FinFET Strain Relaxation via Stressor Cladding
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Solution Overview
Problem
Strain relaxation at the ends of SiGe or Si fins in FinFET devices leads to device degradation and variation, as existing methods fail to maintain uniform stress across the fins during fabrication.
Innovation Solution
The use of a stressor material, different from the fin material, is wrapped around the ends of the fins to prevent or recover strain relaxation, with compressive nitride fill for SiGe fins and tensile nitride fill for Si fins, ensuring uniform strain across the fin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If SiGe or Si fins are cut into desired lengths to meet design requirements, then the fins can be configured to specific dimensions, but strain relaxes at fin ends causing device degradation and variation
Solution Approach 1:
Stressor material is deposited and wrapped around the fin ends before final device operation to preemptively maintain strain. The stressor material is applied in advance to counteract the strain relaxation that would otherwise occur at the cut fin ends, preventing the problem before it affects device performance.
Solution Approach 2:
A stressor material layer is introduced as an intermediary element between the fin and the environment. This intermediate layer transfers and maintains mechanical strain to the fin, acting as a mediator that compensates for strain loss at the fin ends without requiring changes to the fin structure itself.
2Manufacturing precision
If stressor material is deposited at and wrapped around fin ends, then strain relaxation is prevented and strain uniformity is improved, but device structure and fabrication process become more complex
Solution Approach 1:
The stressor material deposition is merged with existing fabrication steps such as shallow trench isolation formation. By combining multiple functions into a single process step or sequence, the overall device complexity is minimized while still achieving the goal of maintaining strain uniformity at fin ends.
Solution Approach 2:
The stressor material has different physical and mechanical properties than the surrounding dielectric materials. By changing material parameters (such as stress characteristics, elasticity, and adhesion properties), the fin structure maintains uniform strain distribution without requiring complex geometric modifications or additional process steps.
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 effectively maintains and enhances compressive or tensile strain in FinFET devices, reducing device degradation and variation by providing mechanical support and efficient strain transfer, thereby improving the reliability and performance of CMOS technology beyond the 7 nm node.
Implementation Method 1
The cladding stressor material wrapped around the end of the fin imposes strain more efficiently and provides a mechanical support to the fins
Data Source
AI summary
Various methods and structures for fabricating a strained semiconductor fin of a FinFET device. A strained semiconductor fin structure includes a substrate, a semiconductor fin disposed on the substrate, the semiconductor fin having two fin ends, and a stressor material cladding wrapped around a portion of each of the two fin ends forming a strained semiconductor fin that includes at least one strained channel fin having stressor cladding wrapped around at least one end of the strained channel fin thereby straining the at least one strained channel fin. The stressor cladding can be a compressive nitride stressor to compressively strain a compressively strained silicon germanium fin. The stressor cladding can be a tensile nitride stressor to tensily strain a tensily strained silicon fin.