JP3710573B2 - Electrode structure of gallium nitride compound semiconductor light emitting device - Google Patents

Electrode structure of gallium nitride compound semiconductor light emitting device Download PDF

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JP3710573B2
JP3710573B2 JP25787996A JP25787996A JP3710573B2 JP 3710573 B2 JP3710573 B2 JP 3710573B2 JP 25787996 A JP25787996 A JP 25787996A JP 25787996 A JP25787996 A JP 25787996A JP 3710573 B2 JP3710573 B2 JP 3710573B2
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electrode
gallium nitride
compound semiconductor
bonding
semiconductor light
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JPH10107318A (en
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俊雄 幡
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Sharp Corp
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Sharp Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は、青色から紫外光領域で発光可能な窒化ガリウム系化合物半導体発光素子の電極構造に関し、特に、窒化ガリウム系化合物半導体層上に透光性電極を有する窒化ガリウム系化合物半導体発光素子の電極構造に関する。
【０００２】
【従来の技術】
従来の窒化ガリウム系化合物半導体発光素子の電極構造として、特開平７−１０６６３号公報に記載の窒化ガリウム系化合物半導体発光素子を図７に示す。
【０００３】
まず、絶縁性のサファイア基板１の上に、ｎ型窒化ガリウム系化合物半導体層２、ｐ型窒化ガリウム系化合物半導体層３が形成され、更にその表面上にＮｉ及びＡｕを積層した合金からなる透光性電極４と、Ａｕ単体、またはＡｕに加えて、Ｔｉ、Ｎｉ、Ｉｎ、Ｐｔから少なくとも１種類を含む合金からなるボンディング用電極５が形成されている。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。
【０００４】
【発明が解決しようとする課題】
しかし、透光性電極４は、発光波長領域にて透光性を保つため非常に薄い膜で形成されている。そのため、透光性電極４とｐ型窒化ガリウム系化合物半導体層３とのオーミック特性を得るために、熱処理中（アニール中）に露出した表面から透光性電極のＮｉが変質し、そのためオーミック特性が悪化し、発光効率の低下を招くことになる。このようなＮｉの変質が生じるのは、窒化ガリウム系材料はオーミック接触を十分に行うことが困難であるため、高い温度で熱処理を行う必要があるからである。
【０００５】
さらに、透光性電極４は、非常に薄い膜であるので、ｐ型窒化ガリウム系化合物半導体層３及びボンディング用電極５との密着性が悪く、ワイヤーボンディング時に剥がれ易くなる問題が生じた。
【０００６】
従って、ワイヤーボンディング時に透光性電極４及びボンディング用電極５の剥れをなくすことでワイヤーボンディグ時の歩留りが向上し、且つ、発光効率の低下を押さえることのできる信頼性に優れた窒化ガリウム系化合物半導体発光素子の電極構造を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明は、上記問題を解決するためになされたもので、窒化ガリウム系化合物半導体発光層の上にＮｉからなる薄膜とＡｕからなる薄膜が少なくとも１組以上交互に積層された透光性電極を有し、前記透光性電極上にボンディング用電極を有し、前記透光性電極は、Ｎｉからなる薄膜とＡｕからなる薄膜が少なくとも１組以上交互に積層され、窒化ガリウム系化合物半導体側がＮｉからなり、表面側がＡｕからなることを特徴とする。このような構造を形成することにより、透光性電極のＮｉの変質を防ぐことができ、窒化ガリウム系化合物半導体層と透光性電極とのオーミック特性を維持し、それに伴う発光効率の低下を生じさせないことが可能となる。
【０００８】
また、窒化ガリウム系化合物半導体発光層の上にボンディング用電極を有し、前記ボンディング用電極を覆うようにＮｉからなる薄膜とＡｕからなる薄膜が少なくとも１組以上交互に積層された透光性電極を有し、前記透光性電極は、窒化ガリウム系化合物半導体側がＮｉからなり、表面側がＡｕからなることを特徴とする。
【０００９】
また、ボンディング用電極を覆うようにＮｉとＡｕからなる多層構造の透光性電極を形成することにより、ｐ型窒化ガリウム系化合物半導体層とボンディング用電極の付着力を一層強めることができる。さらに多層構造の透光性電極の最表面をＡｕにすることでＡｕワイヤーと付着力を強めることができる。そのため、ワイヤーボンディング時にボンディング用電極の剥がれを少なくすることが可能となる。
【００１０】
また、多層構造の透光性電極とＡｕからなるボンディング用電極Ａｕの間に密着性を向上させるＮｉからなるボンディング用電極を形成することにより、ｐ型窒化ガリウム系化合物半導体層とボンディング用電極Ａｕの付着力が強くなる。
【００１１】
【発明の実施の形態】
本発明を具体的な実施の形態に基づいて説明する。
【００１２】
（実施の形態１）
本発明によって作製された窒化ガリウム系化合物半導体発光素子の電極構造の摸式図を図１に示す。
【００１３】
絶縁性のサファイア基板１の上に、ｎ型窒化ガリウム系化合物半導体層２、ｐ型窒化ガリウム系化合物半導体層３が形成され、更にその表面上にＮｉ、Ａｕの順に交互に積層された透光性電極７と、Ｎｉ単体からなるボンディング用電極８とＡｕ単体からなるボンディング用電極９が形成されている。透光性電極７は、最もｐ型窒化ガリウム系化合物半導体層３側はＮｉからなり、最も表面側はＡｕからなる。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。
【００１４】
上記のような本発明の窒化ガリウム系化合物半導体発光素子の製造工程について図４に示す。
【００１５】
まず、ＭＯＣＶＤ法で、絶縁性のサファイア基板１上に、ｎ型窒化ガリウム系化合物半導体層２を積層する。次に、ｐ型窒化ガリウム系化合物半導体層３を積層し、ｐ型窒化ガリウム系化合物半導体層３の表面の所望の領域に電子ビーム蒸着法でＮｉとＡｕとを交互に２．５ｎｍずつ積層した透光性電極７を形成する。
透光性電極７の膜厚は、発光波長において十分透過する厚さに設定する。
【００１６】
ｐ型窒化ガリウム系化合物層３と透光性電極７のＮｉとのオーミック特性を得るため、５００℃のアニールを３分間行う。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。この時の製造工程断面図を図４（ａ）に示す。
【００１７】
次に、透光性電極７上に電子ビーム蒸着法でＮｉからなるボンディング用電極８を形成し、更に、Ａｕからなるボンディング用電極９を形成する。この時の製造工程断面図を図４（ｂ）に示す。
【００１８】
本実施の形態では、透光性電極７はＮｉとＡｕとを交互に積層した多層構造からなるが、アニール温度に対して熱的に安定な金属からなる薄膜とＮｉとからなる多層構造でもよい。熱的に安定な金属としては、Ａｕ、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｈ等の少なくとも１種からなる金属が好ましい。透光性電極７の形成方法は、電子ビーム蒸着法、真空蒸着法、スパッタリング法を用いてもよい。Ａｕからなるボンディング用電極９は、Ａｕワイヤーとの密着性向上させるためにＡｕを用いた。
【００１９】
（実施の形態２）
本発明によって作製された別の窒化ガリウム系化合物半導体発光素子の電極構造の摸式図を図２に示す。
【００２０】
絶縁性のサファイア基板１の上に、ｎ型窒化ガリウム系化合物半導体層２、ｐ型窒化ガリウム系化合物半導体層３が形成され、更にその表面上に、Ｎｉからなるボンディング用電極８が形成されている。更に、その上に、Ａｕからなるボンディング用電極９が形成されており、Ａｕからなるボンディング用電極９を覆うようにＮｉとＡｕとを交互に積層した透光性電極１０が形成されている。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。透光性電極１０は、ｐ型窒化ガリウム系化合物半導体層側はＮｉからなり、表面側はＡｕからなっている。
【００２１】
上記のような本発明の窒化ガリウム系化合物半導体発光素子の製造工程について図５に示す。
【００２２】
まず、実施の形態１と同様に形成されたｐ型窒化ガリウム系化合物半導体層３の表面に、電子ビーム蒸着法で形成されたＮｉからなるボンディング用電極８を形成し、その上に電子ビーム蒸着法で形成されたＡｕからなるボンディング用電極９を形成した。次に、Ｎｉからなるボンディング用電極８と、Ａｕからなるボンディング用電極９のアニールを５００℃、３分間行う。この時の製造工程断面図を図５（ａ）に示す。
【００２３】
Ａｕからなるボンディング用電極９を覆うように、ｐ型窒化ガリウム系化合物半導体層３の表面の所望の領域にＮｉとＡｕの順に交互に積層した透光性電極１０を電子ビーム蒸着法で１５ｎｍの厚さで形成する。次に、透光性電極１０のアニールを４００℃、３分で行う。この時の製造工程断面図を図５（ｂ）に示す。
【００２４】
透光性電極１０は、２層構造でなくとも多層構造としても、ｐ型窒化ガリウム系化合物半導体層側をＮｉとし、表面側をＡｕの順に構成にしておればよい。多層膜構造とした時の製造工程断面図を図５（ｃ）に示す。
【００２５】
次に、ワイヤーボンディングを行うと、透光性電極１０が薄膜であるため、透光性電極１０を突き破ってボンディング用電極９と接続される。
【００２６】
ここで、ボンディング用電極８、９のアニールは透光性電極１０のアニールの前に行われている上に、透光性電極１０のアニール温度はボンディング用電極８、９のアニールの温度より低いため、透光性電極１０の変質が発生することはない。さらに、Ａｕからなるボンディング用電極９の表面上にＮｉとＡｕとを積層させる構造の透光性電極１０を形成することにより、ｐ型窒化ガリウム系化合物半導体層３とＮｉからなるボンディング用電極８の付着力を強めることができる。
【００２７】
透光性電極１０は熱的に安定な金属であるＡｕ、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｈ等の少なくとも１種とＮｉからなる多層構造でも構わない。Ａｕからなるボンディング用電極９はＡｕワイヤーとの接着性向上のためＡｕを用いた。
【００２８】
透光性電極の形成方法として、電子ビーム蒸着法、真空蒸着法、スパッタリング法等を用いることができる。
【００２９】
（実施の形態３）
本発明のまた別の実施の形態によって作製された窒化ガリウム系化合物半導体発光素子の電極構造の摸式図を図３に示す。
【００３０】
絶縁性のサファイア基板１の上に、ｎ型窒化ガリウム系化合物半導体層２、ｐ型窒化ガリウム系化合物半導体層３が形成され、その上にＮｉからなる第１の透光性電極１１が形成され、その上にＮｉからなるボンディング用電極８が形成されている。更に、その上に、Ａｕからなるボンディング用電極９が形成されており、Ａｕからなるボンディング用電極９を覆うように電子ビーム蒸着法で２．５ｎｍずつの膜厚でＮｉとＡｕとを交互に積層した第２の透光性電極１２が形成されいる。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。第２の透光性電極１２は、第１の透光性電極側がＮｉであり、表面側がＡｕである。
【００３１】
上記のような本発明の窒化ガリウム系化合物半導体発光素子の製造工程について図６に示す。
【００３２】
まず、実施の形態１と同様に形成されたｐ型窒化ガリウム系化合物半導体３の表面に、電子ビーム蒸着法で２．５ｎｍの膜厚のＮｉからなる第１の透光性電極１１を形成する。また、ｎ型窒化ガリウム系化合物半導体層２上にｎ型電極６を形成した。この時の製造工程断面図を図６（ａ）に示す。
【００３３】
この上に、電子ビーム蒸着法で形成されたＮｉからなるボンディング用電極８を形成する。この時の製造工程断面図を図６（ｂ）に示す。
【００３４】
その上に電子ビーム蒸着法で形成されたＡｕからなるボンディング用電極９を形成した。ｐ型ボンディング用電極９を覆うように、ＮｉとＡｕとを順に交互に積層した第２の透光性電極１２を電子ビーム蒸着法で２．５ｎｍずつの膜厚で形成する。この時の製造工程断面図を図６（ｃ）に示す。
【００３５】
第１の透光性電極１１とＡｕからなるボンディング用電極９の密着力を向上させるために、第１の透光性電極１１とＡｕからなるボンディング用電極９の間にＮｉからなるボンディング用電極８を形成している。このためワイヤーボンディング時にボンディング用電極８、９の剥がれがなくなる。
【００３６】
本実施の形態では、第１の透光性電極１１としてＮｉ単体を使用したが、ＮｉとＡｕとの積層構造や交互に積層することで二層膜、多層膜としてもよい。この時の断面図を図６（ｄ）、図６（ｅ）に示す。また、第２の透光性電極１２も、ＮｉとＡｕとの積層構造や複数層交互に積層した多層膜としても、第２の透光性電極１２の表面をＡｕとすれば構わない。
【００３７】
第１、第２の透光性電極形成方法は、電子ビーム蒸着法、真空蒸着法、スパッタリング法等を用いる。
【００３８】
実施の形態３において作製された窒化ガリウム系化合物半導体発光素子は、ｐ型窒化ガリウム系化合物半導体層３上の第１の透光性電極１１のＮｉからなる膜の膜厚を厚くできる自由度があるため、オーミック特性及び密着性がより向上できる。
【００３９】
また、本実施の形態では、ｎ型窒化ガリウム系化合物半導体層の上にｐ型窒化ガリウム系化合物半導体層を積層させた窒化ガリウム系化合物半導体発光素子を用いたが、ｐ型窒化ガリウム系化合物半導体層の上にｎ型窒化ガリウム系化合物半導体層を積層させた窒化ガリウム系化合物半導体発光素子を用いても構わない。
【００４０】
【発明の効果】
本発明によれば、電極を発光透光面とする窒化ガリウム系化合物半導体発光素子において、透光性電極がＮｉと熱的に安定な金属とを交互に積層した多層構造であることによって、ボンディング時にかかる力によっても窒化ガリウム系化合物半導体層とボンディング用電極との剥がれが生じないように密着性を向上できる。また、透光性電極の窒化ガリウム系化合物半導体側にＮｉ、表面側に熱的に安定な金属を配置するように多層構造を形成することにより、アニール中に生じるＮｉの変質を防ぐことができ、窒化ガリウム半導体層と透光性電極のオーミック特性を維持することができる。
【００４１】
また、ボンディング用電極を覆うようにＮｉ及びＡｕからなる多層構造の透光性電極を形成することにより、ｐ型窒化ガリウム系化合物半導体層とボンディング用電極の付着力を一層強めることができる。また、ボンディング用電極のアニール温度が透光性電極のアニール温度より高く、かつ、ボンディング用電極のアニールを透光性電極のアニールの前に行うことにより、透光性電極の変質が発生することなく、透光性電極とボンディング用電極の密着力を強くできる。
【００４２】
そのために、オーミック特性とボンディング時の電極剥がれの問題が解決でき、発光効率及び信頼性の良好な窒化ガリウム系化合物半導体発光素子の電極構造が実現できる。
【００４３】
さらに、ボンディング電極をＮｉで形成することで、透光性電極とボンディング用電極との密着力を向上させるために透光性電極とボンディング用電極の間に密着力が向上する。
【００４４】
また、熱的に安定な金属として、Ａｕ、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｈが好ましい。
【図面の簡単な説明】
【図１】実施の形態１に記載の窒化ガリウム系化合物半導体発光素子の電極構造の摸式図である。
【図２】実施の形態２に記載の本発明の窒化ガリウム系化合物半導体発光素子の電極構造の摸式図である。
【図３】実施の形態３に記載の本発明の窒化ガリウム系化合物半導体発光素子の電極構造の模式図である。
【図４】実施の形態１に記載の窒化ガリウム系化合物半導体発光素子の電極構造の作製工程を示す図である。
【図５】実施の形態２に記載の窒化ガリウム系化合物半導体発光素子の電極構造の作製工程を示す図である。
【図６】実施の形態３に記載の窒化ガリウム系化合物半導体発光素子の電極構造の作製工程を示す図である。
【図７】従来の窒化ガリウム系化合物半導体発光素子の電極構造の摸式図である。
【符号の説明】
１ 絶縁性のサファイア基板
２ ｎ型窒化ガリウム系化合物半導体層
３ ｐ型窒化ガリウム系化合物半導体層
４ 透光性電極
５ ボンディング用電極
６ ｎ型電極
７ 透光性電極
８ Ｎｉからなるボンディング用電極
９ Ａｕからなるボンディング用電極
１０ 透光性電極
１１ 第１の透光性電極
１２ 第２の透光性電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode structure of a gallium nitride-based compound semiconductor light-emitting device capable of emitting light in a blue to ultraviolet region, and in particular, an electrode of a gallium nitride-based compound semiconductor light-emitting device having a translucent electrode on a gallium nitride-based compound semiconductor layer. Concerning structure.
[0002]
[Prior art]
As an electrode structure of a conventional gallium nitride compound semiconductor light emitting device, a gallium nitride compound semiconductor light emitting device described in JP-A-7-10663 is shown in FIG.
[0003]
First, an n-type gallium nitride-based compound semiconductor layer 2 and a p-type gallium nitride-based compound semiconductor layer 3 are formed on an insulating sapphire substrate 1, and a transparent layer made of an alloy in which Ni and Au are stacked on the surface thereof. A bonding electrode 5 made of an alloy containing at least one kind of Ti, Ni, In, and Pt in addition to the photoelectrode 4 and Au alone or Au. An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2.
[0004]
[Problems to be solved by the invention]
However, the translucent electrode 4 is formed of a very thin film in order to maintain translucency in the emission wavelength region. Therefore, in order to obtain ohmic characteristics between the translucent electrode 4 and the p-type gallium nitride compound semiconductor layer 3, Ni of the translucent electrode is altered from the surface exposed during the heat treatment (during annealing). As a result, the luminous efficiency is reduced. Such Ni alteration occurs because a gallium nitride-based material is difficult to perform ohmic contact sufficiently, and thus heat treatment must be performed at a high temperature.
[0005]
Furthermore, since the translucent electrode 4 is a very thin film, the adhesion between the p-type gallium nitride compound semiconductor layer 3 and the bonding electrode 5 is poor, and there is a problem that the translucent electrode 4 is easily peeled off during wire bonding.
[0006]
Therefore, by eliminating the peeling of the translucent electrode 4 and the bonding electrode 5 at the time of wire bonding, the yield at the time of wire bonding is improved, and the gallium nitride excellent in reliability that can suppress the decrease in luminous efficiency An object of the present invention is to provide an electrode structure of a compound semiconductor light emitting device.
[0007]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problem. A translucent electrode in which at least one pair of Ni thin films and Au thin films are alternately stacked on a gallium nitride compound semiconductor light emitting layer is provided. And having a bonding electrode on the translucent electrode, wherein the translucent electrode is formed by alternately laminating at least one pair of thin films made of Ni and thin films made of Au, and the gallium nitride compound semiconductor side is Ni The surface side is made of Au. By forming such a structure, the Ni of the translucent electrode can be prevented from being altered, the ohmic characteristics of the gallium nitride compound semiconductor layer and the translucent electrode are maintained, and the luminous efficiency associated therewith is reduced. It is possible not to cause it.
[0008]
A translucent electrode having a bonding electrode on a gallium nitride-based compound semiconductor light-emitting layer, wherein at least one pair of Ni thin films and Au thin films are alternately stacked so as to cover the bonding electrodes The translucent electrode is characterized in that the gallium nitride compound semiconductor side is made of Ni and the surface side is made of Au.
[0009]
Further, by forming a multi-layer translucent electrode made of Ni and Au so as to cover the bonding electrode, the adhesion between the p-type gallium nitride compound semiconductor layer and the bonding electrode can be further increased. Furthermore, by making the outermost surface of the translucent electrode having a multilayer structure Au, adhesion with the Au wire can be strengthened. Therefore, it is possible to reduce peeling of the bonding electrode during wire bonding.
[0010]
Further, a p-type gallium nitride compound semiconductor layer and a bonding electrode Au are formed by forming a bonding electrode made of Ni that improves adhesion between the translucent electrode having a multilayer structure and the bonding electrode Au made of Au. The adhesion of becomes stronger.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described based on specific embodiments.
[0012]
(Embodiment 1)
A schematic diagram of an electrode structure of a gallium nitride-based compound semiconductor light-emitting device manufactured according to the present invention is shown in FIG.
[0013]
An n-type gallium nitride compound semiconductor layer 2 and a p-type gallium nitride compound semiconductor layer 3 are formed on an insulating sapphire substrate 1, and Ni and Au are alternately stacked on the surface in this order. , A bonding electrode 8 made of Ni alone and a bonding electrode 9 made of Au alone are formed. The translucent electrode 7 is made of Ni on the most p-type gallium nitride compound semiconductor layer 3 side, and made of Au on the most surface side. An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2.
[0014]
FIG. 4 shows the manufacturing process of the gallium nitride compound semiconductor light emitting device of the present invention as described above.
[0015]
First, the n-type gallium nitride compound semiconductor layer 2 is stacked on the insulating sapphire substrate 1 by MOCVD. Next, the p-type gallium nitride compound semiconductor layer 3 is stacked, and Ni and Au are alternately stacked in a desired region on the surface of the p-type gallium nitride compound semiconductor layer 3 by 2.5 nm each by electron beam evaporation. The translucent electrode 7 is formed.
The film thickness of the translucent electrode 7 is set to a thickness that allows sufficient transmission at the emission wavelength.
[0016]
In order to obtain ohmic characteristics between the p-type gallium nitride compound layer 3 and Ni of the translucent electrode 7, annealing at 500 ° C. is performed for 3 minutes. An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2. A manufacturing process sectional view at this time is shown in FIG.
[0017]
Next, a bonding electrode 8 made of Ni is formed on the translucent electrode 7 by an electron beam evaporation method, and a bonding electrode 9 made of Au is further formed. A manufacturing process sectional view at this time is shown in FIG.
[0018]
In the present embodiment, the translucent electrode 7 has a multilayer structure in which Ni and Au are alternately laminated, but may have a multilayer structure composed of a thin film made of a metal that is thermally stable with respect to the annealing temperature and Ni. . As the thermally stable metal, a metal composed of at least one of Au, Cu, Pt, Pd, Rh and the like is preferable. As a method for forming the translucent electrode 7, an electron beam evaporation method, a vacuum evaporation method, or a sputtering method may be used. The bonding electrode 9 made of Au was made of Au in order to improve the adhesion with the Au wire.
[0019]
(Embodiment 2)
FIG. 2 shows a schematic diagram of an electrode structure of another gallium nitride-based compound semiconductor light-emitting device manufactured according to the present invention.
[0020]
An n-type gallium nitride compound semiconductor layer 2 and a p-type gallium nitride compound semiconductor layer 3 are formed on an insulating sapphire substrate 1, and a bonding electrode 8 made of Ni is formed on the surface thereof. Yes. Furthermore, a bonding electrode 9 made of Au is formed thereon, and a translucent electrode 10 in which Ni and Au are alternately laminated so as to cover the bonding electrode 9 made of Au is formed. An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2. The translucent electrode 10 is made of Ni on the p-type gallium nitride compound semiconductor layer side and made of Au on the surface side.
[0021]
FIG. 5 shows a manufacturing process of the gallium nitride compound semiconductor light emitting device of the present invention as described above.
[0022]
First, a bonding electrode 8 made of Ni formed by an electron beam evaporation method is formed on the surface of a p-type gallium nitride compound semiconductor layer 3 formed in the same manner as in the first embodiment, and an electron beam evaporation is formed thereon. A bonding electrode 9 made of Au formed by the method was formed. Next, annealing of the bonding electrode 8 made of Ni and the bonding electrode 9 made of Au is performed at 500 ° C. for 3 minutes. A manufacturing process sectional view at this time is shown in FIG.
[0023]
A translucent electrode 10 in which Ni and Au are alternately stacked in a desired region on the surface of the p-type gallium nitride compound semiconductor layer 3 so as to cover the bonding electrode 9 made of Au is formed by electron beam evaporation to have a thickness of 15 nm. Form with thickness. Next, annealing of the translucent electrode 10 is performed at 400 ° C. for 3 minutes. A manufacturing process sectional view at this time is shown in FIG.
[0024]
Even if the translucent electrode 10 is not a two-layer structure but a multilayer structure, the p-type gallium nitride compound semiconductor layer side may be Ni and the surface side may be Au. FIG. 5C shows a cross-sectional view of the manufacturing process when the multilayer structure is adopted.
[0025]
Next, when wire bonding is performed, since the translucent electrode 10 is a thin film, the translucent electrode 10 is pierced and connected to the bonding electrode 9.
[0026]
Here, the annealing of the bonding electrodes 8 and 9 is performed before the annealing of the translucent electrode 10, and the annealing temperature of the translucent electrode 10 is lower than the annealing temperature of the bonding electrodes 8 and 9. Therefore, the translucent electrode 10 is not altered. Further, by forming a translucent electrode 10 having a structure in which Ni and Au are laminated on the surface of the bonding electrode 9 made of Au, the p-type gallium nitride compound semiconductor layer 3 and the bonding electrode 8 made of Ni are formed. Can increase the adhesive strength.
[0027]
The translucent electrode 10 may have a multilayer structure composed of at least one of Au, Cu, Pt, Pd, Rh and the like which are thermally stable metals and Ni. The bonding electrode 9 made of Au was made of Au in order to improve the adhesion with the Au wire.
[0028]
As a method for forming the light-transmitting electrode, an electron beam evaporation method, a vacuum evaporation method, a sputtering method, or the like can be used.
[0029]
(Embodiment 3)
FIG. 3 shows a schematic diagram of an electrode structure of a gallium nitride-based compound semiconductor light-emitting device manufactured according to still another embodiment of the present invention.
[0030]
An n-type gallium nitride compound semiconductor layer 2 and a p-type gallium nitride compound semiconductor layer 3 are formed on an insulating sapphire substrate 1, and a first translucent electrode 11 made of Ni is formed thereon. A bonding electrode 8 made of Ni is formed thereon. Further, a bonding electrode 9 made of Au is formed thereon, and Ni and Au are alternately formed in a thickness of 2.5 nm by electron beam evaporation so as to cover the bonding electrode 9 made of Au. A laminated second translucent electrode 12 is formed. An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2. As for the 2nd translucent electrode 12, the 1st translucent electrode side is Ni and the surface side is Au.
[0031]
The manufacturing process of the gallium nitride compound semiconductor light emitting device of the present invention as described above is shown in FIG.
[0032]
First, on the surface of the p-type gallium nitride compound semiconductor 3 formed in the same manner as in the first embodiment, the first translucent electrode 11 made of Ni having a thickness of 2.5 nm is formed by electron beam evaporation. . An n-type electrode 6 was formed on the n-type gallium nitride compound semiconductor layer 2. A manufacturing process sectional view at this time is shown in FIG.
[0033]
On this, a bonding electrode 8 made of Ni formed by electron beam evaporation is formed. A manufacturing process sectional view at this time is shown in FIG.
[0034]
A bonding electrode 9 made of Au formed by electron beam evaporation was formed thereon. A second translucent electrode 12 in which Ni and Au are alternately laminated in order is formed to have a film thickness of 2.5 nm by electron beam evaporation so as to cover the p-type bonding electrode 9. A manufacturing process sectional view at this time is shown in FIG.
[0035]
In order to improve the adhesion between the first translucent electrode 11 and the bonding electrode 9 made of Au, the bonding electrode made of Ni is placed between the first translucent electrode 11 and the bonding electrode 9 made of Au. 8 is formed. For this reason, the bonding electrodes 8 and 9 are not peeled off during wire bonding.
[0036]
In the present embodiment, Ni alone is used as the first translucent electrode 11, but a multilayer structure of Ni and Au may be used, or alternatively, a two-layer film or a multilayer film may be formed. Sectional views at this time are shown in FIGS. 6 (d) and 6 (e). Further, the second translucent electrode 12 may also be a laminated structure of Ni and Au or a multilayer film in which a plurality of layers are alternately laminated as long as the surface of the second translucent electrode 12 is Au.
[0037]
As the first and second translucent electrode forming methods, an electron beam evaporation method, a vacuum evaporation method, a sputtering method, or the like is used.
[0038]
The gallium nitride compound semiconductor light-emitting device manufactured in the third embodiment has a degree of freedom to increase the thickness of the Ni film of the first translucent electrode 11 on the p-type gallium nitride compound semiconductor layer 3. Therefore, ohmic characteristics and adhesion can be further improved.
[0039]
In this embodiment, a gallium nitride compound semiconductor light emitting device in which a p-type gallium nitride compound semiconductor layer is stacked on an n-type gallium nitride compound semiconductor layer is used. However, a p-type gallium nitride compound semiconductor is used. A gallium nitride compound semiconductor light emitting element in which an n-type gallium nitride compound semiconductor layer is stacked on the layer may be used.
[0040]
【The invention's effect】
According to the present invention, in a gallium nitride-based compound semiconductor light-emitting device using an electrode as a light-transmitting light-transmitting surface, the light-transmitting electrode has a multilayer structure in which Ni and a thermally stable metal are alternately stacked. Adhesion can be improved so that peeling between the gallium nitride compound semiconductor layer and the bonding electrode does not occur even with a force applied sometimes. In addition, by forming a multi-layer structure in which Ni is placed on the gallium nitride compound semiconductor side of the translucent electrode and a thermally stable metal is placed on the surface side, it is possible to prevent Ni deterioration that occurs during annealing. The ohmic characteristics of the gallium nitride semiconductor layer and the translucent electrode can be maintained.
[0041]
Further, by forming a multi-layer translucent electrode made of Ni and Au so as to cover the bonding electrode, the adhesion between the p-type gallium nitride compound semiconductor layer and the bonding electrode can be further increased. Further, the annealing temperature of the bonding electrode is higher than the annealing temperature of the translucent electrode, and the annealing of the bonding electrode is performed before the annealing of the translucent electrode, thereby causing the alteration of the translucent electrode. In addition, the adhesion between the translucent electrode and the bonding electrode can be increased.
[0042]
Therefore, the problem of ohmic characteristics and electrode peeling at the time of bonding can be solved, and an electrode structure of a gallium nitride-based compound semiconductor light-emitting element with good luminous efficiency and reliability can be realized.
[0043]
Further, by forming the bonding electrode with Ni, the adhesion between the translucent electrode and the bonding electrode is improved in order to improve the adhesion between the translucent electrode and the bonding electrode.
[0044]
Further, Au, Cu, Pt, Pd, and Rh are preferable as the thermally stable metal.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an electrode structure of a gallium nitride-based compound semiconductor light-emitting element described in Embodiment 1;
2 is a schematic diagram of an electrode structure of a gallium nitride-based compound semiconductor light-emitting element according to the present invention described in Embodiment 2. FIG.
3 is a schematic diagram of an electrode structure of a gallium nitride-based compound semiconductor light-emitting element according to the present invention described in Embodiment 3. FIG.
4 is a diagram showing a manufacturing process of an electrode structure of the gallium nitride-based compound semiconductor light-emitting element described in Embodiment 1; FIG.
5 is a diagram showing a manufacturing process of an electrode structure of a gallium nitride-based compound semiconductor light-emitting element described in Embodiment 2; FIG.
6 is a diagram showing a manufacturing process of an electrode structure of a gallium nitride-based compound semiconductor light-emitting element described in Embodiment 3; FIG.
FIG. 7 is a schematic diagram of an electrode structure of a conventional gallium nitride-based compound semiconductor light emitting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulating sapphire substrate 2 N-type gallium nitride compound semiconductor layer 3 P-type gallium nitride compound semiconductor layer 4 Translucent electrode 5 Bonding electrode 6 N-type electrode 7 Translucent electrode 8 Bonding electrode 9 made of Ni Bonding electrode 10 made of Au Translucent electrode 11 First translucent electrode 12 Second translucent electrode

Claims (7)

窒化ガリウム系化合物半導体発光層の上に、Ｎｉからなる薄膜とＣｕ、Ｐｄ、Ｒｈの群から１つ以上選択された金属よりなる薄膜とが交互に１組み以上積層されてなる透光性電極を有し、
前記透光性電極上にボンディング用電極を有し、
前記透光性電極は、窒化ガリウム系化合物半導体側にＮｉからなる薄膜が位置し、表面側に前記選択された金属からなる薄膜が位置する構造である
ことを特徴とする窒化ガリウム系化合物半導体発光素子の電極構造。On the gallium nitride-based compound semiconductor light-emitting layer, a thin film made of Ni and Cu, Pd, a translucent electrode and the thin film made of one or more metal selected from the group are laminated alternately one set or more Rh Have
Having a bonding electrode on the translucent electrode;
The translucent electrode has a structure in which a thin film made of Ni is located on the gallium nitride compound semiconductor side and a thin film made of the selected metal is located on the surface side. The electrode structure of the element. 前記透光性電極は、Ｎｉからなる薄膜とＣｕ、Ｐｄ、Ｒｈの群から１つ以上選択された金属よりなる薄膜とが交互に２組み以上積層されてなるものである
ことを特徴とする請求項１に記載の窒化ガリウム系化合物半導体発光素子の電極構造。The translucent electrode claims, characterized in that a thin film made of Ni and Cu, Pd, and a thin film made of one or more metal selected from the group consisting of Rh are those formed by laminating alternately two sets or more Item 2. An electrode structure of a gallium nitride-based compound semiconductor light-emitting device according to Item 1 . 窒化ガリウム系化合物半導体発光層の上に、ボンディング用電極を有し、
前記ボンディング用電極の上に、当該ボンディング用電極の上面を全面的に覆う、Ｎｉからなる薄膜と熱的に安定な金属からなる薄膜とが交互に１組み以上積層されてなる透光性電極を有し、
前記透光性電極は、窒化ガリウム系化合物半導体側にＮｉからなる薄膜が位置し、表面側に前記選択された金属からなる薄膜が位置する構造である
ことを特徴とする窒化ガリウム系化合物半導体発光素子の電極構造。On the gallium nitride compound semiconductor light emitting layer, it has a bonding electrode,
A translucent electrode in which one or more pairs of thin films made of Ni and thin films made of a thermally stable metal are alternately stacked on the bonding electrode so as to cover the entire upper surface of the bonding electrode. Have
The translucent electrode is positioned a thin film made of Ni to a gallium nitride-based compound semiconductor side, gallium nitride-based compound, wherein the thin film made of the selected metal on the surface side of the structure you location position Electrode structure of semiconductor light emitting device. 前記熱的に安定な金属が、Ｃｕ、Ｐｄ、Ｒｈの群から１つ以上選択された金属よりなるThe thermally stable metal is made of one or more metals selected from the group consisting of Cu, Pd, and Rh.
ことを特徴とする請求項３に記載の窒化ガリウム系化合物半導体発光素子の電極構造。The electrode structure of the gallium nitride-based compound semiconductor light-emitting device according to claim 3. 窒化ガリウム系化合物半導体発光層の上に、第１の透光性電極を有し、前記第１の透光性電極上にボンディング用電極を有し、
前記ボンディング用電極の上に、当該ボンディング用電極を覆うように、Ｎｉからなる薄膜と熱的に安定な金属からなる薄膜とが交互に１組み以上積層されてなる第２の透光性電極を有し、
前記第２の透光性電極は、第１の透光性電極側にＮｉからなる薄膜が位置し、表面側に熱的に安定な金属からなる薄膜が位置する構造である
ことを特徴とする窒化ガリウム系化合物半導体発光素子の電極構造。On the gallium nitride compound semiconductor light emitting layer, it has a first translucent electrode, and has a bonding electrode on the first translucent electrode,
On the bonding electrode so as to cover the bonding electrode, the second light-transmitting electrode and a thin film made of a thin film and thermally stable metal composed of Ni are laminated alternately one set or more Have
The second translucent electrode has a structure in which a thin film made of Ni is located on the first translucent electrode side, and a thin film made of a thermally stable metal is located on the surface side. Electrode structure of gallium nitride compound semiconductor light emitting device. 前記熱的に安定な金属が、Ａｕ、Ｃｕ、Ｐｔ、Ｐｄ、Ｒｈの少なくとも１種類からなる
ことを特徴とする請求項５に記載の窒化ガリウム系化合物半導体発光素子の電極構造。It said thermally stable metal, Au, Cu, Pt, Pd , an electrode structure of a gallium nitride-based compound semiconductor light-emitting device according to claim 5, characterized in that it consists of at least one of Rh. 前記ボンディング用電極は、Ｎｉからなるボンディング用電極と、その上にＡｕからなるボンディング用電極が積層された構造である
ことを特徴とする請求項１乃至６に記載の窒化ガリウム系化合物半導体発光素子の電極構造。Said bonding electrodes, and the bonding electrode made of Ni, the gallium nitride-based compound semiconductor light-emitting device according to claim 1 to 6 bonding electrode made of Au thereon characterized in that it is a laminated structure Electrode structure.
JP25787996A 1996-09-30 1996-09-30 Electrode structure of gallium nitride compound semiconductor light emitting device Expired - Fee Related JP3710573B2 (en)

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