Atomic layer deposition (ALD) is a chemically self-limiting deposition technique that is based on the sequential use of a gaseous chemical process. In most cases, ALD reactions use two chemical precursors which react with a surface one at a time in a sequential, self-limiting manner. A thin film results from repeating the deposition sequence as many times as needed to reach a certain thickness. The major characteristic of the films is their conformality and the fact that the amount of control provided by an ALD arrangement (where the reacting precursors are spatially separated) allows to obtain very thing deposited layers (as fine as ~0.1 Å per cycle). Precursor selection is key in ALD processes, namely finding molecules which will have enough reactivity to produce the desired films, but are stable enough to be handled and safely delivered to the reaction chamber.
Silicon-based ALD Materials