STI Region Layout With Dummy Diffusion for Threshold Voltage Stability
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Solution Overview
Problem
Oxygen migration from silicon oxide in the STI region into high-k gate insulating films causes threshold voltage changes in transistors, particularly in semiconductor devices.
Innovation Solution
Incorporating dummy diffusion regions with lower impurity concentration between adjacent STI regions and covering them with conductive patterns to reduce oxygen migration and prevent ion implantation, while using high-k materials for gate insulating films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-k materials are used for gate insulating films to improve transistor performance, then transistor efficiency is improved, but oxygen migration from STI region causes threshold voltage change
Solution Approach 1:
A dummy diffusion region is introduced as an intermediary structure between the STI region and the transistor active region. This dummy diffusion region acts as a buffer that intercepts and reduces oxygen migration from the silicon oxide STI region to the gate insulating film, thereby preventing threshold voltage changes while allowing the use of high-k materials for improved transistor efficiency.
Solution Approach 2:
The harmful oxygen migration path is extracted and isolated by introducing the dummy diffusion region. The dummy diffusion region specifically targets and removes the oxygen migration issue from the system, separating the STI region's oxygen content from the gate insulating film to prevent threshold voltage instability.
2Reliability
If STI region is made of silicon oxide to provide insulation, then insulating performance is improved, but oxygen migration occurs into gate insulating film
Solution Approach 1:
The dummy diffusion region serves as an intermediary layer between the silicon oxide STI region and the gate insulating film. It maintains the insulating performance of the STI region while acting as a barrier that reduces oxygen migration to the gate insulating film, thereby eliminating the harmful effect without compromising the insulating function.
Solution Approach 2:
The dummy diffusion region is strategically placed only in specific areas where oxygen migration is problematic. It creates a localized solution that addresses the oxygen migration issue at the STI-gate insulating film interface without altering the overall silicon oxide STI structure, maintaining local quality control to prevent harmful oxygen migration while preserving insulating performance.
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 approach effectively prevents threshold voltage changes in transistors by reducing oxygen migration and ensuring reliable transistor performance even with high-k gate insulating films.
Implementation Method 1
oxygen contained in the STI region migrates into a gate insulating film
Implementation Method 2
covering them with conductive patterns to reduce oxygen migration and prevent ion implantation
Data Source
AI summary
Disclosed herein is an apparatus that includes: a semiconductor substrate including first and second STI regions arranged in a first direction, a first diffusion region having a first conductivity type surrounded by the first STI region, a second diffusion region having a second conductivity type surrounded by the second STI region, and a third diffusion region extending in a second direction such that the third diffusion region is arranged between the first and second STI regions; a first gate electrode including a first polycrystalline silicon film covering a part of the first diffusion region to form a P-channel MOS transistor; a second gate electrode including a second polycrystalline silicon film covering a part of the second diffusion region to form an N-channel MOS transistor; and a third polycrystalline silicon film extending in the second direction such that the third polycrystalline silicon film covers the third diffusion region.