Buried-Gate Light Receiving Element for High-Speed ToF Charge Transfer
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Solution Overview
Problem
Existing time of flight (ToF) sensors require high-speed transfer of electric charges generated by light reception to improve signal-to-noise ratio for accurate distance measurement, which is challenging due to the need for rapid charge distribution.
Innovation Solution
A light receiving element and device incorporating a semiconductor substrate with buried gate portions in distribution gates to facilitate high-speed transfer of electric charges to electric charge accumulation units, enhancing the efficiency of charge distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light reception is repeatedly performed at short intervals to increase signal amount, then signal-to-noise ratio is improved, but electric charge transfer speed must be increased
Solution Approach 1:
The distribution gate is divided into multiple gates (first distribution gate and second distribution gate) that operate at different timings. This segmentation allows electric charges to be transferred to different accumulation units in sequence, enabling high-speed transfer by preventing overlap and conflict in charge transfer paths.
Solution Approach 2:
The patent implements dynamic control of gate timing where the first and second distribution gates are activated at different time intervals. This dynamic timing control optimizes the transfer speed of electric charges by coordinating the operation of multiple gates to handle the high-frequency light reception requirements.
2Productivity
If distribution gates are added to increase transfer capacity, then charge distribution efficiency is improved, but device complexity increases
Solution Approach 1:
Multiple distribution gates share common structural elements and control mechanisms. The gates are integrated into a unified architecture where they can be controlled by a centralized control unit, reducing the overall complexity despite having multiple gates. The gates also share common accumulation units at different timings.
Solution Approach 2:
The distribution gates are designed with multi-functional capability, serving both as transfer paths for electric charges and as controllable switches for timing-based distribution. This universal design reduces the need for separate specialized components, thereby managing complexity while maintaining high transfer efficiency.
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
The solution enables high-speed transfer of electric charges with low power consumption, improving the signal-to-noise ratio and enabling accurate distance measurement in ToF sensors.
Implementation Method 1
a photoelectric conversion unit which is provided in the semiconductor substrate and converts light into electric charges
Data Source
AI summary
A light receiving element including: a semiconductor substrate; a photoelectric conversion unit (PD) in the semiconductor substrate that converts light into electric charges; a first electric charge accumulation unit (MEM) in the semiconductor substrate to which the electric charges are transferred from the photoelectric conversion unit; a first distribution gate on a front surface of the semiconductor substrate that distributes the electric charges from the photoelectric conversion unit to the first electric charge accumulation unit; a second electric charge accumulation unit (MEM) in the semiconductor substrate to which the electric charges are transferred from the photoelectric conversion unit; and a second distribution gate on the front surface of the semiconductor substrate that distributes the electric charges from the photoelectric conversion unit to the second electric charge accumulation unit, in which the first and second distribution gates each have a pair of buried gate portions.