Fin Transfer Gate Image Sensor Reducing Image Lag
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Solution Overview
Problem
Image sensors face challenges in efficiently capturing incident light due to image lag, which degrades image quality as charge from previous exposures remains in photodiodes, affecting the performance of ever-decreasing pixel sizes.
Innovation Solution
The implementation of fin-like structures in transfer gates and a uniform doping profile throughout the photodiode depth, allowing for high-speed and accurate charge transfer from photodiodes to floating diffusion regions, reducing image lag and improving image sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is decreased to improve sensor integration, then manufacturing density is improved, but light capture efficiency deteriorates and image lag increases
Solution Approach 1:
The transfer gate is extended vertically into the substrate to form fin structures, transitioning from a planar 2D gate to a 3D structure. This vertical extension increases the effective gate width and charge transfer capability without increasing the lateral pixel footprint, thereby maintaining high integration density while improving charge transfer efficiency and reducing image lag
Solution Approach 2:
The transfer gate is divided into multiple fin structures that extend vertically into the substrate. These segmented fins collectively provide a larger total gate width for charge transfer, enabling efficient charge removal from photodiodes while maintaining compact pixel dimensions for high-density sensor integration
2Reliability
If charge transfer speed is increased to reduce image lag, then image quality is improved, but transfer gate complexity increases
Solution Approach 1:
The transfer gate utilizes the vertical dimension by extending fins into the substrate, increasing the effective transfer area without adding lateral complexity. This 3D configuration accelerates charge transfer speed to reduce image lag while maintaining a relatively simple planar layout that fits within standard pixel designs
Solution Approach 2:
The transfer gate structure is modified by changing the vertical parameter (fin depth into substrate) rather than lateral dimensions. This parameter change increases the gate width effective for charge transfer, improving transfer speed and reducing image lag without significantly increasing overall device 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 solution enhances the speed and accuracy of charge reading, reduces image lag, and maintains full well capacity, thereby improving the quality of electronic images captured by image sensors.
Implementation Method 1
each photosensitive element absorbs a portion of incident image light. Photosensitive elements included in the image sensor, such as photodiodes, each generate image charge upon absorption of the image light
Data Source
AI summary
A device includes a photodiode, a floating diffusion region, a transfer gate, and a channel region. The photodiode is disposed in a semiconductor material. The photodiode is coupled to generate charges in response to incident light. The photodiode has a substantially uniform doping profile throughout a depth of the photodiode in the semiconductor material. The floating diffusion region is disposed in the semiconductor material. The transfer gate is disposed between the photodiode and the floating diffusion region, wherein the transfer gate includes a plurality of fin structures. The channel region associated with the transfer gate is in the semiconductor material proximate to the transfer gate. The transfer gate is coupled to transfer the charge from the photodiode to the floating diffusion region through the channel region in response to a transfer signal coupled to be received by the transfer gate.