Volume 87, Issue 3, 01 February 2000
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
87(2000); http://dx.doi.org/10.1063/1.371980View Description Hide Description
Plasma-surface interactions during plasma etching are important in that, in addition to determining the rate and quality of the etch, they can also influence the properties of the bulk plasma. To address this coupling of bulk and surface processes the surface kinetics model (SKM) was developed as a module in the two-dimensional hybridplasma equipment model (HPEM) with the goal of combining plasma chemistry and surface chemistry in a self-consistent fashion. The SKM obtains reactive fluxes to the surface from the HPEM, and generates the surface species coverages and the returning fluxes to the plasma by implementing a user defined surface reaction mechanism. Although the SKM is basically a surface-site-balance model, extensions to those algorithms have been made to include an overlying passivation layer through which reactants and products diffuse. Etching of Si in an inductively coupled plasma sustained in was investigated using the SKM. Results from parametric studies are used to demonstrate the sensitivity of etching rates and polymer thickness to the sticking coefficient of fluorocarbon radicals on the reactor walls, polymer erosion rates and F atom diffusion through the polymer layer.
87(2000); http://dx.doi.org/10.1063/1.371981View Description Hide Description
A two-dimensional hybrid model for an electron cyclotron resonance (ECR) plasma reactor is improved by taking into account the microwave absorption. With this code, the velocity and angle distribution function of ions in the source and downstream areas, and the ion current density at the substrate surface in an extended ECR plasma reactor were investigated. The spatial profiles as well as the dependence of these distribution functions on pressure and microwave power were discussed. It is shown that the results are in good agreement with many experimental measurements.
87(2000); http://dx.doi.org/10.1063/1.371982View Description Hide Description
Particle size and number density are measured versus discharge operating time (t) in pure silane, capacitively coupled rf discharges.Discharge conditions are those typically used to produce amorphous silicon devices, except the temperature is 300 K. Particle radii from 4 to 25 nm are observed, where is determined from the rate of particle diffusive loss in the plasma afterglow. The scattered light intensity then yields the particle number density. We generally observe a consistent with initial rapid growth to followed by a constant at a rate consistent with growth due to reactions. However, at higher pressures and film growth rates, or rf voltage, the particle growth rate exceeds that due to indicating additional growth mechanisms. Particle density increases orders of magnitude when pressure and rf voltage increase by small amounts. Measurement of the particle spatial distribution in the afterglow, when most particles are neutral, shows that they have sufficient sticking probability on the upper electrode to yield essentially equal deposition on both electrodes.
87(2000); http://dx.doi.org/10.1063/1.371983View Description Hide Description
It is shown that particle diffusion in the afterglow of a dusty plasma can be used to establish several properties of the active plasma. Specifically, the ratio of the average mass of light negative and positive ions, and a limit for the ratio of electron to ion charge densities can be determined. From the afterglow decay of visible particles, with and without electrode bias, the charged fraction of particles can be measured. An afterglow ambipolar-diffusion model is developed to relate this neutral fraction to the densities and masses of electrons and light ions in the active plasma. We then use this technique to analyze a silane radio-frequency plasma. In the active plasma positive charge is dominated by small cations, and the negative charge by small anions, with x and This analysis establishes that the electron density is less than 10% of the ion density in the operating discharge and that the anion/cation average mass ratio is ∼6.