A hybrid kinetic Monte Carlo method for simulating silicon films grown by plasma-enhanced chemical vapor deposition

We present a powerful kinetic Monte Carlo (KMC) algorithm that allows one to simulate the growth of nanocrystalline silicon by plasma enhanced chemical vapor deposition (PECVD) for film thicknesses as large as several hundreds of monolayers. Our method combines a standard n-fold KMC algorithm with an efficient Markovian random walk scheme accounting for the surface diffusive processes of the species involved in PECVD. These processes are extremely fast compared to chemical reactions, thus in a brute application of the KMC method more than 99% of the computational time is spent in monitoring them. Our method decouples the treatment of these events from the rest of the reactions in a systematic way, thereby dramatically increasing the efficiency of the corresponding KMC algorithm. It is also making use of a very rich kinetic model which includes 5 species (H, SiH3, SiH2, SiH, and Si 2H5) that participate in 29 reactions. We have applied the new method in simulations of silicon growth under several conditions (in particular, silane fraction in the gas mixture), including those usually realized in actual PECVD technologies. This has allowed us to directly compare against available experimental data for the growth rate, the mesoscale morphology, and the chemical composition of the deposited film as a function of dilution ratio.open1

Comparative study of plasma-deposited fluorocarbon coatings on different substrates

International audienceThe deposition of hydrophobic fluorocarbon coatings from C 2 F 6 and C 2 F 6 -H 2 rf discharges on different substrates was examined. Polyester textile, glass and two different ceramic compounds were used as substrates. The effect of the total gas pressure, the rf power dissipation and the deposition time on the hydrophobic character of the samples was investigated. Films deposited on polyester textiles at low pressure (0.03 mbar) and power consumption (16 mW/cm 2) using pure C 2 F 6 presented the highest water contact angles (~150 o). On the other hand, the addition of hydrogen was necessary in order to deposit stable hydrophobic coatings on glass and ceramic substrates. Coatings deposited on glass at intermediate deposition rates (~100 Å/min) and pressures presented the highest angles (~105 o). Concerning the heavy clay ceramics, samples treated in low pressure (0.05 mbar) and low power (16 mW/cm 2) discharges showed the highest contact angles The deposition time was found to play an important role on the hydrophobicity and long term behavior of porous and rough substrates

Simulation of cylindrical electron cyclotron wave resonance argon discharges

International audienceA fluid model of a cylindrical electron cyclotron wave resonance (ECWR) Argon discharge is presented. The results for a 1 mTorr Argon discharge were checked against the analytical theory, simulation and experimental data. The basic plasma properties as power dissipation, magnetic field, electric potential, electron density and temperature were very well reproduced by using pre-defined boundary conditions for the magnetic potential. The results of this model were further used as inputs for the simulation of plasma expansion into a diffusion region, allowing thus fast and complete modeling of a typical ECWR plasma reactor