Symmetric Distribution Gate Layout for TOF Light Receivers
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Solution Overview
Problem
TOF sensors face challenges in maintaining high distance measurement accuracy due to manufacturing variations, which affect the uniform performance of distribution transistors and result in measurement errors.
Innovation Solution
A light receiving device with a configuration of light receiving elements on a semiconductor substrate, where distribution gates are axially symmetric with respect to the center axis of the photoelectric conversion unit, ensuring equal charge distribution performance across all elements, thus minimizing the impact of manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light receiving elements are used without specific symmetric configuration, then manufacturing process is simpler, but distance measurement accuracy deteriorates due to manufacturing variations affecting distribution transistor performance
Solution Approach 1:
The patent applies asymmetry principle by intentionally designing the distribution gates in a symmetric configuration relative to the photoelectric conversion unit's center axis. This symmetric layout ensures that both distribution gates experience identical manufacturing variations, causing errors to cancel out rather than accumulate, thereby maintaining uniform performance across different light receiving elements despite manufacturing tolerances.
Solution Approach 2:
The patent changes the geometric parameters of the distribution gates by positioning them at symmetric locations relative to the photoelectric conversion unit. By adjusting the spatial arrangement (positioning parameters) of the gates to be mirror-symmetric with respect to the center axis, the design compensates for manufacturing variations and ensures consistent charge distribution performance.
2Reliability
If distribution gates are positioned asymmetrically or without specific configuration, then device layout is more flexible, but charge distribution uniformity deteriorates leading to measurement errors
Solution Approach 1:
The patent employs symmetry (the opposite of asymmetry) by configuring the distribution gates to be positioned symmetrically with respect to the center axis of the photoelectric conversion unit. This symmetric arrangement ensures that charge distribution uniformity is maintained because any deviations in one gate are compensated by the corresponding gate on the opposite side, making the system robust against manufacturing variations.
Solution Approach 2:
The symmetric configuration creates equipotential conditions for charge distribution by ensuring that both distribution gates are equidistant from the photoelectric conversion unit's center. This geometric equipotentiality ensures that charges are distributed uniformly to the adjacent light receiving elements, preventing measurement errors caused by uneven charge allocation.
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 ensures high accuracy in distance measurement by maintaining uniform performance of distribution transistors across all light receiving elements, even with manufacturing variations, thereby enhancing the reliability of the TOF sensor.
Implementation Method 1
a first photoelectric conversion unit that converts light into electric charges
Data Source
AI summary
In a light receiving device, a light receiving element includes a first photoelectric conversion unit (PD) that converts light into electric charges, a first electric charge storage unit (MEM) to which the electric charges are transferred from the first photoelectric conversion unit, a first distribution gate, a second electric charge storage unit (MEM) to which the electric charges are transferred from the first photoelectric conversion unit, and a second distribution gate, in which the first and second distribution gates are provided at positions axially symmetric to each other with respect to a first center axis extending so as to pass through the center of the first photoelectric conversion unit, in a direction intersecting the column direction at a predetermined angle, when viewed from above the semiconductor substrate.