Libraries Functional Statistical Verification

Process variability at advanced technology nodes has become a key challenge for standard cell library designers. VarMan For Library™ (LibVar) is a new generation tool that provides efficient and reliable solutions for standard cell statistical functional verification while preserving brute force Monte Carlo (MC) accuracy. LibVar allows designers to accurately address statistical variation analysis 10 times faster than MC reducing global verification time from months to days.


Libraries functional verification is a heavy task where thousands of Monte Carlo need to be run on hundreds or thousands of corners resulting in a tremendous number of MC runs. Functional verification phase could thus need huge time and resources software (SPICE simulator) and hardware (CPUs).

Figure 1: Monte Carlo vs LibVar flow


  • Explore parameter space to generate fails
    • Search simulations of PVTSC’s that trigger fails
    • Adaptive exploration
  • Estimate failure zones of each measurements
    • Fast statistical capture of failure zones
    • Robustness against noisy/spurious simulations
  • Simulate fail/near fail candidate samples of Monte Carlo
  • Impressive simulation time speed-up: up to 10X
  • More speedup with share of work among cell PVTSC’s
  • Non-Intrusive tool: Designed to be simply integrated into golden characterization flow without any modification
  • Smart Simulation Manager: Simulation results management, High simulation throughput through LSF/SGE cluster


  • Breakthrough analysis techniques
    • Unique engine for standard cells statistical verification
    • Adaptive search, cover & simulation of the MC fails
  • Reliable and mature technology
    • Tested and validated by major players on most advanced technology nodes
  • SPICE simulator and environment independent
    • Supports all golden SPICE simulators and design environments
    • Supports most advanced market design kits
    • Batch mode support
  • No need to change design flow, PDK independent

Figure 2: Customer achieves faster verification (10x) while keeping full exhaustive corners coverage


  • Statistical functional verification of full standard cell library with Monte Carlo (MC) simulations                                    


  Success story: Major customer

   FlipFlop, 28nm FDSOI
   Measurements: 278
   Global speedups: 9x


Digital library, 28nm FDSOI

  • 40 cells with parasitic elements, up to 100 PVTSC corners per cells
  • 100’s of performance (output voltages/digital levels)
  • Simulation time: from 1 min to 4 min  


Technical Specifications

  • Batch Scripting language
  • Multi-CPU, Multi-Machine (LSF/OGE)