WO2004062274A1 - 固体撮像装置 - Google Patents
固体撮像装置 Download PDFInfo
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- WO2004062274A1 WO2004062274A1 PCT/JP2003/016550 JP0316550W WO2004062274A1 WO 2004062274 A1 WO2004062274 A1 WO 2004062274A1 JP 0316550 W JP0316550 W JP 0316550W WO 2004062274 A1 WO2004062274 A1 WO 2004062274A1
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- 238000003384 imaging method Methods 0.000 title claims abstract description 44
- 238000001514 detection method Methods 0.000 claims abstract description 60
- 238000006243 chemical reaction Methods 0.000 claims abstract description 41
- 230000007704 transition Effects 0.000 claims description 15
- 230000004044 response Effects 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims 2
- 230000035945 sensitivity Effects 0.000 abstract description 4
- 238000009825 accumulation Methods 0.000 description 18
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- 230000003321 amplification Effects 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 238000003199 nucleic acid amplification method Methods 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 206010034960 Photophobia Diseases 0.000 description 3
- 208000013469 light sensitivity Diseases 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
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- 241000282376 Panthera tigris Species 0.000 description 1
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- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
-
- 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
-
- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/50—Control of the SSIS exposure
- H04N25/57—Control of the dynamic range
- H04N25/571—Control of the dynamic range involving a non-linear response
- H04N25/573—Control of the dynamic range involving a non-linear response the logarithmic type
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/65—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to reset noise, e.g. KTC noise related to CMOS structures by techniques other than CDS
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
- H04N25/779—Circuitry for scanning or addressing the pixel array
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
- H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
- H04N3/14—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices
- H04N3/15—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices for picture signal generation
- H04N3/1506—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices for picture signal generation with addressing of the image-sensor elements
- H04N3/1512—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices for picture signal generation with addressing of the image-sensor elements for MOS image-sensors, e.g. MOS-CCD
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
- H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
- H04N3/14—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices
- H04N3/15—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices for picture signal generation
- H04N3/155—Control of the image-sensor operation, e.g. image processing within the image-sensor
Definitions
- the present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device generally called as an image sensor.
- an amplification type solid-state imaging device that has an amplifying function for each pixel and reads it out by a scanning circuit, in particular, a CMO (Complementary Metal Oxide Semiconductor) type driving circuit and signal processing circuit around the pixel line.
- Type image sensors are widely used.
- the CMO S type image sensor it is necessary to form a photoelectric conversion unit, an amplification unit, a pixel selection unit, and the like in one pixel, and usually a photoelectric composed of a photodiode (hereinafter sometimes abbreviated as PD).
- PD photodiode
- Tr MOS transistors
- Figure 1 shows the configuration of one pixel in the case of PD + 3 Tr system in OA. Wherein one photodiode, 3 detection node, 4 reset unit consisting of MO S transistor, 5 power supply voltage V D is applied at the drain.
- Reference numeral 6 denotes an amplifying unit made up of MOS transistors
- 7 denotes a pixel selection unit made up of MOS transistors
- 8 denotes a signal line
- ⁇ R s denotes a reset clock
- ⁇ 3 denotes a pixel selection clock.
- Figure 10 0 shows the operation of Figure 1 OA in potentiore.
- FIGs. 1 1 A and 1 IB in order to increase the dynamic range of the incident light, a method has been proposed in which the photocurrent is logarithmically compressed and read.
- Figure 11A shows this example with a circuit configuration with one pixel.
- 1 is a photodiode
- 3 is a detection node
- 4 is a logarithmic compression transistor
- 5 is a drain
- the power supply voltage V D is applied.
- FIG. 6 is an amplifying unit
- 7 is a pixel selecting unit
- 8 is a signal line
- ⁇ 3 is a pixel selecting clock
- V D is a power supply voltage.
- the major difference from the case of Fig. 10A is that a DC (direct current) potential V D is applied to the gate of transistor 4 and the logarithmic compression is performed without performing a reset operation. This operation will be described below.
- Fig. 11B shows the operation of transistor 4 in Fig. 11A in terms of a potential relationship.
- the gate voltage of transistor 4 is fixed at DC potential V D , so the potential is constant: ⁇ (H).
- the transistor 4 performs a weak inversion operation, that is, an operation in which the subthreshold current Isubth flows. Since the source potential V s is changed to sub Suretsushorudo current Isubth equals to the photocurrent Ip, after all, source over the ground potential V s is proportional to log (Ip), i.e. a value obtained by the photocurrent logarithmic transformation. This makes it possible to respond over a very wide range of incident light, and to achieve a very wide dynamic range.
- the logarithmic conversion type image sensor shown in Fig. 1 1 A and 1 IB is a device that detects the steady state in which photocurrent and subthreshold current are balanced. In low incident light quantity, it is shown in Fig. 10 A and 1 OB.
- the method of increasing the signal charge by increasing the accumulation time like the accumulation type image sensor cannot be used.
- the lower limit value Itnin of the photocurrent that can be logarithmically converted is restricted by the photodiode current, an increase in dark current due to a rise in temperature causes a significant decrease in low-light sensitivity. For these reasons, the low-light sensitivity of a logarithmic conversion image sensor is usually inferior to that of a storage imager.
- FIG. 12 A shows the configuration of one pixel.
- 1 is a photodiode
- 3 is a detection node
- 4 is a reset unit
- 5 is a drain
- the power supply voltage V D is applied.
- Reference numeral 6 denotes an amplification unit
- 7 denotes a pixel selection unit
- 8 denotes a signal line
- ⁇ s denotes a pixel selection clock.
- a power source voltage V D and a voltage V H sufficiently higher than the power source voltage V D are alternately applied to the gate V G of the reset unit 4 through a switch 9 at a constant cycle.
- the operation of Fig. 1 2A is shown by potential in Fig. 1 2B, and by timing in Fig. 1 2C.
- FIGS. 1A, 1 2 B, and 1 2 C first, in the period T 2 , the voltage V H is applied to the gate V G of the reset unit 4 by the switch 9.
- the potential ⁇ ( ⁇ ⁇ ) under the gate of the reset unit 4 becomes deeper than the power supply voltage V D , and the potential of the detection node 3 is reset to the power supply voltage V D.
- the supply voltage is applied to V D to the gate V G of the reset unit 4 by switch 9 in the period 1 ⁇ .
- the potential G (V D ) under the gate of the reset unit 4 becomes shallower than the power supply voltage V D , and the potential of the detection node 3 is in a floating state.
- the amount of decrease is proportional to the incident light intensity and the accumulation period. Therefore, in the accumulation for a certain period, the change amount ⁇ Vs 1 of the potential V s of the detection node 3 is proportional to the incident light intensity.
- the potential V s of the detection node 3 is a certain potential value ⁇ .
- the reset unit 4 performs a weak inversion operation, that is, an operation in which the subthreshold current Isubth flows.
- the potential V s of the detection node 3 is the above value ⁇ so that the subthreshold current Isubth becomes equal to the photocurrent Ip. Since changes to the change in AV S 2 from, eventually, the value AV S 2 is proportional to log (Ip), a value of immediate Chi photocurrent log transformed.
- an object of the present invention is to provide a solid-state imaging device that can solve various problems as described above and achieve both a wide dynamic range and high low-light sensitivity.
- a photodiode and a first transistor are provided in series between the ground and the drain, and a signal corresponding to a current or a charge generated in the photodiode in response to light input is transmitted to the photodiode.
- a signal corresponding to a current or a charge generated in the photodiode in response to light input is transmitted to the photodiode.
- a solid-state imaging device comprising a control unit that alternately and repeatedly performs a linear operation period for obtaining a photoelectric conversion signal
- first level and second level are set to a level where the signal charge potential becomes deeper and shallower, respectively, just below the gate of the first transistor. Just do it.
- first level and second level correspond to high level and low level respectively.
- the linear operation period in which the gate potential is set to the second level and a linear photoelectric conversion signal is obtained is alternately repeated.
- a photoelectric conversion signal logarithmically converted can be obtained at the detection node. Therefore, a logarithmic signal with a wide dynamic range is output by extracting the signal from the detection node and transferring it.
- a linear photoelectric conversion signal can be obtained at the detection node. Therefore, by extracting the signal from the detection node and transferring it, a linear signal with low illuminance and high sensitivity is output. Therefore, according to this solid-state imaging device, both a wide dynamic range and high low illuminance sensitivity can be achieved.
- the photo diode and the detection node are connected with force S. That is, one terminal of the photodiode and the detection node may be short-circuited.
- a second transistor is connected between the photodiode and the detection node.
- the second transistor since the second transistor is connected between the photodiode and the detection node, the capacitance of the detection node can be reduced, and the charge-voltage conversion during the rare type operation period. Efficiency can be increased.
- the photodiode has a buried channel structure.
- the photodiode since the photodiode has a buried channel structure, the dark current generated in the photodiode can be greatly reduced. Therefore, the lower limit of the photoelectric current that can be logarithmically converted can be expanded during the logarithmic operation period. Also, during the linear operation period, dark current noise Can be reduced.
- the logarithmic operation period and the linear operation period are alternately repeated every frame, and the detection node potential is read out as a linear signal immediately before the transition from the linear operation period to the logarithmic operation period.
- Control is performed so that the detection node potential is read out as a logarithmic signal within the logarithmic operation period after a lapse of a certain period after transition to the logarithmic operation period.
- the logarithmic operation period and the linear operation period are alternately repeated for each frame.
- the photoelectrically converted charge starts to be accumulated in the detection node.
- the detection node is charged most. A lot is also accumulated. If the charge is read out as a linear signal, a highly sensitive output can be obtained.
- the charge can be read out from the detection node as a logarithmic signal within the logarithmic operation period after a certain period of time has elapsed since the transition to the logarithmic operation period.
- a first frame memory for storing a signal read from the detection node of each pixel within the logarithmic operation period under a condition in which light is irradiated to each pixel at a uniform intensity
- a subtracting unit that subtracts and outputs a signal recorded in the first frame memory in association with each pixel from a signal read in an arbitrary frame.
- readout is performed from the detection node of each pixel during the logarithmic operation period ⁇ ⁇ under the condition that light is irradiated with a uniform intensity to each pixel.
- the subtracting unit subtracts the signal recorded in the first frame memory from the signal read during the logarithmic operation period in association with each pixel and outputs the result.
- a second frame memory that records the signal read from the detection node every time immediately before the transition from the logarithmic type operation period to the rare type operation period under the subject imaging condition, and a logarithm from the linear type operation period.
- a subtractor for subtracting the signal recorded in the second frame memory from the signal read from the detection node immediately before the transition to the mold operation period in association with each pixel.
- the special provision is to provide
- FIGS. 1A and IB are two-dimensional images of an embodiment to which the solid-state imaging device of the present invention is applied. It is a figure which shows the circuit structure of the pixel used for a sensor.
- FIGS. 1 and 1B are diagrams showing potential distributions in the logarithmic operation of the pixels shown in FIGS. 1 and 1B.
- 3A and 38 are diagrams showing the potential distribution of the pixel shown in FIGS. 18 and 1B during a reair operation.
- 4A, 4B, and 4C are cross-sectional views when the pixel shown in FIGS. 1A and 1B is formed on a semiconductor substrate.
- FIG. 5 is a diagram showing a circuit configuration of a two-dimensional image sensor according to an embodiment to which the solid-state imaging device of the present invention is applied.
- FIG. 6 is a diagram showing the operation timing of the two-dimensional image sensor shown in FIG. 7A, 7B, and 7C are diagrams showing logarithmic signals and reureer signals obtained by the present invention in relation to incident light intensity.
- 8A and 8B are diagrams showing a system for performing image signal processing in the two-dimensional image sensor of the present invention.
- 9A, 9B, and 9C are diagrams showing other examples of operation timing in the two-dimensional image sensor of the present invention.
- FIGS. 10A and 1OB are diagrams for explaining the operation of the pixel in the conventional linear conversion type solid-state imaging device.
- FIGS. 11A and 11B are diagrams for explaining the operation of the pixels of the conventional logarithmic conversion type solid-state imaging device.
- 12A, 12B, 12C, and 12D are diagrams for explaining the operation of a pixel in a solid-state imaging device that adds a conventional transformation characteristic and a logarithmic transformation characteristic.
- FIG. 5 is a diagram showing a two-dimensional image sensor 10 according to an embodiment of the present invention in a circuit configuration with 2 ⁇ 2 pixels.
- 11 is a pixel having a circuit configuration described later
- 12 is a line for a reset clock applied to the first transistor
- 13 is a line for a pixel selection clock (
- 14 Is the line for the signal Vsig
- 15 is the supply voltage V D.
- the reset clock ⁇ R and the pixel selection clock ⁇ s are sequentially output in the vertical direction in units of rows by the reset scanning circuit 16 and the vertical readout scanning circuit 17, respectively.
- the signal Vsig read from each pixel in units of rows is sequentially read out in the horizontal direction to the horizontal signal line 18 by the signal from the horizontal scanning circuit 19.
- the signal from the horizontal signal line 18 is output as an output signal OS via the amplifier circuit 20.
- the overall operation of the two-dimensional image sensor 10 is controlled by a CPU (Central Processing Unit) 90 as an example of a control unit.
- a CPU Central Processing Unit
- FIG. 1A illustrates the circuit configuration of each pixel 11 shown in FIG.
- 1 is a photodiode
- 3 is a detection node
- 4 is a first transistor
- 5 is a drain
- a power supply voltage V D is applied.
- 6 amplification unit comprising a MO S transistor
- 7 pixel selection unit consisting of MO S transistor
- phi beta represents the reset clock
- phi 3 is pixel selection clock.
- Photodiode 1 and first transistor 4 are provided in series between daland (ground) and drain 5. Using this pixel 11, logarithmic operation and linear operation are performed as follows.
- Fig. 2 (b) shows the potential relationship when logarithmic operation is performed using the pixel in Fig. 1A.
- the gate of the first transistor 4 is held at the DC level, and its potential is a constant value (H).
- the source potential V s of the first transistor 4 becomes deeper than the constant value G (H)
- the transistor 4 performs a weak inversion operation and a subthreshold current Isubth flows.
- the source potential V s changes so that the subthreshold current Isubth becomes equal to the photocurrent Ip.
- V S K 1 ⁇ log (Ip) + 2 ... (1)
- the source potential V s is a value V s (log) obtained by logarithmically converting the photocurrent I p.
- K 2 are constants. This makes it possible to respond over a very wide range of incident light, and to achieve a very wide dynamic range.
- Fig. 3 (b) shows the potential relationship when linear operation is performed using the pixel in Fig. 1A.
- a pulse ⁇ is applied to the first transistor 4.
- the gate of the first transistor 4 is held at a high level for a sufficiently long period until signal accumulation starts, and the source potential V s is the photocurrent Ip and the suppression threshold current.
- the value V s (log) is equal to Isubth.
- the photocurrent I p is linearly converted.
- ⁇ is the accumulation time
- ⁇ is the capacity of the detection node 3 shown in FIG. 1A.
- FIG. 1B illustrates a circuit configuration different from that of FIG. 1A of each pixel 11 shown in FIG.
- the circuit configuration of FIG. 1B is different from that of FIG. 1A in that a second transistor 2 is interposed between the photodiode 1 and the detection node 3.
- a DC potential ⁇ ⁇ is applied to the gate of transistor 2.
- Fig. 2 (b) shows the potential relationship when logarithmic operation is performed using the pixels in Fig. 1 (b).
- Photodiode 1 the photocurrent I p is generated, but since the second gut potential Trang register 2 phi tau is a DC potential, the steady state current corresponding to the second tigers Njisuta 2 in photocurrent I [rho The current of photodiode 1 is held at a constant value.
- the potential phi kappa gate of the first transistor 4 is a DC voltage flows sub Threading Scholl de current Isubth.
- the V s of the detection node 3 is a value obtained by logarithmically converting the photocurrent I p V s (log). This makes it possible to respond over a very wide range of incident light, and to achieve a very wide dynamic range.
- FIG. 3B shows the potential relationship when the linear operation is performed using the pixels in Figure 1B.
- Photodiode 1 generates photocurrent I p, but the potential ⁇ ⁇ of the gate of second transistor 2 is a DC potential, so that in a steady state, a current corresponding to photocurrent I p flows through the gate.
- the potential of diode 1 is held constant.
- a pulse ⁇ is applied to the gate of the first transistor 4.
- the first transistor 4 is held at a high level for a sufficiently long period before the signal accumulation starts, and the source potential becomes a value V s (log) at which the photocurrent Ip and the subthreshold current become equal.
- ⁇ 3 ( ⁇ ⁇ AT) / C 2 ... (3)
- the photocurrent Ip is linearly converted.
- ⁇ is the accumulation time and C 2 is the capacity of the detection node 3 shown in FIG. 1B.
- FIG. 4A schematically shows a cross-sectional structure when the pixel shown in Fig. 1A is fabricated on a semiconductor substrate.
- FIG. 4B and FIG. 4C schematically show a cross-sectional structure when the pixel of FIG. 1B is fabricated on a semiconductor substrate.
- 101 is a semiconductor substrate
- 102 is a pixel isolation region
- 103 is a power sword of photodiode 1 (see FIGS. 1A and 1B)
- 104 is a drain 5
- 111 is a first transistor 4.
- 105 is an independent detection node and is separated from the force sword 103 of the photodiode 1 via the second transistor 112.
- FIGS. 4A schematically shows a cross-sectional structure when the pixel shown in Fig. 1A is fabricated on a semiconductor substrate.
- FIG. 4B and FIG. 4C schematically shows a cross-sectional structure when the pixel of FIG. 1B is fabricated on a semiconductor substrate.
- 101 is a semiconductor
- photodiode 1 has a simple PN junction structure and is formed at the same time as drain 104.
- the photodiode has a buried channel structure and is formed separately from the drain. The That is, the signal charge storage layer 106 is formed on the substrate side, and the high concentration pinning layer 107 is formed on the surface side.
- buried channel structure photodiodes can significantly reduce the drain current compared to simple PN junction structures. This makes it possible to expand the lower limit Imin of the photocurrent that can be logarithmically converted during logarithmic operation. In addition, dark current noise can be reduced even in linear operation.
- FIG. 6 shows the operation timing of the two-dimensional image sensor 10 shown in FIG.
- ⁇ ⁇ (1) and ⁇ ⁇ (2) are the reset clocks in the first row and the second row
- ⁇ 3 (1) and s (2) are the pixels in the first row and the second row.
- the selected clock, OS represents the output signal.
- 1 H represents one horizontal scanning period
- IV represents one frame period. Focusing on the pixels in the first row, First, in the frame as a logarithmic operation period (shown at the left end in Fig. 6), the reset clock, that is, the gate potential ⁇ R (1) of the first transistor 4 (see Figs. 1A and 1B) is set to the high level. This is maintained and the photoelectric conversion signal logarithmically converted to the detection node 3 is obtained.
- the gate potential ⁇ ⁇ (1) of the first transistor 4 is changed from a high level to a low level, and a transition is made to a linear type operation period. Then, by accumulating the photoelectrically converted charge in the detection node 3 only for one frame period, a linear photoelectric conversion signal is obtained at the detection node 3.
- the pixel selection clock ⁇ 3 (1) is turned on immediately before the gate potential ⁇ R (1) changes from the high level to the full level, and the logarithmically converted photoelectric conversion signal Log (l) is output as the output signal OS. To do.
- the output signal OS includes a logarithmically converted photoelectric conversion signal Log (1), Log (2), etc. in 1 H units, a linear photoelectric conversion signal Lin (1),
- FIG. 7A and 7B show the logarithmically converted photoelectric conversion signal Vs (log) and the linear photoelectric conversion signal Vs (lin) obtained as the potential of the detection node 3 of the pixel. It is the figure which expressed logarithm log (Ip) on the horizontal axis.
- the converted photoelectric conversion signal Vs (log) does not depend on the length of the readout period, which in the case of Fig. 6 is one frame period (referred to as "IV period" as appropriate).
- the output of the linear photoelectric conversion signal Vs (lin) becomes larger as the IV period becomes longer because the IV period becomes the signal accumulation period.
- Figure 7A corresponds to the case where the IV period is long
- Figure 7B corresponds to the case where the IV period is short.
- the value of Vs (log) with respect to the incident light intensity is limited by the dark current, but the upper P ⁇ value is extremely high compared to the linear photoelectric conversion signal Vs (lin).
- the value of the linear photoelectric conversion signal Vs (lin) with respect to the incident light intensity is the form in which the signal obtained by the re-transformation is superimposed on the value of the previous logarithmic conversion photoelectric conversion signal Vs (log).
- ⁇ Vs Vs (lin) —Vs (log).
- Fig. 7A when the accumulation period is long, the value of A Vs is sufficiently larger than Vs (log), and Vs (lin) is a linear graph that is almost the same as A Vs.
- Fig. 7B when the accumulation period is short as shown in Fig. 7B, the value of ⁇ Vs is lower than Vs (log) on the low incident light intensity side, and Vs (lin) is a non-linear graph that changes significantly from ⁇ Vs. It becomes.
- FIG. 7C is a diagram showing the output signal in the image sensor according to the present invention with the logarithm log (I p) of the incident light intensity as the horizontal axis.
- the solid line indicates the average value ⁇ O S) of the entire pixel
- the dotted line indicates the value O S ij of a specific pixel (the address is the pixel in the i-th row and the j-th column).
- the response of each pixel is accompanied by a specific offset variation A Vij, and the value of A Vij varies from pixel to pixel. Therefore, if the response of each pixel is used as it is as a video signal, ⁇ V ij will greatly deteriorate the image quality as a rough fixed pattern noise.
- FIG. 8A illustrates a circuit configuration 30 for solving the problem related to the fixed pattern noise.
- this circuit configuration 30 an analog signal of the image sensor 3 1 (same as the image sensor 10 shown in FIG.
- the signal from the AD conversion 33 is branched, and one is directly guided to the difference circuit 37 as an example of the subtracting unit, and the other is sent through the frame memory 34 as the first frame memory to the difference circuit 37. Led to.
- a logarithmically converted photoelectric conversion signal is output from the image sensor 31 under the condition that light is irradiated with a certain intensity (indicated as Ipi in FIG. 7C) for each pixel, The signal is recorded in the frame memory 34 in units of pixels. As a result, offset variation A Vij for each pixel is recorded in the frame memory 34.
- the difference circuit 37 subtracts the signal recorded in the frame memory 34 from the signal read out in an arbitrary frame under the subject imaging condition in association with each pixel.
- offset variation A Vij is canceled in all the frame signals, that is, the logarithmically converted photoelectric conversion signal OS (log) and the linear photoelectric conversion signal OS (lin), and an image signal without a fixed Zalanoze can be obtained. it can.
- the linear photoelectric conversion signal OS (lin) in Fig. 8A has the offset variation ⁇ V ij canceled, but the logarithmic and linear characteristics are added. Yes. For this reason, if the linear characteristic value is sufficiently larger than the logarithmic characteristic value as shown in Fig. 7A, it is almost normal, and there is no problem. However, as shown in Fig. 7B, the linear characteristic value becomes smaller at some incident light levels. When the value is lower than the logarithmic characteristic value, it becomes a problem because the characteristic is not reusable Fig. 8B illustrates another circuit configuration 40 for solving the problem related to the linear characteristic. In 40, the analog signal from the image sensor 31 according to the present invention is converted into a digital signal by the AD converter 33.
- the signal from the 80 converter 3 3 is branched into three, and the first signal The branch is directly led to the difference circuit 3 7 as an example of the subtracting unit 7.
- the second branch is the difference circuit 3 via the frame memory 3 4 as the first frame memory and the switching switch 3 6.
- the third branch is used as the second frame memory.
- the frame memory 3 5 and the switching switch 3 6 are guided to the difference circuit 3 7.
- the frame memory 3 4 has light with a uniform intensity for each pixel as in FIG.
- the photoelectric conversion signal logarithmically converted from the image sensor 31 is recorded on a pixel basis under the condition where the image sensor 31 is irradiated, whereby the offset variation A Vij for each pixel is recorded in the frame memory 34.
- the logarithmic signal that is read immediately before the reset gate potential changes from high level to low level under subject imaging conditions is rewritten and recorded in the frame memory 35.
- the switching switch 3 6 reads linear signals. Since it is sometimes connected to the frame memory 35 side, the above-mentioned frame is generated from the linear signal read immediately before the reset gate potential changes from the first level to the high level.
- the signal recorded in the video memory 35 is subtracted corresponding to each pixel, so that only the net linear signal corresponding to the signal charge accumulated during the photointegration period is read out. Random noise that accompanies the operation is canceled out by the above subtraction process, so that not only fixed noise but also random noise can be greatly reduced.
- FIG. 9A shows the same case as FIG. 6, but FIG. 9B shows a case where a linear operation period of 1 frame and a logarithmic operation period of 2 frames are alternately repeated.
- Fig. 9C shows a case where a 1-frame reusable operation period and a 3-frame log-type operation period are repeated alternately.
- other combinations are of course possible.
Abstract
Description
Claims
Priority Applications (2)
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US10/540,761 US7502060B2 (en) | 2002-12-27 | 2003-12-24 | Solid-state imaging device providing wide dynamic range and high low-illuminance sensitivity |
EP03768142A EP1580987A4 (en) | 2002-12-27 | 2003-12-24 | SOLID STATE IMAGE DEVICE |
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JP2002379240A JP4185771B2 (ja) | 2002-12-27 | 2002-12-27 | 固体撮像装置 |
JP2002-379240 | 2002-12-27 |
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WO2004062274A1 true WO2004062274A1 (ja) | 2004-07-22 |
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PCT/JP2003/016550 WO2004062274A1 (ja) | 2002-12-27 | 2003-12-24 | 固体撮像装置 |
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US (1) | US7502060B2 (ja) |
EP (1) | EP1580987A4 (ja) |
JP (1) | JP4185771B2 (ja) |
KR (1) | KR100725764B1 (ja) |
CN (1) | CN100380933C (ja) |
TW (1) | TWI240570B (ja) |
WO (1) | WO2004062274A1 (ja) |
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JP2013058960A (ja) * | 2011-09-09 | 2013-03-28 | Konica Minolta Advanced Layers Inc | 固体撮像装置 |
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- 2003-12-24 US US10/540,761 patent/US7502060B2/en not_active Expired - Fee Related
- 2003-12-24 EP EP03768142A patent/EP1580987A4/en not_active Withdrawn
- 2003-12-24 WO PCT/JP2003/016550 patent/WO2004062274A1/ja not_active Application Discontinuation
- 2003-12-24 CN CNB2003801099974A patent/CN100380933C/zh not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
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US20060044436A1 (en) | 2006-03-02 |
JP4185771B2 (ja) | 2008-11-26 |
CN100380933C (zh) | 2008-04-09 |
TWI240570B (en) | 2005-09-21 |
EP1580987A4 (en) | 2007-10-24 |
TW200425729A (en) | 2004-11-16 |
US7502060B2 (en) | 2009-03-10 |
JP2004214772A (ja) | 2004-07-29 |
KR20050087856A (ko) | 2005-08-31 |
KR100725764B1 (ko) | 2007-06-08 |
CN1757227A (zh) | 2006-04-05 |
EP1580987A1 (en) | 2005-09-28 |
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