Time-of-Flight Pixel Charge Storage Under Modulation Gates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Time-of-flight pixel designs in sensors require significant space for charge demodulation and storage, which limits their compactness and efficiency in applications like 3D cameras.
Innovation Solution
The design integrates charge storage below the modulation gates, allowing for simultaneous demodulation and storage under a single photogate, with transfer gates and a drain gate managing charge flow to reduce space requirements and enable efficient readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If separate demodulation and storage structures are used, then charge handling functionality is achieved, but pixel area increases
Solution Approach 1:
The patent combines demodulation and storage functions into a single integrated structure. The storage region is positioned directly below the photogate, allowing the same structural elements to serve both demodulation and charge storage purposes, thereby reducing the overall pixel area while maintaining full functionality
Solution Approach 2:
The photogate structure serves multiple functions: it acts as both the modulation gate for demodulation and the storage region for charge carriers. This multi-functional design eliminates the need for separate dedicated storage structures, reducing pixel complexity and area
2Area of moving object
If charge storage is integrated below photogates, then space requirement is reduced, but charge carrier management complexity increases
Solution Approach 1:
The patent uses dynamic voltage control of the photogate to manage charge carriers. By adjusting the photogate voltage between accumulation mode (attracting and storing charges) and readout mode (releasing charges to the floating diffusion), the system efficiently manages charge carriers without requiring complex static structures
Solution Approach 2:
The integrated storage region below the photogate automatically captures and holds charge carriers through the photogate's electric field during the accumulation phase, and automatically transfers them to the floating diffusion during the readout phase, eliminating the need for additional active management components
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 configuration significantly reduces the space needed for each pixel, enabling noise-reduced correlated double sampling and efficient charge handling, suitable for both front and back side illuminations.
Implementation Method 1
the charges photogenerated in the silicon are deflected by a modulated voltage on the photogates GA and GB and the concomitant formation of the known charge carrier swing in the direction of the storage regions MA and MB
Implementation Method 2
the idea according to the invention, as sketched in FIG. 1, is that the charges photogenerated in the silicon are deflected by a modulated voltage on the photogates GA and GB
Data Source
AI summary
The invention relates to a light transit time pixel comprising —at least one modulation gate (GA, GB) which has a photoactive region (FAB) and a storage region (MA, MB), said storage region (MA, MB) having a locally increased n-type doping below the modulation gate (GA, GB) and delimiting the photoactive region (FAB) of the modulation gate (GA, GB), —at least one transfer gate (TXA, TXB) which adjoins the storage region (MA, MB) of the modulation gate (GA, GB), —at least one reading diode (DA, DB) which follows the transfer gate (TXA, TXB), —at least one drain gate (DG) which adjoins one side of the light-sensitive region (FAB) of the modulation gate (GA, GB), and —at least one drain diode (DD) which follows the drain gate (DG).