Self-Aligned Via-First Interconnects for Overlay and Leakage Control
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Solution Overview
Problem
Conventional interconnect structure formation processes, such as trench-first and via-first processes, face challenges in maintaining CD uniformity and overlay control, especially at small pitches, leading to issues like via-to-trench space window limitations, leakage between metal lines, and residue of bottom anti-reflective coating in via holes.
Innovation Solution
A via-first process is employed where a via pattern is formed in a first hard mask, followed by a trench pattern in a second hard mask, allowing the via hole to be defined by both masks, resulting in self-aligned metal vias to overlying metal lines, which maintains distance between metal lines and neighboring vias, controlling leakage and eliminating bridging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trench-first process is used to form interconnect structures, then metal lines are formed first providing a defined pattern, but via-formation process window is limited due to surface topography and overlay control becomes difficult
Solution Approach 1:
The patent inverts the conventional trench-first sequence by forming via patterns before trench patterns. This reversal allows via holes to be defined by the intersection of via pattern and trench pattern, eliminating surface topography issues and improving via patterning precision without increasing process complexity
Solution Approach 2:
The patent segments the patterning process into distinct via pattern formation and trench pattern formation steps, where each pattern is formed independently and then combined. This segmentation allows precise control of via patterns without being constrained by trench-induced surface topography
2Manufacturing precision
If via-first process is used to form interconnect structures, then via patterns are formed before trench patterns, but overlay shift of trench patterns from via patterns causes leakage between metal lines
Solution Approach 1:
The patent employs self-aligned patterning where the via pattern and trench pattern automatically align through their geometric intersection. The via holes are self-defined by the overlapping regions of the via pattern and trench pattern, eliminating overlay shift issues and ensuring reliable spacing control without additional alignment steps
Solution Approach 2:
The patent merges the via pattern and trench pattern formation into a unified self-aligned process where both patterns are defined simultaneously through their geometric intersection. This merging ensures precise via-to-trench spacing control and prevents leakage by eliminating relative overlay shifts between the two patterns
3Ease of manufacture
If conventional via-first process is used, then via patterns are formed independently, but residue of bottom anti-reflective coating in via holes is difficult to remove
Solution Approach 1:
The patent performs preliminary patterning where the via pattern is formed first, followed by trench pattern formation that automatically defines the final via hole boundaries. This preliminary action allows better control of via hole geometry and facilitates easier removal of bottom anti-reflective coating residue through improved etch access and geometry control
Data Source
AI summary
A structure includes a dielectric layer, and a metal line in the dielectric layer. The metal line has a first straight edge and a second straight edge extending in a lengthwise direction of the metal line. The first straight edge and the second straight edge are parallel to each other. A via is underlying and joined to the metal line. The via has a third straight edge underlying and vertically aligned to the first straight edge, and a first curved edge and a second curved edge connecting to opposite ends of the third straight edge.