What is ALD?
Atomic Layer Deposition (ALD) is an advanced thin film coating method which is used to fabricate ultrathin, highly uniform and conformal material layers for several applications. ALD uses sequential, self-limiting and surface controlled gas phase chemical reactions to achieve control of film growth in the nanometer/sub-nanometer thickness regime. Due to the film formation mechanism - the gases won't react until in touch with the surface which means the film growth proceeds by consecutive atomic layers "up" from the surface - the ALD film is dense, crack-, defect- and pinhole-free and its thickness and structural and chemical quality can be precisely controlled on atomic scale. ALD process is also repeatable and it can be performed in relatively low temperatures. This gives the possibility to construct not only single material layers but also doped, mixed or graded layers and nanolaminates. The list of ALD materials is wide, ranging from e.g. oxides, nitrides, fluorides and sulfides to ternary compounds, metals (even noble ones) and polymers.
The number of ALD applications has grown exponentially over the past few years and nowadays the method is used in e.g. semiconductor industries such as IC (integrated circuits), sensor, III-V device, and MEMS/NEMS (micro/nanoelectromechanical systems) manufacturing, optics and optoelectronics, antitarnishing and wear protection, and renewable energy applications such as solar power. Other large scale applications include also corrosion protection, energy storage and production (e.g. advanced thin film batteries and fuel cells), biocompatible coatings for medical devices and implants, water purification, advanced lighting devices such as OLEDs, ecological packaging materials, moisture- and gas-tight encapsulant layers, decorative coatings, anti-cracking layers for glass, and water repelling coatings.