[comp.lsi] MOSIS Spice parameters

smb@MIMSY.UMD.EDU (Steve M. Burinsky) (09/11/87)

If I'm not mistaken, the way MOSIS derives Spice parameters for a
given run is to adjust various model parameters to fit parametric
curves from devices on the test structures.  Thus, the parameters
they distribute may have very little in common with those of the
actual devices on a given run -- they just happen to produce similar
parametric curves.

daasch@psueea.UUCP (Robert Daasch) (09/14/87)

In article <8709102152.AA05876@mimsy.umd.edu> smb@MIMSY.UMD.EDU (St
>given run is to adjust various model parameters to fit parametric
>curves from devices on the test structures.  Thus, the parameters
>they distribute may have very little in common with those of the
>actual devices on a given run -- they just happen to produce similar
>parametric curves.

Agreed with a but...

It mystifies me how any parametric fit to test structures would
produce counter intuitive results.  Generally it is intuition from
the physics of the device that bounds the fitting procedure.  So
when I see the p device with a VT0 > 0 and junction depths several
orders of magnitude out of whack, I don't use that set of device
parameters.

Maybe the fitting utility doesn't write out a model deck and MOSIS
people play rock, paper and scissors for "who TYPES in the models 
this week."

Rob D.
..!tektronix!psueea!daasch.uucp

P.S. He says sheepishly, a couple runs we did do weren't completely
bogus.