Back-illuminated CMOS image sensors
First Claim
1. A method for fabricating a back-illuminated image sensor that includes a sensor layer disposed between an insulating layer and a circuit layer electrically connected to the sensor layer, wherein a frontside of the sensor layer is adjacent to the circuit layer and a backside of the sensor layer is adjacent to the insulating layer, the back-illuminated image sensor further including an imaging area comprising a plurality of photodetectors disposed in the frontside of the sensor layer, the method comprising:
- forming at least one shallow trench isolation (STI) region in the sensor layer, including thermal oxidation of the at least one STI region;
forming an implanted sensor layer by implanting the sensor layer with an n-type dopant from the frontside and through the sensor layer to form an n-type well in the sensor layer adjacent to the backside of the sensor layer, wherein implanting the sensor layer with the n-type dopant occurs after the thermal oxidation of the at least one STI region to reduce thermal diffusion of dopants in the n-type well; and
doping the implanted sensor layer with a p-type dopant to form the plurality of photodetectors doped with the p-type dopant in the frontside of the sensor layer.
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Abstract
A back-illuminated image sensor includes a sensor layer disposed between an insulating layer and a circuit layer electrically connected to the sensor layer. An imaging area includes a plurality of photodetectors is formed in the sensor layer and a well that spans the imaging area. The well can be disposed between the backside of the sensor layer and the photodetectors, or the well can be a buried well formed adjacent to the backside of the sensor layer with a region including formed between the photodetectors and the buried well. One or more side wells can be formed laterally adjacent to each photodetector. The dopant in the well has a segregation coefficient that causes the dopant to accumulate on the sensor layer side of an interface between the sensor layer and the insulating layer.
28 Citations
6 Claims
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1. A method for fabricating a back-illuminated image sensor that includes a sensor layer disposed between an insulating layer and a circuit layer electrically connected to the sensor layer, wherein a frontside of the sensor layer is adjacent to the circuit layer and a backside of the sensor layer is adjacent to the insulating layer, the back-illuminated image sensor further including an imaging area comprising a plurality of photodetectors disposed in the frontside of the sensor layer, the method comprising:
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forming at least one shallow trench isolation (STI) region in the sensor layer, including thermal oxidation of the at least one STI region; forming an implanted sensor layer by implanting the sensor layer with an n-type dopant from the frontside and through the sensor layer to form an n-type well in the sensor layer adjacent to the backside of the sensor layer, wherein implanting the sensor layer with the n-type dopant occurs after the thermal oxidation of the at least one STI region to reduce thermal diffusion of dopants in the n-type well; and doping the implanted sensor layer with a p-type dopant to form the plurality of photodetectors doped with the p-type dopant in the frontside of the sensor layer. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification