CMOS Image Sensor Pixel Isolation for Lower Optical Crosstalk
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Solution Overview
Problem
Existing CMOS image sensors face challenges in optimizing optical properties such as crosstalk reduction and light absorption, which affect sensitivity and signal-to-noise ratio (SNR) performance.
Innovation Solution
The image sensor incorporates a substrate with pixel isolation patterns, low-refractive index patterns, and light blocking patterns within an insulating structure to isolate color filters and reduce direct contact, enhancing light efficiency and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If color filters are placed in direct contact to reduce structural complexity, then manufacturing is easier, but crosstalk between adjacent pixels increases
Solution Approach 1:
The patent divides the space between adjacent color filters by introducing pixel isolation patterns that extend from the substrate and low-refractive index patterns that fill the gaps. This segmentation physically separates adjacent color filters, preventing direct contact and reducing optical crosstalk between neighboring pixels while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent introduces intermediary structures between adjacent color filters, specifically the low-refractive index patterns and pixel isolation patterns that act as mediators. These intermediary elements prevent direct contact between color filters, reducing crosstalk while adding minimal structural complexity compared to complete isolation structures.
2Object-affected harmful factors
If light blocking patterns are placed close to pixel isolation patterns to improve light blocking efficiency, then crosstalk reduction improves, but light absorption by isolation patterns increases
Solution Approach 1:
The patent applies local quality by using low-refractive index patterns specifically in the regions where light blocking is most critical (between pixel isolation patterns and adjacent to color filters), while maintaining other regions with standard properties. This localized application of low-refractive index material reduces light absorption by the isolation structure itself while maintaining effective light blocking where needed.
Solution Approach 2:
The patent changes the refractive index parameter of the material in specific regions by introducing low-refractive index patterns. This parameter change reduces light absorption and scattering by the isolation structure, allowing light to pass more efficiently to the photodiode while still maintaining the light blocking function through proper geometric arrangement of the patterns.
3Object-affected harmful factors
If pixel isolation patterns extend deeply to improve isolation effectiveness, then crosstalk reduction improves, but manufacturing complexity and material usage increase
Solution Approach 1:
The patent segments the isolation function across multiple components: substrate-level pixel isolation patterns, low-refractive index patterns in the gaps, and light blocking patterns. This segmentation allows each component to be shallower and simpler individually, while collectively providing effective isolation without requiring any single structure to extend deeply through the entire device.
Solution Approach 2:
The patent addresses isolation needs by moving to another dimension - using low-refractive index patterns that fill the horizontal gaps between pixel isolation patterns rather than requiring excessive vertical depth. This dimensional approach to isolation reduces the need for deep structures while maintaining effectiveness.
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 improves optical properties by reducing crosstalk and increasing light reception, thereby enhancing sensitivity and SNR characteristics.
Implementation Method 1
a low-refractive index pattern between adjacent color filters of the color filters to at least partially isolate the adjacent color filters from direct contact with each other
Implementation Method 2
a light blocking pattern vertically overlapping with the pixel isolation pattern
Implementation Method 3
Each of the unit pixel regions may include a photodiode. The photodiode may convert incident light into an electrical signal
Data Source
AI summary
An image sensor includes a substrate, a pixel isolation pattern in the substrate and defining unit pixel regions in the substrate, color filters on the substrate and corresponding to the unit pixel regions, respectively, a low-refractive index pattern between adjacent color filters of the color filters to at least partially isolate the adjacent color filters from direct contact with each other, an insulating structure between the substrate and the color filters, and a light blocking pattern vertically overlapping with the pixel isolation pattern. The light blocking pattern is within the insulating structure and is isolated from direct contact with the low-refractive index pattern.