JP2009070901A - Imaging element, imaging apparatus and method of driving imaging element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging element capable of preventing deterioration in transfer efficiency by ensuring the saturation quantity of signal charges from vertical charge transfer sections to a horizontal charge transfer section. <P>SOLUTION: This imaging element is provided with: a plurality of photoelectric conversion sections 12; a plurality of vertical charge transfer sections 14 for transferring signal charges generated in the photoelectric conversion sections 12 in a column direction; a horizontal charge transfer section 16 for transferring the charges transferred from the vertical charge transfer sections 14 in a row direction; transfer connection sections 18 formed on the end of downstream side of the transfer direction of the plurality of vertical charge transfer sections 14; and a barrier wall 23 formed between the horizontal charge transfer section 16 and the transfer connection sections 18, and working as a potential barrier of signal charges to be transferred. In the horizontal charge transfer section 16, a plurality of charge transfer stages, which work as a charge accumulating region or a barrier region in response to an applied voltage, are formed, the plurality of vertical charge transfer sections 14 are each connected to each of the charge transfer stages, and the potentials of the barrier walls 23a, 23b are different for each of the plurality of vertical charge transfer sections 14 connected to each of the charge transfer stages. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image sensor that generates a signal charge in response to incident light and transfers the signal charge to an output unit, an image pickup apparatus including the image sensor, and a method for driving the image sensor.

  2. Description of the Related Art Conventionally, in an imaging device such as a digital camera, an image sensor is used as an image sensor for generating a signal charge according to incident light and outputting the signal charge to generate image data. As the imaging device, a plurality of photoelectric conversion units are arranged in the row direction and the column direction in the imaging region, and a signal charge is generated by receiving incident light in each photoelectric conversion unit, and the signal read from the photoelectric conversion unit A solid-state device including a vertical charge transfer unit (VCCD) that transfers charges in the column direction and a horizontal charge transfer unit (HCCD) that transfers signal charges transferred from the downstream side of each vertical charge transfer unit in the row direction. There is an image sensor. The horizontal charge transfer unit is arranged in series in the transfer direction and has a plurality of charge transfer stages. A horizontal drive signal is input from the drive circuit to each of the plurality of charge transfer stages. At the time of charge transfer, the charge transfer stage operates as a charge accumulation region or a barrier region in accordance with the applied voltage level of the horizontal drive signal, whereby the signal charge is horizontally transferred in the horizontal charge transfer unit.

  As an image pickup apparatus including a solid-state image pickup device, an image pickup apparatus having a still image recording mode and a moving image recording mode has been developed. In such an imaging apparatus, the number of pixels of a still image is a high pixel such as 4 million to 6 million pixels, but the number of pixels at the time of moving image capturing is a small number of pixels in order to realize high-speed processing. For this reason, in the moving image recording mode, a part of the signal charge is added (vertical addition) in the vertical charge transfer unit, and further, the signal charge is transferred from the vertical charge transfer unit to the horizontal charge transfer unit, and then the signal is transferred to the horizontal charge transfer unit. By adding charges (horizontal addition), image data in which pixels are substantially thinned out is generated.

  In order to realize horizontal addition, the solid-state imaging device is provided with a line memory at a portion (transfer connecting portion) that is a joint between the vertical charge transfer portion and the horizontal charge transfer portion on the downstream side in the transfer direction of the vertical charge transfer portion. Yes. Since the line memory temporarily accumulates the signal charge vertically transferred by the vertical charge transfer unit in a predetermined column and then transfers it to the horizontal charge transfer unit, the signal charge can be added in the horizontal charge transfer unit. Conventionally, as a configuration in which a line memory or the like is provided at a joint between a vertical charge transfer unit and a horizontal charge transfer unit, for example, there is a configuration shown in the following patent document.

  Further, when the number of pixels is increased without increasing the size of the horizontal charge transfer unit, problems such as a decrease in charge transfer capacity, an increase in power consumption, and a deterioration in transfer efficiency of the horizontal charge transfer unit occur. Therefore, a configuration in which a plurality of vertical charge transfer units are connected to each of a plurality of charge transfer stages of the horizontal charge transfer unit has been studied.

JP 2007-134438 A JP 2003-258236 A

  By the way, in the transfer connection part which becomes a joint of a line memory etc. between the vertical charge transfer part and the horizontal charge transfer part, there is a trade-off relationship between the transfer efficiency of the signal charge and the saturation amount of the signal charge. In particular, in a configuration in which a plurality of vertical charge transfer units are connected to each of a plurality of charge transfer stages of the horizontal charge transfer unit, as in the above-described conventional technique, the interval between all the charge transfer stages and the vertical charge transfer unit. , Will form the same barrier. Then, in the case of an image sensor in which the amount of signal charge generated by the photoelectric conversion unit is different, it is necessary to drive the charge transfer stage in accordance with the vertical charge transfer unit having a large amount of signal charge. There is a concern that the transfer time may be lost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image pickup device and an image pickup apparatus that can secure a saturation amount of signal charges from a vertical charge transfer unit to a horizontal charge transfer unit and prevent a decrease in transfer efficiency. And it is providing the drive method of an image pick-up element.

The above object of the present invention is achieved by the following configurations.
(1) A plurality of photoelectric conversion units that are arranged in the column direction and the row direction of the imaging region and generate signal charges according to incident light;
A plurality of vertical charge transfer units that transfer signal charges generated in the photoelectric conversion unit in a column direction;
A horizontal charge transfer unit for transferring the signal charge transferred from the downstream in the transfer direction of each of the plurality of vertical charge transfer units in a row direction;
A transfer connection portion formed at an end on the downstream side in the transfer direction of the plurality of vertical charge transfer portions;
A barrier formed between the horizontal charge transfer unit and the transfer connection unit and functioning as a potential barrier of the transferred signal charge,
The horizontal charge transfer unit is formed with a plurality of charge transfer stages that operate as a charge accumulation region or a barrier region according to an applied voltage, and a plurality of the vertical charge transfer units are connected to each of the plurality of charge transfer stages. An image pickup device, wherein the potential height of the barrier is different for each of the plurality of vertical charge transfer units connected to each charge transfer stage.
(2) The transfer connection portion is provided independently above each of the plurality of charge storage regions connecting each of the plurality of vertical charge transfer portions and the horizontal charge transfer portion, and above each of the plurality of charge storage regions. A line memory having a memory electrode,
The image pickup device according to (1), wherein a voltage can be independently applied to each of the memory electrodes.
(3) Among the plurality of vertical charge transfer units connected to one charge transfer stage, the barrier on the downstream side in the transfer direction of the vertical charge transfer unit having a large amount of signal charge to be transferred is another vertical charge. The imaging device according to (1) or (2), wherein a dimension in a column direction is larger than the barrier on the downstream side in the transfer direction of the transfer unit.
(4) A pixel column formed by arranging predetermined pixels corresponding to the row direction of the plurality of photoelectric conversion units is formed, and the downstream side in the transfer direction of the vertical charge transfer unit that transfers signal charges of the pixel column The barriers having different potential heights are formed according to the amount of signal charges generated in the pixel columns, according to any one of (1) to (3), Image sensor.
(5) A first pixel column including R pixels and B pixels and a second pixel column including G pixels are formed corresponding to the row direction of the plurality of photoelectric conversion units, and the barrier includes the first pixel column. The potential height is higher on the downstream side in the transfer direction of the vertical charge transfer unit for transferring the signal charges of the two pixel columns than on the downstream side in the transfer direction of the vertical charge transfer unit for transferring the signal charges on the first pixel column. The imaging device according to any one of (1) to (4) above, wherein
(6) A first pixel column composed of R pixels and G pixels, or G pixels and B pixels, and a second pixel column composed of W pixels are formed corresponding to the row direction of the plurality of photoelectric conversion units. The barrier includes a downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charges of the second pixel column, and a downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charges of the first pixel column. The imaging device according to any one of (1) to (4), wherein the potential height is higher than that of the imaging device.
(7) The imaging device according to any one of (1) to (6), wherein the barrier is an impurity diffusion region formed by ion implantation of impurities.
(8) An imaging device including the imaging device according to (1) to (7) above.
(9) A plurality of photoelectric conversion units that are arranged in the column direction and the row direction of the imaging region and generate signal charges according to incident light;
A plurality of vertical charge transfer units that transfer signal charges generated in the photoelectric conversion unit in a column direction;
A horizontal charge transfer unit for transferring the signal charge transferred from the downstream in the transfer direction of each of the plurality of vertical charge transfer units in a row direction;
A transfer connection portion formed at an end on the downstream side in the transfer direction of the plurality of vertical charge transfer portions;
A barrier that functions as a potential barrier for transferred signal charges, formed between the horizontal charge transfer section and the transfer connection section,
A plurality of the vertical charge transfer units are connected to each of a plurality of charge transfer stages formed in the horizontal charge transfer unit, and the potential of the barrier for each of the plurality of vertical charge transfer units connected to each charge transfer stage. The transfer connection portions are provided independently of each other above the plurality of charge storage regions and the plurality of charge storage regions that connect each of the plurality of vertical charge transfer portions and the horizontal charge transfer portion. A line memory having a memory electrode, wherein when the signal charge is transferred from the line memory to the horizontal charge transfer unit, the transfer time varies depending on the potential height of the barrier. A method for driving an image sensor, wherein a signal is applied.
(10) Of the plurality of vertical charge transfer units connected to one charge transfer stage, the barrier on the downstream side in the transfer direction of the vertical charge transfer unit having a large amount of signal charge to be transferred is another vertical charge. The image sensor driving method according to (9) above, wherein the dimension in the column direction is larger than the barrier on the downstream side of the transfer unit in the transfer direction.
(11) A pixel column in which predetermined pixels are arranged corresponding to the row direction of the plurality of photoelectric conversion units is formed, and the transfer direction downstream side of the vertical charge transfer unit that transfers signal charges of the pixel column The image sensor driving method according to (9) or (10), wherein the barriers having different potential heights are formed according to the amount of signal charges generated in the pixel columns. .
(12) Corresponding to the row direction of the plurality of photoelectric conversion units, a first pixel column including R pixels and B pixels and a second pixel column including G pixels are formed, and the barrier includes the first pixel column. The potential height is higher on the downstream side in the transfer direction of the vertical charge transfer unit for transferring the signal charges of the two pixel columns than on the downstream side in the transfer direction of the vertical charge transfer unit for transferring the signal charges on the first pixel column. The image pickup element driving method according to any one of (9) to (11) above, wherein:
(13) A first pixel column including R pixels and G pixels, or G pixels and B pixels, and a second pixel column including W pixels are formed corresponding to the row direction of the plurality of photoelectric conversion units. The barrier includes a downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charges of the second pixel column, and a downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charges of the first pixel column. The image sensor driving method according to any one of (9) to (11) above, wherein the potential height is higher than that of the image sensor.
(14) The image sensor driving method according to any one of (9) to (13), wherein the barrier is an impurity diffusion region formed by ion implantation of impurities.

  The imaging device of the present invention has a configuration in which a plurality of vertical charge transfer units are connected to each charge transfer stage of the horizontal charge transfer unit, and a barrier is provided to each of the plurality of vertical charge transfer units connected to each charge transfer stage. The potential height is different. Then, when the signal charge is transferred from the transfer connection portion to the horizontal charge transfer portion, the saturation amount of the signal charge can be increased with a barrier having a high potential height although the transfer speed is reduced. On the other hand, a barrier having a low potential height can improve the transfer rate although the saturation amount of signal charge is reduced. According to such a configuration, in a predetermined pixel arrangement, when there are pixels with a large amount of signal charge generated by the photoelectric conversion unit and pixels with a small amount of signal charge, the column direction of pixels with a large amount of signal charge A barrier with a high potential height is formed on the downstream side in the transfer direction of the vertical charge transfer unit arranged in the vertical direction, and the potential height is set on the downstream side in the transfer direction of the vertical charge transfer unit arranged in the column direction of the pixel with a low signal charge. A low barrier can be formed. At this time, the saturation amount of the signal charge can be ensured by increasing the potential height of the barrier on the downstream side in the transfer direction of the vertical charge transfer unit of the pixel column with a large amount of signal charge. In addition, by adjusting the transfer time of each transfer connection portion according to the potential height of the barrier, it is possible to improve transfer efficiency while securing a saturation amount of signal charge. In this case, it is only necessary to lengthen the transfer time only for the transfer connection portion that transfers the signal charge to the barrier having a high potential, so that the decrease in the frame rate can be minimized.

  ADVANTAGE OF THE INVENTION According to this invention, the saturation amount of the signal charge from a vertical charge transfer part to a horizontal charge transfer part can be ensured, and the imaging device which can prevent the fall of transfer efficiency, an imaging device, and the drive method of an image sensor can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an image sensor according to the present invention. The solid-state imaging device 10 has an imaging area partitioned on a semiconductor substrate such as silicon, and a plurality of photoelectric conversion elements in the column direction (vertical direction in FIG. 1) and the row direction (horizontal direction in FIG. 1) of the imaging area. 12 are arranged in a matrix. The photoelectric conversion element 12 is configured to photoelectrically convert incident light and generate a signal charge corresponding to the incident light, and can be configured by, for example, a photodiode.

  Between the columns of the photoelectric conversion elements 12, vertical charge transfer units 14 extending in the column direction are provided. The vertical charge transfer unit 14 includes a plurality of charge transfer electrodes arranged in the column direction, and a vertical drive signal is input to each charge transfer electrode. Each of the plurality of charge transfer electrodes and a transfer channel formed on the semiconductor substrate surface side corresponding to each charge transfer electrode constitute a transfer stage. By inputting a predetermined vertical drive signal to each transfer stage, the signal charge is transferred along the column direction. A line memory 18 functioning as a transfer connection unit is connected to the final transfer stage located at the end in the transfer direction of each vertical charge transfer unit 14. Each of the line memories 18 is connected to the horizontal charge transfer unit 16. The horizontal charge transfer unit 16 transfers the signal charge transferred from the line memory 18 in the row direction (left direction in FIG. 1) and outputs it from the output amplifier 22.

FIG. 2 is an enlarged view illustrating a configuration of a part surrounded by a broken line of the image sensor shown in FIG.
As shown in FIG. 2, the line memory 18 has a charge storage region 21 that connects each of the vertical charge transfer units 14 and the horizontal charge transfer unit 16. The charge storage region 21 can be, for example, an impurity diffusion region formed by ion-implanting n-type impurity ions into a p-well layer formed on the n-type semiconductor substrate of the image sensor 10. Further, the line memory 18 has a memory electrode 25 provided independently on the charge storage region 21. In the line memory 18, a separation region 24 for ensuring electrical insulation with respect to the line memory 18 adjacent in the row direction is provided at a boundary portion with the adjacent line memory 18. 2 shows a state in which the memory electrode 25 of the line memory 18 is seen through for the sake of explanation.

  The horizontal charge transfer unit 16 includes an electrode set including a pair of transfer electrode 26a and transfer electrode 26b, and has a configuration in which the electrode sets are arranged in series in the horizontal direction. When the horizontal charge transfer unit 16 is driven in two phases, the electrode set includes a first electrode set to which the horizontal transfer pulse φH1 is applied and a second electrode set to which the horizontal transfer pulse φH2 is applied. One electrode group and second electrode group are alternately arranged in the horizontal direction. In such a configuration, one lower region of the first electrode set and the second electrode set operates as a charge storage region according to the level of the applied voltage of the applied horizontal transfer pulses φH1, φH2, and the other The lower region operates as a barrier region between the charge storage regions. As described above, in the horizontal charge transfer path 2, a plurality of charge transfer stages that operate as a barrier region or a charge storage region according to the applied voltage are formed by the overlapping portion of the first electrode set and the second electrode set. .

  Each of the adjacent vertical charge transfer paths 14 is connected to each charge transfer stage of the horizontal charge transfer unit 16 via a charge storage region 21. Of the two charge storage regions 21 connected to each charge transfer stage, a line memory pulse is applied to the memory electrode 25 above the charge storage region 21 on the upstream side (right side in the figure) of the horizontal charge transfer unit 16 in the charge transfer direction. φLM1 is applied, and a line memory pulse φLM2 is applied to the memory electrode 25 above the charge storage region 21 on the downstream side (left side in the figure) of the horizontal charge transfer path 16 in the charge transfer direction. The line memory pulses φLM1 and φLM2 can take a high level state and a low level state, respectively, and function as drive signals when signal charges are transferred from the line memory 18 to the horizontal charge transfer unit 16.

  A barrier 23 that functions as a potential barrier for signal charges transferred to the horizontal charge transfer unit 16 is formed between the horizontal charge transfer unit 16 and the line memory 18. The barrier 23 can be an impurity diffusion region formed by implanting impurity ions into the surface of the semiconductor substrate of the image sensor 10.

  According to the imaging device 10 of the present embodiment, two vertical charge transfer units 14 are connected to one charge transfer stage of the horizontal charge transfer unit 16, and the charge accumulation connected to the two vertical charge transfer units 14. By making it possible to independently apply voltages to the two memory electrodes 25 above the region 21, it is possible to select the charges transferred from the line memory 18 to the horizontal charge transfer path 16. For this reason, the charge transfer capacity of the horizontal charge transfer unit 14 can be increased without increasing the power consumption. In addition, since the number of charge transfer stages can be reduced, it is possible to prevent deterioration of transfer efficiency.

  In the present embodiment, two vertical charge transfer paths 14 are connected to each charge transfer stage of the horizontal charge transfer unit 16, but in the image pickup device according to the present invention, each charge transfer stage is connected to each charge transfer stage. The number of vertical charge transfer paths 1 may be three or more.

  The imaging device 10 has a configuration in which the potential height of the barrier 23 is different for each of the two vertical charge transfer units 14 connected to the charge transfer stage of the horizontal charge transfer unit 16. Specifically, out of the two vertical charge transfer units 14 connected to one charge transfer stage, the vertical charge transfer unit having a large amount of signal charge to be transferred (in this embodiment, the vertical charge transfer on the right side in FIG. 2). The barrier 23b on the downstream side in the transfer direction of the transfer portion) is compared with the barrier 23a on the downstream side in the transfer direction of the other vertical charge transfer portions (the left vertical charge transfer portion in FIG. 2). It is formed so that the size becomes large. The procedure for forming the barrier 23a will be described later.

  FIG. 3 is a diagram showing a potential gradient at the time of signal charge transfer in a portion indicated by a dotted line of the image sensor in FIG. FIG. 4 is a diagram illustrating a potential gradient in a state where a signal charge is held in a portion indicated by a dotted line of the image sensor in FIG. In FIG. 3A and FIG. 4A, “left side” means a potential indicated by a dotted line on the downstream side in the transfer direction of the left vertical charge transfer unit in FIG. 2, and FIG. In b), “right side” means a potential indicated by a dotted line on the downstream side in the transfer direction of the vertical charge transfer unit on the right side of FIG.

  FIG. 3 shows a state in which a signal charge is transferred from the line memory 18 to the horizontal charge transfer unit 16 by applying a low voltage to the line memory 18 and applying a high voltage to the horizontal charge transfer unit 16. Yes. Since the barrier 23b on the downstream side in the transfer direction of the right line memory 18 has a higher potential height than the barrier 23a on the downstream side in the transfer direction of the left line memory 18, the transfer rate of the signal charge is slow. The saturation amount of the signal charge becomes larger than that on the left side. On the contrary, the barrier 23a on the downstream side in the transfer direction of the left line memory 18 has a lower potential height than the barrier 23b on the downstream side in the transfer direction of the right line memory 18, so that the transfer rate of the signal charge is high. Although faster, the amount of signal charge saturation is smaller than on the right side.

  FIG. 4 shows a state in which a signal charge is not transferred from the line memory 18 to the horizontal charge transfer unit 16 but is held by applying a low voltage to the line memory 18 and the horizontal charge transfer unit 16. The barrier 23 b on the downstream side in the transfer direction of the right line memory 18 has a higher potential height than the barrier 23 a on the downstream side in the transfer direction of the left line memory 18.

  In the present embodiment, the line memory 18 is formed at the end of each vertical charge transfer unit 14 on the downstream side in the transfer direction and functions as a transfer connection unit. However, the transfer connection unit is not limited to this. . For example, without forming the line memory 18, the signal charge is transferred from the vertical charge transfer unit to the horizontal charge transfer unit with the final transfer stage at the downstream end in the transfer direction of the vertical charge transfer unit 14 as the transfer connection unit. It can also be configured. At this time, a barrier is formed between the vertical charge transfer unit 14 and the horizontal charge transfer unit 16, and a plurality of vertical charge transfer units 14 are connected to each of the charge transfer stages of the horizontal charge transfer unit 16. What is necessary is just to set it as the structure from which the potential height of the barrier 23 differs for every some vertical electric charge transfer part 14 connected to.

  The imaging device 10 of the present invention has a configuration in which a plurality of vertical charge transfer units 14 are connected to each charge transfer stage of the horizontal charge transfer unit 16, and a plurality of vertical charge transfer units 14 connected to each charge transfer stage. The potential height of the barrier 23 (23a, 23b) is different for each. Then, when the signal charge is transferred from the line memory 18 to the horizontal charge transfer unit 16, the saturation rate of the signal charge can be increased in the barrier 23b having a high potential height although the transfer speed is decreased. On the other hand, the barrier 23a having a low potential height can improve the transfer speed although the saturation amount of the signal charge is reduced. According to such a configuration, in a predetermined pixel arrangement, when there are a pixel with a large amount of signal charge generated by the photoelectric conversion unit 12 and a pixel with a small amount of signal charge, the column direction of the pixel with a large amount of signal charge A barrier 23b having a high potential height is formed on the downstream side in the transfer direction of the vertical charge transfer unit 14 arranged in the vertical direction, and a potential is formed on the downstream side in the transfer direction of the vertical charge transfer unit arranged in the column direction of the pixel having a small signal charge amount. The barrier 23a having a low height can be formed. At this time, the saturation amount of the signal charge can be ensured by increasing the potential height of the barrier 23 on the downstream side in the transfer direction of the vertical charge transfer unit 14 of the pixel column having a large signal charge amount. Further, by adjusting the transfer time of each line memory 18 according to the potential height of the barrier 23, the transfer efficiency can be improved while securing the saturation amount of the signal charge. By so doing, it is possible to minimize the decrease in the frame rate by controlling the transfer time for only the line memory 18 that transfers the signal charge to the high potential barrier 23b.

  FIG. 5 is a diagram illustrating an example of a procedure for forming a barrier of the image sensor. As shown in FIG. 5, in the embodiment described below, members having the same configuration / action as those already described are denoted by the same or corresponding reference numerals in the drawing. Simplify or omit.

  Before forming the barrier 23, the transfer electrode 26a on the side where the barrier 23a having a low potential height of the horizontal charge transfer portion 16 is formed in advance is formed of the first polysilicon. Thereafter, impurity ions of the barrier 23 are ion-implanted by ion implantation of a long strip-shaped region extending in the horizontal direction between the line memory 18 and the horizontal charge transfer unit 16 by the mask M forming the barrier 23. In FIG. 5, regions where impurity ions are implanted by the mask M are indicated by hatching. At this time, a part of the region to be ion-implanted overlaps with a part of the transfer electrode 26a, and the ion is not implanted in the overlapping region. As a result, the barrier 23 is not formed and the transfer region 26a is not formed. A barrier 23b having a long dimension is formed in the vertical direction (vertical direction in FIG. 5). Thereafter, the transfer electrode 26b is formed of the second polysilicon on the downstream side in the transfer direction of the barrier 23b (the lower side in FIG. 5). In this way, by performing ion implantation once using one mask M, the shape corresponding to the position of the vertical charge transfer unit 14 is changed without changing the ion concentration or the like implanted at the time of ion implantation. The different barriers 23 can be formed by self-alignment.

Next, the procedure of the driving method of the image sensor will be described with reference to the image sensor having the above configuration.
FIG. 6 shows a timing chart when signal charges are transferred from the line memory of the image sensor to the horizontal charge transfer unit. 6A shows a case where transfer is performed from the barrier 23a having a low potential height corresponding to the left vertical charge transfer unit 14 to the horizontal charge transfer unit 14 in the image sensor 10 shown in FIG. b) shows a case where transfer is performed from the barrier 23b having a high potential corresponding to the right vertical charge transfer unit 14 to the horizontal charge transfer unit 14.

  As shown in FIGS. 6A and 6B, when signal charges are transferred from the barrier 23b having a high potential to the horizontal charge transfer unit 16, the transfer time is longer than that of the barrier 23a having a low potential. Become. At this time, in order to avoid problems such as vertical stripes due to transfer failure, the transfer time t2 of the line memory 18 on the upstream side in the transfer direction of the barrier 23b with high potential is set to the upstream side in the transfer direction on the barrier 23a with low potential height. Control is performed so as to be longer than the transfer time t1 of the line memory 18. In the conventional imaging device, when the saturation amount of the signal charge is increased, it is necessary to lengthen the transfer time in all lines including the line with a small saturation amount. As described above, in a configuration in which barriers having different potential heights are provided, a reduction in frame rate can be minimized by controlling the length of the transfer time of the line memory for each barrier. The length of the transfer time can be controlled by applying line memory pulses having different transfer times (high-level or low-level periods) to the memory electrodes 25 of the line memory 18. In this embodiment, it is only necessary to lengthen the transfer time of the line memory for only half the lines. In the case of performing blankingless driving or the like during horizontal transfer, shortening the transfer time of the line memory 18 greatly affects the frame rate, so the effect is remarkable.

  In the imaging device 10 of the above-described embodiment, a pixel column in which predetermined pixels are arranged corresponding to the row direction of the plurality of photoelectric conversion units 12 arranged in the row direction and the column direction of the imaging region is formed. A barrier 23 having a different potential height can be formed on the downstream side in the transfer direction of the vertical charge transfer unit 14 for transferring the signal charge according to the amount of signal charge generated in the pixel column.

  FIG. 7 is a diagram illustrating a configuration having a pixel array including R pixels, G pixels, and B pixels corresponding to the photoelectric conversion unit of the image sensor. FIG. 8 is a diagram illustrating a configuration having a pixel array including R pixels, G pixels, B pixels, and W pixels corresponding to the photoelectric conversion unit of the image sensor.

  In the pixel array shown in FIG. 7, among the pixels arranged in the column direction and the row direction, each of the pixel columns arranged in the column direction is located at a position where the pixels are shifted by 1/2 pitch with respect to the adjacent pixel columns. Is provided. In addition, first pixel columns that are R pixels and B pixels and second pixel columns that are G pixels are alternately arranged in the row direction. Usually, the amount of signal charge read from the pixel column of the G pixel is larger than the amount of signal charge read from the pixel column of the R pixel and B pixel. For this reason, a barrier 23a having a high potential is arranged on the downstream side in the transfer direction of the vertical charge transfer unit 14 corresponding to the first pixel column with a small amount of signal charge, and corresponds to the second pixel column with a large amount of signal charge. The barrier 23b having a high potential is arranged downstream of the vertical charge transfer unit 14 in the transfer direction. In this way, it is possible to ensure the saturation amount of the signal charge in the line memory 18 according to the difference in the amount of signal charge based on the pixel arrangement.

  8, as in FIG. 7, among the pixels arranged in the column direction and the row direction, each of the pixel columns arranged in the column direction has half the pixels with respect to the adjacent pixel columns. It is provided at a position shifted by the pitch. In addition, first pixel columns made up of R pixels and G pixels, or G pixels and B pixels, and second pixel columns made up of only W (white) pixels are alternately arranged in the row direction. Usually, the amount of signal charge read from the second pixel column of W pixels is larger than the amount of signal charge read from the first pixel column consisting of R pixels and G pixels, or G pixels and B pixels. For this reason, a barrier 23a having a high potential is arranged on the downstream side in the transfer direction of the vertical charge transfer unit 14 corresponding to the first pixel column with a small amount of signal charge, and corresponds to the second pixel column with a large amount of signal charge. The barrier 23b having a high potential is arranged downstream of the vertical charge transfer unit 14 in the transfer direction. In this way, it is possible to ensure the saturation amount of the signal charge in the line memory 18 according to the difference in the amount of signal charge based on the pixel arrangement.

  According to the imaging device including the imaging device according to the present invention, it is possible to improve the transfer efficiency from the vertical charge transfer unit to the horizontal charge transfer unit. Further, the saturation amount of the signal charge can be ensured appropriately, and it is possible to avoid the occurrence of problems such as vertical stripes in the output image.

It is a figure which shows the structure of the image pick-up element concerning this invention. It is an enlarged view explaining the structure of the site | part enclosed by the broken line of the image pick-up element shown in FIG. It is a figure which shows the potential gradient at the time of the transfer of a signal charge of the part shown with the dotted line of the image pick-up element of FIG. It is a figure which shows the potential gradient in the state holding the signal charge of the part shown with the dotted line of the image pick-up element of FIG. It is a figure explaining an example of the procedure which forms the barrier of an image sensor. 3 shows a timing chart when signal charges are transferred from a line memory of an image sensor to a horizontal charge transfer unit. It is a figure which shows the structure which has a pixel arrangement | sequence which consists of R pixel, G pixel, and B pixel corresponding to the photoelectric conversion part of an image pick-up element. It is a figure which shows the structure which has a pixel arrangement | sequence which consists of R pixel, G pixel, B pixel, and W pixel corresponding to the photoelectric conversion part of an image pick-up element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image sensor 12 Photoelectric conversion part 14 Vertical charge transfer part 16 Horizontal charge transfer part 18 Line memory (transfer connection part)
23 (23a, 23b) Barrier

Claims (14)

A plurality of photoelectric conversion units arranged in the column direction and the row direction of the imaging region and generating signal charges according to incident light;
A plurality of vertical charge transfer units that transfer signal charges generated in the photoelectric conversion unit in a column direction;
A horizontal charge transfer unit for transferring the signal charge transferred from the downstream in the transfer direction of each of the plurality of vertical charge transfer units in a row direction;
A transfer connection portion formed at an end on the downstream side in the transfer direction of the plurality of vertical charge transfer portions;
A barrier formed between the horizontal charge transfer unit and the transfer connection unit and functioning as a potential barrier of the transferred signal charge,
The horizontal charge transfer unit is formed with a plurality of charge transfer stages that operate as a charge accumulation region or a barrier region according to an applied voltage, and a plurality of the vertical charge transfer units are connected to each of the plurality of charge transfer stages. An image pickup device, wherein the potential height of the barrier is different for each of the plurality of vertical charge transfer units connected to each charge transfer stage. A plurality of charge storage regions each connecting the plurality of vertical charge transfer units and the horizontal charge transfer unit; and a memory electrode provided independently above each of the plurality of charge storage regions. A line memory having
The image sensor according to claim 1, wherein a voltage can be independently applied to each of the memory electrodes.   Among the plurality of vertical charge transfer units connected to one charge transfer stage, the barrier on the downstream side in the transfer direction of the vertical charge transfer unit having a large amount of signal charge to be transferred is connected to the other vertical charge transfer unit. The image sensor according to claim 1, wherein a dimension in a column direction is larger than the barrier on the downstream side in the transfer direction.   A pixel column formed by arranging predetermined pixels corresponding to the row direction of the plurality of photoelectric conversion units is formed, and on the downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charge of the pixel column, 4. The image pickup device according to claim 1, wherein the barrier having different potential heights is formed according to the amount of signal charge generated in a pixel column. 5.   A first pixel column including R pixels and B pixels and a second pixel column including G pixels are formed corresponding to the row direction of the plurality of photoelectric conversion units, and the barrier includes the second pixel column. The vertical charge transfer unit for transferring the signal charge of the vertical charge transfer unit has a higher potential height than the transfer direction downstream side of the vertical charge transfer unit for transferring the signal charge of the first pixel column. The imaging device according to any one of claims 1 to 4.   Corresponding to the row direction of the plurality of photoelectric conversion units, a first pixel column composed of an R pixel and a G pixel or a G pixel and a B pixel and a second pixel column composed of a W pixel are formed, The barrier is such that the downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charge of the second pixel column is lower than the transfer direction downstream side of the vertical charge transfer unit that transfers the signal charge of the first pixel column. The image sensor according to claim 1, wherein the potential height is high.   The imaging device according to claim 1, wherein the barrier is an impurity diffusion region formed by ion implantation of impurities.   An imaging device comprising the imaging device according to claim 1. A plurality of photoelectric conversion units arranged in the column direction and the row direction of the imaging region and generating signal charges according to incident light;
A plurality of vertical charge transfer units that transfer signal charges generated in the photoelectric conversion unit in a column direction;
A horizontal charge transfer unit for transferring the signal charge transferred from the downstream in the transfer direction of each of the plurality of vertical charge transfer units in a row direction;
A transfer connection portion formed at an end on the downstream side in the transfer direction of the plurality of vertical charge transfer portions;
A barrier that functions as a potential barrier for transferred signal charges, formed between the horizontal charge transfer section and the transfer connection section,
A plurality of the vertical charge transfer units are connected to each of a plurality of charge transfer stages formed in the horizontal charge transfer unit, and the potential of the barrier for each of the plurality of vertical charge transfer units connected to each charge transfer stage. The transfer connection portions are provided independently of each other above the plurality of charge storage regions and the plurality of charge storage regions that connect each of the plurality of vertical charge transfer portions and the horizontal charge transfer portion. A line memory having a memory electrode, wherein when the signal charge is transferred from the line memory to the horizontal charge transfer unit, the transfer time varies depending on the potential height of the barrier. A method for driving an image sensor, wherein a signal is applied.   Among the plurality of vertical charge transfer units connected to one charge transfer stage, the barrier on the downstream side in the transfer direction of the vertical charge transfer unit having a large amount of signal charge to be transferred is connected to the other vertical charge transfer unit. The image sensor driving method according to claim 9, wherein a dimension in a column direction is larger than the barrier on the downstream side in the transfer direction.   A pixel column formed by arranging predetermined pixels corresponding to the row direction of the plurality of photoelectric conversion units is formed, and on the downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charge of the pixel column, 11. The image sensor driving method according to claim 9, wherein the barriers having different potential heights are formed according to the amount of signal charges generated in a pixel column.   A first pixel column including R pixels and B pixels and a second pixel column including G pixels are formed corresponding to the row direction of the plurality of photoelectric conversion units, and the barrier includes the second pixel column. The vertical charge transfer unit for transferring the signal charge of the vertical charge transfer unit has a higher potential height than the transfer direction downstream side of the vertical charge transfer unit for transferring the signal charge of the first pixel column. The method for driving an imaging device according to claim 9.   Corresponding to the row direction of the plurality of photoelectric conversion units, a first pixel column composed of an R pixel and a G pixel or a G pixel and a B pixel and a second pixel column composed of a W pixel are formed, The barrier is such that the downstream side in the transfer direction of the vertical charge transfer unit that transfers the signal charge of the second pixel column is lower than the transfer direction downstream side of the vertical charge transfer unit that transfers the signal charge of the first pixel column. 12. The image sensor driving method according to claim 9, wherein the potential height is high.   The image sensor driving method according to claim 9, wherein the barrier is an impurity diffusion region formed by ion implantation of impurities.

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