Optical Color Sensor Planarization for Uniformity
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Solution Overview
Problem
Optical color sensors in digital camera systems suffer from color image aberrations due to non-uniformity in pixel-to-pixel color transmission, which is not adequately addressed by existing solutions such as low viscosity color resist application and spin-on planarization layers, resulting in significant color transmission non-uniformity.
Innovation Solution
The solution involves actively planarizing a passivation layer before applying color filters, using chemical mechanical planarization (CMP) and depositing layers of encapsulating and top passivation materials, followed by forming color filters in a specific sequence (green, red, blue) and a planar transparent layer, and finally adding microlenses to enhance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If low viscosity color resist is applied in a unique spin recipe onto a standard passivation surface, then transmission matching is optimized through photolithography coating process, but the topographical features of the surface limit the reduction of non-uniformity
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical planarization (CMP) of the passivation layer before depositing the color filter layer. This pre-planarization step removes surface topographical features that would otherwise constrain the uniformity of subsequent color resist application, enabling better transmission matching without being limited by surface irregularities.
Solution Approach 2:
The patent replaces the mechanical spin-coating process with a deposition process performed in a chemical vapor deposition (CVD) reactor. This substitution allows for more uniform color filter layer formation by eliminating the limitations imposed by surface topography that affect spin-coating uniformity, thereby improving transmission matching.
2Manufacturing precision
If a spin on the planarization layer is inserted between the passivation and the color filter layer, then planarization is improved, but integration issues associated with the bondpad interface occur and non-uniformity remains on the order of about 200 Angstroms peak to trough
Solution Approach 1:
The patent replaces the mechanical spin-on planarization process with chemical mechanical planarization (CMP). This substitution achieves superior planarization uniformity (reducing non-uniformity from 200 Angstroms to about 20 Angstroms peak to trough) while avoiding the integration issues and bondpad interface problems associated with spin-on methods.
Solution Approach 2:
The patent changes the planarization method from spin-on to CMP, fundamentally altering the process parameters and mechanism. This parameter change enables achievement of much tighter uniformity specifications (20 Angstroms vs 200 Angstroms) while simplifying the overall integration process by eliminating bondpad interface complications.
3Productivity
If color filters are formed directly on the passivation layer, then the manufacturing process is simplified, but significant color transmission non-uniformity occurs
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical planarization (CMP) of the passivation layer before depositing the color filter layer. This pre-planarization step creates a uniformly flat surface that enables subsequent color filter deposition with high uniformity, achieving both manufacturing precision and process efficiency.
Solution Approach 2:
The patent replaces spin-coating with CVD deposition performed after CMP planarization. This combination achieves superior color transmission uniformity while maintaining manufacturing efficiency, as the CVD process can conformally deposit uniform layers on the planarized surface without the limitations of spin-coating.
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 color filter non-uniformity from 200 Angstroms to 20 Angstroms peak to trough, improving pixel color transmission uniformity and reducing the occurrence of yellow striations in images, while also simplifying the manufacturing process and reducing costs.
Implementation Method 1
The passivation layer is planarized and color filters are formed over the passivation layer
Implementation Method 2
microlenses are formed on the planar transparent layer over the color filters
Data Source
AI summary
An optical color sensor system is provided including providing a substrate having an optical sensor therein and forming a passivation layer over the substrate. The passivation layer is planarized and color filters are formed over the passivation layer. A planar transparent layer is formed over the color filters and microlenses are formed on the planar transparent layer over the color filters.