Patent Document

BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a light-emitting device and the method of manufacturing the same, and in particular to a light-emitting device comprising a light-emitting chip, bonding pads and a eutectic interface between the light-emitting chip and the bonding pads. 
         [0003]    2. Description of the Related Art 
         [0004]    The light-emitting diodes (LEDs) of the solid-state lighting elements have the characteristics of low power consumption, low heat generation, long operational life, shockproof, small volume, quick response and good opto-electrical property like light emission with a stable wavelength so the LEDs have been widely used in household appliances, indicator light of instruments, and opto-electrical products, etc. 
         [0005]    Though the LEDs have been widely used in light-emitting device in daily life, the method of manufacturing the LEDs has its drawbacks. Especially, when the LED is covered by a wavelength tuning material layer, such as layer comprising phosphor material, the wavelength tuning material layer might collapse during the process. The collapse of wavelength tuning material layer not only reduces the yield of mass production but also influences the COA (color over angle) of an LED. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    A method of manufacturing a light-emitting device, comprising providing a temporary substrate; forming a bonding pad layer having a first width on the temporary substrate; providing a first substrate; forming a light-emitting chip having a second width on the first substrate; and connecting the light-emitting chip and the bonding pad. The first width is larger than the second width. 
         [0007]    A light-emitting device, comprising a light-emitting chip comprising multiple electrodes; an optical layer on the light-emitting chip; multiple bonding pads connecting to the electrodes of the light-emitting chip; and a eutectic bonding interface between the electrodes and the bonding pads. 
         [0008]    A light-emitting device, comprising a substrate; an array of light-emitting chips each comprising multiple electrodes on the substrate; an array of optical layers on the light-emitting chips respectively; and multiple bonding pads connecting to the multiple electrodes and the optical layers respectively, such that multiple eutectic bonding interfaces are formed between the multiple bonding pads and the multiple electrode correspondingly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1   a - 1   b  show a top view and a cross-sectional view of a structure related to a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0010]      FIGS. 2   a - 2   b  show a top view and a cross-sectional view of a structure related to a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0011]      FIGS. 3   a - 3   b  show a top view and a cross-sectional view of a structure related to a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0012]      FIGS. 4-8  show a cross-sectional view of a structure related to a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0013]      FIG. 9  shows a cross-sectional view of a light-emitting device in accordance with an embodiment of the present disclosure. 
           [0014]      FIG. 10  shows a cross-sectional view of a structure related to a light-emitting device in accordance with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0015]    To better and concisely explain the disclosure, the same name or the same reference number given or appeared in different paragraphs or figures along the specification should has the same or equivalent meanings while it is once defined anywhere of the disclosure. 
         [0016]    The following shows the description of the embodiments of the present disclosure in accordance with the drawings. 
         [0017]      FIGS. 1   a - 1   b  show a top view and a cross-sectional view of a structure related to a light-emitting device  100  in accordance with an embodiment of the present disclosure. At the step of process depicted in  FIGS. 1   a - 1   b , a temporary substrate  2  is provided and a seed layer  4  is then formed on the temporary substrate  2 . The seed layer  4  is for forming bonding pads later. As shown in  FIGS. 2   a - 2   b , a photoresist layer  6  and multiple bonding pads are formed on the seed layer  4 . The  FIG. 2   b  is a cross-sectional view of  FIG. 2   a  along the line A 1 -A 2 . The photoresist layer  6  is formed on the seed layer  4  as a mask, and part of the photoresist layer  6  is etched to form an array of trenches to expose the seed layer  4 . The etching process can be a lithography process or an etching process. Then, a metal material is formed in the trenches and contacted with the seed layer  4  to form the bonding pads which are surrounded by the photoresist layer  6  as shown in  FIG. 2   b.    
         [0018]    The process of forming the bonding pads in the trenches can be deposition, and the material filled in the trenches comprises Cu, Ni, Au, W and Ti. The bonding pads comprise a first pad  82  and a second pad  84  arranged in a row to be connected to a same light-emitting chip, and the first pad  82  has a width L 1 . In this embodiment, the top surfaces of the bonding pads and the photoresist layer  6  opposing to the temporary substrate  2  are not flat. Since the flatness of the top surfaces affects the bonding strength between the chips and the bonding pads, a planarization process is needed to planarize the top surfaces so the height of the photoresist layer  6  can be about the same as that of the bonding pads, and the bonding strength between the chips and the bonding pads is therefore improved. Besides, the characteristics, such as the size and the shape, of the first pad  82  can be the same with or different from that of the second pad  84 . Furthermore, the size can be the length, width, or the height. 
         [0019]    In the steps depicted in  FIGS. 3   a - 3   b , a first substrate  12  is provided and the light-emitting chips are placed on the first substrate  12 . The  FIG. 3   b  is a cross-sectional view of  FIG. 3   a  along the line B 1 -B 2 . The light-emitting chips such as a first chip  140  with a width L 2 , a second chip  142 , and a third chip  144  are placed with a space between each other, and each of the light-emitting chips comprises two electrodes (not shown). In another embodiment, the light-emitting chips are epitaxially grown on the first substrate  12  and the distances between any two light-emitting chips can be the same or be different from each other. The light-emitting chips are capable of emitting same or different incoherent visible or invisible lights. The visible lights can be same or different color; the invisible lights can be UV light or infrared light. In order to bond the light-emitting chips and the bonding pads, the light-emitting chips are arranged in an orientation corresponding to the positions of the bonding pads. For example, the second chip  142  is arranged to be connected to the first pad  82  and the second pad  84  in the following steps. Besides, in order to bond the bonding pads and the light-emitting chips, alignment marks (not shown in the figure) are optionally formed on the surface of the first substrate  12  and/or on the surface of the photoresist layer  6 . 
         [0020]    As shown in  FIG. 4 , the bonding pads in  FIGS. 2   a - 2   b  and the light-emitting chips in  FIGS. 3   a - 3   b  are bonded so gaps  10  are formed between the light-emitting chips, and a minimum distance between two adjacent bonding pads is different from that the gap  10 . An alignment process is performed before bonding the bonding pads and the light-emitting chips, and the bonding process comprises increasing temperature and increasing pressure on the bonding pads and/or on the light-emitting chips. In this embodiment, the width L 1  of the first pad  82  or the width of the second pad  84  is larger than the width L 2  of the second chip  142  to facilitate the alignment of the connection. The alignment process can be performed by matching the positions of the flat sides on the circumferences of the carrier supporting the bonding pads and of the carrier supporting the light-emitting chips. Or, the alignment process can be performed by matching the positions of the alignment marks on the carriers. In this embodiment, the alignment process is performed by moving and rotating the carriers like the temporary substrate  2  and the first substrate  12  to match the flat side (not shown) of the temporary substrate  2  and flat side (not shown) of the first substrate  12 . In another embodiment, the positions of the temporary substrate  2  and the first substrate  12  are adjusted to match the alignment marks on the first substrate  12  and on the temporary substrate  2 . Then, the second chip  142  is bonded with the first pad  82  and the second pad  84  by eutectic bonding. After bonding, the temporary substrate  2  and the seed layer  4  are removed to expose a surface of the photoresist layer  6  opposing to the first substrate  12 . A second substrate  22  is then connected to the surface as shown in  FIG. 5 . The minimum distance between adjacent two bonding pads is different from that between adjacent two light-emitting chips. 
         [0021]    Referring to  FIGS. 6˜7 , the first substrate  12  is removed to expose a surface of the second chip  142  and a surface of the photoresist layer  6 , and an optical layer  16  is formed on the light-emitting chips. The optical layer  16  covers the light-emitting chips, the bonding pads, and the photoresist layer  6 . As shown in  FIG. 7 , the optical layer  16  is formed on top surfaces and sidewalls of the light-emitting chips. The optical layer  16  comprises a transparent material and a wavelength conversion material. The material of the transparent material can be silicone. In this embodiment, the optical layer  16  is formed by forming a first portion of the transparent material on the light-emitting chips, forming the wavelength conversion material on the first portion and forming a second portion of the optical layer  16  on the wavelength conversion material. The process of forming the wavelength conversion material can be deposition, coating, dispersing or spreading. Furthermore, the wavelength conversion material can be mixed with a transparent material which is a binder; also can be silicone. To be specific, the optical layer  16  forms a stack of “transparent material—wavelength conversion material—transparent material”. In this embodiment, the transparent material and the wavelength conversion material are formed on the second substrate  22 . In another embodiment, the optical layer  16  is formed in advance by forming a mixture comprising a transparent material and a wavelength conversion material, curing the mixture to form a strip or a sheet, and attaching the strip or sheet on the light-emitting chips. The optical layer  16  can also be formed as an array of strips or sheets in advance and then attached to the light-emitting chips. The particles of the wavelength conversion material can be distributed in the optical layer  16  uniformly, randomly or close to the surfaces of light extraction of the light-emitting chips. In other words, the particles can be distant from or in contact with the second chip  142 . 
         [0022]    Referring to  FIG. 8 , a third substrate  32  is attached to the optical layer  16 , and the structure is turned over so the third substrate  32  is at the bottom of the structure. Then, the second substrate  22  and the photoresist layer  6  are removed to expose parts of the surface that are not covered by the first pad  82  or the second pad  84 . The third substrate  32  can be a carrier supporting the light-emitting chips and the optical layer  16  during the process of removing the photoresist layer  6  and the second substrate  22 . A cutting process is performed to singulate the optical layer  16 . Then, the third substrate  32  is removed to form a light-emitting device  100  as shown in  FIG. 9 . In this embodiment, the light-emitting device  100  comprises one light-emitting chip. In another embodiment, the light-emitting device  100  comprises a plurality of light-emitting chips. Moreover, the plurality of light-emitting devices  100 , either comprising one chip or multiple chips, can be attached to another substrate. Then the substrate with light-emitting devices  100  can be stretched for different process requirements. 
         [0023]    The process to singulate the optical layer  16  and remove the third substrate  32  can be realized in two different methods. The first method is to perform the cutting on the optical layer  16  from the surface having the bonding pads formed thereon in a direction towards the third substrate  32 . The optical layer  16  along with the third substrate  32  is then separated by splitting. In another embodiment, the cutting process is performed on both the optical layer  16  and the third substrate  32 , so the optical layer  16  and the third substrate  32  can be separated without additional splitting process. After the cutting process, the second chip  142  along with the bonding pads  82 ,  84  and the optical layer  16  can be picked from the substrate  32  and a light-emitting device  100  as shown in  FIG. 9  is formed. 
         [0024]    The second method is to perform the cutting processes at least twice. The first cutting process forms multiple trenches on the surface of the optical layer  16  having the bonding pads formed thereon, and the trenches protrude into the optical layer  16  without separating the optical layer  16 . Referring to  FIG. 10 , the fourth substrate  42  is provided to connect with the bonding pads, and the structure is turned over so the fourth substrate  42  is at the bottom side. In one embodiment, the fourth substrate  42  can be a blue tape which can be stretched. A second cutting process is then applied on the surface of the third substrate  32  opposite to the optical layer  16 . The second cutting process forms trenches (not shown) extending from the third substrate  32  to the trenches (not shown) in the optical layer  16 . So, the optical layer  16  along with the third substrate  32  is separated. The separated third substrate  32  is then removed. Next, the second chip  142  with the bonding pads  82  and  84  and the optical layer  16  can be picked from the fourth substrate  42  to form a light-emitting device  100  as shown in  FIG. 9 . In another embodiment, the third substrate  32  is removed before the second cutting process and the second cutting process is applied on the surface of the optical layer  16  opposite to the bonding pads. 
         [0025]    The first method is more likely to be applied when the “distance” is sufficient to pick the light-emitting device from the third substrate  32 , and the second method is more likely to be applied while the “distance” is too small. The “distance” represents the minimum distance between two sidewalls of two bonding pads separately connected to two neighboring chips. For example, the “distance” is the length D in  FIG. 8 . While the length D is small, the picking process is performed with risk of damaging the light-emitting device. So, the fourth substrate  42  is applied to be stretched to enlarge the length D for picking process as mentioned above. The fourth substrate  42  can also be PVC. The length D is designed to be small for manufacturing as many light-emitting devices as possible on one substrate. The small length D avoids the optical layer  16  from protruding from the part that is not covered by the chip. The small length D also avoids the optical layer protrude from contacting the sidewalls of the bonding pads during the turning process in manufacturing. 
         [0026]    Referring to  FIG. 9 , the light-emitting device  100  comprises an optical layer  16  on the second chip  142  and the first pad  82  and the second pad  84 . In other words, both of the first pad  82  and the second pad  84  are under the optical layer  16 . The optical layer  16  has a width larger than that of the second chip  142  so the effect of scattering the light emitted from the second chip  142  is improved, and the viewing angle of the light emitted from the second chip  142  is therefore increased. Each of the surfaces of the bonding pads comprises a portion directly contacted with the optical layer  16  and not covered by the second chip  142 . The bonding pads can support the optical layer  16  and prevent the optical layer  16  from collapse. The particles of the wavelength conversion material are spread within the optical layer  16  and surround the second chip  142  so the light passing through the sidewall of the second chip  142  can be converted by the wavelength conversion material, and the uniformity of COA (color over angle) of the light-emitting device  100  can be improved. The cross-sectional shape of the optical layer  16  is a rectangular. In another embodiment, the cross-sectional shape of the optical layer  16  can be a quadrangle comprising a trapezoid. 
         [0027]    As mentioned above, the second chip  142  further comprises two electrodes (not shown), and the electrodes are respectively connected to the first pad  82  and the second pad  84 . In this embodiment, the connection is formed by a bonding process, and the bonding process is performed under a range of temperature between 100˜400° C. and a pressure of about 5800 kgf on a 4″ wafer (the area is about 81 cm 2 ). Under the circumstances, the interfaces between the pads and the electrodes are formed to be eutectic bonding interfaces. To be more specific, the first interface  1420  (between the first pad  82  and one electrode) and the second interface  1422  (between the second pad  84  and the other electrode) are eutectic bonding interfaces, and both comprise eutectic metal alloy. The eutectic metal alloy has a eutectic point lower than 400° C. In another embodiment, the eutectic point is between 100˜400° C. 
         [0028]    It will be apparent to those having ordinary skill in the art that various modifications and variations can be made to the devices in accordance with the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.

Technology Category: 5