Conductive Polymer Grid for Image Sensor Crosstalk
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Solution Overview
Problem
Existing image sensors face issues with crosstalk between color filters due to metal grids corroding and oxide grids having a constant refractive index, leading to decreased sensitivity and susceptibility to electrostatic charges during semiconductor processes.
Innovation Solution
An image-sensor structure incorporating a conductive polymer element with a low-refractive-index component, such as fluoroacrylic polymers, filled between color filters and a light shielding layer, electrically connected to a grounding pad to improve signal-to-noise ratio and release electrostatic charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal grid is used to prevent crosstalk between color filters, then crosstalk is reduced, but the grid becomes corroded during color filter processes
Solution Approach 1:
The patent employs a composite structure consisting of a lower refractive index layer (with refractive index 1.3-1.6) and an upper refractive index layer (with refractive index 1.6-1.8). This composite material approach allows the grid to maintain both crosstalk prevention capability and resistance to corrosion during color filter processes, as the specific material composition provides chemical stability while maintaining optical performance.
2Stability of the object's composition
If an oxide grid is used to avoid corrosion, then material stability is improved, but the refractive index variation between grid and color filters decreases
Solution Approach 1:
The patent changes the refractive index parameters of the grid materials to optimize performance. The lower refractive index layer has a refractive index of 1.3-1.6 and the upper refractive index layer has a refractive index of 1.6-1.8, creating sufficient refractive index variation (greater than 0.2) between the grid and color filters. This parameter optimization maintains both material stability and effective crosstalk prevention.
3Measurement precision
If electrostatic charges are generated on the wafer during high-speed rotation, then measurement accuracy is improved, but dark current increases
Solution Approach 1:
The patent introduces a conductive layer as an intermediary between the wafer and the measurement system. This conductive layer serves as a mediator that dissipates electrostatic charges generated during high-speed rotation, preventing charge accumulation that would otherwise cause high dark current. The intermediary layer maintains measurement accuracy while eliminating the harmful electrostatic effects.
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 conductive polymer element enhances the signal-to-noise ratio and effectively addresses electrostatic charge issues by increasing the refractive index variation and providing a path for charge release, thereby improving device performance.
Implementation Method 1
the first conductive polymer element is electrically connected to a grounding pad
Implementation Method 2
an adjustable refractive index (which is capable of further increasing the variation of the refractive index between the grid and the color filters)
Data Source
AI summary
An image-sensor structure is provided. The image-sensor structure includes a substrate, a plurality of photoelectric conversion units formed in the substrate, a plurality of separated color filters formed above the substrate and the photoelectric conversion units, a first light shielding layer surrounding the separated color filters, and a first conductive polymer element blended with a low-refractive-index component filled between the individual separated color filters and between the all separated color filters and the first light shielding layer, wherein the first conductive polymer element is electrically connected to a grounding pad.