Image Sensor Gate Oxide Asymmetry for Carrier Trapping Control
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Solution Overview
Problem
Existing semiconductor devices and image sensors face challenges in achieving improved electrical and optical characteristics, particularly in the design of the gate insulating pattern and impurity regions which affect the performance and efficiency of transistors.
Innovation Solution
The semiconductor device and image sensor designs incorporate a gate insulating pattern with specific edge portions and a center portion, where the first edge portion has a first thickness and the second edge portion has a second thickness smaller than the first, along with impurity regions on both sides of the gate electrode in the active region, to enhance electrical characteristics and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate insulating pattern with uniform thickness is used, then the manufacturing process is simple, but carrier trapping occurs at the interface between the active region and device isolation layer, degrading electrical characteristics
Solution Approach 1:
The gate insulating pattern is designed with different thicknesses at different locations: a first thickness at the first edge portion adjacent to the device isolation layer, and a second thickness at the second edge portion that is greater than the first thickness. This local variation in thickness prevents carrier trapping at the interface while maintaining manufacturing feasibility through selective epitaxial growth.
Solution Approach 2:
The gate insulating pattern exhibits asymmetric thickness distribution across the active region, with the second edge portion having a greater thickness than the first edge portion. This asymmetric design creates a potential barrier that prevents carrier trapping at the device isolation layer interface, improving electrical characteristics without requiring complex multi-layer structures.
2Reliability
If the gate insulating pattern thickness is increased uniformly, then carrier trapping is reduced, but the channel length increases and current flow is restricted
Solution Approach 1:
Instead of uniformly increasing the gate insulating pattern thickness, the invention applies local quality by increasing the thickness only at the second edge portion (away from the device isolation layer) while maintaining a smaller first thickness at the first edge portion. This selective thickness variation prevents carrier trapping at the interface while preserving adequate current flow through the channel region.
3Reliability
If impurity regions are added on both sides of the gate electrode, then electrical characteristics are improved, but the device structure becomes more complex
Solution Approach 1:
The impurity regions are merged with the existing active region structure during the same fabrication process steps. The first and second impurity regions are formed simultaneously with the gate insulating pattern through selective epitaxial growth, combining multiple functions into a single integrated structure rather than adding separate components.
Data Source
AI summary
Disclosed are a semiconductor device and an image sensor including the same. The semiconductor device includes a device isolation layer defining an active region on a semiconductor substrate, a gate electrode crossing the active region, a gate insulating pattern between the gate electrode and the semiconductor substrate, a first impurity region provided at a first side of the gate electrode in the active region, and a second impurity region provided at a second side of the gate electrode in the active region, and the gate insulating pattern includes a first edge portion adjacent to a first sidewall of the device isolation layer, a second edge portion adjacent to a second sidewall of the device isolation layer, and a center portion between the first and second edge portions, and the first edge portion has a first thickness, and the second edge portion has a second thickness smaller than the first thickness.