KR100983841B1 - Light-emitting diode and fabrication method thereof - Google Patents

Abstract

The light emitting diode 10 has a light extraction surface and includes a transparent substrate 14, a compound semiconductor layer 13 bonded to the transparent substrate, a light emitting portion 12 included in the compound semiconductor layer, and a light emitting portion [[Al _X Ga _1-X ) _Y In _1-Y P, 0 ≤ X ≤ 1, 0 ≤ Y ≤ 1], the light emitting layer 133, the first electrode of different polarity provided on the surface of the light emitting diode opposite to the light extraction surface ( 15, a second electrode 16, and a reflective metal film 17 formed of the first electrode. The transparent substrate has a first side 142 which is substantially perpendicular to the light emitting surface of the light emitting layer on the side close to the light emitting layer and a second side surface 143 which is inclined with respect to the light emitting surface on the side away from the light emitting layer. The first and second electrodes are mounted on the electrode terminals 43 and 44, respectively.

Light emitting diodes, transparent substrates, semiconductor layers, light emitting layers, reflective metal films

Description

LIGHT-EMITTING DIODE AND FABRICATION METHOD THEREOF

Cross reference of related application

This application claims 35 U.S.C. U.S. Provisional Patent Application No. 60 / 773,677, filed February 16, 2006 and U.S. Patent Application No. 60 / 773,678, filed February 16, 2006, pursuant to §119 (e). 35 U.S.C. claiming benefit over the filing date of Japanese Patent Application No. 2006-030475, filed February 8, 2006, and Japanese Patent Application No. 2006-032028, filed February 9, 2006, pursuant to § 111 (b). An application filed under § 111 (a).

The present invention provides a semiconductor layer comprising a light emitting layer composed of aluminum phosphide-gallium-indium [(Al _X Ga _1-X ) _Y In _1-Y P, 0 ≦ X ≦ 1, 0 <Y ≦ 1] and bonded to a transparent substrate. A light emitting diode having a light emitting diode and a method of manufacturing the same.

A light emitting diode (LED) capable of emitting red, orange, yellow or yellow green visible light, comprising: aluminum phosphide-gallium-indium [(Al _X Ga _1-X ) _Y In _1-Y P, 0 ≦ X ≦ 1, Compound semiconductors having a light emitting layer consisting of 0 <Y ≤ 1] are known. In this type of LED, a light emitting portion having a light emitting layer consisting of [(Al _X Ga _1-X ) _Y In _1-Y P, 0 ≦ X ≦ 1, 0 <Y ≦ 1] is generally used for light emitted from the light emitting layer. It is formed on a substrate material such as gallium arsenide (GaAs) that is optically opaque and mechanically not so strong.

Therefore, recently, in order to obtain a high brightness visible LED and improve the mechanical strength of the device, it is possible not only to remove opaque substrate materials such as GaAs and transmit the emitted light, but also to have excellent mechanical strength than ever developed. A technique for constituting a bonded LED by newly bonding a support layer has been developed (for example, Japanese Patent No. 3230638, Japanese Patent Laid-Open No. 6-302857, Japanese Patent Application Laid-Open No. 2002-246640, Japanese Patent No. 2588849 and See Japanese Patent Laid-Open No. 2001-57441.

In order to obtain a high brightness visible LED, a method of improving the light extraction effect by using the element shape has been used. In the configuration of an element having electrodes formed on the front and rear surfaces of a semiconductor light emitting diode, techniques of high luminance are disclosed by using side surfaces (for example, Japanese Patent Laid-Open No. 58-34985 and US Pat. No. 6229160). Reference).

Although junction LEDs have made it possible to provide high brightness LEDs, there is still a need for higher brightness LEDs. Many shapes for the device have been proposed, but this is too complicated for electrodes to be formed on the front and back of the light emitting diode, respectively. The device structure in which two electrodes are formed on the opposite side of the light emitting diode is complicated in shape and is not optimized in the lateral state and the electrode arrangement.

The present invention relates to the provision of a light emitting diode having two electrodes opposite to a light extraction surface, and has an object to provide a light emitting diode having high light extraction efficiency and high luminance.

The present invention has a light extraction surface and a transparent substrate, a compound semiconductor layer bonded to the transparent substrate, a light emitting portion included in the compound semiconductor layer, a light emitting portion contained in [(Al _X Ga _1-X ) _Y In _1-Y P, A light emitting layer consisting of 0 ≦ X ≦ 1, 0 <Y ≦ 1], comprising a first electrode and a second electrode of different polarities provided on the surface of the light emitting diode facing the light extraction surface, and a reflective metal film formed of the first electrode The light emitting diode is provided in the first embodiment, and the transparent substrate has a first side that is substantially perpendicular to the light emitting surface of the light emitting layer on the side close to the light emitting layer and a second side that is inclined with respect to the light emitting surface on the side away from the light emitting layer, The first and second electrodes are mounted on electrode terminals disposed on the mounting substrate, respectively.

The second embodiment of the present invention provides the light emitting diode according to the first embodiment, and the second electrode is formed on the side of the surface of the light emitting diode opposite to the first electrode and also at the corner position of the compound semiconductor layer.

A third embodiment of the present invention provides a light emitting diode according to the second embodiment, wherein the second electrode is positioned below the inclined structure of the second side surface.

A fourth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, and the transparent substrate is made of n-type GaP.

A fifth embodiment of the present invention provides a light emitting diode according to the first or second embodiment, and the transparent substrate has a plane orientation of (100) or (111).

A sixth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, wherein the transparent substrate has a thickness in the range of 50 μm to 300 μm.

A seventh embodiment of the present invention includes the light emitting diode according to the first or second embodiment, and the light emitting portion has an outermost layer having a thickness in the range of 0.5 µm to 20 µm.

An eighth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, and the light emitting portion has an outermost layer made of GaP.

A ninth embodiment of the present invention includes the light emitting portion according to the eighth embodiment, and the light emitting portion has an outermost layer made of Ga _x P _{1 -x} (0.5 <X <0.7).

A tenth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, wherein the second side surface and the plane parallel to the light emitting surface form an angle in the range of 55 ° to 80 °.

An eleventh embodiment of the present invention includes the light emitting portion according to the first or second embodiment, and the first side has a width in the range of 30 μm to 100 μm.

A twelfth embodiment of the present invention includes the light emitting portion according to the first embodiment, and the second electrode has a circumference mounted on the semiconductor layer.

A thirteenth embodiment of the present invention includes the light emitting portion according to the first embodiment, and the first electrode is in a lattice shape.

A fourteenth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, and the first electrode is a linear electrode having a width of 10 µm or less.

A fifteenth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, the light emitting portion includes a GaP layer, and the second electrode is formed on the GaP layer.

A sixteenth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, wherein the first electrode has an n-type polarity and the second electrode has a p-type polarity.

A seventeenth embodiment of the present invention includes the light emitting diode according to the first or second embodiment, and the second side surface of the transparent substrate has a rough surface.

In addition, the present invention is to form a light emitting portion comprising a light emitting layer consisting of (Al _x Ga _1-X ) _Y In _1-Y P (0 ≤ X ≤ l, 0 <Y ≤ l), a compound semiconductor comprising a light emitting portion Bonding the layer to the transparent substrate, forming a first electrode and a second electrode having a different polarity than the first electrode, on the surface of the compound semiconductor layer opposite to the transmissive substrate and facing the main light extraction surface; The electrode is formed on the surface of the compound semiconductor layer opposite to the first electrode and on the outermost layer of the light emitting portion, forming a reflective metal film on the surface of the first electrode, and close to the light emitting layer on the side of the transparent substrate. Forming a first side surface substantially perpendicular to the light emitting surface of the light emitting layer on the side, and forming a second side surface inclined with respect to the light emitting surface on the side away from the light emitting layer by dicing. 18 rooms It provided in the form.

A nineteenth embodiment of the present invention includes the method of manufacturing a light emitting diode according to the eighteenth embodiment, wherein the second electrode is a corner of the compound semiconductor layer further exposed on the side opposite to the first electrode on the surface of the compound semiconductor layer. Is formed.

A twentieth embodiment of the present invention includes a method of manufacturing a light emitting diode according to the eighteenth or nineteenth embodiment, wherein the first aspect is formed by a scribe and break method.

A twenty-first embodiment of the present invention includes the method for manufacturing a light emitting diode according to the eighteenth or nineteenth embodiment, wherein the first side is formed by a dicing method.

The present invention further provides that the light emitting diode according to any one of the first to seventeenth embodiments is mounted with the surface facing down.

The present invention not only makes it possible to efficiently extract light from the light emitting portion of the light emitting diode (LED), but also enables the LED of high brightness to be supplied.

The foregoing and other objects, characteristic attributes, and advantages are apparent to those skilled in the art by the following description with reference to the accompanying drawings.

1 is a plan view of a semiconductor light emitting diode included in the first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II of FIG. 1.

3 is a cross-sectional view of the epitaxial wafer included in the first embodiment and the first comparative example of the present invention.

4 is a cross-sectional view of a bonded wafer included in a first embodiment and a first comparative example of the present invention.

5 is a plan view of a light emitting diode included in a first embodiment and a first comparative example of the present invention.

6 is a cross-sectional view of a light emitting diode included in a first embodiment and a first comparative example of the present invention.

7 is a plan view of a semiconductor light emitting diode included in the second embodiment of the present invention.

8 is a cross-sectional view taken along the line VII-VII of FIG. 7.

9 is a plan view of a semiconductor light emitting diode included in a first comparative example.

10 is a cross-sectional view taken along the line VII-VII of FIG. 9.

The light emitting part included in the present invention is a compound semiconductor laminate structure including a light emitting layer made of (Al _x Ga _1-X ) _Y In _1-Y P (0 ≦ X ≦ l, 0 <Y ≦ l). The light emitting layer may be formed of (Al _x Ga _1-X ) _Y In _{1 -Y} P (0 ≦ X ≦ l, 0 <Y ≦ l) at one of conductive n or p. The light emitting layer may be composed of one of a structure of a single quantum well (SQW) and a multi-quantum well (MQW). However, the light emitting layer may have an MQW structure in order to obtain excellent monochromatic light emission. desirable. The barrier layer forming the quantum well (QW) structure and the structure forming the well layer (Al _x Ga _1-X ) _Y In _1-Y P (0 ≦ X ≦ l, 0 <Y ≦ l) A quantum level that derives the expected wavelength of the emitted light is determined to form in the well layer.

In order to obtain high-density light emission, the most advantageous light emitting portion is composed of a so-called double hetero (DH) structure composed of a light emitting layer and a cladding layer disposed on opposite sides of the light emitting layer so as to face each other, so that a carrier destined to induce radiation recombination and light emission. To be restricted. The cladding layer is formed of a semiconductor material having a higher refractive index and a higher refractive index than the structure (Al _x Ga _1-X ) _Y In _1-Y P (0 ≤ X ≤ l, 0 <Y ≤ l) forming the light emitting layer. It is preferable. If the light emitting layer is formed of (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P to emit, for example, yellow green light of about 570 nm, the clad layer is formed of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (Y. Hosokawa et al., J. Crystal Growth, 221 (2000), 652-656). Between the light emitting layer and the cladding layer, an intermediate layer is provided which appropriately changes the band so that these layers overlap to smooth the discontinuity. In this case, the intermediate layer is preferably formed of a semiconductor material having an intermediate forbidden band between the light emitting layer and the cladding layer.

This invention bonds a transparent substrate (transparent support layer) to the semiconductor layer containing a light emitting layer. The transparent support layer has a strength sufficient to mechanically support the light emitting portion, is wide enough to prevent the light emitted from the light emitting portion, and is formed of an optically transparent material. For example, Group III-V compound semiconductor crystals, such as potassium phosphide (GaP), aluminum gallium arsenide (AlGaAs), and gallium nitride, group II-VI semiconductor crystals, such as zinc sulfide (ZnS) and zinc selenide (ZnSe), And Group IV semiconductor crystals such as hexagonal or cubic silicon carbide (SiC) can be used to form the transparent support layer.

The transparent support layer preferably has a thickness of about 50 μm or more so as to mechanically support the light emitting portion with sufficient strength. In addition, the transparent support layer preferably has a thickness that does not exceed about 300 μm to facilitate the performance of the mechanical process after the bonding step. Optimally, a compound semiconductor LED having a light emitting layer consisting of (Al _x Ga _1-X ) _Y In _1-Y P (0 ≦ X ≦ l, 0 <Y ≦ l) is less than about 50 μm and less than about 300 μm. It has a transparent support layer formed of an n-type GaP single crystal having a thickness.

For example, if a transparent support layer made of gallium phosphide (GaP) is bonded to the outermost layer of the light emitting portion, while the transparent support layer is bonded, the III is different from the lattice constant from other III-V compound semiconductor components of the light emitting portion. By having the outermost layer of the light emitting portion made of the Group-V compound semiconductor material, the relaxation function of the stress applied to the light emitting portion can be exercised. Accordingly, it is possible to prevent the light emitting layer from being damaged during the bonding process, and to stably provide a compound semiconductor (LED) capable of emitting light having an expected wavelength, for example. The outermost layer of the light emitting layer to which the transparent support layer (transparent substrate) can be ideally bonded has a thickness of 0.5 μm or more so as to sufficiently relieve the stress applied to the light emitting portion while the transparent support layer is bonded. If the outermost layer has an extremely large thickness, the excess thickness causes stress to the emitting layer while the outermost layer is disposed due to the lattice constant difference from the other constituent layers of the light emitting portion. In order to prevent such damage, the outermost layer is ideally set to a thickness of 20 µm or less.

In particular, transparent gallium phosphide (GaP) is suitable for transmitting the light emitted from the light emitting layer consisting of (Al _x Ga _1-X ) _Y In _1-Y P (0 ≦ X ≦ l, 0 <Y ≦ l) to the outside. When selected as the support layer, a strong junction can be formed by forming the outermost layer using a semiconductor material containing gallium (Ga) and phosphorus (P) as constituent elements and containing more Ga than P. The outermost layer is particularly suited to be formed of Ga _x P _1-x (0.5 <X <0.7) of nonstoichiometric composition.

It is preferable that the surface of the transparent support layer intended to be connected and the surface of the outermost layer of the light emitting portion are formed of a single crystal and have the same plane orientation. It is preferred that the two surfaces always have a face 100 or face 111. In order to obtain the outermost layer of the light emitting portion having the surface 100 or the surface 111 as the surface, a substrate having the surface 100 or the surface 111 may be used as the surface when the outermost layer of the light emitting portion is formed on the substrate. . If a gallium arsenide (GaAs) single crystal having a surface 100 as the surface is used as the substrate, for example, the outermost layer of the formed light emitting portion may have the surface 100 as the surface.

The light emitting unit may be formed on one of a group III-V compound semiconductor single crystal substrate, such as gallium arsenide (GaAs), indium phosphide (InP), or gallium phosphide (GaP), or a silicon (Si) substrate. The light emitting portion is preferably formed in the DH structure in which the carrier and the emitted light tend to induce radiation recombination as described above. Thereafter, the light emitting layer is preferably formed in the SQW structure or the MQW structure in order to obtain the emission light having excellent monochromaticity. As a specific example of the method of forming the constituent layer of the light emitting portion, organometallic chemical vapor deposition (MOCVD) method, molecular beam epitaxy (MBE) method and liquid phase epitaxy (LPE) method are cited.

Between the substrate and the light emitting portion is inserted a buffer layer that supports the function of mitigating the lattice mismatch between the material of the substrate and the constituent layers of the light emitting portion and an etch stop layer used for selective etching. In the constituent layer of the light emitting unit, a contact layer for reducing contact resistance of the ohmic electrode, a current diffusion layer for diffusing the device driving current in a planar manner through the entire light emitting unit, a current blocking layer for limiting the region through which the device driving current passes, and a current blocking layer may be provided. Can be. If a contact layer, a current diffusion layer, or the like is provided, it can be included in the light emitting portion, and the transparent substrate is bonded to the outermost layer.

If the surface of the transparent support layer or the outermost layer of the light emitting portion to which the support layer is bonded has a planarity of 0.3 nm or less as the rms value, particularly strong bonding can be achieved. A plan view of this grade can be obtained by chemical mechanical polishing (CMP) method using, for example, an abrasive comprising a silicon carbide (SiC) fine system or a cerium (Ce) fine system. If the CMP-treated surface is further treated with an acid solution or an alkaline solution, a clean surface can be obtained by removing foreign substances or impurities adhered to the surface in the polishing process as well as improving the flatness of the surface.

The outermost layer of the transparent support layer or the light emitting portion is easily bonded in a vacuum of 1 × 10 ⁻² Pa or less, and preferably bonded at a pressure of 1 × 10 ⁻³ Pa or less. In particular, a strong bond can be formed if the flat surfaces resulting from polishing are bonded to each other. When these two surfaces are joined, it is important to irradiate each of the surfaces to be bonded with an atomic beam or ion beam having an energy of 50 eV or more and eventually activate the surface. The term " activation " as used herein refers to creating a clean surface in which an impurity layer or contaminant layer containing carbon and oxide film present on the surface to be bonded is removed. When this irradiation is made on the surface of one of the constituent layers of the transparent support layer and the light emitting portion, both of these layers are strongly and reliably bonded. If this irradiation is made on both of these surfaces, they can be bonded more strongly.

As the irradiated species efficiently demonstrating the induction of strong conjugation, hydrogen (H) atoms, hydrogen molecules (H ₂ ) and hydrogen ions (molecular formula: H ⁺ ) can be exemplified. When a beam containing an element present in the surface area to be bonded is irradiated, an excellent bond in strength can be formed. When gallium phosphide (GaP) to which zinc (Zn) is added is used for the transparent support layer, for example, an irradiation surface to be joined by an atom or ion beam containing gallium (Ga), phosphorus (P) or zinc (Z) Can be strongly bonded. However, when the electrical resistance of the surface of the transparent support layer or the outermost layer of the light emitting portion is high, irradiation of such a surface by a beam mainly containing ions can charge the surface. Since the charging of such a surface induces electrical repulsion, since a strong bond cannot be formed, it is preferable that activation of the surface by irradiation of the ion beam is used to activate a surface excellent in electrical conduction.

In addition, in the surface region of the transparent support layer or the constituent layer of the light emitting portion, the activation of the surface is stably achieved by using a beam of inert gas such as helium (He), neon (Ne), argon (Ar) or krypton (Kr). Can be. Among other beams, the use of argon (Ar) atom (monoatomic) beams is suitable for preparing surface activation in a short time. Since helium (He) has a smaller atomic weight than argon (Ar), there is a disadvantage in that time is wasted in activating the surface to be bonded by the He beam. On the other hand, the use of krypton (Kr) beams having a higher atomic weight than argon is not suitable because it can damage the surface by impact.

When the surfaces of the transparent support layer and the outermost layer of the light emitting portion are joined in opposite overlapping states, a mechanical pressure suitable for affecting the entirety of the surface to be bonded is suitable for strongly joining these two surfaces. Specifically, a pressure in the range of 5 g · cm ⁻² or more and 100 g · cm ⁻² or less is irradiated in the vertical direction (vertical direction) to the bonded surface. If one or both of the transparent support layer and the outermost layer of the light emitting portion are bent, this method has the effect of eliminating warpage and bonding the layers with constant strength.

The transparent support layer and the light emitting portion are bonded at the above-mentioned preferred vacuum degree while one or both of the transparent support layer and the outermost layer of the light emitting portion are maintained at 100 ° C. or lower, preferably 50 ° C. or lower, more preferably at room temperature. If the bonding is carried out in an environment that maintains a high temperature exceeding 500 ° C., the excess temperature is provided in the light emitting part and (Al _x Ga _{1 -x} ) _Y In _{1 - Y} P (0 ≦ X ≦ 1, 0 <Y ≦ 1 It also adversely affects the stable production of a compound semiconductor (LED) that thermally denatures the light-emitting layer consisting of) and emits light of an expected wavelength.

The present invention manufactures a high brightness compound semiconductor (LED) by bonding the support layer to the outermost layer of the light emitting portion, thereby allowing the support layer to mechanically support the light emitting portion, thereby removing the substrate used to form the light emitting portion and thus Therefore, the extraction of light emitted to the outside can be efficiently improved. In particular, if an optically opaque material is used for the substrate which reliably absorbs the light emitted from the light emitting layer consisting of (Al _x Ga _{1- x} ) _Y In _{1 - Y} P (0 ≦ X ≦ 1, 0 <Y ≦ 1) As described above, the method of removing the substrate can be used to ensure that the LED of high brightness is stably manufactured. When a layer made of a material which is easy to absorb light emitted from a light emitting layer such as a buffer layer is inserted between the substrate and the light emitting portion, the removal of such an insertion layer together with the substrate is an advantage in high luminance of the LED. The substrate may be removed by mechanical cutting, polishing, physical dry or chemical wet etching, or a combination thereof. In particular, by the selective etching method using the difference in the etching rate of the included material, it is possible to remove only the selected substrate and to evenly remove the substrate as well as excellent reproducibility.

In the present invention, the main light extraction surface of the light emitting diode is next to the transparent substrate side, and the first electrode and the second electrode having a different polarity from the first electrode are formed on the side opposite to the transparent substrate. The first electrode and the second electrode are connected with the electrode terminal on the side opposite to the transparent substrate (see FIG. 6). In the present invention, the arrangement of the electrodes aims at high luminance. By adopting this arrangement, there is no need to supply current to the transparent substrate to which it is attached. This in turn makes it possible to bond to a substrate having a high transmittance and to obtain a high luminance.

The present invention has a first side that is substantially perpendicular to the light emitting surface of the light emitting layer at a position near the light emitting layer and a second side which is inclined with respect to the light emitting surface at a position away from the light emitting layer as the side of the transparent substrate. It is preferable that the inclination is made toward the inner side of the semiconductor layer, as shown in FIG. The reason why the present invention uses such a structure is to efficiently extract light emitted from the light emitting layer toward the transparent substrate to the outside. That is, part of the light emitted from the light emitting layer toward the transparent substrate side may be reflected from the first side surface and extracted through the second side surface. In addition, the light reflected from the second side may be extracted through the first side. By the synergistic effect of the first side and the second side, the light extraction probability is improved.

The present invention also has a second electrode formed at the exposed corner of the semiconductor layer, as shown in FIGS. 1 and 2. The second electrode is preferably formed at a position below the inclined structure forming the second side surface (a position lower than the inclined surface so that the electrode does not overlap the inclined surface). By having the second electrode at this position, the present invention can obtain high luminance. By adopting such a structure, the efficiency of light extraction through the inclined surface is improved and high luminance is realized.

In the present invention, it is preferable that the angle formed between the second side face and the plane parallel to the light emitting portion is in the range of 55 ° to 80 ° (indicated by α in FIG. 2). The selection of this range makes the light extraction to the outside of the light reflected from the light emitting diodes efficient. Moreover, it is preferable that this invention forms a 1st side surface in the width | variety D (thickness direction) of the range of 30 micrometers-100 micrometers. By keeping the width of the first side within this range, the light reflected from the reflective metal film is efficiently led through a part of the first side to the second side and consequently radiated through the main light extraction surface to emit light of the light emitting diode. Improve the efficiency.

It is preferable that this invention has the circumference | surroundings of a 2nd electrode by the structure enclosed by the semiconductor layer. The choice of this structure can achieve the effect of lowering the operating voltage. By enclosing the second electrode on all sides by the first electrode it is possible for current to flow in all directions, resulting in a lower operating voltage.

The present invention preferably has a first electrode formed of a linear electrode having a width of 10 μm or less. Linear electrodes are shaped like gratings, nets, combs, and the like. This structure brings the effect of high luminance. By narrowing the width of the electrode, the passage area of the reflective metal film can be increased to realize high luminance. The electrode can be made of any one of known materials, preferably a gold-germanium alloy. The electrode material does not reflect light because a light absorption layer is formed at the junction interface of the semiconductor layer.

Thus, on the side of the first electrode of the light emitting diode, the reflective metal film is formed away from the n electrode. Gold, platinum, titanium, etc. can be used as a reflecting film. The reflective metal film is preferably formed on the entire surface except for the electrode portion. Optionally, it may be formed on the electrode to cover the first electrode.

The present invention forms a light emitting portion in the structure including the GaP layer and allows the second electrode to be formed in the GaP layer. This structure has the effect of lowering the operating voltage. By forming the second electrode on the GaP layer, it produces the effect of making an ideal ohmic contact and lowering the operating voltage.

In the present invention, it is preferable that the first electrode be n-type polarity and the second electrode be p-type polarity. The choice of this structure leads to a high luminance effect. Forming the first electrode in the p-type worsens the diffusion of the current and leads to a decrease in the luminance. Forming the first electrode in the n-type strengthens the diffusion of the current and brings a high luminance effect.

It is preferable that this invention roughens the inclined surface of a transparent substrate. The selection of this structure has the effect of enhancing the light extraction efficiency through the inclined surface. By making the inclined surface rough, total reflection through the inclined surface is suppressed and the light extraction efficiency is lowered. Roughening the surface can be achieved, for example, by chemical etching by adding hydrochloric acid to perhydrogenated phosphate (a mixture of phosphoric acid and hydrogen peroxide).

The light emitting diode of the present invention is manufactured by the following process.

First, for example, a light emitting part including a light emitting layer made of (Al _x Ga _1-x ) _Y In _{1 -Y} P (0 ≦ X ≦ 1, 0 <Y ≦ 1) is formed on a GaAs substrate. Thereafter, the transparent semiconductor substrate is bonded to the compound semiconductor layer including the light emitting portion, and the GaAs substrate is removed. This transparent substrate side functions as a main light extraction surface. After removing the substrate, a first electrode and a second electrode having a different polarity than the first electrode are formed on a surface facing the main light extraction surface remaining. The first electrode is obtained by adhering a metal film to the surface from which the substrate has been removed by vapor deposition, and then removing portions except the electrode by performing necessary patterning on the deposited metal film using photolithography means. The second electrode is formed at the corner of the semiconductor layer exposed on the side opposite to the first electrode. After the first electrode is formed, the reflective metal film is formed on the first surface side of the first electrode. The reflective metal film may cover the first electrode. Next, a first side that is substantially perpendicular to the light emitting surface of the light emitting layer on the side of the transparent substrate is formed at a position close to the light emitting portion layer, and a second side that is inclined with respect to the light emitting surface is formed at a position away from the light emitting layer by the dicing method. . Thus, a light emitting diode is obtained.

In the present invention, formation of the second side surface by the dicing method has an effect of improving the production rate. The second aspect can be manufactured by combining methods such as wet etching, dry etching, scribing and laser processing, but a dicing method showing high productivity is most suitable as a manufacturing method.

The present invention preferably forms the first side surface by the scribe and brake method or the dicing method. By adopting the former manufacturing method, the manufacturing cost can be reduced. This method eliminates the cost of cutting during chip separation, so that a good quality light emitting diode can be manufactured and the manufacturing cost can be reduced. The latter method may have a high luminance effect. By adopting this manufacturing method, the light extraction efficiency through the first aspect can be improved and high luminance can be realized.

The present invention will now be described in detail below with reference to the first embodiment, but is not limited thereto.

First embodiment:

1 and 2 show light emitting diodes fabricated in this embodiment. 1 is a plan view and FIG. 2 is a sectional view taken along II-II of FIG. 1. 3 is a cross-sectional view of a laminated structure of a semiconductor epitaxial wafer used in a semiconductor light emitting diode.

The semiconductor light emitting diode 10 fabricated in this embodiment is a red light emitting diode (LED) having an AlGaInP light emitting portion 12.

In the present embodiment, the present invention will be described in detail with reference to the case where a light emitting diode is fabricated by bonding the epitaxial stack structure (epitaxial wafer) deposited on the GaAs substrate 11 to the GaP substrate 135.

The LED 10 uses an epitaxial wafer having a semiconductor layer 13 sequentially stacked on a semiconductor substrate 11 on which a silicon-doped n-type GaAs single crystal having a surface inclined 15 ° from the surface 100 is formed. Is produced. The stacked semiconductor layer is a silicon-doped n-type GaAs buffer layer 130, a silicon-doped n-type _{(Al 0 .5 Ga 0 .5)} 0.5 In 0 .5 P contact layer, a silicon-doped n-type (Al _0.7 Ga _{0.3) 0.5} in _0.5 P lower cladding layer (132 a), a non-doped _{(Al 0 .2 Ga 0 .8)} 0.5 in 0 .5 P and (Al _0.7 Ga _0.3) emitting layer 20 consisting of a pair of _0.5 in _0.5 P 133, a magnesium-doped p-type _{(Al 0.7 Ga 0.3) 0.5 in} 0.5 P cladding layer and the (Al Ga _{0 .5 0 .5) 0 .5 0.5} in the intermediate layer 134 consisting of a thin film of the P, And magnesium-doped p-type GaP layer 135.

In the present embodiment, the constituent semiconductor layers 130 to 135 constitute group _III of trimethyl aluminum ((CH ₃ ) ₃ Al), trimethyl gallium ((CH ₃ ) ₃ Ga), and trimethyl indium ((CH ₃ ) ₃ In). An epitaxial wafer was formed by laminating on the GaAs substrate 11 by low pressure MOCVD used as the raw material of the element. As the magnesium-doped raw material, biscyclopentadienyl magnesium (bis (C ₅ H ₅ ) ₂ Mg) was used. As the silicon-doped raw material, disilane (Si ₂ H ₆ ) was used. Hydrogen phosphide (PH3) or arsine (AsH ₃ ) was used as a raw material for group V constituent elements. The GaP layer 135 was increased at 750 ° C., and the other constituent semiconductor layers 130 to 134 including the semiconductor layer 13 were increased at 730 ° C.

GaAs buffer layer 130 has a carrier concentration of about 2 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 0.2 μm. _{(Al 0 .5 Ga 0 .5)} 0.5 In 0 _.5 contact layer consisting of P has a carrier concentration of about 2 × 10 ^-3 and a layer thickness of about ¹⁸ ㎝ 1.5㎛. The n clad layer 132 has a carrier concentration of about 8 × 10 ¹⁷ cm ⁻³ and a layer thickness of about 1 μm. The undoped light emitting layer 133 has a layer thickness of 0.8 μm. The p clad layer 134 has a carrier concentration of about 2 × 10 ¹⁷ cm ⁻³ and a layer thickness of about 1 μm. GaP layer 135 has a carrier concentration of about 3 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 9 μm.

The p-type GaP layer 135 had an area reaching to a depth of about 1 mu m from the surface polished to be mirror processed. By polishing, the surface of the p-type GaP layer 135 had a roughness of 0.18 nm. On the other hand, an n-type GaP substrate 14 adhered to the mirror polished surface of the p-type GaP layer 135 was provided. Silicon and tellurium were added to the bonded GaP substrate 14 such that the carrier concentration of the substrate was about 2 × 10 ¹⁷ cm ⁻³ . A single crystal with a plane orientation of (111) was used. The GaP substrate 14 prepared for adhesion had a diameter of 50 mm and a thickness of 250 μm. The GaP substrate 14 was stopped when the rms value became 0.12 nm before being mirror polished and bonded to the p-type GaP layer 135.

The GaP substrate 14 and the epitaxial wafer were brought into a general semiconductor material bonding apparatus, and then the inside of the apparatus was evacuated to a vacuum of 3 x 10 ^-5 Pa. Thereafter, the GaP substrate 14 mounted in the apparatus in which the member made of the carbon material is removed to avoid contaminants such as carbon is heated in a vacuum at a temperature of about 800 ° C, while the surface of the GaP substrate 14 It was irradiated with Ar ions accelerated to an energy of 800 eV. As a result, a bonding layer 141 of non-stoichiometric configuration was formed on the surface of the GaP substrate 14. After formation of the bonding layer 141, the irradiation of Ar ions was stopped and the GaP substrate 14 was cooled to room temperature.

Next, two surfaces of the GaP substrate 14 and the GaP layer 135 provided in the surface region of the non-stoichiometric bonding layer 141 were irradiated with an Ar beam that had been neutralized by electron collision for three minutes. . Thereafter, in the adhesion apparatus maintained in the vacuum state, the surfaces of the two layers 135 and 14 were overlapped, loaded to show a pressure of 20 g / cm 2 at each surface, and mutually bonded at room temperature (see FIG. 4). . The bonded wafer was taken out of the vacuum tube of the bonding apparatus and the inside of the bond was analyzed. As a result, the presence of the Ga _{0 .6} P _{0 .4} non-stoichiometric configuration bonding layer 141 was detected in the joint. The bonding layer 141 had a thickness of about 3 nm. By the general method of SIMS analysis, the bonding layer 141 was found to have an oxygen atom concentration of 7 × 10 ¹⁸ cm ⁻³ and a carbon atom concentration of 9 × 10 ¹⁸ cm ⁻³ .

Next, the GaAs substrate 11 and the GaAs buffer layer 130 were selectively removed from the wafer manufactured by bonding by ammonia-based etching.

On the surface of the contact layer 131, a gold-germanium-nickel alloy (composed of 87% gold by mass, 12% germanium by mass, and 1% nickel by mass) is approximately as first ohmic electrode 15 by vacuum deposition. It was formed to a thickness of 0.5 μm. By a general photolithography method, the ohmic electrode 15 was formed by patterning an electrode on this film and removing portions of the film except the electrode pattern, as shown in FIG. Thereafter, the reflective metal film 17 was formed by depositing platinum having a thickness of 0.2 mu m and gold having a thickness of 1 mu m by a vacuum evaporation method which covers a region where the electrode and the film are removed.

Next, the epitaxial layers 131 to 134 were selectively removed, and the GaP layer 135 was exposed to a region allocated to form a p electrode. On the surface of the GaP layer, the p-type ohmic electrode 16 was formed by depositing 0.2 µm thick AuBe, 1 µm thick gold, 0.2 µm thick platinum, and 2.0 µm thick gold by vacuum deposition.

Low resistance p-type and n-type ohmic electrodes are prepared by heat treatment performed at 450 ° C. for 10 minutes to produce the necessary alloys (see FIGS. 1 and 2).

Next, a V-shaped groove is inserted from the surface of the GaP substrate 14 by a dicing saw blade, the second side 143 having an inclination angle α of 70 ° and the first having a width D of 80 μm. Side 142 is formed.

While the light emitting diode was protected by resistance, the inclined surface was roughened by using a combination of perhydrogenated phosphate and hydrochloric acid. The concave and convex forming the rough surface differed by about 500 nm in the horizontal plane.

Next, the wafer was separated into chips by cutting at 350 μm intervals from the surface side after the dicing saw blade to the wafer. The contaminants generated by the crushing layer and dicing were removed by etching with a mixture of sulfuric acid and hydrogen peroxide to complete the fabrication of the semiconductor light emitting diode (chip) 10.

As schematically shown in FIGS. 5 and 6, the LED lamp 42 is assembled with an LED chip 10 fabricated as described above. This LED lamp 42 is provided between the n-type ohmic electrode 15 of the LED chip 10 and the n-electrode terminal 43 disposed on the first surface of the mounting substrate 45 and the p-type ohmic electrode 16 and p. Manufacture by fixing the LED chip 10 adhered to the mounting substrate 45 through the bonding by the gold bump 46 between the electrode terminals 44 and then sealing the joint portion of the resulting general epoxy resin 41. It became.

When a current passes between the n-type and p-type ohmic electrodes 15 and 16 via the n-electrode terminal 43 and the p-electrode terminal 44 disposed on the first surface of the mounting substrate 45, the lamp 42 Emitted red light having a main wavelength of 620 nm. During the passage of 20 mA of current in the forward direction, a forward voltage (Vf) of about 1.96 V was generated. This showed that the proper placement of the electrodes and the good ohmic properties represented by each ohmic electrode 15 and 16 were reflected. It was found that the emitted luminescence intensity induced a high luminance of 650 mcd when the forward current was set to 20 mA. This showed that the improvement of the light extraction efficiency to the outside was reflected to remove the fracture layer generated during cutting the wafer into the chip and the configuration of the high-efficiency light emitting portion of the light emission.

Second embodiment:

FIG. 7 is a plan view showing a second embodiment of a light emitting diode envisioned by the present invention, and FIG. 8 is a cross-sectional view along the line VIII-VIII of FIG.

The light emitting diodes shown in Figs. 7 and 8 were manufactured under the same conditions as in the first embodiment.

When a current passed between the n-type and p-type ohmic electrodes 15 and 16 via the n electrode terminal and the p electrode terminal disposed on the first surface of the mounting substrate, the lamp emitted red light having a main wavelength of 620 nm. During the passage of 20 mA of current in the forward direction, a forward voltage (Vf) of about 2.10 V was generated. This showed that the proper placement of the electrodes and the good ohmic properties represented by each ohmic electrode 15 and 16 were reflected. It was found that the emitted luminescence intensity induced a high luminance of 850 mcd when the forward current was set to 20 mA. This showed that the improvement of the light extraction efficiency to the outside was reflected to remove the fracture layer generated during cutting the wafer into the chip and the configuration of the high efficiency light emitting part of the light emission.

First Comparative Example:

Similarly to the first embodiment, the transparent substrate 14 is bonded to the semiconductor layer 13 except that the side surface of the transparent substrate is formed perpendicular to the light emitting layer, so that the p-type and An n-type ohmic electrode was formed.

Next, the wafer was separated into chips by cutting at 350 μm intervals from the surface side after the dicing saw blade to the wafer. The contaminants generated by the crushing layer and dicing were removed by etching with a mixture of sulfuric acid and hydrogen peroxide to complete the fabrication of the semiconductor light emitting diode (chip) 10.

As schematically shown in Figs. 5 and 6, the LED lamp 42 is assembled with an LED chip 10 fabricated as described above. The LED lamp 42 is not only between the n-type ohmic electrode 15 of the LED chip 10 and the n-type electrode disposed on the first surface of the mounting substrate 45, but also the p-type ohmic electrode 16 and the p-electrode terminal. It was produced by fixing the LED chip 10 fixed to the mounting substrate 45 through the bonding by the gold bumps 46 between the 44 and then sealing the joint portion of the resultant general epoxy resin 41.

When a current passes between the n-type and p-type ohmic electrodes 15 and 16 via the n electrode terminal and the p electrode terminal disposed on the first surface of the mounting substrate 45, the lamp 42 has a main wavelength of 620 nm. Red light having emitted. During the passage of 20 mA of current in the forward direction, a forward voltage (Vf) of about 2.30 V was generated. The emitted luminescence intensity was 250 mcd while the forward current passed at 20 mA.

The light emitting diode of the present invention can emit red, orange, yellow or yellow green light. Therefore, it can be used as various display lamps.

Claims (22)

Has a light extraction surface; A transparent substrate; A compound semiconductor layer bonded to the transparent substrate; A light emitting part included in the compound semiconductor layer; A light emitting layer included in the light emitting part and formed of (Al _x Ga _1-X ) _Y In _{1 -Y} P (0 ≦ X ≦ l, 0 <Y ≦ l); First and second electrodes of different polarities provided on the surface of the light emitting diode opposite the light extraction surface; And a reflective metal film formed on the first electrode. The transparent substrate has a first side that is substantially perpendicular to the light emitting surface of the light emitting layer on a side close to the light emitting layer; And a second side surface inclined with respect to the light emitting surface on the side away from the light emitting layer; Wherein the first and second electrodes are mounted on electrode terminals disposed on a mounting substrate, respectively. The method of claim 1, The second electrode is formed on the side of the light emitting diode that faces the first electrode and at a corner position of the compound semiconductor layer. The method of claim 2, And the second electrode is located under the inclined structure of the second side surface. The method according to claim 1 or 2, The transparent substrate is a light emitting diode, characterized in that made of n-type GaP. The method according to claim 1 or 2, The transparent substrate has a plane orientation of (100) or (111). The method according to claim 1 or 2, Wherein the transparent substrate has a thickness in the range of 50 μm to 300 μm. The method according to claim 1 or 2, Wherein the light emitting part has an outermost layer having a thickness in a range of 0.5 μm to 20 μm. The method according to claim 1 or 2, And the light emitting part has an outermost layer made of GaP. The method of claim 8, _Wherein the light emitting part has an outermost layer made of Ga _χ P _{1 -χ} (0.5 <X <0.7). The method according to claim 1 or 2, And the plane parallel to the second side surface and the light emitting surface forms an angle in the range of 55 ° to 80 °. The method according to claim 1 or 2, The first side has a light emitting diode, characterized in that having a width in the range of 30㎛ to 100㎛. The method of claim 1, The second electrode has a periphery surrounded by a semiconductor layer. The method of claim 1, The first electrode is a light emitting diode, characterized in that the grid shape. The method according to claim 1 or 2, The first electrode is a light emitting diode, characterized in that the linear electrode having a width of 10㎛ or less. The method according to claim 1 or 2, The light emitting portion comprises a GaP layer; The second electrode is formed on the GaP layer. The method according to claim 1 or 2, The first electrode has an n-type polarity; The second electrode has a p-type polarity, characterized in that the light emitting diode. The method according to claim 1 or 2, And the second side surface of the transparent substrate has a rough surface. Forming a light emitting part including a light emitting layer including (Al _x Ga _1-X ) _Y In _{1 -Y} P (0 ≦ X ≦ 1, O <Y ≦ 1); Bonding the compound semiconductor layer including the light emitting part to a transparent substrate; A first electrode and a second electrode having a different polarity than the first electrode are formed on the surface of the compound semiconductor layer opposite to the transparent substrate and opposite the main light extraction surface, wherein the second electrode is formed of the compound semiconductor layer. Forming a surface on the outermost layer of the light emitting portion on a side opposite to the first electrode; Forming a reflective metal film on a surface of the first electrode; And A first side that is substantially perpendicular to the light emitting surface of the light emitting layer is formed on the side of the transparent substrate close to the light emitting layer, and a second side that is inclined with respect to the light emitting surface is formed on the side away from the light emitting layer by a dicing method. Method of manufacturing a light emitting diode comprising the step. The method of claim 18, And the second electrode is formed on the side of the compound semiconductor layer facing the first electrode and at the corner of the exposed compound semiconductor layer. 20. The method according to claim 18 or 19, The first side is a method of manufacturing a light emitting diode, characterized in that formed by the scribe and brake method. 20. The method according to claim 18 or 19, The first side surface is formed by a dicing method. The light emitting diode according to any one of claims 1 to 3, 12 or 13 is mounted with the surface facing down.

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