Variable Fin Pitch Semiconductor Device With Cavity Work Function Metal
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Solution Overview
Problem
Conventional semiconductor device fabrication processes involving multiple work function metal (WFM) layers are complex and prone to altering threshold voltages due to residual metal removal processes, making it difficult to achieve scaled semiconductor devices effectively.
Innovation Solution
A semiconductor device design featuring semiconductor fins with varying fin pitches and the use of two work function metal layers, where the first layer is partially filled in trenches with a cavity, allowing for different concentrations and thicknesses of the second layer, thereby generating distinct threshold voltages without the need for excessive WFM layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple work function metal layers are used to achieve threshold voltage variation, then threshold voltage control is improved, but fabrication process complexity increases
Solution Approach 1:
The patent applies local quality by creating cavities in the first work function metal layer at specific locations (in second fin trenches) to achieve different work function metal concentrations where needed. This allows different threshold voltages for different fin regions without requiring multiple separate metal layers throughout the entire structure, thus maintaining threshold voltage control while reducing overall fabrication complexity.
Solution Approach 2:
The patent segments the work function metal structure by dividing it into regions with different concentrations through the cavity formation. The first work function metal layer is present in some trenches but not others, creating distinct segments with different electrical properties that achieve threshold voltage variation without needing multiple complete metal layers.
2Manufacturing precision
If multiple work function metal layers are used to achieve threshold voltage variation, then threshold voltage control is improved, but residual metal removal processes alter the threshold voltage
Solution Approach 1:
The patent extracts or removes the first work function metal layer in specific regions by forming cavities where the metal layer is absent. This selective removal allows precise control over where work function metal is present or absent, enabling threshold voltage variation without requiring multiple layers that would need complex residual metal removal processes.
Solution Approach 2:
The patent performs preliminary action by forming the cavities in the first work function metal layer before subsequent processing steps. This pre-established structure ensures that the threshold voltage characteristics are determined early in the fabrication process, preventing alterations from later residual metal removal operations.
3Adaptability or versatility
If the number of work function metal layers is increased, then threshold voltage variation capability is improved, but the number of fabrication processes increases
Solution Approach 1:
The patent changes the parameter of work function metal concentration by creating cavities that result in different amounts of metal presence in different regions. This parameter change approach provides threshold voltage variation capability without increasing the number of metal layers, thereby maintaining fabrication efficiency.
Solution Approach 2:
The patent applies partial action by forming the first work function metal layer only in certain trenches (first fin trenches) but not in others (second fin trenches), creating cavities where the metal is absent. This partial presence of the metal layer achieves the needed threshold voltage variation without requiring complete multiple layers across all structures.
Data Source
AI summary
A semiconductor device includes a plurality of first semiconductor fins formed on a semiconductor substrate to define first fin trenches. At least one second semiconductor fin is formed on the semiconductor substrate to define second fin trenches. A first work function metal layer is formed in the first and second fin trenches. The first work function metal layer formed in the second trenches has a first cavity formed therein such that the at least one second semiconductor fin realizes a different concentration of the first work function metal layer with respect to the plurality of first semiconductor fins.