Nitrogen Profile Control in High-K Gate Dielectrics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for improving the reliability of gate dielectric in MOS transistors by diffusing nitrogen into the gate dielectric result in nitrogen accumulation at the interface with the transistor substrate, leading to reduced carrier mobility and adverse effects, with reduced control over nitrogen distribution and amount when lowering the nitrogen plasma power.
Innovation Solution
A sacrificial layer is formed on the gate dielectric, exposed to a nitridation source like nitrogen plasma, and then removed, allowing controlled nitrogen absorption and distribution within the gate dielectric without adverse effects on the substrate interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen is diffused into the gate dielectric by exposing to nitrogen plasma, then the reliability of the gate dielectric is improved, but nitrogen accumulates at the interface with the transistor substrate causing reduced carrier mobility
Solution Approach 1:
The gate dielectric is divided into two regions with different nitrogen concentrations: a first region near the transistor substrate interface with lower nitrogen concentration and a second region farther from the interface with higher nitrogen concentration. This segmentation allows the dielectric to benefit from nitrogen strengthening while minimizing interface degradation.
Solution Approach 2:
Different regions of the gate dielectric are given different nitrogen concentrations tailored to their specific functional requirements. The region near the interface has lower nitrogen to maintain carrier mobility, while regions farther from the interface have higher nitrogen to enhance reliability and breakdown voltage.
2Length of moving object
If the thickness of the gate dielectric is reduced to continue transistor scaling, then transistor size is reduced, but the reliability of the gate dielectric deteriorates
Solution Approach 1:
The gate dielectric employs non-uniform nitrogen distribution where regions closer to the transistor substrate have lower nitrogen concentration to maintain interface quality and carrier mobility, while regions farther from the interface have higher nitrogen concentration to provide sufficient breakdown voltage and reliability, enabling thin dielectric structures to maintain both size reduction and reliability.
3Object-affected harmful factors
If the nitrogen plasma power is reduced to decrease nitrogen accumulation at the interface, then interface quality is improved, but control over total nitrogen amount and distribution is reduced
Solution Approach 1:
A nitrogen-containing layer is deposited on the gate dielectric before plasma treatment. This preliminary layer acts as a nitrogen source that releases nitrogen during subsequent thermal processing, enabling precise control over the nitrogen profile without requiring direct plasma exposure of the dielectric interface, thus maintaining both interface quality and manufacturing precision.
Solution Approach 2:
The nitrogen-containing layer serves as an intermediary between the plasma source and the gate dielectric. It controls nitrogen release through thermal diffusion, providing precise control over nitrogen distribution and total amount while preventing direct plasma damage to the interface, thereby maintaining both interface quality and manufacturing precision.
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 maintains the total nitrogen amount in the gate dielectric while reducing nitrogen concentration at the interface, improving transistor performance by optimizing nitrogen distribution and reducing adverse effects.
Implementation Method 1
diffuses nitrogen into the gate dielectric to meet this need. This is accomplished by exposing the gate dielectric to a nitrogen containing plasma
Implementation Method 2
exposing the gate dielectric to a nitrogen containing plasma
Data Source
AI summary
Metal Oxide Semiconductor (MOS) transistors fabricated using current art may utilize a nitridation process on the gate dielectric to improve transistor reliability. Nitridation by the current art, which involves exposing the gate dielectric to a nitridation source, produces a significant concentration of nitrogen at the interface of the gate dielectric and the transistor substrate, which adversely affects transistor performance. This invention comprises the process of depositing a sacrificial layer on the gate dielectric prior to nitridation, exposing the sacrificial layer to a nitridation source, during which time nitrogen atoms diffuse through the sacrificial layer into the gate dielectric, then removing the sacrificial layer without degrading the gate dielectric. Work associated with this invention on high-k gate dielectrics has demonstrated a 20 percent reduction in nitrogen concentration at the gate dielectric—transistor substrate interface.