Small Particle Growth in Silane Radio-Frequency Discharges

Published

February 1, 2000

Author(s)

M A. Childs, Alan Gallagher

Abstract

Particle size and number density are measured versus discharge operating time in pure silane, capacitively-coupled RF discharges. Dischargeconditions are those typically used to produce amorphous silicon devices, except the temperature is 300K. Particle radii (r_p) of 4-25 mn areobserved, where r_p 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 an initial rapid growth to r_p {difference} 2 nm, followed by a constant r_p growth rate that is consistent withgrowth due to SiH₃ reactions. However, at higher pressures and film growth rates, or RF voltage, the particle growth rate exceeds that due to SiH₃, indicatiing 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. An afterglow model is developed to explain this dominance of neutral particles shortly after discharge termination. The model and data confirms that the plasma positive ion density greatly exceeds the electron density, and that the average netgative ion mass exceeds the average positive ion mass.

Citation

Journal of Applied Physics

Volume

87

Issue

No. 3

Pub Type

Journals

Keywords

discharge, particles, silane

Citation

Childs, M. and Gallagher, A. (2000), Small Particle Growth in Silane Radio-Frequency Discharges, Journal of Applied Physics (Accessed July 26, 2024)