Why ALD?

ALD has several benefits over other thin film coating technologies such as chemical or physical vapor deposition (CVD/PVD) or sputtering. All of these stem from the fact that ALD is a surface controlled method whereas other thin film technologies represent so-called source controlled deposition. In source controlled method the precursors react already before they hit the surface which means the resulting film is not necessarily uniform or very conformal, neither can it be properly grown on very small surface details or high aspect ratio structures such as deep trenches in silicon wafers (one central component in today's and tomorrow's electronics manufacturing), and also there can be cracks and pinholes left in the film which renders it useless in e.g. corrosion protection, medical implant coating or encapsulant layer manufacturing.

With conventional thin film methods it is also impossible to achieve atomic-level structural and thickness control of the film. ALD can be used to improve the quality of other thin films, though - for example with PVD it is easy to produce relatively thick layers and fast, and ALD has been successfully used as a "sealant" on these layers, blocking possible pinholes and cracks in the underlying PVD film. ALD is also gentler to the surface compared to ion bombardment -based coating methods.

Download pdf "Introduction to Picosun and Atomic Layer Deposition"