Asymmetric Image Sensor Active Region for RTS Noise Reduction
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Solution Overview
Problem
Conventional image sensors face issues with noise generation due to channel regions contacting device isolation sidewalls, leading to random telegraph signal (RTS) noise, dark current, and white spot, which affect image clarity and reliability.
Innovation Solution
The image sensor employs an asymmetric active region structure where the channel region between source/drain regions does not contact the sidewalls of the device isolation layer, preventing noise generation and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the channel region contacts the device isolation sidewalls, then device structure is simplified, but noise generation increases (RTS noise, dark current, white spot)
Solution Approach 1:
The patent applies asymmetry by creating an asymmetric active region structure where the channel region is positioned away from the device isolation sidewalls. The active region includes a first active region and a second active region with different configurations, preventing symmetric contact between the channel and isolation structures, thereby reducing noise while maintaining structural integrity.
Solution Approach 2:
The patent introduces a spatial dimension solution by adjusting the horizontal positioning of the active region relative to the device isolation structure. By creating a gap in the horizontal plane between the channel region and the isolation sidewalls, the patent eliminates noise contact pathways without increasing vertical complexity.
2Object-generated harmful factors
If the channel region does not contact the device isolation sidewalls, then noise generation is reduced, but device structure becomes more complex
Solution Approach 1:
The patent applies local quality by creating a localized gap only in the critical region where the channel meets the device isolation sidewall. The asymmetric active region structure maintains normal contact in non-critical areas while creating a noise-preventing gap only where needed, thus reducing overall device complexity increase.
3Ease of manufacture
If conventional symmetric active region structure is used, then manufacturing is simpler, but image clarity deteriorates due to noise
Solution Approach 1:
The patent transitions from a symmetric active region structure to an asymmetric one, where the first and second active regions have different configurations relative to the gate electrode and device isolation. This asymmetric design prevents the channel from contacting noise-generating isolation sidewalls while remaining compatible with standard manufacturing processes.
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 reduces noise and increases the reliability of the image sensor, enabling the capture of clear images by preventing contact between the channel region and the device isolation sidewalls.
Implementation Method 1
Each of the pixels includes a photodiode (PD). Generally, the photodiode is configured to transform an incident light into an electrical signal.
Data Source
AI summary
An image sensor includes: a first device isolation part in a substrate and defining an active region; a first gate electrode having a first and second gate sidewalls; and a first impurity region and a second impurity region adjacent to the first and second gate sidewalls, wherein the active region includes: a first active central part; a first active protrusion; and a second active protrusion, wherein the first device isolation part has a first isolation sidewall overlapping the first active central part, and wherein a first straight line is at least partially spaced apart from the first isolation sidewall, wherein the first straight line links a first point, at which the first active protrusion meets the first active central part, to a second point, at which the second active protrusion meets the first active central part.