L-Shaped Gate Line Segmentation for FinFET Vt Stability
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Solution Overview
Problem
The miniaturization of semiconductor devices, particularly fin field effect transistors (Fin FETs), faces challenges such as gate line entanglement and uneven thickness of the work function metal layer, leading to instability of the threshold voltage (Vt) due to the shrinking pitch and width of fin structures.
Innovation Solution
A method involving a first and second cutting process to remove parts of the gate line above and under the fin structures and on shallow trench isolation (STI), respectively, forming L-shaped gate trenches that are filled with insulating material to create stable gate isolations, thereby untangling the metal layers and ensuring even thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the pitch and width of fin structures are shrunk to achieve miniaturization, then device density is improved, but gate line entanglement and uneven metal layer thickness occur leading to Vt instability
Solution Approach 1:
The gate line is divided into multiple segments by removing portions above and under the fin structures through first and second cutting processes. This segmentation prevents entanglement and ensures uniform metal layer thickness in the remaining gate line portions, resolving the contradiction between miniaturization and manufacturing precision.
Solution Approach 2:
Specific portions of the gate line are extracted (removed) through cutting processes to eliminate the entangled sections. By taking out the problematic portions above and under the fins, the remaining gate line maintains proper configuration and uniform metal deposition, achieving both miniaturization and precision.
2Productivity
If continuous miniaturization is pursued to increase device density, then productivity is improved, but gate line stability deteriorates due to entanglement and uneven thickness
Solution Approach 1:
The gate line is segmented into discrete portions by removing sections above and under the fin structures. This segmentation ensures that the remaining gate line portions are stable and free from entanglement, maintaining reliable threshold voltage even as device density increases through miniaturization.
Solution Approach 2:
Different portions of the gate line are treated differently: sections above and under the fins are removed while sections between fins are retained. This local quality approach ensures that the gate line has the appropriate configuration in critical areas, maintaining reliability while enabling miniaturization for improved productivity.
3Adaptability or versatility
If the gate line is formed across fin structures with small pitch, then device integration is improved, but gate line entanglement occurs resulting in uneven work function metal layer thickness
Solution Approach 1:
The gate line is divided into separate segments by removing portions above and under the fin structures. This segmentation allows the gate line to adapt to high-density fin structures while maintaining proper shape and uniform metal layer thickness in the retained portions, achieving both integration and geometric quality.
Solution Approach 2:
Instead of trying to maintain a continuous gate line across all fin structures, the approach is inverted by removing the gate line portions that would cause entanglement. This inversion strategy preserves the gate line in areas where it provides benefit while eliminating problematic sections, maintaining both integration and shape quality.
Data Source
AI summary
A semiconductor device includes: a substrate having a first fin-shaped structure and a second fin-shaped structure thereon, a shallow trench isolation (STI) around the first fin-shaped structure and the second fin-shaped structure, a gate isolation directly on the second fin-shaped structure, and a gate line on the STI and the first fin-shaped structure. Preferably, the gate line includes a L-shaped structure.