Wrapper Cells Automate High-Speed Signal Routing in ICs
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Solution Overview
Problem
In large-scale integrated circuit designs, the placement and routing of high-speed signal lines, particularly clock signals, face challenges due to high impedance and susceptibility to electromigration, which can lead to signal attenuation and degradation, necessitating complex manual intervention by design engineers.
Innovation Solution
The introduction of 'wrapper cells' with geometrical dimensions matching standard cells, which define electrical paths including vias from lower to upper metal layers, allowing computerized place-and-route tools to automatically route signal connections through these paths, reducing impedance and electromigration susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual routing intervention is used for high-speed signal lines, then signal quality can be maintained, but design complexity and time consumption increase significantly
Solution Approach 1:
The patent introduces a special cell type acting as an intermediary between standard cells and routing infrastructure. This cell includes a via structure that automatically connects signal terminals in lower metal layers to upper metal layers, mediating the connection without requiring manual routing intervention while maintaining signal integrity
Solution Approach 2:
The routing path is prepared in advance by pre-defining the via structure and upper metal layer connection points within the special cell. This preliminary preparation eliminates the need for complex manual routing decisions during the design process, as the path is already established before routing begins
2Reliability
If complex manual routing is performed for clock signals, then electromigration susceptibility can be reduced, but productivity decreases
Solution Approach 1:
The special cell is self-configuring in that it automatically provides the appropriate via structure and upper metal layer connection based on its cell type. The cell serves itself by having pre-defined routing paths that eliminate the need for manual electromigration optimization, allowing standard place-and-route tools to handle the routing automatically
Solution Approach 2:
The patent changes the routing parameters by introducing fixed via locations and upper metal layer connection points as inherent properties of the special cell. This parameter transformation converts a complex manual optimization problem into a straightforward automated routing task with predetermined parameters
3Extent of automation
If standard place-and-route tools are used without special cells, then routing flexibility is maintained, but automation capability for high-speed signals is insufficient
Solution Approach 1:
The special cell serves multiple functions: it acts as a standard cell for logic implementation, provides automatic via structure for inter-layer connectivity, and defines upper metal layer connection points for routing. This multi-functionality allows standard place-and-route tools to automatically handle high-speed signal routing while maintaining the flexibility to adapt to different cell types and routing requirements
Data Source
AI summary
A method for circuit design includes providing one or more wrapper cells for use with a library of standard cells in design of an IC. Each wrapper cell has geometrical dimensions matching a corresponding group of one or more of the standard cells and defines an electrical path, including at least one via, from a location of a terminal in a lower metal layer in the standard cells in the corresponding group to a location in an upper metal layer. A computerized place-and-route tool receives a layout of the IC including a wrapper cell superimposed over one of the standard cells in the corresponding group. The place-and-route tool automatically routes a signal connection through the upper metal layer and the at least one via defined by the superimposed wrapper cell to the predefined signal terminal in the lower metal layer in the one of the standard cells.