸着法、クラッド法等を用いることもできる。   In the method for producing a copper bonding wire of the present invention, as described above, the coating layer is preferably heat-treated at a temperature of 50 ° C. to 150 ° C. for a time of 30 seconds to 60 minutes. In addition, a plating method can be preferably used for forming the Zn layer. In addition to the plating method, a sputtering method, a vacuum evaporation method, a cladding method, or the like can also be used.

また、その他の実施の形態として、最終製品サイズ、形状に加工する前に、予め亜鉛からなるめっきを行い、その後、最終製品サイズ、形状に加工し、被覆層を０．６μｍ以下とする方法で製造したものであってもよい。   Further, as another embodiment, before processing into the final product size and shape, plating with zinc is performed in advance, and then processing into the final product size and shape to make the coating layer 0.6 μm or less. It may be manufactured.

また、拡散層６は、例えば、表面処理層５のアモルファス層７を形成する前に、銅を主成分とする心材の表面に、亜鉛を被覆し、５０℃以上の温度で雰囲気加熱、或いは、油浴、塩浴中で保持することにより製造することができる。また、通電による抵抗発熱を利用して製造することもできる。拡散層６の形成後、その外周に、前述の方法と同様にして、アモルファス層７を形成する。   Further, the diffusion layer 6 is, for example, coated with zinc on the surface of a core material mainly composed of copper before the amorphous layer 7 of the surface treatment layer 5 is formed, and heated at a temperature of 50 ° C. or higher, or It can manufacture by hold | maintaining in an oil bath and a salt bath. Moreover, it can also manufacture using the resistance heat_generation | fever by electricity supply. After the formation of the diffusion layer 6, the amorphous layer 7 is formed on the outer periphery in the same manner as described above.

なお、表面処理層は、ボンディングワイヤとしての線材に形成してもよいし、ボンディングリボンのような平角形状の心材の場合、片面だけに形成してもよいし、両面に形成してもよい。本発明においては、ボンディングリボンをボンディングワイヤの定義に含めるものとする。   The surface treatment layer may be formed on a wire material as a bonding wire, or in the case of a flat core material such as a bonding ribbon, it may be formed only on one side or on both sides. In the present invention, the bonding ribbon is included in the definition of the bonding wire.

（実施の形態の効果）
本実施の形態によれば、表面処理層の表面への銅の拡散、及び心材２への酸素の侵入を抑制ないし低減させるバリア層として機能する表面処理層３或いは５を形成したので、ボンディングワイヤの保管時にボンディングワイヤ表面に酸化膜が成長するのを抑制でき、耐食性（耐酸化性）を有するため、ボンディング時の接続信頼性を向上させることができる。 (Effect of embodiment)
According to the present embodiment, since the surface treatment layer 3 or 5 functioning as a barrier layer that suppresses or reduces the diffusion of copper to the surface of the surface treatment layer and the penetration of oxygen into the core material 2 is formed, the bonding wire is formed. Since the oxide film can be prevented from growing on the surface of the bonding wire during storage, and has corrosion resistance (oxidation resistance), the connection reliability at the time of bonding can be improved.

以下、本発明を実施例によってさらに具体的に説明するが、本発明はこれらの実施例にのみ制限されるものではない。   EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to these examples.

本発明の実施例１〜８、比較例１〜３、及び従来例１〜４の銅ボンディングワイヤの構成を表１に示す。また、後述する評価項目についての評価結果も表１に示す。   Table 1 shows configurations of the copper bonding wires of Examples 1 to 8, Comparative Examples 1 to 3, and Conventional Examples 1 to 4 of the present invention. Table 1 also shows evaluation results for evaluation items described later.

表１における実施例１〜８、及び比較例１〜３は、概略として、基材としての銅からなる心材上に、種々の厚さの亜鉛の被覆層を電解めっきにより形成し、作製したものである。   Examples 1 to 8 and Comparative Examples 1 to 3 in Table 1 were prepared by forming, by electrolytic plating, zinc coating layers of various thicknesses on a core material made of copper as a base material. It is.

すなわち、実施例１〜８の銅ボンディングワイヤは、無酸素銅からなる線に、亜鉛めっきの厚さを変えた被覆層を形成し、その後、大気中で焼鈍をして作製したものである。   In other words, the copper bonding wires of Examples 1 to 8 were prepared by forming a coating layer having a different galvanizing thickness on a wire made of oxygen-free copper and then annealing in the atmosphere.

一方、比較例１の銅ボンディングワイヤは、銅系材料の特性に及ぼす亜鉛層の厚さの影響を評価すべく、厚さを変化させた亜鉛層を形成し、その後、実施例１と同様の加熱処理をしたものであり、比較例２及び３の銅ボンディングワイヤは、銅系材料の特性に及ぼす加熱処理条件の影響を評価すべく、加熱処理をせずに（比較例２）、又は加熱処理条件を変化させ（比較例３）、作製したものである。   On the other hand, in order to evaluate the influence of the thickness of the zinc layer on the properties of the copper-based material, the copper bonding wire of Comparative Example 1 is formed with a zinc layer having a changed thickness, and then the same as in Example 1 The copper bonding wires of Comparative Examples 2 and 3 were heat-treated without heat treatment (Comparative Example 2) or heat treatment in order to evaluate the influence of heat treatment conditions on the properties of the copper-based material. The processing conditions were changed (Comparative Example 3).

さらに従来例として、無酸素銅（従来例１）、高純度銅（６Ｎ）（従来例２）、無酸素銅の表面にＰｄめっきを施したもの（従来例３）、Ａｕワイヤ（従来例４）を用意した。   Further, as conventional examples, oxygen-free copper (conventional example 1), high-purity copper (6N) (conventional example 2), an oxygen-free copper surface plated with Pd (conventional example 3), Au wire (conventional example 4) ) Was prepared.

以下に、各実施例、比較例及び従来例の詳細を説明する。   Details of each example, comparative example, and conventional example will be described below.

［実施例１］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．０７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、５０℃の温度で１０分間、大気中で加熱処理して、表面処理層を備えた銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．００３μｍの厚さに形成されていることを確認した。 [Example 1]
A Zn layer having a thickness of 0.07 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, it heat-processed in air | atmosphere for 10 minutes at the temperature of 50 degreeC, and produced the copper bonding wire provided with the surface treatment layer. The surface treatment layer composed of zinc (Zn), oxygen (O), and copper (Cu) has a thickness of 0.003 μm by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例２］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．１７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、５０℃の温度で１時間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．００６μｍの厚さに形成されていることを確認した。 [Example 2]
A Zn layer having a thickness of 0.17 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 1 hour at the temperature of 50 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O), and copper (Cu) has a thickness of 0.006 μm by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例３］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．２７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１００℃の温度で５分間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０１μｍの厚さに形成されていることを確認した。 [Example 3]
A Zn layer having a thickness of 0.27 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 5 minutes at the temperature of 100 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.01 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例４］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．６０μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１００℃の温度で５分間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０２μｍの厚さに形成されていることを確認した。 [Example 4]
A Zn layer having a thickness of 0.60 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 5 minutes at the temperature of 100 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.02 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例５］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ１．３３μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１２０℃の温度で１０分間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０５μｍの厚さに形成されていることを確認した。 [Example 5]
A Zn layer having a thickness of 1.33 μm was formed by electrolytic plating on a 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 10 minutes at the temperature of 120 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O), and copper (Cu) is 0.05 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例６］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ２．６７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１５０℃の温度で３０秒間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．１μｍの厚さに形成されていることを確認した。 [Example 6]
A Zn layer having a thickness of 2.67 μm was formed on the 4N copper (purity: 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 30 seconds at the temperature of 150 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.1 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例７］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ１７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１５０℃の温度で３０秒間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．６μｍの厚さに形成されていることを確認した。 [Example 7]
A Zn layer having a thickness of 17 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 30 seconds at the temperature of 150 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.6 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［実施例８］
酸素濃度、硫黄濃度、チタン濃度が、それぞれ７〜８ mass ppm、５ mass ppm、１３ mass ppmである希薄銅合金からなる直径１ｍｍの銅線を作製した。この銅線に、電解めっきにより厚さ０．２７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１５０℃の温度で３０秒間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０１μｍの厚さに形成されていることを確認した。 [Example 8]
A copper wire having a diameter of 1 mm made of a dilute copper alloy having oxygen concentration, sulfur concentration, and titanium concentration of 7 to 8 mass ppm, 5 mass ppm, and 13 mass ppm, respectively, was produced. A 0.27 μm thick Zn layer was formed on the copper wire by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 30 seconds at the temperature of 150 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.01 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［比較例１］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ３１．７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、１００℃の温度で５分間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、１μｍの厚さに形成されていることを確認した。 [Comparative Example 1]
A Zn layer having a thickness of 31.7 μm was formed on the 4N copper (purity: 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 5 minutes at the temperature of 100 degreeC was produced. A surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is formed to a thickness of 1 μm by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. Confirmed that it has been.

［比較例２］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．６７μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０２μｍの厚さに形成されていることを確認した。 [Comparative Example 2]
A Zn layer having a thickness of 0.67 μm was formed on the 4N copper (purity: 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.02 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［比較例３］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ０．３３μｍのＺｎ層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。その後、４００℃の温度で３０秒間、大気中で加熱処理した銅ボンディングワイヤを作製した。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、亜鉛（Ｚｎ）、酸素（Ｏ）及び銅（Ｃｕ）から構成される表面処理層が、０．０２μｍの厚さに形成されていることを確認した。 [Comparative Example 3]
A Zn layer having a thickness of 0.33 μm was formed by electrolytic plating on 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. Then, the copper bonding wire heat-processed in air | atmosphere for 30 seconds at the temperature of 400 degreeC was produced. The surface treatment layer composed of zinc (Zn), oxygen (O) and copper (Cu) is 0.02 μm thick by performing Auger analysis in the depth direction from the surface of the produced copper bonding wire. It was confirmed that it was formed.

［従来例１］
直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線を、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。 [Conventional example 1]
A 4N copper (purity 99.99% by weight) wire having a diameter of 1 mm was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing.

［従来例２］
直径１ｍｍの６Ｎ銅（純度９９．９９９９重量％）線を、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。 [Conventional example 2]
A 6N copper (purity 99.9999% by weight) wire having a diameter of 1 mm was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing.

［従来例３］
心材２として直径１ｍｍの４Ｎ銅（純度９９．９９重量％）線に、電解めっきにより厚さ１．６７μｍのパラジウム（Ｐｄ）層を形成した。その後、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。作製した銅ボンディングワイヤに対し、表面から深さ方向のオージェ分析を行うことで、Ｐｄで構成される表面処理層が、０．０５μｍの厚さに形成されていることを確認した。 [Conventional Example 3]
A palladium (Pd) layer having a thickness of 1.67 μm was formed on the 4N copper (purity 99.99 wt%) wire having a diameter of 1 mm as the core material 2 by electrolytic plating. Thereafter, the wire was drawn to a diameter of 0.03 mm, and then the copper core material was softened by electrical annealing. By performing Auger analysis in the depth direction from the surface of the produced copper bonding wire, it was confirmed that the surface treatment layer composed of Pd was formed to a thickness of 0.05 μm.

［従来例４］
直径１ｍｍの金（純度９９．９９重量％）線を、直径０．０３ｍｍまで伸線加工を行い、更に続けて、通電焼鈍により銅心材を軟質化させた。 [Conventional example 4]
A wire with a diameter of 1 mm (purity: 99.99% by weight) was drawn to a diameter of 0.03 mm, and the copper core material was softened by electrical annealing.

［評価方法］
表１における各銅ボンディングワイヤに形成された表面処理層は、オ一ジェ分光分析の結果から求めた。 [Evaluation method]
The surface treatment layer formed on each copper bonding wire in Table 1 was obtained from the results of Auger spectroscopic analysis.

表１におけるアモルファス層の存在の確認は、ＲＨＥＥＤ分析（Ｒｅｆｌｅｃｔｉｏｎ Ｈｉｇｈ Ｅｎｅｒｇｙ Ｅｌｅｃｔｒｏｎ Ｄｉｆｆｒａｃｔｉｏｎ）により行った。アモルファス層の存在を示すハローパターンが確認できたものを「有」、結晶質の構造を示す電子線の回折斑点が確認できたものを「無」とした。   The presence of the amorphous layer in Table 1 was confirmed by RHEED analysis (Reflection High Energy Electron Diffraction). “Yes” indicates that the halo pattern indicating the presence of the amorphous layer was confirmed, and “No” indicates that the diffraction spot of the electron beam indicating the crystalline structure was confirmed.

表１における作製した各銅ボンディングワイヤのボール硬さ、接続不良率（％）、ループ形状の各評価及び総合評価は、以下のようにして行った。   Each evaluation and comprehensive evaluation of ball hardness, connection failure rate (%), and loop shape of each copper bonding wire produced in Table 1 were performed as follows.

ボール硬さは、フリーエアボールを形成した後、ボールの断面の材料硬さをビッカス硬度計で測定した。６０Ｈｖ以下を◎、６０Ｈｖを超え７０Ｈｖ以下を○、７０Ｈｖを超え８０Ｈｖ以下を△とした。また、実際のワイヤボンディングの際に、この測定硬さに比例して、アルミパッドのダメージ（アルミスプラッシュ）が大きいことを目視にて確認した。   Regarding the ball hardness, after forming a free air ball, the material hardness of the cross section of the ball was measured with a Bickus hardness meter. 60Hv or less was evaluated as ◎, 60Hv and 70Hv or less as ◯, 70Hv and 80Hv or less as Δ In actual wire bonding, it was visually confirmed that the damage (aluminum splash) of the aluminum pad was large in proportion to the measured hardness.

接続不良率は、サンプル数ｎ＝３０のワイヤボンディング及びプルテストにより評価した。ボンディングの未接着及びプルテストによる接続強度が導体強度の７０％以下であるものを不良と判断し、それらの不良数をテスト総数で除した値を接続不良率とした。   The connection failure rate was evaluated by wire bonding and a pull test with the number of samples n = 30. A case where the bonding strength of bonding and the connection strength by the pull test was 70% or less of the conductor strength was judged as a failure, and a value obtained by dividing the number of failures by the total number of tests was defined as a connection failure rate.

ループ形状は、ループ高さのばらつきで評価し、ループ高さばらつきが±１５０μｍ以内を◎、±１５０μｍを超え±３００μｍ以内を○、±３００μｍを超える場合を△とした。   The loop shape was evaluated based on the variation in the loop height, and the case where the variation in the loop height was within ± 150 μm was marked as ◎, the case where it exceeded ± 150 μm and within ± 300 μm was marked as ◯, and the case where it exceeded ± 300 μm was marked as Δ.

これらの項目及びコストを合わせ総合的に評価して、◎最良、○良好、△不足、×不適と判断した。   These items and costs were combined and evaluated comprehensively, and judged as ◎ best, ○ good, △ insufficient, × unsuitable.

［評価結果］
図３は、実施例３に係る銅ボンディングワイヤの恒温（１００℃）保持試験における３６００時間試験品の、表層からスパッタを繰り返しながら深さ方向のオージェ元素分析を行った結果を示すグラフである。横軸は表面からの深さ（ｎｍ）、縦軸は原子濃度（ａｔ％）を表し、実線は酸素（Ｏ）の含有比率としての原子濃度（ａｔ％）、長い破線は亜鉛（Ｚｎ）の原子濃度、短い破線は銅（Ｃｕ）の原子濃度を示している。酸素侵入深さは、表面から１０ｎｍ程度であり、特に深さ０〜３ｎｍの表層部位における平均元素含有比率を（深さ０〜３ｎｍでの各元素の最大原子濃度−最小原子濃度）／２と定義すると、実施例３では、亜鉛（Ｚｎ）が６０ａｔ％、酸素（Ｏ）が３３ａｔ％、銅（Ｃｕ）が７ａｔ％であった。 [Evaluation results]
FIG. 3 is a graph showing the results of Auger elemental analysis in the depth direction while repeating sputtering from the surface layer of a 3600 hour test product in the constant temperature (100 ° C.) holding test of the copper bonding wire according to Example 3. The horizontal axis represents the depth from the surface (nm), the vertical axis represents the atomic concentration (at%), the solid line represents the atomic concentration (at%) as the oxygen (O) content ratio, and the long broken line represents zinc (Zn). Atomic concentration, a short broken line indicates an atomic concentration of copper (Cu). The oxygen penetration depth is about 10 nm from the surface, and in particular, the average element content ratio in the surface layer portion of the depth of 0 to 3 nm is (maximum atomic concentration of each element at the depth of 0 to 3 nm−minimum atomic concentration) / 2. When defined, in Example 3, zinc (Zn) was 60 at%, oxygen (O) was 33 at%, and copper (Cu) was 7 at%.

また、他の実施例を含めると、上記平均元素含有比率は、亜鉛（Ｚｎ）が３５〜６８ａｔ％、酸素（Ｏ）が３０〜６０ａｔ％、銅（Ｃｕ）が０〜１５ａｔ％の範囲にあることがわかった。   When other examples are included, the average element content ratio is in the range of 35 to 68 at% for zinc (Zn), 30 to 60 at% for oxygen (O), and 0 to 15 at% for copper (Cu). I understood it.

一方、比較例１の銅ボンディングワイヤは、亜鉛（Ｚｎ）が３３ａｔ％、酸素（Ｏ）が４１ａｔ％、銅（Ｃｕ）が２６ａｔ％であり、比較例２の銅ボンディングワイヤは、亜鉛（Ｚｎ）が５ａｔ％、酸素（Ｏ）が４６ａｔ％、銅（Ｃｕ）が４９ａｔ％であった。   On the other hand, the copper bonding wire of Comparative Example 1 has 33 at% zinc (Zn), 41 at% oxygen (O), and 26 at% copper (Cu), and the copper bonding wire of Comparative Example 2 has zinc (Zn). Was 5 at%, oxygen (O) was 46 at%, and copper (Cu) was 49 at%.

図４は、本発明の実施例３、比較例１、及び従来例１に係る銅ボンディングワイヤの恒温（１００℃）保持試験における、表層からの酸素侵入深さ（酸化膜厚さ）の時間変化を示すグラフ図である。酸素侵入深さは、各時間保持したサンプル表面から、スパッタを繰り返しながら、深さ方向にオージェ分析を行うことで求めた。図４において、横軸は１００℃等温保持時間（ｈ）、縦軸は酸素侵入深さ（ｎｍ）を表し、実線は実施例３、破線は従来例１の酸素侵入深さを示している。なお、比較例１は点で示されている。   FIG. 4 shows the time change of the oxygen penetration depth (oxide film thickness) from the surface layer in the constant temperature (100 ° C.) holding test of the copper bonding wires according to Example 3, Comparative Example 1, and Conventional Example 1 of the present invention. FIG. The oxygen penetration depth was determined by performing Auger analysis in the depth direction while repeating sputtering from the sample surface held for each time. In FIG. 4, the horizontal axis represents the 100 ° C. isothermal holding time (h), the vertical axis represents the oxygen penetration depth (nm), the solid line represents Example 3, and the broken line represents the oxygen penetration depth of Conventional Example 1. Note that Comparative Example 1 is indicated by dots.

実施例３では、図３に示すように、３６００時間保持経過後の状態で、表面近傍での酸素濃度が増加しているものの、その侵入深さは試験前と殆ど変化せず約０．０１μｍ以下であり、実施例３の銅ボンディングワイヤは高い耐酸化性を示した。   In Example 3, as shown in FIG. 3, the oxygen concentration in the vicinity of the surface increased after 3600 hours of retention, but the penetration depth hardly changed from that before the test and was about 0.01 μm. The copper bonding wire of Example 3 showed high oxidation resistance.

一方、図４に示すように、恒温保持試験前の従来例１では酸素を含む層の厚さが表面から約０．００６μｍ程度と、恒温保持試験前の実施例３と同程度の深さであったが、３６００時間保持試験後の従来例１では、表面近傍での酸素濃度が恒温保持試験前に比較して顕著に増加し、従来例１の酸素侵入深さは約０．０３６μｍと試験前の５倍以上となった。また、試験後の従来例１は外観上も赤茶系に変色しており、明らかに酸素を含む層が厚く形成されていると判断することができた。また、無酸素銅に１μｍのＺｎ層を形成した比較例１は、１０００時間保持試験後に既に酸素侵入深さが約０．０８０μｍに達していた。   On the other hand, as shown in FIG. 4, in the conventional example 1 before the constant temperature holding test, the thickness of the layer containing oxygen is about 0.006 μm from the surface, which is the same depth as in Example 3 before the constant temperature holding test. However, in Conventional Example 1 after the 3600 hour holding test, the oxygen concentration in the vicinity of the surface increased significantly compared to before the constant temperature holding test, and the oxygen penetration depth of Conventional Example 1 was about 0.036 μm. More than 5 times before. In addition, Conventional Example 1 after the test was discolored to a reddish brown color from the outside, and it was apparent that the layer containing oxygen was clearly formed thick. In Comparative Example 1 in which a 1 μm Zn layer was formed on oxygen-free copper, the oxygen penetration depth had already reached about 0.080 μm after the 1000 hour holding test.

耐食性に優れた実施例３の表面をＲＨＥＥＤ分析した結果を図５に示す。電子線の回折像は、ハローパターンを示しており、表面にアモルファス層が形成されていることがわかった。一方、耐食性に劣る従来例１は、銅及び酸素で構成される結晶質であることが確認された。   The result of the RHEED analysis of the surface of Example 3 excellent in corrosion resistance is shown in FIG. The diffraction pattern of the electron beam showed a halo pattern, and it was found that an amorphous layer was formed on the surface. On the other hand, it was confirmed that the prior art example 1 which is inferior in corrosion resistance is crystalline composed of copper and oxygen.

（ボール硬さ）
ボール硬さについて、実施例１〜８、比較例１〜３、及び従来例１、２，４のボンディングワイヤは全て良好な特性を示した。実施例８及び素材全体の純度が高い従来例２、及び従来例４は、更にやわらかいボールを形成していた。実施例８において、◎の結果となった理由は、添加したチタンが不純物である硫黄をトラップすることで、銅母材（マトリックス）が高純度化し、素材の軟質特性が向上したためであると考えられる。 (Ball hardness)
Regarding the ball hardness, the bonding wires of Examples 1 to 8, Comparative Examples 1 to 3, and Conventional Examples 1, 2, and 4 all showed good characteristics. In Example 8 and Conventional Example 2 and Conventional Example 4 in which the purity of the entire material is high, softer balls were formed. In Example 8, the reason that the result of ◎ was obtained is that the added titanium traps sulfur, which is an impurity, so that the copper base material (matrix) is highly purified and the soft characteristics of the material are improved. It is done.

一方、従来例３に示すＰｄ被覆したボンディングワイヤは、ボールが硬い結果となった。これは、心材のＣｕ中へＰｄが固溶した場合、その値がごく微量であってもボールが硬くなり易いことを示している。一方、実施例に示すＺｎ被覆は、Ｃｕ中へＺｎが固溶したとしても、硬さの上昇は少ない、この理由として、ＣｕとＺｎは原子半径がほぼ同等であるため、固溶による歪の発生が小さく、硬さへの影響が小さいためと考えられる。   On the other hand, the Pd-coated bonding wire shown in Conventional Example 3 resulted in a hard ball. This indicates that when Pd is dissolved in Cu as the core material, the ball tends to be hard even if the value is very small. On the other hand, the Zn coating shown in the examples shows little increase in hardness even when Zn is dissolved in Cu. The reason for this is that Cu and Zn have substantially the same atomic radius. This is considered to be because the occurrence is small and the influence on hardness is small.

（接続信頼性）
接続信頼性に関して、実施例１〜８については、不良率がゼロの優れた特性を示した。一方、同じくＺｎ系の表面処理層を持つ比較例１〜３であっても、良好な特性が得られない場合が認められた。比較例１のように、亜鉛の厚さが厚い場合、比較例２のようにめっき後の加熱処理を実施していない場合、比較例３のようにめっき後に過剰な加熱処理を行った場合等、表層にアモルファスが形成されないものはいずれも、評価結果は不良となった。従来例１、２についても、銅の酸化による接着不良が発生した。また、従来例２は、強度が不十分なネック切れが発生した。これは、高純度銅であるため、結晶粒が粗大化し強度低下が生じたためである。従来例３、４は、良好な特性を示した。 (Connection reliability)
Regarding the connection reliability, Examples 1 to 8 showed excellent characteristics with a defect rate of zero. On the other hand, even in Comparative Examples 1 to 3 having a Zn-based surface treatment layer, it was recognized that good characteristics could not be obtained. When the thickness of zinc is thick as in Comparative Example 1, when heat treatment after plating is not performed as in Comparative Example 2, when excessive heat treatment is performed after plating as in Comparative Example 3, etc. In all cases where no amorphous layer was formed on the surface layer, the evaluation results were poor. Also in Conventional Examples 1 and 2, poor adhesion due to copper oxidation occurred. Further, in the conventional example 2, the neck breakage with insufficient strength occurred. This is because of the high purity copper, the crystal grains are coarsened and the strength is reduced. Conventional Examples 3 and 4 showed good characteristics.

以上の結果から、Ｚｎ処理を行った場合の加熱処理の条件としては、酸素を１％以上含む雰囲気中で５０℃以上であることが好ましいことが確認された。   From the above results, it was confirmed that the heat treatment condition when performing the Zn treatment is preferably 50 ° C. or higher in an atmosphere containing 1% or more of oxygen.

（ループ形状）
ループ形状に関して、軟質である反面ループが安定しなかった従来例２以外は良好であった。特に、実施例８はより安定したループ特性を示した。 (Loop shape)
Regarding the loop shape, it was good except for the conventional example 2 in which the loop was soft but the loop was not stable. In particular, Example 8 showed more stable loop characteristics.

（コスト）
コスト（経済性）に関して、４Ｎの銅（従来例１）、及び本発明の実施例１〜８、比較例１〜３は、材料そのものの耐食性に優れていながら材料コストが高い貴金属コーティング等を必要とせず、安価なＺｎを使用し、しかもその厚さが極めて薄いため、生産性と経済性に極めて優れている。従来例２の高純度銅は、従来例３のＰｄや従来例４のＡｕよりは安価であるものの、製造方法が特殊であるため４Ｎ銅をベースとした材料よりも高価にならざるを得ない。 (cost)
Regarding cost (economic efficiency), 4N copper (conventional example 1), and Examples 1 to 8 and Comparative Examples 1 to 3 of the present invention require a precious metal coating having a high material cost while being excellent in the corrosion resistance of the material itself. However, since inexpensive Zn is used and its thickness is extremely thin, it is extremely excellent in productivity and economy. Although the high purity copper of Conventional Example 2 is less expensive than Pd of Conventional Example 3 or Au of Conventional Example 4, it has to be more expensive than a material based on 4N copper because of its special manufacturing method. .

導電率と熱伝導率について、銅、及び銅を心材とした実施例１〜８が優れていることは言うまでもない。   Needless to say, Examples 1 to 8 using copper and copper as the core material are excellent in terms of electrical conductivity and thermal conductivity.

これらの結果から総合的に判断すると、表面処理により酸化劣化を低減させ、優れたワイヤボンディング特性、及び高い導電性と経済性を併せ持つ、ボンディングワイヤ材料として、実施例１〜８に示す本実施例の銅ワイヤボンディングが提案できる。   Judging from these results comprehensively, this example shown in Examples 1 to 8 as a bonding wire material that reduces oxidation deterioration by surface treatment and has both excellent wire bonding characteristics and high conductivity and economy. Copper wire bonding can be proposed.

なお、本発明は、上記実施の形態、上記実施例に限定されず種々に変形実施が可能である。   In addition, this invention is not limited to the said embodiment and said Example, A various deformation | transformation implementation is possible.

１：銅ボンディングワイヤ
２：心材
３：表面処理層（アモルファス層）
４：銅ボンディングワイヤ
５：表面処理層
６：拡散層
７：アモルファス層 1: Copper bonding wire 2: Core material 3: Surface treatment layer (amorphous layer)
4: Copper bonding wire 5: Surface treatment layer 6: Diffusion layer 7: Amorphous layer

Claims (6)

銅を主成分とする心材と、
前記心材の表面に形成された、銅よりも酸素との親和性が高い金属である亜鉛及び酸素を含有するアモルファス層を有する表面処理層と、
を備えた銅ボンディングワイヤ。 A heartwood mainly composed of copper;
A surface treatment layer having an amorphous layer containing zinc and oxygen, which is a metal having a higher affinity with oxygen than copper, formed on the surface of the core material;
With copper bonding wire. 前記アモルファス層は、前記心材から拡散した銅をさらに含有する請求項１に記載の銅ボンディングワイヤ。   The copper bonding wire according to claim 1, wherein the amorphous layer further contains copper diffused from the core material. 前記表面処理層は、前記アモルファス層の下に、さらに、銅及び銅よりも酸素との親和性が高い金属、又は、銅、銅よりも酸素との親和性が高い金属及び酸素を含有する拡散層を有する請求項１又は請求項２に記載の銅ボンディングワイヤ。   The surface treatment layer further includes a metal having a higher affinity with oxygen than copper and copper, or a metal having a higher affinity with oxygen than copper and copper and a diffusion containing oxygen under the amorphous layer. The copper bonding wire according to claim 1 or 2 which has a layer. 前記表面処理層の厚さは、３ｎｍ以上０．６μｍ以下である請求項１〜３のいずれか１項に記載の銅ボンディングワイヤ。 The thickness of the surface treatment layer, a copper bonding wire according to any one of claims 1 to 3, in 3nm or more 0.6μm or less. 銅を主成分とする心材の表面に、銅よりも酸素との親和性が高い金属である亜鉛からなる被覆層を形成し、形成された前記被覆層を、５０℃以上１５０℃以下の温度で、３０秒以上６０分以下の時間で加熱処理することによって、表面処理層を形成する銅ボンディングワイヤの製造方法。 A coating layer made of zinc, which is a metal having a higher affinity with oxygen than copper, is formed on the surface of the core material mainly composed of copper, and the formed coating layer is formed at a temperature of 50 ° C. or higher and 150 ° C. or lower. The manufacturing method of the copper bonding wire which forms a surface treatment layer by heat-processing in 30 seconds or more and 60 minutes or less. 前記表面処理層の厚さは、３ｎｍ以上０．６μｍ以下である請求項５に記載の銅ボンディングワイヤの製造方法。
The method for producing a copper bonding wire according to claim 5 , wherein the thickness of the surface treatment layer is 3 nm or more and 0.6 μm or less.
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