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how to determine the subthreshold process paramter?

MenghanSun

Dear all,

I have a question that i couldn't find an answer to in this forum. I wish to find out the subthreshold process paramter (sometimes referred to as process slope, subthreshold slope) of a given MOS device.

Id = u*Cox*(Vt^2)*(W/L)*exp( (VGS-Vth) / m*Vt ) * [1 - exp(-VDS/VT)]

The "m" is the subtreshold slope. I ran the DC simulation, use OPT on a MOSFET, I can find a big list of device parameters, region, self-gain, betaeff, and etc. However, I can't find the "m" the subthreshold slope.

Could anyone tell me how to find out the subtreshold slope "m" in cadence, Any help is appreciated. Thank you!

Menghan

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  • Andrew Beckett

    Not sure where that equation comes from - you need to remember that any such equation may only reflect a specific model, and most modern transistor models are rather more complex than this (although it doesn't look like any basic transistor models either to me, but it may just be how it's written).

    I could see that many of the "Philips" (now NXP) models (e.g. MOS11, MOS902 etc) have a parameter for subthreshold slope (this is a model parameter, called "mo" or "mor"), but there doesn't seem to be anything like that for bsim3v3, bsim4. So I suspect the model formulation doesn't have any similar parameter and it's not something the models compute and spit out either (I've not found any requests for this as an output or operating point parameter).

    So given that you didn't say which model you're using, or which simulator you're using, or which version of the tools you're using, I rather doubt this can be answered. However, even knowing that, it doesn't look to me as if the equation you've described matches any of the models (from a very quick scan through the model documentation, which is in cdnshelp) in Spectre.

    Regards,

    Andrew.

  • Arefinn
    in reply to Andrew Beckett

    Hi, I am using Cadence Virtuoso ADE L to simulate my circuit and I want to figure out the subthreshold factor. Can you help me out how to do so?

  • Andrew Beckett
    in reply to Arefinn
    Arefinn said:
    Can you help me out how to do so?

    Not unless you both read the thread here (especially the last sentence in my reply to which you posted your question) and can provide a lot more information. What is this "subthreshold factor" you refer to? Which simulator and device models are you using? Which version of the tools are you using? Please provide a reference for any equation you might mention.

  • Arefinn
    in reply to Andrew Beckett

    

    and I am using the kit GPDK090

Reply
  • Arefinn
    in reply to Andrew Beckett

    

    and I am using the kit GPDK090

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