Convex Pixel Filter Structure for CMOS Sensors With Lower Color Mixing
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Solution Overview
Problem
In solid-state imaging elements without on-chip lenses, color mixture and reduced quantum efficiency occur due to light transmission through low-refractive index partitions between pixels, necessitating improved performance to minimize these issues.
Innovation Solution
A solid-state imaging element with a semiconductor substrate and a filter layer where each pixel has a curved filter surface, and an inter-pixel light shielding section using a low-refractive index material, which reduces light transmission between pixels and maintains light concentration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If partitions including transparent material with lower refractive index are provided between pixels to suppress color mixture, then color mixture is reduced, but quantum efficiency decreases due to light transmission through partitions
Solution Approach 1:
The patent changes the refractive index parameter of the partition material by applying a high-refractive-index film (first refractive index n1) over the low-refractive-index partition material (second refractive index n2). This creates a composite structure where n1 > n2, transforming the optical properties to reduce light transmission through partitions while maintaining color mixture suppression. The gradient refractive index structure effectively redirects light that would otherwise transmit through the partition, improving quantum efficiency without sacrificing color isolation.
Solution Approach 2:
The patent creates a composite light shielding structure by combining two materials with different refractive indices: a base partition material with low refractive index and an overlay film with high refractive index. This composite structure leverages the complementary properties of both materials - the low-refractive-index material provides good color isolation, while the high-refractive-index overlay reduces light transmission. The combination resolves the contradiction by achieving both color mixture suppression and improved quantum efficiency simultaneously.
2Object-affected harmful factors
If on-chip lens height is reduced or no on-chip lens is used to prevent color mixture in miniaturized pixels, then color mixture is reduced, but light concentration efficiency decreases
Solution Approach 1:
The patent changes the refractive index parameter distribution in the inter-pixel region by introducing a high-refractive-index film over the low-refractive-index partition material. This creates a refractive index gradient that enhances light concentration toward the pixel center without requiring a tall on-chip lens. The refractive index contrast at the partition interfaces redirects stray light away from adjacent pixels, maintaining color isolation while improving light concentration efficiency for miniaturized pixel structures.
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 reduces color mixture and increases quantum efficiency by refracting light away from inter-pixel light shielding sections, even in miniaturized pixels, thereby enhancing imaging performance.
Implementation Method 1
an inter-pixel light shielding section including a low-refractive index material having a refractive index lower than that of the filter is provided between the pixels
Data Source
AI summary
The present disclosure relates to a solid-state imaging element, a manufacturing method, and electronic equipment capable of further improving performance. The solid-state imaging element includes a semiconductor substrate having a photoelectric conversion section provided for each pixel and a filter layer provided on a light-receiving side of the semiconductor substrate. In the filter layer, a filter whose surface shape is formed in a convex shape is provided for each pixel, and an inter-pixel light shielding section including a low-refractive index material having the refractive index lower than that of the filter is provided between the pixels. Then, the surfaces of the filters are formed in a convex shape by forming the filters on base materials that are provided in a pattern smaller than a pixel pitch by coating such that the filters are convex relative to an insulating film formed on the surface of the semiconductor substrate. The present technology is applicable, for example, to CMOS image sensors.