The purpose of design migration is to take an existing circuit and adapt it to be manufactured in a new foundry or process node.  While the components that make up the design will be changed, the overall architecture, hierarchy and layout topology will be maintained and updated where required.  This delivers a huge saving in time and resources while retaining the value of the original circuit.

Design reuse is critical to the semiconductor market and process migration enables the rapid delivery of analog and mixed signal(AMS) IP.  Product vendors can migrate and simulate in new processes in a matter of days to evaluate performance and pursue licensing opportunities which would otherwise have been lost.

While digital circuits can be recreated from high-level descriptions, analog IP is usually redesigned each time a new process or technology is required.  Design migration technology overcomes this problem by adapting existing circuits to be translated to a new technology in a fraction of the time needed for a redesign. 

Migration involves transferring and adapting the schematic, layout and other files such as test benches to meet the design rules and component parameters of a new process.  In many cases, the transfer could involve stepping to  the next smallest geometry available or replicating the circuit in the same process node with a new foundry to provide a second source or to increase licensing options. 

  Starting the Migration 

The migration process starts by examining the contents of the circuit to be transferred and how its components can be mapped to the requirements of the new foundry's rules.  This will identify all of the elements types used in the source circuit which is then used to build mapping information that describes how each one should be modified to match the new process.

Reviewing the database and identifying the components it contains will give engineers a clear picture of how well the circuit matches the new technology with a very low overhead in time and resources.  IN2FAB's migration services group can perform this work in a migration feasibility study to deliver a clear picture of the migration process along with the time and costs for the project.

All of the migration processing takes place directly on the design databases.  Most companies use the Open Access™ database as a platform for their designs and IN2FAB's migration systems use software from Cadence Design Systems as a design platform.  This ensures that the migration works directly with the process design kits (PDKs)provided by the foundries and ensures 100% compatibility with elements and models for design and simulation.

  Schematics and Simulation  

When the design study is complete and the component mapping tables are in place, the schematics can be migrated to the new process in preparation for simulation.  Symbols from the original foundry are replaced by those from the new one and the parameters updated to match the requirements of the new PDK. 

Though it may first appear relatively simple at first glance, migrating schematics is usually much more complex than it looks. Tools must handle physical differences in symbols and then deal with the hidden details of parameter names, values and interactions.  Once the files are created to migrate a circuit between two technologies, they can easily be reused for subsequent designs.

Migration tools must cope with all of the circuit complexity automatically.  Symbols can change size, pins can move and  others deleted while new connections can even lead to shorts in densly packed areas.  Translating the parameters is usually even more complex, particularly when moving to a new foundry.  Component construction and parameters can be completely different and size limits may also differ meaning that it's rarely as simple as changing some property names.  All of these issues are resolved as part of the automated migration flow to allow entire designs to be migrated in a single pass.

Schematic and model files for test benches are migrated in a similar way to connect the migrated database to new models and then the design is ready for simulation.  Core functionality can be tested quickly followed by simulation in to the process corners.  Engineers may choose to update some parameters for performance but they will be working on familiar circuits and can make small modifications where required.

 Layout Migration 

Layout migration is the most complex part of the process and it requires specialized tools to transfer and process the data.  Earlier layout migration tools worked on polygon level data from GDS2 files and ran as a "compactor" that would push the shapes in the layout based on the design rules for the new process.  Compactors can work well for regular structures such as memories and standard cells have always struggled to deal with analog layout.

A more effective approach is to use a migration system that works at the PDK level, replacing parameterized cells from the original layout with those from the new PDK.  The parameters within the cells are adjusted as necessary and placed in the new layout to form the core of the circuit and the routing and other layout is transferred alongside.  This ensures that the layout components are already correct in the target process as they will be placed directly from the new foundry's PDK.

Translating a circuit in this way preserves the full integrity of the source design.  The hierarchy and topology of the circuit is maintained along with the critical placement and matching of transistors and routing.  More advanced structures such as vias, multi-part paths and fluid guard rings are translated in the same way, maintaining their structure and integrity in the migrated layout.  All of the layout data is fully editable as parameterized structures after migration rather than being reduced to a huge array of polygons.

Layout adjustment tools then process the migrated data to resolve differences in rules that cause breaks in the interconnect.  Groups of components are aligned and the interconnect updated as required.  The migrated layout can also be edited manually based on extracted simulation data or update the circuit to match new schematic requierments.

Running all of the migration within editing tools gives complete control of the process and 100% compatibility with PDKs from any source.   

IN2FAB has migrated hundreds of circuits using this process across different technologies including all of the world's major silicon foundries.  Circuits have ranged from small IP blocks such as PLL or bandgaps, large IP like HDMI, Bluetooth and entire chips. 

Design migration is the fastest way to move IP to a new process while preserving design integrity and meeting the demands of tight schedule.