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CFD-ACE+ and CFD-TOPO Coupling Print E-mail

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.

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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.


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.

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Figure 2. Reading the output from CFD-ACE+

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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.

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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.

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Figure 5. Reactor model result: contour plot of electron density and power deposition

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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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