Uniaxially Strained Fin Transistor via SiGe Epitaxy
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Solution Overview
Problem
In the fabrication of non-planar transistors, such as tri-gate and FinFETs, existing technologies face challenges in achieving full depletion and enhancing channel mobility, which are crucial for improving transistor performance and speed.
Innovation Solution
The use of strain-inducing materials with lattice mismatch, such as silicon germanium or silicon carbide, is employed to form strained fins within the transistors, combined with techniques like epitaxial growth and ion doping to create regions of higher strain, thereby increasing channel mobility and transistor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If non-planar transistor structures are used, then channel mobility is enhanced, but achieving full depletion becomes difficult
Solution Approach 1:
The patent applies parameter changes by introducing uniaxial strain through selective epitaxial growth of SiGe materials with different germanium concentrations in source/drain regions versus the fin channel. This strain modification changes the physical parameters of the channel, enhancing carrier mobility while maintaining the fin structure's ability to achieve full depletion through its geometric configuration.
Solution Approach 2:
The patent implements local quality by creating different material compositions in different regions: the fin channel maintains a composition optimized for depletion, while source/drain regions incorporate higher Ge content to induce uniaxial strain locally. This localized differentiation allows simultaneous optimization of both mobility (in source/drain) and depletion (in channel) without compromise.
2Speed
If strain-inducing materials with lattice mismatch are used, then channel mobility increases, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-straining the epitaxial film during the growth process itself, rather than applying strain afterward. The SiGe layers are grown with controlled Ge concentrations that inherently create the desired uniaxial strain in the fin channel, eliminating the need for separate strain introduction steps and simplifying the overall manufacturing process.
Solution Approach 2:
The patent replaces mechanical strain introduction methods (such as post-growth processing or external stress application) with a materials-based approach. By controlling the lattice mismatch through compositional design during epitaxial growth, the strain is introduced inherently through the material structure itself, reducing manufacturing complexity.
3Reliability
If uniaxial strain is introduced through material composition, then electrical resistance decreases, but control over strain distribution becomes more difficult
Solution Approach 1:
The patent precisely controls strain distribution by assigning different Ge concentrations to specific locations: source/drain regions receive higher Ge content to induce compression, while the fin channel maintains lower Ge content for optimal depletion. This localized compositional control ensures strain is distributed exactly where needed, simultaneously reducing resistance in current paths and maintaining precision in the channel region.
Solution Approach 2:
The strain distribution is predetermined and built-in during the epitaxial growth process itself. By planning the Ge concentration profile in advance and executing it through controlled growth sequences, the patent achieves precise strain distribution without requiring complex post-processing adjustments or feedback control mechanisms.
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 allows for full depletion of the fin and enhanced channel mobility, leading to reduced electrical resistance, increased current, and improved speed in microelectronic devices.
Implementation Method 1
the first material and the second material presenting a lattice mismatch between respective crystalline structures thereof
Implementation Method 2
The use of strain-inducing materials with lattice mismatch, such as silicon germanium or silicon carbide, is employed to form strained fins within the transistors, combined with techniques like epitaxial growth
Implementation Method 3
combined with techniques like epitaxial growth and ion doping to create regions of higher strain, thereby increasing channel mobility and transistor efficiency
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
A method and a device made according to the method. The method comprises providing a substrate base portion (102) and a substrate fin (107) extending from the substrate base portion, the fin comprising silicon and germanium; a gate structure (132) covers the fin and epitaxial source and drains (140, 142) comprising germanium are epitaxially grown in recesses formed on both sides of the gate.