Electrically Aware Routing for Analog IC Layout
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Solution Overview
Problem
Existing placement and routing (P&R) tools for integrated circuits (ICs) often fail to effectively address the matching and symmetry constraints of analog circuits, leading to a performance gap between pre-layout and post-layout simulations, requiring manual layouts that are time-consuming and error-prone, and are heavily dependent on designer experience.
Innovation Solution
An electrically aware routing flow that determines electrical constraints from performance specifications, converts them into physical constraints, and uses sensitivity checks to optimize net routing, incorporating track-based and mesh routing to ensure compliance with electrical constraints, thereby reducing the performance gap and improving layout efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automated P&R tools are used for routing, then productivity is improved, but manufacturing precision deteriorates due to inability to satisfy matching and symmetry constraints
Solution Approach 1:
The routing process is segmented into two distinct phases: a first routing pass that satisfies electrical constraints (matching and symmetry) and a second routing pass that optimizes for performance metrics. This segmentation allows each pass to focus on specific requirements without compromising the other, resolving the contradiction between automated routing efficiency and constraint satisfaction.
Solution Approach 2:
Electrical constraints such as matching and symmetry are satisfied in advance during the first routing pass before the second pass optimizes for performance. This preliminary action ensures that critical constraints are met before subsequent routing decisions are made, enabling automated tools to maintain both productivity and precision.
2Productivity
If P&R tools minimize distance between connections, then productivity is improved, but measurement precision deteriorates leading to large performance gap between pre-layout and post-layout simulations
Solution Approach 1:
The routing process is divided into two passes: the first pass satisfies electrical constraints with adequate routing, and the second pass optimizes for minimum distance and performance. This segmentation allows the design to achieve both simulation accuracy and routing efficiency without compromising either.
Solution Approach 2:
The system performs pre-layout simulations to evaluate routing quality and provides feedback to guide the routing optimization process. This feedback mechanism allows the P&R tool to adjust routing decisions to minimize the performance gap between pre-layout and post-layout simulations while maintaining productivity.
3Manufacturing precision
If manual routing is used to satisfy electrical constraints, then manufacturing precision is improved, but loss of time increases and productivity deteriorates
Solution Approach 1:
The P&R tool is enhanced with electrical awareness capabilities that enable it to automatically satisfy matching and symmetry constraints without requiring manual intervention. The tool serves itself by incorporating electrical constraint checking and optimization algorithms, eliminating the need for time-consuming manual routing while maintaining precision.
Solution Approach 2:
The routing algorithm dynamically adjusts routing parameters such as track selection, via placement, and net ordering based on electrical constraints. By changing these parameters automatically, the system achieves manual-quality constraint satisfaction without the time cost of manual routing.
4Manufacturing precision
If design rules become more complex due to process improvements, then manufacturing precision is improved, but device complexity increases leading to more iterations and reduced productivity
Solution Approach 1:
The system performs preliminary electrical constraint analysis and incorporates design rule considerations into the routing process before final layout generation. This preliminary action accounts for complex design rules and process variations in advance, reducing the need for iterative adjustments and maintaining productivity despite increased device complexity.
Solution Approach 2:
The P&R tool incorporates feedback loops that evaluate routing decisions against complex design rules and process specifications. This feedback mechanism allows the system to automatically adjust routing to satisfy evolving design rules without requiring additional manual iterations, maintaining both precision and productivity.
Data Source
AI summary
A system including computer readable storage media including executable instructions and one or more processors configured to execute the executable instructions to obtain a schematic netlist and a performance specification for an integrated circuit, determine electrical constraints for nets in the schematic netlist based on the performance specification, determine physical constraints from the electrical constraints, rout the nets in the schematic netlist based on the electrical constraints and the physical constraints, and provide a data file of a layout.