JP2010045289A - Light-emitting element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element having a structure in which bonding strength of a light extraction side electrode is increased and thus a wire bonding portion is hardly peeled off from the electrode even if a stress repeatedly acts in a state of resin molding. <P>SOLUTION: In a main surface of a light extraction side of a laminate constituting the light-emitting element 100, concave portions LP are distributedly formed on a forming region of a light extraction side metal electrode 9, and the light extraction side metal electrode 9 is formed in a manner that the inside of each of the concave portions LP is covered in a close-contact manner together with its opening surrounding region. The light extraction side metal electrode 9 is formed in a manner of encroaching on the concave portions LP formed on the uppermost layer portion of the light emission side compound semiconductor layer 20, and as a result of an increase in close-contact area, the bonding strength of the electrode 9 can be remarkably increased. In addition, a wire bonding portion 16 is bonded to the light extraction side metal electrode 9 and molded, even if a repeated shearing stress due to heat cycle or the like acts between the both in this state, the electrode 9 encroaches on the concave portions LP to cause a so-called anchor effect and peeling hardly occurs. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting device and a method for manufacturing the same.

JP 11-191641 A Japanese Patent Laid-Open No. 9-293905

  Semiconductor light-emitting devices have been developed with high-luminance types based on AlGaInP, InAlGaN, etc., but as a result of many years of progress in materials and device structures, the photoelectric conversion efficiency inside the devices has gradually reached the theoretical limit. Approaching. Therefore, when an element with higher luminance is to be obtained, the light extraction efficiency from the element is extremely important. In order to increase the light extraction efficiency, a method generally employed is a method of molding the periphery of the light emitting element chip with a resin having a high refractive index. Specifically, as in Patent Document 1, a light-emitting element in which an element chip is covered with an epoxy resin is widely known. In this case, in order to use the bottom surface (second main surface) of the element chip as the light emission driving end, the bottom surface is bonded to the metal stage via a conductive adhesive layer such as an Ag paste, while the top surface forming the light extraction surface ( On the first main surface side, a current-carrying wire is bonded to a light extraction side electrode (bonding pad) that covers a part of the upper surface via a wire ball (see Patent Document 2), and the periphery is made of a high resin such as epoxy resin. Cover with a refractive index resin and mold.

  By the way, when the element chip is molded with a resin, many resins expand due to an influence of a temperature rise at the time of light emission driving, a temperature difference between day and night of use environment temperature, or direct sunlight in midsummer. At the time of expansion, there is a defect that shear stress repeatedly acts between the electrode and the wire bond portion bonded thereto, and the wire bond portion is easily peeled off from the electrode. In order to solve this problem, an attempt has been made to change the resin used for the mold from a hard epoxy resin to a silicone resin having high flexibility, but there is a limit to stress relaxation by changing the resin.

  An object of the present invention is to increase the bonding strength of the light extraction side electrode, and thus a light emitting element having a structure in which the wire bond portion is not easily peeled off from the electrode even when a repeated stress is applied in a resin mold state, and a manufacturing method thereof. It is to provide.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-described problems, the light-emitting element of the present invention includes:
It consists of a laminated body of compound semiconductors, a part of one main surface of the laminated body is covered with a light extraction side metal electrode for energization, and the area around the light extraction side metal electrode on the main surface is used as a light extraction surface In addition, in the surface layer portion of the light extraction side compound semiconductor layer that is the compound semiconductor layer forming the light extraction surface, concave portions are dispersedly formed in the formation region of the light extraction side metal electrode, and the light extraction side metal electrode covers the inner surface of the concave portion. Further, it is characterized in that it is closely coated together with the area around the opening.

In addition, the method for manufacturing the light emitting device of the present invention includes:
A concave portion forming step of dispersing concave portions in a region where the light extraction side metal electrode for energization is to be formed on the main surface on the light extraction surface side of the compound semiconductor laminate; The light extraction side metal electrode forming step of closely covering the opening peripheral region with the light extraction side metal electrode is performed in this order.

  According to the present invention, the main surface on the light extraction side of the laminated body constituting the light emitting element is formed with the concave portions dispersed in the light extraction side metal electrode formation region, and the inner surface of the concave portion is closely covered together with the peripheral region of the opening. The light extraction side metal electrode was formed in a shape. As a result, the light extraction side metal electrode is formed so as to bite into the recess formed in the surface layer portion of the light extraction side compound semiconductor layer in advance, and as a result of increasing the contact area, the bonding strength of the electrode can be greatly increased. Moreover, even if a wire bond part is bonded to the light extraction side metal electrode and molded, and the repeated shear stress due to thermal cycle or the like acts between the two in that state, the electrode enters into the concave portion and causes a so-called anchor effect. , And hardly cause peeling.

  The recesses can be formed as a plurality of holes in a scattered manner in the formation region of the light extraction side metal electrode. Thereby, a recessed part can be uniformly formed in a light extraction surface, and the adjustment of the formation density of a recessed part and the dimension of each recessed part is also easy. Such holes can be drilled with a laser beam. By adopting a laser beam, a large number of holes with the same size and depth can be formed quickly, and the size and depth of each hole can be easily adjusted by the beam output and the beam diameter.

  On the other hand, it is possible to form the recesses by dry etching (for example, ion etching). In this case, the main surface of the light extraction side compound semiconductor layer is covered with an appropriate etching resist, and a window corresponding to the formation region of the recess is patterned by exposure and development, and then the dry etching is performed to form the recess. It can be formed in a lump.

  When recesses are formed by laser beam drilling or dry etching, altered layers (compounds with altered composition or oxide layers) may remain on the inner surfaces of the recesses. If such a deteriorated layer is formed, the adhesion to the light extraction side electrode may be hindered. Therefore, the deteriorated layer may be removed by wet etching, and then the light extraction side metal electrode may be formed. desirable.

  The light extraction side metal electrode can be formed to have a thickness smaller than the depth of the recess. In this case, when the light extraction side metal electrode is formed following the shape of the inner surface of the recess, the main surface on the opposite side of the light extraction side metal electrode is in close contact with the inner surface of the recess. An electrode recess having a shape is formed. And when the wire bond part for bonding the wire for element energization is joined to the main surface of such a light extraction side metal electrode, this wire bond part fills the above-mentioned electrode crevice to the light extraction side metal electrode. Tightly bonded. In other words, the concave shape of the underlying compound semiconductor layer is transferred to the electrode surface as an electrode concave portion, and bonding is performed in such a manner that the bonding side portion of the wire bond portion is filled therein, so that the wire bond portion becomes the electrode concave portion and eventually light. The anchor effect is further enhanced by greatly biting into the recesses of the light extraction side compound semiconductor layer via the extraction side metal electrode. For example, if a well-known shear test is performed after bonding the wire bond part, the fracture mode changes from bond-chip / chip interfacial debonding fracture to bond-in-bond fracture mode (for example, fracture at the root of the recess bite). The shear bond strength is greatly improved.

  The recesses can be dispersedly formed on the light extraction surface. The concave portion formed on the light extraction surface does not contribute to improving the bonding strength of the light extraction side electrode or the wire bond portion, but the total area of the light extraction surface is increased by the amount of the concave portion to improve the light extraction efficiency. Can do.

  In this case, the recess is formed on both the electrode formation region and the surrounding light extraction surface, that is, the entire main surface of the light extraction side compound semiconductor layer. Therefore, the concave portions are dispersedly formed over the entire main surface of the compound semiconductor wafer formed as a laminate, and the light extraction side metal electrodes are individually formed in the regions to be the respective element chips of the compound semiconductor wafer after the formation of the concave portions. Then, it is efficient to adopt a process of dicing the compound semiconductor wafer into element chips. In order to form the recesses uniformly over the wafer and the entire surface of the element, it is naturally desirable to form the recesses according to a predetermined arrangement pattern. In this case, the recesses are arranged and formed on the main surface of the light extraction side compound semiconductor layer along a predetermined direction extending over the region covered with the light extraction side metal electrode and the light extraction surface.

  Next, surface roughening protrusions by anisotropic etching can be further dispersed and formed on the inner surface of the recesses formed on the light extraction surface. In such a light emitting device, the concave portions are also dispersedly formed on the light extraction surface in the concave portion formation step, and after the light extraction side metal electrode formation step is finished, the light extraction surface not covered with the light extraction side metal electrode is formed. It can be manufactured by carrying out an anisotropic etching process in which the inner surface of the recess is subjected to an anisotropic etching process to roughen the surface and further form the protrusions in a dispersed manner.

  According to the above configuration, compared to the case where the light extraction surface is formed flat, the total area of the surface to be roughened is increased by the amount of forming the concave portion, and the surface is further roughened, and the protruding portion is superimposed. As a result, the total amount of roughening protrusions can be increased. As a result, it is possible to further increase the light extraction area of the device and to further improve the light extraction efficiency as compared with the conventional method in which only the surface roughening process by anisotropic etching is performed.

  When a concave portion is formed on the light extraction surface by laser beam drilling or dry etching, if the above-mentioned deteriorated layer remains on the inner surface of the concave portion, the anisotropic etching process for surface roughening may be hindered. Also, it is desirable that the deteriorated layer is removed also by wet etching on the light extraction surface with respect to the recess, and then the inner surface of the recess is anisotropically etched.

  The roughened projections can also be formed in a distributed manner in the region that forms the opening periphery of the recess of the light extraction surface. Further, surface roughening projections by anisotropic etching can be dispersedly formed on the side surface where the concave portion of the light extraction side compound semiconductor layer is not formed. Thereby, the light extraction efficiency in the opening peripheral region of the recess or the side surface portion of the light extraction side compound semiconductor layer can be improved, and the light emission luminance of the entire device can be further increased.

  As described above, it is efficient to form the recesses on the light extraction surface in a dispersed state over the entire main surface in the state of the light emitting element wafer (that is, before dicing into the element chips). When it is desired to form a rough surface protrusion other than the inner surface of the recess (especially the side surface of the chip), after dicing the light emitting element wafer into the element chip, each element chip is immersed in an anisotropic etching solution to form the recess. It is efficient to perform an anisotropic etching process on the inner surface.

  The laminated body constituting the light emitting element can be configured to include a light emitting layer part and a current diffusion layer that is laminated on the light emitting layer part and has a thickness larger than that of the light emitting layer part. By forming the current diffusion layer, it is possible to improve the current diffusion effect in the element surface and improve the light extraction efficiency from the side surface of the layer. In this case, a recess having a sufficient depth can be easily formed by using the current diffusion layer as the light extraction side compound semiconductor layer. Further, by further forming the roughened protrusions, the light emission luminance of the entire device is greatly improved.

The light emitting layer portion is, for example, a compound represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), The first conductive type cladding layer, the active layer, and the second conductive type cladding layer, each of which is composed of a compound having a lattice matching composition with GaAs, can be formed to have a double hetero structure in which the layers are stacked in this order. Further, the current diffusion layer can be formed as a GaP light extraction layer having a thickness of 10 μm or more.

The light-emitting layer portion is formed of (Al _x Ga _1-x ) _y In _1-y P mixed crystal (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1; hereinafter also referred to as AlGaInP mixed crystal or simply AlGaInP). By adopting a double hetero structure in which a thin AlGaInP active layer is sandwiched between an n-type AlGaInP clad layer and a p-type AlGaInP clad layer having a larger band gap than that, for example from green A high-luminance element can be realized in a wide wavelength range up to red. If the current spreading layer is formed as a light extraction layer whose thickness is increased to a certain value (ie, 10 μm or more) by GaP, not only the current diffusion effect in the element surface is improved but also light extraction from the side surface of the layer. Since the amount increases, the light extraction efficiency can be further increased. The light extraction layer needs to be formed of a compound semiconductor having a band gap energy larger than the photon energy of the emitted light beam so that the emitted light beam can be efficiently transmitted and the light extraction efficiency can be increased. GaP is particularly suitable as a light extraction layer of an AlGaInP light-emitting element because it has a large band gap energy and a small absorption of emitted light flux.

  The light emitting element to which the present invention is applied is not limited to the AlGaInP system, and the present invention is similarly applied to other various light emitting elements such as a GaAs system, AlGaAs system, GaP system, InAlGaN system, or MgZnO system. Applicable.

  When the concave portions formed on the light extraction surface are roughened and the projections are dispersedly formed, it is necessary to set the volume of the concave portion inside the concave portions to be rough and set larger than the volume of the projections. When the GaP light extraction layer is formed with a plurality of holes in the form of scattered dots, the opening diameter of the holes (if there is an opening other than a circle, the value converted to the diameter of a circle of the same area) is 1 μm. It is preferable that the hole depth is not less than 50 μm and the hole depth is not less than 0.5 μm and not more than 25 μm. Further, the rough surface protrusions formed by anisotropic etching may be formed on the inner surface of the hole so that the average height is 0.1 μm or more and 5 μm or less.

  In this case, after the main surface of the GaP light extraction layer (becomes a light extraction surface) is the (100) plane and the above-mentioned concave portions are dispersedly formed on the main surface of the GaP light extraction layer composed of the (100) surface, Acetic acid, hydrofluoric acid, nitric acid, iodine and water are contained so that the sum thereof is 90% by mass or more, and the total mass content of acetic acid, hydrofluoric acid, nitric acid and iodine is higher than the mass content of water. It is preferable that the surface is roughened by etching with an anisotropic etchant to form a protrusion. By using such an anisotropic etching solution, the formation of irregularities by the principle of anisotropic etching proceeds remarkably, and as a result, the surface of the GaP light extraction layer can be roughened and the protrusions can be formed efficiently and inexpensively. . The total amount of acetic acid, hydrofluoric acid, nitric acid, iodine and water is 90% by mass or more, and if the content is less than this, the surface is roughened and the projections cannot be formed efficiently. Further, even if the total mass content of acetic acid, hydrofluoric acid, nitric acid and iodine is lower than the mass content of water, the surface is similarly roughened and the protrusions cannot be formed efficiently. The balance obtained by subtracting the total of acetic acid, hydrofluoric acid, nitric acid, iodine and water from 100% by mass is within the range where the anisotropic etching effect on GaP on the (100) plane is not impaired. (For example, carboxylic acid other than acetic acid) may be occupied.

An anisotropic etchant
Acetic acid (converted to CH ₃ COOH): 37.4% by mass or more and 94.8% by mass or less,
Hydrofluoric acid (converted to HF): 0.4 mass% or more and 14.8 mass% or less,
Nitric acid (in terms of HNO ₃ ): 1.3% by mass or more and 14.7% by mass or less,
Iodine (I ₂ equivalent): It is preferable to use a material containing 0.12% by mass to 0.84% by mass and having a water content of 2.4% by mass to 45% by mass. . If any component is out of the above composition range, the anisotropic etching effect on the (100) surface of the GaP single crystal is not sufficient, and the surface roughening protrusion is sufficiently formed on the first main surface of the GaP light extraction layer. become unable. More preferably, the anisotropic etchant is
Acetic acid (converted to CH ₃ COOH): 45.8 mass% or more and 94.8 mass% or less,
Hydrofluoric acid (converted to HF): 0.5% by mass or more and 14.8% by mass or less,
Nitric acid (converted to HNO ₃ ): 1.6 mass% or more and 14.7 mass% or less,
Iodine (I ₂ equivalent): It is contained in the range of 0.15% by mass or more and 0.84% by mass or less, and the water content is 2.4% by mass or more and 32.7% by mass or less. Is good. That is, in order to enhance the anisotropic etching effect on the (100) plane of the GaP single crystal, in particular, the water content is kept low as described above, and the function of the acid main solvent is assigned to acetic acid instead of water. Can be said to be important.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a light emitting device 100 according to an embodiment of the present invention. The light emitting element 100 includes a light emitting layer portion 24 and a GaP light extraction layer (here, p-type) 20 formed on the first main surface side of the light emitting layer portion 24. Further, a GaP transparent substrate 90 is disposed on the second main surface side of the light emitting layer portion 24. The light emitting layer portion 24 includes the active layer 5 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) mixed crystal. , p-type _{(Al z Ga 1-z)} y In 1-y P ( except x <z ≦ 1) p-type cladding layer made of (first-conductivity-type cladding layer) 6 and n-type _{(Al z Ga 1-z} ) having a sandwiched by the _y In _1-y P (except x <n-type cladding layer made of z ≦ 1) (second-conductivity-type cladding layer) 4. In the light emitting device 100 of FIG. 1, the p-type AlGaInP cladding layer 6 is disposed on the first main surface side (upper side in the drawing), and the n-type AlGaInP cladding layer 4 is disposed on the second main surface side (lower side in the drawing). ing. The term “non-dope” as used herein means “does not actively add dopant”, and contains a dopant component inevitably mixed in a normal manufacturing process (for example, 1 × 10 ¹³ to 1 × The upper limit of about 10 ¹⁶ / cm ³ is not excluded. The light emitting layer portion 24 is grown by the MOVPE method. The n-type cladding layer 4 and the p-cladding layer 6 have a thickness of, for example, 0.8 μm or more and 4 μm or less (preferably 0.8 μm or more and 2 μm or less), and the active layer 5 has a thickness of 0.4 μm or more and 2 μm or less, for example. (Desirably 0.4 μm or more and 1 μm or less). The total thickness of the light emitting layer portion 24 is, for example, 2 μm to 10 μm (desirably 2 μm to 5 μm).

  Next, the GaP light extraction layer 20 (light extraction side compound semiconductor layer) is formed in a thick film of 10 μm or more and 200 μm or less (desirably 40 μm or more and 200 μm or less: in this embodiment, for example, 100 μm), as shown in FIG. The light extraction side metal electrode 9 is formed so as to cover a part (here, the central portion) of the first main surface, and the surrounding main surface region is a light extraction surface 20p.

  On the first main surface of the GaP light extraction layer 20, holes LP as concave portions are dispersedly formed in the covering region of the light extraction side metal electrode 9, and the light extraction side metal electrode 9 covers the inner surface of each hole LP. A close coating is provided along with the area around the opening. One end of an electrode wire 17 is joined to the light extraction side metal electrode 9 via a wire bond portion 16. Further, a bonding alloyed layer 9a made of an AuBe alloy or the like is formed between the light extraction side metal electrode 9 and the GaP light extraction layer 20 so as to follow the inner surface of the hole LP. As disclosed in Patent Document 2, the wire bond portion 16 forms a wire ball by spark discharge at the tip of the wire protruding from the capillary tip, and this is formed on the tip end surface of the capillary with the light extraction side metal electrode 9 (bonding pad). For example, it is formed by welding by a thermosonic method or the like.

  The light extraction side metal electrode 9 and the GaP light extraction layer are formed by forming the light extraction side metal electrode 9 so as to bite into the holes LP formed in the surface layer portion of the GaP light extraction layer 20 (light extraction side compound semiconductor layer). As a result of increasing the contact area with 20, the bonding strength of the electrode can be significantly increased. In addition, the wire bond portion 16 is joined to the light extraction side metal electrode 9 to mold the entire element, and even if repeated shear stress due to a thermal cycle or the like acts between them, the electrode enters the hole LP. In this way, a so-called anchor effect is produced and peeling or the like hardly occurs.

  2, 3, and 4 are enlarged schematic views of A part, B part, and C part surrounded by broken lines in FIG. 1. The light extraction side metal electrode 9 is formed to a thickness smaller than the depth d of the hole LP. When the light extraction side metal electrode 9 is formed so as to follow the inner surface shape of the hole LP, the hole LP is formed on the main surface on the opposite side of the light extraction side metal electrode 9 that is in close contact with the inner surface of the hole LP. As a result, an electrode recess LPF having a shape corresponding to is generated. The wire bond portion 16 is pressurized toward the electrode recess LPF in a heated and softened state, and joined while causing plastic flow into the electrode recess LPF. As a result, the wire bond portion 16 is tightly bonded to the light extraction side metal electrode 9 so as to fill the electrode recess LPF. That is, the hole LP shape of the underlying compound semiconductor layer is transferred to the electrode surface as an electrode recess LPF, and bonding is performed so that the bonding side portion of the wire bond portion 16 is filled therein. The anchor effect is further enhanced by greatly biting into the hole LP of the light extraction side compound semiconductor layer through the LPF and the light extraction side metal electrode 9. For example, when a well-known shear test is performed on the wire bond portion 16, the fracture mode can be changed from the debonding fracture between the bond portion / chip to the fracture mode within the bond portion above the hole LP, and the shear bonding strength Is greatly improved. In order to sufficiently enhance the effect of improving the shear strength by forming the hole LP, it is effective to ensure the depth d of the hole LP to be 0.5 μm or more.

  Next, as shown in FIG. 1, a large number of holes LP similar to those formed in the covering region of the light extraction side electrode 9 are dispersedly formed on the light extraction surface 20p. The holes LP are arranged in a grid pattern at regular intervals in the two vertical and horizontal directions so as to extend over the light extraction surface 20p and the covering region of the light extraction side electrode 9. As shown in FIGS. 2 and 3, the roughened protrusions F by the anisotropic etching process are uniformly formed on the inner surface of the hole LP opened in the light extraction surface 20p. Further, the roughened projections F are also distributed and formed in a region PA that forms the opening periphery of the hole LP of the light extraction surface 20p. Furthermore, as shown in FIGS. 2 and 4, the roughened projections F are also formed on the side surfaces SS where the holes LP of the GaP light extraction layer 20 and the GaP transparent substrate 90 are not formed.

  Since the GaP light extraction layer 20 is formed thick as described above, the light emission drive current by energization through the light extraction side metal electrode 9 is diffused in the element surface, and the light emitting layer portion 24 is uniformly distributed in the surface. It functions as a current diffusion layer that emits light. In addition, the extracted light flux from the layer side surface portion SS is also increased, and the luminance of the entire light emitting element (integrated sphere luminance) is increased. GaP has a larger band gap energy than AlGaInP forming the active layer 5, and absorption of the luminous flux is suppressed.

  Then, the total surface area of the light extraction surface 20p is increased by the formation of the hole LP, and the surface is further roughened, and the protrusion F is superimposed on the surface to thereby roughen the protrusion compared to the case where the hole LP is not formed. The total amount of part F increases. As a result, the light extraction area of the element can be further increased, and as a result, the light extraction efficiency can be further improved. Further, as shown in FIGS. 2 and 4, the same surface roughening protrusion F is formed on the side surface portion SS, and the light extraction efficiency from the side surface is improved. In addition, as shown in FIG. 3, in the area | region coat | covered with the light extraction side metal electrode 9, the surface roughening protrusion part F is not formed in the inner surface of the hole LP.

  In this embodiment, the GaP light extraction layer 20 is grown by the HVPE method (may be the MOVPE method). A connection layer 20J made of a GaP layer is formed between the GaP light extraction layer 20 and the light emitting layer part 24 by the MOVPE method in a form following the light emitting layer part 24. The connection layer 20J may be an AlGaInP layer that gradually changes the lattice constant difference (and hence the mixed crystal ratio) between the light emitting layer portion 24 made of AlGaInP and the GaP light extraction layer 20. Note that the GaP light extraction layer 20 can be formed by bonding a GaP single crystal substrate instead of an epitaxially grown layer by the HVPE method.

The GaP transparent substrate 90 is formed by bonding a GaP single crystal substrate (may be an epitaxially grown layer by HVPE method: reference numeral 91 is a connection layer made of AlGaInP), and the entire surface of the second main surface. Is covered with a back electrode 15 made of an Au electrode or the like. The crystal orientation of the GaP transparent substrate 90 coincides with the light emitting layer portion 24 (that is, the off-angle angle is adjusted). The thickness of the GaP transparent substrate 90 is, for example, not less than 10 μm and not more than 200 μm. The back electrode 15 also serves as a reflection layer for the luminous flux that arrives from the light emitting layer portion 24 through the GaP transparent substrate 90, and contributes to the improvement of light extraction efficiency. Further, between the back electrode 15 and the GaP transparent substrate 90, bonding alloyed layers 15c made of AuGeNi alloy or the like for reducing the contact resistance between them are dispersedly formed in the form of dots. In both the GaP light extraction layer 20 and the GaP transparent substrate 90, the dopant concentration is adjusted to 5 × 10 ¹⁶ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less (in addition, immediately below the bonding alloying layer 9a). In the case where a high-concentration doped region for increasing the contact resistance is formed, it means the dopant concentration in the region excluding this region).

  The main light extraction region (first main surface) 20p of the GaP light extraction layer 20 has an uneven reference plane substantially coincident with the (100) plane of the GaP single crystal (however, 1 ° to 25 °) (For example, an off-angle of 15 ° may be given), and the roughened projection F contacts the flat (100) crystal main surface with an anisotropic etching solution described later, as shown in FIG. This is formed by anisotropic etching. Similarly, the side surface portion SS (FIG. 1) is a surface that substantially coincides with the {100} surface.

  As shown in FIG. 6A, the outer surface of the roughened projection F is formed mainly of {111} plane (more than 50% of the projection surface) due to the chemical anisotropic etching characteristics of GaP single crystal. . If anisotropic etching progresses ideally, the roughened projection F on the {100} plane is a pyramid-like external form surrounded by four {111} planes having different plane orientations as shown in FIG. 6B. However, due to various factors, hemispherical (FIG. 6B), ellipsoidal (FIG. 6C), conical (FIG. 6D), mushroom (FIG. 6E), triangular pyramid (FIG. 6F), etc. Various protrusion forms can occur. The average height of the protrusions is, for example, 0.1 μm or more and 5 μm or less, and the average distance between the protrusions is 0.1 μm or more and 10 μm or less. And the hole LP which forms this has an opening diameter of 1 μm or more and 50 μm or less, an opening depth of 0.5 μm or more and 25 μm or less, and an arrangement interval of 0.1 μm or more and 20 μm or less.

Hereinafter, a method for manufacturing the light emitting device 100 of FIG. 1 will be described.
First, as shown in Step 1 of FIG. 7, a GaAs single crystal substrate 1 having a main surface of (100) plane is prepared as a growth substrate. Next, as shown in step 2, an n-type GaAs buffer layer 2 is epitaxially grown on the main surface of the substrate 1 by 0.5 μm, for example, and an AlGaInP connection layer 91 (4 μm) is further grown. 1 μm thick n-type cladding layer 4 (n-type dopant is Si), 0.6 μm thick active layer (non-doped) 5 and (Al _x Ga _1-x ) _y In _1-y P A p-type cladding layer 6 having a thickness of 1 μm (p-type dopant is Mg: C from organometallic molecules can also contribute as a p-type dopant) is epitaxially grown in this order. Each dopant concentration of the p-type cladding layer 6 and the n-type cladding layer 4 is, for example, 1 × 10 ¹⁷ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less. Further, as shown in step 3 of FIG. 8, the connection layer 20 </ b> J is epitaxially grown on the p-type cladding layer 6.

Epitaxial growth of each of the above layers is performed by a known MOVPE method. The following materials can be used as source gases for the source components of Al, Ga, In (indium), and P (phosphorus);
Al source gas; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa), etc .;
In source gas; trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas: trimethyl phosphorus (TMP), triethyl phosphorus (TEP), phosphine (PH ₃ ), etc.

Proceeding to Step 4, the GaP light extraction layer 20 made of p-type GaP is grown by the HVPE method. Specifically, in the HVPE method, GaCl, which is a group III element, is heated and held at a predetermined temperature in a container, and hydrogen chloride is introduced onto the Ga, thereby causing GaCl by the reaction of the following formula (1). And is supplied onto the substrate together with the H ₂ gas that is a carrier gas.
Ga (liquid) + HCl (gas) → GaCl (gas) + 1 / 2H ₂ (1)
The growth temperature is set to, for example, 640 ° C. or more and 860 ° C. or less. Further, P which is a group V element supplies PH ₃ onto the substrate together with H ₂ which is a carrier gas. Furthermore, Zn which is a p-type dopant is supplied in the form of DMZn (dimethyl Zn). GaCl is excellent in reactivity with PH _3, and the GaP light extraction layer 20 can be efficiently grown by the reaction of the following formula (2):
GaCl (gas) + PH ₃ (gas)
→ GaP (solid) + HCl (gas) + H ₂ (gas) (2)

  When the growth of the GaP light extraction layer 20 is completed, the process proceeds to step 5 in FIG. 9, and the GaAs substrate 1 is removed by wet etching using an etchant such as an ammonia / hydrogen peroxide mixture. Then, the process proceeds to Step 6, and a separately prepared n-type GaP single crystal substrate is attached to the second main surface side of the light emitting layer portion 24 from which the GaAs substrate 1 has been removed (the second main surface of the connection layer 91). In addition, a GaP transparent substrate 90 is obtained, and a light emitting element wafer W is obtained.

  When the above steps are completed, as shown in step 7 of FIG. 10, the first main surface of the GaP light extraction layer 20 is sequentially irradiated with the laser beam LB while changing the position, as shown in FIG. A plurality of holes LP are dispersedly formed. The arrangement form of the holes LP is not particularly limited, and various arrangements such as a lattice shape, a staggered shape, a concentric circle shape or a spiral shape can be adopted, and the relative movement between the laser beam LB and the light emitting element wafer W in the arrangement direction of the holes LP to be formed. By repeatedly irradiating the laser beam LB repeatedly while stopping, the holes LP can be arranged in an intended pattern. For example, a method of forming the hole LP in a form in which the light emitting element wafer W is fixed and the laser beam LB is scanned can be exemplified, but the light emitting element wafer W may be moved while the laser beam LB is fixed.

  In addition, as shown in FIG. 11, on the inner surface of the hole LP formed by drilling with the laser beam LB, a composition altered layer in which the compound composition is shifted from the stoichiometric ratio (for example, in the case of the GaP light extraction layer 20, the P composition May be less than the stoichiometric ratio) or an oxide film may remain as the altered layer DL. Therefore, as shown in FIG. 13, the composition-altered layer is removed by wet etching. A sulfuric acid-hydrogen peroxide aqueous solution can be used as the etching solution SEA. Specifically, for example, concentrated sulfuric acid (sulfuric acid concentration 98%): hydrogen peroxide solution (hydrogen peroxide concentration 30%): water volume ratio of 3: 1: 1 can be used, and the liquid temperature is 30 ° C. It is good to adjust to 70 ° C. or lower. Note that hydrofluoric acid may be used if only the oxide film is removed.

  Returning to FIG. 10, a photoresist layer for electrode patterning is formed on the first main surface of the GaP light extraction layer 20 and the second main surface of the GaP transparent substrate 90, and the window portion for the electrode is patterned by exposure and development. Then, a metal layer for forming a bonded alloying layer is formed thereon by sputtering or vacuum vapor deposition, and unnecessary vapor deposited metal is lifted off together with the photoresist layer, and further heat treatment for alloying (so-called sintering treatment) is performed. The bonded alloyed layers 9a and 15c (see FIG. 1; not shown in FIG. 10). And the light extraction side metal electrode 9 and the back surface electrode 15 are formed so that these joining alloying layers 9a and 15c may be covered, respectively (process 8). On the first main surface side of the GaP light extraction layer 20, metal is uniformly deposited on the inner surface of the hole LP by sputtering or vapor deposition (particularly, when sputtering is used, the inner surface of the hole LP is relatively uniform. The metal can be deposited with a sufficient thickness), and the bonding alloying layer 9a and the light extraction side metal electrode 9 are formed in a shape following the inner surface of the hole LP.

  Subsequently, the process proceeds to Step 9 where the light emitting element wafer W is diced along two <100> directions to be diced into individual element chips 100 '. In the present embodiment, a flexible resin adhesive sheet AS is attached to the second main surface (back surface) of the light emitting element wafer W, and half dicing is performed from the first main surface side to the middle position of the wafer thickness. Thereafter, the expanding process is performed in which the adhesive sheet AS is spread and separated into the element chip 100 ′, but full dicing may be performed. At the time of the dicing, a processing damage layer having a relatively high crystal defect density is formed on the side surface portion of each element chip, which may hinder the surface roughening process described later. Therefore, it is desirable to remove the processing damage layer by immersing the element chip after dicing in an etching solution made of the sulfuric acid-hydrogen peroxide solution.

  Subsequently, as shown in Step 10, each element chip 100 ′ is immersed in an anisotropic etching solution EA to perform an anisotropic etching process. The anisotropic etching solution EA contacts the surface region of the element chip 100 ′ that is not covered with the metal electrodes 9 and 15, specifically, both the light extraction surface 20 p and the side surface portion SS. As a result, a roughened projection F is formed on the inner surface of each hole LP, the area surrounding the opening, and the entire side surface portion SS. Note that the formation of the rough protrusions F on the light extraction surface 20 and the side surface portion SS can be omitted.

An anisotropic etching solution is an aqueous solution containing acetic acid, hydrofluoric acid, nitric acid, and iodine. Specifically,
Acetic acid (converted to CH ₃ COOH): 37.4% by mass or more and 94.8% by mass or less,
Hydrofluoric acid (converted to HF): 0.4 mass% or more and 14.8 mass% or less,
Nitric acid (in terms of HNO ₃ ): 1.3% by mass or more and 14.7% by mass or less,
Iodine _{(I 2} equivalent): it contains in the range of 0.12 mass% or more 0.84 wt% or less, and those water content below 45 wt% to 2.4 wt%, more desirably,
Acetic acid (converted to CH ₃ COOH): 45.8 mass% or more and 94.8 mass% or less,
Hydrofluoric acid (converted to HF): 0.5% by mass or more and 14.8% by mass or less,
Nitric acid (converted to HNO ₃ ): 1.6 mass% or more and 14.7 mass% or less,
Iodine (I ₂ conversion): It is contained in the range of 0.15% by mass or more and 0.84% by mass or less, and the water content is 2.4% by mass or more and 32.7% by mass or less. The liquid temperature is suitably 40 ° C. or higher and 60 ° C. or lower.

  When the surface roughening and the formation of the protruding portion F are completed, the element chip is washed with water and dried, and then the light emitting element of FIG. 1 is completed through wire bonding.

Hereinafter, various modifications of the light emitting device of the present invention will be described.
As shown in FIG. 11, when the laser beam LB is used, the hole LP having a substantially circular opening shape can be formed. On the other hand, as shown in FIG. 12, the GaP light extraction layer 20 (light extraction side compound semiconductor layer) is covered with an etching resist ER, and a window corresponding to the formation region of the hole LP is formed by patterning by exposure and development. It is also possible to form the holes LP in a lump by performing dry etching. Even when dry etching is used, an altered layer DL may be formed on the inner surface of the hole LP, and it is desirable to remove the altered composition layer by wet etching as in FIG.

  In this case, the hole LP having a desired opening shape can be formed according to the patterning shape of the window. FIG. 14 shows an example in which holes LP having a square opening shape are arranged in a lattice pattern. At this time, the light emitting element wafer is so formed that the inner wall surfaces of the holes LP are {100} planes orthogonal to each other (that is, (010) plane and (001) plane if the main surface of the wafer is (100) plane)). If the formation orientation of the hole LP with respect to is determined, the bottom surface and side surface of the hole LP both become {100} planes advantageous for anisotropic etching, and the surface roughening and the protruding portion can be formed more remarkably.

  Moreover, it replaces with a hole and as shown in FIG. 15, it is also possible to form the groove | channel LG arranged at a predetermined interval as a recessed part. FIG. 16 shows an example in which such a set of grooves LG is formed in a lattice shape in two directions intersecting each other. The groove LG may be formed by patterning by dry etching, or may be formed by continuous irradiation while moving the laser beam in the groove forming direction. Also here, the groove LG can be formed so that the inner wall surface is a {100} plane.

  FIG. 17 shows an example of a light emitting device in which the formation of the hole LP in the light extraction surface 20p is omitted. In this case, the light extraction surface 20p (or the side surface portion SS) may be either roughened or not formed with the roughened protrusion F. FIG. 18 shows an example of a light emitting element that is used as an element substrate without removing the GaAs substrate 1 which is an opaque substrate. In any case, the other points are completely the same as those of the light emitting element of FIG. 1, and the same reference numerals are given to the common portions and the detailed description is omitted.

  Next, FIG. 19 shows that concentric holes are formed by laser beam drilling (laser output: about 100 mW) on the main surface of the GaP light extraction layer grown by the HVPE method, which forms the first main surface of the light emitting element wafer. It is an optical microscope image which shows an example (magnification: about 100 times). The diameter of the wafer is 50 mm, the left shows the vicinity of the wafer center, and the right shows the vicinity of the outer periphery. FIG. 20 shows an enlarged view of one of the holes. The hole has an opening diameter of about 11 μm and a depth of about 4.0 μm.

  In FIG. 21, the lower right is a light emitting element chip (No. 4) in which neither hole formation (laser perforation) nor anisotropic etching (frost) is performed in the GaP light extraction layer, and the upper right is light emission in which only laser perforation is performed. Element chip (No. 3), the lower left is a light emitting element chip (No. 2) that has undergone only anisotropic etching (frost), and the upper left is a light emitting element chip (No. that has undergone anisotropic etching (frost) after laser drilling. It is an optical microscope observation image which respectively shows 1). The depth of the hole formed by laser drilling is about 6.0 μm, and the value of the arithmetic mean roughness Ra of the main surface measured by the method defined in JIS-B0601 (1994) is also shown. . It can be seen that the arithmetic average roughness Ra is slightly lower by adding an anisotropic etching process as compared with the light emitting element chip that has been subjected only to laser drilling. The anisotropic etching treatment uses an etching solution having a composition of 81.7% by mass of acetic acid, 5% by mass of hydrofluoric acid, 5% by mass of nitric acid, 0.3% by mass of iodine, and 8% by mass of water. For example, it is performed at 25 ° C. for 150 seconds.

Wire bonding was performed on each of the chips of No. 3 and No. 4 using a gold wire using a commercially available wire bonding machine (Cuelink & Sofa Co., Ltd .: 4125D). The wire ball diameter for forming the bonding portion is 80 μm. Further, the obtained bond portion has an area S0 of 5024 μm ² in a plan view (that is, an orthographic projection region with respect to a projection plane parallel to the main surface of the multilayer body).

  A share test was performed on the bond part of each chip using a commercially available share tester (Think MBS200). As a result, while the shear strength of the chip of No. 4 (comparative example) covered with the light extraction side electrode 9 without forming the hole portion was 77.9 gmf, the hole portion was formed and this The shear strength of the chip of No. 3 (Example) covered with the extraction-side electrode 9 was clearly improved to 79.9 gmf. In No. 4, the bond part peeled off at the interface with the GaP light extraction layer, whereas in No. 3, fracture occurred in the bond part. In No. 3, since the concave portions were dispersedly formed at the bonding positions of the bonding portions, it was confirmed that the shear strength dependence of the shear strength was sufficiently small.

  FIG. 22 shows the measurement results of the light emission output PO, the integrating sphere luminance PV, and the directly above luminance IV when each of the above light emitting element chips is caused to emit light at various drive current values. The average value of 10 is shown). The light-emitting element chip (No. 1) subjected to both hole formation (laser drilling) and anisotropic etching (frost) is compared with the light-emitting element chip (No. 2) subjected to anisotropic etching (frost) alone. As a result, it was confirmed that PO was improved by 7.49%, PV by 10.7%, and IV by 6.37%.

The side surface cross-sectional schematic diagram which shows the 1st example of the light emitting element of this invention, and the enlarged plan view of the optical extraction side electrode periphery. The A section enlarged view of FIG. Similarly B section enlarged view. Similarly C section enlarged view. The figure which shows notionally the formation form of the surface roughening protrusion by anisotropic etching on GaP {100} surface. The perspective view which shows the 1st example of the external shape of the roughening protrusion part on a GaP {100} surface. The perspective view which similarly shows a 2nd example. The perspective view which shows a 3rd example similarly. The perspective view which similarly shows a 4th example. The perspective view which similarly shows a 5th example. The perspective view which similarly shows the 6th example. Process explanatory drawing which shows the manufacturing method of the light emitting element of FIG. Process explanatory drawing following FIG. Process explanatory drawing following FIG. Process explanatory drawing following FIG. The schematic diagram which shows a mode that a recessed part is drilled and formed by a laser beam. The schematic diagram which shows a mode that a recessed part is drilled and formed by dry etching. The schematic diagram which shows a mode that the altered layer of a recessed part inner surface is removed by wet etching. The top view which shows the 1st modification of the recessed part formation form to a light extraction surface. The top view which shows a 2nd modification similarly. The top view which shows a 3rd modification similarly. The side surface cross-sectional schematic diagram which shows the 2nd example of the light emitting element of this invention, and the enlarged plan view of the optical extraction side electrode periphery. The side surface cross-sectional schematic diagram which shows the 3rd example of the light emitting element of this invention. The image which shows the example of the recessed part drilling pattern by a laser beam. The enlarged image of FIG. The optical microscope image which image | photographed the test element used for the effect confirmation evaluation of this invention in the light extraction surface side. The figure which shows the result of the effect confirmation evaluation performed using the test element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 1st conductivity type clad layer 5 Active layer 6 2nd conductivity type clad layer 9 Light extraction side metal electrode 16 Wire bond part 20 GaP light extraction layer 20p Light extraction surface SS Side surface part 24 Light emitting layer part W Light emitting element wafer F Surface roughness Protrusion part LP hole (concave part)
LG groove 100 light emitting element

Claims (20)

  Composed of a laminate of compound semiconductors, a part of one main surface of the laminate is covered with a light extraction side metal electrode for energization, and a region around the light extraction side metal electrode of the main surface is a light extraction surface. In addition, in the surface layer portion of the light extraction side compound semiconductor layer that is the compound semiconductor layer that forms the light extraction surface, recesses are dispersedly formed in the formation region of the light extraction side metal electrode, and the light extraction side metal electrode is A light-emitting element, wherein the inner surface of the recess is closely covered together with the area around the opening.   The light emitting device according to claim 1, wherein the concave portions are formed in a dispersed manner as a plurality of holes.   The light emitting device according to claim 2, wherein the hole is formed by drilling with a laser beam.   The light extraction side metal electrode has a thickness smaller than the depth of the concave portion, and has a shape corresponding to the concave portion on the main surface opposite to the inner surface of the concave portion of the light extraction side metal electrode. A wire bonding portion for bonding an element energizing wire to the main surface of the light extraction side metal electrode is formed in a shape that follows the shape of the inner surface of the recess in a shape that generates an electrode recess. The light emitting device according to any one of claims 1 to 3, wherein the light emitting device is tightly bonded in a form of filling.   The light emitting device according to claim 4, wherein the depth d of the recess is 0.5 μm or more.   The light emitting device according to any one of claims 1 to 5, wherein the concave portions are also formed to be dispersed on the light extraction surface.   The said recessed part is arranged and formed with respect to the said main surface of the said light extraction side compound semiconductor layer along the predetermined direction over the coating area | region by the said light extraction side metal electrode, and the said light extraction surface. Item 7. The light-emitting element according to any one of items 6.   8. The light emitting device according to claim 6, wherein the light extraction surface is formed by further dispersing and roughening protrusions by anisotropic etching on the inner surface of the recess.   The light-emitting element according to claim 7 or 8, wherein the surface-roughening protrusion is dispersedly formed in a region of the light extraction surface that forms the periphery of the opening of the recess. The concave portions are formed as a plurality of holes in a scattered manner,
The hole has an opening diameter of 1 μm or more and 50 μm or less, a hole depth of 0.5 μm or more and 25 μm or less, and the rough surface protrusion has a protrusion height of 0.1 μm or more and 5 μm or less on the inner surface of the hole. The light emitting device according to claim 9 formed.   11. The surface roughening protrusion by anisotropic etching is dispersedly formed on a side surface of the light extraction side compound semiconductor layer where the concave portion is not formed. The light emitting element according to item.   The laminated body of the compound semiconductor includes a light emitting layer portion and a current diffusion layer that is stacked on the light emitting layer portion and has a thickness larger than that of the light emitting layer portion, and the current diffusion layer is the light extraction side compound. The light emitting device according to claim 1, which constitutes a semiconductor layer. Among the compounds represented by the composition formula (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), the light emitting layer portion is lattice-matched with GaAs. A first conductivity type cladding layer, an active layer and a second conductivity type cladding layer each composed of a compound having a composition to be formed as having a double heterostructure laminated in this order,
The light emitting element according to claim 12, wherein the current diffusion layer is formed as a GaP light extraction layer having a thickness of 10 μm or more.   A recessed portion forming step of forming recessed portions in a region where the light extraction side metal electrode for energization is to be formed on the main surface on the light extraction surface side of the compound semiconductor laminate, and the inner surface of the recess in the formation region, A method of manufacturing a light emitting device, wherein a light extraction side metal electrode forming step of closely covering the opening peripheral region with the light extraction side metal electrode is performed in this order.   The method for manufacturing a light-emitting element according to claim 14, wherein the recess is formed by laser beam drilling.   The method for manufacturing a light-emitting element according to claim 14, wherein the recess is formed by dry etching.   17. After the formation of the concave portion, the altered layer remaining on the inner surface of the concave portion is removed by wet etching, and then the inner surface of the concave portion is closely covered with the light extraction side metal electrode together with the area around the opening. The manufacturing method of the light emitting element as described in any one of.   The concave portions are dispersedly formed on the entire surface of the main surface of the compound semiconductor wafer formed as the laminated body, and the light extraction side metal electrodes are individually provided in regions to be element chips of the compound semiconductor wafer after the concave portions are formed. The method for manufacturing a light-emitting element according to claim 14, wherein the compound semiconductor wafer is formed and then diced into the element chip.   In the recess forming step, the recesses are dispersedly formed on the light extraction surface, and after completion of the light extraction side metal electrode formation step, the recesses of the light extraction surface that are not covered with the light extraction side metal electrode are formed. 19. The light emitting device according to claim 14, wherein an anisotropic etching process is performed in which the inner surface is subjected to an anisotropic etching process to roughen the surface and further form protrusions in a dispersed manner. Method.   20. The method for manufacturing a light-emitting element according to claim 19, wherein each dicing element chip is immersed in an anisotropic etching solution, and the anisotropic etching process is performed on the inner surface of the concave portion forming the light extraction surface.