What is the atomic layer deposition reaction?

Atomic Layer Deposition (ALD) Reaction

Atomic Layer Deposition (ALD) is a thin film deposition technique that allows for the precise and controlled growth of thin films on substrates. This method is based on the sequential use of a gas phase chemical process. The ALD process utilizes self-limiting, surface-controlled reactions to deposit conformal thin films. This technique is highly beneficial for applications requiring precise thickness control and uniformity over complex surfaces.

ALD occurs in a cyclic process comprising four main steps:

1. Pulsing of the precursor A: The first precursor is pulsed into the reaction chamber, where it adsorbs onto the substrate surface in a self-limiting manner. Excess precursor is purged from the chamber.
2. Purging of the reaction chamber: Inert gas is used to purge the reaction chamber, removing excess precursor and reaction byproducts.
3. Pulsing of the precursor B: A second precursor is introduced into the chamber, reacting with the adsorbed layer to form the desired film. This reaction is also self-limiting.
4. Purging of the reaction chamber: The chamber is again purged with inert gas to remove any excess second precursor and reaction byproducts.

This cycle is repeated until the desired film thickness is achieved. The self-limiting nature of the reactions ensures atomic-scale control over the film thickness, making ALD an ideal technique for the fabrication of nanoscale materials and devices.

ALD is widely used in various applications, including semiconductor device fabrication, photovoltaics, and protective coatings. Its ability to produce high-quality, uniform films at low temperatures makes it particularly useful for materials sensitive to high temperatures.