Origin of area selective plasma enhanced chemical vapor deposition of microcrystalline silicon

Plasma-enhanced chemical vapor deposition of silicon from a SiF4/H-2/Ar gas mixture is observed on a SiOxNy surface, while under the same plasma conditions, silicon films do not grow on AlOx or on Al surfaces. Transmission electron microscopy confirms that the silicon deposited on SiOxNy has a microcrystalline structure. After the plasma process, fluorine is detected in abundance on the AlOx surface by x-ray photoelectron spectroscopy and energy dispersive x-ray chemical analyses. This suggests that Al-F bonds are formed on this surface, blocking any deposition of silicon on it. In situ ellipsometry studies show that deposition can be initiated on AlOx surfaces by increasing the temperature of the electrodes or increasing the RF plasma power, leading to a loss of selectivity.