Patent Publication Number: US-11031380-B2

Title: Manufacturing method of micro LED display module

Description:
This application claims priority to Taiwan Patent Application No. 106119263 filed on Jun. 9, 2017, which issued as Taiwan Patent No. I611573B on Jan. 11, 2018. 
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a light emitting diode (LED), and particularly, to a manufacturing method of micro LED display module. 
     Descriptions of the Related Art 
     Conventional light emitting diodes (LEDs) are mostly used as backlights of liquid crystal devices (LCDs) or directly as light emitting pixel points of the LEDs. However, when being used directly as light emitting pixel points of the LEDs, the conventional LEDs are mostly used for large-sized advertisement panels but seldom used in consumer electronic products due to the low resolution thereof. 
     As a kind of new display technology, micro LEDs have been developed in recent years. The micro LEDs are accomplished by miniaturizing and thinning LEDs into the micrometer scale and arraying them. In addition to having the advantages of the conventional inorganic LEDs such as high color saturation, high efficiency, high brightness and fast response and, when being used in a display device, being capable of displaying through self-emission without the need of a backlight, the micro LEDs also have the advantages of power saving, and simple in structure, thin and lightweight, and more importantly, the micro LEDs further have a super high resolution. 
     Besides, as compared with the organic LEDs, colors of the micro LEDs are easy to be accurately adjusted, and furthermore, the micro LEDs have advantages such as longer service life-time, higher brightness, less residual image, and better material stability. 
     Generally when micro LEDs described in Taiwan Patent No. 201640697A or the paper “Zhao Jun Liu et al., Monolithic LED Microdisplay on Active Matrix Substrate Using Flip-Chip Technology, IEEE Journal of Selected Topics In Quantum Electronics, pp. 1-5 (2009)” are used to manufacture a display module, micro LEDs of different colors must be manufactured in different batches respectively and are then attached in batches to a control circuit board, then a passivation layer and electrodes are formed through a physical deposition process, and the resulting structure is packaged to complete a micro LED display module. 
     However, because of the minimum volume of the micro LEDs, it is difficult to transfer (pick up and place) and wire bond the micro LEDs during the process of attaching the micro LEDs of different colors in batch, and this leads to low product yield, low production efficiency and high production cost. 
     SUMMARY OF THE INVENTION 
     The present invention provides a manufacturing method of micro LED display module, in which a plurality of micro LEDs is produced in an array form and disposed on a driver chip block so that each of the micro LED pixels is driven individually by pixel electrodes on the driver chip block; and a light transmissive conductive layer or structure (e.g., a semiconductor layer) inside the micro LEDs is used as a common electrode of the plurality of pixels. In this way, each of the micro LEDs can be addressed by the driver chip so as to emit light separately. Besides, the plurality of micro LEDs which are produced in an array form and can be transferred easily in the manufacturing process. 
     In addition, for the display of full-color images by the micro LED display module, a RGB (Red, Green, Blue) color layer may be further disposed, for example, a RGB color filter or quantum dots sprayed layer may be disposed. Therefore, a micro LED display module of high resolution can be produced; and the problem of low product yield that would otherwise be caused during the process of transferring the micro LEDs can be mitigated. 
     To achieve the aforesaid objectives, the present invention provides a manufacturing method of micro light emitting diode (LED) display module, the method comprising the following steps: preparing a LED wafer and a driver circuit wafer, wherein a portion of the LED wafer is defined as a LED block, the LED block has a first semiconductor layer, a light emitting layer and a second semiconductor layer, the light emitting layer is disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer connects with a substrate, one of the first semiconductor layer and the second semiconductor layer is a N-type semiconductor layer and the other is a P-type semiconductor layer, and a chip size portion of the driver circuit wafer is defined as a driver chip block; etching the LED block to form a plurality of trenches arranged crisscrossingly, wherein the trenches define a plurality of micro LED pixels arranged in an array, each of the trenches at least penetrates through the second semiconductor layer and the light emitting layer; bonding the LED block and the driver chip block to each other, wherein the second semiconductor layer is electrically connected to a plurality of pixel electrodes of the driver chip block, and each of the micro LED pixels corresponds to one of the pixel electrodes; and removing the substrate; disposing a light transmissive conductive layer on the first semiconductor layer, wherein the light transmissive conductive layer has a common electrode corresponding to the micro LED pixels; and disposing a color layer on the light transmissive conductive substrate, wherein the color layer is a RGB color layer. 
     To achieve the aforesaid objectives, the present invention provides a micro LED display module, which comprises: a driver chip block, having a plurality of pixel electrodes; a LED block, being disposed on the driver chip block and comprising two semiconductor layers and a plurality of trenches, wherein the light emitting layer is disposed between the two semiconductor layers, one of the two semiconductor layers is electrically connected to the pixel electrodes and the other is connected to a light transmissive conductive layer, the LED block is located between the light transmissive conductive layer and the driver chip block, the trenches define a plurality of micro LED pixels arranged in an array, each of the trenches at least penetrates through the light emitting layer and the semiconductor layer that is electrically connected to the pixel electrodes, each of the micro LED pixels corresponds to one of the pixel electrodes, one of the two semiconductor layers is a N-type semiconductor layer and the other is a P-type semiconductor layer; a circuit board electrically connected to the driver chip block, wherein the driver chip block is located between the LED block and the circuit board; and a color layer, being disposed on the light transmissive conductive layer, wherein the light transmissive conductive layer is located between the color layer and the LED block, and the color layer is a RGB color layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a LED wafer according to the present invention; 
         FIG. 2  is a schematic view of a LED block according to the present invention; 
         FIG. 3  is a schematic cross-sectional view of a LED block according to the present invention; 
         FIG. 4  is a schematic view of a driver circuit wafer according to the present invention; 
         FIG. 5  is a schematic view of a driver chip block according to the present invention; 
         FIGS. 6A to 6I  are schematic views of a first embodiment and other alternative embodiments according to the present invention; 
         FIGS. 7A to 7L  are schematic views of a second embodiment and other alternative embodiments according to the present invention; 
         FIGS. 8A to 8G  are schematic views of a third embodiment and other alternative embodiments according to the present invention; 
         FIGS. 9A to 9H  are schematic views of a fourth embodiment and other alternative embodiments according to the present invention; 
         FIGS. 10 to 11  are schematic views illustrating a step of disposing a color layer according to the present invention; and 
         FIG. 10A  is a partially enlarged view of a color filter according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinbelow, possible implementations of the present invention will be described with reference to embodiments thereof. However, it shall be firstly appreciated that, this is not intended to limit the scope of the present invention. 
     Please refer to  FIG. 1  to  FIG. 5 , which show a LED wafer  110 , a LED block  111 , a driver circuit wafer  120  and a driver chip block  121  to be initially prepared in the manufacturing process of the present invention. For convenience of describing the embodiments of the present invention, unless otherwise stated in this specification, the LED block  111  may represent a portion of the LED wafer  110  which is still integrally connected with other portions of the LED wafer  110  or may be a portion that has already been diced from the LED wafer  110 ; and the driver chip block  121  may represent a portion of the driver circuit wafer  120  which is still integrally connected with other portions of the driver circuit wafer  120  or may be a driver chip that has already been diced from the driver circuit wafer  120 . Each driver chip block  121  has a plurality of pixel electrodes  122  thereon, and each of the pixel electrodes  122  can independently drive a micro LED pixel. 
     That is, the time point at which the LED block  111  is diced from the LED wafer  110  and/or the driver chip block  121  is diced from the driver circuit wafer  120  may be any time point between the step of preparing the LED wafer and the driver circuit wafer and the step of electrically connecting the driver chip block with a circuit board. 
     In the present invention, when the LED wafer  110  and the driver circuit wafer  120  are prepared, some blank regions (e.g., regions where no semiconductor layer, light emitting layer, and pixel electrodes are provided) may be reserved for subsequently disposing electrode pads thereon or for performing dicing procedures thereon. 
     In addition, some lines shown in the drawings are only imaginary lines used in subsequent processes such as etching or dicing processes, and there may be no such lines in practice. 
     Please refer to  FIG. 6C ,  FIG. 6D ,  FIG. 6E ,  FIG. 6G  and  FIG. 6H , which show a first embodiment of the present invention. The manufacturing method of a micro LED display module  600  of this embodiment comprises the following steps. 
     Initially, a LED wafer  610  and a driver circuit wafer  620  are prepared. A portion of the LED wafer  610  is defined as a LED block  611 , and a chip size portion of the driver circuit wafer  620  is defined as a driver chip block  621 . The LED block  611  has a first semiconductor layer, a light emitting layer  616  and a second semiconductor layer. The light emitting layer  616  is disposed between the first semiconductor layer and the second semiconductor layer. The first semiconductor layer connects with a substrate  612 . More specifically, one of the first semiconductor layer and the second semiconductor layer is a N-type semiconductor layer and the other is a P-type semiconductor layer; and in this embodiment, the first semiconductor layer is a N-type semiconductor layer  613  and the second semiconductor layer is a P-type semiconductor layer  617 . The N-type semiconductor layer  613  comprises a N-type doped layer  614  and a N-type buffer layer  615 , and the N-type doped layer  614  is located between the N-type buffer layer  615  and the light emitting layer  616 . The P-type semiconductor layer  617  further comprises a P-type doped layer  618  and a P-type buffer layer  619 , and the P-type doped layer  618  is located between the P-type buffer layer  619  and the light emitting layer  616 . In some embodiments of the present invention, there may not be the N-type or P-type buffer layer. Further speaking, the driver chip block  621  has a layer of integrated circuit (IC) and a plurality of pixel electrodes (on IC layer), wherein each of the pixel electrodes can be independently driven. The N-type doped layer  614  is a negative-pole semiconductor layer that is rich in electrons, and the P-type doped layer  618  is a positive-pole semiconductor layer that is rich in holes. The N-type buffer layer  615  is a transition layer between the N-type doped layer  614  and outside materials. The P-type buffer layer  619  is a transition layer between the P-type doped layers  618  and outside materials. 
     Referring next to  FIG. 6C  and  FIG. 6D , the LED block  611  and the driver chip block  621  are bonded to each other so that the P-type semiconductor layer  617  is electrically connected to a plurality of pixel electrodes of the driver chip block  621 . Preferably, to prevent influence on properties of the material, the LED block  611  and the driver chip block  621  are bonded by a low-temperature hybrid connection technology at a temperature lower than 200° C. to adhere the LED block  611  and the pixel electrodes of the driver chip block  621  together. It can be understood that, electrode pads may be additionally disposed to facilitate adhesion or electrical conduction. It shall be appreciated that, in this embodiment, the LED block  611  and the driver chip block  621  have already been diced from the LED wafer and the driver circuit wafer respectively before the bonding step is performed. Further in another embodiment as shown in  FIG. 6A , the whole LED wafer  610  may be bonded to the driver circuit wafer  620 ; or as shown in  FIG. 6B , the LED block  611  may be diced from the LED wafer in advance and then bonded to the driver circuit wafer  620 . 
     Referring next to  FIG. 6E , the substrate  612  is removed and the LED block  611  is etched to form a plurality of trenches  631  arranged crisscrossingly. The trenches  631  define a plurality of micro LED pixels  630  arranged in an array (i.e., a micro LED array), and each of the micro LED pixels  630  corresponds to one of the pixel electrodes. In this way, each of the micro LED pixels  630  can be powered separately by a corresponding pixel electrode. It shall be appreciated that, the size of each of the micro LED pixels  630  is usually at the micrometer scale. 
     Referring next to  FIG. 6F , non-conductive glue  632  is filled into the trenches  631  to improve the structural strength between the micro LED pixels  630 . In other embodiments of the present invention, this step may be omitted. 
     Referring next to  FIG. 6G , a light transmissive conductive layer  640  is disposed on the N-type semiconductor layer  631 . More specifically, the light transmissive conductive layer  640  comprises a glass layer coated with an ITO conductive film, and the ITO conductive film is electrically connected with each of the micro LED pixels  630 , so that the ITO conductive film is the common electrode corresponding to the micro LED pixels  630 . Moreover, the light transmissive conductive layer  640  is electrically connected to the driver chip block  621  via a conductive glue  650  (or other conductors). With a potential difference between the ITO conductive film and the pixel electrodes, each of the micro LED pixels  630  can be controlled to light up. 
     Referring next to  FIG. 6H , the driver chip block  621  is electrically connected to a circuit board  660  (a printed circuit board (PCB) or a flexible circuit board). Further speaking, the driver chip block  621  is disposed on the circuit board  660  and is electrically connected to the circuit board  660  through wire bonding. It shall be appreciated that, when this step is performed, the driver chip block  621  and the LED block  611  have already been diced from the driver circuit wafer and the LED wafer respectively (i.e., have been in the form of an independent LED pixel array and an independent driver chip respectively). In another embodiment as shown in  FIG. 6I , the conductive glue  650  may not connect the driver chip block  621 , but connect the light transmissive conductive layer  640  and the circuit board  660 . In some embodiments, the conductive glue may not be provided, and instead, the ITO conductive film is electrically connected to other external power sources as long as there is a potential difference between the ITO conductive film and the pixel electrodes to allow each micro LED pixel to light up. 
     Through the aforesaid steps, the micro LED display module  600  as shown in  FIG. 6H  can be produced. The micro LED display module comprises the driver chip block  621 , the LED block  611 , the light transmissive conductive layer  640 , and the circuit board  660 . The driver chip block  621  has a plurality of pixel electrodes. The LED block  611  is disposed on the driver chip block  621 . The LED block  611  has the first semiconductor layer, the light emitting layer  616 , the second semiconductor layer and a plurality of trenches  631 . The light emitting layer  616  is located between the first semiconductor layer and the second semiconductor layer. The second semiconductor layer is electrically connected to the pixel electrodes. The trenches  631  define the plurality of micro LED pixels  630  arranged in an array form. Each of the trenches  631  penetrates through the first semiconductor layer, the second semiconductor layer and the light emitting layer  616 . Each of the micro LED pixels  630  corresponds to one of the pixel electrodes. One of the first semiconductor layer and the second semiconductor layer is the N-type semiconductor layer  613  and the other is the p-type semiconductor layer  617 . Each of the trenches  631  is filled with the non-conductive glue  632  therein. 
     The light transmissive conductive layer  640  is disposed on the LED block  611  and connected to the first semiconductor layer. The LED block  611  is located between the light transmissive conductive layer  640  and the driver chip block  621 . The circuit board  660  is electrically connected to the driver chip block  621 , and the driver chip block  621  is located between the LED block  611  and the circuit board  660 . The conductive glue  650  is disposed between the light transmissive conductive layer  640  and the driver chip block  621  to electrically connect the light transmissive conductive layer  640  and the driver chip block  621 . The light transmissive conductive layer  640  comprises the glass layer coated with the ITO conductive film, and the ITO conductive film is electrically connected to each of the micro LED pixels  630 . In another embodiment as shown in  FIG. 6I , the conductive glue  650  may also be disposed between the light transmissive conductive layer  640  and the driver chip block  621  to electrically connect the light transmissive conductive layer  640  and the driver chip block  621 . 
     Please refer to  FIG. 7A ,  FIG. 7B ,  FIG. 7E ,  FIG. 7F ,  FIG. 7G ,  FIG. 7H  and  FIG. 7I , which show a second embodiment of the present invention. A manufacturing method of a micro LED display module  700  according to this embodiment comprises the following steps. 
     Initially, a LED wafer  710  and a driver circuit wafer  720  are prepared. A portion of the LED wafer  710  is defined as a LED block  711 , and a chip size portion of the driver circuit wafer  720  is defined as a driver chip block  721 . The LED block  711  has a first semiconductor layer, a light emitting layer  716  and a second semiconductor layer. The light emitting layer  716  is disposed between the first semiconductor layer and the second semiconductor layer. The first semiconductor layer connects with a substrate  712 . One of the first semiconductor layer and the second semiconductor layer is a N-type semiconductor layer and the other is a P-type semiconductor layer. More specifically, the first semiconductor layer is a N-type semiconductor layer  713  and the second semiconductor layer is a P-type semiconductor layer  717 . The N-type semiconductor layer  713  comprises a N-type doped layer  714  and a N-type buffer layer  715 , and the N-type doped layer  714  is located between the N-type buffer layer  715  and the light emitting layer  716 . The P-type semiconductor layer  717  further comprises a P-type doped layer  718  and a P-type buffer layer  719 , and the P-type doped layer  718  is located between the P-type buffer layer  719  and the light emitting layer  716 . In some embodiments of the present invention, there may not be the N-type or P-type buffer layer. 
     Referring to  FIG. 7A , the LED block  711  is etched to form a plurality of trenches  731  arranged crisscrossingly. The trenches  731  define a plurality of micro LED pixels  730  arranged in an array (i.e., a micro LED array), and each of the trenches  731  at least penetrates through the P-type semiconductor layer  717  and the light emitting layer  716 . Further speaking, each of the trenches  731  does not penetrate through the N-type semiconductor layer  713 , and the N-type semiconductor layer  713  is a common electrode corresponding to the micro LED pixels  730 . In other embodiments of the present invention, each of the trenches may penetrate through the N-type semiconductor layer or penetrate through only the N-type doped layer as long as there is a common electrode for the light transmissive conductive layer. It can be understood that, the step of etching the LED block may etch the whole LED wafer, or etch only the LED block  711  that has been diced. 
     Referring next to  FIG. 7B , non-conductive glue  732  is filled into the trenches  731  to improve the structural strength between the micro LED pixels  730 . In other embodiments of the present invention, this step may be omitted. 
     Referring next to  FIG. 7E  and  FIG. 7F , the LED block  711  and the driver chip block  721  are bonded to each other so that the P-type semiconductor layer  717  is electrically connected to a plurality of pixel electrodes of the driver chip block  721 . Preferably, to prevent influence on properties of the material, the LED block  711  and the driver chip block  721  are bonded by a low-temperature hybrid connection technology at a temperature lower than 200° C. Each of the micro LED pixels  730  corresponds to one of the pixel electrodes. In this way, each micro LED pixel  730  can be independently driven by a corresponding pixel electrode. It shall be appreciated that, the size of each micro LED pixels  730  is usually at the micrometer scale. In this embodiment of the present invention, the LED block  711  and the driver chip block  721  have already been diced from the LED wafer  710  and the driver circuit wafer  720  respectively before the bonding step is performed. It can be understood that, in another embodiment as shown in  FIG. 7C , the whole LED wafer  710  may be bonded to the driver circuit wafer  720  and a dicing process is performed subsequently; or as shown in  FIG. 7D , the LED block  711  may be diced from the LED wafer  710  in advance and then bonded to a corresponding position on the driver circuit wafer  720 , and a dicing process is performed subsequently. 
     Referring next to  FIG. 7G , the substrate is removed. 
     Referring next to  FIG. 7H , a light transmissive conductive layer  740  is disposed on the N-type semiconductor layer  713 , wherein the light transmissive conductive layer  740  has a common electrode corresponding to the micro LED pixels  730 . Further speaking, the light transmissive conductive layer  740  comprises a glass layer coated with an ITO conductive film, and the ITO conductive film is electrically connected with each of the micro LED pixels  730 . So that the ITO conductive film is the common electrode corresponding to the micro LED pixels  730 . Moreover, the light transmissive conductive layer  740  is electrically connected to the driver chip block  721  via a conductive glue  750  so that, with a potential difference between the ITO conductive film and the pixel electrodes, each of the micro LED pixels  730  can be controlled to light up. In another embodiment as shown in  FIG. 7K  and  FIG. 7L , the light transmissive conductive layer  741  may also be an ITO conductive layer formed through physical sputtering instead of having a glass layer. 
     Referring next to  FIG. 7I , the driver chip block  721  is electrically connected to a circuit board  760 . It shall be appreciated that, when this step is performed, the driver chip block  721  and the LED block  711  have already been diced from the driver circuit wafer  720  and the LED wafer  710  respectively (i.e., have been in the form of an independent LED pixel array and an independent driver chip respectively). In another embodiment as shown in  FIG. 7J , the conductive glue  750  may not connect the driver chip block  721 , but connect the light transmissive conductive layer  740  and the circuit board  760 . In some embodiments of the present invention, the conductive glue may not be provided, and instead, the ITO conductive film is electrically connected to other external power sources as long as there is a potential difference between the ITO conductive film and the pixel electrodes to allow each micro LED pixel to light up. 
     Through the aforesaid steps, a micro LED display module  700  as shown in  FIG. 7I  can be produced in this embodiment of the present invention. The micro LED display module  700  comprises the driver chip block  721 , the LED block  711 , the light transmissive conductive layer  740 , and the circuit board  760 . The driver chip block  721  has a plurality of pixel electrodes. The LED block  711  is disposed on the driver chip block  721 . The LED block  711  has the first semiconductor layer, the light emitting layer  716 , the second semiconductor layer and a plurality of trenches  731 . The light emitting layer  716  is located between the first semiconductor layer and the second semiconductor layer. The second semiconductor layer is electrically connected to the pixel electrodes. The trenches  731  define the plurality of micro LED pixels  730  arranged in an array form. Each of the trenches  731  penetrates through the second semiconductor layer and the light emitting layer  716 . Each of the micro LED pixels  730  corresponds to one of the pixel electrodes. One of the first semiconductor layer and the second semiconductor layer is the N-type semiconductor layer  713  and the other is the p-type semiconductor layer  717 . Each of the trenches  731  is filled with the non-conductive glue  732  therein. 
     The light transmissive conductive layer  740  is disposed on the LED block  711  and connected to the first semiconductor layer. The LED block  711  is located between the light transmissive conductive layer  740  and the driver chip block  721 . The circuit board  760  is electrically connected to the driver chip block  721 , and the driver chip block  721  is located between the LED block  711  and the circuit board  760 . The conductive glue  750  is disposed between the light transmissive conductive layer  740  and the driver chip block  721  to electrically connect the light transmissive conductive layer  740  and the driver chip block  721  respectively. The light transmissive conductive layer  740  comprises a glass layer coated with an ITO conductive film, and the ITO conductive film is electrically connected to each of the micro LED pixels  730  (of course, the light transmissive conductive layer  741  may also have only the ITO conductive layer but not have the glass layer as shown in  FIG. 7L ). In another embodiment as shown in  FIG. 7J , the conductive glue  750  may also be disposed between the light transmissive conductive layer  740  and the driver chip block  721  to electrically connect the light transmissive conductive layer  740  and the driver chip block  721  respectively. 
     Please refer to  FIG. 8A ,  FIG. 8B ,  FIG. 8C ,  FIG. 8D ,  FIG. 8E  and  FIG. 8F , which show a third embodiment of the present invention. A manufacturing method of a micro LED display module  800  according to this embodiment comprises the following steps. 
     Initially, a LED wafer  810  and a driver circuit wafer are prepared. A portion of the LED wafer  810  is defined as a LED block  811 , and a chip size portion of the driver circuit wafer  820  is defined as a driver chip block  821 . The LED block  811  has a first semiconductor layer, a light emitting layer  816  and a second semiconductor layer. The light emitting layer  816  is disposed between the first semiconductor layer and the second semiconductor layer. The first semiconductor layer connects with a substrate  812 . One of the first semiconductor layer and the second semiconductor layer is a N-type semiconductor layer and the other is a P-type semiconductor layer. More specifically, the first semiconductor layer is a N-type semiconductor layer  813  and the second semiconductor layer is a P-type semiconductor layer  817 . The N-type semiconductor layer  813  comprises a N-type doped layer  814  and a N-type buffer layer  815 , and the N-type doped layer  814  is located between the N-type buffer layer  815  and the light emitting layer  816 . The P-type semiconductor layer  817  further comprises a P-type doped layer  818  and a P-type buffer layer  819 , and the P-type doped layer  818  is located between the P-type buffer layer  819  and the light emitting layer  816 . In some embodiments of the present invention, there may not be the N-type or P-type buffer layer. 
     A light transmissive conductive layer  840  is disposed on the P-type semiconductor layer  817  of the LED block  811 . Further speaking, the light transmissive conductive layer  840  comprises a glass layer coated with an ITO conductive film, and the ITO conductive film is electrically connected with the P-type semiconductor layer  817 . In this embodiment of the present invention, as shown in  FIG. 8A , this step is actually to bond the LED wafer  810  and the light transmissive conductive layer  840  to each other, and the light transmissive conductive layer  840  is an ITO glass wafer. After the step is finished, the LED block  811  is diced from the LED wafer  810 , as shown in  FIG. 8B . In other embodiments of the present invention, the LED block  811  may be diced from the LED wafer  810  in another subsequent step. 
     Next, as described in  FIG. 8C , the substrate  812  is removed, and the LED block  811  is etched to form a plurality of trenches  831  arranged crisscrossingly. The trenches  831  define a plurality of micro LED pixels  830  arranged in an array, and each of the trenches  831  at least penetrates through the N-type semiconductor layer  813  and the light emitting layer  816 . In this embodiment of the present invention, each of the trenches  831  does not penetrate through the P-type semiconductor layer  817 , and the ITO conductive film and the P-type semiconductor layer  817  act as a common electrode corresponding to the micro LED pixels  830 . In other embodiments of the present invention, each of the trenches may penetrate through the P-type semiconductor layer or penetrate through only the P-type doped layer, so that all of the micro LED pixels can move in an array instead of moving individually. It can be understood that, the whole LED wafer may be etched in the step of etching the LED block. 
     Referring next to  FIG. 8D , non-conductive glue  832  is filled into the trenches  831  to improve the structural strength between the micro LED pixels  830 . In other embodiments of the present invention, this step may be omitted. 
     Referring next to  FIG. 8E , the LED block  811  and the driver chip block  821  are bonded to each other so that the N-type semiconductor layer  813  is electrically connected to a plurality of pixel electrodes of the driver chip block  821 . Preferably, to prevent influence on properties of the material, the LED block  811  and the driver chip block  821  are bonded by a low-temperature hybrid connection technology at a temperature lower than 200° C. Each of the micro LED pixels  830  corresponds to one of the pixel electrodes. In this way, each of the micro LED pixels  830  can be independently driven by the corresponding pixel electrode. It shall be appreciated that, the size of each of the micro LED pixels  830  is usually at the micrometer scale. In this embodiment of the present invention, the LED block  811  and the driver chip block  821  have already been diced from the LED wafer and the driver circuit wafer respectively before the bonding step is performed. It can be understood that, in other embodiments of the present invention, it may be that the whole LED wafer is bonded to the driver circuit wafer; or the LED block is diced from the LED wafer in advance and then bonded to a corresponding position on the driver circuit wafer, then the driver circuit wafer is diced in another subsequent step. 
     Referring next to  FIG. 8F , the driver chip block  821  is electrically connected to a circuit board  860 . It shall be appreciated that, when this step is performed, the driver chip block  821  and the LED block  811  have already been diced from the driver circuit wafer and the LED wafer respectively (i.e., have been in the form of an independent LED pixel array and an independent driver chip respectively). In this embodiment of the present invention, the light transmissive conductive layer  840  is electrically connected to the driver chip block  821  via a conductive glue  850  so that, with a potential difference between the ITO conductive film and the pixel electrodes, each of the micro LED pixels  830  can be controlled to light up. In other embodiments as shown in  FIG. 8G , the conductive glue  850  may electrically connect the light transmissive conductive layer  840  and the circuit board  860  but not connect the driver chip block  821 . In some embodiments of the present invention, the conductive glue may not be disposed and, instead, the ITO conductive film is electrically connected to other external power sources as long as there is a potential difference between the ITO conductive film and the pixel electrodes to allow each micro LED pixel to light up. 
     Through the aforesaid steps, a micro LED display module  800  as shown in  FIG. 8F  can be produced in this embodiment of the present invention. The micro LED display module comprises the driver chip block  821 , the LED block  811 , the light transmissive conductive layer  840 , and the circuit board  860 . The driver chip block  821  has the plurality of pixel electrodes. The LED block  811  is disposed on the driver chip block  821 . The LED block  811  has the first semiconductor layer, the light emitting layer  816 , the second semiconductor layer and the plurality of trenches  831 . The light emitting layer  816  is located between the first semiconductor layer and the second semiconductor layer. The second semiconductor layer is electrically connected to the pixel electrodes. The trenches  831  define the plurality of micro LED pixels  830  arranged in an array form. Each of the trenches  831  penetrates through the second semiconductor layer and the light emitting layer  816 . Each of the micro LED pixels  830  corresponds to one of the pixel electrodes. One of the first semiconductor layer and the second semiconductor layer is the N-type semiconductor layer  813  and the other is the P-type semiconductor layer  817 . Each of the trenches  831  is filled with the non-conductive glue  832  therein. 
     The light transmissive conductive layer  840  is disposed on the LED block  811  and connected to the first semiconductor layer. The LED block  811  is located between the light transmissive conductive layer  840  and the driver chip block  821 . The circuit board  860  is electrically connected to the driver chip block  821 , and the driver chip block  821  is located between the LED block  811  and the circuit board  860 . A conductive glue  850  is disposed between the light transmissive conductive layer  840  and the driver chip block  821  to electrically connect the light transmissive conductive layer  840  and the driver chip block  821  respectively. The light transmissive conductive layer  840  comprises a glass layer coated with the ITO conductive film, and the ITO conductive film is electrically connected to each of the micro LED pixels  830 . In another embodiment as shown in  FIG. 8G , the conductive glue  850  may also be disposed between the light transmissive conductive layer  840  and the driver chip block  821  to electrically connect the light transmissive conductive layer  840  and the driver chip block  821  respectively. 
     Please refer to  FIG. 9A ,  FIG. 9B ,  FIG. 9E ,  FIG. 9F  and  FIG. 9G , which show a fourth embodiment of the present invention. A manufacturing method of a micro LED display module having a light transmissive substrate according to this embodiment comprises the following steps. 
     Initially, a LED wafer  910  and a driver circuit wafer  920  are prepared. A portion of the LED wafer  910  is defined as a LED block  911 , and a chip size portion of the driver circuit wafer  920  is defined as a driver chip block  921 . The LED block  911  has a first semiconductor layer, a light emitting layer  916  and a second semiconductor layer. The light emitting layer  916  is disposed between the first semiconductor layer and the second semiconductor layer. The first semiconductor layer connects with a light transmissive substrate  912 . One of the first semiconductor layer and the second semiconductor layer is a N-type semiconductor layer and the other is a P-type semiconductor layer. More specifically, the first semiconductor layer is a N-type semiconductor layer  913  and the second semiconductor layer is a P-type semiconductor layer  917 . The N-type semiconductor layer  913  comprises a N-type doped layer  914  and a N-type buffer layer  915 , and the N-type doped layer  914  is located between the N-type buffer layer  915  and the light emitting layer  916 . The P-type semiconductor layer  917  further comprises a P-type doped layer  918  and a P-type buffer layer  919 , and the P-type doped layer  918  is located between the P-type buffer layer  919  and the light emitting layer  916 . In some embodiments of the present invention, there may not be the N-type or P-type buffer layer. The light transmissive substrate has good light transmissivity with respect to the visible band, e.g., may be a sapphire substrate. Referring to  FIG. 9A , the LED block  911  is etched to form a plurality of trenches  931  arranged crisscrossingly. The trenches  931  define a plurality of micro LED pixels  930  arranged in an array, and each of the trenches  931  penetrates through the P-type semiconductor layer  917  and the light emitting layer  916 . Further speaking, each of the trenches  931  does not penetrate through the N-type semiconductor layer  913 , and the N-type semiconductor layer  913  has a common electrode corresponding to the micro LED pixels  930 . In other embodiments of the present invention, each of the trenches may also penetrate through the N-type semiconductor layer as long as at least a part of the N-type semiconductor layer can act as a common electrode. It can be understood that, the step of etching the LED block may etch the whole LED wafer, or etch only the LED block  911  that has been diced. The N-type semiconductor layer  913  has a common electrode corresponding to the micro LED pixels  930 , and the common electrode has a protrusion  970  that protrudes in the horizontal direction. In this embodiment of the present invention, the N-type buffer layer  915  has the protrusion  970 , which is generated during the step of etching the LED block, and the N-type buffer layer  915  acts as the common electrode of the micro LED pixels. 
     Referring next to  FIG. 9B , a non-conductive glue  932  is filled into the trenches  931  to improve the structural strength between the micro LED pixels  930 . In other embodiments of the present invention, this step may be omitted. 
     Referring next to  FIG. 9E  and  FIG. 9F , the LED block  911  and the driver chip block  921  are bonded to each other so that the P-type semiconductor layer  917  is electrically connected to a plurality of pixel electrodes of the driver chip block  921 . Preferably, to prevent influence on properties of the material, the LED block  911  and the driver chip block  921  are bonded by a low-temperature hybrid connection technology at a temperature lower than 200° C. Each of the micro LED pixels  930  corresponds to one of the pixel electrodes. In this way, each micro LED pixel  930  can be independently powered by the corresponding pixel electrode. It shall be appreciated that, the size of each micro LED pixels  930  is usually at the micrometer scale. In this embodiment of the present invention, the LED block  911  and the driver chip block  921  have already been diced from the LED wafer and the driver circuit wafer respectively before the bonding step is performed. It can be understood that, in another embodiment as shown in  FIG. 9C , the whole LED wafer  910  is bonded to the driver circuit wafer  920 ; or as shown in  FIG. 9D , the LED block  911  is diced from the LED wafer  910  first and then bonded to a corresponding position on the driver circuit wafer  920 , and a dicing process is performed subsequently. 
     Besides, the protrusion  970  is electrically connected to the driver chip block  921  via a conductive glue  950  so that, with a potential difference between the N-type buffer layer  915  and the pixel electrodes, each of the micro LED pixels  930  can be controlled to light up. 
     It shall be appreciated that, this embodiment does not need to remove the light transmissive substrate  912 . 
     Referring next to  FIG. 9G , the driver chip block  921  is electrically connected to a circuit board  960 . It shall be appreciated that, when this step is performed, the driver chip block  921  and the LED block  911  have already been diced from the driver circuit wafer  920  and the LED wafer  910  respectively (i.e., have been in the form of an independent LED pixel array and an independent driver chip respectively). In another embodiment as shown in  FIG. 9H , the conductive glue  950  may not connect the driver chip block  921 , but connect the protrusion  970  and the circuit board  960 . In some embodiments of the present invention, the conductive glue  950  may not be provided, and instead, the ITO conductive film is electrically connected to other external power sources as long as there is a potential difference between the ITO conductive film and the pixel electrodes to allow each micro LED pixel  930  to light up. 
     Through the aforesaid steps, a micro LED display module having a light transmissive substrate as shown in  FIG. 9G  can be produced in this embodiment of the present invention. The micro LED display module comprises the driver chip block  921 , the LED block  911 , and the circuit board  960 . The driver chip block  921  has a plurality of pixel electrodes. The LED block  911  is disposed on the driver chip block  921 . The LED block  911  has the first semiconductor layer, the light emitting layer  916 , the second semiconductor layer and the plurality of trenches  931 . The light emitting layer  916  is located between the first semiconductor layer and the second semiconductor layer. The second semiconductor layer is electrically connected to the pixel electrodes. The trenches  931  define the plurality of micro LED pixels  930  arranged in an array form. Each of the trenches  931  penetrates through the second semiconductor layer and the light emitting layer  916 . Each of the micro LED pixels  930  corresponds to one of the pixel electrodes. Each of the trenches  931  is filled with the non-conductive glue  932  therein. The first semiconductor layer has the protrusion  970  that protrudes in the horizontal direction. The first semiconductor layer is connected to the light transmissive substrate  912  and located between the light transmissive substrate  912  and the light emitting layer  916 . 
     The circuit board  960  is electrically connected to the driver chip block  921 , and the driver chip block  921  is located between the LED block  911  and the circuit board  960 . A conductive glue  950  is disposed between the protrusion  970  and the driver chip block  921  to electrically connect the protrusion  970  and the driver chip block  921  respectively. In another embodiment as shown in  FIG. 9H , the conductive glue  950  may also be disposed between the protrusion  970  and the circuit board  960  to electrically connect the protrusion  970  and the circuit board  960  respectively. 
     Referring to  FIG. 10 , to have each of the micro LED display modules of all the aforesaid embodiments emit light of different colors, a color layer  170  (a RGB color layer) may be additionally disposed to emit light of three colors from the micro LED display module. Further speaking, the color layer  170  is formed by spraying a corresponding RGB quantum dot on each of the micro LED pixels so that the quantum dots are excited by the micro LED pixels to emit light of the three colors. Further speaking, the color layer  170  has a plurality of red, blue and green pixel regions  171 ,  172 ,  173 , each of which corresponds to one of the micro LED pixels, and the color layer  170  has a plurality of full-color display dots (units capable of displaying light of the three colors). Each of the full-color dots has at least three-pixel regions  171 ,  172 ,  173  adjacent to each other, at least including one red pixel region  171 , one blue pixel region  172  and one green pixel region  173 . Preferably, to satisfy requirements of the manufacturing process, one full-color display dot may include four-pixel regions adjacent to each other (e.g., one red pixel region  171 , one blue pixel region  172  and two green pixel regions  173  as shown in  FIG. 10A ) so that the full-color display dots are arranged regularly. In other embodiments as shown in  FIG. 11 , the color layer  180  may also be a RGB color filter. 
     In the various embodiments of the present invention, novel structures and methods have been described for to a micro LED display module and a manufacturing method thereof. The various embodiments of the structures and methods of this invention that are described above are illustrative only of the principles of this invention and are not intended to limit the scope of the invention to the particular embodiment described. Thus, the invention is limited only by the following claims.