Solid-state image pickup device in which charges overflowing a memory during a charge transfer period are directed to a floating diffusion and method of driving same

• US 9,054,009 B2
• Filed: 12/06/2011
• Issued: 06/09/2015
• Est. Priority Date: 12/15/2010
• Status: Expired due to Fees

• Current Assignee: Sony Semiconductor Solutions Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Oike, Yusuke, Sakano, Yorito, Mabuchi, Keiji
• Primary Examiner(s): LUU, THANH X
• Application Number:
  US13/312,430
• Publication Number:
  US 20120153125A1
• Time in Patent Office: 1,281 Days
• Field of Search: 250/208.1, 348/302
• US Class Current: 1/1
• CPC Class Codes: H01L 27/14612 involving a transistor
• CPC Class Codes: H01L 27/14656 Overflow drain structures
• CPC Class Codes: H04N 25/53 Control of the integration time
• CPC Class Codes: H04N 25/531 by controlling rolling shutters in CMOS SSIS
• CPC Class Codes: H04N 25/532 by controlling global shutters in CMOS SSIS
• CPC Class Codes: H04N 25/533 by using differing integration times for different sensor regions
• CPC Class Codes: H04N 25/709 Circuitry for control of the power supply
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

A CMOS image sensor has an image array as a matrix of unit pixels each including at least a photodiode, a memory for holding a charge stored in the photodiode, a floating diffusion region for converting the charge in the memory into a voltage, a first transfer gate for transferring the charge from the photodiode to the memory, a second transfer gate for transferring the charge from the memory to the floating diffusion region, and a resetting transistor for resetting the charge in the floating diffusion region. The unit pixels are driven to set the potential of a potential barrier at a boundary between the memory and the floating diffusion region to a potential such that a charge overflowing the memory is transferred to the floating diffusion region, when the first transfer gate is turned on. The CMOS image sensor operates in a global shutter mode for capturing moving images.

Claims

1. A solid-state image pickup device comprising:

(1) a plurality of pixels, each pixel including at least (a) a photoelectric transducer, (b) a charge holder configured to hold a charge that has been transferred from said photoelectric transducer, (c) a charge-voltage converter configured to convert the charge into a voltage, (d) a first transfer element configured to transfer the charge from said photoelectric transducer to said charge holder by setting a first potential barrier at a boundary between said photoelectric transducer and said charge holder, (e) a second transfer element configured to transfer the charge from said charge holder to said charge-voltage converter by setting a second potential barrier at a boundary between said charge holder and said charge-voltage converter, and (f) a resetter configured to reset the charge in said charge-voltage converter; and

(2) a drive controller configured to control driving of the plurality of pixels, wherein,

the drive controller is configured such that during a charge transfer period between exposure periods, said drive controller (a) first effects a reset of said charge-voltage converter and said charge holder by applying a reset voltage to said charge-voltage converter while applying a first transfer voltage to the second transfer element to cause the second potential barrier to allow all charges in the charge holder to flow into the charge-voltage converter, and (b) then effects a transfer of charge from said photoelectric transducer to said charge-voltage converter by applying a second transfer voltage to the first transfer element to set the first potential barrier to a level allowing all of the charges to flow from the photoelectric transducer to the charge holder while also applying to said second transfer element a third transfer voltage which sets the second potential barrier to a level such that some, but not all, of the charges flowing into the charge holder can overflow into the charge-voltage converter, and

the drive controller is configured such that, during the charge transfer period, the drive controller applies the second transfer voltage for a period of time that is shorter in duration than a period of time in which the drive controller applies the third transfer voltage.

2. The solid-state image pickup device according to claim 1, wherein after said drive controller turns off said first transfer element by discontinuing application of the second transfer voltage to the first transfer element, said drive controller is configured to turn off said second transfer element by discontinuing application of the first transfer voltage to the second transfer element.

3. The solid-state image pickup device according to claim 1, wherein before said drive controller turns off said first transfer element by discontinuing application of the second transfer voltage to the first transfer element, said drive controller is configured to apply to said second transfer element, said third transfer voltage which sets a potential of the second potential barrier at the boundary between said charge holder and said charge-voltage converter to a potential which is higher than a potential of said photoelectric transducer in a depleted state.

4. The solid-state image pickup device according to claim 3, wherein before said drive controller turns off said second transfer element by discontinuing the application of the third transfer voltage to the second transfer element, said drive controller is configured to turn off said first transfer element.

5. The solid-state image pickup device according to claim 1, wherein said drive controller is configured to apply a negative voltage to said first transfer element and said second transfer element when said first transfer element and said second transfer element are turned off.

6. The solid-state image pickup device according to claim 5, further comprising a voltage reader configured to read a voltage corresponding to the charge in said charge-voltage converter, wherein said drive controller is configured to control driving of the plurality of pixels to enable said voltage reader to:

read a voltage as a first signal level corresponding to the charge in said charge-voltage converter,

read a voltage as a reset level corresponding to the charge in said charge-voltage converter which is reset by said resetter, and

read a voltage as a second signal level corresponding to the charge transferred from said charge holder to said charge-voltage converter by said second transfer element after the charge in said charge-voltage converter is reset by said resetter.

7. A method of driving a solid-state image pickup device including (1) a plurality of pixels each including at least (a) a photoelectric transducer, (b) a charge configured to hold a charge stored in said photoelectric transducer, (c) a charge-voltage converter configured to convert the charge held by said charge holder into a voltage, (d) a first transfer element configured to transfer the charge from said photoelectric transducer to said charge holder by setting a first potential barrier at a boundary between said photoelectric transducer and said charge holder, and (e) a second transfer element configured to transfer the charge from said charge holder to said charge-voltage converter by setting a second potential barrier at a boundary between said charge holder and said charge-voltage converter, and (f) a resetter configured to reset the charge in said charge-voltage converter;

and (2) a drive controller which controls driving of the plurality of pixels, wherein said method comprises;

the drive controller is configured such that during a charge transfer period between exposure periods, the drive controller (a) first effects a reset of said charge-voltage converter and said charge holder by applying a reset voltage to said charge-voltage converter while applying a first transfer voltage to the second transfer element to cause the second potential barrier to allow all charges in the charge holder to flow into the charge-voltage converter, and (b) then effects a transfer of charge from said photoelectric transducer to said charge-voltage converter by applying a second transfer voltage to the first transfer element to set the first potential barrier to a level allowing all of the charges to flow from the photoelectric transducer to the charge holder while also applying to said second transfer element a third transfer voltage which sets the second potential barrier to a level such that some, but not all, of the charges flowing into the charge holder can overflow into the charge-voltage converter, and

the drive controller is configured such that, during the charge transfer period, the drive controller applies the second transfer voltage for a period of time that is shorter in duration than a period of time in which the drive controller applies the third transfer voltage.

8. An electronic instrument comprising:

(1) a solid-state image pickup device including a plurality of pixels, each pixel including at least (a) a photoelectric transducer, (b) a charge holder configured to hold a charge that has been transferred from said photoelectric transducer, (c) a charge-voltage converter configured to convert the charge held by said charge holder into a voltage, (d) a first transfer element configured to transfer the charge from said photoelectric transducer to said charge holder by setting a first potential barrier at a boundary between said photoelectric transducer and said charge holder, (e) a second transfer element configured to transfer the charge from said charge holder to said charge voltage converter by setting a second potential barrier at a boundary between said charge holder and said charge voltage converter, and (f) a resetter configured to reset the charge in said charge voltage converter; and

(2) a drive controller configured to control driving of the plurality of pixels, wherein,

the drive controller is configured such that, during a charge transfer period between exposure periods, the drive controller (a) first effects a reset of said charge-voltage converter and said charge holder by applying a reset voltage to said charge-voltage converter while applying a first transfer voltage to the second transfer element to cause the second potential barrier to allow all charges in the charge holder to flow into the charge-voltage converter, and (b) then effects a transfer of charge from said photoelectric transducer to said charge voltage-converter by applying a second transfer voltage to the first transfer element to set the first potential barrier to a level allowing all of the charges to flow from the photoelectric transducer to the charge holder while also applying to said second transfer element a third transfer voltage which sets the second potential barrier to a level such that some, but not all, of the charges flowing into the charge holder can overflow into the charge-voltage converter, and

the drive controller is configured such that, during the charge transfer period, the drive controller applies the second transfer voltage for a period of time that is shorter in duration than a period of time in which the drive controller applies the third transfer voltage.

9. A solid-state image pickup device comprising:

at least one pixel including a photoelectric transducer, a charge holder, a charge-voltage converter, a first transfer element configured to effect transfer of charge from the photoelectric transducer to the charge holder by setting a first potential barrier at a first boundary between the photoelectric transducer and the charge holder, a second transfer element configured to effect transfer of charge from the charge holder to the charge-voltage converter by setting a second potential barrier at a second boundary between the charge holder and the charge-voltage converter, and a reset element configured to reset the charge-voltage converter; and

a drive controller configured to control the driving of the at least one pixel, wherein,

the drive controller is configured such that, during a charge transfer period between exposure periods, the drive controller (a) first effects a reset of said charge-voltage converter and said charge holder by applying a reset voltage to said charge-voltage converter while applying a first transfer voltage to the second transfer element to cause the second potential barrier to allow all charges in the charge holder to flow into the charge-voltage converter, and (b) then effects a transfer of charge from said photoelectric transducer to said charge-voltage converter by applying a second transfer voltage to the first transfer element to set the first potential barrier to a level allowing all of the charges to flow from the photoelectric transducer to the charge holder while also applying to said second transfer element a third transfer voltage which sets the second potential barrier to a level such that some, but not all, of the charges flowing into the charge holder can overflow into the charge-voltage converter, and

the drive controller is configured such that, during the charge transfer period, the drive controller applies the second transfer voltage for a period of time that is shorter in duration than a period of time in which the drive controller applies the third transfer voltage.

10. The solid-state image pickup device of claim 9, wherein the drive controller is configured to apply the second transfer voltage and then apply a third transfer voltage to the second transfer element, the third transfer voltage setting a potential of the second potential barrier at the boundary between said charge holder and said charge voltage converter to a potential which is higher than a potential of said photoelectric transducer in a depleted state.