Strained Semiconductor Nanoribbons with Ge Gradient Channels
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Solution Overview
Problem
Existing transistor architectures face challenges in maintaining sufficient strain on semiconductor channels, leading to poor device performance as devices scale down in size, particularly in gate-all-around and forksheet architectures.
Innovation Solution
Depositing a germanium-containing material such as silicon germanium (SiGe) or germanium tin (GeSn) over nanowires and annealing to drive the material throughout, creating a composition gradient along the nanowires, resulting in intrinsically strained channels with varying germanium or tin concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If gate-all-around and forksheet architectures are used to maximize semiconductor surface area, then device scaling is improved, but strain on semiconductor channels is insufficient leading to poor device performance
Solution Approach 1:
The patent applies local quality by creating a composition gradient within the nanoribbon channel, where germanium concentration varies spatially (higher in the middle, lower at ends). This localized compositional variation generates targeted compressive strain in the channel region, improving carrier mobility and device performance without requiring changes to the overall transistor architecture.
Solution Approach 2:
The patent changes the material composition parameter of the nanoribbon by incorporating germanium at varying concentrations along the channel length. This parameter change (from pure silicon to silicon-germanium alloy with gradient) induces lattice mismatch strain that enhances carrier mobility, directly addressing the performance issue while maintaining the scaled-down architecture.
2Reliability
If material is deposited over nanowires to create strain, then device performance is improved, but nanoribbon thickness increases
Solution Approach 1:
The patent replaces the mechanical approach of depositing external strain-inducing materials with a chemical/compositional approach. Instead of adding a separate strain layer, the strain is generated intrinsically through composition modulation within the nanoribbon itself (silicon-germanium gradient), eliminating the need for additional thickness while maintaining strain benefits.
Solution Approach 2:
The patent uses composite materials by creating a silicon-germanium alloy nanoribbon with spatially varying composition. The gradient structure combines regions of different germanium concentrations within a single nanoribbon, generating internal strain through lattice mismatch while keeping the overall structure thin and integrated.
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 technique enhances device performance by imparting compressive strain, especially for PMOS devices, while maintaining a thinner nanoribbon structure, thus improving transistor efficiency.
Implementation Method 1
annealing to drive the material throughout, creating a composition gradient along the nanowires
Implementation Method 2
The change in material composition along the length of the nanoribbon imparts a compressive strain
Data Source
AI summary
Techniques are provided herein to form semiconductor devices having nanowires with an increased strain. A thin layer of silicon germanium or germanium tin can be deposited over one or more suspended nanoribbons. An anneal process may then be used to drive the silicon germanium or germanium tin throughout the one or more semiconductor nanoribbons, thus forming one or more nanoribbons with a changing material composition along the lengths of the one or more nanoribbons. In some examples, at least one of the one or more nanoribbons includes a first region at one end of the nanoribbon having substantially no germanium, a second region at the other end of the nanoribbon having substantially no germanium, and a third region between the first and second regions having a substantially uniform non-zero germanium concentration. The change in material composition along the length of the nanoribbon imparts a compressive strain.