FinFET Channel With Gradient Germanium Concentration
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Solution Overview
Problem
Existing FinFET devices face challenges in achieving optimal performance due to limitations in channel region material composition and stress distribution, which affect carrier speed and threshold voltage stability.
Innovation Solution
A FinFET device structure is developed with a first material layer having a gradient germanium concentration for increased carrier speed and a second portion with a constant germanium concentration to improve threshold voltage stability, formed using chemical vapor deposition and etching processes to minimize defects and lattice mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a uniform germanium concentration is used in the channel region, then the manufacturing process is simple, but the carrier speed and threshold voltage stability are insufficient
Solution Approach 1:
The channel region is divided into multiple portions with different germanium concentrations. Specifically, the channel includes a first portion with a first germanium concentration and a second portion with a second germanium concentration that is higher than the first. This local variation in material composition optimizes carrier speed in different regions while managing threshold voltage characteristics, resolving the contradiction between performance and simplicity.
2Speed
If the germanium concentration is increased to improve carrier mobility, then carrier speed increases, but threshold voltage stability deteriorates
Solution Approach 1:
Different portions of the channel are assigned different germanium concentrations to balance carrier mobility and threshold voltage stability. The first portion has a lower germanium concentration to maintain threshold voltage stability, while the second portion has a higher germanium concentration to enhance carrier mobility. This spatial differentiation resolves the contradiction between speed and stability.
Solution Approach 2:
The germanium concentration parameter is varied across the channel region rather than maintaining a uniform value. By changing the concentration parameter from the first portion to the second portion, the patent achieves both improved carrier mobility in the high-concentration region and maintained threshold voltage stability in the low-concentration region, resolving the contradiction between these two performance metrics.
3Speed
If a higher germanium concentration is used throughout the channel, then carrier mobility improves, but defects and lattice mismatch increase
Solution Approach 1:
The channel structure implements local quality variation by having a first portion with lower germanium concentration and a second portion with higher germanium concentration. This gradual transition and localized high-concentration region provide the carrier mobility benefits of high germanium content while limiting the overall defect density and lattice mismatch that would occur if the entire channel had uniformly high germanium concentration, thus resolving the contradiction between speed and reliability.
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 approach enhances carrier mobility and stability of the threshold voltage, reducing defects and maintaining the integrity of fin structures, thereby improving the overall performance of FinFET devices.
Implementation Method 1
formed using chemical vapor deposition and etching processes
Data Source
AI summary
A fin field effect transistor (FinFET) device structure and method for forming the same are provided. The FinFET device structure includes a fin structure extending above a substrate. The fin structure includes a channel region, a portion of the channel region is made of silicon germanium (SiGe), and the silicon germanium (SiGe) has a gradient germanium (Ge) concentration. The FinFET device structure includes a gate structure formed on the channel region of the fin structure.