Non-uniform wire routing via variable mandrel pitch SADP
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Solution Overview
Problem
Conventional self-aligned double patterning (SADP) processes result in uniform wire spacing, which is undesirable for varying wire spacing requirements to reduce same-metal cross-capacitance and improve signal performance.
Innovation Solution
The method involves forming mandrels with varying pitches within the SADP range, where some mandrels are spaced closer than others, allowing spacers to either form gaps or extend continuously, enabling non-uniform trench formation and metal routing pitches that can vary between regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SADP process is used to form wire routing, then pitch smaller than TMP can be achieved, but wire spacing becomes uniform which increases same-metal cross-capacitance
Solution Approach 1:
The patent applies local quality by forming different spacer configurations in different regions: in first regions, spacers have gaps exposing the first work surface to create larger wire spacing, while in second regions, spacers extend continuously to create smaller wire spacing. This allows different wire pitches in different locations, reducing cross-capacitance for critical signals while maintaining dense routing for non-critical signals.
Solution Approach 2:
The wire routing is segmented into different regions with different spacing characteristics. The first work surface is divided into first regions and second regions, with each region having different spacer configurations (gapped vs. continuous), enabling differentiated wire spacing to optimize for different signal types.
2Ease of manufacture
If uniform wire spacing is used to simplify manufacturing, then process complexity is reduced, but signal performance deteriorates due to increased cross-capacitance
Solution Approach 1:
The patent uses local quality to apply different spacer configurations in different regions based on signal requirements. Critical signals (clock, high-fanout, speed-critical) receive larger spacing through gapped spacers, while non-critical signals maintain smaller spacing with continuous spacers, optimizing signal performance without excessive complexity.
Solution Approach 2:
The spacer configuration is made dynamic by allowing gaps to form in certain regions while remaining continuous in others, based on the underlying mandrel pattern. This dynamic approach enables the routing to adapt to different signal requirements while using a uniform spacer formation process.
Data Source
AI summary
A plurality of elongated, substantially parallel mandrels are formed on a first work surface, the mandrels being spaced apart a distance in the range between the resolution limit and twice the resolution limit. Spacers are formed on the work surface extending from sidewalls of the mandrels. First portions of the work surface are exposed through gaps in the spacers near the midpoint between a majority of adjacent mandrels; but at least one pair of adjacent mandrels is close enough together that the spacers extend continuously between the adjacent mandrels. The mandrels are then removed, thereby exposing second portions of the work surface. The exposed first and second portions are etched down to a second work surface; and the exposed portions of the second work surface are etched to form trenches in that surface. A wire routing is formed by filling the trenches with a metal such as copper.