FinFET Sidewall Doping via Mandrel Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The geometry of multi-fin double-gate fin field-effect transistors (FinFETs) complicates doping due to shadowing effects during conventional angled ion implantation, limiting circuit density and requiring challenging fin expansion techniques.
Innovation Solution
A method involving forming mandrels on a silicon layer, etching to create silicon islands, ion-implanting sidewalls, growing epitaxial material, and removing mandrels to form dense finFET structures with self-aligned extensions, allowing for lower dose and energy implants at steeper angles without a blocking mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional angled ion implantation is used for doping extensions in FinFETs, then doping can be achieved, but shadowing effects occur due to blocking resists which limits circuit density
Solution Approach 1:
The patent applies preliminary action by forming sacrificial mandrels and performing sidewall ion implantation before fin formation. This sequence allows dopant atoms to be precisely deposited on the sidewalls of the sacrificial structures, which then become self-aligned extensions after mandrel removal, eliminating shadowing effects and enabling higher circuit density while maintaining doping precision
Solution Approach 2:
The patent transitions from conventional planar doping to three-dimensional sidewall doping. By implanting dopants on the vertical sidewalls of sacrificial mandrels rather than on a flat surface, the method achieves precise dopant placement in the vertical dimension, eliminating shadowing issues and enabling self-aligned extension formation that improves both doping precision and circuit density
2Manufacturing precision
If chevron layout with tilted implants is used, then doping can be achieved, but the method is limited to chevron layout schemes reducing versatility
Solution Approach 1:
The patent segments the doping process into distinct stages: forming sacrificial mandrels, performing sidewall implantation, removing mandrels, and forming fins. This segmentation allows the same sidewall implantation technique to be applied to various fin configurations (straight, chevron, bent), providing layout flexibility while maintaining doping precision through the self-aligned nature of the process
Solution Approach 2:
The sidewall ion implantation method serves multiple functions and is applicable to various FinFET layouts including straight fins, chevron fins, and bent fins. The self-aligned extension formation mechanism works universally across different fin geometries, making the process versatile while maintaining precise dopant placement
3Manufacturing precision
If end-etched fins with orthogonal implants are used, then doping can be achieved, but fin expansion with selective silicon on very small structures is very challenging
Solution Approach 1:
The patent performs dopant implantation on the sidewalls of sacrificial mandrels before the fins are formed. This preliminary doping action eliminates the need for subsequent fin expansion processes, as the dopant atoms are already in place on the sidewalls and will become self-aligned extensions when the mandrels are removed and fins are formed, greatly simplifying manufacturing
Solution Approach 2:
The sidewall ion implantation creates self-aligned extensions that automatically position themselves relative to the fin structures. The dopant distribution on the mandrel sidewalls self-aligns with the future fin locations, eliminating the need for complex fin expansion processes and making the manufacturing of small-structure FinFETs much easier
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 formation of dense finFET structures with lower resistance and improved integration, minimizing damage to the silicon lattice and enabling single-crystalline finFETs with reduced recrystallization challenges.
Implementation Method 1
ion-implanting sidewalls of the at least one silicon island to form doped regions on the sidewalls
Implementation Method 2
growing epitaxial material on the doped sidewall regions
Data Source
AI summary
FinFET end-implanted-semiconductor structures and methods of manufacture are disclosed herein. The method includes forming at least one mandrel on a silicon layer of a substrate comprising an underlying insulator layer. The method further includes etching the silicon layer to form at least one silicon island under the at least one mandrel. The method further includes ion-implanting sidewalls of the at least one silicon island to form doped regions on the sidewalls. The method further includes forming a dielectric layer on the substrate, a top surface of which is planarized to be coplanar with a top surface of the at least one mandrel. The method further includes removing the at least one mandrel to form an opening in the dielectric layer. The method further includes etching the at least one silicon island to form at least one fin island having doped source and drain regions.