SiGe FDSOI Gate Stack With Nitrogen Barrier Against Ge Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing FDSOI devices with SiGe channels face issues of germanium diffusion into the gate dielectric, reducing reliability and performance due to the silicon channel's low stress and Ge atom migration.
Innovation Solution
An FDSOI device structure featuring a SiGe channel with a nitrogen passivation layer and a metal gate stack structure, including a gate oxide, high-k dielectric, and TiN layers, along with raised SiGe source-drain regions, is developed to prevent Ge diffusion and enhance stress, thereby improving device reliability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiGe channel is used to increase stress in channels, then hole mobility is improved significantly, but Ge atoms diffuse into the gate dielectric, reducing reliability and performance
Solution Approach 1:
A nitrogen passivation layer is introduced as an intermediary between the SiGe channel and the gate dielectric. This nitrogen layer acts as a diffusion barrier that prevents Ge atoms from migrating into the gate dielectric while allowing the SiGe channel to maintain its stress-enhancing function for improved hole mobility
Solution Approach 2:
The device structure uses a composite approach by combining SiGe channel material with a nitrogen-based passivation layer. This composite structure leverages the stress-inducing properties of SiGe while the nitrogen layer provides the necessary barrier function to prevent Ge diffusion, thus resolving the contradiction between performance enhancement and reliability
2Device complexity
If silicon channel is used, then device structure is simple, but stress in channels is insufficient, limiting hole mobility improvement
Solution Approach 1:
The channel material composition is changed from pure silicon to SiGe alloy, altering the material parameters to achieve higher stress levels. The germanium content in the SiGe channel is optimized to provide sufficient stress for improved hole mobility while managing the associated Ge diffusion risk through the nitrogen passivation layer
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
The proposed structure effectively prevents Ge diffusion into the gate dielectric, increasing the reliability and performance of FDSOI devices by maintaining higher stress levels and improving hole mobility.
Implementation Method 1
a nitrogen passivation layer disposed on the SiGe channel layer
Implementation Method 2
oxidizing the SiGe layer by means of high-temperature oxidation, so that Ge in the SiGe layer diffuses into the SOI layer
Implementation Method 3
forming a SiGe layer on the SOI layer by means of epitaxial deposition
Data Source
AI summary
FDSOI device fabrication method is disclosed. The method comprises: disposing a buried oxide layer on the silicon substrate; disposing a SiGe channel on the buried oxide layer, disposing a nitrogen passivation layer on the SiGe channel layer; disposing a metal gate on the nitrogen passivation layer, and attaching sidewalls to sides of the metal gate; and disposing source and drain regions on the nitrogen passivation layer at both sides of the metal gate, wherein the source and drain regions are built in a raised SiGe layer. The stack structure of the SiGe layer and the nitrogen passivation layer forms the gate channel. This stack structure avoids the low stress of the silicon channel in the conventional device. In addition, it prevents the Ge diffusion from the SiGe channel to the gate dielectric in the conventional device. Thereby the invention improves reliability and performance of the device.