Atomic Layer Deposition (ALD)

Atomic layer deposition (ALD) is a technique to coat surfaces with thin films. The coating is deposited atomic layer by atomic layer so that the chemical composition and coating thickness can exactly be defined.

Functional principle

Classical ALD

The surface to be coated has to be pretreated to become chemically reactive. The substrate is put into a vacuum chamber and heated in there. After reaching the required temperature the chamber is filled with a certain amount of coating gas. Due to the temperature the molecules of the gas react with the surface of the substrate. Because of the chemistry only exactly one molecule layer can be attached to the surface. In the next process step the gas in the chamber is exchanged with another gas and the coated layer is chemically activated. Afterwards the gas in the chamber is again exchanged to deposit another molecule layer. By repeating the activation and coating process steps an ALD coating is created.

Scheme of ALD of Al2O3
Scheme of ALD of Al2O3

Since the classic ALD requires temperatures of several 100 °C this technique cannot be used to coat temperature-sensitive materials like plastics. To keep the temperature low PEALD uses plasma instead of high temperature to deliver the necessary activation energy. The advantages to the classical ALD are:

  • The process temperature is lower than 100 °C
  • A pretreatment of the surface is not necessary because this is done by an initial plasma surface activation

Plasma Electronic is a specialist in PEALD offering solutions for the following applications:

  • Oxide coatings as barrier for molecules and gases of all kind
  • Oxide- or nitride coatings with exactly defined optical properties
  • Coatings as high-k-dielectric
  • Corrosion protection coatings

We also offer the development of coatings. Contact us!

The advantages of ALD compared to chemical vapor deposition (CVD) are:

  • The coating thickness is homogeneous
  • The chemical composition of the film is exactly defined
  • It is possible to coat parts with almost every form homogeneously
  • Much less defects in the coating
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