Self-Aligned SiGe FinFET With Relaxed Channel Region
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing FinFET technologies face mechanical instability and structural limitations due to dislocation defects when high germanium concentration is introduced into the channel, leading to strained and damaged lattice structures, which restrict the aspect ratio of the fins.
Innovation Solution
A self-aligned SiGe FinFET device is fabricated with a relaxed channel region that initially accepts germanium, avoiding lattice strain and defects by segmenting the silicon fins to elastically relax the lattice before introducing germanium, resulting in a structurally stable film with a germanium concentration greater than 85%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high germanium concentration is introduced into the channel, then carrier mobility is enhanced, but lattice strain and dislocation defects occur causing mechanical instability
Solution Approach 1:
The fin is divided into multiple segments separated by sacrificial gates, creating isolated regions that can accommodate high germanium concentrations without generating dislocation defects. Each segment acts as an independent relaxed region, allowing the channel to maintain structural stability while achieving enhanced carrier mobility through high Ge content.
Solution Approach 2:
Sacrificial gates are formed before introducing germanium into the channel. These pre-positioned gates create the segmented structure in advance, establishing relaxed regions that prevent lattice strain from developing during subsequent germanium incorporation processes.
2Speed
If germanium is introduced into the channel, then electron mobility increases, but dislocation defects damage the crystal lattice
Solution Approach 1:
The channel is segmented into multiple regions by sacrificial gates, allowing germanium to be introduced into isolated segments. This segmentation prevents the propagation of dislocation defects across the entire channel, maintaining crystal lattice integrity while achieving high electron mobility in each germanium-containing segment.
Solution Approach 2:
Germanium is introduced locally into specific channel segments rather than uniformly throughout the entire channel. Each segment has high germanium concentration for enhanced electron mobility, while the overall channel structure maintains lattice integrity through the segmented architecture.
3Reliability
If germanium-rich film is created, then carrier mobility is enhanced, but aspect ratio is restricted due to mechanical instability
Solution Approach 1:
The fin structure is segmented into multiple sections separated by sacrificial gates, creating a mechanically stable architecture that can support high aspect ratios. Each segment contains germanium for enhanced carrier mobility, while the segmented configuration prevents mechanical instability that would otherwise limit the aspect ratio of germanium-rich structures.
Solution Approach 2:
Sacrificial gates are formed before germanium introduction to establish the segmented structure. This preliminary segmentation creates a mechanically stable framework that allows subsequent germanium incorporation without compromising the aspect ratio, enabling high carrier mobility while maintaining the desired fin geometry.
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 enables the creation of a nearly pure germanium film that is substantially stress-free and defect-free, enhancing carrier mobility and transistor performance while maintaining a high aspect ratio, thus overcoming the limitations of mechanically unstable germanium-rich films.
Implementation Method 1
segmenting the silicon fins to elastically relax the lattice
Implementation Method 2
a new SiGe crystal layer is grown from the surface of a bulk silicon crystal, while maintaining the same crystal structure of the underlying bulk silicon crystal
Data Source
AI summary
A self-aligned SiGe FinFET device features a relaxed channel region having a high germanium concentration. Instead of first introducing germanium into the channel and then attempting to relax the resulting strained film, a relaxed channel is formed initially to accept the germanium. In this way, a presence of germanium can be established without straining or damaging the lattice. Gate structures are patterned relative to intrinsic silicon fins, to ensure that the gates are properly aligned, prior to introducing germanium into the fin lattice structure. After aligning the gate structures, the silicon fins are segmented to elastically relax the silicon lattice. Then, germanium is introduced into the relaxed silicon lattice, to produce a SiGe channel that is substantially stress-free and also defect-free. Using the method described, concentration of germanium achieved in a structurally stable film can be increased to a level greater than 85%.