Much has been made of and will continue to be said on the march of Moore’s Law. While economics of scale and performance vs. power are the main justifications, there are increased design challenges that make designs of prior decades seem quaint by comparison. Smaller transistors allow for lower cost per function and more power efficiency, but they also come with increased variation effects, making performance vs. power vs. yield tradeoffs a necessary part of the design flow.
With each successive process shrink, there is a corresponding increase in the number of SPICE simulations required to push design performance while ensuring manufacturability. Solido Design Automation provides solutions for reducing the number of simulations needed during design and verification, while still providing the same or more visibility into design choices, impacts on yield and risk. As a leading provider of efficient variation analysis tools, Solido continues to collaborate with TSMC to deliver effective analysis capabilities on the latest nanometer technologies, supporting designers of memory, standard cell, low power, and analog/RF circuits.
Memory designers have perhaps the greatest challenge in maximizing their design performance within the capabilities of a particular process technology, needing to validate yield and performance to 4-6 sigma on bit cells and sense amps and 2-4 sigma at the array level. While Monte Carlo is the preferred solution, it’s simply impractical to simulate the billions of points needed for 6-sigma analysis. Since the analysis still has to be done, a number of approaches have evolved that seek to bypass Monte Carlo, but they each suffer limitations in accuracy, scalability and, especially, verifiability.
Solido’s Memory+ Suite goes back to the core Monte Carlo analysis designers trust and handles the billions of samples with intelligent adaptive techniques to focus simulation resources towards the high-sigma tails of the distribution. Since Memory+ uses actual Monte Carlo samples, it is able to provide simulation results around the target sigma, high-sigma corners for use in design development and even the full PDF. These options give designers the detailed insights they need into non-linear effects, design sensitivities to make informed sizing decisions.
Unlike other approaches, Solido’s Memory+ is able to handle the more severe non-linear responses, rendering it applicable to a broad range of memory cells. In the following example, a 3- or 4-sigma analysis would appear linear with extrapolation completely missing the failure regions occurring at +/- 4.5-sigma.
Additionally, with the full PDF available for both the bit cell and sense amp, Memory+ can provide 3-sigma analysis at the system level, allowing designers to explore performance vs. yield tradeoffs directly. The following table shows the results of a 3-sigma analysis on a 256Mb SRAM array using the Memory+ System Memory tool, enabling visibility into the tradeoff between timing and system-level yield, in a matter of minutes. The tool is also applicable to system-level DRAM analysis.
Using memory design as just one example, Solido is able to provide designers with the necessary tools to analyze yield and performance, faster and with more consistent quality than before. As shown with Memory+, memory designers can quickly analyze designs at the cell level to 6-sigma and the system-level to 3-sigma, while keeping Monte Carlo and SPICE level accuracy.