JP4887915B2 - Solid-state imaging device - Google Patents

Description

  The present invention relates to a solid-state imaging device. More specifically, the present invention relates to a technique suitable for application to, for example, a solid-state imaging apparatus that obtains imaging information by detecting light incident from the outside. In particular, the present invention relates to an imaging apparatus that enables imaging using wavelength components other than visible light (for example, infrared light). Here, the solid-state imaging device includes both an element-like device and a device obtained by combining a plurality of devices.

  There are various physical quantity distribution detection semiconductor devices in which a plurality of unit components (for example, pixels) that are sensitive to changes in physical quantity such as light and radiation input from the outside such as electromagnetic waves are arranged in a line or matrix form. Used in the field.

  For example, in the field of video equipment, a CCD (Charge Coupled Device) type, a MOS (Metal Oxide Semiconductor) type, or a CMOS (Complementary Metal-oxide Semiconductor) type solid that detects changes in light (an example of an electromagnetic wave) that is an example of a physical quantity. An imaging device is used. These read out, as an electrical signal, a physical quantity distribution converted into an electrical signal by a unit component (a pixel in a solid-state imaging device).

  For example, in a solid-state imaging device, a photodiode that is a photoelectric conversion element (light receiving element; photosensor) provided in an imaging unit (pixel unit) of a device unit receives electromagnetic waves input from outside such as light and radiation. The signal charges are detected and generated and accumulated, and the accumulated signal charges (photoelectrons) are read out as image information.

Recently, a mechanism for capturing an image by visible light and an image by infrared light has been proposed (see, for example, Patent Documents 1 to 7). For example, by preparing an infrared light emitting point in advance and tracking it, the position of the infrared light emitting point in the visible light image can be detected. In addition, a clear image can be obtained by irradiating infrared light and taking an image even at night, for example, without visible light. Furthermore, sensitivity can be improved by incorporating infrared light in addition to visible light.
JP 2004-103964 A Japanese Patent Laid-Open No. 10-210486 JP 2002-369049 A Japanese Patent Laid-Open No. 06-121325 JP 09-166493 A Japanese Patent Laid-Open No. 09-130678 JP 2002-142228 A

  The mechanism described in Patent Document 1 is a single plate type that utilizes the difference in absorption coefficient depending on the wavelength in the depth direction of the semiconductor.

  In addition, the mechanisms described in Patent Documents 2 to 4 use a wavelength separation optical system such as a wavelength separation mirror or prism as an input optical system, and receive visible light and infrared light with separate imaging elements. It is.

  The mechanism described in Patent Document 5 is a single-plate type that uses a rotary wavelength resolving optical system as an input optical system and receives visible light and infrared light with the same imaging device. For example, when an infrared light cut filter is inserted / extracted as a rotating mechanism and an infrared light cut filter is inserted, a visible color image that is not affected by near infrared light or infrared light is displayed in red. When the external light cut filter is extracted, an image obtained by adding the light intensities of visible light and near infrared light is output.

  The mechanism described in Patent Document 6 uses a stop optical system having a wavelength resolving function as an input optical system, and receives visible light and infrared light with the same imaging device.

  Further, the mechanism described in Patent Document 7 is a system in which four types of color filters having separate filter characteristics are regularly arranged in each pixel of an image sensor having sensitivity to visible light and near-infrared light. A visible light color image and a near-infrared light image are obtained independently by performing a matrix operation on the output of each pixel provided with a color filter.

  44A and 44B are diagrams for explaining the mechanism of the sensor described in Patent Document 1. FIG. 44A shows the light absorption spectrum characteristics of the semiconductor layer, and FIG. 44B shows the cross-sectional structure of the device. It is a schematic diagram.

  In this mechanism, the light absorption coefficient of the Si (silicon) semiconductor decreases in the order of blue, green, red, and infrared light as shown in FIG. 44A, that is, blue light and green contained in the incident light L1. With respect to light, red light, and infrared light, by utilizing the location dependence due to the wavelength in the depth direction of the semiconductor, as shown in FIG. 44 (B), from the surface of the Si semiconductor to the depth direction. Layers for detecting each color light of visible light (blue, green, red) and infrared light are sequentially provided.

  However, the mechanism described in Patent Document 1 using the difference in absorption coefficient depending on the wavelength does not decrease the amount of light that can be detected theoretically, but the layer that detects blue light absorbs to some extent when red light or green light passes through. In order to receive, those lights will be detected as blue light. For this reason, even if a blue signal is not originally present, if a green or red signal is input, a blue signal is also generated and a false signal is generated, so that sufficient color reproducibility cannot be obtained.

  In order to avoid this, it is necessary to perform correction by signal processing by calculation for all three primary colors, and a circuit necessary for the calculation is separately required. Therefore, the circuit configuration is complicated and large in size, and the cost is increased. Become expensive. Further, for example, when one of the three primary colors is saturated, the original value of the saturated light is not known, resulting in a calculation error. As a result, the signal is processed differently from the original color. .

  As shown in FIG. 44A, most semiconductors have absorption sensitivity to infrared light. Therefore, for example, in a solid-state imaging device (image sensor) using Si semiconductor, for example, it is usually necessary to put an infrared cut filter made of glass as an example of a color reduction filter in front of the sensor.

  Therefore, in order to receive only infrared light, or visible light and infrared light as signals, it is necessary to remove the infrared cut filter or reduce the rate of infrared light cut.

  However, in this case, infrared light is mixed with visible light and incident on the photoelectric conversion element, so that the color of the visible light image is different from the original one. Therefore, it is difficult to obtain an appropriate image by dividing a visible light image and infrared light alone (or a mixture of infrared light and visible light) simultaneously.

  In addition to the above-described problems, the use of an infrared cut filter as in a normal solid-state imaging device also reduces the sensitivity because some of the visible light is cut. Further, the use of an infrared cut filter increases the cost.

  Further, the mechanisms described in Patent Documents 2 to 4 require a large input optical system because of a wavelength resolving optical system such as a wavelength separating mirror or prism.

  In addition, the mechanism described in Patent Document 5 is an infrared light cut filter insertion / extraction mechanism, so that the apparatus becomes large, and the operation of the infrared light cut filter cannot be performed automatically.

  Further, since the mechanism described in Patent Document 6 is an aperture optical system having a wavelength resolving function, the apparatus becomes large. In addition, although both an infrared image and a visible light image can be obtained simultaneously, the image sensor can output only an electric signal obtained by synthesizing the visible light image and the infrared image, and only the visible light image or only the infrared image can be output. Cannot output.

  On the other hand, since the mechanism described in Patent Document 7 performs wavelength separation by arranging four types of color filters, there is no problem that the input optical system as in Patent Documents 2 to 6 becomes large. There is a problem with arithmetic processing. In other words, the mechanism described in Patent Document 7 performs a matrix operation on the output of each pixel in which four types of color filters having different filter characteristics are arranged, so that a visible light color image and a near-infrared light image are independent of each other. Although the visible light image and the infrared image can be output individually and simultaneously, when obtaining the visible light image, it is necessary to perform an arithmetic process with the infrared light component. Become significant.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a new solid-state imaging device capable of solving at least one of the above-described problems.

  As an example, a solid-state imaging device having a new mechanism for independently obtaining a visible light color image and a near-infrared light image with the same image sensor is provided.

  As another example, when the same image sensor captures both visible light and infrared light simultaneously, it solves the problem that the hue caused by removing the infrared light cut filter differs from the original one. The present invention provides a mechanism capable of simultaneously capturing an image with visible light and an image with infrared light or ultraviolet light with accurate hue.

  As another example, there is provided a mechanism capable of solving the high cost due to the use of a thick glass infrared cut filter as in a normal image sensor.

  The solid-state imaging device according to the present invention uses a laminated film having a structure in which a plurality of layers having different refractive indexes are laminated to separate the wavelength components of the passing wavelength region component and the reflected wavelength region component, thereby individually separating both component signals. This is characterized in that the detection unit is configured to acquire them independently or simultaneously.

  That is, the solid-state imaging device according to the present invention has an imaging region including a plurality of pixels arranged two-dimensionally, and each of the plurality of pixels includes a light receiving element formed in a base, and the plurality of pixels A stacked portion is formed above the light receiving element of the first pixel included in the first layer, an intralayer lens is formed above the light receiving element of the second pixel included in the plurality of pixels, and the stacked portion is refracted. The solid-state imaging device includes a laminated structure including a plurality of layers having different rates, reflects incident light in a predetermined wavelength region, and the intra-layer lens is formed in an intermittent region of the laminated portion.

  According to the present invention, the wavelength component of the pass wavelength region component and the reflected wavelength region component are separated by using a laminated film having a structure in which a plurality of layers having different refractive indexes are laminated, and the component signals of both are detected by individual detection units. I tried to do it.

  As a result, it is possible to acquire physical information related to the passing wavelength region component in which the influence of the reflected wavelength region component can be ignored with a single semiconductor device (for example, an image sensor). At this time, for example, an expensive glass-made optical member for cutting infrared rays as in the prior art that cuts infrared light that is a reflected wavelength region component with respect to visible light, which is an example of a passing wavelength region component, becomes unnecessary. The difference in absorption coefficient due to the wavelength in the depth direction of the semiconductor is not utilized, and the problem of color reproducibility due to this does not occur.

  In addition, when the transmission wavelength region component and the reflection wavelength region component are separately detected and the signal output of both components is acquired simultaneously, the reflection wavelength region component is cut in advance by the laminated film for the transmission wavelength region component. Unlike the mechanism described in Japanese Patent Application Laid-Open No. 2002-142228, when obtaining a signal of a passing wavelength region component that is hardly affected by the reflected wavelength region component, there is no need to perform an arithmetic process with the reflected wavelength region component. is there.

Of course, since the signals of the passing wavelength region component and the reflected wavelength region component can be detected separately and simultaneously, for example, by using a structure that separately detects infrared light, ultraviolet light, and visible light, the image of visible light and red Images from external light and ultraviolet light can be taken simultaneously. At this time, the visible light is further divided into the three primary color signal components and detected so that an image of visible light with an accurate hue and an image of infrared light or ultraviolet light can be simultaneously captured. Become.
In addition, according to the present invention, since the in-layer lens is formed in the intermittent region of the laminated portion, the space in the intermittent region can be used, and even if an in-layer lens is provided, a special layer thickness is provided as a lens portion. There is no need to add, and the thickness of the layer on the light receiving portion does not become too thick.

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

<< Concept of Dielectric Multilayer Image Sensor >>
FIG. 1 is a diagram for explaining the concept of a demultiplexing image sensor that separates electromagnetic waves for each predetermined wavelength using a dielectric laminated film. Here, a spectral image sensor that separates light, which is an example of electromagnetic waves, for each predetermined wavelength will be described as an example.

  As shown in FIG. 1, the dielectric laminated film 1 is a layer having a predetermined thickness dj in which the refractive index nj (j is a positive integer of 2 or more; the same shall apply hereinafter) differs between adjacent layers (refractive index difference Δn). Is a laminated member having a structure in which a plurality of layers are laminated. As a result, as described later, it has a characteristic of reflecting a predetermined wavelength region component of the electromagnetic wave and passing the rest.

  The number of layers of each dielectric layer 1_j forming the dielectric laminated film 1 is counted without counting the thick layers (n0th layer 1_0 and kth layer 1_k) on both sides as the number of layers, for example, the first layer To the k-th layer side. Substantially, the dielectric laminated film 1 is configured except for the thick layers (the 0th layer 1_0 and the kth layer 1_k) on both sides.

  When light is incident on the dielectric multilayer film 1 having such a structure, the reflectance (or transmittance) has a certain dependency on the wavelength λ due to interference in the dielectric multilayer film 1. The effect increases as the refractive index difference Δn of light increases.

  In particular, when this dielectric laminated film 1 has a periodic structure and certain conditions (for example, conditions d to λ / 4n of the thickness d of each layer), when incident light L1 such as white light is incident, a certain specific Only the reflectance of light in the wavelength range (specific wavelength range light) is effectively increased to make most of the reflected light component L2, that is, the transmittance is reduced, and the reflectance of light in other wavelength ranges is increased. By making it low, most of the transmitted light component L3 can be obtained, that is, the transmittance can be increased.

  Here, the wavelength λ is the center wavelength in a certain wavelength range, and n is the refractive index of the layer. In the present embodiment, the spectral image sensor 10 is realized by utilizing the wavelength dependency of the reflectance (or transmittance) of the dielectric laminated film 1.

<Basic configuration of demultiplexing image sensor using dielectric multilayer film>
FIG. 2 is a conceptual diagram illustrating a basic configuration of a demultiplexing image sensor using a dielectric laminated film. Here, FIG. 2 shows an example in which infrared light IR (InfraRed) and visible light VL (Visible Light) are dispersed. The dielectric laminated film 1 is formed so as to have a high reflectance with respect to infrared light IR having a wavelength λ (mainly longer wavelength than 780 nm) in the infrared region which is longer than visible light VL. Thus, the infrared light IR can be transmitted by cutting the infrared light IR and not forming such a dielectric laminated film 1.

  The members (layer materials) of each dielectric layer 1_j constituting the dielectric laminated film 1 are at least two types because the dielectric laminated film 1 is composed of a plurality of layers. Any of the body layers 1_j may be made of different layer materials, or two (or more) layers may be laminated alternately or in any order. Further, the dielectric laminated film 1 may be configured with basic first and second layer materials, and a part thereof may be replaced with a third (or more) layer material. This will be specifically described below.

<Configuration of multi-wavelength demultiplexing image sensor using dielectric laminated film>
FIG. 3 is a diagram illustrating a configuration example in which the basic configuration of the spectral image sensor 10 illustrated in FIG. 2 is applied to a plurality of wavelength separation configurations.

  As described with reference to FIG. 2, the infrared light IR can be cut or transmitted depending on whether or not the dielectric laminated film 1 is formed. By applying this, for a plurality of detection units (for example, photodiodes) constituting the unit pixel matrix 12, a part of the laminated film is regularly removed by aligning with the detection units corresponding to each wavelength, that is, For each pixel (cell), infrared light is cut or not, so that only visible light VL and infrared light IR are picked up, or only visible light VL is picked up and infrared light IR and visible. Imaging in which the light VL is mixed can be performed simultaneously.

  It is not affected by the infrared light IR when capturing a monochrome image or a color image in the daytime, and can be imaged with the infrared light IR at night. If necessary, the other image can be output simultaneously. Even in that case, an image of only the infrared light IR that is not affected by the visible light VL can be obtained in the daytime.

  That is, the spectral image sensor 11 that supports multi-wavelength demultiplexing includes the dielectric layered film 1 that can reflect the infrared light IR as described above, and each pixel constituting the unit pixel matrix 12 in which the pixels are regularly arranged. By forming it on the photodiode that forms the main part of the infrared ray, it is possible to reflect infrared light IR, and based on the pixel signal obtained from this pixel, only visible light VL that is hardly affected by infrared light IR. Monochrome image can be obtained. Unlike the mechanism described in Japanese Patent Application Laid-Open No. 2002-142228, when obtaining a monochrome image of visible light VL that is hardly affected by infrared light IR, there is no need to perform arithmetic processing with components of infrared light IR. It is.

  Further, a color filter 14 having a predetermined wavelength transmission characteristic in the visible light VL region is provided as an example of an optical member for separating the wavelength region component into a predetermined wavelength region component on the photodiode on which the dielectric laminated film 1 is formed. By providing, an image of only a specific wavelength region in the visible light VL region that is hardly affected by the infrared light IR can be obtained.

  In addition, the color filters 14x having different wavelength transmission characteristics in the visible light VL region are integrally aligned with the photodiodes corresponding to each wavelength (color-specific) on the plurality of photodiodes constituting the unit pixel matrix 12. By arranging regularly, the visible light VL region can be separated by wavelength (by color), and by performing synthesis processing based on each pixel signal obtained from these pixels by color, A color image (visible light color image) of only visible light VL that is hardly affected by infrared light IR is obtained. Unlike the mechanism described in Japanese Patent Application Laid-Open No. 2002-142228, when obtaining a color image of visible light VL that is hardly affected by infrared light IR, there is no need to perform arithmetic processing with components of infrared light IR. It is.

  Further, in the same image pickup device (spectral image sensor 11), for example, by providing pixels in the unit pixel matrix 12 that do not partially form the dielectric multilayer film 1, by performing matrix calculation on the output of each pixel, It is always possible to independently obtain a monochrome image or color image of visible light VL and an image of infrared light IR. Further, a part of the dielectric multilayer film 1 integrally formed on the photodiode is not partially formed so that the dielectric multilayer film 1 is partially formed. Unlike the case where a separate optical member having no dielectric laminated film 1 is provided on the image pickup device, the problem of alignment does not occur.

  For example, imaging with only visible light VL (monochrome imaging or color imaging) that is almost completely unaffected by infrared light IR and imaging that mixes infrared light IR and visible light VL are performed simultaneously. Can do. In addition, the effect of visible light VL is achieved by combining (specifically, differential processing) a component that includes only visible light VL (monochrome image component or color image component) and a component that mixes infrared light IR and visible light VL. It is also possible to perform imaging using only infrared light IR that does not receive substantially any of the above.

  In the above, “substantially unaffected” means that the human visual sense is ultimately taken into account. Generally, if a clear difference cannot be recognized by human visual sense, It may be “received”. In other words, it is only necessary to obtain an infrared image (an example of physical information) that can ignore the influence of the pass wavelength region (visible light VL) on the infrared light IR side, and a reflected wavelength region component (infrared) on the visible light VL side. It is only necessary to obtain a normal image (an example of physical information) that can ignore the influence of (light IR).

  The color filter 14 includes a blue component B (for example, a transmittance of about 1 at a wavelength λ = 400 to 500 nm and a transmission rate of about 1 for other wavelengths) that is the three primary colors of visible light VL (wavelength λ = 380 to 780 nm), and a green component G. (For example, the transmittance is approximately 1 at a wavelength λ = 500 to 600 nm, and approximately zero at others), and the primary color filter centering on the red component R (for example, the transmittance is approximately 1 at wavelengths λ = 600 to 700 nm and approximately zero at others) It may be.

  Alternatively, yellow Ye (for example, transmittance is approximately zero at wavelength λ = 400 to 500 nm, approximately 1 for others), magenta Mg (for example, transmittance is approximately zero at wavelength λ = 500 to 600 nm, approximately 1 for others), cyan Cy It may be a complementary color filter having substantially zero transmittance for the three primary color components of visible light, such as (for example, the wavelength λ = 600 to 700 nm and the transmittance is substantially zero, otherwise approximately 1).

  Since the complementary color filter is more sensitive than the primary color filter, the sensitivity of the imaging apparatus can be increased by using a complementary color filter in which the transmitted light in the visible region is the complementary color of each of the three primary colors. it can. On the other hand, the use of a primary color filter has an advantage that the color signal of the primary color can be acquired without performing the difference processing, and the signal processing is simplified.

  Note that the transmittance of “approximately 1” means an ideal state, and the transmittance in the wavelength region is much larger than the transmittance in other wavelength regions. That's fine. Some of them may have “transmittance other than“ 1. ”Also, the transmittance is“ nearly zero ”, which is also an ideal state, and the transmittance in that wavelength region. May be much smaller than the transmittance in other wavelength regions, and some may have “non-zero” transmittance.

  In addition, both the primary color system and the complementary color system need only pass the wavelength region component of a predetermined color (primary color or complementary color) in the visible light VL region, which is a transmission wavelength region component, and are reflected wavelength region components. It does not matter whether the infrared light IR region is transmitted, that is, the transmittance for the infrared light IR. This is because the infrared light IR component is cut by the dielectric laminated film 1.

  For example, as shown in FIG. 3, the dielectric multilayer film 1 is not formed only on one pixel 12IR in a unit pixel matrix 12 composed of four pixels (cells), and other red (R), green ( While forming the dielectric laminated film 1 on the pixels 12R, 12G, and 12B for the three colors G) and blue (B), the corresponding red (R), green (G), and blue (B) 3 Primary color filters 14R, 14G, and 14B are provided.

  Further, in order to increase sensitivity, as shown in FIG. 3, in the pixel 12IR in which the dielectric laminated film 1 is not formed, the color filter so that not only the infrared light IR but also the visible light VL simultaneously contributes to the signal. Do not put 14C. By doing so, the infrared light pixel 12IR can substantially function as a pixel that serves not only for the infrared light IR but also for the infrared light IR and the visible light VL.

  In particular, by dividing the unit pixel matrix 12 composed of four pixels into the pixels 12R, 12G, 12B, and 12IR in this way, the entire configuration of the image sensor (spectral image sensor 11) can be arranged without any gap, so that the design can be improved. It becomes easy.

  In this way, by combining one image based on each color component of red (R), green (G), and blue (B) obtained from the three pixels 12R, 12G, and 12B, infrared light can be synthesized. A color image of visible light VL that is almost unaffected by IR (so-called normal color image) is obtained, and at the same time, infrared light based on a component that mixes infrared light IR and visible light VL obtained from the pixel 12IR. It is possible to take images related to IR.

  Here, “image related to infrared light IR” means an image of only infrared light IR that is not substantially affected by visible light VL, or an image in which infrared light IR and visible light VL are mixed. . In order to obtain an image of only the infrared light IR that is hardly affected by the visible light VL with the configuration shown in FIG. 3, for example, a component in which the infrared light IR obtained from the pixel 12IR and the visible light VL are mixed, It is preferable to take a difference from each color component of red (R), green (G), and blue (B) obtained from the three pixels 12R, 12G, and 12B. Even without providing a green filter 14G or a black filter 14BK, which will be described later, blue, red, and green obtained from the output of the pixel 12IR that receives visible light VL and infrared light IR by the three pixels 12R, 12G, and 12B. This is because the intensity of the infrared light IR can be obtained by reducing the intensity of.

  In addition, when considering applications such as optical communication applications and applications that detect the position by tracking infrared emission points, such as applications that simultaneously capture infrared IR images that are not substantially affected by visible light VL, On the pixel 12IR, a color filter 14C that transmits at least the infrared light IR that is the reflected wavelength region component and the predetermined wavelength component of the visible light VL that is the transmitted wavelength region component may be inserted.

  For example, by providing a green filter 14G that transmits infrared light IR and green light G as the color filter 14C, a mixed component of infrared light IR and green visible light LG can be obtained from the pixel 12IR. By taking the difference from the green component of only the visible light VL obtained from the pixel 12G, an image of only the infrared light IR that is hardly affected by the visible light VL (here, the green light G) is obtained. Although it is necessary to provide the green filter 14G, the process becomes simpler than the case of reducing the blue, red, and green intensities obtained by the three pixels 12R, 12G, and 12B without providing the green filter 14G.

  Alternatively, when the black filter 14BK that passes the infrared light IR and absorbs only the visible light VL is provided as the color filter 14C, the visible light VL is absorbed by the black filter 14BK, so that the infrared light is transmitted from the pixel 12IR. A component of only the light IR is obtained, and an image of only the infrared light IR that is hardly affected by the visible light VL can be obtained without performing the difference processing.

  It should be noted that R, G, and B color filters that are generally used at present are highly transmissive with respect to each of R, G, and B in the visible light band, for example, other colors (for example, G and B for R). ) Is low, but the transmittance outside the visible light band is not specified, and is usually higher than the transmittance of other colors (for example, G or B for R). It has sensitivity in the region and has light transmission in the infrared region. However, in this embodiment, even such a characteristic having a high transmittance outside the visible light band is not affected.

<< Design method of dielectric laminated film; Infrared light cut example >>
<Design method of thickness dj>
4-6 is a figure explaining the basic concept of the method of designing the dielectric laminated film 1. FIG. Here, a design example will be described in which the dielectric laminated film 1 is composed of basic first and second layer materials and selectively reflects infrared light IR.

As shown in the structural diagram of FIG. 4, the dielectric laminated film 1 used in the present embodiment has thick silicon oxide SiO ₂ on both sides (hereinafter, the light incident side is referred to as the 0th layer and the opposite side is referred to as the kth layer). A plurality of dielectric layers 1_j made of first and second layer materials are stacked between each other (hereinafter referred to as SiO2). In the illustrated example, a general material is used for both the first and second layer materials forming the dielectric layer 1_j, and silicon nitride Si ₃ N ₄ (hereinafter referred to as SiN) is used as the first layer material. These are alternately laminated by using two kinds of silicon oxide SiO2 as the second layer material. In addition, the structure of the dielectric laminated film 1 assumes that there are sufficiently thick silicon oxide SiO2 layers above and below (d0 = dk = ∞).

  Such a dielectric laminated film 1 can effectively increase the reflectance by satisfying the condition of the following formula (1).

  Here, dj (j is the layer number; hereinafter the same) is the thickness of each dielectric layer 1_j constituting the dielectric multilayer film 1, nj is the refractive index of each dielectric layer 1_j, and λ0 is the reflection The center wavelength in the wavelength region (hereinafter referred to as the reflection center wavelength).

  The number of layers of each dielectric layer 1_j constituting the dielectric laminated film 1 is counted, for example, in order from the first layer to the k-th layer side without counting the thick silicon oxide SiO2 on both sides as the number of layers. , SiN layer / SiO 2 layer / SiN layer 3 layers, SiN layer / SiO 2 layer / SiN layer / SiO 2 layer / SiN layer 5 layers. FIG. 4 shows a seven-layer structure.

  Further, the refractive index nα = 2.03 of the silicon nitride SiN forming the odd-numbered layer, the zeroth-numbered, even-numbered and k-th layers, with the reflection center wavelength λ0 = 900 nm of the infrared light IR being the reflection wavelength region. The refractive index nβ = 1.46 of the silicon oxide SiO2 forming the refractive index difference Δn is 0.57.

  Further, according to the above formula (1), the silicon nitride SiN thickness dα (= d1, d3,..., J = odd) is 111 nm, and the silicon oxide SiO2 layer thickness dβ (= d2, d4,..., J = even). Is 154 nm.

  FIG. 5 shows the result (reflection spectrum diagram) of the reflectance R calculated by the effective Fresnel coefficient method for the structure of FIG. 4 using a general material while changing the number of layers. You can see the number-dependent characteristics.

  From the results of FIG. 5, it can be seen that as the number of layers increases, the reflectance R increases with the reflection center wavelength λ0 = 900 nm of the infrared light IR as the center. Furthermore, it can be seen that the infrared light IR and the visible light VL are substantially separated by selecting the wavelength 900 nm as the reflection center wavelength λ0 in this way. Here, it can be seen that the reflectivity R is 0.5 or more by using 5 layers or more, and particularly the reflectivity exceeds 0.7 by using 7 layers or more.

  FIG. 6 is a diagram illustrating the variation dependency (relationship with variation) of the thickness of the dielectric layer 1_j. Here, the result (reflection spectrum diagram) calculated by changing the thickness dj of each dielectric layer 1_j by ± 10% is shown by taking the case of seven layers as an example.

  Conditional expression (1) is an ideal calculated value by the Fresnel coefficient method, but in reality, the condition of expression (1) is gentle and wide. For example, it has been found by calculation using the Fresnel coefficient method that the reflectivity can be effectively increased even if there is an error in the thickness dj of ± 10%.

  For example, as shown in FIG. 6, it has been found that the reflectance R can be effectively increased even if the thickness dj varies. For example, a sufficient reflectance R of 0.5 or more is obtained at the reflection center wavelength λ0 = 900 nm of the infrared light IR, and the entire infrared light IR (mainly longer wavelength side than 780 nm) is obtained. However, it turns out that reflection is strong. Therefore, in practice, if the thickness dj of the dielectric layer 1_j is in the range of the following formula (2), taking into account variations, a sufficient effect can be obtained in effectively increasing the reflectance. Become.

<Design method of reflection center wavelength λ0>
7 to 9 are diagrams for explaining conditions of the reflection center wavelength λ0. The numerical condition of the thickness dj depends on the bandwidth ΔλIR of the infrared reflection region of the spectrum. As shown in FIG. 7A showing the concept of the reflection spectrum, when the bandwidth ΔλIR of the infrared reflection region is wide, reflection with visible light VL is remarkable unless the center wavelength λ0 is provided on the long wavelength side. Become. On the contrary, as shown in FIG. 7B showing the concept of the reflection spectrum, when the bandwidth ΔλIR of the infrared reflection region is narrow, it is close to the visible light VL unless the center wavelength λ0 is provided on the short wavelength side. Reflection in the infrared region does not occur.

  By the way, if the infrared light IR in the range of 0.78 μm ≦ λ ≦ 0.95 μm in the infrared region is reflected from the graph of the absorption spectrum of silicon Si shown in FIG. As you can see it will be enough. This is because light having a wavelength longer than the wavelength of 0.95 μm is hardly absorbed inside the silicon Si and is not photoelectrically converted. Therefore, the reflection center wavelength λ0 may be selected so that infrared light IR having a wavelength in the range of 0.78 μm ≦ λ ≦ 0.95 μm can be reflected.

  Further, even in the visible light VL, it may be considered that the light in the range of 640 to 780 nm in the red (R) region does not particularly affect the performance of the image sensor even if it is reflected or not because of low visibility. . Therefore, there is no problem even if reflection occurs in the wavelength region of 640 to 780 nm.

  Further, the bandwidth ΔλIR of the infrared reflection region becomes wider when the refractive index difference Δn of the dielectric laminated film 1 is large, and conversely becomes narrower when the refractive index difference Δn is small. Therefore, the bandwidth λIR of the infrared reflection region is narrow in the case of the SiN / SiO 2 multilayer film and wide in the case of the Si / SiO 2 multilayer film.

  From these facts, in the case of a SiN / SiO 2 multilayer film (refractive index difference Δn = 0.57), 780 nm ≦ λ0 ≦ 950 nm is calculated from the reflection center wavelengths λ0 of 780 nm and 950 nm shown in the reflection spectrum diagram of FIG. If it is in the range, it can be seen that the above-mentioned conditions are substantially satisfied. Incidentally, FIG. 8 has a laminated structure as shown in FIG. 13 described later, and is calculated by changing only the film thickness dj of the dielectric layer 1_j so that λ0 = 780 nm and λ0 = 950 nm.

  Similarly, in the case of a Si / SiO 2 multilayer film (refractive index difference Δn = 2.64), as shown in the reflection spectrum diagram of FIG. 9, the above condition is substantially satisfied if it is in the range of 900 nm ≦ λ0 ≦ 1100 nm.

  From the above, in the combination of silicon nitride SiN or silicon Si and silicon oxide SiO2, the following formula (3-1) should be satisfied as the reflection center wavelength λ0. Preferably, the following formula (3-2) is satisfied. These mean that it is ideal that the vicinity of 900 nm be the reflection center wavelength λ0.

  Of course, the materials shown above are only examples, and the effects as described above are not necessarily limited to the combination of silicon oxide SiO2 and silicon nitride SiN layer, and the refractive index difference is 0.3 or more, more preferably It was estimated by calculation that a similar effect can be obtained by selecting a material having 0.5 or more.

For example, the composition of the SiN film may vary slightly depending on the manufacturing conditions. Further, as the dielectric layer 1_j constituting the dielectric laminated film 1, alumina Al ₂ O ₃ , zirconia ZrO ₂ (refractive index 2.05), titanium oxide TiO _{2 in} addition to silicon oxide SiO 2 and silicon nitride SiN. (Refractive index 2.3 to 2.55), oxides such as magnesium oxide MgO and zinc oxide ZnO (refractive index 2.1), polycarbonate PC (refractive index 1.58), and acrylic resin PMMA (refractive index 1.49). ) And other semiconductor materials such as silicon carbide SiC (refractive index 2.65) and germanium Ge (refractive index 4 to 5.5) can also be used.
By using a polymer material, an optical filter having characteristics not found in conventional glass can be configured. That is, it can be made of plastic and is lightweight and excellent in durability (high temperature, high humidity, impact).

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; First Embodiment >>
10 to 14 are views for explaining a first embodiment of the spectral image sensor 10 that supports the single wavelength demultiplexing using the dielectric laminated film 1. The first embodiment is configured using a basic design method of a demultiplexing image sensor using a dielectric laminated film. Here, the spectral image sensor 10 is designed to receive the visible light VL component by cutting the infrared light IR by using the dielectric laminated film 1 that selectively reflects the infrared light IR. An example is given.

  4 to 6 is a semiconductor element layer in which the refractive index of the sensing element such as a silicon (Si) photodetector formed on the dielectric laminated film 1 is larger than each dielectric layer 1_j forming the dielectric laminated film 1 In manufacturing the above, the distance from the semiconductor element layer to the dielectric laminated film 1, that is, the thickness dk of the silicon oxide SiO2 layer forming the kth dielectric layer 1_k is important.

  As shown in the structural diagram of FIG. 10, this is due to an interference effect with the reflected light L4 from the surface of the silicon substrate 1_ω, which is the surface of a semiconductor element layer (photodetector, etc.) made of silicon Si (refractive index 4.1), for example. This means that the spectrum of the total reflected light LRtotal changes.

  FIG. 11 is a reflection spectrum diagram for explaining the dependence of the total reflected light LRtotal on the variation of the thickness dk of the silicon oxide SiO2 layer forming the dielectric layer 1_k. Here, the calculation result of the dielectric multilayer film 1 having the seven-layer structure shown in FIG. 4 while changing the thickness dk of the dielectric layer 1_k is shown. In each figure in FIG. 11, the horizontal axis is the wavelength λ (μm), and the vertical axis is the reflectance R.

  As can be seen from each diagram in FIG. 11, when the thickness is dk = 0.154 μm, that is, when the reflection center wavelength λ0 of the infrared light IR is a value satisfying the conditional expression (1), the reflection spectrum is almost the same. It can be seen that infrared light IR (wavelength λ ≧ 780 nm) is strongly reflected without being affected. On the other hand, it can be seen that another vibration occurs in the spectrum of thickness dk = 0.3 to 50 μm, compared to the reflection spectrum of thickness dk = ∞. As a result, it can be seen that there is a wavelength region in which the reflection in the infrared is dip-shaped.

  However, when the thickness dk = 2.5 μm or more, the half width of the infrared dip becomes 30 nm or less, and particularly when the thickness dk = 5.0 μm or more, the half width becomes 20 nm or less. On the other hand, the half-value width is sufficiently narrowed, so that the averaged reflectance is obtained. Further, it can be seen that the reflectance with visible light VL is high with respect to the spectrum having a thickness dk = 0.3 to 1.0 μm. From these facts, it can be said that the thickness dk = 0.154 μm, that is, the value satisfying the conditional expression (1) is optimal.

  FIG. 12 is a reflection spectrum diagram illustrating the variation dependency of the thickness dk of the silicon oxide SiO2 layer forming the dielectric layer 1_k, and is calculated by changing the value of the thickness dk, particularly in the vicinity of the thickness dk = 0.154 μm. The results are shown. In each figure in FIG. 12, the horizontal axis is the wavelength λ (μm), and the vertical axis is the reflectance R.

  As can be seen from this result, reflection with visible light VL can be suppressed if the thickness dk = 0.154 to 0.16 μm with the thickness dk = 0.154 μm satisfying the conditional expression (1) as the center. I understand.

  From the above, the optimum structure of the spectroscopic image sensor 10 is, as shown in the structural diagram of FIG. 13, substantially the dielectric layered film 1A having an eight-layer structure including the kth dielectric layer 1_k. The calculation result of the reflection spectrum is as shown in the reflection spectrum diagram of FIG. In other words, the dielectric laminated film 1A has a structure in which a layer made of silicon oxide SiO2 that is the second layer material is provided for four periods on the silicon substrate 1_ω.

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; Second Embodiment >>
FIGS. 15 to 18 are diagrams illustrating a second embodiment of the spectral image sensor 10 that supports the single wavelength demultiplexing using the dielectric laminated film 1. The second embodiment is configured by applying a modification (No. 1) of the design method of the first embodiment, and is based on the method described in FIGS. 10 to 14 in the visible light region. It is modified so as to reduce reflection.

  In the first modification, the refractive index nk of the kth dielectric layer 1_k and the refractive index nω of the silicon substrate 1_ω (= 4) are provided between the kth dielectric layer 1_k and the silicon substrate 1_ω. .1) is characterized in that a third layer material having an intermediate refractive index is added.

  Corresponding to this deformation, in the constant design of the first to seventh layers of the dielectric laminated film 1, the reflection center wavelength λ0 of the infrared light IR is changed to 852 nm on the lower side instead of 900 nm. The thickness dα (= d1, d3,..., J = odd) of silicon nitride SiN is 105 nm, and the thickness dβ (= d2, d4,..., J = even) of the silicon oxide SiO2 layer is 146 nm. This is because the reflectance of visible light is reduced by newly inserting a thin SiN layer (30 nm), and at the same time, the reflectance near the boundary between visible light and infrared light is reduced to 780 nm. This is to compensate for this decrease by shifting to, that is, to efficiently cut infrared light near the boundary. Of course, the reflection center wavelength λ0 of the infrared light IR may be kept at 900 nm.

  Specifically, in the structure of the first modified example shown in FIG. 15, a third silicon nitride SiN layer 1_γ having a relatively thin thickness dγ is provided between the silicon oxide SiO2 of the kth layer and the silicon substrate 1_ω. It has a laminated structure as a layer material. Here, the thickness dγ = 0.030 μm. The calculation result of the reflection spectrum is as shown in FIG.

  The third layer material added in the first modification is the same as the silicon nitride SiN that is the first layer material, but any member having a refractive index larger than that of the silicon substrate 1_ω may be used. Other members may be used.

  The spectroscopic image sensor 10 having the dielectric multilayer film 1 of the modification of the first example is substantially composed of a seven-layer dielectric multilayer film 1, a k-th dielectric layer 1_k (silicon oxide SiO2 layer), and Including the two layers of the silicon nitride SiN layer 1_γ, the dielectric multilayer film 1B having a nine-layer structure as a whole is provided.

  In the structure of the second modification example shown in FIG. 17, the third layer material added in the first modification example and the silicon substrate 1_ω have a refractive index smaller than that of the third layer material. The fourth layer material is laminated. Specifically, a silicon oxide SiO2 layer 1_δ is used as a fourth layer material between a silicon nitride SiN layer 1_γ having a thickness dγ and a silicon substrate 1_ω, and the thickness dδ = It is 0.010 μm. The calculation result of the reflection spectrum is as shown in FIG.

  The fourth layer material added in the second modification is the same as the second layer material, silicon oxide SiO2, but is smaller than the third layer material (silicon nitride SiN in this example). Any member having a refractive index may be used, and other members may be used.

  The spectral image sensor 10 having the dielectric multilayer film 1 of the modification of the second example substantially includes a seven-layer dielectric multilayer film 1 and a k-th dielectric layer 1_k (silicon oxide SiO2 layer). A dielectric laminated film 1C having a 10-layer structure as a whole is provided, including three layers of the silicon nitride SiN layer 1_γ and the silicon oxide SiO2 layer 1_δ. In other words, the dielectric multilayer film 1C has a structure in which five layers of silicon oxide SiO2 that is the second layer material are provided on the silicon substrate 1_ω.

  In the first example and the second example, there is a difference in the presence or absence of the silicon oxide SiO 2 layer 1_δ, but as can be seen from FIGS. 16 and 18, the reflectance with visible light VL is sufficiently lowered. Moreover, the effect which can reduce a dark current is acquired by adding silicon oxide SiO2 layer 1_delta like a 2nd example. It should be noted that the relationship between the thicknesses of both layers is preferably dδ << dγ so that the effect of adding the silicon nitride SiN layer 1_γ is not reduced by adding the silicon oxide SiO 2 layer 1_δ.

  In this way, an intermediate refractive index nγ (= nSiN) between the refractive index nk (= nSiO2) and the refractive index nω (= nSi) between the silicon oxide SiO2 of the kth layer and the silicon substrate 1_ω. By adding a thin silicon nitride SiN layer 1_γ as an intermediate layer as an intermediate member, reflection by visible light VL can be suppressed. This is understood when considered as follows.

  First, when the wavelength of visible light VL is λVL, the intermediate refractive index of the layer is Nm, and the thickness of the layer is dm, the conditional expression (4) is obtained from the theory of the low reflection film similar to the conditional expression (1). When the conditional expression (4) is satisfied, a sufficient effect is exhibited.

  Here, since the wavelength λVL indicates the entire visible light VL, the wavelength range is given by Expression (5).

  In each modification of the first example and the second example, the silicon nitride SiN layer 1_γ is added as an intermediate layer and the refractive index is nγ (= nSiN = Nm). Can be transformed as shown in the equation (6) showing the thickness dm of the intermediate layer, that is, the thickness dγ of the silicon nitride SiN layer 1 — γ.

  Although it is ideal that the thickness dm of the intermediate layer satisfies the expression (6), it may be slightly deviated from that, and according to an experiment, there is a margin especially for the thinner one. As can be seen from FIG. 18, as an example, it was confirmed that there was an effect even when dm = 30 nm. Of course, since an intermediate layer (third layer material) is added between the silicon oxide SiO2 of the kth layer and the silicon substrate 1_ω, the thinner one is larger than 0 nm (not including 0 nm). Needless to say. That is, when an intermediate layer is added between the kth silicon oxide SiO2 and the silicon substrate 1_ω, the thicknesses dm and dγ of the intermediate layer only need to satisfy Expression (7).

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; Third Embodiment >>
FIGS. 19 to 24 are views for explaining a third embodiment of the spectral image sensor 10 that supports the single wavelength demultiplexing using the dielectric laminated film 1. Here, FIGS. 19 to 22 are diagrams for explaining the dielectric laminated film 1 constituting the spectral image sensor 10 of the third embodiment, and FIGS. 23 to 24 are dielectric laminated films of the third embodiment. 1 is a diagram for explaining a spectral image sensor 10 that supports single wavelength demultiplexing using 1. FIG.

  The third embodiment is configured by applying a modification (No. 2) of the design method of the first embodiment, in that the number of dielectric layers 1_j forming the dielectric multilayer film 1 is reduced. Has characteristics. In reducing the number of layers, a member (layer material) having a refractive index larger than that of the basic first and second layer materials constituting the dielectric multilayer film 1 is added in the dielectric multilayer film 1. Characterized by points.

  In adding this member having a large refractive index, the larger one of the basic two layer materials may be replaced with the fifth layer material having a larger refractive index. The dielectric laminated film 1 of this modified example (No. 2) is substantially a dielectric laminated film 1D having a structure including the fifth layer material 1_η. In other words, the dielectric multilayer film 1D has a structure in which a layer made of silicon oxide SiO2 that is the second layer material is provided for N periods on the silicon substrate 1_ω.

  Regarding the thickness dη of the fifth layer material, when the refractive index is nη, the conditional expression (8) is obtained from the theory of the low reflection film similar to the conditional expression (1), and the conditional expression (8) When satisfied, it will show a sufficient effect.

  For example, in the example shown in the structural diagram of FIG. 19, a silicon nitride layer having a refractive index = 4.1 higher than silicon nitride SiN and silicon oxide SiO 2 and having a thickness dη = 61 nm is used as the fifth layer material. Instead of SiN, only one layer is added (in place of the intermediate third dielectric layer 1_3). The calculation result of the reflection spectrum is as shown in the reflection spectrum diagram shown in FIG.

  Here, FIG. 22 shows the calculation result when the total number of layers is changed when the silicon nitride SiN forming the middle layer of the dielectric multilayer film 1 having an odd total number of layers is changed to silicon Si. ing.

  In FIG. 19, in the constant design of each layer of the dielectric laminated film 1, the reflection center wavelength λ0 of the infrared light IR is changed to 1000 nm instead of 900 nm, and the thickness dα (= d1, d3) of the silicon nitride SiN is changed. ,...; J = odd) is 123 nm, and the thickness dβ (= d2, d4,...; J = even) of the silicon oxide SiO 2 layer is 171 nm.

  Further, in the example shown in the structural diagram of FIG. 21, in the constant design of each layer of the dielectric laminated film 1, the reflection center wavelength λ0 of the infrared light IR is set to 900 nm, and the thickness dα of silicon nitride SiN (= d1, .., j = odd) is 111 nm, the thickness dβ (= d2, d4,...; j = even) of the silicon oxide SiO 2 layer is 154 nm, and a silicon Si layer having a thickness dη = 55 nm is used as the fifth layer material. Instead of silicon nitride SiN, only one layer is added. The calculation result of the reflection spectrum is as shown in the reflection spectrum diagram shown in FIG.

  The fifth layer material added in the second modification is the same as the silicon substrate 1_ω that forms the semiconductor element layer, but is larger than the dielectric layer 1_j other than the fifth layer material that forms the dielectric multilayer film 1. Any member having a refractive index may be used, and other members may be used.

  As can be seen from the calculation results of the reflection spectra shown in FIG. 20 and FIG. # A4-8, a layer material having a refractive index larger than that of the dielectric layer 1_j other than the fifth layer material forming the dielectric multilayer film 1 is used. By adding, sufficient reflectance can be obtained with a small number of layers. In particular, in the case of five layers, it can be seen that the bandwidth in the visible light VL is sufficiently wide and is optimal for separating the visible light VL and the infrared light IR.

  As described with reference to FIGS. 10 to 12 in the first embodiment, when the dielectric multilayer film 1D is formed on the semiconductor element layer (silicon substrate 1_ω), the dielectric multilayer film 1D is formed from the semiconductor element layer. Distance, that is, the thickness dk of the silicon oxide SiO2 layer forming the kth dielectric layer 1_k is important.

  As shown in the structural diagram of FIG. 23, this is due to an interference effect with the reflected light LR from the surface of the silicon substrate 1_ω, which is the surface of a semiconductor element layer (photodetector, etc.) made of silicon Si (refractive index 4.1). This means that the spectrum of the total reflected light LRtotal changes.

  FIG. 24 is a reflection spectrum diagram for explaining the dependence of the total reflected light LRtotal on the thickness dk of the silicon oxide SiO2 layer forming the dielectric layer 1_k in the five-layered dielectric laminated film 1D shown in FIG. It is. In each figure in FIG. 24, the horizontal axis is the wavelength λ (μm), and the vertical axis is the reflectance R.

  As can be seen from each figure in FIG. 24, when the thickness dk = 0.15 μm, that is, when the reflection center wavelength λ0 of the infrared light IR satisfies the value dk = 0.154 μm that satisfies the conditional expression (1). Further, it can be seen that the reflection spectrum is hardly affected, and the infrared light IR (wavelength λ ≧ 780 nm) is strongly reflected. On the other hand, it can be seen that another vibration occurs in the spectrum of thickness dk = 0.3 to 50 μm, compared to the reflection spectrum of thickness dk = ∞. As a result, it can be seen that there is a wavelength region in which the reflection in the infrared is dip-shaped. This is the same as described with reference to FIGS. 11 and 12 in the first embodiment.

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; Fourth Embodiment >>
FIGS. 25 and 26 are diagrams illustrating a fourth embodiment of the spectral image sensor 10 compatible with single wavelength demultiplexing using the dielectric laminated film 1.

  The fourth embodiment is a modification of the third embodiment in which the number of dielectric layers 1_j forming the dielectric multilayer film 1 is reduced, and is characterized in that the number of layers is further reduced. Have. Specifically, in reducing the number of layers, a plurality of members (layers) having a refractive index larger than the basic first and second layer materials constituting the dielectric multilayer film 1 in the dielectric multilayer film 1. It is characterized by the addition of material. In adding a plurality of members having a large refractive index, the larger one of the basic two layer materials may be replaced with a fifth layer material having a larger refractive index. . The dielectric multilayer film 1 of this modification is substantially a dielectric multilayer film 1E having a structure including a plurality of fifth layer materials 1_η.

  The plurality of fifth layer materials 1_η may be members having a refractive index larger than that of the dielectric layer 1_j other than the fifth layer material forming the base dielectric multilayer film 1 as in the third embodiment. That's fine. Further, all of the plurality of members may be the same member or different members.

  Regarding the thickness dηp of the plurality of fifth layer materials, when the refractive index is nηp, the conditional expression (9) is obtained from the theory of the low reflection film similar to the conditional expression (1), and the conditional expression (9 ) Will be fully effective.

  For example, in the example shown in the structural diagram of FIG. 25, a dielectric laminated film 1E having a three-layer structure is formed, and a thickness dη = 61 nm having a refractive index = 4.1 higher than that of silicon nitride SiN and silicon oxide SiO2. Two layers of silicon Si layers are provided as a fifth layer material in place of silicon nitride SiN. The calculation result of the reflection spectrum is as shown in the reflection spectrum diagram shown in FIG. In other words, the dielectric laminated film 1E has a structure in which a layer made of silicon oxide SiO2 that is the second layer material is provided for two periods on the silicon substrate 1_ω.

  In the constant design of each layer of the dielectric laminated film 1, the reflection center wavelength λ0 of the infrared light IR is set to 1000 nm, and the thickness dη (= d1, d3) of the silicon Si layer as the fifth layer material is 61 nm. The thicknesses dβ (= d2) and dk of the silicon oxide SiO 2 layer are 171 nm.

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; Fifth Embodiment >>
FIGS. 27 and 28 are diagrams for explaining a fifth embodiment of the spectral image sensor 10 compatible with single wavelength demultiplexing using the dielectric laminated film 1.

  In the fifth embodiment, the spectral image sensor 10 of the third or fourth embodiment is modified so as to reduce reflection in the visible light region as in the second embodiment.

  In the example shown in the structural diagram of FIG. 27, with respect to the dielectric multilayer film 1E of the fourth embodiment shown in FIG. 25, the k-th layer is provided between the k-th dielectric layer 1_k and the silicon substrate 1_ω. A third layer material having an intermediate refractive index is added to the refractive index nk of the dielectric layer 1_k of the eye and the refractive index nω (= 4.1) of the silicon substrate 1_ω. Unlike the second embodiment, the reflection center wavelength λ0 of the infrared light IR is kept at 1000 nm. Of course, as in the second embodiment, the reflection center wavelength λ0 of the infrared light IR may be changed to a lower side instead of 1000 nm.

  Specifically, in the structure shown in FIG. 27, as in the first modification of the second embodiment, silicon having a relatively thin thickness dγ between the silicon oxide SiO2 in the k-th layer and the silicon substrate 1_ω. The nitride SiN layer 1_γ is stacked as a third layer material. Here, the thickness dγ = 0.030 μm. The calculation result of the reflection spectrum is as shown in the reflection spectrum diagram shown in FIG. The spectral image sensor 10 having the dielectric multilayer film 1 of this modification is substantially composed of a dielectric multilayer film 1 of three layers, a dielectric layer 1_k (silicon oxide SiO2 layer) of the kth layer, and silicon nitride. As a whole, including the two layers of the SiN layer 1_γ, the dielectric laminated film 1F having a five-layer structure is provided.

  The third layer material added in this modification is the same as the silicon nitride SiN that is the first layer material, but any member having a higher refractive index than the silicon substrate 1_ω may be used. It may be a member.

  Although not shown, like the second modification example in the second embodiment, a refractive index smaller than that of the third layer material is provided between the third layer material added in this modification example and the silicon substrate 1_ω. It is also possible to have a structure in which a fourth layer material having a thickness is laminated.

  In any case, as in the second embodiment, the reflectance in the visible light VL region can be reduced, and in particular, the reflectance in the blue B component (wavelength near 420 nm) and the green G component (wavelength near 520 nm) is slightly higher. Although increasing, the reflectance in the red R component (wavelength near 600 nm) can be sufficiently lowered, and is suitable for separation from infrared light IR.

<Imaging device with spectral image sensor; CCD compatible>
29 and 30 are circuit diagrams in the case where the spectral image sensors 10 and 11 described in the above embodiment are applied to an imaging apparatus using an interline transfer type CCD solid-state imaging device (IT_CCD image sensor). The imaging apparatus 100 is an example of a physical information acquisition apparatus according to the present invention.

  Here, FIG. 29 shows a structure in which the infrared light IR is detected while dividing the visible light VL band into R, G, and B color components as in FIG. The light B, the green light G, the red light R, and the infrared light IR are each independently detected, and the pixels (photoelectric conversion elements) 12B for each wavelength in one unit pixel matrix 12 substantially. , 12G, 12R, and the pixel 12IR that does not have the dielectric laminated film 1.

  For example, as shown in FIG. 29A, the CCD solid-state imaging device 101 is provided with a plurality of vertical transfer CCDs 122 arranged in the vertical transfer direction in addition to the unit pixel matrix 12. The charge transfer direction of the vertical transfer CCD 122, that is, the readout direction of the pixel signal is the vertical direction (X direction in the figure).

  Further, between the vertical transfer CCD 122 and each unit pixel matrix 12, a MOS transistor forming a readout gate 124 (124B, 124G, 124R, 124IR for each wavelength) is interposed, and the boundary of each unit cell (unit component). The part is provided with a channel stop (not shown).

  As can be seen from FIG. 29, one unit pixel matrix 12 has a structure in which the blue light B, the green light G, the red light B, and the infrared light IR are independently detected. In the pixel matrix 12, pixels 12B, 12G, 12R, and 12IR are formed for each wavelength (color). An imaging area is provided by a plurality of vertical transfer CCDs 122 that are provided for each vertical column of the sensor units 112 configured to include these unit pixel matrices 12 and vertically transfer the signal charges read from the sensor units by the read gate 124. 110 is configured.

  Here, as the arrangement of the color filters 14, for example, blue, green, red, IR, blue, green, red, IR,... In the vertical direction (X direction) of the vertical transfer CCD 122 on the light receiving surface side of the silicon substrate 1_ω. In the same row direction (Y direction) of the plurality of vertical transfer CCDs 122, the order is blue, green, red, IR, blue, green, red, IR,.

  The signal charges accumulated in the unit pixel matrix 12 (each pixel 12B, 12G, 12R, 12IR) of the sensor unit 112 are applied to the readout gate 124 by applying a drive pulse φROG corresponding to the readout pulse ROG to the same vertical column. To the vertical transfer CCD 122. The vertical transfer CCD 122 is driven to transfer by a drive pulse φVx based on a vertical transfer clock Vx such as 3 phase to 8 phase, for example, and the read signal charge is one scanning line (one line) in a part of the horizontal blanking period. Are transferred in the vertical direction one by one in order. This vertical transfer for each line is called a line shift.

  Further, the CCD solid-state imaging device 101 includes a horizontal transfer CCD 126 extending in a predetermined (for example, left and right) direction adjacent to each transfer destination side end of the plurality of vertical transfer CCDs 122, that is, the vertical transfer CCD 122 in the last row. (H register unit, horizontal transfer unit) are provided for one line. The horizontal transfer CCD 126 is driven by, for example, drive pulses φH 1 and φH 2 based on the two-phase horizontal transfer clocks H 1 and H 2, and the signal charge for one line transferred from the plurality of vertical transfer CCDs 122 is transferred to the horizontal blanking period. The data is sequentially transferred in the horizontal direction in the subsequent horizontal scanning period. For this reason, a plurality of (two) horizontal transfer electrodes corresponding to two-phase driving are provided.

  At the end of the transfer destination of the horizontal transfer CCD 126, for example, an output amplifier 128 having a charge-voltage conversion unit having a floating diffusion amplifier (FDA) configuration is provided. The output amplifier 128 is an example of a physical information acquisition unit. In the charge-voltage conversion unit, the signal charge horizontally transferred by the horizontal transfer CCD 126 is sequentially converted into a voltage signal, amplified to a predetermined level, and output. From this voltage signal, a pixel signal is derived as a CCD output (Vout) corresponding to the amount of incident light from the subject. The interline transfer type CCD solid-state imaging device 11 is configured as described above.

  The pixel signal derived from the output amplifier 128 as the CCD output (Vout) is input to the image signal processing unit 140 shown in FIG. The image signal processing unit 140 receives an image switching control signal from an image switching control unit 142 which is an example of a signal switching control unit.

  The image switching control unit 142 outputs the output of the image signal processing unit 140 to a monochrome image or a color image of visible light VL that is hardly affected by infrared light IR, and infrared light that is hardly affected by visible light VL. Command to switch to either one of IR images, or both of them, or a mixed image of visible light VL and infrared light IR, that is, a pseudo-monochrome image or a pseudo-color image in which the brightness of infrared light IR is added To do. That is, simultaneous imaging output and switching imaging output of an image of visible light VL and an image related to infrared light IR are controlled.

  This command may be an external input for operating the imaging device, or the image switching control unit 142 may command switching by an automatic process based on visible light luminance without infrared light IR of the image signal processing unit 140.

  Here, the image signal processing unit 140, for example, a synchronization process that simultaneously synchronizes the imaging data R, G, B, and IR of each pixel, and a vertical stripe noise correction process that corrects a vertical stripe noise component caused by a smear phenomenon or a blooming phenomenon. , WB control processing for controlling white balance (WB) adjustment, gamma correction processing for adjusting the gradation level, and dynamic range expansion processing for expanding the dynamic range using pixel information of two screens having different charge accumulation times Alternatively, YC signal generation processing for generating luminance data (Y) and color data (C) is performed. As a result, an image (so-called normal image) in the visible light VL band based on the imaging data (R, G, B, and IR pixel data) of the primary colors of red (R), green (G), and blue (B) is obtained. It is done.

  Further, the image signal processing unit 140 generates an image related to the infrared light IR using the pixel data of the infrared light IR. For example, in the pixel 12IR in which the dielectric laminated film 1 is not formed, when not including the color filter 14C so that not only the infrared light IR but also the visible light VL simultaneously contributes to the signal, the pixel data from the pixel 12IR By using, a highly sensitive image can be obtained. Alternatively, when the green filter 14G is inserted as the color filter 14C, a mixed image of the infrared light IR and the green visible light LG is obtained from the pixel 12IR, but the difference from the green component obtained from the pixel 12G is obtained. By taking it, an image of only infrared light IR can be obtained. Alternatively, when the black filter 14BK is provided as the color filter 14C, an image of only the infrared light IR can be obtained by using pixel data from the pixel IR.

  Each image generated in this manner is sent to a display unit (not shown) and presented to the operator as a visible image, or stored and stored in a storage device such as a hard disk device as it is, or to other functional units. Sent as processed data.

  FIG. 30 shows a structure for independently detecting visible light VL (blue light, green light, and red light) and infrared light IR. Although the detailed description is omitted, the basic configuration is the same as that shown in FIG. 29, and the visible light VL pixel 12W is formed in one unit pixel matrix 12 (photodiode group) substantially. However, the pixel 12IR does not have the dielectric laminated film 1. Basically, the arrangement of the color filter 14 is different, and the other points are the same as those in FIG.

  Here, the arrangement of the color filters 14 is, for example, visible light VL, infrared light IR, visible light VL, infrared light IR in the vertical direction (X direction) of the vertical transfer CCD 122 on the light receiving surface side of the silicon substrate 1_ω. In this order, visible light VL, infrared light IR, visible light VL, infrared light IR,... Are also arranged in the same row direction (Y direction) of the plurality of vertical transfer CCDs 122. .

<Image sensor using spectral image sensor; CMOS compatible>
31 and 32 are circuit diagrams when the spectral image sensor 10 described in the above embodiment is applied to an imaging apparatus using a CMOS solid-state imaging device (CMOS image sensor). The imaging apparatus 100 is an example of a physical information acquisition apparatus according to the present invention.

  Here, like FIG. 3, FIG. 31 shows a structure in which infrared light IR is detected while dividing the visible light VL band into R, G, B color components, and the blue light in the visible light VL is shown. The light B, the green light G, the red light R, and the infrared light IR are each independently detected, and the pixels (photoelectric conversion elements) 12B for each wavelength in one unit pixel matrix 12 substantially. , 12G, 12R, and the pixel 12IR that does not have the dielectric laminated film 1.

  FIG. 32 shows a structure in which visible light VL (blue light, green light, and red light) and infrared light IR are independently detected, and substantially one unit pixel matrix 12 (photodiode group). In this structure, a pixel 12W for visible light VL is formed, and a pixel 12IR that does not have the dielectric laminated film 1 is provided. Basically, only the arrangement of the color filters 14 is different (similar to FIG. 30), and the other points are the same as those of FIG.

  When the spectral image sensor is applied to the COMS, each cell (photoelectric conversion element) 12B, 12G, 12R, 12IR in the unit pixel matrix 12 has one cell amplifier. Therefore, in this case, the structure is as shown in FIG. The pixel signal is amplified by a cell amplifier and then output through a noise cancellation circuit or the like.

  For example, the CMOS solid-state imaging device 201 includes a pixel unit in which a plurality of pixels including a light receiving element (an example of a charge generation unit) that outputs a signal corresponding to the amount of incident light is arranged in rows and columns (that is, in a two-dimensional matrix). A signal output from each pixel is a voltage signal, and a CDS (Correlated Double Sampling) processing function unit, a digital conversion unit (ADC), etc. are provided in parallel in a column. It is a so-called typical column type.

  Specifically, as shown in FIG. 31, the CMOS solid-state imaging device 201 includes a pixel unit (imaging unit) 210 in which a plurality of pixels 12 are arranged in rows and columns, and a drive provided outside the pixel unit 210. A control unit 207, a column processing unit 226, and an output circuit 228 are provided.

  Note that an AGC (Auto Gain Control) circuit having a signal amplifying function or the like may be provided in the same semiconductor region as the column processing unit 226 if necessary before or after the column processing unit 226. When AGC is performed before the column processing unit 226, analog amplification is performed. When AGC is performed after the column processing unit 226, digital amplification is performed. If the n-bit digital data is simply amplified, the gradation may be lost. Therefore, it is preferable to perform digital conversion after amplification by analog.

  The drive control unit 207 has a control circuit function for sequentially reading signals from the pixel unit 210. For example, the drive control unit 207 includes a horizontal scanning circuit (column scanning circuit) 212 that controls column addresses and column scanning, a vertical scanning circuit (row scanning circuit) 214 that controls row addresses and row scanning, And a communication / timing control unit 220 having functions such as an inter-interface function and an internal clock generation function.

  The horizontal scanning circuit 212 has a function of a reading scanning unit that reads a count value from the column processing unit 226. Each element of these drive control units 207 is formed integrally with a pixel unit 210 in a semiconductor region such as single crystal silicon using a technique similar to a semiconductor integrated circuit manufacturing technique, and is an example of a solid-state imaging that is an example of a semiconductor system It is configured as an element (imaging device).

  In FIG. 31, for the sake of simplicity, some of the rows and columns are omitted, but in reality, tens to thousands of pixels 12 are arranged in each row and each column. The pixel 12 typically includes an intra-pixel amplifier (cell amplifier; pixel signal generation unit) 205 (color) having a unit pixel matrix 12 as a light receiving element (charge generation unit) and an amplification semiconductor element (for example, a transistor). Separately, 205B, 205G, 205R).

  Further, as can be seen from FIG. 31, one unit pixel matrix 12 has a structure for independently detecting blue light B, green light G, red light R, and infrared light IR, and substantially one unit. In the pixel matrix 12, pixels 12B, 12G, 12R, and 12IR are formed for each wavelength (color).

  Here, the arrangement of the color filters 14 is, for example, blue, green, red, IR, blue, green, red, IR,... In the X direction on the light receiving surface side of the silicon substrate 1_ω, and orthogonal to the X direction. Also in the Y direction, the order is blue, green, red, IR, blue, green, red, IR,.

  As the intra-pixel amplifier 205, for example, a floating diffusion amplifier configuration is used. As an example, with respect to the charge generation unit, a read selection transistor that is an example of a charge readout unit (transfer gate unit / read gate unit), a reset transistor that is an example of a reset gate unit, a vertical selection transistor, and a floating diffusion As a CMOS sensor having a source follower-amplifying transistor, which is an example of a detection element for detecting a change in potential, a sensor composed of four general-purpose transistors can be used.

  Alternatively, as described in Japanese Patent No. 2708455, an amplifying transistor connected to a drain line (DRN) and an in-pixel amplifier for amplifying a signal voltage corresponding to the signal charge generated by the charge generating unit It is also possible to use a transistor composed of three transistors, including a reset transistor for resetting 205 and a read selection transistor (transfer gate portion) scanned from a vertical shift register via a transfer wiring (TRF). it can.

  The pixels 12 are connected to the vertical scanning circuit 214 via a row control line 215 for row selection and to the column processing unit 226 via a vertical signal line 219, respectively. Here, the row control line 215 indicates the entire wiring that enters the pixel from the vertical scanning circuit 214. As an example, the row control line 215 is arranged in a direction parallel to the long scatterer 3.

  The horizontal scanning circuit 212 and the vertical scanning circuit 214 include, for example, a shift register and a decoder, and start an address selection operation (scanning) in response to a control signal given from the communication / timing control unit 220. Yes. Therefore, the row control line 215 includes various pulse signals (for example, a reset pulse RST, a transfer pulse TRF, a DRN control pulse DRN, etc.) for driving the pixels 12.

  Although not shown, the communication / timing control unit 220 is a master via a functional block of a timing generator TG (an example of a read address control device) that supplies a clock signal necessary for the operation of each unit and a pulse signal of a predetermined timing, and a terminal 220a. A communication interface functional block for receiving a clock CLK0, receiving data DATA for instructing an operation mode or the like via a terminal 220b, and outputting data including information of the CMOS solid-state imaging device 201 via a terminal 220c.

  For example, the horizontal address signal is output to the horizontal decoder and the vertical address signal is output to the vertical decoder, and each decoder receives it and selects the corresponding row or column, and the pixel 12 and the column processing unit 226 via the drive circuit. Drive.

  At this time, since the pixels 12 are arranged in a two-dimensional matrix, an analog pixel signal generated by the in-pixel amplifier (pixel signal generation unit) 205 and output in the column direction via the vertical signal line 219 is row-by-row. (Column parallel) to access and capture (vertical) scan reading, and then access the row direction, which is the arrangement direction of the vertical columns, and read out pixel signals (for example, digitized pixel data) to the output side (horizontal ) It is preferable to speed up reading of pixel signals and pixel data by performing scanning reading. Of course, not only scanning reading but also random access for reading out only necessary pixel 12 information by directly addressing the pixel 12 to be read out is possible.

  In the communication / timing control unit 220, a clock CLK1 having the same frequency as the master clock (master clock) CLK0 input via the terminal 220a, a clock obtained by dividing the clock CLK1, and a low-speed clock obtained by further dividing the clock are used as devices. For example, a horizontal scanning circuit 212, a vertical scanning circuit 214, a column processing unit 226, and the like.

  The vertical scanning circuit 214 selects a row of the pixel portion 210 and supplies a necessary pulse to the row. For example, a pulse is supplied to a vertical decoder that defines a readout row in the vertical direction (selects a row of the pixel unit 210) and a row control line 215 for the pixel 12 on the readout address (in the row direction) defined by the vertical decoder. And a vertical drive circuit for driving. Note that the vertical decoder selects a row for electronic shutter in addition to a row from which a signal is read.

  The horizontal scanning circuit 212 sequentially selects column circuits (not shown) in the column processing unit 226 in synchronization with the low-speed clock CLK2, and guides the signal to a horizontal signal line (horizontal output line) 218. For example, a horizontal decoder that defines a read column in the horizontal direction (selects individual column circuits in the column processing unit 226), and a read address defined by the horizontal decoder, the selection switch 227 causes the column processing unit 226 to A horizontal drive circuit for guiding each signal to a horizontal signal line 218. For example, if the horizontal signal line 218 corresponds to the number of bits n (n is a positive integer) handled by the column AD circuit, for example, 10 (= n) bits, 10 horizontal signal lines 218 are arranged corresponding to the number of bits.

  In the CMOS solid-state imaging device 201 having such a configuration, the pixel signal output from the pixel 12 is supplied to the column circuit of the column processing unit 226 via the vertical signal line 219 for each vertical column. Here, the signal charges accumulated in the unit pixel matrix 12 (the respective pixels 12B, 12G, 12R, and 12IR) are read out through the vertical signal lines 219 in the same vertical column.

  Each column circuit of the column processing unit 226 receives a pixel signal for one column and processes the signal. For example, each column circuit has an ADC (Analog Digital Converter) circuit that converts an analog signal into, for example, 10-bit digital data using, for example, a low-speed clock CLK2.

  In addition, by devising the circuit configuration, the signal level (noise level) immediately after pixel reset and the true signal (depending on the amount of received light) for the voltage mode pixel signal input via the vertical signal line 219 A process for obtaining a difference from the level Vsig can be performed. Thereby, it is possible to remove a noise signal component called fixed pattern noise (FPN) or reset noise.

The analog pixel signal (or digital pixel data) processed by the column circuit is transmitted to the horizontal signal line 218 via the horizontal selection switch 217 driven by the horizontal selection signal from the horizontal scanning circuit 212, and further output. Input to the circuit 228. Note that 10 bits is an example, and other bit numbers such as less than 10 bits (for example, 8 bits) and more than 10 bits (for example, 14 bits) may be used.

  With such a configuration, pixel signals are sequentially output for each vertical column for each row from the pixel unit 210 in which the unit pixel matrix 12 (pixels 12B, 12G, 12R, and 12IR) as the charge generation unit is arranged in a matrix. Is done. Then, one image corresponding to the pixel unit 210 in which the light receiving elements are arranged in a matrix, that is, a frame image, is shown as a set of pixel signals of the entire pixel unit 210.

  The output circuit 228 corresponds to the output amplifier 128 in the CCD solid-state image sensor 101, and in the subsequent stage, as shown in FIG. 140 is provided. As in the case of the CCD solid-state imaging device 101, the image signal processing unit 140 receives an image switching control signal from the image switching control unit 142.

  As a result, the red (R), green (G), and blue (B) primary color imaging data (R, G, B, and IR pixel data) or the visible light VL band based on the visible light VL pixel data can be obtained. An image (so-called normal image) can be obtained, and an image related to the infrared light IR can be obtained by using the pixel data of the infrared light IR.

  Although illustration is omitted, the visible light VL band is divided into R, G, and B color components by removing the infrared light IR pixel 12IR while using FIG. 29 and FIG. 31 as basic configurations. It is also possible to adopt a structure that detects the above.

  As the arrangement of the color filters 14, for example, blue, green, red, green, blue, green, red, green, blue,... In the vertical direction (X direction) of the vertical transfer CCD 122 on the light receiving surface side of the silicon substrate 1_ω. Also, the same row direction (Y direction) of the plurality of vertical transfer CCDs 122 is arranged in the order of blue, green, red, green, blue, green, red, green, blue,. Alternatively, a so-called Bayer arrangement in which two G colors and one R color and B color are arranged in the unit pixel matrix 12 of 2 rows and 2 columns may be employed. Further, the color reproduction range may be extended by adding a fourth color (for example, emerald) to the three colors B, G, and R.

  In these cases, only the visible light VL region is imaged, but it is not necessary to place an infrared cut filter in front of the sensor as an example of a color reduction filter. Costs can be significantly reduced by eliminating the need for expensive infrared cut filters. Further, by eliminating the need for an infrared cut filter having a thickness or weight, the optical system can be made light and compact. Of course, an infrared cut filter insertion / extraction mechanism is not required, and the apparatus does not become large.

  Of course, this is advantageous in terms of cost, for example, because the existing infrared filter cut out of glass is replaced with a dielectric laminated film, and the imaging sensor and the dielectric laminated film are separated (detection). This is also true even if the portion and the dielectric laminated film are not integrated.

  For example, it is advantageous in terms of cost as compared with the case of using an existing infrared cut filter made of glass, and can provide an imaging device such as a digital camera that is compact and excellent in portability.

Further, in the configuration in which the infrared cut filter is placed in front of the sensor, the glass substrate is placed in front of an image sensor such as a CCD or CMOS, so that an air / glass interface is generated in the middle of the optical path. Therefore, even visible light desired to be transmitted is reflected at the interface, which causes a problem of lowering sensitivity. Further, since the number of such interfaces increases, the angle of refraction at oblique incidence (within the glass) varies depending on the wavelength, causing defocus due to a change in the optical path.
On the other hand, by using a dielectric laminated film, there is an advantage that the defocus due to such a wavelength is eliminated.

<< Specific Example of Manufacturing Process >>
FIG. 33 is a diagram showing a specific process example for manufacturing the spectral image sensor having the sensor structure described in the above embodiment. FIG. 33 shows an example of a manufacturing process of a spectral image sensor including a light receiving unit for infrared light IR and a light receiving unit for visible light VL.

  In manufacturing this structure, a general CCD or CMOS structure circuit as shown in FIG. 29 and FIG. 30 or FIG. 31 and FIG. 32 is first formed (FIG. 33A). Thereafter, an SiO 2 film and SiN are sequentially stacked on the Si photodiode by using, for example, CVD (Chemical Vapor Deposition) (FIG. 33B).

  Thereafter, for example, only one of the four pixels is etched by using an RIE (Reactive Ion Etching) method or the like, so that an opening reaching the lowermost SiO2 film is provided in the light receiving part for infrared light IR ( FIG. 33 (E)).

  Thereafter, in order to protect the dielectric laminated film 1 and the like, an SiO 2 film is laminated again on the dielectric laminated film 1 having an opening partly by using, for example, CVD (FIG. 33F). . Of course, this process is not essential.

  At this time, a photoresist in which an opening is provided in a light receiving portion for infrared light IR may be used so that the three pixels (for R, G, and B components) for visible light VL are not etched. (FIGS. 33 (C) and (D)). In this case, it is necessary to remove the photoresist before laminating the SiO 2 film on the dielectric laminated film 1 (FIG. 33 (D) → (E)).

  Although not shown in the figure, color filters and microlenses may be formed thereon so as to correspond to the pixels.

  Further, when some infrared light IR leaks and enters a photoelectric conversion element (photodiode or the like) for visible light VL, a weak infrared cut filter may be inserted in the whole. For example, if an infrared cut filter of 50% or less is inserted, the infrared light IR will be reduced in the infrared light IR photoelectric conversion element (photodiode, etc.) even if it is cut to a level where there is almost no problem with the visible light VL. Condensation is sufficient to provide sufficient sensitivity.

  In such a manufacturing process, etching is performed up to the surface of the Si substrate, that is, an opening reaching the lowermost SiO2 film is provided in the light receiving portion for infrared light IR (FIG. 33E), and thus damage caused by etching. May be a problem. In this case, it is also possible to reduce the damage by increasing the thickness d of the SiO2 layer immediately above the Si substrate.

  Here, when dk = 2.5 μm or more, the half-value width of the dip in the infrared IR region of the reflection spectrum becomes narrow as shown in FIG. 11, so the reflectance averaged for general broad natural light. Therefore, infrared light can be reflected. Therefore, the thickness dk of the kth dielectric layer 1_k is preferably 2.5 μm or more. More desirably, the thickness is 5 μm or more.

  Further, a pixel wiring as a unit signal is read out from an imaging unit (detection region) from a metal wiring for a photodiode, an amplifier in a pixel, etc. formed on the silicon substrate 1_ω, that is, an amplifier in a pixel as a unit signal generation unit. When the wiring layer forming the signal line for forming the dielectric layer 1 is formed immediately above the silicon substrate 1_ω, the dielectric layered film 1 is located at a certain distance on the silicon substrate 1_ω rather than the structure in which the dielectric layer film 1 is provided directly on the silicon substrate 1_ω. By forming the dielectric laminated film 1 above the metal wiring, the process can be facilitated, and the merit of reducing the cost can be obtained. As will be described in detail later, a good result can be obtained to some extent by increasing the number of layers forming the dielectric laminated film 1. Hereinafter, a spectral image sensor considering metal wiring will be described.

<< Demultiplexing Image Sensor Using Dielectric Multilayer Film; Sixth Embodiment >>
34 to 40 are views for explaining a sixth embodiment of the spectral image sensor 10 that supports the single wavelength demultiplexing using the dielectric laminated film 1. In the sixth embodiment, based on the method described with reference to FIGS. 10 to 14, in consideration of metal wiring, the dielectric multilayer film 1 is placed on the silicon substrate 1_ω on the upper side that is a certain distance away from the silicon substrate 1_ω. It is characterized in that it is formed integrally with a detector such as a photodiode.

  For example, when considering a CMOS structure as shown in FIG. 34, when one wiring layer is provided on a semiconductor element layer on which a detection unit such as a photodiode is formed and the thickness thereof is about 0.7 μm, the photodiode When the multilayer film structure is integrally formed on approximately 0.7 μm above the silicon substrate 1_ω on which the dielectric layer is formed, the dielectric laminated film 1 may be formed after the process of the first wiring layer. In this way, a wiring layer can be provided in the kth layer having a thickness dk≈0.7 μm.

  Further, as shown in FIG. 35, when three wiring layers are provided on the semiconductor element layer and the total thickness thereof is about 3.2 μm, it is approximately 3.2 μm than the silicon substrate 1_ω on which the photodiode and the like are formed. When the multilayer film structure is integrally formed thereon, the dielectric laminated film 1 may be formed after the process of the uppermost third wiring layer. In this way, a wiring layer can be provided in the kth layer having a thickness dk = 3.2 μm.

  Here, “approximately 3.2 μm” is described, as shown in the figure, in this example, a SiO 2 layer (δ layer) having a thickness of about 10 nm is provided on the silicon substrate 1_ω, and the thickness is 65 nm. This is because an approximately SiN layer (γ layer) is provided, and “3.2 μm” means the thickness of the k layer excluding these γ and δ layers.

  The color filter 14 and the microlens may be formed after the dielectric laminated film 1 is formed.

  As the spectral image sensor 10 corresponding to these, for example, in FIG. 36, the seven-layer structure of the second embodiment shown in FIG. 17 is used, while the kth dielectric layer 1_k (silicon oxide SiO2 layer) and silicon nitride. The thickness of the dielectric layer 1_k of the kth layer is set to 700 nm based on the dielectric laminated film 1C having three layers of the SiN layer 1_γ and the silicon oxide SiO2 layer 1_δ. In addition, a relatively thin silicon nitride SiN layer 1_γ having a thickness dγ = 65 nm or 100 nm is stacked as a third layer material between the silicon oxide SiO2 of the kth layer and the silicon substrate 1_ω. A dielectric laminated film 1C in which a silicon oxide SiO 2 layer 1_δ as a fourth layer material having a refractive index smaller than that of the third layer material is laminated with a thickness dδ = 10 nm between the layer material 3 and the silicon substrate 1_ω. I have to.

  In FIG. 37, the basic dielectric multilayer film 1 has a nine-layer structure, and the thickness of the kth dielectric layer 1_k is set to 700 nm or 3.2 μm. Further, a relatively thin silicon nitride SiN layer 1_γ having a thickness dγ = 65 nm is laminated as a third layer material between the kth layer silicon oxide SiO2 and the silicon substrate 1_ω, and this additional third layer is added. A dielectric laminated film 1C in which a silicon oxide SiO 2 layer 1_δ as a fourth layer material having a refractive index smaller than that of the third layer material is laminated with a thickness dδ = 10 nm between the layer material and the silicon substrate 1_ω. Yes.

  The calculation results of these reflection spectra are as shown in FIGS. As can be seen from FIGS. 37 and 36, the wiring process is facilitated by forming the dielectric laminated film 1 on the upper side of the silicon substrate 1_ω by about 0.7 μm or 3.2 μm. To be precise, since the SiO2 layer as the fourth layer material and the SiN layer as the third layer material have thicknesses of 10 nm and 65 nm (or 100 nm), respectively, immediately above the silicon substrate 1_ω. On the top.

  Here, in the dielectric laminated film 1 having the SiN film and the SiO 2 film, the case of 7 layers and the case of 9 layers have been shown. However, as can be seen from FIG. It can be seen that when the number of layers of the structure is increased, the reflectance R in the infrared IR region exceeds 0.9 and becomes sufficient.

  As can be seen from FIG. 40, in the seven-layer structure in which the thickness dk of the kth dielectric layer 1_k is 3.2 μm, the dip in the infrared light reflection region is large, and as a result, the reflection is greatly reduced. I understand. However, it can also be seen that when the number of layers is increased to 9 layers, these dips become smaller and reflection in the infrared light IR region becomes sufficient.

  Further, as can be seen from FIG. 38, when the thickness dγ of the SiN layer as the third layer material is thick, the reflection in the visible light VL region becomes high. This is because, as described in the second embodiment, the third layer material provided as the intermediate layer is intended to reduce reflection in the visible light region, and the dielectric layer provided as the intermediate layer. It is ideal that the thickness dγ of 1_γ satisfies the formula (6), and it is considered that the thinner one has a sufficient margin but the larger one has a smaller margin.

  As described above, after the conventional wiring process is performed, the formation of the dielectric laminated film 1 is easier to manufacture, and it is unnecessary to examine a new process, which is good in terms of cost. That is, by producing a CMOS structure as shown in FIG. 35, the process can be facilitated and an effective effect can be obtained. If the wiring process is performed after the dielectric laminated film 1 is formed, it is a big difference from the fact that the process becomes difficult, for example, the dielectric laminated film 1 is removed.

<Specific example 1 of sensor structure; compatible with CCD>
FIG. 41 and FIG. 42 show the infrared light IR alone or the mixed component of the infrared light IR and the visible light VL, and the two wavelength components of the visible light VL, which are produced by taking the above manufacturing process as an example, separately as images. It is a figure explaining the 1st structural example of the CCD solid-state image sensor which enabled it to image. Here, FIG. 41 is a sketch (perspective view) showing a structural example. FIG. 42 is a cross-sectional structure diagram in the vicinity of the substrate surface.

  In the structure of the CCD solid-state imaging device 101 shown in FIG. 41, only the unit pixel matrix 12 consisting of four pixels is shown. However, in reality, a vertical CCD is arranged in parallel in one direction with respect to the pixels. It is a structure in which multiple rows are arranged repeatedly.

  Of the four pixels in the periodic array forming the unit pixel matrix 12, the dielectric laminated film 1 is not formed on one pixel 12IR, and a mixed component of infrared light IR and visible light VL is received, and the other three The dielectric laminated film 1 is formed on the two pixels 12B, 12G, and 12R, and the color filter 14 (14R, 14B, and 14B) is provided thereon, and the corresponding blue B and green in the visible light VL are provided. The three primary colors G and red R are received. The circuit configuration shown in FIG. 29 was adopted.

  FIG. 42 showing a cross-sectional structure near the substrate surface shows a pixel that receives only visible light VL. The pixel 12IR that receives the mixture of the infrared light IR and the visible light VL has a structure without the dielectric laminated film and the color filter 14. That is, after the SiN layer and the SiO 2 layer are sequentially laminated by the CVD method with the structure shown in FIG. 13 as in the manufacturing process steps described in FIG. 33, infrared light IR is applied by the lithography technique and the RIE method. It is removed only at the pixels that receive light. Thereafter, the SiO2 layer was laminated again and planarized.

By using an image sensor made with such a structure, it is possible to simultaneously capture an image of three primary colors of visible light VL and an image of only infrared light IR or an image of a mixture of infrared light IR and visible light VL. I understood.
For example, by using the pixel data from the pixel 12IR that receives the mixed component of the infrared light IR and the visible light VL as they are, an image of the mixed component of the infrared light IR and the visible light VL can be obtained, and the sensitivity is increased. can do. Further, an image of visible light VL is obtained together with an image of a mixed component of infrared light IR and visible light VL. By taking the difference between the two, an image of only infrared light IR can be obtained.

<Specific example 2 of sensor structure; compatible with CCD>
FIG. 43 illustrates a second configuration example of a CCD solid-state imaging device manufactured by taking the above manufacturing process as an example so that two wavelength components of only infrared light IR and visible light VL can be separately imaged simultaneously. It is a figure to do. Here, FIG. 43 is a sketch showing a structural example.

  In the structure of the CCD solid-state imaging device 101 shown in FIG. 43, only the unit pixel matrix 12 consisting of four pixels is shown, but in actuality, this is repeated in the horizontal direction and further repeated in the vertical direction. .

  Of the four pixels in the periodic array forming the unit pixel matrix 12, one pixel 12IR receives only infrared light IR (or a mixture of infrared light IR and visible light VL), and the other three pixels 12B, 12G, The 12R receives the three primary colors of blue B, green G, and red R corresponding to the visible light VL. The circuit configuration shown in FIG. 29 was adopted.

  The difference from the first configuration example is that the visible light VL is cut off and only the infrared light IR can be received by using the black filter 14BK as the color filter 14 on the pixel 12IR of the infrared light IR. It is a point. Other configurations and structures are the same as those in the first configuration example.

  It has been found that by using the imaging device manufactured in such a second configuration example, it is possible to simultaneously capture an image of three primary colors of visible light and an image of infrared light. That is, when the black filter 14BK that absorbs only the visible light VL is provided as the color filter 14C, the visible light VL can be absorbed by the black filter 14BK, and the image data from the pixel 12IR of the infrared light IR is added. Based on this, an image of only infrared light IR is obtained.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such changes or improvements are added are also included in the technical scope of the present invention.

  Further, the above embodiments do not limit the invention according to the claims (claims), and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. Absent. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  The structure described above shows an embodiment of the present invention, and as described above, has a structure in which a plurality of layers having different refractive indexes and a predetermined thickness are stacked between adjacent layers, Other similar structures can be used to enable wavelength separation using a laminated member (dielectric laminated film) having a characteristic of reflecting a predetermined wavelength region component of electromagnetic waves and allowing the remainder to pass therethrough.

  Furthermore, the above-described technique is not necessarily limited to visible light and infrared light spectroscopy. For example, spectroscopy and detection of visible light and ultraviolet light are possible, and ultraviolet light as well as visible light can be detected and imaged simultaneously. In addition, the visible light detected at the same time is not limited to detecting a monochrome image without splitting, and the visible light band is split into, for example, three primary color components using the color filters for each color as described above. Can also detect color images.

  Accordingly, it is possible to simultaneously acquire image information of ultraviolet light that cannot be seen by the eye, corresponding to an image image (monochrome image or color image) of visible light that can be seen by the eye. This expands the application as a key device for new information systems such as photosynthetic surveillance cameras.

  For example, the visible light VL and the visible light VL are obtained by using the dielectric laminated film 1 in which the visible light VL is a reflected wavelength region component and the passing wavelength region component is a lower wavelength side (for example, ultraviolet light) than the visible light VL. It is also possible to perform spectroscopy and detection on the lower wavelength side (for example, ultraviolet light).

  For example, although not shown, in FIG. 41, the dielectric laminated film 1 that reflects a wavelength component of visible light VL or more is formed on one pixel 12IR out of four pixels of the periodic array forming the unit pixel matrix 12. Thus, only the wavelength lower than the visible light VL (ultraviolet light) is received, the dielectric laminated film 1 is not formed on the other three pixels 12B, 12G, and 12R, and the color filter 14 (14R, 14B, 14B), the corresponding three primary colors of blue B, green G and red R in the visible light VL are received together with the low wavelength side (ultraviolet light).

  In order to obtain a visible light VL signal as a reflected wavelength region component that is substantially unaffected by the transmitted wavelength region component, an arithmetic process with the ultraviolet light component that is the transmitted wavelength region component may be performed. In addition, if the thing with the transmittance | permeability with respect to the ultraviolet-light component which is a passage wavelength area component is used as a characteristic of the color filter 14 (14R, 14B, 14B), it is a low wavelength side (ultraviolet light) from visible light VL. ) Is removed by the color filter 14 (14R, 14B, 14B), so this calculation process is not necessary.

<< Other Examples of Manufacturing Process and Device Structure >>
FIG. 45 shows a cross-sectional structure of the image sensor in this embodiment.
In FIG. 33, the SiO 2 film is embedded in the area from which the dielectric laminated film 1 has been removed (area 101 in FIG. 45), but in this embodiment, a lens 102 is formed. Become.
Thereby, compared with FIG. 35, it becomes the structure which suppressed the loss of condensing as much as possible, suppressing the whole height and eliminating a lens.
The manufacturing process that is characteristic of FIGS. 46 to 48 will be described.
FIG. 46A is obtained from FIG. Next, as shown in FIG. 46B, a resist pattern 103 is formed by a lithography process.
Next, using this resist as a mask, isotropic etching is performed to obtain a shape as shown in FIG. The isotropic etching at this time may be either wet etching or dry etching.
Thereafter, the remaining resist is removed, resulting in FIG.
Next, the SiO 2 film 104 is entirely thinned by anisotropic etching, and the result is shown in FIG. In the anisotropic etching at this time, the processing is performed under the condition that the selective ratio between the uppermost SiN film 105 of the dielectric laminated film 1 and the SiO 2 film 104 as the material to be etched is high (the etching rate of SiO 2 is fast). Is desirable.
Next, a material having a higher refractive index than the SiO 2 film 104, here, a SiN film 106 is deposited (FIG. 47F).
Next, a resist 107 is applied (FIG. 47G), and then the entire surface is etched back (FIG. 47H). As etching conditions at this time, it is desirable that the SiN film 106 and the resist 107 have the same etching rate.
Finally, a passivation SiN 108 is deposited, resulting in FIG.
The subsequent steps are for manufacturing color filters, on-chip lenses, etc., and these may be performed using existing processes.

It is a figure explaining the concept of the demultiplexing image sensor which separates electromagnetic waves for every predetermined wavelength using a dielectric laminated film. It is a conceptual diagram explaining the basic composition of the demultiplexing image sensor using a dielectric laminated film. FIG. 3 is a diagram illustrating a configuration example in which the basic configuration of the spectral image sensor illustrated in FIG. 2 is applied to a plurality of wavelength separation configurations. It is a structure figure explaining the basic concept of the method of designing a laminated film. It is a reflection spectrum figure explaining the basic concept of the method of designing a laminated film. It is a reflection spectrum figure explaining the basic concept of the method of designing a laminated film. It is a figure explaining the conditions of reflection center wavelength (lambda) (the figure which showed the concept of the reflection spectrum). It is a reflection spectrum figure explaining the conditions of reflection center wavelength (lambda). It is a reflection spectrum figure explaining the conditions of reflection center wavelength (lambda). 1 is a structural diagram illustrating a first embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. FIG. It is a reflection spectrum figure explaining 1st Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a figure (reflection spectrum figure; details) explaining 1st Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. 1 is a structural diagram illustrating a first embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. FIG. It is a reflection spectrum figure explaining 1st Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. FIG. 5 is a structural diagram illustrating a second embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 2nd Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. FIG. 5 is a structural diagram illustrating a second embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 2nd Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. FIG. 6 is a structural diagram illustrating a third embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 3rd Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. FIG. 6 is a structural diagram illustrating a third embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 3rd Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. FIG. 6 is a structural diagram illustrating a third embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 3rd Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a structure figure explaining 4th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 4th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a structure figure explaining 5th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 5th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a circuit diagram (R, G, B, infrared light IR correspondence) at the time of applying a laminated film to an IT_CCD image sensor. FIG. 6 is a circuit diagram (corresponding to visible light VL and infrared light IR) when a laminated film is applied to an IT_CCD image sensor. It is a circuit diagram (R, G, B, infrared light IR correspondence) at the time of applying a laminated film to a CMOS solid-state image sensor. FIG. 6 is a circuit diagram (corresponding to visible light VL and infrared light IR) when a laminated film is applied to a CMOS solid-state imaging device. It is a figure which shows the example of a process which manufactures a spectral image sensor. FIG. 11 is a structural diagram illustrating a sixth embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. FIG. 11 is a structural diagram illustrating a sixth embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. FIG. 11 is a structural diagram illustrating a sixth embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. FIG. 11 is a structural diagram illustrating a sixth embodiment of a spectral image sensor that supports single wavelength demultiplexing using a laminated film. It is a figure explaining 6th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 6th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a reflection spectrum figure explaining 6th Embodiment of the spectral image sensor corresponding to a single wavelength demultiplexing using a laminated film. It is a figure (perspective view) explaining the 1st structural example of the CCD solid-state image sensor which enabled it to image two wavelength components of infrared light and visible light separately as an image simultaneously. It is a figure (sectional structure diagram) explaining the 1st structural example of the CCD solid-state image sensor which enabled it to image two wavelength components of infrared light and visible light separately as an image simultaneously. It is a figure (perspective view) explaining the 2nd structural example of the CCD solid-state image sensor which enabled it to image two wavelength components of infrared light and visible light separately as an image simultaneously. It is a figure explaining the mechanism of the sensor given in patent documents 1. It is sectional structure drawing of the image sensor in a present Example. It is a figure which shows the example of a manufacturing process. It is a figure which shows the example of a manufacturing process. It is a figure which shows the example of a manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dielectric laminated film 10, 11 ... Spectral image sensor, 12 ... Unit pixel matrix, 100 ... Imaging device, 101 ... CCD solid-state image sensor, 122 ... Vertical transfer CCD, 124 ... Read-out gate, 126 ... Horizontal transfer CCD, DESCRIPTION OF SYMBOLS 128 ... Output amplifier, 201 ... CMOS solid-state image sensor, 205 ... In-pixel amplifier, 207 ... Drive control part, 219 ... Vertical signal line, 226 ... Column processing part.

Claims (1)

An imaging region including a plurality of pixels arranged two-dimensionally;
Each of the plurality of pixels includes a light receiving element formed in the substrate,
A stacked portion is formed above the light receiving element of the first pixel included in the plurality of pixels;
An in-layer lens is formed above the light receiving element of the second pixel included in the plurality of pixels;
The laminated portion includes a laminated structure composed of a plurality of layers having different refractive indexes, reflects incident light in a predetermined wavelength region,
The in-layer lens is formed in an intermittent region of the laminated portion.

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