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Sophisticated Variation Modeling

As a newly-developed process is prepared for delivery into the production world, one of the last things that has to happen to effect a transition is the development of compact models for use in design simulation. And, of course, these days, such a model must account for process variations, which means covering the wide range of corners that a process can have to capture the statistics.

We’ve seen some of this before with Solido, but according to newcomer GSS, whom my colleague Dick Selwood explored at some length back when GSS was getting started, most other tools model processes as Gaussian, and the world isn’t actually Gaussian. Also, the existing tools help with simulation, but they don’t create a model.

Well, GSS has now released their tool. It works as a “wrapper” to a simulator, as these tools are wont to do. So it doesn’t do the actual simulation; you pick whatever simulator you want to work with, along with the circuit and model strategy, and the GSS tool creates the corners to be run – on the order of a couple thousand runs. Because of the independence of the runs, this scales perfectly with additional processors; you specify the number of processors and it handles the load management.

It then builds a model with statistical features that no other models have; the model itself has time-dependent capabilities for characteristics that evolve over time. In this manner, they say that it bridges TCAD and production EDA in a way that no other tool does.

They announced their tool in a somewhat indirect fashion, focusing on the possibility of unforeseen SRAM yield issues at the 20-nm node. You can see more about the details of that discussion in their release.

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