JP4850641B2 - Solid-state imaging device and imaging system - Google Patents

Description

  The present invention relates to a solid-state imaging device, and more particularly to an output unit that outputs a signal from the solid-state imaging device to the outside.

  In recent years, solid-state imaging devices for digital cameras and video cameras have made remarkable progress, and the number of pixels has been increasing for the purpose of improving the resolution of images. Along with this, it is important to improve the reading speed in order to ensure the continuous shooting performance necessary for the camera and the frame rate in the case of moving images. As a method for improving the readout speed in a solid-state imaging device, a configuration in which pixel signals are divided into a plurality of readout channels and parallel readout is performed as disclosed in Patent Document 1 is disclosed.

Further, Patent Document 2 discloses a configuration using a fully differential output amplifier as a configuration for differentially interfacing in order to obtain good matching with a subsequent signal processing IC.
Japanese Patent Laid-Open No. 10-224697 JP 2004-186790 A

  However, Patent Documents 1 and 2 have not sufficiently studied the arrangement of the signal path up to the output terminal after differential output. At the same time, the examination on the arrangement of the plurality of output terminals was not sufficient. In particular, in a configuration in which reading is performed divided into a plurality of read channels, the signal path of adjacent read channels or the arrangement relationship between the output terminals is important. Depending on this arrangement relationship, electrical color mixing may occur between adjacent readout channels. The output signal level itself varies depending on the shooting conditions. In the case of the differential output format, the forward signal is output on the positive side and the inverted signal is output on the negative side with respect to the reference level. At this time, if the output terminals arranged in succession to the output terminal that outputs the normal rotation signal are output terminals that output the inverted signal of the adjacent read channel as the output terminal arrangement order, they are mutually connected by capacitive coupling. Crosstalk tends to occur so as to cancel out the signals.

  This phenomenon is particularly affected when there is an output difference between adjacent readout channels. If the waveform at low luminance output is affected by the waveform at high luminance output, the difference from the actual output will be proportionally large. . In some cases, a color that does not originally exist in the dark part of the image may be generated, resulting in a false color.

  Further, even in the case where the output form of the differential output is such that the output of one signal path is output as the reference voltage, if the reference voltage changes depending on the output signal of the adjacent readout channel, the electrical color mixture is similarly caused. May be caused.

  In view of the above problems, an object of the present invention is to reduce the influence of mutual signals between adjacent read channels such as the crosstalk.

  The solid-state imaging device of the present invention includes a pixel region in which a plurality of pixels are arranged, a plurality of amplifiers that amplify signals from the pixel region, and a plurality of output terminals that output the output signals of the amplifiers to the outside. A solid-state imaging device having a plurality of signal paths for transmitting signals from the amplifier to a plurality of output terminals, wherein the amplifier has a differential output configuration for outputting a first signal and a second signal, The plurality of output terminals have a plurality of first output terminals to which the first signal is transmitted and a plurality of second output terminals to which the second signal is transmitted. The arrangement order of the plurality of output terminals is characterized in that the first output terminals or the second output terminals are continuous.

  According to the present invention, it is possible to read out signals in parallel in a plurality of readout channels and to output high-quality signals in a configuration using a differential output configuration amplifier.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to these examples, and can be appropriately changed and combined within a range not exceeding the gist of the invention.

Example 1
FIG. 1 illustrates in detail a configuration of a solid-state imaging device that amplifies a signal output from a pixel region with a plurality of amplifiers and then outputs the signals to the outside, particularly from an amplifier to an output terminal (output pad) that is output to the outside. FIG.

  In FIG. 1, reference numeral 101 denotes a pixel region in which a plurality of pixels are arranged, and reference numeral 102 denotes an amplifier that amplifies a signal output from the pixel region. Here, there are only two amplifiers, but there may be more amplifiers. Reference numeral 1 denotes a signal path through which a signal is output from the amplifier 102. Reference numeral 2 denotes an input / output terminal for exchanging signals with the outside. It can also be called an input / output pad. A plurality of input / output terminals are provided and include at least output terminals 2a to 2d from which signals are output from the amplifier via the signal path 1. In addition, for example, an input terminal for supplying power to the amplifier 102 is included.

  Here, one readout channel includes an amplifier 101a (101b), signal paths 1a, 1b (1c, 1d), and output terminals 2a, 2b (2c, 2d). It can be said that the readout channel is a minimum unit of a signal path for reading out a signal of a single pixel to the outside. Therefore, it can be said that the configuration of FIG. 1 has two readout channels.

  The amplifier is an output unit having a differential output configuration, and is configured to output a first signal and a second signal. FIG. 2 shows an example of an amplifier having a differential input-differential output configuration (fully differential type) that can be used for the amplifier. 201 and 202 are a non-inverting input terminal and an inverting input terminal, respectively. 203 is an output terminal for outputting the first signal, and 204 is an output terminal for outputting the second signal. In this way, a signal obtained by amplifying the differential signal of the input signals from the two input terminals 201 and 202 is output from the first output terminal 203, and this inverted output is output from the second output terminal 204. More specifically, it can be said that the configuration is such that a waveform obtained by inverting the phase of the output waveform of one signal (first signal) is output as the other signal (second signal). A signal from the first output terminal of the amplifier is transmitted to the output terminals 2a and 2d. A signal from the second output terminal of the amplifier is transmitted to 2b and 2c.

  FIG. 3 shows an example of a configuration of a signal output unit that transmits a signal from the pixel region to the amplifier. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted. Here, pixels are arranged in a matrix in the pixel region 101, and are read out to a plurality of horizontal common output lines CH for each column. Here, CH11 and CH12 are read out signals having a correlation with each other. For example, an S + N signal obtained by superimposing a noise signal (N signal) due to variation in the transistors constituting the pixel on a pixel signal (S signal) is read on one side, and an N signal is read on the other side. By processing these with the amplifier 102, a signal with reduced noise can be output. The set of horizontal common output lines (CH11, CH12) and the corresponding amplifier constitute the above-described readout channel. Therefore, it can be said that the configuration of FIG. 3 has two readout channels.

  As shown in FIG. 1, the arrangement order of the plurality of output terminals from which signals are output from the amplifiers 102a and 102b arranged adjacent to each other is such that the first output terminals or the second output terminals are continuously arranged. Yes. However, the arrangement order here is the arrangement order at a plurality of output terminals that output signals from the amplifier. If the arrangement order of the plurality of output terminals is maintained, other terminals can be arranged between them. The other terminal is a terminal 301 different from the output terminal, for example, a dummy terminal, a power supply terminal, a driving pulse terminal for reading a signal from the pixel region, and the like.

  Although the output terminal has been described here, it is desirable that the same arrangement order be adopted in the signal path for transmitting a signal from the amplifier to the output terminal. Here, the signal path can be constituted by a wiring formed of metal, for example.

  A specific arrangement order of the output terminals in FIG. 1 will be described. A first output terminal 2a that outputs a first output of the amplifier 102a; a second output terminal 2b that outputs a second output; a second output terminal 2c that outputs a second output of 102b arranged adjacent to the amplifier 102a; The first output terminals 2d for outputting the first output are arranged in this order. Corresponding signal paths (1a to 1d) have the same arrangement order.

  In this arrangement, even if the signal affects between adjacent output terminals or signal paths, both output waveforms have amplitudes on the negative side or the positive side and the same polarity side with respect to the reference voltage. have. Therefore, it becomes possible to reduce the influence of capacitive coupling. If the output level is the same, crosstalk due to capacitive coupling can be theoretically prevented from occurring.

  The effect of capacitive coupling between adjacent output terminals or signal paths is particularly important in the case of a solid-state imaging device as compared with a general analog IC. A solid-state imaging device often has a color selective transmission layer such as a color filter in order to acquire color information for color reproduction. As an example of the color arrangement of this color filter, a Bayer arrangement is used. In the case of a solid-state imaging device having a plurality of readout channels, readout of pixel signal outputs in each column is often assigned to each channel in order for each column. In the present embodiment, the pixel signals of the first column are read from the first channel, the pixel signals of the first column are read from the second channel, and the pixel signals of the odd column are sequentially read from the first channel. As the channel signal, the even-numbered pixel signals are read out as the second channel signal. When the above-described arrangement of color filters and the method of assigning each column output signal to the readout channel are employed, different colors are often assigned to the outputs of adjacent readout channels. For example, looking at a row in the Bayer array, the first readout channel is red, the adjacent second readout channel is green, the next row is green for the first channel, and the second channel is for the second channel. It becomes blue.

  When crosstalk with other channels occurs, the color data necessary for color reproduction are shifted from each other, and color reproducibility called color mixing (S / N deterioration of color components) may occur. Further, a color called a false color that did not actually exist may appear in the image, and in the imaging apparatus, it is particularly important to reduce the above-described capacitive coupling. If the output terminal interval and the signal path interval are separated by a considerable amount, the influence of capacitive coupling that can be ignored in some cases can be reduced. However, the solid-state imaging device has a characteristic that a large part of the semiconductor substrate (chip) is occupied by the pixel region for imaging, so that the readout circuit such as the amplifier described above is arranged only in a limited area around the chip. I can't. For this reason, it is practically impossible to separate the output wiring intervals so that the influence of capacitive coupling can be ignored.

  Further, when the arrangement order of the amplifiers and the corresponding output terminals is determined, the layout (order) of the wirings constituting the signal path is determined in consideration of the symmetry of the two signal paths in the same readout channel. If the symmetry is greatly different, the SN characteristic may be deteriorated due to the difference in symmetry. In order to make the symmetry in the same readout channel and other readout channels as close as possible, it is not preferable to frequently go back and forth between a plurality of wiring layers in the respective signal paths or cross the wirings in the layout. Therefore, the layout of wiring and output terminals is limited, and the arrangement order of a plurality of amplifiers and their output terminals affects the layout of the signal path. Therefore, a good signal can be output by this embodiment.

  Here, the configuration of the amplifier described in FIG. 2 and the configuration of readout from the pixel region to the amplifier described in FIG. 3 can be applied to the embodiments described later.

  As described above, according to the present embodiment, signals can be read in parallel by a plurality of read channels, and a high-quality signal can be output in a configuration using an amplifier having a differential output configuration.

(Example 2)
The solid-state imaging device of the present embodiment will be described. The difference from the first embodiment is that the output output from the amplifier is different. Specifically, a reference signal and an image signal based on the reference signal are output.

  In the configuration of FIG. 1, the output terminals 2a and 2d may be output terminals for outputting an image signal, and 2b and 2c may be output terminals for outputting a reference signal.

  The amplifier may be configured such that one of the differential outputs outputs a reference voltage of the output unit, and the other outputs a signal (amplitude) with respect to the reference voltage.

  The order of arrangement of the output terminals is the same as in the first embodiment, and the output terminals from which the signals are output from the amplifiers 102a and 102b arranged adjacent to each other are continuous between the first output terminals or between the second output terminals. Are arranged. Specifically, the first output terminal 2a that outputs the first output of the amplifier 102a, the second output terminal 2b that outputs the second output, and the second output of 102b that is arranged adjacent to the amplifier 102a. The two output terminals 2c and the first output terminal 2d for outputting the first output are arranged in this order. Corresponding signal paths (1a to 1d) have the same arrangement order. The output terminals 2b and 2c are used for outputting a reference signal, and 2a and 2d can be used for outputting an image signal based on the reference signal.

  Also in this embodiment, since the adjacent output terminal or signal path is the reference level of the adjacent readout channel, the amplitude change is smaller than that of the image signal. Therefore, crosstalk caused by capacitive coupling between the signal of the first readout channel and the signal of the second readout channel can be reduced.

(Example 3)
The solid-state imaging device of the present embodiment will be described. The difference from the first embodiment is that it has a shield structure in which a predetermined voltage is supplied between signal paths corresponding to amplifiers adjacent to each other. As the predetermined voltage, for example, a ground potential can be considered.

  FIG. 5 is a diagram for explaining the solid-state imaging device of the present embodiment. In the configuration of the solid-state imaging device that amplifies the signal output from the pixel region with a plurality of amplifiers and then outputs the amplified signal to the outside, particularly from the amplifier. It is a figure for demonstrating in detail to the output terminal output outside.

  When the output path and the shield structure are formed by wiring, it is preferable to form the output path and the shield structure by the same wiring layer. As an example of a material for forming the wiring layer, AlCu can be used.

  In addition, a shield structure can be configured by providing another upper layer or lower layer metal wiring in addition to the same layer metal wiring. As a result, between the signal paths adjacent to each other, the electric lines of force extend more than the shield lines, the electric lines of force generated between the signal paths are reduced, and the mutual capacitive coupling is weakened. Therefore, according to the present embodiment, it is possible to further reduce the electrical color mixture of adjacent readout channels due to crosstalk.

Example 4
The solid-state imaging device of the present embodiment will be described. The difference of the present embodiment from the first to third embodiments is that a plurality of output terminals are arranged on two different sides of the semiconductor chip constituting the solid-state imaging device.

  FIG. 6 is a diagram for explaining the solid-state imaging device according to the present embodiment. In the configuration of the solid-state imaging device that amplifies signals output from the pixel region with a plurality of amplifiers and outputs the signals to the outside, particularly from the amplifiers. It is a figure for demonstrating in detail to the output terminal output outside. Components similar to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, output terminals are distributed and arranged on a plurality of sides of a semiconductor chip on which a solid-state imaging device is configured. The amplifiers 102a and 102b are arranged adjacent to each other. The first output terminal 2a that outputs the first output of the amplifier 102a, the second output terminal 2b that outputs the second output, the second output terminal 2c that outputs the second output of 102b, and the first output are output on one side. The first output terminals 2d are arranged in this order. Corresponding signal paths (1a to 1d) have the same arrangement order. Also, on the other side, a first output terminal 2e that outputs the first output of the amplifier 102c, a second output terminal 2f that outputs the second output, and a second output of 102d that is arranged adjacent to the amplifier 102c. The two output terminals 2g and the first output terminal 2h for outputting the first output are arranged in this order. Corresponding signal paths (1a to 1d) have the same arrangement order.

  In a color imaging device in which pixels are arranged two-dimensionally, it is common to provide a color filter in order to acquire color information for color reproduction. The color filter of this color selective transmission layer generally uses, for example, red, green, blue, or a combination of cyan, magenta, yellow, etc. Here, an example of a Bayer array using red, green, and blue is used here. I will give you a description.

  Further, in the case of a solid-state imaging device in which pixels are arranged in a matrix and have a plurality of readout channels, readout of pixel signal outputs in each column is often assigned to each readout channel in order for each column. That is, the pixel signal in the first column is read as the first channel signal, and the pixel signal in the second column is read as the second channel signal. The pixel signal in the third column is read as a third channel signal, and the pixel signal in the fourth column is read as a fourth channel signal. That is, the pixel signals in the (4n + 1) th column are sequentially read as the first channel signal and the pixel signals in the (4n + 2) th column are sequentially read out as the second channel signal. The pixel signal in the (4n + 3) column is read as the third channel signal, and the pixel signal in the (4n + 4) column is read as the fourth channel signal. Here, n is 0 and a positive integer.

  In this arrangement, if attention is paid to a certain row in the pixel region, for example, the first readout channel is red, the second readout channel is green, the third readout channel is red, and the fourth readout channel is Is assigned as green. The next row is called green output for the first readout channel, blue output for the second readout channel, green output for the third readout channel, and blue output for the fourth readout channel. It becomes assignment. In other words, the color output assigned to the terminals and wirings adjacent between the read channels is always the same color regardless of which row is read on either side. In other words, such a configuration includes color filters arranged in a Bayer array, and signals from pixels of the same color arranged in each row are a plurality of the plurality of pixels arranged in one of the two regions. It can be said that it is transmitted to the output terminal.

  Therefore, if terminals are arranged as in the present embodiment, it is possible to suppress electrical color mixing between readout channels. Furthermore, the influence of the slight remaining electrical color mixture is also within the same color range, and it is possible to read out a high-quality signal with little color mixture from the viewpoint of variation in color ratio (color reproduction).

  In this embodiment, an image pickup apparatus using a Bayer array color filter is taken as an example. However, even if not an image pickup apparatus having such a color filter arrangement, either one of the pixel regions is sandwiched in one line of output. The present invention can be applied to an imaging apparatus in which pixel data of the same color is output to an output terminal on one side arranged in a region.

  In this embodiment, an example is described in which output terminals are arranged in two regions facing each other across a pixel region, and a signal is read out. However, the present invention is not limited to this. For example, the effects described in this embodiment can be obtained even if the output terminals are arranged in two regions facing each other as shown in FIG. In FIG. 6, the amplifier and the signal path are omitted.

  The newly added 2i to 2l will be described. 2i and 2l correspond to a first output terminal for outputting a first output of the amplifier. 2j and 2k correspond to the second output terminal for outputting the second output of the amplifier. 2i and 2j correspond to outputs from the same amplifier, and 2k and 2l correspond to outputs from the same amplifier.

  Accordingly, the first signals or the second signals of the adjacent amplifiers are similarly arranged on adjacent sides.

(Application to imaging system)
FIG. 8 illustrates an example of a circuit block when the solid-state imaging device described in the first to fourth embodiments is applied to a camera. A shutter 1001 is provided in front of the taking lens 1002 and controls exposure. The amount of light is controlled by the diaphragm 1003 as necessary, and an image is formed on the solid-state imaging device 1004. A signal output from the solid-state imaging device 1004 is processed by a signal processing circuit 1005 and converted from an analog signal to a digital signal by an A / D converter 1006. The output digital signal is further processed by a signal processing unit 1007. The processed digital signal is stored in the memory 1010 or sent to an external device through the external I / F 1013. The solid-state imaging device 1004, the imaging signal processing circuit 1005, the A / D converter 1006, and the signal processing unit 1007 are controlled by a timing generation unit 1008, and the entire system is controlled by an overall control unit / arithmetic unit 1009. In order to record an image on the recording medium 1012, the output digital signal is recorded through a recording medium control I / F unit 1011 controlled by the overall control unit / arithmetic unit.

It is a top view for demonstrating the solid-state imaging device of 1st Example. It is a figure for demonstrating an example of an amplifier. It is a figure for demonstrating the structure which outputs the signal from a pixel area to an amplifier. It is a top view for demonstrating the modification of 1st Example. It is a top view for demonstrating the solid-state imaging device of 3rd Example. It is a top view for demonstrating the solid-state imaging device of 4th Example. It is a top view for demonstrating the solid-state imaging device of 4th Example. It is a block diagram for demonstrating an imaging system.

Explanation of symbols

101 Pixel region 102 Amplifier 1 Signal path 2 Output terminal

Claims (6)

A pixel region in which a plurality of pixels are arranged;
A plurality of amplifiers for amplifying signals from the pixel region;
A plurality of output terminals for outputting the output signal of the amplifier to the outside;
A solid-state imaging device having a plurality of signal paths for transmitting signals from the amplifier to a plurality of output terminals,
The amplifier has a differential output configuration for outputting a first signal and a second signal;
The plurality of output terminals include a plurality of first output terminals to which the first signal is transmitted and a plurality of second output terminals to which the second signal is transmitted.
2. A solid-state imaging device according to claim 1, wherein the plurality of output terminals from which signals are output from adjacent amplifiers are arranged such that the first output terminals or the second output terminals are continuously arranged.   The solid-state imaging device according to claim 1, wherein the second signal is a signal obtained by inverting the phase of the first signal.   3. The shield according to claim 1, wherein a shield to which a predetermined voltage is supplied is disposed between a plurality of signal paths for transmitting signals from amplifiers adjacent to each other to a plurality of output terminals. A solid-state imaging device according to claim 1.   The solid-state imaging device according to claim 1, wherein the plurality of output terminals are divided into two regions facing each other across the pixel region.   The pixels are arranged in a matrix and have a Bayer array color filter, and signals from pixels of the same color arranged in each row are the plurality of pixels arranged in one of the two regions. The solid-state imaging device according to claim 4, wherein the solid-state imaging device is transmitted to the output terminal.   The solid-state imaging device according to claim 1, an optical system that forms an image of light on the solid-state imaging device, and a signal processing circuit that processes an output signal from the solid-state imaging device. An imaging system characterized by that.

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