Patent Publication Number: US-2023163108-A1

Title: Micro led display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 110143436 filed in Taiwan, Republic of China on Nov. 22, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technology Field 
     The present disclosure relates to a display device and, in particular, to a micro LED (micro light-emitting diode) display device. 
     Description of Related Art 
     Now the world is paying attention to the future display technology, and the micro light-emitting diode (micro LED) is one of the most promising technologies. In brief, micro LED is a technology of miniaturizing and matrixing LED, thereby arranging millions or even tens of millions of dies, which are smaller than 100 microns and thinner than a hair, on a substrate. 
     In the application of current micro LED display devices, such as the VR or AR device requiring high resolution (e.g. more than 2500 PPI) and ultra-high brightness (e.g. more than 10,000 nits), since the sub-pixels (micro LEDs) has ultra-high brightness, the light leakage from one sub-pixel may interfere the other neighboring sub-pixels. In addition, the surface of the micro LED can be damaged by the etching process, which will decrease the light-emitting efficiency. 
     Therefore, it is desired to provide a micro LED display device that can prevent the damage of the surface of micro light-emitting component caused by the manufacturing process so as to remain the light-emitting efficiency, and improve the light interference issue between the sub-pixels. 
     SUMMARY 
     One or more exemplary embodiments of this disclosure are to provide a novel micro LED display device that can prevent the damage of the surface of micro light-emitting component so as to remain the light-emitting efficiency, and improve the light interference issue between the sub-pixels. 
     In an exemplary embodiment, a micro LED display device of this disclosure includes a circuit substrate, an epitaxial structure layer, and a metal reflective layer. The circuit substrate includes a display area and a non-display area adjacent to the display area. The epitaxial structure layer is disposed on the circuit substrate and includes a first surface facing the circuit substrate, a second surface away from the circuit substrate, and a plurality of ion implantation regions facing the circuit substrate. The ion implantation regions define a plurality of micro LED units spaced apart from each other. The micro LED units are electrically connected to the circuit substrate and are individually controlled to emit light. The first surface is a planar surface within the display area, the second surface has a plurality of grooves, and each of the grooves corresponds to one of the ion implantation regions. The metal reflective layer includes a plurality of reflective portions. The reflective portions are correspondingly disposed in the grooves and protruded from the second surface of the epitaxial structure layer. The reflective portions define a plurality of light transmission regions spaced apart from each other, and each of the light transmission regions corresponds to one of the micro LED units. 
     In one embodiment, the epitaxial structure layer further includes a continuous semiconductor layer, and the semiconductor layer is a common layer of the micro LED units. 
     In one embodiment, each of the micro LED units includes a first type semiconductor layer, a light-emitting layer and a second type semiconductor layer stacked in order, and an implantation depth of the ion implantation region is greater than a maximum vertical distance between the first surface and the light emitting-layer of the micro LED unit adjacent to the ion implantation region. 
     In one embodiment, the ion implantation regions of the epitaxial structure layer do not emit light. 
     In one embodiment, the micro LED display device further includes a light conversion layer disposed in a part of the light transmission regions, and the light conversion layer is configured to convert a wavelength of a light emitted from the corresponding micro LED unit. 
     In one embodiment, the circuit substrate further includes a plurality of conductive electrodes, and one of the conductive electrodes is electrically connected to one of the micro LED units via a conductive member. 
     In one embodiment, the first surface of the epitaxial structure layer further has a concave portion in the non-display area, and the circuit substrate outputs a common electrode signal to the epitaxial structure layer through a conductive member connecting to the concave portion. 
     In one embodiment, the epitaxial structure layer further includes an outside surface, and the circuit substrate outputs a common electrode signal to the epitaxial structure layer through a conductive member connecting to the outside surface. 
     In one embodiment, the reflective portion and the corresponding ion implantation region are overlapped in a direction perpendicular to the first surface. 
     In one embodiment, a distance between the reflective portion and the corresponding ion implantation region is greater than 0 and is less than or equal to 2 µm. 
     In one embodiment, the reflective portion directly contacts the corresponding ion implantation region. 
     In one embodiment, each of the reflective portions includes a first stacked layer located in the corresponding groove, and a second stacked layer protruding from the corresponding groove. 
     In one embodiment, the micro LED display device further includes a light-shielding structure, which includes a plurality of light-shielding portions arranged on the reflective portions and exposing the light transmission regions. 
     In one embodiment, one side of each of the reflective portions away from the epitaxial structure layer is configured with a concave portion, and a material of each of the light-shielding portions is filled into the corresponding concave portion. 
     In one embodiment, the micro LED display device further includes a light transmission layer disposed at one side of the light conversion layer away from the epitaxial structure layer. 
     In one embodiment, the micro LED display device further includes a light filter layer disposed at one side of the light conversion layer away from the epitaxial structure layer. The light filter layer includes a plurality of light filter portions, the light conversion layer includes a plurality of light conversion portions, and the light filter portions respectively correspond to the light conversion portions. 
     In one embodiment, the micro LED display device further includes a light filter substrate disposed at one side of the metal reflective layer away from the epitaxial structure layer. The light filter substrate includes a plurality of light filter portions, the light conversion layer includes a plurality of light conversion portions, and the light filter portions respectively correspond to the light conversion portions. 
     In one embodiment, the width of the micro LED unit is 2~5 µm. 
     In one embodiment, the product of the maximum brightness and the resolution of the micro LED display device is greater than 10 8 . 
     As mentioned above, without utilizing the conventional etching process in the manufacturing of micro LED units, this disclosure implants ions on the first surface of the epitaxial structure layer facing the circuit substrate to form a plurality of separated ion implantation regions, thereby defining a plurality of micro LED units. Accordingly, this disclosure can prevent the damage of the sidewall of micro light-emitting component, thereby remaining the light-emitting efficiency. In addition, this disclosure further provides a metal reflective layer for increasing the conductivity of common electrode to enhance the light-emitting efficiency of micro LED display device. Moreover, the metal reflective layer has a reflection or light concentrating function, which can avoid the light crosstalk problem between sub-pixels and thus match the demand for high-resolution display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present disclosure, and wherein: 
         FIG.  1 A  is a schematic diagram showing a micro LED display device according to an embodiment of this disclosure; 
         FIG.  1 B  is a sectional view of the micro LED display device of  FIG.  1 A  along the line A-A; 
         FIG.  1 C  is a schematic diagram showing a micro LED display device according to another embodiment of this disclosure; and 
         FIGS.  2 A to  2 F  are schematic diagrams showing micro LED display devices according to different embodiments of this disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The present disclosure will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
       FIG.  1 A  is a schematic diagram showing a micro LED display device according to an embodiment of this disclosure, and  FIG.  1 B  is a sectional view of the micro LED display device of  FIG.  1 A  along the line A-A.  FIG.  1 C  is a schematic diagram showing a micro LED display device according to another embodiment of this disclosure. 
     As shown in  FIGS.  1 A and  1 C , the micro LED display device  1  includes a plurality of pixels P, which are arranged in a matrix with multiple rows and columns. Referring to  FIG.  1 A , each pixel P of this embodiment includes three sub-pixels arranged side by side, and each sub-pixel includes a micro LED unit  121 . That is, each pixel P includes three micro LED units  121  arranged side by side. In other embodiments, the three sub-pixels in each pixel P can be arranged in a different way. For example, two of the three sub-pixels are arranged up and down, and the third one of the three sub-pixels is located beside the other two sub-pixels. To be noted, other arrangements are also acceptable. In different embodiments, each pixel P may include four or more sub-pixels. Taking the pixel P including four sub-pixels as an example, the four sub-pixels can be arranged side by side, or in a 2*2 array (see  FIG.  1 C ), or any of other suitable arrangements. Referring to  FIG.  1 C , each of the upper two sub-pixels includes a green micro LED unit  121 , and the lower two sub-pixels include a blue micro LED unit  121  and a red micro LED unit  121 , respectively. This disclosure is not limited thereto, and the colors of the micro LED units  121  and the arrangement thereof can be optionally determined based on the requirement. 
     As shown in  FIG.  1 B , the micro LED display device  1  of this embodiment can be an active matrix (AM) LED micro display device or a passive matrix (PM) LED micro display device. The micro LED display device  1  includes a circuit substrate  11 , an epitaxial structure layer  12 , and a metal reflective layer  13 . In addition, the micro LED display device  1  of this embodiment further includes a light conversion layer  14  and a light-shielding structure  15 . 
     The circuit substrate  11  includes a display are a display area A 1  and a non-display area A 2 . The display area A 1  indicates the light-emitting area of the micro LED display device  1 , which corresponds to the positions of the pixels P (the micro LED units  121 ) of the panel. The non-display area A 2  is located adjacent to the display area A 1 . For example, the non-display area A 2  can be located at the periphery of the display area A 1  (the micro LED units  121 ). The circuit substrate  11  has a bonding surface S 111 . In this embodiment, the bonding surface S 111  is the upper surface of the circuit substrate  11 . The circuit substrate  11  is a driving substrate for driving the micro LED units  121  to emit light. For example, the circuit substrate  11  may be a complementary metal-oxide-semiconductor (CMOS) substrate, a liquid crystal on silicon (LCOS) substrate, or a thin-film transistor (TFT) substrate, or any of other driving substrates with working circuits, but this disclosure is not limited thereto. In some embodiments, the micro LED display device  1  is a micro display applied to AR or VR applications. The length of the circuit substrate  11  can be, for example but not limited to, less than or equal to 1 inch, the PPI (pixels per inch) thereof can be greater than 1000 or 2500, and the brightness thereof is greater than 10,000 nits. In other embodiments, the length of the circuit substrate  11  can be greater than 1 inch, and the PPI thereof is not limited. 
     The epitaxial structure layer  12  is disposed on the bonding surface S 111  of the circuit substrate  11 , and the epitaxial structure layer  12  includes a first surface S 121  facing the circuit substrate  11 , a second surface S 122  away from the circuit substrate  11 , and a plurality of ion implantation regions I facing the circuit substrate  11 . The ion implantation regions I define a plurality of micro LED units  121  spaced apart from each other. In other words, the ion implantation regions I are formed at one side of the epitaxial structure layer  12  facing the circuit substrate  11 . The micro LED units  121  are electrically connected to the circuit substrate  11  and are individually controlled to emit light. Thus, the circuit substrate  11  can control (drive) the micro LED units  121  to emit light. Herein, the ion implantation regions I are formed by an ion implantation process such as an ICP (Inductively Couple Plasma) Mesa process. The first surface S 121  of the epitaxial structure layer  12  facing the circuit substrate  11  is a planar surface within the display area A 1 . Specifically, as shown in  FIG.  1 B , the first surface S 121  is coplanar with the surfaces of the ion implantation regions I. In other words, the first surface S 121  and the surfaces of the ion implantation regions I can together form a continuous co-plane. In some embodiments, the ions implanted into the epitaxial structure layer  12  can be, for example but not limited to, As ions, Ar ions, or Kr ions. These implanted ions can destroy the original characteristics of (the light-emitting layer of) the epitaxial structure layer  12 , thereby defining a plurality of micro LED units  121  spaced apart from each other. For example, the implanted As ions can neutralize the electron holes in a P-type semiconductor layer of the epitaxial structure layer  12 , thereby reducing the number of electron holes so as to decrease the number of photons generated in the combination of the light-emitting layer and electrons. In addition, the implanted Ar ions can destroy the epitaxial lattice, so that the impedance is increased so as to generate the insulation effect. In this embodiment, the first surface S 121  of the epitaxial structure layer  12  is a planar surface in the display area A 1  and is substantially parallel to the bonding surface S 111  of the circuit substrate  11 . In addition, the second surface S 122  of the epitaxial structure layer  12  away from the circuit substrate  11  has a plurality of grooves G, and each groove G corresponds to one of the ion implantation regions I (i.e. one groove G corresponds to one ion implantation region I). 
     In this embodiment, each micro LED unit  121  can provide the light source for one corresponding sub-pixel, and each micro LED unit  121  comprises a first type semiconductor layer  121   a , a light-emitting layer  121   b , and a second type semiconductor layer  121   c , which are stacked in order. The light-emitting layer  121   b  is sandwiched between the first type semiconductor layer  121   a  and the second type semiconductor layer  121   c . For example, the first type semiconductor layer  121   a  is an N-type semiconductor layer, the second type semiconductor layer  121   c  is a P-type semiconductor layer, and the light-emitting layer  121   b  is a multiple quantum well (MQW) layer. This disclosure is not limited thereto. Specifically, the epitaxial structure layer  12  of this embodiment comprises one continuous first type semiconductor layer  121   a , and the micro LED units  121  commonly utilizes the same one first type semiconductor layer  121   a . To be noted, this disclosure is not limited thereto. In different embodiments, the first type semiconductor layer  121   a  can be a P-type semiconductor layer, the second type semiconductor layer  121   c  can be an N-type semiconductor layer. In this case, the micro LED units  121  commonly utilizes the same P-type semiconductor layer. Moreover, the light-emitting layer  121   b  of the micro LED units  121  can generate and emit light, and the ion implantation regions I of the epitaxial structure layer  12  do not generate light because that the implanted ions change the electrical property and the electrons and the holes can’t recombine in the ion implantation regions I of the epitaxial structure layer  12  (including parts of the original light-emitting layer). 
     In some embodiments, in the direction D perpendicular to the first surface S 121  of the epitaxial structure layer  12 , the maximum distance between the first surface S 121  and the light-emitting layer  121   b  of the epitaxial structure layer  12  can be, for example, 0.6 \~0.7 µm, and the minimum distance between the second surface S 122  and the light-emitting layer  121   b  of the epitaxial structure layer  12  can be, for example, 3-3.5 µm. In some embodiments, the implantation depth of the ion implantation region I is greater than the maximum vertical distance between the first surface S 121  and the light-emitting layer  121   b  of the adjacent epitaxial structure layer  12 . In some embodiments, the width of the ion implantation region I can be, for example, 0.5 \~3 µm, and the width of the micro LED unit  121  can be, for example, 2 \~5 µm. To be noted, the above-mentioned values are for illustrations, and are not to limit the scope of this disclosure. In some embodiments, the width of the micro LED unit  121 , which is defined as the pixel pitch, can be, for example, 3 \~10 µm. In practice, when the width of the micro LED unit  121  is 2 \~3 µm, this disclosure can further improve the light-emitting efficiency of micro LED display device and achieve the requirement of high resolution. In some embodiments, the width of the micro LED unit  121  (i.e. the pixel pitch) is 2 \~5 µm, and this configuration is suitable for manufacturing an ultra LED display device. In this case, the product of the maximum brightness (nits) and the resolution (PPI) of the micro LED display device is greater than 10 8 . 
     In addition, the circuit substrate  11  of this embodiment further includes a plurality of conductive electrodes (111,  112 ), which are disposed corresponding to the micro LED units  121  of the epitaxial structure layer  12  (e.g. in the one-to-one arrangement). In this embodiment, each conductive electrode is electrically connected to the corresponding circuit layer (not shown) of the circuit substrate  11 . Accordingly, the circuit substrate  11  can transmit the individually controlled electric signal to the conductive electrode through the corresponding circuit layer, thereby driving the corresponding micro LED unit  121  to emit light. One of the conductive electrodes can be electrically connected to one of the micro LED units  121  via a conductive member C. The conductive electrodes of this embodiment may include a plurality of first electrodes  111  ( FIG.  1 B  shows four first electrodes  111 ) and a second electrode  112 . Each first electrode  111  is electrically connected to the second type semiconductor layer  121   c  of one corresponding micro LED unit  121  via one corresponding conductive member C, and the second electrode  112  is the common electrode of the epitaxial structure layer  12  and is electrically connected to the first semiconductor layers  121   a  of the corresponding micro LED units  121  via one corresponding conductive member C. The above-mentioned conductive members C can include, for example but not limited to, indium, tin, copper, silver, gold, or an alloy thereof (e.g., copper plus any of the above-mentioned metals (excluding tin)), and this disclosure is not limited. 
     In order to obtain the uniform brightness and reduce the power consumption, the micro LED display device  1  of this embodiment does not electrically connect the semiconductor layer of micro LEDs (e.g., the first type semiconductor layer  121   a ) to the circuit substrate  11  with the conventional metal grid. In this embodiment, the first surface S 121  of the epitaxial structure layer  12  further has a concave portion U in the non-display area A 2 , and the conductive member C is filled in the concave portion U and contacts the epitaxial structure layer  12  (i.e. the first type semiconductor layer  121   a ). Therefore, the common electrode signals can be transmitted from the circuit substrate  11  to the epitaxial structure layer  12  via the common electrode (i.e. the second electrode  112 ) and the conductive member C connected to the concave portion U. In addition, the micro LED display device  1  of this embodiment further includes a solder resist layer  113  disposed between the bonding surface S 111  and the epitaxial structure layer  12 . The solder resist layer  113  can not only provide a buffer during the pressing process to avoid the breaking of the epitaxial structure layer  12 , but also prevent a short circuit between the first electrode  111  and the second electrode  112 . The material of the solder resist layer  113  may include, for example but is not limited to, an inorganic dielectric material (e.g., silicon nitride or silicon oxide), or an organic polymer material (e.g., photoresist or ink). 
     The metal reflective layer  13  includes a plurality of reflective portions  131 , which are correspondingly disposed in the grooves G and protruded from the second surface S 122  of the epitaxial structure layer  12 . In this embodiment, each reflective portion  131  fully fills the corresponding groove G and protrudes from the second surface S 122  toward the direction away from the circuit substrate  11 , thereby forming the metal reflective layer  13 . Herein, each reflective portion  131  of the metal reflective layer  13  and the corresponding ion implantation region I are overlapped in the direction D perpendicular to the first surface S 121 . The metal reflective layer  13  directly contacts the first type semiconductor layer  121   a  of the epitaxial structure layer  12  so as to electrically connect the corresponding micro LED unit  121 . In addition, the metal reflective layer  13  further electrically connects the circuit substrate  11 . For example, the metal reflective layer  13  can be electrically connected to the second electrode  112  of the circuit substrate  11  via the first type semiconductor layer  121   a  of the epitaxial structure layer  12 . In each reflective portion  131  of this embodiment, the reflective material located inside the groove G is the same as the reflective material protruding from the second surface S 122  of the epitaxial structure layer  12 . However, this disclosure is not limited thereto. In different embodiments, the material of a part of the reflective portion  131  located inside the groove G can be different from the material of a part of the reflective portion  131  protruding from the groove G. In other words, a first kind of reflective material is formed inside the groove G, and then a second kind of reflective material is formed on the first kind of reflective material, thereby forming the reflective portion  131  with two different materials. That is, each reflective portion  131  includes a first stacked layer located in the corresponding groove G, and a second stacked layer protruding from the corresponding groove G (the material of the first stacked layer is different from that of the second stacked layer). Certainly, the material of the first stacked layer can be the same as that of the second stacked layer, and this disclosure is not limited thereto. 
     The reflective portions  131  of the metal reflective layer  13  can define a plurality of light transmission regions  132  spaced apart from each other, and each of the light transmission regions  132  corresponds to one of the micro LED units  121 . That is, the light transmission regions  132  correspond to the micro LED units  121  respectively (in the one-to-one manner). In this embodiment, each light transmission region  132  overlaps with the corresponding micro LED unit  121  in the direction D perpendicular to the first surface S 121 . Herein, each light transmission region  132  can be a through hole formed on the metal reflective layer  13 , and the through hole communicates the upper and lower surfaces of the metal reflective layer  13 . Accordingly, the light emitted from the micro LED units  121  corresponding to the light transmission regions  132  can pass through the through holes (light transmission regions  132 ) and be outputted upwardly. That is, the light emitted from the micro LED units  121  can pass through the through holes to display images. The material of the metal reflective layer  13  can be a conductive metal material, such as silver, aluminum, copper, titanium, chromium or nickel, or their alloys. In other embodiments, the metal reflective layer  13  can be formed by stacking a plurality of layers. For example, a high-conductive material is provided to contact the epitaxial structure layer  12 , and one or more composite layers (e.g. a layer of high-reflective material, barrier layer, etc.) are formed on the high-conductive material. Herein, the barrier layer is configured to prevent the reaction of the metal material and the light conversion layer  14 , which may decrease the light conversion efficiency. 
     Namely, the reflective portion  131  is used to reflect (block) the light emitted from the micro LED unit  121 . Since there is one micro LED unit  121  configured between two reflective portions  131 , the light emitted from the micro LED unit  121  can be reflected by the reflective portion  131  surrounding the upper side of the micro LED unit  121  and then outputted via the through hole. Therefore, the arrangement of the reflective portions  131  can improve the light-emitting efficiency, and at the same time prevent the problem of light crosstalk between the sub-pixels (the micro LED units  121 ). The closer the reflective portion  131  is to the light-emitting layer  121   b  of the adjacent micro LED unit  121 , the better the reflection (light blocking) effect. In this embodiment, the distance between the reflective portion  131  and the corresponding ion implantation region I may be greater than 0 and less than or equal to 2 µm. In other words, each reflective portion  131  is disposed adjacent to but not in contact with the corresponding ion implantation region I. In addition, when applied to devices with high brightness and high current density (e.g. AR device), the configuration of the reflective portions  131  can also reduce power consumption and improve the current crowding effect. 
     In this embodiment, the depth  d   1  of the groove G of the epitaxial structure layer  12  is less than the shortest distance  d   2  between the top surface of the corresponding reflective portion  131  and the second surface S 122  ( d   1 &lt; d   2 ), but this disclosure is not limited thereto. In different embodiments, the depth  d   1  may be greater than the shortest distance  d   2 . In different embodiments, the depth  d   1  and the shortest distance  d   2  are substantially equal. In some embodiments, the depth  d   1  of the groove G is, for example, 3 µm. In some embodiments, the shortest distance  d   2  between the top surface of the reflective portion  131  and the second surface S 122  is, for example, 9 µm. 
     The light conversion layer  14  is disposed in a part of the light transmission regions  132 , and the light conversion layer  14  is configured to convert the wavelengths of lights emitted from the corresponding micro LED units  121 . In this embodiment, the light conversion layer  14  includes a plurality of separated light conversion portions  141   a  and  141   b , which are located in the corresponding light transmission regions  131 , respectively. Each light conversion portion  141   a  or  141   b  corresponds to one of the micro LED unit  121 . Specifically, in three sub-pixels of one pixel P, the light transmission regions  131  in two sub-pixels are filled with the materials of light conversion portions  141   a  and  141   b  for converting the lights into different wavelengths. Herein, the light conversion layer  14  (the light conversion portion  141   a  or  141   b ) includes a light conversion material, such as quantum dots, phosphorescent material or fluorescent material. In this embodiment, the light conversion material includes quantum dots, which can form the light conversion portions  141   a  and  141   b . The quantum dots of different sizes can be excited to produce lights of different colors. For example, the quantum dots of different sizes can be excited by blue light to produce red light and green light. The shape of the light conversion portions  141   a  and  141   b  of the present embodiment is, for example, an inverted cone shape, and the cross-sectional shape thereof is, for example, a polygonal shape (e.g., an inverted trapezoid shape), but this disclosure is not limited thereto. 
     In this embodiment, the micro LED display device  1  further includes a light filter layer  16  disposed at one side of the light conversion layer  14  away from the epitaxial structure layer  12 . The light filter layer  16  is also filled into a part of the light transmission regions  132 . The light filter layer  16  includes a plurality of light filter portions  161   a  and  161   b , and the light filter portions  161   a  and  161   b  are disposed corresponding to and overlapped with the light conversion portions  141   a  and  141   b , respectively (e.g. in one-to-one manner). In practice, after the reflective portions  131  of the metal reflective layer  13  defines the plurality of separated light transmission regions  132 , the material of the light conversion portions  141   a  and  141   b  and the material of the light filter portions  161   a  and  161   b  are disposed in the corresponding light transmission regions  131  in order. Accordingly, the light conversion portion  141   a  and the light filter portion  161   a  can be formed corresponding to one of the micro LED units  121  (i.e., the region of one sub-pixel), and the light conversion portion  141   b  and the light filter portion  161   b  can be formed corresponding to another one of the micro LED units  121 . In this embodiment, the light filter portions  161   a  and  161   b  may include different light filter materials for different color lights, such as a red light filter material and a green light filter material, respectively. Accordingly, in each of the light conversion regions  132  corresponding to the light conversion portions  141   a  and  141   b  and the light filter portions  161   a  and  161   b , the light (e.g. blue light) emitted from the corresponding sub-pixel (i.e., the corresponding micro LED unit  121 ) can be converted by the corresponding light conversion portion (141a or  141   b ) to generate the desired color light (e.g., red light or green light), which will pass through the corresponding light filter portion (161a or  161   b ) and then being outputted. In other embodiments, for example, if the thickness of the light conversion portions  141   a  and  141   b  is large enough to make the color purity of light reach the requirement, it is possible to remove the light filter layer  16  (the light filter portions  161   a  and  161   b ). In addition, when a thicker light conversion layer  14  (the light conversion portions  141   a  and  141   b ) is used to obtain a higher color purity of light, a thicker conductive portion  131  is also needed. In different embodiments, the micro LED units  121  may be cooperated with other corresponding light conversion portions (and/or light filter portions) so as to generate the light of different color (e.g., yellow light or white light), but this disclosure is not limited thereto. To be noted, the “depth”, “thickness”, “distance” or “height” mentioned in this disclosure refers to the depth, thickness, distance or height in the direction D perpendicular to the bonding surface S 111  or the first surface S 121  of the epitaxial structure layer  12 , and the “width” mentioned in this disclosure refers to the width in the direction parallel to the bonding surface S 111  or the first surface S 121  of the epitaxial structure layer  12   
     The light-shielding structure  15  includes a plurality of light-shielding portions  151 , and the light-shielding portions  151  are disposed on the reflective portions  131 . Each of the light-shielding portions  151  is located around the corresponding light transmission region  132 , and the light-shielding portions  151  do not cover the light transmission regions  132 . In other words, the light-shielding structure  15  does not block the corresponding light transmission region  132  (the light conversion portion  141   a ,  141   b  or the light filter portion  161   a ,  161   b ) in the direction D perpendicular to the first surface S 121  of the epitaxial structure layer  12 , so that the light can be outputted. The material of the light-shielding structure  15  (including the light-shielding portions  151 ) can be a conductive or insulation opaque material (e.g., a black material) for shielding or absorbing the light so as to prevent the decrease of display quality caused by the reflection of environmental light (e.g. glare, decrease in contrast, etc.). 
     As mentioned above, when the micro LED display device  1  is enabled, for example, the first electrode  111  can have a high potential, and the second electrode  112  can have a ground potential or a low potential. The current generated by the potential difference between the first electrode  111  and the second electrode  112  (i.e., the driving voltage) can enable the corresponding micro LED units  121  to emit the corresponding red light, green light and blue light. More specifically, in the micro LED display device  1 , the driving element (e.g., an active element such as TFT) of the circuit substrate  11  can control to apply different voltages through the corresponding conductive patterns and/or circuit layers, thereby making the corresponding first electrodes  111  have different high potentials. Accordingly, the micro LED units  121  can emit blue light, and the emitted light can then be converted to the red light and green light by the light conversion portions  141   a ,  141   b  and the light filter portions  161   a ,  161   b . The spatial distribution of these light beams with different colors and different intensities can form an image that can be seen by viewers, so that the micro LED display device  1  can function as a full-color display device. 
     Different from the conventional process of manufacturing the micro LED units by etching, this embodiment implants ions on the first surface S 121  facing the circuit substrate  11  to form a plurality of separated ion implantation regions I, thereby defining a plurality of micro LED units  121 . Accordingly, this embodiment can prevent the damage of the surface of micro light-emitting component, thereby remaining the light-emitting efficiency. In addition, the micro LED display device  1  of this embodiment further includes a metal reflective layer  13  for assisting the current transmission of each micro LED unit  121  and increasing the conductivity of common electrode to enhance the light-emitting efficiency of micro LED units  121 . Moreover, (the reflective portion  131  of) the metal reflective layer  13  has a reflection or light concentrating function, which can avoid the light crosstalk problem between sub-pixels (micro LED units  121 ). 
       FIGS.  2 A to  2 F  are schematic diagrams showing micro LED display devices according to different embodiments of this disclosure. 
     As shown in  FIG.  2 A , the component configurations and connections of the micro LED display device  1   a  of this embodiment are most the same as those of the micro LED display device  1  of the previous embodiment. Unlike the previous embodiment, the micro LED display device  1   a  of this embodiment further includes a light transmission layer  17 , which is disposed at one side of the light conversion layer  14  away from the epitaxial structure layer  12 . In this embodiment, the light transmission layer  17  covers parts of the light-shielding structure  15  (the light-shielding portion  151 ) and the light filter layer  16  (the light filter portions  161   a  and  161   b ), and a part of the material of the light transmission layer  17  fills into the light transmission regions  132 , which are not configured with the light conversion layer  14  (and the light filter layer  16 ). The light transmission layer  17  can be a light transmission film, and the material thereof may include, for example, acrylic (e.g. PMMA with a density of 1.18 g/cm 3 ), epoxy (with a density of 1.1~1.4 g/cm 3 ), or polyurethane (PU), but this disclosure is not limited thereto. For example, the material of the light transmission layer  17  may include inorganic materials, such as silicon oxide (SiO x ), titanium dioxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), silicon nitride (SiN x ), or the like. In addition, the thickness of the light transmission layer  17  can be less than or equal to 20 µm, and preferably less than 0.5 µm (e.g., 0.15 µm). If the light transmission layer  17  has a thinner thickness, the light transmission layer  17  covers the side walls of the light transmission regions  132 , which are not configured with the light conversion structure  14  and the light filter layer  16 . In other words, the light transmission layer  17  forms a nonplanar surface, which is based on the geometry of the covered layers, instead of forming a planar surface in a whole. In some embodiments, the light transmission layer  17  can be, for example but not limited to, an anti-reflection film, an anti-glare film, an anti-finger printing film, a waterproof and antifouling film, or an anti-scratch film, or a combination thereof, and this disclosure is not limited. The light transmission layer  17  of this embodiment can be applied to any of other embodiments of this disclosure. 
     As shown in  FIG.  2 B , the component configurations and connections of the micro LED display device  1   b  of this embodiment are most the same as those of the micro LED display device of the previous embodiment. Unlike the previous embodiment, in the micro LED display device  1   b  of this embodiment, the epitaxial structure layer  12  further includes an outside surface S 123 , the outside surface S 123  connects the first surface S 121  and the second surface S 122 , and the conductive member C extends from the second electrode  112  to the outside surface S 123  of the epitaxial structure layer  12 . The circuit substrate  11  outputs a common electrode signal to the epitaxial structure layer  12  through the common electrode (the second electrode  112 ) and the conductive member C connecting to the outside surface S 123 . The feature of this embodiment that transmits the common electrode signal to the epitaxial structure layer  12  through the conductive member C connecting to the outside surface S 123  can be applied to any of other embodiments of this disclosure. 
     As shown in  FIG.  2 C , the component configurations and connections of the micro LED display device  1   c  of this embodiment are most the same as those of the micro LED display device of the previous embodiment. Unlike the previous embodiment, in the micro LED display device  1   c  of this embodiment, the vertical distance  d   2  between the top surface of each reflective portion  131  and the second surface S 122  is almost the same as the depth  d   1  of the groove G ( d   1  ≒  d   2 , e.g. about 3 µm). Moreover, one side (top surface) of each reflective portion  131  away from the epitaxial structure layer  12  is configured with a concave portion  1311 , and the material of each light-shielding portion  151  is filled into the corresponding concave portion  1311 . 
     As shown in  FIG.  2 D , the component configurations and connections of the micro LED display device  1   d  of this embodiment are most the same as those of the micro LED display device of the previous embodiment. Unlike the previous embodiment, in the micro LED display device  1   d  of this embodiment, the depth  d   1  of the groove G is greater than the distance  d   2  between the top surface of the corresponding reflective portion  131  and the second surface S 122  ( d   1 &gt; d   2 ) 
     As shown in  FIG.  2 E , the component configurations and connections of the micro LED display device  1   e  of this embodiment are most the same as those of the micro LED display device of the previous embodiment. Unlike the previous embodiment, in the micro LED display device  1   e  of this embodiment, each reflective portion  131  directly contacts the corresponding ion implantation region I so as to obtain the best reflection (light blocking) effect, thereby further decreasing the problem of light crosstalk and improving the display quality. 
     As shown in  FIG.  2 F , the component configurations and connections of the micro LED display device  1   f  of this embodiment are most the same as those of the micro LED display device of the previous embodiment. Unlike the previous embodiment, the micro LED display device  1   f  of this embodiment includes a light filter substrate  18 , which is disposed at one side of the metal reflective layer  13  away from the epitaxial structure layer  12 , instead of the light filter layer  16 . In this embodiment, the light filter substrate  18  includes a plurality of light filter portions  181   a  and  181   b , and a substrate  182 . The light filter portions  181   a  and  181   b  are arranged on a surface of the substrate  182  facing the light conversion layer  14 , and the light filter portions  181   a  and  181   b  are located corresponding to the light conversion portions  141   a  and  141   b , respectively (in a one-to-one manner). In this embodiment, the light filter portions  181   a  and  181   b  may also include different light filter materials for different color lights, such as a red light filter material and a green light filter material, respectively. Accordingly, in each of the light conversion regions  132  corresponding to the light conversion portions  141   a  and  141   b  and the light filter portions  181   a  and  181   b , the light (e.g. blue light) emitted from the corresponding sub-pixel (i.e., the corresponding micro LED unit  121 ) can be converted by the corresponding light conversion portion (141a or  141   b ) to generate the desired color light (e.g., red light or green light), which will pass through the corresponding light filter portion ( 181   a  or  181   b ) and then being outputted. The light filter substrate  18  of this embodiment can be applied to any of other embodiments of this disclosure. 
     In summary, without utilizing the conventional etching process in the manufacturing of micro LED units, this disclosure implants ions on the first surface of the epitaxial structure layer facing the circuit substrate to form a plurality of separated ion implantation regions, thereby defining a plurality of micro LED units. Accordingly, this disclosure can prevent the damage of the sidewall of micro light-emitting component, thereby remaining the light-emitting efficiency. In addition, this disclosure further provides a metal reflective layer for increasing the conductivity of common electrode to enhance the light-emitting efficiency of micro LED display device. Moreover, the metal reflective layer has a reflection or light concentrating function, which can avoid the light crosstalk problem between sub-pixels and thus match the demand for high-resolution display. 
     Although the disclosure has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the disclosure.