Vertical-Gate Image Sensor Layout for Avalanche ToF Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in achieving high reliability, sensitivity, and compact size while effectively utilizing the avalanche phenomenon for precise distance measurement and three-dimensional image capture.
Innovation Solution
The image sensor design incorporates a semiconductor substrate with a photoelectric conversion region, a photocharge collection region, a floating diffusion region, a charge multiplication region, and a vertical gate electrode, which together enable efficient avalanche amplification and precise current measurement, reducing dark current and minimizing sensor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional image sensor structure is used, then the device can perform basic image sensing, but the reliability and sensitivity are limited due to dark current and inability to perform high-precision distance measurement
Solution Approach 1:
The image sensor divides the sensing region into distinct functional zones: a photoelectric conversion region for light detection, a charge multiplication region for signal amplification, and a photocharge collection region for charge accumulation. This segmentation allows each region to optimize its specific function, with the charge multiplication region enabling avalanche breakdown for high-precision distance measurement while the photoelectric conversion region maintains reliable image sensing, thus resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent introduces a vertical gate electrode that extends in the depth direction of the semiconductor substrate, creating a three-dimensional structure. This vertical dimension allows the gate electrode to control the charge multiplication region effectively, enabling controlled avalanche breakdown for precise distance measurement (e.g., ToF sensing) while maintaining the two-dimensional image sensing function, thereby achieving both high reliability and high measurement precision.
2Volume of moving object
If the sensor size is reduced for compact design, then the device occupies less space, but the sensitivity and avalanche amplification performance deteriorate
Solution Approach 1:
The vertical gate electrode extending into the substrate depth provides effective control over the charge multiplication region without increasing the lateral footprint of the sensor. This three-dimensional structure enables compact sensor design while maintaining sufficient charge multiplication capability for high sensitivity, as the vertical dimension compensates for the reduced lateral dimensions.
Solution Approach 2:
The patent optimizes the doping concentration and depth of the charge multiplication region to achieve effective avalanche amplification in a compact volume. By carefully controlling the impurity concentration gradient and the vertical extent of the multiplication region, the sensor achieves high sensitivity without requiring large lateral dimensions, thus resolving the contradiction between compact size and sensitivity.
3Reliability
If dark current is not minimized, then the sensor structure can be simpler, but the reliability and sensitivity for precise measurement are compromised
Solution Approach 1:
The separation of the photoelectric conversion region from the charge multiplication region prevents dark current generated in the multiplication region from reaching the photocharge collection region. This spatial segmentation isolates the high-field avalanche region where dark current would be problematic, allowing the sensor to achieve high measurement reliability while maintaining a relatively simple overall structure.
Solution Approach 2:
The vertical gate electrode acts as an intermediary control element that regulates charge flow between the photoelectric conversion region and the charge multiplication region. By controlling the potential distribution, the gate electrode minimizes dark current leakage while enabling signal amplification, thus improving measurement reliability without requiring complex additional structures.
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 design enhances the reliability and sensitivity of the image sensor, allowing for high-precision distance measurement and three-dimensional image capture with reduced dark current and a compact form factor.
Implementation Method 1
a photoelectric conversion region in a semiconductor substrate
Implementation Method 2
using an avalanche phenomenon
Data Source
AI summary
An image sensor is provided. The image sensor includes: a photoelectric conversion region in a semiconductor substrate; a photocharge collection region provided in the photoelectric conversion region; a floating diffusion region in the semiconductor substrate that is spaced apart from the photocharge collection region along a vertical direction; a charge multiplication region between the photocharge collection region and the floating diffusion region; and a vertical gate electrode which extends into the semiconductor substrate and overlaps the photocharge collection region along the vertical direction. A side surface of the vertical gate electrode is adjacent to the floating diffusion region and the charge multiplication region.