Abstract:
Pixel sensor cells, method of fabricating pixel sensor cells and design structure for pixel sensor cells. The pixel sensor cells including: a photodiode body in a first region of a semiconductor layer; a floating diffusion node in a second region of the semiconductor layer, a third region of the semiconductor layer between and abutting the first and second regions; and dielectric isolation in the semiconductor layer, the dielectric isolation surrounding the first, second and third regions, the dielectric isolation abutting the first, second and third regions and the photodiode body, the dielectric isolation not abutting the floating diffusion node, portions of the second region intervening between the dielectric isolation and the floating diffusion node.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of solid-state image sensing devices; more specifically, it relates to CMOS based pixel sensor cell devices, methods of fabricating CMOS based pixel sensor cell devices and design structures for CMOS based pixel sensor cell devices. 
       BACKGROUND 
       [0002]    Current CMOS (complementary metal oxide semiconductor) based image sensors suffer from one of two deficiencies depending upon the shutter system used. In rolling shutter systems the pixel sensor cells are exposed at different times. In global shutter systems, the signal strength from the pixel sensor cells can vary. In both cases, less than ideal images are produced. Accordingly, there exists a need in the art to mitigate the deficiencies and limitations described hereinabove. 
       SUMMARY 
       [0003]    A first aspect of the present invention is a pixel sensor cell, comprising: a photodiode body in a first region of a semiconductor layer; a floating diffusion node in a second region of the semiconductor layer, a third region of the semiconductor layer between and abutting the first and second regions; and dielectric isolation in the semiconductor layer, the dielectric isolation surrounding the first, second and third regions, the dielectric isolation abutting the first, second and third regions and the photodiode body, the dielectric isolation not abutting the floating diffusion node, portions of the second region intervening between the dielectric isolation and the floating diffusion node. 
         [0004]    A second aspect of the present invention is a method of fabricating a pixel sensor cell, comprising: forming a photodiode body in a first region of a semiconductor layer; forming a floating diffusion node in a second region of the semiconductor layer, a third region of the semiconductor layer between and abutting the first and second regions; and forming dielectric isolation in the semiconductor layer, the dielectric isolation surrounding the first, second and third regions, the dielectric isolation abutting the first, second and third regions and the photodiode body, the dielectric isolation not abutting the floating diffusion node, portions of the second region intervening between the dielectric isolation and the floating diffusion node. 
         [0005]    A third aspect of the present invention is a design structure comprising design data tangibly embodied in a machine-readable medium, the design data being used for designing, manufacturing, or testing an integrated circuit, the design data comprising information describing a pixel sensor cell the pixel sensor cell comprising: a photodiode body in a first region of a semiconductor layer; a floating diffusion node in a second region of the semiconductor layer, a third region of the semiconductor layer between and abutting the first and second regions; and dielectric isolation in the semiconductor layer, the dielectric isolation surrounding the first, second and third regions, the dielectric isolation abutting the first, second and third regions and the photodiode body, the dielectric isolation not abutting the floating diffusion node, portions of the second region intervening between the dielectric isolation and the floating diffusion node. 
         [0006]    These and other aspects of the invention are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The features of the invention are set forth in the appended claims. The invention itself, however, will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1A  is a top view and  FIGS. 1B ,  1 C,  1 D and  1 E are cross-sections through respective lines  1 B- 1 B,  1 C- 1 C,  1 D- 1 D and  1 E- 1 E of  FIG. 1A  illustrating fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0009]      FIG. 2A  is a top view and  FIGS. 2B ,  2 C,  2 D and  2 E are cross-sections through respective lines  2 B- 2 B,  2 C- 2 C,  2 D- 2 D and  2 E- 2 E of  FIG. 2A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0010]      FIG. 3A  is a top view and  FIGS. 3B ,  3 C,  3 D and  3 E are cross-sections through respective lines  3 B- 3 B,  3 C- 3 C,  3 D- 3 D and  3 E- 3 E of  FIG. 3A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0011]      FIG. 4A  is a top view and  FIGS. 4B ,  4 C,  4 D and  4 E are cross-sections through respective lines  4 B- 4 B,  4 C- 4 C,  4 D- 4 D and  4 E- 4 E of  FIG. 4A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0012]      FIG. 5A  is a top view and  FIGS. 5B ,  5 C,  5 D and  5 E are cross-sections through respective lines  5 B- 5 B,  5 C- 5 C,  5 D- 5 D and  5 E- 5 E of  FIG. 5A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0013]      FIG. 5F  is a cross-section illustrating gate structures through line  5 B- 5 B of  FIG. 5A ; 
           [0014]      FIG. 6A  is a top view and  FIGS. 6B ,  6 C,  6 D and  6 E are cross-sections through respective lines  6 B- 6 B,  6 C- 6 C,  6 D- 6 D and  6 E- 6 E of  FIG. 6A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0015]      FIG. 7A  is a top view and  FIGS. 7B ,  7 C,  7 D and  7 E are cross-sections through respective lines  7 B- 7 B,  7 C- 7 C,  7 D- 7 D and  7 E- 7 E of  FIG. 7A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0016]      FIG. 8A  is a top view and  FIGS. 8B ,  8 C,  8 D and  8 E are cross-sections through respective lines  8 B- 8 B,  8 C- 8 C,  8 D- 8 D and  8 E- 8 E of  FIG. 8A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0017]      FIG. 9A  is a top view and  FIGS. 9B ,  9 C,  9 D and  9 E are cross-sections through respective lines  9 B- 9 B,  9 C- 9 C,  9 D- 9 D and  9 E- 9 E of  FIG. 9A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention; 
           [0018]      FIGS. 10A ,  10 B,  10 C and  10 D illustrate alternative structures for the storage node of a pixel sensor cell according to embodiments of the present invention; 
           [0019]      FIG. 11  is a top view of illustrating interconnections of the structural elements in a pixel sensor cell circuit; 
           [0020]      FIG. 12  is a circuit diagram of a pixel sensor cell circuit according to embodiments of the present invention. 
           [0021]      FIG. 13  is a diagram illustrating an array of global shutter pixel sensor cells according to embodiments of the present invention; and 
           [0022]      FIG. 14  shows a block diagram of an exemplary design flow  400  used for example, in semiconductor IC logic design, simulation, test, layout, and manufacture. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Solid state imaging devices contain CMOS based pixel sensor cells arranged in an array of rows and columns and a shutter mechanism to expose the pixel sensor cell array. 
         [0024]    In rolling shutter methodology the image is captured on a row-by-row basis. For a given row the image is captured by photodiodes, transferred to floating diffusion nodes, and then the nodes are read out to column sample circuits before moving on to the next row. This repeats until the all the pixel sensor cell rows are captured and read out. In the resulting image each row represents the subject at a different time. Thus for highly dynamic subjects (such as objects moving at a high rate of speed) the rolling shutter methodology can create image artifacts. 
         [0025]    In a global shutter methodology, the image is captured for the whole frame in the photodiodes at the same time for all the rows and columns of the pixel sensor cell array. Then the image signal is transferred to the floating diffusion nodes where it is stored until it is read out on a row-by-row basis. The global shutter method solves the problem with image capture of high speed subjects, but introduces the problem of charge level change on the charge storage node of the pixel sensor cell. 
         [0026]    In the rolling shutter method, the image signal is held in the charge storage nodes for a significantly shorter time than the actual time of exposure of the photodiode, and this hold time is the same for all pixel sensor cells in the array, making correction for charge level change in storage node simple with standard CDS techniques. In the global shutter method, the image signal is held in the storage node for varying amounts of time. The time in the first row being the shortest time (the time to read out a single row) with the time in the last row being the longest time (the time to read all rows). Thus any charge generation or leakage occurring on storage node can have a significant impact to the signal being read out of the row. 
         [0027]    In order to improve on the global shutter efficiency the embodiments of the present invention reduce the amount of change to the charge being held on the floating diffusion node of the pixel sensor cell. The embodiments of the present invention use unique well and floating diffusion node ion implantation design levels/masks to create floating diffusion nodes that have minimal dark current generation and leakage caused by stray carriers that may be generated in adjacent semiconductor regions. In embodiments of the present invention, the drain ion implant design level/mask leaves a space between the floating diffusion node and the dielectric isolation sidewalls. The well ion implantation design level/mask is designed such that the well extends under the floating diffusion node and the dielectric isolation. 
         [0028]    Optionally, an electron shield ion implantation design level/mask is provided. Optionally, a dielectric trench sidewall passivation ion implantation design level/mask is provided, which reduces carrier generation that can occur along the dielectric isolation sidewall surfaces. Optionally a surface pinning ion implantation design level/mask is provided which passivates the surface of the photodiode and the floating diffusion node. The fabrication process infra is presented in a preferred order, but other orders are possible. 
         [0029]      FIG. 1A  is a top view and  FIGS. 1B ,  1 C,  1 D and  1 E are cross-sections through respective lines  1 B- 1 B,  1 C- 1 C,  1 D- 1 D and  1 E- 1 E of  FIG. 1A  illustrating fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 1A ,  1 B,  1 C,  1 D and  1 E, formed on semiconductor layer  100  is dielectric trench isolation  105 . In one example, semiconductor layer  100  is a single crystal silicon substrate or an epitaxial single crystal silicon layer on a single crystal silicon or semiconductor substrate. In one example, semiconductor layer is an upper semiconductor layer (which may be a single crystal silicon layer) of a semiconductor-on-insulator substrate comprising the upper semiconductor layer separated from a lower semiconductor layer (which may be a single crystal silicon layer) by a buried oxide (BOX) layer. Dielectric isolation  105  is formed, for example, by photolithographically defining and etching a trench in substrate  100 , then filling the trench with a dielectric material (e.g., SiO2) and performing a chemical-mechanical-polish to coplanarize a top surface  106  of dielectric isolation with a top surface  107  of substrate  100 . In one example, semiconductor layer  100  is doped P-type. 
         [0030]    A photolithographic process is one in which a photoresist layer is applied to a surface of a substrate, the photoresist layer exposed to actinic radiation through a patterned photomask (fabricated based on a design level) and the exposed photoresist layer developed to form a patterned photoresist layer. When the photoresist layer comprises positive photoresist, the developer dissolves the regions of the photoresist exposed to the actinic radiation and does not dissolve the regions where the patterned photomask blocked (or greatly attenuated the intensity of the radiation) from impinging on the photoresist layer. When the photoresist layer comprises negative photoresist, the developer does not dissolve the regions of the photoresist exposed to the actinic radiation and does dissolve the regions where the patterned photomask blocked (or greatly attenuated the intensity of the radiation) from impinging on the photoresist layer. After processing (e.g., an etch or an ion implantation), the patterned photoresist is removed. Processing results in a physical change to the substrate. 
         [0031]      FIG. 2A  is a top view and  FIGS. 2B ,  2 C,  2 D and  2 E are cross-sections through respective lines  2 B- 2 B,  2 C- 2 C,  2 D- 2 D and  2 E- 2 E of  FIG. 2A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 2A ,  2 C and  2 D an optional dielectric passivation layer  110  is formed in semiconductor layer  100  along selected surfaces of dielectric isolation. Dielectric passivation layer  110  is formed, in one example, by photolithographically defining and then ion implanting a selected region of substrate  100 . In one example, dielectric passivation layer  100  is doped P-type. In  FIGS. 2C and 2D  dielectric passivation layer  110  extends along the sidewalls and bottom surfaces of dielectric isolation  105 .  FIG. 2C  illustrates a region of semiconductor layer  100  where a photodiode will be subsequently formed and  FIG. 2D  illustrates a region of the semiconductor layer  100  where a floating diffusion node will be subsequently formed. 
         [0032]      FIG. 3A  is a top view and  FIGS. 3B ,  3 C,  3 D and  3 E are cross-sections through respective lines  3 B- 3 B,  3 C- 3 C,  3 D- 3 D and  3 E- 3 E of  FIG. 3A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 3A ,  3 B and  3 E, first and second wells  115 A and  115 B are formed in semiconductor layer  100 . First and second P-wells  115 A and  115 B are simultaneously formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, first and second wells  115 A and  115 B are doped P-type. In  FIGS. 3B and 3E , first and second wells  115 A and  115 B extends along the bottom surfaces of dielectric isolation  105 . Wells are not formed in  FIG. 3C  (where the photodiode will be subsequently formed) and  FIG. 3D  (where the floating diffusion node will be subsequently formed). 
         [0033]      FIG. 4A  is a top view and  FIGS. 4B ,  4 C,  4 D and  4 E are cross-sections through respective lines  4 B- 4 B,  4 C- 4 C,  4 D- 4 D and  4 E- 4 E of  FIG. 4A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 4A ,  4 B and  4 D, an optional electron shield  120  formed in semiconductor layer  100 . Electron shield  120  is formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, electron shield  120  is doped P-type. In  FIGS. 4B and 4E , electron shield  120  is a buried layer and does not extend to top surface  107  of semiconductor layer  100 , a region of semiconductor layer  100  above electron shield  120  intervening. Electron shield  120  extends along the bottom surfaces of dielectric isolation  105 . In  FIG. 4D , (where the floating diffusion node will be subsequently formed) electron shield  120  abuts (i.e., abuts) dielectric passivation layer  110  and extend under dielectric passivation  105 . If dielectric passivation layer  110  is not present, electron shield  120  abuts dielectric isolation  105 . 
         [0034]      FIG. 5A  is a top view and  FIGS. 5B ,  5 C,  5 D and  5 E are cross-sections through respective lines  5 B- 5 B,  5 C- 5 C,  5 D- 5 D and  5 E- 5 E of  FIG. 5A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 5A and 5B  gate electrodes  125 ,  130 ,  135 ,  140  and  145  are foamed. Bold lines illustrate perimeters of gate electrodes  125 ,  130 ,  135 ,  140  and  145 . In one example, gate electrodes  125 ,  130 ,  135 ,  140  and  145  may be simultaneously formed by depositing a gate dielectric layer, then a polysilicon layer on the gate dielectric later followed by photolithographically defining and then etching away unprotected (by the patterned photoresist layer) regions of the polysilicon layer. 
         [0035]      FIG. 5F  is a cross-section illustrating gate structures through line  5 B- 5 B of  FIG. 5A . In  FIG. 5F , gate dielectric layers  126 ,  131 ,  136 ,  141  and  146  intervene between respective gate electrodes  125 ,  130 ,  135 ,  140  and  145  and semiconductor layer  100 . There are five gate electrodes as the completed pixel sensor cell will be a five-transistor pixel sensor cell. 
         [0036]      FIG. 6A  is a top view and  FIGS. 6B ,  6 C,  6 D and  6 E are cross-sections through respective lines  6 B- 6 B,  6 C- 6 C,  6 D- 6 D and  6 E- 6 E of  FIG. 6A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 6A ,  6 B and  6 C, a photodiode body  150  is Rained in semiconductor layer  100 . Photodiode body  150  is formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, photodiode body  150  is doped N-type. When photodiode body is N-type and semiconductor layer  100  is P-type, photodiode body  150  forms the cathode and semiconductor layer  100  forms the anode of the photodiode. In  FIGS. 6B and 6C , photodiode body  150  does not extend as deep into semiconductor layer  100  as dielectric isolation and abuts dielectric passivation layer  110 . In  FIGS. 6B and 6C , photodiode body  150  is a buried structure and does not extend to top surface  107  of semiconductor layer  100 , a region of semiconductor layer  100  above photodiode body  150  intervening. In  FIG. 6C , photodiode body  150  abuts dielectric isolation passivation layer  110 . If dielectric isolation passivation layer  110  is not present, then photodiode body  150  abuts dielectric isolation  105  directly. 
         [0037]      FIG. 7A  is a top view and  FIGS. 7B ,  7 C,  7 D and  7 E are cross-sections through respective lines  7 B- 7 B,  7 C- 7 C,  7 D- 7 D and  7 E- 7 E of  FIG. 7A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 7A ,  7 B,  7 C and  7 D, an optional pinning layer  155  is formed in semiconductor layer  100 . Pinning layer  155  is formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, pinning layer  155  is doped P-type. In  FIGS. 7B and 7D , pinning layer  155  extends from top surface  107  of semiconductor layer  100  to photodiode body  150 . In  FIG. 7D , (where the floating diffusion node will be subsequently formed) pinning layer  155  extends from top surface  107  of semiconductor layer  100 , toward but does not abut electron shield  120  if electron shield  120  is present. If electron shield  120  is present, a region of semiconductor layer intervenes  100  between pinning layer  155  and electron shield  120 . In  FIG. 7D , pinning layer  155  abuts dielectric isolation  105  and overlaps opposite side of electron shield  120 . A region of top surface  107  of semiconductor layer  100  is exposed between regions of pinning layer  155 . In  FIG. 7D , if dielectric passivation layer  110  is present, pinning layer  155  abuts dielectric passivation layer  105 . 
         [0038]      FIG. 8A  is a top view and  FIGS. 8B ,  8 C,  8 D and  8 E are cross-sections through respective lines  8 B- 8 B,  8 C- 8 C,  8 D- 8 D and  8 E- 8 E of  FIG. 8A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 8A ,  8 B and  8 E, source/drains  160 A,  160 B,  160 C and  160 D are formed in semiconductor layer  100 . Source/drains  160 A,  160 B,  160 C and  160 D are simultaneously formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, source/drains  160 A,  160 B,  160 C and  160 D are doped N-type. In  FIG. 8C  (where the photodiode has been formed),  FIG. 8D , where the floating diffusion node will be formed) first source/drains have not been formed. Source/drains  160 A,  160 B,  160 C and  160 D extend from top surface  107  of semiconductor layer  100  a distance that lees than the distance dielectric isolation extend into semiconductor layer  100 . 
         [0039]      FIG. 9A  is a top view and  FIGS. 9B ,  9 C,  9 D and  9 E are cross-sections through respective lines  9 B- 9 B,  9 C- 9 C,  9 D- 9 D and  9 E- 9 E of  FIG. 9A  illustrating continuing fabrication of a pixel sensor cell according to embodiments of the present invention. In  FIGS. 9A ,  9 B and  9 D, a floating diffusion node  165  is formed in semiconductor layer  100 . Floating diffusion node  165  is formed, in one example, by photolithographically defining and then ion implanting selected regions of substrate  100 . In one example, floating diffusion node  165  is doped N-type. In  FIGS. 9B and 9D , floating diffusion node  165  extends from top surface  107  of semiconductor layer  100  into but not through electron shield  120  (if electron shield  120  is present).  FIG. 9D  illustrates the floating diffusion node (FD node) with all optional elements. It is a feature of the embodiments of the present invention that floating diffusion node  165  does not abut dielectric isolation  105 . It is a feature of the embodiments of the present invention that floating diffusion node  165  does not abut pinning layer  155  (if pinning layer  155  is present). It is a feature of the embodiments of the present invention that floating diffusion node  165  does not extend to dielectric isolation passivation layer  110  (if dielectric isolation passivation layer  110  is present). In  FIG. 9D , a region of semiconductor layer  100  intervenes between floating diffusion node and dielectric isolation  105  and/or dielectric isolation passivation layer  110  and/or pinning layer  155 . 
         [0040]      FIGS. 10A ,  10 B,  10 C and  10 D illustrate alternative structures for the storage node of a pixel sensor cell according to embodiments of the present invention.  FIGS. 10A ,  10 B,  10 C and  10 D illustrate four possible combinations of the structural elements defining charge storage nodes according to the embodiments of the present invention. 
         [0041]    In  FIG. 10A , a first charge storage node  170  includes floating diffusion node  165  and semiconductor layer  100 . Floating diffusion node  165  does not abut dielectric isolation  105 , semiconductor layer  100  intervening between floating diffusion node  165  and dielectric isolation  105 . This is the minimum number of elements for a floating diffusion node according to embodiments of the present invention. 
         [0042]    In  FIG. 10B , a second charge storage node  175  includes floating diffusion node  165 , semiconductor layer  100  and electron shield  120 . Floating diffusion node  165  does not extend to dielectric isolation  105 , semiconductor layer  100  intervening between floating diffusion node  165  and dielectric isolation  105 . Electron shield  120  abuts dielectric isolation  105 . Electron shield  120  does not abut top surface  107  of semiconductor layer  100 , regions of semiconductor layer  100  intervening between electron shield  120  and top surface  107  of semiconductor layer  100 . Floating diffusion node  165  extends into semiconductor layer  100  but not to electron shield  120 , a region of semiconductor layer  100  intervening between floating diffusion node  165  and electron shield  120 . Alternatively, floating diffusion node  165  extends to electron shield  120  or extends part way into electron shield  120 . 
         [0043]    In  FIG. 10C , a third charge storage node  180  includes floating diffusion node  165 , semiconductor layer  100 , electron shield  120 , and dielectric isolation passivation layer  110 . Dielectric isolation passivation layer  110  abuts sidewalls and bottom surface of dielectric isolation  105 . Floating diffusion node  165  does not abut dielectric isolation passivation layer  110 , a region of semiconductor layer  100  intervening between floating diffusion node  165  and dielectric isolation passivation layer  110 . Electron shield  120  abuts dielectric isolation passivation layer  110 . Electron shield  120  does not abut top surface  107  of semiconductor layer  100 , regions of semiconductor layer  100  intervening between electron shield  120  and top surface  107  of semiconductor layer  100 . Floating diffusion node  165  extends into semiconductor layer  100  but not to electron shield  120 , a region of semiconductor layer  100  intervening between floating diffusion node  165  and electron shield  120 . Alternatively, floating diffusion node  165  extends to electron shield  120  or extends part way into electron shield  120 . 
         [0044]    In  FIG. 10D , a fourth charge storage node  185  includes floating diffusion node  165 , semiconductor layer  100 , electron shield  120 , dielectric isolation passivation layer  110  and pinning layer  155 . Dielectric isolation passivation layer  110  abuts sidewalls and a bottom surface of dielectric isolation  105 . Floating diffusion node  165  does not abut dielectric isolation passivation layer  110 , semiconductor layer  100  intervening between floating diffusion node  165  and dielectric isolation passivation layer  110 . Electron shield  120  abuts dielectric isolation passivation layer  110 . Electron shield  120  does not abut top surface  107  of semiconductor layer  100 , regions of semiconductor layer  100  intervening between electron shield  120  and top surface  107  of semiconductor layer  100 . Floating diffusion node  165  extends into semiconductor layer  100  from top surface  107  but not to electron shield  120 , a region of semiconductor layer  100  intervening between floating diffusion node  165  and electron shield  120 . Alternatively, floating diffusion node  165  extends to electron shield  120  or extends part way into electron shield  120 . Pinning layer  155  extends from top surface  107  into semiconductor layer  100  and along top surface  107  toward floating diffusion node  165  but does not abut floating diffusion node  165 , a region of semiconductor layer  100  intervening. Alternatively, pinning layer  155  extends to abut floating diffusion node  165 . Pinning layer  155  abuts dielectric isolation  105 , dielectric passivation layer  110  and regions of semiconductor layer  100  but not electron shield  120 . A region of semiconductor layer  100  intervenes between pinning layer  155  and electron shield  120 . 
         [0045]    Other possible combinations for charge storage nodes according to embodiments of the present invention include floating diffusion node  165  with a region of semiconductor layer  100  intervening between floating diffusion node  165  and dielectric isolation  105  in combination with (i) only dielectric isolation passivation layer  110 , (ii) only dielectric isolation passivation layer  110  and pinning layer  155 , (iii) only pinning layer  155 , and (iv) only pinning layer  155  and electron shield  120 . 
         [0046]      FIG. 11  is a top view of illustrating interconnections of the structural elements in a pixel sensor cell circuit.  FIG. 11  is similar to  FIG. 9 . In  FIG. 11 , source/drain  160 A is connected to Vdd, gate  125  is connected to a global shutter signal (GS), gate  130  is connected to a transfer gate signal (TG), floating diffusion node  165  is connected to gate  140 , gate  135  is connected to a reset gate signal (RG), source/drain  160 B is connected to Vdd, gate  145  is connected to a row select signal (RS), and source/drain  160 D is connected to Data Out. 
         [0047]      FIG. 12  is a circuit diagram of a pixel sensor cell circuit according to embodiments of the present invention. In  FIG. 12 , circuit  200  describes device of  FIG. 11 . Circuit  200  includes NFETs T 1  (reset transistor), T 2  (source follower), T 3  (row select transistor), T 4  (global shutter transistor) and T 5  (transfer gate), and photodiode D 1  (photon detector). The gate of NFET T 1  is connected to RG, the gate of NFET T 2  is connected to the floating diffusion node (FD Node), the gate of NFET T 3  is connected to RS, the gate of NFET T 4  is connected to GS and the gate of NFET T 5  is connected to TG. The drains of NFETS T 1 , T 2  and T 4  are connected to Vdd. The source of NFET T 1  is connected to the FD Node, the drain of NFET T 2  to the source of NFET T 3  and the source of NFET T 3  to Data Out. The source of NFET T 4  is connected to the source of NFET T 5  and the drain of NFET T 5  is connected to FD Node. The cathode of diode D 1  is connected to the sources of NFETS T 4  and T 5  and the anode of diode D 1  is connected to GND. Diode D 1  is the pinned photo diode of  FIG. 11 . 
         [0048]    Circuit  200  utilizes NFETs. However, NFETs T 1 , T 2 , T 3 , T 4  and T 5  can be replaced by PFETs. In a circuit utilizing PFETs, the doping type of elements of  FIG. 11  are changed. Semiconductor layer  100 , dielectric passivation layer  110 , wells  115 A and  115 B, electron shield  120  and pinning layer  155  are doped N-type and photodiode body  150 , source/drains  160 A,  160 B,  160 C and  160 D and floating diffusion node  165  are doped P-type. Also Vdd and GND are reversed, and the anode of diode D 1  is connected to the now drains of now PFETS T 4  and T 5 . 
         [0049]      FIG. 13  is a diagram illustrating an array of global shutter pixel sensor cells according to embodiments of the present invention. In  FIG. 13 , an image sensor  300  includes an array  305  of pixel sensor cells P (rows are horizontal and columns vertical), pixel sensor cell drivers  3190  and a column sampler  315 . Each pixel sensor cell P is a circuit  200  of  FIG. 11 . The GS, TG, RG, and RS signals of  FIG. 12  are connected to pixel sensor cells P from pixel sensor cell row drivers  310 . The Data Out signals of  FIG. 12  from pixel sensor cells P are connected to column sampler  315 . 
         [0050]    In operation a global exposure is performed by (1) pulsing GS on/off (on=high for an NFET, off=low for an NFET) to charge the photodiode (exposure starts at off), (2) resetting FD Node by pulsing RG on/off, and (3) puling TG on/off to move the charge to FD Node. Readout is performed by (1) turning on RS to read all columns in a selected row and (2) pulsing RG on/off after reading the selected row. Readout steps (1) and (2) are repeated for each row sequentially, starting with the first row and ending with the last row. 
         [0051]      FIG. 14  shows a block diagram of an exemplary design flow  400  used for example, in semiconductor IC logic design, simulation, test, layout, and manufacture. Design flow  400  includes processes and mechanisms for processing design structures or devices to generate logically or otherwise functionally equivalent representations of the design structures and/or devices described above and shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . The design structures processed and/or generated by design flow  400  may be encoded on machine-readable transmission or storage media to include data and/or instructions that when performed or otherwise processed on a data processing system generate a logically, structurally, mechanically, or otherwise functionally equivalent representation of hardware components, circuits, devices, or systems. Design flow  400  may vary depending on the type of representation being designed. For example, a design flow  400  for building an application specific IC (ASIC) may differ from a design flow  400  for designing a standard component or from a design flow  400  for instantiating the design into a programmable array, for example a programmable gate array (PGA) or a field programmable gate array (FPGA). 
         [0052]      FIG. 14  illustrates multiple such design structures including an input design structure  420  that is preferably processed by a design process  410 . In one embodiment, the design structure  420  comprises input design data used in a design process and comprising information describing an embodiment of the invention with respect to a CMOS imaging cell as shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . The design data in the form of schematics or HDL, a hardware description language (e.g., Verilog, VHDL, C, etc.) may be embodied on one or more machine-readable media. For example, design structure  420  may be a text file, numerical data or a graphical representation of an embodiment of the invention as shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . Design structure  420  may be a logical simulation design structure generated and processed by design process  410  to produce a logically equivalent functional representation of a hardware device. Design structure  420  may also or alternatively comprise data and/or program instructions that when processed by design process  410 , generate a functional representation of the physical structure of a hardware device. Whether representing functional and/or structural design features, design structure  420  may be generated using electronic computer-aided design (ECAD) such as implemented by a core developer/designer. When encoded on a machine-readable data transmission, gate array, or storage medium, design structure  420  may be accessed and processed by one or more hardware and/or software modules within design process  410  to simulate or otherwise functionally represent an electronic component, circuit, electronic or logic module, apparatus, device, or system such as those shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . As such, design structure  420  may comprise files or other data structures including human and/or machine-readable source code, compiled structures, and computer-executable code structures that when processed by a design or simulation data processing system, functionally simulate or otherwise represent circuits or other levels of hardware logic design. Such data structures may include hardware description language (HDL) design entities or other data structures conforming to and/or compatible with lower-level HDL design languages such as Verilog and VHDL, and/or higher-level design languages such as C or C++. 
         [0053]    Design process  410  preferably employs and incorporates hardware and/or software modules for synthesizing, translating, or otherwise processing a design/simulation functional equivalent of the components, circuits, devices, or logic structures shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13  to generate a netlist  480  which may contain design structures such as design structure  420 . Netlist  480  may comprise, for example, compiled or otherwise processed data structures representing a list of wires, discrete components, logic gates, control circuits, I/O devices, models, etc. that describes the connections to other elements and circuits in an integrated circuit design. Netlist  480  may be synthesized using an iterative process in which netlist  480  is re-synthesized one or more times depending on design specifications and parameters for the device. As with other design structure types described herein, netlist  480  may be recorded on a machine-readable data storage medium or programmed into a programmable gate array. The medium may be a non-volatile storage medium such as a magnetic or optical disk drive, a programmable gate array, a compact flash, or other flash memory. Additionally, or in the alternative, the medium may be a system or cache memory, buffer space, or electrically or optically conductive devices and materials on which data packets may be transmitted and intermediately stored via the Internet, or other networking suitable means. 
         [0054]    Design process  410  may include hardware and software modules for processing a variety of input data structure types including netlist  480 . Such data structure types may reside, for example, within library elements  430  and include a set of commonly used elements, circuits, and devices, including models, layouts, and symbolic representations, for a given manufacturing technology (e.g., different technology nodes, 32 nm, 45 nm, 90 nm, etc.). The data structure types may further include design specifications  440 , characterization data  450 , verification data  460 , design rules  470 , and test data files  485  which may include input test patterns, output test results, and other testing information. Design process  410  may further include, for example, standard mechanical design processes such as stress analysis, thermal analysis, mechanical event simulation, process simulation for operations such as casting, molding, and die press forming, etc. One of ordinary skill in the art of mechanical design can appreciate the extent of possible mechanical design tools and applications used in design process  410  without deviating from the scope and spirit of the invention. Design process  410  may also include modules for performing standard circuit design processes such as timing analysis, verification, design rule checking, place and route operations, etc. 
         [0055]    Design process  410  employs and incorporates logic and physical design tools such as HDL compilers and simulation model build tools to process design structure  420  together with some or all of the depicted supporting data structures along with any additional mechanical design or data (if applicable), to generate a output design structure  490  comprising output design data embodied on a storage medium in a data format used for the exchange of layout data of integrated circuits and/or symbolic data format (e.g. information stored in a GDSII (GDS 2 ), GL 1 , OASIS, map files, or any other suitable format for storing such design structures). In one embodiment, the second design data resides on a storage medium or programmable gate array in a data format used for the exchange of data of mechanical devices and structures (e.g. information stored in an IGES, DXF, Parasolid XT, JT, DRG, or any other suitable format for storing or rendering such mechanical design structures). Similar to design structure  420 , design structure  490  preferably comprises one or more files, data structures, or other computer-encoded data or instructions that reside on transmission or data storage media and that when processed by an ECAD system generate a logically or otherwise functionally equivalent form of one or more of the embodiments of the invention shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . In one embodiment, design structure  490  may comprise a compiled, executable HDL simulation model that functionally simulates the devices shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . Design structure  490  may also employ a data format used for the exchange of layout data of integrated circuits and/or symbolic data format (e.g. information stored in a GDSII (GDS 2 ), GL 1 , OASIS, map files, or any other suitable format for storing such design data structures). Design structure  490  may comprise information such as, for example, symbolic data, map files, test data files, design content files, manufacturing data, layout parameters, wires, levels of metal, vias, shapes, data for routing through the manufacturing line, and any other data required by a manufacturer or other designer/developer to produce a device or structure as described above and shown in  FIGS. 9A ,  9 B,  9 C,  9 D,  9 E,  10 A,  10 B,  10 C,  10 D,  11 ,  12  and  13 . Design structure  490  may then proceed to a stage  495  where, for example, design structure  490  proceeds to tape-out, is released to manufacturing, is released to a mask house, is sent to another design house, is sent back to the customer, etc. 
         [0056]    The description of the embodiments of the present invention is given above for the understanding of the present invention. It will be understood that the invention is not limited to the particular embodiments described herein, but is capable of various modifications, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, it is intended that the following claims cover all such modifications and changes as fall within the true spirit and scope of the invention.