JP2005109370A - Solid state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid state imaging device having a plurality of imaging regions such as an AF sensor and a compound eye image sensor, which can reduce a chip size and improve an optical characteristic. <P>SOLUTION: OB pixels are arranged inside a plurality of imaging regions. The OB pixels and effective pixels are controlled independently of each other. OB Outputting is carried out in an arbitrary period. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device having a plurality of imaging regions, and more particularly to a phase difference detection type autofocus sensor and a compound eye imaging area sensor.

  FIG. 10 shows a planar layout of a conventional phase difference detection type autofocus sensor. In the figure, 900 is a Si semiconductor substrate, 901 is an AF circuit block, 902 is a signal amplifier circuit, 903 is a power supply circuit, 904 is an AGC circuit, 905 is a logic circuit, 906 is a dummy pixel, 907 is a light-shielding (OB) pixel, Reference numeral 908 denotes an effective pixel. In the phase difference detection type autofocus, in order to detect a phase difference between two subject images, two imaging areas of an A image (a standard part) and a B image (a reference part) are required. Further, an opaque (OB) pixel for obtaining a reference signal is required. Usually, since it is necessary to perform OB pixel output before effective pixel output, it is possible to read out before the effective pixel output period by arranging the OB pixel at the head of the effective pixel. Using the difference signal between the OB pixel signal and the effective pixel signal as a video signal, serial output is performed from the solid-state imaging device to the outside using a scanning circuit.

  In the conventional AF sensor, the light-shielding pixel (OB pixel) is formed in the leading area of the A image. Since the A image and the B image are continuously read out, the OB pixel dedicated to the B image is basically unnecessary (the reference output of the B image is also used as the A image).

Further, in the phase difference detection type autofocus sensor, the same AE sensor is used between the two imaging areas of the A image (reference portion) and the B image (reference portion) for detecting the phase difference between the two subject images. An AEAF integrated sensor provided on a substrate is disclosed (for example, see Patent Document 1).
JP 2003-140031 A

  However, in the above conventional example, since the OB pixel is configured at the head of the effective pixel region, the solid-state imaging device having a plurality of imaging regions, particularly a phase difference detection type AF sensor or compound eye type in which the photoelectric conversion element region is determined from the optical design. The area sensor has a drawback that the chip size cannot be reduced. Further, when applied to a four-eye imaging area sensor which is one of solid-state imaging devices for compound eye imaging, the result is as shown in FIG. 11, and there are many useless areas (areas in which no semiconductor element is created) in the semiconductor chip, and the chip size is further increased. It had the disadvantage of becoming larger.

  Further, in the above conventional example, if dummy pixels are provided on both sides of the OB pixel in order to reduce the light fluctuation of the OB pixel output, there is a disadvantage that the chip size is increased. On the other hand, if the dummy pixels are reduced by giving priority to the chip size, the distance measuring ability at the time of ultra-high brightness photographing is reduced.

  The object of the first invention related to the present application is to realize a solid-state imaging device capable of reducing the chip size.

  The object of the second invention related to the present application is to realize a solid-state imaging device that suppresses output fluctuations of OB pixels in a high luminance state without increasing the chip size.

  It is another object of the present invention to realize the same reading method as in the past and eliminate the need for a new signal processing system.

  In order to achieve the above object, a first invention according to the present application is a solid-state imaging device provided with an OB pixel for outputting a dark reference signal in a region inside a plurality of imaging regions. To do.

  The second invention according to the present application is characterized in that a dummy pixel is arranged between the OB pixel and the effective pixel.

  The third invention according to the present application is characterized in that the same reading method as the conventional one can be realized by separately controlling the OB pixel and the effective pixel. Here, the same reading method as in the conventional case means that effective pixels are read after reading OB pixels.

  In the first configuration, since the OB pixels conventionally provided outside are formed in the semiconductor regions between the imaging regions that have not been used effectively conventionally, a solid-state imaging device with a reduced chip size can be realized.

  In the second configuration, since it is possible to provide more dummy pixels than before without increasing the chip size, it is possible to provide a solid-state imaging device in which optical crosstalk from effective pixels is suppressed. .

  In the third configuration, the same signal readout method as in the prior art can be performed by performing control to read out the effective pixel after reading out the OB pixel.

  As described above, according to the present invention, a phase difference detection type AF sensor with a reduced chip size can be realized. Therefore, in an autofocus camera using the solid-state imaging device, the camera can be downsized and improved in performance. The price has been reduced. The same effect can be expected regardless of digital, analog, single-lens reflex camera, and compact.

  According to the present invention, a compound eye type area sensor with a reduced chip size is possible, so that in a digital camera using the solid-state imaging device, the camera is downsized, improved in performance, and reduced in price. Similar effects can be expected not only for digital cameras but also for mobile devices such as mobile phones and PDAs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a drawing that best represents the features of the present invention, and is a schematic plan layout diagram of a solid-state imaging device to which the present invention is applied. The solid-state imaging device of the present embodiment shows an AF sensor having a photometric function. Further, it is a multipoint AF sensor that performs distance measurement for a plurality of positions. In FIG. 1, 100 is a Si semiconductor substrate, 101 is an AF sensor block for performing distance measurement, 102 is a signal amplification circuit for amplifying a signal from the AF sensor block, and 103 is a power supply circuit for operating an analog circuit. , 104 is an AGC circuit for determining the accumulation time of the AF sensor and the gain of the signal output circuit, 105 is a logic circuit for driving the sensor, 106 is an AE photodiode for performing photometry, and 107 is an AE photodiode. AE circuit for logarithmically compressing and outputting the above signal, 108 a thermometer for measuring the temperature of the chip, and 109 a multiplexer circuit for selecting and reading out various analog signals.

  The AF sensor block 101 includes a pair of linear sensor circuits shown in FIG. 3 in order to perform autofocus by a phase difference detection method. An imaging lens is provided on each linear sensor, and a subject image is formed on the linear sensor by each imaging lens. The distance to the subject can be calculated from the imaging position on the linear sensor, the focal length of the imaging lens, and the interval (baseline length) of the imaging lens.

  In the AF sensor circuit, 110 is an aperture dummy pixel, 111 is a light-shielding dummy pixel, 112 is an OB pixel, and 114 is an effective pixel. The structure of 111 light-shielding dummy pixels and 112 OB pixels are the same. Further, the structures of the 110 opening dummy pixels and the 114 effective pixels are the same. The OB pixel is obtained by shielding the effective pixel photodiode with AL or the like. Therefore, if there is stray light or crosstalk from adjacent pixels, the output potential from the OB pixel will fluctuate. In order to prevent this, a dummy pixel is usually provided between the OB pixel and the light-shielding pixel.

  Next, a specific circuit diagram of the AF sensor circuit 101 is shown in FIG. The CMOS linear AF sensor shown here is a circuit previously proposed by the present applicant in Japanese Patent Laid-Open No. 2000-180706. In the figure, 1 is a pn junction photodiode that performs photoelectric conversion, 2 is a reset MOS transistor that resets the potential of the photodiode to VRES, 3 is a differential amplifier, and 1 to 3 constitute an amplifying photoelectric conversion element To do. Reference numeral 4 denotes a clamp capacitor, and 5 denotes a MOS switch for inputting a clamp potential, and 4 and 5 constitute a clamp circuit. 6 to 9 are switching MOS transistors, 10 is a differential amplifier for detecting a minimum value, 11 is a differential amplifier for detecting a maximum value, and each differential amplifier constitutes a voltage follower circuit. Reference numeral 12 denotes a minimum value output MOS switch, 13 denotes a maximum value output MOS switch, 14 denotes an OR circuit, 15 denotes a scanning circuit, and 16 and 17 denote constant current MOS transistors. The final stage is an NMOS source follower circuit for the minimum value detection circuit, and the final stage is a PMOS source follower circuit for the maximum value detection circuit. Reference numeral 18 denotes a common output line for outputting a signal from the pixel. In this circuit configuration, by providing a feedback type noise clamp circuit in front of the maximum value detection circuit and the minimum value detection circuit, reset noise generated by the photodiode, sensor amplifier, maximum value detection circuit, and minimum value detection circuit The generated FPN can be removed. In addition, a voltage follower circuit in which the final output stage is a source follower type is configured for each pixel, and at the time of minimum value output, the constant current source in the output stage of each voltage follower is turned off, and the output line connected to the constant current source is connected. By the common connection, the maximum value of the video signal can be obtained. Further, when outputting the video signal, a serial video signal can be obtained by turning on the constant current source at the output stage of each voltage follower and sequentially connecting each voltage follower circuit to the output line. By this operation, the maximum value detection circuit and the signal output circuit can be used together, so that the chip can be miniaturized.

  Next, the output order of AF signals in the photometry / ranging solid-state imaging device of the present embodiment will be described. In this embodiment, as shown in FIG. 11, since the driving pulse for OB pixel output and the driving pulse for the scanning circuit for outputting the effective pixel are independent, the output from the OB pixel is performed in an arbitrary period. It becomes possible. Normally, output is performed in the following form.

OB ₁ output-> A image effective pixel serial output-> B image effective pixel serial output OB ₂ output-> A image effective pixel serial output-> B image effective pixel serial output OB ₃ output-> A image effective pixel serial output- > B image effective pixel serial output By changing the order of the OB pulse and the scanning circuit pulse, the order of the region 1, the region 2, and the region 3 can be changed as a matter of course. Also, it is possible to output only a specific area.

FIG. 3 shows a schematic cross-sectional structure diagram of the solid-state imaging device for photometry / ranging in the present embodiment. For the sake of explanation, the number of pixels is reduced for illustration. In the figure, 120 is an N type Si substrate, 121 is an N ⁻ type epitaxial layer, 122 is a PWL, 123 is an NWL, 124 is an N ⁺ type impurity layer, 123 PWL and 124 are an N ⁺ type impurity layer and PN A junction photodiode is formed. Further, 125 is a gate oxide film, 126 is a thick oxide film (LOCOS) that is an element isolation region, 127 is a POL wiring that also serves as a gate of a MOS transistor, 128 is an interlayer insulating film, 129 is an AL wiring, and 130 is a light shielding film. An AL film 131 is a SiON film which is a surface protective film. A pixel 132 in which a light shielding film is formed on the photodiode is an OB pixel. In order to make the dark current behavior of the OB pixel and the effective pixel the same, it is desirable to make the photodiode structure the same and to form a light shielding film at a high position.

  In the present invention, the OB pixel is provided in the region between the A image and the B image, in this embodiment, on the final pixel side of the A image, and a sufficient number of dummy pixel groups are provided between the effective pixel and the OB pixel. This makes it possible to prevent fluctuations in the OB pixel output without increasing the chip size. As an actual configuration, it is desirable to provide the same opening dummy pixel as the effective pixel next to the effective pixel, and to provide the OB pixel by providing several same light-shielding dummy pixels as the OB pixel next to the opening dummy pixel. Furthermore, it is more preferable if a light-shielding dummy pixel can be formed after the OB pixel.

  According to the present embodiment, a compact solid-state imaging device for distance measurement capable of distance measurement even in an extremely high brightness state can be realized. Further, the present invention can be applied not only to a CMOS sensor but also to, for example, a CCD, BASIS, SIT, CMD, AMI, VMIS and the like.

  FIG. 4 shows a planar layout in the second embodiment to which the present invention is applied. In the present embodiment, a case is shown where the center is applied to a three-point ranging AF sensor corresponding to cross ranging (simultaneous ranging of vertical line detection and horizontal line detection). In the figure, 140 is a Si substrate, 141 is an OB pixel, 142 is a dummy pixel, and 143 is an effective pixel. Also in this embodiment, the chip area can be reduced by forming the OB pixel in the region between the A image and the B image. Although the present embodiment has been described as a three-point ranging AF sensor, the same configuration can be applied to cases corresponding to five-point ranging as shown in FIG. 5 and cases corresponding to seven-point ranging as shown in FIG. Is possible. Naturally, it is possible to cope with further multi-point AF such as 11-point AF.

  Also in this embodiment, by providing an OB pixel between two linear sensors that detect a phase difference, the chip area of the AF sensor can be reduced. In addition, it is possible to prevent adverse effects such as crosstalk due to light incident on a chip peripheral region where a light shielding layer cannot be formed.

  FIG. 7 shows a planar layout in the third embodiment to which the present invention is applied. In this embodiment, an example applied to an area type AF sensor is shown. This area type AF sensor is disclosed in Japanese Patent Laid-Open No. 11-191867 by the present applicant. In the first embodiment and the second embodiment, the phase difference detection type distance measurement is performed by the linear sensor pair. However, in this embodiment, the phase difference detection type distance measurement is performed by the area sensor pair. By using the area sensor, it is possible to auto-focus on a wider area. Also in this embodiment, by providing the OB pixel in the area between the area sensors provided for detecting the phase difference, the chip area of the area type AF sensor can be reduced. Similarly, it is possible to prevent an adverse effect due to light incident on a chip peripheral region where a light shielding layer cannot be formed.

  FIG. 8 shows a planar layout in the fourth embodiment to which the present invention is applied. In this embodiment, an example applied to an area sensor for compound eye imaging will be shown. Since the actual number of effective pixels and OB pixels (horizontal and vertical) of the area sensor is very large, the number of pixels is reduced in the drawing for explanation. The optical arrangement of this compound-eye imaging area sensor is disclosed by the present applicant in Japanese Patent Application Laid-Open Nos. 2002-43555 and 2002-141488.

  In FIG. 8, 150 is a Si substrate, 151 and 152 are G imaging area sensors, 153 is an R imaging area sensor, and 154 is a B imaging area sensor. The reason why there are two surfaces 151 and 152 for G is to increase the resolution and to divert an image processing system for an area sensor using a conventional Bayer array color filter.

  In this embodiment, R, G1, B, and G2 OB pixels are formed inside four imaging areas, respectively, so that the chip size can be reduced.

  First, an OB pixel signal corresponding to the R pixel area is output by a pulse from the logic circuit. Thereafter, a signal from an effective pixel on the same horizontal line as the OB pixel is serially output by driving the HSR. The above operation is also performed for G1, G2, and B.

OB _R , R, R, R, R ---
OB _G1 , G1, G1, G1, G1 ---
OB _G2 , G2, G2, G2, G2 ---
OB _B , B, B, B, B ---
Since the solid-state imaging device according to the present embodiment uses an XY address type driving method, various driving methods are possible. Therefore, the output of the signal is not limited to the above form, and a reading method corresponding to a Bayer array color filter may be used. In this case, after reading the OB signal of the R pixel and the OB signal of the G1 pixel, by alternately driving the HSR of R and G1,
OB _R , OB _G1 , R, G1, R, G1, R, G1 ---
OB _G2 , OB _B , G2, B, G2, B, G2, B ---
Can be output. In addition, both interlace scanning and progressive scanning can be used.

  In this embodiment, by providing OB pixels between a plurality of area sensors, the chip area can be reduced as compared with the conventional compound eye area sensor shown in FIG.

  Next, an image pickup apparatus using the distance measuring solid-state image pickup apparatus described in the first to third embodiments will be described. FIG. 9 is a block diagram showing an embodiment in which a solid-state imaging device for explaining the fifth embodiment is used in a lens shutter digital compact camera (imaging device). In this figure, 201 is a barrier that serves as a lens switch and a main switch, 202 is a lens that forms an optical image of a subject on the solid-state image sensor 204, 203 is a diaphragm for varying the amount of light that has passed through the lens 202, and 204 is This is a solid-state imaging device for capturing the subject imaged by the lens 202 as an image signal.

  Reference numeral 205 denotes a photometric distance measuring solid-state imaging device described in the first embodiment. Reference numeral 206 denotes an imaging signal processing circuit that processes a signal from the solid-state imaging device 204, 207 denotes an A / D converter that performs analog-digital conversion on the image signal, photometry signal, and distance measurement signal, and 208 denotes an output from the A / D converter 207. A signal processing unit that compresses various corrections and data into the image data that has been processed, 209 is a timing for outputting various timing signals to the solid-state imaging device 204, the imaging signal processing circuit 206, the A / D converter 207, the signal processing unit 208, etc. A generation unit 210 is an overall control / calculation unit that controls various calculations and the entire camera, and 211 is a memory unit for temporarily storing image data.

  Further, 212 is an interface unit for recording or reading on a recording medium, 213 is a removable recording medium such as a semiconductor memory for recording or reading image data, and 214 is an interface for communicating with an external computer or the like. Part.

  Next, an operation at the time of photographing with such a lens shutter digital compact camera will be described. When the barrier 201 is opened, the main power supply is turned on, then the control system power supply is turned on, and the power supply of the imaging system circuit such as the A / D converter 207 is turned on.

  Based on the signal output from the AF circuit block of the solid-state imaging device 205, the overall control / calculation unit 210 calculates the distance to the subject by triangulation. Thereafter, the feeding amount of the lens 202 is calculated, and the lens 202 is driven to a predetermined position to be focused.

  Next, in order to control the exposure amount, the signal output from the AE sensor of the solid-state imaging device 205 is converted by the A / D converter 207 and then input to the signal processing unit 208, and the exposure calculation is performed based on the data. Is performed by the overall control / arithmetic unit 210. The brightness is determined based on the result of the photometry, and the overall control / calculation unit 210 adjusts the aperture 203 and the shutter speed according to the result.

  After that, after the exposure conditions are set, the main exposure with the solid-state image sensor 204 starts. When the exposure is completed, the image signal output from the solid-state imaging device 204 is A / D converted by the A / D converter 207, passes through the signal processing unit 208, and is written in the memory unit 211 by the overall control / calculation unit 210. Thereafter, the data stored in the memory unit 211 is recorded on the removable recording medium 213 through the recording medium control I / F unit 212 under the control of the overall control / arithmetic unit 210. Further, it may be directly input to a computer or the like through the external I / F unit 214.

  In particular, in the external measurement AF sensor, the amount of incident light is large, and the output fluctuation of the OB pixel becomes severe due to crosstalk from the sensor periphery. Therefore, the structure in which the OB pixel is provided inside the chip as in the present invention has a great effect. There is. The solid-state imaging device for photometry and distance measurement according to the present invention can be used not only for a digital compact camera but also for a silver salt camera or the like. The same effect can be obtained even when used for a single-lens reflex camera.

Schematic sensor layout diagram of the first embodiment of the present invention AF sensor circuit diagram of the first embodiment of the present invention Sensor sectional view in the first embodiment of the present invention Schematic sensor layout diagram of the second embodiment of the present invention Another embodiment of the second embodiment of the present invention Another embodiment of the second embodiment of the present invention Schematic sensor layout diagram of the third embodiment of the present invention Schematic sensor layout diagram of the fourth embodiment of the present invention The circuit block diagram of 5th Example of this invention The figure explaining the conventional AF sensor The figure explaining the conventional compound eye type area sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 pn photodiode 2 Reset MOS transistor 3 CMOS differential amplifier 4 Clamp capacity | capacitance 5, 6, 7, 8, 9 MOS switch 10 Minimum value detection differential amplifier 11 Maximum value detection differential amplifier 12, 13 MOS switch 14 OR Circuit 15 Scan circuit 16, 17 Constant current MOS transistor 18 Common output line 100, 120, 140, 150, 900 N-type Si substrate 101 AF sensor block 102 Signal amplification circuit 103 Power supply circuit 104 AGC circuit 105 Logic circuit 106 Photo of AE sensor Diode region 107 AE signal processing circuit 108 Thermometer 109 Multiplexer circuit 110 Open dummy pixel 111, 142 Light-shielding dummy pixel 112, 132, 141 OB pixel 113, 143 Effective pixel 121 N-type epitaxial layer 12 PWL
123 NWL
124 N ⁺ impurity layer 125 thin oxide film 126 LOCOS
127 POL wiring 128 Interlayer insulating film 129 AL wiring 130 Light shielding film 131 Protective film 151, 152 G area sensor 153 R area sensor 154 B area sensor 201 Barrier 202 Shooting lens 203 Diaphragm 204 Solid imaging device 205 Photometric distance measuring solid Imaging device 206 Imaging signal processing circuit 207 AD converter 208 Signal processing unit 209 Timing generator 210 Overall control / arithmetic unit 211 Memory 212 Internal interface 213 Recording medium 214 External interface

Claims (9)

  In a solid-state imaging device provided with two photoelectric conversion element regions arranged at a predetermined distance on the same semiconductor substrate, a light-shielding pixel that outputs a dark reference signal is provided inside the two photoelectric conversion element regions. A solid-state imaging device.   2. The solid-state imaging device according to claim 1, wherein the photoelectric conversion element region is a linear sensor.   3. The solid-state imaging device for distance measurement according to claim 2, wherein linear sensors are arranged at a predetermined distance in order to perform autofocus by phase difference detection.   In a solid-state imaging device for distance measurement provided with a plurality of linear sensors arranged at a predetermined distance in order to perform phase difference detection type multi-point distance measurement, each linear sensor is arranged in an area inside the linear sensor. A solid-state imaging device for ranging, characterized in that light-shielding pixels for outputting a dark reference signal are arranged adjacent to each other.   The solid-state imaging device according to claim 1, wherein the photoelectric conversion element region is an area sensor.   6. The solid-state imaging device according to claim 5, wherein area sensors are arranged at a predetermined distance in order to perform area-type autofocus by phase difference detection.   6. The solid-state imaging device for compound eye imaging according to claim 5, wherein the solid-state imaging device is an area sensor for performing compound eye imaging.   8. The solid-state imaging device according to claim 1, wherein the output of the OB pixel can be output in an arbitrary period independently of the output of the effective pixel. 9. The solid-state imaging device according to claim 8, wherein a signal is output to the effective pixel row by a scanning circuit, and the OB pixel is output with an independent control pulse.

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