FinFET Gate Self-Aligned Junctions for Abrupt Profiles
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Solution Overview
Problem
FinFETs face challenges in achieving abrupt junctions while minimizing short channel effects and source/drain resistance, with channel doping leading to carrier mobility decrease and random dopant fluctuation, which affects chip variability.
Innovation Solution
The formation of abrupt junctions is achieved by diffusing dopants from an epitaxial semiconductor layer into a semiconductor fin, followed by annealing to create a dopant-containing fin, removing the sacrificial gate stack, and regrowing the channel region to form self-aligned abrupt junctions with a functional gate stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If greater source/drain doping is used to reduce resistance, then source/drain resistance decreases, but junction depth increases causing short channel effects
Solution Approach 1:
The source/drain structure is segmented into multiple regions with different doping concentrations: heavily doped extension regions adjacent to the channel for low resistance, and lightly doped or undoped channel regions for minimizing short channel effects. This segmentation allows each region to be optimized independently for its specific function.
Solution Approach 2:
Different doping concentrations are applied to different spatial locations within the source/drain structure. The extension regions receive heavy doping to reduce resistance, while the channel regions maintain light or no doping to prevent short channel effects, achieving local optimization of electrical properties.
2Manufacturing precision
If channel doping is used to control junction profile, then junction formation is achieved, but carrier mobility decreases and random dopant fluctuation increases
Solution Approach 1:
The doping function is extracted from the channel region and relocated to the extension regions. The channel is kept lightly doped or undoped to maintain high carrier mobility and minimize random dopant fluctuation, while the extension regions are heavily doped to provide the necessary junction formation and low resistance contact.
Solution Approach 2:
Dopants are pre-loaded into the extension regions before channel formation, creating a dopant-containing semiconductor fin structure. This preliminary doping action ensures that when the channel is subsequently formed through epitaxial regrowth, abrupt junctions are automatically created at the channel-extension interfaces without requiring channel doping.
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 reduces resistance under the gate spacer and minimizes short channel effects, maintaining high carrier mobility and reducing chip variability by eliminating channel doping.
Implementation Method 1
diffusing dopants from an epitaxial semiconductor layer that is formed on portions of a semiconductor fin located on opposite sides of a sacrificial gate structure into the semiconductor fin to form a dopant-containing semiconductor fin by an anneal
Implementation Method 2
form a dopant-containing semiconductor fin by an anneal
Implementation Method 3
A channel region is epitaxially regrown at least from the sidewalls of the remaining portions of the dopant-containing semiconductor fin
Data Source
AI summary
After forming an epitaxial semiconductor layer on portions of a semiconductor located on opposite sides of a sacrificial gate structure, dopants from the epitaxial semiconductor layer are diffused into the semiconductor fin to form a dopant-containing semiconductor fin. A sacrificial gate stack is removed to provide a gate cavity that exposes a portion of the dopant-containing semiconductor fin. The exposed portion of the dopant-containing semiconductor fin is removed to provide an opening underneath the gate cavity. A channel which is undoped or less doped than remaining portions of the dopant-containing semiconductor fin is epitaxially grown at least from the sidewalls of the remaining portions of the dopant-containing semiconductor fin. Abrupt junctions are thus formed between the channel region and the remaining portions of the dopant-containing semiconductor fin.