Deep-Trench Charge Transfer for High-Frequency IR Image Sensing
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Solution Overview
Problem
Current image sensor devices face challenges in achieving high-frequency photogenerated charge transfer with good efficiency, particularly in the infrared wavelength range used for time-of-flight measurements, leading to low detection sensitivity and heat dissipation issues.
Innovation Solution
The development of an integrated device with deep trench isolation structures and alternating bias voltages to efficiently transfer photogenerated charges in two directions, utilizing trenches with insulated conductive regions and storage potential wells to enhance charge transfer efficiency at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If photogenerated charges are transferred at high frequency in conventional planar structures, then transfer speed increases, but transfer efficiency decreases due to deep charge generation in silicon substrates
Solution Approach 1:
The invention segments the charge transfer path by introducing deep trenches that divide the semiconductor substrate into isolated regions. These trenches create independent transfer channels that guide photogenerated charges from deep generation locations to collection points, maintaining high transfer efficiency even at high frequencies by preventing charge loss in conventional planar structures
Solution Approach 2:
The invention transitions from conventional two-dimensional planar charge transfer to three-dimensional transfer by creating deep trenches extending vertically into the substrate. This vertical dimension allows efficient collection of charges generated at various depths, particularly addressing the problem of deep charge generation in infrared wavelength applications
2Measurement precision
If infrared wavelengths (750-950 nm) are used for time-of-flight measurements, then detection capability is provided, but charge transfer efficiency decreases due to deep charge generation in silicon substrates
Solution Approach 1:
The deep trench structure segments the substrate to create isolated charge transfer regions, ensuring that charges generated at different depths by infrared wavelengths are efficiently collected through dedicated vertical paths, preventing recombination losses that would reduce detection sensitivity
Solution Approach 2:
The trenches act as intermediary structures that facilitate the transfer of deeply generated charges from infrared absorption locations to collection regions, serving as guided pathways that maintain charge integrity throughout the transfer process
3Ease of manufacture
If conventional planar structures are used for charge transfer, then manufacturing simplicity is maintained, but transfer efficiency is low for deeply generated charges
Solution Approach 1:
The deep trench segmentation can be integrated into conventional CMOS fabrication processes using standard deep trench isolation techniques, maintaining manufacturing simplicity while dramatically improving charge transfer efficiency through the three-dimensional charge guidance paths
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 solution enables high-frequency charge transfer with improved sensitivity and reduced dark current, allowing for high-quality photonic demodulation and efficient detection of three-dimensional images.
Implementation Method 1
transferring charges photogenerated in a portion of a semiconductor layer
Implementation Method 2
biasing of the first conductive regions to a first voltage to form a volume accumulation of holes... while the second conductive regions are biased to a second voltage greater than the first voltage
Data Source
AI summary
A device for transferring charges photogenerated in a portion of a semiconductor layer delimited by at least two parallel trenches, each trench including, lengthwise, at least a first and a second conductive regions insulated from each other and from the semiconductor layer, including the repeating of a first step of biasing of the first conductive regions to a first voltage to form a volume accumulation of holes in the area of this portion located between the first regions, while the second conductive regions are biased to a second voltage greater than the first voltage, and of a second step of biasing of the first regions to the second voltage and of the second regions to the first voltage.