Low Defect Replacement Fins for FinFET Devices
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Solution Overview
Problem
The integration of alternative semiconductor materials like III-V materials on silicon substrates for FinFET devices is challenging due to lattice constant differences, leading to defects and manufacturing inefficiencies.
Innovation Solution
The method involves orienting substrate fins in specific crystallographic directions to form replacement fins with minimal defects, using semiconductor materials different from the substrate, and constructing a gate structure around these fins to enhance device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternative semiconductor materials like III-V materials are integrated on silicon substrates for FinFET devices, then device performance and drive current density are improved, but defects are generated due to lattice constant differences
Solution Approach 1:
The patent uses a silicon-germanium (SiGe) intermediate layer as a buffer between the silicon substrate and the III-V material layer. This intermediate layer acts as a mediator that gradually transitions the lattice constant, reducing the abrupt mismatch between silicon and III-V materials. The SiGe layer with graded composition (increasing Ge content from bottom to top) serves as a transition zone that minimizes defect generation while enabling the integration of high-performance III-V channel materials for FinFET devices
Solution Approach 2:
The patent employs lattice constant grading by varying the germanium composition in the SiGe buffer layer. The composition is changed progressively from lower Ge content near the silicon substrate to higher Ge content near the III-V layer. This parameter change (composition gradient) creates a gradual lattice constant transition, reducing misfit dislocations and defects while maintaining the ability to grow high-quality III-V fins for enhanced device performance
2Speed
If the channel length of FETs is decreased to improve operating speed and increase density, then switching speed is improved, but short channel effects increase making it difficult to control electrical potential
Solution Approach 1:
The patent transitions from planar FET architecture to FinFET architecture, moving the channel from a two-dimensional planar structure to a three-dimensional vertically-oriented fin structure. This dimensional change allows the channel to extend vertically from the substrate while the gate wraps around three sides of the fin, providing superior electrostatic control over the shortened channel. The vertical fin structure enables effective gate control of electrical potential even at reduced channel lengths, maintaining reliability while improving switching speed
Data Source
AI summary
One illustrative device disclosed herein includes a substrate fin formed in a substrate comprised of a first semiconductor material, wherein at least a sidewall of the substrate fin is positioned substantially in a <100> crystallographic direction of the crystalline structure of the substrate, a replacement fin structure positioned above the substrate fin, wherein the replacement fin structure is comprised of a semiconductor material that is different from the first semiconductor material, and a gate structure positioned around at least a portion of the replacement fin structure.