JP2011066453A - Semiconductor light emitting element, and semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element and a semiconductor light emitting device which improve efficiency of extracting light emitted from an active layer. <P>SOLUTION: The semiconductor light emitting element has a substrate which has first and second major surfaces and has light translucency to light of first wavelength band, a semiconductor lamination structure which is provided on the first major surface of the substrate and includes an active layer 3 emitting light of the first wavelength band and in which a first rough surface is formed in at least part of a surface, a dielectric film provided on the first rough surface, a bonding pad 7A provided on the dielectric film, a fine line electrode 7B which is provided on the semiconductor layer structure and is electrically connected to the semiconductor lamination structure and the bonding pad, and a second electrode provided on the second major surface of the substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor light-emitting element and a semiconductor light-emitting device, and more particularly to a semiconductor light-emitting element and a semiconductor light-emitting device with improved extraction efficiency of light emitted from an active layer.

Semiconductor light-emitting elements such as LEDs (light emitting diodes) and LDs (laser diodes) provide various emission wavelengths, are small in size, have high luminous efficiency, and have a long lifetime. Display devices, lighting devices, communication devices, sensors Widely used for
In these semiconductor light emitting devices, a semiconductor multilayer film including an n-type clad layer, an active layer, a p-type clad layer, etc. is directly grown on a substrate made of GaAs, sapphire, or the like, or bonded to a different substrate. In addition, electrodes are formed on each of the n-type layer and the p-type layer. (For example, Patent Documents 1 and 2)

However, in the case of such a semiconductor light emitting device, the extraction efficiency of light emitted from the active layer is not always sufficiently high.
That is, the light emitted downward from the active layer is incident on the electrode provided under the substrate. However, in the vicinity of the contact portion with the electrode, an alloying region with the electrode material is formed on the substrate, so that light emitted from the active layer is easily absorbed, and there is a problem that loss occurs inside the chip. is there.

  Further, there is a problem that the light reflected by the lower electrode is attenuated by light absorption when passing through the active layer, and the reflected light cannot be fully utilized.

  On the other hand, there is also a problem that total reflection tends to occur on the side surface of the chip. That is, such an LED is usually processed into a rectangular parallelepiped shape having six smooth surfaces by cleaving or dicing and covered with a mold resin or the like. However, due to the large difference between the high refractive index of the semiconductor crystal (about 3.5) and the low refractive index of the mold resin (about 1.5), total reflection tends to occur at these interfaces. For this reason, the probability that the light emitted inside the chip is extracted outside the chip is lowered.

  As a measure for improving the light extraction efficiency, there is a method of roughening the surface by wet etching or the like to form irregularities (for example, Patent Document 2). However, it is not effective to roughen the surface to extract light emitted from the chip mounted on the mounting member toward the bottom surface.

JP 2002-353502 A JP 2001-217467 A

  It is an object of the present invention to provide a semiconductor light emitting element and a semiconductor light emitting device with improved extraction efficiency of light emitted from an active layer.

  In order to solve the above-described problem, according to one embodiment of the present invention, a substrate having first and second main surfaces and having a light-transmitting property with respect to light in a first wavelength band, and A semiconductor multilayer structure including an active layer that is provided on a main surface of the first light source and that emits light of the first wavelength band, and a first rough surface is formed on at least a part of the surface; A dielectric film provided on a rough surface, a bonding pad provided on the dielectric film, and provided on the semiconductor multilayer structure, electrically connected to the semiconductor multilayer structure and the bonding pad And a second electrode provided on the second main surface of the substrate. A semiconductor light emitting device is provided.

  According to yet another aspect of the present invention, a mounting member and any one of the semiconductor light emitting elements mounted on the mounting member are provided, and the mounting member includes the substrate of the semiconductor light emitting element. There is provided a semiconductor light emitting device characterized by having a reflection part for reflecting light emitted from the side surface of the semiconductor light emitting device.

1 is a schematic view illustrating a cross-sectional structure of a semiconductor light emitting element according to a first embodiment of the invention. 3 is a schematic view illustrating the extraction path of light emitted from an active layer 3. FIG. It is process sectional drawing showing a part of manufacturing process of the semiconductor light-emitting device of embodiment of this invention. It is process sectional drawing showing a part of manufacturing process of the semiconductor light-emitting device of embodiment of this invention. 2 is a photomicrograph showing a rough surface 9 formed on the back surface of the GaP substrate 1. It is a schematic diagram which illustrates the form of the back surface of the board | substrate 1 in embodiment of this invention. It is a schematic diagram which illustrates the form of the back surface of the board | substrate 1 in embodiment of this invention. It is a schematic diagram which illustrates the form of the back surface of the board | substrate 1 in embodiment of this invention. It is a schematic diagram which illustrates the form of the back surface of the board | substrate 1 in embodiment of this invention. It is a schematic cross section showing the semiconductor light emitting element concerning the modification of embodiment of this invention. 4 is a schematic diagram for explaining light extraction on a rough surface 9; FIG. It is the schematic diagram which illustrated the extraction path | route of the light in the modification of embodiment of this invention. It is a schematic diagram showing the semiconductor light-emitting device concerning the other modification of embodiment of this invention. It is a schematic diagram which illustrates the cross-sectional structure of the state which mounted the semiconductor light-emitting device of embodiment of this invention on the mounting member. It is process sectional drawing which illustrates the process formed by dry etching. It is process sectional drawing which illustrates the process formed by dry etching. It is a schematic cross section showing the semiconductor light emitting element concerning the modification of embodiment of this invention. 1 is a schematic view illustrating a cross-sectional structure of a semiconductor light emitting element according to an embodiment of the invention. It is a top view which illustrates the electrode pattern formed in the surface of a semiconductor light emitting element. 1 is a schematic cross-sectional view of a semiconductor light emitting device studied by the inventor in the course of reaching the present invention. It is a schematic diagram which illustrates a mode that the light scattered under bonding pad 7A is reflected toward the side surface of an element, and is taken out outside. It is a schematic cross section showing the semiconductor light emitting element concerning the modification of embodiment of this invention. It is a schematic cross section showing a semiconductor light emitting element concerning the 2nd modification of an embodiment of the present invention. 1 is a schematic view illustrating a cross-sectional structure of a semiconductor light emitting element according to an embodiment of the invention. It is an enlarged view of a bonding pad portion of a semiconductor light emitting device. It is the schematic diagram which illustrated a mode that a part of light emission produced under the fusion | melting part 80 was taken out from the clearance gap between extending electrode parts 7D. It is a schematic diagram which illustrates the electrode pattern in embodiment of this invention. It is a schematic diagram showing the other specific example of the electrode pattern in embodiment of this invention. It is a schematic diagram showing the semiconductor light emitting element concerning the modification of embodiment of this invention. It is a schematic cross section showing the semiconductor light emitting element concerning the other modification of embodiment of this invention. It is a schematic cross section showing the semiconductor light emitting element concerning the further another modification of embodiment of this invention. 1 is a schematic cross-sectional view illustrating a semiconductor light emitting device according to an embodiment of the present invention. It is a schematic cross section showing the other specific example of a semiconductor light-emitting device. It is a schematic cross section showing still another specific example of the semiconductor light emitting device. It is a schematic cross section showing still another specific example of the semiconductor light emitting device. It is a schematic cross section showing still another specific example of the semiconductor light emitting device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic view illustrating the cross-sectional structure of the semiconductor light emitting device according to the first embodiment of the invention.
That is, the semiconductor light emitting device of this example has a structure in which the cladding layer 2, the active layer 3, the cladding layer 4, and the current diffusion layer 5 are laminated on the substrate 1 in this order. An electrode 7 is provided on the current diffusion layer 5 via a contact layer (not shown). On the other hand, an electrode 8 is formed on a part of the back surface side of the substrate 1, and the remaining part is an uneven rough surface 9, and a reflective film 10 is deposited on the surface.

  The substrate 1 is translucent to the light emitted from the active layer 3. For example, the substrate 1 can be made of p-type GaP, the clad layer 2 can be made of p-type InAlP, the active layer 3 can be made of InGaAlP, the clad layer 4 can be made of n-type InAlP, and the current diffusion layer 5 can be made of n-type InGaAlP. In this case, n-type GaAs can be used as a contact layer provided between the current diffusion layer 5 and the electrode 7.

  Since it is difficult to directly epitaxially grow the InGaAlP-based compound semiconductor layer on the GaP substrate 1, the laminated structure 6 of the InGaAlP-based compound semiconductor is once epitaxially grown on the GaAs substrate, and the p-type is formed thereon by the wafer bonding technique. The laminated structure of this example can be formed by bonding the GaP substrate 1 and removing the GaAs substrate by etching or the like.

  Moreover, as the reflective film 10, for example, a metal such as gold (Au), a dielectric, or the like can be used. At this time, for example, silicon oxide, silicon nitride, or the like may be used, and so-called “HR (High Reflectance) coating” in which the reflectance is maximized from the relationship between the refractive index and the thickness may be used. Furthermore, a DBR (Distributed Bragg Reflector) in which two types of semiconductor layers having different refractive indexes are alternately stacked may be used as the reflective film 10.

In the present embodiment, by providing the rough surface 9 and the reflective film 10 on the back surface of the substrate 1, the extraction efficiency of light emitted downward from the active layer 3 can be improved.
FIG. 2 is a schematic view illustrating the extraction path of light emitted from the active layer 3.
The light emitted from the active layer 3 is scattered in the direction of the side surface 1S of the substrate 1 by the rough surface 9 and the reflective film 10 as shown by the arrows in FIG. Since the scattered light is incident on the side surface 1S of the substrate 1 at a relatively small angle (an angle perpendicular to the side surface 1S), it is emitted to the outside without being totally reflected at the side surface 1S. As described above, since such a semiconductor light emitting device is usually sealed with a translucent resin having a refractive index of about 1.5, light emitted from the inside of the chip is at the interface between the semiconductor layer and the resin. Easy to be totally reflected. On the other hand, in this embodiment, light can be scattered by the rough surface 9 and the reflective film 10 and can be incident on the side surface 1S of the substrate 1 at a small angle, so that the light is not totally reflected. Can be taken out.

  If a flat reflective film is provided on the back surface of the substrate 1 without providing the rough surface 9, the light emitted downward from the active layer 3 is reflected upward by the reflective film. However, in this case, since the reflected light passes through the active layer 3, loss occurs due to reabsorption. On the other hand, in this embodiment, by providing the rough surface 9, light can be scattered in the direction of the side surface 1S, and loss due to absorption can be suppressed.

  If the electrode 8 is formed on the entire back surface of the substrate 1, an alloying region is formed at the interface between the substrate 1 and the electrode 8, and light emitted from the active layer 3 is absorbed and loss occurs. On the other hand, according to the present embodiment, there is no alloying region on the rough surface 9, and light can be reflected with high efficiency by the rough surface 9 and the reflective film 10. As a result, loss due to absorption can be suppressed.

Next, the manufacturing method will be described by taking as an example the case where the present embodiment is applied to an InGaAlP light emitting element.
3 and 4 are process cross-sectional views showing a part of the manufacturing process of the semiconductor light emitting device of this embodiment.
First, as shown in FIG. 3A, an InAlP etching stop layer 94, a GaAs contact layer 26, an InGaAlP current diffusion layer 5, an n-type InAlP cladding layer 4, and an InGaAlP active layer 3 are formed on an n-type GaAs substrate 92. The p-type InAlP cladding layer 2, the InGaP adhesive layer 34, and the InAlP cover layer 96 are grown. As the n-type GaAs substrate 92, for example, a mirror-finished substrate having a diameter of 3 inches, a thickness of 350 μm, a silicon (Si) doping and a carrier concentration of about 1 × 10 ¹⁸ / cm ³ can be used.

The thickness of the etching stopper layer 94 can be 0.2 μm. The GaAs contact layer 26 has a thickness of 0.02 μm and a carrier concentration of 1 × 10 ¹⁸ / cm ³ . The InGaAlP current diffusion layer 5 is made of InGaAlP and can have a thickness of 1.5 μm. The n-type cladding layer 4 is made of InAlP and can have a thickness of 0.6 μm. The active layer 3 is made of InGaAlP and can have a thickness of 0.4 μm. The p-type cladding layer 2 is made of InAlP and can have a thickness of 0.6 μm. The thickness of the InGaP adhesive layer 34 can be 0.1 μm, and the thickness of the InAlP cover layer 96 can be 0.15 μm.

  Next, this epitaxial wafer was washed with a surfactant, immersed in a mixed solution of ammonia 1 and hydrogen peroxide solution 15 in a volume ratio, and the back side of the GaAs substrate 92 was etched to adhere to the back side of the epitaxial wafer. Reaction products and the like during epitaxial growth are removed.

  Next, after the epitaxial wafer is washed again with a surfactant, the outermost InAlP cover layer 96 is removed with phosphoric acid, and the InGaP adhesive layer 34 is exposed.

  Thereafter, as shown in FIG. 3B, the GaP substrate 1 is bonded. Hereinafter, the direct bonding process will be described.

  For example, a GaP substrate 1 having a diameter of 3 inches, a thickness of 300 μm, and a p-type mirror-finished (100) orientation can be used. A high concentration layer may be formed on the surface of the GaP substrate 1 in order to reduce the electrical resistance of the adhesion interface. As a pretreatment for direct bonding, the GaP substrate 1 is washed with a surfactant, immersed in dilute hydrofluoric acid to remove the natural oxide film on the surface, washed with water, and then dried with a spinner. In addition, after removing the cover layer 96 on the surface of the epitaxial wafer, the dilute hydrofluoric acid treatment is performed for removing the oxide film in the same manner as the GaP substrate 1, followed by washing with water and spinner drying. All of these pretreatments are desirably performed in a clean atmosphere in the clean room.

  Next, the epitaxial wafer that has been subjected to the pretreatment is placed with the InGaP adhesive layer 34 facing upward, and the GaP substrate 1 is placed thereon so that the mirror surface faces downward, and is closely adhered at room temperature.

  Next, as a final step of direct bonding, wafers that are in close contact at room temperature are arranged in a quartz boat and placed in a diffusion furnace to perform heat treatment. The heat treatment temperature may be 800 ° C., the time may be 1 hour, and the atmosphere may be argon containing 10% hydrogen. By this heat treatment, the GaP substrate 1 and the InGaP adhesive layer 34 are integrated, and the adhesion is completed.

  Next, as shown in FIG. 3C, the GaAs substrate 92 of the epitaxial wafer is removed. That is, the bonded wafer is immersed in a mixed solution of ammonia and hydrogen peroxide solution, and the GaAs substrate 92 is selectively etched. This etching stops at the InAlP etching stop layer 94. Next, etching is performed with phosphoric acid at 70 ° C., and the InAlP etching stop layer 94 is selectively removed.

Through the above steps, an LED adhesive substrate in which the GaP transparent substrate 1 and the InGaAlP-based semiconductor multilayer structure 6 are joined is obtained.
Next, as shown in FIG. 4A, the n-side electrode 7 is formed on the GaAs contact layer 26, and the p-side electrode 8 is formed on the back surface of the GaP substrate 1.
In order to prevent absorption by the GaAs contact layer 26, the contact layer 26 around the n-side electrode 7 is removed by etching.

  For example, the n-side electrode 7 may have a stacked structure of AuGe (250 nm) / Mo (150 nm) / AuGe (250 nm) / Au (300 nm) in this order from the contact layer 26 side. Moreover, as the p-side electrode 8, for example, a metal containing 5% zinc (Zn) in gold (Au) can be used. A eutectic solder layer such as AuSn (1000 nm) may be further provided on the surface of the p-side electrode 8 via Au (100 nm).

Next, as shown in FIG. 4B, the rough surface 9 is formed on the back surface of the substrate 1.
First, the protective film 11 is formed on the n-side electrode 7 and the p-side electrode 8 respectively. As the material of the protective film 11, for example, a resist, silicon oxide, silicon nitride, or the like can be used.

  Thereafter, the back surface of the GaP substrate 1 exposed around the p-side electrode 8 is etched to form a rough surface 9. As etching conditions, for example, a method of immersing in concentrated hydrofluoric acid for about 10 minutes can be used.

  FIG. 5 is an electron micrograph showing the rough surface 9 formed on the back surface of the GaP substrate 1 by this method. By hydrofluoric acid etching, the back surface of the substrate 1 is covered with a pyramid having a width and height of approximately 1 micrometer. The rough surface 9 made of such an aggregate of pyramids provides a high scattering effect on the light emitted downward from the active layer 3.

Thereafter, as shown in FIG. 4C, the reflective film 10 is deposited on the rough surface 9.
Specifically, for example, the reflective film 10 can be formed by depositing gold (Au) by vacuum deposition. Thereafter, the protective film 11 provided on both surfaces of the wafer is removed, and the chip is separated by a method such as dicing, whereby the semiconductor light emitting device of this embodiment is obtained.

  In the case where a metal is used as the material of the reflective film 10, when alloyed with the substrate 1, the reflectance is reduced and a loss occurs. Therefore, when a heat treatment (sinter) is required to reduce the contact resistance between the n-side electrode 7 and the p-side electrode 8, the reflective film 10 may be formed after the heat treatment.

  On the other hand, an ohmic metal can be used as the material of the reflective film 10. That is, when light absorption due to alloying with the substrate 1 is not so large, ohmic metal may be used as the material of the reflective film 10.

  As described above, in this embodiment, by etching the back surface of the GaP substrate 1 with hydrofluoric acid, the rough surface 9 with a high scattering effect can be formed, and the light extraction efficiency can be improved.

6 to 9 are schematic views illustrating the form of the back surface of the substrate 1 in this embodiment.
That is, the p-side electrode 8 may be formed in a circular shape near the center of the back surface of the substrate 1 as shown in FIG. 6, or may be formed in a square shape as shown in FIG. Further, as shown in FIG. 8, the p-side electrode 8 may be provided by being divided into a plurality of patterns. When the pattern is divided into a plurality of patterns, the concentration of current can be relaxed, and the current can be uniformly injected into the active layer 3 to emit light in a wide region.

  On the other hand, as shown in FIG. 9, the first pattern 8A may be provided near the center of the back surface of the substrate 1 and connected to the thin line-shaped second pattern 8B extending to the periphery. Even in this case, the current can be uniformly injected into the active layer 3 to emit light in a wide region.

  6 to 9 are merely examples. For example, the pattern shape of the p-side electrode 8 may be a polygonal shape, an elliptical shape, or other various shapes. The same applies to the number and arrangement thereof, and various modifications are also included in the scope of the present invention.

FIG. 10 is a schematic cross-sectional view showing a semiconductor light emitting element according to a modification of the present embodiment. In the figure, the same elements as those described above with reference to FIGS. 1 to 9 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this modification, the side surface 1S of the substrate 1 is tapered and the substrate 1 is formed in a truncated pyramid shape. A rough surface 9 is formed on the side surface 1S. Further, the reflective film 10 is provided on the surface of the rough surface 9 in the region from the bottom surface of the substrate 1, that is, the lower surface where the p-side electrode 8 is provided to the middle of the side surface 1 </ b> S.

The rough surface 9 on which the reflective film 10 is not provided has an effect of increasing light extraction efficiency.
FIG. 11 is a schematic diagram for explaining light extraction on the rough surface 9.
That is, when the conical rough surface 9 is formed on the side surface 1S of the substrate 1, the light traveling in the direction of the arrow A inside the substrate 1 is incident on the surface of the rough surface 9 at an angle larger than the critical angle. Then, it is totally reflected in the direction of arrow B. However, when the reflected light enters the opposing rough surface 9, the incident angle becomes smaller than the critical angle and can be taken out from the substrate 1. As described above, when the light traveling through the substrate 1 is incident on the convex portion of the rough surface 9, it can be extracted outside as indicated by the arrow C after repeating total reflection.

FIG. 12 is a schematic view illustrating the light extraction path in this modification.
As described above with reference to FIG. 11, light can be extracted to the outside with high efficiency on the rough surface 9 where the reflective film 10 is not provided.
On the other hand, in a state where the semiconductor light emitting element is mounted with an adhesive 30 such as silver paste or solder, the adhesive 30 may crawl up to the side surface of the chip as illustrated. In this way, light cannot be extracted at the portion where the adhesive 30 has been scooped up. On the other hand, in this modified example, the light extraction can be promoted by depositing the reflective film 10 on the rough surface 9 in the vicinity of the mount surface of the chip. That is, in the region where the adhesive 30 crawls up, the light inside the chip is reflected by the reflective film 10 and can be taken out to the outside. As a result, the light extraction efficiency can be improved.

  The taper of the side surface 1S of the substrate 1 in this modification can be formed by dicing, for example. That is, a V-shaped groove can be formed by dicing the substrate 1 from the back side using a dicing blade having a V-shaped cross section. Alternatively, a V-shaped groove can be formed by etching. By separating the chip along the V-shaped groove formed in this manner, a tapered side surface 1S is obtained. At this time, the rough surface 9 can be formed by performing the roughening process as described above with reference to FIG. 4B after the V-shaped groove is formed or after separation into chips.

FIG. 13 is a schematic view showing a semiconductor light emitting element according to another modification of the present embodiment.
That is, in this modification, only the lower part of the substrate 1 is processed into a tapered shape. A rough surface 9 is formed on the side surface 1S of the substrate 1. Furthermore, the reflective film 10 is deposited on the rough surface 9 in the tapered portion.
In this way, it is possible to prevent light from being shielded due to the scooping up of the adhesive 30, and at the same time, the light reflected by the reflective film 10 is likely to enter the vertical side surface 1S as illustrated by the arrow A. As a result, the light extraction efficiency can be further increased.

  In order to manufacture the semiconductor light emitting device of this modification, the depth of the groove when the V-shaped groove is formed on the back surface of the substrate 1 using a V-shaped dicing blade or etching. You can adjust. After forming the V-shaped groove, the remaining part is cut off with a scribe or a thin dicing blade. If it carries out like this, the side surface of a V-shaped groove | channel will become a taper part, and the remaining part will become a perpendicular | vertical side surface.

(Second Embodiment)
Next, as a second embodiment of the present invention, a semiconductor light emitting device having a recess on the back surface of the chip will be described.
FIG. 14 is a schematic view illustrating a cross-sectional structure in a state where the semiconductor light emitting element of this embodiment is mounted on a mounting member.
That is, the semiconductor light emitting device of this embodiment also includes the substrate 1 and the semiconductor multilayer structure 6. The semiconductor multilayer structure 6 appropriately includes an active layer, a clad layer, and the like, and emits light by injecting a current through the electrodes 7 and 8. This semiconductor light emitting element is mounted on a mounting member 28 such as a lead frame or a mounting substrate by an adhesive 30.

  And in this embodiment, the conical recessed part 20 is provided in the back surface of the semiconductor light-emitting element so that it may not overlap with the side surface 15 of a board | substrate. The recess 20 may have a pyramid shape or a cone shape. The electrode 8 is provided, for example, near the center of the recess. By providing such a recess 20, the light extraction efficiency can be increased. This point will be described below in comparison with a comparative example.

  That is, as a comparative example, a case where the back surface of the semiconductor light emitting element is formed flat and an electrode is provided near the center thereof. However, when such a semiconductor light emitting device is mounted on a mounting member, an adhesive such as silver paste or solder may protrude around the device and crawl up to the side surface of the device. Therefore, light cannot be taken out at the portion where the adhesive has crawled up. On the other hand, light emitted downward from the active layer is reflected by the flat back surface of the element, and this reflected light is absorbed by the active layer, causing a loss.

On the other hand, in the present embodiment, by providing the conical recess 20 on the back surface of the semiconductor light emitting element, as shown in FIG. 14, the light emitted from the active layer is directed toward the side surface 1S of the substrate. It can be reflected and taken outside without going through the active layer. That is, loss due to absorption of the active layer can be suppressed.
Furthermore, since the recessed part 20 absorbs the excess adhesive 30, the creeping of the adhesive 30 to the side surface 1S of the element can be suppressed. Accordingly, the light reflected toward the side surface 1 </ b> S in the recess 20 is extracted outside without being blocked by the adhesive 30.

The side surface of the recess 20 in the semiconductor light emitting device of the present embodiment has an inclination angle of, for example, about 25 degrees to 45 degrees with respect to the mount surface of the device. Such a recess 20 can be formed by, for example, dry etching or laser processing.
15 and 16 are process cross-sectional views illustrating a process for forming by dry etching.
That is, first, as shown in FIG. 15A, a mask layer 40 made of a relatively flexible material such as a resist is formed on the back surface of the substrate 1 where the recess is to be formed.

Next, as shown in FIG. 15B, the press 42 is pressed against the mask layer 40. Here, the press 42 is formed with a protrusion 42P corresponding to the recess 20 to be formed.
When the press is pressed in this way, a concave portion 44 corresponding to the protrusion 42P is formed in the mask layer 40 as shown in FIG.

  Next, as shown in FIG. 16A, etching is performed from above the mask layer 40 by anisotropic etching such as ion milling or RIE (reactive ion etching). Then, the mask layer 40 is etched and the pattern is transferred to the underlying substrate 1. When the etching of the mask layer 40 proceeds as shown in FIG. 16B and the mask layer 40 is completely etched as shown in FIG. 16C, the recess 20 is formed on the surface of the underlying substrate 1. Is formed.

  In addition to the process described above, the recess 20 can be formed on the back surface of the substrate 1 by laser processing, for example. In this case, the back surface of the substrate 1 is irradiated while being scanned with a laser, and is sequentially etched by a predetermined amount. By gradually reducing the laser scanning range, the conical recess 20 can be formed.

FIG. 17 is a schematic cross-sectional view showing a semiconductor light emitting element according to a modification of the present embodiment.
In this modification, the reflective film 10 is deposited on the portion of the recess 20 where the electrode 8 is not formed. As the reflective film 10, the various films described above with reference to the first embodiment can be used.

By providing the reflective film 10, the reflectance of light in the recess 20 can be further increased. As a result, light emitted downward from the active layer can be reflected with high efficiency and extracted through the side surface 1S.
Further, in the present embodiment, a rough surface as described above with reference to FIG. 11 may be provided on the side surface 1S.

(Third embodiment)
Next, as a third embodiment of the present invention, a semiconductor light emitting device with reduced light loss under a bonding pad will be described.
FIG. 18 is a schematic view illustrating the cross-sectional structure of the semiconductor light emitting element according to this embodiment.
FIG. 19 is a plan view illustrating an electrode pattern formed on the surface of the semiconductor light emitting device.
Also in these drawings, the same elements as those described above with reference to FIGS. 1 to 17 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the electrode 7 formed on the semiconductor multilayer structure 6 has a bonding pad 7A and a thin wire electrode portion 7B connected thereto. The bonding pad 7A is a part for connecting a gold wire or the like for connecting to an external circuit (not shown). On the other hand, the thin wire electrode part 7B is a part for obtaining electrical contact with the semiconductor layer through the ohmic GaAs layer 26. The size of one side of the chip is approximately 200 micrometers to 1 millimeter, the diameter of the bonding pad 7A is approximately 100 micrometers to 150 micrometers, and the line width of the thin wire electrode portion 7B is approximately 2 micrometers. It can be set to about 10 to 10 micrometers.

  In this embodiment, a rough surface 9 is formed on the surface of the semiconductor multilayer structure 6 under the bonding pad 7A, and a dielectric layer 50 is further provided thereon. The rough surface 9 can be similar to that described above with respect to the first embodiment. The dielectric layer 50 can be formed by, for example, SOG (spin on glass). If such a structure is provided under the bonding pad 7A, the light extraction efficiency from the semiconductor light emitting device can be improved. Hereinafter, this point will be described with reference to a comparative example.

  FIG. 20 is a schematic cross-sectional view of a semiconductor light emitting device studied by the inventors in the course of reaching the present invention.

  In the case of this comparative example, the surface of the semiconductor multilayer structure 6 is flat, and a current blocking layer 52 made of a semiconductor is provided thereon. For example, when the semiconductor stacked structure is made of an InGaAlP-based compound semiconductor that emits red light, non-doped InGaP or the like can be used as the current blocking layer 52. The current blocking layer 52 has a role of blocking current injection from the bonding pad 7A to the semiconductor layer therebelow. That is, even if light is emitted under the bonding pad 7A, the light is shielded by the bonding pad 7A and cannot be easily taken out. For this reason, such a current blocking layer 52 is provided to form a non-light emitting region NE under the bonding pad 7A.

  However, in the structure of this comparative example, when light emission generated by current injection from the thin wire electrode portion 7B is directed below the bonding pad 7A as indicated by the arrow A, it is absorbed by the GaAs contact layer 26 and lost. There is a problem that occurs. Further, the light reflected under the bonding pad 7A travels toward the opposing electrode 8 as indicated by the arrow B, and is absorbed in the alloying region formed in the vicinity of the electrode 8, so that the loss occurs. Will occur. On the other hand, the light emitted under the thin wire electrode 7B is incident on the side surface 1S of the substrate 1 at a relatively large incident angle, and thus is easily totally reflected on the side surface 1S. For this reason, there also exists a problem that the extraction efficiency of light falls.

In contrast, in the present embodiment, first, the dielectric layer 50 is provided under the bonding pad 7A, whereby the current blocking effect and the effect of increasing the reflectance can be obtained. That is, since the dielectric layer 50 is insulative, current can be reliably interrupted, and light emission under the bonding pad 7A can be reliably suppressed.
Furthermore, by providing the dielectric layer 50, the light emitted from the active layer 3 can be reflected with high efficiency. For example, when silicon oxide is used as the material of the dielectric layer 50, if the refractive index n of the underlying InGaAlP layer is 3.2 and the refractive index n of silicon oxide is 1.45, the criticality of total reflection at these interfaces is critical. The angle is as small as about 27 degrees. That is, of the light emitted from the active layer and incident on the dielectric layer 50, the light having an incident angle of 27 degrees or more is totally reflected. In this case, reflection of about 14 percent occurs even for light having an incident angle of 27 degrees or less. Thus, by providing the dielectric layer 50, the light emitted from the active layer 3 can be reflected with high efficiency.

  Furthermore, according to this embodiment, light can be scattered by providing the rough surface 9 on the surface of the semiconductor multilayer structure 6. As a result, as illustrated by an arrow A in FIG. 21, the light scattered under the bonding pad 7A can be reflected toward the side surface 1S of the device and extracted outside.

FIG. 22 is a schematic cross-sectional view showing a semiconductor light emitting element according to a modification of the present embodiment.
That is, in the present modification, the rough surface 9 is provided on the side surface 1S of the substrate 1. By providing such a rough surface 9, it is possible to increase the light extraction efficiency using multiple reflection as described above with reference to FIG. That is, light emitted under the thin wire electrode portion 7B and light scattered on the rough surface 9 under the bonding pad 7A can be extracted from the side surface 1S with high efficiency.

  FIG. 23 is a schematic cross-sectional view showing a semiconductor light emitting element according to a second modification of the present embodiment. That is, in this modification, the side surface 1S of the substrate 1 is formed to be inclined in a tapered shape. In this way, light emitted under the thin wire electrode portion 7B and light reflected under the bonding pad 7A can be incident on the side surface 1S at a smaller incident angle. As a result, total reflection on the side surface 1S can be suppressed, and the light extraction efficiency can be further increased. Further, in this modified example, a rough surface 9 similar to that shown in FIG. 22 may be provided on the side surface 1S.

(Fourth embodiment)
Next, as a fourth embodiment of the present invention, a semiconductor light emitting device with improved light extraction efficiency from below the bonding pad will be described.
FIG. 24 is a schematic view illustrating the cross-sectional structure of the semiconductor light emitting element of this embodiment.
FIG. 25 is an enlarged view of a bonding pad portion of the semiconductor light emitting device. In these drawings, the same elements as those described above with reference to FIGS. 1 to 23 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the electrode 7 formed on the upper surface of the element is formed by the bonding pad 7C and the extended electrode portion 7D. However, the pattern area of the bonding pad 7 </ b> C is smaller than the fused portion 80 of a wire such as gold (Au) connected thereto. For example, when a gold wire having a diameter of about 20 micrometers to 30 micrometers is ball bonded, the fused portion 80 has a substantially circular shape having a diameter of about 80 micrometers to 120 micrometers. On the other hand, the diameter of the bonding pad 7C of the light emitting device of the present embodiment is, for example, about 40 micrometers to 70 micrometers. Then, in order to ensure the strength against wire bonding and diffuse the current over a wide range, the extending electrode portion 7D is extended from the bonding pad 7C. Under the bonding pad 7C and the extended electrode portion 7D, both have a structure in which current can be injected through a contact layer (not shown).

FIG. 26 is a schematic view illustrating a state in which a part of the light emission generated under the fusion part 80 is taken out from the gap between the stretched electrodes 70.
In general, light emitted under the bonding pad 7C is blocked by the bonding pad 7C and cannot be taken out as it is. Further, in the case of a structure in which current is injected into the semiconductor layer under the bonding pad 7C, an alloying region 18 of metal and semiconductor is formed under the bonding pad 7C. The alloying region 18 absorbs light emission, so that loss occurs. Therefore, if the bonding pad 7C is formed larger than the size of the fused portion 80 of the wire, the light extraction efficiency is lowered.

On the other hand, according to the present embodiment, the size of the bonding pad 7C is made smaller than that of the fused portion 80 of the wire, so that the light emission generated under the fused portion 80 as shown in FIG. A part of can be taken out from the gap of the extending electrode portion 7D. Therefore, in the case of this embodiment, the substrate 1 is not necessarily transparent to the light emitted from the active layer 3. However, in the present embodiment, the same effect can be obtained even when the substrate 1 is applied to a transparent semiconductor light emitting device.
FIG. 27 is a schematic view illustrating an electrode pattern in this embodiment.
That is, a bonding pad 7C smaller than the fused portion 80 of the wire is provided, and the narrow extended electrode portions 7F are radially connected. Light emission generated under the fusion part 80 can be taken out from between the stretched electrode parts 7F. Further, by extending the narrow wire electrode portion 7E having a narrower width to the periphery of the chip, it becomes possible to uniformly inject current over a wide range and to emit light in a wide range.

FIG. 28 is a schematic diagram illustrating another specific example of the electrode pattern in the present embodiment.
That is, in this specific example, a wide stretched electrode portion 7D is formed at a portion below the fused portion 80, and a narrow stretched electrode portion 7F is formed at other portions. By forming the extended electrode portion 7D wide under the fused portion 80, the strength against wire bonding can be increased. That is, the semiconductor layer can be more reliably protected against pressure, ultrasonic waves, and the like applied during wire bonding. Further, by forming the narrow extended electrode portion 7F and the narrow wire electrode portion 7E in the outer portion of the fused portion 80, the current is uniformly injected over a wide range, and the light emission is not blocked. Can be taken out with high efficiency.

FIG. 29A is a schematic plan view in which a portion of the electrode 7 of the semiconductor light emitting device according to the modification of the present embodiment is enlarged, and FIG. 29B is a schematic cross-sectional view thereof.
That is, in this modified example, the electrode 7 (stretched electrode portions 7D and 7F, bonding, and the like) is under the fusion portion 80 (for example, the portion of the fusion portion 80 represented by a one-dot chain line in FIGS. 27 and 28). The surface of the semiconductor layer where the pad 7C or the like is not formed is covered with a transparent film 21 that is transparent to light emission. By providing such a transparent film 21, the strength against wire bonding can be increased. Also, the semiconductor layer can be protected when the semiconductor light emitting element is sealed with resin. Furthermore, by providing the transparent film 21, it is possible to more efficiently extract a part of light emission generated under the bonding pad 7 </ b> C to the outside. That is, as exemplified by the arrow A in FIG. 29, the light emitted under the bonding pad 7C is incident on the transparent film 21 and reflected by the surface of the transparent film 21 to propagate through the transparent film 21. it can. In this way, the light emitted under the fusion part 80 can be taken out by propagating through the transparent film 21.

  At this time, the transparent film 21 may be formed of a material having a refractive index smaller than that of a transparent resin (with a refractive index of about 1.5) that seals the light emitting element. Such a transparent film 21 can be formed by, for example, an SOG (Spin On Glass) method. When the SOG method is used, as a raw material, for example, an inorganic silicate-based or organic silicate-based liquid SOG material such as methylsiloxane is applied to the surface of the wafer by spin coating. Thereafter, a transparent silicon oxide film is obtained by performing a heat treatment at 300 to 400 ° C., for example. The silicon oxide film thus obtained has a refractive index of 1.4 or less, and can be used as the transparent film 21 in this modification.

  In addition, when the thickness of the transparent film 21 is approximately the same as the thickness of the electrode 7, the strength against wire bonding can be increased. However, even when the transparent film 21 is thinner than the electrode 7, the light extraction effect can be obtained.

  In this modified example as well, as described above with respect to the first embodiment, an uneven rough surface is formed on the back surface of the translucent substrate, and as described above with respect to the second embodiment. In addition, when a recess is provided on the back surface of the light-transmitting substrate, the light extraction efficiency can be further improved.

  FIG. 30 is a schematic cross-sectional view showing a semiconductor light emitting element according to another modification of the present embodiment. That is, in this modification, the rough surface 9 is formed on the surface of the semiconductor layer. By forming the rough surface 9, the light extraction efficiency can be increased by using multiple reflection as described above with reference to FIG. That is, light emitted from the active layer 3 can be extracted with high efficiency in both the region below the fused portion 80 and the other light emitting region.

FIG. 31 is a schematic cross-sectional view showing a semiconductor light emitting element according to still another modified example of the present embodiment.
That is, this modification example has a structure in which the modification example shown in FIG. 29 and the modification example shown in FIG. 30 are combined. By providing the transparent film 21 and the rough surface 9 under the fusion part 80, the reflection effect and the scattering effect are promoted, and light emitted under the fusion part 80 is taken out to the outside with higher efficiency. Is possible.

(Fifth embodiment)
Next, a semiconductor light-emitting device equipped with the semiconductor light-emitting element of the present invention will be described as a fifth embodiment of the present invention. That is, a high-luminance semiconductor light-emitting device can be obtained by mounting the semiconductor light-emitting element described above with respect to the first to fourth embodiments on a lead frame, a substrate, or the like.

FIG. 32 is a schematic cross-sectional view showing the semiconductor light emitting device of this embodiment. In other words, the semiconductor light emitting device of this specific example is a resin-encapsulated semiconductor light emitting device called “bullet type” or the like.
A cup portion 102C is provided on the top of the lead 102, and the semiconductor light emitting element 101 is mounted on the bottom surface of the cup portion 102C with an adhesive or the like. The other lead 103 is wired with a wire 104. The inner wall surface of the cup portion 102C constitutes a light reflecting surface 102R, and the light emitted from the semiconductor light emitting element 101 can be reflected and extracted upward. In this specific example, in particular, light emitted from the side surface of the transparent substrate of the semiconductor light emitting element 101 can be reflected upward by the light reflecting surface 102R.

  The periphery of the cup portion 102C is sealed with a light transmissive resin 107. The light extraction surface 107E of the resin 107 forms a condensing curved surface, and the light emitted from the semiconductor light emitting element 101 can be appropriately condensed to obtain a predetermined light distribution.

  FIG. 33 is a schematic cross-sectional view illustrating another specific example of the semiconductor light emitting device. That is, in this specific example, the resin 107 that seals the semiconductor light emitting element 101 is rotationally symmetric with the optical axis 107C as the central axis, and has a shape that retreats and converges in the direction of the semiconductor light emitting element 101 at the center. . By employing the resin 107 having such a shape, a light distribution characteristic that disperses light over a wide angle can be obtained.

  FIG. 34 is a schematic cross-sectional view showing still another specific example of the semiconductor light emitting device. That is, this specific example is called a “surface mount type”, and the semiconductor light emitting element 101 is mounted on the lead 102 and connected to the other lead 103 by the wire 104. These leads 102 and 103 are molded in a first resin 109, and the semiconductor light emitting element 101 is sealed with a second resin 107 having translucency. The first resin 109 has enhanced light reflectivity, for example, by dispersing fine particles of titanium oxide. The inner wall surface 109R acts as a light reflecting surface, and guides the light emitted from the semiconductor light emitting element 101 to the outside. That is, light emitted from the side surface of the semiconductor light emitting element 101 can be extracted upward.

  FIG. 35 is a schematic cross-sectional view showing still another specific example of the semiconductor light emitting device. That is, this specific example is also referred to as “surface mount type”, and the semiconductor light emitting element 101 is mounted on the lead 102 and connected to the other lead 103 by the wire 104. The tips of the leads 102 and 103 are molded together with the semiconductor light emitting element 101 in a resin 107 having translucency.

FIG. 36 is a schematic cross-sectional view showing still another specific example of the semiconductor light emitting device. In this specific example, a structure similar to that described above with reference to FIG. 32 is employed, but a phosphor 108 is further provided so as to cover the semiconductor light emitting element 101. The phosphor 108 has a role of absorbing light emitted from the semiconductor light emitting element 101 and converting the wavelength. For example, ultraviolet light or blue light primary light is emitted from the semiconductor light emitting element 101, and the phosphor 108 absorbs the primary light and emits secondary light having different wavelengths such as red and green. For example, three kinds of phosphors can be mixed, and ultraviolet light emitted from the semiconductor light emitting element 101 can be absorbed by the phosphor 108 to emit white light composed of blue light, green light, and red light.
The phosphor 108 may be applied to the surface of the semiconductor light emitting element 101 or may be contained in the resin 107.

  In any of the semiconductor light emitting devices shown in FIGS. 32 to 36, by providing the semiconductor light emitting element described above with respect to the first to fourth embodiments, light can be efficiently emitted from the upper surface and side surfaces of the semiconductor light emitting element 101. The semiconductor light emitting device with high brightness can be provided by taking it out.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, various modifications relating to the structure of the semiconductor light emitting element and the semiconductor light emitting device are also included in the scope of the present invention.
For example, those appropriately modified by those skilled in the art regarding the details of the layer structure constituting the semiconductor light emitting element are also included in the scope of the present invention as long as they include the gist of the present invention. For example, in addition to the InGaAlP system, various active layers such as a Ga _x In _1-x As _y N _1-y (0 ≦ x ≦ 1, 0 ≦ y <1) system, an AlGaAs system, an InGaAsP system, etc. Materials can also be used. Similarly, various materials can be used for the cladding layer, the light guide layer, and the like.
The wafer bonding described as a representative example of an LED manufacturing method having a substrate that transmits light can also be applied to an LED that obtains a transparent substrate by thick epitaxial growth, such as a conventionally known AlGaAs type.

  In addition, the shape and size of the semiconductor light emitting device that are appropriately designed by those skilled in the art are also included in the scope of the present invention as long as they include the gist of the present invention.

Furthermore, semiconductor light-emitting elements and semiconductor light-emitting devices obtained by combining any of the embodiments of the present invention are also within the scope of the present invention. Specifically, for example, the same applies to the semiconductor light-emitting element and the semiconductor light-emitting device obtained by combining the first embodiment of the present invention and any one of the second to fourth embodiments of the present invention. Belongs to the scope of the present invention. For example, the third embodiment and the fourth embodiment may be combined. Any other technically possible combination is similarly included in the scope of the present invention.
In addition, all semiconductor light-emitting elements and semiconductor light-emitting devices that can be implemented by those skilled in the art based on the semiconductor light-emitting elements and semiconductor light-emitting devices described above as embodiments of the present invention are similarly included in the scope of the present invention. Belonging to.

DESCRIPTION OF SYMBOLS 1 Board | substrate 1S Side surface 2 Clad layer 3 Active layer 4 Clad layer 5 Current diffusion layer 6 Semiconductor laminated structure 7,8 Electrode 7A, 7C Bonding pad 7B, 7E Fine wire electrode part 7D, 7F Extending electrode part 7C Bonding pad 7E Fine wire electrode Part 8A, 8B Electrode pattern 9 Rough surface 10 Reflective film 11 Protective film 18 Alloyed region 20 Recessed part 21 Transparent film 26 Contact layer 28 Mounting member 30 Adhesive 50 Dielectric layer 52 Current blocking layer 80 Fusion part

Claims (7)

A substrate having first and second main surfaces and having translucency for light in the first wavelength band;
A semiconductor multi-layer structure including an active layer provided on the first main surface of the substrate and emitting light of the first wavelength band, wherein a first rough surface is formed on at least a part of the surface; ,
A dielectric film provided on the first rough surface;
A bonding pad provided on the dielectric film;
A thin wire electrode portion provided on the semiconductor multilayer structure and electrically connected to the semiconductor multilayer structure and the bonding pad;
A second electrode provided on the second main surface of the substrate;
A semiconductor light emitting device comprising:   2. The semiconductor light emitting device according to claim 1, wherein a side surface of the substrate is inclined in a tapered shape.   The semiconductor light emitting element according to claim 1, wherein a rough surface is formed on a side surface of the substrate.   4. The semiconductor light emitting element according to claim 1, wherein the rough surface formed on the side surface of the substrate is an aggregate of pyramids.   5. The semiconductor light emitting element according to claim 1, wherein the dielectric film is mainly composed of SOG. A mounting member;
The semiconductor light emitting element according to any one of claims 1 to 5 mounted on the mounting member,
With
The mounting member has a reflecting portion that reflects light emitted from a side surface of the substrate of the semiconductor light emitting element. A wire connected to the semiconductor light emitting device;
7. The semiconductor light emitting device according to claim 6, further comprising a bonding pad having a pattern provided on the semiconductor laminated structure, connected to the fused portion of the wire, and smaller than the fused portion. Semiconductor light emitting device.