Structural Color Filter Using Semiconductor Gratings
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Solution Overview
Problem
Conventional color filters based on organic dyes or chemical pigments are sensitive to UV irradiation, high temperature, and moisture, leading to rapid performance deterioration, and require complex alignment processes, while structural color filters using silver or gold nanostructures face issues with cost and color degradation over time, and sensitivity to incident light angles.
Innovation Solution
A structural color filter comprising a substrate with a metal layer and ultra-thin semiconductor gratings made of amorphous silicon, arranged in specific patterns to produce constant colors regardless of incident light angles, using aluminum or silver for the metal layer and employing a single patterning process to reduce manufacturing costs and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional color filters use organic dyes or chemical pigments, then color filtering function is achieved, but performance deteriorates rapidly due to sensitivity to UV irradiation, high temperature, and moisture
Solution Approach 1:
The patent replaces unstable organic dyes and chemical pigments with inorganic semiconductor materials (such as silicon, germanium, or their alloys) that form stable gratings. These inorganic structures are resistant to UV irradiation, high temperature, and moisture, eliminating the rapid performance deterioration characteristic of organic-based filters while maintaining the color filtering function through structural coloration rather than chemical absorption.
Solution Approach 2:
The patent employs composite structures combining metal layers (such as aluminum or silver) with semiconductor grating structures. This composite approach creates a system where the metal provides optical resonance enhancement and the semiconductor grating provides stable, angle-insensitive color filtering. The combination achieves both high reliability and resistance to environmental factors while enabling efficient color generation.
2Loss of energy
If structural color filters use silver or gold nanostructures, then optical absorption loss is reduced in the visible-light region, but cost increases and color degradation occurs over time
Solution Approach 1:
The patent replaces expensive precious metals (silver and gold) with inexpensive semiconductor materials such as silicon, germanium, or their alloys. These semiconductor gratings achieve the necessary optical resonance and color generation without the high cost of precious metals. Additionally, the semiconductor materials provide long-term color stability without the oxidation and sulfation problems that plague silver and gold structures over time.
Solution Approach 2:
The patent changes the material parameter from precious metals to semiconductors, fundamentally altering the optical mechanism from plasmonic resonance to photonic resonance in semiconductor gratings. This parameter change maintains low optical absorption loss while eliminating the cost and stability issues associated with silver and gold. The semiconductor bandgap properties enable precise color control through grating geometry rather than material composition.
3Manufacturing precision
If multilayer thin film structure is used to adjust thickness for color adjustment, then color accuracy is improved, but manufacturing complexity increases requiring three independent lithography processes
Solution Approach 1:
The patent segments the color filtering function into spatially separated grating structures rather than relying on multiple stacked thin films. Each semiconductor grating is elongated in a first direction and arranged spaced apart in a second direction, creating distinct optical paths for different colors. This segmentation allows single-lithography patterning to define all color-grating geometries simultaneously, eliminating the need for multiple sequential lithography processes while maintaining precise color control through grating dimensions and spacing.
Solution Approach 2:
The patent transitions from adjusting color through thickness variation in the vertical dimension (multilayer thin films) to adjusting color through dimensional variations in the lateral plane (grating width, spacing, and pattern geometry). This dimensional shift allows all color filters to be patterned in a single lithography step by varying the grating parameters in the lateral direction, dramatically simplifying manufacturing while preserving color accuracy.
4Area of moving object
If pixel size is reduced in conventional color filters, then resolution is improved, but alignment process becomes more complicated and highly accurate
Solution Approach 1:
The patent creates a universal grating structure where the same semiconductor grating geometry and arrangement can generate multiple colors (red, green, blue, or other wavelengths) by varying only the grating parameters (width, spacing, period) rather than requiring different materials or layered structures for each color. This universality allows all color filters to be fabricated using a single lithography process and identical deposition steps, eliminating complex alignment requirements even as pixel size decreases, since the entire color filter array follows the same fabrication paradigm.
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
The solution achieves constant color production across varying incident angles and reduces manufacturing complexity and costs by using a single patterning process for different colors, enhancing the stability and efficiency of the color filter.
Implementation Method 1
In order to trigger one of the photonic resonance mode and the plasmonic resonance mode, silver (Ag) or gold (Au) nano-structures with a dimension smaller than the visible-light wavelength are used
Implementation Method 2
Silver (Ag) and gold (Au) have low optical absorption loss in the visible-light region compared to other metals
Data Source
AI summary
The present disclosure provides a structural color filter comprising: a substrate; a metal layer disposed on the substrate; and semiconductor gratings disposed on the metal layer, wherein each of the semiconductor gratings is elongated in a first direction, wherein the semiconductor gratings are arranged to be spaced apart from each other in a second direction perpendicular to the first direction, wherein the semiconductor gratings have the same thickness, wherein the thickness is smaller than a wavelength of visible-light.