Color Filter Array Planarization for Microlens Focal Alignment
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Solution Overview
Problem
Conventional CMOS imager devices face issues with cross-talk and reduced light capture efficiency due to uncontrollably shifted focal points of microlenses caused by contraction and uneven surfaces of color filter arrays, exacerbated by asymmetrical pixel cell architectures.
Innovation Solution
The formation of color filter arrays with substantially gapless surfaces using conforming layers that fill gaps between base material layers, reducing contraction and maintaining optical alignment with photosensitive regions, thereby minimizing focal point shifts and enhancing light capture efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional color filter arrays are patterned and reflowed over photosensors, then color filtering is achieved, but the patterned structures contract resulting in an uneven surface that causes uncontrollably shifted focal points of microlenses
Solution Approach 1:
A planarization layer is formed over the color filter array before forming the microlenses. This preliminary action creates a uniform surface that prevents the color filter contraction from affecting microlens focal point alignment, thereby resolving the surface uniformity issue while maintaining manufacturing precision
Solution Approach 2:
The planarization layer acts as an intermediary between the contracting color filter array and the microlenses. It absorbs the surface irregularities caused by color filter contraction and provides a stable, uniform base for microlens formation, preventing focal point shifts
2Ease of manufacture
If spaces or gaps exist between color filters in the array, then fabrication is simplified, but subsequently formed microlens precursors assume a bowed or uneven topmost surface causing increased cross-talk
Solution Approach 1:
The planarization layer is formed preliminarily over the color filter array, including over any gaps between color filters. This preliminary action fills and flattens the gaps, creating a uniform surface for microlens precursor formation that prevents the bowed surface effect and reduces cross-talk
Solution Approach 2:
The planarization layer extracts and removes the harmful effect of gaps between color filters by filling them in, thereby eliminating the cause of the bowed surface and subsequent microlens misalignment that leads to cross-talk
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 approach significantly reduces cross-talk and improves light capture efficiency by maintaining precise alignment of microlenses with photosensitive regions, leading to improved quantum efficiency in CMOS imager devices.
Implementation Method 1
The conforming layers are formed over the base material layers and fill gaps between the base material layers
Implementation Method 2
During reflow of the color filter array, however, the patterned structures typically contract resulting in an uneven surface
Data Source
AI summary
A pixel cell with a photosensitive region formed in association with a substrate, a color filter formed over the photosensitive region, the color filter comprising a first material layer and a second material layer formed in association with the first shaping material layer.