Multi-Layer Reflective Structure for Image Sensor Light Directionality
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Solution Overview
Problem
Conventional image sensor devices suffer from reduced photosensitivity due to inefficient light directionality to photodiodes, despite the use of micro lens arrays and color filter arrays.
Innovation Solution
A CMOS image sensor (CIS) structure incorporating a multi-layer reflective structure with refractive indexes N1 > N2 > N3, surrounding a translucent structure and featuring a micro lens, enhances light reflection and reduces light cross-talk by using concentric layers to direct light more effectively to the photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a micro lens array is used to direct light to photodiodes, then light directionality is improved, but photosensitivity is reduced due to light loss
Solution Approach 1:
The patent implements a nested multi-layer reflective structure where outer reflective layers with lower refractive indexes surround inner reflective layers with higher refractive indexes. This nested configuration creates multiple internal reflections that progressively trap and redirect light toward the photodiode, converting light loss into useful light directionality and improving photosensitivity.
Solution Approach 2:
The patent employs composite reflective layers with different refractive indexes (N1, N2, N3 where N1>N2>N3) to create a multi-functional optical structure. Each layer with distinct refractive index properties contributes differently to light reflection and trapping, collectively achieving enhanced light directionality while minimizing energy loss.
2Device complexity
If conventional single-layer reflective structures are used, then device complexity is low, but light trapping efficiency is insufficient
Solution Approach 1:
The patent divides the reflective structure into multiple segmented layers, each with specific refractive index characteristics. This segmentation allows each layer to perform a specialized function in the light trapping process, with outer layers handling initial light redirection and inner layers providing progressive trapping, thereby improving overall efficiency while maintaining manageable structural complexity.
Solution Approach 2:
The patent transitions from conventional single-layer reflective structures to a multi-dimensional multi-layer configuration surrounding the photodiode. This dimensional expansion creates multiple reflection pathways and increases the probability of light interception and redirection, significantly enhancing light trapping efficiency without excessive complexity increase.
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 multi-layer reflective structure effectively traps and directs light to the photodiode, enhancing photosensitivity and reducing light loss, thereby improving the overall performance of the image sensor device.
Implementation Method 1
The reflective structure includes a first reflective layer surrounding the translucent structure, a second reflective layer surrounding the first reflective layer, and a third reflective layer surrounding the second reflective layer
Implementation Method 2
The first, second, and third reflective layers respectively have refractive indexes N1, N2, and N3, wherein N1>N2>N3
Data Source
AI summary
A CIS structure is provided, including a translucent structure, a reflective structure surrounding the translucent structure, and a micro lens disposed on a side of the translucent structure. The reflective structure includes a first reflective layer surrounding the translucent structure, a second reflective layer surrounding the first reflective layer, and a third reflective layer surrounding the second reflective layer. The first, second, and third reflective layers respectively have refractive indexes N1, N2, and N3, wherein N1>N2>N3.