JP2016163015A - Ultraviolet light-emitting element and manufacturing method of same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet light-emitting element, excellent in light emitting efficiency, having a small performance variation and a manufacturing method of the same.SOLUTION: An ultraviolet light-emitting element 100 includes: a substrate 10; a semiconductor laminate part 20, including a light-emitting layer 22, formed on a first principle plane S1 side of the substrate 10; a first electrode part 31 and a second electrode part 32, for providing the semiconductor laminate part 20 with power; a recess part 11, formed at a part on a second principle plane S2 side positioned on the opposite side of the first principle plane S1 of the substrate; and an optical member 40, disposed at the recess part 11.SELECTED DRAWING: Figure 1

Description

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

Semiconductor elements using a nitride substrate are used in various electronic devices, and are applied to arithmetic processing devices, optical devices such as light emitting elements and light receiving elements, and various sensors. In order to bring out the characteristics of these nitride semiconductor devices to the maximum, a technique for processing the device front and back surfaces is widely used.
In the semiconductor light emitting device, the light transmittance at the interface is improved by roughing the back surface of the nitride substrate in order to improve the total reflection of the nitride substrate and improve the light extraction efficiency from the semiconductor light emitting device. A technique for improving the frequency is often used. For example, Patent Document 1 describes a technique for forming a concavo-convex structure on the surface of a semiconductor layer by forming a nitride semiconductor layer so that a hexagonal pyramid cavity is provided.

  A method of forming a thin film having a refractive index smaller than that of the substrate on the back surface of the substrate is also used. For example, Patent Document 2 describes a method of increasing light extraction efficiency by applying a thin film having a refractive index of 1.8 or more to the back surface of a substrate of a semiconductor light emitting element.

JP 2005-277423 A JP 2010-510671 A

In the case where a concavo-convex structure is formed in a semiconductor light emitting element to improve the light output, the interval between the concavo-convex needs to be equal to or less than the emission wavelength and regularly arranged. However, since the wavelength of the light emitted from the ultraviolet light emitting element is as short as 300 nm or less, it is difficult to form the uneven structure applied to the ultraviolet light emitting element.
On the other hand, although a method for forming a thin film having a high refractive index on the back surface of the substrate is simple, it is necessary to control the thickness of the thin film thinly and stably. Particularly in the case of an ultraviolet light emitting element, many organic thin films or inorganic thin films containing an organic solvent absorb ultraviolet light. For this reason, it is important to suppress the absorption of ultraviolet light by making the above thin film as thin as possible. In addition, the thinner the thin film, the more rapidly the light interference effect changes due to variations in film thickness. Therefore, when a thin film is formed on the back surface of the substrate, if the film thickness cannot be controlled stably, the performance variation as a semiconductor light emitting element will increase.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an ultraviolet light emitting element having high luminous efficiency and small performance variation and a method for manufacturing the ultraviolet light emitting element.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following ultraviolet light-emitting device and the manufacturing method thereof, and have completed the present invention.
That is, an ultraviolet light emitting element according to an aspect of the present invention includes a substrate, a semiconductor stacked portion including a light emitting layer formed on the first main surface side of the substrate, and a first for supplying power to the semiconductor stacked portion. A first electrode portion and a second electrode portion; a concave portion formed in a part of the second main surface side of the substrate opposite to the first main surface; and an optical member disposed in the concave portion. It is characterized by providing.

  According to another aspect of the present invention, there is provided a method for manufacturing an ultraviolet light emitting element, including a substrate, a semiconductor stacked portion including a light emitting layer formed on a first main surface side of the substrate, and supplying power to the semiconductor stacked portion. A recess forming step of forming a recess by dry etching on a part of a second main surface located on the opposite side of the first main surface of a semiconductor wafer including a first electrode portion and a second electrode portion for An optical member injecting step of injecting an optical member into the concave portion and a smoothing step of smoothing the thickness of the injected optical member are provided.

  According to one embodiment of the present invention, an ultraviolet light-emitting element with high emission efficiency and small performance variation can be provided.

It is a cross-sectional schematic diagram which shows the ultraviolet light emitting element 100 which concerns on the 1st Embodiment of this invention. It is a cross-sectional schematic diagram which shows the ultraviolet light emitting element 200 which concerns on the 2nd Embodiment of this invention. It is a cross-sectional schematic diagram which shows the ultraviolet light emitting element 300 which concerns on the 3rd Embodiment of this invention. It is a cross-sectional schematic diagram which shows the ultraviolet light emitting element 400 which concerns on the 4th Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing method (the 1) of the ultraviolet light emitting element 100 which concerns on the 5th Embodiment of this invention. It is a cross-sectional schematic diagram which shows the manufacturing method (the 2) of the ultraviolet light emitting element 100 which concerns on the 5th Embodiment of this invention. It is a cross-sectional schematic diagram which shows the ultraviolet light emitting elements 600 and 700 which concern on the 1st, 2nd comparative form of this invention.

Hereinafter, a mode for carrying out the present invention (this embodiment) will be described.
<Embodiment>
(1) Ultraviolet Light-Emitting Element The ultraviolet light-emitting element according to this embodiment is for supplying power to a substrate, a semiconductor laminate including a light-emitting layer formed on the first main surface side of the substrate, and the semiconductor laminate. A first electrode portion and a second electrode portion, and a concave portion formed on a part of the second main surface located on the opposite side of the first main surface of the substrate (that is, facing the first main surface); And an optical member disposed in the recess.
An ultraviolet light emitting element with high luminous efficiency is realized by having a recess in a part on the second main surface side of the substrate and arranging the optical member in this recess.

(2) Method for Manufacturing Ultraviolet Light Emitting Element A method for manufacturing an ultraviolet light emitting element according to this embodiment includes a substrate, a semiconductor stacked portion including a light emitting layer formed on the first main surface side of the substrate, and the semiconductor stacked portion. A recess is formed by dry etching on a part of the second main surface of the semiconductor wafer including the first electrode portion and the second electrode portion for supplying power to the first main surface, which is opposite to the first main surface. A concave portion forming step, an optical member injection step of injecting an optical member into the concave portion, and a smoothing step of smoothing the thickness of the injected optical member.

A recess forming step for forming a recess by dry etching on a part of the second main surface of the semiconductor wafer, an optical member injection step for injecting an optical member into the recess, and a smoothing step for smoothing the thickness of the injected optical member It is possible to manufacture an ultraviolet light emitting element with small performance variation and high reliability.
Hereinafter, each component in the manufacturing method of the ultraviolet light emitting device and the ultraviolet light emitting device according to the present embodiment described above will be described. The characteristics of each constituent element described below can be applied individually or in combination without departing from the technical idea of the present invention.

(3) Substrate In the present embodiment, the substrate is capable of forming a semiconductor stacked portion including a light emitting layer on the first main surface side, and is one on the second main surface side located on the opposite side of the first main surface. If it can form a recessed part in a part, it will not restrict | limit in particular. Examples of the substrate include an aluminum nitride (AlN) substrate and a sapphire (Al ₂ O ₃ ) substrate.

(3.1) Method for forming recesses The method for forming the recesses on the second main surface of the substrate is not particularly limited, but is formed by removing a part of the substrate from the viewpoint of reducing the thickness of the ultraviolet light emitting element. Preferably there is. For example, there is a method in which a region other than the region where the concave portion of the substrate is formed is covered with a protective layer, and the substrate is dry etched by RIE or the like using this protective layer as a mask. Similarly, there may be mentioned a method in which a region other than the region where the concave portion is formed is covered with a protective layer, and the substrate is wet-etched with an alkaline chemical using the protective layer as a mask.

Hereinafter, a specific example in the case of wet etching will be described as an example of the present embodiment.
First, a protective layer is formed on the second main surface of the substrate. The protective layer is not particularly limited as long as it can reduce the influence of the second main surface of the substrate in wet etching. Examples thereof include an adhesive tape used for dicing such as a UV tape, an adhesive film, or a resist. Is mentioned. The protective layer is preferably in close contact with the second main surface without entrainment of bubbles or gaps, and preferably has chemical resistance such that the protective layer or the adhesive layer is not deteriorated by an alkaline chemical solution.

Subsequently, the substrate on which the protective layer is formed is dipped in an alkaline chemical solution, and wet etching is performed. The type of alkaline chemical solution is not particularly limited, but the hydrogen ion concentration index (pH) of the chemical solution is preferably pH> 12. For example, the chemical solution contains sodium hydroxide, potassium hydroxide, or ammonia. Is preferred.
Next, the process of removing a protective layer is performed. The method for removing the protective layer is not particularly limited, but a method that does not damage the substrate, the semiconductor laminated portion, and the electrode portion is preferable. In addition to mechanically removing the protective layer, the protective layer may be a chemical solution such as an organic solvent. It is preferable to remove it chemically. After removing the protective layer, in order to clean the second main surface, it is preferable to perform cleaning with an organic solvent or an aqueous solution, or surface cleaning with oxygen plasma, sputtering, or the like.

(3.2) Side surface of substrate It is preferable that at least a part of the side surface of the substrate is covered with an optical member from the viewpoint of improving the reliability of the ultraviolet light emitting element. Since the side surface of the substrate is covered with the optical member, a large amount of ultraviolet light emitted from the side surface of the substrate is reflected at the interface between the side surface of the substrate and the optical member. For this reason, it becomes possible to suppress deterioration by the ultraviolet-ray of sealing resin which seals a board | substrate through an optical member, and the reliability of an ultraviolet light emitting element improves. Furthermore, since a part of the light reflected at the interface between the optical member and the side surface of the substrate is emitted from the second main surface side of the substrate, there is an effect that the light output is improved. Further, from the viewpoint of suppressing the deterioration of the sealing resin and improving the light output, it is also preferable that at least a part of the first main surface of the substrate is covered with an optical member.

  The method of covering at least a part of the side surface of the substrate with the optical member is not particularly limited, but in the optical member injection step, the injection amount of the optical member to be injected is larger than the volume of the recess, and in the smoothing step, A method of attaching an optical member to at least a part of a side surface of a substrate by smoothing the optical member so that the thickness of a portion of the optical member disposed inside the concave portion is the same as the depth of the concave portion. It is preferable from the viewpoint of production efficiency.

(3.3) Refractive Index of Substrate From the viewpoint of improving light extraction efficiency, the refractive index of the substrate is preferably 1.7 or more. Examples of the substrate material having a refractive index of 1.7 or more include an aluminum nitride substrate and a sapphire substrate.

(3.4) Concave portion From the viewpoint of improving the light extraction efficiency, for example, when viewed in cross section, the width of the concave portion on the second main surface side of the substrate is preferably wider than the width of the light emitting layer. However, when the difference between the width of the light emitting layer and the width of the substrate is originally small, if the width of the concave portion is made extremely wider than the width of the light emitting layer, the width of the region other than the concave portion of the substrate becomes extremely small. Should be noted because it becomes difficult.
From the viewpoint of improving light extraction efficiency, for example, when viewed in cross section, the depth of the recess on the second main surface side of the substrate is preferably 10 nm or more and 5 μm or less.

(4) Semiconductor laminated part In this embodiment, a semiconductor laminated part contains the light emitting layer formed in the 1st main surface side of a board | substrate. From the viewpoint of device characteristics for sterilization applications and the like, the central emission wavelength (that is, the central wavelength of light emitted from the light emitting layer) is preferably 230 nm or more and 320 nm or less.
From the viewpoint of improving the light emission efficiency, it is preferable that the semiconductor stacked portion has a first semiconductor layer of the first conductivity type and a second semiconductor layer on the second conductivity side so as to sandwich the light emitting layer. From the viewpoint of efficiently emitting ultraviolet light, each layer of the semiconductor stacked portion is preferably composed of In _x Al _y Ga _1-xy N (0 ≦ x + y ≦ 1). “First conductivity type” and “second conductivity type” mean that when one is an n-type conductivity type, the other is a p-type conductivity type. That is, when the first conductivity type is n-type, the second conductivity type is p-type, and when the first conductivity type is p-type, the second conductivity type is n-type.

(4.1) First Semiconductor Layer The first semiconductor layer is made of, for example, indium aluminum gallium nitride (InAlGaN) doped with impurities or aluminum gallium nitride (AlGaN) doped with impurities. Examples of the impurity include magnesium (Mg) as a p-type impurity and silicon (Si) as an n-type impurity.

For example, the first semiconductor layer has a plurality of layers composed of In _x Al _y Ga _1-xy N (0 ≦ x + y ≦ 1), and at least a part of the plurality of layers is a lattice of the light emitting layer. It is distorted in a pseudo-lattice matching to approach the parameters. Alternatively, the first semiconductor layer has one or a plurality of layers of In _x AlyGa _1-xy N (0 ≦ x + y ≦ 1), and xy in the composition formula changes with the thickness (that is, along the thickness direction). Or a composition that changes linearly or stepwise).

  Of the first semiconductor layer, the portion including the interface with the substrate preferably has substantially the same composition as the substrate. As a result, two-dimensional growth of the first semiconductor layer is promoted, and inconvenient island formation can be avoided. Further, by avoiding such island formation, it is possible to avoid an undesirable elastic strain relaxation in the first semiconductor layer and the subsequent growth layer.

(4.2) Light-Emitting Layer The light-emitting layer includes, for example, a multiple quantum well (“MQW”) layer. The MQW layer includes a plurality of quantum wells, and each quantum well is made of, for example, InAlGaN or AlGaN. For example, the MQW layer includes an Al _x Ga _1-x N quantum well and an Al _y Ga _1-y N quantum well, one of which is stacked on the other. Here, _x of the Al _x Ga _1-x N quantum well and _{y of} the Al _y Ga _1-y N quantum well are different from each other. The difference between x and y is preferably large enough to obtain good confinement of electrons and holes in the active region. This can increase the ratio of radioactive recombination to non-radioactive recombination.

In the MQW layer including the Al _x Ga _1-x N quantum well and the Al _y Ga _1-y N quantum well, when the values of x and y are exemplified, the difference between x and y is about 0.05, and x is About 0.35 and y is about 0.4. If the difference between x and y is excessively large (for example, greater than about 0.3), inconvenient island formation occurs during the formation of the MQW layer. For this reason, the difference between x and y is preferably 0.3 or less, for example.

In addition, the MQW layer may include a plurality of periods with a pair of Al _x Ga _1-x N quantum wells and Al _y Ga _1-y N quantum wells as one period, and the total thickness (that is, the total thickness) is It may be less than about 50 nm.
The emissive layer may also have an optional thin electron block (or hole block if n-type contact is placed on top of the device) layer. The electron blocking layer may be made of Al _x Ga _1-x N doped with one or more impurities such as Mg, for example. The thickness of the electron block layer is, for example, about 20 nm.

(4.3) Second Semiconductor Layer The second semiconductor layer formed on the light emitting layer is made of, for example, InAlGaN doped with impurities or AlGaN doped with impurities. Examples of the impurity include magnesium (Mg) as a p-type impurity and silicon (Si) as an n-type impurity.

The second semiconductor layer is doped n-type or p-type, but has a conductivity opposite to that of the first semiconductor layer. For example, when the first semiconductor layer is doped with n-type impurities such as Si and exhibits n-type conductivity, the second semiconductor layer is doped with p-type impurities such as Mg and exhibits p-type conductivity. ing. The thickness of the second semiconductor layer is, for example, about 50 nm to about 100 nm.
The second semiconductor layer may have a cap layer containing a semiconductor material doped to the second conductivity type. When the second semiconductor layer exhibits p-type conductivity, the cap layer includes, for example, Mg-doped GaN and has a thickness of about 10 nm to about 200 nm, preferably about 50 nm.

(5) Electrode unit The first electrode unit and the second electrode unit are electrodes for supplying power to the light emitting layer. In the present embodiment, the arrangement of each of the first electrode portion and the second electrode portion is not particularly limited. However, when the semiconductor stacked portion has a mesa structure, one of the first electrode portion and the second electrode portion is arranged on the mesa top portion. An example is shown in which the other of the first electrode portion and the second electrode portion is disposed on the mesa bottom. In addition, there is an example in which the first electrode portion and the second electrode portion are arranged on the upper surface and the lower surface of the element, respectively.

  For example, the second electrode portion is electrically connected to the second semiconductor layer at the top of the mesa, and the first electrode portion is electrically connected to the first semiconductor layer at the bottom of the mesa. The semiconductor stacked portion is partially covered with an insulating layer. By this insulating layer (not shown), the second electrode part (that is, the electrode part electrically connected to the second semiconductor layer at the top of the mesa) is electrically insulated from the light emitting layer and the first semiconductor layer at the bottom of the mesa.

  Each of the first electrode portion and the second electrode portion is made of a conductive material, and is made of, for example, gold (Au), nickel (Ni), aluminum (Al), titanium (Ti), or a combination thereof. For example, the first electrode portion connected to the p-type semiconductor layer is made of a Ni / Au alloy, and the second electrode portion connected to the n-type semiconductor layer is a Ti / Al / Ti / Au stack. It is configured. The first electrode part and the second electrode part are formed by sputtering or vapor deposition, for example.

  The first electrode part and the second electrode part may also include an ultraviolet (UV) reflector. The UV reflector redirects photons that emit light toward the first electrode portion and the second electrode portion (i.e., prevents photons from escaping from the semiconductor stack) and a desired light emitting surface (e.g., It is designed to improve the extraction efficiency of photons generated in the active region of the device by redirecting the photons towards the bottom surface.

(6) Optical member In this embodiment, an optical member is arrange | positioned at the recessed part by the side of the 2nd main surface of a board | substrate. From the viewpoint of improving the light extraction efficiency, the refractive index of the optical member is preferably smaller than the refractive index of the substrate. When the refractive index of the optical member is smaller than the refractive index of the substrate, the light reflection at the interface between the substrate and the optical member can be reduced and the output can be improved.

  Moreover, it is preferable that an optical member is equipped with both the characteristics that it is resistant to UVC (ultraviolet C), and an ultraviolet-ray transmittance is 80% or more in the area | region of a wavelength of 260-300 nm. Furthermore, since the optical member and the lens may be combined, the optical member may be adhesive. Examples of the material of the optical member include, but are not limited to, a silicone material, an epoxy material, and a thin film containing metal oxide nanoparticles. As a silicone resin applicable to the optical member, Dow Corning JCR series, Schott Deep UV200, or the like can be used. In addition, titanium oxide, zirconium oxide, zinc oxide, tantalum oxide, hafnium oxide, niobium oxide, lanthanum oxide, strontium oxide, yttrium oxide, tin oxide, and antimony oxide can be used as the material of the metal oxide nanoparticles. It is not limited to the above materials.

  Further, from the viewpoint of manufacturing variation and reliability improvement, it is preferable that the thickness of the optical member substantially coincides with the depth of the recess. That is, it is preferable that the thickness of the portion of the optical member disposed inside the recess is the same as or substantially the same as the depth of the recess. As an example of a method for substantially matching the thickness of the optical member and the depth of the concave portion, an optical member having a volume larger than the concave portion is injected into the concave portion, and then a squeegee is applied to the surface other than the concave portion on the second main surface side of the substrate. And a method of smoothing the optical member by moving the squeegee in the direction of the substrate plane.

(7) Lens In this embodiment, it is preferable that a lens is provided on the second main surface side of the substrate, and at least a part of the back surface of the lens is in contact with a portion of the optical member disposed inside the recess. . The lens material may be any material such as quartz or sapphire that is UV transmissive in the UVC region, but in order to fix the lens to the second main surface of the UV light emitting element, the width of the lens must be wider than the width of the recess. Is preferred.
In the present embodiment, the method for providing the lens is not particularly limited. For example, it can be realized by further including a step of arranging the lens on the second main surface side of the substrate after the smoothing step. In this case, as described above, the optical member is preferably a material having adhesiveness.

(8) Individualization process The manufacturing method of the ultraviolet light emitting element which concerns on this embodiment is further equipped with the individualization process which separates an ultraviolet light emitting element after a recessed part formation process and before an optical member injection | pouring process. May be.
A specific example of the singulation process will be described below.
The elements can be separated into individual pieces along a scribe line arranged between a plurality of elements formed on the semiconductor wafer. The individualizing process of LSI semiconductor elements is usually performed by blade dicing. However, when a nitride substrate is used as a semiconductor wafer, since the nitride substrate is very hard, it is difficult to cut the nitride substrate with a desired width by blade dicing, and defects such as chipping tend to occur in the nitride substrate. Therefore, there is a problem that productivity is low. Therefore, in this embodiment, it is preferable to form a groove in the scribe line by irradiating laser light from the first main surface of the substrate, and then mechanically divide the substrate along this groove. The means for forming the groove using laser light is not particularly limited, but the wavelength of the laser light is preferably 365 nm or 265 nm.

  Next, alignment is performed on a line scribed with a laser, and the substrate is cleaved by pressing a metal blade or the like onto the line from the first main surface side with an appropriate force. Thereby, the ultraviolet light emitting element can be separated. In the singulation process, not only a single ultraviolet light emitting element is singulated, but also a form in which a plurality of ultraviolet light emitting elements are included is included. That is, by separating into pieces including a plurality of ultraviolet light emitting elements, an ultraviolet light emitting element in which a plurality of independent light emitting layers are arranged in an array in the plane direction can be formed. It is included in this embodiment.

(9) Mounting Step Further, in the method for manufacturing the ultraviolet light emitting element according to the present embodiment, the first electrode portion, the second electrode portion, and the wiring substrate are formed after the recess forming step and before the optical member injection step. You may further provide the mounting process to connect.
The mounting process includes a first electrode part and a second electrode part formed on the first main surface side of the substrate included in the ultraviolet light emitting element, and an electrode part (also referred to as a bump part) on a connection substrate called a submount, for example. Are electrically connected to each other. As a material for the submount substrate, a ceramic substrate, an alumina substrate, or an aluminum nitride substrate with high heat dissipation is preferably used. In addition, a method called flip chip is used for connection, and an appropriate heat or ultrasonic wave is applied between the electrode portion of the submount substrate and the first electrode portion and the second electrode portion formed on the first main surface side of the ultraviolet light emitting element. Bond with weight. The material of the electrode part of the submount substrate should be excellent in heat dissipation and excellent in bonding property with the first electrode part and the second electrode part. Gold (Au), silver (Ag), copper ( A material made of a material such as Cu) or gold tin (AuSn) or a combination thereof is preferably used.

(10) Sealing Step The method for manufacturing an ultraviolet light emitting element according to the present embodiment may further include a sealing step for sealing the first main surface side and the side surface of the substrate after the smoothing step. A thermosetting resin or the like is used for the sealing member. As described above, in general, thermosetting resin is likely to be deteriorated by ultraviolet rays and may affect the product life. However, if at least a part of the side surface of the substrate is covered with an optical member, the thermosetting resin is emitted from the side surface of the substrate. A lot of ultraviolet rays are reflected at the interface between the side surface and the optical member. For this reason, it becomes possible to suppress degradation of the sealing member due to ultraviolet rays emitted from the side surface of the substrate.
Below, the 1st-5th embodiment is each demonstrated using drawing as a specific aspect of this embodiment. In addition, the first and second comparative forms compared with the present embodiment will also be described. Note that, in each drawing described below, parts having the same configuration are denoted by the same reference numerals, and repeated description thereof is omitted.

<First Embodiment>
FIG. 1 is a schematic cross-sectional view illustrating a configuration example of an ultraviolet light emitting device 100 according to the first embodiment. The ultraviolet light emitting element according to the first embodiment includes a substrate 10, a semiconductor stacked unit 20 formed on the first main surface S <b> 1 side of the substrate 10, and a first electrode unit for supplying power to the semiconductor stacked unit 20. 31 and the second electrode portion 32, the concave portion 11 formed on a part of the second main surface S2 side opposite to the first main surface S1 of the substrate 10, and the optical member 40 disposed in the concave portion 11 And comprising. The semiconductor stacked unit 20 includes a first conductive type first semiconductor layer 21, a light emitting layer 22, and a second conductive type second semiconductor layer 23. Further, the first electrode portion 31 is electrically connected to the first semiconductor layer 21, and the second electrode portion 32 is electrically connected to the second semiconductor layer 23. Further, the width 11 a of the recess 11 is preferably wider than the width 22 a of the light emitting layer 22 when viewed in cross section as shown in FIG.

  The ultraviolet light emitting element 100 according to the first embodiment has a recess 11 in a part of the substrate 10 on the second main surface S2 side, and the optical member 40 is disposed in the recess 11. Thereby, an ultraviolet light emitting element having higher luminous efficiency is realized as compared with the ultraviolet light emitting element (first comparative example) shown in FIG. Moreover, since the thickness of the optical member 40 can be adjusted by the depth of the recessed part 11 compared with the ultraviolet light emitting element (2nd comparison form) shown in below-mentioned FIG.7 (b), the optical member 40 is used. It is thin and can be manufactured while suppressing variations in film thickness. Therefore, an ultraviolet light-emitting element having a small manufacturing variation and exhibiting desired optical characteristics is realized.

<Second Embodiment>
FIG. 2 is a schematic cross-sectional view showing a configuration example of the ultraviolet light emitting element 200 according to the second embodiment. As shown in FIG. 2, in the ultraviolet light emitting element 200 according to the second embodiment, the first electrode portion 31 and the second electrode portion 32 are connected to the bump electrode portion 51 of the mounting substrate 50, respectively. The portion located between the mounting substrate 50 and the first main surface S1 of the substrate 10 and the side surface S3 of the substrate 10 are covered with the sealing resin 60 (that is, sealed). The second main surface S2 of the substrate 10 and the optical member 40 are not covered with the sealing resin 60. Other configurations are the same as those of the ultraviolet light emitting device 100 according to the first embodiment.

<Third Embodiment>
FIG. 3 is a schematic cross-sectional view illustrating a configuration example of an ultraviolet light emitting element 300 according to the third embodiment. As shown in FIG. 3, in the ultraviolet light emitting element 300 according to the third embodiment, the side surface S <b> 3 of the substrate 10 is covered with the optical member 40 ′, and the outside thereof is covered with the sealing resin 60. Other configurations are the same as those of the ultraviolet light emitting element 300 according to the second embodiment.

  Since the side surface S3 of the substrate 10 is covered with the optical member 40 ', a large amount of ultraviolet light emitted from the side surface S3 of the substrate 10 is reflected at the interface between the side surface S3 and the optical member 40'. For this reason, it becomes possible to suppress that the part which seals side surface S3 through the optical member 40 'among sealing resin 60 especially deteriorates with an ultraviolet-ray, and the reliability of an ultraviolet light emitting element improves. Furthermore, since a part of the light reflected at the interface between the optical member 40 ′ and the side surface S 3 is emitted from the second main surface S 2 side of the substrate 10, there is an effect that the light output of the ultraviolet light emitting element is improved.

<Fourth Embodiment>
FIG. 4 is a schematic cross-sectional view illustrating a configuration example of an ultraviolet light emitting device 400 according to the fourth embodiment. As shown in FIG. 4, the ultraviolet light emitting element 400 according to the fourth embodiment is provided with a lens 70 on the second main surface S <b> 2 side of the substrate 10, and a part of the back surface of the lens 70 is in the recess 11. It is in contact with the arranged optical member 40. In addition, when viewed in cross section as shown in FIG. 4, the width 70 a of the lens 70 is preferably wider than the width 11 a of the recess 11. Other configurations are the same as those of the ultraviolet light emitting device 100 according to the first embodiment.

  By forming the lens 70 in a desired shape, it is possible to obtain an ultraviolet light emitting element having desired optical characteristics by condensing and diffusing the light generated in the light emitting layer 22. In the ultraviolet light emitting element 400 according to the fourth embodiment, the lens 70 can be easily mounted if the optical member 40 is a material having adhesiveness.

<Fifth Embodiment>
Fig.5 (a)-FIG.6 (c) are cross-sectional schematic diagrams which show the manufacturing method of the ultraviolet-ray light emitting element which concerns on 5th Embodiment.
As shown in FIG. 5A, first, in the recess forming step, the substrate 10, the semiconductor stacked portion 20 formed on the first main surface S1 side of the substrate 10, and the semiconductor stacked portion 20 are electrically connected. A substrate 10 including a first electrode part 31 and a second electrode part 32 is prepared. And the protective layer 80 is formed in a part of 2nd main surface S2 of this prepared board | substrate 10. FIG. Here, the substrate 10 is a semiconductor wafer. The protective layer 80 is, for example, a pattern made of a photoresist (that is, a resist pattern). Using this protective layer 80 as a mask, the second main surface S2 side of the substrate 10 is dry etched or wet etched. Thereby, as shown in FIG. 5B, the recess 11 is formed on the second main surface S <b> 2 side of the substrate 10.

Next, as shown in FIG. 5C, in the singulation process, the substrate 10 is divided into a plurality of ultraviolet light emitting elements.
Next, in the optical member injection step, the optical member 40 is injected into the formed recess 11 as shown in FIG. Next, in the smoothing step, the thickness of the injected optical member 4 is smoothed. For example, as shown in FIG. 6B, after the squeegee 90 is prepared in a region of the second main surface S2 of the substrate 10 where the recess 11 is not formed, the squeegee 90 is moved in the plane direction (that is, the second main surface S2). The thickness of the optical member 40 is smoothed by moving in a direction parallel to the surface S2. In this example, it is preferable that the optical member 40 has fluidity at the time of injection and can be cured by a predetermined treatment. Through the above steps, the ultraviolet light emitting device 100 is completed as shown in FIG.

According to the fifth embodiment, the thickness of the optical member is controlled to a desired thickness with high accuracy compared to the case where the optical member is stretched and formed on the plane of a flat substrate (second comparative embodiment described later). Is possible.
In the fifth embodiment, the volume of the injected optical member 40 (that is, the injection amount) may be larger than the volume of the recess 11. Thereby, the surplus part of the optical member 40 can be cast on the side surface of the substrate 10 and the side surface of the substrate 10 is also covered with the optical member 40 (for example, the ultraviolet light emitting element 300 according to the third embodiment). Can be formed. Further, by further increasing the volume of the optical member 40 injected into the concave portion 11, not only the side surface of the substrate 10 but also the first main surface side of the substrate 10 can be covered with the optical member 40.

<First comparative form>
FIG. 7A is a schematic cross-sectional view showing a configuration example of the ultraviolet light emitting element 600 according to the first comparative embodiment. As shown in FIG. 7A, the ultraviolet light emitting device 600 according to the first comparative embodiment includes a substrate 110, a semiconductor stacked portion 120 formed on the first main surface S101 side of the substrate 110, and a semiconductor stacked portion 120. The first electrode part 131 and the second electrode part 132 for supplying electric power to the power source are provided. The semiconductor stacked unit 120 includes a first conductive type first semiconductor layer 21, a light emitting layer 22, and a second conductive type second semiconductor layer 23. Further, the first electrode portion 31 is electrically connected to the first semiconductor layer 21, and the second electrode portion 32 is electrically connected to the second semiconductor layer 23. In the ultraviolet light emitting element 600, no recess is formed on the second main surface S102 side of the substrate 110.

<Second comparative form>
FIG. 7B is a schematic cross-sectional view showing a configuration example of the ultraviolet light emitting element 700 according to the second comparative embodiment. As shown in FIG. 7B, the ultraviolet light emitting element 700 according to the second comparative embodiment includes an optical member 140 disposed on the second main surface S102 side of the substrate 110. That is, the optical member 140 is stretched and formed on the flat second main surface S102 where no recess is formed. Other configurations are the same as those of the first comparative embodiment.

<Effect of embodiment>
The embodiment of the present invention has the following effects.
(1) The concave portion 11 is formed on the second main surface S2 side of the substrate 10, and the optical member 40 is disposed in the concave portion 11. Thereby, compared with the case where there is no optical member 40 (for example, 1st comparative form), reflection of the light in 2nd main surface S2 of the board | substrate 10 can be reduced, and the light extraction efficiency from the board | substrate 10 is possible. Will improve. For this reason, the ultraviolet light emitting element with high luminous efficiency can be provided.

(2) Moreover, it is easy to make the thickness of the optical member 40 substantially coincide with the depth of the recess 11, and the thickness of the optical member 40 can be adjusted by the depth of the recess 11. Thereby, since the dispersion | variation in the thickness of the optical member 40 can be reduced, the dispersion | variation in the performance of an ultraviolet light emitting element can be made small. For example, by reducing the variation in the thickness of the optical member 40, it is possible to reduce the variation in the absorption of ultraviolet rays and the variation in the light interference effect in the optical member 40. Thereby, the dispersion | variation in the optical output of an ultraviolet light emitting element can be made small.

(3) Since the side surface S3 of the substrate 10 is covered with the optical member 40 ', a large amount of ultraviolet light emitted from the side surface S3 is reflected at the interface between the side surface S3 and the optical member 40'. For this reason, since it can suppress that the part which covers side surface S3 especially through 40 'among sealing resin 60 via ultraviolet rays can suppress by ultraviolet rays, the reliability of an ultraviolet light emitting element is improved. Can do. Furthermore, since a part of the light reflected at the interface between the optical member 40 ′ and the side surface S 3 is emitted from the second main surface S 2 side of the substrate 10, the light output of the ultraviolet light emitting element can be improved.

Examples of the present invention and comparative examples will be described below.
[Example 1]
First, an AlN layer is 4 μm, an N-type Al _0.7 Ga _0.3 N layer is 2 μm, an AlGaN layer as a light-emitting layer, a P-type Al _{0. A 1} Ga _0.9 N layer and a P-type GaN layer 200 nm were stacked. Next, this laminated film is formed in a mesa structure in order to apply electric power from the outside, a first electrode part is formed on a part of the surface of the N-type Al _0.7 Ga _0.3 N layer, and P A second electrode portion was formed on a part of the surface of the type GaN layer. Through the above steps, a semiconductor wafer having an ultraviolet light emitting element pattern was prepared.

Next, a protective layer made of a resist was formed on a part of the second main surface of the AlN single crystal substrate of this semiconductor wafer, and dry etching was performed by chlorine gas plasma to form a recess having a depth of 1 μm.
Next, a silicone resin was injected into the formed recess as an optical material in an amount substantially equal to the volume of the recess, and the silicone resin was smoothed so as to fill the recess. Thereafter, the silicone resin was cured at 150 ° C. for 1 hour, and the silicone resin was cured to obtain an ultraviolet light emitting device.

Next, the obtained ultraviolet light emitting element is mounted on a mounting substrate (submount substrate) having a bump electrode portion having a pattern corresponding to the pattern of the first electrode portion and the second electrode portion, and the mounting substrate and the second of the substrate are mounted. The region sandwiched between the main surfaces was sealed with an epoxy resin to obtain an ultraviolet light emitting element mounted on a mounting substrate.
When the cross section of the obtained ultraviolet light emitting element was confirmed with a scanning electron microscope, the thickness of the silicone resin filled in the recesses was 1 μm over the entire region.

[Example 2]
An ultraviolet light-emitting device was obtained in the same manner as in Example 1 except that the amount of silicone resin injected was larger than the volume of the recess.
When the cross section of the obtained ultraviolet light emitting element was confirmed with a scanning electron microscope, the thickness of the silicone resin filled in the recesses was 1 μm over the entire region. It was also confirmed that the side surface of the substrate was also covered with silicone resin.

[Example 3]
After injecting the silicone resin, an ultraviolet light emitting device was obtained in the same manner as in Example 1 except that the silicone resin was cured after setting a lens on the second main surface of the AlN single crystal substrate from above. .
When the cross section of the obtained ultraviolet light emitting element was confirmed with a scanning electron microscope, the thickness of the silicone resin filled in the recesses was 1 μm over the entire region. That is, it was confirmed that the thickness of the silicone resin was made uniform by installing the lens in the same manner as in Example 1.

[Comparative Example 1]
Implemented except that no recess was formed by dry etching and that the silicone resin was placed on the second main surface of the AlN single crystal substrate and the silicone resin was smoothed so that the thickness of the silicone resin was the smallest. An ultraviolet light emitting device was obtained in the same manner as in Example 1.
When the cross section of the obtained ultraviolet light emitting element was confirmed with a scanning electron microscope, it was confirmed that the thickness of the silicone resin varied in the range of 15 μm to 50 μm.

[Comparative Example 2]
An ultraviolet light-emitting device was obtained in the same manner as in Example 1 except that the concave portions were not formed by dry etching and that the silicone resin was not injected and smoothed.
[Comparison between Examples and Comparative Examples]
A constant current of 100 mA was applied to each of the ultraviolet light-emitting elements (10 elements each) obtained in Examples 1 and 2 and Comparative Examples 1 and 2, and the central wavelength of each element was 230 to 320 nm by an integrating sphere. The light intensity of the wavelength was measured, and the average light intensity of Examples 1 to 3 and Comparative Example 1 when the average light intensity of the ultraviolet light-emitting device of Comparative Example 2 was set to 1 is shown in Table 1. In addition, a constant current of 300 mA was continuously applied to the ultraviolet light-emitting devices obtained in Example 2 and Comparative Examples 1 and 2 under the condition of a temperature of 85 ° C. and a humidity of 85% for 500 hours, Table 1 also shows the results of observing the cross section of the ultraviolet light emitting element and confirming the presence or absence of deterioration of the sealing resin.

  In Example 1, the light intensity was improved by 1.2 times compared to Comparative Example 2. Since the refractive index of the AlN single crystal substrate is high, all of the emitted light with an incident angle of 25 ° or more to the outside is reflected. Therefore, in the structure as in Comparative Example 2, it is difficult to extract the emitted light inside. . In contrast, Example 1 has a silicone resin (optical member) whose refractive index is smaller than that of an AlN single crystal substrate and is very thin as 1 μm and has a uniform thickness, so that reflected light is reduced and light extraction efficiency is improved. However, the light intensity is considered to be improved.

  In Example 2, the light intensity was improved 1.3 times compared to Comparative Example 2. In Example 2, the deterioration of the silicone resin and the sealing resin was not confirmed even after the energization test. In the ultraviolet light emitting element of Example 2, the side surface of the AlN single crystal substrate having a large refractive index is covered with the silicone resin having a small refractive index, so that the ultraviolet light is reflected at the interface between the side surface of the AlN single crystal substrate and the silicone resin. . Thereby, while preventing deterioration of sealing resin, it is thought that the reflected light was taken out from the 2nd main surface of the AlN single crystal substrate, and the light intensity improved.

  On the other hand, in Comparative Example 1, the light intensity was reduced to 0.6 times compared to Comparative Example 2. This is considered to be due to the fact that the transmittance of the ultraviolet light is lowered because the thickness of the silicone resin varies in a thick range of 15 μm to 50 μm. Furthermore, the light intensity of the ultraviolet light emitting element of Comparative Example 1 after the energization test was 0.5 times that of the ultraviolet light emitting element of Comparative Example 2 before the energization test.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as an ultraviolet light emitting element used for measuring equipment, sterilizing equipment, and the like and a method for producing the same.

DESCRIPTION OF SYMBOLS 10 Substrate 11 Recess 20 Semiconductor laminated part 21 First semiconductor layer 22 Light emitting layer 23 Second semiconductor layer 31 First electrode part 32 Second electrode part 40 Optical member 50 Mounting substrate 51 Bump electrode part 60 Sealing resin 70 Lens 80 Protective layer 100, 200, 300, 400 Ultraviolet light emitting element

Claims (15)

A substrate,
A semiconductor laminate including a light emitting layer formed on the first main surface side of the substrate;
A first electrode portion and a second electrode portion for supplying power to the semiconductor stacked portion;
A recess formed in a part of the second main surface side located on the opposite side of the first main surface of the substrate;
And an optical member disposed in the recess.   The ultraviolet light emitting element according to claim 1, wherein at least a part of a side surface located between the first main surface and the second main surface is covered with the optical member. A lens disposed on the second main surface side;
The ultraviolet light emitting element according to claim 1, wherein at least a part of the back surface of the lens is in contact with the optical member disposed in the concave portion.   The ultraviolet light emitting element according to any one of claims 1 to 3, wherein the substrate has a refractive index of 1.7 or more.   The ultraviolet light emitting element according to any one of claims 1 to 4, wherein a refractive index of the optical member is lower than a refractive index of the substrate.   The ultraviolet light-emitting element according to claim 1, wherein the ultraviolet transmittance of the optical member is 80% or more in a wavelength region of 260 nm or more and 300 nm or less.   The ultraviolet light-emitting element according to claim 1, wherein the width of the concave portion is wider than the width of the light-emitting layer when viewed in cross section.   The ultraviolet light emitting element according to any one of claims 1 to 7, wherein a depth of the concave portion is 10 nm or more and 5 µm or less.   The ultraviolet light emitting element according to any one of claims 1 to 8, wherein a thickness of a portion of the optical member disposed inside the recess is the same as a depth of the recess.   The ultraviolet light emitting element according to claim 1, wherein the emission wavelength is 230 nm or more and 320 nm or less. A semiconductor wafer comprising: a substrate; a semiconductor stacked portion including a light emitting layer formed on the first main surface side of the substrate; and a first electrode portion and a second electrode portion for supplying power to the semiconductor stacked portion A recess forming step of forming a recess by dry etching on a part of the second main surface located on the opposite side of the first main surface;
An optical member injection step of injecting an optical member into the recess,
And a smoothing step of smoothing the thickness of the injected optical member. In the optical member injection step,
The injection amount of the optical member to be injected is larger than the volume of the recess,
In the smoothing step,
The optical member is smoothed so that the thickness of the portion of the optical member disposed inside the recess is the same as the depth of the recess, and the optical member is provided on at least a part of the side surface of the substrate. The manufacturing method of the ultraviolet light emitting element of Claim 11 made to adhere.   The manufacturing method of the ultraviolet light emitting element according to claim 11 or 12, further comprising a lens arranging step of arranging a lens on the second main surface side after the smoothing step.   14. The singulation step of dividing the semiconductor wafer into pieces into a plurality of ultraviolet light emitting elements after the recess formation step and before the optical member injection step. The manufacturing method of the ultraviolet light emitting element of a term.   The mounting process which connects the said 1st electrode part and the said 2nd electrode part to a wiring board after the said recessed part formation process and before the said optical member injection | pouring process is further provided in any one of Claims 11-14. The manufacturing method of the ultraviolet-ray light emitting element of description.

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