Patent Publication Number: US-2022216257-A1

Title: Image sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0000109 filed on Jan. 4, 2021 in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to an image sensor. More particularly, the disclosure relates to a complementary metal oxide semiconductor (CMOS) image sensor. 
     2. Description of the Related Art 
     An image sensor, as a semiconductor device, converts optical information into electrical signals. Examples of the image sensor may include a charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor. 
     The image sensor may be configured in the form of a package and, in this case, the package may have a structure allowing light to be incident on a light receiving surface or sensing area while protecting the image sensor. 
     Recently, research has been conducted on a backside illumination (BSI) image sensor in which incident light is irradiated through a rear surface of a semiconductor substrate so that pixels formed in the image sensor can have improved light receiving efficiency and light sensitivity. 
     SUMMARY 
     Aspects of the disclosure provide an image sensor with improved quality. 
     In accordance with an aspect of the disclosure, an image sensor includes a substrate including a first surface on which light is incident and a second surface opposite to the first surface; a plurality of unit pixels in the substrate, each of the plurality of unit pixels including a respective photoelectric conversion layer; a plurality of color filters on the first surface of the substrate; a grid pattern on the first surface of the substrate, the grid pattern defining a respective light receiving area of each of the plurality of unit pixels; and a plurality of microlenses on the plurality of color filters, each of the plurality of microlenses corresponding to a respective one of the plurality of unit pixels, wherein the plurality of unit pixels includes a first pixel and a second pixel sharing a first color filter of the plurality of color filters, and wherein a first light receiving area of the first pixel is different from a second light receiving area of the second pixel. 
     In accordance with an aspect of the disclosure, an image sensor includes a light receiving region in which a plurality of unit pixels are arranged; a first color filter on a substrate; a first merged pixel including a first group of unit pixels sharing the first color filter among the plurality of unit pixels; and a grid pattern defining a respective light receiving area of each of the first group of unit pixels across the first color filter, wherein the first merged pixel includes a first pixel and a second pixel farther than the first pixel from a center of the light receiving region, and wherein a first light receiving area of the first pixel is smaller than a second light receiving area of the second pixel. 
     In accordance with an aspect of the disclosure, an image sensor includes a plurality of unit pixels in a substrate; a first color filter on the substrate; a first merged pixel including a first group of unit pixels sharing the first color filter among the plurality of unit pixels; and a grid pattern defining a respective light receiving area of each of the plurality of unit pixels across the first color filter, wherein the first merged pixel includes a first central pixel and a plurality of first peripheral pixels surrounding the first central pixel, and wherein a light receiving area of each of the plurality of first peripheral pixels is smaller than a light receiving area of the first central pixel. 
     However, aspects of the disclosure are not restricted to the one set forth herein. The above and other aspects of the disclosure will become more apparent to one of ordinary skill in the art to which the disclosure pertains by referencing the detailed description of the disclosure given below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an example block diagram illustrating an image sensor according to some embodiments. 
         FIG. 2  is an example circuit diagram explaining a unit pixel of an image sensor according to some embodiments. 
         FIG. 3  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments. 
         FIG. 4  is an example partial layout diagram illustrating a first region and a second region of  FIG. 3 . 
         FIG. 5  is a cross-sectional view taken along lines A-A and B-B of  FIG. 4 . 
         FIG. 6  is an enlarged view illustrating area E of  FIG. 5 . 
         FIGS. 7 and 8  are various example partial layout diagrams illustrating first to third regions of  FIG. 3 . 
         FIG. 9  is an example partial layout diagram illustrating a first region, a second region, and a fourth region of  FIG. 3 . 
         FIGS. 10 and 11  are various schematic layout diagrams of a light receiving region in an image sensor according to some embodiments. 
         FIG. 12  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments. 
         FIG. 13  is an example partial layout diagram illustrating a first region of  FIG. 12 . 
         FIG. 14  is a cross-sectional view taken along line C-C of  FIG. 13 . 
         FIG. 15  is an example partial layout diagram illustrating a second region of  FIG. 12 . 
         FIG. 16  is a cross-sectional view taken along line D-D of  FIG. 15 . 
         FIGS. 17 to 19  are various example partial layout diagrams illustrating the first to third regions of  FIG. 12 . 
         FIG. 20  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments. 
         FIG. 21  is an example partial layout diagram illustrating a first region and a second region of  FIG. 20 . 
         FIG. 22  is a schematic layout diagram explaining an image sensor according to some embodiments. 
         FIG. 23  is a schematic cross-sectional view illustrating an image sensor according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     It will be understood that when an element or layer is referred to as being “over,” “above,” “on,” “below,” “under,” “beneath,” “connected to” or “coupled to” another element or layer, it can be directly over, above, on, below, under, beneath, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly over,” “directly above,” “directly on,” “directly below,” “directly under,” “directly beneath,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numerals refer to like elements throughout. 
     Spatially relative terms, such as “over,” “above,” “on,” “upper,” “below,” “under,” “beneath,” “lower,” and the like, may be used herein for ease of description to describe one element&#39;s or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that 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. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     For the sake of brevity, conventional elements to semiconductor devices may or may not be described in detail herein for brevity purposes. 
     Although the terms first, second, etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the disclosure. 
     Hereinafter, image sensors according to example embodiments will be described with reference to  FIGS. 1 to 23 . 
       FIG. 1  is an example block diagram illustrating an image sensor according to some embodiments.  FIG. 2  is an example circuit diagram explaining a unit pixel of an image sensor according to some embodiments. 
     Referring to  FIG. 1 , the image sensor according to some embodiments may include an active pixel sensor array (APS)  10 , a row decoder  20 , a row driver  30 , a column decoder  40 , a timing generator  50 , a correlated double sampler (CDS)  60 , an analog-to-digital converter (ADC)  70 , and an input/output (I/O) buffer  80 . 
     The APS  10  may include a plurality of unit pixels arranged two-dimensionally and may convert an optical signal into an electrical signal. The APS  10  may be driven by driving signals such as a pixel selection signal, a reset signal, and a charge transfer signal received from the row driver  30 . Further, the electrical signal converted by the APS  10  may be provided to the CDS  60 . 
     The row driver  30  may provide the APS  10  with a plurality of driving signals to drive a plurality of unit pixels according to the decoding result of the row decoder  20 . When the unit pixels are arranged in a matrix, driving signals may be provided for each row. 
     The timing generator  50  may provide a timing signal and a control signal to the row decoder  20  and the column decoder  40 . 
     The CDS  60  may receive the electrical signal generated by the APS  10 , and may hold and sample the received signal. The CDS  60  may double-sample a certain noise level and a signal level according to the electrical signal, and may output a difference level corresponding to a difference between the noise level and the signal level. 
     The ADC  70  may convert an analog signal corresponding to the difference level outputted from the CDS  60  into a digital signal, and may output the digital signal. 
     The I/O buffer  80  may latch digital signals, and the latched signals may be sequentially outputted as the digital signals to an image signal processor according to the decoding result of the column decoder  40 . 
     Referring to  FIG. 2 , each of the unit pixels may include a photoelectric conversion element PD, a transfer transistor TG, a floating diffusion region FD, a reset transistor RG, a source follower transistor SF, and a select transistor SEL. 
     The photoelectric conversion element PD may generate electric charges in proportion to an amount of light incident from the outside. The photoelectric conversion element PD may be coupled with the transfer transistor TG that transfers the generated and accumulated charges to the floating diffusion region FD. The floating diffusion region FD converts the charges into a voltage, and has a parasitic capacitance so that the charges can be stored cumulatively. 
     One end of the transfer transistor TG may be connected to the photoelectric conversion element PD, and the other end of the transfer transistor TG may be connected to the floating diffusion region FD. The transfer transistor TG may be formed of a transistor driven by a predetermined bias (e.g., a transfer signal TX). That is, the transfer transistor TG may transfer the charges generated from the photoelectric conversion element PD to the floating diffusion region FD in response to the transfer signal TX. 
     The source follower transistor SF may amplify a change in the electrical potential of the floating diffusion region FD that has received the charges from the photoelectric conversion element PD and output the amplified change to an output line VOUT. When the source follower transistor SF is turned on, a predetermined electrical potential, e.g., a power voltage VDD, provided to the drain of the source follower transistor SF, may be transferred to the drain region of the select transistor SEL. 
     The select transistor SEL may select a unit pixel to be read on a row basis. The select transistor SEL may be formed of a transistor driven by a select line through which a predetermined bias (e.g., a row select signal SX) is applied. 
     The reset transistor RG may periodically reset the floating diffusion region FD. The reset transistor RG may be formed of a transistor driven by a reset line through which a predetermined bias (e.g., a reset signal RX) is applied. When the reset transistor RG is turned on by the reset signal RX, a predetermined electrical potential, e.g., the power voltage VDD, provided to the drain of the reset transistor RG may be transferred to the floating diffusion region FD. 
       FIG. 3  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments.  FIG. 4  is an example partial layout diagram illustrating a first region and a second region of  FIG. 3 .  FIG. 5  is a cross-sectional view taken along lines A-A and B-B of  FIG. 4 .  FIG. 6  is an enlarged view illustrating area E of  FIG. 5 . 
     Referring to  FIG. 3 , the image sensor according to some embodiments includes a light receiving region APS. 
     A plurality of unit pixels UP that receive light and generate electrical signals may be disposed in the light receiving region APS. The unit pixels UP may be arranged two-dimensionally (e.g., in a matrix form) in a plane including a first direction X and a second direction Y. The active pixel sensor array  10  of  FIG. 1  may include a region corresponding to the light receiving region APS. 
     The light receiving region APS may include a first region Ito a fourth region IV. The first region I may include the unit pixels UP adjacent to a center CP of the light receiving region APS. The second region II may include the unit pixels UP that are farther than the first region I from the center CP of the light receiving region APS. For example, the second region II may be spaced apart from the first region I in the first direction X. The third region III may include the unit pixels UP that are spaced apart from the first region I in a diagonal direction. For example, the second region II may be spaced apart from the third region III in the second direction Y. The fourth region IV may include the unit pixels UP that are farther than the second region II from the center CP of the light receiving region APS. For example, the fourth region W may be spaced apart from the second region II in the first direction X. 
     Each of the unit pixels UP may generate an electrical signal by sensing a predetermined color. For example, each of the unit pixels UP may receive light passing through one of a first color filter RP, a second color filter GP, and a third color filter BP to generate an electrical signal. 
     The first color filter RP, the second color filter GP, and the third color filter BP may include a red color filter, a green color filter, and a blue color filter, respectively. However, this is merely example, and the first color filter RP, the second color filter GP, and the third color filter BP may include a yellow filter, a magenta filter, and a cyan filter, respectively, or may further include a white filter. 
     The first color filter RP, the second color filter GP, and the third color filter BP may filter different colors. As an example, the first color filter RP may be a red color filter, the second color filter GP may be a green color filter, and the third color filter BP may be a blue color filter. 
     In some embodiments, the first color filter RP, the second color filter GP, and the third color filter BP may be arranged in a Bayer pattern. For example, two second color filters GP may be arranged along a diagonal direction other than the first direction X and the second direction Y. The first color filter RP may be arranged along the first direction X together with one second color filter GP, and may be arranged along the second direction Y together with the other second color filter GP. In addition, the third color filter BP may be arranged along the second direction Y together with one second color filter GP, and may be arranged along the first direction X together with the other second color filter GP. The first color filter RP and the third color filter BP may be arranged along a diagonal direction other than the first direction X and the second direction Y. 
     In some embodiments, at least some adjacent unit pixels UP may form a merged pixel that shares one color filter. For example, four unit pixels UP arranged in a 2×2 array may share one of the first color filter RP, the second color filter GP, and the third color filter BP. 
     Referring to  FIGS. 3 to 6 , the image sensor according to some embodiments includes a first substrate  110 , a photoelectric conversion layer  112 , a pixel isolation pattern  120 , a first electronic element TR 1 , a first wiring structure IS 1 , a surface insulating layer  140 , a color filter  170 , a grid pattern  150 , and a microlens  180 . 
     The first substrate  110  may be a semiconductor substrate. For example, the first substrate  110  may be a bulk silicon or silicon-on-insulator (SOI) substrate. The first substrate  110  may be a silicon substrate, or may include other materials such as silicon germanium, indium antimonide, lead tellurium compound, indium arsenide, indium phosphide, gallium arsenide, or gallium antimonide. Alternatively, the first substrate  110  may have an epitaxial layer formed on a base substrate. 
     The first substrate  110  may include a first surface  110   a  and a second surface  110   b  opposite to each other. In embodiments to be described later, the first surface  110   a  may be referred to as a back surface of the first substrate  110 , and the second surface  110   b  may be referred to as a front surface of the first substrate  110 . In some embodiments, the first surface  110   a  of the first substrate  110  may be a light receiving surface on which light is incident. That is, the image sensor according to some embodiments may be a backside illuminated (BSI) image sensor. 
     The photoelectric conversion layer  112  may be formed in the first substrate  110 . The plurality of photoelectric conversion layers  112  may be arranged to correspond to the plurality of unit pixels UP such that each photoelectric conversion layer  112  corresponds to a respective unit pixel UP. For example, the photoelectric conversion layers  112  may be arranged two-dimensionally (e.g., in a matrix form) in a plane including the first direction X and the second direction Y and may be disposed in the unit pixels UP. The photoelectric conversion layer  112  may generate electric charges in proportion to an amount of light incident from the outside. 
     The photoelectric conversion layer  112  may be formed by doping impurities into the first substrate  110 . For example, the photoelectric conversion layer  112  may be formed by ion-implanting n-type impurities into the first substrate  110  which is of a p-type. In some embodiments, the photoelectric conversion layer  112  may have a potential slope in a third direction Z crossing the surface (e.g., the first surface  110   a  or the second surface  110   b ) of the first substrate  110 . For example, the impurity concentration of the photoelectric conversion layer  112  may decrease from the second surface  110   b  toward the first surface  110   a.    
     The photoelectric conversion layer  112  may include, for example, at least one of a photodiode, a phototransistor, a photogate, a pinned photodiode, an organic photodiode, quantum dots, or a combination thereof, but is not limited thereto. 
     The pixel isolation pattern  120  may be formed in the first substrate  110 . The pixel isolation pattern  120  may define the plurality of unit pixels UP in the first substrate  110 . For example, the pixel isolation pattern  120  may be formed in a grid shape in plan view, and may surround each of the unit pixels UP arranged in a matrix form. 
     In some embodiments, the pixel isolation pattern  120  may penetrate the first substrate  110 . For example, the pixel isolation pattern  120  may continuously extend from the second surface  110   b  of the first substrate  110  to the first surface  110   a  of the first substrate  110 . 
     In some embodiments, the pixel isolation pattern  120  may have a width that decreases as it moves away from the second surface  110   b  of the first substrate  110 . Here, the width means a width in a direction parallel to the surface (e.g., the first surface  110   a  or the second surface  110   b ) of the first substrate  110 . This may be due to the characteristics of an etching process for forming the pixel isolation pattern  120 . For example, a process of etching the first substrate  110  to form the pixel isolation pattern  120  may be performed on the second surface  110   b  of the first substrate  110 . 
     In some embodiments, the pixel isolation pattern  120  may include a conductive filling pattern  122  and an insulating spacer layer  124 . For example, an isolation trench defining the plurality of unit pixels UP may be formed in the first substrate  110 . The insulating spacer layer  124  may extend along the side surface of the isolation trench. The conductive filling pattern  122  may be formed on the insulating spacer layer  124  to fill the remaining region of the isolation trench. The insulating spacer layer  124  may electrically insulate the conductive filling pattern  122  from the first substrate  110 . 
     The conductive filling pattern  122  may include, for example, polysilicon (poly Si), but is not limited thereto. In some embodiments, a ground voltage or a negative voltage may be applied to the conductive filling pattern  122 . In this case, an electrostatic discharge (ESD) bruise defect of the image sensor may be effectively prevented. Here, the ESD bruise defect refers to a phenomenon in which electric charges generated by ESD or the like are accumulated in the first substrate  110 , causing spots such as bruises in a generated image. 
     The insulating spacer layer  124  may include, for example, at least one of silicon oxide, aluminum oxide, tantalum oxide, or a combination thereof, but is not limited thereto. In some embodiments, the insulating spacer layer  124  may include a low refractive index material having a lower refractive index than that of the first substrate  110 . In this case, the insulating spacer layer  124  may refract or reflect light incident obliquely on the photoelectric conversion layer  112  to improve light collection efficiency, thereby improving the quality of the image sensor. Further, the insulating spacer layer  124  may prevent photocharges generated in a specific unit pixel UP by incident light from moving to adjacent unit pixels UP by random drift. 
     The first electronic element TR 1  may be formed on the second surface  110   b  of the first substrate  110 . The first electronic element TR 1  may include various transistors for processing the electrical signals generated from the unit pixels UP. For example, the first electronic element TR 1  may include transistors such as the transfer transistor TG, the reset transistor RG, the source follower transistor SF, or the select transistor SEL described above with reference to  FIG. 2 . 
     In some embodiments, the first electronic element TR 1  may include a vertical transfer transistor. For example, the first electronic element TR 1  including the above-described transfer transistor TG may partially extend into the first substrate  110 . The transfer transistor TG may reduce the area of the unit pixel UP, thereby enabling high integration of the image sensor. 
     The first wiring structure IS 1  may be formed on the second surface  110   b  of the first substrate  110 . The first wiring structure IS 1  may include one or a plurality of wires. For example, the first wiring structure IS 1  may include a first inter-wire insulating layer  130  and a plurality of first wires  132  in the first inter-wire insulating layer  130 . In  FIG. 5 , the arrangement and the number of layers of wires constituting the first wiring structure IS 1  are merely examples, and the technical spirit of the disclosure is not limited thereto. 
     In some embodiments, the first wires  132  may be electrically connected to the unit pixels UP. For example, the first wire  132  may be connected to the first electronic element TR 1 . 
     The surface insulating layer  140  may be formed on the first surface  110   a  of the first substrate  110 . The surface insulating layer  140  may extend along the first surface  11   a  of the first substrate  110 . The surface insulating layer  140  may include, for example, at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, hafnium oxide, or a combination thereof, but is not limited thereto. 
     In some embodiments, the surface insulating layer  140  may be formed of multiple films. For example, the surface insulating layer  140  may include an aluminum oxide film, a hafnium oxide film, a silicon oxide film, a silicon nitride film, and a hafnium oxide film that are sequentially stacked on the first surface  110   a  of the first substrate  110 . 
     The surface insulating layer  140  may function as an antireflection layer to prevent reflection of light incident on the first substrate  110 . Accordingly, the light receiving rate of the photoelectric conversion layer  112  may be improved. In addition, the surface insulating layer  140  may function as a planarization layer to allow the color filters  170  and the microlenses  180 , which will be described later, to be formed with a uniform height. 
     The color filter  170  may be formed on the first surface  110   a  of the first substrate  110 . For example, the color filter  170  may be formed on the surface insulating layer  140 . The plurality of color filters  170  may be arranged two-dimensionally (e.g., in a matrix form) in a plane including the first direction X and the second direction Y. For example, the color filter  170  may include the first color filter RP, the second color filter GP, and the third color filter BP described above with reference to  FIG. 3 . 
     Each of the first region I and the second region II may include a merged pixel that shares one of the plurality of color filters  170 . As an example, the first region I may include a first merged pixel P 11  to P 14  (i.e., a first group of unit pixels) sharing the first color filter RP, and the second region II may include a second merged pixel P 21  to P 24  sharing the first color filter RP. However, this is merely an example, and each of the first merged pixel P 11  to P 14  and the second merged pixel P 21  to P 24  may share a different color filter. For example, the first merged pixel P 11  to P 14  may share the first color filter RP, and the second merged pixel P 21  to P 24  may share the second color filter GP or the third color filter BP other than the first color filter RP. 
     The grid pattern  150  may be formed on the first surface  110   a  of the first substrate  110 . For example, the grid pattern  150  may be formed on the surface insulating layer  140 . The grid pattern  150  may be formed in a grid shape in plan view and surround each of the unit pixels UP arranged in a matrix form. For example, the grid pattern  150  may be formed to overlap the pixel isolation pattern  120  in the third direction Z. 
     The grid pattern  150  may cross the color filter  170  from an edge to an opposite edge. For example, the grid pattern  150  may be formed in a grid shape in plan view and surround each of the color filters  170  arranged in a matrix form. In addition, as described above, since one color filter  170  may be shared by a plurality of unit pixels UP, the grid pattern  150  may cross the inside of one color filter  170 . 
     The grid pattern  150  may define a light receiving area of each of the unit pixels UP. Herein, the light receiving area may mean an area in which light incident toward the first surface  110   a  of the first substrate  110  can pass through the grid pattern  150  in plan view. For example, as shown in  FIG. 4 , the grid pattern  150  may define light receiving areas S 11  to S 14  of the first merged pixel P 11  to P 14  and light receiving areas S 21  to S 24  of the second merged pixel P 21  to P 24 . As the width of the grid pattern  150  increases, the light receiving areas S 11  to S 14  of the first merged pixel P 11  to P 14  and the light receiving areas S 21  to S 24  of the second merged pixel P 21  to P 24  may decrease. 
     The light receiving areas of the unit pixels UP included in the merged pixel may vary depending on positions where the unit pixels UP are disposed. 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. For example, the light receiving areas S 21  and S 23  of the pixels P 21  and P 23  may be smaller than the light receiving areas S 11  and S 13  of the pixels P 11  and P 13 . As an example, a width W 21  of the grid pattern  150  defining the light receiving areas S 21  and S 23  on the left surfaces of the pixels P 21  and P 23  (i.e., a second portion of the grid pattern  150 ) may be greater than a width W 11  of the grid pattern  150  defining the light receiving areas S 11  and S 13  on the left surfaces of the pixels P 11  and P 13  (i.e., a first portion of the grid pattern  150 ). A width W 23  of the grid pattern  150  defining the light receiving areas S 21  and S 22  on the top surfaces of the pixels P 21  and P 22  may be the same as a width W 13  of the grid pattern  150  defining the light receiving areas S 11  and S 12  on the top surfaces of the pixels P 11  and P 12 . A width W 24  of the grid pattern  150  defining the light receiving areas S 23  and S 24  on the top surfaces of the pixels P 23  and P 24  may be the same as a width W 14  of the grid pattern  150  defining the light receiving areas S 13  and S 14  on the top surfaces of the pixels P 13  and P 14 . The term “same” as used herein not only means being completely identical but also includes a minute difference that may occur due to a process margin and the like. 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the second merged pixel P 21  to P 24  may decrease as the unit pixels are closer to the center CP of the light receiving region APS. For example, the light receiving areas S 21  and S 23  of the pixels P 21  and P 23  may be smaller than the light receiving areas S 22  and S 24  of the pixels P 22  and P 24 . For example, the width W 21  of the grid pattern  150  defining the light receiving areas S 21  and S 23  on the left surfaces of the pixels P 21  and P 23  may be greater than a width W 22  of the grid pattern  150  defining the light receiving areas S 22  and S 24  on the left surfaces of the pixels P 22  and P 24 . 
     In some embodiments, the light receiving areas of the unit pixels UP included in the first merged pixel P 11  to P 14  may be the same. For example, the light receiving area S 11  of the pixel P 11 , the light receiving area S 12  of the pixel P 12 , the light receiving area S 13  of the pixel P 13 , and the light receiving area S 14  of the pixel P 14  may be the same. As an example, the width W 11  of the grid pattern  150  defining the light receiving areas S 11  and S 13  on the left surfaces of the pixels P 11  and P 13  may be the same as a width W 12  of the grid pattern  150  defining the light receiving areas S 12  and S 14  on the left surfaces of the pixels P 12  and P 14 . The width W 13  of the grid pattern  150  defining the light receiving areas S 11  and S 12  on the top surfaces of the pixels P 11  and P 12  may be the same as the width W 14  of the grid pattern  150  defining the light receiving area S 13  and S 14  on the top surfaces of the pixels P 13  and P 14 . 
     In some embodiments, the grid pattern  150  may include a first material pattern  152  and a second material pattern  154  as shown, e.g., in  FIG. 5 . The first material pattern  152  and the second material pattern  154  may be sequentially stacked on the surface insulating layer  140 . The first material pattern  152  and the second material pattern  154  may include different materials. As an example, the first material pattern  152  may be a metal pattern, and the second material pattern  154  may be an oxide pattern. As another example, the first material pattern  152  may be a first metal pattern, and the second material pattern  154  may be a second metal pattern different from the first metal pattern. 
     The metal pattern may include, for example, at least one of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), tungsten (W), aluminum (Al), copper (Cu) or a combination thereof, but is not limited thereto. In some embodiments, the first material pattern  152  including the metal pattern may prevent the electric charges generated by ESD or the like from being accumulated on the surface (e.g., the first surface  110   a ) of the first substrate  110 , thereby effectively preventing the ESD bruise defect. 
     The oxide pattern may include, for example, at least one of metal oxide such as titanium oxide, tantalum oxide, tungsten oxide, aluminum oxide, copper oxide, silicon oxide, or a combination thereof, but is not limited thereto. In some embodiments, the second material pattern  154  may include a low refractive index material having a lower refractive index than that of silicon (Si). In this case, the second material pattern  154  may refract or reflect light incident obliquely on the photoelectric conversion layer  112  to improve light collection efficiency, thereby improving the quality of the image sensor. 
     In some embodiments, the height of the grid pattern  150  may be lower than the height of the color filter  170 . For example, as shown in  FIGS. 5 and 6 , with respect to the top surface of the surface insulating layer  140 , a height H 1  of the top surface of the grid pattern  150  may be lower than a height H 2  of the top surface of the color filter  170 . For example, with respect to the top surface of the surface insulating layer  140 , the height H 1  of the top surface of the grid pattern  150  may be about 3000 Å to about 5000 Å, and the height H 2  of the top surface of the color filter  170  may be about 5000 Å to about 10000 Å. In this case, the grid pattern  150  may not completely separate the color filters  170 . For example, as illustrated, the first color filter RP and the second color filter GP may be in contact with each other on the top surface of the grid pattern  150 . 
     In some embodiments, the height of the color filter  170  may decrease toward the edge of the color filter  170 . For example, as shown in  FIGS. 5 and 6 , with respect to the top surface of the surface insulating layer  140 , the height H 2  of the top surface of the first color filter RP may decrease toward the second color filter GP. This may be due to the characteristics of a process for forming the color filter  170  on the grid pattern  150 . In some embodiments, the edge of the color filter  170  may include a convex curved surface  170   c.  The height of the convex curved surface  170   c  of the first color filter RP may decrease toward the second color filter GP. 
     In some embodiments, a first passivation layer  160  may be further formed on the surface insulating layer  140  and the grid pattern  150 . The first passivation layer  160  may conformally extend along the profiles of the top surface of the surface insulating layer  140  and the side and top surfaces of the grid pattern  150 . The first passivation layer  160  may be interposed between the surface insulating layer  140  and the color filter  170  and between the grid pattern  150  and the color filter  170 . 
     The first passivation layer  160  may prevent damage to the surface insulating layer  140  and the grid pattern  150 . The first passivation layer  160  may include, for example, aluminum oxide, but is not limited thereto. 
     The microlens  180  may be formed above the first surface  110   a  of the first substrate  110 . For example, the microlens  180  may be formed on the color filter  170 . The plurality of microlenses  180  may be arranged to correspond to the plurality of unit pixels UP such that each microlens  180  corresponds to a respective unit pixel UP. For example, the plurality of microlenses  180  may be arranged two-dimensionally (e.g., in a matrix form) in a plane including the first direction X and the second direction Y. 
     The microlens  180  may have a convex shape and may have a predetermined radius of curvature. Accordingly, the microlens  180  may condense light incident on the photoelectric conversion layer  112 . The microlens  180  may include, for example, a light transmitting resin, but is not limited thereto. 
     In some embodiments, a second passivation layer  185  may be formed on the microlens  180 . The second passivation layer  185  may extend along the surface of the microlens  180 . The second passivation layer  185  may include inorganic oxide. For example, the second passivation layer  185  may include at least one of silicon oxide, titanium oxide, zirconium oxide, hafnium oxide, or a combination thereof, but is not limited thereto. As an example, the second passivation layer  185  may include low temperature oxide (LTO). 
     The second passivation layer  185  may protect the microlens  180  from the outside. For example, the second passivation layer  185  including inorganic oxide may cover and protect the microlens  180  including an organic material such as a light transmitting resin. In addition, the second passivation layer  185  may improve the quality of the image sensor by improving light collection efficiency of the microlens  180 . For example, the second passivation layer  185  may fill a space between the microlenses  180 , thereby reducing reflection, refraction, scattering, and the like of incident light reaching the space between the microlenses  180 . 
     In order to improve the performance of the image sensor, a merged pixel in which a plurality of adjacent unit pixels share one color filter is used. For example, the merged pixel has an advantage of being able to provide a bright image by operating as one pixel in a dark place of the image sensor, and provide a detailed image by being rearranged (re-mosaic) in a bright place of the image sensor. 
     Meanwhile, as the image sensor becomes increasingly highly integrated, there is a problem in that the sensitivity of each of the unit pixels constituting one merged pixel varies depending on its position. For example, in an electronic device including the image sensor, light incident from the outside may pass through a module lens and reach a light receiving region of the image sensor. In this case, the amount of light passing through the center portion of the module lens may be greater than the amount of light passing through the edge portion of the module lens. Accordingly, the sensitivities of the unit pixels adjacent to the center of the light receiving region among the unit pixels constituting one merged pixel may be greater than the sensitivities of the unit pixels away from the center of the light receiving region among the unit pixels constituting the one merged pixel. This difference in sensitivity causes a deterioration in the quality of an image generated when the merged pixel is rearranged (re-mosaic). 
     However, the image sensor according to some embodiments may improve the quality of a generated image by varying the light receiving areas depending on the positions of the unit pixels UP constituting the merged pixel. For example, as described above, in the second merged pixel P 21  to P 24 , the light receiving areas S 21  and S 23  of the pixels P 21  and P 23  closer to the center CP of the light receiving region APS may be smaller than the light receiving areas S 22  and S 24  of the pixels P 22  and P 24  farther away from the center CP of the light receiving region APS. Accordingly, a difference in sensitivity between the pixels P 21  and P 23  and the pixels P 22  and P 24  may be reduced, thereby providing the image sensor with improved quality. 
     In addition, the above sensitivity difference between the unit pixels constituting one merged pixel may increase as the unit pixels are farther away from the center of the light receiving region. However, the image sensor according to some embodiments may improve the quality of a generated image by varying the light receiving areas depending on the positions of the merged pixels. For example, as described above, the light receiving areas S 21  and S 23  of the pixels P 21  and P 23  in the second merged pixel P 21  to P 24 , which is away from the center CP of the light receiving region APS, may be smaller than the light receiving areas S 11  and S 13  of the pixels P 11  and P 13  in the first merged pixel P 11  to P 14 , which is adjacent to the center CP of the light receiving region APS. Accordingly, the image sensor with improved quality may be provided. 
       FIGS. 7 and 8  are various example partial layout diagrams illustrating first to third regions of  FIG. 3 . For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 6  may be recapitulated or omitted. 
     Referring to  FIGS. 3, 7 and 8 , in the image sensor according to some embodiments, the third region III spaced apart diagonally from the first region I may include a third merged pixel P 31  to P 34  that shares one of the plurality of color filters  170 . 
     For example, the third region III may include the third merged pixel P 31  to P 34  sharing the first color filter RP. However, this is merely an example, and the third merged pixel P 31  to P 34  may share the second color filter GP or the third color filter BP. The grid pattern  150  may define light receiving areas S 31  to S 34  of the third merged pixel P 31  to P 34 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. For example, the light receiving areas S 31 , S 32 , and S 33  of the pixels P 31 , P 32 , and P 33  may be smaller than the light receiving areas S 11 , S 12 , and S 13  of the pixels P 11 , P 12 , and P 13 . 
     In  FIG. 7 , as an example, widths W 31  and W 33  of the grid pattern  150  defining the light receiving areas S 31 , S 32 , and S 33  of the pixels P 31 , P 32 , and P 33  may be greater than the widths W 11  and W 13  of the grid pattern  150  defining the light receiving areas S 11 , S 12 , and S 13  of the pixels P 11 , P 12 , and P 13 . A width W 34  of the grid pattern  150  defining the light receiving areas S 33  and S 34  on the top surfaces of the pixels P 33  and P 34  may be the same as the width W 14  of the grid pattern  150  defining the light receiving areas S 13  and S 14  on the top surfaces of the pixels P 13  and P 14 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the third merged pixel P 31  to P 34  may decrease as the unit pixels are closer to the center CP of the light receiving region APS. For example, the light receiving area S 31  of the pixel P 31  may be smaller than the light receiving areas S 32  and S 33  of the pixels P 32  and P 33 . 
     In  FIG. 7 , as an example, the width W 31  of the grid pattern  150  defining the light receiving areas S 31  and S 33  on the left surfaces of the pixels P 31  and P 33  may be greater than a width W 32  of the grid pattern  150  defining the light receiving areas S 32  and S 34  on the left surfaces of the pixels P 32  and P 34 . The width W 33  of the grid pattern  150  defining the light receiving areas S 31  and S 32  on the top surfaces of the pixels P 31  and P 32  may be greater than the width W 34  of the grid pattern  150  defining the light receiving areas S 33  and S 34  on the top surfaces of the pixels P 33  and P 34 . 
     In  FIG. 8 , as another example, the width W 22  of the grid pattern  150  between the pixels P 21  and P 23  and the pixels P 22  and P 24  may be greater than the width W 12  of the grid pattern  150  between the pixels P 11  and P 13  and the pixels P 12  and P 14 . The width W 24  of the grid pattern  150  between the pixel P 21  and the pixel P 23  may be greater than a width W 26  of the grid pattern  150  between the pixel P 22  and the pixel P 24 . 
     In  FIG. 8 , as another example, the width W 32  of the grid pattern  150  between the pixel P 31  and the pixel P 32  may be greater than the width W 12  of the grid pattern  150  between the pixel P 11  and the pixel P 12 . The width W 32  of the grid pattern  150  between the pixel P 31  and the pixel P 32  may be greater than a width W 38  of the grid pattern  150  between the pixel P 33  and the pixel P 34 . The width W 34  of the grid pattern  150  between the pixel P 31  and the pixel P 33  may be greater than a width W 36  of the grid pattern  150  between the pixel P 32  and the pixel P 34 . 
       FIG. 9  is an example partial layout diagram illustrating a first region, a second region, and a fourth region of  FIG. 3 . For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 6  may be recapitulated or omitted. 
     Referring to  FIGS. 3 and 9 , in the image sensor according to some embodiments, the fourth region IV spaced apart from the second region II in the first direction X includes a fourth merged pixel P 41  to P 44  that shares one of the plurality of color filters  170 . 
     As an example, the fourth region IV may include the fourth merged pixel P 41  to P 44  that shares the first color filter RP. However, this is merely example, and the fourth merged pixel P 41  to P 44  may share the second color filter GP or the third color filter BP. The grid pattern  150  may define light receiving areas S 41  to S 44  of the fourth merged pixel P 41  to P 44 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. For example, the light receiving areas S 41  and S 43  of the pixels P 41  and P 43  may be smaller than the light receiving areas S 21  and S 23  of the pixels P 21  and P 23 . As an example, a width W 41  of the grid pattern  150  defining the light receiving areas S 41  and S 43  on the left surfaces of the pixels P 41  and P 43  may be greater than the width W 21  of the grid pattern  150  defining the light receiving areas S 21  and S 23  on the left surfaces of the pixels P 21  and P 23 . A width W 43  of the grid pattern  150  defining the light receiving areas S 41  and S 42  on the top surfaces of the pixels P 41  and P 42  may be the same as the width W 23  of the grid pattern  150  defining the light receiving areas S 21  and S 22  on the top surfaces of the pixels P 21  and P 22 . A width W 44  of the grid pattern  150  defining the light receiving areas S 43  and S 44  on the top surfaces of the pixels P 43  and P 44  may be the same as the width W 24  of the grid pattern  150  defining the light receiving areas S 23  and S 24  on the top surfaces of the pixels P 23  and P 24 . 
       FIGS. 10 and 11  are various schematic layout diagrams of a light receiving region in an image sensor according to some embodiments. For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 6  may be recapitulated or omitted. 
     Referring to  FIG. 10 , in the image sensor according to some embodiments, at least some of the unit pixels UP include a first focus pixel FP  1 . 
     The first focus pixel FP 1  may include a first sub-pixel LUP 1  and a second sub-pixel RUP 1 . The first sub-pixel LUP 1  and the second sub-pixel RUP 1  may be arranged along, for example, the first direction X. 
     Referring to  FIG. 11 , in the image sensor according to some embodiments, at least some of the unit pixels UP further include a second focus pixel FP 2 . 
     The second focus pixel FP 2  may include a third sub-pixel LUP 2  and a fourth sub-pixel RUP 2 . The third sub-pixel LUP 2  and the fourth sub-pixel RUP 2  may be arranged along the second direction Y crossing the first direction X. 
     Each of the first focus pixel FP 1  and the second focus pixel FP 2  may perform an auto focus (AF) function. For example, since the first focus pixel FP 1  and the second focus pixel FP 2  may each include two sub-pixels (the first sub-pixel LUP 1  and the second sub-pixel RUP 1 , or the third sub-pixel LUP 2  and the fourth sub-pixel RUP 2 ), it is possible to perform the auto focus function using a phase detection AF (PDAF). 
       FIG. 12  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments.  FIG. 13  is an example partial layout diagram illustrating a first region of  FIG. 12 .  FIG. 14  is a cross-sectional view taken along line C-C of  FIG. 13 .  FIG. 15  is an example partial layout diagram illustrating a second region of  FIG. 12 .  FIG. 16  is a cross-sectional view taken along line D-D of  FIG. 15 . For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 6  may be recapitulated or omitted. 
     Referring to  FIG. 12 , in the image sensor according to some embodiments, nine unit pixels UP arranged in a 3×3 array may share one of the first color filter RP, the second color filter GP, and the third color filter BP. 
     Referring to  FIGS. 12 to 14 , in the image sensor according to some embodiments, the first region I includes a first merged pixel P 11  to P 19  that shares one of the plurality of color filters  170 . 
     For example, the first region I may include the first merged pixel P 11  to P 19  that shares the first color filter RP. The grid pattern  150  may define light receiving areas S 11  to S 19  of the first merged pixel P 11  to P 19 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the first merged pixel P 11  to P 19  may decrease as the unit pixels are closer to the edge of the first color filter RP. For example, the first merged pixel P 11  to P 19  may include a first central pixel P 15  and a plurality of first peripheral pixels P 11  to P 14  and P 16  to P 19 . The first peripheral pixels P 11  to P 14  and P 16  to P 19  may surround the first central pixel P 15  in plan view as shown, e.g., in  FIG. 13 . In this case, each of the light receiving areas S 11  to S 14  and S 16  to S 19  of the first peripheral pixels P 11  to P 14  and P 16  to P 19  may be smaller than the light receiving area S 15  of the first central pixel P 15 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the first peripheral pixels P 11  to P 14  and P 16  to P 19  may decrease as the unit pixels are closer to the vertex of the first color filter RP. For example, the pixels P 11 , P 13 , P 17 , and P 19  may be disposed adjacent to the vertex of the first color filter RP, and the pixels P 12 , P 14 , P 16 , and P 18  may be disposed away from the vertex of the first color filter RP. In this case, each of the light receiving areas S 11 , S 13 , S 17 , and S 19  of the pixels P 11 , P 13 , P 17 , and P 19  may be smaller than each of the light receiving areas S 12 , S 14 , S 16 , and S 18  of the pixels P 12 , P 14 , P 16 , and P 18 . 
     As an example, a width W 11  of the grid pattern  150  defining the light receiving area S 11  on the left surface of the pixel P 11  may be greater than widths W 12  and W 13  of the grid pattern  150  defining the light receiving area S 12  on the left and right surfaces of the pixel P 12 . The width W 12  of the grid pattern  150  between the pixel P 11  and the pixel P 12  may be greater than a width W 14  of the grid pattern  150  between the pixel P 14  and the pixel P 15 . 
     As an example, a width W 15  of the grid pattern  150  defining the light receiving area S 13  on the top surface of the pixel P 13  may be greater than widths W 16  and W 17 of the grid pattern 150  defining the light receiving area S 16  on the top and bottom surfaces of the pixel P 16 . The width W 16  of the grid pattern  150  between the pixel P 13  and the pixel P 16  may be greater than a width W 18  of the grid pattern  150  between the pixel P 12  and the pixel P 15 . 
     Referring to  FIGS. 12, 15, and 16 , in the image sensor according to some embodiments, the second region II includes a second merged pixel P 21  to P 29  that shares one of the plurality of color filters  170 . 
     As an example, the second region II may include the second merged pixel P 21  to P 29  sharing the first color filter RP. The grid pattern  150  may define light receiving areas S 21  to S 29  of the second merged pixel P 21  to P 29 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the second merged pixel P 21  to P 29  may decrease as the unit pixels are closer to the edge of the first color filter RP. For example, the second merged pixel P 21  to P 29  may include a second central pixel P 25  and a plurality of second peripheral pixels P 21  to P 24  and P 26  to P 29 . The second peripheral pixels P 21  to P 24  and P 26  to P 29  may surround the second central pixel P 25  in plan view. In this case, each of the light receiving areas S 21  to S 24  and S 26  to S 29  of the second peripheral pixels P 21  to P 24  and P 26  to P 29  may be smaller than the light receiving area S 25  of the second central pixel P 25 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. For example, the light receiving areas S 21  and S 27  of the pixels P 21  and P 27  may be smaller than the light receiving areas S 11  and S 17  of the pixels P 11  and P 17 . For example, a width W 21  of the grid pattern  150  defining the light receiving area S 21  on the left surface of the pixel P 21  may be greater than the width W 11  of the grid pattern  150  defining the light receiving area S 11  on the left surface of the pixel P 11 . For example, the light receiving areas S 22  and S 28  of the pixels P 22  and P 28  may be smaller than the light receiving areas S 12  and S 18  of the pixels P 12  and P 18 . As an example, a width W 22  of the grid pattern  150  defining the light receiving area S 22  on the left surface of the pixel P 22  may be greater than the width W 12  of the grid pattern  150  defining the light receiving area S 12  on the left surface of the pixel P 12 . 
     In some embodiments, the width W 22  of the grid pattern  150  defining the light receiving area S 22  on the left surface of the pixel P 22  may be smaller than the width W 21  of the grid pattern  150  defining the light receiving area S 21  on the left surface of the pixel P 21 , and may be greater than a width W 23  of the grid pattern  150  defining the light receiving area S 23  on the left surface of the pixel P 23 . 
       FIGS. 17 to 19  are various example partial layout diagrams illustrating the first to third regions of  FIG. 12 . For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 16  may be recapitulated or omitted. 
     Referring to  FIGS. 12 and 17 to 19 , in the image sensor according to some embodiments, the third region III spaced apart diagonally from the first region I includes a third merged pixel P 31  to P 39  that shares one of the plurality of color filters  170 . 
     As an example, the third region III may include the third merged pixel P 31  to P 39  that shares the first color filter RP. The grid pattern  150  may define light receiving areas S 31  to S 39  of the third merged pixel P 31  to P 39 . 
     Referring to  FIGS. 12 and 17 , in the image sensor according to some embodiments, the first merged pixel P 11  to P 19 , the second merged pixel P 21  to P 29 , and the third merged pixel P 31  to P 39  may be arranged in the same shape. 
     For example, the light receiving areas S 31 , S 33 , S 37 , and S 39  of the pixels P 31 , P 33 , P 37 , and P 39  may be the same as the light receiving areas S 11  and S 21  of the pixels P 11  and P 21 . The light receiving areas S 32 , S 34 , S 36 , and S 38  of the pixels P 32 , P 34 , P 36 , and P 38  may be the same as the light receiving areas S 12  and S 22  of the pixels P 12  and P 22 . The light receiving area S 35  of the pixel P 35  may be the same as the light receiving areas S 15  and S 25  of the pixels P 15  and P 25 . 
     Referring to  FIGS. 12 and 18 , in the image sensor according to some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. 
     For example, since both the second region II and the third region III may be spaced apart from the first region I in the first direction X, the light receiving areas S 21 , S 27 , S 31 , and S 37  of the pixels P 21 , P 27 , P 31  and P 37  may be smaller than the light receiving areas S 11  and S 17  of the pixels P 11  and P 17 . In addition, since the second region II may be spaced apart from the third region III in the second direction Y, the light receiving areas S 31  and S 33  of the pixels  31  and  33  may be smaller than the light receiving areas S 21  and S 23  of the pixels P 21  and P 23 . 
     Referring to  FIGS. 12 and 19 , in the image sensor according to some embodiments, the light receiving areas of at least some of the peripheral pixels may increase as the peripheral pixels are farther away from the center CP of the light receiving region APS. 
     For example, the light receiving areas S 22  and S 28  of the pixels P 22  and P 28  may be greater than the light receiving areas S 12  and S 18  of the pixels P 12  and P 18 . Further, the light receiving areas S 36  and S 38  of the pixels P 36  and P 38  may be greater than the light receiving areas S 16  and S 18  of the pixels P 16  and P 18 . 
       FIG. 20  is a schematic layout diagram of a light receiving region in an image sensor according to some embodiments.  FIG. 21  is an example partial layout diagram illustrating a first region and a second region of  FIG. 20 . For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 19  may be recapitulated or omitted. 
     Referring to  FIG. 20 , in the image sensor according to some embodiments, sixteen unit pixels UP arranged in 4×4 array may share one of the first color filter RP, the second color filter GP, and the third color filter BP. 
     Referring to  FIGS. 20 and 21 , in the image sensor according to some embodiments, the first region I includes a first merged pixel P 11  to P 116  that shares one of the plurality of color filters  170 , and the second region II includes a second merged pixel P 21  to P 216  that shares one of the plurality of color filters  170 . 
     As an example, the first region I may include the first merged pixel P 11  to P 116  sharing the first color filter RP, and the second region II may include the second merged pixel P 21  to P 216  sharing the first color filter RP. The grid pattern  150  may define light receiving areas S 11  to S 116  of the first merged pixel P 11  to P 116  and light receiving areas S 21  to S 216  of the second merged pixel P 21  to P 216 . 
     In some embodiments, the light receiving areas of at least some of the unit pixels UP may decrease as the unit pixels are farther away from the center CP of the light receiving region APS. In some embodiments, the light receiving areas of at least some of the unit pixels UP included in the second merged pixel P 21  to P 216  may decrease as the unit pixels are closer to the center CP of the light receiving region APS. For example, the light receiving areas S 21 , S 25 , S 29 , and S 213  of the pixels P 21 , P 25 , P 29 , and P 213  may be smaller than the light receiving areas S 11 , S 15 , S 19 , and S 113  of the pixels P 11 , P 15 , P 19 , and P 113 . As an example, a width W 21  of the grid pattern  150  defining the light receiving areas S 21 , S 25 , S 29 , and S 213  on the left surfaces of the pixels P 21 , P 25 , P 29 , and P 213  may be greater than a width W 11  of the grid pattern  150  defining the light receiving areas S 11 , S 15 , S 19 , S 113  on the left surfaces of the pixels P 11 , P 15 , P 19 , and P 113 . 
       FIG. 22  is a schematic layout diagram explaining an image sensor according to some embodiments.  FIG. 23  is a schematic cross-sectional view illustrating an image sensor according to some embodiments. For simplicity of description, redundant parts of the description made with reference to  FIGS. 1 to 6  may be recapitulated or omitted. 
     Referring to  FIGS. 22 and 23 , the image sensor according to some embodiments may include a sensor array region SAR, a connection region CR, and a pad region PR. 
     The sensor array region SAR may include an area corresponding to the APS  10  shown in  FIG. 1 . For example, in the sensor array region SAR, a plurality of unit pixels (e.g., UP in  FIG. 3 ) may be arranged two-dimensionally (e.g., in a matrix form). 
     The sensor array region SAR may include a light receiving region APS and a light blocking region OB. Active pixels that receive light to generate active signals may be arranged in the light receiving region APS. Optical black pixels that generate optical black signals by blocking light may be arranged in the light blocking region OB. The light blocking region OB may be formed, for example, along the periphery of the light receiving region APS, but this is merely an example. 
     In some embodiments, the photoelectric conversion layer  112  may not be formed in a part of the light blocking region OB. For example, the photoelectric conversion layer  112  may be formed in the first substrate  110  in the light blocking region OB adjacent to the light receiving region APS, but may not be formed in the first substrate  110  in the light blocking region OB spaced apart or farther way from the light receiving region APS. In some embodiments, dummy pixels may be formed in the light receiving region APS adjacent to the light blocking region OB. 
     The connection region CR may be formed around the sensor array region SAR. The connection region CR may be formed on one side of the sensor array region SAR, but this is merely example. Wires are formed in the connection region CR, and may be configured to transmit and receive electrical signals of the sensor array region SAR. 
     The pad region PR may be formed around the sensor array region SAR. The pad region PR may be formed adjacent to the edge of the image sensor according to some embodiments, but this is merely an example. The pad region PR may be connected to an external device or the like to allow the image sensor according to some embodiments to transmit and receive electrical signals to and from the external device. 
     The connection region CR is shown to be interposed between the sensor array region SAR and the pad region PR, but this is merely an example. The arrangement of the sensor array region SAR, the connection region CR, and the pad region PR may vary depending on the requirement. 
     In some embodiments, the first wiring structure IS 1  may include the first wire  132  in the sensor array region SAR and a second wire  134  in the connection region CR. The first wire  132  may be electrically connected to the unit pixels (e.g., UP of  FIG. 3 ) of the sensor array region SAR. For example, the first wire  132  may be connected to the first electronic element TR 1 . At least a part of the second wire  134  may be electrically connected to at least a part of the first wire  132 . For example, at least a part of the second wire  134  may extend from the sensor array region SAR. Accordingly, the second wire  134  may be electrically connected to the unit pixels (e.g., UP of  FIG. 3 ) of the sensor array region SAR. 
     The image sensor according to some embodiments may further include a second substrate  210 , a second wiring structure IS 2 , a first connection structure  350 , a second connection structure  450 , a third connection structure  550 , an element isolation pattern  115 , a light blocking filter  270 C, and a third passivation layer  380 . 
     The second substrate  210  may be a bulk silicon or silicon-on-insulator (SOI) substrate. The second substrate  210  may be a silicon substrate, or may include other materials such as silicon germanium, indium antimonide, lead tellurium compound, indium arsenide, indium phosphide, gallium arsenide, or gallium antimonide. Alternatively, the second substrate  210  may have an epitaxial layer formed on a base substrate. 
     The second substrate  210  may include a third surface  210   a  and a fourth surface  210   b  opposite to each other. In some embodiments, the third surface  210   a  of the second substrate  210  may face the second surface  110   b  of the first substrate  110 . 
     In some embodiments, a second electronic element TR 2  may be formed on the third surface  210   a  of the second substrate  210 . The second electronic element TR 2  may be electrically connected to the sensor array region SAR, and may transmit and receive an electrical signal to and from each of the unit pixels (e.g., UP of  FIG. 3 ) of the sensor array region SAR. For example, the second electronic element TR 2  may include electronic elements constituting the row decoder  20 , the row driver  30 , the column decoder  40 , the timing generator  50 , the CDS  60 , the ADC  70 , or the input/output buffer  80  shown in  FIG. 1 . 
     The second wiring structure IS 2  may be formed on the third surface  210   a  of the second substrate  210 . The second wiring structure IS 2  may be attached to the first wiring structure IS 1 . For example, as shown in  FIG. 23 , the top surface of the second wiring structure IS 2  may be attached to the bottom surface of the first wiring structure IS 1 . 
     The second wiring structure IS 2  may include one or a plurality of wires. For example, the second wiring structure IS 2  may include a second inter-wire insulating layer  230  and a plurality of wires  232 ,  234 , and  236  in the second inter-wire insulating layer  230 . In  FIG. 23 , the number of layers and arrangements of wires constituting the second wiring structure IS 2  are merely examples, and are not limited thereto. 
     At least some of the wires  232 ,  234 , and  236  of the second wiring structure IS 2  may be connected to the second electronic element TR 2 . In some embodiments, the second wiring structure IS 2  may include a third wire  232  in the sensor array region SAR, a fourth wire  234  in the connection region CR, and a fifth wire  236  in the pad region PR. In some embodiments, the fourth wire  234  may be an uppermost wire among a plurality of wires in the connection region CR, and the fifth wire  236  may be an uppermost wire among a plurality of wires in the pad region PR. 
     The first connection structure  350  may be formed in the light blocking region OB. The first connection structure  350  may be formed on the surface insulating layer  140  of the light blocking region OB. In some embodiments, the first connection structure  350  may be in contact with the pixel isolation pattern  120 . For example, a first trench  355   t  exposing the pixel isolation pattern  120  may be formed in the first substrate  110  and the surface insulating layer  140  in the light blocking region OB. The first connection structure  350  may be formed in the first trench  355   t  to be in contact with the pixel isolation pattern  120  in the light blocking region OB. In some embodiments, the first connection structure  350  may extend along the profiles of the side and bottom surfaces of the first trench  355   t.    
     In some embodiments, the first connection structure  350  may be electrically connected to the conductive filling pattern  122  to apply a ground voltage or a negative voltage to the conductive filling pattern  122 . Accordingly, the electric charges generated by ESD or the like may be discharged to the first connection structure  350  through the conductive filling pattern  122 , and the ESD bruise defect may be effectively prevented. 
     The second connection structure  450  may be formed in the connection region CR. The second connection structure  450  may be formed on the surface insulating layer  140  in the connection region CR. The second connection structure  450  may electrically connect the first substrate  110  to the second substrate  210 . For example, a second trench  455   t  exposing the second wire  134  and the fourth wire  234  may be formed in the first substrate  110 , the first wiring structure IS 1 , and the second wiring structure IS 2  in the connection region CR. The second connection structure  450  may be formed in the second trench  455   t  to connect the second wire  134  to the fourth wire  234 . In some embodiments, the second connection structure  450  may extend along the profiles of the side and bottom surfaces of the second trench  455   t.    
     The third connection structure  550  may be formed in the pad region PR. The third connection structure  550  may be formed on the surface insulating layer  140  in the pad region PR. The third connection structure  550  may electrically connect the second substrate  210  to an external device or the like. 
     For example, a third trench  550   t  exposing the fifth wire  236  may be formed in the first substrate  110 , the first wiring structure IS 1 , and the second wiring structure IS 2  in the pad region PR. The third connection structure  550  may be formed in the third trench  550   t  to be in contact with the fifth wire  236 . In addition, a fourth trench  555   t  may be formed in the first substrate  110  in the pad region PR. The third connection structure  550  may be formed in the fourth trench  555   t  and be exposed. In some embodiments, the third connection structure  550  may extend along the profiles of the side and bottom surfaces of the third trench  550   t  and the fourth trench  555   t.    
     Each of the first connection structure  350 , the second connection structure  450 , and the third connection structure  550  may include, for example, at least one of titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), tungsten (W), aluminum (Al), copper (Cu), or a combination thereof, but is not limited thereto. In some embodiments, the first connection structure  350 , the second connection structure  450 , and the third connection structure  550  may be formed at the same level. The term “the same level” as used herein means being formed by the same manufacturing process. 
     In some embodiments, a first pad  355  filling the first trench  355   t  may be formed on the first connection structure  350 . In some embodiments, a second pad  555  filling the fourth trench  555   t  may be formed on the third connection structure  550 . Each of the first pad  355  and the second pad  555  may include, for example, at least one of tungsten (W), copper (Cu), aluminum (Al), gold (Au), silver (Ag), or an alloy thereof, but is not limited thereto. In some embodiments, the first pad  355  and the second pad  555  may be formed at the same level. 
     In some embodiments, a first filling insulating layer  460  filling the second trench  455   t  may be formed on the second connection structure  450 . In some embodiments, a second filling insulating layer  560  filling the third trench  550   t  may be formed on the third connection structure  550 . Each of the first filling insulating layer  460  and the second filling insulating layer  560  may include, for example, at least one of silicon oxide, aluminum oxide, tantalum oxide, or a combination thereof, but is not limited thereto. In some embodiments, the first filling insulating layer  460  and the second filling insulating layer  560  may be formed at the same level. 
     In some embodiments, the first passivation layer  160  may cover the first connection structure  350 , the first pad  355 , the second connection structure  450 , and the third connection structure  550 . For example, the first passivation layer  160  may extend conformally along the profiles of the first connection structure  350 , the first pad  355 , the second connection structure  450 , and the third connection structure  550  as shown, e.g., in  FIG. 23 . In some embodiments, the first passivation layer  160  may expose the second pad  555 . 
     The element isolation pattern  115  may be formed in the first substrate  110 . For example, an element isolation trench  115   t  may be formed in the first substrate  110 . The element isolation pattern  115  may be formed in the element isolation trench  115   t.  In some embodiments, the element isolation pattern  115  may extend from the first surface  110   a  of the first substrate  110  into the first substrate  110 . In some embodiments, the element isolation pattern  115  may be spaced apart from the second surface  110   b  of the first substrate  110 . 
     In  FIG. 23 , it is shown that the element isolation pattern  115  is formed only around the second connection structure  450  in the connection region CR and around the third connection structure  550  in the pad region PR, but this is merely an example. For example, the element isolation pattern  115  may also be formed around the first connection structure  350  in the light blocking region OB. 
     The element isolation pattern  115  may include, for example, at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, hafnium oxide, or a combination thereof, but is not limited thereto. In some embodiments, the element isolation pattern  115  may be formed at the same level as the surface insulating layer  140 . 
     The light blocking filter  270 C may cover at least a part of the light blocking region OB. For example, the light blocking filter  270 C may be formed on the first connection structure  350  and the second connection structure  450 . The light blocking filter  270 C may include, for example, a blue filter, but is not limited thereto. 
     The third passivation layer  380  may be formed on the light blocking filter  270 C. For example, the third passivation layer  380  may be formed to cover a part of the first passivation layer  160  in the light blocking region OB, the connection region CR, and the pad region PR. In some embodiments, the second passivation layer  185  may extend along the surface of the third passivation layer  380 . The third passivation layer  380  may include, for example, a light transmitting resin, but is not limited thereto. In some embodiments, the third passivation layer  380  may include the same material as that of the microlens  180 . 
     In some embodiments, the second passivation layer  185  and the third passivation layer  380  may expose the second pad  555 . For example, an exposure opening ER that exposes the second pad  555  may be formed in the second passivation layer  185  and the third passivation layer  380 . Accordingly, the second pad  555  may be connected to the external device or the like to allow the image sensor according to some embodiments to transmit and receive electrical signals to and from the external device. That is, the second pad  555  may be an input/output pad of the image sensor according to some embodiments. 
     In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications may be made to embodiments without substantially departing from the principles of the disclosure. Therefore, embodiments of the disclosure are used in a generic and descriptive sense only and not for purposes of limitation.