Modeling Nucleation of Nanoparticles in Fluorocarbon PlasmasMaren VanOtterloo, Advisors: Steven Girshick (ME) and Jeff Roberts (Chem) |
| Fluorocarbon plasmas
are commonly used as etchants in integrated circuit fabrication due to
selectivity and anisotropic capabilities. Nanoparticles have been observed
in these systems, both in the plasma and on surrounding surfaces, but
little is known about how the particles form. Ideally, particle formation
would be controllable leading towards elimination of particles where unwanted,
such as in IC fabrication, or towards deliberate particle production,
like in fabrication of a fluorocarbon nanoparticle composite for use as
a low-k material. However, without a fundamental understanding of how
these particles nucleate and grow, controllability is not possible. My
research involves developing a computational model that will predict gas-phase
nucleation in fluorocarbon plasma systems, accounting for particle production
via chemical reactions, and particle growth by coagulation and surface
reactions.
The model consists of four interconnected subroutines: base chemistry, plasma model, nucleation, and aerosol model, as illustrated below. The base chemistry model specifies the important species (neutral, ionized, and excited states) and corresponding thermochemical properties; the plasma model determines ion and electron densities and electron temperature. Chemical mechanisms to describe growth of CxFy clusters are modeled using the nucleation subroutine while surface reactions, coagulation, particle charging, and particle transport are all simulated in the aerosol model. Once completed, the model will predict the time evolution of species concentrations and determine the prevalent clustering pathways.
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