Light Receiving Element with Dual Charge Storage for Low kTC Noise
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Solution Overview
Problem
Existing light receiving elements in TOF sensors face challenges in achieving a wide dynamic range while minimizing kTC noise to ensure high accuracy in distance measurement.
Innovation Solution
The light receiving element incorporates a photoelectric conversion unit, a first charge accumulation unit, and a second charge accumulation unit, each comprising a stack of an electrode, an insulating layer, and a semiconductor layer, with the second unit having a semiconductor layer and an insulating layer embedded in a trench, to reduce kTC noise and enhance dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of accumulated charges is increased to ensure a wide dynamic range, then the signal-to-noise ratio is improved, but the influence of kTC noise increases
Solution Approach 1:
The charge accumulation function is divided into multiple independent accumulation units (first charge accumulation unit and second charge accumulation unit). Each unit accumulates charges separately and can be independently controlled, allowing the system to accumulate sufficient charges for wide dynamic range while managing kTC noise through selective readout and correlation processing of multiple measurements.
2Quantity of substance
If multiple charge accumulation units are added to increase dynamic range, then the accumulated charge amount increases, but the device complexity increases
Solution Approach 1:
Multiple charge accumulation units share common structural elements including the photoelectric conversion unit, charge transfer pathways, and readout circuitry. The accumulation units use identical internal structures (electrode, insulating layer, semiconductor layer stacks), allowing for standardized fabrication and reduced overall device complexity despite having multiple accumulation units.
Solution Approach 2:
Each charge accumulation unit is designed with a universal structure that can accumulate charges from the photoelectric conversion unit and be read out through shared circuitry. The accumulation units serve multiple functions: accumulating charges for wide dynamic range, enabling repeated measurements for noise reduction, and providing redundant data for correlation processing.
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 allows for high-accuracy distance measurement by effectively reducing kTC noise and ensuring a wide dynamic range, thereby improving the signal-to-noise ratio.
Implementation Method 1
a photoelectric conversion unit that is provided in a semiconductor substrate and converts light into a charge
Data Source
AI summary
To provide a light receiving element including: a photoelectric conversion unit (PD) that is provided in a semiconductor substrate and converts light into a charge; a first charge accumulation unit (MEM) to which the charge is transferred from the photoelectric conversion unit; a second charge accumulation unit (MEM) to which the charge is transferred from the photoelectric conversion unit, in which each of the first and second charge accumulation units includes a stack of an electrode, a first insulating layer, and a semiconductor layer.