Protective Dielectric Arch for Via Chamfer Control
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Solution Overview
Problem
Conventional dual damascene processes in semiconductor fabrication lead to chamfering at the tops of vias, causing shorting between adjacent interconnects due to unprotected via sidewalls during the trench etch step.
Innovation Solution
A protective dielectric arch is formed over the center metal line to control via chamfer angle and dimensions, preventing contact between the interconnect and adjacent metal lines by using a conformal spacer and dielectric cap to create a non-contact position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If vias are patterned before trenches in a dual damascene process, then via-first process enables interconnect formation, but via sidewalls are etched causing chamfering that leads to shorting between adjacent interconnects
Solution Approach 1:
A protective dielectric arch is formed over the via sidewalls before the trench etch step. This preliminary protective structure prevents the etch from attacking the via sidewalls, thereby avoiding chamfering and subsequent shorting while maintaining the via-first process sequence
Solution Approach 2:
The protective dielectric arch acts as an intermediary layer between the via structure and the trench etch process. This intermediate protective structure isolates the via sidewalls from the etchant, preventing harmful interactions while allowing the trench to be etched separately
2Device complexity
If no protective structure is used during trench etch, then process simplicity is maintained, but via chamfering occurs causing shorting between interconnects
Solution Approach 1:
The protective dielectric arch is formed in advance before the trench etch, establishing precise geometric boundaries that control the final via dimensions and prevent chamfering. This preliminary structure ensures manufacturing precision without requiring complex in-process adjustments
3Reliability
If protective dielectric arch is formed, then via chamfer angle and dimensions are controlled preventing shorts, but process steps are added increasing fabrication complexity
Solution Approach 1:
The formation of the protective dielectric arch is merged with the existing dielectric deposition and patterning steps in the dual damascene process. By integrating the protective structure formation into the existing process flow rather than adding completely separate steps, the increase in fabrication complexity is minimized while achieving reliable shorting prevention
Data Source
AI summary
Chamfer-less via interconnects and techniques for fabrication thereof with a protective dielectric arch are provided. In one aspect, a method of forming an interconnect includes: forming metal lines in a first dielectric; depositing an etch stop liner onto the first dielectric; depositing a second dielectric on the etch stop liner; patterning vias and a trench in the second dielectric, wherein the vias are present over at least one of the metal lines, and wherein the patterning forms patterned portions of the second dielectric/etch stop liner over at least another one of the metal lines; forming a protective dielectric arch over the at least another one of the metal lines; and filling the vias/trench with a metal(s) to form the interconnect which, due to the protective dielectric arch, is in a non-contact position with the at least another one of the metal lines. An interconnect structure is also provided.