Deep Trench Isolated Photodiodes for Dense Low-Dark-Current Pixels
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Solution Overview
Problem
Current photodiode technologies face challenges in miniaturization and improving sensitivity while maintaining low noise and jitter, especially in detecting single photons.
Innovation Solution
The development of a photodiode device with a layer of semiconductor material, pixels with diode structures and conductive layers, deep trench isolation structures, and vertical conductive layers that extend from the conductive layer to contacts on both sides of the DTI structures, enhancing pixel density and fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If photodiode size is reduced for miniaturization, then device density increases, but noise and jitter increase reducing detection sensitivity
Solution Approach 1:
The patent transitions from planar pixel arrangement to a three-dimensional structure by forming vertical conductive layers that extend through the substrate thickness. This vertical dimension allows electrical connections to pass through the substrate without occupying lateral pixel area, enabling smaller pixel footprints while maintaining electrical performance and reducing noise through optimized current paths.
Solution Approach 2:
The patent divides the substrate into multiple pixels separated by deep trench isolation structures. These trenches create electrical isolation between adjacent pixels, preventing noise coupling and allowing each miniaturized pixel to operate independently with reduced jitter, thus maintaining detection sensitivity despite smaller size.
2Productivity
If pixel density is increased, then fill factor improves, but dark current increases reducing signal quality
Solution Approach 1:
The deep trench isolation structures physically segment the substrate into isolated pixel regions. This segmentation creates electrical barriers that prevent dark current generated in one pixel from affecting adjacent pixels, allowing high pixel density while maintaining low dark current levels through effective electrical isolation.
Solution Approach 2:
The deep trench isolation structures act as intermediary elements between adjacent pixels. These trenches, filled with insulating material, serve as mediators that block electrical interaction between pixels, preventing dark current propagation while allowing the pixels to be positioned closely together for high density.
3Reliability
If deep trench isolation structures are added, then pixel isolation improves, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the deep trench isolation structures: they provide electrical isolation between pixels, serve as mechanical support, and act as barriers to dark current. This merging of functions achieves excellent pixel isolation while avoiding the need for additional separate isolation components, thereby limiting the increase in device complexity.
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 design achieves higher pixel density and improved fill factor, maintaining or increasing photon detection probability while minimizing dark current, thus addressing the need for further miniaturization and sensitivity enhancement in photodiode technology.
Implementation Method 1
Semiconductor photodiodes are a category of photodetectors that use a P-N diode to convert incident photons into current
Implementation Method 2
Avalanche photodiodes are a highly biased photodiodes in which photo-generated carriers are multiplied by avalanche breakdown in the device
Data Source
AI summary
A photodiode device includes a layer of semiconductor material, a plurality of pixels, each of the pixels including a diode structure on a first side of the layer of semiconductor material and a conductive layer on a second side of the layer of semiconductor material, deep trench isolation (DTI) structures isolating adjacent pixels from one another, a first vertical conductive layer over a first side of each DTI structure, and a second vertical conductive layer over a second side of each DTI structure. The first vertical conductive layer extends from the conductive layer to a first contact on the first side of each DTI structure, and the second vertical conductive layer extends from the conductive layer to a second contact on the second side of each DTI structure.