CMOS Image Sensor Gate Electrode Segmentation for Plasma Damage Protection
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Solution Overview
Problem
CMOS image sensors face damage to the photodiode region during the fabrication process due to multiple plasma exposures, which weakens the sensor's performance.
Innovation Solution
A CMOS image sensor design where the gate electrode of the reset transistor encloses a part of the photodiode region, minimizing damage by forming a conductive plug within this enclosed area, and using an epitaxial layer to enhance photodiode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple plasma exposure processes are used during fabrication, then manufacturing precision is improved, but the photodiode region suffers damage reducing reliability
Solution Approach 1:
The gate electrode is divided into two distinct parts: a first gate electrode positioned over the transistor region and a second gate electrode positioned over the photodiode region. This segmentation allows different plasma exposure conditions to be applied to each region, protecting the photodiode while maintaining manufacturing precision in the transistor area.
Solution Approach 2:
Different gate electrode structures are applied to different regions: the transistor region receives a standard gate electrode structure suitable for high-precision plasma processing, while the photodiode region receives a protected structure that minimizes plasma exposure. This local differentiation resolves the contradiction by optimizing each region for its specific requirements.
2Device complexity
If the gate electrode structure is simplified, then device complexity is reduced, but plasma damage to the photodiode region increases
Solution Approach 1:
The gate electrode is segmented into two functional parts with different configurations. The first gate electrode for the transistor region can be simplified, while the second gate electrode for the photodiode region is specifically designed to enclose and protect the photodiode area during plasma processes, adding protection without significantly increasing overall device complexity.
Solution Approach 2:
The second gate electrode acts as an intermediary protective structure between the plasma environment and the photodiode region. It serves as a physical barrier that reduces plasma damage while maintaining electrical functionality, thus protecting the photodiode without requiring complete structural simplification.
3Object-affected harmful factors
If the gate electrode encloses more of the photodiode region, then plasma damage is reduced, but the active area for light detection decreases
Solution Approach 1:
The gate electrode system is segmented into two zones: the first gate electrode covers the transistor region, and the second gate electrode covers only the necessary peripheral area of the photodiode region for protection. This segmentation ensures minimal enclosure of the photodiode active area while still providing sufficient plasma protection during fabrication processes.
Solution Approach 2:
The protective gate electrode structure is applied locally only where plasma protection is needed (peripheral photodiode region), rather than enclosing the entire photodiode area. This localized approach maintains maximum active detection area while providing targeted protection against plasma damage.
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 reduces plasma damage to the photodiode region, enhancing the image sensor's characteristics and photosensitivity by protecting the critical light-receiving area and improving low-voltage operation.
Implementation Method 1
an image sensor is a semiconductor device that transforms an optical image to electrical signals
Implementation Method 2
using an epitaxial layer to enhance photodiode performance
Data Source
AI summary
A CMOS image sensor capable of improving characteristics of the image sensor by preventing damage to a photodiode region and a method for manufacturing the same are provided. The CMOS image sensor includes: a semiconductor substrate on which a device isolation region and an active region are defined; a photodiode region formed at the active region; a conductive plug formed on the photodiode region for connecting the photodiode region to a metal wiring; and a transistor formed enclosing the conductive plug.