Dual STI Isolation Layout for Mixed-Voltage Transistor Regions
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Solution Overview
Problem
Existing semiconductor manufacturing processes for high voltage and medium voltage transistors are not suitable for low voltage transistors, leading to current leakage and performance degradation due to different spacing requirements and susceptibility to punch-through current leakage.
Innovation Solution
Implementing a dual shallow trench isolation (STI) technique to form isolation regions between low voltage and medium voltage transistor regions with deeper isolation depths, using different design rules to minimize current leakage and increase transistor density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing semiconductor manufacturing processes are used for high voltage and medium voltage transistors, then these transistors can operate at higher voltages, but low voltage transistors experience current leakage and performance degradation due to different spacing requirements
Solution Approach 1:
The patent divides the transistor regions into distinct zones with different isolation depths. Low voltage transistor regions are provided with deeper isolation regions compared to medium voltage transistor regions, allowing each voltage type to have optimized spacing and isolation characteristics. This segmentation prevents punch-through current leakage in low voltage transistors while maintaining the performance of medium voltage transistors.
2Reliability
If deeper isolation regions are formed between low voltage and medium voltage transistor regions, then current leakage is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies different isolation depths to different regions of the semiconductor device. Specifically, isolation regions adjacent to low voltage transistor regions are formed deeper than isolation regions adjacent to medium voltage transistor regions. This local differentiation provides enhanced electrical isolation where needed (near low voltage transistors) while avoiding unnecessary complexity in other areas, thus balancing reliability improvement with manufacturing feasibility.
Data Source
AI summary
A semiconductor device is formed such that isolation regions between a medium voltage transistor region and a low voltage transistor region are manufactured to have different properties than isolation regions between low voltage transistors in the low voltage transistor region. A dual STI technique described herein is used to form the isolation regions between the low voltage transistors in the low voltage transistor region using low voltage transistor isolation design rules may, and additional STI formation operations may be performed to form the isolation regions between the low voltage transistor region and the medium voltage transistor region. In particular, the dual STI technique described herein may be used to form the isolation regions between the low voltage transistor region and the medium voltage transistor region such that these isolation regions are deeper than other isolation regions in the semiconductor device.