LCoS Color Filter Planarization via Inorganic-Organic Film Stack
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Solution Overview
Problem
Conventional methods for fabricating color filter arrays in LCoS panels, such as CMP, result in uneven height and issues like discoloration and Newton rings due to inadequate planarization.
Innovation Solution
A method involving a substrate with MOS transistors, a pixel electrode array with non-coplanar color filters, an inorganic film covering the filters and gaps between them, and an organic film on top, using spin coating and PECVD processes to achieve planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP process is used to planarize the material layer on color filters, then the surface should be flattened, but the color filter array still exhibits uneven height causing discoloration and Newton ring
Solution Approach 1:
The invention segments the planarization function into two distinct components: an inorganic film (such as spin-on-glass or PECVD oxide) that provides rigid structural support and gap filling, and an organic film (such as photoresist or planarizing resin) that provides additional planarization and protection. This segmentation allows each material to optimize its properties for its specific function, achieving better overall planarization than a single material could provide.
Solution Approach 2:
The invention uses a composite structure combining inorganic and organic films together. The inorganic film layer (e.g., SiO2 from PECVD or spin-on-glass) provides mechanical strength and gap-filling capability, while the organic film layer (e.g., positive or negative photoresist) adds compliance and additional planarization. This composite approach resolves the contradiction by combining the advantages of both material types to achieve superior surface flatness without the defects of single-material solutions.
2Ease of manufacture
If conventional CMP process is used for planarization, then the process should be simple, but it results in discoloration and Newton ring on the display image
Solution Approach 1:
The inorganic film acts as an intermediary layer between the uneven color filter array and the subsequent liquid crystal layer. It fills the gaps between color filters and provides a uniform base surface, mediating the interface between the non-planar color filters and the require planar liquid crystal layer, thereby preventing direct contact that would cause Newton rings and discoloration.
Solution Approach 2:
The invention changes the material parameters by introducing films with different refractive indices and mechanical properties. The inorganic film (e.g., PECVD oxide with high refractive index) and organic film (e.g., photoresist with lower refractive index) create an optical gradient that reduces interference effects, while their combined thickness and compliance adjust the mechanical interface to eliminate Newton rings.
3Adaptability or versatility
If color filters are made non-coplanar with gaps between them, then the color filter array should be more flexible in design, but the surface uniformity deteriorates
Solution Approach 1:
The inorganic and organic films are deposited as preliminary layers before the liquid crystal layer is assembled. This preliminary planarization action creates a uniform surface foundation that compensates for the non-coplanar color filter arrangement, allowing the color filters to maintain their design flexibility while the overlying films establish the required surface uniformity for optimal liquid crystal performance.
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 effectively addresses the planarization issues, reducing fabrication costs and improving optical performance by eliminating discoloration and Newton rings in LCoS panels.
Implementation Method 1
forming an inorganic film on the color filters and within the gap
Implementation Method 2
forming an organic film on the inorganic film entirely
Data Source
AI summary
A liquid crystal on silicon (LCoS) panel is disclosed. The LCoS panel includes: a substrate having at least one metal-oxide semiconductor (MOS) transistor thereon; a pixel electrode array disposed on the substrate; a plurality of color filters with at least two different colors disposed on the pixel electrode array, wherein adjacent color filters comprise a gap therebetween and at least two of the color filters are not coplanar; an inorganic film disposed on the color filters and within the gap; and an organic film covering the inorganic film entirely.