JP2013243241A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor light-emitting element with high reliability by efficiently preventing migration of silver to a semiconductor.SOLUTION: A semiconductor light-emitting element has at least a first-conductivity-type semiconductor layer and a second-conductivity-type semiconductor layer, includes a first electrode connected to the first-conductivity-type semiconductor layer and a second electrode connected to the second-conductivity-type semiconductor layer, and is configured such that the first electrode and the second electrode are disposed on the same surface side of the first-conductivity-type semiconductor layer. The second electrode includes a stack of a first metal film containing a silver alloy or silver, a second metal film covering the first metal film and containing an aluminum alloy composed mainly of aluminum or aluminum, and a third metal film formed by sequentially stacking aluminum, an electroconductive metal, a gold alloy composed mainly of gold or gold on the second metal film and having a smaller area than the second metal film in a top view.

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to improvement of an electrode in a semiconductor light emitting device.

Conventionally, in a flip chip type nitride semiconductor light emitting device, a structure made of a silver alloy or silver is used as an electrode material for making an ohmic contact as a p-electrode. Since the silver alloy or silver efficiently reflects the light generated in the light emitting layer of the semiconductor light emitting element, a high luminance semiconductor light emitting element can be realized.
However, when silver is used as the p-side electrode material, a part of the surface of the silver electrode is exposed for connection to the outside, so that migration occurs and is promoted, and the emission intensity and lifetime are reduced. There was a problem of inviting.

Therefore, in order to prevent the surface of the silver electrode from being exposed, the silver electrode is completely covered with an electrode material not containing silver, or a plurality of through holes are provided between the silver electrode and the electrode material not containing silver and the silver electrode. There has been proposed a method for preventing migration of silver by disposing an SiO ₂ film having an electrical connection between a silver-free electrode and a silver electrode through the through hole (for example, Patent Document 1). .

JP 2003-168823 A

  However, when a silver electrode is covered with an electrode material that does not contain silver, there has been a problem that the silver of the silver electrode diffuses into the electrode material that does not contain silver due to the heat treatment after electrode formation or the heat treatment conditions. In particular, aluminum is described as an electrode material that does not contain silver, but it has been thought that aluminum cannot be used in practice. This is because metal bonding with a gold bump or the like used for bonding to the mounting substrate side becomes extremely poor.

In addition, when an SiO ₂ film is disposed between an electrode material not containing silver and a silver electrode, there is a problem in that the contact resistance between the two increases even though the electrical connection is ensured by the through hole. It was.
Furthermore, even if silver migration to the electrode material that does not contain silver is suppressed by physical blocking by the SiO ₂ film, it has not yet reached the point of effectively preventing silver migration to the nitride semiconductor layer, There has still been a problem that it is impossible to suppress a decrease in light emission intensity and a decrease in lifetime of the light emitting element due to silver migration.

  Therefore, the present invention has been made in view of the above problems. That is, the present invention effectively prevents migration of silver to a nitride semiconductor when a silver alloy having high reflection efficiency or an electrode having silver is formed in contact with the nitride semiconductor layer. An object is to obtain a highly reliable semiconductor light emitting device.

  The inventors of the present invention have conducted intensive research on silver migration of silver alloys or electrodes made of silver. As a result, silver migration in electrodes made of silver alloys or silver comes into contact with other electrode materials or semiconductors. In addition to heat treatment in the contact state or energization in the contact state, the electric field strength at the time of energization and the slight moisture and humidity around the semiconductor light emitting element act on the silver, It is known that this migration is likely to occur. Therefore, the inventors have found that the migration of silver can be dramatically avoided by reducing the electric field strength during energization and isolating the silver alloy or silver electrode from moisture and humidity. The invention has been completed.

  The present invention has at least a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, and is connected to the first electrode connected to the first conductivity type semiconductor layer and to the second conductivity type semiconductor layer. A second light emitting device, wherein the first electrode and the second electrode are arranged on the same surface side of the first conductivity type semiconductor layer, and the second electrode comprises: A silver alloy or a first metal film containing silver, a second metal film covering the first metal film and containing aluminum as a main component or aluminum, and aluminum as a main component on the second metal film An aluminum alloy or aluminum, a conductive metal, and a gold alloy or gold mainly composed of gold, and a third metal film having a smaller area than the second metal film in a top view. Related to semiconductor light emitting devicesAs the migration prevention film, an aluminum alloy containing aluminum as a main component or a second metal film containing aluminum is used. These also have the characteristic of high reflectivity. That is, the light emitted from the light emitting layer of the semiconductor light emitting element is efficiently reflected at the interface between the second metal film and the second conductive type semiconductor layer, and the light emission loss can be minimized. A semiconductor light emitting device with luminous efficiency can be obtained. In particular, since the current density is high in the region facing the first electrode, the emission intensity is relatively high, and more effects can be obtained. Further, by forming the third metal film, the bonding with the bumps on the mounting substrate side becomes extremely good. Thereby, migration of the silver alloy or silver used for the first metal film can be prevented, and a highly reliable semiconductor light emitting device can be obtained.

An aluminum oxide film is formed on the outermost surface of the second metal film other than the joint surface between the second metal film and the third metal film. Thereby, there is an effect that electrode damage in various manufacturing processes of semiconductor light emitting elements can be suppressed, and that a robust structure can be obtained with respect to various environments when used in a light emitting device.
The bonding surface between the second metal film and the third metal film preferably has a larger surface area in the aluminum layer than in the aluminum oxide layer. This is because the bonding between the second metal film and the third metal film can be further strengthened. More preferably, the aluminum of the second metal film and the aluminum of the third metal film are bonded without interposing aluminum oxide.
Preferably, the first metal film is completely covered with the second metal film. This is because silver migration can be further suppressed.
The second metal film outside the outer circumference of the first metal film is preferably 1 μm to 8 μm. This means that the shortest distance from the outer periphery of the first metal film to the outer periphery of the second metal film is 1 μm to 8 μm. The contact portion between the second metal film and the second conductivity type semiconductor layer is preferably a small area as much as possible, but it is because silver migration can be more effectively suppressed.
A protective film or a dielectric multilayer film is formed to cover the second conductive semiconductor layer, the second metal film, and a part of the third metal film. Thereby, electrode damage in the manufacturing process of the semiconductor light emitting device can be suppressed, and occurrence of leakage can be suppressed.

It is preferable that the third metal film of the second electrode and the first electrode are formed of the same material. The same material means not only in the case of a single layer but also in the case where a plurality of layers are laminated, each of the plurality of layers is the same material. More preferably, the third metal film of the second electrode and the first electrode are preferably formed with the same thickness. The same material means not only a single layer but also a plurality of layers having the same thickness when a plurality of layers are laminated.
It is preferable that a second metal bump is further formed on the second electrode. The second metal bump functions as a bump, and the bonding with the mounting substrate side can be further strengthened.

  According to the semiconductor light emitting device of the present invention, it is possible to suppress migration of silver used for the first metal film. In addition, a semiconductor light emitting element with high luminous efficiency can be provided. Furthermore, the bonding with the gold bumps on the mounting substrate side becomes extremely good. As described above, a highly reliable semiconductor light emitting device can be obtained.

1 is a schematic plan view of a semiconductor light emitting element in an embodiment. It is a schematic sectional drawing (part) of the semiconductor light-emitting device in an embodiment.

Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to the present invention will be described using embodiments and examples. However, the present invention is not limited to this embodiment and example.
FIG. 1 is a schematic plan view of a semiconductor light emitting device according to an embodiment. FIG. 2 is a schematic cross-sectional view (a part) of the semiconductor light emitting element in the embodiment. For convenience of explanation, in the cross-sectional view, the second electrode is disposed at the center of the second conductivity type semiconductor layer. Further, for convenience of explanation, the scales of the actual product and the drawings do not match.
In this specification, a portion described as an upper surface indicates a side on which an electrode is formed. Light from the semiconductor light emitting element is mainly emitted from the side opposite to the side where the electrodes are formed.

The semiconductor light emitting device 100 of the present invention has at least a first conductivity type semiconductor layer 10 and a second conductivity type semiconductor layer 30. In general, in the semiconductor light emitting device 100, a light emitting layer 20 is disposed between the first conductive semiconductor layer 10 and the second conductive semiconductor layer 30. The semiconductor light emitting device 100 includes a first electrode 40 connected to the first conductive semiconductor layer 10 and a second electrode 50 connected to the second conductive semiconductor layer 30, and the first electrode 40. And the second electrode 50 are disposed on the same surface side of the first conductive semiconductor layer 10. In the specification, the first conductive type semiconductor layer 10 and the second conductive type semiconductor layer 30 and the light emitting layer 20 or the first conductive type semiconductor layer 10 and the second conductive type semiconductor layer 30 are simply referred to as “semiconductors”. May be described as “layer”.
The size of the semiconductor light emitting device 100 is not particularly limited. For example, the semiconductor light emitting device 100 has not only a substantially square shape such as 1 mm on a side or 1.4 mm on a top view, but also a substantially rectangular shape such as a length of 700 μm and a width of 350 μm. It may be a thing.

  In the top view, the exposed first conductive semiconductor layer 10 is obtained by removing a part of the second conductive semiconductor layer 30 by etching or the like. In one semiconductor light emitting device 100, the exposed area of the first conductive semiconductor layer 10 and the area of the second conductive semiconductor layer 30 are preferably set to about 1:10 to 50, for example. The first electrode 40 is formed on the exposed surface of the first conductive semiconductor layer 10. The second electrode 50 is formed on the surface of the second conductive semiconductor layer 30. Therefore, the first electrode 40 and the second electrode 50 are disposed on the same plane in a top view.

  Here, the first conductivity type indicates p-type or n-type, and the second conductivity type indicates a conductivity type different from the first conductivity type, that is, n-type or p-type. Preferably, the first conductive semiconductor layer 10 is n-type, and the second conductive semiconductor layer 30 is p-type. The first conductive semiconductor layer 10 and the second conductive semiconductor layer 30 are usually formed on the substrate 70, but the substrate 70 may be removed.

In the second electrode 50, a first metal film 52, a second metal film 54, and a third metal film 56 are laminated in order from the second conductivity type semiconductor layer side 30. The first metal film 52 contains a silver alloy or silver. The second metal film 54 covers the first metal film 52 and contains an aluminum alloy or aluminum containing aluminum as a main component. The third metal film 56 is laminated on the second metal film 54 in the order of an aluminum alloy or aluminum mainly composed of aluminum, a conductive metal, and a gold alloy or gold mainly composed of gold. When viewed from above, the third metal film 56 has a smaller area than the second metal film 54.
A second metal bump 58 may be further formed on the second electrode 50. The second metal bump 58 is substantially circular in top view.
In the top view, the first electrodes 40 are arranged in four rows / rows, and the third metal films 56 of the second electrodes 50 are arranged in five rows so as to sandwich the first electrodes 40. . Out of the five rows of the third metal film 56, each outer row has only about half the size of the inner three rows. One row of the third metal film 56 may be divided into two, three or more and may not be divided.
The first metal film 52 covers a part of the upper surface of the second conductive semiconductor layer 30. The first metal film 52 preferably covers 80% or more of the upper surface of the second conductive semiconductor layer 30, and preferably covers 90% or more, more preferably 95% or more. The light emitted from the semiconductor layer is irradiated to the second electrode 50, particularly the first metal film 52, reflected, and the light is extracted to the semiconductor layer side. Thereby, the emission intensity of the semiconductor light emitting device 100 can be improved.

The second metal film 54 other than the bonding surface between the second metal film 54 and the third metal film 56 has an aluminum oxide 55 formed on the outermost surface. The thickness of the aluminum oxide 55 is preferably about 3 nm to 100 nm. The bonding surface between the second metal film 54 and the third metal film 56 is other than the bonding surface between the second metal film 54 and the second conductive semiconductor layer 30, and the second metal film 54 and the second metal film 54. Naturally, the joint surface with the first metal film 52 is also removed.
The bonding surface between the aluminum of the second metal film 54 and the aluminum of the third metal film 56 preferably has a larger surface area in the aluminum layer than in the aluminum oxide layer. More preferably, the aluminum of the second metal film 54 and the aluminum of the third metal film 56 are joined without the presence of aluminum oxide.
The thickness of the second metal film 54 is preferably about 0.5 μm to 8 μm.

The first metal film 52 is preferably completely covered with the second metal film 54. Therefore, the first metal film 52 is sandwiched between the second metal film 54 and the second conductive semiconductor layer 30.
The second metal film 54 outside the outer periphery of the first metal film 52 is preferably 1 μm to 8 μm. The first metal film 52 is covered with the second metal film 54, and the thickness of the second metal film 54 is 0.5 μm to 8 μm. Further, the second metal film is disposed outside the first metal film 52 by 1 μm to 8 μm in the horizontal direction (direction parallel to the second conductive semiconductor layer 30). As a result, silver migration from the first metal film 52 is suppressed.
A protective film 60 or a dielectric multilayer film is formed on the semiconductor light emitting device 100 so as to cover the second conductive type semiconductor layer 30, the second metal film 54, and the third metal film 56. It is preferable that The third metal film 56 does not need to cover the entire exposed portion, and may cover only the side surface, for example.

  The material and film thickness of the first electrode 40 are not limited, and can usually be formed of a single layer film or a laminated film of a conductive material that can be used as an electrode. The first electrode 40 is preferably disposed at a distance from the second conductive semiconductor layer 30 in the horizontal direction. These distances can be appropriately adjusted depending on the size of the semiconductor light emitting element 100 to be obtained, the material, size, and arrangement of the first electrode 40 and the second electrode 50. The shortest horizontal distance between the first electrode 40 and the second conductive semiconductor layer 30 may be, for example, about 0.5 μm or more, and preferably about 3 to 10 μm.

  The second electrode 50 is preferably in direct contact with the second conductive semiconductor layer 30 and is in ohmic contact. Here, the ohmic connection has a meaning normally used in the field, and refers to, for example, a junction whose current-voltage characteristic is a straight line or a substantially straight line. It also means that the voltage drop and power loss at the junction during device operation are negligibly small.

One or two or more of the second metal bumps 58 formed on the second electrode 50, that is, on the third metal film 56, are formed. The second metal bump 58 has a function as a bump and facilitates bonding to the mounting substrate side.
The first metal bump 48 is preferably formed on the first electrode 40. The number of the first metal bumps 48 is preferably one, but a plurality of two or more may be formed. The first metal bump 48 has a function as a bump and facilitates bonding to the mounting substrate side.
The first metal bumps 48 and the second metal bumps 58 are preferably formed to have the same height with respect to the substrate 70. That is, the first metal bump 48 has the light emitting layer 20, the second conductivity type semiconductor layer 30, and the first portion corresponding to the amount of etching of the first conductivity type semiconductor layer 10 compared to the second metal bump 58. The two electrodes 50 have an extra thickness. In order to form the first metal bump 48 and the second metal bump 58 so as to have the same height with respect to the substrate 70, the height can be adjusted using a surface sprayer. This is because it can be firmly bonded to a flat mounting substrate. However, the first metal bump 48 and the second metal bump 58 may have the same height. That is, the first metal bump 48 has the light emitting layer 20, the second conductivity type semiconductor layer 30, and the first portion corresponding to the amount of etching of the first conductivity type semiconductor layer 10 compared to the second metal bump 58. The two electrodes 50 are lowered from the substrate 70. This is because it can be mounted by arranging metal bumps having different heights on the mounting substrate side.

(Each component of the semiconductor light emitting device)
(Semiconductor layer, substrate)
Hereinafter, each component of the semiconductor light emitting device will be described.
As described above, the first conductive semiconductor layer and the second conductive semiconductor layer are generally formed on a substrate.
As said board | substrate, well-known insulating substrates, such as a sapphire, a spinel, SiC, GaN, GaAs, and an electroconductive board | substrate can be used, for example. Of these, a sapphire substrate is preferable. The insulating substrate may be finally removed or may not be removed.

The first conductive semiconductor layer, the second conductive semiconductor layer, and the light emitting layer (semiconductor layer) are not particularly limited, but are nitride semiconductors, for example, In _X Al _Y Ga _{1-X-. A} gallium nitride compound semiconductor such as YN (0 ≦ X, 0 ≦ Y, X + Y <1) is preferably used. The semiconductor layer may have a single layer structure, but may have a laminated structure such as a homostructure, a heterostructure, or a double heterostructure having a MIS junction, a PIN junction, or a PN junction, a superlattice structure, a quantum effect, or the like. It may be a single quantum well structure or a multiple quantum well structure in which thin films where the above occurs are stacked. The semiconductor layer may be doped with either n-type or p-type impurities. The semiconductor layer can be formed by a known technique such as metal organic chemical vapor deposition (MOCVD), hydride vapor deposition (HVPE), molecular beam epitaxy (MBE), or the like. The film thickness of the semiconductor layer is not particularly limited, and various film thicknesses can be applied.

Examples of the laminated structure of the semiconductor layers include those shown in the following (1) to (5).
(1) A buffer layer (film thickness: 20 nm) made of GaN, an n-side contact layer (4 μm) made of Si-doped n-type GaN, and a light emitting layer having a single quantum well structure made of undoped In _0.2 Ga _0.8 N (3 nm), a p-type cladding layer (0.2 μm) made of Mg-doped p-type Al _0.1 Ga _0.9 N, and a p-side contact layer (0.5 μm) made of Mg-doped p-type GaN.

(2) A buffer layer (thickness: about 10 nm) made of AlGaN, an undoped GaN layer (1 μm), an n-side contact layer (5 μm) made of GaN containing 4.5 × 10 ¹⁸ / cm ^{3 of} Si, and made of undoped GaN An n-side first multilayer film layer composed of a lower layer (300 nm), an intermediate layer (30 nm) made of GaN containing Si of 4.5 × 10 ¹⁸ / cm ³ , and an upper layer (5 nm) made of undoped GaN ( (Total film thickness: 335 nm), undoped GaN (4 nm) and undoped In _0.1 Ga _0.9 N (2 nm) are laminated alternately and 10 layers each, and a superlattice structure in which undoped GaN (4 nm) is further laminated N-side second multilayer film (total film thickness: 64 nm), undoped GaN barrier layer (25 nm), and In _0.3 Ga _0.7 N well layer (3n m) and a light emitting layer having a multiple quantum well structure (total film thickness: 193 nm) in which 6 layers are alternately stacked alternately and a barrier layer (25 nm) made of undoped GaN is stacked, Mg is 5 × 10 ¹⁹ / cm ³ includes _Al 0.15 _Ga 0.85 N and (4 nm) and a Mg containing _{^{5 × 10 19 / cm 3 in}} 0.03 Ga 0.97 N (2.5nm) are laminated alternately one by repeating five layers Furthermore, a p-side multilayer film layer (total film thickness: 36.5 nm) having a superlattice structure in which Al _0.15 Ga _0.85 N (4 nm) containing 5 × 10 ¹⁹ / cm ^{3 of} Mg is laminated, and 1 × A p-side contact layer (120 nm) made of GaN containing 10 ²⁰ / cm ³ .

(3) AlGaN buffer layer (film thickness: about 10 nm) undoped GaN layer (1 μm), n-side contact layer (5 μm) made of GaN containing Si 4.5 × 10 ¹⁸ / cm ³ , lower layer made of undoped GaN (300 nm), an n-side first multilayer film layer (total of 3 layers of an intermediate layer (30 nm) made of GaN containing Si of 4.5 × 10 ¹⁸ / cm ³ and an upper layer (5 nm) made of undoped GaN (Thickness: 335 nm), undoped GaN (4 nm) and undoped In _0.1 Ga _0.9 N (2 nm) are repeatedly stacked alternately in 10 layers, and further, undoped GaN (4 nm) is stacked. n-side second multilayer film layer (total film thickness: 64 nm), barrier layer (25 nm) made of undoped GaN, and well layer (3 nm) made of In _0.3 Ga _0.7 N ) And In _0.02 Ga _0.98 N, a first barrier layer (10 nm) and a second barrier layer (15 nm) made of undoped GaN are repeatedly stacked alternately in six layers. Light-emitting layer having a structure (total film thickness: 193 nm) (the layer that is alternately and repeatedly stacked is preferably in the range of 3 to 6 layers), Al _0.15 Ga _0.85 N (containing 5 × 10 ¹⁹ / cm ^{3 of} Mg) 4 nm) and 5 × the Mg ¹⁰ 19 / cm ³ comprises _in 0.03 _Ga 0.97 N (2.5nm) and is 5 × further Mg are stacked in alternating repeating five layers ¹⁰ 19 / cm ³ containing Al P-side multilayer layer (total film thickness: 36.5 nm) having a superlattice structure in which _0.15 Ga _0.85 N (4 nm) is stacked, p-side contact made of GaN containing 1 × 10 ²⁰ / cm ^{3 of} Mg Layer (120 nm).

Of these, the lower layer (300 nm) made of undoped GaN provided on the n side is the first layer (150 nm) made of undoped GaN from the bottom, and the second layer made of GaN containing 5 × 10 ¹⁷ / cm ^{3 of} Si. By using a lower layer of a three-layer structure consisting of (10 nm) and a third layer (150 nm) made of undoped GaN, it becomes possible to suppress the variation in Vf with the lapse of the driving time of the light emitting element.

  Furthermore, GaN or AlGaN (200 nm) may be formed between the p-side multilayer film layer and the p-side contact layer. This layer is undoped and exhibits p-type due to diffusion of Mg from adjacent layers. By providing this layer, the electrostatic withstand voltage of the light emitting element is improved. This layer may be omitted when used in a light emitting device provided with an electrostatic protection function separately, but when an electrostatic protection means such as an electrostatic protection element is not provided outside the light emitting element, an electrostatic withstand voltage is not required. Since it can improve, providing is preferable.

(4) Buffer layer, undoped GaN layer, n-side contact layer made of GaN containing 6.0 × 10 ¹⁸ / cm ^{3 of} Si, undoped GaN layer (the above is an n-type nitride semiconductor layer having a total film thickness of 6 nm), Si Of multiple quantum wells (total film thickness: 100 nm) in which 5 layers of GaN barrier layers and InGaN well layers containing 2.0 × 10 ¹⁸ / cm ³ are alternately stacked, and Mg is 5.0 × 10 ^A p-type nitride semiconductor layer (film thickness: 130 nm) made of GaN containing ¹⁸ / cm ³ .

  Furthermore, an InGaN layer (30 to 10 nm, preferably 5 nm) may be provided on the p-type nitride semiconductor layer. Thereby, this InGaN layer becomes a p-side contact layer in contact with the electrode. Thus, even a layer not doped with Mg functions as a p-type nitride semiconductor layer for forming a p-electrode if the film thickness is relatively smaller than that of an adjacent p-type semiconductor layer.

(5) Buffer layer, undoped GaN layer, n-side contact layer made of GaN containing 1.3 × 10 ¹⁹ / cm ^{3 of} Si, undoped GaN layer (the above is an n-type nitride semiconductor layer with a total film thickness of 6 nm), Si Is a multiple quantum well light emitting layer (total film thickness: 80 nm) in which 7 layers of GaN barrier layers and InGaN well layers containing 3.0 × 10 ¹⁸ / cm ³ are alternately stacked, and Mg is 2.5 × 10 ^A p-type nitride semiconductor layer made of GaN containing ²⁰ / cm ³ . An InGaN layer (30 to 10 nm, preferably 5 nm) may be formed on the p-type nitride semiconductor layer as a p-side contact layer.

A semiconductor light emitting device constituted by these semiconductor layers is generally quadrangular or substantially similar in shape when viewed from above, and the first conductivity type semiconductor layer has a first region in a part of one semiconductor light emitting device. A part of the two-conductivity-type semiconductor layer and the light emitting layer, optionally the first semiconductor layer, in the depth direction is removed to expose the surface.
(electrode)

The second electrode is formed by laminating a first metal film, a second metal film, and a third metal film in order from the second conductivity type semiconductor layer side. The first metal film contains a silver alloy or silver. The meaning of “contained” means containing at least 85% silver. The second metal film covers the first metal film and contains an aluminum alloy or aluminum containing aluminum as a main component. The meaning of “contained” means containing at least 85% aluminum. The third metal film is laminated on the second metal film in the order of aluminum, a conductive metal, a gold alloy containing gold as a main component or gold, and has a smaller area than the second metal film in a top view. It is.
The first metal film is ohmic-connected to the second conductive type semiconductor layer so as to efficiently input current and to reflect light from the light emitting layer efficiently.

The first metal film may be a silver single layer film, a silver alloy single layer film, or a laminated film containing silver or a silver alloy in the lowermost layer.
Examples of the silver alloy include silver, Ni, Pt, Co, Au, Pd, Ti, Mn, V, Cr, Zr, Rh, Cu, Al, Mg, Bi, Sn, Ir, Ga, Nd, Ru, and Re. And an alloy of one or more electrode materials selected from the group consisting of: The Ni is not easily alloyed with silver, but may contain Ni element in the silver film.

The composition of the first metal film may be inclined from the second conductive semiconductor layer side to the second metal film side. For example, the second conductive type semiconductor layer side may be a silver film or an alloy containing silver and an element other than silver up to about 1%, and the second metal film side may be about 5% with silver. An alloy containing elements other than silver may be used.
The film other than the lowermost layer may be silver or a silver alloy, or may be formed of an electrode material that does not contain silver or a silver alloy. In addition, the films other than the lowermost layer substantially do not react with silver, a single layer film of two or more kinds of metal or alloy selected from the group including these electrode materials and Ni, or a laminated film of two or more layers. A metal film or the like is preferable.

  A preferable example of the first metal film is a single layer film of silver, and further has a two-layer structure of metal (upper) / silver or silver alloy (lower) that does not substantially react with silver, noble metal (upper) / Two-layer structure of silver or silver alloy (bottom), noble metal (top) / three-layer structure of metal (medium) / silver or silver alloy (bottom) that does not substantially react with silver, two layers of noble metal (top) / silver A 4-layer structure of metal (medium) / silver or silver alloy (bottom) that does not substantially react is more preferable. Examples of the noble metal include platinum group metals and gold. Among them, Pt and gold are preferable.

  As a metal that does not substantially react with silver, a metal that does not substantially react with silver at a temperature of 1000 ° C. or less, specifically, nickel (Ni), ruthenium (Ru), osmium (Os), iridium (Ir) , Titanium (Ti), vanadium (V), niobium (Nb), tantalum (Ta), cobalt (Co), iron (Fe), chromium (Cr), tungsten (W), and the like. Of these, Ni is preferable.

  The film thickness of the first metal film is not particularly limited. For example, in the case of a silver or silver alloy single layer, the film thickness that can effectively reflect light from the light emitting layer, specifically, 20 nm to 1 μm. About 50 nm to 300 nm, preferably about 100 nm. In the case of a laminated structure, the total film thickness is about 50 nm to 5 μm and about 50 nm to 1 μm. Within this range, the silver or silver alloy film contained therein can be appropriately adjusted. In the case of a laminated structure, the silver or silver alloy film and the film laminated thereon may have the same shape by patterning in the same process. It is preferable to coat with a film laminated thereon (preferably a metal film that does not react with silver). As a result, no matter what electrode material is formed as a part of the first metal film on the metal film that does not react with silver, it does not come into direct contact with the silver or silver alloy film. Can be blocked.

  The first metal film may be crystallized at least at the interface with the semiconductor layer depending on the stacked state, for example, when a nickel film is disposed immediately above the silver single layer film. By crystallization of the first metal film, better ohmic properties with the semiconductor layer can be ensured. Here, crystallization is, for example, a method of observing a cross section by transmission electron microscopy (TEM), a method of observing by scanning electron microscopy (SEM), a method of measuring an electron diffraction pattern, or an ultra-thin film evaluation apparatus. It means that the interface of crystal grains can be visually recognized by an observation method or the like. It is preferable that the crystal grains in this case can be visually recognized as having a diameter (length, height, or width) of, for example, about 10 nm to 100 nm.

  The method for crystallizing the first metal film at the interface with the semiconductor layer is performed after the first metal film is formed by a known method such as a vapor deposition method, a sputtering method, or an ion beam assisted vapor deposition method. And a method of performing a heat treatment in a temperature range of about 300 to 600 ° C. for about 10 to 30 minutes in an air atmosphere or a nitrogen atmosphere.

  It is preferable that the second metal film completely or substantially completely covers the first metal film, and that the second metal film partially contacts (or covers) the upper surface of the second conductive semiconductor layer. “Completely or substantially completely covering” means that the second metal film is not actively subjected to processing that exposes the first metal film. Therefore, it is more preferable that the entire upper surface and the entire side surface of the first metal film are substantially covered.

  Since the second electrode is intended to efficiently reflect light from the light emitting layer as described above, the relationship between the second conductive semiconductor layer and the first metal film is as follows. As long as it is satisfied, it is preferable that the first metal film and the second conductive type semiconductor layer are formed on a substantially entire surface with a large area. Thereby, light from the light emitting layer can be extracted with high efficiency.

  The second metal film covers the first metal film and contains an aluminum alloy or aluminum containing aluminum as a main component. This aluminum alloy containing aluminum as a main component means one containing 90% or more of aluminum, but more preferably containing 95% or more of aluminum. For example, AlCu containing 98% Al and 2% Cu.

The second metal film does not need to be a single layer of aluminum, and may be a multilayer of two or more layers. For example, a three-layer structure film such as the AlCu / W / Ti or Al / W / Ti film is preferable.
Further, it is preferable that a metal that does not substantially react with silver is disposed at the interface between the second metal film and the first metal film.

Moreover, it is preferable to arrange a conductive material usually used for connection with other terminals such as wire bonding, such as gold or platinum, on the upper surface (connection region) of the second metal film on these electrodes. . Furthermore, it is preferable that a material having good adhesion with a protective film or a dielectric multilayer film described later is disposed on the upper surface of the second metal film.
The film thickness of the second metal film is not particularly limited, and specifically, it is preferably adjusted as appropriate in the range where the total film thickness is about 0.5 μm to 4.0 μm.

The third metal film preferably functions as a pad electrode. Therefore, the third metal film is disposed on a part of the upper surface of the second metal film. The number of the third metal films formed in the semiconductor light emitting element is not necessarily one, and preferably has two or more. The third metal film can have various shapes such as a rectangle, a square, a rounded corner, a circle, and an ellipse when viewed from above. For example, in the case of a square semiconductor light emitting device having a side of 1400 μm, the third metal film can be a substantially rectangular shape having a side of 1200 to 1350 μm and the other side of 10 to 300 μm. Moreover, it can also be set as the substantially circular shape whose diameter is 10 micrometers-100 micrometers, and a substantially elliptical shape whose major axis is 20 micrometers-150 micrometers, and whose minor axis is 10 micrometers-130 micrometers.
The third metal film is laminated on the second metal film in the order of an aluminum alloy or aluminum mainly composed of aluminum, a conductive metal, and a gold alloy or gold mainly composed of gold. These metals may be diffused with each other.

Here, the conductive metal is not particularly limited. For example, zinc (Zn), nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium. (Ir), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), chromium (Cr), tungsten (W), lanthanum (La), copper (Cu), silver (Ag), yttrium (Y), tin (Sn) and other metals, alloys, ITO, ZnO ₂ , SnO Examples thereof include a single layer film or a laminated film of a conductive oxide film. Moreover, the gold alloy which has gold as a main component says what contains 50% or more of gold, Preferably it is 80% or more. More preferably, gold: tin is 80:20.

The first electrode is formed on the first conductive semiconductor layer.
The first electrode is preferably made of the same material as the third metal film of the second electrode.
The first electrode preferably functions as a pad electrode. Therefore, the first electrode is disposed on a part of the upper surface of the second conductive semiconductor layer. The number of the first electrodes formed in the semiconductor light emitting element is not necessarily one, and it is preferable to have two or more. In addition, the first electrode can have various shapes such as a rectangle, a square, rounded corners, a circle, and an ellipse when viewed from above. For example, a substantially circular shape having a diameter of 10 μm to 100 μm, a substantially elliptical shape having a major axis of 20 μm to 150 μm, and a minor axis of 10 μm to 130 μm can be used. The first electrode is preferably smaller than the third metal film.

The first electrode is laminated in the order of aluminum alloy or aluminum containing aluminum as a main component, aluminum, conductive metal, and gold alloy or gold containing gold as a main component. These metals may be diffused with each other.
Here, the conductive metal is not particularly limited. For example, zinc (Zn), nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium. (Ir), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), chromium (Cr), tungsten (W), lanthanum (La), copper (Cu), silver (Ag), yttrium (Y), tin (Sn) and other metals, alloys, ITO, ZnO ₂ , SnO Examples thereof include a single layer film or a laminated film of a conductive oxide film. Moreover, the gold alloy which has gold as a main component says what contains 50% or more of gold, Preferably it is 80% or more. More preferably, gold: tin is 80:20.

(Protective film, dielectric multilayer film)
It is preferable that a protective film or a dielectric multilayer film covering the surface of the second metal film is provided. The protective film or the dielectric multilayer film covers, for example, part or all of the outer periphery of the second metal film, and covers part or all of the upper surface and / or the side surface of the first and second semiconductor layers. More preferably, it is formed. The protective film or the dielectric multilayer film is preferably formed so as to cover the side surface of the third metal film.
As the protective film, an oxide film (SiO ₂ , Al ₂ O ₃ ) and a nitride film are preferably used, and a nitride film is more preferable. Typical examples of the nitride film include a single-layer film or a laminated film such as SiN, TiN, and SiO _x N _y . Among these, a single layer film of SiN or the like is preferable. Thus, it is considered that by using a nitride film as a protective film covering the electrode, nitrogen atoms capture moisture or moisture and effectively prevent moisture or moisture from being applied to the electrode made of silver and a silver alloy. Migration can be prevented.
However, since the migration of the first metal film is prevented by the second metal film, the protective film may be SiO ₂ . Thus, the semiconductor light emitting device can be easily manufactured.
The protective film or the dielectric multilayer film does not need to completely cover the electrode, and the electrode is preferably covered except for a region necessary for connection with other terminals. The film thickness of the protective film or the dielectric multilayer film is suitably about 400 to 1000 nm, for example.

(Mounting board)
The semiconductor light emitting element is usually mounted on a mounting substrate by flip chip mounting (face down mounting) to constitute a semiconductor light emitting device.
The mounting substrate may be provided with wiring on at least a surface facing the electrode of the semiconductor light emitting element, and the protection element or the like may be arbitrarily formed, and the flip-chip mounted semiconductor light emitting element is fixed and supported. . The mounting substrate is preferably made of a material having substantially the same thermal expansion coefficient as that of the semiconductor light emitting element, for example, aluminum nitride relative to the nitride semiconductor light emitting element. Thereby, the influence of the thermal stress generated between the mounting substrate and the semiconductor light emitting element can be reduced. Further, silicon that can be added with a function such as an electrostatic protection element and is inexpensive may be used. The wiring pattern is not particularly limited. For example, it is preferable that a pair of positive and negative wiring patterns be insulated and separated so as to surround one another.
When the mounting substrate is connected to the lead electrode, wiring may be provided by a conductive member from the surface facing the semiconductor light emitting element to the surface facing the lead electrode.

A semiconductor light emitting device according to Example 1 is shown in FIGS. However, the description overlapping with the embodiment may be omitted.
The semiconductor light emitting device 100 has a size of 1.4 mm in length and 1.4 mm in width.
In this semiconductor light emitting device 100, a buffer layer (not shown) made of Al _0.1 Ga _0.9 N and a non-doped GaN layer (not shown) are stacked on a sapphire substrate 70, and a As a one-conductivity-type semiconductor layer (n-type semiconductor layer) 10, an n-side contact layer made of Si-doped GaN, a superlattice n-type clad in which GaN layers (4 nm) and InGaN layers (2 nm) are alternately stacked 10 times A light emitting layer 20 having a multiple quantum well structure in which a GaN layer (25 nm) and an InGaN layer (3 nm) are alternately stacked 3 to 6 times, and a second conductivity type semiconductor layer (p-type) as the semiconductor layer) 30, Mg-doped _{the Al} 0.1 _{Ga 0.9} N _layer, (4 nm) and Mg-doped InGaN layer (2 nm) and superlattice p-type cladding layer stacked 10 times alternately, Mg-doped GaN p-side contact layer made which are stacked in this order.

  In a partial region of the first conductivity type semiconductor layer (n-type semiconductor layer) 10, the light emitting layer 20 and the second conductivity type semiconductor layer (p-type semiconductor layer) 30 stacked thereon are removed, and the first A part of the one-conductivity-type semiconductor layer (n-type semiconductor layer) 10 itself in the thickness direction is removed and exposed, and the first electrode is formed on the exposed first-conductivity-type semiconductor layer (n-type semiconductor layer) 10. (N electrode) 40 is formed.

A second electrode (p electrode) 50 is formed on the second conductive semiconductor layer (p-type semiconductor layer) 30. The second electrode 50 is formed in the order of the first metal film 52, the second metal film 54, and the third metal film 56 from the second conductivity type semiconductor layer 30 side.
In the top view, the first electrodes 40 are arranged in four rows / columns, and the third metal films 56 of the second electrodes 50 are arranged in five rows so as to sandwich the rows of the first electrodes 40. Out of the five rows of the third metal film 56, each one row on the outer side has only about half the size of the inner three rows. One row of the third metal film 56 is divided into two. Further, 8 to 9 second metal bumps 58 are formed on the third metal film 56 in a row. Further, one first metal bump 48 is formed on one first electrode 40.
The first metal film 52 is laminated with a thickness of 100 nm in the order of Ag / Ni / Ti / Ru from the second conductivity type semiconductor layer 30 side. The first metal film covers about 90% of the upper surface of the second conductivity type semiconductor layer 30.

The second metal film 54 is laminated at 2000 nm / 100 nm / 3 nm in the order of AlCu / Ru / Ti from the first metal film 52 side. The second metal film 54 completely covers the first metal film 52. The distance (thickness) from the outer periphery of the first metal film 52 to the outer periphery of the second metal film 54 is about 4 to 4.5 μm.
The third metal film 56 is laminated at 500 nm / 150 nm / 50 nm / 450 nm in the order of AlCuSi / Ti / Pt / Au from the second metal film 54 side. The third metal film 56 is formed in five rows on a part of the second metal film 54. One third metal film 56 in the outer two rows is 600 μm long and 90 μm wide. The inner three rows of third metal films 56 are 1300 μm long and 180 μm wide.
At the junction between the second metal film 54 and the third metal film 56, the second metal film 54 is formed so as to expose AlCu by etching or the like. As a result, the junction between the second metal film 54 and the third metal film 56 is joined by the AlCu of the second metal film 54 and the AlCuSi of the third metal film 56. As a result, the bonding between the second metal film 54 and the third metal film 56 can be strengthened.

The first electrode 40 and the third metal film 56 have the same stacked structure and the same thickness. This is because the first electrode 40 and the third metal film 56 are stacked in the same process.
Aluminum oxide 55 is formed on the surface of the second metal film 54 other than the portion covered with the third metal film 56. From the viewpoint of adhesion, it is preferable that no aluminum oxide is formed at the interface between the third metal film 56 and the second metal film 54.

The second metal bump 58 is formed with a weight ratio of Au / Sn of 80:20. The second metal bump 58 has a diameter of 70 μm.
The first metal bump 48 is formed of Au: Sn at a weight ratio of 80:20. The first metal bump 48 has a diameter of 60 μm. The second metal bump 58 and the first metal bump 48 have the same laminated structure.
The surfaces of the first conductive semiconductor layer 10 and the second conductive semiconductor layer 30, the second metal film 54, and the third metal film 56 are covered with a protective film 60. However, the protective film 60 may be configured such that the third metal film 56 and the first electrode 40 are not covered with the protective film 60. Protective film 60 made of SiO _2. The thickness of the protective film 60 is 400 nm.
By forming the aluminum oxide 55 on the surface of the second metal film 54 that is not bonded to the third metal film 56, the adhesion with the protective film 60 can be enhanced. This is because the protective film 60 and the second metal film 54 are both oxides. In particular, since the aluminum oxide 55 is formed on the side surface of the second metal film 54, the adhesion with the protective film 60 can be improved.

A semiconductor light emitting device according to Example 2 will be described. Since the semiconductor light emitting device according to Example 2 is substantially the same as Example 1 except that the laminated structure of the second electrode is different, the description of the overlapping portion is omitted.
The first metal film 52 is laminated with a film thickness of 100 nm / 200 nm in the order of Ag / Ru from the second conductivity type semiconductor layer 30 side.
The second metal film 54 is an AlCu single film having a thickness of 2000 nm.
The third metal film 56 is laminated at 500 nm / 200 nm / 450 nm in the order of AlCuSi / Ni / Au from the second metal film 54 side.

  The semiconductor light emitting device of the present invention can be suitably used for a semiconductor light emitting device constituting various light sources such as a backlight light source, a display, illumination, and a vehicle lamp.

DESCRIPTION OF SYMBOLS 10 1st conductivity type semiconductor layer 20 Light emitting layer 30 2nd conductivity type semiconductor layer 40 1st electrode 50 2nd electrode 52 1st metal film 54 2nd metal film 56 3rd metal film 60 Protective film 70 Substrate 100 Semiconductor light emitting element

Claims (8)

A first electrode having at least a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, connected to the first conductivity type semiconductor layer, and a second electrode connected to the second conductivity type semiconductor layer The first electrode and the second electrode are arranged on the same surface side of the first conductivity type semiconductor layer,
The second electrode includes a first metal film containing silver alloy or silver,
A second metal film covering the first metal film and containing aluminum alloy or aluminum containing aluminum as a main component;
On the second metal film, an aluminum alloy or aluminum containing aluminum as a main component or aluminum, a conductive metal, and a gold alloy or gold containing gold as a main component are laminated in this order. A third metal film having a small area;
A semiconductor light emitting element characterized by being laminated.   2. The semiconductor light emitting element according to claim 1, wherein an aluminum oxide film is formed on an outermost surface of the second metal film other than a bonding surface between the second metal film and the third metal film.   3. The semiconductor light emitting element according to claim 1, wherein a bonding surface between the second metal film and the third metal film has a larger surface area in the aluminum layer than in the aluminum oxide layer.   4. The semiconductor light emitting device according to claim 1, wherein the first metal film is completely covered with a second metal film. 5.   5. The semiconductor light emitting element according to claim 1, wherein the second metal film outside the outer periphery of the first metal film is 2 μm to 7 μm.   A protective film or a dielectric multilayer film is formed to cover the second conductive semiconductor layer, the second metal film, and a part of the third metal film. The semiconductor light emitting element according to any one of 1 to 5.   7. The semiconductor light emitting element according to claim 1, wherein the third metal film of the second electrode and the first electrode are formed of the same material.   8. The semiconductor light emitting device according to claim 1, wherein a second metal bump is further formed on the second electrode. 9.