Monte Carlo simulation for device mismatch

This seems a rather artificial thing to do. If you have statistical models available, you can just run with mismatch. Otherwise I suggest you start by looking at this good overview: 

There's nothing in IC5141 ADE to allow you to apply mismatch to only selected instances. That is available in IC61X though in ADE XL.

Regards,

Andrew.

Thanks Andrew.

I have wrote code for statistical blocks.

Now I have to create threshold difference between two inverters. So, I thought that it would be better to do Montecarlo for a specific PMOS. 

Montecarlo is working fine. But I dont know how to select specific device in montecarlo. I am using IC5.1 version.

Is there any alternative way is there to create a threshold difference between two inverter?

If you've set up the code for statistical blocks, particularly the mismatch variation, and have models which are in subckts (following the document I told you about), then each device will have different random parameters and so you should then get a mismatch in the Vt (if it's the Vt that your random parameters are affecting) between the devices. You don't need to run monte carlo on just one device - they both will get random values according to the distribution which will differ from each other in some random way.

So this should create a threshold difference.

Regards,

Andrew.

Thanks Andrew..

parameters tox=4.1e-9
parameters vth0 = 0.3662473

statistics
{
process
{

vary tox dist=gauss std=0.09
vary vth0 dist=gauss std=0.09

}
mismatch
{

vary tox dist=gauss std=0.09
vary vth0 dist=gauss std=0.09

}

This is the piece of code I written. I am very new to Monte carlo simulation. Can you please suggest what all the modification I need to do in the code to get the mismatch variation.

// T58F SPICE BSIM3 VERSION 3.1 PARAMETERS
//
// SPICE 3f5 Level 8, Star-HSPICE Level 49, UTMOST Level 8
//
// DATE: Oct 31/05
// LOT: T58F WAF: 9005
// Temperature_parameters=Default

model cmosn bsim3v3 type=n
+version = 3.1 tnom = 27 tox = 4.1e-9
+xj = 1e-7 nch = 2.3549e17 vth0 = 0.3662473
+k1 = 0.5864999 k2 = 1.127266e-3 k3 = 1e-3
+k3b = 0.0294061 w0 = 1e-7 nlx = 1.630684e-7
+dvt0w = 0 dvt1w = 0 dvt2w = 0
+dvt0 = 1.2064649 dvt1 = 0.4215486 dvt2 = 0.0197749
+u0 = 273.8094484 ua = -1.40499e-9 ub = 2.408323e-18
+uc = 6.504826e-11 vsat = 1.355009e5 a0 = 2
+ags = 0.4449958 b0 = 1.901075e-7 b1 = 4.99995e-6
+keta = -0.0164863 a1 = 3.868769e-4 a2 = 0.4640272
+rdsw = 123.3376355 prwg = 0.5 prwb = -0.197728
+wr = 1 wint = 0 lint = 1.690044e-8
+xl = 0 xw = -1e-8 dwg = -4.728719e-9
+dwb = -2.452411e-9 voff = -0.0948017 nfactor = 2.1860065
+cit = 0 cdsc = 2.4e-4 cdscd = 0
+cdscb = 0 eta0 = 2.230928e-3 etab = 6.028975e-5
+dsub = 0.0145467 pclm = 1.3822069 pdiblc1 = 0.1762787
+pdiblc2 = 1.66653e-3 pdiblcb = -0.1 drout = 0.7694691
+pscbe1 = 8.91287e9 pscbe2 = 7.349607e-9 pvag = 1.685917e-3
+delta = 0.01 rsh = 6.7 mobmod = 1
+prt = 0 ute = -1.5 kt1 = -0.11
+kt1l = 0 kt2 = 0.022 ua1 = 4.31e-9
+ub1 = -7.61e-18 uc1 = -5.6e-11 at = 3.3e4
+wl = 0 wln = 1 ww = 0
+wwn = 1 wwl = 0 ll = 0
+lln = 1 lw = 0 lwn = 1
+lwl = 0 capmod = 2 xpart = 0.5
+cgdo = 8.23e-10 cgso = 8.23e-10 cgbo = 1e-12
+cj = 9.466429e-4 pb = 0.8 mj = 0.3820266
+cjsw = 2.608154e-10 pbsw = 0.8 mjsw = 0.102322
+cjswg = 3.3e-10 pbswg = 0.8 mjswg = 0.102322
+cf = 0 pvth0 = -2.199373e-3 prdsw = -0.9368961
+pk2 = 1.593254e-3 wketa = -2.880976e-3 lketa = 7.165078e-3
+pu0 = 6.777519 pua = 5.505418e-12 pub = 8.84133e-25
+pvsat = 2.006286e3 peta0 = 1.003159e-4 pketa = -6.759277e-3
+noimod=2.0e+00 noia=1.3182567385564e+19
+noib=144543.977074592 noic=-1.24515784572817e-12 ef=0.92 em=41000000
// *
// *
// * flicker noise parameters above added manually from some other process
// *
model cmosp bsim3v3 type=p
+version = 3.1 tnom = 27 tox = 4.1e-9
+xj = 1e-7 nch = 4.1589e17 vth0 = -0.3906012
+k1 = 0.5341312 k2 = 0.0395326 k3 = 0
+k3b = 7.4916211 w0 = 1e-6 nlx = 1.194072e-7
+dvt0w = 0 dvt1w = 0 dvt2w = 0
+dvt0 = 0.5060555 dvt1 = 0.2423835 dvt2 = 0.1
+u0 = 115.6894042 ua = 1.573746e-9 ub = 1.874308e-21
+uc = -1e-10 vsat = 1.130982e5 a0 = 1.9976555
+ags = 0.4186945 b0 = 1.949178e-7 b1 = 6.422908e-7
+keta = 0.0166345 a1 = 0.4749146 a2 = 0.300003
+rdsw = 198.321294 prwg = 0.5 prwb = -0.4986647
+wr = 1 wint = 0 lint = 2.94454e-8
+xl = 0 xw = -1e-8 dwg = -2.798724e-8
+dwb = -4.83797e-10 voff = -0.095236 nfactor = 2
+cit = 0 cdsc = 2.4e-4 cdscd = 0
+cdscb = 0 eta0 = 1.035504e-3 etab = -4.358398e-4
+dsub = 1.816555e-3 pclm = 1.3299898 pdiblc1 = 1.766563e-3
+pdiblc2 = 7.728395e-7 pdiblcb = -1e-3 drout = 1.011891e-3
+pscbe1 = 4.872184e10 pscbe2 = 5e-10 pvag = 0.0209921
+delta = 0.01 rsh = 7.7 mobmod = 1
+prt = 0 ute = -1.5 kt1 = -0.11
+kt1l = 0 kt2 = 0.022 ua1 = 4.31e-9
+ub1 = -7.61e-18 uc1 = -5.6e-11 at = 3.3e4
+wl = 0 wln = 1 ww = 0
+wwn = 1 wwl = 0 ll = 0
+lln = 1 lw = 0 lwn = 1
+lwl = 0 capmod = 2 xpart = 0.5
+cgdo = 6.35e-10 cgso = 6.35e-10 cgbo = 1e-12
+cj = 1.144521e-3 pb = 0.8468686 mj = 0.4099522
+cjsw = 2.490749e-10 pbsw = 0.8769118 mjsw = 0.3478565
+cjswg = 4.22e-10 pbswg = 0.8769118 mjswg = 0.3478565
+cf = 0 pvth0 = 2.302018e-3 prdsw = 9.0575312
+pk2 = 1.821914e-3 wketa = 0.0222457 lketa = -1.495872e-3
+pu0 = -1.5580645 pua = -6.36889e-11 pub = 1e-21
+pvsat = 49.8420442 peta0 = 2.827793e-5 pketa = -2.536564e-3
+ noimod=2.0e+00 noia=3.57456993317604e+18 noib=2500
+ noic=2.61260020285845e-11 ef=1.1388 em=41000000
// *
// *
// * flicker noise parameters above added manually from some other process// *

parameters vth0=0.3662473
parameters dvt0=1.2064649

statistics
{
process
{
vary vth0 dist=gauss std=9 percent=yes
vary dvt0 dist=gauss std=9 percent=yes

}
mismatch
{

vary dvt0 dist=gauss std=9 percent=yes
vary vth0 dist=gauss std=9 percent=yes

}
}
subckt NMOS_VTL (a b c d)
parameters w=350e-9 l=180e-9

M7 (a b c d) cmosn w=w l=l dvt0=0.5060555 vth0=0.3662473
end NMOS_VTL

This is the code which I have written.

Is this correct?

I am getting same output for all runs..

please suggest me as I am new to perform monte carlo simulation

That won't work, because for mismatch to work you have to have parameterised models within the subckt - and in this case you are instantiating cmosn and trying to pass model parameters to the instance of cmosn. vth0 and dvt0 are model parameters, not instance parameters.

You'd need to use something like:

subckt NMOS_VTL (D G S B)
parameters w=350e-9 l=180e-9

M7 (D G S B) cmosn w=w l=l 

model cmosn bsim3v3 type=n ...
+ vth0=vth0 dvt0=dvt0 
+ // other parameters
ends NMOS_VTL

in other words, put the model inside the subckt, and parameterize the model definition with the global parameters you've specified as having distributions.

This is covered in the monte carlo modelling guide that I referred to earlier in this thread.

Regards,

Andrew.

Thanks Andrew for your reply.

May I know how to find out the threshold voltage for each MOS after running Montecarlo simulation?

With regards,

Dinesh

model cmosn bsim3v3 type=n
+version = 3.1 tnom = 27 tox = 4.1e-9
+xj = 1e-7 nch = 2.3549e17 vth0 = 0.3662473
+k1 = 0.5864999 k2 = 1.127266e-3 k3 = 1e-3
+k3b = 0.0294061 w0 = 1e-7 nlx = 1.630684e-7
+dvt0w = 0 dvt1w = 0 dvt2w = 0
+dvt0 = 1.2064649 dvt1 = 0.4215486 dvt2 = 0.0197749
+u0 = 273.8094484 ua = -1.40499e-9 ub = 2.408323e-18
+uc = 6.504826e-11 vsat = 1.355009e5 a0 = 2
+ags = 0.4449958 b0 = 1.901075e-7 b1 = 4.99995e-6
+keta = -0.0164863 a1 = 3.868769e-4 a2 = 0.4640272
+rdsw = 123.3376355 prwg = 0.5 prwb = -0.197728
+wr = 1 wint = 0 lint = 1.690044e-8
+xl = 0 xw = -1e-8 dwg = -4.728719e-9
+dwb = -2.452411e-9 voff = -0.0948017 nfactor = 2.1860065
+cit = 0 cdsc = 2.4e-4 cdscd = 0
+cdscb = 0 eta0 = 2.230928e-3 etab = 6.028975e-5
+dsub = 0.0145467 pclm = 1.3822069 pdiblc1 = 0.1762787
+pdiblc2 = 1.66653e-3 pdiblcb = -0.1 drout = 0.7694691
+pscbe1 = 8.91287e9 pscbe2 = 7.349607e-9 pvag = 1.685917e-3
+delta = 0.01 rsh = 6.7 mobmod = 1
+prt = 0 ute = -1.5 kt1 = -0.11
+kt1l = 0 kt2 = 0.022 ua1 = 4.31e-9
+ub1 = -7.61e-18 uc1 = -5.6e-11 at = 3.3e4
+wl = 0 wln = 1 ww = 0
+wwn = 1 wwl = 0 ll = 0
+lln = 1 lw = 0 lwn = 1
+lwl = 0 capmod = 2 xpart = 0.5
+cgdo = 8.23e-10 cgso = 8.23e-10 cgbo = 1e-12
+cj = 9.466429e-4 pb = 0.8 mj = 0.3820266
+cjsw = 2.608154e-10 pbsw = 0.8 mjsw = 0.102322
+cjswg = 3.3e-10 pbswg = 0.8 mjswg = 0.102322
+cf = 0 pvth0 = -2.199373e-3 prdsw = -0.9368961
+pk2 = 1.593254e-3 wketa = -2.880976e-3 lketa = 7.165078e-3
+pu0 = 6.777519 pua = 5.505418e-12 pub = 8.84133e-25
+pvsat = 2.006286e3 peta0 = 1.003159e-4 pketa = -6.759277e-3
+noimod=2.0e+00 noia=1.3182567385564e+19
+noib=144543.977074592 noic=-1.24515784572817e-12 ef=0.92 em=41000000
// *
// *
// * flicker noise parameters above added manually from some other process
// *
model cmosp bsim3v3 type=p
+version = 3.1 tnom = 27 tox = 4.1e-9
+xj = 1e-7 nch = 4.1589e17 vth0 = -0.3906012
+k1 = 0.5341312 k2 = 0.0395326 k3 = 0
+k3b = 7.4916211 w0 = 1e-6 nlx = 1.194072e-7
+dvt0w = 0 dvt1w = 0 dvt2w = 0
+dvt0 = 0.5060555 dvt1 = 0.2423835 dvt2 = 0.1
+u0 = 115.6894042 ua = 1.573746e-9 ub = 1.874308e-21
+uc = -1e-10 vsat = 1.130982e5 a0 = 1.9976555
+ags = 0.4186945 b0 = 1.949178e-7 b1 = 6.422908e-7
+keta = 0.0166345 a1 = 0.4749146 a2 = 0.300003
+rdsw = 198.321294 prwg = 0.5 prwb = -0.4986647
+wr = 1 wint = 0 lint = 2.94454e-8
+xl = 0 xw = -1e-8 dwg = -2.798724e-8
+dwb = -4.83797e-10 voff = -0.095236 nfactor = 2
+cit = 0 cdsc = 2.4e-4 cdscd = 0
+cdscb = 0 eta0 = 1.035504e-3 etab = -4.358398e-4
+dsub = 1.816555e-3 pclm = 1.3299898 pdiblc1 = 1.766563e-3
+pdiblc2 = 7.728395e-7 pdiblcb = -1e-3 drout = 1.011891e-3
+pscbe1 = 4.872184e10 pscbe2 = 5e-10 pvag = 0.0209921
+delta = 0.01 rsh = 7.7 mobmod = 1
+prt = 0 ute = -1.5 kt1 = -0.11
+kt1l = 0 kt2 = 0.022 ua1 = 4.31e-9
+ub1 = -7.61e-18 uc1 = -5.6e-11 at = 3.3e4
+wl = 0 wln = 1 ww = 0
+wwn = 1 wwl = 0 ll = 0
+lln = 1 lw = 0 lwn = 1
+lwl = 0 capmod = 2 xpart = 0.5
+cgdo = 6.35e-10 cgso = 6.35e-10 cgbo = 1e-12
+cj = 1.144521e-3 pb = 0.8468686 mj = 0.4099522
+cjsw = 2.490749e-10 pbsw = 0.8769118 mjsw = 0.3478565
+cjswg = 4.22e-10 pbswg = 0.8769118 mjswg = 0.3478565
+cf = 0 pvth0 = 2.302018e-3 prdsw = 9.0575312
+pk2 = 1.821914e-3 wketa = 0.0222457 lketa = -1.495872e-3
+pu0 = -1.5580645 pua = -6.36889e-11 pub = 1e-21
+pvsat = 49.8420442 peta0 = 2.827793e-5 pketa = -2.536564e-3
+ noimod=2.0e+00 noia=3.57456993317604e+18 noib=2500
+ noic=2.61260020285845e-11 ef=1.1388 em=41000000
// *
// *
// * flicker noise parameters above added manually from some other process// *

simulator lang=spectre

parameters vth0=0.3662473
parameters dvt0=1.2064649

statistics
{
process
{
vary dvt0 dist=gauss std=9 percent=yes

}
mismatch
{

vary dvt0 dist=gauss std=100 percent=yes

}
}
inline subckt NFET (D G S B)
parameters w=350e-9 l=180e-9
NFET (D G S B) cmosn w=w l=l vth0 =0.5+ dvt0/sqrt(l*w)
model cmosn bsim3v3 type=n
+vth0 =vth0 dvt0 = dvt0
+tnom = 27 tox = 4.1e-9
+xj = 1e-7 nch = 2.3549e17
+k1 = 0.5864999 k2 = 1.127266e-3 k3 = 1e-3
+k3b = 0.0294061 w0 = 1e-7 nlx = 1.630684e-7
+dvt0w = 0 dvt1w = 0 dvt2w = 0
+ dvt1 = 0.4215486 dvt2 = 0.0197749
+u0 = 273.8094484 ua = -1.40499e-9 ub = 2.408323e-18
+uc = 6.504826e-11 vsat = 1.355009e5 a0 = 2
+ags = 0.4449958 b0 = 1.901075e-7 b1 = 4.99995e-6
+keta = -0.0164863 a1 = 3.868769e-4 a2 = 0.4640272
+rdsw = 123.3376355 prwg = 0.5 prwb = -0.197728
+wr = 1 wint = 0 lint = 1.690044e-8
+xl = 0 xw = -1e-8 dwg = -4.728719e-9
+dwb = -2.452411e-9 voff = -0.0948017 nfactor = 2.1860065
+cit = 0 cdsc = 2.4e-4 cdscd = 0
+cdscb = 0 eta0 = 2.230928e-3 etab = 6.028975e-5
+dsub = 0.0145467 pclm = 1.3822069 pdiblc1 = 0.1762787
+pdiblc2 = 1.66653e-3 pdiblcb = -0.1 drout = 0.7694691
+pscbe1 = 8.91287e9 pscbe2 = 7.349607e-9 pvag = 1.685917e-3
+delta = 0.01 rsh = 6.7 mobmod = 1
+prt = 0 ute = -1.5 kt1 = -0.11
+kt1l = 0 kt2 = 0.022 ua1 = 4.31e-9
+ub1 = -7.61e-18 uc1 = -5.6e-11 at = 3.3e4
+wl = 0 wln = 1 ww = 0
+wwn = 1 wwl = 0 ll = 0
+lln = 1 lw = 0 lwn = 1
+lwl = 0 capmod = 2 xpart = 0.5
+cgdo = 8.23e-10 cgso = 8.23e-10 cgbo = 1e-12
+cj = 9.466429e-4 pb = 0.8 mj = 0.3820266
+cjsw = 2.608154e-10 pbsw = 0.8 mjsw = 0.102322
+cjswg = 3.3e-10 pbswg = 0.8 mjswg = 0.102322
+cf = 0 pvth0 = -2.199373e-3 prdsw = -0.9368961
+pk2 = 1.593254e-3 wketa = -2.880976e-3 lketa = 7.165078e-3
+pu0 = 6.777519 pua = 5.505418e-12 pub = 8.84133e-25
+pvsat = 2.006286e3 peta0 = 1.003159e-4 pketa = -6.759277e-3
+noimod=2.0e+00 noia=1.3182567385564e+19
+noib=144543.977074592 noic=-1.24515784572817e-12 ef=0.92 em=41000000
ends NFET Hi andrew.. This is the spectre code I modified.. When I run this code I am still not getting any variation.. Pls help me..

Hi Andrew, In the file which you have referred they modelled montecarlo using resistors. In the prosess paprameters they have declared mismatch parameter. I am trying to find out the mismatch parameter for the transistor. Can you pls provide a sample code to vary threshold voltage of invereters so that We can follow the same..

Hi, Can you please tell me what is meant by instance parameter?