JP5848600B2 - Nitride semiconductor light emitting device and method for manufacturing nitride semiconductor light emitting device - Google Patents

Description

  The present invention relates to a nitride semiconductor light emitting device and a method for manufacturing a nitride semiconductor light emitting device.

  Conventionally, nitride semiconductors are expected as semiconductor materials for light-emitting elements and power devices because of their band structure and chemical stability, and their application has been attempted.

  In particular, in recent years, nitride semiconductor light emitting elements that emit light from ultraviolet light to visible light, particularly nitride LEDs (light emitting diodes) using nitride semiconductors, have been actively developed as light sources for lighting devices and display devices. It has become.

  In a nitride LED, an n-type nitride semiconductor layer, an active layer made of a nitride semiconductor layer, and a p-type nitride semiconductor layer are stacked in this order on a substrate, and an n-side electrode is formed on the n-type nitride semiconductor layer. And a p-side electrode is formed on the p-type nitride semiconductor layer.

  And in nitride LED, light is light-emitted from an active layer by injecting an electric current from said electrode. Light generated from the active layer is extracted to the outside mainly through the p-type nitride semiconductor layer upward, that is, in the direction opposite to the substrate.

  One of the performance improvements required for such a nitride LED is an improvement in luminous efficiency, and various approaches have been taken for that purpose.

  For example, in Patent Document 1, an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are stacked in this order, and then the thickness of the p-type nitride semiconductor layer to the n-type nitride semiconductor layer is increased. A nitride semiconductor light emitting device formed by etching up to a portion to form a mesa and bringing an n-side electrode into contact with an n-type nitride semiconductor layer at the peripheral portion of the mesa is disclosed (for example, FIG. 3, FIG. 4 and FIG. 6 etc.).

  The nitride semiconductor light-emitting device described in Patent Document 1 has the above structure, thereby suppressing the increase in drive voltage and the occurrence of uneven light emission and improving the light emission efficiency.

JP 2004-228290 A

  However, in Patent Document 1, although the n-side electrode is formed at the peripheral edge of the mesa of the nitride semiconductor light emitting device, the drive voltage is increased by increasing the contact area between the n-side electrode and the n-type nitride semiconductor layer. No reduction has been done.

  In order to increase the contact area between the n-side electrode and the n-type nitride semiconductor layer without changing the light emitting area of the nitride semiconductor light emitting device, there is a method of increasing the area of the nitride semiconductor light emitting device itself. However, in this method, the number of nitride semiconductor light emitting elements that can be taken out from the original wafer is reduced, so that the manufacturing cost per nitride semiconductor light emitting element increases.

  Further, in order to increase the contact area between the n-side electrode and the n-type nitride semiconductor layer without changing the area of the nitride semiconductor light emitting device itself, there is only a method for reducing the light emitting area of the nitride semiconductor light emitting device. Therefore, even if the drive voltage can be reduced, the light emission amount is reduced, and thus the light emission efficiency cannot be improved.

  In view of the above circumstances, an object of the present invention is to provide a nitride semiconductor light emitting device and a nitride semiconductor capable of producing a nitride semiconductor light emitting device with low driving voltage and high light emission efficiency while suppressing an increase in manufacturing cost. It is providing the manufacturing method of a light emitting element.

The present invention relates to a substrate having a main surface, an n-type nitride semiconductor layer stacked on the main surface of the substrate, an active layer comprising a nitride semiconductor layer stacked on the n-type nitride semiconductor layer, A p-type nitride semiconductor layer stacked on the layer; and an n-side electrode in contact with the n-type nitride semiconductor layer. The p-type nitride semiconductor layer, the active layer, and the n-type nitride semiconductor layer A peripheral portion of the n-type nitride semiconductor layer has a stepped structure including a main surface and side surfaces of the n-type nitride semiconductor layer, and the stepped structure is main surface, and a middle side surface continuous to the bottom major surface, which is composed of a middle of the main surface leading to the middle of the side surface, bottom major surface of the n-type nitride semiconductor layer, the bottom major surface middle side, and an n-side electrode so as to cover the middle of the main surface continuous to the side surface of the middle directly disposed Tei Ru nitride semiconductor continuing to It is a light emitting element.

  Here, in the nitride semiconductor light emitting device of the present invention, it is preferable that the stepped structure and the n-side electrode are arranged so as to surround the mesa.

  In the nitride semiconductor light emitting device of the present invention, it is preferable that the n-side electrode extends toward the center of the nitride semiconductor light emitting device.

  In addition, the nitride semiconductor light emitting device of the present invention preferably further includes an insulating film disposed so as to cover a part of the n-side electrode.

  Furthermore, the present invention provides a method for manufacturing any one of the nitride semiconductor light emitting devices described above, the step of laminating an n-type nitride semiconductor layer on a main surface of a substrate, A step of laminating an active layer, a step of laminating a p-type nitride semiconductor layer on the active layer, and etching a part of each of the n-type nitride semiconductor layer, the active layer, and the p-type nitride semiconductor layer N-type nitridation exposed by the step of forming a mesa, the step of forming a peripheral groove by etching a portion to be the peripheral portion of the n-type nitride semiconductor layer, the step of forming a mesa, and the step of forming a peripheral groove Forming an n-side electrode so as to be in contact with the surface of the nitride semiconductor layer.

  Here, in the method for manufacturing a nitride semiconductor light emitting device of the present invention, it is preferable that the n-side electrode is formed by sputtering in the step of forming the n-side electrode.

  Moreover, it is preferable that the manufacturing method of the nitride semiconductor light-emitting device of this invention further includes the process of heat-processing an n side electrode after the process of forming an n side electrode.

  Moreover, it is preferable that the manufacturing method of the nitride semiconductor light-emitting device of the present invention further includes a step of forming an insulating film so as to cover a part of the n-side electrode after the step of forming the n-side electrode.

  In the method for manufacturing a nitride semiconductor light emitting device of the present invention, it is preferable that the insulating film is formed by sputtering or plasma CVD in the step of forming the insulating film.

  Moreover, it is preferable that the manufacturing method of the nitride semiconductor light emitting element of this invention further includes the process of dividing | segmenting into the nitride semiconductor light emitting element in the position of a peripheral groove after the process of forming an n side electrode.

  Moreover, it is preferable that the manufacturing method of the nitride semiconductor light-emitting device of this invention further includes the process of forming a scribe line in the inside or back surface of the board | substrate under a peripheral groove | channel before the process of dividing | segmenting.

  According to the present invention, it is possible to provide a nitride semiconductor light emitting device and a method for manufacturing the nitride semiconductor light emitting device capable of producing a nitride semiconductor light emitting device with low driving voltage and high light emission efficiency while suppressing an increase in manufacturing cost. can do.

(A) is typical sectional drawing of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) is typical of the upper surface of the nitride semiconductor light-emitting diode element of Embodiment 1 shown to (a). It is a top view. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the nitride semiconductor light-emitting diode element according to the first embodiment. FIG. (A) is typical sectional drawing illustrating another part of the manufacturing process of an example of the manufacturing method of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) looks at (a) from the upper surface. FIG. (A) is typical sectional drawing illustrating another part of the manufacturing process of an example of the manufacturing method of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) looks at (a) from the upper surface. FIG. (A) is typical sectional drawing illustrating another part of the manufacturing process of an example of the manufacturing method of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) looks at (a) from the upper surface. FIG. (A) is typical sectional drawing illustrating another part of the manufacturing process of an example of the manufacturing method of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) looks at (a) from the upper surface. FIG. (A) is typical sectional drawing illustrating another part of the manufacturing process of an example of the manufacturing method of the nitride semiconductor light-emitting diode element of Embodiment 1, (b) looks at (a) from the upper surface. FIG. FIG. 6 is a schematic plan view of the upper surface of a nitride semiconductor light emitting diode element according to a second embodiment. (A) is a schematic plan view of a modified example of the shape of the scribe line, (b) is a schematic plan view of another modified example of the shape of the scribe line, and (c) is a shape of the peripheral groove. It is a typical top view of the modification of.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

[Embodiment 1]
<Structure>
FIG. 1A shows a schematic cross-sectional view of the nitride semiconductor light-emitting diode element according to the first embodiment which is an example of the nitride semiconductor light-emitting element of the present invention, and FIG. 2 is a schematic plan view of the upper surface of the nitride semiconductor light-emitting diode device shown in FIG. FIG. 1A shows a cross section taken along the line XY of FIG.

  As shown in FIGS. 1A and 1B, the nitride semiconductor light-emitting diode device 100 of the first embodiment includes a substrate 101 having a main surface 101a and a buffer layer on the main surface 101a of the substrate 101. 102, an n-type contact layer 103, an n-type SLS layer 104, an active layer 105 made of a nitride semiconductor layer, a p-type carrier block layer 106, and a p-type contact layer 107 are stacked in this order.

  The p-type contact layer 107, the p-type carrier block layer 106, the active layer 105, the n-type SLS layer 104, and a part of the n-type contact layer 103 constitute a mesa 110.

  The peripheral portion of the n-type contact layer 103 has a stepped structure including the main surface 103 a and the side surface 103 b of the n-type contact layer 103. Here, the staircase structure includes a lowermost main surface 103a of the n-type contact layer 103, an intermediate side surface 103b continuous with the lowermost main surface 103a, and an intermediate main surface 103c continuous with the intermediate side surface 103b. It is configured.

  Above the mesa 110, a p-side electrode 108 is provided on the p-type contact layer 107, and a p-side pad electrode 122 is provided on the p-side electrode 108. An n-side electrode 121 is provided at the bottom of the mesa 110 so as to be in contact with the n-type contact layer 103.

  The insulating film 123 covers the entire top surface of the nitride semiconductor light emitting diode element 100 except for a part of the n-side electrode 121 and the p-side pad electrode 122.

  As shown in FIG. 1A and FIG. 1B, a peripheral groove 120 is formed on the periphery of the nitride semiconductor light emitting diode element 100, and is divided at the peripheral groove 120. That is, each nitride semiconductor light emitting diode element 100 is formed by being divided by the peripheral groove 120 and the scribe line 124. A part of the scribe line 124 used for dividing the nitride semiconductor light emitting diode element 100 is formed on the side surface of the substrate 101.

  The n-side electrode 121 includes an n-type contact layer 103 that forms a middle main surface 103 c (a surface equivalent to the main surface of the substrate 101) that forms the bottom of the mesa 110 and a side wall of the peripheral groove 120. The middle side surface 103b and the lowermost main surface 103a of the n-type contact layer 103 constituting the bottom surface of the peripheral groove 120 are provided in contact with each other.

  In this specification, “mesa” means a convex structure formed by removing a part of the laminated structure of the nitride semiconductor layers. Further, in this specification, “the upper surface of the mesa” means the upper surface of the convex protrusion of the convex structure, and “the side surface of the mesa” means the side of the convex protrusion of the convex structure. As used herein, “the bottom of the mesa” means an area excluding the top of the mesa and the side surface of the mesa.

  In the nitride semiconductor light emitting diode element 100, the n-side electrode 121 is provided so as to directly cover the lowermost main surface 103a, the intermediate side surface 103b, and the intermediate main surface 103c of the n-type contact layer 103.

  Therefore, in the nitride semiconductor light emitting diode device 100, the n-side electrode 121 not only contacts the middle main surface 103 c of the n-type contact layer 103 that forms the bottom of the mesa 110, but also the outermost surface of the n-type contact layer 103. Since the lower main surface 103a and the middle side surface 103b are also in contact with each other, the n-side electrode 121 and the light emitting area of the nitride semiconductor light emitting diode element 100 and the area of the nitride semiconductor light emitting diode element 100 itself are not changed. The contact area with the n-type contact layer 103 can be increased.

  Thereby, in the nitride semiconductor light emitting diode element 100, the sacrifice of the light emitting area and the number of elements that can be taken out from the original wafer can be suppressed, so that not only an increase in manufacturing cost can be suppressed, but also the driving voltage is low, An element with high luminous efficiency can be obtained.

  In addition, the stepped structure of the n-type contact layer 103 and the n-side electrode 121 are preferably disposed so as to surround the mesa 110. In this case, since the current injected from the upper surface of the mesa 110 through the p-side pad electrode 122 flows so as to spread toward the n-side electrode 121 disposed so as to surround the mesa 100, the current in the plane of the active layer 105 Can be uniformly injected. Thereby, the nitride semiconductor light emitting diode element 100 with little light emission unevenness can be obtained.

  The n-side electrode 121 preferably extends toward the center of the nitride semiconductor light emitting diode element 100. In this case, since the n-side electrode 121 exists not only in the peripheral portion of the nitride semiconductor light emitting diode element 100 but also in the vicinity of the central portion, the substantial current path length can be shortened and the active region can be reduced. The current can be injected more uniformly in the plane of the layer 105. As a result, the driving voltage can be further reduced, the light emission efficiency can be further improved, and the nitride semiconductor light emitting diode element 100 with less light emission unevenness can be obtained.

  The insulating film 123 is preferably arranged so as to cover a part of the n-side electrode 121. Since the formation area of the n-side electrode 121 located in the vicinity of the mesa 110 is increased, the side surface of the mesa 110 (by the slight deformation of the n-side electrode 121 or the presence of foreign matter in the process after the n-side electrode 121 is formed). In particular, there is a high possibility that a short circuit will occur between the p-type carrier block layer 106, the p-type contact layer 107, and the p-side electrode 108) and the n-side electrode 121, and it is necessary to avoid a situation in which a leak current is generated. . Therefore, since the insulating film 123 is disposed so as to cover a part of the n-side electrode 121, the occurrence of the short circuit can be suppressed, and the manufacturing yield of the nitride semiconductor light emitting diode element 100 is improved. The manufacturing cost of the nitride semiconductor light emitting diode element 100 can be further reduced.

<Manufacturing method>
Hereinafter, an example of a method for manufacturing the nitride semiconductor light-emitting diode element 100 of the first embodiment will be described.

(Lamination of nitride semiconductor layers)
First, as shown in the schematic cross-sectional view of FIG. 2, on the main surface 101a of the substrate 101, the buffer layer 102, the n-type contact layer 103, the n-type SLS layer 104, the active layer 105 made of a nitride semiconductor layer, p Type carrier block layer 106 and p type contact layer 107 are laminated in this order, for example, by MOCVD.

  As the substrate 101, for example, a sapphire substrate can be used, and as the buffer layer 102, for example, an AlN layer can be stacked.

  For example, an n-type GaN layer can be stacked as the n-type contact layer 103, and an n-type InGaN / GaN superlattice layer can be stacked as the n-type SLS layer 104, for example.

  As the active layer 105, for example, an active layer having a multiple quantum well structure composed of an alternating stacked body of InGaN quantum well layers and InGaN barrier layers can be stacked.

  As the p-type carrier block layer 106, for example, a p-type AlGaN layer can be laminated, and as the p-type contact layer 107, for example, a p-type GaN layer can be laminated.

  Here, when stacking an n-type nitride semiconductor layer, for example, Si is used as an n-type dopant, and when stacking a p-type nitride semiconductor layer, for example, Mg is used as an impurity as a p-type dopant. It can be incorporated into the crystal.

  Next, the wafer after the p-type contact layer 107 is laminated is heat-treated. Thereby, the p-type dopant in the p-type nitride semiconductor layer (p-type carrier block layer 106 and p-type contact layer 107) is activated, and the function as a p-type semiconductor is exhibited. The heat treatment can be performed, for example, by heating the wafer after the p-type contact layer 107 is laminated in a nitrogen atmosphere at 800 ° C. for 10 minutes.

(Formation of p-side electrode)
Next, after acid-treating the surface of the p-type contact layer 107, the p-side electrode 108 is formed on the surface of the p-type contact layer 107. Here, as the p-side electrode 108, for example, ITO (Indium Tin Oxide) having a thickness of 180 nm can be formed, but the present invention is not limited to this. The p-side electrode 108 may be a light-transmitting conductive film such as IZO, IGZO, AZO, or ZnO, and is not limited to these oxide films, and may be a metal film. The acid treatment can be performed, for example, by immersing the surface of the p-type contact layer 107 in hydrofluoric acid for 3 minutes, washing with water, and drying.

  Next, the p-side electrode 108 is heat-treated. The nitride semiconductor light emitting diode element 100 has a structure in which light emitted from the active layer 105 is extracted mainly from the p-side electrode 108 side. When the heat treatment of the p-side electrode 108 is performed, light absorption in the emission wavelength region of the p-side electrode 108 tends to be suppressed. For example, when the wavelength distribution of light emitted from the active layer 105 is about 450 nm, for example, heat treatment of the p-side electrode 108 can increase the transmittance of light having a wavelength near 450 nm. In addition, the heat treatment of the p-side electrode 108 has an effect of reducing the contact resistance between the p-type contact layer 107 and the p-side electrode 108 and reducing the sheet resistance of the p-side electrode 108 itself.

  The heat treatment of the p-side electrode 108 is performed, for example, by heating the p-side electrode 108 at 500 ° C. for 10 minutes in a mixed atmosphere of nitrogen and oxygen, and further heating at 800 ° C. for 10 minutes in a nitrogen atmosphere. Can be done.

(Mesa formation)
Next, as shown in the schematic cross-sectional view of FIG. 3A and the schematic plan view of FIG. 3B, the p-side electrode 108, the p-type contact layer 107, the p-type carrier block layer 106, and the active layer 105. The mesa 110 is formed by etching a part of each of the n-type SLS layer 104 and the n-type contact layer 103. FIG. 3A shows a cross section taken along line XY of FIG.

  Here, the formation of the mesa 110 can be performed as follows, for example. First, the p-side electrode 108 is patterned by removing a part of the p-side electrode 108 using a known photolithography technique and etching technique. Here, for example, a hydrochloric acid aqueous solution can be used for etching the p-side electrode 108.

  Next, the area of the wafer on which the mesa 110 is to be formed is covered with a photomask (not shown) using photolithography technology again. Then, using the photomask, a part of each of the p-type contact layer 107, the p-type carrier block layer 106, the active layer 105, the n-type SLS layer 104, and the n-type contact layer 103 by a known dry etching technique. Is dry-etched. As a result, a mesa 110 including the p-type contact layer 107, the p-type carrier block layer 106, the active layer 105, the n-type SLS layer 104, and a part of the n-type contact layer 103 is formed.

  Here, dry etching can be performed using, for example, a chlorine-based gas (chlorine, chlorine tetrachloride, or a mixed gas thereof) as a process gas using an ICP etching apparatus. The etching depth can be, for example, about 0.5 μm, but is not particularly limited. A depth reaching the n-type contact layer 103 is sufficient.

(Formation of peripheral groove)
Next, as shown in the schematic cross-sectional view of FIG. 4A and the schematic plan view of FIG. 4B, the peripheral groove 120 is formed by etching the portion that becomes the peripheral portion of the n-type contact layer 103. To do. FIG. 4A shows a cross section taken along line XY of FIG.

  Here, the formation of the peripheral groove 120 can be performed as follows, for example. First, the above-described photomask (not shown) is patterned by using a photolithography technique so that a region of the wafer other than the portion corresponding to the portion between the elements after the mesa 110 is formed is exposed.

  Next, the peripheral groove 120 is formed by a known dry etching technique (for example, an ICP etching apparatus). Here, the depth of the peripheral groove 120 can be set to about 2 μm, for example.

(Formation of n-side electrode and p-side pad electrode)
Thereafter, as shown in FIGS. 4A and 4B, an n-side electrode 121 is formed so as to be in contact with the surface of the n-type contact layer 103 exposed by forming the mesa 110 and the peripheral groove 120. Further, the p-side pad electrode 122 is formed on the p-side electrode 108. The n-side electrode 121 and the p-side pad electrode 122 can be manufactured as follows, for example.

  First, a photomask (not shown) is manufactured by a photolithography technique so as to cover part of the surface of the p-side electrode 108 and part of the surface of the n-type contact layer 103. Next, films made of electrode materials of the n-side electrode 121 and the p-side pad electrode 122 are formed by sputtering, and lift-off is performed. Thereby, the n-side electrode 121 and the p-side pad electrode 122 are performed. In the first embodiment, the n-side electrode 121 and the p-side pad electrode 122 are simultaneously formed in the same layer structure. The structure of the n-side electrode 121 and the p-side pad electrode 122 can be, for example, a laminate of Ni layer / Pt layer / Au layer.

  Here, the n-side electrode 121 is preferably formed by sputtering. The side surface of the stepped structure of the n-type contact layer 103, that is, the inner surface portion of the side wall of the peripheral groove 120 is covered with the n-side electrode 121, thereby contributing to an increase in contact area with the n-side electrode 121. Therefore, as the depth of the peripheral groove 120 increases, the contact area between the inner surface portion of the side wall of the peripheral groove 120 and the n-side electrode 121 increases. When the n-side electrode 121 is formed by the sputtering method, even when the peripheral groove 120 is deep, the step coverage (covering degree against the step) of the peripheral groove 120 of the n-side electrode 121 can be improved. Since disconnection and thinning of the side electrode 121 can be suppressed, the contact area with the n-type contact layer 103 can be increased, and the n-side electrode 121 with reduced contact resistance can be efficiently formed. As a result, the nitride semiconductor light emitting diode device 100 with high yield, reduced drive voltage, and high light emission efficiency can be manufactured, and therefore an increase in manufacturing cost of the nitride semiconductor light emitting diode device 100 can be suppressed.

  As a sputtering method used for forming the n-side electrode 121, for example, any method such as a parallel plate sputtering method, a magnetron sputtering method, or an ECR sputtering method may be used, as long as it is appropriately selected depending on the electrode material to be formed. Good.

  Thereafter, the n-side electrode 121 and the p-side pad electrode 122 are heat-treated. Here, the heat treatment of the n-side electrode 121 and the p-side pad electrode 122 can be performed, for example, by heating the n-side electrode 121 and the p-side pad electrode 122 in a nitrogen atmosphere at 400 ° C. for 5 minutes.

  In addition, after the n-side electrode 121 is formed, the n-side electrode 121 is preferably heat-treated. When dividing into individual nitride semiconductor light emitting diode elements 100, the n-side electrode 121 is also simultaneously divided at the position of the peripheral groove 120, and therefore the n-side electrode 121 may be peeled off. However, when the n-side electrode 121 is heat-treated after the n-side electrode 121 is formed, the adhesion between the n-type contact layer 103 and the n-side electrode 121 is increased. An n-side electrode 121 that is not easily peeled off can be formed. Thereby, since the manufacturing yield of the nitride semiconductor light emitting diode element 100 is improved, an increase in the manufacturing cost of the nitride semiconductor light emitting diode element 100 can be suppressed. Further, since the contact resistance between the n-type contact layer 103 and the n-side electrode 121 can be reduced by the heat treatment of the n-side electrode 121, the driving voltage of the nitride semiconductor light emitting diode element 100 can be lowered. At the same time, the luminous efficiency can be improved.

  The heat treatment conditions for the n-side electrode 121 can be as described above. However, the conditions for improving the adhesion between the n-type contact layer 103 and the n-side electrode 121 and reducing the contact resistance can be realized. In the case where the materials of the n-type contact layer 103 and the n-side electrode 121 are different, heat treatment capable of improving the adhesion between the n-type contact layer 103 and the n-side electrode 121 and reducing the contact resistance. Since the conditions change, it can be changed as appropriate.

(Formation of insulating film)
Next, as shown in the schematic cross-sectional view of FIG. 5A and the schematic plan view of FIG. 5B, an insulating film 123 is formed so as to cover a part of the n-side electrode 121. Here, as the insulating film 123, for example, a SiO ₂ film having a thickness of 220 nm is formed on the entire surface of the wafer by plasma CVD, and one of the n-side electrode 121 and the p-side pad electrode 122 is formed by photolithography technique and etching technique. It can be formed by removing and opening only the SiO ₂ film above the portion. The opening portion of the insulating film 123 serves as a portion for bonding a metal wire or the like (not shown) that is connected to supply electricity from the outside when the nitride semiconductor light emitting diode element 100 is mounted. FIG. 5A shows a cross section taken along line XY of FIG.

  Here, the insulating film 123 is preferably formed so as to cover a part of the n-side electrode 121 after the n-side electrode 121 is formed. When dividing into individual nitride semiconductor light emitting diode elements 100, the n-side electrode 121 is also simultaneously divided at the position of the peripheral groove 120, and therefore the n-side electrode 121 may be peeled off. However, when the insulating film 123 is formed so as to cover a part of the n-side electrode 12121 after the formation of the n-side electrode 121, the insulating film 123 covers the n-side electrode 121 from above, so that the nitride semiconductor When the light emitting diode element 100 is divided, the n-side electrode 121 can be made difficult to peel off. Thereby, since the manufacturing yield of the nitride semiconductor light emitting diode element 100 is improved, an increase in the manufacturing cost of the nitride semiconductor light emitting diode element 100 can be suppressed.

  The insulating film 123 is preferably formed by a sputtering method or a plasma CVD method. As with the n-side electrode 121, the insulating film 123 is also formed on the inner surface portion of the side wall of the peripheral groove 120. However, when the insulating film 123 is formed by sputtering or plasma CVD, the peripheral groove is formed. Since the step coverage of the insulating film 123 with respect to the inner surface portion of the side wall 120 can be increased and the step-off and thinning of the insulating film 123 can be suppressed, the insulating film 123 is protected so as to protect the n-side electrode 121. Can be formed efficiently. Since the manufacturing yield of the nitride semiconductor light emitting diode element 100 is improved, an increase in the manufacturing cost of the nitride semiconductor light emitting diode element 100 can be suppressed.

  As a sputtering method used for forming the insulating film 123, for example, any method such as a parallel plate sputtering method, a magnetron sputtering method, or an ECR sputtering method may be used, and may be appropriately selected depending on an electrode material to be formed. .

  The insulating film 123 may be any material that can suppress a short circuit between the above-described n-type nitride semiconductor layer and p-type nitride semiconductor layer. For example, an oxide film such as zirconium oxide, hafnium oxide, titanium oxide, or tantalum oxide, A nitride film such as silicon nitride, titanium nitride, or tungsten nitride, or a multilayer structure including a plurality of films selected from these films can be used.

In the first embodiment, an SiO ₂ film is formed as the insulating film 123, and the element except for a portion where a metal wire or the like to be connected to supply electricity from the outside when the nitride semiconductor light emitting diode element 100 is mounted is removed. It covers the surface. In this case, in addition to the above effect, when the light generated from the active layer 105 is extracted to the outside, the difference in refractive index between the nitride semiconductor layer and the outside (air) at the wavelength of the light is reduced. can do. Further, when the p-side contact electrode 108 is made of ITO, the difference in refractive index at the wavelength of this light between the p-side contact electrode 108 and the outside (air) can be reduced. Therefore, since the light generated from the active layer 105 can be extracted more efficiently, the light emission efficiency of the nitride semiconductor light emitting diode element 100 can be improved.

(Thinning board)
Next, as shown in the schematic cross-sectional view of FIG. 6A and the schematic plan view of FIG. 6B, the back surface side of the substrate 101, that is, the side on which each nitride semiconductor layer of the substrate 101 is laminated. The surface opposite to this surface is ground to reduce the thickness of the substrate 101 and further polish, so that the back surface of the substrate 101 is mirror-finished. Here, the substrate 101 is thinned to a thickness of about 90 μm, for example. FIG. 6A shows a cross section taken along line XY in FIG.

(Formation of scribe line)
Next, as shown in FIGS. 6A and 6B, a scribe line 124 is formed in the region of the substrate 101 below the peripheral groove 120. The scribe line 124 can be formed, for example, by irradiating laser light from the back side of the substrate 101 with a laser scribing apparatus. Here, when the focal point of the laser beam is set to be inside the substrate 101, only the region below the peripheral groove 120 and inside the substrate 101 is melted as shown in FIGS. 6 (a) and 6 (b). The scribe line 124 can be formed. Thus, when the scribe line 124 is formed by laser light irradiation, it is useful in that the structure such as the peripheral groove 120 is not easily broken.

  The scribe line 124 is formed in, for example, a line shape including a melted portion of about 25 μm from a position having a depth of about 20 μm from the back surface side of the substrate 101 toward the front surface side of the substrate 101.

  It is preferable to form a scribe line 124 in the region of the substrate 101 below the peripheral groove 120 before the division of the nitride semiconductor light emitting diode element 100 described later. Usually, before dividing into nitride semiconductor light emitting diode elements 100, scribe lines such as a diamond scriber are inscribed between the elements, and the elements are divided along the scribe lines using a break device or the like. However, according to this configuration, since the n-side electrode 121 is formed together with the peripheral groove 120 on the surface of the substrate 101, the scribe line 124 is placed at a location other than the surface of the substrate 101, that is, the inside of the substrate 101 or the back surface of the substrate 101. By scribing, the element can be divided without destroying the structure of the n-side electrode 121 other than the part to be divided. Therefore, the nitride semiconductor light emitting diode device 100 can be manufactured with a high yield, and the manufacturing cost can be reduced.

(Division of wafer)
Next, as shown in the schematic cross-sectional view of FIG. 7A and the schematic plan view of FIG. 7B, the wafer after the scribe line 124 is formed is divided into individual nitride semiconductor light-emitting diode elements. 100 is made. Here, the nitride semiconductor light emitting diode element 100 can be divided by, for example, using a break device and pushing the break blade against the scribe line 124 from the back side of the substrate 101. As a result, the substrate 101 is broken at the scribe line 124 and the peripheral groove 120 to be divided into the nitride semiconductor light emitting diode elements 100. FIG. 7A shows a cross section taken along line XY of FIG.

  After the step of forming the n-side electrode 121, it is preferable to divide into individual nitride semiconductor light emitting diode elements 100 at the position of the peripheral groove 120. In this case, since the n-side electrode 121 is also divided during the division into the nitride semiconductor light-emitting diode element 100, the n-side electrode 121 is in contact with the end of the n-type contact layer 103 of the nitride semiconductor light-emitting diode element 100. A structure can be made. Therefore, the contact area with the n-side electrode 121 can be increased by effectively using the surface of the n-type contact layer 103 as much as possible. Thereby, since the contact area between the n-type contact layer 103 and the n-side electrode 121 can be increased, the nitride semiconductor light-emitting diode element 100 having a low driving voltage and high luminous efficiency can be manufactured.

(Other)
In the first embodiment, the case where the peripheral groove 120 is formed in all the peripheral portions of the mesa 110 and the peripheral portion of the mesa 110 is used more effectively is described. For example, the peripheral portion of the mesa 110 is described. It is not necessary to form the peripheral groove 120 on all four sides, and a form other than the formation on all four sides such as only one side, only two sides, or only three sides of the peripheral part of the mesa 110 may be adopted.

  In the first embodiment, the n-side electrode 121 and the p-side pad electrode 122 are simultaneously formed of the same material and the same layer structure, but the present invention is not limited to this. That is, the n-side electrode 121 and the p-side pad electrode 122 may be formed of different materials and / or different layer structures. The side pad electrode 122 may be formed separately.

  In the first embodiment, the shape of the scribe line 124 is linear, but the shape can be arbitrarily changed. For example, as shown in the schematic plan view of FIG. 9A, the shape of the scribe line 124 may be a broken line. For example, as shown in the schematic plan view of FIG. 9B, the shape of the scribe line 124 may be a dotted line in which dots are arranged in a straight line.

  Moreover, in Embodiment 1, although the shape of the peripheral groove | channel 120 is made into linear form, the shape can be changed arbitrarily. For example, as shown in the schematic plan view of FIG. 9C, the peripheral groove 120 may have a zigzag shape. When the shape of the peripheral groove 120 is zigzag, the drive voltage of the nitride semiconductor light emitting diode device 100 may be reduced compared to the case where the shape of the peripheral groove 120 is linear.

  In the first embodiment, the case where the mesa 110 and the peripheral groove 120 are formed by dry etching using, for example, an ICP etching apparatus has been described. However, they may be formed by dry etching using an RIE apparatus. The peripheral groove 120 can also be formed using a laser scribing device if the depth direction and width direction can be controlled more finely. When the peripheral groove 120 is formed using a laser scribing apparatus, the entire surface of the wafer is covered in advance with a resist film or the like, thereby preventing foreign matter (debris) generated by the laser scribing process from attaching. it can.

  In the first embodiment, the peripheral groove 120 is formed after the mesa 110 is formed. However, the mesa 110 may be formed after the peripheral groove 120 is formed.

  In Embodiment 1, the case where the active layer 105 whose emission wavelength distribution center is around 450 nm is used is exemplified. However, if the emission wavelength is in the range from the ultraviolet region to the visible region, the active layer is used. The composition of each nitride semiconductor layer including 105, each electrode material, and each manufacturing process can be adjusted as appropriate to change to a nitride semiconductor light emitting device having a structure with a desired emission wavelength. For example, in order to obtain light in the ultraviolet region, the active layer 105 may be formed of a nitride semiconductor layer made of an AlGaN system having a high Al composition ratio (for example, about 60 atomic%). Further, for example, in order to obtain light emission in a long wavelength region such as green light, the active layer 105 composed of an InGaN-based nitride semiconductor layer having a high In composition ratio (for example, about 40 atomic%). You can do it.

In the first embodiment, the conductivity types of p-type and n-type may be reversed.
[Embodiment 2]
FIG. 8 is a schematic plan view of the upper surface of a nitride semiconductor light-emitting diode element 200 according to Embodiment 2, which is another example of the nitride semiconductor light-emitting element of the present invention.

  The nitride semiconductor light-emitting diode element 200 according to the second embodiment is characterized in that the shapes of the p-side pad electrode 122, the mesa 110, and the n-side electrode 121 are different. That is, in the second embodiment, the mesa 110 has a shape in which the bottom portion of the mesa 110 is narrowly entered from the side surface of the mesa 110 into which the n-side electrode 121 enters the inside toward the inside of the mesa 110. Yes. In addition, the p-side contact electrode 108 also enters the inside in the same way along the shape.

  Furthermore, the n-side electrode 121 formed in contact with the main surface of the n-type contact layer 103 is directed toward the center of the nitride semiconductor light-emitting diode element 200 along the groove shape in which the mesa 110 is inserted. And has a single-branched structure extending. On the other hand, the p-side pad electrode 122 has a two-branch structure that sandwiches the one-branch structure of the n-side electrode 121.

  In the nitride semiconductor light-emitting diode element 200, since the n-side electrode 121 is connected not only to the peripheral part of the element but also to the central part, the light emission unevenness of the nitride semiconductor light-emitting diode element 200 can be more suitably suppressed. . Furthermore, since the contact area with the n-type contact layer 103 is further increased, the driving voltage of the nitride semiconductor light-emitting diode element 200 can be more suitably reduced.

  In the nitride semiconductor light emitting diode element 200, an operating current is injected from the p-side pad electrode 122 having a double-branched structure into the p-side electrode 108. When the p-side contact electrode 108 is made of a light-transmitting conductive film such as ITO, the current in the horizontal direction is less likely to be diffused than the metal film, but the p-side pad electrode 122 is used as in the second embodiment. By adopting such a branched structure, the current injected from the p-side pad electrode 122 can be uniformly diffused by the p-side electrode 108, so that uneven emission of the nitride semiconductor light-emitting diode element 200 can be suppressed.

  Since the description other than the above in the second embodiment is the same as that in the first embodiment, the description thereof is omitted.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The nitride semiconductor light emitting device of the present invention can be used for nitride semiconductor light emitting devices used in various light source devices such as general illumination devices, liquid crystal display backlights, projector devices, headlights, and spotlights.

  100,200 Nitride semiconductor light emitting diode device, 101 substrate, 101a main surface, 102 buffer layer, 103 n-type contact layer, 103a bottom main surface, 103b middle side surface, 103c middle main surface, 104 n-type SLS layer , 105 active layer, 106 p-type carrier block layer, 107 p-type contact layer, 108 p-side electrode, 110 mesa, 120 peripheral groove, 121 n-side electrode, 122 p-side pad electrode, 123 insulating film, 124 scribe line.

Claims (11)

A substrate having a main surface;
An n-type nitride semiconductor layer stacked on the main surface of the substrate;
An active layer made of a nitride semiconductor layer stacked on the n-type nitride semiconductor layer;
A p-type nitride semiconductor layer stacked on the active layer;
An n-side electrode in contact with the n-type nitride semiconductor layer,
Having a mesa composed of the p-type nitride semiconductor layer, the active layer, and a part of the n-type nitride semiconductor layer;
The peripheral portion of the n-type nitride semiconductor layer has a stepped structure including the main surface and side surfaces of the n-type nitride semiconductor layer,
The step-like structure is composed of a lowermost main surface, a middle side surface continuous to the lowermost main surface, and a middle main surface continuous to the middle side surface,
The n-side electrode is arranged so as to directly cover the lowermost main surface of the n-type nitride semiconductor layer, the middle side surface continuous to the lowermost main surface, and the middle main surface continuous to the middle side surface. Tei Ru, nitride semiconductor light emitting device.   The nitride semiconductor light emitting element according to claim 1, wherein the stepped structure and the n-side electrode are disposed so as to surround the mesa.   The nitride semiconductor light emitting device according to claim 1, wherein the n-side electrode extends toward a central portion of the nitride semiconductor light emitting device.   The nitride semiconductor light emitting element according to any one of claims 1 to 3, further comprising an insulating film disposed so as to cover a part of the n-side electrode. A method for producing the nitride semiconductor light emitting device according to claim 1,
Laminating the n-type nitride semiconductor layer on the main surface of the substrate;
Laminating the active layer on the n-type nitride semiconductor layer;
Laminating the p-type nitride semiconductor layer on the active layer;
Forming the mesa by etching a part of each of the n-type nitride semiconductor layer, the active layer, and the p-type nitride semiconductor layer;
Forming a peripheral groove by etching a portion to be the peripheral portion of the n-type nitride semiconductor layer;
Forming an n-side electrode in contact with the surface of the n-type nitride semiconductor layer exposed by the step of forming the mesa and the step of forming the peripheral groove. .   6. The method for manufacturing a nitride semiconductor light emitting element according to claim 5, wherein, in the step of forming the n-side electrode, the n-side electrode is formed by a sputtering method.   The method for manufacturing a nitride semiconductor light emitting element according to claim 5, further comprising a step of heat-treating the n-side electrode after the step of forming the n-side electrode.   The manufacturing method of a nitride semiconductor light emitting element according to claim 5, further comprising a step of forming an insulating film so as to cover a part of the n-side electrode after the step of forming the n-side electrode. Method.   The method for manufacturing a nitride semiconductor light emitting element according to claim 8, wherein in the step of forming the insulating film, the insulating film is formed by a sputtering method or a plasma CVD method.   The manufacturing method of a nitride semiconductor light emitting device according to claim 5, further comprising a step of dividing the nitride semiconductor light emitting device at the position of the peripheral groove after the step of forming the n-side electrode. Method.   The method for manufacturing a nitride semiconductor light emitting element according to claim 10, further comprising a step of forming a scribe line inside or on the back surface of the substrate below the peripheral groove before the dividing step.

Images