Solid state imaging element and electronic device to obtain high sensitivity of light on a long wavelength side
The present disclosure relates to a solid state imaging element and an electronic device that make it possible to improve sensitivity to light on a long wavelength side. A solid state imaging element according to a first aspect of the present disclosure has a solid state imaging element in which a large number of pixels are arranged vertically and horizontally, the solid state imaging element includes a periodic concave-convex pattern on a light receiving surface and an opposite surface to the light receiving surface of a light absorbing layer as a light detecting element. The present disclosure can be applied to, for example, a CMOS and the like installed in a sensor that needs a high sensitivity to light belonging to a region on the long wavelength side, such as light in the infrared region.
1. A solid state imaging element, comprising:
a light detecting element disposed in a silicon layer;
a first concave-convex pattern on a first surface of the silicon layer, the first surface being a light receiving surface;
an interconnection layer disposed below the silicon layer; and
a reflecting mirror structure on a lower side of the light detecting element,
wherein the silicon layer is made of single-crystal Si,
wherein the interconnection layer is planar,
wherein the light detecting element is disposed between a first isolation structure and a second isolation structure, and
wherein the first concave-convex pattern has an inverted pyramid shape.
2. The solid state imaging element according to claim 1 , wherein the light detecting element detects infra-red (IR) light.
3. The solid state imaging element according to claim 1 , further comprising:
a second concave-convex pattern on a second surface of the silicon layer that is opposite the first surface.
4. The solid state imaging element according to claim 3 , wherein a period of the first concave-convex pattern on the first surface and a period of the second concave-convex pattern on the second surface vary based on a wavelength of light that is to be sensed.
5. The solid state imaging element according to claim 3 , wherein the first concave-convex pattern and the second periodic concave-convex pattern are one of one-dimensional or two-dimensional.
6. The solid state imaging element according to claim 3 , wherein a first crystal plane of the first surface and the second surface is (100), and wherein a second crystal plane of a wall surface of the first concave-convex pattern is (111).
7. The solid state imaging element according to claim 1 , wherein a period of the first concave-convex pattern is 1 um or less.
8. The solid state imaging element according to claim 1 , wherein the first and second isolation structures are made of a material of a first refractive index lower than a second refractive index of the light detecting element.
9. The solid state imaging element according to claim 1 , wherein the first and second isolation structures comprise metal reflecting walls.
10. The solid imaging element according to claim 1 , wherein the interconnection layer serves as the reflecting mirror structure.
11. An electronic device, comprising:
a solid state imaging element, wherein the solid state imaging element comprises:
a light detecting element disposed in a silicon layer;
a first concave-convex pattern on a first surface of the silicon layer, the first surface being a light receiving surface;
an interconnection layer disposed below the silicon layer; and
a reflecting mirror structure on a lower side of the light detecting element,
wherein the silicon layer is made of single-crystal Si,
wherein the interconnection layer is planar,
wherein the light detecting element is disposed between a first isolation structure and a second isolation structure, and
wherein the first concave-convex pattern has an inverted pyramid shape.
12. The solid state imaging element according to claim 1 , wherein the interconnection layer is disposed from a first region corresponding to a first trench to a second region corresponding to a second trench, wherein the first trench includes the first isolation structure, and wherein the second trench includes the second isolation structure.
13. The solid state imaging element according to claim 1 , further comprising:
a second concave-convex pattern on a second surface of the silicon layer that is opposite the first surface, wherein, in a cross sectional view, a width of part of the first concave-convex pattern is different from a width of a part of the second concave-convex pattern.
14. The solid state imaging element according to claim 1 , wherein a widest section of the inverted pyramid shape period has a width that is less than or equal to a period of the first concave-convex pattern.
15. The solid state imaging element according to claim 14 , wherein a depth of the inverted pyramid shape is less than the width of the widest section.
16. The solid state imaging element according to claim 1 , wherein the inverted pyramid shape has a base surface and a tip surface that are parallel to the first surface.
17. The solid state imaging element according to claim 1 , wherein a depth of the inverted pyramid shape is between 0.3*W 1 and 1.0*W 1 , where W 1 is a width of a widest part of an opening that defines the inverted pyramid shape in the concave-convex pattern.