Quantum Dot Optical Filter for Solid-State Imaging
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Solution Overview
Problem
Solid-state imaging devices face challenges with color mixing and drift due to light leakage between pixels, especially with the miniaturization of pixels and increased complexity in manufacturing processes, which affect the accuracy of color reproduction.
Innovation Solution
A solid-state imaging device is designed with an optical filter layer containing quantum dots directly formed on the semiconductor substrate, providing a color filter with higher refractive indexes than the surrounding layer, allowing precise control of optical characteristics and reducing light leakage by positioning the filter close to the light-receiving portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters made of organic dye material are used, then color separation is achieved, but the color filters decompose in high temperature plasma deposition processes
Solution Approach 1:
The patent changes the material parameter from organic dye to inorganic quantum dots, which have different thermal stability characteristics. Quantum dots can withstand high temperature plasma deposition processes (typically 200-400°C) without decomposition, while maintaining their optical filtering properties. This parameter change resolves the contradiction between achieving color separation and maintaining filter stability during manufacturing.
Solution Approach 2:
The patent uses composite structures where quantum dots are embedded in a matrix material (such as silicon oxide or silicon nitride). This composite approach combines the optical filtering capability of quantum dots with the structural stability and process compatibility of the matrix material, allowing the color filter to survive high temperature plasma deposition while maintaining color separation accuracy.
2Productivity
If pixels are miniaturized to increase resolution, then device density improves, but light leakage between pixels increases causing color mixing
Solution Approach 1:
The patent introduces quantum dot-based optical filters as intermediary layers between adjacent pixels. These filters act as mediators that selectively absorb or block light wavelengths, preventing light leakage from one pixel from reaching adjacent pixels. The quantum dots provide sharp optical cutoff characteristics that effectively isolate miniaturized pixels while maintaining high device density.
Solution Approach 2:
The patent applies different quantum dot compositions or sizes at different locations to create localized optical filtering properties. By tailoring the quantum dot characteristics to specific pixel positions and requirements, the system achieves effective light isolation for each miniaturized pixel while maintaining overall high density arrangement.
3Measurement precision
If conventional color filters are used, then color filtering is achieved, but manufacturing process complexity increases due to multiple deposition steps
Solution Approach 1:
The patent merges the color filter formation process with the existing semiconductor manufacturing flow by using quantum dots that can be deposited using standard plasma CVD or atomic layer deposition techniques already employed for other device layers. This consolidation eliminates the need for separate, specialized color filter deposition equipment and processes, reducing overall manufacturing complexity while maintaining color filtering capability.
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 configuration effectively prevents color drift and mixing, even with increased pixel size reduction and varying lens settings, while offering process-damage resistance and flexibility in optical filter design.
Implementation Method 1
quantum dots having substantially equal diameters are formed in a layer. The quantum dots have higher refractive indexes than the refractive index of the layer in which the quantum dots are embedded
Data Source
AI summary
A solid-state imaging device includes a light-receiving portion, an optical filter layer, and quantum dots. The light receiving portion, where a photoelectric conversion is carried out, is formed in a semiconductor substrate. The optical filter layer is directly formed on or formed through another layer on the surface of the semiconductor substrate in which the light-receiving portion is formed. Quantum dots having substantially equal diameters are formed in the optical filter layer. The quantum dots have higher refractive indexes than the refractive index of the optical filter layer in which the quantum dots are embedded.