Patent Publication Number: US-2021167233-A1

Title: Photodiode and manufacturing method thereof

Description:
FIELD OF INVENTION 
     The present invention relates to the field of display, and in particular, to a photodiode and a method of manufacturing the same. 
     BACKGROUND OF INVENTION 
     At present, fingerprint recognition technology has been widely used in small and medium-sized panels, including capacitive, ultrasonic, and optical methods. Compared with capacitive and ultrasonic fingerprint recognition technology, optical fingerprint recognition technology has better stability, stronger antistatic ability, better penetrability, and lower cost. Optical fingerprinting technology uses a principle of refraction and reflection of light. When light irradiates a finger, it is received by a photosensitive sensor after being reflected by the finger. The photosensitive sensor can convert a light signal into an electrical signal for reading. Because fingerprint valley and ridge reflect light differently, reflected light intensities of the valley and ridge received by the photosensitive sensor are different, and thus magnitudes of converted current or voltage are different. Therefore, special points in the fingerprint can be captured to provide specific information. 
     TECHNICAL PROBLEM 
     In recent years, commonly used photosensitive sensors are vertical PIN diodes made of amorphous silicon. For a photosensitive sensor, the greater a photo-generated current, the higher a sensitivity of fingerprint recognition. Factors that affect the photo-generated current of a diode are a width of a depletion layer, an area of a diode structure, and a reflectivity of a diode surface. The wider the width of the depletion layer, the more light energy can be absorbed by an intrinsic layer, and electron-hole pairs can be separated by a built-in electric field, so that the photocurrent is greater, and response is better. However, if the depletion layer is too large, a carrier transit time would be too long, thereby reducing response speed of a device. 
     Therefore, how to improve the sensitivity of fingerprint recognition by increasing the photo-generated current of the photosensitive sensor under a premise that the response speed of the device is satisfied, is a problem that panel manufacturers in the world are trying to overcome. 
     SUMMARY OF INVENTION 
     The present application provides a photodiode and a preparation method thereof, which can improve the sensitivity of fingerprint recognition by increasing the photo-generated current of a photosensitive sensor under the premise that the response speed of the device is satisfied. 
     The present application provides a photodiode, including: a P electrode, an N electrode, a conductive channel configured to connect the P electrode and the N electrode, and a light-absorbing layer pattern; wherein the light-absorbing layer pattern is defined on the conductive channel, and the light-absorbing layer pattern exposes a part of the conductive channel. 
     The conductive channel includes a first conductive channel pattern, a second conductive channel pattern, and a third conductive channel pattern, the second conductive channel pattern is positioned between the first conductive channel pattern and the third conductive channel pattern, the first conductive channel pattern and the third conductive channel pattern are comb-like structures, and the first conductive channel pattern, the second conductive channel pattern, and the third conductive channel pattern mesh with each other. 
     The first conductive channel pattern includes a first main portion and a plurality of first branch portions, and the plurality of first branch portions are disposed at intervals on a first side of the first main portion. The third conductive channel pattern includes a second main portion and a plurality of second branch portions, and the plurality of second branch portions are disposed at intervals on a second side of the second main portion. The first side and the second side are disposed opposite to each other, and the plurality of first branch portions and the plurality of second branch portions is respectively staggered. 
     In the photodiode provided in the present application, at least one of the second branch portions is disposed between adjacent ones of the first branch portions. 
     In the photodiode provided in the present application, when one of the second branch portions is disposed between adjacent ones of the first branch portions, the plurality of first branch portions is disposed at equal intervals on the first main portion, and the plurality of second branch portions is disposed at equal intervals on the second main portion. 
     In the photodiode provided in the present application, when at least two of the second branch portions are disposed between adjacent ones of the first branch portions, a width of the plurality of first branch portions is greater than a width of the second branch portion. In the photodiode provided in the present application, the first main portion includes a first area and a second area that are interconnected, the second main portion includes a third area and a fourth area that are interconnected, wherein the first area is disposed opposite to the third area, and the second area is disposed opposite to the fourth area. The plurality of first branch portions is disposed on the first area at intervals, and the plurality of second branch portions are disposed at intervals on the third area. 
     In the photodiode provided in the present application, the P electrode is disposed on the conductive channel and extends along one side of the conductive channel, and the N electrode is disposed on the conductive channel and extends along the other side of the conductive channel. 
     In the photodiode provided in this application, an insulating layer is disposed on the conductive channel and the light-absorbing layer pattern, and a first via-hole and a second via-hole are formed on the insulating layer; and wherein the P electrode is connected to the conductive channel through the first via-hole, and the N electrode is connected to the conductive channel through the second via-hole. 
     The present application further provides a photodiode, including a P electrode, an N electrode, and a conductive channel configured to connect the P electrode and the N electrode; wherein the conductive channel includes a first conductive channel pattern, a second conductive channel pattern, and a third conductive channel pattern, the second conductive channel pattern is positioned between the first conductive channel pattern and the third conductive channel pattern, the first conductive channel pattern and the third conductive channel pattern are comb-like structures, and the first conductive channel pattern, the second conductive channel pattern, and the third conductive channel pattern mesh with each other. 
     In the photodiode provided in the present application, the first conductive channel pattern includes a first main portion and a plurality of first branch portions, and the plurality of first branch portions are disposed at intervals on a first side of the first main portion; the third conductive channel pattern includes a second main portion and a plurality of second branch portions, and the plurality of second branch portions are disposed at intervals on a second side of the second main portion; the first side and the second side are disposed opposite to each other, and the plurality of first branch portions and the plurality of second branch portions each are respectively staggered. 
     In the photodiode provided in the present application, at least one of the second branch portions is disposed between adjacent ones of the first branch portions. 
     In the photodiode provided in the present application, when one of the second branch portions is disposed between adjacent ones of the first branch portions, the plurality of first branch portions is disposed at equal intervals on the first main portion, and the plurality of second branch portions is disposed at equal intervals on the second main portion. 
     In the photodiode provided in the present application, when at least two of the second branch portions are disposed between adjacent ones of the first branch portions, a width of the plurality of first branch portions each is greater than a width of the second branch portion. 
     In the photodiode provided in the present application, the first main portion includes a first area and a second area that are interconnected, the second main portion includes a third area and a fourth area that are interconnected, wherein the first area is disposed opposite to the third area, and the second area is disposed opposite to the fourth area. The plurality of first branch portions is disposed on the first area at intervals, and the plurality of second branch portions are disposed at intervals on the third area. 
     In the photodiode provided in the present application, the light-absorbing layer pattern is defined on the conductive channel, and the light-absorbing layer pattern exposes a part of the conductive channel. 
     In the photodiode provided in the present application, the P electrode is disposed on the conductive channel and extends along one side of the conductive channel, and the N electrode is disposed on the conductive channel and extends along the other side of the conductive channel. 
     In the photodiode provided in this application, an insulating layer is disposed on the conductive channel and the light-absorbing layer pattern, and a first via-hole and a second via-hole are formed on the insulating layer; and wherein the P electrode is connected to the conductive channel through the first via-hole, and the N electrode is connected to the conductive channel through the second via-hole. 
     The present application also provides a method of manufacturing a photodiode, including: 
     Providing a substrate on which a light-shielding layer pattern and a buffer layer are sequentially formed. Forming a conductive channel on the buffer layer, and subjecting the conductive channel to an ion doping treatment to form a first conductive channel pattern, a second conductive channel pattern, and a third conductive channel pattern, wherein the second conductive channel pattern is positioned between the first conductive channel pattern and the third conductive channel pattern, the first conductive channel pattern and the third conductive channel pattern are comb-like structures, and the first conductive channel pattern, the second conductive channel pattern, and the third conductive channel pattern mesh with each other. Forming a P electrode and an N electrode on the conductive channel, wherein the P electrode and the N electrode are configured to connect to the conductive channel. 
     BENEFICIAL EFFECT 
     In the photodiode and the manufacturing method thereof provided by the present application, the conductive channels of the photodiode are configured to comb-like structures that mesh with each other, which increases the junction area of the diode and thereby increases the photo-generated current. In addition, the light-absorbing layer is added to the conductive channel, which can fully absorb the light reflected by the fingerprint to generate more electron-hole pairs, so that the photo-generated current is increased. Therefore, the sensitivity of fingerprint recognition can be improved by increasing the photo-generated current of the photosensitive sensor under the premise that the response speed of the device is satisfied. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       In order to explain the technical solution in this application more clearly, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the description are some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts. 
         FIG. 1  is a schematic diagram of a first structure of a photodiode according to an embodiment of the present application. 
         FIG. 2  is a schematic diagram of a first structure of a conductive channel according to an embodiment of the present application. 
         FIG. 3  is a schematic diagram of a second structure of a conductive channel according to an embodiment of the present application. 
         FIG. 4  is a schematic diagram of a third structure of a conductive channel according to an embodiment of the present application. 
         FIG. 5  is a schematic diagram of a fourth structure of a conductive channel according to an embodiment of the present application. 
         FIG. 6  is a schematic diagram of a second structure of a photodiode according to an embodiment of the present application. 
         FIG. 7  is a schematic diagram of a third structure of a photodiode according to an embodiment of the present application. 
         FIG. 8  is a schematic flowchart of a method of manufacturing a photodiode according to an embodiment of the present application. 
         FIG. 9  is a schematic flowchart of a sub-process of a method of manufacturing a photodiode according to an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The technical solutions in the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall into the scope of protection of the present application. 
     Please refer to  FIG. 1 , which is a schematic diagram of a first structure of a photodiode according to an embodiment of the present application. As shown in  FIG. 1 , the photodiode provided in the embodiment of the present application includes a P electrode  101 , an N electrode  102 , and a conductive channel  103  configured to connect the P electrode  101  and the N electrode  102 , wherein the conductive channel  103  includes a first conductive channel pattern  1031 , a second conductive channel pattern  1032 , and a third conductive channel pattern  1033 . 
     The second conductive channel pattern  1032  is positioned between the first conductive channel pattern  1031  and the third conductive channel pattern  1033 , the first conductive channel pattern  1031  and the third conductive channel pattern  1033  are comb-like structures, and the first conductive channel pattern  1031 , the second conductive channel pattern  1032 , and the third conductive channel pattern  1033  mesh with each other. 
     It can be understood that the conductive channel patterns of the photodiodes in the prior art are all rectangular designs. The conductive channel of the photodiode provided by the present application adopts a comb-like design and mesh with each other. Compared with the original contact surface of a straight line, the contact surface has many polylines, so that the contact area of the PN junction of the photodiode is increased, and the photo-generated current is improved. Therefore, a technical effect of improving a sensitivity of fingerprint recognition of a photosensitive sensor is achieved. 
     In one embodiment, a material of the first conductive channel pattern  1031  is boron ion-doped polysilicon, a material of the second conductive channel pattern  1032  is amorphous silicon, and a material of the third conductive channel pattern  1033  is phosphorus ion-doped polysilicon. 
     Specifically, please refer to  FIG. 2 , which is a schematic diagram of a first structure of a conductive channel according to an embodiment of the present application. The conductive channel provided in the present application includes a first conductive channel pattern  201 , a second conductive channel pattern  202 , and a third conductive channel pattern  203 , wherein the first conductive channel pattern  201  includes a first main portion  2011  and a plurality of first branch portions  2012 . The plurality of first branches  2012  are disposed at intervals on a first side  2013  of the first main portion  2011 . The third conductive channel pattern  203  includes a second main portion  2031  and a plurality of second branch portions  2032 , and the plurality of second branch portions  2032  are disposed at intervals on a second side  2033  of the second main portion  2031 . The first side  2013  and the second side  2033  are disposed opposite to each other, and the plurality of first branch portions  2012  and the plurality of second branch portions  2032  are respectively staggered. 
     Both the first conductive channel pattern  201  and the third conductive channel pattern  203  are comb-like structures, and the first conductive channel pattern  201 , the second conductive channel pattern  202 , and the third conductive channel pattern  203  mesh with each other. 
     In one embodiment, a shape of the first branch portions  2012  and the second branch portions  2032  includes one of a semi-ellipse, a rectangle, or a triangle, wherein when the shape of the first branch portions  2012  and the second branch portions  2032  are rectangular, an area of the PN junction in the photodiode is largest, so as to achieve the best technical effect of improving the sensitivity of fingerprint recognition of the photosensitive sensor. Because difficulties of forming different shapes are different, and the technical effects achieved are different, the specific shape of the first branch portions  2012  and the second branch portions  2032  is determined according to the specific process flow. 
     Specifically, please refer to  FIG. 3 , which is a schematic diagram of a second structure of a conductive channel according to an embodiment of the present application. The conductive channel provided in the present application includes a first conductive channel pattern  301 , a second conductive channel pattern  302 , and a third conductive channel pattern  303 . The first conductive channel pattern  301  includes a first main portion  3011  and a plurality of first branch portions  3012 . The plurality of first branch portions  3012  are disposed at intervals on the first side  3013  of the first main portion  3011 . The third conductive channel pattern  303  includes a second main portion  3031  and a plurality of second branch portions  3032 . The plurality of second branch portions  3032  are disposed at intervals on the second side  3033  of the second main portion  3031 . The first side  3013  and the second side  3033  are disposed opposite to each other, and the plurality of first branch portions  3012  and the plurality of second branch portions  3032  are respectively staggered. 
     Both the first conductive channel pattern  301  and the third conductive channel pattern  303  are comb-like structures. In addition, the first conductive channel pattern  301 , the second conductive channel pattern  302 , and the third conductive channel pattern  303  mesh with each other. 
     One of the second branch portions  3032  is disposed between adjacent ones first branch portions  3012 , the plurality of first branch portions  3012  are disposed at equal intervals on the first main portion  3011 , and the plurality of second branch portions  3032  are disposed at equal intervals on the second main portion  3031 . 
     Further, please refer to  FIG. 4 , which is a schematic diagram of a third structure of a conductive channel provided by an embodiment of the present application. 
     The difference between the conductive channel shown in  FIG. 4  and the conductive channel shown in  FIG. 3  is that in the conductive channel shown in  FIG. 4 , two of the second branch portions  3032  are provided between the adjacent first branch portions  3012 . A thickness of the first branch portions  3012  is greater than that of the second branch portions  3032 . 
     It can be understood that the thickness of the first branch portions  3012  in the conductive channel shown in  FIG. 4  is relatively thick, so when the first branch portions  3012  are manufactured, the process is simpler. Compared with  FIG. 3 , an area of the PN junction in the photodiode is not as large as that in  FIG. 3 , so the technical effect of improving the sensitivity of the photosensitive sensor fingerprint recognition is not as good as the conductive channel shown in  FIG. 3 . However, the process of manufacturing the conductive channel shown in  FIG. 4  is simpler and less prone to failure, thereby reducing costs. 
     Further, please refer to  FIG. 5 , which is a schematic diagram of a fourth structure of a conductive channel according to an embodiment of the present application. The difference between the conductive channel shown in  FIG. 5  and the conductive channel shown in  FIG. 3  is that the first main portion  3011  includes a first region  30111  and a second region  30112  connected to each other. The second main portion  3031  includes a third region  30311  and a fourth region  30312  connected to each other, wherein the first region  30111  and the third region  30311  are disposed opposite to each other, the second region  30112  and the fourth region  30312  are disposed opposite to each other, a plurality of the first branch portions  3012  are disposed at intervals on the first region  30111 , and a plurality of the second branch portions  3032  are disposed at intervals on the third region  30311 . 
     It can be understood that the first branch portions  3012  and the second branch portions  3032  shown in  FIG. 5  are arranged in different regions. In this way, the first branch portions  3012  and the second branch portions  3032  can be manufactured in different regions, and it is not necessary to manufacture the second branch portions  3032  in the interval between the adjacent first branch portions  3012  after the first branch portions  3012  are manufactured. Therefore, the difficulty of the manufacturing process is reduced, the yield is increased, and the cost is reduced. 
     In the photodiodes provided in the present application, the conductive channels of the photodiodes are arranged in comb-like structures and mesh with each other, thereby increasing the junction area of the diodes and further increasing the photo-generated current. Therefore, the sensitivity of the fingerprint recognition is improved by increasing the photo-generated current of the photosensitive sensor under the premise that the response speed of the device is satisfied. 
     Specifically, please refer to  FIG. 6 , which is a schematic diagram of a second structure of a photodiode according to an embodiment of the present application. As shown in  FIG. 6 , the photodiode provided in the embodiment of the present application includes a P electrode  401 , an N electrode  402 , a conductive channel  403  configured to connect the P electrode  401  and the N electrode  402 , a light-absorbing layer pattern  404 , and an insulating layer  405 . 
     The conductive channel  403  includes a first conductive channel pattern  4031 , a second conductive channel pattern  4032 , and a third conductive channel pattern  4033 , the light-absorbing layer pattern  404  is disposed on the conductive channel  403 , and the light-absorbing layer pattern  404  exposes a part of the conductive channel  403 . The insulating layer  405  is disposed on the conductive channel  403  and the light-absorbing layer pattern  404 , and a first via-hole  4051  and a second via-hole  4052  are formed on the insulating layer  405 , wherein the P electrode  401  is connected to the conductive channel  403  through the first via-hole  4051 , and the N electrode  402  is connected to the conductive channel  403  through the second via-hole  4052 . 
     It can be understood that a material of the light-absorbing layer pattern  404  is amorphous silicon, and in order to ensure sufficient absorption of light, a thickness of the light-absorbing layer pattern  404  is at least  1000  angstroms. 
     Further, please refer to  FIG. 7 , which is a schematic diagram of a third structure of a photodiode according to an embodiment of the present application. As shown in  FIG. 7 , the photodiode provided in the embodiment of the present application includes a P electrode  501 , an N electrode  502 , a conductive channel  503  configured to connect the P electrode  501  and the N electrode  502 , and a light-absorbing layer pattern  404 . 
     The conductive channel  503  includes a first conductive channel pattern  5031 , a second conductive channel pattern  5032 , and a third conductive channel pattern  5033 . The light-absorbing layer pattern  504  is disposed on the conductive channel  503 , and the light-absorbing layer pattern  504  exposes a part of the conductive channel  503 . The P electrode  501  is disposed on the conductive channel  503  and extends along one side of the conductive channel  503 . The N electrode  502  is disposed on the conductive channel  503  and extends along the other side of the conductive channel  503 . 
     In the photodiode and the manufacturing method thereof provided by the present application, by adding a light-absorbing layer on the conductive channel, the light reflected by the fingerprint can be fully absorbed, and more electron-hole pairs can be generated, thereby increasing the photo-generated current. Therefore, the technical problem of improving the sensitivity of fingerprint recognition by increasing the photo-generated current of the photosensitive sensor under the premise that the response speed of the device is satisfied is solved. 
     Specifically, please refer to  FIG. 8 , which is a schematic flowchart of a method of manufacturing a photodiode according to an embodiment of the present application. The method includes the following steps:  601 , providing a substrate on which a light-shielding layer pattern and a buffer layer are sequentially formed.  602 , forming a conductive channel on the buffer layer, and performing an ion doping treatment on the conductive channel to form a first conductive channel pattern, a second conductive channel pattern, and a third conductive channel pattern. The second conductive channel pattern is positioned between the first conductive channel pattern and the third conductive channel pattern. Both the first conductive channel pattern and the third conductive channel pattern are comb-like structures, and the first conductive channel pattern, the second conductive channel pattern, and the third conductive channel pattern mesh with each other.  603 , forming a P electrode and an N electrode on the conductive channel, wherein the P electrode and the N electrode are configured to connect to the conductive channel. 
     Further, please refer to  FIG. 8  and  FIG. 9 .  FIG. 9  is a schematic flowchart of a sub-process of a method of manufacturing a photodiode according to an embodiment of the present application. With reference to  FIG. 8  and FIG.  9 , process  602  specifically includes:  6021 , forming a conductive channel on the buffer layer;  6022 , performing a boron ion doping treatment on one side of the conductive channel to form the first conductive channel pattern, wherein the first conductive channel pattern is a comb-like structure;  6023 , doping phosphorus ions on the other side of the conductive channel to form the third conductive channel pattern, wherein the third conductive channel pattern is a comb-like structure;  6024 , etching away the polysilicon where the conductive channel is not ion-treated and filling it with amorphous silicon to form the second conductive channel pattern, and the first conductive channel pattern, the second conductive channel pattern, and the third conductive channel pattern mesh with each other; and  6025 , performing a rapid annealing process on the first conductive channel pattern and the third conductive channel pattern to activate ions in the first conductive channel pattern and the third conductive channel pattern. 
     It can be understood that the first conductive channel pattern and the third conductive channel pattern are subjected to rapid annealing treatment so that the ions in the first conductive channel pattern and the third conductive channel pattern are activated. Therefore, the contact resistance of the first conductive channel pattern and the third conductive channel pattern with the P electrode and the N electrode can be reduced, thereby the photo-generated current of the photodiode is further increased. 
     In one embodiment, forming a P electrode on the conductive channel needs to extend along one side of the conductive channel to the buffer layer and cover one side of the conductive channel, and forming an N electrode on the conductive channel needs to extend along the other side of the conductive channel to the buffer layer and cover the other side of the conductive channel. After the P electrode and the N electrode are formed, a light-absorbing layer pattern needs to be formed on the conductive channel, and an insulating layer is provided on the P electrode, the N electrode, the conductive channel, and the light-absorbing layer pattern. 
     In one embodiment, before forming the P electrode and the N electrode on the conductive channel, it is necessary to form a light-absorbing layer pattern on the conductive channel and provide an insulating layer on the conductive channel and the light-absorbing layer pattern, and then, a first via-hole and a second via-hole are provided on the insulating layer, a P electrode is connected to the conductive channel at the first via-hole, and an N electrode is connected to the conductive channel at the second via-hole. 
     In the method of manufacturing a photodiode provided by the present application, the conductive channel of the photodiode is configured to comb-like structures that mesh with each other, which increases a junction area of the diode and thereby increases the photo-generated current. In addition, a light-absorbing layer is added to the conductive channel, which can fully absorb the light reflected by the fingerprint to generate more electron-hole pairs, so that the photo-generated current is increased. Therefore, the sensitivity of fingerprint recognition can be improved by increasing the photo-generated current of a photosensitive sensor under the premise that the response speed of the device is satisfied. 
     The foregoing provides a detailed introduction to the embodiment of the present application. Specific examples are used to explain the principle and embodiments of the present application. The description of the above embodiments is only used to help understand the present application. In addition, for those skilled in the art, according to the idea of the present application, there can be changes in the specific embodiment and the scope of the application. As described above, the content of the specification should not be construed as a limitation on the present application.