Light-emitting element and method for manufacturing a light-emitting element

Abstract

The present invention provides a light-emitting element and a method for manufacturing a light-emitting element that can suppress a decrease in the bonding strength of the element components. [Solution] The semiconductor structure comprises a transparent substrate having light-transmitting properties, a light-transmitting layer formed on the transparent substrate, and a semiconductor structure layer disposed on the light-transmitting layer and including a first semiconductor layer having a first conductivity type, an active layer formed on the first semiconductor layer, and a second semiconductor layer formed on the active layer having a second conductivity type opposite to the first conductivity type. At least one region of the bonding surface of the semiconductor structure layer with the light-transmitting layer has a protrusion pattern consisting of multiple protrusions, and there are regions on the bonding surface where there is no protrusion pattern or the height of the protrusions differs from region to region within the bonding surface.

Description

Technical Field

[0001] The present invention relates to a light-emitting element and a method for manufacturing the light-emitting element.

Background Art

[0002] A semiconductor light-emitting element in which a support substrate and a semiconductor structure layer are joined is disclosed. For example, Patent Document 1 discloses a light-emitting element having a support substrate, a gallium nitride (GaN) film as a group III nitride film, and an epitaxial layer formed on the GaN film, wherein the support substrate and the GaN film are bonded via a bonding film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the light-emitting element disclosed in Patent Document 1, for example, when the bonding is completed with air remaining at the bonding interface during the bonding of the support substrate and the GaN film, the air that has not escaped outside the element may form voids at the bonding interface. [[ID=3十七]]

[0005] When voids occur at the bonding interface between the support substrate and the GaN film, the bonding strength between the support substrate and the GaN film decreases, and for example, there is a risk that the support substrate and the GaN film may peel off during the use of the light-emitting element.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide a light-emitting element and a method for manufacturing the light-emitting element capable of suppressing a decrease in the bonding strength of element constituent members.

Means for Solving the Problems

[0007] It should be noted that there seems to be an error in the original text where "[[ID=第十九]]" is used. It should probably be a correct ID number. Also, the translation is done as accurately as possible while following the given rules, but some terms might need further context-based optimization in a more practical patent translation scenario.The light-emitting element according to the present invention comprises a light-transmitting transparent substrate, a light-transmitting light-transmitting layer formed on the transparent substrate, and a semiconductor structure layer disposed on the light-transmitting layer and including a first semiconductor layer having a first conductivity type, an active layer formed on the first semiconductor layer, and a second semiconductor layer formed on the active layer having a second conductivity type opposite to the first conductivity type, wherein a protrusion pattern consisting of multiple protrusions is formed in at least one region of the bonding surface of the semiconductor structure layer with the light-transmitting layer, and there are regions on the bonding surface where there is no protrusion pattern or the height of the protrusions differs from region to region within the bonding surface.

[0008] Furthermore, the present invention relates to a method for manufacturing a light-emitting element, comprising: a semiconductor structure layer formation step of forming a semiconductor structure layer by forming a first semiconductor layer having a first conductivity type on one main surface of a flat support substrate, forming an active layer on the first semiconductor layer, and forming a second semiconductor layer having a second conductivity type on the active layer; a protrusion pattern formation step of forming a protrusion pattern consisting of a plurality of protrusions in at least one region on one main surface of the semiconductor structure layer; a light-transmitting layer formation step of forming a light-transmitting layer having light-transmitting properties that has been flattened by embedding the protrusion pattern; a bonding step of bonding the light-transmitting layer and a light-transmitting transparent substrate by direct bonding; and a support substrate removal step of removing the support substrate, characterized in that there is a region without a protrusion pattern on one main surface of the semiconductor structure layer or the height of the protrusions differs from region to region within one main surface of the semiconductor structure layer. [Brief explanation of the drawing]

[0009] [Figure 1] This is a top view of the light-emitting element according to Example 1. [Figure 2] This is a cross-sectional view of the light-emitting element according to Example 1. [Figure 3] This is a cross-sectional view of the light-emitting element according to Example 1. [Figure 4] This is a cross-sectional view showing an example of the manufacturing process for a light-emitting element according to Example 1. [Figure 5] This is a cross-sectional view showing an example of the manufacturing process for a light-emitting element according to Example 1. [Figure 6]It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 7] It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 8] It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 9] It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 10] It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 11] It is a cross-sectional view showing an example of a manufacturing process of a light-emitting element according to Example 1. [Figure 12] It is a cross-sectional view of a light-emitting element according to Example 2. [Figure 13] It is a cross-sectional view of a light-emitting element according to Example 3.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are given to the same components, and the description of overlapping components is omitted.

Example

[0011] [Outline of Light-Emitting Element 100] With reference to FIGS. 1 to 3, the configuration of the light-emitting element 100 according to Example 1 will be described. FIG. 1 is a top view of the light-emitting element 100 according to Example 1. FIGS. 2 and 3 are cross-sectional views along the 2-2 line and the 3-3 line of the light-emitting element 100 shown in FIG. 1, respectively. In FIGS. 2 and 3, the vertical direction in the figure is the height direction of the light-emitting element 100, and the horizontal direction in the figure is the width direction of the light-emitting element 100.

[0012] The light-emitting element 100 is a light-emitting diode (Light Emission Diode: LED) including a transparent substrate 11, a light-transmitting layer 13 formed on the transparent substrate 11, and a semiconductor structure layer EM including an n-type semiconductor layer 15, an active layer 17, and a p-type semiconductor layer 19 formed on the light-transmitting layer 13.

[0013] In addition, in FIG. 1, the protective film 21 formed on the upper surface of the light-emitting element 100 is omitted. Also, in FIG. 1, in order to clearly show the structure and positional relationship of each member, the first region A1 and the second region A2 on the lower surface of the n-type semiconductor layer 15, which will be described later, are shown by solid lines, and the n electrode NE and the p electrode PE are shown by dashed-dotted lines.

[0014] [Transparent substrate 11] First, the transparent substrate 11 will be described. The transparent substrate 11 is a flat substrate having a rectangular upper surface shape and having insulation and translucency. In the light-emitting element 100 of the present embodiment, the transparent substrate 11 is made of sapphire (Al2O3). Also, in the light-emitting element 100 of the present embodiment, the thickness of the transparent substrate 11 is set to 100 μm.

[0015] [Light-transmitting layer 13] Next, the light-transmitting layer 13 will be described. The light-transmitting layer 13 is a layer having translucency formed on the upper surface 11S of the transparent substrate 11. The lower surface 13S of the light-transmitting layer 13 is joined to the upper surface 11S of the transparent substrate 11 by direct bonding.

[0016] The light-transmitting layer 13 is made of a material having the same hardness as the transparent substrate 11 in order to prevent cracks or the like from occurring in the light-transmitting layer 13 during bonding by direct bonding. In the light-emitting element 100 of the present embodiment, the light-transmitting layer 13 has a hardness of about 2000 kg / mm 2 with respect to the sapphire transparent substrate 11 having a hardness of about 2200 kg / mm 2 and is made of amorphous silicon nitride (Si3N4). In addition to Si3N4, for example, amorphous silicon oxide (SiO2) or titanium oxide (TiO2) may be used for the light-transmitting layer 13.

[0017] [Semiconductor structure layer EM] Next, the configuration of the semiconductor structure layer EM and the electrodes and protective films formed on the semiconductor structure layer EM will be described. The semiconductor structure layer EM is a semiconductor laminate composed of an n-type semiconductor layer 15, an active layer 17, and a p-type semiconductor layer 19 as described above.

[0018] The n-type semiconductor layer 15 is an n-type semiconductor layer composed of a first n-type semiconductor layer 15A bonded to the light-transmitting layer 13 and a second n-type semiconductor layer 15B with a rectangular top surface partially formed on the first n-type semiconductor layer 15A. In the light-emitting element 100 of this embodiment, the n-type semiconductor layer 15 is made of aluminum gallium arsenide (AlGaAs).

[0019] The first n-type semiconductor layer 15A has a composition ratio of Al x1 Ga (1-x1) When Al is used, the Al composition is 0.18, and it functions as a current diffusion layer that uniformly diffuses the current flowing within the layer in the light-emitting element 100. In addition, the first n-type semiconductor layer 15A made of AlGaAs has a hardness of approximately 700 kg / mm². 2 Therefore, it has lower hardness compared to the translucent layer 13 described above.

[0020] On the lower surface of the first n-type semiconductor layer 15A, that is, the bonding surface of the first n-type semiconductor layer 15A with the light-transmitting layer 13, a protrusion pattern consisting of multiple triangular pyramidal protrusions is formed. In other words, the protrusion pattern formed on the lower surface of the first n-type semiconductor layer 15A is embedded by the light-transmitting layer 13.

[0021] The protrusion pattern formed on the lower surface of the first n-type semiconductor layer 15A consists of a first protrusion pattern C1 and a second protrusion pattern C2, the height of which is lower than that of the first protrusion pattern C1.

[0022] First, the first protrusion pattern C1 will be described. As shown in Figure 1, the first protrusion pattern C1 is formed in the first region A1, which has a grid-like top surface shape. The first region A1 consists of elongated regions that form the grid, in other words, strip-shaped regions that extend vertically and horizontally in a top view, with both ends of each of these regions reaching the edges of the bottom surface of the first n-type semiconductor layer 15A.

[0023] In other words, each end of the strip-shaped region in the longitudinal direction reaches an opposing side. To put it another way, as shown in Figure 3, the first projection pattern C1 is formed such that its formation region extends from one end to the other on the lower surface of the first n-type semiconductor layer 15A.

[0024] As shown in Figures 2 and 3, each of the protrusions constituting the first protrusion pattern C1 is arranged periodically at the same height. In the light-emitting element 100 of this embodiment, the height H1 of each protrusion constituting the first protrusion pattern C1 is 1 μm, and the spacing between each protrusion is 0.5 μm or less. In the light-emitting element 100 of this embodiment, the thickness of the first n-type semiconductor layer 15A including the first protrusion pattern C1 is 5 μm.

[0025] Next, the second protrusion pattern C2 will be described. As shown in Figure 1, the second protrusion pattern C2 is formed in the second region A2, which has a rectangular upper surface shape, and is the area of ​​the lower surface of the first n-type semiconductor layer 15A excluding the first region A1. Therefore, each of the second region A2 is arranged in a square grid pattern in a plan view taken from a direction perpendicular to the lower surface of the first n-type semiconductor layer 15A.

[0026] As shown in Figure 2, each of the protrusions constituting the second protrusion pattern C2 is arranged periodically at the same height as the others. In the light-emitting element 100 of this embodiment, the height H2 of each protrusion constituting the second protrusion pattern C2 is set to 0.3 μm, and the spacing between each protrusion is set to 0.5 μm or less.

[0027] In this embodiment, when the wavelength λ of the infrared light emitted from the active layer 17 (described later) is 940 nm, it is preferable that the height H1 of the protrusions in the first protrusion pattern C1 and the height H2 of the protrusions in the second protrusion pattern C2 are at least λ / 4 = 235 nm.

[0028] The second n-type semiconductor layer 15B has a composition ratio of Al y1 Ga (1-y1)When As is used, the Al composition is 0.32, and in the light-emitting element 100, it functions as a cladding layer that sandwiches the active layer 17 together with the p-type semiconductor layer 19, which will be described later. In the light-emitting element 100 of this embodiment, the thickness of the second n-type semiconductor layer 15B is 0.5 μm.

[0029] The active layer 17 is formed across the upper surface of the second n-type semiconductor layer 15B and is a semiconductor layer that emits light through the recombination of electrons and holes. When the light-emitting element 100 is driven, the active layer 17 emits infrared light, for example, with a peak wavelength of 940 nm.

[0030] In the light-emitting element 100 of this embodiment, the active layer 17 has a multi-quantum well (MQW) structure in which five layers each of well layers made of indium gallium arsenide (InGaAs) and barrier layers made of gallium arsenide phosphide (GaAsP) are alternately stacked. In the light-emitting element 100 of this embodiment, the total thickness of the active layer 17 is 0.13 μm.

[0031] The p-type semiconductor layer 19 is a p-type semiconductor layer made of AlGaAs formed across the upper surface of the active layer 17. The p-type semiconductor layer 19 is constructed by stacking a cladding layer, a current diffusion layer, and a contact layer in that order (none of which are shown). In the light-emitting element 100 of this embodiment, the thickness of the p-type semiconductor layer 19 is 1.13 μm.

[0032] Next, the n-electrode NE and the p-electrode PE will be described. The n-electrode NE is formed in a region on the upper surface of the first n-type semiconductor layer 15A where the second n-type semiconductor layer 15B is not formed, and is electrically connected to the first n-type semiconductor layer 15A. The n-electrode NE is formed by stacking titanium (Ti) and gold (Au) in this order on the upper surface of the first n-type semiconductor layer 15A, for example.

[0033] The p-electrode PE is formed on the upper surface of the p-type semiconductor layer 19 and is electrically connected to the p-type semiconductor layer 19. For example, the p-electrode PE is formed by stacking nickel (Ni) and Au in that order on the upper surface of the p-type semiconductor layer 19.

[0034] Furthermore, to achieve better ohmic contact between the p-type semiconductor layer 19 and the p-electrode PE, a transparent indium tin oxide (ITO) electrode may be provided, for example.

[0035] Next, the protective film 21 will be described. The protective film 21 is an insulating thin film that is continuously formed from the upper surface of the first n-type semiconductor layer 15A, through the sides of the second n-type semiconductor layer 15B, the active layer 17, and the p-type semiconductor layer 19, while exposing the n-electrode NE and the p-electrode PE, to the upper surface of the p-type semiconductor layer 19.

[0036] The protective film 21 insulates the n electrode NE and the p electrode PE from each other and protects the semiconductor structural layer EM, particularly the sides of the active layer 17. The protective film 21 is made of an insulating material such as SiO2 or Si3N4.

[0037] In the light-emitting element 100, a voltage is applied to the p electrode PE and the n electrode NE, causing a current to flow between the p electrode PE and the n electrode NE. This current flows through the active layer 17 of the semiconductor structural layer EM, causing light in the infrared region to be emitted.

[0038] When an electric current flows through the active layer 17, the infrared light emitted from the active layer 17 can either travel directly to the transparent substrate 11, for example, or be reflected by the p electrode PE before being incident on the transparent substrate 11. Therefore, in the light-emitting element 100, the lower surface of the transparent substrate 11 becomes the light-emitting surface of the light-emitting element 100.

[0039] [Suppression of reduction in bonding strength of element components] Here, using Figures 1 and 2, we will explain how to suppress the reduction in bonding strength between the transparent substrate 11 and the light-transmitting layer 13 covering the protrusion pattern on the lower surface of the first n-type semiconductor layer 15A in the light-emitting element 100.

[0040] In the manufacturing of the light-emitting element 100 of this embodiment, when joining the transparent substrate 11 and the light-transmitting layer 13, a direct bonding method is employed in which the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13 are subjected to surface activation treatment, and then the upper surface 11S and the lower surface 13S are bonded together and subjected to pressure and heat treatment.

[0041] For example, when direct bonding is performed such that uniform pressure is applied to the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13, the outer periphery of the bonding surface may be bonded before the central part. When this occurs, there is no escape route for the air trapped during the bonding of the upper surface 11S and the lower surface 13S, or for the water vapor released by heating, making it difficult for the air and water vapor to escape from the device.

[0042] In this way, if air or water vapor remains at the bonding interface between the upper surface 11S and the lower surface 13S, voids may form at the bonding interface when the bonding between the transparent substrate 11 and the light-transmitting layer 13 is completed. For example, if voids form at the bonding interface between the upper surface 11S and the lower surface 13S, the bonding strength between the transparent substrate 11 and the light-transmitting layer 13 will decrease, and consequently, there is a risk of delamination between the transparent substrate 11 and the light-transmitting layer 13. In particular, since the location and size of voids that occur in such cases cannot be controlled, the possibility of delamination may become very high depending on the location and size.

[0043] In the light-emitting element 100 of this embodiment, as described above, a protrusion pattern is formed on the lower surface of the first n-type semiconductor layer 15A, consisting of a first protrusion pattern C1 formed in a grid-like first region A1 extending to the edge of the lower surface, and a second protrusion pattern C2 formed in a rectangular second region A2, the height of which the protrusions is lower than that of the first protrusion pattern C1.

[0044] Here, the grid-like portion on the first region A1 on the lower surface of the first n-type semiconductor layer 15A of the light-transmitting layer 13 is referred to as the grid-like portion. Also, the rectangular portion on the second region A2 on the lower surface of the first n-type semiconductor layer 15A of the light-transmitting layer 13 is referred to as the rectangular portion.

[0045] In the light-emitting element 100 of this embodiment, the first n-type semiconductor layer 15A has lower hardness than the light-transmitting layer 13, as described above. Also, the lattice-like portion of the light-transmitting layer 13 has a larger, or in other words, taller, protrusion pattern compared to the rectangular portion of the light-transmitting layer 13, and when viewed in cross-section, the proportion of protrusions is larger.

[0046] Therefore, after the lower surface 13S of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11 come into contact during bonding, the lattice-shaped portion of the first n-type semiconductor layer 15A has more room to deform, or in other words, to be crushed, than the rectangular portion of the light-transmitting layer 13. Consequently, pressure is applied first to the rectangular portion of the light-transmitting layer 13, which has less room to deform, and then to the lattice-shaped portion of the light-transmitting layer 13.

[0047] Therefore, when the light-emitting element 100 is manufactured and the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13 are bonded together and pressed, the pressure applied to the upper surface 11S is reduced in the lattice-shaped portion of the light-transmitting layer 13 because it contains more protrusions than the rectangular portion of the light-transmitting layer 13. As a result, in the light-emitting element 100 of this embodiment, the bonding is completed later in the lattice-shaped portion of the light-transmitting layer 13 than in the rectangular portion of the light-transmitting layer 13 because the pressure applied to the upper surface 11S is reduced.

[0048] Therefore, according to the light-emitting element 100 of this embodiment, even if air or water vapor remains at the bonding interface between the rectangular portion of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11 when the bonding is completed, the bonding interface between the grid-like portion of the light-transmitting layer 13 and the upper surface 11S becomes a pathway for the air or water vapor to escape to the outside of the element. As a result, the air or water vapor remaining at the bonding interface between the rectangular portion and the upper surface 11S can easily escape to the outside of the element by traveling along the bonding interface between the grid-like portion of the light-transmitting layer 13 and the upper surface 11S before the bonding is completed.

[0049] In other words, in the light-emitting element 100 of this embodiment, when directly bonding the transparent substrate 11 and the light-transmitting layer 13, the rectangular portion and the grid-like portion of the light-transmitting layer 13 are sequentially bonded to the upper surface 11S of the transparent substrate 11, thereby suppressing the retention of air or water vapor at the bonding interface between the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13.

[0050] Therefore, in the light-emitting element 100 of this embodiment, air and water vapor can easily escape to the outside of the element when the transparent substrate 11 and the light-transmitting layer 13 are joined, making it less likely for voids to form at the bonding interface when the bonding between the transparent substrate 11 and the light-transmitting layer 13 is completed.

[0051] Therefore, the light-emitting element 100 of this embodiment can suppress the decrease in bonding strength between the transparent substrate 13 and the transparent substrate 11 caused by voids that form at the bonding interface between the transparent substrate 11 and the light-transmitting layer 13.

[0052] Furthermore, in the light-emitting element 100 of this embodiment, the protrusion pattern formed on the lower surface of the first n-type semiconductor layer 15A is composed of multiple protrusions. This makes it less likely for total internal reflection of light traveling from the semiconductor structural layer EM to the light-transmitting layer 13 to occur at the bonding interface between the semiconductor structural layer EM and the light-transmitting layer 13. Therefore, the light output can be improved compared to, for example, the case where the protrusion pattern consists of a single protrusion.

[0053] Furthermore, in the light-emitting element 100 of this embodiment, the transparent substrate 11 and the light-transmitting layer 13 are joined by direct bonding without an adhesive layer during bonding. Therefore, for example, if an adhesive is used during bonding, it is possible to prevent a decrease in light extraction efficiency due to total internal reflection of emitted light at the bonding interface between the transparent substrate 11 and the adhesive.

[0054] In this embodiment, the light-emitting element 100 is assumed to have a first protrusion pattern C1 and a second protrusion pattern C2 consisting of protrusions smaller in height than the protrusions of the first protrusion pattern C1 formed on the lower surface of the first n-type semiconductor layer 15A. However, the second protrusion pattern C2 is not necessarily required to be formed. For example, the protrusion pattern may be formed only in the first region A1, and the second region A2 may be a flat surface without a protrusion pattern.

[0055] Even if the light-emitting element 100 has such a configuration, by utilizing the fact that the rectangular portion and the grid-like portion of the light-transmitting layer 13 are sequentially bonded to the upper surface 11S of the transparent substrate 11, as described above, voids that occur when bonding the transparent substrate 11 and the light-transmitting layer 13 can be reduced. Furthermore, considering the need to minimize total internal reflection of emitted light at the bonding interface between the transparent substrate 11 and the light-transmitting layer 13, it is preferable that the area of ​​the second region A2 is smaller than that of the first region A1.

[0056] In the light-emitting element 100 of this embodiment, the first region A1 is assumed to extend to the edge of the lower surface of the first n-type semiconductor layer 15A. However, it is not necessary for it to extend completely to the edge; for example, it may terminate inside the edge of the lower surface.

[0057] Even in this case, compared to the case where no protrusion pattern is provided on the lower surface of the first n-type semiconductor layer 15A, air and water vapor can more easily escape to the outside of the device by traveling along the bonding interface between the lattice-like portion of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11, thereby reducing the amount of voids that occur at the bonding interface after the bonding of the transparent substrate 11 and the light-transmitting layer 13 is completed.

[0058] In the light-emitting element 100 of this embodiment, the upper surface shape of the first region A1 is described as being grid-like, but it is not limited to this, and may be striped, for example. Also, if the first region A1 is striped, for example, its edges only need to reach at least one of two opposing sides of the lower surface of the first n-type semiconductor layer 15A.

[0059] In the light-emitting element 100 of this embodiment, the shape of each protrusion in the projection pattern provided on the lower surface of the first n-type semiconductor layer 15A is not limited to a triangular pyramidal shape, but may be, for example, a truncated triangular pyramidal shape or a hemispherical shape.

[0060] In addition, in the light-emitting element 100 of this embodiment, a protrusion pattern similar to the protrusion pattern provided on the lower surface of the first n-type semiconductor layer 15A may be provided on the upper surface 11S of the transparent substrate 11. In this case, it is preferable to provide the protrusion patterns on the lower surface of the first n-type semiconductor layer 15A and the upper surface 11S of the transparent substrate 11 so that the first protrusion pattern C1 and the second protrusion pattern C2 face each other, in order to allow air and water vapor to escape as much as possible when the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13 are joined.

[0061] In this embodiment, the first n-type semiconductor layer 15A is made of a material with lower hardness than the light-transmitting layer 13. However, the embodiment is not limited to this, and the light-transmitting layer 13 may be made of a material with lower hardness than the first n-type semiconductor layer 15A. In this case, the same effects as in this embodiment may be obtained by forming the protrusion pattern on the lower surface of the first n-type semiconductor layer 15A in the opposite manner to that of Embodiment 1.

[0062] Specifically, the first region A1 on the lower surface of the first n-type semiconductor layer 15A, where the first protrusion pattern C1 is formed, is rectangular in shape when viewed from above, and the second region A2 on the lower surface of the first n-type semiconductor layer 15A, where the second protrusion pattern C2 is formed, is grid-like in shape when viewed from above. In other words, each of the first regions A1 on the lower surface of the first n-type semiconductor layer 15A is formed in a square grid shape.

[0063] In such cases, when the transparent substrate 11 and the light-transmitting layer 13 are joined, pressure is first applied to the rectangular portion of the light-transmitting layer 13 corresponding to the first region A1 of the first n-type semiconductor layer 15A, where there is little room for deformation, and then pressure is applied to the lattice-like portion of the light-transmitting layer 13 corresponding to the second region A2. As a result, similar to Example 1, even if air or water vapor remains at the bonding interface between the rectangular portion of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11, the bonding interface between the lattice-like portion of the light-transmitting layer 13 and the upper surface 11S acts as a pathway for the air or water vapor to escape to the outside of the device.

[0064] Therefore, even when the light-transmitting layer 13 is made of a material with lower hardness than the first n-type semiconductor layer 15A, by forming the protrusion pattern on the lower surface of the first n-type semiconductor layer 15A in the opposite manner to that of Example 1, it is possible to suppress the retention of air and water vapor at the bonding interface between the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13.

[0065] [Manufacturing method for light-emitting element 100] The manufacturing method of the light-emitting element 100 in this embodiment will be described below with reference to Figures 1, 2, and 4 to 11. Each of Figures 4 to 11 is a cross-sectional view showing an example of the manufacturing process of the light-emitting element 100.

[0066] First, as shown in Figure 4, a semiconductor structural layer EM is formed on the upper surface of a support substrate 25, which is a wafer made of gallium arsenide (GaAs) (semiconductor structural layer formation process). Specifically, a p-type semiconductor layer 19, an active layer 17, a second n-type semiconductor layer 15B, and a first n-type semiconductor layer 15A are epitaxially grown on the support substrate 25 in this order at a growth temperature of, for example, 1000 to 1200°C using a known crystal growth method such as metal-organic chemical vapor deposition (MOCVD).

[0067] Next, as shown in Figure 5, a protrusion pattern consisting of a first protrusion pattern C1 and a second protrusion pattern C2 is formed on the upper surface of the semiconductor structure layer EM, that is, on the upper surface of the first n-type semiconductor layer 15A in the figure (protrusion pattern formation step).

[0068] Specifically, first, the entire upper surface of the first n-type semiconductor layer 15A is etched using an acid-based wet etching method, and the surface is roughened so that the height of the protrusions formed on the upper surface of the first n-type semiconductor layer 15A is at least equal to or greater than the height of the first protrusion pattern C1.

[0069] Next, a photoresist is applied to the upper surface of the first n-type semiconductor layer 15A, which has been roughened using photolithography. Exposure is then performed using a mask corresponding to the grid-like first region A1 shown in Figure 1, followed by development. This process leaves the photoresist only in the first region A1.

[0070] Next, the upper surface of the first n-type semiconductor layer 15A is etched by dry etching. At this time, the protrusions in the areas without photoresist, i.e., the protrusions in the second region A2 shown in Figure 1, are etched while retaining the shape from the wet etching process. On the other hand, in the first region A1 where photoresist is present, the photoresist itself is gradually etched away, and once the photoresist is gone, the etching process continues while retaining the shape from the wet etching process.

[0071] Through the above process, a protrusion pattern can be formed on the upper surface of the first n-type semiconductor layer 15A, consisting of a first protrusion pattern C1 formed in the first region A1 and a second protrusion pattern C2 formed in the second region A2, which is shorter in height than the protrusions of the first protrusion pattern C1.

[0072] Furthermore, in this process, when the entire wafer, which is the support substrate 25, is viewed from above, each of the strip-shaped regions extending in the vertical and horizontal directions that constitute the first region A1 on which the first protrusion pattern C1 is formed is formed in such a manner that it is continuous with adjacent light-emitting elements 100 before individualization.

[0073] Next, as shown in Figure 6, a translucent layer 13 is formed to embed the protrusion pattern (translucent layer formation step). In this step, for example, amorphous Si3N4 is used to form a thick film layer to embed the protrusion pattern using plasma CVD or sputtering, and then the surface of the formed thick film layer is planarized using polishing techniques such as chemical mechanical polishing (CMP).

[0074] Next, as shown in Figure 7, the semiconductor structure layer EM on which the light-transmitting layer 13 is formed is inverted, and the light-transmitting layer 13 and the transparent substrate 11, which is a wafer made of sapphire, are directly bonded (bonding process). Specifically, both the lower surface 13S of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11 are subjected to surface activation treatment with oxygen plasma, and after this treatment, both surfaces are bonded together and subjected to pressurization and heat treatment.

[0075] In this process, as described above, even if, for example, air or water vapor remains at the bonding interface between the rectangular portion of the light-transmitting layer 13 and the upper surface 11S of the transparent substrate 11 when the bonding is completed, the air or water vapor can escape to the outside of the element by traveling along the bonding interface between the grid-like portion of the light-transmitting layer 13 and the upper surface 11S before the bonding between the grid-like portion of the light-transmitting layer 13 and the upper surface 11S is completed.

[0076] Therefore, in this process, air and water vapor can easily escape to the outside of the element when the transparent substrate 11 and the light-transmitting layer 13 are bonded, thereby suppressing the formation of voids at the bonding interface when the bonding between the transparent substrate 11 and the light-transmitting layer 13 is completed.

[0077] Next, as shown in Figure 8, the support substrate 25 used to form the semiconductor structural layer EM is removed (support substrate removal step). In this step, the support substrate 25 is removed by wet etching with a mixture of ammonia water and hydrogen peroxide water, for example.

[0078] Next, as shown in Figure 9, a portion of the second n-type semiconductor layer 15B, the active layer 17, and the p-type semiconductor layer 19 is removed by wet etching or dry etching. This partially exposes the upper surface of the first n-type semiconductor layer 15A, and a semiconductor structure layer EM with the shape shown in Figure 2 can be obtained.

[0079] Next, as shown in Figure 10, a p-electrode PE is formed on the upper surface of the p-type semiconductor layer 19 (p-electrode formation step). The p-electrode PE can be formed by depositing Ni and Au in that order on the upper surface of the p-type semiconductor layer 19 using, for example, a vapor deposition method, and then performing an annealing treatment to alloy them.

[0080] Next, as shown in Figure 11, an n electrode NE is formed on the upper surface of the first n-type semiconductor layer 15A (n electrode formation step). The p electrode PE can be formed by depositing Ti and Au in this order on the upper surface of the first n-type semiconductor layer 15A using, for example, a vapor deposition method, and then performing an annealing treatment to alloy them.

[0081] Next, a protective film 21 is formed to cover the upper surface of the semiconductor structural layer EM (protective film formation step). Specifically, a mask is applied to the p electrode PE and the n electrode NE, and an insulating film made of SiO2 is formed on the upper surface of the semiconductor structural layer EM using, for example, a sputtering method, and then the mask is removed. This allows the protective film 21 to be formed.

[0082] Finally, the back side of the transparent substrate 11 (the side opposite to the side where the semiconductor structure layer EM is formed) is mechanically polished so that the transparent substrate 11 has a predetermined thickness, and then each of the light-emitting elements 100 is separated into individual pieces by dicing (partitioning step). Through the above steps, the light-emitting elements 100 can be manufactured.

[0083] When mounting the light-emitting element 100 manufactured by the above process onto a submount substrate, for example, the light-emitting element 100 is mounted by flip-chip mounting. Specifically, the light-emitting element 100 can be mounted by joining the n electrode NE and p electrode PE of the light-emitting element 100 to the n-side wiring pad and p-side wiring pad provided on the submount substrate, respectively, via a bonding member such as gold-tin (AuSn) solder. [Examples]

[0084] The light-emitting element 200 according to Example 2 will be described with reference to Figure 12. Figure 12 is a cross-sectional view of the light-emitting element 200 along the line 2-2 in Figure 1, similar to Example 1. The light-emitting element 200 is similar to the light-emitting element 100 in Example 1, except that the structure of the transparent substrate 11 is different.

[0085] In the light-emitting element 200 of this embodiment, the transparent substrate 11 has grooves 11G formed in a region facing the first region A1 on the upper surface 11S of the transparent substrate 11 and extending to the edge of the upper surface 11S. That is, the grooves 11G have a grid shape in a plan view taken from a direction perpendicular to the upper surface 11S of the transparent substrate 11.

[0086] In the light-emitting element 200 of this embodiment, the width of each groove 11G is 100 μm and the depth is 0.5 μm or more. In addition, in the light-emitting element 200 of this embodiment, the distance between adjacent grooves 11G is 400 μm.

[0087] In the light-emitting element 200 of this embodiment, similar to Embodiment 1, when directly bonding the transparent substrate 11 and the light-transmitting layer 13, the rectangular portion and the grid-like portion of the light-transmitting layer 13 are sequentially bonded to the upper surface 11S of the transparent substrate 11. This makes it possible to suppress the retention of air and water vapor at the bonding interface between the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13.

[0088] In particular, in the light-emitting element 200 of this embodiment, a groove 11G is formed on the upper surface 11S of the transparent substrate 11, extending to the edge of the upper surface 11S. This makes it easier to release air and water vapor remaining at the bonding interface when the upper surface 11S of the transparent substrate 11 and the lower surface 13S of the light-transmitting layer 13 to the outside of the element. Therefore, the number of voids that occur at the bonding interface between the light-transmitting layer 13 and the transparent substrate 11 after direct bonding can be reduced.

[0089] Therefore, with the light-emitting element 200 of this embodiment, similar to embodiment 1, it is possible to suppress the decrease in bonding strength between the transparent substrate 13 and the transparent substrate 11 caused by voids that occur at the bonding interface between the transparent substrate 11 and the light-transmitting layer 13. [Examples]

[0090] Next, the light-emitting element 300 according to Example 3 will be described using Figure 13. Figure 13 is a cross-sectional view of the light-emitting element 300 along the line 2-2 in Figure 1, similar to Example 1. The light-emitting element 300 differs from the light-emitting element 100 of Example 1 in the manner in which the protrusion pattern is formed in the first n-type semiconductor layer 15A, but is otherwise similar to the light-emitting element 100. In Figure 13, the center line CA passing through the center of the lower surface of the first n-type semiconductor layer 15A is shown as a dashed line.

[0091] In the light-emitting element 300 of this embodiment, the projection pattern formed on the lower surface of the first n-type semiconductor layer 15A consists of three types of projection patterns of different heights, with the height of the projections increasing from the center line CA passing through the center of the lower surface of the first n-type semiconductor layer 15A toward the outer edge of the lower surface.

[0092] Specifically, as shown in Figure 13, the projection pattern consists of a first projection pattern C1 (dotted line in the figure) formed on the center line CA, a second projection pattern C2 (double dotted line in the figure) formed around the first projection pattern C1 and taller than the first projection pattern C1, and a third projection pattern C3 (dashed line in the figure) formed around the second projection pattern C2 and taller than the second projection pattern C2.

[0093] In the light-emitting element 300 of this embodiment, the third protrusion pattern C3, which has the highest protrusion height among the first protrusion patterns C1 to the third protrusion patterns C3, reaches the edge of the lower surface of the first n-type semiconductor layer 15A.

[0094] In the light-emitting element 300 of this embodiment, pressure is applied to the upper surface 11S of the transparent substrate 11 in the following order: the first portion of the light-transmitting layer 13 including the first protrusion pattern C1, the second portion of the light-transmitting layer 13 including the second protrusion pattern C2, and the third portion of the light-transmitting layer 13 including the third protrusion pattern C3.

[0095] In other words, in the light-emitting element 300 of this embodiment, pressure is applied sequentially from the center outward of the first n-type semiconductor layer 15A, gradually driving out air and water vapor from the center outward of the light-emitting element 300. Therefore, the number of voids that occur at the bonding interface between the light-transmitting layer 13 and the transparent substrate 11 after direct bonding can be reduced.

[0096] Therefore, with the light-emitting element 300 of this embodiment, similar to embodiment 1, it is possible to suppress the decrease in bonding strength between the transparent substrate 13 and the transparent substrate 11 caused by voids that occur at the bonding interface between the transparent substrate 11 and the light-transmitting layer 13.

[0097] In the manufacturing of the light-emitting element 300 of this embodiment, when forming the protrusion pattern shown in Figure 13 on the first n-type semiconductor layer 15A, heat treatment (130°C, 2 minutes) is performed in the post-bake process after development of the photoresist, causing a slope to occur in the photoresist from the edge of the semiconductor structure layer EM. By performing etching in this state, the protrusion pattern shown in Figure 13 can be obtained.

[0098] In this embodiment, the light-emitting element 300 is shown as an example to have a protrusion pattern consisting of three different heights of protrusions formed on the lower surface of the first n-type semiconductor layer 15A. However, the embodiment is not limited to this, and the protrusion pattern may consist of only two types, as in Embodiment 1, or it may consist of four or more types. [Explanation of symbols]

[0099] 100, 200, 300 light-emitting elements 11 Transparent substrate 13 Translucent layer 15 n-type semiconductor layer 17 Active layer 19 p-type semiconductor layer 21 Protective film 25 Support substrate

Claims

1. A transparent substrate that is light-transmitting, A light-transmitting layer formed on the transparent substrate, The semiconductor structure layer comprises a first semiconductor layer having a first conductivity type disposed on the light-transmitting layer, an active layer formed on the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type formed on the active layer, A light-emitting element is characterized in that a protrusion pattern consisting of multiple protrusions is formed in at least one region of the bonding surface of the semiconductor structural layer with the light-transmitting layer, and there are regions on the bonding surface where the protrusion pattern is absent or the height of the protrusions differs from region to region within the bonding surface.

2. The light-emitting element according to claim 1, characterized in that a first projection pattern is formed in a first region of the bonding surface, a second projection pattern is formed in a second region of the bonding surface consisting of projections that are shorter in height than the projections of the first projection pattern, and the first region extends to the end of the bonding surface.

3. The light-emitting element according to claim 2, characterized in that the first region is lattice-shaped in a plan view taken from a direction perpendicular to the lower surface of the first semiconductor layer.

4. The light-emitting element according to claim 1, characterized in that a first projection pattern is formed in the first region of the bonding surface, the second region of the bonding surface is a flat surface, and the first region extends to the end of the bonding surface.

5. The light-emitting element according to claim 1 or 2, characterized in that the height of the projection increases from the center of the bonding surface toward the outer edge of the bonding surface.

6. The light-emitting element according to claim 2, characterized in that the transparent substrate has a groove formed in a region of the upper surface of the transparent substrate that is opposite to the first region of the bonding surface and that extends to the edge of the upper surface of the transparent substrate.

7. The light-emitting element according to claim 1 or 2, characterized in that the light-transmitting layer is made of an amorphous material.

8. The light-transmitting layer is Si ３ N ４ SiO ２ and TiO ２ The light-emitting element according to claim 7, characterized by comprising any of the above.

9. The light-emitting element according to claim 1 or 2, characterized in that the transparent substrate is made of sapphire.

10. The light-emitting element according to claim 1 or 2, characterized in that the active layer emits light with wavelengths in the infrared region.

11. A semiconductor structural layer formation step involves forming a first semiconductor layer having a first conductivity type on one main surface of a flat support substrate, forming an active layer on the first semiconductor layer, and forming a second semiconductor layer having a second conductivity type on the active layer to form a semiconductor structural layer, A protrusion pattern formation step of forming a protrusion pattern consisting of a plurality of protrusions in at least one region of one main surface of the semiconductor structural layer, A light-transmitting layer formation step, in which the aforementioned protrusion pattern is embedded to form a flattened light-transmitting layer, A bonding step in which the light-transmitting layer and a light-transmitting transparent substrate are bonded together by direct bonding, The process includes a support substrate removal step of removing the support substrate, A method for manufacturing a light-emitting element, characterized in that there is a region on one main surface of the semiconductor structural layer where the protrusion pattern is absent, or the height of the protrusions differs in different regions within the one main surface of the semiconductor structural layer.

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