Patent Publication Number: US-2022216381-A1

Title: Micro led display device and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to China Application Serial Number 202110003650.1, filed Jan. 4, 2021, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     Field of Invention 
     The present disclosure relates to a micro light emitting diode (LED) device and a method of manufacturing the micro LED display device. 
     Description of Related Art 
     Micro light emitting diodes (LEDs) have advantages of display techniques of liquid crystal displays and organic LEDs, and can be considered as a display technique of the latest generation. The type of light field of micro LEDs is typically a Lambertian distribution. Thus, micro LEDs applied in image display devices require additional structures for collocation, such as color conversion layer, optical fiber coupler, lens array, etc. 
     Color conversion layer converts light from blue micro LEDs to red, green, and blue lights (i.e., three primary colors). Given that only blue light micro LEDs are used, a greatest NTSC standard from mixing red, green, and blue light cannot be achieved. Additionally, optical fiber coupler couples red, green, and blue light into a same optical fiber, but the related technical difficulty and fabrication cost are high. Furthermore, each micro LED of the lens array needs to be configured to a corresponding lens, using the lens to restrict the wide angle light of the micro LED so as to achieve the desired type of light field. This fabrication method has a high cost and is difficult to achieve light uniformity. 
     Most current micro LED display devices are in research and development stages. Achieving mass production standard for these display and fabrication techniques is a significant challenge. 
     SUMMARY 
     An aspect of the present disclosure provides a micro light emitting diode (LED) display device. 
     According to some embodiments of the present disclosure, a micro LED display device includes a substrate, a plurality of LED dies, a protection layer, and a funnel-tube structure array. The plurality of micro LED dies are located on the substrate. The protection layer covers the micro LED dies and the substrate. The funnel-tube structure array is located on the protection layer, and includes a plurality of funnel-tube structures. Each of the funnel-tube structures has a top surface facing away from the protection layer. The funnel-tube structures respectively overlap the micro LED dies in a vertical direction, and widths of the funnel-tube structures are gradually increased from the protection layer to the top surfaces of the funnel-tube structures. 
     In some embodiments of the present disclosure, each of the funnel-tube structures has a sloped edge, an acute angle is included between the sloped edge and the protection layer, and the acute angle is in a range from 45 degrees to 85 degrees. 
     In some embodiments of the present disclosure, a material of the funnel-tube structures includes negative photoresist. 
     In some embodiments of the present disclosure, the micro LED dies include a red micro LED die, a green micro LED die, and a blue micro LED die, the funnel-tube structures are transparent and have a refractive index in a range from 1.5 to 2. 
     In some embodiments of the present disclosure, the micro LED dies are blue micro LED dies, and the funnel-tube structures include a red photoresist, a green photoresist, and a blue photoresist. 
     In some embodiments of the present disclosure, wherein a material of the funnel-tube structures includes titanium dioxide or quantum dots. 
     In some embodiments of the present disclosure, areas of the top surfaces of the funnel-tube structures are greater than areas of bottom surfaces of the funnel-tube structures. 
     In some embodiments of the present disclosure, lengthwise axes of the funnel-tube structures respectively pass through centers of the micro LED dies. 
     In some embodiments of the present disclosure, the funnel-tube structures directly contact the protection layer. 
     In some embodiments of the present disclosure, the protection layer is located between the funnel-tube structures and the micro LED dies. 
     Another aspect of the present disclosure provides a method of manufacturing a micro LED display device. 
     According to some embodiments of the present disclosure, a method of manufacturing a micro LED display device includes: disposing a plurality of micro LED dies on a substrate; forming a protection layer covering the micro LED dies and the substrate; and forming a funnel-tube structure array having a plurality of funnel-tube structures on the protection layer, wherein the funnel-tube structures respectively overlap the micro LED dies in a vertical direction, and widths of the funnel-tube structures are gradually increased from the protection layer to top surfaces of the funnel-tube structures. 
     In some embodiments of the present disclosure, forming the funnel-tube structure array on the protection layer includes: forming a negative photoresist on the protection layer; exposing the negative photoresist to ultraviolet light; and etching the negative photoresist to form the funnel-tube structure array. 
     In some embodiments of the present disclosure, exposing the negative photoresist to ultraviolet light includes: passing the ultraviolet light through a plurality of translucent regions of a photomask, wherein the translucent regions respectively align with the micro LED dies in a vertical direction, and a width of each of the translucent regions is greater than or equal to a width of each of the micro LED dies. 
     In some embodiments of the present disclosure, the method of manufacturing the micro LED display device further includes placing the photomask near a top surface of the negative photoresist. 
     In some embodiments of the present disclosure, etching the negative photoresist is performed such that the negative photoresist has a sloped edge, and an acute angle is included between the sloped edge and the protection layer. 
     In some embodiments of the present disclosure, forming the funnel-tube structure array on the protection layer includes: forming a positive photoresist on the protection layer; exposing the positive photoresist to ultraviolet light; etching the positive photoresist to form a plurality of openings above the micro LED dies; and forming a filling material in the openings of the positive photoresist to form the funnel-tube structure array. 
     In some embodiments of the present disclosure, exposing the positive photoresist to ultraviolet light includes passing the ultraviolet light through a plurality of translucent regions of a photomask, wherein the translucent regions respectively align with the micro LED dies in a vertical direction, and a width of each of the translucent regions is greater than or equal to a width of each of the micro LED dies. 
     In some embodiments of the present disclosure, the method of manufacturing the micro LED display device further includes placing the photomask near a top surface of the positive photoresist. 
     In some embodiments of the present disclosure, the method of manufacturing the micro LED display device further includes after forming the filling material in the openings of the positive photoresist, removing the positive photoresist. 
     In some embodiments of the present disclosure, etching the positive photoresist is performed such that the positive photoresist has a sloped edge, and an obtuse angle is included between the sloped edge and the protection layer. 
     In the aforementioned embodiments of the present disclosure, since the micro LED display device has the funnel-tube structure located on the protection layer, and the width of the funnel-tube structure is gradually increased from the protection layer to the top surface of the funnel-tube structure, when the micro LED die under the funnel-tube structure emits light, the light emitted by the micro LED die can enter the funnel-tube structure and be totally internally reflected at the sloped edge of the funnel-tube structure. As a result, a light emitting efficiency of the micro LED display device can be increased, and light at a wide angle from the micro LED die can be restricted, thereby achieving a desired type of light field and facilitating a light uniformity of the micro LED display device. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  shows a top view of a micro light emitting diode (LED) display device according to embodiments of the present disclosure. 
         FIG. 2  shows a cross-sectional view of the micro LED display device of  FIG. 1  along a line  2 - 2 . 
         FIG. 3  shows a flowchart of a method of manufacturing a micro LED display device according to some embodiments of the present disclosure. 
         FIG. 4 ,  FIG. 5 , and  FIG. 7  show cross-sectional views of intermediate steps of the method of manufacturing the micro LED display device of  FIG. 3 . 
         FIG. 6  shows a bottom view of a photomask of  FIG. 5 . 
         FIG. 8  shows a flowchart of a method of manufacturing a micro LED display device according to other embodiments of the present disclosure. 
         FIG. 9  to  FIG. 12  show cross-sectional views of intermediate steps of the method of manufacturing the micro LED display device of  FIG. 8 . 
         FIG. 13  shows a perspective view of funnel-tube structures and an array of micro LED dies array according to some embodiments of the present disclosure. 
         FIG. 14  shows an illumination distribution of the funnel-tube structures and the array of the micro LED dies of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated  90  degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
       FIG. 1  shows a top view of a micro light emitting diode (LED) display device  100  according to embodiments of the present disclosure.  FIG. 2  shows a cross-sectional view of the micro LED display device  100  of  FIG. 1  along a line  2 - 2 . Referring to  FIG. 1  and  FIG. 2 , the micro LED display device  100  includes a substrate  110 , a plurality of micro LED (μLED) dies  120 , a protection layer  130 , and a funnel-tube structure array  141  having a plurality of funnel-tube structures  140 . The micro LED dies  120  are located on the substrate  110 . The micro LED dies  120  can be red, green, or blue micro LED dies, and the die arrangement is not limited in the present disclosure. The substrate  110  may have a transistor and an electrode to light up the micro LED dies  120 . The protection layer  130  covers the micro LED dies  120  and the substrate  110 . A material of the protection layer  130  may be transparent acrylic adhesive, but is not limited thereto. The protection layer  130  can prevent the underlying micro LED dies  120  and conductive lines from being corroded. 
     The funnel-tube structure array  141  is located on the protection layer  130 . The funnel-tube structure  140  has a refractive index greater than the refractive index of the micro LED die  120 . The micro LED die  120  has a refractive index greater than the refractive index of the protection layer  130 . The funnel-tube structure  140  has a top surface  142  facing away from the protection layer  130 , and a bottom surface  144  facing toward the protection layer  130 . The funnel-tube structures  140  respectively overlap the micro LED dies  120  in a vertical direction, and a width W 1  of the funnel-tube structure  140  is gradually increased from the protection layer  130  toward the top surface  142  of the funnel-tube structure  140 . In other words, the funnel-tube structure  140  has a sloped edge  146 , and an area of the top surface  142  of the funnel-tube structure  140  is greater than an area of the bottom surface  144  of the funnel-tube structure  140 . For example, a radius of the top surface  142  is in the range from 3 μm to 30 μm, a radius of the bottom surface  144  is in the range from 0 μm to 15 μm, a height of the funnel-tube structure  140  is in the range from 3 μm to 10 μm. Additionally, an acute angle θ 1  is included between the sloped edge  146  of the funnel-tube structure  140  and the protection layer  130 . In some embodiments, the acute angle θ 1  between the sloped edge  146  of the funnel-tube structure  140  and the protection layer  130  may be in the range from 45 degrees to 85 degrees, thereby facilitating total internal reflection (TIR) inside the funnel-tube structure  140 . 
     Since the micro LED display device  100  has the funnel-tube structure  140  located on the protection layer  130 , and the width W 1  of the funnel-tube structure  140  is gradually increased from the protection layer  130  to the top surface  142  of the funnel-tube structure  140 , when the micro LED die  120  under the funnel-tube structure  140  emits light, the light L emitted by the micro LED die  120  can enter the funnel-tube structure  140  and be totally internally reflected at the sloped edge  146  of the funnel-tube structure  140 . As a result, a light emitting efficiency of the micro LED display device  100  is increased, and light at a wide angle from the micro LED die  120  are restricted, thereby achieving a desired type of light field and facilitating a light uniformity of the micro LED display device  100 . 
     In some embodiments, a material of the funnel-tube structure  140  can be a negative photoresist, titanium dioxide, or quantum dots (QDs), the manufacturing method of which can use a photolithography technique (described in  FIG. 3  to  FIG. 12 ) to form an opening O 1  between two neighboring funnel-tube structures  140 , thereby forming the array of the funnel-tube structures  140 . Neighboring funnel-tube structures  140  can be formed by red, green, and blue photoresists (described in  FIG. 3  to  FIG. 7 ), or be formed by filling red, green, and blue quantum dots into etched photoresist (described in  FIG. 8  to  FIG. 12 ). In some embodiments, the micro LED dies  120  may include red micro LED dies, green micro LED dies, and blue micro LED dies. The funnel-tube structure  140  is transparent and has a refractive index in a range from 1.5 to 2, thereby facilitating to transmit light upward. Furthermore, in some embodiments, the micro LED dies  120  are all blue micro LED dies, and the funnel-tube structures  140  include red photoresist, green photoresist, and blue photoresist. 
     In some embodiments, a lengthwise axis Z of the funnel-tube structure  140  may pass through the center of the micro LED die  120 , such that the funnel-tube structure  140  is aligned with the micro LED die  120 . Moreover, the funnel-tube structure  140  may directly contact a top surface of the protection layer  130 , and the protection layer  130  is located between the funnel-tube structure  140  and the micro LED die  120 . 
     The micro LED display device  100  further includes a cover  150 , which serves as an upper substrate of the micro LED display device  100 , and can protect the funnel-tube structure  140  and prevent the funnel-tube structure  140  from being contaminated. 
     It is to be noted that connections and relationships between elements, materials, and functions already described are not repeated below. In the following description, a method of manufacturing the micro LED display device  100  of  FIG. 2  is to be explained. 
       FIG. 3  shows a flowchart of a method of manufacturing a micro LED display device according to some embodiments of the present disclosure. In step S 1 , a plurality of micro LED dies are disposed on a substrate. Then in step S 2 , a protection layer is formed to cover the micro LED dies and the substrate. Then in step S 3 , a negative photoresist is formed on the protection layer. Then in step S 4 , the negative photoresist is exposed to ultraviolet light. Then in step S 5 , the negative photoresist is etched to form a funnel-tube structure array. In some embodiments, the method of manufacturing the micro LED display device is not limited to the above steps S 1  to S 5 , and can further include other steps between two of the above steps, or steps S 1  to S 5  can each include multiple detailed steps. In the following description, each step of the method of manufacturing the abovementioned micro light emitting display device is to be explained. 
       FIG. 4 ,  FIG. 5 , and  FIG. 7  show cross-sectional views of intermediate steps of the method of manufacturing the micro LED display device of  FIG. 3 . Referring to  FIG. 4 , the micro LED die  120  can be located on the substrate  110  by a method of transferring, the micro LED dies  120  on the substrate  110  may be of the same color (such as blue) or different colors (such as red, green, and blue), and the arrangement of the micro LED dies  120  may be determined as deemed necessary by design. After the micro LED dies  120  are located on the substrate  110 , the protection layer  130  may be formed to cover the micro LED dies  120  and the substrate  110 . 
     Referring to  FIG. 4  and  FIG. 5 , after forming the protection layer  130 , a negative photoresist  140   a  can be formed on the protection layer  130 . A thickness of the micro LED dies  120  may be about 7 μm. A thickness of the protection layer  130  being close to the thickness of the micro LED dies  120  has a positive effect on the light emitting efficiency. In some embodiments, the negative photoresist  140   a  may be formed on the protection layer  130  by spin coating. Then, the negative photoresist  140   a  can be exposed to ultraviolet light UV. In this step, a photomask  200  can be placed near the top surface of the negative photoresist  140   a,  and allow the ultraviolet light UV to pass through a plurality of translucent regions  202  of the photomask  200 , thereby exposing the negative photoresist  140   a  to light. The translucent regions  202  of the photomask  200  respectively align with the micro LED dies  120  in a vertical direction, and a width W 2  of each of the translucent regions  202  is greater than or equal to a width W 3  of each of the micro LED dies  120 , such that the negative photoresist  140   a  above the micro LED dies  120  are preserved in subsequent steps. Additionally, a material of the photomask  200  may be glass, but is not limited thereto. The negative photoresist  140   a  may be transparent, and may have a refractive index of 1.79, but the present disclosure is not limited in this regard. 
       FIG. 6  shows a bottom view of the photomask  200  of  FIG. 5 . Referring to  FIG. 5  and  FIG. 6 , a light shielding region  204  of the photomask  200  surrounds the translucent regions  202 . The ultraviolet light UV can pass through the translucent regions  202  of the photomask  200 , but is blocked by the light shielding region  204 . A strength of the ultraviolet light UV decreases from a center of the translucent region  202  toward the light shielding region  204 . A region of the negative photoresist  140   a  exposed to light through the translucent region  202  of the photomask  200  is insoluble, and a region of the negative photoresist  140   a  not exposed to light through the translucent region  202  of the photomask  200  is soluble. The above step can be performed by contact exposure. When the ultraviolet light UV passes through the translucent regions  202  of the photomask  200 , a diffraction effect occurs. 
     Referring to  FIG. 7 , after exposing and developing the negative photoresist  140   a,  the negative photoresist  140   a  can be etched. Due to the diffraction effect, an edge (a sidewall) of the exposed and developed negative photoresist  140   a  is not perpendicular to the protection layer  130 , such that the funnel-tube structure  140  can be formed. Neighboring funnel-tube structures  140  may be formed by red, green, and blue negative photoresist  140   a.  After the step of etching the negative photoresist  140   a,  the negative photoresist  140   a  can have the sloped edge  146 , and the acute angle θ 1  is included between the sloped edge  146  and the protection layer  130 . The acute angle θ 1  may be in a range from 45 degrees to 85 degrees. 
     After the above steps, the funnel-tube structure array  141  made of the negative photoresist  140   a  may be formed on the protection layer  130 , wherein the funnel-tube structures  140  respectively overlap the micro LED dies  120  in a vertical direction, and the width W 1  of each of the funnel-tube structures  140  is gradually increased from the protection layer  130  toward the top surface  142  of the funnel-tube structure  140 . In other words, the width W 1  of the funnel-tube structure  140  is increased in a direction away from the micro LED die  120  (upward). Using slit diffraction effect combined with semiconductor manufacturing techniques, the array of the funnel-tube structures  140  can be made. The manufacturing method of the present disclosure related to the funnel-tube structure  140  can be applied to mass production, and has advantages of simple fabrication and low cost. 
     After forming the funnel-tube structures  140 , the cover  150  (see  FIG. 2 ) can be disposed on the funnel-tube structures  140  of  FIG. 7 , so as to obtain the micro LED display device  100  of  FIG. 2 . 
     It is to be noted that connections and relationships between elements, materials, and functions already described are not repeated below. In the following description, another method of manufacturing the micro LED display device  100  of  FIG. 2  is to be explained. 
       FIG. 8  shows a flowchart of a method of manufacturing a micro LED display device according to other embodiments of the present disclosure. In step S 1 ′, a plurality of micro LED dies are disposed on a substrate. Then in step S 2 ′, a protection layer is formed to cover the micro LED dies and the substrate. Then in step S 3 ′, a positive photoresist is formed on the protection layer. Then in step S 4 ′, the positive photoresist is exposed to ultraviolet light. Then in step S 5 ′, the positive photoresist is etched to form a plurality of openings above the micro LED dies. Then in step S 6 ′, a filling material is formed in the openings to form a funnel-tube structure array. In some embodiments, the method of manufacturing the micro LED display device is not limited to the above steps Si&#39; to S 6 ′, and can further include for example other steps between two of the above steps, or steps S 1  to S 5  can each include multiple detailed steps. In the following description, each step of the method of manufacturing the abovementioned micro light emitting display device is to be explained. 
       FIG. 9  to  FIG. 12  show cross-sectional views of intermediate steps of the method of manufacturing the micro LED display device of  FIG. 8 . Referring to  FIG. 9 , the method of forming the micro LED dies  120 , the protection layer  130 , and the substrate  110  is similar to the method of  FIG. 4 . The micro LED die  120  may be located on the substrate  110  by a method of transferring, the micro LED dies  120  on the substrate  110  may be of the same color (such as blue) or different colors (such as red, green, and blue), and the arrangement of the micro LED dies  120  may be determined as deemed necessary by design. After the micro LED dies  120  are located on the substrate  110 , the protection layer  130  can be formed to cover the micro LED dies  120  and the substrate  110 . 
     After forming the protection layer  130 , a positive photoresist  140   b  can be formed on the protection layer  130 . In some embodiments, the positive photoresist  140   b  can be formed on the protection layer  130  by spin coating. Then, the positive photoresist  140   b  can be exposed to ultraviolet light UV. In this step, a photomask  200  can be placed near the top surface of the positive photoresist  140   b,  and allow the ultraviolet light UV to pass through a plurality of translucent regions  202  of the photomask  200 , thereby exposing the positive photoresist  140   b  to light. The translucent regions  202  of the photomask  200  respectively align with the micro LED dies  120  in a vertical direction, and a width W 2  of each of the translucent regions  202  is greater than or equal to a width W 3  of each of the micro LED dies  120 , such that the positive photoresist  140   b  directly above the micro LED dies  120  is removed in subsequent steps. Additionally, a material of the photomask  200  may be glass, but is not limited thereto. The positive photoresist  140   b  may be transparent, but the present disclosure is not limited in this regard. 
     The photomask  200  of  FIG. 9  has a same bottom view as that of  FIG. 6 . 
     Referring to  FIG. 6  and  FIG. 9 , the light shielding region  204  of the photomask  200  surrounds the translucent regions  202 . The ultraviolet light UV can pass through the translucent regions  202  of the photomask  200 , but is blocked by the light shielding region  204 . A strength of the ultraviolet light UV decreases from a center of the translucent region  202  toward the light shielding region  204 . A region of the positive photoresist  140   b  exposed to light through the translucent region  202  of the photomask  200  is soluble, and a region of the positive photoresist  140   b  not exposed to light through the translucent region  202  of the photomask  200  is insoluble. The above step may be performed by contact exposure. When the ultraviolet light UV passes through the translucent regions  202  of the photomask  200 , a diffraction effect occurs. 
     Referring to  FIG. 10 , after exposing and developing the positive photoresist  140   b,  the positive photoresist  140   b  can be etched to form openings  02  above the micro LED dies  120 . Due to the diffraction effect, an edge (a sidewall) of the exposed and developed positive photoresist  140   b  is not perpendicular to the protection layer  130 , such that the positive photoresist  140   b  can have a sloped edge  141 . An obtuse angle θ 2  is included between the sloped edge  141  and the protection layer  130 . The obtuse angle θ 2  can be in a range from 95 degrees to 135 degrees. 
     Referring to  FIG. 10  and  FIG. 11 , after the openings  02  of the positive photoresist  140   b  are formed, a filling material  160  can be formed in the openings O 2  of the positive photoresist  140   b.  In some embodiments, the filling material  160  includes titanium dioxide or quantum dots. The filling material  160  may form the funnel-tube structure  140  in subsequent steps. The quantum dots can improve the color rendering and increase the light emitting efficiency. 
     Neighboring funnel-tube structures  140  can be formed by filling red, green, and blue quantum dots after etching the positive photoresist  140   b.  In other embodiments, the designer can select an appropriate filling material  160  as the funnel-tube structure  140 , thereby increasing the flexibility of the material selection. 
     Referring to  FIG. 11  and  FIG. 12 , after forming the filling material  160  in the openings O 2  of the positive photoresist  140   b,  the positive photoresist  140   b  can be removed, such that two neighboring filling materials  160  have an opening O 3  therebetween. Due to the sloped edge  141  of the positive photoresist  140   b  of  FIG. 11 , the filling material  160  may have a sloped edge  146  after filling the filling material  160  in the positive photoresist  140   b,  an acute angle θ 1  is included between the sloped edge  146  and the protection layer  130 . The acute angle θ 1  may be in a range from 45 degrees to 85 degrees, and is supplementary with the obtuse angle θ 2  of  FIG. 10 . 
     After the above steps, the funnel-tube structure array  141  made of the filling material  160  (such as titanium dioxide or quantum dots) can be formed on the protection layer  130 , wherein the funnel-tube structures  140  respectively overlap the micro LED dies  120  in a vertical direction, and the width W 1  of the funnel-tube structure  140  is gradually increased from the protection layer  130  toward the top surface  142  of the funnel-tube structure  140 . In other words, the width W 1  of the funnel-tube structure  140  is increased in a direction away from the micro LED die  120  (upward). Using slit diffraction effect combined with semiconductor manufacturing techniques, the array of the funnel-tube structures  140  can be made. The manufacturing method of the present disclosure related to the funnel-tube structure  140  can be applied to mass production, and has advantages of simple fabrication and low cost. 
     After forming the funnel-tube structures  140 , the cover  150  (see  FIG. 2 ) may be disposed on the funnel-tube structures  140  of  FIG. 12 , so as to obtain the micro LED display device  100  of  FIG. 2 . 
       FIG. 13  shows a perspective view of the funnel-tube structures  140  and an array of the micro LED dies  120  according to some embodiments of the present disclosure. In some embodiments, the funnel-tube structures  140  and the micro LED dies  120  are arranged in a 3×3 array, but the present disclosure is not limited thereto. The funnel-tube structures  140  and the micro LED dies  120  are arranged in an X direction and a Y direction. Each of the funnel-tube structures  140  has the sloped edge  146  and the opposite top surface  142  and bottom surface  144 . The sloped edge  146  is located between the top surface  142  and the bottom surface  144 , and adjoins the top surface  142  and the bottom surface  144 . The bottom surface  144  of the funnel-tube structure  140  faces toward the micro LED die  120 , and the top surface  142  of the funnel-tube structure  140  faces away from the micro LED die  120 . The top surface  142  and the bottom surface  144  of the funnel-tube structure  140  may be rectangular (such as square). In some embodiments, dimensions (such as width or area) of the top surface  142  of the funnel-tube structure  140  are greater than those of the micro LED die  120 . Dimensions (such as width or area) of the bottom surface  144  of the funnel-tube structure  140  are greater than or equal to those of the micro LED die  120 . 
       FIG. 14  shows an illumination distribution of the funnel-tube structures  140  and the array of the micro LED dies  120  of  FIG. 13 . Referring to  FIG. 13  and  FIG. 14 , the funnel-tube structures  140  respectively stand on the micro LED dies  120 , thereby creating functions similar to pixels. Compared with vertical structures, the funnel-tube structures  140  can better enhance light uniformity of the micro LED dies  120 , and increases the light emitting efficiency. It can be seen from  FIG. 14 , that the illumination distribution of the funnel-tube structures  140  and the array of the micro LED dies  120  is very uniform. 
     In summary of the above, because the micro LED display device has the funnel-tube structures located on the protection layer, and the widths of the funnel-tube structures are gradually increased from the protection layer toward the top surfaces of the funnel-tube structures, when the micro LED dies under the funnel-tube structure emit light, the light emitted by the micro LED dies can enter the funnel-tube structures and be totally internally reflected at the sloped edges of the funnel-tube structures. As a result, a light emitting efficiency of the micro LED display device can be increased, and light at a wide angle from the micro LED die is restricted, thereby achieving a desired type of light field and facilitating a light uniformity of the micro LED display device. Additionally, the method of manufacturing the micro LED display device can form the funnel-tube structures made of the negative photoresist or the filling material on the protection layer. Using slit diffraction combined with semiconductor fabrication techniques, an array of the funnel-tube structures can be made. The method of manufacturing the micro LED display device can be applied to mass production, and has advantages of simple fabrication and low cost. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.