TOF Image Sensor Well Structure for Low-Power Depth Sensing
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Solution Overview
Problem
Current image sensing devices face challenges in reducing power consumption while maintaining effective depth image characteristics, particularly in applications like automotive and medical imaging where high-performance and low power consumption are crucial.
Innovation Solution
The design incorporates a semiconductor substrate with a photoelectric conversion region and a circuit region, featuring a unique well structure with different impurity doping levels and depths, which enables efficient charge carrier generation and processing, reducing power consumption while improving depth image quality through the use of a current-assisted photonic demodulator structure for TOF methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional well structure is used in the circuit region, then manufacturing is simpler, but power consumption increases and depth image characteristics deteriorate
Solution Approach 1:
The well structure is segmented into multiple regions with different impurity concentrations and depths. The circuit region is divided into a first well region (deeper, higher impurity concentration) and a second well region (shallower, lower impurity concentration), allowing each region to be optimized independently for power consumption and performance characteristics.
Solution Approach 2:
Different regions of the well structure are assigned different local qualities through varying impurity concentrations and depths. The first well region has higher impurity concentration and greater depth to reduce leakage, while the second well region has lower impurity concentration and lesser depth to maintain performance, achieving local optimization throughout the structure.
2Reliability
If the well region is extended deeper in the substrate, then leakage is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The deep well structure is segmented into two distinct well regions rather than forming a single uniform deep well. This segmentation allows the leakage-reduction function to be distributed across multiple zones with different characteristics, achieving reliable leakage control while simplifying the manufacturing process compared to forming a single uniform deep structure.
Solution Approach 2:
Instead of extending a single well uniformly to a great depth throughout the entire circuit region, the first well region is extended deeper only in specific areas where leakage is most problematic, while the second well region provides shallower coverage in other areas. This partial action approach achieves sufficient leakage reduction without the excessive manufacturing complexity of a uniform deep well structure.
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 approach effectively reduces power consumption while enhancing depth image characteristics, enabling more efficient and accurate distance measurements in image sensing applications, such as automotive and medical imaging, by concentrating pixel current in the photoelectric conversion region and minimizing leakage.
Implementation Method 1
a photoelectric conversion region supported by the semiconductor substrate and structured to generate charge carriers from incident light and capture the charge carriers using an electric potential difference
Data Source
AI summary
An image sensing device includes a semiconductor substrate, a photoelectric conversion region structured to generate charge carriers from incident light and capture the charge carriers using an electric potential difference caused by a demodulation control signal applied to the photoelectric conversion region, and a circuit region disposed adjacent to the photoelectric conversion region, the circuit region including a plurality of pixel transistors that generate and output a pixel signal corresponding to the charge carriers captured by the photoelectric conversion region. The circuit region includes a first well region formed to have a first length in a first direction, and a second well region formed below the first well region such that a lower end of the first well region is in contact with an upper end of the second well region, and formed to have a second length shorter than the first length in the first direction.