Atomic layer deposition

Atomic layer deposition is a vapor-phase thin-film process that exposes a surface to reactants in sequence. Self-limiting surface reactions control growth in nearly uniform increments, even on complex shapes.

Self-limiting reaction: A reaction that stops when available reactive sites are consumed or the surface becomes covered. Each ALD exposure ends when its surface reaction saturates.
High-k dielectric: An insulating material with a higher dielectric constant than silicon dioxide. ALD deposits high-k gate dielectrics as uniform, very thin layers.
Chemical vapor deposition: A process that forms solid films through chemical reactions of vapor-phase precursors. CVD can deposit faster, while ALD separates reactions into self-limiting exposures.
Tuomo Suntola: A Finnish physicist who developed and commercialized atomic layer deposition. Suntola’s work established industrial ALD for thin-film electroluminescent displays.
Precursor (chemistry): A compound that participates in a chemical reaction to produce another substance. ALD alternates volatile precursors that react with the surface in sequence.
Gate-all-around FET: A transistor whose gate surrounds its semiconductor channel on all sides. Conformal ALD forms gate materials around the channel’s full circumference.
Physical vapor deposition: A family of methods that deposits films by physically transporting vaporized material to a surface. PVD often has directional coverage, unlike ALD’s strong conformality.
Atomic layer epitaxy: The historical name for an early form of atomic layer deposition, especially for crystalline films. This name marked ALD’s origins in controlled, sequential surface growth.
Surface chemistry: The study of chemical processes occurring at interfaces between materials. ALD growth depends on reactions at the film’s exposed surface.
Solid-state battery: A battery that uses a solid electrolyte instead of a liquid electrolyte. ALD coatings can stabilize interfaces between battery materials.

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