Standard deviation of threshold voltage

Hi,
I want to do the variability analysis on my design and hence I need sigma of vth and u0 (standard deviation of threshold voltage and mobility) for monte carlo simulations. I have the 90nm PDK as well, but I dont know where these values are written. Can you please tell me how to get these values?

[P.S: I can access PVT corners (fast, typical, slow) but I do not want to run worst case analysis. Rather I want to perform variability analysis].

If your foundry says anything about what corners represent,
you can probably fake some statistics. But foundries' WAT
limits vs capability vs model over-coverage is always an
internal negotiation and outcomes vary. Your WAT range
could be nominal +/- 3 sigma or could be +/- 5 sigma with
the models sandbagged to +/- 6 sigma.

Now going by simple WAT limits you will gain no insight to
correlation; this is important (Tox tracks 1:1 pretty much
between N and P; VT to a lesser extent, but somewhat).
If you were serious and funded, you might ask the foundry
for raw WAT dumps and crunch the correlations yourself.
I'd bet, however, that this material exists pre-chewed and
it's more a matter of getting to the right person and
convincing them you deserve the data.