JP2009302243A - Imaging device and method of driving image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device that stably multiplies electric charges generating in a photoelectrically converting device at a uniform multiplication factor irrespective of a location, thereby preventing an irregularities of an image. <P>SOLUTION: This imaging device includes: an image sensor 5 which contains a light receiving part 100 containing a photoelectrically converting device 110 and a vertical electric charge transfer path 120 for transferring the electric charges read from the photoelectrically converting device 110 in a vertical direction, and a storage part 200 containing an electric charge storing region 210 for storing the electric charges transferred from the vertical electric charge transfer path 120, and storage control electrodes S1 to S8 provided above the electric charge storing region 210 for controlling an electric charge storing operation in the electric charge storing region 210; and an image sensor driving part 10 for applying a given voltage to any one of the storage control electrodes S1 to S8 while the electric charges generated in the photoelectrically converting device 110 are transferred through the vertical electric charge transfer path 120 and are stored in the electric charge storing region 210, so that an avalanche multiplication can generate in the electric charge storing region 210 to drive to multiply the electric charges. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus having a charge transfer type imaging device.

  In charge transfer type imaging devices such as CCD (Charge Coupled Device) image sensors, conventionally, avalanche multiplication is generated in the charge transfer channel of the CCD, and sensitivity is increased by performing charge multiplication during charge transfer. The technique of making it known is known (for example, refer to Patent Documents 1 and 2).

Japanese Patent No. 2609363 Japanese Patent No. 3484261

  Patent Documents 1 and 2 do not specify which of the horizontal CCD and the vertical CCD causes the avalanche multiplication, but it is considered easy to design the avalanche multiplication in the vertical CCD. . In general, in a CCD image sensor, a p-well layer is formed on an n-type semiconductor substrate, and an n-type impurity is implanted into the p-well layer to form a vertical CCD charge transfer channel. Then, after the charge transfer channel is formed, a manufacturing process is performed in which a photodiode is formed by implanting an n-type impurity into a p-well layer around the charge transfer channel.

  As described above, when a process for forming a photodiode is performed after the charge transfer channel is formed, the uniformity of the characteristics of the charge transfer channel is impaired due to the influence of this process. If the uniformity of the characteristics of the charge transfer channel is impaired, when avalanche multiplication occurs in the charge transfer channel, the multiplication factor varies depending on the position of the charge transfer channel, resulting in unevenness in the image. End up.

  In addition, with the recent miniaturization, the width of the charge transfer channel has been reduced. For this reason, an electric field is not easily applied to the charge transfer channel, and it is difficult to stably perform avalanche multiplication.

  The present invention has been made in view of the above circumstances, and an imaging apparatus capable of preventing image unevenness by stably multiplying charges generated in a photoelectric conversion element at a uniform multiplication factor regardless of location. The purpose is to provide.

  The imaging device of the present invention is an imaging device having a charge transfer type imaging device, and the imaging device receives a light from a subject and transfers a charge read from the photoelectric conversion device. A light receiving unit including a charge transfer path, a charge storage area connected to the charge transfer path and storing charges transferred from the charge transfer path, and charges in the charge storage area provided above the charge storage area A storage unit including a plurality of storage control electrodes for controlling the storage operation, and the charge generated in the photoelectric conversion element is transferred through the charge transfer path and stored in the charge storage region, Drive means for applying a predetermined voltage to the accumulation control electrode to cause avalanche multiplication in the charge accumulation region to increase the charge.

  With this configuration, charge multiplication is performed in the storage portion where there is no photoelectric conversion element. Since the storage portion only needs to have a structure capable of storing charges, the structure is not complicated like the light receiving portion, and variations in characteristics are less likely to occur in the manufacturing process. Therefore, the charge multiplication factor can be made almost uniform at any position in the storage unit, and the occurrence of image unevenness can be suppressed. Further, since it is not necessary to provide a photoelectric conversion element in the storage portion, the width of the charge storage region can be made larger than the width of the charge transfer path. For this reason, the voltage required to generate avalanche multiplication is more likely to be applied to the charge accumulation region than the charge transfer path, and the multiplication can be performed more stably than when avalanche multiplication is performed in the charge transfer path. It can be carried out.

  In the imaging device of the present invention, the light receiving section is provided above the charge transfer path, and includes a plurality of transfer electrodes for controlling a charge transfer operation in the charge transfer path, and the charge of the accumulation control electrode The width in the transfer direction is larger than the width in the transfer direction of the charge of the transfer electrode.

  With this configuration, the capacity of the charge accumulation packet formed on the charge transfer path corresponding to one photoelectric conversion element can be increased on the charge accumulation region. For this reason, it is possible to prevent the overflow of the charge generated by the charge multiplication operation. Further, since the area of the accumulation control electrode becomes larger than that of the transfer electrode, it is possible to reduce the resistance of the accumulation control electrode.

  In the imaging device of the present invention, the plurality of accumulation control electrodes have the same shape.

  With this configuration, the multiplication operation can be stably performed under any accumulation control electrode.

  In the image pickup apparatus of the present invention, the driving unit changes the predetermined voltage according to shooting conditions.

  With this configuration, it is possible to set an optimum multiplication factor according to the shooting situation.

  In the imaging apparatus of the present invention, among the plurality of storage control electrodes, at least the electrode to which the predetermined voltage is applied has a wiring for applying the voltage from above the electrode in the longitudinal direction of the electrode. Connected at regular intervals.

  With this configuration, the voltage is applied evenly over the entire accumulation control electrode, so that the charge multiplication factor can be made more uniform.

  The image sensor driving method of the present invention is a charge transfer type image sensor driving method, wherein the image sensor receives a light from a subject and a charge read from the photoelectric converter. A light receiving section including a charge transfer path to transfer, a charge storage area connected to the charge transfer path and storing charges transferred from the charge transfer path, and the charge storage area provided above the charge storage area A storage unit including a plurality of storage control electrodes for controlling the charge storage operation of the first charge, and after the charge generated in the photoelectric conversion element is stored in the charge storage region, a part of the storage control electrodes is predetermined. Is applied to cause avalanche multiplication in the charge accumulation region to increase the charge.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which can multiply the electric charge which generate | occur | produced in the photoelectric conversion element stably with a uniform multiplication factor, and can prevent an image nonuniformity can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a digital camera which is an example of an imaging apparatus for explaining an embodiment of the present invention.
The imaging system of the illustrated digital camera includes a photographic lens 1, a CCD type imaging device 5, a diaphragm 2 provided between both, an infrared cut filter 3, and an optical low-pass filter 4.

  A system control unit 11 that performs overall control of the electrical control system of the digital camera controls the flash light emitting unit 12 and the light receiving unit 13 and controls the lens driving unit 8 to adjust the position of the photographing lens 1 to the focus position and zoom. The exposure amount is adjusted by adjusting the aperture amount of the aperture 2 via the aperture drive unit 9.

  In addition, the system control unit 11 drives the imaging device 5 via the imaging device driving unit 10 and outputs the subject image captured through the photographing lens 1 as a color signal. An instruction signal from the user is input to the system control unit 11 through the operation unit 14.

  The electric control system of the digital camera further includes an analog signal processing unit 6 for performing analog signal processing such as correlated double sampling processing connected to the output of the image sensor 5, and RGB output from the analog signal processing unit 6. And an A / D conversion circuit 7 for converting the color signal into a digital signal, which are controlled by the system control unit 11.

  Furthermore, the electric control system of this digital camera generates image data by performing main memory 16, memory control unit 15 connected to main memory 16, interpolation calculation, gamma correction calculation, RGB / YC conversion processing, and the like. A digital signal processing unit 17, a compression / decompression processing unit 18 that compresses image data generated by the digital signal processing unit 17 into a JPEG format or decompresses compressed image data, and a digital signal processing unit 17 that integrates photometric data. The integration unit 19 for obtaining the gain of white balance correction performed by the camera, the external memory control unit 20 to which the removable recording medium 21 is connected, and the display control unit 22 to which the liquid crystal display unit 23 mounted on the back of the camera is connected. These are connected to each other by a control bus 24 and a data bus 25, and are controlled by commands from the system control unit 11. That.

FIG. 2 is a schematic plan view showing a schematic configuration of the image sensor 5 of the digital camera shown in FIG.
The imaging element 5 includes a plurality of photoelectric conversion elements 110 and a light receiving unit 100 including a plurality of vertical charge transfer paths 120 that transfer charges read from the photoelectric conversion elements 110 in a vertical direction, and a plurality of vertical charge transfer paths 120. A storage unit 200 including a plurality of charge storage regions 210 that store the charges transferred from the vertical charge transfer path 120 and a row of charges transferred from the plurality of charge storage regions 210 in a vertical direction. A horizontal charge transfer path 300 that transfers in a horizontal direction orthogonal to the output, and an output unit 400 that converts the charge transferred through the horizontal charge transfer path 300 into a voltage signal corresponding to the charge amount and outputs the voltage signal.

  The photoelectric conversion element 110 and the vertical charge transfer path 120 are formed in the semiconductor substrate. The arrangement of the photoelectric conversion elements 110 is such that two photoelectric conversion element groups each made up of a large number of photoelectric conversion elements 110 arranged in a square lattice at the same pitch are perpendicular to each other by about ½ of the arrangement pitch of each photoelectric conversion element group. This is a so-called honeycomb arrangement that is shifted in the horizontal and horizontal directions. Hereinafter, a column composed of a plurality of photoelectric conversion elements 110 arranged in the vertical direction is referred to as a photoelectric conversion element column, and a line composed of the plurality of photoelectric conversion elements 110 arranged in the horizontal direction is referred to as a photoelectric conversion element row.

  The vertical charge transfer path 120 is formed on the right side corresponding to each photoelectric conversion element array (only a part is shown in FIG. 2). The vertical charge transfer path 120 is formed by, for example, an n-type impurity implanted in a p-well layer formed on an n-type silicon substrate.

  The light receiving unit 100 further includes a plurality of types (eight types in this embodiment) of transfer electrodes V1 to V8 provided in the vertical direction above the vertical charge transfer path 120. The transfer electrodes V <b> 1 to V <b> 8 are arranged so as to meander in the horizontal direction between the respective photoelectric conversion element rows so as to avoid the photoelectric conversion elements 110 constituting them.

  An 8-phase transfer pulse for controlling the transfer of the charges read out to the vertical charge transfer path 120 is applied to the transfer electrodes V1 to V8 by a first driver included in the image sensor driving unit 10.

  The light receiving unit 100 further reads a charge between each photoelectric conversion element 110 and the corresponding vertical charge transfer path 120 to read out the charges generated in each photoelectric conversion element 110 to the vertical charge transfer path 120. A portion 140 is provided. The charge reading unit 140 is formed by, for example, a part of a p-well layer formed on an n-type silicon substrate. In the example of FIG. 2, the charge reading unit 140 is provided in the same direction (obliquely lower right direction in the drawing) with respect to each photoelectric conversion element 110.

  In the light receiving unit 100, an element isolation region 130 is further formed, whereby the photoelectric conversion element 110 and the vertical charge transfer path 120 not corresponding thereto are separated.

  The transfer electrodes V2, V4, V6, and V8 are formed so as to cover the charge reading unit 140, respectively, and also function as read electrodes for reading charges from the photoelectric conversion element 110 to the vertical charge transfer path 120.

  The transfer electrodes V2, V4, V6, and V8 each have a middle level (hereinafter referred to as M, for example, 0V) transfer pulse for forming a charge accumulation packet for accumulating charges in the vertical charge transfer path 120, and vertical charge transfer. A low level (hereinafter referred to as L, for example, -8 V) transfer pulse lower than M for forming a barrier for the charge storage packet in the path 120 and a charge from each photoelectric conversion element 110 to the vertical charge transfer path 120 It is possible to apply a pulse for reading and a reading pulse having a level higher than M (for example, 15 V). L and M transfer pulses can be applied to the transfer electrodes V1, V3, V5 and V7 other than the transfer electrodes V2, V4, V6 and V8.

  In the storage unit 200, a plurality of types (eight types in the example of FIG. 2) of storage control electrodes S1 to S8 for controlling the charge storage operation in the charge storage region 210 are arranged above the charge storage region 210 in the vertical direction. Is provided. The accumulation control electrodes S1 to S8 are each linear in the horizontal direction and all have the same shape. Further, the vertical width of the storage control electrodes S1 to S8 is larger than the vertical width of the transfer electrodes V1 to V8. Further, the number of storage control electrodes provided corresponding to one charge storage region 210 is equal to or more than the number of transfer electrodes provided corresponding to one vertical charge transfer path 120.

  An 8-phase control pulse for controlling the charge accumulation operation in the charge accumulation region 210 is applied to the accumulation control electrodes S <b> 1 to S <b> 8 by a second driver included in the image sensor driving unit 10. Note that the first driver and the second driver independently apply pulses.

  The accumulation control electrodes S1 to S8 each have the above-described M control pulse for forming a charge accumulation packet for accumulating charges in the charge accumulation region 210 and the above-described L for forming a barrier for the charge accumulation packet. These control pulses can be applied. Furthermore, a multiplication pulse having a level higher than M necessary for causing avalanche multiplication in the charge accumulation region 210 can be applied to the accumulation control electrodes S1 and S5.

  Note that the storage unit 200 is shielded from light by a light shielding film, and has a configuration in which light does not enter. The storage unit 200 is also provided with an element isolation region 130 in the same manner as the light receiving unit 100, so that adjacent charge storage regions 210 are separated from each other.

  As described above, the image pickup device 5 has substantially the same configuration as the FIT (Frame Interline Transfer) type image pickup device, and includes the transfer electrodes V1 to V8 of the light receiving unit 100 and the storage control electrodes S1 to S8 of the storage unit 200. The difference from the FIT image sensor is that each electrode can be controlled independently and the vertical width of each electrode is different.

  Hereinafter, a driving method of the imaging device 5 configured as described above will be described. Hereinafter, a driving method at the time of two-field readout for reading out signals from the image sensor 5 in two fields will be described as an example.

  After the exposure period, the first driver applies an M transfer pulse to the transfer electrodes V2 to V7, applies an L transfer pulse to the transfer electrodes V1 and V8, and transfers vertical charges below the transfer electrodes V2 to V7. A charge accumulation packet is formed in the path 120. Thereafter, a read pulse is applied to each of the transfer electrode V2 and the transfer electrode V4, and charges are read from the photoelectric conversion element 110 corresponding to the transfer electrode V2 and the transfer electrode V4 to the vertical charge transfer path 120 corresponding to the photoelectric conversion element 110. .

  After reading the charge, the first driver and the second driver control the transfer pulse applied to the transfer electrodes V1 to V8 and the control pulse applied to the storage control electrodes S1 to S8, respectively, and charge storage packets. The charge inside is transferred in the vertical direction, and all the read out charges are temporarily accumulated in the charge accumulation region 210 in the accumulation unit 200.

  In the period until the first driver and the second driver store all the charges in the storage unit 200, the pulse pattern applied to each of the transfer electrodes V1 to V8 corresponds to each of the storage control electrodes S1 to S8. A pulse is applied so as to be the same as the pulse pattern applied to. That is, by driving one channel region including the vertical charge transfer path 120 and the charge storage region 210 connected thereto with an eight-phase pulse, the charge read from the photoelectric conversion element 110 is converted into the charge storage region 210. Transfer to and accumulate here. Up to this point, the driving is the same as that of the FIT image sensor.

  FIG. 3 is a diagram showing a change in the potential of the charge storage region 210 when charge multiplication is performed in the first field of the image sensor shown in FIG. In FIG. 3, the blocks with the letters “S1” to “S8” represent the storage control electrodes S1 to S8, respectively.

  When all the charges read from the photoelectric conversion element 110 are accumulated in the charge accumulation region 210, the potential below the charge accumulation region 210 is, for example, as shown at time t1 in FIG. 3, accumulation control electrodes S2 to S7. A charge storage packet is formed below, and a barrier is formed below storage control electrodes S1 and S8.

  From this state, the second driver applies the multiplication pulse to the accumulation control electrode S5 only for a short period. As a result, as shown at time t2 in FIG. 3, only the potential below the storage control electrode S5 becomes higher in the potential below the charge storage region 210, and the charge below the storage control electrodes S2 to S7 is added to this increased portion. Charges stored in the accumulated packet flow in, avalanche multiplication occurs, and charge multiplication is performed.

  When the application of the multiplication pulse to the storage control electrode S5 is completed, the potential below the charge storage region 210 returns to the same state as that at time t1, as shown at time t3 in FIG.

  The second driver multiplies the charge at the set multiplication factor by repeating the driving at times t1 to t3 a plurality of times.

  When the charge multiplication is completed, the second driver controls the accumulation control electrodes S1 to S8 with an eight-phase pulse and transfers the charge for one row to the horizontal charge transfer path 300. The transferred charge is transferred to the output unit 400 by driving an H driver included in the image sensor driving unit 10, and is converted into a voltage signal from the output unit 400 and output.

  When the output of the voltage signal corresponding to the charge for one row is completed, the second driver performs driving such that the next row of charge is transferred to the horizontal charge transfer path 300. Repeat until no more. When voltage signals corresponding to all the read charges are output, the first field ends.

  When the second field is started, the first driver applies an M transfer pulse to the transfer electrodes V1, V2, V3, V6, V7, and V8, and applies an L transfer pulse to the transfer electrodes V4 and V5. Then, a charge accumulation packet is formed in the vertical charge transfer path 120 below the transfer electrodes V1, V2, V3, V6, V7, and V8. Thereafter, a read pulse is applied to each of the transfer electrode V6 and the transfer electrode V8, and the charge is read from the photoelectric conversion element 110 corresponding to the transfer electrode V6 and the transfer electrode V8 to the vertical charge transfer path 120 corresponding to the photoelectric conversion element 110. .

  After reading the charge, the first driver and the second driver control the transfer pulse applied to the transfer electrodes V1 to V8 and the control pulse applied to the accumulation control electrodes S1 to S8, respectively, and charge storage packets. The charge inside is transferred in the vertical direction, and all the read out charges are temporarily accumulated in the charge accumulation region 210 in the accumulation unit 200.

  FIG. 4 is a diagram showing a change in potential of the charge accumulation region 210 when charge multiplication is performed in the second field of the image sensor shown in FIG. In FIG. 4, the blocks with the letters “S1” to “S8” represent the storage control electrodes S1 to S8, respectively.

  When all the electric charges read from the photoelectric conversion element 110 are accumulated in the charge accumulation region 210, the potential below the charge accumulation region 210 is, for example, as shown at time t1 in FIG. , S3, S6, S7, S8, a charge storage packet is formed, and a barrier is formed below the storage control electrodes S4, S5.

  From this state, the second driver applies the multiplication pulse to the accumulation control electrode S1 only for a short period. As a result, as shown in time t2 in FIG. 4, only the potential below the storage control electrode S1 becomes higher as the potential below the charge storage region 210, and the storage control electrodes S1, S2, S3, Charges in the charge storage packets below S6, S7, and S8 flow in, avalanche multiplication occurs, and charge multiplication is performed.

  When the application of the multiplication pulse to the storage control electrode S1 is completed, the potential below the charge storage region 210 returns to the same state as that at time t1, as shown at time t3 in FIG.

  The second driver multiplies the charge at the set multiplication factor by repeating the driving at times t1 to t3 a plurality of times.

  When the charge multiplication is completed, the second driver controls the accumulation control electrodes S1 to S8 with an eight-phase pulse and transfers the charge for one row to the horizontal charge transfer path 300. The transferred charge is transferred to the output unit 400 by driving the H driver, and is converted into a voltage signal from the output unit 400 and output.

  When the output of the voltage signal corresponding to the charge for one row is completed, the second driver performs driving such that the next row of charge is transferred to the horizontal charge transfer path 300. Repeat until no more. When a voltage signal corresponding to all the read charges is output, the second field ends.

  As described above, in the digital camera of this embodiment, charge multiplication is performed in the storage unit 200 where the photoelectric conversion element 110 does not exist. Since the storage unit 200 only needs to have a configuration capable of storing charges, the structure is not complicated like the light receiving unit 100, and variations in characteristics are less likely to occur in the manufacturing process. That is, in the light receiving unit 100, since it is necessary to perform the process of forming the photoelectric conversion element 110 after forming the vertical charge transfer path 120, the characteristics of the vertical charge transfer path 120 vary, but the storage unit 200 Since only the charge storage region 210 needs to be formed, the characteristics of the charge storage region 210 can be made uniform. Therefore, the charge multiplication factor can be made almost uniform at any position in the storage unit 200, and the occurrence of image unevenness can be suppressed.

  In the imaging device 5 of the present embodiment, the horizontal width of the charge accumulation region 210 is larger than the horizontal width of the vertical charge transfer path 120. For this reason, the charge accumulation region 210 is more easily subjected to a multiplication pulse than the vertical charge transfer path 120, and the charge multiplication is more stable than when avalanche multiplication is performed in the vertical charge transfer path 120. Can be done.

  In the imaging device 5 of the present embodiment, the vertical width of the storage control electrodes S1 to S8 is larger than the vertical width of the transfer electrodes V1 to V8. For this reason, the capacity of one charge storage packet formed in the charge storage region 210 can be made larger than the capacity of one charge storage packet formed in the vertical charge transfer path 120. Therefore, it is possible to prevent the overflow of the charge generated by the charge multiplication operation.

  Further, since the areas of the accumulation control electrodes S1 to S8 are larger than those of the transfer electrodes V1 to V8, it is possible to reduce the resistance of the accumulation control electrodes S1 to S8.

  Further, when compared with the case where the vertical width of the storage control electrodes S1 to S8 and the vertical width of the transfer electrodes V1 to V8 are the same, the vertical of the barrier at the time of charge multiplication as shown in FIGS. The length of the direction can be increased. Therefore, when returning from the state at time t2 in FIG. 3 and FIG. 4 to the state at time t3, it is possible to prevent the electric charge from jumping to the adjacent charge accumulation packet, and it is possible to prevent color mixing and the like. Become.

  Further, according to the imaging device 5 of the present embodiment, since the shape of the accumulation control electrodes S1 to S8 is the same, the multiplication operation can be stably performed under any accumulation control electrode.

  In the above description, it is assumed that pulses are applied independently to the transfer electrodes V1 to V8 and the accumulation control electrodes S1 to S8. However, the storage control electrodes S2, S3, S4, S6, S7, and S8 other than the storage control electrodes S1 and S5 to which the multiplication pulse is applied are the same pulses as the transfer electrodes V2, V3, V4, V6, V7, and V8, respectively. Since the pattern is applied, these may be connected to the first driver by common wiring, and only the storage control electrodes S1 and S5 may be independently pulsed by the second driver.

  In the above description, the multiplication pulse is applied to the storage control electrodes S1 and S5 from the state at time t1 in FIGS. 3 and 4, but the present invention is not limited to this. For example, taking FIG. 3 as an example, a multiplication pulse may be applied to one of the accumulation control electrodes S2, S3, S4, S6, S7, or the accumulation control electrodes S2, S3, S4, S5, S6. , S7, a multiplication pulse may be applied to a plurality (but not more than 5) of electrodes, or a multiplication pulse may be applied to the storage control electrode S8 or S1.

  In addition, the second driver changes the number of times the multiplication pulse is applied, the number of electrodes to which the multiplication pulse is applied, etc. according to the photographing conditions (the brightness of the subject, the set photographing sensitivity), etc. May be. In this way, when the multiplication factor may be low, the power consumption can be reduced and the time until the completion of photographing can be shortened, thereby enabling efficient control.

  In the above description, the arrangement of the photoelectric conversion elements 110 in the light receiving unit 100 is a honeycomb arrangement. However, the arrangement is not limited to this, and various known arrangements can be employed. For example, as shown in FIG. 5, the photoelectric conversion elements 110 may be arranged in a square lattice pattern.

(Second embodiment)
In the present embodiment, a method of connecting wirings for applying pulses to the accumulation control electrodes S1 to S8 of the image sensor 5 described in the first embodiment will be described.

FIG. 6 is a diagram showing a schematic configuration of an image sensor according to the second embodiment of the present invention. In FIG. 6, the same components as those in FIG.
When connecting each of the storage control electrodes S1 to S8 and the second driver, it is common to connect a wiring to each end of the storage control electrodes S1 to S8. However, since the accumulation control electrodes S1 to S8 have a shape elongated in the horizontal direction, the resistance at the central portion of the accumulation control electrodes S1 to S8 is higher than that at the end. As a result, even under the same accumulation control electrode, the degree of application of the multiplication pulse becomes worse as it goes to the center, and the multiplication factor changes depending on the location, resulting in image unevenness.

  Therefore, in the present embodiment, as shown in FIG. 6, for the storage control electrodes S1 and S5 to which the multiplication pulse is applied, wirings 220 and 230 for applying the control pulse and the multiplication pulse from above the electrodes. Are connected at regular intervals in the longitudinal direction (horizontal direction) of the electrodes. For the accumulation control electrodes other than the accumulation control electrodes S1 and S5, wiring is connected to the end portions as in the conventional case.

  As shown in FIG. 6, the wiring 220 is provided between the accumulation control electrodes S1 to S8 and the light shielding film on the storage control electrodes S1 to S8, and the wiring 220a extending in the horizontal direction and the vertical direction branched from the wiring 220a. The wiring line 220b extends. The wiring 220b is provided over each charge storage region 210, and is electrically connected to the storage control electrode S1 at a portion overlapping the storage control electrode S1 above each charge storage region 210. Yes.

  The wiring 230 is provided between the accumulation control electrodes S1 to S8 and the light shielding film, and includes a wiring 230a extending in the horizontal direction and a wiring 230b extending in the vertical direction branched from the wiring 230a. Yes. The wiring 230b is provided over each charge storage region 210, and is electrically connected to the storage control electrode S5 at a portion overlapping the storage control electrode S5 above each charge storage region 210. Yes.

  As described above, according to the imaging device 5 of the present embodiment, it is possible to apply the multiplication pulse uniformly in the horizontal direction to the accumulation control electrode to which the multiplication pulse is applied. For this reason, occurrence of image unevenness can be prevented. Further, unlike the light receiving unit 100, the storage unit 200 does not include the photoelectric conversion element 110, so that the wirings 220 and 230 can be easily routed. Further, since the thickness of the wirings 220 and 230 can be ensured by the absence of the photoelectric conversion element 110, the resistance of the wirings 220 and 230 can be reduced.

  In the above description, the wiring is connected to the accumulation control electrode to which the multiplication pulse is applied only at a predetermined interval in the longitudinal direction from above, but the other accumulation control electrodes are wired in the same manner. May be connected.

The figure which shows schematic structure of the digital camera which is an example of the imaging device for describing one Embodiment of this invention FIG. 1 is a schematic plan view showing a schematic configuration of an image sensor of the digital camera shown in FIG. The figure which showed the change of the potential of the charge storage area | region at the time of performing charge multiplication in the 1st field of the image pick-up element shown in FIG. The figure which showed the change of the potential of the charge storage area | region at the time of performing charge multiplication in the 2nd field of the image pick-up element shown in FIG. The figure which showed another example of the photoelectric conversion element arrangement | sequence of the image pick-up element shown in FIG. The figure which shows schematic structure of the image pick-up element of 2nd embodiment of this invention.

Explanation of symbols

5 Image sensor 10 Image sensor drive unit 100 Light receiving unit 110 Photoelectric conversion device 120 Vertical charge transfer path 200 Storage unit 210 Charge storage region S1 to S8 Storage control electrode

Claims (6)

An imaging device having a charge transfer type imaging device,
The image pickup device is connected to the charge transfer path, a light receiving unit including a photoelectric conversion element that receives light from a subject, a charge transfer path that transfers charges read from the photoelectric conversion element, and the charge transfer path A charge storage region for storing the charge transferred from the storage unit, and a storage unit including a plurality of storage control electrodes for controlling a charge storage operation in the charge storage region provided above the charge storage region,
After the charge generated in the photoelectric conversion element is transferred through the charge transfer path and accumulated in the charge accumulation region, a predetermined voltage is applied to some of the accumulation control electrodes to increase the avalanche in the charge accumulation region. An image pickup apparatus including a drive unit that performs a drive to increase the electric charge by generating a double. The imaging apparatus according to claim 1,
The light receiving portion is provided above the charge transfer path, and includes a plurality of transfer electrodes for controlling a charge transfer operation in the charge transfer path;
An imaging device in which a width of the charge transfer direction of the accumulation control electrode is larger than a width of the transfer electrode in the charge transfer direction. The imaging apparatus according to claim 1 or 2,
An imaging apparatus in which the plurality of accumulation control electrodes have the same shape. The imaging apparatus according to any one of claims 1 to 3,
An imaging apparatus in which the driving means changes the predetermined voltage in accordance with imaging conditions. The imaging apparatus according to any one of claims 1 to 4,
Among the plurality of accumulation control electrodes, at least the electrode to which the predetermined voltage is applied is connected with wiring for applying the voltage from above the electrode at regular intervals in the longitudinal direction of the electrode. Imaging device. A method for driving a charge transfer type imaging device,
The image pickup device is connected to the charge transfer path, a light receiving unit including a photoelectric conversion element that receives light from a subject, a charge transfer path that transfers charges read from the photoelectric conversion element, and the charge transfer path A charge storage region for storing the charge transferred from the storage unit, and a storage unit including a plurality of storage control electrodes for controlling a charge storage operation in the charge storage region provided above the charge storage region,
After accumulating the charge generated in the photoelectric conversion element in the charge accumulation region, a predetermined voltage is applied to some of the accumulation control electrodes to cause avalanche multiplication in the charge accumulation region and A driving method of an image sensor that performs driving for multiplication.

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