Optical sensor and signal readout method therefor, and solid-state image pickup device and signal readout method therefor
One of the problems addressed by the present invention is to provide an optical sensor, a solid-state imaging device, and a signal readout method therefor that greatly contribute to a further development of industry and to the realization of a more secure and safe society. One of the solutions provided by the present invention is an optical sensor comprising a light reception element, a storage capacitor for storing charges, and a transfer switch for transferring, to the storage capacitor, a charge generated by light input into the light reception element. The storage capacitor includes a floating diffusion capacitor and a lateral overflow integration capacitor. The transfer switch is an LDD-MOS transistor of which a drain area has a specific impurity concentration.
1. An optical sensor, comprising:
a light receiving element;
a storage capacitor configured to store a charge;
a transfer switch configured to transfer, to the storage capacitor, a charge generated by light input to the light receiving element; and
a pixel signal output line,
wherein the pixel signal output line has a signal readout path connected thereto,
wherein the storage capacitor includes a floating diffusion capacitor (C FD ) and a lateral overflow integration capacitor (C LOFIC ),
wherein the transfer switch includes an LDD-MOS transistor,
wherein a concentration (N D ) of semiconductor impurities in a drain region of the LDD-MOS transistor and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfy the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
wherein a first pixel output signal subjected to charge-to-voltage conversion by the floating diffusion capacitor (C FD ) and a second pixel output signal subjected to charge-to-voltage conversion by a combination of the floating diffusion capacitor (C FD ) and the lateral overflow integration capacitor (C LOFIC ) are input to the signal readout path, and
wherein the first pixel output signal is amplified by an amplification factor larger than 1 when the first pixel output signal is an ultra-high sensitive signal.
2. A multi-pixel optical sensor, comprising:
a row of plurality of two-dimensionally arranged pixel units, each including:
a light receiving element;
a storage capacitor configured to store a charge; and
a transfer switch configured to transfer, to the storage capacitor, a charge generated by light input to the light receiving element,
the storage capacitor including a floating diffusion capacitor (C FD ) and a lateral overflow integration capacitor (C LOFIC ),
the transfer switch including an LDD-MOS transistor,
a concentration (N D ) of semiconductor impurities in a drain region of the LDD-MOS transistor and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfying the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
a pixel signal output line, to which each of the plurality of two-dimensionally arranged pixel units is sequentially connected; and
a signal readout path unit configured to execute amplification by using an amplification factor larger than 1 and another amplification factor different from the amplification factor in a different manner, the signal readout path unit being connected to the pixel signal output line at a position downstream of a position at which a last pixel unit in the row of plurality of two-dimensionally arranged pixel units is connected to the pixel signal output line,
wherein a first pixel output signal subjected to charge-to-voltage conversion by the floating diffusion capacitor (C FD ) and a second pixel output signal subjected to charge-to-voltage conversion by a combination of the floating diffusion capacitor (C FD ) and the lateral overflow integration capacitor (C LOFIC ) are input to the signal readout path.
3. A signal readout method to be executed by an optical sensor, the optical sensor including, for each pixel unit:
a light receiving element;
a storage capacitor configured to store a charge; and
a transfer switch configured to transfer, to the storage capacitor, a charge generated by light input to the light receiving element,
the storage capacitor including a floating diffusion capacitor and a lateral overflow integration capacitor,
the transfer switch including an LDD-MOS transistor,
a concentration (N D ) of semiconductor impurities in a drain region of the LDD-MOS transistor and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfying the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
the optical sensor further including:
a pixel signal output line, to which each pixel unit is connected; and
a signal readout path connected to the pixel signal output line,
the signal readout method comprising:
subjecting, by the floating diffusion capacitor, an amount of charges that contribute to readout to charge-to-voltage conversion so as to form a first pixel output signal;
subjecting, by a combination of the floating diffusion capacitor and the lateral overflow integration capacitor, the amount of charges that contribute to readout to charge-to-voltage conversion so as to form a second pixel output signal;
inputting the first pixel output signal and the second pixel output signal to the signal readout path; and
amplifying the first pixel output signal in the signal readout path by a plurality of amplifiers including at least one amplifier having an amplification factor larger than 1.
4. An image pickup device, comprising:
a plurality of pixel units each including:
a light receiving element (PD);
a switch for transfer (T);
a switch for overflow (S);
a switch for resetting (R);
the light receiving element (PD), the switch for transfer (T), the switch for overflow (S), and the switch for resetting (R) are connected in series in the stated order,
a floating diffusion capacitor (C FD ) and a source-follower switch (SF), which are connected to a line between the switch for transfer (T) and the switch for overflow ( 5 ); and
a lateral overflow integration capacitor (C LOFIC ), which is connected to a line between the switch for overflow (S) and the switch for resetting (R),
the source-follower switch (SF) including a MOS transistor,
a concentration (N D ) of semiconductor impurities in a drain region in the switch for transfer (T) and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfying the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
the light receiving elements (PD) of the plurality of pixel units forming an array of two-dimensionally arranged pixels;
a pixel row output signal line, to which the plurality of pixel units are sequentially connected; and
a reading unit connected to the pixel row output signal line,
wherein a first pixel output signal subjected to charge-to-voltage conversion by the floating diffusion capacitor (C FD ) and a second pixel output signal subjected to charge-to-voltage conversion by a combination of the floating diffusion capacitor (C FD ) and the lateral overflow integration capacitor (C LOFIC ) are input to the reading unit, and
wherein the first pixel output signal is amplified in a signal readout path by a plurality of amplifiers including at least one amplifier having an amplification factor larger than 1.
5. A signal readout method for an image pickup device, the signal readout method comprising:
preparing an image pickup device including:
a plurality of pixel units each including:
a light receiving element (PD);
a switch for transfer (T);
a switch for overflow (S);
a switch for resetting (R);
the light receiving element (PD), the switch for transfer (T), the switch for overflow (S), and the switch for resetting (R) are connected in series in the stated order,
a floating diffusion capacitor (C FD ) and a source-follower switch (SF), which are connected to a line between the switch for transfer (T) and the switch for overflow (S); and
a lateral overflow integration capacitor (C LOFIC ), which is connected to a line between the switch for overflow (S) and the switch for resetting (R),
the source-follower switch (SF) including a MOS transistor,
a concentration (N D ) of semiconductor impurities in a drain region in the switch for transfer (T) and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfying the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
the light receiving elements (PD) of the plurality of pixel units forming an array of two-dimensionally arranged pixels;
a pixel row output signal line, to which the plurality of pixel units are sequentially connected; and
a reading unit connected to the pixel row output signal line;
subjecting, by the floating diffusion capacitor (C FD ), an amount of charges that contribute to readout to charge-to-voltage conversion so as to form a first pixel output signal;
subjecting, by a combination of the floating diffusion capacitor (C FD ) and the lateral overflow integration capacitor (C LOFIC ), the amount of charges that contribute to readout to charge-to-voltage conversion so as to form a second pixel output signal;
inputting the first pixel output signal and the second pixel output signal to a signal readout path; and
amplifying the first pixel output signal in the signal readout path by a plurality of amplifiers including at least one amplifier having an amplification factor larger than 1.
6. An optical sensor, comprising:
(1) a pixel unit having a photoelectric conversion function,
the pixel unit including:
a storage capacitor configured to store a charge subjected to photoelectric conversion; and
a transfer switch configured to transfer the charge to the storage capacitor;
the storage capacitor including a floating diffusion capacitor (C FD ) and a lateral overflow integration capacitor (C LOFIC ),
the transfer switch including an LDD-MOS transistor,
a concentration (N D ) of semiconductor impurities in a drain region of the LDD-MOS transistor and a concentration (N) of semiconductor impurities in a diffusion region provided adjacent to the drain region satisfying the following relationships:
1 <N/N D ≤100 (1); and
0< N≤ 1.0×10 20 cm −3 (2),
(2) a pixel signal output line connected to the pixel unit; and
(3) a signal readout path connected to the pixel signal output line,
wherein a first pixel output signal subjected to charge-to-voltage conversion by the floating diffusion capacitor (C FD ) and a second pixel output signal subjected to charge-to-voltage conversion by a combination of the floating diffusion capacitor (C FD ) and the lateral overflow integration capacitor (C LOFIC ) are input to the signal readout path, and
wherein the first pixel output signal is amplified by an amplification factor larger than 1 when the first pixel output signal is an ultra-high sensitive signal.