Home > Community > Forums > Custom IC Design > Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ?

Email

* Required Fields

Recipients email * (separate multiple addresses with commas)

Your name *

Your email *

Message *

Contact Us

* Required Fields
First Name *

Last Name *

Email *

Company / Institution *

Comments: *

 Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? 

Last post Wed, Sep 11 2013 10:04 AM by Alex Liao. 6 replies.
Started by Alex Liao 06 Sep 2013 03:33 PM. Topic has 6 replies and 642 views
Page 1 of 1 (7 items)
Sort Posts:
  • Fri, Sep 6 2013 3:33 PM

    • Alex Liao
    • Top 200 Contributor
    • Joined on Wed, May 22 2013
    • Posts 37
    • Points 575
    Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? Reply

    After any Spectre simulation, does U0 in model parameter field mean the low-field mobility of the very original one or the one infulenced by STI/WPE or any other issues? Simply put, ,

    This image gives the equation of u0 under STI's influence. Is the u0 in ADE Result => Print Model Parameter list reflecting U0ref (may be a constant) or U0(already consider STI influence). If the case is the former (the initial constant) and then U0( influenced by STI) is invisiable to user; if it is the latter(influenced by STI) and then U0(the initial constant) is invisiable.  How about the vth0? Does the simulation result reflect final vth0 considering any layout or other issues or only give default value which is used to compute effecitive vth0 via inner equation?

     

    Regards,

    Alex 

    • Post Points: 20
  • Mon, Sep 9 2013 1:21 AM

    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? Reply

    No, model parameters are model parameters; they are not affected by the instance's conditions.

    Andrew.

    • Post Points: 20
  • Tue, Sep 10 2013 11:20 AM

    • Alex Liao
    • Top 200 Contributor
    • Joined on Wed, May 22 2013
    • Posts 37
    • Points 575
    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? Reply

    Hi Andrew,

     

    If so, the model parameters keep unchanged. But those effects has to be reflected in certain way in real simulation. Which part has been changed under those effects from simulation perspective?

    Is my following understanding correct? All those layout dependent issues are considered in such way that they are reflected in electrical or performance-related indicators or parameters.  For example, the mobility affected by  STI are considered in calculation of Ids. The Ids in older technology which does not consider any STI is different from the Ids in modern advanced technology whcih does consider STI effect. This impact is physically reflected in the calculation of Ids in modern simulation. While all model parameters still keep the same.

    From simulation side, are there more ways to see or compare STI impact, any indicators?

     

    Regards,

    Alex. 

    • Post Points: 20
  • Wed, Sep 11 2013 1:04 AM

    • berndfi
    • Top 100 Contributor
    • Joined on Tue, Sep 11 2012
    • Neubiberg, Bavaria
    • Posts 66
    • Points 1,250
    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? Reply
    • Post Points: 20
  • Wed, Sep 11 2013 7:12 AM

    • Alex Liao
    • Top 200 Contributor
    • Joined on Wed, May 22 2013
    • Posts 37
    • Points 575
    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BISM4.5 model, Spectre7.2 ? Reply

    Hi Berndfi,

     I have reviewed the pdf file. From what I learned from this file, it seems the Cadence Assura activate the calculation of STI indicator, i.e., the result of SA,SB/SAref,SBref. However, in Virtuoso I can still measure that dimension. The STI impact is like this:

    Layout Geometry => SA/SB (reflective) => mobility/velocity/Vth (physical/electrical root reason) => Performance (gain/bandwidth/phase margin) observed after simulation. The only invisiable part seems to be the root reason part. Model parameters are there without any consideration of STI. But effecitive mobility/velocity/Vth does consider STI effect because this is recorded in manual or the pdf file you provide. Are those effecitive mobility/velocity/Vth  observerable or user-editable in Cadence environment or any other ADE tools?

    Regards,

    Alex 

    • Post Points: 20
  • Wed, Sep 11 2013 7:43 AM

    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BSIM4.5 model, Spectre7.2? Reply

    Alex,

    The device model equations manual describes how the equations work (although it has a few omissions here and there, and sometimes you need to look at the Berkeley site to get the full model equations).

    As I said before, you wouldn't expect to see effective information in the model parameters, because these are the input model parameters. You can however get a number of useful effective parameters for each instance by doing a dc operating point and then you'll get the "Operating Point Parameters". See "spectre -h bsim4" and you'll see there's a large number of parameters, including id, ids, vth, betaeff, gm. gds and many capacitances. I don't believe there's any output of effective mobility though.

    You should see the effect of STI in the performance/behaviour of the transistors - for example, the id variation in a current mirror caused by STI (as in Bernd's presentation).

    (BTW, I'm not sure why the email subject headers are ending up as gobbledegook - I'm guessing it's something to do with either the length of the subject line or the characters in it).

    Regards,

    Andrew.

    • Post Points: 20
  • Wed, Sep 11 2013 10:04 AM

    • Alex Liao
    • Top 200 Contributor
    • Joined on Wed, May 22 2013
    • Posts 37
    • Points 575
    Re: Does u0 and vth0 viewed in simulation result reflect default constant value or the ones already considering any Layout-dependent effects in such environment: tsmc65nm, BSIM4.5 model, Spectre7.2? Reply
    Thank you, Andrew. Now I understand that any impact of STI can only be observed through those 'Op-Parameters' or electrical indicators. Model parameters are standard and universe. Not any direct output of effective mobility or velocity available. Regards, Alex
    • Post Points: 5
Page 1 of 1 (7 items)
Sort Posts:
Started by Alex Liao at 06 Sep 2013 03:33 PM. Topic has 6 replies.