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Vary transistor parameters using Monte Carlo simulation.

EngTu

Hello colleagues, 

I am using Virtuoso version IC6.1.18 and Spectre -subversion 18.1.0.077.

I have tried both the Classic Spectre Simulation and the ADE XL tool to run Monte Carlo simulations (MCs) on a ring oscillator circuit. The Model Card used for this design is model n bsim3v3 and model p bsim3v3 (myModel.scs).  Simulation configurations were configured on a cfg control file by using the following command in the standalone (Classic Spectre Simulation):

spectre +config cfgMonteCarlo1 inverter_ring.scs

The cfgMonteCarlo1 and the inverter_ring.scs attached to this post.

The simulations were simulated successfully and their results were plotted in the viva XL tool for both tools (Classic Spectre Simulation and the ADE XL).

I read the following documents:

  • Spectre® Circuit Simulator Reference, Product Version 18.1,
  • Spectre® Classic Simulator,
  • Spectre Accelerated Parallel Simulator (APS), and Spectre Extensive Partitioning Simulator (XPS) User Guide, Product Version 18.

Also, I joined the online course Virtuoso Analog Simulation: T3 Monte Carlo Simulations Using ADEXL.

They explained about the commands how to vary transistor parameters in Spectre® Circuit Simulator Reference document and in the T3 online course but when I used these commands to vary transistor parameters by using the statistical blocks (Process and mismatch) as in cfgMonteCarlo2 file showed these errors:

Error found by spectre during hierarchy flattening.

ERROR (SFE-11): Unknown parameter `l' specified in process vary statement.
ERROR (SFE-11): Unknown parameter `vth' specified in process vary statement.
ERROR (SFE-12): Unknown parameter `l' specified in mismatch vary statement.
ERROR (SFE-12): Unknown parameter `vth' specified in mismatch vary statement.

Q1) the parameters are unknown, do I need to match the names of the above parameters as in the Model Card file? They do not exist in the model card at all under these names. So, how could I vary the transistor parameters (Gate length, Gate width, effective mobility, Threshold voltage) using the statistical blocks: Process and mismatch variation?

Q2) if I want to replace the Model Card I have (model n bsim3v3 and model p bsim3v3) with, for example, a PTM model Card 45nm? How could I do this safely without getting errors? I have tried many times and I have got some errors while I am running the simulation.  

Thank you in advance for your help and looking forward to your prompt response.

Turki

  • EngTu

    ------------------------------------------------------------------------

    //cfgMonteCarlo2

    simulator lang=spectre
    vdd_I1 ( vdd 0 ) vsource dc=3.3
    vss_I1 ( vss 0 ) vsource dc=0


    //simulatorOptions options save=all currents=all
    //tran1 tran step=0.010n stop=35n


    mc1 montecarlo variations=all numruns=100
    {
    tran1 tran start=0 stop=100n // a child analysis
    }

    parameters l=200 vth=10 μeff=1 

    statistics {
    process {
    // process: generate random number once per MC run
    vary l dist=gauss std=4 percent=yes 
    vary vth dist=gauss std=5 percent=yes 
    //vary μeff dist=gauss std=21 percent=yes 
    }

    mismatch {
    // mismatch: generate a random number per instance
    vary l dist=gauss std=4 percent=yes
    vary vth dist=gauss std=5 percent=yes 
    //vary μeff dist=gauss std=21 percent=yes 
    }
    }

    simulatorOptions options save=all currents=all

  • EngTu
    in reply to EngTu

    I figured out the issue:

    • The transistor parameters names used in the configuration file //cfgMonteCarlo2 must match the names as in the model cards file for the model n bsim3v3 and model p bsim3v3.
    • Also, the parameters must be defined in the configuration file //cfgMonteCarlo2.

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