Patent Publication Number: US-2015069436-A1

Title: Semiconductor light emitting device and method for manufacturing same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-184846, filed on Sep. 6, 2013; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a semiconductor light emitting device and a method for manufacturing the same. 
     BACKGROUND 
     Conventionally, a method for manufacturing a semiconductor light emitting device has been proposed in which a semiconductor layer is grown by crystal growth on a wafer; electrodes are formed on the semiconductor layer; sealing with a resin body is performed; subsequently, the wafer is removed; a fluorescer layer is formed on the exposed surface of the semiconductor layer; and singulation is performed. According to such a method, fine structural bodies that are formed on the wafer can be packaged as-is; and fine semiconductor light emitting devices can be efficiently manufactured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view showing a semiconductor light emitting device according to a first embodiment; and  FIG. 1B  is a partially-enlarged cross-sectional view showing region A shown in  FIG. 1A ; 
         FIGS. 2A to 2C  are partial cross-sectional views showing a method for manufacturing the semiconductor light emitting device according to the first embodiment; 
         FIG. 3  is a partial cross-sectional view showing a semiconductor light emitting device according to a second embodiment; 
         FIG. 4  is a partial cross-sectional view showing a semiconductor light emitting device according to a third embodiment; 
         FIG. 5  is a partial cross-sectional view showing a semiconductor light emitting device according to a fourth embodiment; 
         FIG. 6  is a cross-sectional view showing a semiconductor light emitting device according to a fifth embodiment; and 
         FIG. 7  is a cross-sectional view showing a semiconductor light emitting device according to a sixth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A semiconductor light emitting device according to an embodiment includes a semiconductor layer, a first resin layer provided on the semiconductor layer, first fluorescer particles disposed in the first resin layer, and a second resin layer provided on the first resin layer to contact the first resin layer. Recesses are made in a surface of the first resin layer contacting the second resin layer. The recesses are filled with portions of the second resin layer. 
     A method for manufacturing a semiconductor light emitting device according to an embodiment includes forming a first resin layer on a semiconductor layer. The first resin layer has first fluorescer particles. The method includes making recesses by removing an upper portion of the first resin layer to cause some of the first fluorescer particles to drop out from the first resin layer. The method includes forming a second resin layer on the first resin layer. Portions of the second resin layer enter the recesses. 
     Embodiments of the invention will now be described with reference to the drawings. 
     First Embodiment 
     First, a first embodiment will be described. 
       FIG. 1A  is a cross-sectional view showing a semiconductor light emitting device according to the embodiment; and  FIG. 1B  is a partially-enlarged cross-sectional view showing region A shown in  FIG. 1A . 
     As shown in  FIG. 1A , the configuration of the entire semiconductor light emitting device  1  according to the embodiment is a rectangular parallelepiped. A semiconductor layer  10  is provided in the semiconductor light emitting device  1 . The semiconductor layer  10  is formed of a compound semiconductor including, for example, gallium nitride (GaN) and is an LED (Light Emitting Diode) layer in which a p-type clad layer  10   p , an active layer  10   a , and an n-type clad layer  10   n  are stacked in order from the lower layer side. As viewed in the thickness direction, the configuration of the semiconductor layer  10  is a rectangle; and at the four corners of the rectangle, the p-type clad layer  10   p  and the active layer  10   a  are removed, and the n-type clad layer  10   n  is exposed at the lower surface of the semiconductor layer  10 . 
     An area of the lower surface of the semiconductor layer  10 , where the n-type clad layer  10   n  is exposed, is a non-emitting region, because the p-type clad layer  10   p  and the active layer  10   a  are removed. While an area of the lower surface of the semiconductor layer  10 , where the p-type clad layer  10   p  is exposed, is a light emitting region. The non-emitting region is smaller than the light emitting region. 
     Also, a fine unevenness that has a period that is about the same as the wavelength of the light emitted by the semiconductor layer  10  is formed in the upper surface of the semiconductor layer  10 . An emission light from the semiconductor layer  10  is emitted primarily from the upper surface of the semiconductor layer  10 . An n-side electrode  11   n  and a p-side electrode  11   p  are provided on the lower surface of the semiconductor layer  10 . The n-side electrode  11   n  is connected to the n-type clad layer  10   n  of the semiconductor layer  10 ; and the p-side electrode  11   p  is connected to the p-type clad layer  10   p  of the semiconductor layer  10 . That is, the n-side electrode  11   n  is connected to the non-emitting region of the semiconductor layer  10 , and the p-side electrode  11   p  is connected to the light emitting region of the semiconductor layer  10 . A sealing member  12  is provided to cover the lower surface and side surface of a structural body that is made of the semiconductor layer  10 , the n-side electrode  11   n , and the p-side electrode  11   p.    
     An interconnect layer  13   n  is provided below the n-side electrode  11   n ; and an n-side pillar  14   n  is provided under the interconnect layer  13   n . The n-side pillar  14   n  is connected to the n-side electrode  11   n  via the interconnect layer  13   n . The interconnect layer  13   n  and the n-side pillar  14   n  consist an n-side extraction electrode. The n-side extraction electrode is connected to the non-emitting region of the semiconductor layer  10  and extends to the light emitting region side of the semiconductor layer  10 . An interconnect layer  13   p  is provided below the p-side electrode  11   p ; and a p-side pillar  14   p  is provided under the interconnect layer  13   p . The p-side pillar  14   p  is connected to the p-side electrode  11   p  via the interconnect layer  13   p . The interconnect layer  13   p  and the p-side pillar  14   p  consist a p-side extraction electrode. 
     A sealing member  15  that is made of, for example, a black resin material is provided to cover the interconnect layers  13   n  and  13   p , the n-side pillar  14   n , and the p-side pillar  14   p . The lower surface of the n-side pillar  14   n  and the lower surface of the p-side pillar  14   p  are exposed at the lower surface of the sealing member  15 . The lower surface of the n-side pillar  14   n  and the lower surface of the p-side pillar  14   p  are substantially coplanar with the lower surface of the sealing member  15 . 
     The sealing member  15  and the sealing member  12  consists an insulating film. A first portion of the insulating film which is located lower than the lower surface of the semiconductor layer  10  supports the semiconductor layer  10  with the n-side extraction electrode and the p-side extraction electrode. A second portion of the insulating film which is located upper than the lower surface of the semiconductor layer  10  surrounds a periphery of the semiconductor layer  10 . 
     In explanation of  FIG. 1 , the direction which goes to the semiconductor layer  10  from the sealing member  15  is made into the “upper”, and the opposite direction is made into the “lower”. However, this naming is expedient and unrelated to the direction of gravity. In explanation of the manufacture method mentioned later, the upper-and-lower notation is reversed to the middle. 
     A resin layer  21  is provided above the semiconductor layer  10  and above the sealing member  12  positioned at the side of the semiconductor layer  10 . The resin layer  21  is formed of a resin material that is transparent or semi-transparent and is formed of, for example, a silicone resin. Many fluorescer particles  22  are dispersed in the resin layer  21 . The fluorescer particles  22  are particles that absorb light of a first color emitted from the semiconductor layer  10  to emit light of a second color. For convenience of illustration, the fluorescer particles  22  are illustrated in  FIG. 1A  as being larger than the actual particles. 
     A resin layer  23  is provided on the resin layer  21 . The resin layer  23  is formed of a resin material that is transparent or semi-transparent and is a layer that selectively reflects or scatters light of a designated color and transmits light of other colors. A lower surface  23   b  of the resin layer  23  contacts an upper surface  21   a  of the resin layer  21 . 
     Then, as shown in  FIG. 1B , many recesses  21   c  are made in the upper surface  21   a  of the resin layer  21 . The recesses  21   c  are filled with a portion of the resin layer  23 . 
     The sizes of the recesses  21   c  are about the same as the sizes of the fluorescer particles  22 . In other words, the sizes of the recesses  21   c  are sizes into which the fluorescer particles can fit. Some of the recesses  21   c  have dish-like configurations; and the diameter of the opening, i.e., the upper end portion, of such a configuration is the maximum diameter of the recess  21   c . Other recesses  21   c  have pot-like configurations; and for such a configuration, the maximum diameter is larger than the diameter of the opening. The distribution of the maximum diameters of the recesses  21   c  having the pot-like configurations substantially matches the distribution of the diameters of the fluorescer particles  22 . Therefore, the maximum diameter of at least one recess  21   c  is within the range of the distribution of the diameters of the fluorescer particles  22 . On the other hand, the distribution of the maximum diameters of the recesses  21   c  having the dish-like configurations is shifted from the distribution of the diameters of the fluorescer particles  22  toward the smaller side. Accordingly, the distribution of the maximum diameters of the recesses  21   c  spreads in a range that is about the same as or less than the distribution of the diameters of the fluorescer particles  22 . 
     The average of the diameters of the fluorescer particles  22  is, for example, about 15 μm. The distribution of the diameters of the fluorescer particles is, for example, not less than 0.1d and not more than 2d, where the average diameter of the fluorescer particles is d. Also, the average diameter d of the fluorescer particles can be defined as, for example, a particle diameter D50 having a volumetric basis. The particle diameter D50 is a volumetric median where the cumulative volume is 50%. In such a case, the maximum diameter of at least one recess  21   c  is within a range that is not less than 0.1×D50 and not more than 2×D50. Other than the volumetric basis, the value of the particle diameter D50 may be calculated using a weight basis or a particle count basis. 
     A method for manufacturing the semiconductor light emitting device according to the embodiment will now be described. 
       FIGS. 2A to 2C  are partial cross-sectional views showing the method for manufacturing the semiconductor light emitting device according to the embodiment. 
     Only the resin layer  21  and the fluorescer particles  22  are shown for convenience of illustration in  FIGS. 2A to 2C . First, as shown in  FIG. 1A , the semiconductor layer  10  is grown by epitaxial growth on a substrate (not shown) for crystal growth; and the semiconductor layer  10  is partitioned by being selectively removed. Then, the n-side electrode  11   n  and the p-side electrode  11   p  are formed; and the sealing member  12  is formed to bury the semiconductor layer  10 , the n-side electrode  11   n , and the p-side electrode  11   p . Continuing, the interconnect layers  13   n  and  13   p  are formed on the sealing member  12 ; the n-side pillar  14   n  and the p-side pillar  14   p  are formed; and the sealing member  15  is formed to bury these components. Then, the semiconductor layer  10  is exposed by removing the substrate for crystal growth; and an unevenness is formed in the exposed surface of the semiconductor layer  10 . 
     Then, as shown in  FIG. 1A  and  FIG. 2A , the resin layer  21  that contains many fluorescer particles  22  is formed above the semiconductor layer  10  and above the sealing member  12 , that is, on the side of the sealing member  12  where the substrate for crystal growth was provided. At this time, the surfaces of the fluorescer particles  22  are covered with the resin layer  21 ; and the fluorescer particles  22  are not exposed at the upper surface  21   a  of the resin layer  21 . 
     Continuing as shown in  FIG. 2B , the upper portion of the resin layer  21  is removed by performing, for example, machining of the upper surface  21   a  of the resin layer  21 . Thereby, some of the fluorescer particles  22  are exposed. 
     Then, as shown in  FIG. 2C , the machining is continued further. Thereby, the exposed fluorescer particles  22  drop out from the resin layer  21 ; and the recesses  21   c  are made where the fluorescer particles  22  dropped out. At this time, the exposed fluorescer particles  22  can be caused to drop out more reliably by appropriately selecting the conditions and tools of the machining. For example, the fluorescer particles  22  can be pulled out from the resin layer  21  by the tool catching on the exposed portions of the fluorescer particles  22  that are partially exposed from the resin layer  21 . Thus, the recesses  21   c  having the pot-like configurations are made. Or, ultrasonic cleaning may be performed to forcibly push out the fluorescer particles  22  that are partially exposed from the resin layer  21 . 
     Continuing as shown in  FIGS. 1A and 1B , the resin layer  23  is formed on the resin layer  21  by coating a resin material. At this time, the resin material of the resin layer  23  also enters the recesses  21   c  of the resin layer  21  to fill the recesses  21   c . Then, to adjust the chromaticity of the light emitted by the semiconductor light emitting device  1 , machining of the upper surface of the resin layer  23  is performed to adjust the thickness of the resin layer  23 . Thus, the semiconductor light emitting device  1  according to the embodiment is manufactured. In this way, the semiconductor light emitting device  1  has a wafer-level package structure. 
     Operations of the semiconductor light emitting device  1  according to the embodiment will now be described. 
     In the semiconductor light emitting device  1 , the semiconductor layer  10  emits, for example, blue light when a voltage is applied between the p-side pillar  14   p  and the n-side pillar  14   n . The fluorescer particles  22  that are disposed inside the resin layer  21  absorb a portion of the light emitted from the semiconductor layer  10  and emit, for example, yellow light. The remainder of the light emitted from the semiconductor layer  10  passes through the resin layer  21 . Thereby, the light that is emitted by the semiconductor light emitting device  1  is white because the blue light and the yellow light are emitted outside the semiconductor light emitting device  1 . 
     At this time, the wavelength of the light emitted by the semiconductor layer  10  fluctuates due to the process conditions, etc. Therefore, the intensity of the light emitted by the fluorescer particles  22  also fluctuates. Thereby, the chromaticity of the light emitted by the semiconductor light emitting device  1  undesirably fluctuates. Therefore, in the embodiment, the chromaticity of the light emitted by the semiconductor light emitting device  1  is adjusted by providing the resin layer  23  and adjusting the thickness of the resin layer  23 . The resin layer  23  reflects or scatters the light emitted from the semiconductor layer  10  or the light emitted from the fluorescer particles  22 . 
     Effects of the embodiment will now be described. 
     In the embodiment, many recesses  21   c  are made in the upper surface  21   a  of the resin layer  21 ; and the resin layer  23  enters the interiors of the recesses  21   c . Therefore, the adhesion between the resin layer  21  and the resin layer  23  is high due to an anchor effect. Thereby, the resin layer  21  does not peel easily from the resin layer  23 ; and discrepancies such as peeling, etc., do not occur easily. As a result, the reliability of the semiconductor light emitting device  1  is high. 
     The contact surface area between the resin layer  21  and the resin layer  23  is large because the resin layer  23  enters the recesses  21   c . Therefore, the transmission efficiency of the light from the resin layer  21  into the resin layer  23  is high; and the light extraction efficiency is high. Further, because an uneven structure is formed at the interface between the resin layer  21  and the resin layer  23 , the total internal reflection component of the light at the interface is reduced. As a result, the transmission efficiency of the light between the resin layer  21  and the resin layer  23  is high. 
     In the embodiment, the recesses  21   c  are made in the upper surface  21   a  of the resin layer  21  by removing the upper portion of the resin layer  21  to expose some of the fluorescer particles  22  included in the resin layer  21  and cause these fluorescer particles  22  to drop out from the resin layer  21 . As a result, the recesses  21   c  can be made easily. 
     In the embodiment, many of the partially-exposed fluorescer particles  22  are forcibly caused to drop out by performing machining of the upper surface of the resin layer  21  by appropriately selecting the conditions and tools of the machining. Thereby, the anchor effect and the effect of increasing the contact surface area described above can be increased by making many recesses  21   c  having pot-like configurations. Further, degradation of the light emission characteristics of the semiconductor light emitting device  1  due to the fluorescer particles  22  being damaged can be suppressed because the fluorescer particles  22  that are damaged by the machining can be removed. 
     Second Embodiment 
     A second embodiment will now be described. 
       FIG. 3  is a partial cross-sectional view showing a semiconductor light emitting device according to the embodiment. 
     For convenience of illustration in  FIG. 3 , the semiconductor layer  10 , the n-side electrode  11   n , the p-side electrode  11   p , the sealing member  12 , the interconnect layers  13   n  and  13   p , the n-side pillar  14   n , the p-side pillar  14   p , and the sealing member  15  are not shown. This is similar for  FIG. 4  described below. 
     In the semiconductor light emitting device  2  according to the embodiment as shown in  FIG. 3 , nanoparticles  26  and micro particles  27  are provided inside the resin layer  23 . The nanoparticles  26  are particles for selectively reflecting or scattering the light. The diameters of the nanoparticles  26  are smaller than those of the fluorescer particles  22 , e.g., 100 nm or less. The nanoparticles  26  are formed of, for example, a metal oxide such as silicon oxide, aluminum oxide, titanium oxide, etc. Moreover, the nanoparticles  26  may be a void. 
     The micro particles  27  are particles for making the recesses in the upper surface of the resin layer  23 . The diameters of the micro particles  27  are about the same as the wavelength of the light emitted by the semiconductor layer  10  or the wavelength of the light emitted by the fluorescer particles  22 , e.g., about several hundred nm. Also, in the embodiment, recesses  23   c  and  23   d  are made in an upper surface  23   a  of the resin layer  23 . The sizes of the recesses  23   c  are about the same as the sizes of the nanoparticles  26 ; and the sizes of the recesses  23   d  are about the same as the sizes of the micro particles  27 . Otherwise, the effects of the embodiment are similar to those of the first embodiment described above. 
     In the embodiment, the resin layer  23  is formed by coating a resin material that includes the nanoparticles  26  and the micro particles  27 . Then, the recesses  23   c  and  23   d  are made in the upper surface  23   a  by exposing some of the nanoparticles  26  and some of the micro particles  27  at the upper surface  23   a  of the resin layer  23  and causing these particles to drop out when the upper surface  23   a  of the resin layer  23  is machined to adjust the thickness of the resin layer  23 . Otherwise, the manufacturing method of the embodiment is similar to that of the first embodiment described above. 
     According to the embodiment, the recesses  23   d  can be made in the upper surface  23   a  of the resin layer  23  by the micro particles  27  being contained in the resin layer  23 . Then, the sizes of the recesses  23   d  can be controlled by selecting the sizes of the micro particles  27 . Thereby, recesses of any size can be made in the upper surface  23   a ; and the light extraction efficiency can be increased. Otherwise, the operations and the effects of the embodiment are similar to those of the first embodiment described above. 
     The nanoparticles  26  also may be dispersed in the resin layer  21 . In such a case, it is favorable for the particle count density of the nanoparticles  26  inside the resin layer  23  to be higher than the particle count density of the nanoparticles  26  inside the resin layer  21 . 
     Third Embodiment 
     A third embodiment will now be described. 
       FIG. 4  is a partial cross-sectional view showing a semiconductor light emitting device according to the embodiment. 
     In the semiconductor light emitting device  3  according to the embodiment as shown in  FIG. 4 , fluorescer particles  28  are provided inside the resin layer  23  in addition to the configuration of the semiconductor light emitting device  2  (referring to  FIG. 3 ) according to the second embodiment described above. The fluorescer particles  28  absorb the light emitted from the semiconductor layer  10  and emit light of a wavelength that is different from that of the light emitted by the semiconductor layer  10  and different from that of the light emitted by the fluorescer particles  22 . For example, the wavelength of the light emitted by the fluorescer particles  28  is longer than the wavelength of the light emitted by the semiconductor layer  10  and shorter than the wavelength of the light emitted by the fluorescer particles  22 . 
     In an example, the semiconductor layer  10  emits blue light; the fluorescer particles  22  emit red light; and the fluorescer particles  28  emit green light. In addition to the recesses  23   c  and  23   d , recesses  23   e  which are where the fluorescer particles  28  dropped out are made in the upper surface  23   a  of the resin layer  23 . Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the second embodiment described above. 
     Fourth Embodiment 
     A fourth embodiment will now be described. 
       FIG. 5  is a partial cross-sectional view showing a semiconductor light emitting device according to the embodiment. 
     As shown in  FIG. 5 , the semiconductor light emitting device  4  according to the embodiment differs from the semiconductor light emitting device  2  (referring to  FIG. 3 ) according to the second embodiment described above in that the micro particles  27  are not provided. In other words, only the nanoparticles  26  are included inside the resin layer  23 . Therefore, the recesses  23   d  are not made in the upper surface  23   a  of the resin layer  23 . Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the second embodiment described above. 
     Fifth Embodiment 
     A fifth embodiment will now be described. 
       FIG. 6  is a cross-sectional view showing a semiconductor light emitting device according to the embodiment. 
     As shown in  FIG. 6 , the semiconductor light emitting device  5  according to the embodiment differs from the semiconductor light emitting device  1  (referring to  FIG. 1A ) according to the first embodiment described above in that the resin layer  23  of the upper layer has a lens configuration. The configuration of the resin layer  23  is, for example, a portion of a sphere. 
     In the embodiment, the light that is emitted from the upper surface  21   a  of the resin layer  21  can be concentrated toward the upward perpendicular direction by the resin layer  23  having the lens configuration. Thereby, the directivity of the light emitted by the semiconductor light emitting device  4  improves. Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the first embodiment described above. 
     Sixth Embodiment 
     A sixth embodiment will now be described. 
       FIG. 7  is a cross-sectional view showing a semiconductor light emitting device according to the embodiment. 
     As shown in  FIG. 7 , the semiconductor light emitting device  6  according to the embodiment differs from the semiconductor light emitting device  1  (referring to  FIG. 1A ) according to the first embodiment described above in that the resin layer  23  is provided to cover the upper surface  21   a  and a side surface  21   d  of the resin layer  21 ; and the resin layer  23  has a lens configuration. 
     In the embodiment, by forming the resin layer  23  in a lens configuration covering the upper surface  21   a  and the side surface  21   d  of the resin layer  21 , the light that is emitted from the side surface  21   d  of the resin layer  21  as well as the light that is emitted from the upper surface  21   a  of the resin layer  21  can pass through the resin layer  23  such that its chromaticity is adjusted and can be concentrated toward the upward perpendicular direction. Thereby, the directivity of the light emitted by the semiconductor light emitting device  5  improves; and the light extraction efficiency increases. Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the first embodiment described above. 
     Although an example is illustrated in the embodiments described above in which machining is performed as the means for removing the upper portions of the resin layers  21  and  23 , this is not limited thereto. For example, the upper portions of the resin layers  21  and  23  may be removed by dry etching. In such a case, for example, after etching the resin layer, the exposed fluorescer particles, etc., can be caused to drop out by performing brush grinding while supplying carbonated water to prevent charge buildup. 
     Moreover, in the embodiments described above, an adhesion layer may be provided between the semiconductor layer  10  and the resin layer  21  to improve adhesion between them. The adhesion layer may be an inorganic layer, for example, a silicon oxide layer, a silicon nitride layer or a silicon oxynitride layer and so on. 
     According to the embodiments described above, a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device having high reliability can be realized. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. Additionally, the embodiments described above can be combined mutually.