JP3344296B2 - Electrodes for semiconductor light emitting devices - Google Patents
Electrodes for semiconductor light emitting devicesInfo
- Publication number
- JP3344296B2 JP3344296B2 JP28877097A JP28877097A JP3344296B2 JP 3344296 B2 JP3344296 B2 JP 3344296B2 JP 28877097 A JP28877097 A JP 28877097A JP 28877097 A JP28877097 A JP 28877097A JP 3344296 B2 JP3344296 B2 JP 3344296B2
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- Prior art keywords
- electrode
- semiconductor
- metal
- layer
- thin film
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/01—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
- H01L24/02—Bonding areas ; Manufacturing methods related thereto
- H01L24/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L24/05—Structure, shape, material or disposition of the bonding areas prior to the connecting process of an individual bonding area
-
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- H01—ELECTRIC ELEMENTS
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- H01L2224/02—Bonding areas; Manufacturing methods related thereto
- H01L2224/04—Structure, shape, material or disposition of the bonding areas prior to the connecting process
- H01L2224/06—Structure, shape, material or disposition of the bonding areas prior to the connecting process of a plurality of bonding areas
- H01L2224/0601—Structure
- H01L2224/0603—Bonding areas having different sizes, e.g. different heights or widths
-
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- H01L2224/42—Wire connectors; Manufacturing methods related thereto
- H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
- H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
- H01L2224/45001—Core members of the connector
- H01L2224/45099—Material
- H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
- H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
- H01L2224/45144—Gold (Au) as principal constituent
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/01005—Boron [B]
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/01022—Titanium [Ti]
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Description
【０００１】[0001]
【発明の属する技術分野】本発明は、半導体発光素子に
用いられる電極に係わり、特に透光性の第１の電極とワ
イヤボンド用の第２の電極とからなる半導体発光素子用
の電極に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode used for a semiconductor light emitting device, and more particularly to an electrode for a semiconductor light emitting device comprising a first light-transmitting electrode and a second electrode for wire bonding.
【０００２】[0002]
【従来の技術】近年、短波長光発光素子用の半導体材料
としてＧａＮ系化合物半導体材料が注目を集めている。
ＧａＮ系化合物半導体は、サファイア単結晶を始めとし
て、種々の酸化物基板や III−Ｖ族化合物半導体を基板
として、その上に有機金属気相化学反応法（ＭＯＣＶＤ
法）や分子線エピタキシー法（ＭＢＥ法）等によって形
成される。2. Description of the Related Art In recent years, GaN-based compound semiconductor materials have attracted attention as semiconductor materials for short-wavelength light-emitting devices.
GaN-based compound semiconductors are made of various oxide substrates such as sapphire single crystals, or III-V compound semiconductors as substrates, and metal organic chemical vapor deposition (MOCVD)
Method) or molecular beam epitaxy method (MBE method).
【０００３】サファイア基板等の電気的に絶縁体である
基板を用いた発光素子では、ＧａＡｓ、ＧａＰ等の半導
体基板を使用した発光素子とは異なり、基板裏面に電極
を設けることができない。よって、正、負一対の電極を
発光素子の同じ面に形成する必要がある。In a light emitting device using a substrate which is an electrically insulating material such as a sapphire substrate, unlike a light emitting device using a semiconductor substrate such as GaAs or GaP, an electrode cannot be provided on the back surface of the substrate. Therefore, it is necessary to form a pair of positive and negative electrodes on the same surface of the light emitting element.
【０００４】また、ＧａＮ系化合物半導体材料の特性と
しては、横方向への電流拡散が小さい。原因は、エピタ
キシャル結晶中に多く存在する基板から表面へ貫通する
転位の存在であることが考えられるが、詳しいことは判
っていない。この特性のため、ＧａＮ系化合物半導体材
料を用いた発光素子では、電極を形成して通電発光させ
た場合でも、発光領域は電極直下に限定され電極の周囲
には広がりにくい。したがって発光領域は電極直下に限
られるため、透光性の電極を用いて、電極を通して発光
を上方に取り出す技術が開示されている（特開平６−３
１４８２２）。Further, as a characteristic of the GaN-based compound semiconductor material, current diffusion in the lateral direction is small. The cause is considered to be the existence of dislocations that penetrate from the substrate to the surface, which are often present in the epitaxial crystal, but the details are not known. Due to this characteristic, in a light-emitting element using a GaN-based compound semiconductor material, even when an electrode is formed and current is emitted, the light-emitting region is limited to immediately below the electrode and does not easily spread around the electrode. Therefore, since the light-emitting region is limited to a region directly below the electrode, a technique of extracting light upward through the electrode using a translucent electrode has been disclosed (Japanese Patent Laid-Open No. 6-3).
14822).
【０００５】ここで、透光性の電極は透光性で導電性を
有する金属酸化物薄膜や金属薄膜などで形成されるが、
金属酸化物薄膜は金線との接着性が悪いため、また金属
薄膜は膜としての強度が小さいため、一般に透光性の電
極には直接外部から電流を注入するためのワイヤを結線
することができない。そのためこの透光性の電極とは別
に、透光性の電極と電気的に導通したワイヤボンド用の
パッド電極を形成し、ここにワイヤを結線して外部から
の電流を透光性の電極に通じる構造の電極が一般に用い
られている。例として特開平６−３１４８２２で開示さ
れた電極の断面構造を図１に示す。図１で１、２はそれ
ぞれ透光性の電極およびパッド電極である。Here, the light-transmitting electrode is formed of a light-transmitting and conductive metal oxide thin film or metal thin film.
Since metal oxide thin films have poor adhesion to gold wires, and metal thin films have low strength as a film, generally a wire for injecting current from the outside directly to a transparent electrode should be connected. Can not. Therefore, separately from this translucent electrode, a pad electrode for wire bonding electrically connected to the translucent electrode is formed, and a wire is connected here to allow external current to flow to the translucent electrode. Electrodes having a common structure are generally used. As an example, FIG. 1 shows a sectional structure of an electrode disclosed in JP-A-6-314822. In FIG. 1, reference numerals 1 and 2 are a translucent electrode and a pad electrode, respectively.
【０００６】図１に示すような構成を持つ電極におい
て、従来透光性電極１を金属の薄膜で形成した場合に、
半導体と電極金属との接触特性の向上を目的とした熱処
理の際に該金属薄膜が液滴状に凝集して塊となり、薄膜
としての連続性を失う「ボールアップ」と呼ばれる現象
が起きていた。そこで我々は、これを抑えるために該金
属薄膜の上に透明な金属酸化物からなる薄膜を形成する
技術を開発した（特願平９−１１８３１５）。In the electrode having the structure shown in FIG. 1, when the conventional translucent electrode 1 is formed of a metal thin film,
During the heat treatment for the purpose of improving the contact characteristics between the semiconductor and the electrode metal, the metal thin film aggregates in a droplet form into a lump, and a phenomenon called "ball-up" occurs, which loses continuity as a thin film. . Therefore, in order to suppress this, we have developed a technique for forming a thin film made of a transparent metal oxide on the metal thin film (Japanese Patent Application No. Hei 9-118315).
【０００７】また、図１に示すパッド電極２は、通常Ａ
ｕやＡｌなどの金属により１μｍ程度の厚い膜厚で形成
される。そのためパッド電極２は透光性を持たず、パッ
ド電極の直下で発生した発光はパッド電極に遮られて外
部に取り出すことができない。従って、パッド電極の直
下の部分の半導体には電流を注入せず、その分の電流を
透光性の電極に流すような構造とすることが半導体発光
素子の発光輝度の向上につながる。そのための素子構造
として、我々はパッド電極の下面において半導体と接触
する金属として、透光性の電極の下面において半導体と
接触する金属よりも接触抵抗値の高い金属を選択して形
成した電極という技術を開発した（特願平９−２３６１
１７）。The pad electrode 2 shown in FIG.
It is formed of a metal such as u or Al with a thickness of about 1 μm. Therefore, the pad electrode 2 does not have translucency, and light emitted immediately below the pad electrode is blocked by the pad electrode and cannot be extracted outside. Therefore, a structure in which a current is not injected into the semiconductor immediately below the pad electrode and the current is flowed to the light-transmitting electrode leads to an improvement in light emission luminance of the semiconductor light emitting element. As an element structure for this purpose, we have selected a metal that has a higher contact resistance than the metal that contacts the semiconductor on the lower surface of the translucent electrode as the metal that contacts the semiconductor on the lower surface of the pad electrode. (Japanese Patent Application 9-2361)
17).
【０００８】[0008]
【発明が解決しようとする課題】従来の透光性電極にお
いては、図１に示したようにパッド電極を透光性の電極
の上に形成する構造が一般的であった。しかし、この様
な構造とした場合には、透光性電極の最上層とパッド電
極の下面の金属との間の接着性が低いと、電極作製の工
程でパッド電極が剥がれて落ちてしまうことがあった。The conventional light-transmitting electrode generally has a structure in which a pad electrode is formed on the light-transmitting electrode as shown in FIG. However, in the case of such a structure, if the adhesiveness between the uppermost layer of the translucent electrode and the metal on the lower surface of the pad electrode is low, the pad electrode may be peeled off during the electrode manufacturing process. was there.
【０００９】また、我々が特願平９−１１８３１５にお
いて開示したように透光性電極を半導体側から順に金属
および金属酸化物という層構造で形成した場合には、一
般に表面側の金属酸化物薄膜には導電性がないため、図
１に示したように透光性電極の上に金属のパッド電極を
形成する構造では、パッド電極と透光性電極の間の導通
を図ることができず、透光性電極に電流を流すことがで
きなかった。このため、該金属酸化物薄膜として導電性
の金属酸化物を用いることが考えられるが、その場合で
も金属酸化物の抵抗率は一般に金属よりも大きいため発
光素子の駆動電圧が高くなってしまうという欠点があっ
た。When the light-transmitting electrode is formed in a layered structure of a metal and a metal oxide in order from the semiconductor side as disclosed in Japanese Patent Application No. Hei 9-118315, a metal oxide thin film on the surface side is generally used. Since there is no conductivity, a structure in which a metal pad electrode is formed on the translucent electrode as shown in FIG. 1 cannot achieve conduction between the pad electrode and the translucent electrode, Current could not be passed through the translucent electrode. For this reason, it is conceivable to use a conductive metal oxide as the metal oxide thin film, but even in such a case, the driving voltage of the light emitting element is increased because the resistivity of the metal oxide is generally higher than that of the metal. There were drawbacks.
【００１０】さらに図１に示した構造の電極では、前述
の特願平９−２３６１１７で示したような半導体と接触
する金属をパッド電極と透光性の電極とで異なる金属と
することができなかった。すなわち、透光性の電極上に
パッド電極を形成した場合、パッド電極下で半導体と接
触する金属は透光性電極の材料と同じであり、パッド電
極と透光性電極でそれぞれ望まれる電気特性を有する金
属を選択して使用することができなかった。Further, in the electrode having the structure shown in FIG. 1, the metal in contact with the semiconductor as described in Japanese Patent Application No. 9-236117 can be different between the pad electrode and the translucent electrode. Did not. That is, when a pad electrode is formed on a translucent electrode, the metal in contact with the semiconductor under the pad electrode is the same as the material of the translucent electrode, and the electrical characteristics desired for the pad electrode and the translucent electrode, respectively. Could not be selected and used.
【００１１】そこで上記の問題点を解決するため、透光
性電極の一部に半導体表面が露出した「窓部」を形成
し、その部分にパッド電極を形成してパッド電極と半導
体とを直接接触させる技術が公開されている（特開平７
−９４７８２）。この技術に係わる電極の構造を図２に
示す。図２において１は透光性電極である。透光性電極
１には窓部３が形成されており、該窓部３にパッド電極
２が形成されている。Therefore, in order to solve the above-mentioned problem, a "window portion" in which the semiconductor surface is exposed is formed in a part of the light-transmitting electrode, and a pad electrode is formed in that part to directly connect the pad electrode and the semiconductor. A contacting technique has been disclosed (Japanese Patent Laid-Open No.
-94782). FIG. 2 shows the structure of an electrode according to this technique. In FIG. 2, reference numeral 1 denotes a translucent electrode. A window 3 is formed in the translucent electrode 1, and a pad electrode 2 is formed in the window 3.
【００１２】図２に示した構造の電極では、透光性電極
において半導体と接触する金属とパッド電極において半
導体と接触する金属とを別の材料にすることができる。
これにより、パッド電極で半導体と接触する金属を半導
体との接着性が強くかつ半導体との接触抵抗が高い金属
とし、透光性電極で半導体と接触する金属を半導体の接
触抵抗が低い金属とすることが可能となった。In the electrode having the structure shown in FIG. 2, the metal in contact with the semiconductor in the translucent electrode and the metal in contact with the semiconductor in the pad electrode can be made of different materials.
As a result, the metal that contacts the semiconductor at the pad electrode is a metal that has strong adhesion to the semiconductor and has a high contact resistance with the semiconductor, and the metal that contacts the semiconductor at the translucent electrode is a metal with a low contact resistance of the semiconductor. It became possible.
【００１３】しかしながら、我々が特願平９−１１８３
１５において採用したように透光性電極の表面を金属酸
化物薄膜とした場合、図２に示した構造の電極では、表
面の金属酸化物は導電性が低いため、透光性電極の金属
層とパッド電極との電気的接触はわずかに透光性電極の
金属層の側面において成されるのみである。さらに例え
ば透光性電極において金属酸化物層が金属層の縁よりわ
ずかでも張り出した形状となっていると、パッド電極を
蒸着により形成する際に透光性電極とパッド電極との側
面での電気接触がうまく得られないことがあった。[0013] However, we have disclosed in Japanese Patent Application No. 9-1183.
In the case where the surface of the translucent electrode is a metal oxide thin film as employed in No. 15, the metal oxide on the surface of the electrode having the structure shown in FIG. Electrical contact between the pad and the pad electrode is made only slightly on the side of the metal layer of the translucent electrode. Further, for example, if the metal oxide layer of the light-transmitting electrode has a shape slightly protruding from the edge of the metal layer, when the pad electrode is formed by vapor deposition, electric power on the side surface of the light-transmitting electrode and the pad electrode is formed. Sometimes contact was not obtained successfully.
【００１４】また、図２に示す構造を持つ電極を形成し
た場合、パッド電極２の下において、図２に４で示すよ
うな、透光性電極１から半導体に電流が注入される領域
が存在する。この領域４からの発光は外部に取り出すこ
とができないので、図２に示す電極構造は、発光の効率
的な取り出しができない。When an electrode having the structure shown in FIG. 2 is formed, there is a region under the pad electrode 2 where current is injected from the translucent electrode 1 into the semiconductor, as shown by 4 in FIG. I do. Since light emitted from the region 4 cannot be extracted to the outside, the electrode structure shown in FIG. 2 cannot extract light efficiently.
【００１５】従って本発明の目的は、半導体側に形成さ
れた金属薄膜と該金属薄膜の上部に形成された金属酸化
物薄膜とを有する透光性の第１の電極（透光性電極）と
金属薄膜よりなるワイヤボンド用の第２の電極（パッド
電極）とからなる半導体発光素子用の電極において、第
１の電極の金属層と第２の電極との電気的接触を確実に
得ることができ、かつ、電極下での発光を有効に取り出
すことのできる構造の電極を提供することにある。さら
に本発明は、上記の電極において、電極とワイヤの接着
強度を改良した電極を提供することを目的とする。Accordingly, an object of the present invention is to provide a light-transmitting first electrode (light-transmitting electrode) having a metal thin film formed on a semiconductor side and a metal oxide thin film formed on the metal thin film. In an electrode for a semiconductor light emitting element including a second electrode (pad electrode) for wire bonding made of a metal thin film, it is possible to reliably obtain electrical contact between the metal layer of the first electrode and the second electrode. It is an object of the present invention to provide an electrode having a structure capable of effectively extracting light emitted under the electrode. A further object of the present invention is to provide an electrode having the above-mentioned electrode, in which the bonding strength between the electrode and the wire is improved.
【００１６】[0016]
【課題を解決するための手段】本発明は、半導体側に形
成された金属薄膜と該金属薄膜の上部に形成された金属
酸化物薄膜とを有する透光性の第１の電極と金属薄膜よ
りなるワイヤボンド用の第２の電極とからなる半導体発
光素子用の電極において、前記第１の電極の一部を前記
第２の電極上の少なくとも一部に重ねて形成したことを
特徴とする。上記の半導体発光素子用の電極において
は、第１の電極において半導体と接触する金属として、
第２の電極において半導体と接触する金属よりも、半導
体に対する単位面積当たりの接触抵抗の小さい金属を用
いることが好ましい。According to the present invention, there is provided a light-transmitting first electrode having a metal thin film formed on a semiconductor side and a metal oxide thin film formed on the metal thin film, and a metal thin film. And a second electrode for wire bonding, wherein a part of the first electrode is formed so as to overlap at least a part of the second electrode. In the above-mentioned electrode for a semiconductor light emitting element, as a metal in contact with the semiconductor in the first electrode,
It is preferable to use a metal having a smaller contact resistance per unit area with respect to the semiconductor than a metal which is in contact with the semiconductor in the second electrode.
【００１７】また本発明は、上記の半導体発光素子用の
電極において、第１の電極が第２の電極上の全面を覆っ
て形成されていることが好ましい。特に上記の半導体発
光素子用の電極においては、第２の電極と重なった部分
の第１の電極の金属酸化物薄膜を除去することが好まし
い。さらに上記の半導体発光素子用の電極において、第
２の電極と重なった部分の第１の電極の金属酸化物薄膜
を除去し、その部分に金線との接着性に優れる金属を積
層することが好ましい。According to the present invention, in the above-mentioned electrode for a semiconductor light emitting device, it is preferable that the first electrode is formed so as to cover the entire surface of the second electrode. In particular, in the above-described electrode for a semiconductor light-emitting element, it is preferable to remove a portion of the metal oxide thin film of the first electrode which overlaps with the second electrode. Further, in the above-mentioned electrode for a semiconductor light-emitting element, it is possible to remove the metal oxide thin film of the first electrode in a portion overlapping with the second electrode and to laminate a metal having excellent adhesion to a gold wire on the portion. preferable.
【００１８】本発明は半導体がＧａＮ系化合物半導体で
ある場合に特に有効に用いることができる。The present invention can be used particularly effectively when the semiconductor is a GaN-based compound semiconductor.
【００１９】[0019]
【発明の実施の形態】本発明は、透光性の第１の電極と
ワイヤボンド用の第２の電極とからなる半導体発光素子
用の電極に関する。透光性の第１の電極は、半導体側に
形成された金属薄膜と該金属薄膜の上部に形成された金
属酸化物薄膜とを有する多層膜によって形成される。す
なわち上記の第１の電極は、膜厚をおよそ１〜１００ｎ
ｍと薄く形成された金属からなる薄膜の上に、保護層と
して透光性の金属酸化物膜を形成した構造を用いる。金
属薄膜や金属酸化物薄膜は、それぞれ数種類の金属或い
は金属酸化物の層からなる多層構造とすることができ
る。金属薄膜を形成する金属は、Ａｕ、Ｐｔ、Ｐｄ、Ｎ
ｉ、Ｃｒ、Ａｌ、Ｔｉ、Ｉｎなどから選ぶことができ
る。また、これらのうちのいくつかを混ぜ合わせた合金
を用いることもできるし、これらのうちのいくつかを積
層して多層構造とすることもできる。また、これらの金
属に対し、Ｂｅ、Ｇｅ、Ｚｎ、Ｍｇなどを不純物として
添加したものを用いても良い。また金属酸化物薄膜の材
料には、透光性であることが良く知られた、ＳｉＯ2、
ＮｉＯ、ＴｉＯ2 、ＳｎＯ、Ｃｒ2 Ｏ3 、ＣｏＯ、Ｚｎ
Ｏ、Ｃｕ2 Ｏ、ＭｇＯ、Ｉｎ2 Ｏ3 やそのいくつかを混
合した金属酸化物を用いることができる。金属酸化物薄
膜の厚さはおよそ１〜１０００ｎｍが好ましい。また、
金属酸化物薄膜は、異なった金属酸化物の多層膜として
も良い。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an electrode for a semiconductor light emitting device comprising a light-transmitting first electrode and a second electrode for wire bonding. The translucent first electrode is formed of a multilayer film including a metal thin film formed on the semiconductor side and a metal oxide thin film formed on the metal thin film. That is, the first electrode has a thickness of about 1 to 100 n.
A structure in which a light-transmitting metal oxide film is formed as a protective layer on a thin film made of a metal formed as thin as m is used. Each of the metal thin film and the metal oxide thin film can have a multilayer structure composed of several types of metal or metal oxide layers. The metal forming the metal thin film is Au, Pt, Pd, N
It can be selected from i, Cr, Al, Ti, In and the like. Also, an alloy obtained by mixing some of these can be used, or some of these can be laminated to form a multilayer structure. Further, a metal obtained by adding Be, Ge, Zn, Mg, or the like as an impurity to these metals may be used. Also, the material of the metal oxide thin film is well known to be translucent, such as SiO 2 ,
NiO, TiO 2 , SnO, Cr 2 O 3 , CoO, Zn
O, Cu 2 O, MgO, In 2 O 3 , or a mixed metal oxide of some of them can be used. The thickness of the metal oxide thin film is preferably about 1 to 1000 nm. Also,
The metal oxide thin film may be a multilayer film of different metal oxides.
【００２０】また上記の第２の電極を形成する金属材料
としては、Ａｕ、Ｐｔ、Ｐｄ、Ｎｉ、Ｃｒ、Ａｌ、Ｔ
ｉ、Ｉｎなどの金属を用いることができる。また、これ
らのうち何種類かを混合した合金や、これらの金属にＢ
ｅ、Ｇｅ、Ｚｎ、Ｍｇなどを不純物として添加させたも
のを用いても良い。また、第２の電極は１種類の金属か
らなる単層として形成できるだけではなく、いくつかの
金属からなる層を組み合わせた多層膜として形成するこ
ともできる。第２の電極を多層膜とし、半導体と接触す
る側に第１の電極の半導体側の金属材料よりも高い接触
抵抗を示す材料を用いることは、半導体発光素子の発光
強度の向上のために有効であり、また第２の電極の表面
の層としてＡｕ、Ａｌ、Ｎｉなどを用いることは、電極
とワイヤの接着性の向上の為に有効である。また第２の
電極は、ワイヤボンドの際の衝撃を緩和し半導体をその
際のダメージから守るために、膜厚を０．７μｍ以上と
することが望ましい。The metal material forming the second electrode includes Au, Pt, Pd, Ni, Cr, Al, T
Metals such as i and In can be used. In addition, alloys in which some of these are mixed, or B
A material to which e, Ge, Zn, Mg, or the like is added as an impurity may be used. Further, the second electrode can be formed not only as a single layer made of one kind of metal, but also as a multilayer film in which layers made of several metals are combined. The use of a material having a higher contact resistance than the metal material on the semiconductor side of the first electrode on the side in contact with the semiconductor is effective for improving the emission intensity of the semiconductor light emitting element. The use of Au, Al, Ni or the like as a layer on the surface of the second electrode is effective for improving the adhesion between the electrode and the wire. The second electrode preferably has a thickness of 0.7 μm or more in order to alleviate the impact at the time of wire bonding and protect the semiconductor from damage at that time.
【００２１】本発明は、半導体側に形成された金属薄膜
と該金属薄膜の上部に形成された金属酸化物薄膜とを有
する透光性の第１の電極と金属薄膜よりなるワイヤボン
ド用の第２の電極とからなる半導体発光素子用の電極に
おいて、前記第１の電極の一部を前記第２の電極上の少
なくとも一部に重ねて形成する。この結果、第１の電極
の下面の金属薄膜と第２の電極表面の金属薄膜とが接触
するので、第１の電極の最表面が金属酸化物薄膜で形成
されるため高抵抗であっても、両電極の電気的接触は良
好となる。また上記の構造の電極では、第１の電極で半
導体に接触する金属が半導体に対して接着性が悪い場合
でも、第２の電極の半導体に接触する金属に半導体に対
する接着性の良い金属を用いることにより、ワイヤボン
ドの際に半導体表面から第２の電極が剥がれてしまう事
を防止することができる。According to the present invention, there is provided a light-transmitting first electrode having a metal thin film formed on a semiconductor side and a metal oxide thin film formed on the metal thin film, and a second electrode for wire bonding comprising a metal thin film. In the electrode for a semiconductor light emitting element including two electrodes, a part of the first electrode is formed so as to overlap at least a part of the second electrode. As a result, the metal thin film on the lower surface of the first electrode and the metal thin film on the surface of the second electrode are in contact with each other. The electrical contact between the two electrodes is improved. Further, in the electrode having the above structure, even if the metal in contact with the semiconductor in the first electrode has poor adhesion to the semiconductor, a metal having good adhesion to the semiconductor is used as the metal in contact with the semiconductor in the second electrode. This can prevent the second electrode from peeling off from the semiconductor surface during wire bonding.
【００２２】ここで、第１の電極において半導体と接触
する金属として、第２の電極において半導体と接触する
金属よりも、半導体に対する単位面積当たりの接触抵抗
の小さい金属を用いることが望ましい。特に第１の電極
の単位面積当たりの接触抵抗値が、第２の電極のそれよ
りも１／５以下の大きさであることが望ましい。このよ
うに第２の電極において半導体と接触する金属材料とし
て、半導体との接触抵抗の高い金属材料を用いることに
より、第２の電極の直下の半導体に電流が注入されるこ
とを防ぐことができる結果、半導体発光素子の発光強度
を向上することが出来る。Here, as the metal that contacts the semiconductor at the first electrode, it is desirable to use a metal having a smaller contact resistance per unit area with respect to the semiconductor than the metal that contacts the semiconductor at the second electrode. In particular, it is desirable that the contact resistance value per unit area of the first electrode is 1/5 or less of that of the second electrode. As described above, by using a metal material having high contact resistance with the semiconductor as the metal material in contact with the semiconductor in the second electrode, current can be prevented from being injected into the semiconductor immediately below the second electrode. As a result, the light emission intensity of the semiconductor light emitting device can be improved.
【００２３】また本発明に係わる構造の電極では、図２
に示した電極構造のように第２の電極（パッド電極）の
下に第１の電極（透光性電極）と半導体が接触する領域
がない。従って第２の電極の直下の半導体に電流が注入
されることを防ぐことが出来る結果、発光はすべて透光
性の第１の電極の下で起こり、発光を効率的に素子の外
部に取り出すことが可能である。In the electrode having the structure according to the present invention, FIG.
There is no region under the second electrode (pad electrode) where the first electrode (translucent electrode) and the semiconductor are in contact, as in the electrode structure shown in FIG. Therefore, current can be prevented from being injected into the semiconductor immediately below the second electrode. As a result, all light emission occurs under the light-transmitting first electrode, and light emission can be efficiently taken out of the element. Is possible.
【００２４】また特に、本発明に係わる電極は、第２の
電極の全面を覆って第１の電極が形成されていることが
望ましい。第１の電極を第２の電極の全面を覆って形成
することにより、第１の電極と第２の電極の接着性の向
上を図ることができる。これによって第１の電極と第２
の電極の間の接着強度が小さい場合でも、第１の電極が
剥がれたり、捲れたりするのを防ぐことが出来る。ま
た、第１の電極と第２の電極の形成の際に両者の位置を
合わせる作業時において、多少両者の相対位置がずれた
としても、第２の電極の全面が第１の電極に重なってい
るため、第１の電極と第２の電極の接触に影響が生じな
い。さらに、一般的な超音波式のワイヤボンダーによる
ワイヤボンディングでは、ワイヤボンドの際の衝撃で第
２の電極上の第１の電極の薄い層が破壊されるため、第
２の電極の表面の層として金線との接着性に優れる金属
が形成されていれば、第２の電極にワイヤである金線を
結線することが可能である。It is particularly desirable that the electrode according to the present invention has the first electrode formed so as to cover the entire surface of the second electrode. By forming the first electrode so as to cover the entire surface of the second electrode, the adhesion between the first electrode and the second electrode can be improved. This allows the first electrode and the second electrode
Even if the bonding strength between the electrodes is low, the first electrode can be prevented from peeling or rolling up. In addition, when the first electrode and the second electrode are formed, the entire surface of the second electrode overlaps with the first electrode even when the relative positions of the two electrodes are slightly shifted during the operation of aligning the two electrodes. Therefore, there is no effect on the contact between the first electrode and the second electrode. Further, in the wire bonding using a general ultrasonic wire bonder, a thin layer of the first electrode on the second electrode is broken by an impact at the time of the wire bonding, so that the layer on the surface of the second electrode is broken. If a metal having excellent adhesion to a gold wire is formed, a gold wire, which is a wire, can be connected to the second electrode.
【００２５】しかし、一般に金属酸化物薄膜はワイヤで
ある金線との接着性に劣るため、上記の様に第１の電極
が第２の電極の全面を覆って形成されている場合には、
第２の電極と重なった部分の第１の電極の金属酸化物薄
膜を除去することが、電極と金線との接着を一層確実に
するために望ましい。第２の電極と重なった部分の第１
の電極については、その全層を除去する必要はなく、金
属酸化物薄膜のみを除去すればよい。また、第２の電極
と重なった部分の第１の電極の全部について金属酸化物
薄膜を除去する必要はなく、ワイヤボンドに必要な面積
分だけ金属酸化物薄膜を除去すればよい。特に、第１の
電極を構成する金属薄膜として金線との接着性に優れる
金属を使用している場合、酸化物薄膜を除去することで
第１の電極の金属薄膜が第２の電極の上面に露出され、
金線と電極を強固に接着させることが可能である。金線
と良好な接着性を有する金属とは、Ａｕ、Ａｌ、Ｎｉな
どである。However, since the metal oxide thin film generally has poor adhesion to a gold wire as a wire, when the first electrode is formed to cover the entire surface of the second electrode as described above,
It is desirable to remove the metal oxide thin film of the first electrode in a portion overlapping with the second electrode in order to further ensure the adhesion between the electrode and the gold wire. The first part of the portion overlapping the second electrode
It is not necessary to remove all layers of the electrode, and only the metal oxide thin film need be removed. Further, it is not necessary to remove the metal oxide thin film from the entire portion of the first electrode that overlaps with the second electrode, and it is sufficient to remove the metal oxide thin film by an area required for wire bonding. In particular, when a metal having excellent adhesion to a gold wire is used as a metal thin film forming the first electrode, the metal thin film of the first electrode is removed by removing the oxide thin film. Exposed to
It is possible to firmly bond the gold wire and the electrode. Examples of the metal having good adhesion to the gold wire include Au, Al, and Ni.
【００２６】なお、上記のように第１の電極の金属薄膜
として金線との接着性に優れる金属を用いている場合は
第１の電極の金属酸化物薄膜を除去することだけで金線
との接着性の改良を図ることができるが、該金属薄膜が
Ａｕ、Ａｌ、Ｎｉ以外の金属で形成されている場合に
は、金属薄膜を露出しただけでは、金線との接着性の改
良を図ることはできない。その場合には、上記のように
して露出させた第１の電極の金属層の上にＡｕ、Ａｌ、
Ｎｉなどの金線との接着性に優れる金属を積層すること
で金線と電極の接着性の向上を図ることができる。When a metal having excellent adhesion to a gold wire is used as the metal thin film of the first electrode as described above, the gold wire and the metal thin film of the first electrode are removed only by removing the metal oxide thin film. However, when the metal thin film is formed of a metal other than Au, Al, and Ni, the adhesion to the gold wire can be improved only by exposing the metal thin film. I can't do it. In that case, Au, Al, and the like are formed on the metal layer of the first electrode exposed as described above.
By laminating a metal having excellent adhesion to a gold wire such as Ni, the adhesion between the gold wire and the electrode can be improved.
【００２７】本発明に係わる電極は、第１の電極よりも
先に第２の電極を形成することで形成することが可能で
ある。第２の電極を積層する方法としては、蒸着法やス
パッタリング法を用いることができる。第２の電極を形
成する方法は、いわゆる「リフトオフ法」によっても構
わないし、一旦全面に金属薄膜を形成しておき、この金
属薄膜上にレジストにより所定の保護膜を形成し、エッ
チング液に含浸して露出した部分の金属薄膜を除去する
方法によっても構わない。The electrode according to the present invention can be formed by forming the second electrode before the first electrode. As a method for stacking the second electrode, an evaporation method or a sputtering method can be used. The method for forming the second electrode may be a so-called “lift-off method”, or a method in which a metal thin film is once formed on the entire surface, a predetermined protective film is formed on the metal thin film with a resist, and the metal film is impregnated with an etching solution. Alternatively, a method of removing the exposed portion of the metal thin film may be used.
【００２８】同様に第１の電極を積層する方法として
も、蒸着法やスパッタリング法を用いることができる。
また、第１の電極の上部に金属酸化物薄膜を形成する場
合、酸化物を蒸着法やスパッタリング法で直接形成する
方法や、蒸着やスパッタで酸化物となる金属の薄膜を形
成しておき、これを酸素を含む雰囲気中で熱処理するこ
とによって、金属薄膜を金属酸化物とする方法を用いる
ことができる。また、第１の電極を形成する方法として
も、第２の電極の形成方法と同様に、前述のリフトオフ
法によっても構わないし、エッチャント液によるエッチ
ングによる方法によっても構わない。Similarly, as a method of laminating the first electrode, a vapor deposition method or a sputtering method can be used.
In the case where a metal oxide thin film is formed over the first electrode, a method in which an oxide is directly formed by an evaporation method or a sputtering method, or a thin film of a metal to be an oxide is formed by evaporation or sputtering, By subjecting this to a heat treatment in an atmosphere containing oxygen, a method can be used in which the metal thin film is converted into a metal oxide. Further, the method of forming the first electrode may be the lift-off method described above or the method of etching with an etchant solution, as in the method of forming the second electrode.
【００２９】また、第２の電極と重なった部分の第１の
電極の金属酸化物薄膜を除去し、その部分にＡｕ、Ａ
ｌ、Ｎｉなどの金線との接着性に優れる金属を積層する
場合も上記と同様の方法を用いることができる。Further, the metal oxide thin film of the first electrode in the portion overlapping with the second electrode is removed, and Au, A
The same method as described above can be used when laminating a metal having excellent adhesion to a gold wire such as l or Ni.
【００３０】また、一般に電極を形成後には熱処理を行
うことによって電極と半導体の間のオーミック接触を実
現する。この場合の通常の熱処理としては、温度を３０
０℃以上とし１分以上熱処理を行う条件が用いられる。
熱処理に際して炉内の圧力は常圧より低くても構わない
し、常圧でも良い。炉内の雰囲気ガスとしては、Ｎ2、
Ｏ2 、Ｈｅ、Ｎｅ、Ａｒ、Ｋｒなどから選ばれた一種類
の気体からなるガスや、それらの混合ガスを用いること
ができる。本発明の実施の際、第１の電極の金属酸化物
薄膜を金属薄膜を酸化雰囲気中で熱処理して金属酸化物
薄膜とする方法で形成するとき、金属薄膜を酸化するた
めの熱処理と上記のオーミック接触を実現するための熱
処理とを兼ねることができる。Generally, ohmic contact between the electrode and the semiconductor is realized by performing a heat treatment after the formation of the electrode. In this case, as a normal heat treatment, a temperature of 30
A condition in which the temperature is set to 0 ° C. or more and the heat treatment is performed for 1 minute or more is used.
During the heat treatment, the pressure in the furnace may be lower than normal pressure, or may be normal pressure. Atmosphere gases in the furnace include N 2 ,
A gas composed of one kind of gas selected from O 2 , He, Ne, Ar, Kr and the like, or a mixed gas thereof can be used. In the practice of the present invention, when the metal oxide thin film of the first electrode is formed by heat-treating the metal thin film in an oxidizing atmosphere into a metal oxide thin film, a heat treatment for oxidizing the metal thin film and It can also serve as heat treatment for realizing ohmic contact.
【００３１】また、第２の電極と重なった部分の第１の
電極の金属酸化物薄膜を除去し、その部分にワイヤボン
ドに適する金属を積層する場合、第２の電極、第１の電
極の残存する層、最後に積層した金線との接着性に優れ
る層のそれぞれの間の接着性を上げるため、最後の層を
積層後熱処理を施すことが好ましい。この場合、第２の
電極上の各層の接着性を向上するための熱処理と、上記
の金属薄膜を酸化するための熱処理あるいはオーミック
接触を実現するための熱処理とを兼ねることができる。In the case where the metal oxide thin film of the first electrode in the portion overlapping with the second electrode is removed and a metal suitable for wire bonding is laminated on that portion, the second electrode and the first electrode In order to increase the adhesion between the remaining layer and the layer having excellent adhesion to the last laminated gold wire, it is preferable to perform a heat treatment after laminating the last layer. In this case, the heat treatment for improving the adhesiveness of each layer on the second electrode and the heat treatment for oxidizing the metal thin film or the heat treatment for realizing ohmic contact can be performed.
【００３２】本発明に係わる半導体発光素子用電極は、
半導体発光素子において電極から横方向への電流拡散が
小さく、透光性の電極を必要とするＧａＮ系化合物半導
体の場合に、特に有効に用いることが出来る。ＧａＮ系
化合物半導体は一般にＡｌＧａＩｎＮで表すことが出来
る。The electrode for a semiconductor light emitting device according to the present invention comprises:
In a semiconductor light emitting device, the current diffusion in the lateral direction from the electrode is small, and it can be used particularly effectively in the case of a GaN-based compound semiconductor that requires a translucent electrode. A GaN-based compound semiconductor can be generally represented by AlGaInN.
【００３３】[0033]
（実施例１）本発明に係わる半導体発光素子用電極の一
例は、図３の断面図で示すような、サファイア基板上
に、ＡｌＮをバッファ層として、ｎ型ＧａＮ層、ＩｎＧ
ａＮ層、ｐ型ＡｌＧａＮ層、ｐ型ＧａＮ層を順に積層し
た半導体基板５のｐ型ＧａＮ層上に、基板側からＡｕＢ
ｅ層６、その上にＡｕ層７を積層した層構造からなる第
２の電極８、基板側からＡｕ層９、その上にＮｉＯ層１
０からなる第１の電極１１を形成して作製した電極であ
る。第１の電極１１の最表面に保護膜として用いたＮｉ
Ｏは導電性の酸化物として知られているが抵抗率は高い
ので、金属層を接触させても良好な導通は取れない。ま
た、第１の電極１１の下面に用いたＡｕ層９はｐ型Ｇａ
Ｎと良好なオーミック接触を実現する金属であり、第２
の電極８の下面に用いたＡｕＢｅ層６は、ｐ型ＧａＮと
高抵抗の接触を形成する合金である。なお、図３で、１
２はｎ側電極である。また図４は、図３で示した半導体
発光素子用電極の平面図であり、図中に８、１１で示し
た部分が本発明に係わる第２の電極および第１の電極で
ある。(Example 1) An example of an electrode for a semiconductor light emitting device according to the present invention is an n-type GaN layer and an InG layer on a sapphire substrate using AlN as a buffer layer as shown in the sectional view of FIG.
AuB is formed on the p-type GaN layer of the semiconductor substrate 5 in which an aN layer, a p-type AlGaN layer, and a p-type GaN layer are sequentially stacked from the substrate side.
e layer 6, a second electrode 8 having a layer structure in which an Au layer 7 is laminated thereon, an Au layer 9 from the substrate side, and a NiO layer 1 thereon.
This is an electrode formed by forming a first electrode 11 made of zero. Ni used as a protective film on the outermost surface of the first electrode 11
O is known as a conductive oxide but has a high resistivity, so that good conductivity cannot be obtained even when a metal layer is brought into contact. The Au layer 9 used on the lower surface of the first electrode 11 is a p-type Ga layer.
N is a metal that achieves good ohmic contact with N
The AuBe layer 6 used on the lower surface of the electrode 8 is an alloy that forms high-resistance contact with p-type GaN. In FIG. 3, 1
2 is an n-side electrode. FIG. 4 is a plan view of the semiconductor light emitting device electrode shown in FIG. 3, and portions indicated by 8 and 11 in the figure are a second electrode and a first electrode according to the present invention.
【００３４】図３、図４に示した半導体発光素子用電極
は、次の手順で作製した。初めに、公知のフォトリソグ
ラフィー技術を用い、ｐ型ＧａＮ層上にＡｕＢｅ層６、
その上にＡｕ層７の構造よりなる第２の電極８を形成し
た。第２の電極８の形成においては、まず、半導体基板
５を真空蒸着装置に入れ、ｐ型ＧａＮ層上の全面に圧力
３×１０-6Ｔｏｒｒにおいて初めに１重量％のＢｅを含
むＡｕＢｅを３００ｎｍの厚さで積層した。続いて、同
じ真空装置内でＡｕを７００ｎｍ蒸着した。ＡｕＢｅ層
６、その上にＡｕ層７の多層薄膜を蒸着した基板５は、
真空装置から取り出した後、一般のフォトリソグラフィ
ーと呼ばれる手法によって、第２の電極の形成される領
域にレジストによる保護膜を形成し、Ａｕエッチング液
に含浸して露出した部分の多層薄膜を除去した。この様
にしてｐ型ＧａＮ層上には、基板側からＡｕＢｅ層６、
その上にＡｕ層７からなる第２の電極８を形成した。The electrodes for the semiconductor light emitting device shown in FIGS. 3 and 4 were manufactured in the following procedure. First, an AuBe layer 6 is formed on the p-type GaN layer using a known photolithography technique.
A second electrode 8 having the structure of the Au layer 7 was formed thereon. In forming the second electrode 8, first, the semiconductor substrate 5 is placed in a vacuum evaporation apparatus, and AuBe containing 1% by weight of Be is first deposited on the entire surface of the p-type GaN layer at a pressure of 3 × 10 −6 Torr with a thickness of 300 nm. The thickness was laminated. Subsequently, 700 nm of Au was deposited in the same vacuum apparatus. The substrate 5 on which the AuBe layer 6 and a multilayer thin film of the Au layer 7 are deposited thereon is
After taking out from the vacuum device, a protective film was formed by a resist in a region where the second electrode was to be formed by a general method called photolithography, and the multilayer thin film in the exposed portion was removed by impregnating with an Au etchant. . In this way, on the p-type GaN layer, the AuBe layer 6,
A second electrode 8 made of the Au layer 7 was formed thereon.
【００３５】続いて、公知のフォトリソグラフィー技術
及び公知のリフトオフ技術を用いて、ｐ型ＧａＮ層上に
Ａｕ層９、その上にＮｉＯ層１０を形成した多層構造の
薄膜からなる第１の電極１１を形成した。第１の電極１
１の形成では、まず、一般にフォトリソグラフィーと呼
ばれる手法によって、第２の電極８を形成済みの半導体
基板５上に第１の電極の形成される領域を露出し、それ
以外の領域にレジストの保護膜を形成した。次に、半導
体基板５を真空蒸着機に入れｐ型ＧａＮ層上に圧力３×
１０-6Ｔｏｒｒにおいて初めにＡｕを２０ｎｍ、続いて
同じ真空室内でＮｉを１０ｎｍ蒸着した。ＡｕとＮｉを
蒸着した基板は、真空室から取り出した後、通常リフト
オフと呼ばれる手順に則って処理し、図４の１１で示す
形状の薄膜を形成した。この後、この基板をアニール炉
においてアルゴンと酸素の比が８：２の混合ガス雰囲気
中で５５０℃で１０分間熱処理し、Ｎｉを酸化させて透
明なＮｉＯとするとともに第１の電極とｐ型ＧａＮのオ
ーミック接触を実現させた。Subsequently, using a known photolithography technique and a known lift-off technique, an Au layer 9 is formed on a p-type GaN layer, and an NiO layer 10 is formed on the first electrode 11 made of a multilayered thin film. Was formed. First electrode 1
In the formation of 1, first, by a technique generally called photolithography, a region where the first electrode is formed is exposed on the semiconductor substrate 5 on which the second electrode 8 has been formed, and the other region is protected with a resist. A film was formed. Next, the semiconductor substrate 5 is placed in a vacuum evaporation machine and a pressure of 3 × is applied on the p-type GaN layer.
At 10 −6 Torr, Au was first deposited to a thickness of 20 nm, and then Ni was deposited to a thickness of 10 nm in the same vacuum chamber. The substrate on which Au and Ni were deposited was taken out of the vacuum chamber, and then processed according to a procedure generally called lift-off to form a thin film having a shape indicated by 11 in FIG. Then, the substrate is heat-treated in an annealing furnace at 550 ° C. for 10 minutes in a mixed gas atmosphere of argon and oxygen at a ratio of 8: 2 to oxidize Ni to obtain transparent NiO and a first electrode and p-type. Ohmic contact of GaN was realized.
【００３６】その後、公知のフォトリソグラフィー技術
を用いて、図３および図４中に１３で示した第２の電極
８に重なった部分の第１の電極の表面は露出させて、第
１の電極１１上にレジスト膜を形成した。続いて基板を
濃塩酸中に含浸し第１の電極の領域１３の部分のＮｉＯ
層を除去した。最後にレジスト膜を除去した。この工程
により、第２の電極８上の領域１３において第１の電極
層はＮｉＯ層が除去され、Ａｕ層だけが残存した。Then, by using a known photolithography technique, the surface of the first electrode overlapping with the second electrode 8 shown in FIG. 3 and FIG. 11, a resist film was formed. Subsequently, the substrate was impregnated with concentrated hydrochloric acid to remove NiO in the region of the first electrode region 13.
The layer was removed. Finally, the resist film was removed. By this step, in the region 13 on the second electrode 8, the NiO layer was removed from the first electrode layer, and only the Au layer remained.
【００３７】更にその後、ドライエッチングによってｎ
側電極を形成する部分のｎ層を露出させ、露出した部分
にＡｌよりなるｎ側電極１２を形成し、ｎ側電極のオー
ミック接触を形成するための熱処理を行った。このよう
にして電極を形成したウエハを４００μｍ角のチップに
切断し、リードフレーム上に載置し結線して発光ダイオ
ードとしたところ、電流２０ｍＡにおける発光出力が８
０μＷ、順方向電圧は２．８Ｖを示した。ワイヤボンデ
ィング作業は、図３および図４で１３で示した領域に金
線のボールを押しつけ、超音波で加熱して結線した。第
２の電極と金線の接着に問題は生じなかった。また、全
作業を通じて半導体と第２の電極の剥がれは生じなかっ
た。また、２インチφの基板から１６０００個のチップ
が得られ、発光強度が７６μＷに満たないチップを取り
除いたところ、収率は９８％であった。Thereafter, n is obtained by dry etching.
The n-layer at the portion where the side electrode is to be formed was exposed, the n-side electrode 12 made of Al was formed at the exposed portion, and heat treatment for forming an ohmic contact with the n-side electrode was performed. The wafer on which the electrodes were formed in this manner was cut into chips of 400 μm square, mounted on a lead frame and connected to form a light emitting diode.
0 μW and a forward voltage of 2.8 V were shown. In the wire bonding operation, a gold wire ball was pressed against the area indicated by 13 in FIGS. 3 and 4 and heated by ultrasonic waves to connect. No problem occurred in the adhesion between the second electrode and the gold wire. In addition, the semiconductor and the second electrode did not peel off during the entire operation. In addition, 16,000 chips were obtained from a substrate having a diameter of 2 inches, and chips with a light emission intensity of less than 76 μW were removed. As a result, the yield was 98%.
【００３８】（実施例２）本発明に係わる半導体発光素
子用透光性電極の一例は、図５の断面図で示すような、
サファイア基板上に、ＡｌＮをバッファ層として、ｎ型
ＧａＮ層、ＩｎＧａＮ層、ｐ型ＡｌＧａＮ層、ｐ型Ｇａ
Ｎ層を順に積層した半導体基板５のｐ型ＧａＮ層上に、
基板側からＡｕＢｅ層１４、間に第１の電極の金属層で
あるＰｄ層１６をはさみ、その上にＡｕ層１５を積層し
た多層構造からなる第２の電極８’、基板側からＰｄ層
１６、ＳｎＯ層１７を積層した多層構造からなる第１の
電極１１’を形成して作製した電極である。第１の電極
１１’の最表層に用いたＳｎＯは導電性の酸化物として
知られているが、金属と比較して抵抗率は高いため金属
を接触させても良好な導通は取れない。また、第１の電
極１１’の下面に用いたＰｄ層１６はｐ型ＧａＮと良好
なオーミック接触を実現する金属であり、第２の電極
８’の下面に用いたＡｕＢｅ層１４は、ｐ型ＧａＮと高
抵抗の接触を形成する合金である。なお、図５で、１
２’はｎ側電極である。また図６は、図５で示した半導
体発光素子用電極の平面図であり、８’、１１’で示し
た部分が本発明に係わる第２の電極および第１の電極で
ある。(Example 2) An example of a light-transmitting electrode for a semiconductor light emitting device according to the present invention is as shown in the sectional view of FIG.
An n-type GaN layer, an InGaN layer, a p-type AlGaN layer, a p-type Ga
On the p-type GaN layer of the semiconductor substrate 5 in which N layers are sequentially stacked,
A second electrode 8 'having a multilayer structure in which an AuBe layer 14 is interposed between the substrate side and a Pd layer 16 which is a metal layer of the first electrode, and an Au layer 15 is laminated thereon, and the Pd layer 16 is interposed from the substrate side , An electrode formed by forming a first electrode 11 ′ having a multilayer structure in which SnO layers 17 are stacked. SnO used for the outermost layer of the first electrode 11 'is known as a conductive oxide, but has a higher resistivity than a metal, so that good conductivity cannot be obtained even when the metal is brought into contact. The Pd layer 16 used on the lower surface of the first electrode 11 ′ is a metal that realizes good ohmic contact with p-type GaN, and the AuBe layer 14 used on the lower surface of the second electrode 8 ′ is a p-type An alloy that forms high resistance contact with GaN. In FIG. 5, 1
2 'is an n-side electrode. FIG. 6 is a plan view of the electrode for a semiconductor light emitting device shown in FIG. 5, and portions indicated by 8 'and 11' are a second electrode and a first electrode according to the present invention.
【００３９】図５、図６に示した半導体発光素子用電極
は、次の手順で作製した。初めに、公知のフォトリソグ
ラフィー技術を用い、ｐ型ＧａＮ層上にＡｕＢｅ単層よ
りなる金属層１４を形成した。ＡｕＢｅ層１４の形成
は、実施例１と同様に行った。続いて、公知のフォトリ
ソグラフィー技術及びリフトオフ技術を用いて、ｐ型Ｇ
ａＮ層上にＰｄ層１６、その上にＳｎＯ層１７を積層し
た多層構造からなる第１の電極１１’を形成した。第１
の電極１１’の形成では、まず一般にフォトリソグラフ
ィーと呼ばれる手法によって、第２の電極のＡｕＢｅ層
１４のみを形成済みの半導体基板５上にレジストにより
第１の電極のパターン以外の部分に保護膜を形成し、該
半導体基板５を真空蒸着機に入れｐ型ＧａＮ層上に圧力
３×１０-6Ｔｏｒｒにおいて初めにＰｄを５ｎｍ、続い
て同じ真空室内でＳｎを１０ｎｍ蒸着した。ＰｄとＳｎ
を蒸着した基板は、真空室から取り出した後、通常リフ
トオフと呼ばれる手順に則って処理し、図６の１１’で
示す形状の薄膜を形成した。The electrodes for the semiconductor light emitting device shown in FIGS. 5 and 6 were manufactured in the following procedure. First, the metal layer 14 made of a single AuBe layer was formed on the p-type GaN layer by using a known photolithography technique. The formation of the AuBe layer 14 was performed in the same manner as in Example 1. Subsequently, using known photolithography technology and lift-off technology, the p-type G
A first electrode 11 'having a multilayer structure in which a Pd layer 16 was stacked on the aN layer and a SnO layer 17 was stacked thereon was formed. First
In the formation of the electrode 11 ′, a protective film is first formed on the semiconductor substrate 5 on which only the AuBe layer 14 of the second electrode has been formed by using a resist on a portion other than the pattern of the first electrode by a method generally called photolithography. The semiconductor substrate 5 was placed in a vacuum deposition machine, and Pd was first deposited to 5 nm on the p-type GaN layer at a pressure of 3 × 10 −6 Torr, and then Sn was deposited to 10 nm in the same vacuum chamber. Pd and Sn
The substrate on which was vapor-deposited was taken out of the vacuum chamber, and then processed according to a procedure generally called lift-off, to form a thin film having a shape indicated by 11 'in FIG.
【００４０】この後、基板５を酸素ガスを雰囲気ガスと
するアニール炉において、５００℃で６０分間熱処理
し、Ｓｎを酸化させて透明なＳｎＯとさせるとともに第
１の電極とｐ型ＧａＮのオーミック接触を実現させた。
その後、一般的なフォトリソグラフィーにより、図５お
よび図６中に１３’で示した第２の電極のＡｕＢｅ層１
４と重なった部分の第１の電極が露出したレジストのパ
ターンを形成した。その後、酸に含浸し領域１３’の部
分の第１の電極１１’のＳｎＯを除去した。使用した酸
はＰｄを溶かさず、ＳｎＯのみを溶かす。第２の電極
８’上の領域１３’において、ＳｎＯ層１７のみが完全
に除去されＰｄ層１６のみが残った。次に、ＳｎＯが取
り除かれた領域１３’を露出し、他の領域にレジストの
保護膜を形成した。この基板５を蒸着機に入れ、第２の
電極を形成したのと同じ手順でＡｕを蒸着した。真空室
から基板を取り出した後、リフトオフの手法に則って処
理し、基板側からＡｕＢｅ層１４、その上に第１の電極
の金属層であるＰｄ層１６をはさみ、その上に領域１
３’にＡｕ層１５を積層した多層構造をもつワイヤボン
ド用の第２の電極８’を完成した。Thereafter, the substrate 5 is subjected to a heat treatment at 500 ° C. for 60 minutes in an annealing furnace using oxygen gas as an atmospheric gas to oxidize Sn to form transparent SnO and to make ohmic contact between the first electrode and p-type GaN. Was realized.
Thereafter, the AuBe layer 1 of the second electrode indicated by 13 'in FIGS. 5 and 6 is formed by general photolithography.
A pattern of a resist in which the first electrode in the portion overlapping with No. 4 was exposed was formed. After that, SnO of the first electrode 11 ′ in the region 13 ′ was removed by impregnation with an acid. The acid used does not dissolve Pd but only SnO. In the region 13 'on the second electrode 8', only the SnO layer 17 was completely removed and only the Pd layer 16 remained. Next, the region 13 'from which SnO was removed was exposed, and a protective film of resist was formed in another region. The substrate 5 was placed in a vapor deposition machine, and Au was vapor-deposited in the same procedure as when the second electrode was formed. After removing the substrate from the vacuum chamber, the substrate is processed according to the lift-off method, and the AuBe layer 14 is sandwiched from the substrate side, and the Pd layer 16 which is the metal layer of the first electrode is sandwiched therefrom.
A second electrode 8 ′ for wire bonding having a multilayer structure in which an Au layer 15 was laminated on 3 ′ was completed.
【００４１】その後、ドライエッチングによってｎ側電
極１２’を形成する部分のｎ層を露出させ、露出した部
分に基板側からＴｉ層、その上にＡｌ層よりなるｎ側電
極１２’を形成し、ｎ側電極のオーミック接触を形成す
るための熱処理を行った。このようにして電極を形成し
たウエハを４００μｍ角のチップに切断し、リードフレ
ーム上に載置し結線して発光ダイオードとしたところ、
電流２０ｍＡにおける発光出力が８０μＷ、順方向電圧
は２．８Ｖを示した。ワイヤボンディング作業では、第
２の電極８’表面のＡｕ層を積層した領域１３’に金線
のボールを押しつけ、超音波で加熱して結線した。第２
の電極と金線の接着には問題は生じなかった。また、全
作業を通じて半導体と第２の電極の剥がれは生じなかっ
た。また、２インチφの基板から１６０００個のチップ
が得られ、発光強度が７６μＷに満たないチップを取り
除いたところ、収率は９８％であった。Thereafter, the n-layer at the portion where the n-side electrode 12 'is to be formed is exposed by dry etching, and a Ti layer is formed on the exposed portion from the substrate side, and an n-side electrode 12' made of an Al layer is formed thereon. Heat treatment for forming an ohmic contact with the n-side electrode was performed. The wafer on which the electrodes were formed in this manner was cut into chips of 400 μm square, mounted on a lead frame and connected to form a light emitting diode.
The emission output at a current of 20 mA was 80 μW, and the forward voltage was 2.8 V. In the wire bonding operation, a gold wire ball was pressed against the region 13 ′ of the surface of the second electrode 8 ′ where the Au layer was laminated, and the connection was performed by heating with ultrasonic waves. Second
No problem occurred in the bonding between the electrode and the gold wire. In addition, the semiconductor and the second electrode did not peel off during the entire operation. In addition, 16,000 chips were obtained from a substrate having a diameter of 2 inches, and chips with a light emission intensity of less than 76 μW were removed. As a result, the yield was 98%.
【００４２】（比較例１）図２に示したような従来の電
極を、実施例１に用いたものと同様の半導体基板上に以
下のように作製した。まず、実施例１と同様の操作によ
って半導体基板のｐ型ＧａＮ上に基板側からＡｕ層、そ
の上にＮｉＯ層構造からなる第１の電極１を形成した。
このとき、実施例１とは異なり、第１の電極のパターン
の中の第２の電極が形成されるべき位置に窓部３を形成
した。続いて、この窓部の位置に前述のリフトオフ法を
用いて基板側からＡｕＢｅ層、Ａｕ層の多層構造からな
る第２の電極２を形成した。Comparative Example 1 A conventional electrode as shown in FIG. 2 was fabricated on a semiconductor substrate similar to that used in Example 1 as follows. First, an Au layer was formed on the p-type GaN of the semiconductor substrate from the substrate side and a first electrode 1 having a NiO layer structure was formed on the Au layer by the same operation as in Example 1.
At this time, unlike the first embodiment, the window portion 3 was formed at the position where the second electrode should be formed in the pattern of the first electrode. Subsequently, a second electrode 2 having a multilayer structure of an AuBe layer and an Au layer was formed at the position of the window from the substrate side by using the lift-off method described above.
【００４３】その後、ドライエッチングによってｎ電極
を形成する部分のｎ層を露出させ、露出した部分にＡｌ
よりなるｎ側電極を形成し、ｎ側電極のオーミック接触
を形成するための熱処理を行った。このようにして電極
を形成したウエハを４００μｍ角のチップに切断し、リ
ードフレーム上に載置し結線して発光ダイオードとした
ところ、電流２０ｍＡにおける発光出力が５０μＷと実
施例１よりも小さく、順方向電圧は１５．０Ｖと実施例
１よりも著しく大きかった。これは、第１の電極の最上
層である金属酸化物層によって第１の電極と第２の電極
との電気的接触が妨げられたことによるものである。Thereafter, the n-layer where the n-electrode is to be formed is exposed by dry etching, and Al
An n-side electrode was formed, and heat treatment for forming an ohmic contact with the n-side electrode was performed. The wafer on which the electrodes were formed in this manner was cut into chips of 400 μm square, mounted on a lead frame and connected to form a light-emitting diode. The light-emitting output at a current of 20 mA was 50 μW, which was smaller than that of Example 1. The direction voltage was 15.0 V, which was significantly higher than that of Example 1. This is because the metal oxide layer, which is the uppermost layer of the first electrode, prevented electrical contact between the first electrode and the second electrode.
【００４４】（比較例２）図１に示したような従来の電
極を、実施例１に用いたものと同様の半導体基板上に以
下のように作製した。まず、実施例１と同様の操作によ
って半導体基板のｐ型ＧａＮ上に基板側からＡｕ、その
上にＮｉＯからなる第１の電極１を形成した。続いて、
この基板上に前述のリフトオフ法を用いて基板側からＡ
ｕＢｅ層およびＡｕ層からなる第２の電極２を形成し
た。Comparative Example 2 A conventional electrode as shown in FIG. 1 was fabricated on a semiconductor substrate similar to that used in Example 1 as follows. First, a first electrode 1 made of Au and NiO was formed on p-type GaN of a semiconductor substrate from the substrate side by the same operation as in Example 1. continue,
A is placed on the substrate from the substrate side using the lift-off method described above.
A second electrode 2 composed of a uBe layer and an Au layer was formed.
【００４５】その後、ドライエッチングによってｎ電極
を形成する部分のｎ層を露出させ、露出した部分にＡｌ
よりなるｎ側電極を形成し、ｎ側電極のオーミック接触
を形成するための熱処理を行った。このようにして電極
を形成したウエハを４００μｍ角のチップに切断し、リ
ードフレーム上に載置し結線して発光ダイオードとしよ
うとしたところ、ほとんどのチップにおいて、主にワイ
ヤボンドの際に第２の電極が剥がれ落ちてしまってい
た。金属で形成された第２の電極と最上層として金属酸
化物を形成した第１の電極との接着性が悪いため、第２
の電極が作業中に剥がれ落ちてしまったものである。Thereafter, the n-layer where the n-electrode is to be formed is exposed by dry etching, and Al
An n-side electrode was formed, and heat treatment for forming an ohmic contact with the n-side electrode was performed. The wafer on which the electrodes were formed in this manner was cut into 400 μm square chips, mounted on a lead frame and connected to form a light emitting diode. In most chips, the second chip was mainly used at the time of wire bonding. Electrodes had peeled off. Since the adhesion between the second electrode formed of metal and the first electrode formed of metal oxide as the uppermost layer is poor, the second electrode
Of the electrodes were peeled off during the operation.
【００４６】[0046]
【発明の効果】本発明の半導体発光素子用電極において
は、透光性の第１の電極を半導体側に形成された金属薄
膜と該金属薄膜の上部に形成された金属酸化物薄膜とを
有する層構造として形成した場合でも、第１の電極と第
２の電極との良好な電気的接触を得ることができる。ま
た、透光性の第１の電極とワイヤボンド用の第２の電極
で半導体に接触する金属を異なる金属とすることができ
る。従って、第２の電極の直下に電流を注入しないよう
に、第２の電極の半導体側の金属として半導体との接触
抵抗の大きい金属を用いることができる。これにより、
電流を効率よく透光性電極に流すことができ発光強度を
向上することができる。また、本発明の半導体発光素子
用電極では、第２の電極と重なった部分の第１の電極の
金属酸化物薄膜を除去したり、さらにその部分にＡｕ、
Ａｌ、Ｎｉなどの金線との接着性に優れる金属を積層す
ることにより、電極と金線との接着性を強固にすること
ができる。According to the electrode for a semiconductor light emitting device of the present invention, the first electrode having a light-transmitting property has a metal thin film formed on the semiconductor side and a metal oxide thin film formed on the metal thin film. Even when formed as a layered structure, good electrical contact between the first electrode and the second electrode can be obtained. In addition, different metals can be used as the metal in contact with the semiconductor in the light-transmitting first electrode and the second electrode for wire bonding. Therefore, a metal having a large contact resistance with the semiconductor can be used as the metal on the semiconductor side of the second electrode so as not to inject a current directly below the second electrode. This allows
A current can be efficiently passed through the translucent electrode, and the light emission intensity can be improved. Further, in the electrode for a semiconductor light emitting device of the present invention, the metal oxide thin film of the first electrode in a portion overlapping with the second electrode is removed, and further, Au,
By laminating a metal having excellent adhesion to a gold wire such as Al or Ni, the adhesion between the electrode and the gold wire can be strengthened.
【図１】従来の半導体発光素子用電極の断面図FIG. 1 is a cross-sectional view of a conventional semiconductor light emitting device electrode.
【図２】別の従来の半導体発光素子用電極の断面図FIG. 2 is a sectional view of another conventional electrode for a semiconductor light emitting device.
【図３】本発明の実施例１に係わる電極の構造の断面図FIG. 3 is a cross-sectional view of an electrode structure according to the first embodiment of the present invention.
【図４】本発明の実施例１に係わる電極の形状の平面図FIG. 4 is a plan view of the shape of an electrode according to the first embodiment of the present invention.
【図５】本発明の実施例２に係わる電極の構造の断面図FIG. 5 is a sectional view of an electrode structure according to a second embodiment of the present invention.
【図６】本発明の実施例２に係わる電極の形状の平面図FIG. 6 is a plan view of an electrode shape according to a second embodiment of the present invention.
１ 透光性電極 ２ パッド電極 ３ 窓部 ４ パッド電極と透光性電極の重なった部分 ５ 半導体基板 ６ ＡｕＢｅ層 ７ Ａｕ層 ８ 第２の電極（パッド電極） ８’ 第２の電極（パッド電極） ９ Ａｕ層 １０ ＮｉＯ層 １１ 第１の電極（透光性電極） １１’ 第１の電極（透光性電極） １２ ｎ側電極 １２’ ｎ側電極 １３ 第１の電極と第２の電極が重なった領域 １３’ 第１の電極と第２の電極が重なった領域 １４ ＡｕＢｅ層 １５ Ａｕ層 １６ Ｐｄ層 １７ ＳｎＯ層 REFERENCE SIGNS LIST 1 translucent electrode 2 pad electrode 3 window 4 overlapping portion of pad electrode and translucent electrode 5 semiconductor substrate 6 AuBe layer 7 Au layer 8 second electrode (pad electrode) 8 ′ second electrode (pad electrode 9) Au layer 10 NiO layer 11 First electrode (light-transmitting electrode) 11 'First electrode (light-transmitting electrode) 12 n-side electrode 12' n-side electrode 13 First electrode and second electrode Overlapping region 13 'A region where the first electrode and the second electrode overlap 14 AuBe layer 15 Au layer 16 Pd layer 17 SnO layer
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平７−94782（ＪＰ，Ａ) 特開 平９−129930（ＪＰ，Ａ) 特開 平９−129933（ＪＰ，Ａ) 実開 昭58−89956（ＪＰ，Ｕ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01L 33/00 ＪＩＣＳＴファイル（ＪＯＩＳ)──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-94782 (JP, A) JP-A-9-129930 (JP, A) JP-A-9-129933 (JP, A) 89956 (JP, U) (58) Field surveyed (Int. Cl. 7 , DB name) H01L 33/00 JICST file (JOIS)
Claims (3)
れた金属薄膜と該金属薄膜の上部に形成された金属酸化
物薄膜とを有する透光性の第１の電極と金属薄膜よりな
るワイヤボンド用の第２の電極とからなる半導体発光素
子用の電極において、前記第１の電極が第２の電極上の
全面を覆って形成され、第２の電極と重なった部分の第
１の電極の金属酸化物薄膜が除去され、その部分に金線
との接着性に優れる金属が積層されていることを特徴と
する半導体発光素子用の電極。1. A light-transmitting first electrode having a metal thin film formed on a semiconductor side and a metal oxide thin film formed on the semiconductor thin film formed on a semiconductor, and a metal thin film. In an electrode for a semiconductor light emitting element including a second electrode for wire bonding, the first electrode is formed to cover the entire surface of the second electrode, and the first electrode in a portion overlapping with the second electrode is formed. An electrode for a semiconductor light emitting device, wherein a metal oxide thin film of an electrode is removed, and a metal excellent in adhesion to a gold wire is laminated on the portion.
は、第２の電極において半導体と接触する金属よりも、
半導体に対する単位面積当たりの接触抵抗が小さいこと
を特徴とする請求項１に記載の半導体発光素子用の電
極。2. The method according to claim 1, wherein the metal contacting the semiconductor at the first electrode is smaller than the metal contacting the semiconductor at the second electrode.
2. The electrode for a semiconductor light emitting device according to claim 1, wherein the contact resistance per unit area with the semiconductor is small.
を特徴とする請求項１または２に記載の半導体発光素子
用の電極。3. The electrode for a semiconductor light emitting device according to claim 1, wherein the semiconductor is a GaN-based compound semiconductor.
Priority Applications (10)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28877097A JP3344296B2 (en) | 1997-10-21 | 1997-10-21 | Electrodes for semiconductor light emitting devices |
| US09/073,765 US6268618B1 (en) | 1997-05-08 | 1998-05-07 | Electrode for light-emitting semiconductor devices and method of producing the electrode |
| DE19861228A DE19861228B4 (en) | 1997-05-08 | 1998-05-08 | Method for producing a transparent electrode |
| DE19820777A DE19820777C2 (en) | 1997-05-08 | 1998-05-08 | Electrode for semiconductor light emitting devices |
| DE19861007A DE19861007B4 (en) | 1997-05-08 | 1998-05-08 | Electrode for light emitting semiconductor device - has high contact resistance wire bonding electrode overlying transparent electrode |
| US09/694,325 US6403987B1 (en) | 1997-05-08 | 2000-10-24 | Electrode for light-emitting semiconductor devices |
| US09/694,319 US6326223B1 (en) | 1997-05-08 | 2000-10-24 | Electrode for light-emitting semiconductor devices and method of producing the electrode |
| US10/136,377 US6800501B2 (en) | 1997-05-08 | 2002-05-02 | Electrode for light-emitting semiconductor devices and method of producing the electrode |
| US10/800,773 US7057210B2 (en) | 1997-05-08 | 2004-03-16 | Electrode for light-emitting semiconductor devices and method of producing the electrode |
| US10/871,578 US20040232429A1 (en) | 1997-05-08 | 2004-06-21 | Electrode for light-emitting semiconductor devices and method of producing the electrode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28877097A JP3344296B2 (en) | 1997-10-21 | 1997-10-21 | Electrodes for semiconductor light emitting devices |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11121804A JPH11121804A (en) | 1999-04-30 |
| JP3344296B2 true JP3344296B2 (en) | 2002-11-11 |
Family
ID=17734497
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28877097A Expired - Fee Related JP3344296B2 (en) | 1997-05-08 | 1997-10-21 | Electrodes for semiconductor light emitting devices |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3344296B2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6876003B1 (en) | 1999-04-15 | 2005-04-05 | Sumitomo Electric Industries, Ltd. | Semiconductor light-emitting device, method of manufacturing transparent conductor film and method of manufacturing compound semiconductor light-emitting device |
| US6287947B1 (en) * | 1999-06-08 | 2001-09-11 | Lumileds Lighting, U.S. Llc | Method of forming transparent contacts to a p-type GaN layer |
| WO2001059851A1 (en) | 2000-02-09 | 2001-08-16 | Nippon Leiz Corporation | Light source |
| JP2001223388A (en) * | 2000-02-09 | 2001-08-17 | Nippon Leiz Co Ltd | Light source device |
| KR100849737B1 (en) | 2007-07-06 | 2008-08-01 | (주)더리즈 | Light emitting diode device and manufacturing method thereof |
| US8431475B2 (en) * | 2007-08-31 | 2013-04-30 | Lattice Power (Jiangxi) Corporation | Method for fabricating a low-resistivity ohmic contact to a p-type III-V nitride semiconductor material at low temperature |
| JP5494005B2 (en) * | 2010-02-26 | 2014-05-14 | 豊田合成株式会社 | Semiconductor light emitting device |
| KR102042258B1 (en) * | 2013-01-29 | 2019-11-07 | 엘지이노텍 주식회사 | Light emitting device |
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1997
- 1997-10-21 JP JP28877097A patent/JP3344296B2/en not_active Expired - Fee Related
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| JPH11121804A (en) | 1999-04-30 |
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