Light Wave Separation Lattices for CMOS Image Sensors
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Solution Overview
Problem
Conventional color filters used in CMOS image sensors face limitations in scalability due to the thickness requirements of resist materials, which affect their ability to resolve colors effectively as pixel sizes decrease, leading to issues with cross-talk and quantum efficiency.
Innovation Solution
The development of light wave separation lattices formed by alternating layers with specific refractive indices, deposited using physical vapor deposition, allowing for precise tuning of refractive indices and reduced contamination, enabling improved color filtering capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If resist materials are used for color filters, then color resolution is achieved, but thickness scalability is limited
Solution Approach 1:
The color filter is divided into multiple thin alternating layers of different materials (e.g., silicon oxide and silicon nitride) with different refractive indices, replacing the conventional single-layer resist structure. This segmentation enables precise color filtering while reducing overall thickness to meet scaling requirements
Solution Approach 2:
The patent uses composite multilayer structures combining materials with different refractive indices (such as silicon oxide with n≈1.46 and silicon nitride with n≈2.0) to achieve the required optical filtering performance in a thinner profile than conventional resist materials
2Area of moving object
If pixel size is reduced in XY direction, then sensor resolution is improved, but cross-talk increases due to insufficient thickness scaling
Solution Approach 1:
The patent addresses the thickness scaling issue by transitioning to a different fabrication approach (PVD deposition of multilayers) that enables precise thickness control in the Z-dimension, allowing the filter structure to scale proportionally with pixel size reduction while maintaining effective optical separation
3Manufacturing precision
If conventional resist materials are used, then color filtering is achieved, but quantum efficiency decreases due to thickness limitations
Solution Approach 1:
The patent changes the material parameters by using inorganic materials with different refractive indices instead of organic resist materials, enabling precise control of layer thicknesses in the range of tens to hundreds of nanometers. This parameter change optimizes both color filtering accuracy and light transmission for improved quantum efficiency
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 enhances the scalability and precision of color filters, reducing the number of process steps, improving throughput, and allowing for more precise control over refractive indices, thereby enhancing the resolution and efficiency of color imaging.
Implementation Method 1
depositing a first layer having a formula ROXNY, atop a substrate by a physical vapor deposition process
Data Source
AI summary
Light wave separation lattices and methods of formation are provided herein. In some embodiments, a light wave separation lattice includes a first layer having the formula ROXNY, wherein the first layer has a first refractive index; and a second layer, different from the first layer, disposed atop the first layer, and having the formula R′OXNY, wherein the second layer has a second refractive index different from the first refractive index, and wherein R and R′ are each one of a metal or a dielectric material. In some embodiments, a method of forming a light wave separation lattice includes depositing a first layer having a predetermined desired refractive index atop a substrate by a physical vapor deposition process; and depositing a second layer, different from the first layer, atop the first layer, wherein the second layer has a predetermined second refractive index different from the first refractive index.