Recessed Separator Layer for Image Sensor Crosstalk Reduction
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Solution Overview
Problem
Conventional POAP image sensors suffer from crosstalk due to continuous photodiode structures, leading to blurred images and reduced resolution, especially when pixel density is increased or multi-layer dielectric structures are used.
Innovation Solution
The image sensor structure features a substrate with a patterned separator layer and a discontinuous first doped amorphous silicon layer, which reduces crosstalk by preventing electrical signal leakage between pixel areas, achieved through a fabrication process involving sequential formation of image sensor interconnect structures, a patterned electrode layer, and a recessed separator layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous photodiode structure is used, then light collection efficiency is improved, but crosstalk between adjacent pixel areas increases
Solution Approach 1:
The continuous photodiode layer is segmented into discrete pixel-level photodiode regions by introducing a patterned separator layer and recessed regions. This segmentation prevents electrical signal leakage between adjacent pixels while maintaining efficient light collection within each pixel area, thereby resolving the crosstalk issue without sacrificing light collection efficiency.
Solution Approach 2:
The separator layer is selectively positioned between adjacent pixel areas to create localized electrical isolation, while the photodiode structure maintains its continuous nature over the pixel area for optimal light collection. This local differentiation allows each region to have the appropriate property: continuity for light collection and separation for crosstalk prevention.
2Quantity of substance
If pixel area is shrunk to increase pixel density, then pixel density is improved, but crosstalk becomes more severe
Solution Approach 1:
By shrinking pixel area while maintaining discrete photodiode regions through the patterned separator layer, the invention enables higher pixel density without increasing crosstalk. The segmentation ensures that even as pixels become smaller and more densely packed, each pixel remains electrically isolated, preventing signal leakage to neighboring pixels.
3Adaptability or versatility
If a multi-layer dielectric structure is used, then device functionality is improved, but crosstalk increases
Solution Approach 1:
The patterned separator layer is integrated within the multi-layer dielectric structure to create discrete photodiode regions. This segmentation approach maintains the benefits of multi-layer dielectric structures for device functionality while preventing crosstalk by electrically isolating adjacent pixels through the recessed separator regions.
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 reduces crosstalk, enhancing image quality and resolution by ensuring that the detected signal in one pixel area does not affect adjacent areas, while also lowering manufacturing costs and improving yield.
Implementation Method 1
POAP image sensors employ photoconductors, such as photoconductor covered active pixels or image sensor cell arrays, to convert optical light into electrical signal
Implementation Method 2
Electrons are generated by incidental light absorbed by photoconductors formed on the top of POAP image sensors, and transported to circuits below the photoconductors
Data Source
AI summary
An image sensor structure includes a plurality of pixels formed on a substrate. Each pixel includes an image senor interconnect structure, a separator layer and an electrode layer, wherein the separator layer has a first thickness an a sidewall of the separator layer is recessed from a sidewall of the electrode layer. A first doped amorphous silicon layer id formed on the electrode layer, wherein the separator layer and the first doped amorphous silicon layer of a pixel are disconnected from that of an adjacent pixel.