Image Sensor Pixel Transfer Gate Segmentation for Dark Current Reduction
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Solution Overview
Problem
Existing image sensors face challenges in minimizing dark current generation due to the overlap of transfer gates with isolation regions, leading to noisy electrons and degraded dark characteristics.
Innovation Solution
The design of a unit pixel in an image sensor includes a transfer gate with first and second portions divided by a reference line, where at least one portion does not overlap the isolation region, minimizing the electric field intensity and reducing noisy electron generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the transfer gate overlaps the isolation region, then the device structure is simplified and manufacturing is easier, but dark current increases and dark characteristics are degraded
Solution Approach 1:
The transfer gate is divided into first and second portions by a reference line. The first portion may overlap the isolation region while the second portion does not overlap the isolation region. This segmentation allows the transfer gate to maintain manufacturing simplicity while reducing overlap with the isolation region to suppress dark current generation.
2Device complexity
If the transfer gate overlaps the isolation region, then the layout is simpler, but noisy electron generation increases
Solution Approach 1:
The transfer gate is segmented into first and second portions relative to a reference line. This segmentation reduces the overlap area between the transfer gate and isolation region, thereby minimizing electric field intensity at the boundary and reducing noisy electron generation while maintaining relatively simple device layout.
3Reliability
If the transfer gate does not overlap the isolation region, then dark characteristics are improved, but the transfer gate structure becomes more complex
Solution Approach 1:
The transfer gate is divided into first and second portions, where the first portion can overlap the isolation region and the second portion does not overlap the isolation region. This segmented approach achieves improved dark characteristics by reducing overall overlap while maintaining manufacturing feasibility and avoiding excessive structural complexity.
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 design enhances the dark characteristic of the image sensor by suppressing noisy electron generation and improving the overall performance by maintaining higher potential levels in the photoelectric conversion region.
Implementation Method 1
a photoelectric conversion region in an active region defined by an isolation region of a semiconductor substrate, the photoelectric conversion region configured to generate electric charges corresponding to incident light
Data Source
AI summary
A unit pixel of an image sensor includes a photoelectric conversion region, a floating diffusion region, and a transfer gate. The photoelectric conversion region is in an active region defined by an isolation region of a semiconductor substrate. The photoelectric conversion region generates electric charges corresponding to incident light. The transfer gate transfers the electric charges to the floating diffusion region, which is located in the active region. The transfer gate includes first and second portions divided relative to a reference line, and at least one of the first or second portions does not overlap the isolation region.