In this work, the microstructure transition from amorphous to microcrystalline silicon is defined in terms of the silane concentration in the plasma as opposed to the silane concentration in the input gas flow. In situ Fourier transform infrared absorption spectroscopy combined with ex situ Raman spectroscopy has been used to calibrate and validate this approach. Results show that a relevant parameter to obtain µc-Si : H from SiH 4 /H 2 mixtures is the plasma composition, which is determined not only by the gas dilution ratio but also by the silane depletion fraction. It is also shown that µc-Si : H can only be deposited efficiently, in terms of gas utilization, at a high rate by using high input concentration and depletion of silane.

Electromagnetic wave propagation effects can give rise to important limitations for processing uniformity in large area, radio-frequency (rf) capacitive plasma reactors. The electromagnetic wavefield solution is derived for a capacitive, high-frequency, cylindrical reactor with symmetric or asymmetric electrode areas containing a uniform plasma slab. It is shown that only two distinct electromagnetic modes are necessary and sufficient to determine the electromagnetic fields everywhere within the reactor except close to the sidewalls. The first mode gives rise to the interelectrode rf voltage standing wave effect associated with high frequencies in large area reactors, and the second mode gives rise to the telegraph effect associated with asymmetric electrode areas, which necessitates the redistribution of rf current along the plasma to maintain rf current continuity. This work gives a unified treatment of both effects which have previously been studied separately, experimentally and theoretically, in the literature. The equivalent circuit of each mode is also derived from its respective dispersion relation. Examples of this electromagnetic wavefield solution show that both modes can cause nonuniformity of the plasma rf potential, depending on the reactor geometry, excitation frequency and plasma permittivity and sheath width, which has consequences for large-area plasma processing.

Articles you may be interested inTime-resolved measurements of ion energy distributions in dual-mode pulsed-microwave/radio frequency plasma Time-resolved measurements of ion energy distributions and optical emissions in pulsed radio-frequency discharges Negative ion mass spectra and particulate formation in radio frequency silane plasma deposition experiments Appl.

Experiments using a lens-shaped circular electrode are described to measure the correction of plasma nonuniformity due to the standing wave effect in a large area very high frequency plasma reactor. This work is the experimental verification of the theoretical reactor design in cylindrical geometry recently presented by L. Sansonnens and J. Schmitt, Appl. Phys. Lett. 82, 182 (2003). It is found that the lens-shaped electrode effectively compensates the standing wave effects by creating a uniform rf vertical electric field in the plasma volume. The plasma is uniform, except for edge effects, for a wide range of parameters and consequently the design is suitable for plasma processing.

Experimental identification of the precursors and processes leading to pariicies is esseniiai ior undersianding pariicuiate contamination in deposition plasmas. We have investigated particle formation in radiofrequency silane plasmas using light scattering (elastic and inelastic) and quadrupole ion mass spectrometry as complementary plasma diagnostics. Negative ions reach high masses (at least 500amu) and are the only elementary species with a residence time on the scale of the powder formation time. Furthermore, a negative-ion polymerization scheme shows that the densities of high-mass anions are strongly diminished at kilohert! power modulation frequencies, at which reduced powder production is also observed.We conclude that negative Ions are the particle precursors and that initial clusters grow by negative-ion polymerization in silane plasmas. In situ light scattering techniques are described to determine palticle size, number density and refractive index self-consistently. Novel, visible photoluminescence measurements from particies suspended in the plasma are ais0 reported. These diagnostics demonstrate that particle evolution proceeds by an agglomeration phase and that the particle properties are different from those of the bulk material early in particle development.