Image sensor and image pickup apparatus

Abstract

Provided is an image sensor in which a length of a pixel portion in a first direction is longer than a length of the pixel portion in a second direction orthogonal to the first direction, characterized in that the pixel portion includes: a plurality of microlenses arranged in a matrix in the first direction and the second direction; and a plurality of photoelectric conversion units provided for each of at least a portion of the plurality of microlenses, and configured to photoelectrically convert light incident on the photoelectric conversion units via each of the microlenses, the plurality of photoelectric conversion portions are arranged in at least one of the first direction and the second direction, and a charge crosstalk rate between the plurality of photoelectric conversion portions arranged in the first direction is higher than a charge crosstalk rate between the plurality of photoelectric conversion portions arranged in the second direction.

Description

Technical Field

[0001] The present invention relates to an image sensor in which pixel portions each including a plurality of photoelectric conversion portions are two-dimensionally arranged, and an image pickup apparatus equipped with the image sensor. Background Art

[0002] Conventionally, as a focus detection method performed by an image pickup apparatus, a so-called imaging plane phase difference method for obtaining a pair of pupil division signals using each focus detection pixel formed in an image sensor and performing phase difference focus detection is known.

[0003] As an example of such an imaging surface phase difference method, Patent Document 1 discloses an imaging device using a two-dimensional image sensor in which a microlens and a plurality of segmented photoelectric conversion units are formed in each pixel. These multiple photoelectric conversion units are configured to receive light from different regions of the exit pupil of the imaging lens via a microlens, thereby achieving pupil segmentation. Then, phase difference focus detection can be performed by calculating the image shift amount based on the phase difference signal as the signal of each photoelectric conversion unit. In addition, a common image signal can be obtained by adding the signals of each photoelectric conversion unit together for each pixel. In addition, Patent Document 1 discloses a structure in which the saturation tolerance of a pixel is increased by arranging multiple types of pixels with different heights of the separation barrier between the photoelectric conversion units.

[0004] In such an image sensor, utilizing a structure in which a plurality of photoelectric conversion units are arranged in the horizontal direction in each pixel and the pupil division direction is the horizontal direction, for example, in a case where the subject has a horizontal stripe texture, etc., there is a situation in which parallax is less likely to occur and the focus detection accuracy decreases.

[0005] In contrast, Patent Document 2 discloses a technique for improving focus detection accuracy by arranging photoelectric conversion units relative to each microlens in two directions, thereby performing pupil division in two directions. In addition, Patent Document 2 discloses a structure in which the intensity of charge leakage to adjacent photoelectric conversion units is different between a structure in which adjacent photoelectric conversion units are separated from each other in the vertical direction and a structure in which adjacent photoelectric conversion units are separated from each other in the horizontal direction. Due to this structure, the oversaturated charge received when the amount of charge that can be accumulated in one photoelectric conversion unit is exceeded leaks to another photoelectric conversion unit placed in a predetermined direction and is accumulated in the other photoelectric conversion unit, and as a result, phase difference focus detection can be performed in the horizontal direction or the vertical direction even when one photoelectric conversion unit is saturated.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-212351

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-107835 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In most conventional image sensors, the aspect ratio is not 1: 1. For this reason, in the case where imaging plane phase difference focus detection pixels for the vertical direction and focus detection pixels for the horizontal direction are arranged on the image sensor, the performance of imaging plane phase difference focus detection is biased toward one of the vertical direction and the horizontal direction, especially in the peripheral portion of the image sensor.

[0012] In the image sensor described in Patent Document 1, the separation state of the photoelectric conversion unit differs depending on the saturation state of the pixel. For this reason, the image sensor described in Patent Document 1 does not control the state of charge crosstalk (a phenomenon in which charge leaks to adjacent photoelectric conversion units) between the photoelectric conversion units in each of the focus detection pixel for the vertical direction and the focus detection pixel for the horizontal direction according to the aspect ratio of the image sensor, and cannot solve the above-mentioned problem.

[0013] In addition, the image sensor in Patent Document 2 does not have a structure for controlling charge crosstalk when the photoelectric conversion unit is not saturated, and Patent Document 2 does not mention the charge crosstalk rate between the photoelectric conversion units based on the aspect ratio of the image sensor, and thus cannot solve the above-mentioned problems.

[0014] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the performance of imaging plane phase difference focus detection using signals output from image sensors having different horizontal lengths and vertical lengths.

[0015] Solutions for solving problems

[0016] To achieve this object, according to an image sensor of the present invention, a length of a pixel portion in a first direction is longer than a length of the pixel portion in a second direction orthogonal to the first direction, and is characterized in that the pixel portion comprises: a plurality of microlenses arranged in a matrix in the first direction and the second direction; and a plurality of photoelectric conversion portions configured to perform photoelectric conversion on light incident on the photoelectric conversion portion via each microlens in at least a part of the plurality of microlenses, a plurality of photoelectric conversion portions corresponding to each microlens being arranged in at least one direction of the first direction and the second direction, and a charge crosstalk rate between the plurality of photoelectric conversion portions in the first direction is higher than a charge crosstalk rate between the plurality of photoelectric conversion portions in the second direction.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to improve the performance of imaging plane phase difference focus detection using signals output from image sensors having different horizontal lengths and vertical lengths.

[0019] Other features and advantages of the present invention will be apparent from the following description in conjunction with the accompanying drawings. Note that throughout the accompanying drawings, the same reference numerals represent the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0021] Figure 1 is a block diagram showing a schematic structure of an image pickup apparatus according to a first embodiment.

[0022] Figure 2 is a diagram schematically showing an example of the overall structure of an image sensor according to the first embodiment.

[0023] Figure 3 is an equivalent circuit diagram of a pixel according to the first embodiment.

[0024] Figure 4A is a schematic diagram showing the structure of a pixel having a first arrangement according to the first embodiment.

[0025] Figure 4B is a schematic diagram showing the structure of a pixel having a first arrangement according to the first embodiment.

[0026] Figure 5A is a schematic diagram showing the structure of a pixel having a second arrangement according to the first embodiment.

[0027] Figure 5B is a schematic diagram showing the structure of a pixel having a second arrangement according to the first embodiment.

[0028] Figure 6 is a diagram showing the relationship between pixels having a first arrangement and a partial pupil area according to the first embodiment.

[0029] Figure 7 is a schematic diagram showing an example of pupil intensity distribution of pixels having a first arrangement according to the first embodiment.

[0030] Figure 8 is a diagram schematically illustrating a sensor entrance pupil of the image sensor according to the first embodiment.

[0031] Fig. 9: is a diagram showing a schematic relationship between the image shift amount between parallax images and the defocus amount according to the first embodiment.

[0032] Fig.10 is a schematic diagram showing the relationship between the charge crosstalk rate and the pupil intensity distribution according to the first embodiment.

[0033] Fig.11A is a schematic diagram showing the structure of a pixel having a third arrangement according to the second embodiment.

[0034] Fig. 11B is a schematic diagram showing the structure of a pixel having a third arrangement according to the second embodiment. DETAILED DESCRIPTION

[0035] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. A plurality of features are described in the embodiments, but are not limited to an invention requiring all such features, and a plurality of such features may be appropriately combined. In addition, in the accompanying drawings, the same reference numerals are given to the same or similar structures, and redundant descriptions thereof are omitted.

[0036] First embodiment

[0037] Overall structure

[0038] Figure 1 1 is a block diagram showing a schematic structure of an image pickup device according to a first embodiment of the present invention. The image pickup device according to this embodiment includes an image sensor 1, an overall control / computation unit 2, an instruction unit 3, a timing generation unit 4, an image pickup lens unit 5, a lens driving unit 6, a signal processing unit 7, a display unit 8, and a recording unit 9.

[0039] The imaging lens unit 5 is used to form an optical image of a subject through the image sensor 1. The imaging lens unit 5, which is illustrated as one lens in the figure, includes a plurality of lenses (including a focus lens and a zoom lens, etc.), and a diaphragm. In addition, the imaging lens unit 5 may be detachable from the main body of the imaging device, or may be formed integrally with the main body.

[0040] The image sensor 1 converts light incident to the image sensor 1 via the camera lens unit 5 into an electric signal and outputs the electric signal. Signals are read out from the pixels of the image sensor 1 so that a pupil division signal (hereinafter referred to as a "phase difference signal") which has been obtained by pupil division and can be used for phase difference focus detection, and an image signal corresponding to the pixel can be obtained.

[0041] The signal processing unit 7 performs predetermined signal processing such as correction processing on the signal output from the image sensor 1 , and outputs a phase difference signal to be used for focus detection and an image signal to be used for recording.

[0042] The overall control / calculation unit 2 performs overall driving and control of the entire imaging apparatus. In addition, the overall control / calculation unit 2 performs calculations for focus detection using the phase difference signal processed by the signal processing unit 7, and performs predetermined signal processing on the image signal, such as calculation processing for exposure control, development for generating an image to be recorded / reproduced, and compression.

[0043] The lens driving unit 6 is a unit for driving the imaging lens unit 5 , and performs focus control, zoom control, iris control, and the like on the imaging lens unit 5 according to a control signal from the overall control calculation unit 2 .

[0044] The instruction unit 3 accepts inputs of instructions to perform imaging, drive mode settings of the imaging device, other various types of settings, and selections (input from the outside through operations performed by a user, etc.), and sends such inputs to the overall control / computing unit 2.

[0045] The timing generation unit 4 generates a timing signal for driving the image sensor 1 and the signal processing unit 7 according to the control signal from the overall control calculation unit 2 .

[0046] The display unit 8 displays a preview image, a reproduced image, and information such as a drive mode setting of the image pickup apparatus.

[0047] The recording unit 9 is equipped with a recording medium (not illustrated) and records an image signal for recording. Examples of the recording medium include semiconductor memories such as flash memories, etc. The recording medium may be detachable from the recording unit 9 or incorporated in the recording unit 9.

[0048] Image Sensor

[0049] Figure 2 It is schematically shown Figure 1 FIG. 2 is a diagram showing an example of the overall structure of an image sensor 1. The image sensor 1 includes a pixel array unit 201, a vertical selection circuit 202, a column circuit 203, and a horizontal selection circuit 204.

[0050] The pixel array unit 201 is a pixel unit in which a plurality of pixels 205 are arranged in a matrix. As a result of the output of the vertical selection circuit 202 being input to the pixel 205 via the pixel drive wiring group 207, the pixel signal of the pixel 205 in the row selected by the vertical selection circuit 202 is read out to the column circuit 203 via the output signal line 206 in a row unit. One output signal line 206 may be provided for each pixel column or a plurality of pixel columns, or a plurality of output signal lines 206 may be provided for each pixel column. The signal read out in parallel is input to the column circuit 203 via the plurality of output signal lines 206, and the column circuit 203 performs processing such as amplification, noise reduction, and A / D conversion on the signal, and holds the processed signal. The horizontal selection circuit 204 sequentially, randomly, or simultaneously selects the signal held in the column circuit 203, and as a result, the selected signal is output to the outside of the image sensor 1 via the horizontal output line and the output unit (not illustrated).

[0051] By sequentially performing the operation of outputting pixel signals of the row selected by the vertical selection circuit 202 to the outside of the image sensor 1 in this manner while changing the row selected by the vertical selection circuit 202, a two-dimensional image signal or a phase difference signal can be read out from the image sensor 1.

[0052] In addition, as an example, the size of the area where focus detection pixels that can be used for imaging plane phase difference focus detection are arranged is 36 mm in width H in the x direction and 24 mm in height V in the y direction.

[0053] Pixel circuit / signal readout

[0054] Figure 3 is a diagram of an equivalent circuit of the pixel 205 according to the present embodiment.

[0055] Each pixel 205 includes two photodiodes 301 (PDA) and 302 (PDB) as photoelectric conversion units. The signal charge obtained and accumulated by the PDA 301 through photoelectric conversion according to the amount of incident light is transferred to the floating diffusion unit (FD) 305 constituting the charge accumulation unit via the transfer switch (TXA) 303. In addition, the charge signal photoelectrically converted and accumulated by the PDB 302 is transferred to the FD 305 via the transfer switch (TXB) 304. By turning on the reset switch (RES) 306, the FD 305 is reset to the voltage of the constant voltage source VDD. In addition, by turning on the RES 306, the TXA 303 and the TXB 304 at the same time, the PDA 301 and the PDB 302 can be reset.

[0056] By turning on the selection switch (SEL) 307 for selecting a pixel, the amplifier transistor (SF) 308 converts the signal charge accumulated in the FD 305 into a voltage, and the signal voltage obtained by the conversion is output from the pixel to the output signal line 206. In addition, the gates of the TXA 303, TXB 304, RES 306, and SEL 307 are connected to the pixel drive wiring group 207, and are controlled by the vertical selection circuit 202.

[0057] Note that in the following description, in this embodiment, the signal charge accumulated in the photoelectric conversion unit is defined as electrons, the photoelectric conversion unit is formed by an N-type semiconductor, and is separated by a P-type semiconductor, but the following structure can also be adopted: the signal charge is defined as electron holes, and the photoelectric conversion unit is formed by a P-type semiconductor and is separated by an N-type semiconductor.

[0058] Next, the operation of reading out the signal charge from the PDA 301 and the PDB 302 after a predetermined charge accumulation time has passed since the PDA 301 and the PDB 302 were reset from the pixel having the above-mentioned structure will be described. First, when the SEL 307 of each pixel in the row selected by the vertical selection circuit 202 is turned on, and the source of the SF 308 and the output signal line 206 are connected to each other, the output signal line 206 enters a state of reading out a voltage corresponding to the voltage of the FD 305. Next, the RES 306 is turned on / off, and the potential of the FD 305 is reset. Thereafter, a waiting period is provided until the output signal line 206 that has undergone the voltage change in the FD 305 is stabilized, and the voltage of the stabilized output signal line 206 is taken in as the signal voltage N by the column circuit 203, subjected to signal processing, and held.

[0059] Then, the TXA 303 is turned on / off, and the signal charge accumulated in the PDA 301 is transferred to the FD 305. The voltage of the FD 305 drops by an amount corresponding to the amount of the signal charge accumulated in the PDA 301. Thereafter, a waiting period is provided until the output signal line 206 that has undergone the voltage change in the FD 305 is stabilized, and the voltage of the stabilized output signal line 206 is taken in as the signal voltage A by the column circuit 203, subjected to signal processing, and held.

[0060] Then, the TXB 304 is turned on / off, and the signal charge accumulated in the PDB 302 is transferred to the FD 305. The voltage of the FD 305 drops by an amount corresponding to the amount of the signal charge accumulated in the PDB 302. Thereafter, a waiting period is provided until the output signal line 206 that has undergone the voltage change in the FD 305 is stabilized, and the voltage of the stabilized output signal line 206 is taken in as a signal voltage (A+B) by the column circuit 203, subjected to signal processing, and held.

[0061] A signal A based on the amount of signal charge accumulated in the PDA 301 can be obtained based on the difference between the signal voltage N and the signal voltage A taken in this way. In addition, a signal B based on the amount of signal charge accumulated in the PDB 302 can be obtained based on the difference between the signal voltage A and the signal voltage (A+B). This difference calculation can be performed by the column circuit 203, or can be performed after the signal is output from the image sensor 1. A phase difference signal can be obtained by using the signal A and the signal B, and an image signal can be obtained by adding the signal A and the signal B together. Alternatively, in the case where the difference calculation is performed after the signal is output from the image sensor 1, the image signal can be obtained by using the difference between the signal voltage N and the signal voltage (A+B).

[0062] In addition, the signal voltage N, the signal voltage A, and the signal voltage B can be read out by performing a readout operation for the PDB 302 similarly to the readout operation for reading out the signal voltage N and the signal voltage A performed for the PDA 301. In this case, the signal A and the signal B obtained from the signal voltage A and the signal voltage B, respectively, can be used as phase difference signals as they are, and an image signal can be obtained by adding the signal voltage A and the signal voltage B together, or adding the signal A and the signal B together.

[0063] Structure of the photoelectric conversion region

[0064] ●Phase difference detection pixel structure in the x direction

[0065] Figure 4A and Figure 4B is a schematic diagram showing a first arrangement of semiconductor regions constituting a pixel 205 according to the present embodiment, Figure 4A is a schematic stereogram, and Figure 4B It is a schematic plan view showing the positional relationship in a plan view. Note that the "plan view" refers to a plane (xy plane) parallel to the side of the gate of the transistor on which the semiconductor substrate is placed, viewed from the z direction or the -z direction. In addition, the "row" direction refers to the x direction, the "column" direction refers to the y direction, and the "depth" direction refers to the z direction.

[0066] like Figure 4A As shown, the pixel 205 having the first arrangement includes a microlens (ML) 401, a PDA 301, a PDB 302, a TXA 303, a TXB 304, and an FD 305. In the first arrangement, the PDA 301 and the PDB 302 are arranged in the x direction and formed in a Si substrate as a semiconductor substrate, the side of the substrate on which the ML 401 is placed is the back side, and the side of the substrate on which the TXAs 303 and 304 and the FD 305 are placed is the front side.

[0067] Most of the light incident on the pixel via the ML 401 undergoes photoelectric conversion on the back side of the substrate where the PDA 301 and the PDB 302 are placed. Here, a potential gradient is formed so that the potential applied to the electrons in the PDA 301 and the PDB 302 decreases in the depth direction, so that the charges generated in the PDA 301 and the PDB 302 are likely to move to the TXA 303 and the TXB 304, respectively.

[0068] In addition, the separation region 400 having a p-type impurity concentration higher than that of the PDA 301 and the PDB 302 is formed so that a potential barrier is formed between the PDA 301 and the PDB 302. Therefore, the PDA 301 and the PDB 302 are electrically separated from each other, making it less likely that the generated charges move between the PDA 301 and the PDB 302. Therefore, in the present embodiment, the division direction of the PDA 301 and the PDB 302 in the first arrangement is the x direction (first direction).

[0069] Phase difference detection pixel structure in the y direction

[0070] Figure 5A and Figure 5B is a schematic diagram showing a second arrangement of semiconductor regions constituting the pixel 205 according to the present embodiment, Figure 5A is a schematic stereogram, and Figure 5B is a schematic plan view showing the positional relationship in a plan view. Note that the definitions of "plan view" and x, y, and z are the same as Figure 4A and Figure 4B These definitions are the same, so their description is omitted.

[0071] like Figure 5A As shown in FIG. 1 , the pixel 205 having the second arrangement includes ML 401, PDA 301, PDB 302, TXA 303, TXB 304, and FD 305. The basic structure of the pixel 205 having the second arrangement is similar to that of FIG. 1 . Figure 4A and Figure 4B The basic structure of the first arrangement in is similar, but the PDA 301 and the PDB 302 are arranged in the y direction, and the separation direction of the photoelectric conversion parts is the y direction (second direction).

[0072] Also in the second arrangement, a potential gradient is formed so that the potential applied to electrons in PDA 301 and PDB 302 decreases in the depth direction, so that the charges generated in PDA 301 and PDB 302 are likely to move to TXA 303 and TXB 304, respectively. In addition, also in the second arrangement, similarly to the first arrangement, a separation region 500 having a p-type impurity concentration higher than that of PDA 301 and PDB 302 is formed between PDA 301 and PDB 302. Therefore, PDA 301 and PDB 302 are electrically divided from each other, so that the generated charges are less likely to move between PDA 301 and PDB 302.

[0073] ●Charge crosstalk rate distribution

[0074] Most of the charges generated in each of PDA 301 and PDB 302 are accumulated in PDA 301 or PDB 302, but can move from PDA 301 to PDB 302 or from PDB 302 to PDA 301 and accumulate. Such a phenomenon that charges move from PDA 301 to PDB 302 or from PDB 302 to PDA 301 is called "charge crosstalk". In a planar view, the ratio at which charge crosstalk occurs (hereinafter referred to as "charge crosstalk rate") is higher in the region closer to separation regions 400 and 500. In addition, a potential gradient is formed in the depth direction in PDA 301 and PDB 302, so that charges are more likely to move toward TXA 303 and TXB 304, and thus the shorter the distance that charges move to TXA 303 or TXB 304, the smaller the charge crosstalk rate becomes. That is, at the same x-coordinate and y-coordinate in PDA 301 and PDB 302, the charge crosstalk rate at a position shorter in distance with respect to TXA 303 and TXB 304 is lower than the charge crosstalk rate at a position closer to ML 401. In the following description, the distribution of the crosstalk rate in PDA 301 and PDB 302 is referred to as "charge crosstalk rate distribution". The steeper the potential gradient in the depth direction in PDA 301 and PDB 302, the lower the charge crosstalk rate distribution becomes in the entire PDA 301 and PDB 302.

[0075] In addition, charge crosstalk may also occur between adjacent pixels. The charge crosstalk that occurs between adjacent pixels is the cause of a decrease in the resolution of a camera signal, etc. For this reason, the charge crosstalk rate between adjacent pixels is desirably lower than the charge crosstalk rate from PDA 301 to PDB 302 or from PDB 302 to PDA 301. Specifically, for example, the charge crosstalk rate can be suppressed to be low by separating adjacent pixels using an insulator or increasing the height of a potential barrier.

[0076] ●Method for detecting phase difference in x direction

[0077] Next, calculation for calculating the defocus amount from the phase difference signal by the overall control calculation unit 2 will be described.

[0078] First, refer to Figures 6 to 9 In the phase difference focus detection in the x direction according to the present embodiment, the image shift amount in the x direction is calculated based on the phase difference signal obtained from the pixel 205 having the first arrangement, and the image shift amount is converted into a defocus amount using a conversion coefficient.

[0079] Figure 6 The first arrangement of pixels 205 is shown along Figure 4B , and a pupil plane at a position at a distance Ds from the imaging plane 600 of the image sensor 1 in the -z axis direction. Note that x, y, and z represent coordinate axes on the imaging plane 600, and x p ,y p and z p Represents the coordinate axes on the pupil plane.

[0080] The pupil plane has a substantially conjugate relationship with the light receiving surface of the image sensor 1 via the ML 401. For this reason, the light beam that has passed through the partial pupil area 601 is received by the PDA 301. In addition, the light beam that has passed through the partial pupil area 602 is received by the PDB 302. In this way, the pupil division direction in the case where the pupil plane is divided in the x direction is the x direction. For this reason, the division direction position dependence of the pupil intensity distribution is formed as follows: Figure 7 The shape shown. Figure 7 , the pupil intensity distribution corresponding to PDA 301 is denoted by 701 , and the pupil intensity distribution corresponding to PDB 302 is denoted by 702 .

[0081] Next, refer to Figure 8The sensor entrance pupil of the image sensor 1 is described. In the image sensor 1 according to the present embodiment, the ML 401 of the pixel 205 is continuously shifted in the center direction of the image sensor 1 according to the image height coordinate on the two-dimensional plane. That is, as the image height increases, the ML 401 is arranged eccentrically in the center direction of the image sensor 1. Note that although the center of the image sensor 1 and the optical axis of the imaging optical system change due to a mechanism for reducing the influence of blurring caused by camera shake or the like by driving the imaging optical system or the image sensor 1, they are roughly consistent. Therefore, a structure is adopted in which the first pupil intensity distribution 701 and the second pupil intensity distribution 702 of the pixels arranged at the respective image height coordinates of the image sensor 1 are substantially consistent on the pupil plane at a position separated from the image sensor 1 by a distance Ds (entrance pupil distance). That is, a structure is adopted in which the first pupil intensity distribution 701 and the second pupil intensity distribution 702 of all the pixels of the image sensor 1 are substantially consistent on the pupil plane at a position separated from the image sensor 1 by a distance Ds. In the present embodiment, the first pupil intensity distribution 701 and the second pupil intensity distribution 702 are referred to as “sensor entrance pupil” of the image sensor 1 .

[0082] Note that it is not necessary to adopt a structure in which all pixels have a single incident pupil distance, and a structure in which the incident pupil distance of pixels up to 80% of the image height is roughly consistent may be adopted, for example, or the pixels can be configured so that the incident pupil is intentionally different for each row or for each detection area.

[0083] Fig. 9 Schematic diagram showing the relationship between the defocus amount and the image shift amount between parallax images. The image sensor 1 (not shown) according to the present embodiment is placed on the imaging plane 600 and is aligned with the imaging plane 600. Figure 6 Similarly, the exit pupil of the imaging lens unit 5 is divided into two (ie, divided into a partial pupil area 601 and a partial pupil area 602 ).

[0084] The defocus amount d is defined so that: the distance from the imaging position of the subject to the imaging plane is defined as the size |d|, the front focus state where the imaging position of the subject is located on the subject side relative to the imaging plane is negative (d<0), and the rear focus state where the imaging position of the subject is located on the opposite side of the subject relative to the imaging plane is positive (d>0). The focusing state of the imaging position of the subject on the imaging plane is defined as d=0. Fig. 9 An example is shown in which the subject on the object plane 901 is in the focused state (d=0), and the subject on the object plane 902 is in the front focus state (d<0). The front focus state (d<0) and the back focus state (d>0) are collectively referred to as a defocus state (|d|>0).

[0085] In the front focus state (d<0), the light beams from the subject on the object plane 902 that pass through the partial pupil area 601 (602) are once gathered, and then diffused along the width Γ1 (Γ2) with the centroid position G1 (G2) of the light beam as the center, and a blurred image is formed on the imaging surface 600. The blurred image is received by the PDA 301 and the PDB 302, and a parallax image is generated. Therefore, in the generated parallax image, the image of the subject on the object plane 902 is blurred by the width Γ1 (Γ2) at the centroid position G1 (G2).

[0086] The blur width Γ1(Γ2) of the subject image increases generally in proportion to the increase in the magnitude |d| of the defocus amount d. Similarly, the magnitude |p| of the image shift amount p (=G2-G1) of the subject image between the parallax images also increases generally in proportion to the increase in the magnitude |d| of the defocus amount d. This applies to the rear focus state (d>0), although the image shift direction of the subject image between the parallax images is opposite to that of the front focus state. In the focused state (d=0), the centroid positions of the subject images between the parallax images coincide (p=0), and no image shift occurs.

[0087] Therefore, with respect to the two phase difference signals obtained using the signals of PDA 301 and PDB 302, as the magnitude of the defocus amount of the parallax image increases, the magnitude of the image offset in the x direction between the two phase difference signals increases. Based on this relationship, phase difference focus detection is performed by converting the image offset calculated by the correlation calculation into the defocus amount while shifting the parallax image in the x direction. The coefficient multiplied when converting the image offset amount into the defocus amount is called a conversion coefficient. In the case where the conversion coefficient is large, a larger defocus amount is calculated based on a smaller image offset amount compared to the case where the conversion coefficient is small, and thus the calculation is likely to be affected by the noise of the phase difference signal, and there is a possibility that the phase difference detection performance will decrease.

[0088] ●Phase difference detection method in the y direction

[0089] As the phase difference detection method in the y direction (second direction) according to the present embodiment, a method similar to the above-described phase difference detection method in the x direction (first direction) using the signal from the pixel 205 having the first arrangement can be used. That is, instead of the pixel 205 having the first arrangement, the phase difference detection in the y direction (second direction) is performed using the signal from the pixel 205 having the second arrangement.

[0090] Charge crosstalk rate

[0091] ●Relationship between the charge crosstalk rate in pupil intensity distribution and phase difference detection performance

[0092] Fig.10 2 is a diagram showing pupil intensity distribution on a pupil plane corresponding to the pixel 205 having the first arrangement. Fig.10 301 and PDB 302 and the relationship between the magnitude of the charge crosstalk rate between PDA 301 and PDB 302 and the phase difference detection performance. The pupil intensity distribution of PDA 301 and the pupil intensity distribution of PDB 302 in the case where the charge crosstalk rate between PDA 301 and PDB 302 is low (small) are respectively referred to as the first pupil intensity distribution 701 and the second pupil intensity distribution 702. In contrast, in the case where the charge crosstalk rate between PDA 301 and PDB 302 is high (large), the signal charge obtained in PDA 301 and PDB 302 increases / decreases, thereby obtaining the pupil intensity distribution 1001 represented by the dotted line and the pupil intensity distribution 1002 represented by the dashed line.

[0093] Here, the distance between the peaks of the pupil intensity distributions corresponding to PDA 301 and PDB 302 is generally related to the acceptable range of the light receiving angle for light incident on the pixel, and the slope of the graph in the region 1004 where the pupil intensity distributions intersect each other is generally related to the basic accuracy of phase difference detection. That is, in Fig.10 In the case where the charge crosstalk rate is low, the slopes of the first pupil intensity distribution 701 and the second pupil intensity distribution 702 in the region 1004 are steep, so the basic accuracy is high, and the distance 703 between the peaks of the first pupil intensity distribution 701 and the second pupil intensity distribution 702 is short, so the acceptable range of the light receiving angle is small. On the other hand, in the case where the charge crosstalk rate is high, the slopes of the pupil intensity distributions 1001 and 1002 in the region 1004 are gentle, so the basic accuracy is low, and the distance 1003 between the peaks of the pupil intensity distribution 1001 and the pupil intensity distribution 1002 is long, so the acceptable range of the light receiving angle is large.

[0094] As described above, in many cases, the performance is biased towards one of the basic accuracy of phase difference detection and the acceptable range of light receiving angle. In particular, in an image sensor of a camera that supports an interchangeable lens (imaging optical system), light with a wide incident angle from various exit pupils needs to be received by the pixel, and the distance between the peaks of the pupil intensity distribution needs to be increased to enable phase difference detection, which limits the basic performance accordingly. The incident angle of the main light from the imaging optical system on the pixel at a higher image height deviates more significantly from the vertical incidence, and thus the acceptable range of light receiving angle needs to be determined taking into account the incident angle of the light received by the pixel at the higher image height. For this reason, as with a conventional image sensor, in the case where the width H in the x direction and the height V in the y direction are different, the acceptable range of light receiving angle depends on the phase difference detection pixel for the direction corresponding to the larger of the width and height. That is, with respect to the phase difference detection pixel corresponding to the smaller of the width and height, the acceptable range of light receiving angle increases more than required.

[0095] Therefore, the image sensor 1 according to the present embodiment is configured so that the charge crosstalk rate in the relatively large pixels 205 having the first arrangement (i.e., the phase difference detection pixels for the first direction corresponding to the width H=36 mm) is higher than the charge crosstalk rate in the relatively small pixels 205 having the second arrangement (i.e., the phase difference detection pixels for the second direction corresponding to the height V=24 mm). By setting the charge crosstalk rate at the peak position of the pupil intensity distribution to about 10% for the pixels 205 having the first arrangement and to about 8% for the pixels 205 having the second arrangement, the phase difference detection performance in the first direction and the second direction can be made as optimal as possible.

[0096] In order to provide different charge crosstalk rates for the pixel 205 having the first arrangement and the pixel 205 having the second arrangement, an ion implantation process is performed so that, for example, the p-type impurity concentrations in the separation regions 400 and 500 of the PDA 301 and the PDB 302 are different. Therefore, the image sensor 1 according to the present embodiment can be realized. In the case of the present embodiment, the impurity concentration of the separation region 400 of the pixel 205 having the first arrangement is set to be lower, and the impurity concentration of the separation region 500 of the pixel 205 having the second arrangement is set to be higher. That is, the magnitude relationship between the impurity concentration of the separation region 400 of the pixel 205 having the first arrangement and the impurity concentration of the separation region 500 of the pixel 205 having the second arrangement is set to be opposite to the magnitude relationship between the width H and the height V.

[0097] Such adjustment of the charge crosstalk rate can be performed by setting the widths of the separation regions of the photoelectric conversion unit to be different from each other. In the case of the present embodiment, the width of the separation region 400 of the pixel 205 having the first arrangement is set to be smaller, and the width of the separation region 500 of the pixel 205 having the second arrangement is set to be larger. That is, the size relationship between the width of the separation region 400 of the pixel having the first arrangement and the width of the separation region 500 of the pixel having the second arrangement is set to be opposite to the size relationship between the width H and the height V.

[0098] In addition, by setting the potential gradient for collecting the charges in the photoelectric conversion portion from the back side of the substrate to the front side of the substrate to be different between the pixels 205 having the first arrangement and the pixels 205 having the second arrangement, it is possible to adjust the charge crosstalk rate between the pixels 205 having the first arrangement and the pixels 205 having the second arrangement. In this case, the potential gradient of the pixels 205 having the first arrangement is set to be more moderate than the potential gradient of the pixels 205 having the second arrangement, that is, the magnitude relationship of the steepness is set to be opposite to the magnitude relationship between the width H and the height V.

[0099] In addition, by combining the impurity concentration, the width of the separation region, and the electrolytic gradient described above, it is possible to adjust so that the charge crosstalk rate in the first direction is higher than the charge crosstalk rate in the second direction.

[0100] In addition, in the above example, the case where the charge crosstalk rate of the pixel 205 having the first arrangement and the charge crosstalk rate of the pixel 205 having the second arrangement are adjusted when the image sensor 1 is manufactured is described, but the present invention is not limited thereto, and a structure that can be adjusted after the image sensor 1 is manufactured may also be adopted. In this case, for example, the charge crosstalk rate can be adjusted by placing an electrode portion in the separation regions 400 and 500 of the PDA 301 and the PDB 302 and controlling the potential of the separation regions 400 and 500. In this case, the potential applied to the separation region 400 of the pixel 205 having the first arrangement is set to be lower than the potential applied to the separation region 500 of the pixel 205 having the second arrangement, that is, the magnitude relationship between the potentials is set to be opposite to the magnitude relationship between the width H and the height V. Note that a deep trench isolation (DTI) coupled to a control wiring may be used as the electrode portion.

[0101] In addition, in the above examples, a description is given that all pixels 205 have the first arrangement or the second arrangement, but the present invention is not limited thereto, and a portion of the pixels 205 may be formed as pixels having the first arrangement or the second arrangement and placed in a discrete manner.

[0102] As described above, according to the first embodiment, when performing imaging surface phase difference focus detection using signals obtained from image sensors having different vertical and horizontal sizes, the focus detection accuracy can be increased while appropriately adjusting the acceptable range of the light receiving angle according to the vertical and horizontal lengths of the image sensor.

[0103] Second embodiment

[0104] Next, a second embodiment according to the present invention will be described. Fig.11A and Fig. 11B The structure of the pixels 205 having the third arrangement of the image sensor 1 according to the present embodiment is shown.

[0105] like Fig.11A and Fig. 11B As shown, in the third arrangement, the pixel 205 is composed of four photodiodes (PD) 1101 to 1104. Hereinafter, these four photodiodes are referred to as PDA 1101, PDB 1102, PDC 1103, and PDD 1104. Fig.11A is a stereogram of a pixel according to this embodiment, Fig. 11B is a schematic plan view showing the positional relationship in a plan view viewed from the ML 401 side (substrate back side), and in this embodiment, the transfer switch and the like are omitted. Note that the definitions of "plan view" and x, y, and z are the same as those in Figure 4A and Figure 4B These definitions are the same, so their description is omitted.

[0106] In the present embodiment, by defining the first direction as the x direction and the second direction as the y direction, phase difference detection in two directions orthogonal to each other can be performed using pixels having the same structure.

[0107] Phase difference detection in the x direction can be performed by using the sum of the signals of PDA 1101 and PDC 1103 (signal A) and the sum of the signals of PDB 1102 and PDD 1104 (signal B), and phase difference detection in the y direction can be performed by using the sum of the signals of PDA 1101 and PDB 1102 (signal C) and the sum of the signals of PDC 1103 and PDD 1104 (signal D). That is, in the present embodiment, similarly to the first embodiment, the pixels are configured so that when the size of the image sensor 1 is set to width H in the x direction × height V in the y direction = 36 mm × 24 mm, the magnitude relationship between the charge crosstalk rate between the photoelectric conversion units corresponding to signal A and signal B and the charge crosstalk rate between the photoelectric conversion units corresponding to signal C and signal D is consistent with the magnitude relationship between the width H and the height V. Similar to the first embodiment, the charge crosstalk rate is adjusted based on the impurity concentration of the separation region 1105 and the separation region 1106, the adjustment of the width, the adjustment of the potential gradient in the photoelectric conversion unit, and the potential control using the electrode.

[0108] As described above, according to the second embodiment, even in the case where each pixel includes a plurality of photoelectric conversion portions divided in two directions, effects similar to those of the first embodiment can be achieved.

[0109] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, in order to inform the public of the scope of the present invention, the following claims are added.

[0110] This application claims the benefit of Japanese Patent Application No. 2022-077695, filed on May 10, 2022, which is hereby incorporated by reference herein.

Claims

1. An image sensor, wherein a length of a pixel portion in a first direction is longer than a length of the pixel portion in a second direction orthogonal to the first direction, characterized in that: The pixel portion includes: a plurality of micro lenses arranged in a matrix in the first direction and the second direction; and a plurality of photoelectric conversion units provided for each of at least a portion of the plurality of microlenses and configured to perform photoelectric conversion on light incident on the photoelectric conversion unit via each of the microlenses, The plurality of photoelectric conversion sections are arranged in at least one of the first direction and the second direction, and A charge crosstalk rate between the plurality of photoelectric conversion portions arranged in the first direction is higher than a charge crosstalk rate between the plurality of photoelectric conversion portions arranged in the second direction.

2. The image sensor according to claim 1, characterized in that The plurality of photoelectric conversion portions are two photoelectric conversion portions arranged in the first direction or the second direction.

3. The image sensor according to claim 1, characterized in that The plurality of photoelectric conversion portions are four photoelectric conversion portions arranged in the first direction and the second direction.

4. The image sensor according to any one of claims 1 to 3, characterized in that: The impurity concentration of the separation region for separating the plurality of photoelectric conversion portions arranged in the first direction is set lower than the impurity concentration of the separation region for separating the plurality of photoelectric conversion portions arranged in the second direction.

5. The image sensor according to any one of claims 1 to 4, characterized in that: The width of a separation region for separating the plurality of photoelectric conversion portions arranged in the first direction is set smaller than the width of a separation region for separating the plurality of photoelectric conversion portions arranged in the second direction.

6. The image sensor according to any one of claims 1 to 5, characterized in that: In the plurality of photoelectric converters arranged in the first direction, a potential gradient from the light incident side to a region where charges obtained by photoelectric conversion are accumulated is made gentler than that in the plurality of photoelectric converters arranged in the second direction.

7. The image sensor according to any one of claims 1 to 6, characterized in that: Also includes: an electrode for controlling a potential of a separation region for separating the plurality of photoelectric conversion parts, The potential of the separation region for separating the plurality of photoelectric conversion parts arranged in the first direction is set to be lower than the potential of the separation region for separating the plurality of photoelectric conversion parts arranged in the second direction.

8. The image sensor according to any one of claims 1 to 7, characterized in that: When the length of the pixel portion in the first direction is 36 mm and the length of the pixel portion in the second direction is 24 mm, the charge crosstalk rate in the first direction between the plurality of photoelectric conversion portions is approximately 10% and the charge crosstalk rate in the second direction is approximately 8%.

9. The image sensor according to any one of claims 1 to 8, characterized in that: Also includes: An output unit for converting the charges obtained by photoelectric conversion using the plurality of photoelectric conversion sections into a signal and outputting the signal.

10. A camera device, characterized in that: include: The image sensor according to any one of claims 1 to 9; as well as The processing unit is used to process the signal output from the image sensor.

11. The imaging device according to claim 10, characterized in that The processing unit performs imaging plane phase difference focus detection based on the signal.

Images