Image Sensing Device With Potential Gradient For ToF Power Reduction
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Solution Overview
Problem
Current image sensing devices, particularly those using CMOS technology for time of flight (ToF) distance sensing, face challenges in balancing performance and power consumption, with existing ToF pixels often requiring higher power to achieve accurate distance measurements.
Innovation Solution
The design incorporates a substrate with conductive contact structures and well regions to generate a potential gradient, allowing for efficient capture of photocharges and reduced power consumption, featuring a layout where control nodes, detection nodes, and control gates are arranged diagonally to enhance signal carrier movement and reduce power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ToF pixels are used to achieve accurate distance measurements, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The pixel structure is divided into multiple specialized regions including control nodes, detection nodes, and well regions. Each region performs a specific function in the photocharge generation, separation, and collection process, enabling efficient distance measurement while reducing overall power consumption through functional specialization
Solution Approach 2:
Different regions within the pixel are doped with different conductivity types (first and second conductivity types) to create localized electrical characteristics. The control nodes, detection nodes, and well regions have tailored doping profiles that optimize their specific functions, improving measurement precision while minimizing power requirements
2Device complexity
If control nodes and detection nodes are arranged in conventional layouts, then device complexity is reduced, but photocharge collection efficiency decreases
Solution Approach 1:
The patent introduces a vertical dimension to the pixel structure by implementing control nodes and detection nodes at different depths within the substrate. The well regions extend vertically to capture photocharges generated at various depths, creating a three-dimensional charge collection architecture that improves efficiency without significantly increasing lateral complexity
3Quantity of substance
If deeper control nodes are used to capture more photocharges, then photocharge capture capability is improved, but power consumption increases
Solution Approach 1:
The well regions serve as intermediary structures between the control nodes and detection nodes. These well regions are doped with a third conductivity type and positioned at intermediate depths, facilitating photocharge collection from deeper regions without requiring the control nodes themselves to be positioned at maximum depth, thereby reducing the power required to maintain deep control node potentials
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 improves the performance of ToF pixels while significantly reducing power consumption, enabling more efficient and accurate distance measurements in image sensing devices.
Implementation Method 1
imaging pixels to receive the incident light from the back side and each imaging pixel structured to produce photocharge in response to received incident light
Implementation Method 2
a plurality of conductive contact structures configured to generate a potential gradient in the substrate and to capture photocharges that are generated in response to the incident light and move by the potential gradient
Data Source
AI summary
An image sensing device includes a substrate including a back side structured to receive incident light and a front side opposite to the back side; imaging pixels to receive the incident light from the back side and each imaging pixel structured to produce photocharge in response to received incident light; a plurality of conductive contact structures configured to generate a potential gradient in the substrate and to capture photocharges that are generated in response to the incident light and move by the potential gradient; and a well region disposed between the plurality of conductive contact structures.