Image Sensor Shallow Trench Edge Doping Leakage Current
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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 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 to reduce leakage current, then leakage current is reduced, but image lag increases
Solution Approach 1:
The patent applies different doping concentrations to different regions: a first well region with higher doping concentration near the trench to reduce leakage current, and a second well region with lower doping concentration under the transfer transistor to minimize image lag. This spatial differentiation of doping properties resolves the contradiction between reducing leakage and preventing image lag.
Solution Approach 2:
The well region is segmented into at least two distinct regions with different doping concentrations: a first well region adjacent to the trench isolation structure and a second well region positioned under the transfer transistor. This segmentation allows each region to be optimized for its specific function, addressing both leakage current and image lag independently.
2Ease of manufacture
If a uniform doping concentration is used in the well region, then manufacturing is simplified, but both leakage current and image lag cannot be effectively controlled
Solution Approach 1:
Instead of uniform doping, the patent implements local quality variation by doping different regions with different concentrations. The first well region receives a first doping concentration while the second well region receives a second doping concentration, allowing simultaneous optimization of leakage current reduction and image lag minimization.
Solution Approach 2:
The doping process is segmented into at least two distinct doping operations or regions, where the first well region is doped with a first concentration and the second well region is doped with a second concentration. This segmented approach enables independent control of each region's electrical properties to address multiple performance requirements.
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 photodetector region provided in a substrate. A dielectric material is disposed within a trench defined by one or more interior surfaces of the substrate. The trench has a depth that extends from an upper surface of the substrate to within the substrate. A doped silicon material is disposed within the trench and has a sidewall facing away from the doped silicon material. The sidewall contacts a sidewall of the dielectric material along an interface extending along the depth of the trench.