Segmented Anti-Reflective Coating for Image Sensor Crosstalk Reduction
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Solution Overview
Problem
Conventional image sensors face challenges in increasing sensitivity and reducing crosstalk due to significant reflection when light passes through insulation layers with large refractive index changes, and the uniform anti-reflective coating is not optimized for different colors of light.
Innovation Solution
The image sensor incorporates an anti-reflective coating layer with sections of varying thickness directly below color filters, each with distinct inherent reflection characteristics, optimizing light reflection for specific colors to enhance sensitivity and reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform anti-reflective coating layer is used, then the manufacturing process is simple, but the sensitivity for different colors of light cannot be optimized
Solution Approach 1:
The ARC layer is divided into multiple sections (first ARC section, second ARC section, third ARC section) with different thicknesses, where each section corresponds to a specific color filter (red, green, blue). This segmentation allows each section to be optimized for its corresponding wavelength range, resolving the contradiction between manufacturing simplicity and color-specific sensitivity optimization.
Solution Approach 2:
Different thicknesses are assigned to different regions of the ARC layer based on the specific optical requirements of each color. The first ARC section has a first thickness optimized for red light, the second for green light, and the third for blue light. This local quality approach enables each region to have optimal reflection characteristics for its specific function.
2Reliability
If the ARC layer thickness is increased to reduce reflection, then light collection improves, but crosstalk between adjacent color filters increases
Solution Approach 1:
The ARC layer is segmented into color-specific sections with different thicknesses. Each section is optimized to reduce reflection for its corresponding color wavelength while maintaining appropriate optical isolation from adjacent sections. This prevents excessive light diffusion that would cause crosstalk, while still achieving high light collection for the intended wavelength.
Solution Approach 2:
The thickness parameter of the ARC layer is varied across different sections to optimize the balance between light collection and crosstalk reduction. By changing the thickness parameter locally for each color section, the system achieves maximum light collection efficiency for each wavelength while preventing excessive lateral light propagation that would cause crosstalk.
3Reliability
If the refractive index difference between insulation layers is large, then the insulation performance is improved, but reflection of light increases significantly
Solution Approach 1:
The ARC layer acts as an intermediary between the first and second insulation layers. By introducing this intermediate layer with gradually varying thickness across different sections, the abrupt refractive index change is softened, reducing reflection losses while maintaining the necessary insulation performance between the insulation layers.
Solution Approach 2:
The thickness parameter of the ARC layer is used to gradually transition the effective refractive index between the two insulation layers. This parameter change approach creates a gradient that reduces reflection at the interface while preserving the electrical insulation function, as the ARC layer material itself maintains the necessary insulating properties.
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 allows for improved color discrimination and increased light collection of desired wavelengths while minimizing the impact of undesired wavelengths, thereby enhancing sensitivity and reducing crosstalk.
Implementation Method 1
The ARC layer comprises a plurality of sections directly below the color filters in a vertical direction, respectively, and the sections have different inherent reflection characteristics
Implementation Method 2
Reflection is more severe when light goes from the second insulation layer 140 to the first insulation layer 120 when the change in refractive index of the first insulation layer 120 and the second insulation layer 140 is large
Data Source
AI summary
The present invention provides an image sensor. The image sensor comprises: a substrate, a plurality of optical elements, a first insulation layer, an anti-reflective coating (ARC) layer, a second insulation layer, and a color filter array. The optical elements are disposed in the substrate. The first insulation layer is disposed on the substrate and the optical elements. The ARC layer is disposed on the first insulation layer. The second insulation layer is disposed on the ARC layer. The color filter array is disposed on the second insulation layer, and the color filter array comprises a plurality of color filters corresponding to a plurality of different colors of light, respectively. The ARC layer comprises a plurality of sections directly below the color filters in a vertical direction, respectively, and the sections have different inherent reflection characteristics. The image sensor of the present invention can increase sensitivity and reduce crosstalk.