CMOS Pixel Isolation Wall Structure for Sensitivity and Color Mixing
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Solution Overview
Problem
Solid-state imaging devices, such as CMOS image sensors, face challenges in improving sensitivity while minimizing color mixing due to oblique light entry, which is exacerbated by increasing the height of inter-pixel light shielding films, leading to reduced sensitivity.
Innovation Solution
A solid-state imaging device with a first wall composed of at least two layers, including a light shielding film and a low refractive index film, is used to isolate pixels, where the refractive index of the low refractive index film is lower than the light shielding film, effectively reducing color mixing while maintaining sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the height of the partition wall between pixels is increased to prevent color mixing, then color mixing is reduced, but sensitivity is greatly reduced
Solution Approach 1:
The partition wall is divided into multiple layers with different refractive indices. The first layer (adjacent to the pixel) has a lower refractive index to maintain light transmission and sensitivity, while the second layer (outer layer) has a higher refractive index to effectively block oblique light from adjacent pixels, thus preventing color mixing. This segmentation allows each layer to perform its specific function optimally.
Solution Approach 2:
Different regions of the partition wall are assigned different refractive indices based on their functional requirements. The inner region (first layer) uses low refractive index material to minimize light loss and maintain sensitivity, while the outer region (second layer) uses high refractive index material to maximize light blocking capability. This local differentiation resolves the contradiction between sensitivity and color mixing prevention.
2Object-affected harmful factors
If a simple single-layer partition wall is used, then the structure is simple, but it cannot effectively reduce color mixing without reducing sensitivity
Solution Approach 1:
The partition wall is constructed using composite materials with different refractive indices arranged in specific layers. This composite structure leverages the optical properties of each material to achieve effective color mixing prevention while maintaining reasonable structural complexity. The first layer uses material with lower refractive index and the second layer uses material with higher refractive index, creating a functionally optimized composite structure.
3Object-affected harmful factors
If the partition wall is made taller to block oblique light, then color mixing is prevented, but light transmission to the pixel is blocked, reducing sensitivity
Solution Approach 1:
The refractive index parameter is varied across different layers of the partition wall. By changing the refractive index from the first layer (lower) to the second layer (higher), the structure optimizes both light transmission and light blocking functions. This parameter change allows the partition wall to be effective at preventing color mixing while maintaining high light transmission efficiency for useful light.
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 enhances sensitivity while effectively reducing color mixing, allowing for improved image resolution without the need for extreme pupil correction, thus improving the robustness of the imaging device.
Implementation Method 1
a low refractive index film of which refractive index is lower than the light shielding film
Data Source
AI summary
The present technology relates to a solid-state imaging device, a manufacturing method, and an electronic device, which can improve sensitivity while improving color mixing. The solid-state imaging device includes a first wall provided between a pixel and a pixel arranged two-dimensionally to isolate the pixels, in which the first wall includes at least two layers including a light shielding film of a lowermost layer and a low refractive index film of which refractive index is lower than the light shielding film. The present technology can be applied to, for example, a solid-state imaging device, an electronic device having an imaging function, and the like.