IC Routing Layout With Non-Preferred Direction Metal Layers
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Solution Overview
Problem
Existing integrated circuit (IC) designs face challenges in efficiently routing wires due to limitations in preferred and non-preferred wiring directions, leading to suboptimal wire connections and congestion.
Innovation Solution
Implementing a novel non-preferred direction (NPD) wiring architecture in ICs, where certain layers have no preferred wiring directions, allowing curvilinear and rectilinear routes, and using EDA tools to optimize routing across multiple layers with alternating preferred directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional preferred direction wiring architecture is used, then manufacturing process is simplified, but wire length increases and via counts increase
Solution Approach 1:
The wiring system is segmented into multiple layers with different routing capabilities. Lower layers (first and second wiring layers) use traditional preferred direction routing for manufacturing simplicity, while upper layers (third and fourth wiring layers) enable non-preferred direction routing to reduce wire length. This segmentation allows each layer to optimize for its specific function.
Solution Approach 2:
The patent introduces a vertical dimension to the routing problem by utilizing multiple wiring layers with different routing constraints. By allowing non-preferred direction routing on upper layers, the system adds a dimensional freedom that reduces the need for long wires and excessive vias, while maintaining manufacturing simplicity on lower layers.
2Adaptability or versatility
If non-preferred direction wiring is allowed on all layers, then wire routing flexibility improves, but manufacturing complexity increases
Solution Approach 1:
Different wiring layers are assigned different routing qualities and constraints. The first and second wiring layers maintain preferred direction constraints for manufacturing simplicity, while the third and fourth wiring layers enable non-preferred direction routing for flexibility. This local differentiation optimizes the overall system by applying the right constraint level to each layer.
Solution Approach 2:
The wiring system is divided into segments with different routing capabilities. Lower layers segment the manufacturing complexity by maintaining traditional constraints, while upper layers segment the routing flexibility needs by enabling non-preferred direction wiring. This segmentation resolves the contradiction by distributing complexity and flexibility across different layers.
3Quantity of substance
If more wiring layers with non-preferred directions are added, then via counts decrease, but device complexity increases
Solution Approach 1:
Instead of enabling non-preferred direction routing on all wiring layers (excessive action), the patent applies it partially only to the third and fourth wiring layers. This partial application is sufficient to reduce via counts while avoiding the increased device complexity that would result from applying non-preferred direction routing to all layers.
Data Source
AI summary
Some embodiments of the invention provide an integrated circuit (IC) that has a novel non-preferred direction (NPD) wiring architecture. In some embodiments, the IC includes a substrate and multiple wiring layers, which include a first set of one or more wiring layers with no preferred wiring directions, and a second set of one or more wiring layers with preferred wiring directions. In some embodiments, the first set of wiring layers includes the third and fourth wiring layers, while the second set of wiring layers includes the fifth and higher metal layers with successive neighboring layers having different (e.g., alternating) preferred wiring directions. The first set of wiring layers in other embodiments includes the third wiring layer but not the fourth wiring layer, which in these embodiments has a preferred wiring direction.