# US 8,569,672 B2 · Pixel of image sensor having electrically controllable pinning layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,569,672 B2 - Document ID: US8569672B2 - Status: Granted - Kind: B2 - Application number: 13/055,559 - Filed: 2009-08-19 - Published: 2011-07-14 - Granted: 2013-10-29 - Earliest claimed: 2008-08-20 - Assignees: Intellectual Ventures II LLC - Applicants: Man Lyun Ha - Inventors: Man Lyun Ha - Web page: https://patentgrep.com/patent/US8569672B2 ## CPC - H10F 39/014: {of CMOS image sensors} - H10F 39/803: {Pixels having integrated switching, control, storage or amplification elements} - H10F 39/807: {Pixel isolation structures} - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract Disclosed are a pinned photodiode having and electrically controllable pinning layer and an image sensor including the pinned photodiode. A predetermined voltage is applied to the pinning layer for the depletion duration of the photodiode in the image sensor, so that stable surface pinning is acquired and the uniform surface pinning is achieved between pixels. ## Claims ### Claim 1 An image sensor, comprising: a pinned photodiode having a pinning layer; and a voltage supply unit coupled to the pinning layer and configured to apply a predetermined voltage to the pinning layer in response to depletion of the pinned photodiode, wherein the voltage supply unit includes: a voltage generator configured to generate the predetermined voltage; and a switching unit configured to transfer the predetermined voltage to the pinning layer in response to a switching control signal. ### Claim 2 (depends on 1) The image sensor of claim 1, further comprising a field stop doping region coupled to the pinning layer and configured to receive the predetermined voltage. ### Claim 3 (depends on 1) The image sensor of claim 1, further comprising: a pixel array including a plurality of pixels, each pixel having a pinned photodiode; wherein the voltage supply unit is configured to apply the predetermined voltage to pinned photodiodes from each pixel in the plurality of pixels. ### Claim 4 (depends on 1) The image sensor of claim 1, wherein the switching control signal is configured to be activated in response to depletion of the pinned photodiode. ### Claim 5 A pixel of an image sensor, the pixel comprising: a pinned photodiode having a pinning layer; a charge transfer transistor including a gate terminal configured to receive a transfer control signal, wherein the charge transfer transistor is configured to transfer charges accumulated by the pinned photodiode to a sensing node in response to the transfer control signal; and a diode coupled between the gate terminal of the charge transfer transistor and the pinning layer and configured to apply a predetermined voltage to the pinning layer. ### Claim 6 (depends on 5) The pixel of claim 5, further comprising a field stop doping region coupled to the pinning layer and configured to receive the predetermined voltage. ### Claim 7 (depends on 5) The pixel of claim 5, wherein the diode comprises at least two diodes coupled in series. ### Claim 8 (depends on 5) The pixel of claim 5, wherein the diode is further configured to receive a voltage input applied to the gate terminal of the charge transfer transistor, lower the received voltage input, and apply the lowered voltage input to the pinning layer. ### Claim 9 (depends on 5) The pixel of claim 5, wherein the diode comprises a PN-junction polysilicon layer including a P-type region formed at a side of the gate terminal of the charge transfer transistor and an N-type region formed at the pinning layer. ### Claim 10 (depends on 5) The pixel of claim 5, further comprising a reset transistor including a gate terminal configured to receive a reset control signal, wherein the reset transistor is configured to reset the sensing node in response to the reset control signal. ### Claim 11 (depends on 10) The pixel of claim 10, further comprising a selective transistor configured to transfer an output of a source follower transistor to a pixel output line. ### Claim 12 (depends on 5) The pixel of claim 5, further comprising a source follower transistor coupled to the sensing node. ### Claim 13 A pixel of an image sensor, the pixel comprising: a pinned photodiode having a pinning layer; a sensing node configured to receive charges accumulated in the pinned photodiode; a reset transistor including a gate terminal configured to receive a reset control signal, wherein the reset transistor is configured to reset the sensing node in response to the reset control signal; and a diode coupled between the gate terminal of the reset transistor and the pinning layer and configured to apply a predetermined voltage to the pinning layer. ### Claim 14 (depends on 13) The pixel of claim 13, further comprising a field stop doping region coupled to the pinning layer and configured to receive the predetermined voltage. ### Claim 15 (depends on 13) The pixel of claim 13, wherein the diode comprises at least two diodes coupled in series. ### Claim 16 (depends on 13) The pixel of claim 13, wherein the diode is further configured to receive a voltage input applied to the gate terminal of the reset transistor, lower the received voltage input, and apply the lowered voltage input to the pinning layer. ### Claim 17 (depends on 13) The pixel of claim 13, wherein the diode comprises a PN-junction polysilicon layer including a P-type region formed at a side of the gate terminal of the reset transistor and an N-type region formed at the pinning layer. ### Claim 18 (depends on 13) The pixel of claim 13, further comprising a source follow transistor coupled to the sensing node. ### Claim 19 (depends on 18) The pixel of claim 18, further comprising a selective transistor configured to transfer an output of the source follower transistor to a pixel output line. ### Claim 20 (depends on 13) The pixel of claim 13, further comprising a charge transfer transistor configured to transfer charges from the pinned photodiode to the sensing node in response to a transfer control signal. ### Claim 21 A method, comprising: etching an upper surface of an epitaxial layer to form an isolation region having sidewalls and a lower portion; forming a photodiode including a first doping region having a first conductivity type and a second doping region having a second conductivity type, wherein the first doping region comprises a pinning layer positioned along the upper surface of the epitaxial layer and a field stop region positioned along the sidewalls and the lower portion of the isolation region; and forming a diode configured to apply a voltage to the first doping region. ### Claim 22 (depends on 21) The method of claim 21, further comprising: forming a sensing node in the epitaxial layer; and forming a gate of a transfer transistor on the upper surface of the epitaxial layer between the photodiode and the sensing node; wherein said forming a diode comprises forming the diode such that the diode couples the gate of the transfer transistor to the pinning layer. ### Claim 23 (depends on 21) The method of claim 21, further comprising: forming a sensing node in the epitaxial layer; and forming a reset transistor configured to reset the sensing node in response to a signal applied to a gate of the reset transistor; wherein said forming a diode comprises forming the diode such that the diode couples the gate of the reset transistor to the pinning layer. ### Claim 24 (depends on 21) The method of claim 21, wherein said forming a diode comprises: depositing a polysilicon layer; masking the polysilicon layer and performing an ion implantation process to form a first region having the first conductivity type; and masking the polysilicon layer and performing an ion implantation process to form, adjacent to the first region, a second region having the second conductivity type. ### Claim 25 (depends on 21) The method of claim 21, wherein said forming a diode comprises forming the diode as a plurality of diodes coupled in series by: depositing a polysilicon layer; masking the polysilicon layer and performing an ion implantation process to form a plurality of first regions having the first conductivity type; and masking the polysilicon layer and performing an ion implantation process to form, interlaced with the plurality of first regions, a plurality of second regions having the second conductivity type. ### Claim 26 A method, comprising: generating a control signal; depleting a photodiode of an image sensor pixel in response to said generating a control signal; developing a voltage from the control signal; and applying the voltage developed from the control signal to a pinning layer of the photodiode in response to said generating a control signal. ### Claim 27 (depends on 26) The method of claim 26, further comprising transferring charge from the photodiode to a sensing node in response to a transfer control signal, wherein: the control signal comprises the transfer control signal; and said depleting occurs in response to said transferring. ### Claim 28 (depends on 26) The method of claim 26, further comprising resetting, in response to a reset control signal, a voltage level of a sensing node used to receive charge collected by the photodiode, wherein: the control signal comprises the reset control signal; and said depleting occurs in response to said resetting. ### Claim 29 (depends on 26) The method of claim 26, wherein said applying further comprises applying the voltage developed from the control signal to a field stop doping region positioned between the photodiode and a photodiode of an adjacent image sensor pixel.