Bologna / 06_TCAD_laboratory_MOSFET_GBB_20150223H1655

Sdevice turn_on_des.cmd (4)

Math

{

*use previous two solutions (if any) to extrapolate next Extrapolate

*use full derivatives in Newton method

Derivatives

*control on relative and absolute errors -RelErrControl

*relative error= 10^(-Digits)

Digits=5

*absolute error Error(electron)=1e8 Error(hole)=1e8

*numerical parameter for space-charge regions eDrForceRefDens=1e10

hDrForceRefDens=1e10

*maximum number of iteration at each step Iterations=20

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Sdevice turn_on_des.cmd (5)

*solver of the linear system Method=ParDiSo

*display simulation time in 'human' units Wallclock

*display max.error information CNormPrint

*to avoid convergence problem when simulating defect-assisted tunneling NoSRHperPotential

}

Solve

{

* EQUILIBRIUM coupled {poisson}

*TURN-ON

*increasing VDS to goal

quasistationary (InitialStep = 0.010 MaxStep = 0.050 MinStep=0.001 Goal {name= "drain" voltage = @vds_fixed@}

plot { range=(0, 1) intervals=1 }

)

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Sdevice turn_on_des.cmd (6)

{coupled {poisson electron hole} }

* increasing VGS to goal

quasistationary (InitialStep = 0.010 MaxStep = 0.050 MinStep=0.001

Goal {name= "gate" voltage = @vgs_goal@}

plot { range=(0, 1) intervals=1 }

)

{coupled {poisson electron hole} }

}

We have thus far written the turn_on_des.cmd file for simulation of the turn-on characteristics (first raise VDS, then sweep VGS).

•Since we have two instances of Sdevice we need to write another input file for the second tool.

Select right Sdevice image tool  Right Click  Edit input  Commands then write (copy) in the file the same commands as in the first command file at the exception of the Solve section that should be modified as follows in the next slide

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Sdevice output_des.cmd (1)

* previous part as turn_on_des.cmd Solve

{

* EQUILIBRIUM coupled {poisson}

*OUTPUT

*increasing VGS to goal

quasistationary (InitialStep = 0.010 MaxStep = 0.050 MinStep=0.001

Goal {name= "gate" voltage = @vgs_fixed@}

plot { range=(0, 1) intervals=1 }

)

{coupled {poisson electron hole} } * increasing VDS to goal

quasistationary (InitialStep = 0.010 MaxStep = 0.050 MinStep=0.001 Goal {name= "drain" voltage = @vds_goal@}

plot { range=(0, 1) intervals=1 }

)

{coupled {poisson electron hole} }

}

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Parameter file, Pre-processing and Run

•Since parameter file is the same for all Sdevice tools we need to write one single sdevice.par

•Write an empty parameter file to keep the parameter default values:

• Select left Sdevice image tool  Right Click  Edit input  Parameter  No  Save

 Quit

DONE SDevice PART

Pre-processing and Run:

Select SDE real nodes  CTRL-R  local:priority  Run

Select left Sdevice real nodes  CTRL-R  local:priority  Run Select right Sdevice real nodes  CTRL-R  local:priority  Run

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Post-processing: energy bands at equilibrium

• Right click on n2  Visualize  Svisual (Select File…)

•Select n2_000000_des  Ok

•Tools  Precision Cuts  Y  0  Plot Band Diagram

energy barrier for electrons to be overcome  apply positive

source

channel

drain

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Post-processing: energy bands at high

• Right click on n6  Visualize  Svisual (Select File…)

•Select n6_000001_des  Ok

•Tools  Precision Cuts  Y  0  Plot Band Diagram

energetic barrier is disappeared

= = 0

 equilibrium no net current flow

source

channel

drain

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Post-processing: electron concentration at high

•Window  Plot_1

•Scalars  eDensity

• Range  1e18 in the maximum value (=SubDop value) in order to see the inversion layer

•Zoom in in the channel region

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Post-processing: energy bands at high and high

• Right click on n2  Visualize  Svisual (Select File…)

•Select n2_000003_des  Ok

•Precision Cuts  Y  0  Plot Band Diagram

it is like an

“inclined plane” for electrons

≠ ≠ 0

current flow

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Post-processing: turn-on characteristics

•Right click on n2  Visualize  Inspect (All Files)

•Select n2_des on the Datasets part  gate  OuterVoltage  To X-Axis  drain  TotalCurrent  To Left-Y-Axis

•Then, select logY on the upper toolbar

•Double click on left Y-Axis  scale  min  1e-11

linscale		logscale

inverse slope ~ 80 mV/dec

~ 0.3 V
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