# [Moved from ASIC Design]: How to solve Convergence Problem in SILVACO TCAD?

1. ## [Moved from ASIC Design]: How to solve Convergence Problem in SILVACO TCAD?

I am simulating a circuit using devices designed using SILVACO ATLAS in Mixed Mode. Now, there is no convergence error while finding IV Characteristics of the designed device but when I'm using that particular device in a circuit, on simulation is giving me a message in the Command Bar which states

Code:
```Warning: Not A Numbers found in currents.
Simulator did not converge.

Error: No solution possible!
Try smaller bias step```
I have checked my structure and mesh and have made every other alteration in the mesh and have also changed the bias step but is still giving me the same Warning and Error.

Is there any other alternate approach to solving this problem apart from changing the mesh and bias step?

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3. ## Re: [Moved from ASIC Design]: How to solve Convergence Problem in SILVACO TCAD?

Sure, here is my input deck:

Code:
```go atlas
#
mesh outf=NFeFET.str master.out
#
x.m loc=0.0 spacing=0.1
x.m loc=0.25 spacing=0.1
x.m loc=0.5 spacing=0.1
x.m loc=4.5 spacing=0.1
x.m loc=4.75 spacing=0.1
x.m loc=5.0 spac=1.0
#
y.m loc=-0.2 spacing=0.2
y.m loc=0.0 spacing=0.2
y.m loc=5.0 spac=1.0
#
#
region num=1 silicon y.min=0.0
region num=2 oxide y.max=0.0
#
electrode num=3 top x.min=0.5 x.max=4.5 name=gate material=n.poly
electrode num=4 bottom name=sub
electrode num=1 x.max=0.25 y.max=0.0 name=source
electrode num=2 x.min=4.75 y.max=0.0 name=drain
#
doping conc=1e15 uniform p.type
doping gaus conc=1e19 n.type junction=0.4 x.max=0.5 ratio=0.1
doping gaus conc=1e19 n.type junction=0.4 x.min=4.5 ratio=0.1
#
models region=2 ferro
material region=2 ferro.ec=20e3 ferro.pr=0.08e-6 ferro.ps=0.1e-6 ferro.epsf=92
#

go atlas
#
mesh outf=PFeFET.str
#
x.m loc=0.0 spacing=0.1
x.m loc=0.25 spacing=0.1
x.m loc=0.5 spacing=0.1
x.m loc=4.5 spacing=0.1
x.m loc=4.75 spacing=0.1
x.m loc=5.0 spac=1.0
#
y.m loc=-0.2 spacing=0.2
y.m loc=0.0 spacing=0.2
y.m loc=5.0 spac=1.0
#
#
region num=1 silicon y.min=0.0
region num=2 oxide y.max=0.0
#
electrode num=3 top x.min=0.5 x.max=4.5 name=gate material=n.poly
electrode num=4 bottom name=sub
electrode num=1 x.max=0.25 y.max=0.0 name=source
electrode num=2 x.min=4.75 y.max=0.0 name=drain
#
doping conc=1e15 uniform n.type
doping gaus conc=1e19 p.type junction=0.4 x.max=0.5 ratio=0.1
doping gaus conc=1e19 p.type junction=0.4 x.min=4.5 ratio=0.1
#
models region=2 ferro
material region=2 ferro.ec=20e3 ferro.pr=0.08e-6 ferro.ps=0.1e-6 ferro.epsf=92
#

go atlas
.begin
#
# DC Point Simulation
#
va 2 0 0
ap 3=drain 2=gate 1=source 1=sub infile=PFeFET.str width=12.
an 3=drain 2=gate 0=source 0=sub infile=NFeFET.str width=8.
vdd 1 0 2.

.nodeset v(2)=0 v(1)=0

.numeric vchange=1.
.options print m2ln noshift

.save outfile=F1_Combo
.end

contact device=ap name=gate n.poly
model device=ap region=2 ferro
material region=2 ferro.ec=20e3 ferro.pr=0.08e-6 ferro.ps=0.1e-6 ferro.epsf=92

contact device=an name=gate n.poly
model device=an region=2 ferro
material region=2 ferro.ec=20e3 ferro.pr=0.08e-6 ferro.ps=0.1e-6 ferro.epsf=92

quit```

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4. ## Re: [Moved from ASIC Design]: How to solve Convergence Problem in SILVACO TCAD?

same problem,seeking for help

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