Solid-state imaging apparatus and driving method thereof
View Patent ↗Each unit pixel includes a photodiode, a reading selection transistor, a reading transistor, an amplifying transistor, a reset transistor, and a horizontal selection transistor, and thus a MOS image sensor of a dot-sequential reading 5-Tr type is formed. The reading selection transistor and the reading transistor are formed with a two-layer gate structure, and gate potential of the reading selection transistor and the reading transistor is set to a negative potential. Thereby, a lower layer of a gate region of the reading transistor and the reading selection transistor is controlled to a negative potential. Thus, depletion in the lower layer region is suppressed to reduce leakage current.
1. A solid-state imaging apparatus comprising:
a plurality of unit pixels arranged in a vertical direction and a horizontal direction in a two-dimensional matrix form; and, within said unit pixels,
photoelectric converting means for accumulating a signal charge according to an amount of light received;
a floating diffusion portion for extracting the signal charge obtained by said photoelectric converting means;
an amplifying transistor for extracting a potential variation by the signal charge of said floating diffusion portion;
a reading transistor for transferring the signal charge accumulated by said photoelectric converting means to the floating diffusion portion on the basis of a line selection signal; and
a reading selection transistor for controlling said reading transistor on the basis of a pixel selection signal;
wherein gate potential of at least one of said reading transistor and said reading selection transistor which is on a side of said photoelectric converting means is set to a negative potential with respect to a well region.
2. A solid-state imaging apparatus as claimed in claim 1 ,
wherein both gate potential of said reading transistor and gate potential of said reading selection transistor are set to a negative potential with respect to the well region.
3. A solid-state imaging apparatus as claimed in claim 1 ,
wherein said reading transistor and said reading selection transistor are connected in series with each other in a channel direction between said photoelectric converting means and the floating diffusion portion, and gate electrodes of said reading transistor and said reading selection transistor are formed in a state of partly overlapping each other.
4. A solid-state imaging apparatus as claimed in claim 1 , further comprising:
a vertical scanner for scanning said unit pixels in a vertical direction to select each of said unit pixels;
a horizontal scanner for scanning said unit pixels in a horizontal direction to select each of said unit pixels; and
an electronic shutter scanner for scanning said unit pixels and performing electronic shutter operation for each of said unit pixels.
5. A solid-state imaging apparatus as claimed in claim 4 , further comprising:
a reset transistor for resetting the signal charge applied to said floating diffusion portion; and
a horizontal selection transistor for sequentially selecting said unit pixels in the horizontal direction.
6. A solid-state imaging apparatus as claimed in claim 5 , further comprising:
a horizontal selection line arranged in correspondence with each column of said unit pixels for transmitting a reset pulse for driving said reset transistor, a horizontal selection pulse for driving said horizontal selection transistor, and a reading pulse for driving said reading selection transistor; and
a vertical selection line arranged in correspondence with each row of said unit pixels for transmitting a line selection pulse for driving said reading transistor.
7. A solid-state imaging apparatus as claimed in claim 5 , further comprising:
a reset/reading line arranged in correspondence with each column of said unit pixels for transmitting a reset pulse for driving said reset transistor and a reading pulse for driving said reading selection transistor;
a horizontal selection line arranged in correspondence with each column of said unit pixels for transmitting a horizontal selection pulse for driving said horizontal selection transistor; and
a vertical selection line arranged in correspondence with each row of said unit pixels for transmitting a line selection pulse for driving said reading transistor.
8. A solid-state imaging apparatus as claimed in claim 5 , further comprising:
a reading line arranged in correspondence with each column of said unit pixels for transmitting a reading pulse for driving said reading selection transistor;
a horizontal selection line arranged in correspondence with each column of said unit pixels for transmitting a reset pulse for driving said reset transistor and a horizontal selection pulse for driving said horizontal selection transistor; and
a vertical selection line arranged in correspondence with each row of said unit pixels for transmitting a line selection pulse for driving said reading transistor.
9. A solid-state imaging apparatus as claimed in claim 5 , further comprising:
an I/V converter circuit for converting a current signal read from each unit pixel on a dot-sequential basis by the scanning of said vertical scanner and said horizontal scanner into a voltage signal; and
a CDS circuit for performing correlated double sampling processing.
10. A driving method of a solid-state imaging apparatus, said solid-state imaging apparatus comprising:
a plurality of unit pixels arranged in a vertical direction and a horizontal direction in a two-dimensional matrix form; and, within said unit pixels, photoelectric converting means for accumulating a signal charge according to an amount of light received; a floating diffusion portion for extracting the signal charge obtained by said photoelectric converting means; an amplifying transistor for extracting a potential variation by the signal charge of said floating diffusion portion; a reading transistor for transferring the signal charge accumulated by said photoelectric converting means to the floating diffusion portion on the basis of a line selection signal; and a reading selection transistor for controlling said reading transistor on the basis of a pixel selection signal;
wherein gate electrodes of said reading transistor and said reading selection transistor are formed by using two electrode layers different from each other, gate potential of at least the transistor on a side of the photoelectric converting means is set to a negative potential, and the gate electrode of said transistor on the side of the photoelectric converting means is controlled to the negative potential in at least a part of a non-selection period.
11. A driving method of a solid-state imaging apparatus as claimed in claim 10 ,
wherein both gate potential of said reading transistor and gate potential of said reading selection transistor are set to a negative potential in at least the part of the non-selection period.
12. A driving method of a solid-state imaging apparatus as claimed in claim 10 ,
wherein said solid-state imaging apparatus further includes:
a vertical scanner for scanning said unit pixels in a vertical direction to select each of said unit pixels;
a horizontal scanner for scanning said unit pixels in a horizontal direction to select each of said unit pixels; and
an electronic shutter scanner for scanning said unit pixels and performing electronic shutter operation for each of said unit pixels.
13. A driving method of a solid-state imaging apparatus as claimed in claim 12 ,
wherein said solid-state imaging apparatus further includes:
a reset transistor for resetting the signal charge applied to said floating diffusion portion; and
a horizontal selection transistor for sequentially selecting said unit pixels in the horizontal direction.
14. A driving method of a solid-state imaging apparatus as claimed in claim 13 , further comprising the steps of:
transmitting a reset pulse for driving said reset transistor, a horizontal selection pulse for driving said horizontal selection transistor, and a reading pulse for driving said reading selection transistor by a horizontal selection line arranged in correspondence with each column of said unit pixels; and
transmitting a line selection pulse for driving said reading transistor by a vertical selection line arranged in correspondence with each row of said unit pixels.
15. A driving method of a solid-state imaging apparatus as claimed in claim 14 ,
wherein a horizontal selection line in an m-th column supplies the horizontal selection pulse to a gate of a horizontal selection transistor in an m-th pixel column, supplies the reading pulse to a gate of a reading selection transistor in the m-th pixel column, and supplies the reset pulse to a gate of a reset transistor in an (m+1)th pixel column; and
a vertical selection line in an n-th row supplies the line selection pulse to a gate of a reading transistor in an n-th pixel row.
16. A driving method of a solid-state imaging apparatus as claimed in claim 13 , further comprising the steps of:
transmitting a reset pulse for driving said reset transistor and a reading pulse for driving said reading selection transistor by a reset/reading line arranged in correspondence with each column of said unit pixels;
transmitting a horizontal selection pulse for driving said horizontal selection transistor by a horizontal selection line arranged in correspondence with each column of said unit pixels; and
transmitting a line selection pulse for driving said reading transistor by a vertical selection line arranged in correspondence with each row of said unit pixels.
17. A driving method of a solid-state imaging apparatus as claimed in claim 16 ,
wherein a horizontal selection line in an m-th column supplies the horizontal selection pulse to a gate of a horizontal selection transistor in an m-th pixel column;
a reset/reading line in the m-th column supplies the reading pulse to a gate of a reading selection transistor in the m-th pixel column and supplies the reset pulse to a gate of a reset transistor in an (m+1)th pixel column; and
a vertical selection line in an n-th row supplies the line selection pulse to a gate of a reading transistor in an n-th pixel row.
18. A driving method of a solid-state imaging apparatus as claimed in claim 13 , further comprising the steps of:
transmitting a reading pulse for driving said reading selection transistor by a reading line arranged in correspondence with each column of said unit pixels;
transmitting a reset pulse for driving said reset transistor and a horizontal selection pulse for driving said horizontal selection transistor by a horizontal selection line arranged in correspondence with each column of said unit pixels; and
transmitting a line selection pulse for driving said reading transistor by a vertical selection line arranged in correspondence with each row of said unit pixels.
19. A driving method of a solid-state imaging apparatus as claimed in claim 18 ,
wherein a horizontal selection line in an m-th column supplies the horizontal selection pulse to a gate of a horizontal selection transistor in an m-th pixel column, and supplies the reset pulse to a gate of a reset transistor in an (m+1)th pixel column;
a reading line in the m-th column supplies the reading pulse to a gate of a reading selection transistor in the m-th pixel column; and
a vertical selection line in an n-th row supplies the line selection pulse to a gate of a reading transistor in an n-th pixel row.