FinFET Doping via Conformal Dopant-Rich Layer Deposition
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Solution Overview
Problem
Current FinFET technology faces challenges with non-conformal doping profiles due to ion implantation, leading to issues like non-uniform device turn-on and defects such as photo resist height induced shadowing effects and pre-amorphization induced twin boundary defects.
Innovation Solution
A method involving the deposition of a dopant-rich layer on the sidewalls of semiconductor fins using plasma-assisted deposition with independent RF and DC power sources, followed by a cap layer and annealing to achieve conformal doping without amorphization, thereby forming a lightly doped drain region with improved uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to form lightly doped drain region, then doping can be achieved, but non-conformal doping profile is created leading to non-uniform device turn-on
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical deposition process (CVD or PECVD) to form the lightly doped drain region. This substitution allows for conformal doping profiles through lateral diffusion, eliminating the shadowing effects and non-uniformity inherent in ion implantation while achieving the desired doping concentration and distribution.
Solution Approach 2:
The patent changes the doping method from physical ion implantation to chemical deposition followed by thermal diffusion. By controlling deposition parameters (temperature, pressure, gas flow) and diffusion parameters (temperature, time, atmosphere), uniform dopant distribution is achieved throughout the fin structure, improving both manufacturing precision and device reliability.
2Ease of manufacture
If tilt implant is used for doping, then doping can be performed, but photo resist height induced shadowing effects occur
Solution Approach 1:
The patent replaces the mechanical tilt implantation process with a chemical vapor deposition process followed by thermal diffusion. This eliminates the shadowing effects caused by photo resist height variations, as the chemical deposition occurs conformally across the entire surface regardless of topography, while still achieving the required doping concentrations.
Solution Approach 2:
The patent performs preliminary chemical deposition of dopant-containing material before thermal diffusion. This preliminary action ensures uniform dopant distribution across the fin structure surface, eliminating shadowing effects that would occur during subsequent processing steps, while maintaining ease of manufacture through standard semiconductor fabrication processes.
3Reliability
If pre amorphization is used during ion implantation, then doping can be achieved, but twin boundary defects are induced
Solution Approach 1:
The patent replaces the mechanical ion implantation process that causes pre-amorphization and twin boundary defects with a chemical deposition and thermal diffusion process. This substitution achieves effective doping without inducing crystal lattice damage, as the thermal diffusion process occurs in the crystalline state without the high-energy ion bombardment that causes amorphization and defect formation.
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 enhances the uniformity of doping profiles, reducing defects and improving the electrical performance of FinFET devices by ensuring consistent dopant distribution and activation.
Implementation Method 1
plasma-assisted deposition
Implementation Method 2
deposition of a dopant-rich layer on the sidewalls of semiconductor fins using plasma-assisted deposition
Implementation Method 3
diffusing the dopant from the dopant-rich layer into the second semiconductor fin by performing an annealing process
Implementation Method 4
followed by a cap layer and annealing to achieve conformal doping without amorphization
Data Source
AI summary
A method of doping a fin field-effect transistor includes forming a plurality of semiconductor fins on a substrate wherein each semiconductor fin of the plurality of semiconductor fins has a top surface and sidewalls. The method includes forming a gate stack over the top surface and sidewalls of each semiconductor fin. The method includes removing a portion of a first semiconductor fin exposed by the gate stack. The method includes growing a first stressor region connected to a remaining portion of the first semiconductor fin. The method includes exposing a second semiconductor fin to a deposition process to form a dopant-rich layer comprising an n-type or a p-type dopant on the top surface and the sidewalls of the second semiconductor fin. The method includes diffusing the dopant from the dopant-rich layer into the second semiconductor fin using an annealing process.