Tapered Pixel Grid Structure for Crosstalk and Light Collection
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Solution Overview
Problem
CMOS image sensors face reduced quantum efficiency due to optical crosstalk and light absorption by grid structures used to separate color filter regions, which also provide optical isolation.
Innovation Solution
Implementing an angled or tapered grid structure that narrows near the top surface to minimize spacing between color filter regions, increasing light collection area while maintaining optical crosstalk protection by widening near the bottom surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grid structure is used to separate color filter regions, then optical crosstalk protection is improved, but quantum efficiency deteriorates due to light absorption and reduced light collection area
Solution Approach 1:
The grid structure implements different width characteristics at different locations: wider at the bottom for optimal crosstalk protection and narrower at the top for reduced light absorption. This local variation in geometric properties allows each region of the grid to optimize its function - the bottom portion provides isolation while the top portion minimizes interference with light collection.
Solution Approach 2:
The grid structure transitions from a two-dimensional planar view to a three-dimensional tapered form. By introducing the vertical dimension with angled sidewalls, the structure achieves both wide base for isolation and narrow top for reduced absorption, effectively resolving the contradiction through spatial dimensionality.
2Reliability
If the grid structure width is increased to improve optical isolation, then crosstalk protection is improved, but the spacing between color filter regions increases reducing light collection area
Solution Approach 1:
The grid structure implements different width characteristics at different locations: wider at the bottom for optimal crosstalk protection and narrower at the top for reduced light absorption. This local variation in geometric properties allows each region of the grid to optimize its function - the bottom portion provides isolation while the top portion minimizes interference with light collection.
Solution Approach 2:
The grid structure transitions from a two-dimensional planar view to a three-dimensional tapered form. By introducing the vertical dimension with angled sidewalls, the structure achieves both wide base for isolation and narrow top for reduced absorption, effectively resolving the contradiction through spatial dimensionality.
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
Enhances quantum efficiency by increasing the surface area for light collection and reducing light absorption, while maintaining effective optical crosstalk protection for the pixel sensors.
Implementation Method 1
a photodiode region configured to convert photons of incident light into a photocurrent of electrons
Data Source
AI summary
A grid structure in a pixel array may be at least partially angled or tapered toward a top surface of the grid structure such that the width of the grid structure approaches a near-zero width near the top surface of the grid structure. This permits the spacing between color filter regions in between the grid structure to approach a near-zero spacing near the top surfaces of the color filter regions. The tight spacing of color filter regions provided by the angled or tapered grid structure provides a greater surface area and volume for incident light collection in the color filter regions. Moreover, the width of the grid structure may increase at least partially toward a bottom surface of the grid structure such that the wider dimension of the grid structure near the bottom surface of the grid structure provides optical crosstalk protection for the pixel sensors in the pixel array.