Abstract:
An image sensor includes an array of pixels comprising a plurality of kernels that repeat periodically and each kernel includes n photosensitive regions for collecting charge in response to light, n is equal to or greater than 2; and a transparent layer spanning the photosensitive regions having n optical paths, at least two of which are different, wherein each optical path directs light of a predetermined spectral band into specific photosensitive regions.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to image sensors having an array of pixels subdivided into kernel of pixels, and more particularly to such image sensors having different optical paths for pixels in the kernel for improving color separation and increasing quantum efficiency. 
       BACKGROUND OF THE INVENTION 
       [0002]    In general, as pixels made using CMOS processes for image sensors scale to smaller dimensions, several performance properties of the imagers using these pixels degrade. One performance property in particular, quantum efficiency (QE), degrades quickly. The loss in performance is confounded with the addition of a color-filter-array (CFA) on top of the pixel array. The purpose of the CFA is to allow for color separation of the incoming light for providing the ability to reconstruct color images. However, for a given wavelength, most of the filters are absorbing. Therefore, any given wavelength effectively sees a series of small apertures above the pixel array. As the pixel pitch shrinks, the size of this effective aperture in the CFA pattern becomes comparable to the wavelength of visible light. Light diffraction diverts light onto adjacent pixels and reduces the effective QE of the targeted color pixel. Consider  FIG. 1   a  for example. For incoming red light, the blue and green CFA of the blue  103  and green pixels  101 ,  104  are effectively blocking. For a Bayer pattern  105 ,  FIG. 1   b  illustrates this creates a small aperture  112  above the red pixel  102  for red light. Especially below 2 μm pixel pitches, diffraction spreads the incoming red light into the adjacent blue and green pixels since the CFA is positioned a finite distance above the active layer of the image sensor where the photons are converted to charge carriers. Diffraction corrupts the effectiveness of the CFA to separate colors, increasing color crosstalk. It also effectively reduces the QE of the red pixel. 
         [0003]      FIG. 2  shows prior art for the cross-section of four pmos pixels through the red and green CFA of a back illuminated image sensor. This will also be used as a reference point for describing the present invention in the Detailed Description of the Invention. 
         [0004]    Still referring to  FIG. 2 , there is shown a photodiode  200  where photo-generated charge carriers are collected. For readout the charge carriers are electrically transferred to a floating diffusion  205  by adjusting the voltage on a transfer gate  201 . The floating diffusion signal feeds the input of the source-follow transistor  203 . The low-impedance output of the source-follower  203  drives the output line  204 . After readout the signal in the floating diffusion  205  is emptied into the reset drain  213  by controlling the voltage on the reset gate  202 . Sidewall isolation  210  between the photodiodes directs photo-generated charge carriers into the nearest photodiode  200  reducing color crosstalk within the device layer. To reduce dark current there is a thin pinning layer  212  at the surface between the silicon and dielectric near the photodiode  200 . To also reduce dark current, there is a thin n-doping layer  211  along the sidewall isolation  210 . Incoming light  250  first passes through the color filter array layer  230 , then an antireflection coating layer  222 , then a spacer layer that is typically silicon dioxide  221  before reaching the active device layer  220 . However, the optical stack  221 ,  222 , and  230  can consist of more or fewer layers depending on application, and often includes a micro-lens array for the top layer.  FIG. 3  provides a single pixel schematic for this non-shared pinned photodiode structure of  FIG. 2 . 
         [0005]      FIG. 4  shows simulation results for QE for a prior art 1.1 μm pixel array with a Bayer pattern. The peak QE for the blue response curve  503  associated with the blue pixel  103  is 40%. The peak QE for the green response curves  501 ,  504  associated with the green pixels  101 ,  104  is 35%. The peak QE for the red response curve  502  associated with the red pixel  102  is 23%. For these simulations the thickness of the dielectric spacer  221  layer is 0.5 μm. Increasing the dielectric spacer thickness  221  degrades performance resulting in lower peak QE and increased color crosstalk. 
         [0006]    Although the presently known and utilized image sensor is satisfactory, there is a need to address the above-described drawback. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to improve color crosstalk between adjacent pixels and increase QE by replacing the CFA with a binary optical path grating. Effective QE can be greater than 100%. 
         [0008]    This object is achieved by adjusting optical path differences for each pixel in a color kernel such that for a specific wavelength the light intensity falling onto the image sensor interferes constructively near the surface of one pixel and destructively for the other pixels within the color kernel. For another specific wavelength, light interferes constructively near the surface of a second pixel and destructively for the other pixels within the color kernel. 
         [0009]    These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention. 
       Advantageous Effect of the Invention 
       [0010]    The present invention has the advantage of improving color crosstalk between adjacent pixels and increasing QE. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed that the invention will be better understood from the following description when taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  shows prior art of a Bayer color filter array pattern; 
           [0013]      FIG. 2  shows prior art of a cross-section of four pixels of a backside illuminated image sensor cut through the red and green portion of the Bayer CFA pattern. Pixel circuitry is for a pmos image sensor; 
           [0014]      FIG. 3  shows prior art of a pmos non-shared pixel schematic; 
           [0015]      FIG. 4  is a plot of wavelength versus QE of a Bayer color filter array; 
           [0016]      FIG. 5  illustrates the first embodiment of this invention. The plan view shows a pixel array with an optical path grating. W, X, Y, and Z represent different thickness of the transparent layer above each pixel within the color kernel; 
           [0017]      FIG. 6  shows a plan view of the color kernel with the optical path grating (W, X, Y, and Z), and more detail of the pixel device structure; 
           [0018]      FIG. 7  shows a cross-section of four pixels of a backside illuminated image sensor cut through the red and green portion of the color kernel of the optical path grating (Y and Z); 
           [0019]      FIG. 8  is a simulated plot of QE versus wavelength for each pixel in the color kernel of  FIG. 4  for 1.1 μm pixel; 
           [0020]      FIG. 9  illustrates how constructive and destructive interference is used to improve color crosstalk and result in QE values for a given pixel at a given wavelength of greater than 100%. Shown are intensity plots of light just above the silicon surface for four different wavelengths for the color kernel of  FIG. 4 . The plots are plan view and the light normal incident. For the four plots the wavelengths are 420 nm, 470 nm, 590 nm, and 650 nm; 
           [0021]      FIG. 10  illustrates the beginning of one method to fabricate the optical path grating. Shown are two cross-sections, each of four pixels. One cross-section is cut through pixels  303  and  304  of  FIG.7 . The other cross-section is cut through pixels  301  and  303  of  FIG. 7 ; 
           [0022]      FIG. 11  is a 3D view of an optical path grating with microlenses; 
           [0023]      FIG. 12  illustrates a method of placing microlenses on the transparent layer; 
           [0024]      FIG. 13  illustrates a method of transferring the microlens pattern to the transparent layer; 
           [0025]      FIG. 14  illustrates a method for performing a first etch; 
           [0026]      FIG. 15  illustrates a method of fabricating the optical path grating after the second resist is patterned; 
           [0027]      FIG. 16  illustrates the final optical path grating after the second etch step; 
           [0028]      FIG. 17  is a 3D view of an optical path grating using two materials with different index of refraction and a microlens array; 
           [0029]      FIG. 18  is a 3D view of an optical path grating using two materials with different index of refraction and a microlens array where a single microlens is placed over four pixels; and 
           [0030]      FIG. 19  is an imaging device having the image sensor array of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    An optical path as defined herein is: 
         [0000]      optical path= n×d,    (Eq. 1) 
         [0000]    where n is the index of refraction and d is the thickness of the material through which the light is passing. 
         [0032]    Turning now to  FIG. 7 , there is shown a portion of an image sensor array  401  of an image sensor of the first embodiment of the present invention. It is noted that, although the cross section only shows four pixels for simplicity, the image sensor array  401  typically includes thousands or millions of pixels. It is further noted that the image sensor array  401  is typically a part of an active pixel sensor as will be discussed in  FIG. 19 . Referring back to  FIG. 7 , the image sensor array  401  includes a plurality of pixels  301  and  302  disposed in an active layer  420 . The pixels  301  and  302  are preferably grouped together in a 2×2 array, hereinafter a color kernel, that repeats over the array as will be described in detail hereinbelow. Although a 2×2 array is preferred, other color kernel sizes may also be used. Each pixel  301  and  302  includes a charge collection region, preferably a pinned photodiode  400 , disposed slightly away from the surface of the active layer that receives the incident light  250 . The configuration of polysilicon gates  401 ,  402 ,  403 , and metal wires  404  opposite the illuminated side of the active layer  420  is called backside illumination. The pinned photodiode  400  collects charge in response to the incident light. The pinned photodiode  400  includes a pinning layer  412  beneath a doped region of opposite conductivity type disposed thereon. Although a pinned photodiode  400  and backside illumination are used for the preferred embodiment, a photodiode may also be used as the charge collection region and front illumination be used as charge collection region, both of which are well known and will not be discussed herein. 
         [0033]    When activated, a transfer gate  401  passes charge from the pinned photodiode  400  to a charge-to-voltage conversion region  405 , preferably a floating diffusion, which converts charge to a voltage signal. An amplifier or buffer  403 , preferably a source follower amplifier, passes the voltage onto an output line for further processing. A reset gate  402  is activated for resetting the floating diffusion  405  to a predetermined signal level. 
         [0034]    A transparent grating layer  300  with a varying thickness is disposed spanning the pixels  301  and  302  (and the pixels not shown in the drawing) for directing the incident light  250  into the active layer  420  as will be described in detail hereinbelow. The transparent layer may be made of either silicon dioxide, silicon nitride or a transparent organic material. 
         [0035]    Referring to the plan view of the image sensor array  401  (commonly referred to as pixel array) in  FIG. 5 , there is shown the 2×2 color kernel  310  having the transparent layer overlaid thereon. The thickness of the transparent layer  300  (see  FIG. 7 ) over each pixel  301 ,  302 ,  303 , and  304  (see  FIGS. 5 and 6  for all four pixels) in the color kernel  310  is different (Y, Z, W, and X). This creates four optical paths. Although the present invention in its preferred embodiment uses thickness to create the different optical paths, materials having different index of refractions may be used to create the different optical paths. In the example, the thickness of the silicon dioxide transparent layer  300  for Y, Z, W, and X are 2.5 μm, 3.0 μm, 1.5 μm, and 2.0 μm, respectively. Consequently, there are four optical paths created. Blue light constructively interferes just above pixel  303  and is effectively directed into this pixel. Likewise, green-blue light is directed into pixel  301 , green-red light is directed into pixel  304 , and red light is directed into pixel  302 . It is noted that the repeating pattern of the transparent layer  300  is repeated for each kernel of pixels. 
         [0036]      FIG. 6  shows a more detailed plan view of the four pixels  301 ,  302 ,  303 , and  304  within a color kernel  310  and the device components buried beneath the imager surface. These components include the photodiode  400 , transfer gate  401 , reset gate  402 , source-follower  403 , source-follower output  404 , floating-diffusion  405 , sidewall isolation  410 , reset drain  413 , and contacts  350  from the metal lines (not shown) to the gates  401 ,  402 ,  403 , and source/drain implant regions  405 ,  413 ,  404 . These device components are also illustrated in the cross-section of  FIG. 7 . The optical stack is simply a transparent layer  300 . Through this cross-section in  FIG. 7  there are only two heights Y and Z. 
         [0037]      FIG. 8  shows simulation results for QE for a 1.1 μm pixel array using the first embodiment of the present invention as describe by  FIGS. 5-7 . The peak QE for the blue response curve  603  associated with the blue pixel  303  is 120%. The peak QE for the green/blue response curve  601  associated with the green/blue pixel  301  is 116%. The peak QE for the green/red response curve  604  associated with the green/red pixel  304  is 105%. The peak QE for the red response curve  604  associated with the red pixel  302  is 86%. The QE for a given wavelength can be greater than 100% for a given pixel because the optical paths are adjusted in such a way to take advantage of constructive and destructive interference. 
         [0038]      FIG. 9  illustrates how constructive and destructive interference leads to QE curves with peaks greater than 100%. Shown are four plan view plots of the light intensity just above the silicon active layer  420  on the illuminated side for different wavelengths. For blue light (420 nm) most of the light intensity  703  is above pixel  303 . Likewise, for green/blue light (470 nm) most of the light intensity  701  is above pixel  301 . Likewise again, for green/red light (590 nm) most of the light intensity  704  is above pixel  304 . Finally, for red light (650 nm) most of the light intensity  702  is above pixel  302 . 
         [0039]    To help visualize the optical path grating,  FIG. 10  shows a 4×4 pixel cutaway of  FIGS. 5-7 . Clearly visible is the optical stack  300  on top of the active layer  420 . The four pixels ( 301 ,  302 ,  303 , and  304 ) within a single color kernel are identified, along with the Δ height differences  1050  between the four transparent pillars. 
         [0040]    As shown in  FIG. 8 , the peak QE for the blue, green/blue, green/red, and red response curves ( 603 ,  601 ,  604 , and  602 ) are at wavelengths of 440 nm, 485 nm, 585 nm, and 645 nm respectively. This is for normal incidence. Unfortunately, tilting the angle of the incoming light away from normal incidence increases the optical path differences for the different pixels. This changes the details of the constructive and destructive interference and results in slight differences for the wavelength at which the QE is a peak for the different response curves. The differences in peak position increase further with increasing tilt angle. When this imager is placed into a camera system, the chief ray at the center of the pixel array is normal incidence, however, the chief ray angle for pixels near the edge of the array can exceed 30 degrees. Since the response curves depend on tilt angle, this leads to color shifts (hue shifts) across the image that are not always easy to correct. 
         [0041]    There are several ways to minimize hue shifts associated with changes in tilt angle of the incident light. One method is to refine the binary optical path grating with more height differences, and optimize this refined system. This involves more etches to provide more possible heights in the transparent layer. This refinement also involves breaking the pixel into sub-pixel regions. For example, consider the case where there are eight possible heights and each pixel is broken up into sixteen-square subregions. With four pixels, this gives 512 degrees of freedom for the optical stack. Using numerical simulation, all cases can be modeled for a range of wavelengths, and the system optimized in such a way that there is good color separation for the four pixels, and the hue shifts are minimal. However, forcing the system to minimize the hue shift is the same as forcing the optical path above each pixel to be the same. The solution to this problem is something that looks like a microlens with a focal point just above the silicon surface. So instead of creating a microlens-like structure using binary optical techniques, it is easier to simply create a series of continuous microlenses. 
         [0042]      FIG. 11  shows an optical path grating similar to the optical path grating of  FIG. 11  where the optical path difference between pixels is Δ  1250  but there is also a microlens above each pixel  1210 . This new structure will have better hue shift performance with changing tilt angle. 
         [0043]      FIGS. 12-16  illustrate a method for fabricating an optical path grating with curved surfaces in the shape of a microlens as in  FIG. 11 . It is noted that  FIGS. 12-16  describe Δ changes referenced by numerals not directly shown in  FIGS. 12-16  but are shown in  FIGS. 10 ,  11 ,  17  and/or  18 . The following described procedure requires fewer lithography steps than that of a Bayer CFA.  FIG. 12  shows two cross-sections of four pixels each, one through pixels  303  and  304  of the color kernel, the other through pixels  301  and  302  of the color kernel. Fabrication of the devices within the active layer  420  is complete, and the back illuminated imager thinned. Silicon dioxide or some other transparent layer  300  of thickness greater than D has been grown or deposited on the illuminated side of the active layer  420 . One top of the layer  300  is a patterned microlens array  1025 . There are numbers of methods for fabricating this microlens array including microgap patterning and reflow and gray scale photolithography. 
         [0044]      FIG. 13  shows the silicon dioxide layer  300  after a 1:1 directional etch that transfers the microlens surface into the transparent layer material. The thickness of layer  300  at the edge of the microlens is D. A resist layer  1020  is applied to a portion of the image array and patterned so that pixels  301  and  302  are covered with resist  1020 , and the pattern leaves exposed the transparent layer  300  within pixels  303  and  304 . The exposed transparent layer  300  is etched a thickness of 2Δ  1030 . 
         [0045]      FIG. 14  shows both cross-sections after a thickness of 2Δ  1030  of the transparent layer is etched and removed as discussed in the previous paragraph. The resist  1020  is then removed. 
         [0046]      FIG. 15  illustrates the next step in the process after the patterned resist  1020  for the first etch is removed as discussed in the previous paragraph. A second resist layer  1040  is applied to the image array and patterned. This pattern exposes the transparent layer  300  within pixels  301 ,  303  and covers the transparent layer  300  within pixels  302  and  304 . The exposed transparent layer  300  is etched and removed. 
         [0047]      FIG. 16  shows both cross-sections after a thickness of Δ  1050  of the transparent layer is etched and removed as discussed in the preceding paragraph. The resist  1040  (of  FIG. 15 ) is removed. The final thicknesses of the transparent layer  300  are D, D-Δ, D-2Δ, and D-3Δ for pixels  302 ,  301 ,  304 , and  303  respectively. 
         [0048]    The optical path grating in  FIG. 11  will have superior hue shift performance to the optical path grating in  FIG. 10 , however, for steeper and steeper angles, the highest pillar of transparent material (pixel  302 ) casts shadows on the shorter pillars (pixels  301 ,  304 , and  303 ) since the material is not 100% transparent. This shadowing leads to hue shifts, the root cause of which is not variations in optical path length, but instead a reduction in light intensity over the shorter pixels. 
         [0049]      FIG. 17  illustrates a way to minimize the hue shifts due to shadowing and optical path length differences. A second transparent material  1320  is inserted between the original optical path grating  300  and the microlens  1430 . To maintain an optical path difference between the different pixels within the color kernel, the index of refraction of the two materials ( 300  and  1320 ) must be different. The microlens array  1430  is placed on top of the planer surface of layer  1320 . The planar microlens array eliminates problems due to shadowing. 
         [0050]    Finally,  FIG. 18  shows a structure similar to  FIG. 17  except the size of the microlens  1530  equals the size of the color kernel and not the individual pixel ( 301 ,  302 ,  303 , and  304 ). This has the advantage of focusing the light bundle from each microlens  1530  through each optical grating block ( 301 ,  302 ,  303 , and  304 ) reducing hue shift even more. 
         [0051]      FIG. 19  is a block diagram of an imaging system that can be used with the image sensor array  401  of present the invention. Imaging system  1200  includes digital camera phone  1202  and computing device  1204 . Digital camera phone  1202  is an example of an image capture device that can use an image sensor incorporating the present invention. Other types of image capture devices can also be used with the present invention, such as, for example, digital still cameras and digital video camcorders. 
         [0052]    Digital camera phone  1202  is a portable, handheld, battery-operated device in an embodiment in accordance with the invention. Digital camera phone  1202  produces digital images that are stored in memory  1206 , which can be, for example, an internal Flash EPROM memory or a removable memory card. Other types of digital image storage media, such as magnetic hard drives, magnetic tape, or optical disks, can alternatively be used to implement memory  1206 . 
         [0053]    Digital camera phone  1202  uses lens  1208  to focus light from a scene (not shown) onto image sensor array  401  of active pixel sensor  1212 . Image sensor array  401  provides color image information using the Bayer color filter pattern in an embodiment in accordance with the invention. Image sensor array  401  is controlled by timing generator  1214 , which also controls flash  1216  in order to illuminate the scene when the ambient illumination is low. 
         [0054]    The analog output signals output from the image sensor array  410  are amplified and converted to digital data by analog-to-digital (A/D) converter circuit  1218 . The digital data are stored in buffer memory  1220  and subsequently processed by digital processor  1222 . Digital processor  1222  is controlled by the firmware stored in firmware memory  1224 , which can be flash EPROM memory. Digital processor  1222  includes real-time clock  1226 , which keeps the date and time even when digital camera phone  1202  and digital processor  1222  are in a low power state. The processed digital image files are stored in memory  1206 . Memory  1206  can also store other types of data, such as, for example, music files (e.g. MP3 files), ring tones, phone numbers, calendars, and to-do lists. 
         [0055]    In one embodiment in accordance with the invention, digital camera phone  1202  captures still images. Digital processor  1222  performs color interpolation followed by color and tone correction, in order to produce rendered sRGB image data. The rendered sRGB image data are then compressed and stored as an image file in memory  1206 . By way of example only, the image data can be compressed pursuant to the JPEG format, which uses the known “Exif” image format. This format includes an Exif application segment that stores particular image metadata using various TIFF tags. Separate TIFF tags can be used, for example, to store the date and time the picture was captured, the lens f/number and other camera settings, and to store image captions. 
         [0056]    Digital processor  1222  produces different image sizes that are selected by the user in an embodiment in accordance with the invention. One such size is the low-resolution “thumbnail” size image. Generating thumbnail-size images is described in commonly assigned U.S. Pat. No. 5,164,831, entitled “Electronic Still Camera Providing Multi-Format Storage Of Full And Reduced Resolution Images” to Kuchta, et al. The thumbnail image is stored in RAM memory  1228  and supplied to display  1230 , which can be, for example, an active matrix LCD or organic light emitting diode (OLED). Generating thumbnail size images allows the captured images to be reviewed quickly on color display  1230 . 
         [0057]    In another embodiment in accordance with the invention, digital camera phone  1202  also produces and stores video clips. A video clip is produced by summing multiple pixels of image sensor array  410  together (e.g. summing pixels of the same color within each 4 column×4 row area of the image sensor array  410 ) to create a lower resolution video image frame. The video image frames are read from image sensor array  410  at regular intervals, for example, using a 15 frame per second readout rate. 
         [0058]    Audio codec  1232  is connected to digital processor  1222  and receives an audio signal from microphone (Mic)  1234 . Audio codec  1232  also provides an audio signal to speaker  1236 . These components are used both for telephone conversations and to record and playback an audio track, along with a video sequence or still image. 
         [0059]    Speaker  1236  is also used to inform the user of an incoming phone call in an embodiment in accordance with the invention. This can be done using a standard ring tone stored in firmware memory  1224 , or by using a custom ring-tone downloaded from mobile phone network  1238  and stored in memory  1206 . In addition, a vibration device (not shown) can be used to provide a silent (e.g. non-audible) notification of an incoming phone call. 
         [0060]    Digital processor  1222  is connected to wireless modem  1240 , which enables digital camera phone  1202  to transmit and receive information via radio frequency (RF) channel  1242 . Wireless modem  1240  communicates with mobile phone network  1238  using another RF link (not shown), such as a 3GSM network. Mobile phone network  1238  communicates with photo service provider  1244 , which stores digital images uploaded from digital camera phone  1202 . Other devices, including computing device  1204 , access these images via the Internet  1246 . Mobile phone network  1238  also connects to a standard telephone network (not shown) in order to provide normal telephone service in an embodiment in accordance with the invention. 
         [0061]    A graphical user interface (not shown) is displayed on display  1230  and controlled by user controls  1248 . User controls  1248  include dedicated push buttons (e.g. a telephone keypad) to dial a phone number, a control to set the mode (e.g. “phone” mode, “calendar” mode” “camera” mode), a joystick controller that includes 4-way control (up, down, left, right) and a push-button center “OK” or “select” switch, in embodiments in accordance with the invention. 
         [0062]    Dock  1251  recharges the batteries (not shown) in digital camera phone  1202 . Dock  1251  connects digital camera phone  1202  to computing device  1204  via dock interface  1252 . Dock interface  1252  is implemented as wired interface, such as a USB interface, in an embodiment in accordance with the invention. Alternatively, in other embodiments in accordance with the invention, dock interface  1252  is implemented as a wireless interface, such as a Bluetooth or an IEEE 802.11b wireless interface. Dock interface  1252  is used to download images from memory  1206  to computing device  1204 . Dock interface  1252  is also used to transfer calendar information from computing device  1204  to memory  1206  in digital camera phone  1202 . 
         [0063]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. For example, the present invention also applies to front-side illuminate image sensors, and image sensors with other device structures, such as 3-transistor pixels, shared 4-transistor pixels, in addition to nmos devices. 
       PARTS LIST 
       [0000]    
       
           100  Bayer CFA pattern 
           101  Green color filter 
           102  Red color filter 
           103  Blue color filter 
           104  Green color filter 
           105  Bayer color kernel 
           112  Effective aperture for red light 
           200  Photodiode implant 
           201  Transfer gate 
           202  Reset gate 
           203  Source/Follower transistor 
           204  Output 
           205  Floating diffusion 
           210  Sidewall isolation 
           211  N-doping layer 
           212  Pinning implant 
           213  Reset Drain 
           220  Active layer 
           221  Dielectric layer 
           222  Anti-reflection layer 
           230  CFA layer 
           250  Normal incident light 
           300  Transparent layer 
           301  Green/Blue pixel 
           302  Red pixel 
           303  Blue pixel 
           304  Green/Red pixel 
           310  Color kernel 
           350  Contacts 
           400  pinned photodiode 
           401  Image sensor array 
           401  Transfer gate 
           402  Red response curve 
           402  Reset gate 
           403  polysilicon gate 
           403  Blue response curve 
           403  Buffer 
           404  Source-follower output 
           404  metal wires 
           404  Implant region 
           404  Green response curve 
           405  Implant region 
           405  Conversion region 
           405  Floating diffusion 
           410  Sidewall isolation 
           412  Pinning layer 
           413  Implant region 
           413  Reset drain 
           420  Active layer 
           501  Green response curve 
           502  Red response curve 
           503  Blue response curve 
           504  Green response curve 
           601  Green/blue response curve 
           602  Red response curve 
           603  Blue response curve 
           604  Green/red response curve 
           701  Intensity peak region for 470 nm light 
           702  Intensity peak region for 650 nm light 
           703  Intensity peak region for 420 nm light 
           704  Intensity peak region for 590 nm light 
           1010  Cross-section through pixels  303  and  304   
           1011  Cross-section through pixels  301  and  302   
           1020  Patterned resist layer 
           1025  Patterned microlens array 
           1030  Etched amount of transparent layer 
           1040  Second patterned resist layer 
           1050  Etched amount of transparent layer 
           1200  Imaging system 
           1202  Imaging Device 
           1204  Computing device 
           1206  Memory 
           1208  Lens 
           1210  Microlens 
           1212  Active Pixel Sensor 
           1214  Timing Generator 
           1216  Flash 
           1218  Analog/digital converter 
           1220  Buffer Memory 
           1222  Processor 
           1224  Firmware 
           1226  Clock 
           1228  RAM 
           1230  Display 
           1232  Audio Codec 
           1234  Microphone 
           1236  Speaker 
           1238  Network 
           1240  Wireless Modem 
           1242  Connection 
           1244  Service provider 
           1246  Internet 
           1248  User Controls 
           1250  Difference in transparent layer thickness between pixels 
           1251  Dock 
           1252  Interface 
           1320  Second transparent material layer 
           1430  Microlens 
           1530  Microlens