Atomic Layer Deposition
Uses alternative pulses of precursors in a vapour form. The chemisorption
or reaction of each precursor pulse with the exposed surface is self limiting,
giving precise thickness control.
Two or more precursors make an atomic layer. This is known as a cycle.
The growth continues in this manner layer-by-layer.
Benefits of ALD
Conformal coating even in high aspect ratio structures
Very thin films with growth precisely controlled by the number of cycles
Pin-hole and particle free deposition
Wide variety of materials possible
Remote Plasma ALD
for radical supply
A "remote plasma" makes sure, the substrates
are NOT in contact with the plasma !
The remote plasma just cracks molecules, so that
very reactive species can be used for the growth process.
Such reactive species often enable a very efficient
plasma preclean of the substrates, lead to cleaner
films and lower the deposition temperature.
It also allows greater process flexibility, e.g. depositing
metals with H2 plasma reduction.