Backside Illumination Image Sensor In-Situ Doping

The patent combines the polysilicon deposition process with in-situ p-type impurity doping into a single integrated process step. The polysilicon layer is deposited while simultaneously incorporating p-type dopants (such as boron) during the deposition itself, rather than requiring separate implantation and annealing steps. This merging of processes eliminates the need for substrate damage repair through annealing, as the in-situ doping creates a beneficial p-type surface layer that passivates the substrate.

The patent applies preliminary action by forming the p-type impurity profile during the polysilicon deposition process itself, before any potential substrate damage occurs. The in-situ doping during deposition creates a protective p-type surface layer in advance, preventing the need for subsequent damage repair steps. This preliminary formation of the impurity profile eliminates the requirement for post-implantation annealing.

The patent merges the impurity introduction process with polysilicon deposition into a single in-situ doping step. The p-type impurity profile is formed concurrently with the polysilicon layer deposition, eliminating the need for separate implantation and annealing steps. This integration maintains precise impurity profile control while significantly reducing total manufacturing time by removing sequential process steps.

The patent utilizes parameter changes in the deposition process itself to control the impurity profile. By adjusting deposition parameters (temperature, pressure, dopant source concentration) during polysilicon deposition, the patent achieves precise control over the p-type impurity distribution without requiring thermal annealing. This parameter control during deposition replaces the need for post-deposition thermal processing.

The patent applies the inversion principle by switching from conventional front-side illumination to backside illumination architecture. Instead of illuminating the sensor through the front surface where metal interconnects and passivation layers block photons, the patent inverts the structure to illuminate from the backside, allowing photons to enter the silicon substrate directly without obstruction. This structural inversion dramatically improves photon capture efficiency despite increased manufacturing complexity.

The patent applies local quality by creating a p-type surface layer specifically at the backside of the substrate where light enters. This localized p-type doping at the illumination surface provides selective passivation and field effect where most needed for photon capture, while maintaining different structural requirements at the front side for sensor element formation. The local p-type surface layer optimizes the backside illumination interface without affecting front-side sensor functionality.