Multi-Layer Image Sensor Stacked Pixel Architecture
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Solution Overview
Problem
As CMOS image sensors scale to smaller dimensions, their optical sensitivity degrades due to decreased quantum efficiency and pixel area, leading to reduced performance in image resolution and detail discrimination.
Innovation Solution
The implementation of an image sensor structure with multiple sensing layers, where each layer has a different effective thickness to absorb specific ranges of wavelengths, enhancing optical sensitivity and modulation transfer function by optimizing pixel design and layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is decreased to increase the number of pixels, then resolution is improved, but optical sensitivity degrades
Solution Approach 1:
The patent transitions from a two-dimensional single-layer pixel structure to a three-dimensional multi-layer structure. By stacking multiple sensing layers vertically, the system increases the total light-absorbing volume without increasing the horizontal pixel area, thereby maintaining high resolution while improving optical sensitivity through enhanced photon capture in the depth dimension.
Solution Approach 2:
The patent implements a nested structure where multiple sensing layers are stacked vertically within a single pixel footprint. Each layer is contained within the vertical space above the substrate, with layers nested one above another. This allows multiple photodetectors to occupy the same horizontal space at different depths, increasing total sensing capacity without reducing pixel density.
2Reliability
If quantum efficiency is increased by enlarging aperture size, then optical sensitivity is improved, but pixel area must increase
Solution Approach 1:
The patent moves the solution from the horizontal plane to the vertical dimension by stacking multiple sensing layers. Instead of enlarging the aperture horizontally, the system increases light capture by extending the sensing volume vertically through multiple layers, each capable of absorbing photons at different wavelengths and depths.
Solution Approach 2:
The patent segments the light absorption function across multiple distinct sensing layers, each optimized for specific wavelength ranges. Rather than requiring a single large aperture to capture all wavelengths, the system divides the spectral detection task across multiple smaller photodetectors stacked vertically, with each layer handling specific portions of the spectrum.
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 multi-layer structure improves optical sensitivity and modulation transfer function, allowing for higher resolution and better discrimination of fine details in images, while maintaining or exceeding the performance of single-layer sensors with equivalent MTF.
Implementation Method 1
The first sensing layer has a first effective thickness to collect light with a first preselected range of wavelengths and the second sensing layer has a second effective thickness to collect light with a second preselected range of wavelengths
Implementation Method 2
Each pixel includes a photosensor, such as a photodiode, that produces a signal corresponding to the intensity of light impinging on that pixel
Data Source
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AI summary
An image sensor includes a first sensor layer having a first array of pixels and a second sensor layer having a second array of pixels. Each of the pixels has an optical center. The first sensor layer is stacked over the second sensor layer such that the optical centers of the first array of pixels are offset from the optical centers of the second array to form a predetermined pattern.