JP2020017943A - Image pickup device - Google Patents

Abstract

To provide an image pickup device of photon counting system, in which reduction in photon detection efficiency depending on the pixel position is restrained.SOLUTION: Multiple pixels are arranged in matrix in the pixel region of an image pickup device. Each pixel has an avalanche multiplication region generating avalanche multiplication by electrons generated by photoelectric conversion, and a counter circuit for counting pulses resulting from avalanche multiplication. In the plan view of each pixel arranged in the pixel region, size of the avalanche multiplication region is smaller than the size of a photoelectric conversion region, and the position of the avalanche multiplication region in at least some pixels arranged in the peripheral region of the pixel region, out of the pixels arranged in the pixel region, is formed at a position shifted from the position of the avalanche multiplication region in the pixel arranged in the central region of the pixel region.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image sensor, and more particularly, to a structure of the image sensor.

  There has been proposed a photodiode array in which avalanche photodiodes (APDs) to which a reverse bias voltage higher than the breakdown voltage is applied are arranged in an array and the number of photons incident on a certain range is detected (Patent Document 1). It has also been proposed to use such a photodiode array as a photon counting type imaging device.

  An APD to which a reverse bias voltage higher than the breakdown voltage is applied generates a photocurrent due to avalanche multiplication every time a photon enters. The number of photons incident on the APD can be detected by counting the pulse signal generated by shaping the voltage change accompanying the generation of the photocurrent into a pulse signal using a counter. For example, since the number of pulses counted during the exposure period corresponds to the amount of incident light during the exposure period, the count value of the counter can be used as pixel data. Since charge transfer and the like are unnecessary, pixel data less affected by circuit noise can be obtained as compared with a conventional CCD or CMOS image sensor, which is advantageous for, for example, imaging in a dark place.

  If a dark current occurs due to crystal defects or the like in a high electric field region where avalanche multiplication occurs in the APD, a pulse signal based on the dark current is counted. By reducing the area of the high electric field region without changing the area of the light receiving region that generates carriers by the incidence of photons, the probability that crystal defects and the like are included in the high electric field region is reduced, and false detection is suppressed. Can be.

JP 2012-174873 A

  In the case of forming an imaging device in which an APD is arranged as an array of pixels, light is incident from almost the front on a pixel arranged at a position with a small image height, but obliquely incident on a pixel arranged at a position with a large image height. Light enters from a direction. That is, the incident angle and the incident position of the light with respect to the light receiving region differ depending on the image height of the pixel. This means that the position where carriers are generated in the pixel due to the incident photon differs depending on the image height of the pixel.

  Therefore, when the area of the high electric field region is formed small to suppress the generation of dark current, the moving distance and direction required for carriers to reach the high electric field region differ depending on the pixel. As a result, carriers may not be able to be accelerated to a speed required to cause avalanche multiplication in a high electric field region. Further, in a pixel in which the moving distance of the carrier to the high electric field region is long, the probability that the carriers recombine and disappear before reaching the high electric field region increases, which causes the detection efficiency of the incident photon to decrease. .

  The present invention has been made in view of such problems of the related art. An object of the present invention is to provide a photon-counting type imaging device in which a reduction in photon detection efficiency depending on the position of a pixel is suppressed.

  The above object is to arrange a plurality of pixels in a matrix having a photoelectric conversion region that generates charges by photoelectric conversion based on incident light and an avalanche multiplication region that generates avalanche multiplication by charges generated by photoelectric conversion. In the planar view of each pixel arranged in the pixel region, the size of the avalanche multiplication region is smaller than the size of the photoelectric conversion region, and among the pixels arranged in the pixel region, in the peripheral region of the pixel region. The position of the avalanche multiplication region in at least some of the arranged pixels is formed at a position shifted from the position of the avalanche multiplication region in the pixel arranged in the central region of the pixel region. This is achieved by an imaging element.

  With such a configuration, according to the present invention, it is possible to provide a photon counting type imaging device in which a reduction in photon detection efficiency depending on the position of a pixel is suppressed.

FIG. 2 is a diagram illustrating an example of an overall configuration of an image sensor according to the first embodiment. Equivalent circuit diagram of the unit pixel of the first embodiment Schematic configuration diagram of a pixel region according to the first embodiment Sectional view of the photodiode according to the first embodiment Sectional view of a photodiode according to a modification of the first embodiment. Sectional view of a photodiode according to another modification of the first embodiment. Sectional view of a photodiode according to still another modification of the first embodiment. Equivalent circuit diagram of a unit pixel in the second embodiment Sectional view of photodiode according to second embodiment Schematic configuration diagram of a pixel region in the third embodiment Xz sectional view of the photodiode in the third embodiment FIG. 2 is a block diagram illustrating a functional configuration example of a camera as an example of an imaging device to which the imaging element according to the first to third embodiments is applied.

  Hereinafter, the present invention will be described in detail based on exemplary embodiments with reference to the accompanying drawings. In the following embodiments, a configuration using an avalanche photodiode (APD) as a photoelectric conversion element will be described as an example of a photon counting type imaging element. However, a configuration using another photoelectric conversion element may be used.

● (1st Embodiment)
FIG. 1 schematically shows a configuration example of an image sensor according to an embodiment of the present invention. The image sensor 100 includes a pixel area 101, a vertical control circuit 102, a horizontal control circuit 103, a timing generator (TG) 104, and a digital output unit 107.

  In the pixel area 101, a plurality of pixels 108 are arranged in a matrix. Here, for simplicity of description, the pixel area 101 in which four pixels are arranged in the horizontal direction and four pixels in the vertical direction is shown, but a large number of pixels such as several million to tens of millions are actually arranged. Is done. The pixel 108 counts a pulse signal caused by the incident photon, and outputs a digital count value as pixel data. Details of this pixel will be described later with reference to FIG.

  The vertical control circuit 102 selects the pixels 108 by the switch 105 in units of one row. In addition, the vertical control circuit 102 sends a control signal to the pixels 108 on a row-by-row basis via a wiring (not shown). Details of this control signal will be described later with reference to FIG.

The horizontal control circuit 103 selects the pixels 108 by the switch 106 in units of one column. Pixel data of one pixel 108 selected by both the vertical control circuit 102 and the horizontal control circuit 103 is output to the digital output unit 107.
The digital output unit 107 sequentially outputs the pixel data output from the pixels 108 to the outside of the image sensor 100.

  The TG 104 outputs a control signal for outputting pixel data from the pixel 108 to the vertical control circuit 102 and the horizontal control circuit 103. The TG 104 also sends a control signal to the digital output unit 107.

  FIG. 2 is an equivalent circuit diagram of the pixel 108. The pixel 108 includes a photodiode 201, a quench resistor 202, an inversion buffer 203, and a counter circuit 204. Note that among the constituent elements of the pixel 108, the photodiode 201 and the counter circuit 204 are formed on separate chips, and signals between the chips are picked up by three-dimensional mounting that is electrically connected by a through silicon via (TSV) or the like. 100 can be realized. Thus, a decrease in the aperture ratio of the photodiode 201 can be suppressed.

  The photodiode 201 is, for example, an avalanche photodiode (APD) and functions as a photoelectric conversion unit. The voltage V <b> 1 is applied to the cathode terminal of the photodiode 201 via the quench resistor 202. The voltage V2 is applied to the anode terminal of the photodiode 201. The voltages V1 and V2 are determined so that a reverse bias voltage larger than the breakdown voltage is applied to the photodiode 201. Here, for example, V1 = 3V and V2 = −20V. In this embodiment, the voltage V2 corresponds to the ground potential of the photodiode 201.

  As a result, the photodiode 201 operates in the Geiger mode, and when a photon enters, carriers generated by photoelectric conversion cause avalanche multiplication, a large photocurrent flows, and a voltage drop occurs in the quench resistor 202. Accordingly, when the cathode terminal voltage of the photodiode 201 decreases and the reverse bias voltage applied to the photodiode 201 falls below the breakdown voltage, the avalanche multiplication stops. As a result, the photocurrent stops flowing, and the cathode terminal voltage of the photodiode 201 returns to V1. Thus, a large voltage change occurs in a short time by one photon incidence. This voltage change is output as a pulse signal by the inversion buffer 203. The quench resistor 202 is a resistance element for stopping the avalanche multiplication of the photodiode 201. The quench resistor 202 may be realized by using a resistance component of a transistor.

  The counter circuit 204 counts a pulse signal output from the inversion buffer 203 every time a photon enters. The counter circuit 204 is supplied with an enable signal (PEN signal) and a reset signal (PRES signal) from the vertical control circuit 102. When the pulse signal is input to the counter circuit 204 while the PEN signal is at the H level, the count value increases by one. When the PEN signal is at the L level, even if a pulse signal is input, the count value does not increase and the current count value is held. When the PRES signal supplied to the counter circuit 204 becomes H level, the count value of the counter circuit 204 is reset to zero. Since the count value of the counter circuit 204 during the predetermined exposure period is a value corresponding to the amount of light received by the photodiode 201 during the exposure period, the count value can be used as pixel data.

  After the predetermined exposure period ends, the count value of the pixel counter circuit 204 selected by both the vertical control circuit 102 and the horizontal control circuit 103 is output to the digital output unit 107 as pixel data.

  FIG. 3 shows a schematic configuration example of the pixel region 101. Here, for the pixel region 101, an x-axis is defined in the horizontal direction, a y-axis in the vertical direction, and a z-axis in the normal direction of the pixel region surface as shown in the figure. It is assumed that light is incident on the pixel area in the positive direction of the z-axis (from the front of the paper). The optical axis of a photographing optical system such as a lens unit intersects the pixel area 101 at an intersection 300. The intersection 300 is referred to as the optical axis center of the pixel area 101. On the other hand, the center of the pixel area 101 is called the image center. The optical axis center and the image center are reference positions of the pixel area. The center of the optical axis and the center of the image may or may not match, but it is assumed here that they match. Therefore, in the following description, the optical axis center is also the image center. Reference numeral 301 denotes a pixel including the center of the optical axis, and 302 denotes an example of a pixel having a large distance (image height) from the center of the optical axis at a peripheral portion of the pixel area. The pixels 301 and 302 have the same y-coordinate. The center of the optical axis and the center of the image may be shifted due to a manufacturing error, optical camera shake correction, or the like. However, the deviation between the center of the optical axis and the center of the image due to these factors is very small with respect to the size of the pixel region 101. Therefore, in the present embodiment, for simplicity of explanation and understanding, the description will be made on the assumption that the center of the optical axis coincides with the center of the image. Further, the pixel area 101 may include light-shielded pixels and dummy pixels in addition to light-receiving pixels for receiving light through the imaging optical system. The image center in the present invention can be the center of the light receiving pixel area excluding the light-shielded pixels and the dummy pixels.

  Here, in the pixel region 101, a region denoted by 303 is a peripheral portion, and the other region is a vicinity of the center of the optical axis or a central region. Note that the boundary between the peripheral portion 303 and the vicinity of the center of the optical axis can be determined by, for example, whether or not the incident angle (x-axis direction) of the light beam entering the center of the pixel is equal to or larger than a threshold, but is determined according to other conditions. Is also good. Hereinafter, the pixel 301 will be described as a pixel representing each pixel included in the vicinity of the optical axis center, and the pixel 302 will be described as a pixel representing each pixel included in the peripheral portion 303.

  4A and 4B are xz sectional views of the photodiodes of the pixels 301 and 302 in the present embodiment, respectively. Here, it is assumed that the imaging element is a back-side illumination type. 4 (c) to 4 (d) are cross-sectional views taken along the line CC 'of FIGS. 4 (a) to 4 (b), and FIGS. 4 (e) to 4 (f) are FIGS. FIG. 5 is a cross-sectional view taken along line DD ′ of FIG. FIGS. 4G to 4H are plan views of the photodiodes of the pixels 301 and 302. FIG. Note that a configuration of the pixel in the xy plane as shown in FIGS. 4C to 4H is referred to as a pixel's planar view.

  In FIG. 4A, a voltage V2 (for example, −20 V) is applied to a P-type semiconductor region P404 as a second conductivity type region via a contact electrode (not shown). P404 functions as an anode terminal of a PN junction photodiode formed between an N-type semiconductor region described later. Note that the electrode to which the voltage V2 is applied may be provided for each photodiode, or may be provided in common for a plurality of photodiodes. In any case, since the voltage V2 is the ground potential of the photodiode, the electrode to which the voltage V2 is applied is desirably provided at a position that is periodic with respect to the photodiodes that are periodically arranged. When a common electrode is provided for a plurality of photodiodes, for example, the electrodes may be provided corresponding to a plurality of photodiodes provided with a color filter of the same color (for example, blue).

  A voltage V1 (for example, 3V) is applied to the N-type semiconductor region N + 402 as the first conductivity type region via the quench resistor 202. N + 402, which is an N-type semiconductor region, functions as a cathode terminal of a PN junction photodiode formed with P404. An electrode (not shown) for applying the voltage V1 is provided near the center of the upper surface of N + 402.

  N-epi 401, which is an N-type epitaxial layer as the first conductivity type, functions as a light receiving region and a photoelectric conversion region. In the N-epi 401, a depletion region is formed between N + 402 to which the voltage V1 is applied and P404 to which the voltage V2 is applied. The N-epi 401 generates an electron-hole pair by photoelectrically converting incident photons. Of the electron-hole pairs, the holes move to P404 due to the drift and are discharged out of the image sensor via a contact electrode (not shown). On the other hand, the electrons move to the high electric field region 407A due to the drift, and are accelerated to cause avalanche multiplication. Hereinafter, the high electric field region 407A for generating the avalanche multiplication is referred to as an avalanche multiplication region. Note that an appropriate potential gradient can be provided in the N-epi 401 in order to efficiently collect electrons in the high electric field region 407A.

  4E, P404 is formed so as to extend to the vicinity of the center of the photodiode, and an avalanche multiplication region 407A is formed in a region where P404 and N + 402 are close to each other. . In this embodiment, as shown in FIG. 4A, N + 402 is formed only near the center of the pixel to reduce the area where the avalanche multiplication region is formed. Thereby, the probability that the avalanche multiplication region is formed in the region where the crystal defect or the like exists in the silicon substrate can be reduced. As a result, it is possible to suppress the occurrence ratio of pixels (defective pixels) in which dark current generated due to a crystal defect or the like in the avalanche multiplication region is avalanche multiplied and is frequently detected. Further, even if the area of the avalanche multiplication region is reduced, photons incident on a wide range in the pixel can be detected by increasing the area of the N-epi 401 as the light receiving region.

  The guard ring N-403 is a first conductivity type region having a lower concentration than N + 402. As shown in the CC ′ cross-sectional view of FIG. 4C, the guard ring N-403 is formed between N + 402 and P404, and relaxes the electric field between N + 402 and P404 to reduce edge breakdown. Has a function to prevent. In order to obtain the effect of preventing the edge breakdown by the guard ring N-403, a certain distance (for example, 1.4 μm or more) is provided between N + 402 and P404 in FIG. A guard ring N-403 is provided. Note that the distance separating N + 402 and P404 by the guard ring N-403 can be changed by the voltage value applied to the photodiode.

  CF 405 is a color filter. In this embodiment, each pixel is provided with a color filter having one of a plurality of colors (for example, three primary colors of red, green, and blue) so as to form a specific arrangement (for example, a Bayer arrangement).

  Here, the reason why the photodiode is of the back-illuminated type in the present embodiment is that the detection efficiency of photons incident on the guard ring N-403 is extremely low. Most of the electrons generated by the photoelectric conversion in the guard ring N-403 move directly to N + 402 due to the drift without reaching the avalanche multiplication region 407A. Therefore, when the photodiode is configured as a front-illuminated type in which light is incident from the side where the guard ring N-403 is formed, the detection efficiency of short-wavelength light photoelectrically converted near the surface of the photodiode decreases. I will. Therefore, as shown in FIGS. 4A to 4H, by using the back-side illumination type of the photodiode, a decrease in the efficiency of detecting short-wavelength light can be suppressed. Note that the shape of the photodiode can be made cylindrical so that the electric field intensity in each region of the photodiode can be smoothly changed. When the photodiode is formed in a cylindrical shape, the light receiving area of the N-epi 401 is reduced, so that a light collecting structure such as a waveguide may be provided.

  As shown in FIGS. 4A and 4B, the pixel 301 located at the center of the optical axis and the pixel 302 at the peripheral portion form a position where N + 402 is formed, that is, an avalanche multiplication region 407A. Position is different. Here, the center position of the N-epi 401 in the x-axis direction is indicated by O1. O1 corresponds to a position of W / 2, where W is the width of the N-epi 401 in the x-axis direction. Similarly, the center position of N + 402 in the x-axis direction is indicated by O2.

  As shown in FIG. 4C, in the pixel 301 located at the center of the optical axis, the center position O2 of N + 402 is equal to the center position O1 of N-epi 401. On the other hand, as shown in FIG. 4D, in the peripheral pixels 302, the center position O2 of N + 402 is shifted from the center position O1 of N-epi 401 by a distance L in the x-axis direction (that is, O2 = O1 + L). ). Here, since the y-axis coordinates of the pixels 301 and 302 are equal, the center position of N + 402 and the center position of N-epi 401 are equal in the y-axis direction regardless of the image height of the pixel. However, when the y-axis coordinates of the pixels 301 and 302 are different, the position of the center position of N + 402 and the center position of N-epi 401 in the y-axis direction can be changed according to the magnitude of the difference between the y-axis coordinates. .

  Further, as shown in FIG. 4A and FIG. 4B, and the DD ′ cross-sectional views of FIG. 4E and FIG. 4F, P404 extends to near the center of the photodiode. The avalanche multiplication region 407A is formed in a region where P404 and N + 402 are close to each other. Here, as shown in FIGS. 4A and 4B, N + 402 has a small horizontal cross-sectional area so that the area where the avalanche multiplication region 407A is formed is small. Thus, the probability that a crystal defect or the like in the silicon substrate exists in the avalanche multiplication region 407A can be reduced. As a result, it is possible to suppress the occurrence ratio of pixels (defective pixels) in which dark current generated due to a crystal defect or the like in the avalanche multiplication region is avalanche multiplied and is frequently detected. Further, even if the area of the avalanche multiplication area 407 is reduced, by increasing the area of the N-epi 401 as the light receiving area, it is possible to detect photons incident on a wide range in the pixel.

  4A and 4B, the incident light with respect to the center position O1 of the N-epi 401 as the light receiving area is indicated by an arrow. As shown in FIG. 4A, a light ray enters the pixel 301 including the center of the optical axis in parallel with the z-axis, whereas as shown in FIG. The incident light is inclined with respect to the z axis.

  At this time, the position at which the photons incident on the light receiving region N-epi 401 at the respective angles are photoelectrically converted follows the probability distribution of an exponential function determined by the absorption coefficient of silicon. Here, the average positions at which the photons incident on each pixel are photoelectrically converted are indicated by 408A and 408B. These average positions 408A and 408B correspond to penetration lengths at which photons incident on silicon at respective angles are photoelectrically converted with a probability of 50%. If the wavelength of the incident light is represented by 550 nm, which is a wavelength near the center of the visible light region, the penetration length is about 1 μm.

  As shown in FIGS. 4A and 4B, the center position (O1) of the avalanche multiplication region 407A in the pixel 301 located at the center of the optical axis is directly above the average position 408A at which incident photons are photoelectrically converted. become. In the peripheral pixels 302, the center position (O2) of the avalanche multiplication region 407B is immediately above the average position 408B where the incident photons are photoelectrically converted. In other words, in each pixel, the distance from the average position where the incident photons are photoelectrically converted to the avalanche multiplication region is almost the same, and the decrease in the photon detection sensitivity at the pixels located away from the optical axis center is reduced. Can be suppressed. This is because an increase in the probability that electrons generated by photoelectric conversion disappear due to recombination during drift movement to the avalanche multiplication region can be suppressed.

  Also, in the peripheral pixels, the direction and position of the electrons generated by the photoelectric conversion entering the avalanche multiplication region are the same as those of the pixels located at the center of the optical axis, so that the electrons increase in the avalanche multiplication region. The acceleration required to generate the doubling can be obtained. This also makes it possible to suppress a decrease in photon detection sensitivity in a pixel arranged at a position distant from the center of the optical axis.

  As described above, in the present embodiment, the avalanche multiplication region (high electric field region) is formed such that the straight line parallel to the optical axis of the imaging optical system passes through the avalanche multiplication region through the average position where the incident photon is photoelectrically converted. Is controlled in the horizontal sectional position of the first conductivity type region (N + 402) in which is formed. The average position at which the incident photons are photoelectrically converted is determined by the distance (light reception) determined from the incident angle of the light beam incident on the center position of the N-epi 401 as the light receiving region and the penetration length of the representative wavelength (for example, 550 nm) of the incident light. (Deviation from the center of the region). Note that this is an example, and an average position at which incident photons are photoelectrically converted in each pixel may be obtained by another method.

  For example, the average position at which the incident photon is photoelectrically converted may be determined in consideration of all the light beams incident on the pixel via the imaging optical system. In the case where the diaphragm of the photographing optical system is variable or the photographing optical system is replaceable, the average position may be calculated for the reference photographing optical system and the aperture value in consideration of the light flux incident on the pixel. .

  In the present embodiment, the average position at which incident photons are photoelectrically converted is determined using the penetration length of 550 nm, which is a wavelength near the center of the visible light region, but the spectral transmission of the color filter provided in each pixel is determined. The penetration length of the wavelength with the highest rate may be used. In this case, even if the pixels have the same image height, pixels having different color filters have different horizontal cross-sectional positions of the first conductivity type region (N + 402) in which the avalanche multiplication region (high electric field region) is formed.

  Further, as described above, the horizontal cross-sectional position of the first conductivity type region (N + 402) where the avalanche multiplication region (high electric field region) is formed not only in the x-axis direction but also in the y-axis direction is controlled. Is also good.

  In the present embodiment, an example has been described in which the position of the center O2 of N + 402 is shifted with reference to the center position O1 of N-epi 401. However, the reference of the shift amount of the center O2 of N + 402 is not limited to the center position O1 of N-epi401. For example, when the pixels 108 are periodically arranged at a predetermined pixel pitch, the midpoint of a straight line connecting the centers of adjacent pixels may be used as a reference. Alternatively, the center of the region defined by P404 or guard ring 403 embedded around the photodiode may be used as a reference. Alternatively, a position of an electrode for applying the voltage V2 periodically arranged in the pixel region 101 may be used as a reference. As an example, as shown in FIGS. 4 (g) and 4 (h), when an electrode position is used as a reference, an electrode 408A and an electrode 408B for applying a voltage V2 and an electrode 409A and an electrode 409B for applying a voltage V1 are used. The amount of deviation is defined by the distance between them.

Next, an application example of the first embodiment to an image sensor having a microlens for each pixel will be described.
FIGS. 5A and 5B are xz sectional views of photodiodes of a pixel 301 ′ located at the center of the optical axis and a peripheral pixel 302 ′ in the first modification of the first embodiment. . 5 (a) to 5 (b), the same components as those in FIGS. 4 (a) to 4 (h) are denoted by the same reference numerals, and description thereof will be omitted.

  As shown in FIGS. 5A and 5B, each pixel includes a microlens (ML) 406 in front of the color filter 405 when viewed from the incident light. The ML 406 focuses the light imaged by the photographing optical system on the N-epi 401, which is a light receiving area. Here, in FIG. 5A and FIG. 5B, light incident on the N-epi 401 through the center of the ML 406 is indicated by arrows. Even in a configuration in which each pixel includes the ML 406, the N + 402 is formed such that the avalanche multiplication regions 407A and 407B are formed immediately above the average positions 408A and 408B where photons incident on the N-epi 401 via the ML 406 are photoelectrically converted. Control the horizontal section position. Therefore, similarly to the configuration shown in FIGS. 4A to 4H, it is possible to suppress the detection efficiency of the incident photon from being reduced in the pixels in the peripheral portion of the pixel region. Here, a case has been described where the average position 408B where the photons are photoelectrically converted is farther away from the optical axis of the microlens as the peripheral pixels are located. However, even when the relationship between the change in the pixel position and the change in the distance between the average position 408 and the optical axis of the microlens is different, the avalanche multiplication region is located immediately above the average position 408 where the photons are photoelectrically converted. 407 can be formed.

  4 (a) to 4 (h) and FIGS. 5 (a) to 5 (b), the avalanche multiplication region (N + 402) is based on the center position O1 of the N-epi 401 as the light receiving region. The configuration in which the center position O2 is shifted by the distance L has been illustrated. However, the center position of the ML 406, the CF 405, or the P 404 may be used as a reference. Further, when a wiring opening or a light blocking member (not shown) is provided, the center position of the wiring opening or the light blocking member may be used as a reference. 4 (a) to 4 (h), avalanche multiplication is possible if the dimension of N + 402 in the x-axis direction is about 1.2 μm. When the size of the strong electric field region is changed in accordance with the pixel pitch, if the pixel pitch is 10 μm or less, the ratio of the size (area) of N + 402 to the pixel size (area) is set to 40% or less.

  FIGS. 6A and 6B are xz sectional views of the photodiodes of the pixel 301 ″ located at the center of the optical axis and the pixel 302 ″ in the peripheral part in the second modification of the first embodiment. . 6 (a) to 6 (b), the same components as those in FIGS. 4 (a) to 4 (h) or FIGS. 5 (a) to 5 (b) are denoted by the same reference numerals, and a description thereof will be given. Is omitted.

  In the modified example shown in FIGS. 5A and 5B, the position where the ML 406 is provided in each pixel is constant irrespective of the position where the pixel is arranged (for example, the center of the light receiving region of the pixel is located at the center). Xy coordinates with the center of the ML 406 are the same). On the other hand, in the present modification, as shown in FIG. 6B, the center position O3 of the ML 406 is shifted by L2 from the center position O1 of the N-epi 401 in the x-axis direction of the peripheral pixel 302 ″. .

  More specifically, in the pixel 302 ″ in the peripheral portion, the center position O3 of the ML 406 is set at the optical axis of the photographing optical system (or the center of the optical axis of the pixel region) with reference to the center position O1 of the light receiving area (N-epi 401). The center position O2 of N + 402 forming the avalanche multiplication region is set to the optical axis (or pixel region) of the photographing optical system with reference to the center position O1 of the light receiving region. (The center of the optical axis in FIG. 2).

  Thereby, even when the incident light is incident with a large inclination with respect to the z-axis, it is possible to suppress a decrease in the detection efficiency of the incident photon. Further, by shifting both N + 402 and ML 406 in the opposite direction, the shift amount can be made smaller than when only one of them is shifted. In particular, by reducing the shift amount L1 of N + 402, the width of the guard ring N-403 decreases due to the proximity of N + 402 and the P404 on the side surface, and it is possible to prevent the occurrence of breakdown on the side surface side. Also, by reducing the shift amount L2 of the ML 406, photons incident near the periphery of the ML 406 may be blocked by an element isolation structure (not shown) formed between pixels, or may be incident on adjacent pixels to cause color mixing. Can be prevented. Note that the ML 406 and the CF 405 may be integrated and the center position may be shifted. When a wiring opening (not shown) is provided, the wiring opening may be formed so as to be shifted in a direction approaching the optical axis.

  Note that if the distance between N + 402 and P404 required to prevent breakdown by guard ring N-403 cannot be obtained by shifting N + 402, guard ring N-403 may be shifted together with N + 402. Similarly to the shift amount of the ML 406, the shift amount L1 of N + 402 can be increased stepwise from the center to the periphery of the pixel region 101.

  FIGS. 7A to 7D are diagrams related to a third modification of the first embodiment. In this modification, the pixel region is divided into three regions, and the combination of the position control of N + 402 and the position control of the ML 406 are made different for the pixels belonging to each region. FIG. 7A shows an example of dividing a pixel area in the present modification. As can be seen from a comparison with FIG. 3, the vicinity of the center of the optical axis (here, also near the center of the image) is divided into a portion 901 near the center of the optical axis and an intermediate portion 902. The peripheral portion 903 may be the same as the peripheral portion 303 of the first embodiment. The boundary of each region is, for example, a pixel in which the incident angle (x-axis direction) of a light ray incident on the center of the pixel is equal to or more than a first threshold and less than a second threshold is defined as an intermediate portion 902, and a pixel in which the angle is equal to or more than a second threshold is defined as a peripheral portion 903. Although it can be determined, it may be determined according to other conditions.

  FIGS. 7B to 7D show a pixel 904 as an example of a pixel located in the vicinity of the optical axis center 901, a pixel 905 as an example of a pixel located in the middle portion 902, and a peripheral portion 903. FIG. 9 is an xz sectional view of a photodiode of a pixel 906 which is an example of a located pixel. 7A to 7D, the same components as those in FIGS. 3 to 6 are denoted by the same reference numerals, and description thereof will be omitted. Here, the pixel 904 is a pixel located at the center of the optical axis.

  As shown in FIG. 7B, the pixel 904 located in the vicinity 901 of the optical axis center has the center position O3 of the ML 406 and the center position O2 of the N + 402 both coincide with the center position O1 of the N-epi 401. ML 406 and N + 402 are provided. On the other hand, as shown in FIG. 7C, for the pixel 905 located in the middle part 902, the center position O3 of the ML 406 is shifted from the center position O1 of the N-epi 401 toward the optical axis center (left side in the figure). Are provided with ML406 shifted by L2. Further, as shown in FIG. 7D, for the pixel 906 located in the peripheral portion 903, the shift of the center position O2 of N + 402 is combined with the shift of the center position O3 of the ML 406 in FIG. 7C. Specifically, the center position O2 of N + 402 is shifted by L1 in a direction away from the center of the optical axis with reference to the center position O1 of N-epi 401.

  As described above, as the distance from the optical axis center increases, the center position of the microlens is first shifted, and then the center position of N + 402 is further shifted. Regarding the pixels located in the intermediate portion 902 and the peripheral portion 903, it is possible to appropriately suppress a decrease in photon detection sensitivity. Note that the pixel located in the intermediate portion 902 may be configured to shift the center position O2 of N + 402 instead of the center position O3 of the ML 406.

  Here, the pixels in the right peripheral portion 303 have been described, but for the pixels in the pixel region in the left peripheral portion 303, the direction in which the average position is shifted is on the left side of the drawing. However, it is common that O2 and O3 are shifted in a direction away from the center of the optical axis.

  As described above, according to the present embodiment, for each of the plurality of pixels arranged in the pixel region, the position of the region where avalanche multiplication occurs and / or the position of the microlens are changed according to the position of the pixel. I tried to make it different. More specifically, for a pixel whose distance from the center of the optical axis is equal to or greater than the threshold, the center of the region where avalanche multiplication occurs occurs more than the pixel which does not have the center of the optical axis with respect to the center of the light receiving region of the pixel. To move away from the camera. Alternatively, or in addition, for a pixel whose distance from the optical axis center is equal to or greater than the threshold, the center of the microlens is shifted in a direction closer to the optical axis center with respect to the center of the light receiving region of the pixel, than the pixel that is not so. I made it. Accordingly, it is possible to suppress a decrease in photon detection efficiency depending on the position of the pixel. When the center of the microlens is shifted with respect to the center of the light receiving area of the pixel, it is preferable to shift the center of the microlens when there is a light-blocking member for preventing color mixing arranged between the pixels. Further, other members such as a color filter provided between the light receiving region of the pixel and the microlens may be shifted together.

● (Second embodiment)
Next, a second embodiment of the present invention will be described. In the present embodiment, the present invention is applied to a pixel having a configuration including a microlens and a plurality of divided light receiving regions. FIG. 8 is an equivalent circuit diagram of a pixel 108 ′ arranged in the pixel region of the image sensor according to the present embodiment. The same components as those of the pixel 108 according to the first embodiment are denoted by the same reference numerals as those in FIG.

  The pixel 108 'included in the image sensor according to this embodiment includes a plurality of photodiodes 201A and 201B. Note that three or more photodiodes may be provided per pixel. The pixel 108 'has quench resistors 202A and 202B, inversion buffers 203A and 203B, and counter circuits 204A and 204B corresponding to the photodiodes 201A and 201B, respectively.

  The voltage V1_A (for example, 3 V) is applied to the cathode terminal of the photodiode 201A via the quench resistor 202A, and the voltage V1_B (for example, 3 V) is applied to the cathode terminal of the photodiode 201B via the quench resistor 202B. . On the other hand, a common voltage V2 (for example, −20 V) is applied to the anode terminals of the photodiodes 201A and 201B. As a result, the individual photodiodes 201A and 201B operate in the Geiger mode, and the avalanche multiplication phenomenon occurs due to the incidence of photons.

  The inverting buffer 203A outputs a voltage change that occurs with the occurrence and termination of the avalanche multiplication in the photodiode 201A as a pulse signal to the counter circuit 204A. Similarly, the inversion buffer 203B outputs to the counter circuit 204B, as a pulse signal, a voltage change that occurs with the occurrence and termination of the avalanche multiplication in the photodiode 201B.

  The counter circuits 204A and 204B are supplied with enable signals (PEN_A, PEN_B) and reset signals (RES_A, RES_B) from the vertical control circuit 102 (FIG. 1). During a predetermined exposure period, the values counted by the counter circuits 204A and 204B are sequentially output to the digital output unit 107 (FIG. 1) as pixel data (SigOUT_A, SigOUT_B).

  As described later, the photodiodes 201A and 201B share one microlens and receive light beams from different partial pupils of the exit pupil of the imaging optical system. Therefore, by reading SigOUT_A and SigOUT_B from a plurality of pixels and detecting the phase difference between the image signal formed from SigOUT_A and the image signal formed from SigOUT_B, the defocus amount of the imaging optical system can be obtained. it can. Further, by adding two pixel data of SigOUT_A and SigOUT_B for each pixel, it is possible to obtain the same pixel data as the pixel data obtained by the pixel 108 of the first embodiment.

  9A and 9B are xz sectional views of the photodiode of the pixel according to the present embodiment. FIG. 9A shows the configuration of the pixel near the center of the optical axis, and FIG. 9B shows the configuration of the photodiode of the peripheral pixel. Here, it is assumed that the vicinity of the center of the optical axis and the peripheral portion are determined as described with reference to FIG. 3 in the first embodiment. 9 (c) and 9 (d) are cross-sectional views taken along the line CC 'of FIGS. 9 (a) and 9 (b), and FIGS. 9 (e) and 9 (f) are FIG. 9 (a). FIG. 10 is a sectional view taken along line DD ′ of FIG. 9B. 9A to 9F, components corresponding to the pixel 108 of the first embodiment are illustrated in FIGS. 4A to 4H to 7A to 7D. The same reference numerals as in FIG.

  In FIG. 9A, N + 402A and N + 402B, which are N-type semiconductor regions as the first conductivity type regions, are formed above the N-epi 401 as the light receiving region. These function as cathode terminals of the photodiodes 201A and 201B, respectively. Voltages V1_A and V1_B are applied to N + 402A and N + 402B via quench resistors 202A and 202B, respectively. As shown in FIGS. 9C and 9D, N-403 is formed around N + 402A and N + 402B as a guard ring.

  P404 is a P-type semiconductor region as a second conductivity type region, and functions as an anode terminal of the photodiodes 201A and 201B. The voltage V2 is applied to P404 via a contact electrode (not shown). As shown in FIGS. 9C and 9D, P404 also exists in a region between N + 402A and N + 402B. Further, as shown in FIGS. 9E and 9F, P404 is formed so as to extend to the vicinity of N + 402A and N + 402B. P404 shown in each figure is formed integrally. Thus, an avalanche multiplication region 1202A is formed in a region where N + 402A and P404 are close, and an avalanche multiplication region 1202B is formed in a region where N + 402B and P404 are close.

  FIGS. 9A and 9B schematically show the exit pupil 1204 of the photographing optical system. In the exit pupil 1204 of the imaging optical system, the average position where light emitted from the partial pupil region 1205 enters the pixel and is photoelectrically converted by the N-epi 401 as the light receiving region is indicated by 1203A and 1203A '. The average positions where light emitted from the partial pupil region 1206 enters the pixel and is photoelectrically converted by the light receiving region N-epi 401 are indicated by 1203B and 1203B '.

  Electrons generated at the average position 1203A or 1203A 'move to the avalanche multiplication region 1202A due to drift and are avalanche multiplied. On the other hand, electrons generated at the average position 1203B or 1203B 'move to the avalanche multiplication region 1202B due to drift and are avalanche multiplied. Electrons generated by photons incident between 1203A and 1203B (1203A 'and 1203B') move to one of avalanche multiplication regions 1202A (1202A ') and 1202B (1202B') due to drift and are avalanche multiplied. .

  9A to 9F, O1 is the center position in the x-axis direction of the N-epi 401 as the light receiving area. OA and OB are the center positions in the x-axis direction of N + 402A and N + 402B, respectively. The distance from O1 to OA is denoted by LA, and the distance from O1 to OB is denoted by LB. As shown in FIG. 9A, N + 402A and N + 402B are formed immediately above the average positions 1203A and 1203B where photons incident from the partial pupil regions 1205 and 1206 are photoelectrically converted. This makes it possible to reduce the distance from the average position where photons are photoelectrically converted to the avalanche multiplication regions 1202A and 1202B, while suppressing the area of the avalanche multiplication regions 1202A and 1202B. Therefore, it is possible to suppress that the electrons generated by the photoelectric conversion recombine and disappear before reaching the avalanche multiplication regions 1202A and 1202B, and that sufficient acceleration cannot be obtained in the avalanche multiplication region.

  On the other hand, in the peripheral pixels shown in FIG. 9B, the average positions where photons incident from the partial pupil regions 1205 and 1206 are photoelectrically converted are 1203A 'and 1203B'. The average positions 1203A 'and 1203B' are shifted in a direction away from the optical axis of the photographing optical system from the average positions 1203A and 1203B where the photons are photoelectrically converted at the pixel in FIG. 9A located at the optical center. Therefore, in the peripheral pixels, N + 402A and N + 402B are formed so as to be shifted from the pixel near the optical axis center in a direction away from the optical axis of the imaging optical system. OA 'and OB' in FIG. 9B are the center positions of N + 402A and N + 402B in the x-axis direction. Here, if the distance from O1 to OA 'is denoted by LA' and the distance from O1 to OB 'is denoted by LB', then LA '<LA, LB'> LB.

  As shown in FIG. 9B, also in the peripheral pixels, N + 402A and N + 402B are formed immediately above the average positions 1203A 'and 1203B' where the photons incident from the partial pupil regions 1205 and 1206 are photoelectrically converted. Thus, the avalanche multiplication regions 1202A 'and 1202B' are also formed immediately above the average positions 1203A 'and 1203B' where the photons are photoelectrically converted. Thus, the distance from the average position at which photons are photoelectrically converted to the avalanche multiplication regions 1202A 'and 1202B' can be reduced while suppressing the area of the avalanche multiplication regions 1202A 'and 1202B'. Therefore, it is possible to suppress that electrons generated by photoelectric conversion recombine and disappear before reaching the avalanche multiplication regions 1202A ′ and 1202B ′, and that sufficient acceleration cannot be obtained in the avalanche multiplication region. .

  Also in the peripheral pixels, the direction and position at which the electrons generated by the photoelectric conversion enter the avalanche multiplication region can be made the same as the pixels near the optical axis center. Therefore, it is possible to sufficiently obtain the acceleration required for the electrons to cause the avalanche multiplication in the avalanche multiplication region. Thus, it is possible to suppress the detection efficiency of the incident photon from being reduced in the pixels in the peripheral portion of the pixel region. Further, the difference between the detection efficiency of the incident photons of the two photodiodes in the pixel can be reduced.

  Here, the pixels in the right peripheral portion 303 have been described, but for the pixels in the pixel region in the left peripheral portion 303, the direction in which the average position is shifted is on the left side of the drawing. However, it is common that O2 is shifted in a direction away from the optical axis center. In this embodiment, an example is shown in which both the center positions of N + 402A and N + 402B in the x-axis direction are shifted. However, depending on the incident angle of light rays from the imaging optical system, only one side may be shifted.

● (Third embodiment)
Next, a third embodiment of the present invention will be described. In the present embodiment, the present invention is applied to a pixel having a configuration including a microlens and a light shielding film that shields a part of a light receiving region. The equivalent circuit of the pixel included in the image sensor according to the present embodiment is the same as that of the first embodiment (FIG. 2).

  An embodiment in which focus detection by a phase difference detection method is possible by blocking a part of a light beam incident on a photodiode via a microlens with a light-shielding film in some pixels in an imaging region will be described.

  FIG. 10A is a schematic diagram of the pixel region 101 of the image sensor according to the present embodiment, and the same components as those in the first embodiment are denoted by the same reference numerals as in FIG. In the present embodiment, as in the first embodiment, the pixel region is divided into the vicinity of the optical center and the peripheral portion 303. Reference numeral 1510 denotes an area of 8 × 8 pixels including the center of the optical axis, and reference numeral 1520 denotes an area of 8 × 8 pixels included in the peripheral portion. FIGS. 10B and 10C are enlarged views of the pixel regions 1510 and 1520, and a black portion indicates a light shielding film.

  The light-shielding film limits light incident on the pixel to a specific partial pupil region of the exit pupil of the imaging optical system by blocking a part of the light receiving region of the pixel. Accordingly, in FIG. 10B, light from different partial pupil regions enters the pixels 1502 and 1503. Pixels 1502 and 1503 are dedicated pixels (focus detection pixels) for acquiring pixel data for phase difference detection. By detecting the phase difference between the image signal generated from the pixel data obtained from the plurality of pixels 1502 and the image signal generated from the pixel data obtained from the plurality of pixels 1503, the defocus amount of the imaging optical system can be reduced. You can ask. On the other hand, the pixel 1501 having no light-shielding film is a pixel (pixel for photographing) for acquiring normal pixel data. Note that pixels 1504 and 1505 show another example of a light-shielding film in which the aperture is larger than those of the pixels 1502 and 1503. The pixels 1501 ′ to 1505 ′ in FIG. 10C correspond to the pixels 1501 to 1505 in FIG. 10B, respectively. Note that the size of the aperture of the light-shielding film actually provided in the pixel may be one type in the entire pixel region.

  As shown in FIG. 10B and FIG. 10C, pixels for focus detection are periodically arranged in a part or the whole of the pixel region 101. Note that the illustrated arrangement pattern of focus detection pixels is an example, and the present invention is not limited to this.

  FIGS. 11A to 11D are xz sectional views of the photodiodes of the pixels 1501 to 1504 in the region near the center of the optical axis. FIGS. 11E to 11H are xz sectional views of the photodiodes of the pixels 1501 ′ to 1504 ′ in the peripheral region. 11 (a) to 11 (h), the same components as those in the first embodiment are denoted by the same reference numerals as in FIGS. 4 (a) to 4 (h), and description thereof will be omitted. .

  As shown in FIGS. 11A to 11H, the focus detection pixels 1501 to 1505 and 1501 ′ to 1505 ′ are made of a metal such as aluminum or tungsten between the color filter 405 and the P404. The configured light shielding films 1601 to 1604 are provided. Note that the light-blocking film 1601 provided in the imaging pixels 1501 and 1501 'is provided so as not to limit the direction (pupil region) of photons incident on the pixels. On the other hand, in the pixels 1502 to 1505 and 1502 'to 1505' for focus detection, the incident direction of photons is restricted to the direction passing through the openings of the light shielding films 1601 to 1604.

  11 (a) to 11 (h), O1 is the center position in the x-axis direction of the N-epi 401 as the light receiving area. O2 is the center position of N + 402 in the x-axis direction. An avalanche multiplication region 407 is formed at a position where N + 402 and P404 are close to each other.

First, with reference to FIGS. 11A to 11D, a position where the avalanche multiplication region 407 is formed in the pixels 1501 to 1504 near the optical axis center will be described.
As shown in FIG. 11A, in the pixel 1501 for photographing, N + 402 is formed so that O1 and O2 match. On the other hand, as shown in FIG. 11B and FIG. 11C, in the focus detection pixels 1502 and 1503, N + 402 is formed such that O2 is located away from O1 by distances L4 and L5 in opposite directions, respectively. I do. Note that L4 = L5 for pixels near the center of the optical axis. In a focus detection pixel 1504 configured to receive a partial pupil region wider than the focus detection pixels 1502 and 1503, N + 402 is formed such that O2 is located at a distance L6 from O1. The direction in which O2 moves away from O1 is equal to the direction in which the opening of the light-shielding film deviates from O1.

  Here, reference numerals 1605 to 1608 in FIGS. 11A to 11D denote average positions at which photons incident on the N-epi 401 from the openings of the light shielding film are photoelectrically converted. As described above, by controlling the distance of the center position O2 of N + 402 with respect to the center O1 of the light receiving region, the avalanche multiplication is performed immediately above the average position 1605 to 1608 at which the photon is photoelectrically converted for each of the pixels 1501 to 1504. A region 407 is formed.

  Therefore, the distance from the average position where the incident photons are photoelectrically converted to the avalanche multiplication region is equal between the focus detection pixels 1502 to 1504 and the imaging pixel 1501. In addition, the directions and positions at which electrons generated by photoelectric conversion enter the avalanche multiplication region are also equal between the focus detection pixels 1502 to 1504 and the imaging pixel 1501. Therefore, compared with the case where the center position O2 of N + 402 is formed so as to coincide with the center O1 of the light receiving area also in the focus detection pixels, the photon detection efficiency of the focus detection pixels with respect to the imaging pixels is reduced. Can be suppressed from decreasing.

Next, a position where the avalanche multiplication region 407 is formed in the peripheral pixels 1501 ′ to 1504 ′ will be described with reference to FIGS.
In the pixels in the peripheral portion 303, the incident angle of light is larger than in the pixel region near the center of the optical axis. Therefore, the average positions 1609 to 1612 where the photons incident on the N-epi 401 as the light receiving region are photoelectrically converted are shifted in the direction (right side in the drawing) away from the center of the optical axis as compared with the average positions 1605 to 1608. Therefore, the center position O2 of N + 402 is formed shifted from L3 'to L6' with respect to the center O1 of the light receiving region. Note that L4 ′ <L4, L5 ′> L5, L6 ′ <L6. Here, the pixels in the pixel region 1520 in the right peripheral portion 303 have been described. However, as for the pixels in the pixel region in the left peripheral portion 303, the shift direction of the average position is on the left side of the drawing, The magnitude relationship between L6 and L4 'to L6' is reversed. However, it is common that O2 is shifted in a direction away from the optical axis center.

  Also in the present embodiment, similarly to the first and second embodiments, it is possible to suppress a decrease in the efficiency of detection of incident photons in peripheral pixels.

  In the present embodiment, an example in which the position of the avalanche multiplication region is changed between the pixel near the optical axis center and the pixel in the peripheral portion, and the position of the avalanche multiplication region is changed between the imaging pixel and the focus detection pixel explained. However, the position of the avalanche multiplication area may be changed only by the imaging pixel and the focus detection pixel. Further, when a plurality of types of focus detection pixels in which the opening positions of the light-shielding layer are shifted are arranged in order to cope with the positional shift of the ML 406 due to a manufacturing error, the avalanche multiplication area is adjusted in accordance with the opening position of the light-shielding layer. N + 402 may be shifted so as to be formed.

  As described above, the present invention has been described in detail based on exemplary embodiments, but the present invention is not limited to these embodiments. All modifications encompassed by the claims are included within the scope of the present invention.

Other Embodiments
In the above-described embodiment, only the position control of the N + 402 and the ML 406 in the x-axis direction has been described in order to facilitate understanding of the gist of the invention. However, the position control of the N + 402 and the ML 406 in the y-axis direction can be performed similarly to the position control in the x-axis direction. Therefore, instead of or in combination with the position control of N + 402 and ML406 in the x-axis direction, the position control of N + 402 and ML406 in the y-axis direction can be performed. When performing position control of N + 402 or ML406 in both the x-axis direction and the y-axis direction, the pixel area can be divided into two or more partial areas depending on the distance (image height) from the optical axis center. Also, the shift amount of N + 402 or ML406 may be different for each pixel instead of being different for each region.

  In the above embodiment, N + 402 is formed such that the center position O1 in the x-axis direction of the N-epi 401, which is the light receiving region, and the O2 in the x-axis direction of N + 402 coincide. However, actually, it is only necessary that the xy cross section (or PN coupling plane) of N + 402 shown in FIGS. 4C and 4D be formed so that O1 includes the xy coordinates.

  Similarly, description has been made assuming that N + 402 is formed immediately above the average position where photons are photoelectrically converted. However, this is because, for example, the xy cross section (or PN section) of N + 402 shown in FIGS. The coupling plane may be formed so as to include the xy coordinates of the average position.

  Note that the configurations described in other embodiments can be combined as appropriate. For example, in the third embodiment, the position of the microlens may be controlled, or the center position O2 of N + 402 may be determined based on the average position corresponding to the color of the color filter.

  In each of the above-described embodiments, the center position O2 of the avalanche multiplication area (N + 402) is shifted in the x-axis and y-axis directions according to the image height of the pixel, but is shifted in the optical axis direction (z-axis direction). Is also good.

  The imaging device described in each embodiment can be used for various applications. FIG. 12 is a block diagram illustrating an example of a functional configuration of a camera 1200 as an example of an imaging device to which the photon counting type imaging device 100 described in the first to third embodiments is applied.

  The taking lens 1201 has a plurality of lenses including a focus lens, an aperture, and / or an ND filter. The taking lens 1201 may or may not be removable. The imaging lens 1201 is an imaging optical system that forms an optical image of a subject on the imaging surface of the imaging device 100. The image sensor 100 is provided with, for example, a color filter of a primary color Bayer array.

  The image processing circuit 1203 applies predetermined signal processing to image data read from the image sensor 100, and generates display image data and recording image data. The image processing circuit 1203 outputs information obtained by applying signal processing to the image data to the control circuit 1206. The image processing circuit 1203 may be a dedicated hardware circuit such as an ASIC designed to realize a specific function, or may execute a specific function by executing software by a programmable processor such as a DSP. A configuration that realizes this may be used.

  Here, the signal processing applied by the image processing circuit 1203 includes preprocessing, color interpolation processing, correction processing, detection processing, data processing processing, evaluation value calculation processing, and the like. The preprocessing includes signal amplification, reference level adjustment, defective pixel correction, and the like. The color interpolation process is a process of interpolating a value of a color component not included in image data read from a pixel, and is also called demosaic process. The correction processing includes white balance adjustment, processing for correcting image brightness, processing for correcting optical aberration of the imaging lens 1201, processing for correcting color, and the like. The detection processing includes detection and tracking processing of a characteristic area (for example, a face area or a human body area), recognition processing of a person, and the like. The data processing includes scaling processing, encoding and decoding processing, header information generation processing, and the like. The evaluation value calculation process is a process of calculating an evaluation value used in the automatic exposure control process and the automatic focus detection process performed by the control circuit 1206. Note that these are examples of signal processing that can be performed by the image processing circuit 1203, and do not limit the signal processing performed by the image processing circuit 1203.

  The memory 1204 is used as a buffer for image data, used as a work area for the image processing circuit 1203 and the control circuit 1206, and used as a video memory of the display device 1208. A part of the memory 1204 is non-volatile, and is used for storing programs and setting values executed by the control circuit 1206, setting values of the camera 1200, UI display data, and the like.

The recording circuit 1205 writes and reads a data file to and from a recording medium 1209, for example, a semiconductor memory card, under the control of the control circuit 1206.
The display device 1208 is, for example, a flat panel display, and displays an image based on a display signal supplied from the control circuit 1206, such as a live view image or a menu screen. Note that the display device 1208 may be a touch display.

  An operation circuit 1207 is a group of input devices such as a switch, a button, a touch pad, and a dial, and is used by a user to give an instruction to the camera 1200. Functions are fixedly or dynamically assigned to each of the input devices included in the operation circuit 1207. Thereby, the input device functions as a shutter button, a moving image recording / stop button, a menu button, a direction key, an enter button, an operation mode switching dial, and the like. Note that when the display device 1208 is a touch display, soft keys realized by a combination of a touch panel and a GUI are included in an input device group included in the operation circuit 1207.

  The control circuit 1206 is, for example, a programmable processor such as a CPU. The control circuit 1206 develops a program stored in a nonvolatile memory included in the memory 1204 into a system memory of the memory 1204, executes the program, and controls the operation of each unit to realize the function of the camera 1200. For example, when an operation of the operation circuit 1207 is detected, the control circuit 1206 executes an operation according to the detected operation.

  The control circuit 1206 controls the operation of the image sensor 100. For example, the control circuit 1206 determines the read mode of the image sensor 100 according to the shooting mode, and controls the operation of the TG 104 so as to output a control signal according to the determined read mode. The shooting mode includes, for example, a still image reading mode and a moving image reading mode. Further, the control circuit 1206 may determine the reading mode according to the setting of the resolution and the frame rate of the image to be shot. For example, the number of pixels to be read, the number of added pixel signals, the number of thinned pixels, and the like may differ depending on the read mode.

  Note that the image sensor 100 according to the embodiment can be applied to other uses. For example, the imaging element 100 can be used for sensing other than visible light such as infrared light, ultraviolet light, and X-ray. Further, the present invention can be applied to an imaging device for measuring a distance by a TOF (Time Of Flight) method, an imaging device provided in a smartphone, a game machine, a personal computer, a tablet device, and the like. Furthermore, the present invention can be applied to a medical device for imaging an endoscope or a blood vessel, a beauty device for observing the skin or the scalp, and a video camera for capturing sports or action moving images. The present invention is also applicable to traffic purpose cameras such as traffic and ship monitoring and drive recorders, cameras for academic use such as astronomical observation and sample observation, home appliances with cameras, and machine vision. In particular, machine vision is not limited to robots in factories and the like, but can be used in agriculture and fisheries.

Reference numeral 100 denotes an image sensor, 201 denotes a photodiode, 202 denotes a quench resistor, 203 denotes an inversion buffer, 204 denotes a counter circuit, 300 denotes the center of the optical axis of the photographing optical system, 301 denotes a pixel near the center of the optical axis, and 302 denotes a pixel in a peripheral portion. , 407, 1202 ... Avalanche multiplication area

Claims (18)

A pixel region in which a plurality of pixels having a photoelectric conversion region that generates an electric charge by photoelectric conversion based on incident light and an avalanche multiplication region that generates an avalanche multiplication by the electric charge generated by the photoelectric conversion is arranged in a matrix. ,
In a plan view of each pixel arranged in the pixel region, the size of the avalanche multiplication region is smaller than the size of the photoelectric conversion region,
Of the pixels arranged in the pixel region, the position of the avalanche multiplication region in at least some of the pixels arranged in the peripheral region of the pixel region is the position of the pixel arranged in the central region of the pixel region. An image pickup element formed at a position shifted from a position of the avalanche multiplication area.   Among the pixels arranged in the pixel region, the position of the avalanche multiplication region of a predetermined pixel is more distant from the reference position of the pixel region than the position of the avalanche multiplication region of another pixel. The imaging device according to claim 1, wherein the imaging device is formed at a shifted position. The pixel further includes a first conductivity type region to which a first voltage is applied, and a second conductivity type region that forms a coupling surface with the first conductivity type region and to which a second voltage is applied,
The imaging device according to claim 2, wherein a position at which the avalanche multiplication region is formed is controlled by a position at which the first conductivity type region or the second conductivity type region is formed.   4. The imaging device according to claim 3, wherein a position where the first conductivity type region or the second conductivity type region is formed in the predetermined pixel is based on an average position where photoelectric conversion occurs in the photoelectric conversion region. 5. element.   The imaging device according to claim 4, wherein the average position is based on a penetration length of light having a wavelength corresponding to a color of a color filter provided in the pixel.   The imaging apparatus according to claim 2, wherein the magnitude of the positional deviation of the avalanche multiplication area is based on a distance between the predetermined pixel and the reference position. element.   The imaging device according to claim 2, wherein the predetermined pixel is a pixel whose distance from the reference position is equal to or greater than a threshold. The pixel further has a microlens,
The imaging apparatus according to claim 2, wherein the predetermined pixel is formed such that a center of the micro lens is shifted in a direction approaching the reference position. element. The pixel further has a microlens,
The predetermined pixel is a pixel whose distance from the reference position is equal to or greater than a threshold,
For the predetermined pixels, and for some of the pixels whose distance from the predetermined position to the reference position is shorter than the predetermined pixels, the center of the microlens is formed at a position shifted in a direction approaching the reference position. The imaging device according to any one of claims 2, 4, and 5, wherein:   The imaging device according to claim 8, wherein the magnitude of the displacement of the position of the microlens is based on a distance between the predetermined pixel and the reference position.   The imaging device according to claim 9, wherein the magnitude of the displacement of the position of the microlens is based on a distance between the predetermined pixel and the reference position.   The predetermined pixel has a plurality of avalanche multiplication regions, and each of the plurality of avalanche multiplication regions is formed at a position shifted in a direction away from the reference position from a position of the avalanche multiplication region. The imaging device according to claim 2, wherein the imaging is performed. The predetermined pixel is a pixel having a light shielding film that shields a part of the light receiving region,
The imaging device according to claim 2, wherein the magnitude of the positional deviation of the avalanche multiplication region is based on a position of an opening of the light shielding film.   The image sensor according to claim 2, wherein the reference position is a center of an optical axis at which an optical axis of a photographing optical system intersects with the pixel region.   The imaging device according to claim 2, wherein the reference position is a center of the pixel region. An avalanche multiplication region that generates avalanche multiplication by electric charges generated by photoelectric conversion, and a pixel region in which a plurality of pixels having an electrode for applying a voltage for the avalanche multiplication are arranged.
An image pickup device, wherein the positions of the electrodes in at least some of the pixels arranged in the pixel region are formed at positions different from the positions of the electrodes in other pixels. . A pixel region in which a plurality of pixels having an avalanche multiplication region that generates avalanche multiplication by electric charges generated by photoelectric conversion is provided,
Of the pixels arranged in the pixel region, the position of the avalanche multiplication region in at least some of the pixels is formed at a position different from the position of the avalanche multiplication region in another pixel. An imaging element characterized by the above-mentioned. An image sensor according to any one of claims 1 to 17,
A processor for controlling a read mode of the image sensor,
An imaging device comprising:

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