JPWO2017069134A1 - Solid-state image sensor - Google Patents

Abstract

The solid-state imaging device (100) includes a plurality of photodiode impurity layers (2) for photoelectric conversion, a visible light filter (8) and a near infrared light filter (9) associated with the photodiode impurity layer (2). The visible light image and the near-infrared light image are simultaneously output to the outside, and the visible light filter (8) does not transmit light having a specific wavelength in visible light.

Description

  The present invention relates to a solid-state imaging device.

  As a conventional solid-state imaging device capable of performing both visible light imaging and near-infrared light imaging, an element as disclosed in Patent Document 1 has been proposed. 22 and 23 are diagrams for explaining a configuration example of a conventional solid-state imaging device. A conventional solid-state imaging device is, for example, a conventional primary color filter array [for two G (green) pixel filters: a visible light filter, as in the solid-state imaging device 1000 shown in FIGS. 1008G, B (blue) pixel filter: 1 pixel: Visible light filter 1008B, R (red) pixel filter: 1 pixel: visible light filter 1008R arranged in a checkered pattern] Was replaced with a near-infrared filter (IR) 1009. Further, as in the solid-state imaging device 2000 shown in FIGS. 23A and 23B, all vertical columns of the conventional complementary color filter array (8 pixels) visible light filters 2008M, 2008C, 2008Y, and 2008G are near red. Some of them became external light filters (IR) 2009.

  An example of an imaging system that acquires a visible light image and a near-infrared light image in a solid-state imaging device in which a near-infrared light filter is added to these primary color / complementary color filters will be briefly described with reference to FIGS. . 24 to 26 are diagrams for explaining a configuration example of a conventional imaging system. When a visible light image is taken with a conventional solid-state imaging device, as shown in FIG. 24A, it may be more appropriate to express a visible light source 1200 (which includes a near-infrared wavelength, so that it is a normal light source). Irradiating light onto the object to be photographed and outputting the image from the element obtained by photographing the image with the conventional solid-state image sensor 1000 or 2000, the output signals of R, G, and B include wavelengths in the near infrared region. (The conventional photodiode and the R • G • B filter also have sensitivity in the near-infrared wavelength region). For this reason, conventionally, an image is constructed by performing a process of subtracting information of IR pixels, which are pixels provided with a filter that transmits only light in the near-infrared wavelength region, from information of R, G, and B outputs.

  On the other hand, when acquiring a near-infrared light image, as shown in FIG. 24B, the near-infrared light source 1100 irradiates the object to be photographed with near-infrared light, and the solid-state imaging device 1000 or 2000 Photographing is performed with pixels, and an image is constructed (as described above, the R, G, and B pixels also have sensitivity in the near-infrared wavelength region). The complementary color filter shown in FIG. 23A is also the same image construction method except that the number of pixels is different from that of the filter array, and the description thereof is omitted here. Since the image is acquired by the above-described method, when a visible light image is acquired, an image is constructed using information of 3/4 pixels for the primary color and 2/3 pixels for the complementary color, and near-infrared light is acquired. It can be seen that the image is acquired by using all pixel information.

  As a supplementary explanation, in the case of a conventional solid-state imaging device that uses only visible light, an IR (infrared) cut filter is provided between the imaging device chip and the imaging optical system, so that the above-mentioned near red There is no need to worry about photoelectric conversion with light in the outer region. Further, an imaging system that can acquire a near-infrared light image using a normal solid-state imaging device without using the solid-state imaging device 1000 or 2000 as shown in FIG. 22 or FIG. 23 has been proposed.

  In addition, as shown in FIG. 25, an imaging system provided with two imaging elements, a solid-state imaging element 4000 for visible light and a solid-state imaging element 3000 for near-infrared light. An element provided with a cut filter 4009 and an apparatus that captures images with an element provided with a bandpass filter 3008 (transmitting only light of a specific IR wavelength) in an optical system have been proposed for obtaining near-infrared light images. In the example shown in FIG. 26, the number of the solid-state imaging device 5000 is one, but a filter switching mechanism is provided in the photographing optical system so that the IR cut filter 4009 and the band-pass filter 3008 can be switched for photographing. Proposed.

  In addition, as in the technique disclosed in Patent Document 2, an optical system that irradiates light from a light source device to a subject to be photographed is provided with a mechanism for switching an IR cut filter or a band pass filter. .

  For example, when the human body is imaged with near-infrared light using such an imaging system, as described in Patent Document 1, hemoglobin in blood vessels (blood) and others Since the absorption and reflection characteristics of the near-infrared light of the human tissue are different, it is possible to obtain blood vessel pattern information of the human body photographed. In addition, for a visible light photographed image, for example, when a palm is photographed, a palm print (palm) pattern of each person can be obtained. By using this together with vein (artery) authentication, individual identification accuracy can be improved. Can be increased. In addition, near-infrared light photography cannot completely photograph only blood vessels, and information such as surrounding tissues is included to some extent. In order to alleviate these problems, there is a case where an image photographed with near-infrared light and an image photographed with visible light are subjected to image processing so as to make only blood vessel information stand out.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2005-191748 (Released on July 14, 2005)” Japanese Patent Publication “JP-A-4-357926 (published on Dec. 10, 1992)”

  Here, when photographing an object to be photographed with the imaging system shown in FIGS. 25 and 26 or the imaging system disclosed in Patent Document 2, it is necessary to prepare two systems of solid-state imaging devices and optical systems, or filter switching For example, a mechanical mechanism for use and a retract space for a filter that is not used are required. In this case, it is impossible to downsize the mobile phone camera system, and it can be said that it is very disadvantageous in terms of cost.

  As described above, in the imaging system using the solid-state image sensor 1000 or 2000 shown in FIG. 22 or FIG. 23 and the solid-state image sensor 1000 or 2000 of the conventional example shown in FIG. Thus, a system capable of capturing both a visible light image and a near-infrared light image has been proposed. However, in the imaging system using the solid-state imaging device 1000 or 2000 of the conventional example shown in FIG. 24, when acquiring a visible light image, an image is constructed by subtracting IR pixel information from all pixel information, When acquiring a near-infrared light image, since it is necessary to construct | assemble an image using the information of all the pixels, (a)-(e) of FIG. 27 and (a)-(e) of FIG. And a visible image and a near-infrared light image are simultaneously acquired as shown in the comparison diagram shown in FIG. 29 and the comparison diagrams shown in FIGS. 29A to 29E and FIG. 30A to 30E. I couldn't. FIGS. 27 to 30 are diagrams showing operations for outputting visible light or near-infrared light data of a conventional imaging system, and FIGS. 27A to 27E respectively show all 1.3 million pixels. FIGS. 28A to 28E show the flow of operations when imaging is performed by irradiating visible light with a readout CCD image sensor (effective pixel number: horizontal 1280 pixels × vertical 960 pixels). The flow of operation when performing imaging by irradiating near infrared light with the CCD imaging device is shown. On the other hand, FIGS. 29 (a) to 29 (e) show the flow of operations when an image is taken with an IR cut filter in the CCD image sensor, and FIGS. 30 (a) to 30 (e). These show the flow of operation | movement at the time of image-capturing, putting a visible light cut filter (visible light cut, infrared transmission) in the said CCD image pick-up element, respectively.

  In the authentication image of veins (arteries), it is more accurate to perform the process of subtracting the information of the visible light image from the near-infrared light image to make only the blood vessel information of the imaged object stand out. Will be possible. However, the visible light image obtained by the conventional solid-state imaging device 1000 or 2000 is formed from information of 3/4 pixels (2/3 pixels in the case of complementary colors), and the visible light image itself is Since it was created by processing with a near-infrared light image, there was a problem that the image processing for vein (artery) authentication would be very complicated.

  The present invention has been made in view of the above problems, and is a solid-state imaging device that simplifies image processing and enables simultaneous acquisition of both a visible light image and a near-infrared light image. The purpose is to provide.

  In order to solve the above-described problem, a solid-state imaging device according to one embodiment of the present invention receives near-infrared light and visible light that are simultaneously irradiated onto an imaging target, and photoelectrically converts the received light. A plurality of photoelectric conversion units that generate electric charge, a plurality of visible light imaging color filters associated with each of a part of the plurality of photoelectric conversion units, and the remaining of the plurality of photoelectric conversion units A plurality of correlated near-infrared color photographing color filters, wherein the visible color photographing color filter and the near-infrared color photographing color filter are two-dimensionally dispersed, Information on the visible light image and near-infrared light image based on the charge generated by the photoelectric conversion unit is output to the outside at the same time, and the visible light photographing color filter does not transmit light of a specific wavelength in visible light. Features.

  According to one embodiment of the present invention, image processing can be simplified, and both a visible light image and a near-infrared light image can be simultaneously acquired. In addition, in an environment of strong light such as sunlight. In this case, it is possible to obtain a good and accurate image.

It is a figure for demonstrating the structure of the solid-state image sensor which concerns on Embodiment 1 of this invention. It is a top view which shows schematic structure of the imaging system containing the said solid-state image sensor. It is a schematic diagram which shows schematic structure of the imaging system containing the said solid-state image sensor. (A)-(e) is a figure which shows the operation | movement for outputting visible light data and infrared-light data with the imaging system containing the said solid-state image sensor, respectively. It is a figure for demonstrating an example of the transmission wavelength setting of each filter in the said solid-state image sensor. It is a structural example of the solid-state image sensor for demonstrating the overflow voltage and electronic shutter voltage of a solid-state image sensor. It is a figure for demonstrating the overflow voltage and electronic shutter voltage of a solid-state image sensor, and is a potential diagram of the B-B 'cross section of FIG. It is a figure explaining the electronic shutter operation | movement of a solid-state image sensor. It is a figure for demonstrating the complementary method of visible light pixel information, and the complementary method of infrared light pixel information regarding the said solid-state image sensor. It is a figure which shows the modification of the arrangement | positioning method of each filter of the solid-state image sensor which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the structure of the solid-state image sensor which concerns on Embodiment 2 of this invention. It is a figure for demonstrating the structure of the solid-state image sensor which concerns on Embodiment 3 of this invention. FIG. 3 is a schematic diagram for obtaining a desired transmitted light wavelength using a two-layer filter in the solid-state imaging device according to the first embodiment of the present invention. It is sectional drawing for demonstrating the example of formation of the filter of the said solid-state image sensor. It is sectional drawing for demonstrating the other example of a filter of the said solid-state image sensor. (A) is a figure which shows the film thickness of each layer which comprises an inorganic filter, (b) is a graph which shows the simulation result of the transmittance | permeability of the multilayer film of an inorganic filter. It is a figure which shows the electron micrograph of the inorganic multilayer filter actually produced. It is sectional drawing for demonstrating the further another example of formation of the filter of the said solid-state image sensor. It is sectional drawing for demonstrating the further another example of formation of the filter of the said solid-state image sensor. It is sectional drawing for demonstrating the further another example of formation of the filter of the said solid-state image sensor. It is a figure for demonstrating the structure of the CMOS type solid-state image sensor which concerns on Embodiment 4 of this invention. It is a figure for demonstrating the structural example of the conventional solid-state image sensor. It is a figure for demonstrating the other structural example of the conventional solid-state image sensor. It is a schematic diagram which shows operation | movement of the structural example of the conventional imaging system. It is a schematic diagram which shows operation | movement of the other structural example of the conventional imaging system. It is a schematic diagram which shows operation | movement of the further another structural example of the conventional imaging system. (A)-(e) is a comparison figure which respectively shows the operation | movement for outputting visible light data with an imaging system. (A)-(e) is a comparison figure which respectively shows the operation | movement for outputting near-infrared-light data with an imaging system. (A)-(e) is a comparison figure which respectively shows the operation | movement for outputting visible light data with an imaging system. (A)-(e) is a comparison figure which respectively shows the operation | movement for outputting near-infrared-light data with an imaging system. It is a comparative example with the structure of the solid-state image sensor which concerns on Embodiment 1 of this invention, and the solid-state image sensor which the applicant proposed. It is a figure for demonstrating the example of the transmission wavelength setting of each filter in the said solid-state image sensor.

  The embodiment of the present invention will be described with reference to FIGS. 1 to 8 and the drawings. Hereinafter, for convenience of explanation, components having the same functions as those described in the specific embodiment may be denoted by the same reference numerals and description thereof may be omitted. In the embodiment of the present invention, as an example of the wavelength of each color, visible light is longer than 380 nm and has a wavelength range of 750 nm or less, blue is longer than 380 nm and has a wavelength range of 490 nm or less, and green is from 490 nm. Description will be made using a long wavelength range of 570 nm or less, red having a wavelength range longer than 570 nm and not more than 750 nm, and infrared light having a wavelength range longer than 750 nm.

Embodiment 1
FIG. 1 is a diagram for explaining the configuration of a solid-state imaging device 100 according to Embodiment 1 of the present invention. FIG. 1A is a view showing a state of a filter array when the solid-state imaging device 100 is viewed from the light incident side, and FIG. 1B is a view taken along line A- in FIG. It is sectional drawing of an A 'cross section. FIG. 2 is a plan view showing a schematic configuration of an imaging system 500 including the solid-state imaging device 100. FIG. 3 is a schematic diagram illustrating a schematic configuration of an imaging system 500 including the solid-state imaging device 100. 4A to 4E are diagrams illustrating operations for outputting visible light data and infrared light data in the imaging system 500, respectively. FIG. 5 is a diagram for explaining an example of transmission wavelength setting of each filter in the solid-state imaging device 100, and FIG. 5A is a graph showing optical characteristics of the near-infrared light filter 9. FIG. 5B is a graph showing the optical characteristics of the visible light filter 8, FIG. 5C is a graph showing the optical characteristics of the near-infrared light pixel, and FIG. These are graphs showing optical characteristics of visible light pixels.

  As shown in FIG. 2, the imaging system 500 of this embodiment includes a solid-state imaging device 100, a near-infrared light source 101, and a visible light source 102 on a substrate 501. The visible light source 102 is disposed so as to sandwich the solid-state imaging device 100 in the X direction. The near-infrared light source 101 is disposed so as to sandwich each visible light source 102 in the Y direction.

  In addition, as illustrated in FIG. 3, the imaging system 500 according to the present embodiment applies near-infrared light from the near-infrared light source 101 and visible light from the visible light source 102 to an imaging target (for example, a hand). By simultaneously irradiating, it is possible to simultaneously output a visible light image and a near-infrared light image. In other words, the solid-state imaging device 100 reads visible light information and near-infrared light information simultaneously (in one frame). That is, charge accumulation / reading / transfer and all processes are simultaneously performed on the visible light pixel and the near-infrared pixel. As the near-infrared light source 101 and the visible light source 102, for example, an LED (light emitting diode) or a laser may be used. Moreover, when using a laser, it is preferable that it is a laser safe even if it enters into eyes, for example, an eye safe laser.

  The solid-state imaging device 100 is not an interlaced readout, but an imaging device [CMOS (Complementary metal-oxide semiconductor) type imaging device or CCD (Charge-coupled) that can read out all pixels as shown in FIGS. device) has a function as an all-pixel readout type CCD].

  4A to 4E respectively irradiate both visible light and near-infrared light with a 1.3 million pixel full-read CCD image sensor (effective pixel number: horizontal 1280 pixels × vertical 960 pixels). The operation when shooting is shown. 27A to 27E and FIG. 28A to FIG. 28E, and FIG. 29A to FIG. 29E and FIG. 30A to FIG. As will be described later, the image processing for obtaining information on all the pixels of the visible light image or the near-infrared light image can be performed more easily and faster than the comparison diagram shown in FIG. Further, the solid-state imaging device 100 is mainly used for biometric authentication, and is capable of constructing an imaging system for biometric authentication with high speed and high accuracy.

  Next, as shown in FIGS. 1A and 1B, the solid-state imaging device 100 includes a silicon substrate 1 (semiconductor substrate), a photodiode impurity layer 2 (photoelectric conversion unit), a charge transfer unit impurity layer 3, Gate electrode 4, light shielding film 5, silicon insulating film 6, planarizing film 7, visible light filter 8 (color filter for visible light photography), near infrared light filter 9 (color filter for near infrared light photography) ) And a condensing microlens 10. Note that the configurations of the gate electrode 4, the light shielding film 5, the silicon insulating film 6, the planarizing film 7, and the condensing microlens 10 are not related to the essence of the present invention, and thus the description thereof is omitted here. .

(Silicon substrate 1)
The silicon substrate 1 is a semiconductor substrate having one conductivity based on silicon. Here, one conductivity is either p-type conductivity or n-type conductivity. For example, as shown in FIG. 6, a P-type impurity layer (Pwell) is formed on the silicon substrate 1.

(Photodiode impurity layer 2, charge transfer portion impurity layer 3)
Within the silicon substrate 1, there are a plurality of regions that generate near-infrared light and visible light that are simultaneously irradiated onto a photographing target (imaging target) and generate charges by photoelectrically converting the received light. Photodiode impurity layer 2 and a plurality of charge transfer portion impurity layers 3 which are regions to which the generated charges are transferred are formed.

  The charges generated in the photodiode impurity layer 2 associated with the visible light filter 8 and the near-infrared light filter 9 to be described later are respectively transmitted through the charge transfer portion impurity layer 3 to a visible light image and a near-red light. Simultaneously output to the outside as information of one pixel of the external light image. In other words, the information of the visible light image and the near-infrared light image based on the charge generated in the photodiode impurity layer 2 is simultaneously output to the outside.

(Visible light filter 8, near infrared light filter 9)
In the solid-state imaging device 100 of the present embodiment, each of the plurality of visible light filters 8 and the same number of near-infrared light filters 9 are associated with each of the plurality of photodiode impurity layers 2 in a two-dimensional manner. (The total number of pixels is about 1.3 million pixels). In other words, the visible light filter 8 is associated with each of a part of the plurality of photodiode impurity layers 2, and the near-infrared light filter 9 is associated with each of the remaining photodiode impurity layers 2. It has been. The visible light filters 8 and the near-infrared light filters 9 are two-dimensionally distributed in the same number. For this reason, when acquiring information on all the pixels of the visible light image, information on pixels associated with a specific near-infrared light filter 9 (hereinafter referred to as “near-infrared light pixels”) It is possible to complement by using information of pixels (hereinafter referred to as “visible light pixels”) associated with the visible light filter 8 arranged in a distributed manner. In addition, when acquiring information on all pixels of a near-infrared light image, information on a specific visible light pixel may be supplemented using information on infrared light pixels arranged in the vicinity thereof. It becomes possible. As described above, the image processing can be simplified, and both the visible light image and the near infrared light image can be simultaneously acquired.

  More specifically, as shown in FIG. 1A, each of the visible light filter 8 and the near-infrared light filter 9 is disposed between the condensing microlens 10 on the photodiode impurity layer 2. Are arranged alternately (for example, in a checkered pattern). Thereby, when acquiring information on all pixels of the visible light image, information on a specific near-infrared light pixel can be supplemented using information on visible light pixels arranged on the top, bottom, left, and right of the pixel. It becomes possible. In addition, when acquiring information on all pixels of a near-infrared light image, information on a specific visible light pixel may be supplemented using information on infrared light pixels arranged on the top, bottom, left, and right of the pixel. It becomes possible. Therefore, compared to a configuration in which the color filter for visible light photography and the color filter for near infrared light photography are not arranged alternately, the information of all pixels of the visible light image or the near infrared light image is obtained. The image processing for obtaining can be simplified.

  The visible light filter 8 does not transmit light having a specific wavelength in visible light, as shown in FIG. Specifically, the visible light filter 8 does not transmit light having a longer wavelength than blue. More specifically, the visible light filter 8 cuts light having a wavelength longer than that of visible light blue (490 nm). The visible light filter 8 may transmit light having a wavelength longer than that of visible light blue (490 nm), or transmit only visible light blue (longer than 380 nm and 490 nm or less). Also good. As shown in FIG. 5A, the near-infrared light filter 9 transmits near-infrared light and does not transmit light having a wavelength shorter than the visible light wavelength. Specifically, the near-infrared light filter 9 cuts light having a wavelength shorter than 750 nm, for example. Thereby, as shown in FIG. 5C and FIG. 5D, the difference between the sensitivity of the near-infrared light pixel and the sensitivity of the visible light pixel is reduced. Here, the sensitivities in FIGS. 5C and 5D indicate the degree to which the photodiode impurity layer 2 has reacted to light. That is, the amount of light incident on the photodiode impurity layer 2 through the visible light filter 8 or the near infrared light filter 9 is shown. The effect of using the visible light filter 8 will be described later in detail.

  The near-infrared light filter 9 is not limited to the above, and may be a film that transmits only light of a specific wavelength.

(Effect of using filter 8 for visible light)
The solid-state imaging device 1500 described in FIGS. 31 and 32 is a means for the applicant to solve the problems with respect to Patent Document 1 and Patent Document 2 by simplifying image processing, and visible light images and near-infrared light. This is proposed as a solid-state imaging device capable of simultaneously acquiring both images. FIG. 31 is a comparative example of the solid-state imaging device 100 of the present invention and the solid-state imaging device proposed by the applicant, and is a diagram for explaining the configuration of the solid-state imaging device 1500. FIG. 31A is a diagram showing a state of the filter array when the solid-state imaging device 1500 is viewed from the light incident side, and FIG. 31B is a diagram of F− shown in FIG. It is sectional drawing of a F 'cross section. FIG. 32 is a diagram for explaining an example of setting the transmission wavelength of each filter in the solid-state imaging device 1500. FIG. 32A is a graph showing optical characteristics of the near-infrared light filter. (B) in FIG. 32 is a graph showing the optical characteristics of the filter for visible light, (c) in FIG. 32 is a graph showing the optical characteristics of the near-infrared light pixel, and (d) in FIG. It is a graph which shows the optical characteristic of a visible light pixel.

  The difference between the solid-state imaging device 1500 and the solid-state imaging device 100 according to the present embodiment is that a visible light filter 8 is provided instead of the visible light filter (visible light transmission / near infrared cut filter) 58. It is a point and other composition is the same. That is, as shown in FIGS. 31 and 32, the silicon substrate 51, the photodiode impurity layer 52, the charge transfer portion impurity layer 53, the gate electrode 54, the light shielding film 55, the silicon insulating film 56, and the planarization film of the solid-state imaging device 1500. 57, a near-infrared light filter (near-infrared light transmission / visible light cut filter) 59, and a condensing microlens 60 include a silicon substrate 1, a photodiode impurity layer 2, and a charge transfer portion impurity of the solid-state imaging device 100. The configuration is the same as that of the layer 3, the gate electrode 4, the light shielding film 5, the silicon insulating film 6, the planarization film 7, the near infrared light filter 9, and the condensing microlens 10.

  As shown in FIGS. 32B and 32D, the visible light filter 58 of the solid-state imaging device 1500 is a filter that does not transmit light having a wavelength of near infrared light or longer. The near-infrared light filter 59 is a filter that does not transmit light having a wavelength shorter than or equal to the visible light wavelength, as shown in FIGS.

  Similarly to the solid-state image sensor 100, the solid-state image sensor 1500 is irradiated with both wavelengths of light simultaneously from the near-infrared light source 101 and the visible light source 102 as shown in FIG. An external light image can be acquired simultaneously. However, the solid-state imaging device 1500 has a problem that, for example, when photographing under strong sunlight, a good image may not be obtained. The above problem will be described in detail below.

  First, the overflow drain and the electronic shutter operation of the all-pixel reading CCD type solid-state imaging device will be described with reference to FIGS. FIG. 6 is a configuration example of a solid-state imaging device 1300 for explaining the overflow voltage and the electronic shutter voltage.

  6 includes an N-type silicon substrate 31, a P-type impurity layer 32 (PWell), a photodiode N-type impurity layer 33, a charge transfer portion impurity layer 34, a gate electrode 35, a light-shielding film 36, and silicon insulation. A film 37, a planarizing film 38, a visible light filter 39, a near-infrared light filter 40, and a condensing microlens 41 are provided. The charge transfer portion impurity layer 34, the gate electrode 35, the light-shielding film 36, the silicon insulating film 37, the planarizing film 38, the near-infrared light filter 40, and the condensing microlens 41 are the solid-state imaging device 100 shown in FIG. The charge transfer portion impurity layer 3, the gate electrode 4, the light shielding film 5, the silicon insulating film 6, the planarizing film 7, the near-infrared light filter 9, and the condensing microlens 10 have the same configuration. The solid-state imaging device 1300 is formed by forming an N-type photodiode impurity layer and a P-type photodiode lower well layer on an N-type substrate, and has a transistor structure toward the deep part of the substrate. The N-type silicon substrate 31 and the P-type impurity layer 32 correspond to the silicon substrate 1 of the solid-state image sensor 100, and the photodiode N-type impurity layer 33 corresponds to the photodiode impurity layer 2 of the solid-state image sensor 100.

  In the CCD type solid-state imaging device, there is a case where charges generated in the photodiode N-type impurity layer 33 when strong light enters the solid-state imaging device 1300 cannot be accumulated in the photodiode N-type impurity layer 33 in some cases. . In this case, an overflow drain is generally provided in order to control a phenomenon in which the overflowed charge flows into a peripheral transfer unit or the like, and recently, a vertical overflow drain (OFD) is often used. OFD will be described below with reference to FIG.

  FIG. 7 is a diagram for explaining the overflow voltage and the electronic shutter voltage of the solid-state imaging device 1300, and is a potential diagram of the B-B ′ cross section of FIG. In other words, FIG. 7 shows a potential structure from the photodiode N-type impurity layer 33 to the deep part of the N-type silicon substrate 31 in the solid-state imaging device 1300, and FIG. 7A shows a charge accumulation state. FIG. 7B shows a charge sweeping state. 7A and 7B, the horizontal axis indicates the substrate depth shown in FIG. 6, and the vertical axis indicates the potential.

  In the normal imaging state, the Pwell 32 applies a DC voltage called an OFD voltage (usually about several volts) to the N-type silicon substrate 31 with the Pwell 32 as the GND potential, as shown in FIG.

  In this state, the potential of the PWell 32 becomes a barrier for preventing charges accumulated in the photodiode N-type impurity layer 33 from being swept out to the N-type silicon substrate 31 with a potential equal to or higher than a predetermined value. Therefore, charges up to the height of the barrier can be accumulated in the photodiode N-type impurity layer 33. In other words, the solid-state imaging device 1300 can determine the amount of charge accumulated in the photodiode N-type impurity layer 33 by adjusting the height of the barrier by the OFD voltage.

  However, excessive charge may be generated in the photodiode N-type impurity layer 33 due to strong light incident on the solid-state imaging device 1300 until the barrier due to the potential of the Pwell 32 is exceeded. In that case, the charges that have overflowed without being accumulated in the photodiode N-type impurity layer 33 are swept out to the N-type silicon substrate 31 side. The charges swept out to the N-type silicon substrate 31 side due to overflow do not particularly affect the image. However, in the case of intense light that is too strong, the overflow drain may not be processed and may flow into the charge transfer portion of the adjacent pixel. This is called a blooming failure, and the image has an image in which a white band flows from surrounding pixels.

  In the charge sweeping state, as shown in FIG. 7B, the Pwell 32 applies a pulse voltage called an electronic shutter voltage (about several volts) from the OFD voltage to the N-type silicon substrate 31 with the Pwell 32 as the GND potential. When the voltage applied to the N-type silicon substrate 31 is increased by the electronic shutter voltage, the barrier of the PWell 32 is pulled to the potential of the N-type silicon substrate 31 and all the barriers disappear. As a result, all charges accumulated in the photodiode N-type impurity layer 33 are swept out to the N-type silicon substrate 31.

  That is, at the time of image acquisition in one frame, this charge accumulation state (a state where an OFD voltage is applied to the N-type silicon substrate 31) and a charge sweep state (an OFD + electronic shutter voltage are applied to the N-type silicon substrate 31). The amount of charge accumulated in the photodiode N-type impurity layer 33 can be adjusted. In other words, the automatic exposure adjustment is performed by changing the time distribution.

  The automatic exposure adjustment will be described with reference to FIG. 8A and 8B are diagrams for explaining the electronic shutter operation of the solid-state imaging device 1300. FIG. 8A shows the case where the light incident on the solid-state imaging device 1300 is strong, and FIG. 8B shows the solid-state imaging. A case where light incident on the element 1300 is weak is shown.

  In the operation of picking up one picture (one frame) in the operation of the solid-state imaging device 1300, first, an electronic shutter voltage is applied to the N-type silicon substrate 31 in the charge sweep time T1. As a result, the charge in the photodiode N-type impurity layer 33 is once swept out to the N-type silicon substrate 31, and the photodiode N-type impurity layer 33 becomes empty. From there, the charge is accumulated in the photodiode N-type impurity layer 33 during the charge accumulation time T2, and then the charge is read out / transferred / output at the read transfer time T3. Note that, during the operation of one frame, light is constantly radiated to the solid-state imaging device 1300.

  The charge sweeping operation at the charge sweeping time T1 is referred to as an electronic shutter. Automatic exposure adjustment can be performed by adjusting the time T1 for sweeping out charges to the N-type silicon substrate 31 by the electronic shutter. Specifically, in the automatic exposure adjustment, when the light incident on the solid-state imaging device 1300 is strong, as shown in FIG. 8A, the electric charge sweep time T1 in one frame is lengthened by an electronic shutter, The charge accumulation time T2 is shortened. When the light incident on the solid-state imaging device 1300 is weak, as shown in FIG. 8B, the charge sweep time T1 is shortened and the charge accumulation time T2 is lengthened by the electronic shutter. That is, in the solid-state imaging device 1300, when strong light such as sunlight is incident on the solid-state imaging device 1300, the automatic exposure adjustment function can change the charge sweeping time T1 to the N-type silicon substrate 31 by the electronic shutter longer. This prevents the photodiode N-type impurity layer 33 from overflowing electric charges and causing the image to fly out.

  Here, in the case where the solid-state imaging device 1300 is a solid-state imaging device that performs charge accumulation / reading / transfer and all processing simultaneously on a visible light pixel and a near-infrared pixel, the visible light filter 39 is shown in FIG. In other words, if the sensitivity of the visible light pixel and the sensitivity of the near-infrared light pixel are greatly different as shown in FIGS. 32 (c) and (d), the following characteristics are obtained. There is a problem like this.

  That is, since the near-infrared light filter 40 is composed of a film that does not transmit light shorter than the near-infrared wavelength, the charge accumulated in the photodiode N-type impurity layer 33 that generates the charge of the near-infrared image. The amount is small. When strong light is incident on the solid-state imaging device 1300, the visible light pixel and the near-infrared pixel are processed at the same time. Therefore, the charge accumulation time T2 is short according to the visible light pixel by automatic exposure adjustment (charge sweep time by the electronic shutter). T1 becomes long). As a result, the charge accumulation amount of the near-infrared image that originally has a small charge accumulation amount is further reduced and the near-infrared image output becomes very small, so that a good and accurate image cannot be acquired.

  The solid-state imaging device 100 is assumed not to transmit a specific wavelength in visible light in order to solve the above problem. Specifically, the visible light filter 8 is a filter film that does not transmit a longer wavelength than blue (490 nm). As a result, the amount of light transmitted by the visible light filter 8 is smaller than, for example, when the visible light filter 8 transmits all visible light. In other words, if the visible light filter 39 has the same characteristics as the visible light filter 8, the difference between the amount of light transmitted by the visible light filter 39 and the amount of light transmitted by the near-infrared light filter 40. And the sensitivity difference between the visible light pixel and the near-infrared light pixel is reduced.

  As described above, when the automatic exposure adjustment is performed using the electronic shutter, the solid-state imaging device 100 can shorten the charge discharge time T1 by the electronic shutter and lengthen the charge accumulation time T2 compared to the solid-state imaging device 1500. As a result, the solid-state imaging device 100 can increase the near-infrared image output as compared with the solid-state imaging device 1500. In other words, in the solid-state imaging device 100, even if automatic exposure adjustment (automatic electronic shutter processing) is performed, the output of the near-infrared light pixel does not become very small. Therefore, imaging is performed by simultaneously irradiating near-infrared light and visible light onto the object to be imaged, and information on the visible light image and near-infrared light image based on the charge generated in the photodiode impurity layer 2 is simultaneously transmitted to the outside. Even in the case of output, a more optimal exposure adjustment can be performed, and a good and accurate image can be acquired even in an environment of strong light such as sunlight.

  Further, since the visible light filter 8 is a filter that does not transmit light having a wavelength longer than that of blue light, the visible light filter 8 can be formed more easily than a filter that transmits a specific wavelength.

(About image processing)
FIG. 9 is a diagram for explaining a complementary method for visible light pixel information and a complementary method for infrared light pixel information with respect to the solid-state imaging device 100. In other words, FIG. 9 shows an example of output signal processing when the present invention is applied to an all-pixel readout type CCD solid-state imaging device having a total number of pixels of 1.3 million pixels. In the embodiment described above, the visible light filter 8 and the near-infrared light filter 9 are alternately arranged (for example, checkered pattern), so that the output of the CCD is from a pixel close to the output circuit unit to visible light pixel information. And near infrared light information are alternately output. In the case of a visible light image, the information that was a near-infrared light pixel with respect to the total number of pixels of 1.3 million is calculated from the visible light pixel information of the upper, lower, left, and right four pixels and complemented as visible light pixel information. Here, “visible light pixel information” is voltage information based on charges photoelectrically converted in the visible light pixel, and “information that was a near infrared light pixel” is arranged by the near infrared light pixel. This is pixel information that is complemented by using visible light image information on the top, bottom, left, and right. In the case of a near-infrared light image, for the total number of pixels of 1.3 million pixels, the information that was a visible light pixel is calculated from the information of the near-infrared light pixels of the upper, lower, left, and right pixels, and the near-infrared light pixel Supplement as information. By performing the processing as described above, an image of 1.3 million pixels of visible light and 1.3 million pixels of near-infrared light can be obtained by relatively simple information processing of pixels. Here, “near-infrared light pixel information” is voltage information due to charges photoelectrically converted in the near-infrared light pixel, and “information that was a visible light pixel” is the arrangement of visible light pixels. This is pixel information that is complemented using near-infrared light image information on the top, bottom, left, and right.

  More specific processing includes using pixel information obtained from a plurality of visible light pixels adjacent to the near-infrared light pixel, and complementing the pixel information of the near-infrared light pixel to complement all pixels related to visible light. Get information. For example, in the example shown in FIG. 9, the pixel information of the near-infrared light pixel is complemented by using the average values of the visible light images adjacent to the near-infrared light pixel in the vertical and horizontal directions. According to the above configuration, it is possible to perform image processing for obtaining information on all pixels of a visible light image with higher accuracy.

  Similarly, by using pixel information acquired from a plurality of near-infrared light pixels adjacent to the visible light pixel, the pixel information of the visible light pixel is complemented to obtain all pixel information related to the near-infrared light. To get. For example, in the example illustrated in FIG. 9, pixel information of visible light pixels is complemented using an average value of near-infrared light images adjacent to the visible light pixels in the upper, lower, left, and right directions. Thereby, the image processing process for obtaining the information of all the pixels of the near-infrared light image can be performed with higher accuracy.

(Modification of filter array)
FIGS. 10A and 10B are diagrams showing modifications of the arrangement method of the filters of the visible light filter 8 and the near-infrared light filter 9, respectively. The arrangement of the visible light pixels and the near-infrared light pixels is not particularly limited as long as half of the total number of pixels is arranged, and the arrangement method shown in these drawings may be adopted. .

(Merit of checkered pattern arrangement)
However, the checkered arrangement of the visible light filter 8 and the near-infrared light filter 9 has the following advantages.

  (1) The number of pixels that can be truly obtained by photoelectric conversion between the visible light image and the near-infrared light image is half the total number of pixels (for example, 1.3 million pixels). In order to obtain an image of 1.3 million pixels in each of the visible light image and the near-infrared light image, it is necessary to supplement the information of the near-infrared light pixel portion in the case of the visible light image. Therefore, calculation is performed from information on visible light pixels on the top, bottom, left, and right of a pixel to be complemented (in this case, a near-infrared light pixel). For this reason, in the case of the filter arrangement as shown in FIGS. 10A and 10B, all pixel information cannot be processed by the same calculation, and the image construction process becomes more complicated. . Note that the pixel information construction on the outermost periphery of the pixel area is a different calculation even in the checkered pattern arrangement.

  (2) In terms of manufacturing process, in the case of the solid-state imaging device 100 of the present embodiment, there is a high possibility that the manufactured filter is particularly thick, particularly in the near-infrared pixel, the filter is thick, and the visible light pixel. Then, when forming a filter such that the filter is thin, there is a possibility that considerable unevenness may be formed on the element. The variation (irregularity) in the element structure causes unevenness in a later process, and the photographed image may be uneven during photographing. Therefore, it is preferable to suppress unevenness in the element structure as much as possible. In the case of the filter arrangement as shown in FIGS. 10A and 10B, when viewed from the entire pixel area, there are places where there are many near-infrared pixels, places where there are many near-infrared pixels, places where there are many visible light pixels, and places where there are few. For this reason, there is a possibility of causing structural unevenness. Since the visible light filter 8 and the near-infrared light filter 9 are arranged in a checkered pattern like the solid-state imaging device 100 of the present embodiment, the same arrangement is obtained at any location as viewed from the entire pixel area. The unevenness of the ground can be minimized.

  (3) The number of visible light pixels and the number of near-infrared light pixels may be equal to half the total number of pixels, respectively, so that all visible light pixels in all vertical columns and near-infrared pixels in all vertical columns are alternately arranged. You may arrange. However, in the case of constructing a visible light image with such an arrangement, for example, the vertical column that was a near-infrared light pixel does not have any information obtained by truly photoelectrically converting visible light, and was obtained by calculation. Since it becomes information, there is a possibility that it is slightly disadvantageous in terms of resolution.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG. FIG. 11 is a diagram for explaining the configuration of the solid-state imaging device according to the second embodiment of the present invention. The solid-state imaging device 100A according to the second embodiment is an example of a variation in transmission wavelength setting of each filter in the solid-state imaging device 100. 11A is a cross-sectional view showing the structure of the solid-state imaging device 100A, and FIGS. 11B and 11C are graphs showing the optical characteristics of the respective filters. FIG. ) And (e) are graphs showing the optical characteristics of the respective pixels. Note that FIG. 11A corresponds to the cross-sectional view taken along the line AA ′ shown in FIG. As shown in FIGS. 11A to 11E, in the solid-state imaging device 100A, a combination of a visible light filter 8A and a near-infrared light filter 9 is used. The visible light filter 8A is a filter film that does not transmit longer wavelengths than the green wavelength (570 nm). Thereby, the solid-state imaging device 100A can form a filter film more easily than the solid-state imaging device 100.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG. FIG. 12 is a diagram for explaining the configuration of the solid-state imaging device according to the third embodiment of the present invention. The solid-state imaging device 100B according to the third embodiment is another example of variations in transmission wavelength setting of each filter in the solid-state imaging device 100. 12A is a cross-sectional view showing a cross-sectional structure of the solid-state imaging device 100B, and FIGS. 12B and 12C are graphs showing optical characteristics of the respective filters. (D) * (e) is a graph which shows the optical characteristic of each pixel. Note that FIG. 12A corresponds to the cross-sectional view of the AA ′ cross section shown in FIG. As shown in FIGS. 12A to 12E, in the solid-state imaging device 100B, a combination of a visible light filter 8B and a near-infrared light filter 9 is used. The visible light filter 8B transmits only a specific wavelength. Specifically, the visible light filter 8B is, for example, a filter film that transmits only the range of 450 to 470 nm. Thereby, the solid-state imaging device 100B can further reduce the sensitivity difference between the visible light pixel and the near-infrared light pixel as compared with the solid-state imaging device 100. The specific wavelength may be, for example, a green wavelength or a blue and green wavelength.

  The photodiode impurity layer 2 (formed by impure portion injection into the silicon substrate 1) of the visible light pixel has sensitivity not only in the visible light but also in the near-infrared wavelength region. In the case of a normal solid-state image sensor, the imaging optical system is provided with an IR cut filter (made up of a film that does not transmit light of near infrared wavelength or more) that cuts the wavelength of near infrared light or more (about 800 nm or more). Although not particularly problematic, when used for vein imaging, it is necessary to put light having a near infrared wavelength or more into the element.

  The solid-state imaging devices 100, 100A, and 100B are suitable for use in vein imaging. In addition, when using an image photographed with a filter film that transmits only light of a specific wavelength, such as the visible light filter 8B, various proposals have been made (for example, plants and fruits). Nurturing status, food spoilage inspection, spot detection on human skin, etc.). When considering such an application, there is a possibility that the detection wavelength needs to be more peaky (photographed only with a more limited wavelength). Even in vein authentication, there is a possibility that the accuracy of authentication increases when the image is captured at a more limited wavelength. When the filter characteristics are limited, it is difficult to obtain the desired spectral characteristics only by forming a single-layer filter, and it is necessary to make a hybrid filter structure with two layers of filters. is there.

  In other words, the visible light filter 8B that transmits only light of a specific wavelength is, as shown in FIG. 13, a hybrid filter structure in which a first filter and a second filter, which are organic filters or inorganic filters, are stacked. Can be formed. Details of the hybrid structure will be described later. FIG. 13 is a schematic diagram for obtaining a desired transmitted light wavelength using a two-layer filter.

  The transmission wavelength setting of each filter is configured by selecting and combining a color filter for visible light photography and a color filter for near-infrared light photography according to the photographing system, authentication system, or object to be emphasized. May be.

[Formation method (or material / structure) of each filter]
The forming method (or material / structure) of each filter according to the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those described in the embodiment are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 14 is a cross-sectional view for explaining an example of forming a filter of the solid-state imaging device 100 according to Embodiment 1 of the present invention. The solid-state imaging device 100 shown in FIG. 1 and the solid-state imaging device 100C shown in FIG. 14 are replaced with a visible light filter 8C and a near-infrared light filter 9 instead of the visible light filter 8 and the near-infrared light filter 9. The difference is that the filter 9C is used. The solid-state imaging device 100C has the same configuration as the solid-state imaging device 100 except for the visible light filter 8C and the near-infrared light filter 9C.

  The visible light filter 8C and the near-infrared light filter 9C are both organic filters (consisting of an organic film mixed with a material that absorbs at least a specific wavelength of light). The visible light filter 8C and the near-infrared light filter 9C are a mixture of a pigment or dye having a characteristic of absorbing light of a specific wavelength in an organic material such as acrylic and a photosensitive material for patterning. It is made of only organic materials.

  In the case of an organic filter, as described above, a pigment or dye material that absorbs a specific wavelength in an organic material and a photosensitive material for pattern formation are generally used. The filter can be formed in a relatively simple process because it can be formed by spin coating, pattern formation (pattern exposure), and development. However, if the ground irregularities previously formed are large, spin coating can be performed. There is a demerit that unevenness is likely to occur.

[Variation 1 of forming method of each filter]
FIG. 15 is a cross-sectional view for explaining a modified example of the filter forming method of the solid-state imaging device 100. The solid-state imaging device 100D shown in FIG. 15 and the solid-state imaging device 100C shown in FIG. 14 are replaced with a visible light filter 8C and a near-infrared light filter 9C instead of the visible light filter 8C and the near-infrared light filter 9C. The other points are the same except that the filter 9D is provided.

  As shown in FIG. 15, the visible light filter 8D and the near-infrared light filter 9D are formed of only an inorganic material having a characteristic of reflecting a specific wavelength by a thin film laminated structure of materials having different refractive indexes. Yes. Specifically, in the example shown in FIG. 15, both the visible light filter 8D (color filter for visible light photography) and the near infrared light filter 9D (color filter for near infrared light photography) are both inorganic. An example is shown in which a filter (consisting of a film that reflects light of a specific wavelength by a laminated structure of inorganic films) is used. However, in the case of an inorganic filter, it can be formed in the normal first half of the semiconductor manufacturing process, but because it has a laminated structure of about 10 thin films, its film formation / etching process is difficult. There is a demerit that the unevenness of the element becomes very large.

  FIG. 16A is a diagram showing the film thickness of each layer constituting the inorganic filter, and FIG. 16B is a graph showing the simulation result of the transmittance of the multilayer film of the inorganic filter. As shown in FIGS. 16A and 16B, an inorganic filter that transmits only light of a desired wavelength can be formed by selecting the refractive index of the laminated film, the number of laminated layers, and the film thickness. . FIG. 17 is a view showing an electron micrograph of an actually produced inorganic multilayer filter. Note that FIG. 17 shows an example of a structural film that is different from the simulation results of (a) and (b) of FIG.

[Variation 2 of forming method of each filter]
FIG. 18 is a cross-sectional view for explaining still another example of forming the filter of the solid-state imaging device 100. The solid-state imaging device 100E shown in FIG. 18 and the solid-state imaging device 100C shown in FIG. 14 are replaced with a visible light filter 8C and a near-infrared light filter 9C instead of the visible light filter 8C and the near-infrared light filter 9C. The other points are the same except that the filter 9E is provided.

  As the visible light filter 8E and the near-infrared light filter 9E, for example, a filter that cuts IR (cuts longer wavelengths than near-infrared light), or transmits light of only red wavelength, only green wavelength, or only blue wavelength. The filter can be formed with a single layer organic filter (organic material mixed with a material that absorbs light of a specific wavelength). However, they do not necessarily transmit only light having a desired wavelength, but transmit light having a wavelength in the vicinity thereof or light having a wavelength apart to some extent. In order to limit the wavelength of light transmitted through each filter, for example, it is necessary to use not only a single-layer organic filter but also a hybrid filter in which another organic filter or an inorganic filter is combined.

  Specifically, as shown in FIG. 18, in the solid-state imaging device 100E, a first filter for visible light 111 (color filter for photographing visible light) and a first filter for near infrared light 112 (near infrared light photographing). Each color filter is composed of an organic filter (consisting of an organic film mixed with a material that absorbs at least a specific wavelength of light). In the solid-state imaging device 100E, the visible light second filter 113 (visible light color filter) and the near infrared light second filter 114 (near infrared light color filter) are each inorganic. It is composed of a filter (a film that reflects light of a specific wavelength by a laminated structure of inorganic films). The visible light filter 8E is configured by laminating a visible light first filter 111 on a visible light second filter 113. The near-infrared light filter 9E is configured by stacking a near-infrared light first filter 112 on a near-infrared light second filter 114.

  In the present modification, the visible light filter 8E may be a laminated (hybrid) filter including an IR cut filter and a blue wavelength transmission filter. Thus, the selection range of the transmission wavelength can be further expanded by using the hybrid structure using both the organic filter film and the inorganic filter film.

[Modification 3 of forming method of each filter]
FIG. 19 is a cross-sectional view for explaining still another example of forming the filter of the solid-state imaging device 100. The solid-state imaging device 100F shown in FIG. 19 and the solid-state imaging device 100C shown in FIG. 14 are replaced with a visible light filter 8C and a near-infrared light filter 9C, and a visible light filter 8F and a near-infrared light filter. The other points are the same except that the filter 9F is provided. Thus, the selection range of the transmission wavelength can be further expanded by using a hybrid structure in which two or more layers of the organic filter film described above are stacked.

  Specifically, as shown in FIG. 19, the solid-state imaging device 100F includes a first filter for visible light 120 (color filter for photographing visible light) and a first filter for near infrared light 121 (near infrared light photographing). Each color filter is composed of an organic filter (consisting of an organic film mixed with a material that absorbs at least a specific wavelength of light). Further, the second filter 122 for visible light (color filter for photographing with visible light) and the second filter for near infrared light 123 (color filter for photographing with near infrared light) are also organic filters (organic It is composed of a film in which a material that absorbs light of a specific wavelength is mixed into the system film. The visible light filter 8F is configured by laminating the visible light first filter 120 on the visible light second filter 122. The near-infrared light filter 9 </ b> F is configured by stacking a near-infrared light first filter 121 on a near-infrared light second filter 123.

[Variation 4 of forming method of each filter]
FIG. 20 is a cross-sectional view for explaining still another example of forming the filter of the solid-state image sensor 100. The solid-state imaging device 100G shown in FIG. 20 and the solid-state imaging device 100C shown in FIG. 14 replace the visible light filter 8C and the near-infrared light filter 9C with a visible light filter 8G and a near-infrared light filter. The other points are the same except that the filter 9G is provided. Thus, the selection range of the transmission wavelength can be further expanded by using a hybrid structure in which two or more layers of the inorganic filter film described above are stacked.

  Specifically, as shown in FIG. 20, the solid-state imaging device 100G includes a first filter for visible light 130 (color filter for photographing visible light) and a first filter for near infrared light 131 (near infrared light photographing). Each color filter is composed of an inorganic filter (consisting of a film that reflects light of a specific wavelength by a laminated structure of inorganic films). Further, the second filter 132 for visible light (color filter for photographing with visible light) and the second filter for near infrared light 133 (color filter for photographing with near infrared light) are respectively inorganic filters (inorganic It is composed of a film that reflects light of a specific wavelength due to the laminated structure of the system film.

  The visible light filter 8G is configured by laminating a visible light first filter 130 on a visible light second filter 132. The near-infrared light filter 9G is configured by stacking a near-infrared light first filter 131 on a near-infrared light second filter 133.

  In reality, it is first considered whether the target spectrum can be obtained with a single-layer structure of an organic filter that is easy to form. It is preferable to make the structure complicated to a hybrid structure of an inorganic filter and an inorganic filter (however, the above-mentioned problem of unevenness during spin coating can be improved to some extent).

  By realizing an imaging system including any of the solid-state imaging devices 100 to 100G described above, a high-speed and high-accuracy vein (artery) authentication / palmprint authentication system is constructed with a simple (small) and low-cost imaging system. can do. In addition, security is improved by authenticating an individual from two pieces of biological information. In particular, since the vein information is invisible information, it is difficult to forge and the security can be further improved. In addition, more optimal exposure adjustment can be performed, and a good and accurate image can be acquired even in an environment of strong light such as sunlight.

[Embodiment 4]
Although the first to third embodiments have described the CCD, the same configuration can be applied to the CMOS type solid-state imaging device. In the present embodiment, a configuration example of the CMOS solid-state imaging device 200 will be described with reference to FIG. FIG. 21 is a diagram for explaining the configuration of a CMOS solid-state imaging device 200 according to Embodiment 4 of the present invention. FIG. 21A is a diagram illustrating a state of a filter array when the CMOS solid-state imaging device 200 is viewed from the light incident side. FIG. 21B is a cross-sectional view taken along the line CC ′ shown in FIG. As shown in FIG. 21B, the CMOS solid-state image sensor 200 (solid-state image sensor) includes a silicon substrate 201 (semiconductor substrate), a photodiode impurity layer 202 (photoelectric conversion unit), a high-concentration impurity layer 203, a gate. An electrode 204, a metal wiring 205, a visible light filter 206 (color filter for photographing visible light), a near infrared light filter 207 (color filter for photographing near infrared light), and a condensing microlens 208 are provided. . Note that the configuration of the gate electrode 204, the metal wiring 205, and the condensing microlens 208 has little relation to the essence of the present invention, and thus the description thereof is omitted here.

(Silicon substrate 201)
The silicon substrate 201 is a semiconductor substrate having one conductivity based on silicon. Here, one conductivity is either p-type conductivity or n-type conductivity.

(Photodiode impurity layer 202, high-concentration impurity layer 203)
Inside the silicon substrate 201, a plurality of photodiode impurity layers 202, which are regions that generate charges by photoelectrically converting received light, and a plurality of high-concentration impurity layers, which are regions to which the generated charges are transferred 203 is formed.

(Visible light filter 206, near infrared light filter 207)
In the CMOS solid-state imaging device 200 of the present embodiment, each of the plurality of visible light filters 206 and the same number of near-infrared light filters 207 are associated with each of the plurality of photodiode impurity layers 202. Two-dimensionally distributed. For this reason, when acquiring information on all the pixels of the visible light image, information on pixels associated with a specific near-infrared light filter 207 (hereinafter referred to as “near-infrared light pixels”) It is possible to complement by using information of pixels (hereinafter referred to as “visible light pixels”) associated with the visible light filter 206 dispersed and arranged. In addition, when acquiring information about all the pixels of the near-infrared light image, the information about the specific visible light image may be supplemented using information about the infrared light pixels arranged in the vicinity thereof. It becomes possible. As described above, the image processing can be simplified, and both the visible light image and the near infrared light image can be simultaneously acquired.

  More specifically, as shown in FIG. 21A, each of the visible light filter 206 and the near-infrared light filter 207 is connected to the condensing microlens 208 on the photodiode impurity layer 202. In the middle part, they are arranged alternately (for example, checkered pattern). Thereby, when acquiring information on all pixels of the visible light image, information on a specific near-infrared light pixel can be supplemented using information on visible light pixels arranged on the top, bottom, left, and right of the pixel. It becomes possible. In addition, when acquiring information on all pixels of a near-infrared light image, information on a specific visible light pixel may be supplemented using information on infrared light pixels arranged on the top, bottom, left, and right of the pixel. It becomes possible. Therefore, compared to a configuration in which the color filter for visible light photography and the color filter for near infrared light photography are not arranged alternately, the information of all pixels of the visible light image or the near infrared light image is obtained. The image processing for obtaining can be simplified.

  The visible light filter 206 does not transmit a specific wavelength in visible light. In this embodiment, the visible light filter 206 does not transmit longer wavelengths than blue light. Specifically, the visible light filter 206 cuts light having a wavelength longer than that of visible light blue (490 nm), for example. The near-infrared light filter 207 does not transmit light having a wavelength shorter than the visible light wavelength. Specifically, the near-infrared light filter 207 cuts light having a wavelength shorter than 750 nm, for example. As a result, the difference between the amount of light transmitted through the visible light filter 206 and the amount of light transmitted through the near-infrared light filter 207 is reduced, and the sensitivity difference between the visible light pixel and the near-infrared light pixel is reduced. Become. Thereby, even if the CMOS type solid-state imaging device 200 performs the automatic exposure adjustment (automatic electronic shutter process), the output of the near-infrared light pixel does not become very small. Therefore, optimal exposure adjustment can be performed, and a good and accurate image can be acquired even in an environment of strong light such as sunlight.

[Summary]
The solid-state imaging device (100) according to the first aspect of the present invention receives a plurality of near-infrared light and visible light that are simultaneously irradiated on an object to be imaged, and generates a plurality of charges by photoelectrically converting the received light. A plurality of visible light photographing color filters (visible light filter 8) associated with each of a part of the plurality of photoelectric conversion portions, and the plurality of the plurality of photoelectric conversion portions (photodiode impurity layer 2). A plurality of near-infrared light photographing color filters (near-infrared light filter 9) associated with each of the remaining photoelectric conversion units, the visible light photographing color filter and the near-infrared light The color filter for light photographing is two-dimensionally dispersed, and information on a visible light image and a near-infrared light image based on the charge generated by the photoelectric conversion unit is output to the outside at the same time, and the visible light photographing Color filter for visible light Kicking does not transmit light of a specific wavelength.

  According to the above configuration, the near-infrared color photographing color filter and the visible color photographing color filter associated with the photoelectric conversion unit are two-dimensionally distributed. Thereby, in an imaging system including the solid-state imaging device, image processing is simplified, and both a captured image of visible light and a captured image of near-infrared light can be simultaneously acquired.

  Further, according to the above configuration, since the visible light photographing color filter does not transmit light of a specific wavelength in visible light, the amount of light transmitted by the visible light photographing color filter of the present invention is, for example, all Compared with a visible light photographing color filter that transmits visible light, the amount of light transmitted is reduced. In other words, the difference between the amount of light transmitted by the visible light color filter and the amount of light transmitted by the near-infrared color filter is reduced, so that the visible light pixel and the near-infrared light pixel The sensitivity difference is reduced.

  As a result, when performing automatic exposure adjustment with an electronic shutter when receiving a near-infrared light and a visible light that are simultaneously irradiated on the object to be photographed, the visible light photographing that transmits all visible light is performed. Compared with the color filter for use, the charge discharging time by the electronic shutter can be shortened and the charge accumulation time can be lengthened. As a result, the near-infrared image output is larger than the color filter for visible light photography that transmits all visible light, so it is possible to adjust exposure more optimally and in strong light environments such as sunlight. Even good and accurate images can be obtained.

  In the solid-state imaging device (100) according to aspect 2 of the present invention, in the above aspect 1, it is preferable that the color filter for visible light imaging (visible light filter 8) does not pass light having a longer wavelength than blue light.

  According to the above configuration, it is possible to create a filter more easily than forming a filter that transmits a specific wavelength.

  In the solid-state imaging device (100) according to aspect 3 of the present invention, in the aspect 1 or 2, the color filter for visible light imaging may be a film that does not transmit light having a wavelength of 490 nm or more.

  According to the above configuration, the limit of the amount of incident light can be further reduced, and accordingly, the limit of the amount of light incident on the color filter for near-infrared light photography is also reduced, so that more optimal exposure adjustment can be performed. . Further, by using, for example, an organic film and an inorganic film as a color filter for visible light photography, manufacturing is facilitated and cost reduction can be realized.

  In the solid-state imaging device (100A) according to aspect 4 of the present invention, in the aspect 1, it is preferable that the color filter for visible light imaging (visible light filter 8A) does not transmit light having a wavelength longer than that of green.

  According to the above configuration, a filter can be formed more easily than forming a filter that does not transmit light having a longer wavelength than blue.

  In the solid-state imaging device (100A) according to aspect 5 of the present invention, in the aspect 4, it is preferable that the color filter for visible light imaging (filter 8A for visible light) is a film.

  According to the said structure, manufacture becomes easy and can implement | achieve cost reduction.

  In the solid-state imaging device (100B) according to aspect 6 of the present invention, in the aspect 1, it is preferable that the color filter for visible light imaging (visible light filter 8B) transmits only light of a specific wavelength.

  According to the above configuration, for example, only the range of 450 to 470 nm can be transmitted, and the amount of incident light can be further reduced, so that more optimal exposure adjustment can be performed.

  In the solid-state imaging device (100B) according to aspect 7 of the present invention, in the aspect 6, it is preferable that the color filter for visible light imaging (visible light filter 8B) is a film.

  According to the said structure, manufacture becomes easy and can implement | achieve cost reduction.

  In the solid-state imaging device (100) according to Aspect 8 of the present invention, in any one of Aspects 1 to 7, the color filter for near-infrared light photographing (near-infrared light filter 9) has a near-infrared wavelength. It is preferable that the film does not transmit light having a shorter wavelength.

  According to the above configuration, since it is possible to prevent the infrared light image information from containing photoelectrically converted information that is shorter than the near-infrared wavelength, for example, when performing vein image capturing, a more vein image Can be made to stand out.

  The solid-state imaging device (100) according to the ninth aspect of the present invention is the solid-state imaging device (100) according to any one of the first to eighth aspects, wherein the near-infrared light color filter (near-infrared light filter 9) has a specific wavelength. A film that transmits only light is preferable.

  According to the above configuration, by appropriately setting the wavelength of light to be transmitted, a solid-state imaging device suitable for, for example, growing conditions of plants and fruits, food spoilage inspection, spot detection on human skin, and the like is realized. be able to.

  The solid-state imaging device (100) according to the tenth aspect of the present invention is preferably capable of reading all pixels in any of the first to ninth aspects.

  According to the above configuration, it is possible to perform image processing for obtaining information on all pixels of a visible light image or a near-infrared light image more easily and at a higher speed.

  The solid-state imaging device (100C) according to aspect 11 of the present invention is the color filter for visible light photography (filter 8C for visible light) and the color for near-infrared light photography in any of the aspects 1 to 10. The filter (near-infrared light filter 9C) is preferably formed of a film in which an organic film is mixed with a material that absorbs at least light of a specific wavelength.

  According to the above configuration, the filter can be formed in a relatively simple process because it can be formed in each step of spin coating on the element (wafer), pattern formation (pattern exposure), and development.

  The solid-state imaging device (100D) according to an aspect 12 of the present invention is the color filter for visible light photography (the visible light filter 8D) and the color for near-infrared light photography in any of the above aspects 1 to 11. The filter (near-infrared light filter 9D) is preferably formed of a film that reflects light of a specific wavelength by a laminated structure of inorganic films.

  According to the above configuration, the filter can be formed during the normal first half process of semiconductor manufacturing.

  The solid-state imaging device (100E) according to aspect 13 of the present invention is the color filter for visible light photography (filter 8E for visible light) and the color filter for near-infrared light photography in any of the above aspects 1-12. (Near-infrared filter 9E) includes a film in which a material that absorbs at least a specific wavelength of light is mixed in an organic film, and a film that reflects light of a specific wavelength by a laminated structure of inorganic films. It is preferable that both are formed.

  According to the above configuration, it is possible to form a filter that can obtain desired spectral characteristics.

  The solid-state imaging device (100) according to the fourteenth aspect of the present invention is the solid-state imaging device (100) according to any one of the first to thirteenth aspects, wherein the number of the visible light photographing color filters (visible light filter 8) and the near infrared light photographing. The number of color filters (near-infrared light filter 9) is preferably the same.

  According to the above configuration, since the number of color filters for visible light photography and the number of color filters for near-infrared light photography are the same, for example, the pixels associated with the color filters for near-infrared light photography It is possible to supplement the pixel information associated with the color filter for near-infrared light photography by using the pixel information associated with the color filter for visible light photography arranged in the vicinity. it can.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

2 Photodiode impurity layer (photoelectric conversion part)
8,8A, 8B, 8C, 8D, 8E, 8F, 8G Visible light filter (color filter for visible light photography)
9, 9C, 9D, 9E, 9F, 9G Near Infrared Light Filter (Color Filter for Near Infrared Light Photography)
100 / 100A / 100B / 100C / 100D / 100E / 100F / 100G Solid-state image sensor 200 CMOS solid-state image sensor (solid-state image sensor)
206 Visible light filter (color filter for visible light photography)
207 Near-infrared filter (color filter for near-infrared light photography)
500 Imaging system

Claims (5)

A plurality of photoelectric conversion units that receive near-infrared light and visible light that are simultaneously irradiated to the imaging target, and generate charges by photoelectrically converting the received light; and
A plurality of visible light photographing color filters associated with each of a part of the plurality of photoelectric conversion units;
A plurality of near infrared light photographing color filters associated with each of the remaining of the plurality of photoelectric conversion units,
The visible light photographing color filter and the near infrared light photographing color filter are two-dimensionally dispersed,
Information of the visible light image and the near-infrared light image based on the charge generated by the photoelectric conversion unit is output to the outside at the same time,
The solid-state imaging device, wherein the visible light color filter does not transmit light having a specific wavelength in visible light.   The solid-state imaging device according to claim 1, wherein the visible light photographing color filter does not transmit light having a longer wavelength than blue light.   The solid-state imaging device according to claim 1, wherein the visible light photographing color filter does not transmit light having a longer wavelength than green.   The solid-state imaging device according to claim 1, wherein the visible light photographing color filter transmits only light of a specific wavelength.   5. The solid-state imaging device according to claim 1, wherein the color filter for photographing near infrared light is a film that does not transmit light having a wavelength shorter than the near infrared wavelength.

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