Vapor Phase Doping for Strained FinFETs
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Solution Overview
Problem
Conventional ion implantation techniques for doping strained semiconductor layers and narrow fin structures in FinFET devices face challenges in achieving conformal doping profiles and maintaining carrier mobility, as they can cause damage and strain relaxation, especially in scaled devices.
Innovation Solution
The method involves using vapor phase deposition to form conformal species-containing layers on strained semiconductor layers or fin structures, followed by rapid thermal processing to diffuse and activate dopants, which helps in achieving conformal dopant profiles without damaging the crystallinity and strain, even in narrow fin structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ion implantation technique is used for doping strained semiconductor layers, then doping can be achieved, but damage and strain relaxation occur leading to decreased carrier mobility
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical vapor deposition process. Instead of physically bombarding the semiconductor layer with ions, dopants are introduced through vapor phase deposition of dopant-containing precursors, followed by thermal annealing to activate the dopants. This substitution eliminates the mechanical damage and strain relaxation caused by ion implantation while achieving the desired doping effect.
Solution Approach 2:
The patent changes the fundamental parameters of the doping process: instead of using high-energy ion beams with specific implantation doses and energies, the method uses vapor phase deposition at controlled temperatures and pressures, followed by thermal annealing at elevated temperatures (e.g., 800-1100°C) for controlled durations. This parameter change transforms the doping mechanism from a mechanical impact process to a thermal diffusion and activation process, preserving the strained semiconductor layer's crystallinity and strain.
2Manufacturing precision
If conventional ion implantation is used on narrow fin structures, then doping can be achieved, but conformal dopant profiles are difficult to obtain due to shadowing effects
Solution Approach 1:
The patent replaces the unidirectional ion beam mechanical system with a vapor phase deposition system. The vapor phase deposition process allows dopant precursors to conformally coat all exposed surfaces of the fin structures, including vertical sidewalls and top surfaces, eliminating the shadowing effects that plague ion implantation on three-dimensional structures. This results in truly conformal dopant profiles that follow the fin geometry.
Solution Approach 2:
The patent transitions from a unidirectional ion implantation approach (one-dimensional flux) to a vapor phase deposition approach that utilizes three-dimensional vapor diffusion and surface reaction. The dopant-containing vapor can access and deposit on all surfaces of the fin structure simultaneously, achieving conformal coverage in all spatial dimensions, including the critical vertical sidewalls that are shadowed in ion implantation.
3Reliability
If thermal annealing is performed after ion implantation, then damage can be recovered, but misfit dislocations form leading to strain relaxation
Solution Approach 1:
The patent performs the doping action preliminarily through vapor phase deposition before any thermal treatment. The dopants are deposited as a separate layer on the strained semiconductor surface, and only after this preliminary doping step is a mild thermal annealing performed to activate the dopants. This preliminary action sequence avoids the high-energy damage of ion implantation that would require aggressive annealing, thereby preventing misfit dislocation formation and strain relaxation.
Solution Approach 2:
The patent changes the thermal processing parameters from the high-temperature, long-duration annealing required after ion implantation damage recovery to a lower-temperature, shorter-duration annealing optimized for dopant activation. The vapor phase deposition method eliminates the need for extensive damage recovery annealing, allowing the use of milder thermal conditions (e.g., 800-1100°C for short times) that activate dopants without providing sufficient thermal energy and time for misfit dislocation formation and strain relaxation.
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 maintains or enhances carrier mobility by ensuring conformal dopant profiles and preserving the initial crystallinity of the semiconductor material, effectively addressing the limitations of conventional ion implantation and thermal annealing methods.
Implementation Method 1
forming a conformal first species containing-layer by vapor phase deposition (VPD) at least on the exposed strained semiconductor layer
Implementation Method 2
performing a first thermal treatment, thereby diffusing at least part of the first species from the first species-containing layer into the (exposed) strained semiconductor layer
Implementation Method 3
activating at least part of the diffused first species in the (exposed) strained semiconductor layer
Data Source
AI summary
A method for introducing species into a strained semiconductor layer comprising: providing a substrate comprising a first region comprising an exposed strained semiconductor layer, loading the substrate in a reaction chamber, then forming a conformal first species containing-layer by vapor phase deposition (VPD) at least on the exposed strained semiconductor layer, and thereafter performing a thermal treatment, thereby diffusing at least part of the first species from the first species-containing layer into the strained semiconductor layer and activating at least part of the diffused first species in the strained semiconductor layer.