Semiconductor light-emitting element comprising an insulating reflection layer including plural opening portions

A semiconductor light-emitting element includes: a laminated semiconductor layer in which an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer are laminated; a transparent conductive layer laminated on the p-type semiconductor layer of the laminated semiconductor layer and composed of a metal oxide having optical transparency to light emitted from the light-emitting layer; an insulating reflation layer laminated on the transparent conductive layer in which plural opening portions are provided to expose part of the transparent conductive layer; a metal reflection layer formed on the insulating reflection layer and inside the opening portions and composed of a metal containing aluminum; and a metal contact layer provided between the part of the transparent conductive layer exposed at the opening portion and the part of the metal reflection layer formed inside the opening portion, which contains an element selected from Group VIA and Group VIII of a periodic table.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC §119 from Japanese Patent Application No. 2012-104044 filed Apr. 27, 2012.

BACKGROUND

1. Technical Field

The present invention relates to a semiconductor light-emitting element.

2. Related Art

In recent years, a flip-chip bonding (FC) mount technology has been developed, in which a semiconductor light-emitting element formed on a substrate that is transparent to light emission wavelength is reversed and mounted on a circuit board (submount) or a package. The flip-chip bonding is a mounting method that extracts light mainly from a surface on a growing substrate side that is opposite to an electrode forming surface, and is also referred to as a face-down mounting. For example, in Japanese Patent Application Laid-Open Publication No. 2010-263016, there is disclosed a semiconductor light-emitting element that includes a substrate made of sapphire, and a laminated semiconductor layer including an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer to be laminated on the substrate, and is mounted by flip-chip bonding.

Incidentally, the semiconductor light emitting element mounted by flip-chip bonding is required to have a high reflectance for outputting light from the light-emitting layer in the direction of the substrate side to improve brightness. As a metal having high reflectivity, silver (Ag) is used.

However, silver (Ag) has high migration properties compared to other elements, and therefore, for example, defects due to a GaN potential is affected and a leakage current occurs in some cases. In addition, for preventing the migration phenomenon, for example, a method of providing a barrier layer to a metal reflection film containing silver (Ag) or the like can be considered; however, a problem of complicating manufacturing processes or the like is further generated.

An object of the present invention is to improve reliability of a metal reflection film in the FC (flip-chip bonding) mounting technology for a semiconductor light-emitting element.

SUMMARY

According to the present invention, there is provided a semiconductor light-emitting element including: a laminated semiconductor layer in which an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer are laminated; a transparent conductive layer that is laminated on the p-type semiconductor layer of the laminated semiconductor layer and is composed of a metal oxide having optical transparency to light emitted from the light-emitting layer; an insulating reflection layer that is laminated on the transparent conductive layer, in which plural opening portions are provided to expose part of the transparent conductive layer; a metal reflection layer that is formed on the insulating reflection layer and inside the opening portions of the insulating reflection layer, and is composed of a metal containing aluminum; and a metal contact layer that is formed at least between the part of the transparent conductive layer exposed at the opening portion and part of the metal reflection layer formed inside the opening portion, and contains an element selected from Group VIA and Group VIII of a periodic table.

Here, it is preferable that the metal contact layer at least contains an element selected from chromium, molybdenum and nickel.

Moreover, it is preferable to include a first metal layer containing aluminum or an aluminum-neodymium alloy and a second metal layer containing tantalum or nickel between the metal contact layer and the metal reflection layer.

Further, it is preferable that the metal reflection layer contains aluminum or an aluminum-neodymium alloy.

Still further, it is preferable that the insulating reflection layer is made of a multilayer insulating layer configured by alternately laminating a first insulating layer having a first refractive index and optical transparency to the light emitted from the light-emitting layer and a second insulating layer having a second refractive index, which is higher than the first refractive index, and optical transparency to the light emitted from the light-emitting layer.

According to the present invention, reliability of a metal reflection film is improved in the FC (flip-chip bonding) mounting technology for a semiconductor light-emitting element.

Moreover, in comparison with a case where a metal contact layer containing an element selected from Group VIA and Group VIII of the periodic table is not provided between a metal reflection layer containing aluminum and a transparent conductive layer, oxidation of the metal reflection layer is suppressed, and thereby increase of a forward voltage (Vf) is suppressed.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments according to the present invention will be described in detail. It should be noted that the present invention is not limited to the following exemplary embodiments, but may be practiced as various modifications within the scope of the gist of the invention. In other words, unless otherwise specified, dimensions, materials, shapes or relative arrangement of components described in the specific examples of the exemplary embodiments do not purport to limit the scope of the present invention, but are merely descriptive examples. Further, each of the figures to be used indicates a specific example for illustration of each exemplary embodiment, and does not represent an actual size thereof. Moreover, in this specification, a phrase such as “the layer A formed above (over) the layer B” not only means the case where the layer A is formed above (over) the layer B with a separation therebetween, but also includes the case where the layer A is formed above (over) the layer B with some layer being interposed therebetween.

FIG. 1is a plan schematic view illustrating a first exemplary embodiment, which is a specific example of a semiconductor light-emitting element.

The semiconductor light-emitting element10shown inFIG. 1has a square planar shape, on a center portion of which an n-electrode layer140as a negative electrode is formed. In the n-electrode layer140, part of an n-electrode bonding layer144used for electrical connection with an outside is exposed. A p-electrode layer130as a positive electrode is formed to cover substantially an entire top surface of a semiconductor layer120, which will be described later (refer toFIG. 2), except for a portion where a part of the semiconductor layer120is removed by etching or the like for forming the n-electrode layer140. In the p-electrode layer130, at each of four portions that are close to four corners of the semiconductor light-emitting element10, part of a p-electrode bonding layer135used for electrical connection with an outside is exposed.

As will be described later, in an insulating reflection layer132(refer toFIG. 2) of the p-electrode layer130, plural opening portions132hare formed. The opening portion132his indicated as a circular blank portion (diameter is 8 μm). InFIG. 1, a pattern is shown in which the plural opening portions132hare arranged with intervals (pitch1) in the entire insulating reflection layer132(refer toFIG. 2) (referred to as “isolation pattern”).

Next, description will be given of a cross-sectional structure of the semiconductor light-emitting element10.

FIG. 2is an II-II cross-sectional schematic view showing the semiconductor light-emitting element10shown inFIG. 1. Here, the semiconductor light-emitting element10is rendered in a state where the semiconductor light-emitting element10is reversed to be subjected to flip-chip mounting in which the substrate110faces upwardly. In the following description, expression such as “on (above or over) the layer” means that each layer is laminated downwardly in the figure.

As shown inFIG. 2, the semiconductor light-emitting element10includes the substrate110, the semiconductor layer120laminated on the substrate110, and the p-electrode layer130as the positive electrode and the n-electrode layer140as the negative electrode formed on the semiconductor layer120.

The semiconductor layer120includes an intermediate layer (buffer layer)121formed on the substrate110and a base layer122laminated on the intermediate layer121. The semiconductor layer120also includes a laminated semiconductor layer126laminated on the base layer122. The laminated semiconductor layer126is configured with, from the base layer122side, an n-type semiconductor layer123, a light-emitting layer124and a p-type semiconductor layer125.

The p-electrode layer130is formed on a top surface of the p-type semiconductor layer125. The n-electrode layer140is formed on an exposed surface in which part of the n-type semiconductor layer123is exposed. Moreover, the p-electrode layer130and the n-electrode layer140include portions to expose surfaces thereof facing downward inFIG. 2for electrical connection with an outside through plated bumps24and25(refer toFIG. 11) to be described later, respectively.

It should be noted that, in the exemplary embodiment, surfaces of the n-electrode layer140and the p-electrode layer130are covered with a protecting layer150except for some parts. The protecting layer150is formed to cover part of side wall surfaces of the p-type semiconductor layer125, the light-emitting layer124and the n-type semiconductor layer123.

In the exemplary embodiment, the p-electrode layer130is configured by laminating: a transparent conductive layer131composed of a metal oxide; the insulating reflection layer132; a metal contact layer137to be described later, which is formed inside the opening portion132hof the insulating reflection layer132; a metal reflection layer133composed of a metal containing aluminum; a p-electrode diffusion-preventing layer134(a first p-electrode diffusion-preventing layer134aand a second p-electrode diffusion-preventing layer134b); the p-electrode bonding layer135and a p-electrode adhesive layer136in order from the p-type semiconductor layer125side.

As a material for constituting the transparent conductive layer131, a conductive metal oxide material that transmits at least 80% of the order of light of wavelength emitted from the light-emitting layer124is used. For example, oxides containing In (indium) are provided. Specific examples include: ITO (indium tin oxide (In2O3—SnO2)); IZO (indium zinc oxide (In2O3—ZnO)); IGO (indium gallium oxide (In2O3—Ga2O3)); and ICO (indium cerium oxide (In2O3—CeO2)). Of these, in particular, a transparent material containing In2O3crystals having a crystal structure of a hexagonal system or a bixbyite structure (for example, ITO or IZO) is preferable. Further, in the case where IZO containing In2O3crystals having a crystal structure of a hexagonal system is used, an amorphous IZO film that has an excellent etching property can be used and processed into a specific shape, and thereafter, by transferring the amorphous state into a structure containing crystals through a heat treatment or the like, processed into an electrode that is more excellent in optical transparency than the amorphous IZO film.

In the exemplary embodiment, the thickness of the transparent conductive layer131is selected from a range of 10 nm to 300 nm. Or, the thickness is preferably selected from a range of 50 nm to 250 nm. In the case where the transparent conductive layer131is excessively thin or thick, there is an unfavorable tendency in terms of light transparency to the light emitted from the light-emitting layer124and the reflected light from the metal reflection layer133.

The sheet resistance of the transparent conductive layer131is, though depending upon the manufacturing method thereof, infinite when the thickness is 10 nm, 250 per square when the thickness is 20 nm, 175 per square when the thickness is 25 nm, 72 per square when the thickness is 50 nm, 29 per square when the thickness is 100 nm, and 15 per square when the thickness is 200 nm.

The insulating reflection layer132is laminated on the transparent conductive layer131, and in combination with the metal reflection layer133, has a function of a reflection film that reflects light outputted from the light-emitting layer124. As a layer structure of the insulating reflection layer132, a single-layer structure or a multilayer structure is used. The insulating reflection layer132having a multilayer structure has a high degree of flexibility in the design for controlling reflectance properties compared to the insulating reflection layer having a single-layer structure, and accordingly, the insulating reflection layer132having a multilayer structure is more preferable.

In the case where the insulating reflection layer132has a single-layer structure, the insulating reflection layer132is configured with a material having transparency of at least of the order of 90% and preferably 95% or more to the light outputted from the light-emitting layer124, a refractive index lower than that of the transparent conductive layer131, and insulating properties. Specific examples of materials constituting the insulating reflection layer132include: SiO2(silicon dioxide); MgF2(magnesium fluoride); CaF2(calcium fluoride); and Al2O3(aluminum oxide). In the exemplary embodiment, as the insulating reflection layer132, SiO2(silicon dioxide) having a refractive index of 1.48 (wavelength of 450 nm) is used. It should be noted that the refractive index of an IZO film constituting the transparent conductive layer131is 2.14 (wavelength of 450 nm).

In the exemplary embodiment, the thickness (H) of the insulating reflection layer132is, in a relation with Q=(λ/4n) defined by use of the refractive index n of the insulating reflection layer132and the wavelength λ (nm) of the light-emitting layer124, set in a relation of formula (1) as shown below. As described above, Q indicates a result of dividing the wavelength λ (nm) of the light-emitting layer124by a four-fold refractive index n.
H=AQ  (1)

Further, it is preferable to set the thickness of the insulating reflection layer132based on the following formula (2). In other words, it is preferable to set the thickness to 5Q (A=5) or more. It is more preferable to set the thickness in a range larger than 5Q (A=5). However, under the constraint of production costs, the thickness is preferably 20Q (A=20) or less.
H≧5Q  (2)

In the exemplary embodiment, it is preferable to set the thickness of the insulating reflection layer132in the range that A exceeds 5, namely, in the case of blue light of the wavelength of 450 nm, in the range of the thickness exceeding 380 nm. From experimental data of the inventors and simulation results, a conclusion that the light emission intensity is particularly increased with a thickness in which A is an odd number, such as A=3, 5, 7, . . . is obtained, and a fact that the thickness in which A=3, 5, 7 and so forth is especially preferred and the output of the semiconductor light-emitting element10depends upon the thickness of the insulating reflection layer132is ascertained. In the exemplary embodiment, it is especially preferable that the thickness of the insulating reflection layer132is in a range that A is an odd number such as 3, 5, 7, . . . ±0.5 as a unit. More specifically, from the inventors' experiments, it is ascertained that the output of the semiconductor light-emitting element10is increased as A is increased (the thickness of the insulating reflection layer132is increased), and further, the light emission intensity is especially and effectively increased with the thickness in which A=3, 5, 7 . . . .

Next, description will be given of an insulating reflection layer having a multilayer structure, which is a specific example of another layer structure.

FIG. 3is a cross-sectional schematic view illustrating the specific example of a layer structure of the insulating reflection layer132. In the exemplary embodiment, the insulating reflection layer132has a multilayer structure that is a laminated body of plural layers different in refractive index. The insulating reflection layer132having a multilayer structure is configured by alternately laminating first insulating reflection layers132ahaving a first refractive index and second insulating reflection layers132bhaving a second refractive index that is higher than the first refractive index. Especially, the exemplary embodiment employs a configuration in which one second insulating reflection layer132bis sandwiched by two first insulating reflection layers132a.

In the specific example shown inFIG. 3, five second insulating reflection layers132bare sandwiched between six first insulating reflection layers132ato provide eleven layers of laminated layer structure in total.

As the first insulating reflection layer132aand the second insulating reflection layer132b, a material having high optical transparent properties to the light emitted from the light-emitting layer124is used. Here, as the first insulating reflection layer132a, for example, SiO2(silicon oxide) or MgF2(magnesium fluoride) can be used, and as the second insulating reflection layer132b, TiO2(titanium oxide), Ta2O5(tantalum oxide), ZrO2(zirconium oxide), HfO2(hafnium oxide) or Nb2O5(niobium oxide) can be used. However, as long as relation in the refractive index with the second insulating reflection layer132bis satisfied, these TiO2, Ta2O5, ZrO2, HfO2or Nb2O5may be used as the first insulating reflection layer132a.

In the exemplary embodiment, SiO2(silicon oxide) is used as the first insulating reflection layer132a, and Ta2O5(tantalum oxide) having a refractive index of 2.21 (to light having wavelength of 450 nm) is used as the second insulating reflection layer132b. These have high optical transparency to the light from the light-emitting layer124with light emission wavelength λ (=400 nm to 450 nm).

Further, when it is assumed that the light emission wavelength of the light-emitting layer124is λ (nm), the refractive index of the first insulating reflection layer132awith respect to the light emission wavelength λ is nLand the refractive index of the second insulating reflection layer132bwith respect to the light emission wavelength λ is nH, the thickness dLof each first insulating reflection layer132aand the thickness dHof each second insulating reflection layer132bare set based on the expressions shown as follows. In the exemplary embodiment, the thickness (H) of the insulating reflection layer132having a multilayer structure is 1000 nm to 1500 nm. R(1) and R(2) are positive real numbers.

In the insulating reflection layer132, the plural opening portions132hare provided to expose part of the transparent conductive layer131. The opening portions132hare formed to penetrate through the insulating reflection layer132, and inside of each opening portion132h, part of the metal reflection layer133is formed.

The diameter of the opening portion132his, in the exemplary embodiment, selected from a range of 5 μm to 30 μm, and preferably selected from a range of 5 μm to 20 μm. InFIGS. 1 and 2, the diameter of the opening portion132his 8 μm. The opening portion132his formed, for example, by a dry etching method, a lift-off method or the like in the insulating reflection layer132formed in advance.

The shape of the opening portion132hin a planar view is not particularly limited, and the shape may be circular, oval, triangular, square, rectangular, trapezoidal, pentagonal or other polygonal one (including star shape), wedge shape or the like. The area of the opening portion132his not particularly limited, and further, the areas of respective plural opening portions132hare same or different.

The plural opening portions132hare provided at predetermined intervals (pitch1). In the exemplary embodiment, pitch1is selected from a range of 10 μm to 120 μm. Further, preferably, pitch1is selected from a range of 20 μm to 100 μm. InFIGS. 1 and 2, pitch1is 40 μm.

The ratio of the sum total of the area of the plural opening portions132hto the entire area of the insulating reflection layer132(area occupancy rate) is selected from a range of 2% to 50%. Moreover, the area occupancy rate is preferably selected from a range of 2% to 7%. InFIGS. 1 and 2, the area occupancy rate is 5%.

In the exemplary embodiment, the plural opening portions132hare formed in the insulating reflection layer132and part of the metal reflection layer133and a conductive body portion including a metal contact layer137to be described later are formed in each opening portion132h, to thereby uniformly pass a current over the entire surface of the p-type semiconductor layer125on the surface of the p-electrode layer130through the transparent conductive layer131. This makes it possible to reduce light emission unevenness in the light-emitting layer124.

In the opening portion132h, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h.

In the exemplary embodiment, in the metal contact layer137, a side surface portion137athereof formed on a side surface inside the opening portion132hof the insulating reflection layer132and a peripheral portion137bformed around the periphery of the opening portion132h, which is on a surface of the insulating reflection layer132on the metal reflection layer133side, are integrally formed.

The metal contact layer137contains an element selected from Group VIA and Group VIII of the periodic table. Specific examples of the elements selected from Group VIA of the periodic table include chromium (Cr) and molybdenum (Mo). A specific example of the element selected from Group VIII of the periodic table is nickel (Ni). Of these, nickel (Ni) is preferable in the exemplary embodiment. By part of the metal reflection layer133formed inside the opening portion132hand the metal contact layer137, the transparent conductive layer131and the metal reflection layer133laminated on the insulating reflection layer132have electrical conduction.

In the exemplary embodiment, the thickness of the metal contact layer137is selected from a range of 1 nm to 5 nm, and the metal contact layer137is preferably formed with a thickness of 3 nm or less, and especially preferably formed with a thickness of 2 nm or less.

It should be noted that the width of the peripheral portion137bthat is formed integrally with the metal contact layer137is 3 μm in the exemplary embodiment.

A method of forming the metal contact layer137with nickel (Ni) is performed according to, for example, the following procedures. A continuous insulating reflection layer132is formed on the transparent conductive layer131, then, plural opening portions132hthat penetrate through the insulating reflection layer132are formed, and thereafter, an Ni (nickel) metal layer with a thickness of the order of 2 nm is formed by a sputtering method on the insulating reflection layer132in which the opening portions132hhave been formed. At this time, the Ni (nickel) metal layer is also formed inside the opening portion132hto form the metal contact layer137at a portion in contact with the transparent conductive layer131. Thereafter, the Ni (nickel) metal layer formed on the insulating reflection layer132is removed except for the peripheral part of the opening portion132h(peripheral portion137b).

In the exemplary embodiment, as the conditions for the sputtering method for forming the Ni (nickel) metal layer, a layer-forming temperature is set to the room temperature and the gas pressure is set to a pressure of the order of 3 Pa, which is higher than a gas pressure in a normal sputtering method. It is considered that, in the case of a thin film having a thickness of the order of 2 nm (5 nm or less), the metal contact layer137formed by the sputtering method under the conditions of low temperature and high pressure has an island film structure.

On the metal contact layer137having this kind of a film structure, further, the metal reflection layer133made of AlNd or the like, which will be described later, is formed.

As described above, by forming the Ni (nickel) metal layer at a part of the opening portion132hof the insulating reflection layer132, where the transparent conductive layer131is exposed, before the metal reflection layer133made of AlNd or the like is formed, it is possible to prevent oxidation in which AlNd removes O (oxygen) from an oxide containing In (indium) (for example, IZO or the like) constituting the transparent conductive layer131, and resistance increases and Vf increases due to the oxidation. Moreover, in comparison with a case where the Ni (nickel) metal layer is formed on an entire surface of the transparent conductive layer131or an entire surface of the insulating reflection layer132in addition to the part of the opening portion132hof the insulating reflection layer132, where the transparent conductive layer131is exposed, the reflectance is improved.

By providing the metal contact layer137, full contact between the transparent conductive layer131composed of a metal oxide and the metal reflection layer133composed of a metal containing aluminum is prevented. Consequently, oxidation of aluminum contained in the metal reflection layer133is prevented, and accordingly, increases in contact resistance or rise in the forward voltage (Vf) is suppressed.

In other words, in the exemplary embodiment, by partially providing the metal contact layer137on the surface of the transparent conductive layer131on the metal reflection layer133side, deterioration in brightness of the semiconductor light-emitting element10is suppressed compared to the case where a film of a metal such as nickel (Ni) is formed on the entire surface of the transparent conducive layer131.

In the exemplary embodiment, the metal reflection layer133is formed to cover substantially an entire region of the insulating reflection layer132. Specific examples of the material constituting the metal reflection layer133include Al (aluminum) and an Al (aluminum)-Nd (neodymium) alloy. Of these, the Al (aluminum)-Nd (neodymium) alloy is preferable. Use of the Al (aluminum)-Nd (neodymium) alloy as the metal reflection layer133improves heat resistance and suppresses deterioration of reflective properties of the metal reflection layer133.

Further, in the exemplary embodiment, since Ag (silver) is precluded from the metal reflection layer133and Al (aluminum) or the Al (aluminum)-Nd (neodymium) alloy is used, leakage current or the like due to migration phenomenon is suppressed.

In the exemplary embodiment, the thickness of the metal reflection layer133is selected from a range of 50 nm to 200 nm, and preferably selected from a range of 80 nm to 150 nm.

In the exemplary embodiment, the n-electrode layer140is formed by laminating a first conductive layer141containing Ni (nickel), a second conductive layer142containing the Al (aluminum)-Nd (neodymium) alloy, a third conductive layer143acontaining Ta (tantalum), a fourth conductive layer143bcontaining Pt (platinum), the n-electrode bonding layer144containing Ag (gold) and an n-electrode adhesive layer145containing Ti (titanium) in order from the n-type semiconductor layer123side.

As the conditions for the sputtering method for forming the first conductive layer141containing Ni (nickel), conditions similar to those for forming the metal contact layer137with Ni (nickel) are employed. That is, it is considered that, in the case of a thin film having a thickness of the order of 2 nm (5 nm or less), the first conductive layer141containing Ni (nickel) formed by the sputtering method under the conditions of low temperature and high pressure has an island film structure.

On the first conductive layer141having this kind of structure, the second conductive layer142containing the Al (aluminum)-Nd (neodymium) alloy is formed. On this occasion, it is considered that Al (aluminum) metal contained in the second conductive layer142enters into the Ni (nickel) metal layer having island film structure, and the second conductive layer142is formed such that part thereof is slightly brought into contact with the n-type semiconductor layer123. Usually, Ni (nickel) having high work function compared to Al (aluminum) has characteristics to hardly make an ohmic contact with the n-type semiconductor layer123in the case of being composed of GaN. However, in the exemplary embodiment, it is considered that an ohmic contact between the first conductive layer141and the n-type semiconductor layer123is available while being interposed with the Ni (nickel) metal film by the action of Al (aluminum) metal entered into the Ni (nickel) metal film.

It should be noted that, in the n-electrode layer140, part of the protecting layer150and the n-electrode adhesive layer145is cutout by a known photolithographic technology to expose part of the n-electrode bonding layer144for forming the plated bump24(refer toFIG. 11), which will be described later, to be used for flip-chip mounting.

Next, description will be given of materials for each of other layers constituting the semiconductor light-emitting element10.

As the substrate110, there is no particular limitation on any substrate as long as group III nitride semiconductor crystals are epitaxially grown on a surface thereof, and accordingly, various kinds of substrate may be selected and used. However, as will be described later, since the semiconductor light-emitting element10of the exemplary embodiment is flip-chip mounted so that the light is extracted from the substrate110side, it is preferable to have transparency to the light emitted from the light-emitting layer124. Accordingly, the substrate110composed of, for example, sapphire, zinc oxide, magnesium oxide, zirconium oxide, magnesium-aluminum oxide, gallium oxide, indium oxide, lithium-gallium oxide, lithium-aluminum oxide, neodium-gallium oxide, lanthanum-strontium-aluminum-tantalum oxide, strontium-titanium oxide, titanium oxide and the like can be used. Among the above-described materials, it is preferable to use sapphire in which C-face is a principal surface as the substrate110.

The intermediate layer121is preferably composed of polycrystal AlxGa1−xN (0≦x≦1), and more preferably, composed of single crystal AlxGa1−xN (0≦x≦1). The intermediate layer121can be, for example, composed of polycrystal AlxGa1−xN (0≦x≦1) with a thickness of 0.01 μm to 0.5 μm. If the thickness of the intermediate layer121is less than 0.01 μm, there are some cases where an effect of the intermediate layer121to mediate the difference in lattice constant between the substrate110and the base layer122cannot be sufficiently obtained. On the other hand, if the thickness of the intermediate layer121is more than 0.5 μm, there is a possibility that the time of forming process of the intermediate layer121becomes longer though there is no change to the function of the intermediate layer121, and accordingly the productivity is decreased. The intermediate layer121has a function of mediating the difference in lattice constant between the substrate110and the base layer122to facilitate the formation of a single crystal layer which is C-axis oriented above the (0001) surface (C-face) of the substrate110. Consequently, on the intermediate layer121, the base layer122having more excellent crystallinity can be laminated.

Further, the intermediate layer121may have a crystal structure of a hexagonal system composed of the group III nitride semiconductor. Moreover, as the crystal of the group III nitride semiconductor constituting the intermediate layer121, the crystal having a single crystal structure is preferably used. Crystals of the group III nitride semiconductor grow not only in an upper direction but also in an in-plane direction to form a single crystal structure by controlling growing conditions. Accordingly, the intermediate layer121can be composed of the group III nitride semiconductor crystals having single crystal structure by controlling layer forming conditions of the intermediate layer121. In the case where the intermediate layer121having such a single crystal structure is formed on the substrate110, the buffer function of the intermediate layer121effectively works, and thereby the group III nitride semiconductor formed thereon becomes a crystal film having excellent orientation property and crystallinity.

As the base layer122, AlxGayInzN (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1) can be used, but it is preferable to use AlxGa1−xN (0≦x<1) because the base layer122with excellent crystallinity can be formed.

The thickness of the base layer122is preferably 0.1 μm or more, more preferably 0.5 μm or more, and most preferably 1 μm or more. The AlxGa1−xN layer having excellent crystallinity is likely to be obtained with these layer thickness or more. Further, in terms of production cost, the thickness of the base layer122is preferably 15 μm or less, and more preferably 10 μm or less.

To improve the crystallinity of the base layer122, it is desirable that the base layer122is not doped with impurities. However, if conductivity of p-type or n-type is needed, acceptor impurities or donor impurities can be added.

FIG. 4is a cross-sectional schematic view illustrating a specific example of the laminated semiconductor layer126. The laminated semiconductor layer126is composed of, for example, a group III nitride semiconductor, which is configured by laminating the n-type semiconductor layer123, the light-emitting layer124and the p-type semiconductor layer125above the substrate110in this order. In the exemplary embodiment, each layer of the laminated semiconductor layer126is configured by plural semiconductor layers. It should be noted that the laminated semiconductor layer126is assumed to further include the base layer122and the intermediate layer121in some cases. Here, the n-type semiconductor layer123performs electrical conduction in which an electron is a carrier, while the p-type semiconductor layer125performs electrical conduction in which a hole is a carrier. It should be noted that the laminated semiconductor layer126with excellent crystallinity can be obtained by an MOCVD method; however, a sputtering method under optimized conditions can form the laminated semiconductor layer126having more excellent crystallinity than that formed by the MOCVD method.

As shown inFIG. 4, the n-type semiconductor layer123, in which an electron is a carrier, is preferably configured with an n-contact layer123aand an n-cladding layer123b. It should be noted that the n-contact layer123acan also serve as the n-cladding layer123b. Further, the above-described base layer122may be included in the n-type semiconductor layer123.

The n-contact layer123ais a layer for providing the n-electrode layer140. The n-contact layer123ais preferably configured with the AlxGa1−xN layer (0≦x<1, preferably 0≦x≦0.5, and more preferably 0≦x≦0.1).

Further, the n-contact layer123ais preferably doped with n-type impurities, and preferably contains the n-type impurities having a density of 1×1017/cm3to 1×1020/cm3, and preferably a density of 1×1018/cm3to 1×1019/cm3on the point that a good ohmic contact with the n-electrode layer140can be maintained. The n-type impurities are not particularly limited, however, Si, Ge, Sn and so on are provided, and Si and Ge are preferably provided.

The thickness of the n-contact layer123ais preferably set to 0.5 μm to 5 μm, and more preferably set in a range of 1 μm to 3 μm. If the thickness of the n-contact layer123ais in the above-described ranges, crystallinity of the semiconductor is suitably maintained.

It is preferable to provide the n-cladding layer123bbetween the n-contact layer123aand the light-emitting layer124. The n-cladding layer123bperforms injection of the carriers into the light-emitting layer124and confinement of the carriers. The n-cladding layer123bcan be formed of AlGaN, GaN, GaInN and so on. It should be noted that, in this specification, materials are referred to as, for example, AlGaN or GaInN with the compositional ratio of each element omitted. Further, the hetero junction structure or the superlattice structure in which the layer is laminated plural times of these structures may also be used. When the n-cladding layer123bis formed of GaInN, the band gap thereof is preferably larger than that of GaInN of the light-emitting layer124.

The thickness of the n-cladding layer123bis not particularly limited, but preferably in a range of 0.005 μm to 0.5 μm, and more preferably in a range of 0.005 μm to 0.1 μm. The n-type doping concentration of the n-cladding layer123bis preferably in a range of 1×1017/cm3to 1×1020/cm3, and more preferably in a range of 1×1018/cm3to 1×1019/cm3. It is preferable to provide the doping concentration in these ranges in terms of maintaining excellent crystallinity and reducing operation voltage of the light-emitting element.

It should be noted that, in the case where the n-cladding layer123bis a layer containing the superlattice structure, the layer may contain a structure in which an n-side first layer composed of the group III nitride semiconductor with a thickness of 100 angstrom or less and an n-side second layer having a different composition from the n-side first layer and composed of the group III nitride semiconductor with a thickness of 100 angstrom or less are laminated, though detailed illustration is omitted. Further, the n-cladding layer123bmay contain a structure in which the n-side first layers and the n-side second layers are alternately and repeatedly laminated, and the structure is preferably an alternating structure of GaInN and GaN or an alternating structure of GaInN having different compositions.

As the light-emitting layer124laminated on the n-type semiconductor layer123, a single quantum well structure or a multiple quantum well structure can be employed. As a well layer124bhaving a quantum well structure, the group III nitride semiconductor layer composed of Ga1−yInyN (0<y<0.4) is usually used. The thickness of the well layer124bmay be the thickness by which quantum effects can be obtained, for example, 1 nm to 10 nm, and preferably 2 nm to 6 nm in terms of light emission output.

Moreover, in the case of the light-emitting layer124having the multiple quantum well structure, the above-described Ga1−yInyN is employed as the well layer124b, and AlzGa1−zN (0≦z<0.3) having a band gap energy larger than that of the well layer124bis employed as a barrier layer124a. The well layer124band the barrier layer124amay be doped or not doped with impurities depending upon a design thereof. It should be noted that, in the exemplary embodiment, the light-emitting layer124is configured to output blue light (light emission wavelength of the order of λ=400 nm to 465 nm).

The p-type semiconductor layer125, in which a hole is a carrier, is usually configured with the p-cladding layer125aand the p-contact layer125b. Further, the p-contact layer125bcan also serve as the p-cladding layer125a. The p-cladding layer125aperforms confinement of carriers within the light-emitting layer124and injection of carriers. The p-cladding layer125ais not particularly limited as long as the band gap energy of the composition thereof is larger than that of the light-emitting layer124and carriers can be confined within the light-emitting layer124, but is preferably composed of AlxGa1−xN (0<x≦0.4).

It is preferable that the p-cladding layer125ais composed of such AlGaN in terms of confinement of carriers within the light-emitting layer124. The thickness of the p-cladding layer125ais not particularly limited, but preferably 1 nm to 400 nm, and more preferably 5 nm to 100 nm. The p-type doping concentration of the p-cladding layer125ais preferably 1×1018/cm3to 1×1021/cm3, and more preferably 1×1019/cm3to 1×1020/cm3. If the p-type doping concentration is in the above ranges, excellent p-type crystals can be obtained without deteriorating crystallinity. Further, the p-cladding layer125amay have a superlattice structure in which the layer is laminated plural times of these structures, and preferably has an alternating structure of AlGaN and AlGaN or an alternating structure of AlGaN and GaN.

The p-contact layer125bis a layer for providing the p-electrode layer130. The p-contact layer125bis preferably composed of AlxGa1−xN (0≦x≦0.4). It is preferable that Al composition is in the above-described range in terms of allowing to maintain excellent crystallinity and good ohmic contact with the p-electrode layer130. It is preferable to contain p-type impurities (dopants) in a concentration of 1×1018/cm3to 1×1021/cm3, and preferably 5×1019/cm3to 5×1020/cm3in terms of maintaining good ohmic contact, preventing cracking and maintaining excellent crystallinity. The p-type impurities are not particularly limited, but, for example, Mg is preferably provided. The thickness of the p-contact layer125bis not particularly limited, but is preferably 10 nm to 500 nm, and more preferably 50 nm to 200 nm. It is preferable to provide the thickness of the p-contact layer125bin these ranges in terms of light emission output.

The p-electrode diffusion-preventing layer134suppresses diffusion of a metal constituting the metal reflection layer133in a contact state with the p-electrode diffusion-preventing layer134. It is preferable to use each layer in the p-electrode diffusion-preventing layer134capable of making an ohmic contact with a layer to contact, and has a small contact resistance with the layer to contact. In the exemplary embodiment, Ta (tantalum) and Pt (platinum) are used as the first p-electrode diffusion-preventing layer134aand the second p-electrode diffusion-preventing layer134b, respectively, in the p-electrode diffusion-preventing layer134.

In the exemplary embodiment, Au (gold) is used as the p-electrode bonding layer135.

The p-electrode adhesive layer136is provided to improve physical adhesive properties between the p-electrode bonding layer135configured with Au (gold) and the protecting layer150. In the exemplary embodiment, the p-electrode adhesive layer136is formed of Ti (titanium). However, other than Ti, for example, it is possible to use Ta (tantalum) or Ni (nickel).

The protecting layer150is formed of silicon oxide such as SiO2. The thickness of the protecting layer150is usually provided in a range of 50 nm to 1 μm. If the thickness of the protecting layer150is excessively thin, there is a possibility of losing the function as the protecting layer, and besides, there is a tendency that the light emission output is reduced in a short period of time depending upon a use environment. Further, if the thickness of the protecting layer150is excessively thick, there is a tendency that costs are increased or cracking occurs.

It should be noted that, in the p-electrode layer130of the semiconductor light-emitting element10, at each of four portions that are close to four corners of the semiconductor light-emitting element10, part of the protecting layer150and the p-electrode adhesive layer136is cutout by a known photolithographic technology to expose part of the p-electrode bonding layer135for forming the plated bump25(refer toFIG. 11), which will be described later, to be used for flip-chip mounting.

Next, other exemplary embodiments of the semiconductor light-emitting element10will be described.

FIG. 5is a cross-sectional schematic view illustrating a second exemplary embodiment of the semiconductor light-emitting element10. It should be noted that the same components as those of the exemplary embodiment shown inFIG. 2will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics, and detailed description thereof will be omitted.

In the opening portion132hhaving been provided in the insulating reflection layer132of the semiconductor light-emitting element10shown inFIG. 5, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h. Further, in the metal contact layer137, a side surface portion137athereof formed on a side surface inside the opening portion132hof the insulating reflection layer132and a peripheral portion137bformed around the periphery of the opening portion132h, which is on a surface of the insulating reflection layer132on the metal reflection layer133side, are integrally formed.

Further, in the exemplary embodiment, an Al-containing metal layer (first metal layer)138that contains same elements as those of the metal reflection layer133and a second metal layer139containing Ta (tantalum) or Ni (nickel) are laminated in order between the metal contact layer137and the metal reflection layer133.

In the Al-containing metal layer (first metal layer)138, Al (aluminum) or the Al (aluminum)-Nd (neodymium) alloy is contained. In the second metal layer139, other than Ta (tantalum) or Ni (nickel), Ti (titanium) or the like may be contained.

As shown inFIG. 5, the Al-containing metal layer (first metal layer)138and the second metal layer139are laminated on the metal contact layer137within an outer edge portion of the peripheral portion137bformed around the opening portion132hof the metal contact layer137as a limit. The metal reflection layer133is formed to cover the Al-containing metal layer (first metal layer)138and the second metal layer139laminated on the metal contact layer137, and is also laminated on the insulating reflection layer132.

By further laminating the Al-containing metal layer (first metal layer)138and the second metal layer139containing Ta (tantalum) or Ni (nickel) on the metal contact layer137formed inside the opening portion132hin the insulating reflection layer132, oxidation of aluminum contained in the metal reflection layer133is further suppressed compared to the first exemplary embodiment shown inFIG. 2.

Moreover, in the exemplary embodiment shown inFIG. 5, the n-electrode layer140is formed by laminating the first conductive layer141containing Ni (nickel), a second conductive layer142acontaining an Al (aluminum)-Nd (neodymium) alloy, a third conductive layer143acontaining Ta (tantalum), a fourth conductive layer142bcontaining an Al (aluminum)-Nd (neodymium) alloy, a fifth conductive layer143bcontaining Ta (tantalum), a sixth conductive layer143ccontaining Pt (platinum), the n-electrode bonding layer144containing Ag (gold) and an n-electrode adhesive layer145containing Ti (titanium) in order from the n-type semiconductor layer123side.

It should be noted that, in the n-electrode layer140, part of the protecting layer150and the n-electrode adhesive layer145is cutout by a known photolithographic technology to expose part of the n-electrode bonding layer144for forming the plated bump24(refer toFIG. 11), which will be described later, to be used for flip-chip mounting.

FIG. 6is a cross-sectional schematic view illustrating a third exemplary embodiment of the semiconductor light-emitting element10. It should be noted that the same components as those of the exemplary embodiment shown inFIG. 2will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics, and detailed description thereof will be omitted.

In the opening portion132hhaving been provided in the insulating reflection layer132of the semiconductor light-emitting element10shown inFIG. 6, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h. Further, in the exemplary embodiment, the Al-containing metal layer (first metal layer)138that contains same elements as those of the metal reflection layer133, the second metal layer139containing Ta (tantalum) or Ni (nickel), a third metal layer139acontaining Pt (platinum) and a fourth metal layer139bcontaining Ta (tantalum) or Ni (nickel) are laminated in order between the metal contact layer137and the metal reflection layer133.

As shown inFIG. 6, part of the metal reflection layer133is formed inside the opening portion132hwhere the fourth metal layer139bis not formed, and is connected with the third metal layer139a. This forms a conductive body portion that makes electrical conduction between the transparent conductive layer131and the metal reflection layer133in the opening portion132h. In the Al-containing metal layer (first metal layer)138, Al (aluminum) or an Al (aluminum)-Nd (neodymium) alloy is contained. In the second metal layer139and the fourth metal layer139b, Ti (titanium) or the like may be contained other than Ta (tantalum) or Ni (nickel).

In the exemplary embodiment shown inFIG. 6, the n-electrode layer140is formed by laminating the first conductive layer141containing Ni (nickel), the second conductive layer142acontaining the Al (aluminum)-Nd (neodymium) alloy, the third conductive layer143acontaining Ta (tantalum), a fourth conductive layer143bcontaining Pt (platinum), a fifth conductive layer143ccontaining Ta (tantalum), a sixth conductive layer142bcontaining the Al (aluminum)-Nd (neodymium) alloy, a seventh conductive layer143dcontaining Ta (tantalum), an eighth conductive layer143econtaining Pt (platinum), the n-electrode bonding layer144containing Ag (gold) and the n-electrode adhesive layer145containing Ti (titanium) in order from the n-type semiconductor layer123side.

It should be noted that, in the n-electrode layer140, part of the protecting layer150and the n-electrode adhesive layer145is cutout by a known photolithographic technology to expose part of the n-electrode bonding layer144for forming the plated bump24(refer toFIG. 11), which will be described later, to be used for flip-chip mounting.

FIG. 7is a plan schematic view illustrating a fourth exemplary embodiment, which is another specific example of arrangement of electrodes in the semiconductor light-emitting element. It should be noted that the same components as those of the exemplary embodiment shown inFIG. 2will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics.

A semiconductor light-emitting element11shown inFIG. 7has a square planar shape. The p-electrode layer130is formed to cover substantially an entire top surface of the semiconductor layer120except for a portion where a part of the semiconductor layer120is removed by etching or the like for forming the n-electrode layer140. In the p-electrode layer130as a positive electrode, part of the p-electrode bonding layer135used for electrical connection with an outside is exposed in the center portion of the semiconductor light-emitting element11. In the n-electrode layer140as a negative electrode, at each of four portions that are close to four corners of the semiconductor light-emitting element11, part of the n-electrode bonding layer144used for electrical connection between the n-electrode layer140and the outside is exposed (referred to as “N-distribution type”).

In the insulating reflection layer132(refer toFIG. 8) of the p-electrode layer130, plural opening portions132hare formed. The opening portion132his indicated as a circular blank portion (diameter is 8 μm). InFIG. 7, a pattern is shown in which the plural opening portions132hare arranged with intervals (pitch1) in the entire insulating reflection layer132(refer toFIG. 8) (referred to as “isolation pattern”).

Next, description will be given of a cross-sectional structure of the semiconductor light-emitting element11.

FIG. 8is a VIII-VIII cross-sectional schematic view showing the semiconductor light-emitting element11shown inFIG. 7. The same components as those of the exemplary embodiments shown inFIGS. 2 to 6will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics, and detailed description thereof will be omitted.

As shown inFIG. 8, the semiconductor light-emitting element11has a layer structure similar to that of the semiconductor light-emitting element10described in the exemplary embodiment shown inFIG. 2. That is, the semiconductor light-emitting element11includes the substrate110, the semiconductor layer120laminated on the substrate110, the p-electrode layer130formed on the p-type semiconductor layer125of the semiconductor layer120and the n-electrode layer140formed on an exposed surface in which part of the n-type semiconductor layer123of the semiconductor layer120is exposed.

In the p-electrode layer130as a positive electrode, part of the center portion of the protecting layer150, which covers the surface of the semiconductor light-emitting element11, and the p-electrode adhesive layer136is removed to expose part of the p-electrode bonding layer135, to thereby make electrical connection with the outside through the plated bump25(refer toFIG. 12) to be described later. In each of the n-electrode layers140as negative electrodes formed to be distributed at four corners on the semiconductor layer120, part of the protecting layer150, which covers the surface of the semiconductor light-emitting element11, and the n-electrode adhesive layer145is removed to expose part of the n-electrode bonding layer144, to thereby make electrical connection with the outside through the plated bump24(refer toFIG. 12) to be described later.

Compared to the above-described semiconductor light-emitting element10, the semiconductor light-emitting element11of the N-distribution type shown inFIGS. 7 and 8indicates a tendency to suppress concentration of light emitted from the light-emitting layer124to the center portion of the semiconductor light-emitting element11.

In the insulating reflection layer132of the semiconductor light-emitting element11, similar to the exemplary embodiment shown inFIG. 2(semiconductor light-emitting element10), the plural opening portions132hare provided to expose part of the transparent conductive layer131. Each of the opening portions132his formed to penetrate through the insulating reflection layer132, and inside thereof, part of the metal reflection layer133is formed. The diameter of the opening portion132h, the intervals (pitch1) between the plural opening portions132hand the ratio of the sum total of the area of the plural opening portions132hto the entire area of the insulating reflection layer132(area occupancy rate) are selected from ranges similar to those in the case of the above-described semiconductor light-emitting element10.

In the opening portion132h, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h. Further, in the metal contact layer137, a side surface portion137athereof formed on a side surface inside the opening portion132hof the insulating reflection layer132and a peripheral portion137bformed around the periphery of the opening portion132h, which is on a surface of the insulating reflection layer132on the metal reflection layer133side, are integrally formed. The elements contained in the metal contact layer137and the thickness of the metal contact layer137are selected from a group and a range, respectively, similar to those in the case of the above-described semiconductor light-emitting element10.

In the semiconductor light-emitting element11, similar to the exemplary embodiment shown inFIG. 2(semiconductor light-emitting element10), the metal reflection layer133is formed to cover substantially an entire region of the insulating reflection layer132. The materials constituting the metal reflection layer133and the thickness of the metal reflection layer133are selected from a group and a range, respectively, similar to those in the case of the above-described semiconductor light-emitting element10.

It should be noted that each of the plural n-electrode layers140of the semiconductor light-emitting element11has the layer structure similar to that in the exemplary embodiment shown inFIG. 2(semiconductor light-emitting element10).

FIG. 9is a cross-sectional schematic view illustrating a fifth exemplary embodiment of the semiconductor light-emitting element. The same components as those of the exemplary embodiment shown inFIGS. 7 and 8(fourth exemplary embodiment) will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics, and detailed description thereof will be omitted.

The semiconductor light-emitting element11shown inFIG. 9has a layer structure similar to that of the semiconductor light-emitting element10described in the second exemplary embodiment shown inFIG. 5. That is, in the opening portion132hhaving been provided in the insulating reflection layer132, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h. Further, in the metal contact layer137, a side surface portion137athereof formed on a side surface inside the opening portion132hof the insulating reflection layer132and a peripheral portion137bformed around the periphery of the opening portion132h, which is on a surface of the insulating reflection layer132on the metal reflection layer133side, are integrally formed.

Further, in the exemplary embodiment, the Al-containing metal layer (first metal layer)138and the second metal layer139are laminated in order between the metal contact layer137and the metal reflection layer133. The elements contained in these layers are selected from a group similar to that in the case of the above-described second exemplary embodiment (semiconductor light-emitting element10).

In the semiconductor light-emitting element11, similar to the second exemplary embodiment shown inFIG. 5(semiconductor light-emitting element10), the metal reflection layer133is formed to cover the Al-containing metal layer (first metal layer)138and the second metal layer139laminated on the metal contact layer137and also cover the insulating reflection layer132. The materials constituting the metal reflection layer133and the thickness of the metal reflection layer133are selected from a group and a range, respectively, similar to those in the case of the above-described semiconductor light-emitting element10.

It should be noted that each of the plural n-electrode layers140of the semiconductor light-emitting element11has the layer structure similar to that in the second exemplary embodiment shown inFIG. 5(semiconductor light-emitting element10).

FIG. 10is a cross-sectional schematic view illustrating a sixth exemplary embodiment of the semiconductor light-emitting element. The same components as those of the exemplary embodiment shown inFIGS. 7 and 8(fourth exemplary embodiment) will be assigned the same signs and names to indicate the same components or members, or those having the same characteristics, and detailed description thereof will be omitted.

The semiconductor light-emitting element11shown inFIG. 10has a layer structure similar to that of the semiconductor light-emitting element10described in the third exemplary embodiment shown inFIG. 6. That is, in the opening portion132hhaving been provided in the insulating reflection layer132, the metal contact layer137is formed at least between a portion of the transparent conductive layer131exposed at the opening portion132hand a portion of the metal reflection layer133formed in the opening portion132h. Further, between the metal contact layer137and the metal reflection layer133, the Al-containing metal layer (first metal layer)138, the second metal layer139, the third metal layer139aand the fourth metal layer139bare laminated in order. It should be noted that the elements contained in these layers are selected from a group similar to that in the case of the above-described third exemplary embodiment (semiconductor light-emitting element10).

As shown inFIG. 10, part of the metal reflection layer133is formed inside the opening portion132hwhere the fourth metal layer139bis not formed, and is connected with the third metal layer139a. This forms a conductive body portion that makes electrical conduction between the transparent conductive layer131and the metal reflection layer133in the opening portion132h. It should be noted that each of the plural n-electrode layers140of the semiconductor light-emitting element11has the layer structure similar to that in the third exemplary embodiment shown inFIG. 6(semiconductor light-emitting element10).

The semiconductor light-emitting elements10and11are, for example, mounted on a submount substrate21(refer toFIGS. 11 and 12) through the following operations. First, a layer of TiW/Au is formed on an entire surface of the wafer of the semiconductor light-emitting element10or11by a known sputtering method, then, a resist in which the n-electrode layer140and the p-electrode layer130are exposed by a known photolithographic technology is formed, and subsequent thereto, an Au layer having a predetermined thickness is grown above the n-electrode layer140and the p-electrode layer130by a known deposition method to form the plated bumps24and25(refer toFIGS. 11 and 12). Unnecessary parts of the resist and the TiW/Au layer are removed by a known etching technology or the like. A light-emitting chip is reversed and provided on a submount20using an AlN substrate (refer toFIGS. 11 and 12) to be described later, and the semiconductor light-emitting element10or11and the submount20are aligned so that submount wirings22and23and the plated bumps24and25of the semiconductor light-emitting element10correspond with each other, and thus electrically connected.

FIG. 11is a cross-sectional schematic view illustrating a specific example of a semiconductor light-emitting device to which any one of the exemplary embodiments is applied.FIG. 12is a cross-sectional schematic view illustrating another specific example of the semiconductor light-emitting device to which any one of the exemplary embodiments is applied. Hereinafter, description will be given based onFIGS. 11 and 12.

In a semiconductor light-emitting device1shown inFIG. 11, the semiconductor light-emitting element10described with reference toFIGS. 1 and 2is mounted on the submount substrate21. The same configurations as those shown inFIGS. 1 and 2will be assigned the same signs, and detailed description thereof will be omitted. In the semiconductor light-emitting device2shown inFIG. 12, the semiconductor light-emitting element11(N-distribution type) described with reference toFIGS. 7 and 8is mounted on the submount substrate21. The same configurations as those shown inFIGS. 7 and 8will be assigned the same signs, and detailed description thereof will be omitted.

As shown inFIGS. 11 and 12, each of the semiconductor light-emitting elements10and11includes the submount20as a specific example of a circuit board that mounts each of the semiconductor light-emitting elements10and11thereon. The submount20secures the semiconductor light-emitting element10or11thereon and provides wirings for supplying electric power to the semiconductor light-emitting element10or11. As shown inFIGS. 11 and 12, the semiconductor light-emitting devices1and2mount the semiconductor light-emitting elements10and11, respectively, on the submounts20by flip-chip bonding.

The submount20includes: the submount substrate21; the submount wirings22and23that are provided on the submount substrate21; the plated bump24as a specific example of a connector that electrically connects the n-electrode layer140of the semiconductor light-emitting element10or11with the submount wirings22; and the plated bump25as a specific example of a connector that electrically connects the p-electrode layer130of the semiconductor light-emitting element10or11with the submount wirings23. In the exemplary embodiment, in the plated bumps24and25, the main bodies are composed of gold (Ag), and portions to contact the surfaces of the n-electrode layer140and the p-electrode layer130, respectively, are formed with two layers of TiW/Au by the sputtering method.

Of the light emitted from the light-emitting layer124(refer toFIGS. 2 and 8) of the semiconductor light-emitting element10or11, light traveling toward the substrate110is extracted to the outside. On the other hand, of the light emitted from the light-emitting layer124, light traveling toward the p-electrode layer130is reflected by the insulating reflection layer132and the metal reflection layer133provided on the p-electrode layer130and proceeds toward the substrate110, and is extracted to the outside.

EXAMPLES

Hereinafter, the present invention will be described further in detail with reference to examples. However, the present invention is not limited to the following examples as long as the scope of the gist thereof is not exceeded.

Examples 1 and 2, Comparative Examples 1 and 2

The semiconductor light-emitting elements10respectively shown inFIG. 2(first exemplary embodiment) andFIG. 5(second exemplary embodiment) were prepared. The plural opening portions132hwere provided in the insulating reflection layer132having a multilayer structure, and the metal contact layer137composed of Ni (nickel) was formed between the transparent conductive layer131composed of IZO (indium zinc oxide) exposed at the opening portion132hand the metal reflection layer133composed of the Al (aluminum)-Nd (neodymium) alloy.

It should be noted that the insulating reflection layer132has a laminated layer structure of 19 layers in total by sandwiching 9 layers of the second insulating reflection layers132bbetween 10 layers of the first insulating reflection layers132a. The first insulating reflection layer132ais composed of SiO2(silicon dioxide) having a thickness dL=76 nm. The second insulating reflection layer132bis composed of Ta2O5(tantalum oxide) having a thickness dH=51 nm. The total thickness (H) of the insulating reflection layer132having the multilayer structure is 1218 nm. The diameter of the opening portion132his 8 μm, pitch1between the plural opening portions132his 40 μm, and the area occupancy rate is 5%.

Next, as shown inFIG. 11, the semiconductor light-emitting devices1in which these semiconductor light-emitting elements10are mounted onto the submounts20by flip-chip bonding were prepared. Subsequently, LED properties were measured for each of the semiconductor light-emitting devices1.

It should be noted that, as Comparative Examples, the semiconductor light-emitting element was formed in each of two cases: a case of a configuration similar to that of the first exemplary embodiment except that the metal contact layer137composed of Ni (nickel) formed in Example 1 was formed on an entire surface of the insulating reflection layer132having a multilayer structure, including a space between the transparent conductive layer131exposed at the opening portion132hand the metal reflection layer133(Comparative Example 1); and a case of a configuration similar to that of the first exemplary embodiment except that an insulating reflection layer of a single-layer structure using SiO2(silicon dioxide) was employed instead of the insulating reflection layer132having the multilayer structure formed in Example 1, the metal contact layer137was not formed, and the metal reflection layer133was composed of Ag (silver) (Comparative Example 2), and then, similar to Example 1, LED properties were measured. The results are shown in Tables 1 and 2.

In Tables 1 and 2, Vf indicates a forward voltage (unit: V) and Po indicates light emission output (unit: mW).

From the results shown in Table 1, it can be learned that the forward voltages (Vf: V) of the semiconductor light-emitting devices1of the flip-chip bonding type prepared in Examples 1 and 2 are substantially the same as that of the case where the metal contact layer137composed of Ni was formed on the entire surface of the insulating reflection layer132having the multilayer structure (Comparative Example 1) or that of the case where the conventional metal reflection layer composed of Ag was employed (Comparative Example 2).

In addition, it can be learned that, by further laminating the Al-containing layer (first metal layer)138and the second metal layer139containing Ta (tantalum) on the metal contact layer137formed inside the opening portion132h(Example 2), oxidation of aluminum contained in the metal reflection layer133is further suppressed compared to the case where only the metal contact layer137was provided (Example 1), and therefore the forward voltage (Vf: V) is reduced.

From the results shown in Table 1, it can be learned that the light emission outputs (Po: mW) of the semiconductor light-emitting devices1of the flip-chip bonding type prepared in Examples 1 and 2 are increased compared to the case where the metal contact layer137composed of Ni was formed on the entire surface of the insulating reflection layer132having the multilayer structure (Comparative Example 1) or the case where the conventional metal reflection layer composed of Ag was employed (Comparative Example 2).