Multilayer Optical Filter Matrix for Image Sensor Miniaturization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensor technologies face challenges in miniaturization and color filtering efficiency due to the use of colored resins, which are inhomogeneous and require thick layers to achieve sufficient filtering, leading to issues with infrared absorption and photon crosstalk, especially at high incidence angles.
Innovation Solution
The implementation of a multilayer optical filtering structure with alternating transparent and metallic layers of constant thickness, where specific transparent layers have variable thicknesses to selectively transmit certain wavelengths, allowing for thinner filters and improved color separation without parasitic light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick resin layers are used for color filtering, then filtering efficiency is improved, but pixel size must be increased which limits miniaturization
Solution Approach 1:
The patent changes the material parameter from organic resin to inorganic material (such as silicon nitride or silicon oxide), which has fundamentally different optical properties. This inorganic material achieves superior filtering efficiency with much thinner layers, directly resolving the contradiction between filtering efficiency and pixel size miniaturization
Solution Approach 2:
The patent employs composite structures combining multiple inorganic layers with different refractive indices (high-index silicon nitride and low-index silicon oxide) to achieve enhanced filtering performance in thin layers, allowing efficient color separation without increasing pixel dimensions
2Ease of manufacture
If resin filters are used, then production is simplified, but inhomogeneity of filtering occurs especially in small pixels
Solution Approach 1:
The patent transitions from organic resin to inorganic materials that can be deposited using standardized semiconductor manufacturing techniques. These inorganic films exhibit superior uniformity and reproducibility across the substrate, eliminating the inhomogeneity problems associated with resin filters while maintaining ease of manufacture through established industrial processes
3Reliability
If resin filters are used, then color filtering is achieved, but infrared filtering capability is lost requiring additional components
Solution Approach 1:
The patent designs the inorganic filter layers to perform multiple functions simultaneously: they provide precise color filtering for visible wavelengths while also inherently blocking infrared wavelengths. This multi-functionality eliminates the need for separate infrared-cut filters, reducing overall device complexity while maintaining superior color filtering performance
4Length of moving object
If thin resin layers are used for miniaturization, then pixel size is reduced, but photon crosstalk increases at high incidence angles
Solution Approach 1:
The patent changes the material parameter from resin to inorganic materials with superior optical properties. These inorganic filters maintain their filtering characteristics at high incidence angles, preventing photon crosstalk even in miniaturized pixels. The material transition enables thin-layer construction without sacrificing angular robustness, directly resolving the crosstalk issue
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 enables efficient color filtering with reduced pixel size, minimal infrared interference, and improved miniaturization potential, while maintaining high transmission efficiency and rejecting unwanted wavelengths, such as infrared beyond 900nm.
Implementation Method 1
Multilayer filters consisting of alternating transparent layers and metallic layers are known for producing photonic band gap structures
Implementation Method 2
transparent metallo-dielectric structures with a photonic bandgap
Implementation Method 3
by modifying the thickness of a single or two transparent layers while, by elsewhere, all other layers are of constant thickness... all the elementary optical filters of the matrix have a thickness smaller than the shortest of the useful wavelengths
Data Source
Figure 1~3
Figure 4A~5
Figure 6A~7
AI summary
The invention concerns an optical filter matrix structure composed of a set of at least two elementary (R, G, B) optical filters, one elementary optical filter being centered on an optimal transmission frequency, characterized in that it comprises a stack of n metallic layers (m1, m2, m3) and n appreciably transparent layers (d1, d2, d3) that alternate between a first nth metallic layer (m1) and an appreciably transparent layer (d3), the n metallic layers (m1, m2, m3) each having a constant thickness and at least one appreciably transparent layer having a variable thickness that determines the optimal transmission frequency of an elementary optical filter, n being a whole number equal to or greater than 2. Application to miniature image sensors.