|HAI LALA MO MATUTUTULUS009991309B1UNILAT (12 ) United States Patent ( 10 ) Patent No. : US 9 , 991 ,309 B1 Yang et al. (45 ) Date of Patent: Jun . 5 , 2018 (54 ) CMOS HAVING (56 ) References Cited ENHANCED NEAR QUANTUM EFFICIENCY U .S . PATENT DOCUMENTS 9 , 880 , 057 B2 * 1 /2018 Cazaux GO1J 5 /0862 (71 ) Applicant: OmniVision Technologies , Inc. , Santa 2012/ 0313204 A1 * 12 /2012 Haddad ...... HOTL 27 / 1462 Clara , CA (US ) 257 / 432 2015 /0287766 Al * 10/ 2015 Kim ...... HOIL 27 / 307 (72 ) Inventors : Cunyu Yang , Milpitas , CA (US ) ; 250 /208 . 1 Cheng Zhao , San Jose , CA (US ) ; Gang 2015 /0340391 A1* 11/ 2015 Webster ...... HO1L 27 / 14605 Chen , San Jose , CA (US ) ; Dyson Tai, 348 / 322 2016 /0005784 Al * 1 /2016 Kiyota ...... HO1L 27 /14609 San Jose , CA (US ) ; Chen -Wei Lu , San 348 / 308 Jose , CA (US ) 2017 /0208277 A1 * 7 /2017 Borthakur ...... H04N 5 /378 (73 ) Assignee : OmniVision Technologies , Inc. , Santa 2017 / 0345851 A1 * 11/ 2017 Yang ...... HO1L 27/ 1461 Clara , CA (US ) * cited by examiner ( * ) Notice : Subject to any disclaimer , the term of this Primary Examiner - Daniel M Pasiewicz patent is extended or adjusted under 35 U . S .C . 154 (b ) by 0 days. days . (57 ) ABSTRACT An image sensor comprises a material having (21 ) Appl. No. : 15 /642 , 177 an illuminated surface and a non - illuminated surface ; a photodiode formed in the semiconductor material extending ( 22 ) Filed : Jul. 5 , 2017 from the illuminated surface to receive an incident light through the illuminated surface , wherein the received inci (51 ) Int. Ci. dent light generates charges in the photodiode ; a transfer H04N 5 /33 ( 2006 .01 ) gate electrically coupled to the photodiode to transfer the H04N 5 /335 ( 2011. 01 ) generated charges from the photodiode in response to a H04N 5 /3745 ( 2011. 01) transfer signal; a floating diffusion electrically coupled to the HOIL 27/ 146 ( 2006 .01 ) transfer gate to receive the transferred charges from the ( 52 ) U .S . CI. photodiode; a near infrared (NIR ) quantum efficiency ( QE ) CPC .. . HOIL 27 / 14649 (2013 .01 ) ; HOIL 27/ 1461 enhancement structure comprising at least two NIR QE ( 2013 .01 ) ; HOIL 27 /1463 (2013 .01 ) ; HOIL enhancement elements within a region of the photodiode, 27/ 1464 (2013 .01 ) ; H04N 5 /332 ( 2013 .01 ) ; wherein the NIR QE enhancement structure is configured to H04N 5 /335 ( 2013 .01 ) ; H04N 5 /3745 modify the incident light at the illuminated surface of the (2013 . 01 ) semiconductor material by at least one of diffraction , deflec (58 ) Field of Classification Search tion and reflection , to redistribute the incident light within CPC ...... HO4N 5 /33 ; H04N 5 /332 ; H04N 5 / 335 ; the photodiode to improve an optical sensitivity, including HO4N 5 / 3745 ; HO1L 27 / 1461 ; HOIL near - infrared light sensitivity , of the image sensor. 27 / 1464 ; HO1L 27 /14649 See application file for complete search history . 20 Claims, 9 Drawing Sheets

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CMOS IMAGE SENSOR HAVING example photodiode in an image sensor, in accordance with ENHANCED NEAR INFRARED QUANTUM an embodiment of the invention . EFFICIENCY FIG . 7A is a top - down view and FIG . 7B is a cross sectional view of FIG . 7A as cut along line G - G ' for an TECHNICAL FIELD example front side illuminated imaging sensor, in accor dance with an embodiment of the invention . This disclosure relates generally to semiconductor image FIG . 8A is a top - down view and FIG . 8B is a cross sensors , and in particular but not exclusively, relates to sectional view of FIG . 8A as cut along line H - H ' for an CMOS image sensors having enhanced near infrared (NIR ) example backside illuminated imaging sensor, in accordance 10 with an embodiment of the invention . Quantum Efficiency ( QE ) . FIG . 9A demonstrates light path through an example BACKGROUND INFORMATION backside illuminated image sensor without NIR QE enhancement structures , FIG . 9B demonstrates the simu Image sensors have become ubiquitous. They are widely lated light density distribution in the backside illuminated used in digital still cameras, cellular phones , security cam 15 image sensor of FIG . 9A , in accordance with an embodiment eras, as well as ,medical , automobile , and other applications. of the invention . The technology used to manufacture image sensors has FIG . 10A demonstrates light path through an example continued to advance at a great pace . For example , the backsideOF illuminated image sensor with a plurality of NIR demands of higher resolution and lower power consumption 20 QEsimulated enhancement light density structures distribution, FIG . in10B the demonstrates backside illumi the have encouraged the further miniaturization and integration nated image sensor of FIG . 10A , in accordance with an of these devices. embodiment of the invention . Detection of near infrared (NIR ) light is useful in auto - FIG . 11 is the simulated OE vs. wavelength of incident motive and night vision applications . However, conven - light for an example backside illuminated image sensor tional image sensor devices may poorly absorb NIR light 25 between the one with and the one without a plurality of NIR due to the band structure of semiconductor materials used in QE enhancement structures , in accordance with an embodi modern microelectronic devices. Even if conventional ment of the invention . image sensors can absorb NIR light, the semiconductor may FIG . 12 is a block diagram schematically illustrating one need to be sufficiently thick . Additional semiconductor example of an imaging system , in accordance with an thickness may complicate other fabrication steps and/ or 30 embodiment of the disclosure . reduce performance . Corresponding reference characters indicate correspond Furthermore , many materials conductive to absorb NIR i ng components throughout the several views of the draw light are very expensive ( either inherently or by virtue of ings . Skilled artisans will appreciate that elements in the fabrication techniques needed to process the materials ), figures are illustrated for simplicity and clarity and have not toxic , and/ or have lower sensitivity to the visible spectrum . 35 necessarily been drawn to scale . For example , the dimen Accordingly , many elements /compounds capable of detect sions of some of the elements in the figures may be exag ing NIR light may not be ideal choices for integration into gerated relative to other elements to help to improve under modern electronic devices . standing of various embodiments of the present invention . Also , common but well- understood elements that are useful BRIEF DESCRIPTION OF THE DRAWINGS 40 or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view Non - limiting and non - exhaustive examples of the inven - of these various embodiments of the present invention . tion are described with reference to the following figures , wherein like reference numerals refer to like parts through DETAILED DESCRIPTION out the various views unless otherwise specified . 45 FIG . 1A is a top -down view and FIG . 1B is a cross - Examples of an apparatus for an image sensor with sectional view of FIG . 1A as cut along line A - A ' for an enhanced NIR QE are described herein . In the following example photodiode in an image sensor, in accordance with description , numerous specific details are set forth to pro an embodiment of the invention . vide a thorough understanding of the examples . However, FIG . 2A is a top - down view and FIG . 2B is a cross - 50 one skilled in the relevant art will recognize that the tech sectional view of FIG . 2A as cut along line B - B ' for an niques described herein can be practiced without one or example photodiode in an image sensor, in accordance with more of the specific details , or with other methods , compo an embodiment of the invention . nents , materials , etc . In other instances, well -known struc FIG . 3A is a top -down view and FIG . 3B is a cross - tures , materials , or operations are not shown or described in sectional view of FIG . 3A as cut along line C - C ' for an 55 details in order to avoid obscuring certain aspects . example photodiode in an image sensor, in accordance with Reference throughout this specification to “ one example ” an embodiment of the invention . or “ one embodiment” means that a particular feature, struc FIG . 4A is a top -down view and FIG . 4B is a cross ture , or characteristic described in connection with the sectional view of FIG . 4A as cut along line D - D ' for an example is included in at least one example of the present example photodiode in an image sensor, in accordance with 60 invention . Thus, the appearances of the phrases " in one an embodiment of the invention . example " or " in one embodiment” in various places FIG . 5A is a top -down view and FIG . 5B is a cross - throughout this specification are not necessarily all referring sectional view of FIG . 5A as cut along line E - E ' for an to the same example . Furthermore , the particular features , example photodiode in an image sensor, in accordance with structures, or characteristics may be combined in any suit an embodiment of the invention . 65 able manner in one or more examples. FIG . 6A is a top - down view and FIG . 6B is a cross - Throughout this specification , several terms of art are sectional view of FIG . 6A as cut along line F -F ' for an used . These terms are to take on their ordinary meaning in US 9 ,991 ,309 B1 the art from which they come, unless specifically defined in the semiconductor material 711 to receive image light herein or the context of their use would clearly suggest through front side surface 706 as an illuminated surface of otherwise . It should be noted that element names and the semiconductor material 711 . In one example , dopants are symbols may be used interchangeably through this docu - implanted into the semiconductor material 711 to form the ment ( e . g . , Si vs . silicon ) ; however , both have identical 5 photodiode 702 . A transfer gate 703 is electrically coupled meaningm . to the photodiode 702 to transfer image charge from the FIG . 12 is a block diagram schematically illustrating one photodiode 702 in response to a transfer signal. In one example of an imaging system , in accordance with an example , the transfer gate 703 includes a poly gate and a embodiment of the disclosure . Imaging system 1200 dielectric thin film between the poly gate and the semicon includes array 1205 , control circuitry 1221 , readout 10 ductor material 711 . A floating diffusion 704 is electrically circuitry 1211 , and function logic 1215 . In one example , coupled to the transfer gate 703 to receive the image charge pixel array 1205 is a two - dimensional (2D ) array of photo from the photodiode 702 . In one example , in order to reduce diodes , or image sensor ( e . g . , pixels P1 , P2 . . . , Pn ) . the dark current caused by the hot electrons, a front side P + As illustrated , photodiodes are arranged into rows ( e . g ., doped layer 707 is disposed on the front side surface 706 . rows R1 to Ry) and columns ( e . g . , column C1 to Cx ) to 15 The front side P + doped layer 707 may be formed with P acquire image data of a person , place , object, etc . , which can type doping by ion implantation or plasma doping process . then be used to render a 2D image of the person , place , In the depicted example in FIG . 7A , a reset transistor object, etc . However , in other examples , it is appreciated that RESET is coupled to the floating diffusion 704 to reset the photodiodes do not have to be arranged into rows and image charge in the floating diffusion 704 . Although not columns and may take other configurations . 20 depicted in FIG . 7A , an amplifier transistor may also be In one example , after the image sensor photodiode /pixel coupled to the floating diffusion 704 to amplify the image in pixel array 1205 has acquired its image data or image charge in the floating diffusion 704 . charge , the image data is readout by readout circuitry 1211 In one example , FIG . 8A is a top - down illustration of an and then transferred to functional logic 1215 . In various example back side illuminated image sensor 800 in the array examples, readout circuitry 1211 may include amplification 25 pixel 1205 of FIG . 12 , in accordance with an embodiment of circuitry , analog -to - digital (ADC ) conversion circuitry , or the invention . FIG . 8B is a cross -sectional illustration of otherwise . Function logic 1215 may simply store the image FIG . 8A as cut along line H -H ' . The back side illuminated data or even manipulate the image data by applying post image sensor 800 comprises a semiconductor material 811 . image effects ( e. g . , crop , rotate , remove red eye , adjust In one example , the semiconductor material 811 is a P type brightness , adjust contrast , or otherwise ) . In one example , 30 doped Si layer. Photodiode 802 is disposed in the semicon readout circuitry 1211 may read out a row of image data at ductor material 811 to receive image light through back side a time along readout column lines ( illustrated ) or may surface 805 as an illuminated surface of the semiconductor readout the image data using a variety of other techniques material 811 . In one example , dopants are implanted into the ( not illustrated ), such as a serial readout or a full parallel semiconductor material 811 to form the photodiode 802 . A readout of all pixels simultaneously . 35 transfer gate 803 is electrically coupled to the photodiode In one example , control circuitry 1221 is coupled to pixel 802 to extract image charge from the photodiode 802 in array 1205 to control operation of the plurality of photo response to a transfer signal. In one example, the transfer diodes in pixel array 1205 . For example , control circuitry gate 803 includes a poly gate and a dielectric thin film 1221 may generate a shutter signal for controlling image between the poly gate and the semiconductor material 811 . acquisition . In one example , the shutter signal is a global 40 A floating diffusion 804 is electrically coupled to the transfer shutter signal for simultaneously enabling all pixels within gate 803 to receive the image charge from the photodiode pixel array 1205 to simultaneously capture their respective 802 . In one example , in order to reduce the dark current image data during a single acquisition window . In another caused by the hot electrons from the front side surface 806 , example , the shutter signal is a rolling shutter signal such a front side P + doped layer 807 is disposed on the front side that each row , column , or group of pixels is sequentially 45 surface 806 . The front side P + doped layer 807 may be enabled during consecutive acquisition windows. In another formed with P type doping by ion implantation or plasma example , image acquisition is synchronized with lighting doping process . In order to reduce the dark current caused by effects such as a flash . the hot electrons from the back side surface 805 , a back side In one example, imaging system 1200 may be included in P + doped layer 814 is also disposed on the back side surface a digital camera , cell phone , computer, automobile or 50 805 . The back side P + doped layer 814 may be formed with the like . Additionally , imaging system 1200 may be coupled P type doping by ion implantation or plasma doping process . to other pieces of hardware such as a processor (general The back side P + doped layer 814 may also be formed by purpose or otherwise ) ,memory elements, output (USB port, depositing a negative charged dielectric material on the wireless transmitter, HDMI port, etc . ) , lighting / flash , elec backside surface 805 . In the depicted example in FIG . 8A , trical input (keyboard , touch display, track pad , mouse , 55 a reset transistor RESET is coupled to the floating diffusion microphone , etc . ) , and / or display. Other pieces of hardware 804 to reset image charge in the floating diffusion 804 . may deliver instructions to imaging system 1200 , extract Although not depicted in FIG . 8A , an amplifier transistor image data from imaging system 1200 , or manipulate image may also be coupled to the floating diffusion to amplify the data supplied by imaging system 1200 . image charge in the floating diffusion 804 . In one example , FIG . 7A is a top - down illustration of an 60 As illustrated in both FIG . 7A -7B and FIG . 8A - 8B , a example front side illuminated image sensor 700 in the array plurality of near infrared (NIR ) quantum efficiency (QE ) pixel 1205 of FIG . 12 , in accordance with an embodiment of enhancement structures are disposed at the illuminated sur the invention . FIG . 7B is a cross -sectional illustration of face in the photodiode and configured to modify the incident FIG . 7A as cut along line G - G '. The front side illuminated light at the illuminated surface of the semiconductor mate image sensor 700 comprises a semiconductor material 711 65 rialby at least one of diffraction , deflection and reflection , to as a substrate . In one example , the semiconductor material redistribute the incident light within the photodiode to 711 is P type doped Si substrate . Photodiode 702 is disposed improve an optical sensitivity , including near- infrared light US 9 ,991 ,309 B1 sensitivity , of the image sensor. In one example , each of the as they have a uniform critical dimensions and shape , and NIR QE enhancement structures comprises at least two NIR are disposed in a periodic pattern with consistent distance QE enhancement elements within a region of the photo - between adjacent NIR QE elements . Some of examples are diode . illustrated in FIG . 1 to FIG . 6 . In the depicted examples in FIG . 7A - 7B , the NIR QE 5 FIG . 1A -6A are top - down views and FIG . 1B -6B are enhancement elements 701 are disposed in the photodiode cross -sectional views of FIG . 1A -6A as cut along lines for 702 at the front side surface 706 where the incident light is an example photodiode 102 in an image sensor ofpixel array received through . In the depicted examples in FIG . 8A -8B , 1205 in FIG . 12 , in accordance with an embodiment of the the NIR QE enhancement elements 801 , which are the same invention . Also depicted are isolation regions 103 . As one as 701 , are disposed in the photodiodes 802 at the backside 10 example , the isolation region 103 surrounds the photodiode surface 805 where the incident light is received through . 102 and extends through the semiconductor material from Since 801 are at the backside surface 805 , they are not the illuminated surface so as to isolate the adjacent photo visible in the top down illustration FIG . 8A . diodes 102 electrically and optically . In one example, the As the examples illustrated in FIG . 7 and FIG . 8 , the NIR isolation regions 103 may include deep trench isolation QE enhancement elements 701 and 801 are arranged into 15 structures. In order to keep the description consistent and rows and columns . Each of the NIR QE enhancement simple , the isolation region is defined with the same number elements has a same shape as a trench structure (701 in 103 and the photodiode is defined with the same number 102 FIGS . 7 and 801 in FIG . 8 ) . In one example , the trench in FIG . 1 to FIG . 6 . structure has 0 . 2 um critical dimension and 0 . 4 um depth . As an illustrated example in FIGS . 1A and 3A , the NIR Each of the NIR QE enhancement elements extends from the 20 QE enhancement elements 101 are arranged as a circle illuminated surface , through the P + doped layer, and into the pattern with one NIR QE enhancement element at the center photodiodes in the semiconductor material. and the rest of NIR QE enhancement elements along the In one example , each of the NIR QE enhancement ele circle . Each two adjacent NIR QE enhancement elements ments comprises a core dielectric material which has a along the circle are separated with the same distance . As an refractive index smaller than the refractive index of the 25 illustrated example in FIGS . 2A and 4A , the NIR QE semiconductor material. As one example , the semiconductor enhancement elements 101 are arranged as a square pattern material is silicon . However, one skilled in the art will with one at the center and the rest at the four corners of the appreciate that any group III elements ( B , Al, Ga, In , Tl) , square . Each two adjacentNIR QE enhancement elements at group IV elements ( C , Si, Ge , Sn , Pb ) , group V elements ( N , the corners are separated with the same distance . P , As, Sb , Bi) , and suitable combinations of these elements , 30 In one example , each of the NIR QE enhancement struc may be used to form the semiconductor material, in accor - tures may also comprise only one NIR QE enhancement dance with the teachings of the present invention . In some element within a region of the photodiode . As an illustrated examples, the core dielectric material may include oxides ) example in FIG . 5A , the NIR QE enhancement element 501 nitrides such as silicon oxide (SiO2 ) , hafnium oxide (HfO2 ) , is formed with a frame pattern which is adjacent to the silicon nitride ( SizN4 ), silicon oxynitirde ( SiO N ) , tantalum 35 isolation region 103 . As an illustrated example in FIG . 6A , oxide ( Ta ,03 ) , titanium oxide ( TiO2) , zirconium oxide the NIR QE enhancement element 601 is formed with a (ZrO2 ) , aluminum oxide (Al2O3 ) , lanthanum oxide (La203 ), cross pattern which is at the center of the photodiode 102 . praseodymium oxide ( Pr203) , cerium oxide (CeO2 ) , neo - As an illustrated example in FIGS . 1B - 2B and 5B -6B , dymium oxide (Nd , O3 ) , promethium oxide ( Pm ,0z ) , each of the NIR QE enhancement elements is formed as a samarium oxide ( Sm , 02) , europium oxide (Eu , 02) , gado - 40 trench structure which has a same critical dimension and a linium oxide (G0 ,0z ) , terbium oxide ( Tb ,0z ) , dysprosium same depth . They extend from the illuminated surface into oxide (Dy203 ) , holmium oxide (Ho , 0z) , erbium oxide the photodiode and are filled with the core dielectric mate (Er203 ) , thulium oxide ( Tm203) , ytterbium oxide ( Yb203) , rial . Although not illustrated , each of the NIR QE enhance lutetium oxide ( Lu ,0z ) , yttrium oxide ( Y ,0z ) , or the like . ment elements may also comprise the liner material disposed Additionally , one skilled in the relevant art will recognize 45 between the photodiode and the core dielectric material. that any stoichiometric combination of the above metals Alternately , as an illustrated example in FIG . 3B - 4B , each of and their oxides /nitrides /oxynitrides may be the NIR QE enhancement elements may also be disposed at used , as long as they have a refractive index smaller than the least partially on the top of the illuminated surface , and refractive index of the semiconductor material, in accor - comprises the core dielectric material. dance with the teachings of the present invention . 50 In an example , FIG . 9A demonstrates incident light path Although not illustrated in FIG . 7 and FIG . 8 , each of the through two adjacent buried ( BCFA ) back NIR QE enhancement elements may also comprise a liner side illuminated ( BSI) image sensors without NIR QE material disposed between the photodiode and the core enhancement structures. The pixel size of each photodiode is dielectric material. In some examples, the liner materialmay 2 . 0 um . The image sensors are built in 3 um thick Si layer. include at least one of a negatively charged high k dielectric 55 A deep trench isolation (DTI ) structure is disposed between material, or a doped semiconductor material. For example , two adjacent photodiodes , a metal grid between two adja a trench could be etched and boron , nitrogen , or arsenic cent color filters, and two microlens on the top of respective could be implanted into the sidewalls of the trench to form color filters . a doped semiconductor material as the liner material. Alter As illustrated in FIG . 9A , for the BCFA BSI image natively, a trench could be etched and hafnium oxide could 60 sensors without NIR QE enhancement structures , the inci be deposited in the trench to form a negatively charged dent light with different wavelength is transmitted into high -k liner material before the core dielectric material is different depth in the Si layer. The incident light with longer deposited into the trench . wavelength may have deeper light path into the Si layer. If In other examples , each of the NIR QE enhancement the thickness of the Si layer is shorter than the depth of the elements may also comprise one shape of a parallelepiped , 65 incident light path , which usually happens to NIR incident a polygon , cylinder , an ellipsoid , a hemispheroid , and a light with wavelength longer than 800 nm , part of incident hemisphere . They may also take other configurations as long light may be transmitted through the Si layer without being US 9 ,991 , 309 B1 absorbed by Si completely . As a result , QE may be low a floating diffusion electrically coupled to the transfer gate accordingly . In one example , FIG . 9B is the simulated to receive the transferred charges from the photodiode ; incident light density distribution in the BCFA BSI image a near infrared (NIR ) quantum efficiency ( QE ) enhance sensors of FIG . 9A . The majority of NIR incident light is ment structure comprising at least two NIR QE distributed along the light path and transmitted through the 5 enhancement elements within a photosensitive region photodiode. FIG . 11 demonstrates the simulated QE of of the photodiode , wherein the NIR QE enhancement incident light with different wavelength based on the same structure is configured to modify the incident light at BCFA BSI image sensors as FIG . 9A . QE of incident light the illuminated surface of the semiconductor material with 850 nm wavelength is - 15 % , and QE with 940 nm by at least one of diffraction , deflection and reflection , wavelength is - 11 % . 10 to redistribute the incident light within the photodiode As a comparison , FIG . 10A also demonstrates the incident to improve an optical sensitivity , including near - infra light path through the same two adjacent BCFA BSI image red light sensitivity , of the image sensor. sensors as FIG . 9A , but with a plurality of NIR QE enhance - 2 . The image sensor of claim 1 , wherein each NIR QE ment structures disposed in the photodiodes at the backside enhancement element of the NIR QE enhancement structure surface . The NIR QE enhancement structures are configured 15 comprises a dielectric material having a refractive index to have the same square pattern as FIG . 2A . Each of the NIR smaller than a refractive index of the semiconductor mate QE enhancement elements has a hemisphere shape with 0 . 2 rial . um radius, which is extended from the backside surface into 3 . The image sensor of claim 1 , wherein the at least two the Si layer and filled with SiO2 . SiO2 has a refractive index NIR QE enhancement elements have a uniform size and about 1 .45 while Si has a refractive index about 3 .673 . When 20 shape , and are disposed in a periodic pattern . the incident light is transmitted from SiO2 into the photo - 4 . The image sensor of claim 1 , wherein each NIR QE diode in the Si layer , the light path gets modified at the enhancement element of the NIR QE enhancement structure backside surface by at least one of diffraction , deflection and comprises a shape of one of a parallelepiped , a polygon , a reflection . Accordingly, the incident light gets redistributed cylinder, an ellipsoids , a hemispheroid , and a hemisphere . within the photodiode as illustrated in FIG . 10B , which 25 5 . The image sensor of claim 1 , wherein the illuminated causes more incident light staying in the Si layer and being surface of the semiconductor material is one of a front side absorbed by Si. As a result , NIR light sensitivity of the surface and a back side surface of the semiconductor mate image sensor is improved . FIG . 11 demonstrates the simu - rial. lated QE of incident light with differentwavelength based on 6 . The image sensor of claim 1 , wherein each NIR QE the same BCFA BSI image sensors as FIG . 10A . QE of 30 enhancement element of the NIR QE enhancement structure incident light with 850 nm wavelength is increased from extends from the illuminated surface of the semiconductor - 15 % to - 40 % , and QE with 940 nm wavelength is material in the photodiode . increased from ~ 11 % to - 34 % . On the other hand , QE of 7 . The image sensor of claim 1 , wherein each NIR QE red , blue and green light is not impacted significantly by enhancement element of the NIR QE enhancement structure NIR QE enhancement structures , because their light path has 35 is disposed at least partially on the illuminated surface of the a depth shorter than the Si layer. Moreover , one skilled in the semiconductor material. art will also appreciate that DTI needs to be deep enough in 8 . The image sensor of claim 1, wherein an isolation order to prevent the optical and electrical cross talk between region surrounds , at least partially , the photodiode , and the two adjacent photodiodes in FIG . 10A and FIG . 10B . isolates the photodiode electrically and optically . The above description of illustrated examples of the 40 9 . The image sensor of claim 1 , further comprising a reset invention , including what is described in the Abstract, is not transistor electrically coupled to the floating diffusion to intended to be exhaustive or to limit the invention to the reset the charges received in the floating diffusion . precise forms disclosed . While specific examples of the 10 . The image sensor of claim 1 , further comprising an invention are described herein for illustrative purposes, amplifier transistor electrically coupled to the floating dif various modifications are possible within the scope of the 45 fusion to amplify the charges received in the floating diffu invention , as those skilled in the relevant art will recognize . sion . These modifications can be made to the invention in light 11. An imaging system , comprising : of the above detailed description . The terms used in the a semiconductor material having an illuminated surface following claims should not be construed to limit the inven and a non - illuminated surface ; tion to the specific examples disclosed in the specification . 50 a plurality of photodiodes formed in the semiconductor Rather , the scope of the invention is to be determined material extending from the illuminated surface to entirely by the following claims, which are to be construed receive an incident light through the illuminated sur in accordance with established doctrines of claim interpre face , wherein the received incident light generates tation . charges in the photodiodes ; 55 a plurality of isolation structures, wherein each of the What is claimed is : plurality of isolation structures is disposed between two 1 . An image sensor, comprising : adjacent photodiodes of the plurality of photodiodes ; a semiconductor material having an illuminated surface a plurality of transfer gates electrically coupled to the and a non - illuminated surface ; plurality of photodiodes to transfer the generated a photodiode formed in the semiconductor material 60 charges from the plurality of photodiodes to one or extending from the illuminated surface to receive an more floating diffusions; incident light through the illuminated surface, wherein A plurality of near infrared (NIR ) quantum efficiency the received incident light generates charges in the (QE ) enhancement structures , wherein each of NIR QE photodiode; enhancement structures comprises at least two NIR QE a transfer gate electrically coupled to the photodiode to 65 enhancement elements within the a photosensitive transfer the generated charges from the photodiode in region of individual photodiode of the plurality of response to a transfer signal; photodiodes, wherein the NIR QE enhancement struc US 9 , 991, 309 B1 10 tures are configured to modify incident light at the structures comprises a dielectric material having a refractive illuminated surface of the semiconductor material by at index smaller than a refractive index of the semiconductor least one of diffraction , deflection and reflection , to material. redistribute the incident light within the photodiode to 16 . The imaging system of claim 11 , wherein at least two pared 5 NIR QE enhancement elements of the NIR QE enhancement improve an optical sensitivity , including near infrared 5 structures have a uniform size and shape , and are disposed light sensitivity , of the image system . in a periodic pattern . 12 . The imaging system of claim 11 , further comprising a 17 . The imaging system of claim 11 , wherein each NIR plurality of reset transistors, wherein each of the plurality of QE enhancement element of the NIR QE enhancement reset transistors electrically coupled to the one or more structures comprises a shape of one of a parallelepiped , a floating diffusions to reset the charges received in the one or polygon , a cylinder , an ellipsoids , a hemispheroid , and a more floating diffusions. hemisphere . 18 . The imaging system of claim 11 , wherein each NIR 13 . The imaging system of claim 11 , further comprising a QE enhancement element of the NIR QE enhancement plurality of amplifier transistors , wherein each of the plu structures extends from the illuminated surface of the semi rality of amplifier transistors electrically coupled to the one 1515 conductor material in the photodiode . or more floating diffusions to amplify the charges received 19 . The imaging system of claim 11 , wherein each NIR in the one or more floating diffusions. QE enhancement element of the NIR QE enhancement 14 . The imaging system of claim 11 , further comprising a structures is disposed at least partially on the illuminated control circuitry and a readout circuitry , wherein the control surface of the semiconductor material. circuitry controls operation of the plurality of photodiodes, 20 20 . The imaging system of claim 11, wherein the illumi and the readout circuitry reads out image data from the nated surface of the semiconductor material is one of a front plurality of photodiodes . side surface and a back side surface of the semiconductor 15 . The imaging system of claim 11, wherein each NIR material. QE enhancement element of the NIR QE enhancement * * * * *