High-k Gate Stack Barrier Layers Reduce Leakage Current
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Solution Overview
Problem
As the feature size of MOS transistors decreases, the thinning of silicon oxide or silicon oxynitride gate insulating layers leads to increased direct tunneling current and leakage current between the gate and channel, resulting in higher power consumption and adverse electric properties.
Innovation Solution
A semiconductor device structure incorporating a high-k dielectric film with a first gate insulating layer, a first barrier layer, a first work function control layer, and a second barrier layer, where the second barrier layer has a thickness less than the first, and a second work function control layer with different materials, to minimize leakage current and improve operating characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the thickness of silicon oxide or silicon oxynitride gate insulating layer is reduced to increase capacitance, then the capacitance between gate and channel increases, but direct tunneling current increases resulting in increased leakage current and power consumption
Solution Approach 1:
The patent employs a composite gate insulating layer structure consisting of a first gate insulating layer (silicon oxide or silicon oxynitride) and a second gate insulating layer (high-k dielectric material). This composite structure allows the first layer to provide good interface characteristics while the second layer provides high capacitance with lower leakage current, thus resolving the contradiction between power consumption and electric properties.
Solution Approach 2:
The patent changes the dielectric constant parameter by introducing a high-k dielectric material in the second gate insulating layer. This allows achieving the required capacitance with a thicker effective insulating layer, thereby reducing direct tunneling current and leakage current while maintaining the necessary capacitance for proper transistor operation.
2Reliability
If the thickness of gate insulating layer is reduced to improve operating characteristics, then capacitance increases, but leakage current between gate and channel increases
Solution Approach 1:
The composite gate insulating layer structure with high-k dielectric material enables achieving high capacitance (improved operating characteristics) while the high-k material's properties reduce direct tunneling current, thereby minimizing leakage current between gate and channel.
Solution Approach 2:
The first gate insulating layer (silicon oxide or silicon oxynitride) acts as an intermediary layer between the substrate and the high-k dielectric material. This intermediary layer provides a good interface that reduces defect density, thereby reducing leakage current while allowing the high-k layer to provide the necessary capacitance for improved operating characteristics.
3Object-generated harmful factors
If conventional silicon oxide film is replaced with high-k dielectric film to reduce leakage current, then leakage current decreases, but metallic materials may penetrate into the gate insulating layer
Solution Approach 1:
The first gate insulating layer (silicon oxide or silicon oxynitride) serves as an intermediary protective layer between the substrate and the high-k dielectric material. This layer prevents metallic materials from penetrating into the gate insulating layer while allowing the high-k layer to function in reducing leakage current.
Solution Approach 2:
The patent employs a protective layer structure beforehand to prevent potential penetration of metallic materials into the gate insulating layer. The first gate insulating layer is formed as a protective barrier before introducing the high-k dielectric material, thus cushioning against the potential harmful effect of metal penetration.
Data Source
AI summary
A semiconductor device using a high-k dielectric film is provided. The semiconductor device comprises a first gate insulating layer on a substrate and a first barrier layer on the first gate insulating layer, the first barrier layer having a first thickness. A first work function control layer is on the first barrier layer. A second barrier layer is present on the first work function control layer, the second barrier layer having a second thickness that is less than the first thickness.