Semiconductor Gate Stack Oxygen Sink for Uniform Threshold Voltage
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Solution Overview
Problem
High-K Metal Gate (HKMG) transistors face challenges in maintaining uniform threshold voltage and reliability due to oxygen vacancies, which are exacerbated by differences in gate lengths and widths during annealing processes, leading to ununiform oxygen vacancy curing and threshold voltage shifts.
Innovation Solution
A semiconductor device and method that incorporates a dummy gate stack with an oxygen sink layer to capture and cure oxygen atoms diffused from the atmosphere, ensuring uniform oxygen vacancy curing across transistors of varying widths and lengths by forming a stacked structure with an interface layer, high-k material, and metal gate electrode, and performing thermal treatment in an oxygen gas atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal treatment is performed in oxygen atmosphere to cure oxygen vacancies, then oxygen vacancy curing is improved, but oxygen vacancy uniformity across transistors of different widths deteriorates due to differential oxygen diffusion
Solution Approach 1:
The patent applies local quality by creating different oxygen sink capacities in different regions. The dummy gate stack is specifically designed with oxygen sink layers that have different oxygen diffusion characteristics compared to the active gate stacks. This local differentiation allows the dummy gate to capture excess oxygen atoms that would otherwise diffuse into the active gates during thermal treatment, thereby maintaining uniform oxygen vacancy levels across transistors of different widths while still achieving effective oxygen vacancy curing.
Solution Approach 2:
The dummy gate stack serves as an intermediary structure between the oxygen atmosphere and the active gate stacks. During thermal treatment in oxygen atmosphere, the dummy gate stack acts as a mediator that selectively captures oxygen atoms through its oxygen sink layers, preventing uncontrolled oxygen diffusion into the active gates. This intermediary role ensures uniform oxygen vacancy curing across all transistors regardless of their width differences.
2Manufacturing precision
If dummy gate stack is added to capture oxygen atoms, then oxygen vacancy uniformity is improved, but device complexity increases
Solution Approach 1:
The patent merges the dummy gate stack with the existing gate structure architecture. The dummy gate stack is formed using the same fabrication processes and material layers (interface layer, high-k material, metal gate electrode) as the active gate stacks. This merging approach allows the dummy gate to perform its oxygen sink function while maintaining structural consistency with the active devices, thereby minimizing additional complexity in the overall device architecture and fabrication process.
Solution Approach 2:
The dummy gate stack is designed with multi-functionality. It serves both as a structural element that can be formed using standard gate fabrication processes and as a functional oxygen sink during thermal treatment. The same stacked structure (interface layer, high-k material, metal gate electrode) that forms the active gates also creates the oxygen sink capability in the dummy gate, allowing one structure to fulfill multiple roles and reducing overall device complexity.
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 enhances the uniformity of oxygen vacancy curing and threshold voltage across transistors, improving their reliability and performance by minimizing oxygen vacancy differences and maintaining uniform threshold voltage, even across gates of different lengths and widths.
Implementation Method 1
oxygen atoms that are diffused from an exterior into the first gate stack and the second gate stack
Implementation Method 2
the dummy gate stack includes an oxygen sink layer for capturing oxygen atoms
Implementation Method 3
performing a thermal treatment in an atmosphere of an oxygen gas to cure oxygen vacancies of the active gate stack
Data Source
AI summary
A semiconductor device includes: a first transistor that includes a first gate stack; a second transistor that includes a second gate stack having a narrower width than the first gate stack; and a dummy gate stack disposed around the first gate stack and the second gate stack, wherein the dummy gate stack includes an oxygen sink layer for capturing oxygen atoms that are diffused from an exterior into the first gate stack and the second gate stack.