Light emitting device and method for manufacturing the same

Abstract

Provided is a light-emitting device that can uniformly supply a large current to a semiconductor layer of a large area of ​​a light-emitting element and has good heat dissipation characteristics. On the bottom surface of a cavity of a Si substrate, a slit-shaped through hole (3) and a through electrode (4) filling the through hole (3) are provided at a position opposite to a first element electrode of the light-emitting element. The length of the upper surface of the through electrode (4) along the long axis direction is greater than the height of the through electrode along the thickness direction of the Si substrate. Between the first element electrode of the light-emitting element and the upper surface of the opposite through electrode, a bonding layer having a shape corresponding to the shape of the upper surface of the through electrode is respectively arranged. The upper surface of the through electrode (4) is bonded to the first element electrode as a whole via the bonding layer.

Description

Technical Field

[0001] The present invention relates to a light-emitting device having a light-emitting element such as an LED mounted thereon, and more particularly to a light-emitting device in which a light-emitting element such as an LED emitting ultraviolet light that requires a large current to be supplied is sealed in an airtight package. Background Art

[0002] LEDs that emit ultraviolet light use AlGaN semiconductors in their light-emitting layers, which are easily degraded by humidity, so it is preferable to seal the package airtightly. However, the structure of sealing by filling resin around visible light LEDs cannot be used for ultraviolet light LEDs because the resin degrades due to ultraviolet light. Therefore, for example, the following structure is used: an ultraviolet light LED mounted on an AlN base is mounted on the bottom surface of a cavity formed by an AlN ceramic sintered body, and the opening of the cavity is sealed with a quartz plate.

[0003] Patent Document 1 discloses a structure in which a through electrode is provided so as to penetrate a substrate made of AlN in the thickness direction, and a die pad for mounting and bonding a light emitting element is arranged on the through electrode and the AlN substrate.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-127254 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In recent years, LEDs that emit large amounts of light and evenly over a large area have been required. Therefore, a packaging structure is needed that can evenly supply large currents to the large-area semiconductor layer of the LED and efficiently conduct the heat generated by the LED to the outside.

[0009] The structure described in Patent Document 1 uses a through electrode, but does not take measures to uniformly supply a large current to the semiconductor layer and conduct the generated heat to the outside. Specifically, there is no disclosure of a structure for reducing resistance and improving thermal conductivity while using a through electrode that is prone to generating voids inside during plating filling.

[0010] An object of the present invention is to provide a light emitting device that can uniformly supply a large current to a semiconductor layer of a large area of ​​a light emitting element and has excellent heat dissipation characteristics.

[0011] Means for solving problems

[0012] In order to achieve the above-mentioned object, in the present invention, a light-emitting device has a light-emitting element and a Si substrate, wherein the light-emitting element has: a semiconductor layer including a light-emitting layer; and a first element electrode and a second element electrode, the first element electrode and the second element electrode being bonded to the semiconductor layer and supplying a current to make the light-emitting layer emit light, and the Si substrate is provided with a cavity, and the light-emitting element is mounted on the bottom surface of the cavity. The first element electrode is arranged on the surface of the semiconductor layer facing the bottom surface side of the cavity. On the bottom surface of the cavity of the Si substrate, a slit-shaped through hole and a through electrode filling the through hole are provided at a position opposite to the first element electrode of the light-emitting element. The length of the upper surface of the through electrode along the long axis direction is greater than the height of the through electrode along the thickness direction of the Si substrate, and the length of the upper surface of the through electrode along the short axis direction is smaller than the height. Between the first element electrode of the light-emitting element and the upper surface of the opposite through electrode, a bonding layer having a shape corresponding to the shape of the upper surface of the through electrode is respectively arranged. The entire upper surface of the through electrode is bonded to the first element electrode via the bonding layer.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide a light emitting device that can uniformly supply a large current to a semiconductor layer having a large area of ​​a light emitting element and has excellent heat dissipation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view of a light emitting device according to an embodiment of the present invention.

[0016] Figure 2 (a) is a top view of the Si substrate 1 of the light emitting device according to the embodiment, and (b) is a bottom view thereof.

[0017] Figure 3 It is a perspective view of the bottom surface region of the cavity 2 of the Si substrate 1 of the light emitting device according to the embodiment.

[0018] Figure 4 It is a cross-sectional view of the light emitting element 5 of the light emitting device according to the embodiment.

[0019] Figure 5 yes Figure 4 Bottom view of the light-emitting element 5.

[0020] Figure 6 (a) and (b) are cross-sectional views of the through-electrode 4 of the Si substrate 1 of the light-emitting device according to the embodiment.

[0021] Figure 7 (a) is an explanatory diagram showing a process of sealing the cavity 2 of the Si substrate 1 of the light emitting device according to the embodiment with the cover member 9, and (b) is an explanatory diagram showing the structure after sealing.

[0022] Figure 8(a) to (e) are cross-sectional views showing the manufacturing process of the light emitting device according to the embodiment.

[0023] Fig. 9 (a) to (d) are cross-sectional views showing the manufacturing process of the light emitting device according to the embodiment.

[0024] Fig.10 (a) to (e) are cross-sectional views showing the manufacturing process of the light emitting device according to the embodiment.

[0025] Fig.11 (a) to (e) are cross-sectional views showing the manufacturing process of the light emitting device according to the embodiment.

[0026] Fig.12 This is a cross-sectional view showing an example in which the inner walls of the through holes 3 and 13 of the Si substrate 1 of the light emitting device according to the embodiment are formed into a concavo-convex shape. DETAILED DESCRIPTION

[0027] A light emitting device according to one embodiment of the present invention will be described with reference to the drawings.

[0028] Figure 1 A cross-sectional view showing a light emitting device according to this embodiment. Figure 2 (a) and (b) show a top view and a bottom view of the substrate 1 of the light emitting device. Figure 3 A perspective view showing the through-electrode 4 of the substrate 1 of the light emitting device.

[0029] The light emitting device of this embodiment is configured by providing a slit-shaped through hole 3 on the bottom surface 2a of a cavity (recess) 2 provided in a Si substrate 1, and further providing a through electrode 4 of a shape filling the slit-shaped through hole 3. Figure 2 (a) and Figure 3 As shown, the length of the upper surface of the through electrode 4 along the major axis direction is designed to be greater than the height of the through electrode 4 (in the thickness direction of the Si substrate 1 ), and the width of the upper surface of the through electrode 4 along the minor axis direction is smaller than the height of the through electrode 4 .

[0030] Furthermore, the light emitting element 5 is mounted on the bottom surface 2 a of the cavity 2 , and the first element electrode 6 on the bottom surface of the light emitting element 5 is directly bonded to the upper surface of the through electrode 4 via the bonding layer 8 .

[0031] In this way, current is supplied by directly connecting the through electrode 4 of a shape filling the slit to the element electrode 6 of the light-emitting element 5. Compared with the case of using a conventional columnar through electrode described in patent document 1, etc., the contact area between the bottom electrode 6 of the light-emitting element 5 and the through electrode 4 is larger in the long axis direction of the upper surface of the through electrode 4, and a large current can be uniformly and efficiently supplied to the first element electrode 6 of the light-emitting element 5.

[0032] In particular, in the case where the shape of the first element electrode 6 is a linear electrode corresponding to the shape of the upper surface of the through electrode 4 that fills the slit, the upper surface of the through electrode 4 is bonded to the entire linear electrode via the bonding layer 8, and current can be supplied to the entire surface of the linear electrode. Therefore, a large current can be uniformly supplied to the linear electrode, and a semiconductor layer in a wide area can emit light efficiently.

[0033] In addition, the through electrode 4 is directly bonded to the element electrode 6 of the light emitting element 5, and the heat generated by the light emitting element 5 can be efficiently dissipated through the through electrode 4. In the bonding between the through electrode 4 and the element electrode 6 of the light emitting element 5, there is no thermal oxide film formed on the Si substrate in the middle. Furthermore, the through electrode 4 in the shape of filling the slit can receive the heat generated by the light emitting element 5 by the entire upper surface, dissipate the heat in the direction parallel to the length direction of the upper surface, and conduct the heat in the height direction. Therefore, the heat generated in the semiconductor layer of the light emitting element 5 can be efficiently conducted through the through electrode 4 in the shape of filling the slit, and dissipated to the outside of the Si substrate 1.

[0034] The through-electrode 4 filling the slit-shaped through-hole 3 is less likely to form a void inside when forming the through-electrode, compared with a large-volume through-electrode whose dimensions in both the longitudinal and width directions are larger than its dimension in the height direction, resulting in reduced resistance and improved heat conduction.

[0035] By making the through electrode 4 slit-shaped, it is possible to suppress problems caused by thermal expansion differences compared to the case of a through electrode having a general columnar shape as described in Patent Document 1, etc. That is, it is possible to suppress cracks and the like from being generated due to the thermal expansion differences among the through electrode 4 made of metal, the substrate 1 made of Si, and the thermal oxide film (SiO2) formed on the surface of the substrate 1 and the inner wall of the through hole. In particular, by making the through electrode 4 slit-shaped, the proportion of the thermal oxide film becomes lower than in the case of a columnar shape, and cracks generated in the thermal oxide film can be suppressed.

[0036] Hereinafter, the light emitting device of this embodiment will be described in more detail.

[0037] like Figure 1 As shown in FIG. 1 , the light emitting device of the present embodiment includes a light emitting element 5 and a Si substrate 1 . The light emitting element 5 includes a semiconductor layer 15 including a light emitting layer, and first and second element electrodes 6 and 7 .

[0038] Here, the first and second element electrodes 6 and 7 are bonded to the bottom surface of the semiconductor layer 15, and supply current to make the light-emitting layer emit light. The cross-sectional structure of the light-emitting element 5 is Figure 4The structure is composed of a semiconductor substrate 15d, an n-type semiconductor layer 15c provided on the entire lower surface of the semiconductor substrate 15d, a light emitting layer 15a and a p-type semiconductor layer 15b provided on the lower surface of the n-type semiconductor layer 15c.

[0039] The stack of the light emitting layer 15a and the p-type semiconductor layer 15b is a rectangular body with a narrower width than length, and multiple (here, 6) of the rectangular stacks are arranged in stripes at predetermined intervals throughout the entire range of the n-type semiconductor layer 15c. The ends of the stack of the light emitting layer 15a and the p-type semiconductor layer 15b are connected to each other. The side surfaces of the stack of the light emitting layer 15a and the p-type semiconductor layer 15b are covered by an insulating layer.

[0040] Figure 5 FIG. 2 shows the shape of the lower surface of the light emitting element 5. The first element electrode 6 is comb-shaped and includes a plurality of linear electrode portions 6a whose width is narrower than their length, and a connecting electrode portion 6b connecting the ends of the linear electrode portions 6a. The linear electrode portions 6a are respectively connected in a manner along the length direction of the lower surface of the stripe-shaped p-type semiconductor layer 15b. Figure 4 As shown, the first element electrode 6 has a stacked structure of a p-electrode 61 and a pad electrode 62 .

[0041] Similarly, the second element electrode 7 is a comb-shaped electrode, including a linear electrode portion 7a having a narrower width than a length, and a connecting electrode portion 7b connecting the ends of the linear electrode portion 7a. The linear electrode portion 7a is respectively arranged in the gap between the stripe-shaped p-type semiconductor layer 15b and the region where the n-type semiconductor layer 15c is exposed. In addition, the second element electrode 6 is a stacked structure of an n-electrode 171 and a pad electrode 172.

[0042] By passing a current between the first element electrode 6 and the second element electrode 7, the current flows through the light emitting layer 15a, causing the light emitting layer 15a to emit light from the upper surface of the semiconductor substrate 15d. In order to improve the light extraction efficiency, the upper surface of the semiconductor substrate 15d is processed with concave and convex surfaces. A protective layer 45 is arranged on the concave and convex surface.

[0043] An example of the composition of each layer of the semiconductor layer 15 of the light emitting element 5 of this embodiment is as follows: Figure 4 As shown, an AlGaN-based light emitting layer 15a is used. The light emitting layer 15a emits ultraviolet light. The AlGaN-based light emitting layer 15a has the property of being degraded by humidity, so the light emitting device of this embodiment prevents moisture from entering by hermetically sealing the light emitting element 5. The sealing structure will be described later.

[0044] On the other hand, the Si substrate 1 is provided with a cavity 2 , and a light emitting element 5 is mounted on the bottom surface of the cavity 2 .

[0045] In the bottom area of ​​the cavity 2 of the Si substrate 1, as Figure 2 As shown in (a), a slit-shaped through hole 3 is provided at a position opposite to the stripe-shaped linear electrode portion 6a of the first element electrode 6 of the light-emitting element 5. A through electrode 4 filling the through hole 3 is provided inside the through hole 3. A back electrode 11 is provided on the back surface of the Si substrate 1 (the surface on the side opposite to the bottom surface area of ​​the cavity 2), and the back electrode 11 is connected to the through electrode 4.

[0046] In addition, a slit-shaped through hole 13 is provided in the bottom surface area of ​​the cavity 2 of the Si substrate 1 at a position opposite to the connection electrode portion 7b of the second element electrode 7. A through electrode 14 is provided inside the through hole 13 to fill the through hole 13. A back electrode 12 is provided on the back surface of the Si substrate 1, and the back electrode 12 is connected to the through electrode 14.

[0047] As described above, the through electrode 4 has a shape in which the length of the long axis direction of the upper surface is greater than the height, and the width of the short axis direction of the upper surface is smaller than the height. Figure 3 The shape of the through-electrode 14 is also the same. Specifically, for example, the length of the upper surface of the through-electrode 4, 14 in the long-axis direction is designed to be 3 times or more, preferably 10 times or more, the width in the short-axis direction.

[0048] Between the linear electrode portion 6a of the first element electrode 6 of the light-emitting element and the upper surface of the corresponding through-electrode 4, a bonding layer 8 having a shape corresponding to the shape of the upper surface of the through-electrode 4 is respectively arranged, and the entire upper surface of the through-electrode 4 is bonded to the linear electrode portion 6a of the first element electrode 6 via the bonding layer 8.

[0049] Similarly, the entire upper surface of the through-electrode 14 is bonded to the connection electrode portion 7 b of the second element electrode 7 via the bonding layer 8 .

[0050] At this time, in the present embodiment, the bonding layer 8 is configured so that a part of it also fills the extremely small gap between the upper part of the inner wall of the through hole 3 of the Si substrate 1 and the upper part of the through electrode 4, thereby hermetically sealing the periphery of the through electrode 4 (see Figure 6 (a), (b)). In addition, Figure 6 This is a diagram emphasizing the gap in order to explain that the bonding layer 8 fills the gap, and the through electrode is basically in close contact with the inner wall of the through hole 3.

[0051] Furthermore, a cover member 9 for closing the opening is mounted on the upper surface of the opening of the cavity 2 , thereby hermetically sealing the periphery of the opening of the cavity 2 .

[0052] That is, a solid phase diffusion bonded portion 70 is provided in a region of Si substrate 1 where lid member 9 is mounted, where Si substrate 1 and lid member 9 are bonded by solid phase diffusion. Solid phase diffusion bonded portion 70 is formed in a ring shape so as to surround light emitting element and cavity 2.

[0053] The solid phase diffusion bonding portion 70 has a material capable of solid phase diffusion bonding with both the cover member 9 side and the Si substrate 1 side, and is formed by making either side a material capable of plastic deformation. In addition, as a material capable of solid phase diffusion, metal or Si can be used, and as a material capable of plastic deformation, metal can be used. For example, the solid phase diffusion bonding portion 70 can be the following structures: (1) a structure in which a metal layer formed on the Si substrate 1 side is bonded to a metal layer formed on the cover member 9 side by solid phase diffusion, (2) a structure in which a metal layer formed on the Si substrate 1 side is bonded to a Si layer formed on the cover member 9 side by solid phase diffusion, (3) a structure in which the Si substrate 1 itself or a Si layer formed on the Si substrate 1 side is bonded to a metal layer formed on the cover member 9 side by solid phase diffusion.

[0054] The solid-phase diffusion bonded portion 70 may be formed in a region where a recessed portion provided in one of the Si substrate 1 and the cover member 9 fits with a projecting portion provided in the other.

[0055] For example, a lower surface of the cover member 9 and an upper surface of the Si substrate 1 (here, the upper surface side of the Si substrate 1) are provided. Figure 7 The concave portion 71 as shown in (a) of FIG. 1 is provided with a convex portion 72 made of a plastically deformable material on the other side (here, the cover member 9 side), and the convex portion 72 is inserted into the concave portion 71 and plastically deformed to fill the concave portion 71, and can become a seal with the concave portion 71. Figure 7 Thus, the inner wall of the concave portion 71 and the convex portion 72 are solid-phase diffusion-bonded to form a solid-phase diffusion-bonded portion 70 that hermetically seals the Si substrate 1 and the lid member 9 .

[0056] The concave portion 71 may be completely filled with the convex portion 72, or may be filled with a void, as long as solid phase diffusion bonding is performed between the inner wall of the concave portion 71 and the convex portion 72. In addition, solid phase diffusion bonding may be formed on the inner side of the inner wall of the concave portion 71, or may be formed on the outer side of the inner wall of the concave portion 71.

[0057] The convex portion 72 is made of a metal having an Au layer on the surface, for example, and can be solid-phase diffused and bonded to the inner wall of the Si substrate 1. In addition, by also providing a metal layer 73 having an Au layer on the inner wall of the Si substrate 1, the convex portion 72 can be bonded to the concave portion 71 by Au-Au solid-phase diffusion.

[0058] For example, the convex portion 72 is Figure 7In the case of the structure (a), a structure in which a Cr layer, a Ni layer, and an Au layer are stacked in order from the cover member 9 can be adopted. In addition, the metal layer 73 of the inner wall of the recess 71 can have a structure in which a Cr layer, a Ni layer, and an Au layer are stacked in order from the Si substrate 1 side.

[0059] In addition, as in the present embodiment, not only is a metal layer 73 formed on the Si substrate 1, but a portion of the Si substrate 1 can also be exposed by locally removing a thermal oxide film (SiO2) formed on the surface of the Si substrate 1, thereby crimping the exposed portion of the Si substrate 1 to the metal layer (protrusion 72) formed on the side of the cover part 9 to form a solid phase diffusion bonding portion 70.

[0060] As in the present embodiment, the recess 71 formed on the Si substrate 1 is not limited to being formed as a groove, and may be formed so that the inner wall of the recess 71 is exposed on the outer side surface of the Si substrate 1 .

[0061] In addition, the combination of the concave portion and the convex portion forming the solid phase diffusion bonding portion 70 may also be configured such that the convex portion is Si and the inner side of the concave portion is a metal layer (plating layer), and the two are pressed together to cause the metal layer inside the concave portion to plastically deform and generate solid phase diffusion to achieve bonding. Specifically, Figure 7 As shown in (a) and (b), a recess 71 is provided on the Si substrate 1 side, a metal layer 73 is provided in the recess 71, and a protrusion 72 composed of Si is installed on the cover part 9 side by anodizing bonding or the like. By pressing the two together, a solid phase diffusion bonding portion can also be formed.

[0062] Furthermore, the structure is not limited to the combination of the concave portion and the convex portion as in the light emitting device of the present embodiment, and a solid phase diffusion bonding portion may be formed on the inner wall of the cavity 2 .

[0063] The cover member 9 is made of a material that transmits the light emitted by the light emitting element 5 , and may be a plate-shaped member or an optical member having desired optical characteristics such as a lens.

[0064] In this way, by filling the periphery of the upper portion of the through electrode 4 with the bonding layer 8 and blocking the opening of the cavity 2 with the cover member 9, the space in the cavity 2 can be hermetically sealed. Thus, even when a semiconductor layer such as an AlGaN-based semiconductor layer that is easily degraded by humidity is used as the semiconductor layer 15 of the light-emitting element 5, the cavity 2 can be kept airtight to prevent the intrusion of moisture and suppress degradation, thereby improving reliability.

[0065] Furthermore, the through electrodes 4 and 14 are made of a metal having a higher melting point than the bonding layer 8, and the upper surfaces of the through electrodes 4 and 14 are designed to be located at a position closer to the inner side of the through holes 3 and 13 than the bottom surface of the cavity 2 of the Si substrate 1. Thus, even when the through electrodes 4 and 14 are formed on the bottom surface of the cavity 2 by plating, it is possible to prevent the through electrodes 4 and 14 from protruding from the bottom surface of the cavity 2 of the Si substrate 1 and becoming an obstacle when mounting the light emitting element 5. Furthermore, by using a material having a lower melting point than the through electrodes 4 and 14 for the bonding layer 8, the upper surfaces of the through electrodes 4 and 14 can be bonded to the first and second element electrodes 6 and 7 by melting the bonding layer 8.

[0066] In addition, a barrier layer 10 is provided between the through electrodes 4 and 14 and the bonding layer 8 to prevent the through electrodes 4 and 14 from mixing with the bonding layer 8. By providing the barrier layer 10, when the bonding layer 8 is melted, the material constituting the through electrodes 4 and 14 is not mixed with the bonding layer 8. Therefore, even when a eutectic alloy such as eutectic solder is used as the bonding layer 8, its melting point and alloy characteristics can be maintained. In addition, the upper surface of the barrier layer 10 is preferably formed to be located at a position closer to the inner side of the through hole 3 than the upper surface of the cavity 2, so as not to become an obstacle when the light-emitting element 5 is mounted.

[0067] For example, the through electrodes 4 and 14 may be made of Cu, and an AuSn layer may be used as the bonding layer 8. In this case, a Ni layer may be used as the barrier layer 10.

[0068] <Method for manufacturing light emitting device>

[0069] Here, a method for manufacturing the light-emitting device of this embodiment will be described.

[0070] like Figure 8 As shown in (a), as the Si substrate 1, a bare Si wafer (thickness 400 μm) with a crystal plane orientation of (100) is prepared. Figure 8 As shown in (b), a resist mask 81 is formed on the surface, and alignment marks 82 and sealing recesses 71 are formed by deep dry etching (DRIE). As an example, the dimensions of the recess 71 are 3 to 5 μm in opening width and 3 to 5 μm in depth.

[0071] like Figure 8 As shown in (c) of FIG. 1 , after the resist mask 81 is removed, thermal oxide films (SiO 2 ) 83 and 84 having a thickness of, for example, about 1 μm are formed on both surfaces of the Si substrate 1 .

[0072] Then, if Figure 8 As shown in (d), a resist mask 85 is formed on the surface of the Si substrate 1 on the side where the recess 71 is formed, and the thermal oxide film 83 in the area that becomes the opening of the cavity 2 is removed by dry etching. Figure 8 As shown in (e), the thermal oxide films 83 and 84 are used as masks to form a cavity 2 by anisotropic etching of Si crystal. As an etching solution, for example, a 25wt% TMAH (tetraammonium hydroxide) solution is used, and etching is performed at 80°C for 13 hours, thereby forming a cavity 2 with a depth of 300μm and a thickness of 100μm on the bottom surface of the Si substrate 1.

[0073] On the other hand, Fig. 9 As shown in (a), a Si substrate is prepared as a support substrate 91, and wax is applied on one side to form a wax layer 92. Fig. 9 As shown in (b), a support substrate 91 is fixed to the surface of the opening side of the cavity 2 of the Si substrate 1 having the cavity 2 formed therein by a wax layer 92. For example, the support substrate 91 is fixed to the Si substrate 1 by heating to 140°C using a wafer bonding machine and pressing with a pressure of 1000N.

[0074] Then, if Fig. 9 As shown in (c), a resist mask 93 is formed on the thermal oxide film 84 of the Si substrate 1, and the thermal oxide film 84 at the positions where the slit-shaped through holes 3 and 13 are to be formed is removed by dry etching using a reactive ion etching device or the like.

[0075] like Fig. 9 As shown in (d), the Si substrate 1 is deep-dry etched using the resist mask 93 and the thermal oxide film 84 as masks using a reactive ion etching apparatus or the like, thereby forming slit-shaped through holes 3 and 13 .

[0076] like Fig.10 As shown in (a), after peeling off from the support substrate 91 and removing the mask 93, as shown in Fig.10 As shown in (b), the Si substrate 1 is immersed in a BHF (buffered hydrofluoric acid) solution to remove the thermal oxide films 83 and 84 from the Si substrate 1.

[0077] like Fig.10 As shown in (c) , a thermal oxide film having a thickness of about 1 μm is formed on the entire surface of the Si substrate 1 including the inner walls of the through holes 3 and 13 .

[0078] like Fig.10 As shown in (d), the Cu electrode 102 for electrolytic plating is attached to the back surface of the Si substrate using an adhesive tape or the like. At this time, no gap is generated between the Si substrate 1 and the Cu electrode.

[0079] like Fig.10As shown in (e), an electrode 103 is arranged on the opening side of the cavity 2 of the Si substrate 1, and a voltage is applied between the electrodes 102 and 103. By electrolytic plating, a Cu layer (95 μm), a Ni layer (5 μm), and an AuSn layer (5 μm) are continuously stacked in order from the Cu electrode 102 side in the through holes 3 and 13 of the Si substrate 1. At the beginning of the plating solution, a copper sulfate solution is used as a plating bath to form a Cu layer. When the Cu layer is formed to a desired thickness, it is changed to a plating bath corresponding to Ni and AuSn to form a Ni layer and an AuSn layer.

[0080] The Cu layer is the through electrode 4 , the Ni layer is the barrier layer 10 , and the AuSn layer is the bonding layer 8 .

[0081] The upper surface of barrier layer (Ni layer) 10 is located inside through holes 3 and 13 relative to the upper surface of thermal oxide film 101 on Si substrate 1. The upper surface of bonding layer 8 protrudes further into cavity 2 than the upper surface of thermal oxide film 101 on Si substrate 1.

[0082] Here, the shape of the through holes 3 and 13 is as follows: the size of the opening in the long axis direction is larger than the height (the thickness direction of the Si substrate 1), and the size of the opening in the short axis direction is smaller than the height. Therefore, by adjusting the additives added to the plating bath and the amount of current passed, a Cu layer, a Ni layer, and an AuSn layer without voids can be formed by plating.

[0083] It should be noted that before electroplating, a seed layer is not formed by sputtering or electroless plating because if a seed layer is formed, voids are easily generated in the through-electrode 4, barrier layer 10, and bonding layer 8 formed by electroplating.

[0084] like Fig.11 As shown in (a), the back electrodes 11 and 12 are formed by a lift-off process on the back side of the Si substrate 1. For example, the back electrodes 11 and 12 are structured such that a Ti layer (0.05 μm), a Cu layer (0.1 μm), a Ni layer (1 μm), and an Au layer (0.5 μm) are stacked in order from the Si substrate 1 side.

[0085] like Fig.11 As shown in (b), a metal layer 73 is formed around at least the inner wall and the opening of the recess 71 of the Si substrate 1. Specifically, for example, a Ti layer (0.05 μm), a Ni layer (0.5 μm), and an Au layer (1 μm) are formed in sequence from the Si substrate 1 side by sputtering using a template mask, thereby forming the metal layer 73.

[0086] like Fig.11As shown in (c), after the light emitting element 5 manufactured separately is mounted on the bottom surface of the cavity 2 in such a manner that the first and second element electrodes 6 and 7 are in contact with the bonding layer 8, the bonding layer 8 is melted by heating, and the first and second element electrodes 6 and 7 are bonded to the through electrodes 4 and 14 through the bonding layer 8. For example, the bonding is performed by heating the bonding layer 8 at 340° C. for 10 seconds. The light emitting element 5 is an LED that emits ultraviolet light.

[0087] At this time, by melting the bonding layer 8, the first and second element electrodes 6 and 7 of the light emitting element 5 and the through electrodes 4 and 14 can be bonded by the bonding layer 8, and the gap between the inner wall of the through holes 3 and 13 and the through electrodes 4 and 14 in the upper part of the through holes 3 and 13 can be filled with the melt of the bonding layer 8. Thus, the through holes 3 and 13 and the through electrodes 4 and 14 can be sealed.

[0088] like Fig.11 As shown in (d), a cover member 9 is prepared, and a convex portion 72 is formed by metal at a position opposite to the concave portion 71 of the Si substrate 1. For example, quartz glass is prepared as the cover member 9, a Cr layer (0.05 μm) is formed by sputtering, and then a Ni layer (1 μm) and an Au layer (5 μm) are stacked thereon by electrolytic plating, and a metal layer in the shape of the convex portion 72 is formed by a lift-off process. The width of the convex portion 72 is, for example, 6 to 10 μm.

[0089] like Fig.11 As shown in (e), the convex portion 72 of the cover member 9 is inserted into the concave portion 71 while applying a load (for example, about 3000N) without heating (below 100°C). The width of the convex portion 72 is larger than the inner diameter of the concave portion 71, so the convex portion 72 is in close contact with the surface of the metal layer 73, and high pressure is locally applied to the concave portion 71 and the metal layer 73 inside thereof, so that the crystals of the Au layer on the outermost surface of the convex portion 72 and the metal layer 73 undergo plastic deformation. During plastic deformation, sliding displacement occurs on the Au crystal surface, and a clean crystal surface appears. The clean crystal surfaces of the Au layers on the convex portion 72 side and the metal layer 73 side form a strong bond with each other. This is solid phase diffusion bonding at the atomic level, and the strength of the bonding surface is as high as the bonding strength of the metal (Au) bulk. As a result, the periphery of the cavity 2 can be sealed with high airtightness.

[0090] It should be noted that in order to promote the sliding displacement of the crystal plane, a temperature of 100°C to 200°C is effective, and by setting the temperature to this degree, the load required for bonding can be reduced. By inserting the protrusion 72 into the recess 71, the temperature rises locally due to frictional heat, so there is no need for additional heating, but due to the reduction of residual stress caused by the load reduction, it can also be heated to below 200°C. In this way, the periphery of the cavity 2 can be bonded to the cover member 9 at a temperature lower than the melting point of the bonding layer 8 (AuSn layer), so that sealing can be performed without remelting the bonding layer 8.

[0091] In this way, the light-emitting device of this embodiment can be manufactured.

[0092] In addition, here, the inner wall of the recessed portion 71 is formed to be perpendicular to the Si substrate 1 , but may be formed to be inclined or may be formed to be a stepped inner wall structure.

[0093] In addition, the outermost surface of the convex portion 72 and the metal layer 73 is not limited to the Au layer, and solid phase bonding can also be performed when the Cu layer or the Ag layer is used as the outermost layer. In this case, since the Cu layer is relatively hard, when the convex portion 72 is inserted into the concave portion 71, it is preferably heated so that the temperature of the insertion portion becomes about 250°C. On the other hand, the surface of the Ag layer is easily oxidized and sulfurized, so it is preferably performed in an inert gas.

[0094] It should be noted that, in this embodiment, Figure 4 and Figure 5 As shown in FIG. 1 , as the light emitting element 5, an example in which the first element electrode 6 has a linear electrode portion 6a arranged in a stripe shape has been described, but the light emitting element 5 of this embodiment is not limited to this structure. A light emitting element 5 in which the first element electrode 6 is arranged on the entire lower surface of the semiconductor layer may also be used. In this case, by Figure 2 By arranging the through-electrode 4 as in (a), current can be efficiently supplied to the entire first element electrode 6 by the through-electrode 4 with few voids, and heat generated by the light-emitting element 5 can be efficiently conducted and dissipated.

[0095] In this embodiment, the inner wall surface of the through holes 3 and 13 is perpendicular to the main plane of the Si substrate 1. Fig.12 As shown, the inner wall of the through holes 3 and 13 may also be made into a concave-convex shape. Fig.12 By making the inner walls of the through holes 3 and 13 uneven in this way, it is possible to improve the adhesion between the inner walls of the through holes 3 and 13 and the through electrodes 4 and 14 and the barrier layer 10, thereby further improving the airtightness.

[0096] In this embodiment, the cavity 2 is formed by performing crystal anisotropic etching on the Si substrate 1, so that a cavity structure having a mirror-like inclined surface and a bottom surface can be formed. In addition, the reflectivity of the inclined surface of the cavity 2 of the Si substrate 1 to ultraviolet light is 50-70%, which is higher than the reflectivity of about 20% of the conventional AlN ceramic package. Therefore, the light-emitting device of this embodiment can utilize the inclined surface and the bottom surface to efficiently reflect the ultraviolet light emitted by the light-emitting element 5, and can improve the light emission efficiency.

[0097] In addition, in the present embodiment, a bonding layer (AuSn layer) 8 that melts when bonding the light emitting element 5 is formed on the upper portion of the through electrode 4, so it is not necessary to make the upper surface of the through electrode 4 protrude from the bottom surface of the cavity 2. Therefore, when the light emitting element 5 is mounted, the upper portion of the through electrode 4 does not become an obstacle, and there is also an advantage that the light emitting element 5 can be mounted on the flat bottom surface of the cavity 2.

[0098] In addition, the light emitting device of this embodiment can set the thickness of the Si substrate 1 at the bottom of the cavity 2 to, for example, 100 μm, which is much thinner than a conventional ceramic package (500 μm) and has excellent heat dissipation properties.

[0099] Furthermore, the light emitting device of this embodiment directly dissipates the heat of the light emitting element 5 by using the through electrodes 4 and 14 filling the slit-shaped through holes 3 and 13 provided on the bottom surface of the relatively thin cavity 2, and thus has excellent heat dissipation.

[0100] In particular, by arranging a plurality of through electrodes 4 and 14, the upper surface area of ​​the through electrodes 4 and 14 can be made 50% or more of the bottom surface area of ​​the light emitting element 5. Therefore, the heat dissipation characteristics can be more than twice as good as those of conventional ceramic packages.

[0101] Furthermore, the light emitting device of this embodiment has good heat dissipation properties, so the amount of current flowing through the light emitting element 5 increases, resulting in an increase in light output.

[0102] The light emitting device of this embodiment can be manufactured in batches using a MEMS (micro electro mechanical systems) process with a Si wafer used as the Si substrate 1, and thus has excellent productivity. In addition, the light emitting device has excellent compatibility with small and thin types.

[0103] Furthermore, since a bare Si wafer is used as the Si substrate 1 , the light emitting device can be manufactured at a low cost compared to a light emitting device in which a cavity is formed of AlN ceramics.

[0104] In the manufacturing method of the light-emitting device of the present embodiment, after the light-emitting element 5 is mounted on the Si substrate 1 via the bonding layer 8, the cover member 9 can be sealed to the opening of the cavity 2 at room temperature, so there is no step of heating to a temperature higher than the melting point of the bonding layer 8. Therefore, the risk of poor bonding due to remelting of the bonding layer 8 can be avoided, and the manufacturing cost can be reduced.

[0105] Furthermore, since the step of sealing the lid member 9 to the opening of the cavity 2 is a step of pressing the lid member 9 to the cavity 2 , it can be performed collectively for each wafer, and thus the productivity is excellent.

[0106] In particular, the sealing process around the cover member 9 and the cavity 2 of the Si substrate 1 can be performed at room temperature, so even when quartz is used as the cover member 9, cracking and peeling caused by stress strain caused by the difference in thermal expansion coefficient between the Si substrate 1 and quartz will not occur. As a result, as the Si substrate 1, a large-diameter wafer of 6 inches or more is used, and the cover member 9 can be mounted and sealed in units of wafers, which greatly improves production efficiency compared to the previous single-chip mounting and can achieve a significant reduction in manufacturing costs.

[0107] In addition, when the first element electrode 6 includes a linear electrode portion 6a, the shape of the through electrode 4 can be made to correspond to the shape of the linear electrode portion 6a on a one-to-one basis. In addition, even in the case of other than the linear electrode portion 6a, the shape of the through electrode 4 can be made to correspond to the electrode. In addition, a square or rectangular through electrode can be formed in combination with the through electrode 4 filling the slit-shaped through hole. Thus, on the surface of the Si substrate 1 at the bottom of the cavity 2, a rewiring pattern for connecting the through electrode 4 to the first element electrode 6 is not required, and the through electrode 4 can be directly connected to the first element electrode 6.

[0108] In addition, in this embodiment, the shape of the through electrode 4 corresponds to the shape of the linear electrode portion 6a in a one-to-one manner, but this embodiment is not limited to the one-to-one correspondence. The shape may be a shape in which a part or all of the through electrodes 4 are connected to each other to form an integral body, and a part or all of the linear electrode portion 6a are connected to each other to form an integral body.

[0109] Furthermore, although AlGaN, which is a light-emitting layer of a light-emitting element that emits ultraviolet light, is easily degraded by water (humidity), the light-emitting device of this embodiment can ensure airtightness in the cavity 2 .

[0110] In addition, as described above, in the light-emitting device of the present embodiment, the through-electrodes 4, 14 and the upper surface of the barrier layer 10 are formed by the electrolytic plating process, and the electrode structure in which the upper surface of the bonding layer (AuSn layer) 8 protrudes from the bottom surface of the cavity 2 by several μm, and the melted AuSn fills the tiny gap between the through-holes 3, 13 and the through-electrodes 4, 14, ensures the airtightness required for the ultraviolet light-emitting element. The present invention is not limited to this structure, and it may also be a structure in which the airtightness of the through-holes 3, 13 is achieved by taking measures for the structure of the back electrodes 11, 12.

[0111] Specifically, the back electrodes 11 and 12 are stacked in the order of Ni layer, Cu layer, Ni layer, and Au layer from the Si substrate 1 side. Thus, the adhesion is improved by the solid phase diffusion of Cu of the through electrodes 4 and 14 and Cu of the Cu layer of the back electrodes 11 and 12, and further, the Ni layer and Au layer of the back electrode can cover the small gap between the through holes 3 and 13 and the through electrode 4. Thus, the airtightness of the through holes 3 and 13 can be ensured.

[0112] Furthermore, in the above-described embodiment, the recessed portions 71 around the cavity 2 are arranged in one row, but by forming the recessed portions 71 in two or more rows, the airtight sealing property can be further improved.

[0113] The light emitting device of this embodiment uses single crystal Si as the Si substrate 1, but polycrystalline Si may also be used. When polycrystalline Si is used as the Si substrate, by performing cavity processing using a dry process, the through hole forming step, the through electrode forming step, and the groove forming step can be performed in the same manner as the steps of the manufacturing method of the light emitting device of this embodiment using a single crystal Si substrate.

[0114] The light emitting device of this embodiment can be used as a light emitting device using a VCSEL (vertical cavity surface emitting laser) element as the light emitting element 5, or a light emitting device in which the VCSEL elements are arranged in an array. In addition, it can be used as an ultraviolet light emitting device using an ultraviolet light LED as the light emitting element 5. Furthermore, as the light emitting element 5, an LED emitting ultraviolet light is used, and as a structure in which a phosphor or a phosphor layer is coated on the cover member 9, a light emitting device of a visible light LED can be provided.

[0115] Description of symbols

[0116] 1…Si substrate, 2…cavity, 2a…bottom of cavity, 3, 13…slit-shaped through hole, 4, 14…through electrode, 5…light-emitting element, 6…first element electrode, 7…second element electrode, 8…joining layer, 11, 12…back electrode, 72…convex portion.

Claims

1. A light emitting device, characterized in that: The light emitting device comprises a light emitting element and a Si substrate. The light emitting element comprises: a semiconductor layer including a light emitting layer; and a first element electrode and a second element electrode, the first element electrode and the second element electrode being bonded to the semiconductor layer and supplying a current for causing the light emitting layer to emit light. The Si substrate is provided with a cavity, and the light emitting element is mounted on the bottom surface of the cavity. The first element electrode is arranged on a surface of the semiconductor layer facing the bottom surface of the cavity. A slit-shaped through hole and a through electrode filling the through hole are provided on the bottom surface of the cavity of the Si substrate at a position facing the first element electrode of the light emitting element. The length of the upper surface of the through electrode along the long axis direction is greater than the height of the through electrode along the thickness direction of the Si substrate, and the length of the upper surface of the through electrode along the short axis direction is smaller than the height. A bonding layer having a shape corresponding to the shape of the upper surface of the through-electrode is arranged between the first element electrode of the light-emitting element and the upper surface of the opposing through-electrode, The entire upper surface of the through electrode is bonded to the first element electrode via the bonding layer. The through electrode is made of a metal having a higher melting point than the bonding layer, and the upper surface of the through electrode is located closer to the inner side of the through hole than the bottom surface of the cavity of the Si substrate. A barrier layer for preventing mixing of the through-electrode and the bonding layer is arranged between the through-electrode and the bonding layer. The upper surface of the barrier layer is located inside the through hole of the bottom surface of the cavity.

2. The light emitting device according to claim 1, characterized in that: A portion of the bonding layer fills a gap between an upper portion of an inner wall of the through hole of the Si substrate and the through electrode.

3. The light emitting device according to claim 1 or 2, characterized in that: A cover member is mounted on an upper surface of the opening of the cavity, and the cover member allows light emitted by the light emitting element to pass therethrough and closes the opening.

4. The light emitting device according to claim 1 or 2, characterized in that: The first element electrode includes a plurality of linear electrode portions whose width is narrower than their length, and the plurality of linear electrode portions are arranged at predetermined intervals in a width direction of the linear electrode portions. A plurality of the through electrodes are provided so as to face the plurality of linear electrode portions, respectively.

5. The light emitting device according to claim 1 or 2, characterized in that: The length of the upper surface of the through electrode along the major axis direction is at least three times the width along the minor axis direction.

6. The light emitting device according to claim 4, characterized in that: The surface of the semiconductor layer facing the bottom surface of the cavity has a region where p-type semiconductor layers and n-type semiconductor layers are alternately arranged in a stripe shape. The first element electrode includes a plurality of linear electrode portions, and each of the plurality of linear electrode portions is joined to a stripe-shaped p-type semiconductor layer.

7. The light emitting device according to claim 3, characterized in that: A solid phase diffusion bonding portion is provided in a region of the Si substrate where the cover member is mounted, and the solid phase diffusion bonding portion bonds the Si substrate and the cover member by solid phase diffusion. The solid phase diffusion bonded portion is formed in a ring shape surrounding the light emitting element.

8. The light emitting device according to claim 7, characterized in that: The solid-phase diffusion bonding portion is any of the following three bonding portions: a bonding portion in which a metal layer formed on the Si substrate side is bonded to a metal layer formed on the cover component side by solid-phase diffusion, a bonding portion in which a metal layer formed on the Si substrate side is bonded to a Si layer formed on the cover component side by solid-phase diffusion, and a bonding portion in which the Si substrate or the Si layer formed on the Si substrate side is bonded to a metal layer formed on the cover component side by solid-phase diffusion.

9. The light emitting device according to claim 7 or 8, characterized in that: The solid-phase diffusion bonded portion is formed in a region where a recessed portion provided on one of the Si substrate and the cover member fits with a projecting portion provided on the other.

10. The light emitting device according to claim 3, characterized in that: One of the lower surface of the component that blocks the opening of the cavity and the upper surface of the Si substrate has a recessed portion, and the other has a protrusion made of a plastically deformable material. The protrusion is inserted into the recessed portion and plastically deformed to fill the recessed portion and fit closely with the recessed portion.

11. The light emitting device according to claim 10, characterized in that: The inner wall of the recessed portion and the protruding portion are bonded by solid phase diffusion.

12. The light emitting device according to claim 6, characterized in that: The second element electrode includes a second linear electrode portion having a width narrower than its length and a connecting electrode portion connecting the second linear electrode portion and the second linear electrode portion. The second linear electrode portions are arranged alternately with the linear electrode portions of the first element electrode and are respectively connected to the stripe-shaped n-type semiconductor layer. The bottom surface of the cavity of the Si substrate further includes a slit-shaped through hole for connecting electrode at a position opposite to the connecting electrode portion and a through electrode for connecting electrode filling the through hole for connecting electrode. The length of the upper surface of the through-electrode for the connection electrode along the long axis direction is greater than the height of the through-electrode along the thickness direction of the Si substrate. A connection electrode bonding layer having a shape corresponding to the shape of the upper surface of the connection electrode through-electrode is arranged between the connection electrode portion of the light emitting element and the upper surface of the connection electrode through-electrode, The entire upper surface of the connection electrode through-electrode is bonded to the connection electrode portion via the connection electrode bonding layer.

13. The light emitting device according to claim 1 or 2, characterized in that: The through electrode is made of Cu, the bonding layer is made of AuSn, and the barrier layer is made of Ni.

14. The light emitting device according to claim 1 or 2, characterized in that: The light emitting element emits ultraviolet light.

15. A light emitting device, characterized in that: The light emitting device comprises a light emitting element and a Si substrate. The light emitting element comprises: a semiconductor layer including a light emitting layer; and a first element electrode and a second element electrode, the first element electrode and the second element electrode being bonded to the semiconductor layer and supplying a current for causing the light emitting layer to emit light. The Si substrate is provided with a cavity, and the light emitting element is mounted on the bottom surface of the cavity. The first element electrode includes three or more linear electrode portions whose width is narrower than their length, and the three or more linear electrode portions are arranged at predetermined intervals in a width direction of the linear electrode portions over the entire surface of the semiconductor layer facing the bottom surface side of the cavity. A through hole and a through electrode filling the through hole are provided on the bottom surface of the cavity of the Si substrate at positions respectively opposite to the three or more linear electrode portions of the light emitting element, wherein the through hole is a slit having an opening shape corresponding to the shape of the linear electrode, A bonding layer having a shape corresponding to the shape of the upper surface of the through-electrode is arranged between the linear electrode portion of the light-emitting element and the upper surface of the through-electrode facing the through-electrode. The entire upper surface of the through electrode is bonded to the linear electrode portion via the bonding layer. The through electrode is made of a metal having a higher melting point than the bonding layer, and the upper surface of the through electrode is located closer to the inner side of the through hole than the bottom surface of the cavity of the Si substrate. A barrier layer for preventing mixing of the through-electrode and the bonding layer is arranged between the through-electrode and the bonding layer. The upper surface of the barrier layer is located inside the through hole of the bottom surface of the cavity.

16. The light emitting device according to claim 15, characterized in that: The through electrode is made of Cu, the bonding layer is made of AuSn, and the barrier layer is made of Ni.

17. The light emitting device according to claim 15 or 16, characterized in that: The light emitting element emits ultraviolet light.

18. A method for manufacturing a light emitting device, characterized in that: The manufacturing method of the light emitting device comprises the following steps: A process of forming a cavity on a Si substrate by etching; A step of forming a slit-shaped through hole on the bottom surface of the cavity by etching, wherein the length of the opening of the upper surface of the through hole along the long axis direction is longer than the thickness of the Si substrate at the bottom surface of the cavity, and the length of the opening along the short axis direction is smaller than the thickness; a plating step of filling the through hole by plating to form a through electrode, and forming a bonding metal layer on the through electrode; and a step of directly mounting a light emitting element on the bonding metal layer exposed on the bottom surface of the cavity, The plating process includes the following steps: forming the through-electrode by plating from the bottom surface of the through-hole to a position below the upper surface of the through-hole; A step of forming a barrier layer by plating from the upper surface of the through electrode to a position below the upper surface of the through hole; and The step of forming the bonding metal layer by plating from the upper surface of the barrier layer to a position above the upper surface of the through hole.

19. The method for manufacturing a light emitting device according to claim 18, characterized in that: In the mounting step, the bonding metal layer is melted to bond to the electrode of the light emitting element, and the gap between the inner wall of the through hole and the through electrode in the upper portion of the through hole is filled with the melt of the bonding metal layer.

20. The method for manufacturing a light emitting device according to claim 18 or 19, characterized in that: The manufacturing method of the light emitting device further comprises the following steps: A step of forming one of a concave portion and a convex portion made of a plastically deformable material around the cavity of the Si substrate; A step of preparing a member covering the opening of the cavity, and forming the other of the concave portion and the convex portion made of the plastically deformable material at a position corresponding to the periphery of the cavity; as well as The step of placing the component on the opening of the cavity, pressing the convex portion into the concave portion, thereby deforming the convex portion and making the convex portion closely contact and bond with the inner wall of the concave portion.

21. The method for manufacturing a light emitting device according to claim 20, characterized in that: In the step of closely adhering and bonding, solid phase diffusion bonding using a load is performed in a heated atmosphere at room temperature or a temperature lower than the melting point of the bonding metal layer.

22. The method for manufacturing a light emitting device according to claim 18 or 19, characterized in that: The Si substrate is single crystal, The step of forming the cavity is a step of performing crystal anisotropic etching on the single crystal Si substrate using an alkaline solution.

23. The method for manufacturing a light emitting device according to claim 18 or 19, characterized in that: The step of forming the through-electrode is a step of filling the through-hole by electrolytic plating.

24. The method for manufacturing a light emitting device according to claim 20, characterized in that: The metal constituting the protrusion is Au, and an Au layer is also provided on the inner wall of the recess. By performing the step of closely contacting and bonding, the Au constituting the protrusion and the Au layer on the inner wall of the recess are Au-Au solid phase diffusion bonded.

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