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DIFFUSE
ATHENA User’s Manual
C.IMPURITIES specifies concentration of the impurities in the ambient gas. (see Section 6.2.10:
“Standard Impurities” for the list of impurity names that can be used, e.g. I.BORON). Units are
atoms/cm3. You can define multiple impurity parameters for ambients with multiple impurities. You
can only use boron, phosphorus and arsenic if you specify the advanced diffusion model (PLS) in the
METHOD statement.
Parameters Related to File Output
DUMP and DUMP.PREFIX specify that a structure file be output at every DUMPth time step. The
files are readable with the STRUCTURE statement or can be displayed using TONYPLOT. The names will
be of the form DUMP.PREFIX<time>.str, where <time> is the current total time of the simulation in
minutes.
TSAVE and TSAVE.MULT specify that intermediate structure files be output when the advanced
PLS diffusion model is used. The structure files named DUMP.PREFIX<time>.str will be output
at time = TSAVE * TSAVE.MULTk, k=0,1,2,... where time is in seconds. The default value for the
parameter DUMP.PREFIX is “at”. The parameter TSAVE.MULT should be greater than 1.0.
Parameters Related to the Model Files for Advanced Diffusion Models
B.MOD, P.MOD, AS.MOD, IC.MOD, and VI.MOD specify direct paths to boron.mod,
phosphorus.mod, arsenic.mod, i.mod, and defect.mod files correspondingly. By default,
these files are in $SILVACO/lib/athena/<version_number>/common/pls directory. You can modify
your own *.mod files inside directories specified by these parameters.
Miscellaneous Parameters
NO.DIFF specifies that impurity diffusion be neglected during the calculation. This can be used to
observe oxidation or silicidation geometry without unnecessary timesteps related to impurity diffusion
REFLOW specifies that a surface tension based reflow of the material is to be performed during the
diffusion step.
Predeposition Example
The following statement specifies a 1000°, 30 minute boron pre-deposition.
DIFFUSE TIME=30 TEMP=1000 C.BORON=1.0E20
Oxidation Example
The following statement instructs the simulator to grow oxide for 30 minutes in a dry oxygen ambient.
DIFFUSE TIME=30 TEMP=1000 DRYO2
Gas Flow Example
The following command performs diffusion with a mixed ambient with relative components of oxygen,
hydrogen, and HC1 of 10, 10, and 0.1 respectively.
DIFFUSE TIME=10 TEMP=1000
F.02=10 F.H2=10 F.HCl=.1
Hydrogen and Oxygen are combined in a ratio 2:1 to form the ambient WETO2. Any excess hydrogen
is considered inert. Any excess oxygen is considered as the ambient DRYO2. Since the total pressure of
the gas flow is defined (or defaults to one atmosphere) the partial pressure of WETO2 will be reduced
if any excess hydrogen or oxygen is present.
File Output Example
The following commands perform diffusion in dry oxygen ambient for 30 minutes at 1000 oC. After
every second timestep a structure file is written with a name prefix TEST. Following the diffusion, the
TONYPLOT statement plots each timestep output file in a manner suitable for creating a diffusion movie.
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