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Sweeping Vth vs L

Arjun RP

Hi all,

I am Arjun, Graduate student pursuing IC Design. I am trying to sweep the Vth of transistor with respect to its length. I saved a file with .scs extension and with the content save M0:all. I selected DC analysis and in the sweep i selected component parameter and transistor M0 where i selected its length "l". I also included the .scs file into model library. But when i run the simulation i am getting a error as given below. 

ERROR (SFE-430) : 'dc' : Sweeping the parameters of a subcircuit instance ('M0') is currently not supported. Please use the spectre sweep instead.

Spectre terminated prematurely due to fatal error.

 What should i do to overcome this error ? Please help me 

  • Spectre does not output the mobility or Cox. That said, I don't think either of these would vary with length (or temperature?). From this post (which is for MOS level 1, but I think it's the same in bsim4), that doesn't appear to be the case.

    You can vary u0 and toxe (Tox, which sets Cox) as model parameters on the dc sweep form - but not sure if that's what you want.

    Regards,

    Andrew.

  • But i think mobility decreases with themperature because as temperature increases , the scattering increases and so the mobility decreases. I would like to learn about that phenomena. So is there a way to sweep mobility vs temperature ? And is there a way to find the mobility and cox value of our process ,so that i can use those values in hand calculation ?
  • I'm sure that something which is dependent upon the mobility parameter in the model is temperature or length dependent. You'll have to work through the documented equations for the model (eg bsim4) though because as I said already, spectre does not output "mobility" or "cox" as an operating point or output parameter. 
  • Thanks for your reply. Will refer to Bsim4 file for the equations

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