Backside-illuminated image sensor and method of manufacturing same
A backside-illuminated image sensor and a method of manufacturing the same are disclosed. The backside-illuminated image sensor is capable of improving sensitivity by including a scattering layer in a substrate that may result in incident light having a path greater than the thickness of the substrate and, simultaneously, of additionally enhancing light sensitivity with respect to a specific wavelength or wavelength band of light passing through one of a plurality of different color filters by a varying depth or thickness of the scattering layer for each unit pixel in the image sensor.
1 . A backside-illuminated image sensor comprising:
a substrate comprising a front surface and a rear surface and a plurality of unit pixels, the plurality of unit pixels comprising first pixels configured to receive blue light, second pixels configured to receive green light, and third pixels configured to receive red light;
a light receiving element at or on the front surface of the substrate in each of the plurality of unit pixels;
a deep trench isolation (DTI) region in the substrate and at a boundary between adjacent ones of the plurality of unit pixels;
a scattering layer in the substrate comprising a first scattering structure in each of the first pixels, a second scattering structure in the substrate and in each of the second pixels, and a third scattering structure in the substrate and in each of the third pixels, wherein each of the first, second and third scattering structures scatter and reflect incident light and have side walls perpendicular to the front surface and the rear surface of the substrate;
a blue color filter on the rear surface of the substrate in each of the first pixels, a green color filter on the rear surface of the substrate in each of the second pixels, and a red color filter on the rear surface of the substrate in each of the third pixels; and
a lens on each of the blue, green and red color filters,
wherein the first scattering structure has a first thickness, the second scattering structure has a second thickness greater than the first thickness, the third scattering structure has a third thickness greater than the second thickness, and the DTI region reflects the incident light scattered by and the incident light reflected by an adjacent one of the first, second and third scattering structures into one of the unit pixels containing the adjacent one of the first, second and third scattering structures and toward the light receiving element.
2 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures extends from the rear surface of the substrate, or a depth adjacent to the rear surface, toward the front surface of the substrate.
3 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures is in a center of the unit pixel.
4 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures has a width smaller than a gap or distance between adjacent DTI regions.
5 . The backside-illuminated image sensor of claim 1 , further comprising:
one or more wiring levels on the front surface of the substrate, wherein each wiring level comprises:
a metal wiring layer; and
an insulation layer covering the metal wiring layer.
6 . The backside-illuminated image sensor of claim 1 , wherein the first scattering structure, the second scattering structure, and the third scattering structure are formed by etching the rear surface of the substrate using separate etching processes.
7 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures comprises a silicon oxide film, a metal film, or a polysilicon film.
8 . The backside-illuminated image sensor of claim 1 , wherein the DTI region comprises one or more films comprising a borophosphosilicate glass (BPSG), a phosphosilicate glass (PSG), a borosilicate glass (BSG), an undoped silicate glass (USG), a silicon dioxide derived from tetraethyl orthosilicate (TEOS), and/or a high-density plasma (HDP)-deposited film derived from silane.
9 . The backside-illuminated image sensor of claim 8 , wherein each of the first, second and third scattering structures includes a same material as the DTI region.
10 . The backside-illuminated image sensor of claim 1 , wherein each of the first, second and third scattering structures includes a same material as the DTI region.
11 . The backside-illuminated image sensor of claim 1 , wherein the third thickness is more than half of a thickness of the substrate.
12 . The backside-illuminated image sensor of claim 1 , wherein each of the first thickness, the second thickness, and the third thickness is sufficient for each of the first scattering structure, the second scattering structure and the third scattering structure to scatter incident light and to reflect incident light reflected by the DTI region at least once.
13 . The backside-illuminated image sensor of claim 12 , wherein each of the second thickness and the third thickness is sufficient for each of the second scattering structure and the third scattering structure to reflect incident light reflected by the DTI region at least twice.