TOF Image Sensor Transfer Gate Segmentation
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Solution Overview
Problem
Existing Time-of-Flight (TOF) image sensors face challenges in efficiently transferring electrons within an extremely short period, which affects their depth sensing capabilities and increases manufacturing costs.
Innovation Solution
The image sensor design incorporates transfer gates located on all sides of the photodiode, allowing for efficient electron transfer to floating diffusion nodes, enabling faster TOF demodulation and improved depth sensing while maintaining or enhancing sensitivity and fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transfer gates are added to enable fast electron transfer in TOF sensors, then electron transfer speed is improved, but device complexity increases
Solution Approach 1:
The photodiode is divided into multiple segments with transfer gates positioned at specific locations (e.g., two opposite sides or four sides) rather than uniformly distributed. This segmentation approach enables efficient electron transfer paths while reducing the overall number of transfer gates needed, thus lowering device complexity while maintaining fast electron transfer speed for TOF applications.
2Measurement precision
If transfer gates are positioned to optimize electron transfer, then TOF demodulation performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
Transfer gates are strategically positioned at specific locations around the photodiode (such as two opposite sides or selected corners) rather than uniformly distributed. This local quality approach concentrates transfer functionality at critical positions, optimizing electron transfer paths for TOF demodulation while reducing the number of precisely positioned elements, thereby lowering manufacturing precision requirements.
3Productivity
If multiple transfer gates are implemented for fast electron transfer, then real-time depth image acquisition is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and implements only the essential transfer gates needed for effective TOF operation, rather than providing complete coverage around the photodiode. By selecting specific positions (e.g., two opposite sides or selected corners among four sides), the design achieves sufficient electron transfer speed for real-time depth imaging while minimizing the number of transfer gates, thus reducing manufacturing cost and complexity.
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 TOF depth sensing capacity of image sensors by improving electron transfer speed and reducing manufacturing complexity, thereby improving real-time depth image acquisition and reducing costs.
Implementation Method 1
a pixel including a photodiode, wherein a transfer gate is located in each of all sides of the photodiode
Implementation Method 2
a pixel including a photodiode, wherein different transfer gates are respectively located in two sides of the photodiode
Data Source
AI summary
An image sensor based on a depth pixel structure is provided. The image sensor may include a pixel including a photodiode, and the photodiode may include a transfer gate to transfer, to a floating diffusion node, an electron generated by a light reflected from an object.