Backside depletion for backside illuminated image sensors
First Claim
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1. A method for fabricating a backside illuminated image sensor, the method comprising:
- providing a substrate having a front side, a backside, and a first thickness;
forming a plurality of sensors in the substrate at the front side, wherein each of the plurality of sensors includes at least a photodiode;
reducing the thickness of the substrate from the first thickness to a second thickness;
after reducing the thickness of the substrate from the first thickness to the second thickness, forming a first doped region in the substrate proximate to the back side, the first doped region having a first conductivity type; and
forming a second doped region in the semiconductor substrate adjacent to the first doped region such that the second doped region is positioned between the first doped region and the backside of the semiconductor substrate, the second doped region having a second conductivity type that is opposite the first conductivity type.
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Abstract
A backside illuminated image sensor is provided which includes a substrate having a front side and a backside, a sensor formed in the substrate at the front side, the sensor including at least a photodiode, and a depletion region formed in the substrate at the backside, a depth of the depletion region is less than 20% of a thickness of the substrate.
42 Citations
20 Claims
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1. A method for fabricating a backside illuminated image sensor, the method comprising:
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providing a substrate having a front side, a backside, and a first thickness; forming a plurality of sensors in the substrate at the front side, wherein each of the plurality of sensors includes at least a photodiode; reducing the thickness of the substrate from the first thickness to a second thickness; after reducing the thickness of the substrate from the first thickness to the second thickness, forming a first doped region in the substrate proximate to the back side, the first doped region having a first conductivity type; and forming a second doped region in the semiconductor substrate adjacent to the first doped region such that the second doped region is positioned between the first doped region and the backside of the semiconductor substrate, the second doped region having a second conductivity type that is opposite the first conductivity type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method comprising:
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providing a semiconductor substrate having a first side and an opposing second side, the semiconductor substrate having a first conductivity type and a first doping concentration; forming a sensor in the semiconductor substrate at the first side; forming a first doped region in the semiconductor substrate proximate to the second side, the first doped region having the first conductivity type and a second doping concentration that is different than the first doping concentration; forming a second doped region in the semiconductor substrate adjacent to the first doped region such that the second doped region is positioned between the first doped region and the second side of the semiconductor substrate, the second doped region having a second conductivity type that is opposite the first conductivity type; and forming a color filter on the second side of the semiconductor substrate that is aligned with the sensor. - View Dependent Claims (11, 12, 13, 14)
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15. A method comprising:
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providing a semiconductor substrate having a first surface and an opposing second surface, wherein the semiconductor substrate has a first thickness extending from the first surface to the second surface; forming a sensing element in the semiconductor substrate proximate the first surface, wherein the sensing element is operable to sense light radiation directed towards the second surface; forming an interconnection layer on the first surface of the semiconductor substrate; removing a portion of the semiconductor substrate including the second surface such that the thickness of the semiconductor substrate is reduced from the first thickness to a second thickness, wherein the second thickness extends from the first surface to an opposing third surface of the semiconductor substrate; after removing the portion of the semiconductor substrate, forming a first doped region in the semiconductor substrate at a first depth from the third surface; forming a second doped region in the semiconductor substrate at a second depth from the third surface, the second depth being less than the first depth such that the second doped region is located between the first doped region and the third surface of the semiconductor substrate; and performing a laser annealing process at the third surface of the semiconductor substrate. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification