JP2009055507A - Method of driving solid-state image pickup device and imaging apparatus driven by the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving a solid-state image pickup element capable of reducing occurrence of white scratch in a state that a dynamic range is extended, and to provide an imaging apparatus driven by the method. <P>SOLUTION: During a term for exposure to photoelectric conversion elements, when reading signal charges from a photoelectric conversion unit to a vertical charge transfer unit while controlling an exposure time by applying a read pulse to a vertical charge transfer electrode that becomes a read electrode for partial photoelectric conversion elements, driving is performed in such a way that the number of vertical charge transfer electrodes for accumulating signal charges read by the read pulse in a vertical charge transfer channel becomes less than the number of vertical charge transfer electrodes for accumulating signal charges in the vertical charge transfer channel when transferring signal charges by the vertical charge transfer unit after the end of the exposure term. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a driving method of a solid-state imaging device and an imaging device driven by the driving method.

  FIG. 11 shows a schematic configuration diagram of a CCD solid-state image sensor as an example of the solid-state image sensor. The CCD type solid-state imaging device 1 is arranged at a predetermined pitch in the horizontal and vertical directions on a semiconductor substrate, and reads out from the photoelectric conversion unit 3 and a plurality of photoelectric conversion units 3 that generate signal charges according to incident light. A plurality of vertical charge transfer units 5 that respectively transfer signal charges in the vertical direction, and a horizontal charge transfer unit 7 that transfers signal charges transferred from the vertical charge transfer unit 5 in the horizontal direction are provided. An output unit 9 that detects a signal charge in the floating diffusion unit and generates an output signal is connected to the downstream side of the horizontal charge transfer unit 7 in the charge transfer direction.

  As shown in the enlarged plan view of one pixel in FIG. 12, the vertical charge transfer unit 5 is formed of an n-type semiconductor layer that is formed along the vertical direction in the drawing in the vicinity of the photoelectric conversion unit 3 and accumulates signal charges. It has a vertical charge transfer channel 11 and a plurality of vertical charge transfer electrodes 13 arranged above the vertical charge transfer channel 11. A drive pulse for charge transfer, for example, φV1 to φV4, is applied to each vertical charge transfer electrode 13. Here, an electrode to which φVi (i is 1 to 4) is applied is expressed as Vi, but in some cases, it is also expressed as a vertical charge transfer electrode.

FIG. 13 is a cross-sectional view along A1-A2 shown in FIG. 12 together with the potential potential distribution diagram, and FIG. 13B is a cross-sectional view along B1-B2 along with the potential potential distribution diagram. As shown in the figure, a gate insulating film 17 is formed on the silicon substrate 15, and a vertical charge transfer electrode (V3 electrode: readout electrode, V4 electrode) 13 is formed on the gate insulating film 17. There is a dangling bond at the interface between the silicon substrate 15 and the gate insulating film 17, and electrons are generated mainly by the generation and recombination thereof. When the generated electrons enter the photoelectric conversion unit 3 that is a photodiode, it causes white scratches. Therefore, at present, in order to reduce white scratches, the photodiode surface is often covered with a P ⁺ layer. As a result, the hole density near the interface is increased, and electrons generated at the interface can be quickly recombined with the holes. Therefore, if the P ⁺ layer on the surface of the photoelectric conversion unit 3 is sufficiently functioning, the main source of electrons causing white scratches is the region between the photoelectric conversion unit 3 and the vertical charge transfer unit 5 (× in the figure). (Shown with a mark). It should be noted that dangling bonds exist in the vertical charge transfer portion 5 as well, but this is not mentioned here.

  As shown in the potential potential diagram of FIG. 13A, when a medium level voltage VM (0 V or the like) is applied to the V3 electrode, dangling bonds are generated at the interface between the silicon substrate and the gate insulating film 17. -Electrons generated centering on recombination enter the photoelectric conversion unit 3 and white scratches are likely to occur. On the other hand, as shown in the potential potential diagram of FIG. 13B, even if the voltage VM is applied to the V4 electrode, the occurrence of white scratches is not particularly problematic.

  Since the V4 electrode is not a readout electrode, it is arranged away from the photoelectric conversion unit 3, and therefore, the potential of the portion corresponding to the readout gate unit 19 is low. Therefore, the readout gate portion 19 is in a state where some holes are accumulated, and electrons generated from dangling bonds existing in this portion are recombined with the holes, so that the occurrence of white scratches is suppressed to some extent.

  FIG. 14 is a chart showing drive signals for the solid-state imaging device during exposure and vertical charge transfer of the photoelectric conversion unit 3. In this chart, in order to expand the dynamic range (saturation signal amount), the pixel read by the V1 electrode is used as a high sensitivity pixel, and the pixel read by the V3 electrode is used as a low sensitivity pixel (Patent Document). 1). The exposure period t1 of the high-sensitivity pixel is from the application of the φOFD shutter pulse 21 that sweeps out signal charges when the mechanical shutter is released until the mechanical shutter is closed. In this exposure period t1, the voltage signals applied to the vertical charge transfer electrodes 13, φV1 to φV4, are set to φV3 and φV4 as medium level voltages VM, and the others as low level voltages VL (−8 V or the like).

The exposure period of the low-sensitivity pixel is a period t2 from when the application of the discharge pulse 23 for discharging the unnecessary signal of the high-sensitivity pixel to the vertical charge transfer unit 5 is completed until the mechanical shutter is closed. In the illustrated example, the exposure period ratio t1 / t2 is set to 3, and the dynamic range is expanded three times. After the mechanical shutter is closed, a high-speed sweeping operation for transferring the signal discharged from the high sensitivity pixel to the output unit 9 through the horizontal charge transfer unit 7 is performed. Thereafter, reading from the low-sensitivity pixel (application of the VH pulse 25 to the V3 electrode) is performed. In this case, since the horizontal charge transfer unit 7 is operated and a signal is output from the output unit 9, the negative voltage VL is applied to the readout electrode of the high-sensitivity pixel. Unlike the state shown, holes are accumulated in the read gate portion 19 and the generated electrons recombine with the holes. As a result, white scratches are less likely to occur in the high sensitivity pixels.
JP-A-2005-72966 Japanese Patent No. 25007027

However, for the above-described low-sensitivity pixels, 0V or positive VM, which is higher than the negative voltage, is applied to the readout electrode during the exposure period t2, so that gate insulation is provided as shown in FIG. There is a problem that electrons generated at the interface between the film 17 and the silicon substrate enter the photoelectric conversion unit 3 and white defects are likely to occur.
That is, when a low level voltage VL is applied to the readout electrode, white scratches are less likely to occur, but when 0 V or a positive voltage VM equal to or higher than VL is applied, unnecessary charges enter the photoelectric conversion unit 3 and white scratches occur. Is likely to occur. Therefore, white scratches are more likely to occur as the number (area) of electrodes to which a voltage of VM or higher is applied increases. 15A and 15B are schematic diagrams showing the state of the voltage applied to the vertical charge transfer electrode during the exposure period. FIG. 15A shows the case of four-phase driving, and FIG. 15B shows the case of eight-phase driving. In the case of the four-phase drive shown in FIG. 15A, VM is applied to the V3 and V4 electrodes during the exposure period, as shown in the example of the waveform of the four-phase drive in FIG. In the case of 8-phase driving shown in FIG. 15B, VM is applied to the V2 to V7 electrodes. Therefore, the number of VM application electrodes indicated by the hatched portion in the drawing, that is, the total electrode area to which the VM is applied increases, and the frequency of white scratches increases.

Patent Document 2 proposes a method of reducing the generation of dark current by applying a negative voltage to all the transfer electrodes of the vertical charge transfer unit to make the surface of the charge transfer channel non-depleted. . This method is effective not only in reducing the generation of dark current in the vertical charge transfer section, but also in reducing white scratches on the pixels. However, there are problems such as an increase in the number of manufacturing steps and a decrease in the maximum charge accumulation amount in the vertical charge transfer unit because of the special configuration in which a potential step is provided in the vertical charge transfer unit. When a configuration in which no potential step is provided in the vertical charge transfer unit is required, when driving to expand the dynamic range, it is necessary to apply a VM voltage to the electrode for accumulating unnecessary charges in the low-sensitivity pixels. Therefore, a negative voltage cannot be applied to all charge transfer electrodes. Thus, the dynamic range expansion drive and the dark current generation reduction method of Patent Document 2 cannot be performed simultaneously.
The present invention has been made in view of the above situation, and an object thereof is to provide a driving method of a solid-state imaging device that reduces the occurrence of white scratches in a state where the dynamic range is expanded, and an imaging device driven thereby.

The above object of the present invention is achieved by the following configurations.
(1) A plurality of photoelectric conversion units arranged at a predetermined pitch in the horizontal direction and the vertical direction and generating signal charges according to incident light, and a plurality of signal charges read from the photoelectric conversion units respectively in the vertical direction A vertical charge transfer unit; and a horizontal charge transfer unit that transfers a signal charge transferred from the vertical charge transfer unit in a horizontal direction. The vertical charge transfer unit is close to the photoelectric conversion unit and extends in a vertical direction. A solid-state imaging device having a vertical charge transfer channel that stores signal charges and a plurality of vertical charge transfer electrodes that are arranged above the vertical charge transfer channel.
During the exposure period to the photoelectric conversion elements, the exposure time is controlled by applying a readout pulse to a vertical charge transfer electrode serving as a readout electrode for a part of the photoelectric conversion elements, and signals from the photoelectric conversion unit When reading the charge to the vertical charge transfer unit,
The number of the vertical charge transfer electrodes for accumulating the signal charge read by the read pulse in the vertical charge transfer channel is equal to the signal charge when the signal charge is transferred by the vertical charge transfer unit after the exposure period ends. A method for driving a solid-state imaging device, wherein the number of vertical charge transfer electrodes stored in a transfer channel is less than the number of vertical charge transfer electrodes.

  According to this solid-state imaging device driving method, the number of vertical charge transfer electrodes for accumulating the signal charge read by the read pulse in the vertical charge transfer channel is determined when the signal charge is transferred by the vertical charge transfer unit after the exposure period ends. Driving is performed so that the number of the vertical charge transfer electrodes for accumulating the signal charge in the vertical charge transfer channel is smaller. As a result, it is possible to achieve both expansion of the dynamic range and reduction of the occurrence of white scratches.

(2) A plurality of photoelectric conversion units arranged at a predetermined pitch in the horizontal direction and the vertical direction and generating signal charges corresponding to incident light, and a plurality of signal charges read from the photoelectric conversion units respectively in the vertical direction A vertical charge transfer unit; and a horizontal charge transfer unit that transfers a signal charge transferred from the vertical charge transfer unit in a horizontal direction. The vertical charge transfer unit is close to the photoelectric conversion unit and extends in a vertical direction. A solid-state imaging device having a vertical charge transfer channel that stores signal charges and a plurality of vertical charge transfer electrodes that are arranged above the vertical charge transfer channel.
During the exposure period to the photoelectric conversion elements, the exposure time is controlled by applying a readout pulse to a vertical charge transfer electrode serving as a readout electrode for a part of the photoelectric conversion elements, and signals from the photoelectric conversion unit When reading the charge to the vertical charge transfer unit,
A method for driving a solid-state imaging device, wherein the number of the vertical charge transfer electrodes for accumulating the signal charges read by the read pulse in the vertical charge transfer channel is one.

  According to this solid-state imaging device driving method, the influence of electrons generated by dangling bonds can be limited to only the minimum necessary electrodes, and the number of electrodes to which a negative voltage is applied can be increased. As a result, the occurrence of white scratches can be greatly reduced.

(3) A method for driving a solid-state imaging device according to (1) or (2),
A method for driving a solid-state imaging device, wherein a negative voltage is applied to other vertical charge transfer electrodes excluding the vertical charge transfer electrode to which the readout pulse is applied during an exposure period for the photoelectric conversion device.

  According to this solid-state imaging device driving method, 0 V or a positive voltage higher than the negative voltage is applied to the minimum necessary vertical charge transfer electrode for charge accumulation, and a negative voltage is applied to the vertical charge transfer electrodes other than the readout electrode. Thus, the occurrence of white scratches can be further reduced.

(4) A method for driving a solid-state imaging device according to (1) or (2),
A solid-state imaging element driving method in which a negative voltage is applied to a vertical charge transfer electrode to which the readout pulse is applied during an exposure period for the photoelectric conversion element.

  According to this solid-state imaging device driving method, a vertical charge transfer electrode in which holes are accumulated in the read gate portion even when a voltage higher than a negative voltage is applied, that is, a vertical charge transfer electrode to which no read pulse is applied, Since 0 V or a positive voltage higher than the negative voltage is applied, unnecessary charges can be prevented from flowing into the photoelectric conversion portion in the readout electrode.

(5) A method for driving a solid-state imaging device according to (1) or (2),
The photoelectric conversion unit is a mixture of a first photoelectric conversion element for long exposure corresponding to high sensitivity pixels and a second photoelectric conversion element for short exposure corresponding to low sensitivity pixels. During the period from the start of exposure of the first photoelectric conversion element to the start of substantial exposure of the second photoelectric conversion element, driving of the solid-state imaging element that applies a negative voltage to all of the vertical charge transfer electrodes Method.

  According to this solid-state imaging device driving method, the negative charge transfer electrode is negatively applied to all the vertical charge transfer electrodes during the period from the start of exposure of the first photoelectric conversion device to the start of substantial exposure of the second photoelectric conversion device. Since the voltage is applied, unnecessary charges can be prevented from flowing into the photoelectric conversion portion within the period.

(6) a solid-state image sensor;
An optical system for forming an optical image on the solid-state imaging device;
An image sensor driving unit that drives the solid-state image sensor based on the driving method of the solid-state image sensor according to any one of (1) to (5);
An imaging apparatus comprising:

  According to this imaging apparatus, it is possible to capture a high-quality image by expanding the dynamic range and reducing the occurrence of white scratches.

  According to the driving method of the solid-state imaging device and the imaging device driven thereby according to the present invention, it is possible to reduce the occurrence of white scratches in the state where the dynamic range is expanded.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a solid-state imaging device driving method and an imaging apparatus driven by the driving method according to the invention will be described in detail with reference to the drawings.
<First Embodiment>
The solid-state imaging device of this embodiment has the same configuration as that shown in FIGS. 11 and 12, and the CCD solid-state imaging device 1 is arranged at a predetermined pitch in the horizontal direction and the vertical direction on the semiconductor substrate, and incident light. Are transferred from the vertical charge transfer unit 5, the plurality of vertical charge transfer units 5 that transfer the signal charges read from the photoelectric conversion unit 3 in the vertical direction, and the vertical charge transfer unit 5. A horizontal charge transfer section 7 for transferring the signal charge in the horizontal direction. An output unit 9 that detects a signal charge in the floating diffusion unit and generates an output signal is connected to the downstream side of the horizontal charge transfer unit 7 in the charge transfer direction.

  Further, as shown in FIG. 12, the vertical charge transfer unit 5 is formed in the vertical direction in the drawing in the vicinity of the photoelectric conversion unit 3 and is formed of an n-type semiconductor layer for accumulating signal charges. And a plurality of vertical charge transfer electrodes 13 disposed above the vertical charge transfer channel 11. A drive pulse for charge transfer, for example, φV1 to φV4, is applied to each vertical charge transfer electrode 13.

FIG. 1 is a chart showing drive signals for a solid-state imaging device during exposure and vertical charge transfer of the photoelectric conversion unit of the present embodiment.
This drive signal is generated from a solid-state image sensor in which high-sensitivity pixels (first photoelectric conversion elements) that perform long-time exposure and low-sensitivity pixels (second photoelectric conversion elements) that perform short-time exposure are mixedly arranged. This is a drive signal when a signal from the sensitivity pixel is taken into the first frame and a signal from the high sensitivity pixel is taken into the second frame. In the high sensitivity pixel, the signal charge is read out to the vertical charge transfer unit 5 by using the vertical charge transfer electrode V1 as a readout electrode, and in the low sensitivity pixel, the signal charge is transferred to the vertical charge transfer unit 5 by using the vertical charge transfer electrode V3 as a readout electrode. Read out.

  When the shutter pulse 21 is applied to φOFD after the mechanical shutter is opened, the accumulated charge in each photoelectric conversion unit 3 is reset and exposure is started. Here, the voltage VM is applied to the vertical charge transfer electrode V3, and the negative voltage VL is applied to the other electrodes V1, V2, and V4. In the high-sensitivity pixel from which the signal charge is read out through the vertical charge transfer electrode V1, the period t1 until the mechanical shutter is closed is the exposure period. Further, the low-sensitivity pixel from which the signal charge is read out through the vertical charge transfer electrode V3 starts exposure after the φV3 discharge pulse 23 is applied, and t2 is an exposure period. Therefore, signal charges are accumulated for one electrode during the exposure period t1, and signal charges are accumulated for two electrodes during the vertical transfer period.

  Here, a schematic diagram showing the state of the voltage applied to the vertical charge transfer electrode during the exposure period is shown in FIG. As shown in FIG. 2, the vertical charge transfer electrode to which the voltage VM higher than the negative voltage VL is applied is only V3 in the exposure period, and the negative voltage VL is applied to the other V1, V2, and V4.

FIG. 3 is an explanatory diagram showing the A1-A2 cross-sectional view shown in FIG. 12 together with the potential potential distribution diagram (a) and the B1-B2 cross-sectional view together with the potential potential distribution diagram (b). . As shown in the figure, a gate insulating film 17 is formed on the silicon substrate 15, and a vertical charge transfer electrode (V3 electrode: readout electrode, V4 electrode) 13 is formed on the gate insulating film 17.
As shown in FIG. 3A, electrons generated by a tangling bond in a region (indicated by x in the figure) between the photoelectric conversion unit 3 and the vertical charge transfer unit 5 are the region, that is, the gate unit 19. Recombination with holes accumulated in (represented by + in the figure) prevents electrons generated by tangling bonds from entering the photoelectric conversion portion. Thereby, the occurrence of white scratches is suppressed.

  On the other hand, as shown in FIG. 3B, in the V4 electrode that is not the readout electrode, the photoelectric conversion unit 3 is formed away from the V4 electrode, so the potential of the portion corresponding to the gate unit 19 is low, Holes are accumulating. For this reason, electrons generated by dangling bonds recombine with holes, so that the occurrence of white scratches is suppressed. Further, since the negative voltage VL is applied to the V4 electrode, holes are easily accumulated, and the occurrence of white scratches is further suppressed.

As described above, in the solid-state imaging device driving method of the present embodiment, the number of vertical charge transfer electrodes for accumulating the signal charges read by the read pulse in the vertical charge transfer channel is determined by the vertical charge transfer unit after the exposure period ends. When the signal charge is transferred, the signal charge is driven to be smaller than the number of vertical charge transfer electrodes for accumulating the signal charge in the vertical charge transfer channel. Thereby, the electrons generated by the dangling bonds can be recombined with the holes, and both the expansion of the dynamic range and the reduction of the occurrence of white scratches can be achieved.
Further, a negative voltage is applied to the other vertical charge transfer electrodes other than the vertical charge transfer electrode to which the read pulse is applied, and the vertical charge transfer electrode for accumulating the signal charge read by the read pulse in the vertical charge transfer channel. Since it is driven so that the number is one, it is possible to limit the influence of electrons generated by dangling bonds to only the minimum necessary electrodes, and greatly reduce white scratches as a whole image. Can do.

Second Embodiment
Next, a second embodiment of the solid-state image sensor driving method according to the present invention will be described.
FIG. 4 is a chart showing drive signals for the solid-state imaging device at the time of exposure and vertical charge transfer of the photoelectric conversion unit of the present embodiment.
1 differs from FIG. 1 in that the φV3 discharge pulse 23A is stepped, the voltage before the discharge pulse 23A is applied is changed from VM to VL, and the voltage of φV4 is changed from VL to VM. . In this driving example, as shown in FIG. 5, the signal charges of the V3 and V4 electrodes are read from the state (a) where the voltage of the V3 electrode is VL (a) to VH (+15 V, etc.) (b), and thereafter The V3 electrode is set to VM so as to have the same potential as the V4 electrode (c). In this state, signal charges are accumulated at positions V3 and V4. Then, by setting the V3 electrode to VL, the signal charge is accumulated in the potential pocket formed by the V4 electrode, and the signal charge is transferred from the state (b) (d).

  The state of the voltage applied to the vertical charge transfer electrode during the exposure period in this case is as shown in FIG. That is, in the exposure period, the vertical charge transfer electrode to which the voltage VM higher than the negative voltage VL is applied is only V4, and the negative voltage VL is applied to the other V1, V2, and V3. Therefore, since the voltage VM is applied only to the vertical charge transfer electrode V4 that is not the read electrode, as shown in FIG. 13B, the region between the photoelectric conversion unit 3 and the vertical charge transfer unit 5 ( The electrons generated by the tangling bonds in the figure (represented by x) are recombined with the holes (shown by + in the figure) accumulated in the region, that is, the gate part (shown in the potential potential diagram) 19. The electrons generated by the tangling bonds do not enter the photoelectric conversion part. Thereby, the occurrence of white scratches is suppressed.

Further, in the V4 electrode that is not the readout electrode, the photoelectric conversion portion 3 is formed away from the V4 electrode, so that the potential of the portion corresponding to the gate portion 19 is low and some holes are accumulated. For this reason, electrons generated by dangling bonds recombine with holes, so that the occurrence of white scratches is suppressed.
In this way, by applying a negative voltage to the vertical charge transfer electrode to which the readout pulse is applied during the exposure period of the photoelectric conversion element, a hole higher than the negative voltage is applied to the readout gate portion. Since 0 V or a positive voltage higher than the negative voltage is applied to the vertical charge transfer electrode in which the charge is accumulated, that is, the vertical charge transfer electrode to which no read pulse is applied, the unnecessary charge flows into the photoelectric conversion unit in the read electrode. Can be prevented.

<Third Embodiment>
Next, a third embodiment of the solid-state image sensor driving method according to the present invention will be described.
FIG. 7 is a chart showing drive signals for the solid-state imaging device during exposure and vertical charge transfer of the photoelectric conversion unit of the present embodiment.
The difference of the second embodiment from FIG. 4 is that the potential of φV4 is changed from VM to VL. In this driving example, as shown in FIGS. 5B and 5C, until the voltage VH of the V3 electrode is applied, it is only necessary to form a potential packet with respect to the V4 electrode, and it is not necessary to hold it at VM. . Therefore, the signal charge is read by setting the potential of the V4 electrode to VL.

That is, when the first photoelectric conversion element for long exposure corresponding to the high sensitivity pixel and the second photoelectric conversion element for short exposure corresponding to the low sensitivity pixel are arranged together, the first photoelectric conversion element is arranged. A negative voltage is applied to all of the vertical charge transfer electrodes from the start of exposure of the conversion element to the start of substantial exposure of the second photoelectric conversion element.
In this case, the state of the voltage applied to the vertical charge transfer electrode during the exposure period is as shown in FIG. 8 before the discharge pulse 23A is applied. That is, the exposure process is pinning exposure, and there is no vertical charge transfer electrode to which the voltage VM higher than the negative voltage VL is applied during most exposure periods. As a result, it is possible to prevent unnecessary charges from flowing into the photoelectric conversion portion within the exposure period, and the effect of suppressing the occurrence of white scratches is increased.

In the above description, the case of four-phase driving has been described. Next, the case where the vertical charge transfer unit is of eight-phase driving will be described.
FIG. 9 is a schematic diagram showing the state of the voltage applied to the vertical charge transfer electrode during the exposure period during 8-phase driving. FIG. 9A shows the case where the VM voltage is applied only to the V2 electrode, and FIG. 9B shows V2, V4 and V6. The case where a VM voltage is applied to three electrodes is shown.
In the case shown in FIG. 9A, the VM voltage is applied only to the V2 electrode during the exposure period, and unnecessary charges are accumulated below the V2 electrode. As a result, white spots in the photoelectric conversion units adjacent to the V2, V5, and V7 electrodes generated in the pixel can be minimized, and white spots in the photoelectric conversion units adjacent to the V2 electrode are as shown in FIG. Compared with the case shown in b), it can be greatly reduced.

  In the case shown in FIG. 9B, the VM voltage is applied to the three electrodes V2, V4, and V6 among the electrodes that are not readout electrodes. As a result, compared to the case shown in FIG. 9A, the area for holding the unnecessary charge is increased, so that the unnecessary charge hardly flows back to the photoelectric conversion unit. Although white scratches generated in the photoelectric conversion unit are larger than those in FIG. 9A, since the VL voltage is applied to all the readout electrodes (V1, V3, V5, and V7 electrodes), FIG. Compared with the case shown in (3), white scratches can be greatly reduced.

<Fourth embodiment>
Next, an embodiment of an imaging apparatus using the above-described solid-state imaging element driving method will be described.
FIG. 10 is a block diagram of the imaging apparatus according to the present invention.
A digital camera 200 as an imaging apparatus shown in the figure includes an imaging lens 41, the above-described solid-state imaging device 100, a diaphragm 43 provided therebetween, an infrared cut filter 45, and an optical low-pass filter 47. The imaging lens 41, the diaphragm 43, the infrared cut filter 45, and the optical low-pass filter 47 function as an optical system that forms an optical image on the solid-state imaging device 100. A CPU 49 that performs overall control of the entire digital camera controls the flash light emitting unit 51 and the light receiving unit 53, controls the lens driving unit 55 to adjust the position of the imaging lens 41 to the focus position, and controls the aperture via the aperture driving unit 57. The amount of opening 43 is controlled to adjust the exposure amount.

  Further, the CPU 49 drives the solid-state image sensor 100 via the image sensor driving unit 59 and outputs the subject image captured through the imaging lens 41 as a color signal. An instruction signal from the user is input to the CPU 49 through the operation unit 61, and the CPU 49 performs various controls according to the instruction.

  The electric control system of the digital camera 200 includes an analog signal processing unit 67 connected to the output of the solid-state imaging device 100, and an A / D conversion that converts RGB color signals output from the analog signal processing unit 67 into digital signals. The circuit 69 is provided and these are controlled by the CPU 49.

  Furthermore, the electric control system of the digital camera 200 includes a memory control unit 73 connected to a main memory (frame memory) 71 and a digital signal for performing image processing such as gamma correction calculation, RGB / YC conversion processing, and image composition processing. A processing unit 75, a compression / expansion processing unit 77 that compresses the captured image into a JPEG image or expands the compressed image, and an integration unit 79 that integrates photometric data and obtains the gain of white balance correction performed by the digital signal processing unit 75. An external memory control unit 83 to which a detachable recording medium 81 is connected, and a display control unit 87 to which a liquid crystal display unit 85 mounted on the rear surface of the camera is connected. These include a control bus 89 and data They are connected to each other by a bus 91 and controlled by a command from the CPU 49.

  When a subject image is captured by the digital camera 200 according to the present embodiment, each photoelectric conversion unit 3 of the solid-state imaging device 1 shown in FIG. 11 accumulates signal charges corresponding to the amount of received light, and the signal charges are first transferred by vertical charge transfer. The data is read to the unit 5 and transferred in the direction of the horizontal charge transfer unit 7 along the vertical charge transfer unit 5.

  At the timing immediately before each signal charge is read out to the vertical charge transfer unit 5, each vertical charge transfer unit 5 and horizontal charge transfer unit 7 are in an empty state by the sweeping-out operation. After the readout process of the injected predetermined charge amount, the signal charge corresponding to the received light amount of each photoelectric conversion unit 3 is read from the solid-state imaging device 100, and the digital signal processing unit 75 generates subject image data.

  According to the digital camera 200, a dynamic range is expanded and a high-contrast image can be obtained, and a high-quality image that is not affected by white scratches can be obtained.

  The present invention can be applied to a CCD type solid-state imaging device as a driving method for reducing the occurrence of white scratches in a state where the dynamic range is expanded, and enables high-quality image acquisition, for example, an electronic camera, This is effective for use with a video camera or a portable terminal.

It is a chart figure which shows the drive signal of a solid-state image sensor at the time of exposure of a photoelectric conversion part, and vertical charge transfer. It is a schematic diagram which shows the state of the applied voltage of the vertical charge transfer electrode in the exposure period shown in FIG. FIG. 13 is an explanatory view showing the A1-A2 cross-sectional view shown in FIG. 12 together with the potential potential distribution diagram in FIG. 12A and the B1-B2 cross-sectional view showing in FIG. It is a chart figure which shows the drive signal of a solid-state image sensor at the time of exposure of a photoelectric conversion part, and vertical charge transfer. It is explanatory drawing which shows the mode of the signal charge of V3 and V4 electrode for every step of (a)-(d). It is a schematic diagram which shows the state of the applied voltage of the vertical charge transfer electrode in the exposure period shown in FIG. It is a chart figure which shows the drive signal of a solid-state image sensor at the time of exposure of a photoelectric conversion part, and vertical charge transfer. It is a schematic diagram which shows the state of the applied voltage of the vertical charge transfer electrode in the exposure period shown in FIG. FIG. 6 is a schematic diagram showing the state of the voltage applied to the vertical charge transfer electrode during the exposure period in 8-phase driving, where (a) shows the case where the VM voltage is applied only to the V2 electrode, and (b) shows 3 of the V2, V4 and V6 electrodes. It is a schematic diagram which shows the case where VM voltage is applied to an electrode. It is a block block diagram of an imaging device. It is a schematic block diagram of the CCD type solid-state image sensor as an example of a solid-state image sensor. FIG. 12 is an enlarged plan view of one pixel shown in FIG. 11. FIG. 13 is an explanatory diagram showing the A1-A2 cross-sectional view shown in FIG. 12 together with the potential potential distribution diagram (a) and the B1-B2 cross-sectional view together with the potential potential distribution diagram (b). It is a chart figure which shows the drive signal of the solid-state image sensor at the time of exposure of the conventional photoelectric conversion part, and vertical charge transfer. It is a schematic diagram which shows the state of the applied voltage of the vertical charge transfer electrode in the conventional exposure period, (a) is a schematic diagram which shows the case of 4 phase drive, (b) is the case of 8 phase drive.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid-state image sensor 3 Photoelectric conversion part 5 Vertical charge transfer part 7 Horizontal charge transfer part 9 Output part 11 Vertical charge transfer channel 13 Vertical charge transfer electrode 17 Gate insulating film 19 Read-out gate part 21 Shutter pulse 23, 23A Discharge pulse 25 VH pulse 100 Solid-state imaging device 200 Digital camera (imaging device)

Claims (6)

A plurality of photoelectric conversion units that are arranged at a predetermined pitch in the horizontal direction and the vertical direction and generate signal charges according to incident light, and a plurality of vertical charge transfers that respectively transfer signal charges read from the photoelectric conversion units in the vertical direction And a horizontal charge transfer unit that transfers the signal charge transferred from the vertical charge transfer unit in the horizontal direction, and the vertical charge transfer unit is formed along the vertical direction in the vicinity of the photoelectric conversion unit. A method for driving a solid-state imaging device having a vertical charge transfer channel for accumulating signal charges, and a plurality of vertical charge transfer electrodes arranged above the vertical charge transfer channel,
During the exposure period to the photoelectric conversion elements, the exposure time is controlled by applying a readout pulse to a vertical charge transfer electrode serving as a readout electrode for a part of the photoelectric conversion elements, and signals from the photoelectric conversion unit When reading the charge to the vertical charge transfer unit,
The number of the vertical charge transfer electrodes for accumulating the signal charge read by the read pulse in the vertical charge transfer channel is equal to the signal charge when the signal charge is transferred by the vertical charge transfer unit after the exposure period ends. A method for driving a solid-state imaging device, wherein the number of vertical charge transfer electrodes stored in a transfer channel is less than the number of vertical charge transfer electrodes. A plurality of photoelectric conversion units that are arranged at a predetermined pitch in the horizontal direction and the vertical direction and generate signal charges according to incident light, and a plurality of vertical charge transfers that respectively transfer signal charges read from the photoelectric conversion units in the vertical direction And a horizontal charge transfer unit that transfers the signal charge transferred from the vertical charge transfer unit in the horizontal direction, and the vertical charge transfer unit is formed along the vertical direction in the vicinity of the photoelectric conversion unit. A method for driving a solid-state imaging device having a vertical charge transfer channel for accumulating signal charges, and a plurality of vertical charge transfer electrodes arranged above the vertical charge transfer channel,
During the exposure period to the photoelectric conversion elements, the exposure time is controlled by applying a readout pulse to a vertical charge transfer electrode serving as a readout electrode for a part of the photoelectric conversion elements, and signals from the photoelectric conversion unit When reading the charge to the vertical charge transfer unit,
A method for driving a solid-state imaging device, wherein the number of the vertical charge transfer electrodes for accumulating the signal charges read by the read pulse in the vertical charge transfer channel is one. A method for driving a solid-state imaging device according to claim 1 or 2,
A method for driving a solid-state imaging device, wherein a negative voltage is applied to other vertical charge transfer electrodes excluding the vertical charge transfer electrode to which the readout pulse is applied during an exposure period for the photoelectric conversion device. A method for driving a solid-state imaging device according to claim 1 or 2,
A solid-state imaging element driving method in which a negative voltage is applied to a vertical charge transfer electrode to which the readout pulse is applied during an exposure period for the photoelectric conversion element. A method for driving a solid-state imaging device according to claim 1 or 2,
The photoelectric conversion unit is a mixture of a first photoelectric conversion element for long exposure corresponding to high sensitivity pixels and a second photoelectric conversion element for short exposure corresponding to low sensitivity pixels. During the period from the start of exposure of the first photoelectric conversion element to the start of substantial exposure of the second photoelectric conversion element, driving of the solid-state imaging element that applies a negative voltage to all of the vertical charge transfer electrodes Method. A solid-state image sensor;
An optical system for forming an optical image on the solid-state imaging device;
An image sensor driving unit that drives the solid-state image sensor based on the solid-state image sensor driving method according to any one of claims 1 to 5,
An imaging apparatus comprising:

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