FinFET LDD Formation for Uniform Sidewall and Top-Surface Doping
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Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in forming lightly-doped drain (LDD) regions in the top surface and sidewalls of fin field effect transistors (FinFETs) without the shadowing effect and plasma sheath effect, especially when fins are separated at a nanoscale distance.
Innovation Solution
The process involves forming a dopant-rich layer on a dielectric layer over the FinFETs using plasma ion assisted deposition (PIAD) and subsequent knock-on implantation, followed by cap layer formation and solid-phase diffusion annealing to drive impurities into the semiconductor fins, ensuring uniform doping across the top surface and sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma doping methods are used to form LDD regions in FinFETs, then doping can be achieved, but shadowing effect and plasma sheath effect occur causing non-uniform doping distribution
Solution Approach 1:
A dopant-rich layer is formed on the dielectric layer before the knock-on implantation process. This preliminary dopant layer serves as a reservoir that ensures uniform doping distribution in the LDD regions, counteracting the non-uniformity caused by shadowing and plasma sheath effects during subsequent processing steps
Solution Approach 2:
The dopant-rich layer acts as an intermediary between the plasma process and the semiconductor fin structure. It mediates the doping process by providing a controlled source of dopants that diffuses uniformly into the LDD regions, eliminating the direct harmful interaction between plasma and the fin structure that causes shadowing and sheath effects
2Productivity
If fins are separated at nanoscale distance to increase device density, then productivity improves, but forming uniform LDD regions becomes more difficult due to enhanced shadowing and plasma sheath effects
Solution Approach 1:
The dopant-rich layer is formed in advance on the dielectric layer covering all fins before any implantation occurs. This preliminary action ensures that even when fins are closely spaced at nanoscale distances, each fin receives uniform dopant distribution from its own dedicated dopant-rich layer, preventing cross-contamination and shadowing effects
Solution Approach 2:
Each fin structure is provided with its own localized dopant-rich layer on the dielectric layer, ensuring that doping is performed locally and uniformly for each fin. This local quality approach maintains manufacturing precision even when device density is increased through closer fin spacing
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 method allows for the formation of LDD regions with desirable depth and uniformity, overcoming the limitations of shadowing and plasma sheath effects, and enabling effective conductivity control in FinFETs.
Implementation Method 1
forming a dopant-rich layer on a dielectric layer over the FinFETs using plasma ion assisted deposition (PIAD)
Implementation Method 2
subsequent knock-on implantation
Implementation Method 3
solid-phase diffusion annealing to drive impurities into the semiconductor fins
Data Source
AI summary
A semiconductor structure includes a substrate, a first semiconductor fin, a second semiconductor fin, and a first lightly-doped drain (LDD) region. The first semiconductor fin is disposed on the substrate. The first semiconductor fin has a top surface and sidewalls. The second semiconductor fin is disposed on the substrate. The first semiconductor fin and the second semiconductor fin are separated from each other at a nanoscale distance. The first lightly-doped drain (LDD) region is disposed at least in the top surface and the sidewalls of the first semiconductor fin.