Backside Illuminated CMOS Sensor Doped Passivation Layer Leakage Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Backside illuminated complementary metal-oxide semiconductor (CMOS) image sensors face issues with leakage current due to defects in the trenches, leading to dark current and electrical cross-talk, which degrades the performance by falsely detecting light in dark environments.
Innovation Solution
A method involving the formation of a passivation layer with dopants of opposite polarity to the radiation-sensing region, implanted from the backside to seal defects in the trenches, and subsequent trench isolation with dielectric material to reduce leakage current and enhance radiation detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If backside illuminated CMOS image sensors are used to improve light detection capability, then sensitivity is improved, but leakage current increases due to trench defects
Solution Approach 1:
A passivation layer is introduced as an intermediary between the radiation-sensing region and the trenches. This passivation layer includes a doped region with dopants of opposite polarity that seals defects in the trenches, thereby blocking leakage current paths while allowing the backside illuminated structure to maintain its light detection sensitivity.
Solution Approach 2:
The harmful leakage current paths are extracted and isolated by forming a doped passivation layer that specifically targets and seals defect regions in the trenches. This removes the harmful effect without altering the fundamental backside illuminated sensor structure that provides good light detection capability.
2Measurement precision
If the substrate is doped to form radiation-sensing regions, then radiation detection capability is improved, but defects in the substrate increase leading to leakage current
Solution Approach 1:
The passivation layer acts as an intermediary that compensates for substrate defects. The doped region within the passivation layer has opposite polarity to the radiation-sensing region, creating a counteracting electric field that seals leakage paths caused by substrate doping defects while preserving radiation detection capability.
Solution Approach 2:
The passivation layer is formed beforehand to seal potential leakage paths before they can cause problems. By pre-doping the passivation layer with opposite polarity dopants, the structure proactively prevents leakage current generation from substrate defects, cushioning against reliability issues before they manifest.
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
The solution effectively reduces dark current and electrical cross-talk, improving the sensitivity and accuracy of the image sensor by minimizing false light detection in dark conditions and enhancing full well capacity.
Implementation Method 1
A doped passivation layer is formed in and on the backside of the substrate. The doped passivation layer includes a doped region with dopants of opposite polarity to the radiation-sensing region.
Implementation Method 2
The doped passivation layer includes a doped region with dopants of opposite polarity to the radiation-sensing region, implanted from the backside to seal defects in the trenches
Implementation Method 3
These devices utilize an array of pixels in a substrate, including photodiodes and transistors that can absorb radiation projected toward the substrate and convert the sensed radiation into electrical signals.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a radiation-sensing region, at least one isolation structure, and a doped passivation layer. The radiation-sensing region is present in the semiconductor substrate. The isolation structure is present in the semiconductor substrate and adjacent to the radiation-sensing region. The doped passivation layer at least partially surrounds the isolation structure in a substantially conformal manner.