Avalanche photodiode sensor and distance measuring device including concave-convex portions for reduced reflectance
Distance measurement accuracy is improved. An avalanche photodiode sensor according to an embodiment includes a first semiconductor substrate and a second semiconductor substrate bonded to a first surface of the first semiconductor substrate, wherein the first semiconductor substrate includes a plurality of photoelectric conversion portions arranged in a matrix and an element separation portion, the plurality of photoelectric conversion portions include a first photoelectric conversion portion, the element separation portion has a first element separation region and a second element separation region, the first photoelectric conversion portion is arranged between the first element separation region and the second element separation region, the first semiconductor substrate further includes a plurality of concave-convex portions on a second surface opposite to the first surface and between the first element separation region and the second element separation region, and the second semiconductor substrate includes a reading circuit connected to each of the photoelectric conversion portions.
1. An avalanche photodiode sensor, comprising:
a first semiconductor substrate; and
a second semiconductor substrate bonded to a first surface of the first semiconductor substrate,
wherein the first semiconductor substrate includes:
a plurality of photoelectric conversion portions arranged in a matrix;
an element separation portion for element-separating the plurality of photoelectric conversion portions from each other,
wherein the plurality of photoelectric conversion portions include a first photoelectric conversion portion,
wherein the element separation portion has a first element separation region and a second element separation region,
wherein the first photoelectric conversion portion is arranged between the first element separation region and the second element separation region,
wherein the first semiconductor substrate further includes a first plurality of concave-convex portions arranged on a second surface of the first semiconductor substrate opposite to the first surface of the first semiconductor substrate and arranged between the first element separation region and the second element separation region, and
wherein the second semiconductor substrate includes a reading circuit connected to each of the photoelectric conversion portions; and
a flattening film extending above and across the first plurality of concave-convex portions and the element separation portion,
wherein a trench is provided on the second surface of the first semiconductor substrate in at least a part of a region defined by the first and second element separation regions, and
wherein a second plurality of concave-convex portions are provided on a bottom surface of the trench.
2. The avalanche photodiode sensor according to claim 1 , wherein the first photoelectric conversion portion includes a cathode region of a first conductive type provided on the first surface of the first semiconductor substrate and an anode region of a second conductive type opposite to the first conductive type, the anode region being provided on the first surface.
3. The avalanche photodiode sensor according to claim 2 , wherein the first plurality of concave-convex portions are arranged in a region corresponding to at least the cathode region or the anode region in a substrate thickness direction of the first semiconductor substrate.
4. The avalanche photodiode sensor according to claim 2 , wherein the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in a region corresponding to the cathode region in a substrate thickness direction of the first semiconductor substrate.
5. The avalanche photodiode sensor according to claim 2 , wherein the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in a region corresponding to the anode region in a substrate thickness direction of the first semiconductor substrate.
6. The avalanche photodiode sensor according to claim 2 , wherein the element separation portion further includes third and fourth element separation regions that define the first photoelectric conversion portion in a different direction from the first and second element separation regions, and
the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in a cross-shaped region that divides a rectangular region defined by the first to fourth element separation regions into four.
7. The avalanche photodiode sensor according to claim 2 , wherein the element separation portion further includes third and fourth element separation regions that define the first photoelectric conversion portion in a different direction from the first and second element separation regions, and
the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate at each of four corners of a rectangular region defined by the first to fourth element separation regions.
8. The avalanche photodiode sensor according to claim 2 , wherein the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in a cross-shaped region corresponding to the cathode region in a substrate thickness direction of the first semiconductor substrate.
9. The avalanche photodiode sensor according to claim 1 , wherein the first photoelectric conversion portion is an avalanche photodiode.
10. The avalanche photodiode sensor according to claim 1 , wherein each of the first and second element separation regions includes a reflective film or a high refractive index film.
11. The avalanche photodiode sensor according to claim 1 , wherein each of the first and second element separation regions penetrates the first semiconductor substrate from the first surface to the second surface.
12. The avalanche photodiode sensor according to claim 1 , wherein the first plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in an entire region defined by the first and second element separation regions.
13. The avalanche photodiode sensor according to claim 1 , wherein the first semiconductor substrate further includes a light transmitting film provided inside the trench.
14. An avalanche photodiode sensor, comprising:
a first semiconductor substrate; and
a second semiconductor substrate bonded to a first surface of the first semiconductor substrate,
wherein the first semiconductor substrate includes:
a plurality of photoelectric conversion portions arranged in a matrix;
an element separation portion for element-separating the plurality of photoelectric conversion portions from each other,
wherein the plurality of photoelectric conversion portions include a first photoelectric conversion portion,
wherein the element separation portion has a first element separation region and a second element separation region,
wherein the first photoelectric conversion portion is arranged between the first element separation region and the second element separation region,
wherein the first semiconductor substrate further includes a first plurality of concave-convex portions arranged on a second surface of the first semiconductor substrate opposite to the first surface of the first semiconductor substrate and arranged between the first element separation region and the second element separation region, and
wherein the second semiconductor substrate includes a reading circuit connected to each of the photoelectric conversion portions; and
a flattening film extending above and across the first plurality of concave-convex portions and the element separation portion,
wherein a trench is provided on the second surface of the first semiconductor substrate in at least a part of a region defined by the first and second element separation regions, and
wherein the first semiconductor substrate further includes a second plurality of concave-convex portions provided on a bottom surface of the trench.
15. The avalanche photodiode sensor according to claim 14 , wherein each of the first and second element separation regions includes a reflective film or a high refractive index film.
16. The avalanche photodiode sensor according to claim 14 , wherein each of the first and second element separation regions penetrates the first semiconductor substrate from the first surface to the second surface.
17. A distance measuring device, comprising:
a light emitting portion configured to emit light of a predetermined wavelength;
an avalanche photodiode sensor configured to generate a pixel signal from received light; and
a calculation unit configured to calculate a distance to an object based on the pixel signal generated by the avalanche photodiode sensor,
wherein the avalanche photodiode sensor includes:
a first semiconductor substrate; and
a second semiconductor substrate bonded to a first surface of the first semiconductor substrate,
wherein the first semiconductor substrate includes:
a plurality of photoelectric conversion portions arranged in a matrix;
an element separation portion for element-separating the plurality of photoelectric conversion portions from each other,
wherein the plurality of photoelectric conversion portions include a first photoelectric conversion portion,
wherein the element separation portion has a first element separation region and a second element separation region,
wherein the first photoelectric conversion portion is arranged between the first element separation region and the second element separation region,
wherein the first semiconductor substrate further includes a plurality of concave-convex portions arranged on a second surface of the first semiconductor substrate opposite to the first surface of the first semiconductor substrate and arranged between the first element separation region and the second element separation region, and
wherein the second semiconductor substrate includes a reading circuit connected to each of the photoelectric conversion portions; and
a flattening film extending above and across the plurality of concave-convex portions and the element separation portion,
wherein a trench is provided on the second surface of the first semiconductor substrate in at least a part of a region defined by the first and second element separation regions, and
wherein the first semiconductor substrate further includes a light transmitting film provided inside the trench.
18. The distance measuring device according to claim 17 , wherein the first photoelectric conversion portion includes a cathode region of a first conductive type provided on the first surface of the first semiconductor substrate and an anode region of a second conductive type opposite to the first conductive type, the anode region being provided on the first surface.
19. The distance measuring device according to claim 18 , wherein the element separation portion further includes third and fourth element separation regions that define the first photoelectric conversion portion in a different direction from the first and second element separation regions, and
the plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate in a cross-shaped region that divides a rectangular region defined by the first to fourth element separation regions into four.
20. The distance measuring device according to claim 18 , wherein the element separation portion further includes third and fourth element separation regions that define the first photoelectric conversion portion in a different direction from the first and second element separation regions, and
the plurality of concave-convex portions are arranged on the second surface of the first semiconductor substrate at each of four corners of a rectangular region defined by the first to fourth element separation regions.