Passivated Planar Photodiode Dark Current Reduction
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Solution Overview
Problem
Existing optoelectronic photodetection devices with passivated planar photodiodes face challenges in reducing dark current due to the presence of passivation layers, which can degrade photodiode performance and are not reproducible, especially when the diffusion length of n-type doping elements is significant.
Innovation Solution
A method involving the production of passivated planar photodiodes with a semiconductor detection portion, a peripheral region doped with a second conductivity type, and an upper region, where the peripheral region is formed by annealing to diffuse doping elements from a peripheral portion, thereby surrounding the central part and reducing the formation of depleted or inversion zones, thus limiting stray surface currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If annealing is performed to transform the depleted zone into a hole accumulation zone, then dark current is reduced, but the dimensions of the first n-doped region are degraded
Solution Approach 1:
The patent applies preliminary action by forming the peripheral portion with second conductivity type doping before the annealing step. This peripheral portion is strategically positioned to surround the central part containing the first n-doped region. During subsequent annealing, this pre-formed peripheral structure prevents unwanted diffusion into the n-doped region, thereby protecting dimensional integrity while still allowing the annealing to transform the depleted zone into a hole accumulation zone for dark current reduction.
Solution Approach 2:
The patent implements local quality by creating distinct doped regions with different conductivity types in specific locations: a peripheral portion with second conductivity type surrounding a central part with first conductivity type. This spatial differentiation of doping characteristics allows the annealing process to have different effects in different zones - reducing dark current in the peripheral depleted zone while preserving the dimensional integrity of the central n-doped region.
2Object-generated harmful factors
If annealing is performed to reduce dark current, then the depleted zone is transformed into an accumulation zone, but the performance of the photodiode is degraded due to undesired modification of doped regions
Solution Approach 1:
The patent applies local quality by creating spatially differentiated doped regions: a peripheral portion with second conductivity type surrounding a central part with first conductivity type. This localized doping strategy ensures that annealing transforms the depleted zone into a hole accumulation zone specifically in the peripheral region where it reduces dark current, while the central n-doped region maintains its intended electrical characteristics and dimensional integrity, thus preserving overall photodiode performance.
Solution Approach 2:
The patent uses preliminary action by pre-forming the peripheral portion with second conductivity type doping before annealing. This preliminary structural preparation ensures that during the annealing process, the peripheral region is already configured to accept and contain the transformed depleted zone, preventing unwanted diffusion into sensitive areas and ensuring reliable photodiode performance while achieving dark current reduction.
3Object-generated harmful factors
If the diffusion length of n-type doping elements is significant, then the annealing step causes undesired modification of the first n-doped region, but the passivation layer still contributes to generating dark current
Solution Approach 1:
The patent implements local quality by creating a peripheral portion with second conductivity type doping that is spatially separated from and surrounds the central part containing the first n-doped region. This localized doping approach with significant diffusion length in mind creates a buffer zone that captures and contains dopant diffusion during annealing, preventing it from reaching and modifying the central n-doped region, while still effectively reducing dark current at the passivation layer interface.
Solution Approach 2:
The patent applies preliminary action by forming the peripheral portion with second conductivity type doping before the annealing step. This preliminary configuration creates a protective barrier that anticipates and prevents the undesired diffusion of n-type doping elements into the first n-doped region during annealing, while still allowing the annealing to effectively transform the depleted zone and reduce dark current from the passivation layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces dark current while preserving the dimensions of the doped regions, improving photodiode performance by avoiding the formation of depleted or inversion zones and maintaining the characteristics of the semiconductor detection portion.
Implementation Method 1
annealing, ensuring diffusion of the doping elements from the peripheral portion to the semiconductor detection portion
Data Source
AI summary
The invention relates to a method for manufacturing at least one passivated planar photodiode 1, comprising the following steps:producing a semiconductor detection portion 10; depositing a dielectric passivation layer 20; producing a peripheral portion 21 made from a doped semiconductor material;diffusion-annealing the doping elements from the peripheral portion 21 into the semiconductor detection portion 10, forming a doped peripheral region 14; producing a doped upper region 11, surrounded by the doped peripheral region 14.