Hard Mask Isolation Structure for Fin Sidewall Coupling Control
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Solution Overview
Problem
As technology nodes become smaller, there is an increased risk of unwanted coupling between semiconductor active regions and/or between semiconductor device components, leading to capacitance degradation, current leakage, and performance loss due to STI loss and exposure of sidewall doped portions of the substrate, which are not adequately addressed by existing isolation structures.
Innovation Solution
A hard mask layer is applied over the isolation structure with a planar profile to prevent gate-to-substrate coupling and protect the isolation structure during semiconductor manufacturing, ensuring effective capacitance and preventing unwanted epitaxial merging of source/drain features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are formed to prevent coupling between active regions, then isolation effectiveness is improved, but the isolation structures may be damaged during manufacturing causing STI loss
Solution Approach 1:
A hard mask layer is deposited over the isolation structure before subsequent manufacturing steps. This preliminary protective action ensures the isolation structure is shielded from damage during etching and processing operations that follow.
Solution Approach 2:
The hard mask layer serves as an intermediary protective element between the isolation structure and harmful etching processes. It absorbs the impact of aggressive etchants and mechanical stresses, preventing direct damage to the isolation structure.
2Reliability
If isolation structures are formed to prevent coupling, then capacitance degradation is reduced, but sidewall doped portions may be exposed leading to gate-to-substrate coupling
Solution Approach 1:
The hard mask layer is deposited in advance to cover and protect the sidewall doped portions. This preliminary action prevents exposure of sensitive doped regions during subsequent processing, eliminating the source of parasitic coupling.
Solution Approach 2:
The hard mask layer acts as an intermediary barrier between the metal gate structure and the exposed doped portions of the substrate. It physically separates these elements, preventing electrical coupling and associated parasitic effects.
3Productivity
If scaling is continued to improve production efficiency and lower costs, then manufacturing productivity is improved, but complexity of IC manufacturing processes increases
Solution Approach 1:
The manufacturing process is segmented into distinct stages with the hard mask deposition being a separate, dedicated step. This segmentation allows for optimized processing at each stage, maintaining productivity while managing complexity through structured process organization.
Solution Approach 2:
The hard mask layer serves multiple functions simultaneously: it protects the isolation structure, covers sidewall doped portions, and provides a planar surface for subsequent processing. This multi-functionality reduces the need for additional separate steps, managing process complexity while maintaining productivity.
Data Source
AI summary
One aspect of the present disclosure pertains to forming a semiconductor stack over a substrate; patterning the semiconductor stack and the substrate to form semiconductor fins having semiconductor stack portions over base portions; depositing an isolation layer over the semiconductor fins; recessing the isolation layer to form an isolation structure surrounding base portions of the semiconductor fins; depositing a hard mask layer over the semiconductor fins and over the isolation structure, the hard mask layer includes bottom portions disposed on the isolation structure, sidewall portions disposed on sidewalls of the semiconductor fins, and top portions disposed on top surfaces of the semiconductor fins; performing a first etching process to recess the top portions of the hard mask layer; and performing a second etching process to planarize the bottom portions of the hard mask layer, thereby forming a hard mask structure with a planarized top surface over the isolation structure.