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There is a growing demand and challenge in different
industries, especially semiconductor and MEMS areas,
to have increased wafer size with reduced feature
size, i.e. high quality process uniformity.
Therefore, it is extremely important to investigate
the multiphysics phenomena on a global scale as well
as to predict accurately the feature evolution based
on a wide range of processes in semiconductor and
MEMS industries.
Most of you are familiar with CFD-ACE+, which is a
powerful modeling tool to simulate a process in a
true multiphysics environment. Some important
applications in the semiconductor industries are
Physical Vapor Deposition (PVD), Chemical Vapor
Deposition (CVD), Plasma Enhanced Chemical Vapor
Deposition (PECVD), Plasma Enhanced Etching,
Sputtering etc. Using CFD-ACE+, one can accurately
model processes involving fluid flow, heat transfer,
species transport, including volume and surface
reactions (depositions and/or etching),
electromagnetism and Plasma.
CFD-TOPO, is a powerful feature scale simulation tool
which predicts 2D and 3D shape evolution due to the
combined effects of chemical species transport and
surface reactions at the gas-solid interface. Since
the shape and orientation of the gas-solid interface
affects the transport of reactants, this prediction
requires the transient solution of a moving interface
problem, the reactant transport, and the balance
between local species fluxes and reaction rates. The
modeling tool can be widely applicable to predict the
effects of depositing into, or etching from,
relatively small topographical features by gas phase
processes.
CFD-TOPO can be an independent modeling tool where
you need to specify the input flux information. Also,
CFD-TOPO can be coupled with a reactor scale model
(CFD-ACE+) to generate the flux information as an
input for CFD-TOPO. Below is the description of
generating the TOPO inputs for fluxes from CFD-ACE+.
The model is for SiO2 deposition in an Inductively
Coupled Plasma reactor with biased wafer chuck,
feature model of resulting trench fill.
CFD-ACE+ Setup
STEP 1: Figure 1 shows CFD-ACE-GUI
for a PECVD simulation for SiO2 deposition. Under
"Out" tab, check "Feature Scale Coupling" box and use
feature model as "CFD-TOPO". Click on "Specify
Coupling Points ..", it will pop up a window where
you need to specify the coordinate points: TOPO
format output causes CFD-ACE+ to generate text files
with species flux data at specified locations (where
surface reactions occur). Flux data will be written
on each solution output.
TIP: Points you choose have to be on the surface
where the surface reaction of your interest
(deposition/etching) occurs.
Figure 1. Specifying the output from CFD-ACE+ to
be used in CFD-TOPO
STEP 2: This step is optional step.
Applying sheath model at boundary causes CFD-ACE+ to
generate text files with ion energy and angular
distributions for CFD-TOPO use. You can activate the
Sheath Model under the BC -> Plasma tab for the
reacting surface.
After the other standard problem settings, you are
ready to run the CFD-ACE+ model. After the simulation
is over, it will generate several input files to be
used in CFD-TOPO.
CFD-TOPO Setup:
STEP 1: Under 'MO" -> "Shared"
tab, check "Read From Ace" box and enter name of
*.FSC file (you can browse it). The *.FSC file is
generated by CFD-ACE+.
In "MO" -> "Chem" tab, click 'Import Feature
Temperature' to update value to that of the sampled
point in the reactor model.
Figure 2. Reading the output from
CFD-ACE+
Figure 3. Importing the feature temperature
STEP 2: Click 'Import Flux Data' to
update values to those at the sampled point in the
reactor model.
Figure 4. Importing flux data into CFD-TOPO
After the other standard problem settings, you are
ready to run the CFD-TOPO model. Results of the
reactor scale simulation and the feature scale
simulation are shown in Figure 5 and 6.
Figure 5. Reactor model result: contour plot of
electron density and power deposition
Figure 6. Feature model result: Effects of
reactor power on feature: at 1000 W, deposition is
limited by SiH2 flux resulting a void formation.
We welcome your discussion and comments about this
note on the ESI CFD
Community forum. A topic has already been started
and you can
find it here. [Access available only to
customers under a current support contract.]
Abhra Roy
Senior Applications Engineer
ESI CFD Customer Support
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