Non-intersecting Trenches for CMOS Image Sensor Color Mixing
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Solution Overview
Problem
The reduction in pixel size and increase in pixel density in CMOS image sensors lead to reduced sensitivity and signal-to-noise ratio, and color mixing due to adjacent pixels receiving light across different wavelength ranges, degrading image quality.
Innovation Solution
The implementation of an image pickup device with trenches formed between pixels, filled with light-shielding material, and an upper layer light shielding material made from insulating or metal materials, arranged in a manner that prevents trench crossing and maintains pixel gaps, reducing color mixing and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is reduced and pixel density is increased, then the number of pixels and pixel density are improved, but sensitivity per unit pixel is reduced and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the substrate into isolated pixel regions using non-intersecting trenches. These trenches segment the continuous substrate into discrete pixel units, preventing optical crosstalk while maintaining high pixel density. The segmentation approach allows each pixel to operate independently with improved signal-to-noise ratio despite reduced pixel size.
2Productivity
If pixel size is reduced and pixel density is increased, then pixel density is improved, but color mixing occurs between adjacent pixels
Solution Approach 1:
The non-intersecting trenches segment the substrate to create isolated pixel regions, preventing obliquely incident light from reaching adjacent pixels. This segmentation effectively blocks color mixing while maintaining high pixel density, as each pixel is optically isolated by the trench structures.
Solution Approach 2:
The trenches act as intermediary light-shielding structures between adjacent pixels. These intermediary elements block stray light and prevent direct optical paths between neighboring pixels, thereby eliminating color mixing without requiring the pixels to be physically farther apart.
3Object-affected harmful factors
If grid-shaped light-shielding material is arranged between adjacent pixels, then color mixing is suppressed, but manufacturing complexity increases due to trench crossing
Solution Approach 1:
The patent segments the light-shielding structure into non-intersecting trenches that do not cross each other. This segmentation approach simplifies manufacturing by eliminating the complex intersection regions that would arise with a complete grid structure, while still providing effective optical isolation between pixels.
Solution Approach 2:
The patent extracts the problematic crossing portions from the grid structure by designing trenches that terminate before intersecting with other trenches. This extraction of the crossing elements simplifies the overall structure and reduces manufacturing complexity while maintaining the light-shielding function.
4Object-affected harmful factors
If trenches are formed between pixels to suppress color mixing, then color mixing is reduced, but pixel size is further reduced
Solution Approach 1:
The patent applies partial action by forming trenches only in specific directions between pixels rather than creating a complete surrounding grid. This partial trench structure provides sufficient optical isolation to suppress color mixing while minimizing the space consumed by trenches, thereby preserving larger pixel active areas.
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 configuration effectively suppresses color mixing and increases the signal-to-noise ratio while allowing for a practical reduction in pixel size and increase in pixel density, improving image quality without the need for chemical mechanical polishing.
Implementation Method 1
a substrate light shielding material that fills the plurality of trenches
Implementation Method 2
obliquely incident light is reflected by the grid-shaped light-shielding material arranged so as to extend between the adjacent pixels
Implementation Method 3
an upper layer light shielding material
Implementation Method 4
the incident light reaches a photodiode (PD) region of a silicon (Si) substrate
Data Source
AI summary
Systems and methods for providing a solid state image sensor (30) are provided. More particularly, an image sensor (30) that suppresses color mixing is provided. Moreover, embodiments of the present disclosure provide for the creation of light blocking features (32) that avoid the creation of stress concentrations. More particularly, embodiments of the present disclosure provide for the creation of light blocking structures (32) using trenches formed in a substrate (44) that are arranged such that no two trenches intersect one another.