Patent Publication Number: US-11031430-B2

Title: Image sensor with dummy lines for minimizing fixed pattern noise (FPN) and electronic apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2017-0153316, filed on Nov. 16, 2017, in the Korean Intellectual Property Office, and entitled: “Image Sensor and Electronic Apparatus Including the Same,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Embodiments relate to an image sensor and an electronic apparatus including the same. 
     2. Description of the Related Art 
     An image sensor may include a plurality of unit pixels arranged in a two-dimensional (2D) array. A unit pixel may include one photodiode and a plurality of pixel transistors. The pixel transistors may include, e.g., a transfer Transistor (TG), a reset transistor (RG), a source-follower transistor (SF), and/or a selection transistor (SEL). 
     SUMMARY 
     The embodiments may be realized by providing an image sensor including a plurality of pixels, each pixel of the plurality of pixels including a photodiode and a transfer transistor, a reset transistor, a source-follower transistor, and a selection transistor, which correspond to the photodiode; a plurality of first interconnection lines connected to gates of the transfer transistor, the reset transistor, and the selection transistor, the plurality of first interconnection lines extending in a first direction; and a plurality of second interconnection lines connected to a source region of the selection transistor, the plurality of second interconnection lines extending in a second direction that intersects the first direction, wherein the plurality of second interconnection lines includes dummy lines on a peripheral area that is outside of a pixel area in which the pixels are located. 
     The embodiments may be realized by providing an image sensor including an upper chip that includes a plurality of pixels arranged in a two-dimensional (2D) array, a plurality of row lines and a plurality of column lines being arranged on the upper chip, the plurality of row lines extending in a first direction, the plurality of column lines extending in a second direction that intersects the first direction; and a lower chip under the upper chip, logic devices for signal processing operations being arranged on the lower chip, wherein the plurality of column lines are connected to source regions of selection transistors of the respective pixels and have a same length in the second direction. 
     The embodiments may be realized by providing an electronic apparatus including an optical system; an image sensor; and a signal processing circuit, wherein the image sensor includes an upper chip that includes a plurality of pixels arranged in a two-dimensional (2D) array, a plurality of row lines and a plurality of column lines being arranged on the upper chip, the plurality of row lines extending in a first direction, and the plurality of column lines extending in a second direction intersecting the first direction; and a lower chip under the upper chip, logic devices for signal processing operations being arranged on the lower chip, and wherein the plurality of column lines are connected to source regions of selection transistors of the respective pixels and have a same length in the second direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will be apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
         FIG. 1A  illustrates a perspective view of an image sensor according to an embodiment, in which an upper chip including pixels is separated from a lower chip including logic devices; 
         FIG. 1B  illustrates a conceptual diagram of a structure of column lines of a pixel area in the upper chip of the image sensor of  FIG. 1A ; 
         FIG. 2A  illustrates a circuit diagram of pixels of the image sensor of  FIG. 1A ; 
         FIG. 2B  illustrates a signal waveform diagram showing the concept of a settling time of an output voltage in the circuit diagram of  FIG. 2A ; 
         FIGS. 3A and 3B  respectively illustrate a conceptual diagram and a perspective view of connection portions between the structure of the column lines of  FIG. 1B  and through vias; 
         FIGS. 4A to 4C  illustrate graphs of capacitances of column lines with respect to positions of through vias and structures of column lines connected to the through vias in test  1 , test  2 , and test  3 , respectively; 
         FIG. 4D  illustrates a graph showing settling times corresponding to connection structures of test  1 , test  2 , and test  3  of  FIGS. 4A to 4C ; 
         FIG. 4E  illustrates an image of a column fixed-pattern noise (CFPN) phenomenon in the connection structure of test  2  of  FIG. 4B ; 
         FIG. 5A  illustrates a circuit diagram of shared pixels of an image sensor according to an embodiment; 
         FIG. 5B  illustrates a schematic plan view of one shared pixel in the circuit diagram of  FIG. 5A ; 
         FIG. 6A  illustrates a circuit diagram of shared pixels of an image sensor according to an embodiment; 
         FIG. 6B  illustrates a schematic plan view of one shared pixel in the circuit diagram of  FIG. 6A ; 
         FIGS. 7A, 8A, and 9A  illustrate conceptual diagrams of structures of column lines of pixel areas in image sensors according to embodiments; 
         FIGS. 7B, 8B, and 9B  illustrate perspective views of connection portions between the structures of the column lines of  FIGS. 7A, 8A, and 9A  and through vias, respectively; 
         FIGS. 10 and 11  illustrate conceptual diagrams of structures of row lines of pixel areas in image sensors according to embodiments; 
         FIGS. 12A and 12B  respectively illustrate a plan view and a cross-sectional view of an image sensor according to an embodiment, in which an upper chip is combined with a lower chip by using through-silicon vias (TSVs); 
         FIG. 13  illustrates a schematic construction diagram of an image sensor according to an embodiment; and 
         FIG. 14  illustrates a schematic construction diagram of an electronic apparatus including an image sensor according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  illustrates a perspective view of an image sensor  1000  according to an embodiment, in which an upper chip  100  including pixels is separated from a lower chip  200  including logic devices.  FIG. 1B  illustrates a conceptual diagram of a structure of column lines of a pixel area PA in the upper chip  100  of the image sensor  1000  of  FIG. 1A . 
     Referring to  FIGS. 1A and 1B , the image sensor  1000  of the present embodiment may have a structure in which the upper chip  100  is stacked on the lower chip  200 . A plurality of pixels may be arranged in a two-dimensional (2D) array on the upper chip  100 . According to an embodiment, the upper chip  100  may include the pixel area PA and a peripheral area PE. A plurality of pixels may be arranged in a 2D array in the pixel area PA, and interconnections, contacts, and through vias may be located in the peripheral area PE to electrically connect the upper chip  100  with the lower chip  200 . In  FIG. 1A , a portion indicated by ‘Pixel Array’ inside a quadrangle illustrated with a dashed line may correspond to the pixel area PA, and a portion outside the quadrangle may correspond to the peripheral area PE. 
     As shown in  FIG. 1B , a plurality of column lines  110  may be located on the upper chip  100  and extend (e.g., lengthwise) in a second direction (y direction). The column lines  110  may be connected to the pixels and signals from the pixels may be output through the column lines  110 . The pixels located on the upper chip  100  and the column lines  110  connected to the pixels will be described in further detail below with reference to  FIG. 2A . 
     The column lines  110  may extend to the peripheral area PE and the pixel area PA and may be connected to through vias  130  in the peripheral area PE. The through vias  130  may be also referred to as through-silicon vias (TSVs) in the sense that the through vias  130  penetrate a silicon substrate. Also, when the through vias  130  penetrate a back side of the silicon substrate, the through vias  130  may be referred to as back-via silicons (BVSs). By using the through vias  130 , the column lines  110  may be electrically connected to logic devices (e.g., analog-to-digital converters (ADCs)) of the lower chip  200 . 
     As shown in  FIG. 1B , a predetermined number of through vias  130  and a predetermined number of column lines  110  connected to the through vias  130  may repetitively form groups. In an implementation, the column lines  110  may be alternately connected to a through via  130  located on an upper side and a through via  130  located on a lower side, in the second direction (y direction). In a first group, column lines  110  connected to through vias  130  located on the upper side may be indicated by solid lines, while column lines  110  connected to through vias  130  located the lower side may be indicated by dashed lines. In a second group, column lines  110  connected to through vias  130  located on the upper side may be indicated by dashed lines, while column lines  110  connected to the through vias  130  located on the lower side may be indicated by solid lines. The column lines  110  connected to the through vias  130  located on the upper side and the column lines  110  connected to the through vias  130  located on the lower side are distinguishably displayed in the above-described manner to easily explain the concept of column fixed-pattern noise (CFPN) in the following descriptions of  FIGS. 2A and 2B and 4A to 4C . Also, in the following drawings, the column lines  110  indicated by the dashed lines and the through vias  130  corresponding thereto may be omitted for brevity. 
     In the image sensor  1000  of the present embodiment, ten (10) through vias  130  located on the upper side and ten through vias  130  located on the lower side may form one group. In an implementation, twenty (20) column lines  110  corresponding to the ten through vias  130  located on the upper side and the ten through vias  130  located on the lower side may be included in the one group. In an implementation, the through vias  130  and the column lines  110  included in one group may be a number other than 20. 
     Although the lower chip  200  is illustrated at each of an upper side and a lower side of  FIG. 1B , this does not mean that two lower chips  200  are provided, and the column lines  110  may be connected to the lower chip  200  through the through vias  130  located on the upper side, and the column lines  110  may be connected to the lower chip through the through vias  130  located on the lower side. Accordingly, the lower chip  200  located on the upper side and the lower chip  200  located on the lower side may be the same lower chip  200 . In  FIG. 1B , reference numeral ‘ 120 ’ may denote elements (e.g., vertical contacts) configured to connect the column lines  110  with pixels. However, the vertical contacts  120  are conceptual indications for connection between the column lines  110  with the pixels. Actual positions or structures of the vertical contacts  120  may be different from those shown in  FIG. 1B , and the vertical contacts are not connected to each other in a first direction (x direction). 
     In the image sensor  1000  of the present embodiment, each of the column lines  110  may include an effective column line  110   e  and a dummy column line  110   d . The effective column line  110   e  may refer to a portion of the column line  110  extending from the pixel area PA to the through via  130  of the peripheral area PE, and the dummy column line  110   d  may refer to a portion of the column line  110  that is connected to the effective column line  110   e  and extends beyond the through via  130  in the second direction (y direction, e.g., away from the pixel area PA). In an implementation, as shown in  FIG. 1B , each of the column lines  110  may include the dummy column line  110   d . In an implementation, only some of the column lines  110  may include the dummy column line  110   d . For example, a longest column line of the column lines  110  may not include the dummy column line  110   d.    
     In the image sensor  1000  of the present embodiment, the column lines  110  may include the dummy column lines  110   d , and may have substantially the same overall length in the second direction (y direction). Thus, a column line  110  having a relatively short effective column line  110   e  may include a relatively long dummy column line  110   d , while a column line  110  having a relatively long effective column line  110   e  may include a relatively short dummy column line  110   d . Therefore, in the image sensor  1000  of the present embodiment, the column lines  110  may include the dummy column lines  110   d , and signals output by the pixels may be uniformized. The uniformization of signals due to the structure of the column lines  110  will be described in further detail below with reference to  FIGS. 2A and 2B . 
     In an implementation, a plurality of row lines, which are connected to the pixels and extend (e.g., lengthwise) in the first direction (x direction), may be located in the upper chip  100 . Signals may be transmitted to the pixels through the row lines. The row lines located in the upper chip  100  will be described in further detail below with reference to  FIGS. 10 and 11 . 
     The lower chip  200  may include logic devices. In an implementation, the lower chip  200  may further include memory devices. The lower chip  200  may be located under the upper chip  100  and electrically connected to the upper chip  100  through the through vias  130 . Thus, signals may be transmitted between the upper chip  100  and the lower chip  200 . A stack structure of the upper chip  100  and the lower chip  200  will be described in further detail below with reference to  FIGS. 11A and 11B . 
     The logic devices of the lower chip  200  may include various circuits configured to process signals from the pixels of the upper chip  100 . In an implementation, the logic devices may include, e.g., an analog signal processing circuit, an ADC circuit, an image signal processing circuit, or a control circuit. 
     In an implementation, a structure of the image sensor  1000  of the present embodiment may be a double stack structure in which the upper chip  100  is stacked on the lower chip  200 . In an implementation, the image sensor of the present embodiment may have a triple stack structure including three stacked chips or a quadruple stack structure including four stacked chips. In the image sensor having the triple stack structure or the quadruple stack structure, an ADC circuit or memory devices may be formed on an additional chip and stacked. In an implementation, the image sensor  1000  of the present embodiment may be, e.g., a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS). 
     In the case of an image sensor (e.g., a CIS) operating at high speed, a difference in settling time may occur between adjacent column lines. The difference in settling time may be caused by a difference in length between metal lines used for signal transmission. The longer the length of a metal line, the longer the setting time due to an increase in an RC time constant. In the image sensor  1000  of the present embodiment, the column lines  110  may include the dummy column lines  110   d  and have the same length so that the column lines  110  may have substantially the same capacitance. Thus, the column lines  110  may have the same resistive-capacitive (RC) delay, thereby uniformizing signal transmission characteristics. As a result, the image sensor  1000  of the present embodiment may uniformly maintain a settling time of an output signal based on the sameness of the RC delay of the column lines  110 . Thus, column fixed pattern noise (CFPN) may be minimized. Accordingly, the image sensor  1000  of the present embodiment may provide improved images of which noise is minimized. 
     Fixed pattern noise (FPN) may occur in an image sensor (e.g., a CIS). In dark conditions without light, pixels having different output values may be generated. This phenomenon may be called “dark signal non-uniformity (DSNU).” Also, when light exists, pixels may have respectively different output values based on a degree to which each of the pixels responds to the light. This phenomenon may be called “photo-response non-uniformity”. Typically, FPN may refer to DSNU. Also, FPN may be divided into column fixed pattern noise (CFPN) caused to column lines and row fixed pattern noise (RFPN) caused to row lines. Here, the CFPN may be expressed by Equation (1):
 
CFPN=1/FSD*[1/( M− 1)*Σ( C   i   −C   i+1 ) 2 ] 1/2   (1).
 
     wherein i denotes a number of a column line, i ranges from 0 to M−2 in Σ, and C i  is an output voltage of an i-th column line. Also, FSD denotes an acronym of Full-Scale Deflection and may correspond to a normalizing constant. From Equation (1), it can be seen that CFPN occurs mainly due to a difference in output voltage between adjacent column lines. For example, as the difference in output voltage between the adjacent column lines increases, the CFPN may also increase. The output voltage may refer to an output voltage in a settling time. In the image sensor  1000  of the present embodiment, lengths of the column lines  110  may be equal to each other by adding the length of the dummy column lines  110   d  to the length of the effective column lines  110   e . Thus, capacitances of the column lines  110  may be substantially equal to each other to thereby uniformize the setting time and minimize CFPN. 
       FIG. 2A  illustrates a circuit diagram of pixels of an image sensor  1000  of  FIG. 1A .  FIG. 2B  illustrates a signal waveform diagram showing the concept of a settling time of an output voltage in the circuit diagram of  FIG. 2A . 
     Referring to  FIGS. 2A and 2B , in the image sensor  1000  of the present embodiment, the upper chip  100  may include a plurality of pixels Px located in a pixel area PA. Also, each of the pixels Px may include a pixel area (refer to PAp in  FIG. 5B ) and a transistor area (refer to PAt in  FIG. 5B ). For example, a photodiode PD, a transfer transistor TG, and a floating diffusion region FD may be located in the pixel area of the pixel Px, while a reset transistor RG, a source-follower transistor SF, and a selection transistor SEL may be located in the transistor area of the pixel Px. 
     Four pixels Px shown in  FIG. 2A  may be some of the pixels Px. Several hundreds of thousands of pixels Px or several millions of pixels Px may be located in a 2D array in the pixel area PA of the upper chip  100  in a first direction (x direction) and a second direction (y direction). A transfer transistor TG, a reset transistor RG, a source-follower transistor SF, and a selection transistor SEL may be referred to as pixel transistors. 
     A photodiode PD, which is a P-N junction diode, may generate charges, for example, negative charges (or electrons) or positive charges (or holes), in proportion to the amount of incident light. The transfer transistor TG may transit the charges generated by the photodiode PD to the floating diffusion region FD, and the reset transistor RG may periodically reset the charges stored in the floating diffusion region FD. Also, the source-follower transistor SF may serve as a buffer amplifier to buffer a signal corresponding to the charges filled in the floating diffusion region FD, and the selection transistor SEL may serve as a switch to select the pixel corresponding thereto. A column line  110  may be connected to a source region of the selection transistor SEL, and a voltage of the source region of the selection transistor SEL may be output as an output voltage Vout through the column line  110 . 
     Meanwhile, the output voltage Vout may have a short settling time to implement a high-speed image sensor. The settling time of the output voltage Vout may be determined by an RC delay of an output voltage (Vout) line. A capacitance component of the RC delay may be most affected by a capacitance of the output voltage (Vout) line, for example, the column line  110 , while a resistance component of the RC delay may be most affected by an output resistance of the source-follower transistor SF. Differences in capacitance among the column lines  110  may occur mainly due to differences in length among the column lines  110 . Accordingly, assuming that output resistances of the source-follower transistors SF are constant to some extent, the differences in capacitance among the column lines  110  may be minimized by minimizing the differences in length among the column lines  110  so that the differences in RC delay among output voltages Vout may be minimized. 
     The settling time of the output voltage Vout will now be briefly described with reference to the signal waveform diagram of  FIG. 2B . When the transfer transistor TG is turned at on-time Ton and turned off at off-time Toff, a drain voltage, e.g., a voltage of the floating diffusion region FD or a gate voltage Vin of the source-follower transistor SF may have a relatively small RC delay as can be seen from a middle signal waveform diagram. In contrast, as can be seen from a lowermost signal waveform diagram, the output voltage Vout may have a relatively large RC delay. In the lowermost signal waveform diagram, a solid line Col 1  and a dashed line Col 2  may be respectively signal waveform diagrams of output voltages Vout of a first column line  110 - 1  and a second column line  110 - 2  in  FIG. 2A . In addition, it is assumed that a certain length difference is between the first column line  110 - 1  and the second column line  110 - 2 . 
     A settling time may refer to a time duration taken for a difference between the output voltage Vout and a final normal state value to fall within a required percentage (%) range. For example, when it is required for the difference to fall within a range of about 1%, the settling time may be set to about 5 times a time constant (τ=RC). In the lowermost signal waveform diagram, a difference in RC delay may occur due to a difference in length between the first and second column lines  110 - 1  and  110 - 2 . As a result, a difference in set settling times Tset 1  and Tset 2  may also occur. However, even if there is the difference in RC delay, when one settling time is commonly applied to both the column lines  110 - 1  and  110 - 2 , e.g., when a second settling time Tset 2  is applied as a common settling time, an output voltage of the first column line  110 - 1  may be determined in a time other than a normal settling time and become different from an output voltage of the second column line  110 - 2 . As described above, since CFPN is DSNU, output voltages of adjacent column lines should be substantially the same. However, a difference in output voltage between the adjacent column lines may occur due to the application of a common settling time, thus resulting in the occurrence of CFPN. For example, when a difference in length between the adjacent column lines is large, differences in capacitance and RC delay between the adjacent column lines may increase and thus, CFPN may worsen. 
       FIG. 3A  illustrates a conceptual diagram of connection portions between the column lines and the through vias in the structure of the column lines  110  of  FIG. 1B .  FIG. 3B  illustrates a perspective view corresponding to a right drawing of  FIG. 3A . 
     Referring to  FIGS. 3A and 3B , a left drawing of  FIG. 3A  is a reference drawing of a structure in which the column lines  110  include only the effective column lines  110   e  but not include dummy column lines, while the right drawing of  FIG. 3A , which corresponds to  FIG. 1B , is a drawing of a structure in which the column lines  110  includes the effective column lines  110   e  and the dummy column lines  110   d . As described above, only the column lines  110  connected to through vias  130  located on an upper side in a second direction (y direction) are illustrated, and the column lines  110  connected to the through vias  130  located on a lower side in the second direction (y direction) are omitted. 
     The through vias  130  may be arranged along a first direction (x direction) to be gradually away from or periodically or regularly spaced farther from the pixel area (refer to PA in  FIG. 1B ) in the second direction (y direction). Thus, even if a fine position difference is between a first through via  130 - 1  located in a first position H 1  and a second through via  130 - 2  located in a second position H 2  in the second direction (y direction), a maximum position difference, which corresponds to about n times a position difference between adjacent through vias, may occur between the first through via  130 - 1  and an n-th through via  130 - n  located in a final n-th position Hn. For reference, the reason why the through vias  130  are not arranged in a line along the first direction (x direction) but arranged away from the pixel area in the second direction (y direction) will now be described. For example, as can be seen from  FIG. 3B , a size (i.e., diameter or width) of the through vias  130  may be greater than that of the column lines  110 , and if the through vias  130  were to be arranged in a line in the first direction (x direction), a process margin may be deficient, and an electrical short could occur between adjacent through vias  130 . 
     As described above, a predetermined number of through vias  130  may repetitively form groups. Accordingly, a first group of n-th through vias  130 - n  may be adjacent to a second group of first through vias  130 - 1 , but there may be a maximum position difference therebetween in the second direction (y direction). Also, a difference between a length of an n-th effective column line  110   e - n  connected to the first group of n-th through vias  130 - n  and a length of a first effective column line  110   e - 1  of the second group of first through vias  130 - 1  may be maximized. Thus, if the column lines  110  were to not include dummy column lines as in the left drawing of  FIG. 3A , CFPN given by Equation (1) may increase due to the difference in length between adjacent column lines  110  between the groups. 
     In contrast, when the column lines  110  include the dummy column lines  110   d , as in the right drawing of  FIG. 3A , the column lines  110  may have substantially the same length regardless of positions of the through vias  130 . For example, a first dummy column line  110   d - 1  connected to the first effective column line  110   e - 1  (that has the smallest length) may have a first length l 1 , which is the greatest length, a second dummy column line  110   d - 2  connected to a second effective column line  110   e - 2  (that has the second smallest length) may have a second length l 2 , which is the second greatest length, and an n-th dummy column line  110   d - n  connected to the final n-th effective column line  110   e - n  (that has the greatest length) may have an n-th length ln, which is the smallest length. Also, all the column lines  110  may include the dummy column lines  110   d  and extend to an extension position He in the second direction (y direction) so that all the column lines  110  may have substantially the same length. 
     Meanwhile, when the column lines  110  have substantially the same length, the column lines  110  may have substantially the same capacitance and substantially the same RC delay. As a result, the column lines  110  may have substantially the same settling time. Accordingly, a difference in output voltage between adjacent column lines  110  may be minimized, thereby minimizing CFPN. 
     In an implementation, there may not be a dummy column line corresponding to the longest effective column line. For example, when the extension position He is substantially the same as a position of the n-th through via  130 - n , the n-th dummy column line may not be present. Also, the lengths of other dummy column lines may be adjusted according to the extension position He. 
       FIGS. 4A to 4C  illustrate graphs of capacitances of column lines with respect to positions of through vias and structures of column lines connected to the through vias in test  1 , test  2 , and test  3 , respectively.  FIG. 4D  illustrates a graph showing settling times corresponding to connection structures of test  1 , test  2 , and test  3  of  FIGS. 4A to 4C .  FIG. 4E  illustrates an image of a CFPN phenomenon in the connection structure of test  2  of  FIG. 4B . 
     Referring to  FIG. 4A , as shown in a square indicated by test  1 , through vias  130   t   1  may be arranged in the form of a caret ({circumflex over ( )}). Thus, the column lines  110   t   1  connected to the through vias  130   t   1  gradually shorten and then gradually lengthen, and capacitances of the column lines  110   t   1  corresponding to the lengths of the column lines  110   t   1  may gradually decrease and then gradually increase. 
     Referring to  FIG. 4B , as shown in a square indicated by test  2 , groups of through vias  130   t   2  may be repeated, and the through vias  130   t   2  included in each group may be arranged along a first direction (x direction) and gradually extend farther away from a top side of the square in a second direction (y direction). Thus, the column lines  110   t   2  connected to the through vias  130   t   2  may gradually lengthen, return to an initially short state, and then gradually lengthen again, and capacitances of the column lines  110   t   2  corresponding to the lengths of the column lines  110   t   2  may gradually increase, abruptly decrease, and then gradually increase again. Positions of the through vias  1301   t   2  and the connection structures of the through vias  130   t   2  with the column lines  110   t   2  shown in  FIG. 4B  may correspond to the left drawing of  FIG. 3A . 
     Referring to  FIG. 4C , as shown in a square indicated by test  3 , through vias  130   t   3  may be arranged in the same manner as in  FIG. 4B . However, the column lines  110   t   3  may include effective column lines  110   e  and dummy column lines  110   d  and may have substantially the same length, and capacitances of the column lines  110   t   3  corresponding to the lengths of the column lines  110   t   3  may be substantially equal. Positions of the through vias  130   t   3  and the connection structures of the through vias  130   t   3  with the column lines  110   t   3  shown in  FIG. 4C  may correspond to the right drawing of  FIG. 3A . 
     Referring to  FIG. 4D , assuming that a settling time is proportional to an RC time constant and a resistance component is constant to some extent, it may be seen that settling times corresponding to the positions of the through vias  130   t   1 ,  130   t   2 , and  130   t   3  and the structures of column lines  110   t   1 ,  110   t   2 , and  110   t   3  connected to the through vias  130   t   1 ,  130   t   2 , and  130   t   3  in test  1 , test  2 , and test  3  assume almost similar shapes to the graphs of the capacitances of the column lines  110   t   1 ,  110   t   2 , and  110   t   3  of  FIGS. 4A to 4C . For example, settling times of the column lines  110   t   1  in test  1  may gradually decrease and then gradually increase, and settling times of the column lines  110   t   2  in test  2  may gradually increase, abruptly decrease, and then increase again. Settling times of the column lines  110   t   3  in test  3  may be maintained substantially the same. 
     Referring to  FIG. 4E , stripes may be observed in portions indicated by arrows. Striped portions may be a result of an increase in CFPN caused by a sharp difference in length between adjacent column lines between groups. Accordingly, in the image sensor  1000  of the present embodiment, the column lines  110  may include the dummy column lines  110   d  and may have substantially the same length. Thus, CFPN may be improved so that the image sensor  1000  of the present embodiment may provide images with minimized noise. 
       FIG. 5A  illustrates a circuit diagram of shared pixels SP of an image sensor  1000   a  according to an embodiment.  FIG. 5B  illustrates a schematic plan view of one shared pixel in the circuit diagram of  FIG. 5A . 
     Referring to  FIGS. 5A and 5B , in the image sensor  1000   a  of the present embodiment, a plurality of shared pixels SP may be arranged in a 2D array in a pixel area (refer to PA in  FIG. 1B ) of an upper chip  100   a . Although  FIG. 5A  illustrates two shared pixels SP 1  and SP 2 , a plurality of shared pixels SP may be actually arranged in a 2D array in the pixel area PA of the upper chip  100   a  in a first direction (x direction) and a second direction (y direction). 
     Each of the shared pixels SP may include a pixel shared area PAs and a transistor area PAt. Four pixels may be arranged in the pixel shared area PAs, and transistors RG, FS, and SET excluding transfer transistors TG may be arranged in the transistor area PAt. In the image sensor  1000   a  of the present embodiment, one photodiode PD may correspond to one pixel. Thus, unless specifically described otherwise below, the photodiode PD and the pixel will be treated as the same concept. 
     In the image sensor  1000   a  of the present embodiment, four pixels may constitute one shared pixel SP. For example, the shared pixel SP may have a structure in which four photodiodes PD 1  to PD 4  surround and share one floating diffusion region FD. In one shared pixel SP, as can be seen from the circuit diagram of  FIG. 5A , one floating diffusion region FD may be shared among the four photodiodes PD 1  to PD 4  due to transfer transistors TG 1  to TG 4  corresponding respectively to the photodiodes PD 1  to PD 4 . For example, a first transfer transistor TG 1  corresponding to a first photodiode PD 1 , a second transfer transistor TG 2  corresponding to a second photodiode PD 2 , a third transfer transistor TG 3  corresponding to a third photodiode PD 3 , and a fourth transfer transistor TG 4  corresponding to a fourth photodiode PD 4  may share the floating diffusion region FD serving as a common drain region. 
     The sharing concept of the shared pixel SP may not only mean that the four photodiodes PD 1  to PD 4  share one floating diffusion region FD, but also mean that the four photodiodes PD 1  to PD 4  share pixel transistors RG, FS, and SEL excluding the transfer transistors TG 1  to TG 4 . For example, the four photodiodes PD 1  to PD 4  included in the shared pixel SP may share a reset transistor RG, a source-follower transistor SF, and a selection transistor SEL. The reset transistor RG, the source-follower transistor SF, and the selection transistor SEL may be located in a second direction (y direction) in the transistor area PAt. In an implementation, the reset transistor RG, the source-follower transistor SF, and the selection transistor SEL may be located in a first direction (x direction) in the transistor area PAt according to a structure in which the photodiodes PD 1  to PD 4  and the transfer transistors TG 1  to TG 4  are arranged in the pixel shared area Pas. 
     Structures and operations of the reset transistor RG, the source-follower transistor SF, and the selection transistor SEL may be substantially the same as those of the reset transistor RG, the source-follower transistor SF, and the selection transistor SEL located in each of the pixels Px of the upper chip  100  of the image sensor  1000  shown in  FIG. 2A  except that the reset transistor RG, the source-follower transistor SF, and the selection transistor SEL are shared among the four photodiodes PD 1  to PD 4 . 
     A connection relationship among the pixel transistors TG, RG, SF, and SEL will be briefly examined with reference to the circuit diagram of  FIG. 5A . The four photodiodes PD 1  to PD 4  may constitute source regions of the four transfer transistors TG 1  to TG 4  corresponding respectively thereto. The floating diffusion region FD may constitute the common drain region of the transfer transistors TG 1  to TG 4  and be connected to the source region of the reset transistor RG by an interconnection  150 . Also, the floating diffusion region FD may also be connected to a gate electrode of the source-follower transistor SF by the interconnection  150 . A drain region may be shared between the reset transistor RG and the source-follower transistor SF and connected to a power supply voltage Vpix. A source region of the source-follower transistor SF and a drain region of the selection transistor SEL may be shared between the source-follower transistor SF and the selection transistor SEL. An output voltage Vout may be connected to a source region of the selection transistor SEL. For example, a voltage of the source region of the selection transistor SEL may be output as the output voltage Vout through a column line  110 . 
     In the image sensor  1000   a  of the present embodiment, a unit shared pixel SP may include four pixels of the pixel shared area PAs and the transistors RG, SF, and SEL of the transistor area PAt corresponding to the pixel shared area Pas. The transfer transistors TG 1  to TG 4  corresponding to the number of the shared photodiodes PD 1  to PD 4  may be located in the pixel shared area PAs. Furthermore, in the image sensor  1000   a  of the present embodiment, column lines  110  may be disposed in a pixel area (refer to PA in  FIG. 1B ) and a peripheral area (refer PE in  FIG. 1B ) of the upper chip  100   a  and connected to source regions of selection transistors SEL of the shared pixels SP. While the column lines  110  are extending in the second direction (y direction), the column lines  110  may include the dummy column lines (refer to  110   d  in  FIG. 1B ) and have substantially the same length in the second direction (y direction). As a result, the image sensor  1000   a  of the present embodiment may uniformize a settling time and improve CFPN based on the column lines  110  having substantially the same length. Therefore, the image sensor  1000   a  of the present embodiment may provide improved images with minimized noise. 
     In an implementation, a unit shared pixel SP may include four pixels. In an implementation, in the image sensor  1000   a  of the present embodiment, the unit shared pixel SP may include two pixels or eight pixels. 
       FIG. 6A  illustrates a circuit diagram of shared pixels SP of an image sensor  1000   b  according to an embodiment, and  FIG. 6B  illustrates a schematic plan view of one shared pixel SP in the circuit diagram of  FIG. 6A . 
     Referring to  FIGS. 6A and 6B , the image sensor  1000   b  of the present embodiment may differ from the image sensor  1000   a  of  FIG. 5A  in that each of shared pixels SP′ of an upper chip  100   b  includes two source-follower transistors SF 1  and SF 2 . For example, in the image sensor  1000   b  of the present embodiment, each of the shared pixels SP′ may include a first source-follower transistor SF 1  and a second source-follower transistor SF 2 , which are adjacent to each other. Also, in the image sensor  1000   b  of the present embodiment, the shared pixel SP′ may include the two source-follower transistors SF 1  and SF 2 , and a structure in which the pixel transistors RG, SF 1 , SF 2 , and SEL may be arranged may be different than in the image sensor  1000   a  of  FIG. 5B . 
     For example, a connection relationship between the pixel transistors TG, RG, SF 1 , SF 2 , and SEL will be briefly examined with reference to the circuit diagram of  FIG. 6A . A connection relationship among photodiodes PD 1  to PD 4 , transfer transistors TG 1  to TG 4 , and a floating diffusion region PD in a pixel shared area PAs may be substantially the same as in the circuit diagram of  FIG. 5A . Meanwhile, the floating diffusion region PD may be connected to gate electrodes of a first source-follower transistor SF 1  and a second source-follower transistor SF 2  and a source region of a reset transistor RG through a first interconnection  150   a.    
     A drain region may be shared between the second source-follower transistor SF 2  and the reset transistor RG, connected to a drain region of the first source-follower transistor SF 1  through a second interconnection  150   b , and connected to a power supply voltage Vpix. A source region may be shared between the first source-follower transistor SF 1  and the second source-follower transistor SF 2  and connected to a drain region of a selection transistor SEL through a third interconnection  150   c . An output voltage Vout may be connected to a source region of the selection transistor SEL. That is, a voltage of the source region of the selection transistor SEL may be output as the output voltage Vout through a column line  110 . 
       FIG. 5B  illustrates a case in which the reset transistor RG and the selection transistor SEL are respectively located on both sides of the source-follower transistor SF. In the image sensor  1000   b  of the present embodiment, as can be seen from  FIG. 6B , the reset transistor RG and the selection transistor SEL may be arranged on one side of the first and second source-follower transistors SF 1  and SF 2 . The arrangement of the reset transistor RG and the selection transistor SEL may be a result of sharing the source and drain regions between the two source-follower transistors SF 1  and SF 2 . For example, when odd source-follower transistors are located, a reset transistor and a selection transistor may be respectively located on both sides of the source-follower transistors. When even source-follower transistors are located, a reset transistor and a selection transistor may be located on one side of the source-follower transistors. Also, as may be seen from  FIG. 6B , when the reset transistor RG and the selection transistor SEL are located on one side of the first and second source-follower transistors SF 1  and SF 2 , a device isolation film  108  may be located between the reset transistor RG and the selection transistor SEL. 
     In the image sensor  1000   b  of the present embodiment, column lines  110  may be located in a pixel area (refer to PA in  FIG. 1B ) and a peripheral area (refer to PE in  FIG. 1B ) of the upper chip  100   b  and connected to the source regions of the selection transistors SEL of the shared pixels SP′. While the column lines  110  are extending in the second direction (y direction), the column lines  110  may include the dummy column lines (refer to  110   d  in  FIG. 1B ) and have substantially the same length in the second direction. As a result, in the image sensor  1000   b  of the present embodiment, a settling time may be uniformized and CFPN may be improved based on the column lines  110  having substantially the same length. Accordingly, the image sensor  1000   b  of the present embodiment may provide improved images of which noise is minimized. 
       FIGS. 7A, 8A, and 9A  illustrate conceptual diagrams of structures of column lines of pixel areas in image sensors according to embodiments.  FIGS. 7B, 8B, and 9B  illustrate perspective views of connection portions between the column lines and the through vias in the structures of the column lines of  FIGS. 7A, 8A, and 9A , respectively. The same descriptions as in  FIGS. 1B, 3A, and 3B  will be simplified or omitted. 
     Referring to  FIGS. 7A and 7B , an image sensor  1000   c  of the present embodiment may differ from the image sensor  1000  of  FIG. 1B  in that vertical contacts  140  and middle interconnections  160  may be further provided in a peripheral area PE of an upper chip  100   c . Also, in the image sensor  1000   c  of the present embodiment, positions of through vias  130   a  may differ from positions of the through vias  130  of the image sensor  1000  of  FIG. 1B . For example, in the image sensor  1000   c  of the present embodiment, the vertical contacts  140  may be located in the peripheral area PE of the upper chip  100   c  along a first direction (x direction) to be away from the pixel area PA in the second direction (y direction), and the column lines  110  may be connected to the vertical contacts  140 . As in the image sensor  1000  of  FIG. 1B , each of the column lines  110  may include an effective column line  110   e  and a dummy column line  110   d . For example, the vertical contacts  140  may be located in substantially the same positions as the through vias  130  of the image sensor  1000  of  FIG. 1B . The vertical contacts  140  may function to connect the column lines  110  with the middle interconnections  160 , and the vertical contacts  140  may be smaller in size (e.g., diameter or width) than the through vias  130 . 
     The middle interconnections  160  may be connected to the vertical contacts  140  and may extend (e.g., lengthwise) in the first direction (x direction). The middle interconnections  160  may be located in a layer disposed directly under a layer in which the column lines  110  are arranged. In an implementation, the middle interconnections  160  may be located, e.g., in a layer disposed directly on a layer in which the column lines  110  are arranged. 
     The through vias  130   a  may be arranged in a line along the second direction (y direction) and may extend in a third direction (z direction). The through vias  130   a  may be connected to the middle interconnections  160 .  FIGS. 7A and 7B  illustrate a case in which the middle interconnections  160  are connected to ends of the through vias  30   a . In an implementation, the through vias  130   a  may further extend upwardly in the third direction (z direction), and the middle interconnections  160  may be connected to side surfaces of the through vias  130   a.    
     Referring to  FIGS. 8A and 8B , an image sensor  1000   d  of the present embodiment may be almost similar to the image sensor  1000   c  of  FIG. 7A  in that vertical contacts  140  and middle interconnections  160  may be further provided in a peripheral area PE of an upper chip  100   d  and through vias  130   a  are arranged in a line in a second direction (y direction). In the image sensor  1000   d  of the present embodiment, additional dummy lines  145  may be further located in the peripheral area PE of the upper chip  100   d . The additional dummy lines  145  may be connected to the middle interconnections  160  and extend beyond the vertical contacts  140  in the first direction (x direction, e.g., away from the through vias  130   a ). The additional dummy lines  145  may serve functions similar to the above-described dummy column lines  110   d  of the column lines  110 . 
     Referring to  FIGS. 9A and 9B , an image sensor  1000   e  of the present embodiment may be almost similar to the image sensor  1000   c  of  FIG. 7A  in that vertical contacts  140  and a middle interconnection  160  may be further provided in a peripheral area PE of an upper chip  100   e  and through vias  130   a  are arranged in a line in a second direction (y direction). The image sensor  1000   e  of the present embodiment, column lines  110   a  may not include dummy column lines. As shown in  FIGS. 9A and 9B , the column lines  110   a  may be connected to the through vias  130   a  through the vertical contacts  140  and the middle interconnections  160 . Also, long middle interconnections  160  may be connected to short column lines  110   a , and short middle interconnections  160  may be connected to long column lines  110   a . Accordingly, when the middle interconnections  160  are included as parts in the column lines  110   a , the overall lengths of the column lines  110   a  may be substantially the same based on positions of the through vias  130   a.    
     In an implementation, even if the column lines  110   a  include the middle interconnections  160 , in case that the overall lengths of the column lines  110   a  are not the same, at least some of the column lines  110   a  may include dummy column lines so that the overall lengths of the column lines  110   a  may be substantially the same. Also, additional dummy lines connected to the middle interconnections  160  may be located instead of the dummy column lines so that the overall lengths of the column lines  110  may be substantially the same. 
       FIGS. 10 and 11  illustrate conceptual diagrams of structures of row lines of pixel areas in image sensors according to embodiments. 
     Referring to  FIG. 10 , in an image sensor  1000   f  of the present embodiment, a plurality of row lines may be located in a pixel area (refer to PA in  FIG. 1B ) of an upper chip  100   f . The row lines may include, e.g., a transfer transistor line  182  connected to a gate electrode of a transfer transistor (refer to TG in  FIG. 2A ), a selection transistor line  184  connected to a gate electrode of a selection transistor (refer to SEL in  FIG. 2A ), and/or a reset transistor line  186  connected to a gate electrode of a reset transistor (refer to RG in  FIG. 2A ). The row lines may be connected to a row drive circuit  190 , and a signal corresponding to an appropriate voltage may be applied from the row drive circuit  190  to the transfer transistor TG, the selection transistor SEL, and the reset transistor RG. The row drive circuit  190  may be included in typical logic devices and located in a lower chip (refer to  200  in  FIG. 1A ). In an implementation, the row drive circuit  190  may be located in an upper chip (refer to  100  in  FIG. 1A ). 
     Meanwhile, capacitances of the transistors TG, SETL and RG included in the pixels Px may be different. Thus, even if the row lines have the same length in a first direction (x direction), differences in RC delay may occur so that the row lines may have respectively different characteristics of transmission of signals to the pixels Px. In the image sensor  1000   f  of the present embodiment, the characteristics of transmission of signals to the pixels Px may be uniformized by adjusting lengths of some of the row lines. For example, when the reset transistor RG has a low capacitance and a signal transmission rate of the reset transistor line  186  is higher than signal transmission rates of the transfer transistor line  182  and the selection transistor line  184 , signal transmission characteristics may be uniformized by adjusting the reset transistor line  186  to a length greater than lengths of the transfer transistor line  182  and the selection transistor line  184 . 
     Referring to  FIG. 11 , in an image sensor  1000   g  of the present embodiment, shared pixels (refer to SP in  FIG. 5A ) may be located in a pixel area (refer to PA in  FIG. 1B ) of an upper chip  100   g . Also, a plurality of row lines may be located in the pixel area of the upper chip  100   g . First to fourth transfer transistor lines  182 - 1 ,  182 - 2 ,  182 - 3 , and  182 - 4  may be located in the row lines and connected to four transfer transistors (refer to TG 1  to TG 4  in  FIG. 5A ) arranged in the shared pixels. For reference, a selection transistor line (refer to  184  in  FIG. 10 ) and a reset transistor line (refer to  186  in  FIG. 10 ) are omitted from  FIG. 11 . 
     Meanwhile, capacitances of the transfer transistors located in the shared pixels SP may different. Thus, even if the transfer transistor lines  182 - 1 ,  182 - 2 ,  182 - 3 , and  182 - 4  have the same length in a first direction (x direction), differences in RC delay may occur so that the transfer transistor lines  182 - 1 ,  182 - 2 ,  182 - 3 , and  182 - 4  may have respectively different characteristics of transmission of signals to the pixels in the shared pixels SP. In the image sensor  1000   g  of the present embodiment, the characteristics of transmission of the signals to the pixels in the shared pixels SP may be uniformized by adjusting lengths of some of the transfer transistor lines  182 - 1 ,  182 - 2 ,  182 - 3 , and  182 - 4 . For example, when the fourth transfer transistor has a low capacitance and a signal transmission rate of the fourth transfer transistor line  182 - 4  is higher than signal transmission rates of the other transfer transistor lines  182 - 1 ,  182 - 2 , and  182 - 3 , signal transmission characteristics may be uniformized by adjusting the fourth transfer transistor line  182 - 4  to a length greater than lengths of the other transfer transistor lines  182 - 1 ,  182 - 2 , and  182 - 3 . 
       FIGS. 12A and 12B  respectively illustrate a plan view and a cross-sectional view of the image sensor  1000  of  FIG. 1A  in which an upper chip  100  is combined with a lower chip  200  by using through vias.  FIGS. 12A and 12B  will be described with further reference to  FIGS. 1A and 1B , and the same descriptions as in  FIGS. 1A and 1B  may be simplified or omitted. 
     Referring to  FIGS. 12A and 12B , in the image sensor  1000  of the present embodiment, the upper chip  100  may include first through vias  130 , and the lower chip  200  may include second through vias  230 . As shown in  FIG. 12B , the upper chip  100  may be electrically connected to the lower chip  200  by the first and second through vias  130  and  230 . 
     For example, the upper chip  100  may include a pixel area PA and a peripheral area PE located outside the pixel area PA. Pixels may be arranged in a 2D array in the pixel area PA, and a plurality of first through vias  130  may be arranged in the peripheral area PE. As shown in  FIG. 12B , a semiconductor substrate  101  may be located in an upper portion of the upper chip  100 , and pixels may be formed in the semiconductor substrate  101 . Also, color filters and microlenses may be formed in an upper portion of the semiconductor substrate  101 . Interconnection layers Mu may be located in a lower portion of the upper chip  100 . 
     As described above, a structure in which the color filters and the microlenses are formed in an opposite direction to the interconnection layers Mu on the basis of the semiconductor substrate  101  in which the pixels are formed may be referred to as a back-side illumination (BSI) structure. Conversely, a structure in which the color filters and the microlenses are formed in the same direction as the interconnection layers Mu on the basis of the semiconductor substrate  101 , e.g., a structure in which the color filters and the microlenses are formed on the interconnection layers Mu, may be referred to as a front-side illumination (FSI) structure. 
     In an implementation, the first through vias  130  may be arranged in outer portions of all four sides of the upper chip  100 . In an implementation, the first through vias  130  may not be formed in the outer portion of at least one of the four sides of the upper chip  100 . Each of the first through vias  130  may be configured to wholly or partially penetrate the upper chip  100 . The first through vias  130  may be electrically connected to the interconnection layers Mu located in the peripheral area PE of the upper chip  100 . 
     The lower chip  200  may include a logic area LA and a peripheral area PEI located outside the logic area LA. Logic devices including an ADC circuit may be located in the logic area LA, and a plurality of second through vias  230  may be located in the peripheral area PEI. As shown in  FIG. 12B , a semiconductor substrate  201  may be located in a lower portion of the lower chip  200 , and interconnection layers Md may be located in an upper portion of the lower chip  200 . Transistors of the logic devices may be formed in the semiconductor substrate  201 . 
     Unlike the first through vias  130 , the second through vias  230  may be formed in only a portion of the upper portion of the lower chip  200  and electrically connected to the interconnection layer Md located in the peripheral area PEI of the lower chip  200 . Also, the first through vias  130  may be integrally connected to the second through vias  230  so that the upper chip  100  may be electrically connected to the lower chip  200  through the first through vias  130  and the second through vias  230 . 
     Meanwhile, a distinction between the first through via  130  and the second through via  230  may be only a convenient distinction as to whether the first through via  130  or the second through via  230  is located in the upper chip  100  or the lower chip  200 . For example, the first through via  130  and the second through via  230  may have an inseparable, integral structure due to the fact that the first through via  130  and the second through via  230  are not separately formed in the upper chip  100  and the lower chip  200 , respectively, but formed as one through via in the upper and lower chips  100  and  200  by using a through-via forming process after the upper chip  100  is combined with the lower chip  200 . In  FIG. 12B , an alternated long and short dash line denotes a boundary along which the upper chip  100  is combined with the lower chip  200 . The upper chip  100  and the lower chip  200  may be stacked and combined on a wafer level and then separated in units of stack chips. In an implementation, the stacking and combination of the upper and lower chips  100  and  200  on a chip level may not be entirely excluded. 
     In the image sensor  1000  of the present embodiment, the upper chip  100  may be electrically connected to the lower chip  200  through the first and second through vias  130  and  230 , and the upper chip  100  may have a BSI structure, so that the first and second through vias  130  and  230  may be formed in the outer portions of the upper and lower chips  100  and  200 . Since the first through vias  130  are configured to penetrate the upper chip  100 , when the first through vias  130  are located in a pixel area PA, an area occupied by the pixels may be reduced, thereby precluding the implementation of a high-resolution image sensor. As described above with reference to  FIG. 1B , in the image sensor  1000  of the present embodiment, while column lines  110  are extending in a second direction (y direction), the column lines  110  may include dummy column lines  110   d  and may have substantially the same length in the second direction (y direction. Accordingly, the image sensor  1000  of the present embodiment may uniformize a settling time and improve CFPN based on the column lines  110  having substantially the same length. Therefore, the image sensor  1000  of the present embodiment may provide improved images with minimized noise. 
       FIG. 13  illustrates a schematic construction diagram of the image sensor  1000  of  FIG. 1A .  FIG. 13  will be described with further reference to  FIGS. 1A and 1B , and the same descriptions as in  FIGS. 1A and 1B  will be simplified or omitted. 
     Referring to  FIG. 13 , the image sensor  1000  of the present embodiment may include a pixel unit PU and a peripheral circuit unit PEU. A plurality of pixels Px may be regularly arranged in a 2D array in the pixel unit PU. In an implementation, the pixels Px may be the pixels Px formed on the upper chip  100  of the image sensor  1000  of  FIG. 2A . In an implementation, the pixels Px may be shared pixels SP formed on the upper chip  100   a  of the image sensor  1000   a  of  FIG. 5A . The pixel unit PU may be formed on the upper chip  100  and include a pixel area and a peripheral area. 
     The peripheral circuit unit PEU may be located adjacent to the pixel unit PU and include a vertical drive circuit  40 , a clock signal processing circuit  50 , a horizontal drive circuit  60 , an output circuit  70 , and a control circuit  80 . The peripheral circuit unit PEU may be formed in a lower chip  200 . However, in some embodiments, the peripheral circuit unit PEU may be partially or wholly formed in the upper chip  100 . 
     The control circuit  80  may control the vertical drive circuit  40 , the clock signal processing circuit  50 , and the horizontal drive circuit  60 . For example, the control circuit  80  may generate clock signals or control signals, which serve as bases for operations of the vertical drive circuit  40 , the clock signal processing circuit  50 , and the horizontal drive circuit  60 , based on a vertical synchronous signal, a horizontal synchronous signal, and a master clock. Also, the control circuit  80  may input clock signals or control signals to the vertical drive circuit  40 , the clock signal processing circuit  50 , and the horizontal drive circuit  60 . 
     The vertical drive circuit  40  may include, e.g., a shifter register. The vertical drive circuit  40  may select a pixel drive interconnection, supply a pulse for driving pixels to the selected pixel drive interconnection, and drive pixels in rows. For example, the vertical drive circuit  40  may sequentially selectively scan pulse to the pixels Px of the pixel unit PU in rows in a vertical direction. Also, the vertical drive circuit  40  may supply pixel signals corresponding to charges generated by photodiodes of the pixels Px to the clock signal processing circuit  50  through column lines  110 . 
     The clock signal processing circuit  50  may be located in each of columns of the pixels Px and perform a signal processing operation (e.g., noise removal) on signals output by the pixels Px in each of the columns of the pixels Px. For example, the clock signal processing circuit  50  may perform a signal processing operation, such as a correlated-double sampling (CDS) operation for removing noise of the pixels Px, a signal amplification operation, and an ADC operation. A horizontal selection switch may be installed at an output terminal of the clock signal processing circuit  50 . 
     The horizontal drive circuit  60  may include, e.g., a shift register. The horizontal drive circuit  60  may sequentially horizontal scan pulses, sequentially select the respective clock signal processing circuits  50 , and output pixel signals of the respective clock signal processing circuits  50  to a horizontal signal line  34 . The output circuit  70  may process signals sequentially supplied from the respective clock signal processing circuits  50  through the horizontal signal line  34 , and output the processed signals. For example, the output circuit  70  may only buffer the signals or perform black level adjustment, thermal non-uniformity correction, or various digital signal processing operations on the signals. 
       FIG. 14  illustrates a schematic construction diagram of an electronic apparatus  2000  including an image sensor  1000  according to an embodiment. 
     Referring to  FIG. 14 , the electronic apparatus  2000  of the present embodiment may include an image sensor  1000 , an optical system  1100 , a shutter  1200 , a drive circuit  1300 , and a signal processing circuit  1400 . The electronic apparatus  2000  of the present embodiment may be, for example, a CMOS camera capable of capturing still images or moving images. 
     The image sensor  1000  may be at least one of the image sensors  1000  and  1000   a  to  1000   g  of  FIGS. 1A to 3B and 5A to 11 . the image sensor  1000  may include a pixel unit PU and a peripheral circuit unit PEU as shown in  FIG. 13  or have a stack structure of the upper chip  100  and the lower chip  200  as shown in  FIG. 1A . 
     The optical system  1100  may be an element configured to guide incident light to a light receiving unit of the image sensor  1000  and include a plurality of optical lenses. For example, the optical system  1100  may image incident light from a subject on an imaging surface of the image sensor  1000  so that charges may be generated and accumulated in the image sensor  1000 . 
     The shutter  1200  may control periods for which light is irradiated to or shielded from the image sensor  1000 . The drive circuit  1300  may supply drive signals to control a transfer operation of the image sensor  1000  and an operation of the shutter  1200 . The image sensor  1000  may transmit signals in response to a drive signal (or a timing signal) supplied from the drive circuit  1300 . 
     The signal processing circuit  1400  may perform various signal processing operations on output signals of the image sensor  1000 . Video signals processed by the signal processing circuit  1400  may be stored in a storage medium (e.g., a memory) or output to a monitor. 
     As is traditional in the field, embodiments are described, and illustrated in the drawings, in terms of functional blocks, units and/or modules. Those skilled in the art will appreciate that these blocks, units and/or modules are physically implemented by electronic (or optical) circuits such as logic circuits, discrete components, microprocessors, hard-wired circuits, memory elements, wiring connections, and the like, which may be formed using semiconductor-based fabrication techniques or other manufacturing technologies. In the case of the blocks, units and/or modules being implemented by microprocessors or similar, they may be programmed using software (e.g., microcode) to perform various functions discussed herein and may optionally be driven by firmware and/or software. Alternatively, each block, unit and/or module may be implemented by dedicated hardware, or as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Also, each block, unit and/or module of the embodiments may be physically separated into two or more interacting and discrete blocks, units and/or modules without departing from the scope herein. Further, the blocks, units and/or modules of the embodiments may be physically combined into more complex blocks, units and/or modules without departing from the scope herein. 
     By way of summation and review, with a reduction in pixel size, an image sensor with a shared pixel structure may be used, and a high-performance image sensor capable of capturing images at high speed may be considered. 
     The embodiments may provide an image sensor capable of minimizing noise and providing improved images. 
     The embodiments may provide an image sensor, which may help uniformize signal transmission characteristics and minimize noise caused thereby to provide improved images. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.