Ferroelectric Gate Structure for Post-Fabrication Channel Strain Tuning
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Solution Overview
Problem
The strain introduced in transistor channels during fabrication can be lost, reducing carrier mobility and degrading device performance, and existing technologies lack the flexibility to adjust strain post-fabrication for optimal device performance.
Innovation Solution
Incorporating a ferroelectric layer, such as hafnium oxide-based materials, between the metal gate and spacer in semiconductor structures, allowing strain adjustment through applied bias voltage, enabling tensile or compressive strain in the channel region to optimize transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strain is introduced in transistor channel during fabrication, then carrier mobility is improved, but strain is lost during fabrication operations reducing device performance
Solution Approach 1:
The patent applies preliminary action by introducing strain into the channel region before completing fabrication operations. The strain is intentionally created in advance (through source/drain extension formation or silicon germanium layer deposition) so that it is present during subsequent processing steps, rather than being applied after fabrication is complete. This preliminary strain introduction helps maintain device performance despite the challenging fabrication environment.
Solution Approach 2:
The patent employs parameter changes by varying the crystal orientation of the channel region (e.g., using <110> or <210> orientations instead of conventional <100>) and adjusting the composition of silicon germanium layers. These parameter changes enable the channel to accommodate and maintain strain throughout fabrication operations, as different crystal orientations and material compositions respond differently to mechanical stress and processing conditions.
2Speed
If strain is introduced to improve carrier mobility, then transistor speed is enhanced, but flexibility to adjust strain post-fabrication is lost
Solution Approach 1:
The patent applies dynamics by making the strain state adjustable and reconfigurable after fabrication. Through the use of silicon germanium layers with controllable composition and thickness, or by applying external stress through dedicated structures, the strain in the channel can be dynamically tuned post-fabrication. This allows optimization of carrier mobility for different device requirements and enables adaptation to varying operational conditions without requiring complete fabrication rework.
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 post-fabrication strain adjustment, enhancing carrier mobility and device performance by applying electrical fields, thereby improving the operational speed and flexibility of transistors.
Implementation Method 1
a ferroelectric layer between the metal gate layer and the substrate, wherein the ferroelectric layer is configured to cause a strain in the channel when applied with an electrical field
Data Source
AI summary
The present disclosure provides a semiconductor device and a method for fabricating a semiconductor device. The semiconductor device includes a substrate, a metal gate layer over the substrate, a channel between a source region and a drain region in the substrate, and a ferroelectric layer, at least a portion of the ferroelectric layer is between the metal gate layer and the substrate, wherein the ferroelectric layer includes hafnium oxide-based material, the hafnium oxide-based material includes a first portion of hafnium oxide with orthorhombic phase, a second portion of hafnium oxide with monoclinic phase, and a third portion of the hafnium oxide with tetragonal phase, wherein a first volume of the first portion is greater than a second volume of the second portion, and the second volume of the second portion is greater than a third volume the third portion.