Plasmonic Filter Copper Cross Patterns Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing high-pass filters that block visible light and allow infrared light to pass often rely on black resin, which degrades at high temperatures and is difficult to precision-deposit on small surfaces, particularly in image sensor applications.
Innovation Solution
A high-pass plasmonic filter design featuring a copper layer interposed between two dielectric layers with cross-shaped patterns, where the arms of adjacent patterns are collinear, and the ratio of arm width to length is between 0.3 and 0.6, with a distance of less than 10 nm, allowing for efficient infrared transmission while blocking visible light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If black resin is used to block visible light and transmit infrared light, then the filtering function is achieved, but the material degrades at high temperatures and cannot withstand thermal treatments
Solution Approach 1:
The patent changes the material parameters by replacing black resin with a metal layer (aluminum, copper, or silver) having specific optical properties. The metal layer thickness is controlled at 50-500 nm to achieve the desired optical filtering while providing thermal stability. This material substitution resolves the contradiction by maintaining the visible light blocking and infrared transmission function while eliminating the thermal degradation issue of black resin.
Solution Approach 2:
The patent creates a composite structure by combining the metal layer with dielectric materials (such as silicon nitride or silicon oxide) on both sides. This composite configuration enhances the overall performance: the metal provides thermal stability and optical filtering, while the dielectric layers provide structural support and protection. The composite material approach allows the filter to withstand thermal treatments while maintaining its optical properties.
2Manufacturing precision
If black resin is used for high-pass filtering, then the filtering performance is achieved, but it is difficult to delimit on small surfaces corresponding to elementary pixels
Solution Approach 1:
The patent introduces a patterned structure with cross-shaped openings in the dielectric layers, segmenting the metal layer into discrete regions. This segmentation allows precise delimitation on small pixel surfaces, as the patterned structure can be accurately defined using standard photolithography techniques. The cross-shaped pattern with controlled arm dimensions (width 20-80 nm, length 50-200 nm) enables precise spatial control of the filtering function on elementary pixel surfaces.
Solution Approach 2:
The patent replaces the mechanical deposition process of black resin with a vapor deposition process for the metal layer. The metal layer is deposited using physical vapor deposition (PVD) techniques such as sputtering or evaporation, which allow for excellent step coverage and precise thickness control at the nanometer scale. This substitution of deposition method enables much better precision on small surfaces compared to black resin deposition.
3Measurement precision
If a narrow bandpass plasmonic filter is used, then the wavelength selectivity is improved, but the transmission bandwidth is reduced to less than a hundred nanometers
Solution Approach 1:
The patent applies local quality by creating regions with different optical properties within the same filter structure. The patterned metal layer creates local plasmonic resonances at specific wavelengths, providing wavelength selectivity. Meanwhile, the overall filter structure maintains high transmission in the infrared range by optimizing the pattern geometry and metal thickness. This local quality approach allows simultaneous achievement of narrowband selectivity and broadband transmission.
Solution Approach 2:
The patent exploits the dynamic response of plasmonic resonances to changes in incident light wavelength. By carefully designing the pattern geometry (cross shape with specific arm dimensions) and metal layer thickness, the filter dynamically responds to different wavelengths through plasmon excitation. The resonant frequency can be tuned by adjusting the pattern dimensions, allowing the filter to selectively transmit or block specific wavelength ranges while maintaining overall infrared transmission.
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 design effectively blocks visible light and allows infrared light to pass without the limitations of black resin, enabling precise fabrication on small surfaces and compatibility with thermal treatments, enhancing the manufacturing process for image sensors.
Implementation Method 1
An embodiment provides an infrared high-pass plasmonic filter comprising, through a copper layer interposed between two layers of a dielectric material, an array of patterns made of the dielectric material
Data Source
AI summary
An infrared high-pass plasmonic filter includes a copper layer interposed between two layers of a dielectric material. An array of patterned openings extend through the copper layer and are filled with the dielectric material. Each patterned opening is in the shape of a greek cross, with the arms of adjacent patterns being collinear. A ratio of the width to the length of each arm is in the range from 0.3 to 0.6, and the distance separating the opposite ends of arms of adjacent patterns is shorter than 10 nm.