Imaging Sensor Reflectance Layer for Wideband Anti-Reflection
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Solution Overview
Problem
Existing solid-state imaging sensors face challenges in suppressing light reflection across a wide wavelength band, particularly due to the difficulty in achieving a deep concavo-convex structure with a narrow pitch, which is technically demanding and results in insufficient reflectance reduction when the structure thickness is less than approximately 100 nm.
Innovation Solution
A solid-state imaging sensor design incorporating a reflectance adjusting layer with a concavo-convex structure on the Si substrate, comprising a first layer with a refractive index lower than the substrate and a second layer with a refractive index lower than the first layer, applied using photolithography or directed self-assembly, to minimize light reflection by optimizing the refractive index and thickness product to less than 3/8 times the wavelength, thereby reducing flare and ghost effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a deep concavo-convex structure with narrow pitch is formed to suppress light reflection, then reflectance is reduced, but manufacturing difficulty increases significantly
Solution Approach 1:
The patent divides the single deep concavo-convex structure into multiple layers (first layer and second layer), each with different refractive indices and depth characteristics. This segmentation allows gradual refractive index transition from air to substrate, achieving effective reflection suppression while using shallower individual layers that are easier to manufacture with standard lithography and etching processes.
Solution Approach 2:
The patent employs composite material structure where the first layer and second layer are made of different materials with progressively varying refractive indices. This composite approach enables optimization of each layer's depth and material properties independently, reducing the need for extremely deep single-layer structures while maintaining anti-reflection effectiveness across wide wavelength bands.
2Ease of manufacture
If the thickness of the concavo-convex structure is reduced to below 100 nm, then manufacturing becomes easier, but reflectance suppression becomes insufficient
Solution Approach 1:
By segmenting the anti-reflection function across multiple layers with different refractive indices, the patent achieves effective reflectance suppression with each layer being thinner than 100 nm. The cumulative effect of multiple shallow layers with graded refractive indices compensates for the reduced individual layer depth, maintaining optical performance while improving manufacturability.
Solution Approach 2:
The patent changes the optical parameters by introducing multiple layers with different refractive indices and optimized thicknesses. This parameter optimization allows each layer to be thinner than 100 nm while the combined structure achieves superior reflectance suppression compared to a single thick layer, balancing manufacturing ease with optical effectiveness.
3Productivity
If pixel size is reduced to increase pixel count, then sensor resolution improves, but sensitivity deteriorates due to reduced aperture ratio
Solution Approach 1:
The patent applies thin film anti-reflection structures (multiple layers with controlled thicknesses) on the pixel surface to minimize light reflection. This increases the amount of incident light that enters the photoelectric conversion unit, thereby improving sensitivity without requiring larger pixel apertures, enabling high pixel count sensors to maintain high sensitivity.
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
The solution effectively suppresses light reflection across a wide wavelength band, enhancing sensitivity and reducing flare and ghost occurrences, while allowing for a thinner configuration than traditional moth-eye structures, thus improving image quality.
Implementation Method 1
The first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate. The second layer includes a material having a refractive index lower than that of the first layer.
Implementation Method 2
The present technology is devised under the situation. In particular, the interference principle of a thin film is applied to the surface of a Si substrate, thereby suppressing the reflection of incident light with a wide wavelength band.
Data Source
AI summary
The present technology relates to a solid state imaging sensor that is possible to suppress the reflection of incident light with a wide wavelength band. A reflectance adjusting layer is provided on the substrate in an incident direction of the incident light with respect to the substrate such as Si and configured to adjust reflection of the incident light on the substrate. The reflectance adjusting layer includes a first layer formed on the substrate and a second layer formed on the first layer. The first layer includes a concavo-convex structure provided on the substrate and a material which is filled into a concave portion of the concavo-convex structure and has a refractive index lower than that of the substrate, and the second layer includes a material having a refractive index lower than that of the first layer. It is possible to reduce the reflection on the substrate such as Si by using the principle of the interference of the thin film. Such a technology can be applied to solid state imaging sensors.