FinFET Spacer Plasma Doping for Uniform Dopant Distribution
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Solution Overview
Problem
The small feature sizes in FinFET devices pose challenges in achieving uniform dopant distribution due to limited implantation angles, leading to non-uniform dopant distribution in the fins, which affects the performance of the devices.
Innovation Solution
A plasma doping process is used to dope the gate seal spacer with arsenic, followed by a high-temperature spike anneal process, and a controlled wet etch process to achieve uniform dopant concentration in the LDD regions, while minimizing fin height loss and on-current degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ion beam implantation is used to dope fins, then the implantation process can be completed, but the dopant distribution becomes non-uniform due to limited implantation angles caused by small pitch between adjacent fins
Solution Approach 1:
The patent replaces the mechanical ion beam implantation system with a plasma-based doping system. Instead of physically implanting ions at limited angles, the method uses plasma to deposit dopant material (such as phosphorus or boron) onto the fin surfaces, allowing uniform coverage regardless of fin pitch. This substitution of the doping mechanism fundamentally resolves the angle limitation problem.
Solution Approach 2:
The patent changes the doping parameters from ion beam energy and angle to plasma deposition conditions (temperature, pressure, gas composition). By controlling plasma parameters such as substrate temperature, plasma power, and dopant gas flow rates, uniform dopant distribution is achieved without being constrained by geometric implantation angles.
2Reliability
If higher dopant concentration is introduced to compensate for non-uniform distribution, then doping effectiveness increases, but fin height loss and on-current degradation worsen
Solution Approach 1:
The patent applies local quality by depositing dopant material selectively on the fin surfaces through plasma exposure. The dopant concentration is controlled to be uniform across the fin top surfaces without excessive penetration that would cause height loss. This localized surface doping achieves effective doping while preserving fin structural integrity and electrical performance.
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 method ensures a substantially uniform dopant concentration from the top to the bottom of the fin, reducing resistance and improving the performance of the FinFET device, with dopant concentration at the bottom being 8 to 15 times higher than conventional ion beam tools, and reducing on-current degradation.
Implementation Method 1
performing a plasma process using a gas comprising As and Xe, where the PR shields the spacer layer in the second region from the plasma process, and the spacer layer shields source/drain regions of the first fin from the plasma process, where the plasma process implants As in the spacer layer
Implementation Method 2
after the removing the PR, performing an anneal process in an ambient comprising O2 and N2 to drive the implanted As from the spacer layer into the source/drain regions of the first fin
Implementation Method 3
after the performing the plasma process, removing the PR using a Sulfuric Peroxide Mixture (SPM) solution
Data Source
AI summary
A method includes forming a spacer layer over a semiconductor fin protruding above a substrate, doping the spacer layer using a first dopant while the spacer layer covers source/drain regions of the semiconductor fin, and performing a thermal anneal process after the doping.