Image Sensor Trench Edge Doping for Leakage and Image Lag
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Solution Overview
Problem
Integrated image sensors face issues with unwanted leakage currents between adjacent pixel regions due to defects in the semiconductor substrate during trench etching, which can lead to dark current and image lag problems, and existing doping implantation processes struggle to balance leakage current and image lag effectively.
Innovation Solution
An integrated image sensor design that includes a photodetector separated from a trench by a first well region with a doped epitaxial material of higher doping concentration within the trench, and a second well region under the transfer transistor with a lower doping concentration to mitigate image lag, thereby reducing leakage currents and improving image sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a higher doping concentration is used in the well region near the trench, then leakage current is reduced, but image lag increases
Solution Approach 1:
The patent applies local quality by implementing different doping concentrations in different regions: a first well region with higher doping concentration near the trench to reduce leakage current, and a second well region under the transfer transistor with lower doping concentration to minimize image lag. This spatial differentiation of doping properties resolves the contradiction between reducing leakage and preventing image lag.
Solution Approach 2:
The patent segments the well region into two distinct regions with different doping concentrations. The first well region (higher doping) addresses leakage current near the trench, while the second well region (lower doping) addresses image lag under the transfer transistor. This segmentation allows each region to be optimized for its specific function without compromising the other.
2Reliability
If a lower doping concentration is used in the well region under the transfer transistor, then image lag is reduced, but leakage current increases
Solution Approach 1:
The patent applies local quality by implementing different doping concentrations in different regions: a first well region with higher doping concentration near the trench to reduce leakage current, and a second well region under the transfer transistor with lower doping concentration to minimize image lag. This spatial differentiation of doping properties resolves the contradiction between reducing leakage and preventing image lag.
Solution Approach 2:
The patent segments the well region into two distinct regions with different doping concentrations. The first well region (higher doping) addresses leakage current near the trench, while the second well region (lower doping) addresses image lag under the transfer transistor. This segmentation allows each region to be optimized for its specific function without compromising the other.
3Ease of manufacture
If uniform doping is applied throughout the substrate, then manufacturing is simplified, but both leakage current and image lag cannot be effectively controlled
Solution Approach 1:
The patent applies local quality by implementing different doping concentrations in different regions: a first well region with higher doping concentration near the trench to reduce leakage current, and a second well region under the transfer transistor with lower doping concentration to minimize image lag. This spatial differentiation of doping properties resolves the contradiction between reducing leakage and preventing image lag.
Solution Approach 2:
The patent segments the well region into two distinct regions with different doping concentrations. The first well region (higher doping) addresses leakage current near the trench, while the second well region (lower doping) addresses image lag under the transfer transistor. This segmentation allows each region to be optimized for its specific function without compromising the other.
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 leakage currents between adjacent pixel regions while minimizing image lag, enhancing the overall performance of the integrated image sensor by increasing the doping concentration of the well region near the trench and maintaining a lower doping concentration under the gate structure.
Implementation Method 1
the doped epitaxial material is arranged within the trench at a location laterally between the one or more dielectric materials and the first well region... the doped epitaxial material has a first doping concentration that is configured to increase a doping concentration of the first well region
Data Source
AI summary
The present disclosure relates to an integrated chip. The integrated chip includes a gate structure on a substrate. A doped region is within the substrate. One or more dielectric materials are within a recess formed by one or more surfaces of the substrate. The doped region is laterally between the gate structure and the recess. A doped epitaxial material is within the recess and between the one or more dielectric materials and the doped region. The doped epitaxial material is asymmetric about a vertical line that extends through a lateral center of the doped epitaxial material.