Patent Publication Number: US-9899453-B2

Title: Pixel of a multi-stacked CMOS image sensor and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This Application is a Divisional of U.S. patent application Ser. No. 13/205,127 filed on Aug. 8, 2011, which claims the benefit of Korean Patent Application No. 10-2011-0010299, filed on Feb. 1, 2011, in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     The following description relates to an image sensor, and more particularly, to a pixel of a multi-stacked complementary metal-oxide semiconductor (CMOS) image sensor and a method for manufacturing the same. 
     2. Description of the Related Art 
     As a resolution of a complementary metal-oxide semiconductor (CMOS) image sensor of a silicon photodiode is increased, a pixel size of an image sensor is reduced. 
     As a pixel size of an image sensor is reduced, a light-receiving area of a photodiode in the pixel is decreased. As a result, a sensitivity of the image sensor may deteriorate. Also, if the pixel size is reduced and a thickness of the pixel remains the same size, an aspect ratio of the pixel may increase, crosstalk between adjacent pixels may increase, and a signal-to-noise ratio (SNR) may decrease. Accordingly, an image quality of the image sensor may deteriorate. 
     The aforementioned problems may be improved by stacking red (R), green (G), and blue (B) layers in the pixel and dividing a photodiode of each of the R, G, and B layers by an oxide layer. 
     After the pixel having a multi-stacked structure is formed, a via hole should be formed to send a signal of each of the R, G, and B layers to a CMOS readout integrated circuit (ROIC). However, this operation may be difficult and may cause complexity in the process. 
     Typically, the via hole in a pixel structure is formed by etching a plurality of material layers. The plurality of layers typically include an organic semiconductor layer, an insulating layer, a transparent electrode layer, and the like. The etching may be performed on each of the plurality of material layers via a wet etching process or via a photolithography process using a photoresist. 
     When the etching is performed on each of the plurality of material layers via the etching process, an organic layer in the pixel may be damaged due to a solution that is used during the etching. 
     Also, when the via hole is formed in the plurality of material layers via the etching process, a conductive material that fills the via hole may contact an electrode of each of the plurality of material layers in the pixel such that a short may occur. Thus, an image sensor manufacturing process may be further complicated by adding a process of depositing an insulating layer in the via hole in order to prevent the short. 
     SUMMARY 
     In one aspect of the present invention, there is provided a pixel of a multi-stacked complementary metal-oxide semiconductor (CMOS) image sensor, the pixel including a light-receiving unit including first through third photodiode layers that are sequentially stacked; an integrated circuit (IC) that is formed below the light-receiving unit; electrode layers that are formed on and below each of the first through third photodiode layers; and a contact plug that connects the electrode layer formed below each of the first through third photodiode layers with a transistor of the IC, wherein the contact plug is separate from the light-receiving unit. 
     The electrode layer that is formed below each of the first through third photodiode layers may extend from the light-receiving unit. 
     The contact plug may be formed between the transistor and a portion of the electrode layer formed below each of the first through third photodiode layers, wherein the portion that extends from the light-receiving unit, and the contact plug may be surrounded by an insulating layer. 
     A portion of the electrode layer that is formed below each of the first through third photodiode layers may include first and second parts that are separate from each other, wherein the portion extends from the light-receiving unit. 
     Each of the first through third photodiode layers may include at least one of an organic semiconductor layer, a crystal silicon layer, an amorphous silicon layer, a CIGS layer, and a quantum dot layer. 
     In another aspect of the present invention, there is provided a method of manufacturing a pixel of a multi-stacked complementary metal-oxide semiconductor (CMOS) image sensor, the method including forming a lower insulating layer on an integrated circuit (IC); forming a first contact hole in the lower insulating layer to expose a first transistor of the IC; forming a first lower electrode layer on the lower insulating layer to fill the first contact hole; sequentially stacking a first organic semiconductor layer and a first upper electrode layer on the first lower electrode layer to be separate from the first contact hole; forming a first interlayer insulating layer to cover the first lower electrode layer, the first organic semiconductor layer, and the first upper electrode layer; forming a second contact hole penetrating through the first interlayer insulating layer and the lower insulating layer, and exposing a second transistor of the IC; forming a second lower electrode layer on the first interlayer insulating layer to fill the second contact hole; sequentially stacking a second organic semiconductor layer and a second upper electrode layer on the second lower electrode layer to be separate from the second contact hole; forming a second interlayer insulating layer to cover the second lower electrode layer, the second organic semiconductor layer, and the second upper electrode layer; forming a third contact hole penetrating through the second interlayer insulating layer, the first interlayer insulating layer, and the lower insulating layer, and exposing a third transistor of the IC; forming a third lower electrode layer on the second interlayer insulating layer to fill the third contact hole; sequentially stacking a third organic semiconductor layer and a third upper electrode layer on the third lower electrode layer to be separate from the third contact hole; and forming an upper insulating layer to cover the third lower electrode layer, the third organic semiconductor layer, and the third upper electrode layer. 
     The forming the first lower electrode layer may include forming a first contact plug that fills the first contact hole; and forming the first lower electrode layer on the lower insulating layer to contact the first contact plug. 
     The forming the second lower electrode layer may include forming a second contact plug that fills the second contact hole; and forming the second lower electrode layer on the first interlayer insulating layer to contact the second contact plug. 
     The forming the third lower electrode layer may include forming a third contact plug that fills the third contact hole; and forming the third lower electrode layer on the second interlayer insulating layer to contact the third contact plug. 
     The forming the first contact hole may further include forming another contact hole to expose a portion of the IC in a region of the lower insulating layer that is separate from the first contact hole. 
     The forming the second contact hole may further include forming another contact hole to expose a portion of the IC in a region of the first interlayer insulating layer that is separate from the second contact hole. 
     The forming the third contact hole may further include forming another contact hole to expose a portion of the IC in a region of the second interlayer insulating layer that is separate from the third contact hole. 
     The forming the first lower electrode layer may include filling the other contact hole formed in the operation of forming the first contact hole with the first lower electrode layer. 
     The forming the second lower electrode layer may include filling the other contact hole formed in the operation of forming the second contact hole with the second lower electrode layer. 
     The forming the third lower electrode layer may include filling the other contact hole formed in the operation of forming the third contact hole with the third lower electrode layer. 
     Each of the first through third photodiode layers may comprise at least one of an organic semiconductor layer, a crystal silicon layer, an amorphous silicon layer, a CIGS layer, and a quantum dot layer. 
     In another aspect of the present invention, there is provided a pixel of a complementary metal-oxide semiconductor (CMOS) image sensor, the pixel including a plurality of pixel units comprising at least a first pixel unit, a second pixel unit, and a third pixel unit, an integrated circuit (IC) configured to control the plurality of pixel units, and a plurality of plugs comprising a first plug that electrically connects the first pixel unit to the IC, a second plug that electrically connects the second pixel unit to the IC, and a third plug that electrically connects the third pixel unit to the IC. 
     The plugs may each be of different heights. 
     The first plug may be shorter in height than the second plug and the second plug may be shorter in height than the third plug. 
     Each pixel unit may comprise an upper electrode layer and a lower electrode layer, and may further comprise an organic semiconductor layer between the upper electrode layer and the lower electrode layer. 
     The lower electrode layer of each pixel unit may further comprise an extended edge that extends out farther than the lower organic semiconductor layer and the upper electrode layer, and that electrically connects to the respective plug. 
     The first plug, the second plug, and the third plug may be formed in parallel to each other on a side of the pixel. 
     The first pixel unit may be included in a first layer of the pixel, the second pixel unit may be included in a second layer of the pixel, and the third pixel unit may be included in a third layer of the pixel, 
     The IC may be below the first layer, the first layer may be below the second layer, and the second layer may be below the third layer. 
     The first plug may extend from the IC through a portion of the first layer, the second plug may extend from the IC through the first layer and through a portion of the second layer, and the third plug may extend from the IC through the first and second layers and through a portion of the third layer. 
     Other features and aspects may be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example of a pixel of a multi-stacked complementary metal-oxide semiconductor (CMOS) image sensor, according to an embodiment of the present invention. 
         FIG. 2  is a diagram illustrating an example of the pixel taken along a  2 - 2 ′ direction of  FIG. 1 , according to an embodiment of the present invention. 
         FIG. 3  is a diagram illustrating an example of the pixel taken along a  3 - 3 ′ direction of  FIG. 1 , according to an embodiment of the present invention. 
         FIG. 4  is a diagram illustrating an example of the pixel taken along a  4 - 4 ′ direction of  FIG. 1 , according to an embodiment of the present invention. 
         FIGS. 5 through 10  are diagrams illustrating examples of methods of manufacturing a pixel of a multi-stacked CMOS image sensor, according to an embodiment of the present invention. 
     
    
    
     Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience. 
     DETAILED DESCRIPTION 
     The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be suggested to those of ordinary skill in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness. 
       FIG. 1  illustrates an example of a pixel of a multi-stacked complementary metal-oxide semiconductor (CMOS) image sensor, according to an embodiment of the present invention. For example, the image sensor may be included in various imaging devices, such as a camera, a mobile terminal such as a smart phone, a tablet, a video recorder, and the like. 
     Referring to  FIG. 1 , pixel  100  includes a light-receiving unit  30  for receiving light incident from an external source. The light-receiving unit  30  is covered by an upper insulating layer  74 . The pixel  100  includes first through third extension electrode units  32 ,  34 , and  36 . The first through third extension electrode units  32 ,  34 , and  36  are connected to the light-receiving unit  30 , and protrude from the light-receiving unit  30 . The first through third extension electrode units  32 ,  34 , and  36  may be arranged at a side of the light-receiving unit  30 . 
     For example, the first through third extension electrode units  32 ,  34 , and  36  may be vertically arranged at a side of the light-receiving unit  30  such as one of the vertical sides of the light-receiving unit  30 . As another example, the first through third extension electrode units  32 ,  34 , and  36  may be arranged at any side of the light-receiving unit  30 . The first through third extension electrode units  32 ,  34 , and  36  include first through third contact plugs  32 P,  34 P, and  36 P, respectively. In this example, the first through third extension electrode units  32 ,  34 , and  36  and the first through third contact plugs  32 P,  34 P, and  36 P are covered by the upper insulating layer  74 . 
     The pixel  100  includes fourth through sixth extension electrode units  42 ,  44 , and  46 . The fourth through sixth extension electrode units  42 ,  44 , and  46  are connected to the light-receiving unit  30 , and protrude from the light-receiving unit  30 . The fourth through sixth extension electrode units  42 ,  44 , and  46  may be positioned at a location that is different from the location of the first through third extension electrode units  32 ,  34 , and  36 . The fourth through sixth extension electrode units  42 ,  44 , and  46  may be connected to a common electrode terminal of a light-receiving device including the pixel  100 . The fourth through sixth extension electrode units  42 ,  44 , and  46  include fourth through sixth contact plugs  42 P,  44 P, and  46 P, respectively, and are connected to the common electrode terminal of the light-receiving device via the fourth through sixth contact plugs  42 P,  44 P, and  46 P. 
       FIG. 2  illustrates an example of the pixel  100  taken along a  2 - 2 ′ direction of  FIG. 1 , according to an embodiment of the present invention. 
     Referring to  FIG. 2 , a lower insulating layer  62  is arranged on a CMOS readout integrated circuit (ROIC)  60  (hereinafter, referred to as ‘IC’). A first contact hole  62   h  is used to expose a first transistor  70 T that is formed in the lower insulating layer  62 . The first transistor  70 T is included in the IC  60 . For example, the first transistor  70 T may be a Field-Effect Transistor (FET). The first contact hole  62   h  is filled with the first contact plug  32 P. 
     A first lower electrode layer  70 L is arranged on the lower insulating layer  62 . The first extension electrode unit  32  that extends from the first lower electrode layer  70 L covers the first contact plug  32 P. The first extension electrode unit  32  may include the same material as the first contact plug  32 P. A first organic semiconductor layer  70 R and a first upper electrode layer  70 U are sequentially stacked on the first lower electrode layer  70 L. The first organic semiconductor layer  70 R may be a photodiode layer. For example, the first organic semiconductor layer  70 R may be a material layer that has photoelectric conversion characteristics with respect to red light. As another example, instead of using the first organic semiconductor layer  70 R, another photodiode layer that has the same or similar photoelectric conversion characteristics with the first organic semiconductor layer  70 R may be used. The first upper electrode layer  70 U and the first organic semiconductor layer  70 R are separate from the first contact hole  62   h.    
     The first lower electrode layer  70 L, the first upper electrode layer  70 U, and the first organic semiconductor layer  70 R form a sub-pixel unit that is included in the pixel  100 , for example, they may form a sub-pixel unit that has photoelectric conversion characteristics with respect to red light. The first lower electrode layer  70 L, the first upper electrode layer  70 U, and the first organic semiconductor layer  70 R are covered by a first interlayer insulating layer  68 . A top surface of the first interlayer insulating layer  68  is planarized. 
     A second lower electrode layer  80 L, a second organic semiconductor layer  80 G, and a second upper electrode layer  80 U are sequentially stacked on the first interlayer insulating layer  68 . For example, the second organic semiconductor layer  80 G may be a material layer that has photoelectric conversion characteristics with respect to green light. The second lower electrode layer  80 L, the second organic semiconductor layer  80 G, and the second upper electrode layer  80 U may form a second sub-pixel unit that is included in the pixel  100 , for example, they may form a sub-pixel unit that has photoelectric conversion characteristics with respect to green light. In this example, the second sub-pixel unit may be positioned above the first upper electrode layer  70 U. The second lower electrode layer  80 L, the second organic semiconductor layer  80 G, and the second upper electrode layer  80 U are covered by a second interlayer insulating layer  72 . A top surface of the second interlayer insulating layer  72  is flat. 
     A third lower electrode layer  90 L, a third organic semiconductor layer  90 B, and a third upper electrode layer  90 U are sequentially stacked on the second interlayer insulating layer  72 . The third lower electrode layer  90 L and the third upper electrode layer  90 U may include a transparent electrode material. The first and second electrode material layers  70 L,  70 U,  80 L, and  80 U may also include a transparent electrode material. For example, the third organic semiconductor layer  90 B may be a material layer that has photoelectric conversion characteristics with respect to blue light. A stack of the third lower electrode layer  90 L, the third organic semiconductor layer  90 B, and the third upper electrode layer  90 U may form a third sub-pixel unit that is included in the pixel  100 , for example, the stack may form a sub-pixel unit that has photoelectric conversion characteristics with respect to blue light. The third sub-pixel unit may be arranged above the second upper electrode layer  80 U. The sub-pixel unit including the third lower electrode layer  90 L, the third organic semiconductor layer  90 B, and the third upper electrode layer  90 U is covered by the upper insulating layer  74 . The upper insulating layer  74  may be a light-transmitting layer. 
       FIG. 3  illustrates an example of the pixel  100  taken along a  3 - 3 ′ direction of  FIG. 1 , according to an embodiment of the present invention. The example of  FIG. 3  illustrates a connection relation between the second lower electrode layer  80 L and the IC  60 . 
     Referring to  FIG. 3 , the second lower electrode layer  80 L has the second extension electrode unit  34  extending from the second organic semiconductor layer  80 G and the second upper electrode layer  80 U which are sequentially stacked. For example, the second organic semiconductor layer  80 G may be a photodiode layer. As another example, instead of using the second organic semiconductor layer  80 G, another photodiode layer that has the same or similar photoelectric conversion characteristics with the second organic semiconductor layer  80 G may be used. The second extension electrode unit  34  is connected to a second transistor  80 T of the IC  60  via the second contact plug  34 P that fills a second contact hole  68   h.    
     The second extension electrode unit  34  and the second contact plug  34 P may be of the same material. The second transistor  80 T may be an FET. The second organic semiconductor layer  80 G and the second upper electrode layer  80 U are separate from the second contact plug  34 P. The second contact hole  68   h  penetrates through the lower insulating layer  62  and the first interlayer insulating layer  68  which are sequentially stacked. As shown in the examples of  FIGS. 2 and 3  which are cross-sectional views of the pixel  100  of  FIG. 1 , taken at different directions, it is possible to see that the first contact hole  62   h  of  FIG. 2  and the second contact hole  68   h  of  FIG. 3  are formed at different positions. 
       FIG. 4  illustrates an example of the pixel  100  taken along a  4 - 4 ′ direction of  FIG. 1 , according to an embodiment of the present invention. The example of  FIG. 4  illustrates a connection relation between the third lower electrode layer  90 L and the IC  60 . 
     Referring to  FIG. 4 , the third lower electrode layer  90 L has the third extension electrode unit  36  extending from the third organic semiconductor layer  90 B and the third upper electrode layer  90 U which are sequentially stacked. For example, the third organic semiconductor layer  90 B may be a photodiode layer that has photoelectric conversion characteristics. As another example, instead of using the third organic semiconductor layer  90 B, another photodiode layer that has the same or similar photoelectric conversion characteristics with the third organic semiconductor layer  90 B may be used. The third extension electrode unit  36  is connected to a third transistor  90 T of the IC  60  via the third contact plug  36 P filling a third contact hole  72   h . For example, third extension electrode unit  36  and the third contact plug  36 P may be the same material. The third transistor  90 T may be an FET. 
     The third organic semiconductor layer  90 B and the third upper electrode layer  90 U are separate from the third contact plug  36 P. The third contact hole  72   h  penetrates through the lower insulating layer  62 , the first interlayer insulating layer  68 , and the second interlayer insulating layer  72  which are sequentially stacked. As shown in the examples of  FIGS. 2 through 4  which are cross-sectional views of the pixel  100  of  FIG. 1 , taken at different directions, it is possible to see that the first contact hole  62   h  of  FIG. 2 , the second contact hole  68   h  of  FIG. 3 , and the third contact hole  72   h  of  FIG. 4  are formed at different positions and are of different heights. In the examples shown in  FIGS. 2-4 , the first contact hole  62   h  is shorter in height than the second contact hole  68   h  and the second contact hole  68   h  is shorter in height than the third contact hole  72   h.    
     As shown in  FIGS. 1 through 4 , the first through third transistors  70 T,  80 T, and  90 T and the first through third lower electrode layers  70 L,  80 L, and  90 L included in the IC  60  are connected to each other via paths (i.e., the first through third contact plugs  32 P,  34 P, and  36 P) that are formed outside the first through third organic semiconductor layers  70 R,  80 G, and  90 B. Thus, it is possible to solve disadvantages of the related art. As is described in a manufacturing method, the paths (i.e., the first through third contact plugs  32 P,  34 P, and  36 P) may be formed via one process. Thus, a CMOS image sensor manufacturing method may be further simplified. 
     Hereinafter, examples of a method of manufacturing a pixel of a multi-stacked CMOS image sensor are described with reference to  FIGS. 5 through 10 . In  FIGS. 5 through 10 , like reference numerals in  FIGS. 1 through 4  denote like elements. 
     Referring to  FIG. 5 , a lower insulating layer  62  is formed on an IC  60 . For example, a material forming the lower insulating layer  62  may include at least one of silicon oxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), and germanium oxide (GeOx). A first contact hole  62   h  is formed in the lower insulating layer  62  to expose a portion of a first transistor  70 T. The first contact hole  62   h  may be formed by a dry etching process or a wet etching process. The dry etching process may use plasma. The wet etching process may use hydrogen fluoride (HF)-based solution. 
     As illustrated in  FIG. 6 , a first lower electrode layer  70 L is formed on the lower insulating layer  62  to fill the first contact hole  62   h . A process of forming the first lower electrode layer  70 L may be divided into two sub-processes. For example, the process may be divided into a first sub-process of forming a contact plug (refer to the contact plug  32 P of  FIG. 2 ) that fills the first contact hole  62   h , and a second sub-process of forming an electrode layer contacting the contact plug. The first lower electrode layer  70 L may be formed of a transparent electrode material such as indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide (AZO). 
     A first organic semiconductor layer  70 R and a first upper electrode layer  70 U are sequentially stacked on the first lower electrode layer  70 L. For example, the first organic semiconductor layer  70 R may be a photodiode layer. The first organic semiconductor layer  70 R and the first upper electrode layer  70 U are formed at positions that are separate from the first contact hole  62   h . For example, the first organic semiconductor layer  70 R may be formed of a material including one or more of Cu-Phthalocyanine or Sn-Phthalocyanine. As another example, instead of using the first organic semiconductor layer  70 R, one or more of a crystal silicon layer, an amorphous silicon layer, a CIGS layer, and a quantum dot layer that have the same or similar photoelectric conversion characteristics with the first organic semiconductor layer  70 R may be used. For example, the quantum dot layer may include one or more of PbSe, PbS, and CdTe, as a quantum dot. 
     The first upper electrode layer  70 U may be formed of the same material or a different transparent conductive material in comparison to the first lower electrode layer  70 L. When the first contact hole  62   h  is formed, another contact hole (not shown) may be formed in another position of the lower insulating layer  62 . Then, when the first lower electrode layer  70 L is formed, the other contact hole may be filled with the first lower electrode layer  70 L. By doing so, the fourth contact plug  42 P (refer to  FIG. 1 ) may be formed. The first organic semiconductor layer  70 R and the first upper electrode layer  70 U may be formed at positions that are separate from the other contact hole. Afterward, a first interlayer insulating layer  68  is formed to cover the first lower electrode layer  70 L, the first organic semiconductor layer  70 R, and the first upper electrode layer  70 U. A top surface of the first interlayer insulating layer  68  is planarized. For example, the first interlayer insulating layer  68  may be formed of the same material as the lower insulating layer  62 . 
       FIGS. 7 and 8  illustrate a manufacturing process with reference to a cross-sectional view taken along a  3 - 3 ′ direction of  FIG. 1 . In the example of  FIGS. 7 and 8 , the first contact hole  62   h , a portion filling the first contact hole  62   h , and the first transistor  70 T of the IC  60  of  FIG. 6  are not illustrated. 
     Referring to  FIG. 7 , a second contact hole  68   h  is formed to sequentially penetrate through the first interlayer insulating layer  68  and the lower insulating layer  62 . The second contact hole  68   h  is formed at a position that is separate from the first lower electrode layer  70 L, the first organic semiconductor layer  70 R, and the first upper electrode layer  70 U. Due to the second contact hole  68   h , a portion of a second transistor  80 T of the IC  60  is exposed. The second transistor  80 T may be separate from the first transistor  70 T. When the second contact hole  68   h  is formed, another contact hole (not shown) may be formed in the lower insulating layer  62  and the first interlayer insulating layer  68 . The other contact hole may be filled with the fifth contact plug  44 P of  FIG. 1 . 
     Referring to  FIG. 8 , a second lower electrode layer  80 L is formed on the first interlayer insulating layer  68  to fill the second contact hole  68   h . Similar to the first lower electrode layer  70 L of  FIG. 6 , a process of forming the second lower electrode layer  80 L may also be divided into two sub-processes. When the second lower electrode layer  80 L is formed, the other contact hole penetrating through the lower insulating layer  62  and the first interlayer insulating layer  68  may be filled with the second lower electrode layer  80 L. For example, the second lower electrode layer  80 L may be formed of the same or different material from the first lower electrode layer  70 L. 
     A second organic semiconductor layer  80 G and a second upper electrode layer  80 U are sequentially stacked on the second lower electrode layer  80 L. The second organic semiconductor layer  80 G may be a photodiode layer. Examples of a material that forms the second organic semiconductor layer  80 G may include at least one of quinacridone, a triphenylamine derivative, and a thiophene derivative. As another example, instead of using the second organic semiconductor layer  80 G, a material layer such as a crystal silicon layer, an amorphous silicon layer, a CIGS layer, and/or a quantum dot layer that have the same or similar photoelectric conversion characteristics with the second organic semiconductor layer  80 G may be used. For example, the quantum dot layer may include PbSe, PbS, or CdTe, as a quantum dot. 
     The second upper electrode layer  80 U may be formed of the same or different material from the first upper electrode layer  70 U. The second organic semiconductor layer  80 G and the second upper electrode layer  80 U may be formed at positions that are separate from the second contact hole  68   h  and the other contact hole. Afterward, a second interlayer insulating layer  72  is formed to cover the second lower electrode layer  80 L, the second organic semiconductor layer  80 G, and the second upper electrode layer  80 U. A top surface of the second interlayer insulating layer  72  is planarized. In this example, the second interlayer insulating layer  72  may be formed of the same material as the first interlayer insulating layer  68 . 
       FIGS. 9 and 10  illustrate a manufacturing process with reference to a cross-sectional view taken along a  4 - 4 ′ direction of  FIG. 1 . Thus, in  FIGS. 9 and 10 , the first contact hole  62   h , a portion filling the first contact hole  62   h , and the first transistor  70 T of the IC  60  of  FIG. 6 , and the second contact hole  68   h , a portion filling the second contact hole  68   h , and the second transistor  80 T of the IC  60  of  FIG. 8  are not illustrated. 
     Referring to  FIG. 9 , a third contact hole  72   h  is formed to sequentially penetrate through the second interlayer insulating layer  72 , the first interlayer insulating layer  68 , and the lower insulating layer  62 . The third contact hole  72   h  is formed at a position that is separate from the first lower electrode layer  70 L, the first organic semiconductor layer  70 R, the first upper electrode layer  70 U, the second lower electrode layer  80 L, the second organic semiconductor layer  80 G, and the second upper electrode layer  80 U. A portion of a third transistor  90 T of the IC  60  is exposed via the third contact hole  72   h . The third transistor  90 T may be separate from the first and second transistors  70 T and  80 T. When the third contact hole  72   h  is formed, another contact hole (not shown) may be formed to sequentially penetrate through the lower insulating layer  62 , the first interlayer insulating layer  68 , and the second interlayer insulating layer  72 . For example, the other contact hole may be filled with the sixth contact plug  46 P of  FIG. 1 . 
     Next, referring to  FIG. 10 , a third lower electrode layer  90 L is formed on the second interlayer insulating layer  72  to fill the third contact hole  72   h . For example, the third lower electrode layer  90 L may be formed of the same material or a different conductive material from the first lower electrode layer  70 L. As described with reference to the first lower electrode layer  70 L, a process of forming the third lower electrode layer  90 L may be divided into two sub-processes. For example, the process may be divided into a first sub-process of forming a contact plug that fills the third contact hole  72   h , and a second sub-process of forming an electrode layer contacting the contact plug on the second interlayer insulating layer  72 . When the third lower electrode layer  90 L is formed, the other contact hole formed together with the third contact hole  72   h  may be filled with the third lower electrode layer  90 L. 
     A third organic semiconductor layer  90 B and a third upper electrode layer  90 U are sequentially stacked on the third lower electrode layer  90 L. For example, the third organic semiconductor layer  90 B may be a photodiode layer. Examples of a material forming the third organic semiconductor layer  90 B include one or more of tetracene, coumarin, an EDOT derivative, rubrene, and the like. As another example, instead of using the third organic semiconductor layer  90 B, a material layer such as a crystal silicon layer, an amorphous silicon layer, a CIGS layer, or a quantum dot layer that have the same or similar photoelectric conversion characteristics with the third organic semiconductor layer  90 B may be used. For example, the quantum dot layer may include PbSe, PbS, or CdTe, as a quantum dot. 
     The third upper electrode layer  90 U may be formed of the same or different material from the first upper electrode layer  70 U. The third organic semiconductor layer  90 B and the third upper electrode layer  90 U may be formed at positions that are separate from the third contact hole  72   h  and the other contact hole. After the third upper electrode layer  90 U is formed, an upper insulating layer  74  may be formed to cover the third lower electrode layer  90 L, the third organic semiconductor layer  90 B, and the third upper electrode layer  90 U. The upper insulating layer  74  may be formed of the same material as the lower insulating layer  62  or may be formed of a different insulating material in comparison to the lower insulating layer  62 . 
     As described herein, in the pixel of the multi-stacked CMOS image sensor, the contact plug that connects the electrode layer included in each sub-pixel unit of the light-receiving unit with the IC of the pixel may be formed by penetrating through the insulating layer around the light-receiving unit. Accordingly, in order to form the contact plug, only the insulating layer around the light-receiving unit may be etched, and thus, the manufacturing process may be simplified. 
     Also, when the contact plug is formed in the multi-stacked CMOS image sensor, a photoelectric conversion layer (the photodiode layer) in the light-receiving unit is not affected by the forming of the contact plug. Thus, it is possible to manufacture a CMOS image sensor that has a higher performance and higher resolution. 
     For example, the CMOS image sensor may be used in digital cameras, cameras for mobile phones, infrared cameras, closed-circuit televisions (CCTVs), cameras for personal computer (PC) communication, and the like. 
     Program instructions to perform a method described herein, or one or more operations thereof, may be recorded, stored, or fixed in one or more computer-readable storage media. The program instructions may be implemented by a computer. For example, the computer may cause a processor to execute the program instructions. The media may include, alone or in combination with the program instructions, data files, data structures, and the like. Examples of computer-readable storage media include magnetic media, such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVDs; magneto-optical media, such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The program instructions, that is, software, may be distributed over network coupled computer systems so that the software is stored and executed in a distributed fashion. For example, the software and data may be stored by one or more computer readable storage mediums. Also, functional programs, codes, and code segments for accomplishing the example embodiments disclosed herein can be easily construed by programmers skilled in the art to which the embodiments pertain based on and using the flow diagrams and block diagrams of the figures and their corresponding descriptions as provided herein. Also, the described unit to perform an operation or a method may be hardware, software, or some combination of hardware and software. For example, the unit may be a software package running on a computer or the computer on which that software is running. 
     A number of examples have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.