WO2022051895A1 - Image sensor and apparatus - Google Patents

Image sensor and apparatus Download PDF

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Publication number
WO2022051895A1
WO2022051895A1 PCT/CN2020/113988 CN2020113988W WO2022051895A1 WO 2022051895 A1 WO2022051895 A1 WO 2022051895A1 CN 2020113988 W CN2020113988 W CN 2020113988W WO 2022051895 A1 WO2022051895 A1 WO 2022051895A1
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WO
WIPO (PCT)
Prior art keywords
backside
dti
contact
semiconductor layer
image sensor
Prior art date
Application number
PCT/CN2020/113988
Other languages
French (fr)
Inventor
Takahashi Seiji
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to CN202080103869.2A priority Critical patent/CN116114068A/en
Priority to PCT/CN2020/113988 priority patent/WO2022051895A1/en
Publication of WO2022051895A1 publication Critical patent/WO2022051895A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1462—Coatings
    • H01L27/14623—Optical shielding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14603—Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
    • H01L27/14605—Structural or functional details relating to the position of the pixel elements, e.g. smaller pixel elements in the center of the imager compared to pixel elements at the periphery
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1463—Pixel isolation structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1464—Back illuminated imager structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14643—Photodiode arrays; MOS imagers

Definitions

  • the present disclosure relates to an image sensor and an apparatus having the image sensor.
  • the apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
  • Embodiments provide an image sensor and an apparatus having the image sensor.
  • the apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
  • the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; and the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, where at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
  • DTI deep trench isolation
  • the fixed charge material is negative fixed charge material
  • the well region of the semiconductor layer is a p-well region
  • each of the plurality of photodiodes is a n-type photodiode.
  • the fixed charge material is positive fixed charge material
  • the well region of the semiconductor layer is a n-well region
  • each of the plurality of photodiodes is a p-type photodiode.
  • the oxide may be SiO2, and the fixed charge material may be SiO2 or a high-k material having a higher relative permittivity than SiO2.
  • the fixed charge material may be a material such as SislSfi, HfCf, AI2O3, Ta20s, ZrCh, TiCh, or a combination thereof, and also a material used for anti -refl ection coating on a backside surface of the semiconductor layer.
  • the at least one backside DTI portion placed farther from the center of the pixel array area than the position facing the backside contact in the optical shielding area may cause reduction of resistance between the backside contact and the front-side contacts. This causes improving stability of bias on the backside metal grid to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of the conventional image sensor.
  • the image sensor according to the first possible implementation form of the first aspect may provide the stability of the bias on the backside metal grid and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
  • a second possible implementation form of the first aspect provides: the image sensor according to the first possible implementation form of the first aspect, where at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
  • the at least one front-side contact in the optical shielding area placed closer to the center of the pixel array area than the position facing the backside contact may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a third possible implementation form of the first aspect provides: the image sensor according to the first or second possible implementation form of the first aspect, where each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
  • the metal core embedded inside the oxide and fixed charge material may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a fourth possible implementation form of the first aspect provides: the image sensor according to any one of the first to third possible implementation forms of the first aspect, where the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a second distance between adjacent two backside DTI portions in the pixel array area.
  • above-mentioned configuration of the backside DTI portions may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a fifth possible implementation form of the first aspect provides: the image sensor according to any one of the first to fourth possible implementation forms of the first aspect, where each backside DTI portion in the pixel array area is located at a position facing an end of the front-side contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area.
  • above-mentioned arrangement of the backside DTI portions and the front-side contacts may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a sixth possible implementation form of the first aspect provides: the image sensor according to any one of the first to fifth possible implementation forms of the first aspect, where a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
  • above-mentioned configuration of the backside DTI portion closest to the backside contact in the optical shielding area may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • the apparatus comprises: an image sensor configured to receive light passing through an optical system; a processor configured to process signals output from the image sensor to generate image data; and a memory configured to store the image data
  • the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, where at least one backside DTI portion and at least one front
  • DTI deep trench isolation
  • the fixed charge material is negative fixed charge material
  • the well region of the semiconductor layer is a p-well region
  • each of the plurality of photodiodes is a n-type photodiode.
  • the fixed charge material is positive fixed charge material
  • the well region of the semiconductor layer is a n-well region
  • each of the plurality of photodiodes is a p-type photodiode.
  • the apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
  • the oxide may be SiO2, and the fixed charge material may be SiO2 or a high-k material having a higher relative permittivity than SiO2.
  • the fixed charge material may be a material such as SislSU, HfO2, AI2O3, Ta2Os, ZrO2, TiO2, or a combination thereof, and also a material used for anti -refl ection coating on a backside surface of the semiconductor layer.
  • the at least one backside DTI portion placed farther from the center of the pixel array area than the position facing the backside contact in the optical shielding area may cause reduction of resistance between the backside contact and the front-side contacts. This causes improving stability of bias on the backside metal grid to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of the conventional image sensor.
  • the image sensor according to the first possible implementation form of the second aspect may provide the stability of the bias on the backside metal grid and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
  • a second possible implementation form of the second aspect provides: the apparatus according to the first possible implementation form of the second aspect, where at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
  • the at least one front-side contact in the optical shielding area placed closer to the center of the pixel array area than the position facing the backside contact may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a third possible implementation form of the second aspect provides: the apparatus according to the first or second possible implementation form of the second aspect, where each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
  • the metal core embedded inside the oxide and fixed charge material may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a fourth possible implementation form of the second aspect provides: the apparatus according to any one of the first to third possible implementation forms of the second aspect, where the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a second distance between adjacent two backside DTI portions in the pixel array area.
  • above-mentioned configuration of the backside DTI portions may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a fifth possible implementation form of the second aspect provides: the apparatus according to any one of the first to fourth possible implementation forms of the second aspect, where each backside DTI portion in the pixel array area is located at a position facing an end of the front- si de contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area.
  • above-mentioned arrangement of the backside DTI portions and the front-side contacts may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • a sixth possible implementation form of the second aspect provides: the apparatus according to any one of the first to fifth possible implementation forms of the second aspect, where a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
  • above-mentioned configuration of the backside DTI portion closest to the backside contact in the optical shielding area may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
  • FIG. 1 is a schematic block diagram for describing configuration of an apparatus according to the embodiment of the present disclosure
  • FIG. 2 shows a top view of an image sensor according to the embodiment of the present disclosure
  • FIG. 3A shows a cross-sectional view of the image sensor according to the embodiment of the present disclosure
  • FIG. 3B is a schematic diagram for describing arrangement of backside DTIs according to the embodiment of the present disclosure
  • FIG. 4 shows a cross-sectional view of the image sensor according to a first variation of the embodiment of the present disclosure
  • FIG. 5 shows a cross-sectional view of the image sensor according to a second variation of the embodiment of the present disclosure
  • FIG. 6 shows a cross-sectional view of the image sensor according to a third variation of the embodiment of the present disclosure.
  • An embodiment described below relates to an image sensor having improved performance and an apparatus with the image sensor.
  • the embodiments may apply to various apparatuses such as a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, and a machine vision.
  • FIG. 1 is a schematic block diagram for describing configuration of an apparatus according to the embodiment of the present disclosure.
  • An apparatus 10 of FIG. 1 is an example of the apparatus according to the embodiment of the present disclosure.
  • the apparatus 10 comprises an optical system 11, an image sensor 12, a processor 13 and a memory 14.
  • the image sensor 12 is an example of the image sensor according to the embodiment of the present disclosure.
  • the optical system 11 comprises at least one lens group including at least one lens, a stop (an iris), and an optical filter such as a infrared ray (IR) cut filter.
  • a lens group including at least one lens, a stop (an iris), and an optical filter such as a infrared ray (IR) cut filter.
  • IR infrared ray
  • the image sensor 12 is configured to receive light passing through the optical system 11 and output image signals in accordance with received light intensity at each pixel.
  • the image sensor 12 may be a solid-state imaging device such as a back-illuminated complementary metal-oxide-semiconductor (CMOS) image sensor.
  • CMOS complementary metal-oxide-semiconductor
  • the processor 13 is configured to generate image data based on the output image signals from the image sensor 12, and store the image data in the memory 14.
  • the processor 13 may be processing circuitry such as a central processing unit (CPU), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a graphics processing unit (GPU).
  • the memory 14 may be a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD), a solid state drive (SSD), a portable storage medium, or the like.
  • the memory 14 may store a program to cause the processor 13 to perform operation for controlling the optical system 11 and/or the image sensor 12.
  • the program may be provided to the apparatus 10 via data-carrying means such as a non-transitory computer readable storage medium, and a local and/or wide area network.
  • FIG. 2 shows a top view of an image sensor according to the embodiment of the present disclosure.
  • FIG. 3A shows a cross-sectional view of the image sensor according to the embodiment of the present disclosure. Specifically, FIG. 3A shows a cross section taken along a III-III line in FIG. 2.
  • FIG. 3B is a schematic diagram for describing arrangement of backside DTIs according to the embodiment of the present disclosure.
  • the image sensor 12 has a pixel array area Al in which a plurality of pixels for receiving incident light are formed, and an optical shielding area A2 in which a backside contact 23a fixed to a given bias is arranged.
  • the backside contact 23a is connected to ground.
  • FIG. 2 shows two areas Bl and B2 represented by a double-dotted line, in which backside DTI grids each including at least one backside DTI portion are arranged.
  • the area Bl of the backside DTI grid is placed in the pixel array area Al, and the area B2 of the backside DTI grid is placed farther from a center of the pixel array area Al than the backside contact 23a.
  • the example of FIG. 2 merely shows one of exemplary embodiments and is not intended to limit a protection scope of the present disclosure.
  • the image sensor 12 has a structure in which a micro-lens array 21, a color filter layer including color filters 22a to 22c, a backside structure, a semiconductor layer (e.g. Si-layer) and a front-side structure are stacked in this order.
  • a micro-lens array 21 a color filter layer including color filters 22a to 22c
  • a backside structure e.g. Si-layer
  • a semiconductor layer e.g. Si-layer
  • the front-side structure includes a plurality of front-side contacts 30a to 30f.
  • the semiconductor layer comprises: a p-type semiconductor region including a p- region 26, a p-well region 27 and p+ regions 29, and a plurality of photodiodes 28a to 28c (n-type semiconductors).
  • the p+ regions 29 are in contact with the front-side contacts 30a to 3 Of, respectively.
  • the plurality of photodiodes 28a to 28c are embedded inside the p-type semiconductor region in the pixel array area Al.
  • the backside structure comprises: the backside metal grid 23, an oxide layer (24a, 24b; e.g.
  • a SiCL layer a SiCL layer
  • a fixed charge material layer 25a, 25b
  • a plurality of backside deep trench isolation (DTI) portions 31a to 32c A portion 24a of the oxide layer is connected to another portion 24b thereof, and a portion 25a of the fixed charge material layer is connected to another portion 25b thereof.
  • a laminate formed by the oxide layer and the fixed charge material layer is disposed between the backside metal grid 23 and the semiconductor layer.
  • Each of the backside DTI portions 3 la to 32c extends to the p-well region 27 of the semiconductor layer.
  • the backside DTI portions 31a and 31b in the optical shielding area A2 are filled with oxide and fixed charge material which are respectively connected to the oxide layer (24a) and the fixed charge material layer (25a).
  • the backside DTI portions 32a to 32c in the pixel array area Al are filled with oxide and fixed charge material which are respectively connected to the oxide layer (24b) and the fixed charge material layer (25b).
  • the fixed charge material may be SiCh or a high-k material having a higher relative permittivity than SiCh.
  • the fixed charge material may be the material such as SislSU, HfCb, AI2O3, Ta20s, ZrCh, TiCh, or a combination thereof.
  • the fixed charge material may be material used for anti-reflection coating on a backside surface of the semiconductor layer.
  • the front-side contacts 30a to 30c are arranged in the optical shielding area A2, and the front-side contacts 30d to 30f are arranged in the pixel array area Al.
  • the front-side contacts 30a to 30f are used for providing voltage to the backside metal grid 23 in the backside structure.
  • the backside metal grid 23 has a backside contact 23a in contact with the p- region 26 in the optical shielding area A2.
  • the backside DTI portions 31a and 3 lb are placed farther from a center of the pixel array area Al than the backside contact 23a, and the backside DTI portion 3 lb is specifically located at a position close to the backside contact 23a.
  • the front-side contacts 30a and 30b are located at positions close to ends of the backside DTI portions 31a and 3 lb, respectively.
  • the front-side contacts 30a and 30b may face the ends of the backside DTI portions 31a and 31b, respectively.
  • at least one front-side contact which is placed farther from the center of the pixel array area Al than a position facing the backside contact 23a, may face a corresponding backside DTI portion in the optical shielding area A2.
  • the resistance between the backside contact 23a and each front-side contact decreases when each relevant front-side contact and a corresponding backside DTI portion thereto are brought close to each other. This causes improving stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
  • the image sensor 12 may provide the stability of the bias on the backside metal grid 23 and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
  • the front-side contacts 30d to 3 Of may be located at a positions close to ends of the backside DTI portions 32a to 32c, respectively.
  • the front-side contacts 30d to 30f may face the ends of the backside DTI portions 32a to 32c, respectively.
  • the photodiode 28a is arranged between the backside DTI portions 32a and 32b, and the photodiode 28b is arranged between the backside DTI portions 32b and 32c. Likewise, each photodiode is arranged between adjacent backside DTI portions in the pixel array area Al. This causes improving isolation of adjacent pixels.
  • each backside DTI portions may have the same width (e.g. D3 and D4 in FIG. 3B).
  • a first distance e.g. DI in FIG. 3B
  • a second distance e.g. D2 in FIG. 3B
  • a distance (e.g. D5 in FIG. 3B) between the backside contact 23a and the backside DTI portion 31b closest to the backside contact 23a in the optical shielding area A2 may be smaller than the thickness (e.g. D6 in FIG. 3B) of the semiconductor layer.
  • the configuration mentioned above may further reduce the dark signal non-uniformity of the pixel signals.
  • FIG. 4 shows a cross-sectional view of the image sensor according to the first variation of the embodiment of the present disclosure.
  • each backside DTI portion has a metal core embedded inside the oxide filled in the backside DTI portion, and an end of the metal core is connected to the backside metal grid 23.
  • each backside DTI portion has a structure in which the metal core is coated with the oxide which is connected to the oxide layer (24a, 24b), and the oxide is coated with the fixed charge material which is connected to the fixed charge material layer (25a, 25b).
  • the first variation may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
  • FIG. 5 shows a cross-sectional view of the image sensor according to the second variation of the embodiment of the present disclosure.
  • the front-side contact 30c shown in FIG. 3A is omitted in the second variation. Accordingly, the image sensor 12 according to the second variation has no front-side contact placed closer to the center of the pixel array area Al than the position facing the backside contact 23a, in the optical shielding area A2. Even in this case, configuration of the remaining front-side contacts and the backside DTI portions may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
  • FIG. 6 shows a cross-sectional view of the image sensor according to a third variation of the embodiment of the present disclosure.
  • each backside DTI portion has a metal core embedded inside the oxide filled in the backside DTI portion, and an end of the metal core is connected to the backside metal grid 23.
  • each backside DTI portion has a structure in which the metal core is coated with the oxide which is connected to the oxide layer (24a, 24b), and the oxide is coated with the fixed charge material which is connected to the fixed charge material layer (25a, 25b).
  • the third variation may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
  • the image sensor 12 may be formed from a substrate such as a bulk silicon, a silicon-on-insulator substrate, a silicon-germanium substrate, a photosensitive substrate, or a combination thereof.
  • the embodiment described above supposes a case that the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region and each of the plurality of photodiodes is a n-type photodiode, another case that the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region and each of the plurality of photodiodes is a p-type photodiode, may also fall with in a scope of the embodiment.
  • An image sensor comprising: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, wherein at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
  • DTI deep trench isolation
  • each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.

Abstract

Provided is an image sensor, where the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, where at least one DTI portion in the optical shielding area is placed farther from a center of the pixel array area than the backside contact.

Description

IMAGE SENSOR AND APPARATUS
TECHNICAL FIELD
[0001] The present disclosure relates to an image sensor and an apparatus having the image sensor. For example, the apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
BACKGROUND
[0002] In recent years, the number of pixels in an image sensor increases to enhance resolution of a generated image. Increase in the number of pixels may cause decrease in a pixel pitch of the image sensor, thereby reducing quantum efficiency at each pixel. In this regard, a method to thicken a photosensitive silicon layer of the image sensor or to skip p-type pixel-to-pixel isolation well of the image sensor is considered in order to enhance the quantum efficiency at each pixel. In addition, a back-illuminated type image sensor is proposed in order to improve receiving sensitivity at each pixel (refer to US 10141365 B2).
[0003] Increasing the thickness of the photosensitive silicon layer or skipping the p-type pixel-to-pixel isolation well results in increase of resistance between backside metal grid and front-side contacts sandwiching the photosensitive silicon layer. Accordingly, even if the conventional back-illuminated type image sensor is adopted, voltage of the backside metal grid becomes unstable, thereby enhancing dark current in the photosensitive silicon layer around a contact of the backside metal grid and increasing dark signal non-uniformity of pixel signals. These issues reduce quality of image data generated based on output from the image sensor. SUMMARY
[0004] Embodiments provide an image sensor and an apparatus having the image sensor. The apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
[0005] A first aspect of the embodiments provides the image sensor. In a first possible implementation form of the first aspect, the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; and the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, where at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
[0006] In an exemplary case, the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region, and each of the plurality of photodiodes is a n-type photodiode. In another exemplary case, the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region, and each of the plurality of photodiodes is a p-type photodiode.
[0007] Optionally, the oxide may be SiO2, and the fixed charge material may be SiO2 or a high-k material having a higher relative permittivity than SiO2. For example, the fixed charge material may be a material such as SislSfi, HfCf, AI2O3, Ta20s, ZrCh, TiCh, or a combination thereof, and also a material used for anti -refl ection coating on a backside surface of the semiconductor layer.
[0008] According to the first possible implementation form of the first aspect, the at least one backside DTI portion placed farther from the center of the pixel array area than the position facing the backside contact in the optical shielding area, may cause reduction of resistance between the backside contact and the front-side contacts. This causes improving stability of bias on the backside metal grid to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of the conventional image sensor.
[0009] For example, the image sensor according to the first possible implementation form of the first aspect may provide the stability of the bias on the backside metal grid and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
[0010] A second possible implementation form of the first aspect provides: the image sensor according to the first possible implementation form of the first aspect, where at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
[0011] According to the second possible implementation form of the first aspect, the at least one front-side contact in the optical shielding area placed closer to the center of the pixel array area than the position facing the backside contact, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0012] A third possible implementation form of the first aspect provides: the image sensor according to the first or second possible implementation form of the first aspect, where each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
[0013] According to the third possible implementation form of the first aspect, the metal core embedded inside the oxide and fixed charge material, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0014] A fourth possible implementation form of the first aspect provides: the image sensor according to any one of the first to third possible implementation forms of the first aspect, where the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a second distance between adjacent two backside DTI portions in the pixel array area.
[0015] According to the fourth possible implementation form of the first aspect, above-mentioned configuration of the backside DTI portions may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0016] A fifth possible implementation form of the first aspect provides: the image sensor according to any one of the first to fourth possible implementation forms of the first aspect, where each backside DTI portion in the pixel array area is located at a position facing an end of the front-side contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area. [0017] According to the fifth possible implementation form of the first aspect, above-mentioned arrangement of the backside DTI portions and the front-side contacts, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0018] A sixth possible implementation form of the first aspect provides: the image sensor according to any one of the first to fifth possible implementation forms of the first aspect, where a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
[0019] According to the sixth possible implementation form of the first aspect, above-mentioned configuration of the backside DTI portion closest to the backside contact in the optical shielding area, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0020] A second aspect of the embodiments provides the apparatus. In a first possible implementation form of the second aspect, the apparatus comprises: an image sensor configured to receive light passing through an optical system; a processor configured to process signals output from the image sensor to generate image data; and a memory configured to store the image data, where the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, where at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
[0021] In an exemplary case, the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region, and each of the plurality of photodiodes is a n-type photodiode. In another exemplary case, the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region, and each of the plurality of photodiodes is a p-type photodiode.
[0022] Optionally, the apparatus may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, a machine vision, or the like.
[0023] Optionally, the oxide may be SiO2, and the fixed charge material may be SiO2 or a high-k material having a higher relative permittivity than SiO2. For example, the fixed charge material may be a material such as SislSU, HfO2, AI2O3, Ta2Os, ZrO2, TiO2, or a combination thereof, and also a material used for anti -refl ection coating on a backside surface of the semiconductor layer.
[0024] According to the first possible implementation form of the second aspect, the at least one backside DTI portion placed farther from the center of the pixel array area than the position facing the backside contact in the optical shielding area, may cause reduction of resistance between the backside contact and the front-side contacts. This causes improving stability of bias on the backside metal grid to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of the conventional image sensor.
[0025] For example, the image sensor according to the first possible implementation form of the second aspect may provide the stability of the bias on the backside metal grid and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
[0026] A second possible implementation form of the second aspect provides: the apparatus according to the first possible implementation form of the second aspect, where at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
[0027] According to the second possible implementation form of the second aspect, the at least one front-side contact in the optical shielding area placed closer to the center of the pixel array area than the position facing the backside contact, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0028] A third possible implementation form of the second aspect provides: the apparatus according to the first or second possible implementation form of the second aspect, where each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
[0029] According to the third possible implementation form of the second aspect, the metal core embedded inside the oxide and fixed charge material, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0030] A fourth possible implementation form of the second aspect provides: the apparatus according to any one of the first to third possible implementation forms of the second aspect, where the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a second distance between adjacent two backside DTI portions in the pixel array area.
[0031] According to the fourth possible implementation form of the second aspect, above-mentioned configuration of the backside DTI portions may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0032] A fifth possible implementation form of the second aspect provides: the apparatus according to any one of the first to fourth possible implementation forms of the second aspect, where each backside DTI portion in the pixel array area is located at a position facing an end of the front- si de contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area.
[0033] According to the fifth possible implementation form of the second aspect, above-mentioned arrangement of the backside DTI portions and the front-side contacts, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
[0034] A sixth possible implementation form of the second aspect provides: the apparatus according to any one of the first to fifth possible implementation forms of the second aspect, where a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
[0035] According to the sixth possible implementation form of the second aspect, above-mentioned configuration of the backside DTI portion closest to the backside contact in the optical shielding area, may cause further reduction of resistance between the backside contact and the front-side contacts, thereby improving the stability of the bias on the backside metal grid and reducing the dark signal non-uniformity of the pixel signals.
BRIEF DESCRIPTION OF DRAWINGS
[0036] FIG. 1 is a schematic block diagram for describing configuration of an apparatus according to the embodiment of the present disclosure,
FIG. 2 shows a top view of an image sensor according to the embodiment of the present disclosure,
FIG. 3A shows a cross-sectional view of the image sensor according to the embodiment of the present disclosure,
FIG. 3B is a schematic diagram for describing arrangement of backside DTIs according to the embodiment of the present disclosure,
FIG. 4 shows a cross-sectional view of the image sensor according to a first variation of the embodiment of the present disclosure,
FIG. 5 shows a cross-sectional view of the image sensor according to a second variation of the embodiment of the present disclosure, and FIG. 6 shows a cross-sectional view of the image sensor according to a third variation of the embodiment of the present disclosure.
DESCRIPTION OF EMBODIMENTS
[0037] The following describes technical solutions of the embodiments, referring to the accompanying drawings. It will be understood that the embodiments described below are not all but just some of embodiments relating to the present disclosure. It is to be noted that all other embodiments which may be derived by a person skilled in the art based on the embodiments described below without creative efforts shall fall within the protection scope of the present disclosure.
[0038] An embodiment described below relates to an image sensor having improved performance and an apparatus with the image sensor. The embodiments may apply to various apparatuses such as a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a security/surveillance camera, a network camera, a video camcorder, an automotive/transport camera, a medical camera, and a machine vision.
[0039] (Configuration of the apparatus) Following describes configuration of an apparatus according to the embodiment of the present disclosure, with reference to FIG.
1. FIG. 1 is a schematic block diagram for describing configuration of an apparatus according to the embodiment of the present disclosure. An apparatus 10 of FIG. 1 is an example of the apparatus according to the embodiment of the present disclosure.
[0040] As shown in FIG. 1, the apparatus 10 comprises an optical system 11, an image sensor 12, a processor 13 and a memory 14. The image sensor 12 is an example of the image sensor according to the embodiment of the present disclosure.
[0041] The optical system 11 comprises at least one lens group including at least one lens, a stop (an iris), and an optical filter such as a infrared ray (IR) cut filter.
[0042] The image sensor 12 is configured to receive light passing through the optical system 11 and output image signals in accordance with received light intensity at each pixel. The image sensor 12 may be a solid-state imaging device such as a back-illuminated complementary metal-oxide-semiconductor (CMOS) image sensor.
[0043] The processor 13 is configured to generate image data based on the output image signals from the image sensor 12, and store the image data in the memory 14. The processor 13 may be processing circuitry such as a central processing unit (CPU), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a graphics processing unit (GPU).
[0044] The memory 14 may be a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (HDD), a solid state drive (SSD), a portable storage medium, or the like.
[0045] Optionally, the memory 14 may store a program to cause the processor 13 to perform operation for controlling the optical system 11 and/or the image sensor 12. The program may be provided to the apparatus 10 via data-carrying means such as a non-transitory computer readable storage medium, and a local and/or wide area network.
[0046] (Structure of the image sensor) Following describes a structure of the image sensor 12, with reference to FIGs. 2, 3A and 3B.
[0047] FIG. 2 shows a top view of an image sensor according to the embodiment of the present disclosure. FIG. 3A shows a cross-sectional view of the image sensor according to the embodiment of the present disclosure. Specifically, FIG. 3A shows a cross section taken along a III-III line in FIG. 2. FIG. 3B is a schematic diagram for describing arrangement of backside DTIs according to the embodiment of the present disclosure.
[0048] As shown in FIG. 2, the image sensor 12 has a pixel array area Al in which a plurality of pixels for receiving incident light are formed, and an optical shielding area A2 in which a backside contact 23a fixed to a given bias is arranged. In an example of FIG. 2, the backside contact 23a is connected to ground. In addition, FIG. 2 shows two areas Bl and B2 represented by a double-dotted line, in which backside DTI grids each including at least one backside DTI portion are arranged. As shown in FIG. 2, the area Bl of the backside DTI grid is placed in the pixel array area Al, and the area B2 of the backside DTI grid is placed farther from a center of the pixel array area Al than the backside contact 23a. The example of FIG. 2 merely shows one of exemplary embodiments and is not intended to limit a protection scope of the present disclosure. [0049] The image sensor 12 has a structure in which a micro-lens array 21, a color filter layer including color filters 22a to 22c, a backside structure, a semiconductor layer (e.g. Si-layer) and a front-side structure are stacked in this order.
[0050] As shown in FIG. 3A, the front-side structure includes a plurality of front-side contacts 30a to 30f. The semiconductor layer comprises: a p-type semiconductor region including a p- region 26, a p-well region 27 and p+ regions 29, and a plurality of photodiodes 28a to 28c (n-type semiconductors). The p+ regions 29 are in contact with the front-side contacts 30a to 3 Of, respectively. The plurality of photodiodes 28a to 28c are embedded inside the p-type semiconductor region in the pixel array area Al. [0051] The backside structure comprises: the backside metal grid 23, an oxide layer (24a, 24b; e.g. a SiCL layer), a fixed charge material layer (25a, 25b), and a plurality of backside deep trench isolation (DTI) portions 31a to 32c. A portion 24a of the oxide layer is connected to another portion 24b thereof, and a portion 25a of the fixed charge material layer is connected to another portion 25b thereof. A laminate formed by the oxide layer and the fixed charge material layer is disposed between the backside metal grid 23 and the semiconductor layer.
[0052] Each of the backside DTI portions 3 la to 32c extends to the p-well region 27 of the semiconductor layer. The backside DTI portions 31a and 31b in the optical shielding area A2 are filled with oxide and fixed charge material which are respectively connected to the oxide layer (24a) and the fixed charge material layer (25a). Likewise, the backside DTI portions 32a to 32c in the pixel array area Al are filled with oxide and fixed charge material which are respectively connected to the oxide layer (24b) and the fixed charge material layer (25b).
[0053] In some exemplary cases, the fixed charge material may be SiCh or a high-k material having a higher relative permittivity than SiCh. For example, the fixed charge material may be the material such as SislSU, HfCb, AI2O3, Ta20s, ZrCh, TiCh, or a combination thereof. Optionally, the fixed charge material may be material used for anti-reflection coating on a backside surface of the semiconductor layer.
[0054] In an example of FIG. 3A, the front-side contacts 30a to 30c are arranged in the optical shielding area A2, and the front-side contacts 30d to 30f are arranged in the pixel array area Al. The front-side contacts 30a to 30f are used for providing voltage to the backside metal grid 23 in the backside structure. The backside metal grid 23 has a backside contact 23a in contact with the p- region 26 in the optical shielding area A2.
[0055] As shown in FIG. 3 A, the backside DTI portions 31a and 3 lb are placed farther from a center of the pixel array area Al than the backside contact 23a, and the backside DTI portion 3 lb is specifically located at a position close to the backside contact 23a.
[0056] The front-side contacts 30a and 30b are located at positions close to ends of the backside DTI portions 31a and 3 lb, respectively.
[0057] Optionally, the front-side contacts 30a and 30b may face the ends of the backside DTI portions 31a and 31b, respectively. As this exemplary case, at least one front-side contact which is placed farther from the center of the pixel array area Al than a position facing the backside contact 23a, may face a corresponding backside DTI portion in the optical shielding area A2.
[0058] The resistance between the backside contact 23a and each front-side contact decreases when each relevant front-side contact and a corresponding backside DTI portion thereto are brought close to each other. This causes improving stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
[0059] For example, the image sensor 12 according to the embodiment of the present disclosure may provide the stability of the bias on the backside metal grid 23 and the reduction of the dark signal non-uniformity of the pixel signals, even when the thickness is more than 3pm (e.g. 10pm).
[0060] In the similar manner, the front-side contacts 30d to 3 Of may be located at a positions close to ends of the backside DTI portions 32a to 32c, respectively. Optionally, the front-side contacts 30d to 30f may face the ends of the backside DTI portions 32a to 32c, respectively.
[0061] As shown in FIG. 3 A, the photodiode 28a is arranged between the backside DTI portions 32a and 32b, and the photodiode 28b is arranged between the backside DTI portions 32b and 32c. Likewise, each photodiode is arranged between adjacent backside DTI portions in the pixel array area Al. This causes improving isolation of adjacent pixels.
[0062] Optionally, each backside DTI portions may have the same width (e.g. D3 and D4 in FIG. 3B). Also, a first distance (e.g. DI in FIG. 3B) between adjacent two backside DTI portions in the optical shielding area A2 may be equal to a second distance (e.g. D2 in FIG. 3B) between adjacent two backside DTI portions in the pixel array area Al .
[0063] In addition, a distance (e.g. D5 in FIG. 3B) between the backside contact 23a and the backside DTI portion 31b closest to the backside contact 23a in the optical shielding area A2 may be smaller than the thickness (e.g. D6 in FIG. 3B) of the semiconductor layer. The configuration mentioned above may further reduce the dark signal non-uniformity of the pixel signals.
[0064] (First variation of the embodiment) Following describes first variation of the embodiment according to the present disclosure, with reference to FIG. 4. FIG. 4 shows a cross-sectional view of the image sensor according to the first variation of the embodiment of the present disclosure.
[0065] As shown in FIG. 4, in the first variation, each backside DTI portion has a metal core embedded inside the oxide filled in the backside DTI portion, and an end of the metal core is connected to the backside metal grid 23. In this case, each backside DTI portion has a structure in which the metal core is coated with the oxide which is connected to the oxide layer (24a, 24b), and the oxide is coated with the fixed charge material which is connected to the fixed charge material layer (25a, 25b).
[0066] Similar to the embodiment described above, the first variation may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
[0067] (Second variation of the embodiment) Following describes second variation of the embodiment according to the present disclosure, with reference to FIG. 5. FIG. 5 shows a cross-sectional view of the image sensor according to the second variation of the embodiment of the present disclosure.
[0068] As shown in FIG. 5, the front-side contact 30c shown in FIG. 3A is omitted in the second variation. Accordingly, the image sensor 12 according to the second variation has no front-side contact placed closer to the center of the pixel array area Al than the position facing the backside contact 23a, in the optical shielding area A2. Even in this case, configuration of the remaining front-side contacts and the backside DTI portions may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
[0069] (Third variation of the embodiment) Following describes third variation of the embodiment according to the present disclosure, with reference to FIG. 6. FIG. 6 shows a cross-sectional view of the image sensor according to a third variation of the embodiment of the present disclosure.
[0070] As shown in FIG. 6, in the third variation, each backside DTI portion has a metal core embedded inside the oxide filled in the backside DTI portion, and an end of the metal core is connected to the backside metal grid 23. In this case, each backside DTI portion has a structure in which the metal core is coated with the oxide which is connected to the oxide layer (24a, 24b), and the oxide is coated with the fixed charge material which is connected to the fixed charge material layer (25a, 25b).
[0071] Similar to the second variation and/or the embodiment described above, the third variation may improve stability of bias on the backside metal grid 23 to reduce dark current, thereby reducing dark signal non-uniformity of pixel signals to enhance quality of image data even though a thickness of the semiconductor layer is larger than that of a conventional image sensor.
[0072] The foregoing disclosure merely discloses exemplary embodiments, and is not intended to limit the protection scope of the present invention. It will be appreciated by those skilled in the art that the foregoing embodiments and all or some of other embodiments and modifications which may be derived based on the scope of claims of the present invention will of course fall within the scope of the present invention.
[0073] For example, the image sensor 12 may be formed from a substrate such as a bulk silicon, a silicon-on-insulator substrate, a silicon-germanium substrate, a photosensitive substrate, or a combination thereof.
[0074] Although the embodiment described above supposes a case that the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region and each of the plurality of photodiodes is a n-type photodiode, another case that the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region and each of the plurality of photodiodes is a p-type photodiode, may also fall with in a scope of the embodiment.
1. An image sensor comprising: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, wherein at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
2. The image sensor according to claim 1, wherein at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
3. The image sensor according to claim 1 or 2, wherein each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
4. The image sensor according to any one of claims 1 to 3, wherein the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a

Claims

second distance between adjacent two backside DTI portions in the pixel array area.
5. The image sensor according to any one of claims 1 to 4, wherein each backside DTI portion in the pixel array area is located at a position facing an end of the front- si de contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area.
6. The image sensor according to any one of claims 1 to 5, wherein a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
7. The image sensor according to any one of claims 1 to 6, wherein the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region, and each of the plurality of photodiodes is a n-type photodiode.
8. The image sensor according to any one of claims 1 to 6, wherein the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region and each of the plurality of photodiodes is a p-type photodiode.
9. An apparatus comprising: an image sensor configured to receive light passing through an optical system; a processor configured to process signals output from the image sensor to generate image data; and a memory configured to store the image data, wherein the image sensor comprises: a front-side structure including a plurality of front-side contacts for providing voltage to a backside metal grid in a backside structure; a semiconductor layer disposed on the front-side structure, wherein a plurality of photodiodes are embedded in a pixel array area of the semiconductor layer; the backside structure including: the backside metal grid which has a backside contact in contact with the semiconductor layer in an optical shielding area, an oxide layer disposed between the backside metal grid and the semiconductor layer, and a plurality of backside deep trench isolation (DTI) portions filled with oxide and fixed charge material that extend to a p-type or n-type well region of the semiconductor layer, wherein at least one backside DTI portion and at least one front-side contact are placed farther from a center of the pixel array area than a position facing the backside contact in the optical shielding area.
10. The apparatus according to claim 9, wherein at least one front-side contact in the optical shielding area is placed closer to the center of the pixel array area than the position facing the backside contact.
11. The apparatus according to claim 9 or 10, wherein each backside DTI portion has a metal core embedded inside the oxide and fixed charge material, and an end of the metal core is connected with the backside metal grid.
12. The apparatus according to any one of claims 9 to 11, wherein the plurality of backside DTI portions have the same width, and a first distance between adjacent two backside DTI portions in the optical shielding area is equal to a second distance between adjacent two backside DTI portions in the pixel array area.
13. The apparatus according to any one of claims 9 to 12, wherein each backside DTI portion in the pixel array area is located at a position facing an end of the front- si de contact, and each of the at least one backside DTI portion placed farther from the center of the pixel array area than the backside contact is located at a position facing an end of the front-side contact in the optical shielding area.
14. The apparatus according to any one of claims 9 to 13, wherein a distance between the backside contact and a backside DTI portion closest to the backside contact in the optical shielding area is smaller than a thickness of the semiconductor layer.
15. The apparatus according to any one of claims 9 to 14, wherein the fixed charge material is negative fixed charge material, the well region of the semiconductor layer is a p-well region, and each of the plurality of photodiodes is a n-type photodiode.
16. The apparatus according to any one of claims 9 to 14, wherein the fixed charge material is positive fixed charge material, the well region of the semiconductor layer is a n-well region and each of the plurality of photodiodes is a p-type photodiode.
PCT/CN2020/113988 2020-09-08 2020-09-08 Image sensor and apparatus WO2022051895A1 (en)

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US20190096929A1 (en) * 2017-09-28 2019-03-28 Taiwan Semiconductor Manufacturing Co., Ltd. Back-side deep trench isolation (bdti) structure for pinned photodiode image sensor
CN209282203U (en) * 2017-12-13 2019-08-20 DB HiTek 株式会社 Back side illumination image sensor

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US20130307104A1 (en) * 2012-05-21 2013-11-21 Taiwan Semiconductor Manufacturing Company, Ltd. Image Sensor Structure to Reduce Cross-Talk and Improve Quantum Efficiency
US9917120B2 (en) * 2015-11-09 2018-03-13 Semiconductor Components Industries, Llc Pixels with high dynamic range and a global shutter scanning mode
US20190096929A1 (en) * 2017-09-28 2019-03-28 Taiwan Semiconductor Manufacturing Co., Ltd. Back-side deep trench isolation (bdti) structure for pinned photodiode image sensor
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