Self-Aligned Spacer Patterning for Mandrel-Trench Connections
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Solution Overview
Problem
Current self-aligned double patterning (SADP) process flows are unable to connect a mandrel formed trench to a non-mandrel formed trench, particularly in advanced interconnects with critical dimensions less than 5 nm to 20 nm.
Innovation Solution
The method involves forming mandrel and non-mandrel structures, creating dielectric spacers, and using a second spacer material that is more etch resistant to connect the mandrel and non-mandrel formed features by etching away a portion of the spacer between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional SADP process flows are used, then feature density is enhanced through multiple patterning, but mandrel formed trenches cannot be connected to non-mandrel formed trenches
Solution Approach 1:
The patent introduces a second dielectric spacer layer that is selectively removed in specific regions to create connection openings. This segments the continuous dielectric spacer structure into protected regions (forming trenches) and removed regions (forming connections), enabling both trench formation and interconnection in the same process flow.
Solution Approach 2:
The second dielectric spacer material is applied with different etch resistance properties in different locations. By using a material that is more etch resistant than the first dielectric spacer, the patent creates local variations in etchability that allow selective removal of connection portions while preserving trench-forming portions, thus enabling localized connection formation.
2Device complexity
If a single lithographic exposure is used, then the process is simple, but sufficient resolution cannot be achieved for advanced interconnects
Solution Approach 1:
The patent employs periodic lithographic exposures with different orientations (e.g., 0度和90度) to progressively build up the pattern. Each exposure cycle deposits additional dielectric spacer material that is then etched back, creating increasingly complex patterns from simple initial mandrels, thereby achieving high resolution through repeated cycles rather than a single complex exposure.
Solution Approach 2:
The patent performs preliminary lithographic exposures and dielectric spacer formations to create mandrel structures and initial trenches before final connection formation. These preliminary actions establish the basic pattern framework that guides subsequent processing steps, enabling resolution enhancement through staged pattern development.
3Manufacturing precision
If mandrel structures are formed to define trenches, then trench formation is precise, but connection between mandrel and non-mandrel trenches becomes impossible
Solution Approach 1:
The second dielectric spacer acts as an intermediary structure that bridges mandrel-formed trenches and non-mandrel trenches. By selectively removing portions of this intermediary spacer, the patent creates connection openings that allow electrical interconnection between previously isolated trench structures, thus enabling manufacturability without compromising trench precision.
Solution Approach 2:
The patent changes the etch resistance parameter of the dielectric spacer by introducing a second material layer with different etch characteristics. This parameter change enables selective etching of connection portions while maintaining the integrity of trench-defining portions, thus allowing both precise trench formation and feasible connection processes.
Data Source
AI summary
A method of forming a structure for etch masking that includes forming first dielectric spacers on sidewalls of a plurality of mandrel structures and forming non-mandrel structures in space between adjacent first dielectric spacers. Second dielectric spacers are formed on sidewalls of an etch mask having a window that exposes a connecting portion of a centralized first dielectric spacer. The connecting portion of the centralized first dielectric spacer is removed. The mandrel structures and non-mandrel structures are removed selectively to the first dielectric spacers to provide an etch mask. The connecting portion removed from the centralized first dielectric spacer provides an opening connecting a first trench corresponding to the mandrel structures and a second trench corresponding to the non-mandrel structures.