Patent Description:
In an imaging apparatus, incidence angles of light are known to differ between a central portion and an outer peripheral portion of an imaging element (for example, refer to PTL <NUM>).

<CIT> refers to an image pickup apparatus including a colour separation element array. The colour separation elements are arranged two dimensionally and configured to separate incident light according to a wavelength so that the light of a first wavelength and a second wavelength are directed into different directions. The colour separation elements comprise first and second partitions that are sequentially arranged along a travelling direction of the incident light.

<CIT> refers to an image sensor having a photosensor layer and a plurality of photo sensing cells. A color separation layer disposed on the photo sensor layer and including color separation elements embedded in a transparent spacer layer. A micro lens array is arranged on the color separation layer, the micro lens array including a plurality of micro lenses. The color separation layer separates light by wavelength. The micro lens array concentrates incident light onto the plurality of color separation elements.

<CIT> refers to a solid-state imaging device to capture an image which is bright through to its periphery when used in a single-lens reflex digital camera that accepts various interchangeable lenses from wide-angle to telephoto. a two-dimensional array of unit pixels includes a light collecting element. The light collecting element is a combination of circular sector shaped light collecting elements having different concentric structures.

There is a problem in that, when an incidence angle deviates, light cannot be efficiently guided to a conversion element and light-receiving efficiency decreases.

An aspect of the present disclosure is to enable light-receiving efficiency to be improved.

The aims of the invention are achieved by the subject matter of independent claim one. Advantageous embodiments of the invention are disclosed in the dependent claims. An imaging element according to an aspect includes: a plurality of photoelectric conversion element groups each including a plurality of photoelectric conversion elements and being arranged in a two-dimensional direction; a transparent layer which faces the plurality of photoelectric conversion element groups and which extends in the two-dimensional direction as a planar direction; and a plurality of structure groups arranged in a planar direction of the transparent layer so as to correspond to the plurality of photoelectric conversion element groups on the transparent layer or inside the transparent layer, wherein each of the plurality of structure groups includes a plurality of structures arranged in a same pattern and is arranged so as to disperse incident light toward each of the photoelectric conversion elements of a corresponding photoelectric conversion element group, and in a plan view, relative positions of the corresponding photoelectric conversion element group and a structure group differ according to two-dimensional positions.

An imaging apparatus according to an aspect includes the imaging element described above and a signal processing unit configured to generate an image signal based on an electric signal obtained from the imaging element.

According to the present disclosure, light-receiving efficiency can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. It is to be understood that shapes, sizes, positional relationships, and the like shown in the drawings are merely schematic and the present invention is not limited thereto. Same portions will be denoted by same reference signs and redundant descriptions will be omitted.

<FIG> is a diagram showing an example of a schematic configuration of an imaging element and an imaging apparatus according to an embodiment. An imaging apparatus <NUM> images an object <NUM> (subject) by using light from the object <NUM> as incident light. In this example, the object <NUM> is shown as an outlined arrow. The incident light is made incident on an imaging element <NUM> via a lens optical system <NUM>. A signal processing unit <NUM> processes an electric signal from the imaging element <NUM> to generate an image signal. As shown in <FIG>, a direction of light incident on the imaging element <NUM> (an incidence angle to the imaging element <NUM>) differs depending on a position of the imaging element <NUM>.

<FIG> is a diagram showing an example of a schematic configuration of an imaging element. In the diagram, an XYZ coordinate system is shown, and an advancing direction of incident light is schematically shown by an arrow. A Z-axis direction corresponds to a stacking direction of a PD layer <NUM> and a transparent layer <NUM> to be described later. An XY planar direction corresponds to a planar direction of these layers.

Hereinafter, a "plan view" indicates viewing in the Z-axis direction (for example, in a Z-axis negative direction) and a "side view" indicates viewing in an X-axis direction or a Y-axis direction (for example, in a Y-axis positive direction). <FIG> is a cross-sectional view showing an example of a schematic configuration of the imaging element <NUM> in a side view.

The imaging element <NUM> includes a wiring layer <NUM>, a PD (photodiode) layer <NUM>, and a transparent layer <NUM>.

To first describe the PD layer <NUM> among the wiring layer <NUM> and the PD layer <NUM>, the PD layer <NUM> includes a plurality of PD groups <NUM> which are provided side by side in a planar direction of the layer (which can also be described as being arranged in a two-dimensional direction (in a two-dimensional pattern)). Each PD group <NUM> includes a plurality of PDs provided side by side in the planar direction of the layer. The plurality of PDs are formed on a semiconductor substrate <NUM>. Charges generated in each PD are converted into an electric signal which becomes a basis of a pixel signal by transistors (not illustrated) or the like and output to the outside of a pixel <NUM> through the wiring layer <NUM>. Several wirings corresponding to each PD are illustrated as wirings <NUM>.

The transparent layer <NUM> is an optical element that disperses incident light toward each of the photoelectric conversion elements of the plurality of PD groups <NUM>. An example of the optical element is a meta-surface, and a case where the transparent layer <NUM> is a meta-surface will be described below. The meta-surface is an element which is made up of a plurality of microstructures having a width equal to or less than a wavelength of light and which may have a two-dimensional structure or a three-dimensional structure. By using a meta-surface for the optical element, a phase and light intensity can be controlled according to characteristics (wavelength, polarization, and incidence angle) of light by merely changing a parameter of the microstructures, and the degree of freedom in design described above is increased in the case of forming a three-dimensional structure. The transparent layer <NUM> is provided so as to face the PD layer <NUM>, and in this example, the transparent layer <NUM> is provided on an upper surface (a surface on a Z-axis positive direction side) of the PD layer <NUM>. The transparent layer <NUM> extends with a planar direction of the PD layer <NUM> as a planar direction of the layer. The transparent layer <NUM> includes a plurality of structure groups <NUM> arranged in a planar direction of the layer. In the example shown in <FIG>, the plurality of structure groups <NUM> are provided inside the transparent layer <NUM>. However, the plurality of structure groups <NUM> may be provided on the transparent layer <NUM>. The plurality of structure groups <NUM> may be provided on a lower surface of a transparent substrate and, in such a case, the transparent layer <NUM> is an air layer. The structure constituting the plurality of structure groups <NUM> is a microstructure having a dimension more or less equal to or smaller than the wavelength (nano-order) of incident light.

A portion of the transparent layer <NUM> where the structure is not provided may have a refractive index lower than that of the structure. An example of a material of such a transparent layer <NUM> is SiO<NUM>. The transparent layer <NUM> may be a void and, in such a case, the refractive index of the transparent layer <NUM> is the refractive index of air.

As described earlier with reference to <FIG>, the angle of incident light to the imaging element <NUM> varies depending on the position on the imaging element <NUM>. In the example shown in <FIG>, the incidence angle of light to the transparent layer <NUM> varies depending on two-dimensional positions (positions on the XY plane). In the imaging element <NUM>, the incidence angle in a two-dimensional central portion (hereinafter, also simply referred to as a "central portion") is <NUM>° in this example and, therefore, the light enters the transparent layer <NUM> perpendicularly. In the imaging element <NUM>, an incidence angle in a two-dimensional outer peripheral portion (hereinafter, also simply referred to as an "outer peripheral portion") deviates from the incidence angle in the central portion. The deviation of the incidence angle becomes larger from the central portion toward the outer peripheral portion.

<FIG> and <FIG> are diagrams showing an example of a schematic configuration of an imaging element in the central portion. <FIG> is a cross-sectional view showing an example of a schematic configuration of the imaging element <NUM> in a side view. <FIG> is a diagram showing an example of a schematic configuration of the imaging element <NUM> in a plan view. Since the PD group <NUM> is located on a lower side (a Z-axis negative direction side) of the structure group <NUM>, the PD group <NUM> is indicated by a broken line in <FIG>.

As a plurality of diodes included in the PD group <NUM>, a PD <NUM>, a PD <NUM>, and a PD <NUM> are exemplified. The PD <NUM>, the PD <NUM> and the PD <NUM> are provided in order in a planar direction of the PD layer <NUM> (in this example, in the X-axis direction). It is assumed that light of a wavelength band in accordance with a corresponding color is incident on the PD <NUM>, the PD <NUM>, and the PD <NUM>. For example, the PD <NUM>, the PD <NUM>, and the PD <NUM> correspond to red (R), green (G), and blue (B).

A structure <NUM>, a structure <NUM>, and a structure <NUM> are exemplified as a plurality of structures included in the structure group <NUM>. The structure <NUM>, the structure <NUM>, and the structure <NUM> are a plurality of structures each arranged in a same pattern. The same pattern means that, for example, a size (width) of each structure and intervals in the planar direction of the transparent layer <NUM> are the same. The size (height) of each structure in the lamination direction may be the same. The structure <NUM>, the structure <NUM>, and the structure <NUM> are arranged so as to disperse incident light respectively toward the PD <NUM>, the PD <NUM>, and the PD <NUM> of the corresponding PD group <NUM>. More specifically, the structure <NUM>, the structure <NUM>, and the structure <NUM> are arranged to disperse incident light toward centers of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>. The incident light is dispersed into, for example, light of a wavelength band corresponding to each color of RGB as described above, and reaches the PD <NUM>, the PD <NUM>, and the PD <NUM> corresponding to each color. In the examples shown in <FIG> and <FIG>, the center of the structure group <NUM> is located above the center of the PD group <NUM> (in this example, on the center of the PD <NUM>).

A principle of spectroscopy by the structure <NUM>, the structure <NUM>, and the structure <NUM> will be described with reference to <FIG> and <FIG>. Hereinafter, the structure <NUM> will be described as an example. The structure <NUM> and the structure <NUM> can also be described in the same manner.

<FIG> and <FIG> are diagrams showing an example of a schematic configuration of a structure. <FIG> shows an example of a plan view (top view) of the structure <NUM>. <FIG> shows an example of a side view of the structure <NUM>.

In this example, the structure <NUM> is a fine columnar structure. The structure <NUM> is made of a material such as SiN which has a refractive index n<NUM> that is higher than a refractive index n<NUM> of other portions of the transparent layer <NUM>, and a thickness h (a length in the Z-axis direction) of the structure is constant.

A bottom surface and a top surface of the structure <NUM> are square. The structure <NUM> acts as an optical waveguide for trapping light inside the structure and propagating the light therein due to a difference in the refractive indexes described above. Accordingly, when light enters from an upper surface side, the light is propagated while being strongly confined inside the structure <NUM>, and the light is subjected to an optical phase delay effect determined by an effective refractive index neff of the optical waveguide and exits from the bottom surface side. Specifically, when a phase of light having propagated over a length corresponding to the thickness of the transparent layer <NUM> is used as a benchmark, an optical phase delay amount φ by the structure <NUM> is expressed by φ = (neff - n<NUM>) × 2πh/ λ, where λ denotes a wavelength of the light in vacuum. Since the optical phase delay amount differs depending on the wavelength λ, a different optical phase delay amount in accordance with a wavelength band (color) is given to light incident on the same structure <NUM>. Since the bottom surface and the top surface of the structure <NUM> are square, there is no change in optical characteristics including an optical phase delay effect even when a polarization direction is changed. It is known that neff is a function of a structural dimension and takes a value that satisfies n<NUM> < neff < n<NUM>. Therefore, by changing the width W of the structure <NUM>, an arbitrary optical phase delay amount can be set. An arbitrary optical phase delay amount can also be set by changing the refractive index of the structure <NUM>. Structures <NUM> having different refractive indices may be made of materials having different refractive indices. This applies likewise to the structure <NUM> and the structure <NUM>.

Referring also to <FIG> and <FIG>, the structure <NUM>, the structure <NUM>, and the structure <NUM> have different widths so as to give light having been transmitted through the structure group <NUM> a different optical phase delay distribution for each wavelength region to change an optical wavefront. Since an outgoing direction (propagation direction) of the light is determined by the optical wavefront, the light transmitted through the structure group <NUM> is spatially separated according to the corresponding colors (wavelength bands) of the PD <NUM>, the PD <NUM>, and the PD <NUM>. In this way, incident light is dispersed toward the PD <NUM>, the PD <NUM>, and the PD <NUM>, respectively.

Since the structure <NUM>, the structure <NUM>, and the structure <NUM> are arranged in the same pattern in each of the plurality of structure groups <NUM>, the relationship between an incidence angle and an outgoing angle of light in each of the structure groups <NUM> is also the same. When the incidence angle is different, the outgoing angle is also different. As described earlier, since the incidence angle in the outer peripheral portion is deviated from the incidence angle in the central portion, the outgoing angle of the light emitted from the transparent layer <NUM> toward the PD layer <NUM> is also deviated. When the outgoing angle is deviated, light can no longer be efficiently guided to the PD <NUM>, the PD <NUM>, and the PD <NUM> of the corresponding PD group <NUM>. Therefore, in the imaging element <NUM>, the relative positions of the PD group <NUM> and the structure group <NUM> are determined in correspondence to the deviation of the incidence angle (or an outgoing angle attributable thereto).

<FIG> and <FIG> are diagrams showing an example of a schematic configuration of an imaging element in an outer peripheral portion. <FIG> is a cross-sectional view showing an example of a schematic configuration of the imaging element <NUM> in a side view. <FIG> is a diagram showing an example of a schematic configuration of the imaging element <NUM> in a plan view.

In the outer peripheral portion, an incidence angle of light incident on the structure group <NUM> is deviated from the incidence angle (<FIG>) in the central portion. Due to the deviation of the incidence angle, an outgoing angle of light emitted from the structure group <NUM> toward the PD group <NUM> is also deviated. However, the relative positions of the PD group <NUM> and the structure group <NUM> are also deviated from the relative positions (<FIG> and <FIG>) in the central portion. In this example, the position of the structure group <NUM> with respect to the PD group <NUM> is shifted to a side of the PD <NUM> of the PD group <NUM> and, specifically, a center position of the structure group <NUM> is positioned above a portion on a side of the PD <NUM> (in this example, above the PD <NUM>) of the PD group <NUM>. A direction (angle) in which the PD group <NUM> is viewed from the structure group <NUM> is also deviated by the amount of deviation of the relative positions of the PD group <NUM> and the structure group <NUM>. The relative positions of the PD group <NUM> and the structure group <NUM> are determined so that the deviation of the direction (angle) in which the PD group <NUM> is viewed from the structure group <NUM> cancels out the deviation of the outgoing angle described above. As a result, even in the outer peripheral portion, the structure group <NUM> disperses incident light toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

Supposing that the relative positions of the PD group <NUM> and the structure group <NUM> in the outer peripheral portion are the same as the relative positions in the central portion, the light dispersed by the structure group <NUM> is no longer directed to the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>. This state will be described with reference to <FIG>.

<FIG> is a diagram showing a comparative example. In an exemplified imaging element 12E, the relative positions of the PD group <NUM> and a structure group 50E are the same as the relative positions in the central portion. The light dispersed by a structure 51E, a structure 52E, and a structure 53E reaches a position separated from the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM> by an amount of deviation of an outgoing angle attributable to a deviation of an incidence angle. As described earlier with reference to <FIG> and <FIG>, this problem is reduced or eliminated by the imaging element <NUM> according to the embodiment.

<FIG> and <FIG> are diagrams showing an example of a schematic configuration of an imaging element in an intermediate portion. The intermediate portion is a portion between the central portion and the outer peripheral portion. <FIG> is a cross-sectional view showing an example of a schematic configuration of the imaging element <NUM> in a side view. <FIG> is a diagram showing an example of a schematic configuration of the imaging element <NUM> in a plan view.

In the intermediate portion, a deviation of an incidence angle is smaller than a deviation (<FIG>) of the incidence angle in the outer peripheral portion. A deviation of an outgoing angle that is attributable to the deviation of the incidence angle is also smaller than a deviation of the outgoing angle in the outer peripheral portion. Therefore, the deviation of the relative positions of the PD group <NUM> and the structure group <NUM> is also smaller than the deviation of the relative positions in the outer peripheral portion. Also in the intermediate portion, the structure group <NUM> disperses incident light toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

As described above, for example, in the imaging element <NUM>, the relative positions of the corresponding PD group <NUM> and the structure group <NUM> differ according to two-dimensional positions (positions with an XY-planer shape). More specifically, when relative positions of the PD group <NUM> and the structure group <NUM> in the central portion are used as a benchmark, the relative positions deviate more toward the outer peripheral portion. Supposing that the relative positions are the same at any position, the light dispersed by the structure group <NUM> reaches a position away from the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM> as described earlier with reference to <FIG>. As a result, light is not efficiently incident on the PD <NUM>, the PD <NUM>, and the PD <NUM> and, for example, problems such as deterioration of light-receiving sensitivity arise. On the other hand, in the imaging element <NUM>, by shifting relative positions of the corresponding PD group <NUM> and the structure group <NUM>, a spectral direction by the structure group <NUM> can be brought close to the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>. As a result, light-receiving efficiency can be improved.

Once again referring to <FIG>, the signal processing unit <NUM> of the imaging apparatus <NUM> will be described. The signal processing unit <NUM> generates a pixel signal based on an electrical signal obtained from the imaging element <NUM>. In order to obtain an electric signal, the signal processing unit <NUM> also controls the imaging element <NUM>. The control of the imaging element <NUM> includes exposure of the pixel <NUM> of the imaging element <NUM>, conversion of an electric charge accumulated in the PD layer <NUM> into an electric signal, reading of the electric signal, and the like.

In the embodiment described above, a method of coping with a problem attributable to a deviation of incident light with relative positions of the PD group <NUM> and the structure group <NUM> has been described. Other various methods may be used in addition to or in place of this method.

For example, the incidence angle itself of the light incident on the transparent layer <NUM> in the outer peripheral portion and the intermediate portion may be made to approach the incidence angle in the central portion. This method will be described with reference to <FIG>.

<FIG> is a diagram showing an example of a schematic configuration of the imaging element in the central portion. An exemplified imaging element 12A differs from the imaging element <NUM> (<FIG> and the like) in that the imaging element 12A includes a transparent layer 5A in place of the transparent layer <NUM> and further includes a plurality of lenses <NUM>. The transparent layer 5A includes a plurality of structure groups 50A.

Each of the plurality of lenses <NUM> is a microlens provided for each of the plurality of structure groups 50A. The lens <NUM> has a shape in accordance with a two-dimensional position. In this example, the lens <NUM> does not change the direction of incident light. A structure 51A, a structure 52A, and a structure 53A of the structure group 50A are arranged so as to disperse light from the lens <NUM> toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

An incidence angle of light incident on the structure group 50A in the outer peripheral portion and the intermediate portion is deviated from the incidence angle (<FIG>) in the central portion. As an example of a method for reducing this deviation, two methods will be described. In the first method, the principle of shifting the position of a structure group with respect to a PD group described heretofore is also applied to the plurality of lenses <NUM>. The first method will now be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing an example of a schematic configuration of the imaging element in the outer peripheral portion. As compared with the central portion (<FIG>), the relative positions of the plurality of lenses <NUM> and the structure group <NUM> are deviated from the relative positions in the central portion. In this example, the positions of the plurality of lenses <NUM> with respect to the structure group 50A are shifted to a side of the PD <NUM> of the PD group <NUM>. The lens <NUM> is arranged so that an incidence angle of light toward the structure group 50A approaches an incidence angle in the central portion. The structure 51A, the structure 52A, and the structure 53A of the structure group 50A are arranged so as to disperse light from the lens <NUM> toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

<FIG> is a diagram showing an example of a schematic configuration of the imaging element in the intermediate portion. As compared with the central portion (<FIG>), the relative positions of the plurality of lenses <NUM> and the structure group <NUM> are deviated from the relative positions in the central portion. This deviation is smaller than the deviation in the outer peripheral portion (<FIG>). The lens <NUM> is arranged so that an incidence angle of light toward the structure group 50A approaches an incidence angle in the central portion. The structure 51A, the structure 52A, and the structure 53A of the structure group 50A are arranged so as to disperse light from the lens <NUM> toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

The second method is a method of providing a lens having a shape in accordance with a two-dimensional position. This method will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing an example of a schematic configuration of the imaging element in the outer peripheral portion. The imaging element 12A is provided with a plurality of lenses <NUM> in place of the plurality of lenses <NUM> in comparison with the central portion (<FIG>). Each of the plurality of lenses <NUM> is a microlens provided for each of the plurality of structure groups 50A. The lens <NUM> is configured so that an incidence angle of light toward the structure group <NUM> approaches an incidence angle in the central portion. The lens <NUM> has a shape in accordance with a two-dimensional position which is a shape having been deformed from the shape of the lens <NUM> (<FIG>). The structure 51A, the structure 52A, and the structure 53A of the structure group 50A are arranged so as to disperse light from the lens <NUM> toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

<FIG> is a diagram showing an example of a schematic configuration of the imaging element in the intermediate portion. The imaging element 12A is provided with a plurality of lenses <NUM> in place of the plurality of lenses <NUM> in comparison with the central portion (<FIG>). Each of the plurality of lenses <NUM> is a microlens provided for each of the plurality of structure groups 50A. The lens <NUM> is configured so that an incidence angle of light toward the structure group <NUM> approaches an incidence angle in the central portion. The lens <NUM> has a shape in accordance with a two-dimensional position which is a shape having been deformed from the shape of the lens <NUM> (<FIG>). The degree of the deformation is smaller than the degree of deformation of the lens <NUM> (<FIG>). The structure 51A, the structure 52A, and the structure 53A of the structure group 50A are arranged so as to disperse light from the lens <NUM> toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

As shown in <FIG>, by differentiating relative positions of the corresponding plurality of lenses <NUM> and the structure group <NUM> in accordance with the two-dimensional positions or providing the lens <NUM>, the lens <NUM> and the lens <NUM> having a shape in accordance with the two-dimensional positions, an incidence angle of light incident on the transparent layer <NUM> in the outer peripheral portion and the intermediate portion can be made to approach an incidence angle in the central portion. Therefore, for example, light is more easily dispersed toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM> of the PD group <NUM> than when only the plurality of structure groups 50A are used. For example, if the incidence angle in the outer peripheral portion and the intermediate portion can be brought sufficiently close to the incidence angle in the central portion using only the lens <NUM> or the like, the relative positions of the corresponding structure group 50A and the PD group <NUM> need not be deviated. This is because each structure group 50A disperses light toward the center of each of the PD <NUM>, the PD <NUM> and the PD <NUM>.

For example, a reflection suppression layer may be provided to suppress reflection of incident light to the PDs. This method will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing an example of a schematic configuration of an imaging element. An exemplified imaging element 12B differs from the imaging element <NUM> (<FIG>) in that the imaging element 12B further includes a reflection suppression layer <NUM>.

The reflection suppression layer <NUM> is provided so as to cover the PD layer <NUM> and suppresses reflection of light incident on the PD layer <NUM>. In this example, the reflection suppressing layer <NUM> is provided between the PD layer <NUM> and the transparent layer <NUM>.

In the example shown in <FIG>, the reflection suppressing layer <NUM> includes a plurality of diffraction gratings <NUM>. The plurality of diffraction gratings <NUM> are periodically arranged in a planar direction of the reflection suppression layer <NUM>. The plurality of diffraction gratings <NUM> have an effective refractive index that differs from the refractive index of the PD layer <NUM>. The effective refractive index is a value of the refractive index when it is assumed that the diffraction grating gives a virtual refractive index, in which case the reflection suppressing layer <NUM> functions as a portion (or a material, a member, or the like) having the effective refractive index. Since a method of realizing a desired effective refractive index by a plurality of periodically-arranged diffraction gratings is known, a brief description will now be given. The effective refractive index is determined by a grating period (arrangement intervals of the diffraction gratings <NUM> in the XY-planar direction), a grating height (the length of the diffraction gratings <NUM> in the Z-axis direction), and the like. The grating period may be set equal to or less than the wavelength of the incident light. Examples of a material of the diffraction gratings <NUM> include resins such as plastic, glass, and the like.

The diffraction grating <NUM> has an effective refractive index of a magnitude between the refractive index of the PD layer <NUM> and the refractive index of a portion opposite to the PD layer <NUM> across the diffraction grating <NUM>. Since the PD layer <NUM> is formed on the semiconductor substrate <NUM>, the refractive index of the PD layer <NUM> may be the same as that of the semiconductor substrate <NUM>. In this example, the refractive index of the portion on the opposite side is the refractive index of the transparent layer <NUM>. Since the diffraction grating <NUM> has an effective refractive index of a magnitude between the refractive indices, the reflection suppression layer <NUM> reduces discontinuity between the refractive index of the PD layer <NUM> and the refractive index of the transparent layer <NUM> and suppresses reflection of light incident on the PD layer <NUM>.

Providing the reflection suppressing layer <NUM> as shown in <FIG> enables reflection of light to be suppressed and enables light to be incident on the PD <NUM>, the PD <NUM> and the PD <NUM> in an efficient manner.

Although an example in which the reflection suppressing layer <NUM> is used together with the transparent layer <NUM> that includes the plurality of structure groups <NUM> has been described above, if light can be made incident in a somewhat efficient manner only by the reflection suppressing layer <NUM>, the plurality of structure groups <NUM> need not be provided. In this case, various known spectroscopic elements may be used instead of the structure groups <NUM>.

In the imaging element 12B described above, a specific PD may not be covered with the diffraction grating <NUM>. An example of the specific PD is a PD which is located immediately below the structure group <NUM> and on which light from the structure group <NUM> is vertically incident. Such a specific PD may be covered with a reflection suppression film instead of the diffraction grating <NUM>. This configuration will be described with reference to <FIG>.

<FIG> is a diagram showing an example of a schematic configuration of an imaging element in a specific PD portion. An exemplified imaging element 12B-<NUM> differs from the imaging element 12B (<FIG>) in that the imaging element 12B-<NUM> includes a reflection suppression layer 7A instead of the reflection suppression layer <NUM>.

The reflection suppression layer 7A includes a reflection suppression film <NUM> in addition to a plurality of diffraction gratings 70A. The plurality of diffraction gratings 70A cover the PD <NUM> and the PD <NUM> while the PD <NUM> is not covered but exposed. Since the configuration of the diffraction grating 70A is the same as that of the diffraction grating <NUM>, a description thereof will not be repeated. The reflection suppression film <NUM> is provided so as to cover the exposed PD <NUM> in a gapless manner. The reflection suppression film <NUM> has a refractive index that differ from that of the PD group <NUM>. The PD <NUM> is a photoelectric conversion element corresponding to, for example, green (G). Examples of a material of the reflection suppressing film <NUM> include resins such as plastic, glass, or the like.

As shown in <FIG>, by using the reflection suppression layer 7A that includes the two kinds of reflection suppression members, namely, the plurality of diffraction gratings <NUM> and the reflection suppression film <NUM>, for example, a reflection suppression amount can be adjusted for each of the PD <NUM>, the PD <NUM>, and the PD <NUM>.

In the above embodiment, an example in which the plurality of structure groups <NUM> are provided in the transparent layer <NUM> has been described. However, the plurality of structure groups <NUM> may be provided on the surface on the transparent layer <NUM> (for example, on a surface on the Z-axis positive direction side).

While SiN and TiO<NUM> have been cited as materials for the structure <NUM> and the like in the embodiment described above, materials are not limited thereto. For example, SiN, SiC, TiO<NUM>, GaN, and the like may be used as materials for the structure <NUM> and the like with respect to light (visible light to near-infrared light) with a wavelength ranging from <NUM> to <NUM>. These materials are suitable due to their high refractive index and a small absorption loss. Si, SiC, SiN, TiO<NUM>, GaAs, GaN, and the like may be used as materials for the structure <NUM> and the like with respect to light (near-infrared light) with a wavelength ranging from <NUM> to <NUM>. These materials are suitable due to their low loss. With respect to light in a near-infrared region of a long wavelength band (such as <NUM> and <NUM> which are communication wavelengths), InP or the like can be used as a material of the structure <NUM> or the like in addition to the materials described above.

When the structure <NUM> and the like are formed through adhesion, coating, and the like, examples of materials include a polyimide such as fluorinated polyimide, BCB (benzocyclobutene), a photocurable resin, a UV epoxy resin, an acrylic resin such as PMMA, and a polymer such as a general resist.

While an example in which SiO<NUM> and an air layer are assumed as materials of the transparent layer <NUM> has been shown in the embodiment described above, materials of the transparent layer <NUM> are not limited thereto. Any material including a general glass material may be used as long as a refractive index of the material is smaller than that of the refractive index of the material of the structure <NUM> and the like and has low loss with respect to the wavelength of incident light. The transparent layer <NUM> may be a transparent layer having a laminated structure made up of a plurality of materials. Furthermore, since a transparent layer <NUM> need only have sufficiently low loss with respect to a wavelength which is to reach a corresponding PD, the transparent layer <NUM> may be made of a same material as that of a color filter or made of an organic material such as a resin.

While the three primary colors of RGB have been described as an example of colors that the PD <NUM>, the PD <NUM>, and the PD <NUM> correspond to in the embodiment described above, the PD <NUM>, the PD <NUM>, and the PD <NUM> may correspond to light (for example, infrared light or ultraviolet light) having wavelengths other than the three primary colors.

While an example in which one PD group <NUM> includes three PDs, namely, the PD <NUM>, the PD <NUM>, and the PD <NUM> has been described in the embodiment described above, one PD group may include two or four or more PDs. These PDs may be arranged in a one-dimensional direction (for example, in the X-axis direction or the Y-axis direction) or in a two-dimensional direction (for example, in the X-axis direction and the Y-axis direction).

While the present invention has been described based on a specific embodiment, it is obvious that the present invention is not limited to the foregoing embodiment and can be modified in various ways without departing from the invention.

For example, the imaging element described above is specified as follows. As described with reference to <FIG> and the like, an imaging element <NUM> includes a plurality of PD groups <NUM>, a transparent layer <NUM>, and a plurality of structure groups <NUM>. Each of the plurality of PD groups <NUM> includes a PD <NUM>, a PD <NUM>, and a PD <NUM> and is arranged in a two-dimensional direction (an XY planar direction). The transparent layer <NUM> faces the plurality of PD groups <NUM> and extends with a two-dimensional direction as a planar direction. The plurality of structure groups <NUM> are arranged on the transparent layer <NUM> or in the transparent layer <NUM> in a planar direction of the transparent layer <NUM> corresponding to the plurality of PD groups <NUM>. Each of the plurality of structure groups <NUM> includes a structure <NUM>, a structure <NUM>, and a structure <NUM> arranged in the same pattern, and is arranged so as to disperse incident light toward each of the PD <NUM>, the PD <NUM>, and the PD <NUM> of the corresponding PD group <NUM>. In a plan view, the relative positions of the corresponding PD group <NUM> and the structure group <NUM> differ according to two-dimensional positions (positions on an XY plane).

In the imaging element <NUM>, the relative positions of the corresponding PD group <NUM> and the structure group <NUM> differ according to two-dimensional positions. Assuming that the relative positions are the same at any two-dimensional position, as described earlier with reference to <FIG>, light dispersed by the structure group <NUM> reaches a position away from the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>. As a result, light is not efficiently incident on the PD <NUM>, the PD <NUM>, and the PD <NUM> and, for example, problems such as deterioration of light-receiving sensitivity arise. On the other hand, in the imaging element <NUM>, by shifting relative positions of the corresponding PD group <NUM> and the structure group <NUM>, a spectral direction by the structure group <NUM> can be brought close to the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM>. Therefore, light-receiving sensitivity can be improved.

When a relative position in a two-dimensional central portion in the imaging element <NUM> is used as a benchmark, a deviation of the relative position becomes larger toward a two-dimensional outer peripheral portion. Thus, a relative position corresponding to the deviation of the incidence angle which becomes larger toward the outer peripheral portion can be determined.

As described with reference to <FIG> and <FIG> and the like, the structure <NUM>, the structure <NUM> and the structure <NUM> are columnar structures having a refractive index that is higher than a refractive index of portions therebetween, at least some structures among the structure <NUM>, the structure <NUM>, and the structure <NUM> have widths that differ from each other in a plan view, and the structure <NUM>, the structure <NUM>, and the structure <NUM> may have a same height in a side view. At least some structures among the structure <NUM>, the structure <NUM>, and the structure <NUM> may have different refractive indices from each other. For example, by arranging the structure <NUM>, the structure <NUM>, and the structure <NUM> configured as described above, the structure group <NUM> (the transparent layer <NUM>) can be equipped with a spectroscopic function and incident light can be dispersed toward the PD <NUM>, the PD <NUM> and the PD <NUM>, respectively. Furthermore, the structures can be manufactured more easily than, for example, a case where a plurality of structures having different heights are provided.

As described with reference to <FIG> and the like, the imaging element 12A includes a plurality of lenses <NUM> each provided so as to correspond to each of a plurality of structure groups 50A, and relative positions of the corresponding structure groups 50A and the lenses <NUM> may differ according to two-dimensional positions in a plan view. Alternatively, as described with reference to <FIG>, <FIG>, <FIG>, and the like, the imaging element 12A may include a lens <NUM>, a lens <NUM>, and a lens <NUM>, each of which is provided with respect to each of the plurality of structure groups 50A and which has a shape in accordance with a two-dimensional position. Therefore, an incidence angle of light that is incident on the transparent layer 5A in the outer peripheral portion and the intermediate portion can be made to approach an incidence angle in the central portion. For example, light is more easily dispersed toward the center of each of the PD <NUM>, the PD <NUM>, and the PD <NUM> of the PD group <NUM> than when only the plurality of structure groups <NUM> are used.

As described with reference to <FIG> and the like, the imaging element 12B may include a plurality of diffraction gratings <NUM> which are periodically provided so as to cover at least a part of the plurality of PD groups <NUM> and which have an effective refractive index with a magnitude that differs from the refractive index of the plurality of PD groups <NUM>. Accordingly, reflection of light is suppressed and light can be made incident on the PD <NUM>, the PD <NUM> and the PD <NUM> in an efficient manner.

As described with reference to <FIG> and the like, the plurality of diffraction gratings <NUM> expose the PD <NUM> among the PD <NUM>, the PD <NUM>, and the PD <NUM> included in each of the plurality of PD groups <NUM> without covering the PD <NUM>, and the imaging element <NUM> may include a reflection suppression film <NUM> which is provided so as to cover the exposed PD <NUM> in a gapless manner and which has a refractive index that differs from the refractive index of the plurality of PD groups <NUM>. For example, by using the reflection suppressing layer 7A including the two kinds of reflection suppression members, namely, the plurality of diffraction gratings <NUM> and the reflection suppression film <NUM>, a reflection suppressing amount can be adjusted for each of the PD <NUM>, the PD <NUM> and the PD <NUM>.

Claim 1:
An imaging element (<NUM>), comprising:
a plurality of photoelectric conversion element groups (<NUM>) each including a plurality of photoelectric conversion elements (<NUM>, <NUM>, <NUM>) and being arranged in a two-dimensional direction;
a transparent layer (<NUM>) which faces the plurality of photoelectric conversion element groups and which extends in the two-dimensional direction as a planar direction;
a plurality of structure groups (<NUM>) arranged in a planar direction of the transparent layer so as to correspond to the plurality of photoelectric conversion element groups on the transparent layer or inside the transparent layer, wherein
each of the plurality of structure groups (<NUM>) includes a plurality of structures (<NUM>, <NUM>, <NUM>) arranged in a same pattern and in the planar direction of the transparent layer and arranged so as to disperse incident light toward each of the photoelectric conversion elements (<NUM>, <NUM>, <NUM>) of a corresponding photoelectric conversion element group,
wherein in a plan view, relative positions of the corresponding photoelectric conversion element group (<NUM>) and a structure group (<NUM>) differ depending on their positions in the two-dimensional plane (XY), and wherein when the relative positions at a central portion in the two-dimensional plane are used as a benchmark, the relative positions deviate more toward an outer periphery portion of the two-dimensional plane.