TOF Pixel Design for High-Resolution 3D Imaging
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Solution Overview
Problem
Existing time-of-flight (TOF) sensors have relatively large pixel dimensions, making them unsuitable for achieving high-resolution three-dimensional imaging, as they exceed 10 μm*10 μm in surface area, which limits their ability to provide detailed distance mappings of scenes.
Innovation Solution
A TOF detection pixel design featuring a semiconductor substrate with a photosensitive area, charge collection area, and charge storage areas, each with specific doping levels and gate structures, allowing for efficient charge transfer and reduced pixel size, potentially smaller than 5 μm*5 μm, enabling more precise distance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If existing TOF pixel designs are used, then the pixel structure is simple and easy to manufacture, but the pixel surface area is large (exceeding 10 μm*10 μm), which limits imaging resolution
Solution Approach 1:
The pixel structure is divided into multiple functional regions including a photosensitive area, charge collection area, and multiple charge storage areas (first, second, and third storage areas). This segmentation allows each region to perform its specific function efficiently while reducing the overall pixel footprint through optimized spatial arrangement.
Solution Approach 2:
The patent utilizes vertical stacking of doped layers (first doped layer, second doped layer, third doped layer) to create three-dimensional charge storage and transfer paths. This vertical dimensionality allows compact integration of multiple functions within a small planar footprint, reducing the pixel surface area while maintaining structural complexity for efficient operation.
2Measurement precision
If pixel size is reduced to improve resolution, then imaging detail improves, but charge collection and storage efficiency may deteriorate
Solution Approach 1:
Different regions of the pixel are assigned different doping types and concentrations optimized for their specific functions: the photosensitive area uses a first doping type for light detection, charge collection areas use a second doping type for efficient charge gathering, and storage areas use a third doping type for charge retention. This local optimization ensures high charge collection efficiency even in small pixels.
Solution Approach 2:
Intrinsically doped regions serve as intermediary zones between the photosensitive area, charge collection area, and storage areas. These intermediate regions facilitate smooth charge transfer between differently doped zones, ensuring efficient charge collection and storage while maintaining electrical isolation where needed, thus preserving reliability in miniaturized pixels.
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 proposed pixel design enables the creation of high-resolution three-dimensional images by allowing for smaller pixel sizes, improving the accuracy and detail of distance measurements in TOF sensors, thereby overcoming the limitations of existing TOF pixels.
Implementation Method 1
a photosensitive area comprising a first doped layer of a first conductivity type
Implementation Method 2
at least two charge storage areas, each comprising a well of the first type more heavily doped than the charge collection area
Data Source
AI summary
A pixel is formed on a semiconductor substrate that includes a photosensitive area having a first doped layer and a charge collection area of a first conductivity type extending through at least part of the first doped layer. At least two charge storage areas, each including a well of the first conductivity type, are separated from the charge collection area at least by a first portion of the first layer. The first portion is covered by a first gate. Each charge storage area is laterally delimited by two insulated conductive electrodes. A second doped layer of the second conductivity type covers the charge collection area and the charge storage areas.