ALD

ALD Basic

• saturated surface-controlled reaction
• Substrate is exposed to the first molecular precursor.
• The first molecular precursor is retained on the surface by chemisorption.
• Second precursor is introduced on the surface, which reacts on the surface of the first precursor.
• Exchange reaction takes place between the two precursors and by-products are formed.
• Exchange reaction continues till the second precursor reacts with first precursor.
• Final reaction : Precursor A + Precursor B → Film AB + by-products
• Sequence is repeated to grow films required.

Advantages

• Advantages of Atomic Layer Deposition
• Atomic layer deposition has several advantages over other techniques due to the actual mechanism used to deposit films.
• ALD is especially advantageous when film quality or thickness is critical.
• ALD is also quite effective at coating ultra high aspect ratio substrates or substrates that would be difficult to coat with other thin film techniques.
• Perfect films
• • Digital thickness control to the atomic level by depositing film one atomic layer at a time-pinhole-free films, over very large areas
  • Excellent repeatability
  • Wide process windows(no sensitivity to temperature or precursor dose variations)
  • Low-defect density
  • Amorphous or crystalline, depending on substrate and temperature
  • Digital control of sandwiches, hetero-structures, nanolaminates, mixed oxides, graded layers, and doping
  • Insensitivity to particle
  • Standard recipes for oxides, nitrides, metals, and semiconductors
• Conformal coating
• • Perfect 3D conformality and 100% step coverage : uniform coatings on flat, inside porous, and around particle samples
  • Flat and smooth coating that copies shape of substrate perfectly
  • Large area thickness uniformity
  • Easy batch scalability
• Challenging substrates
• • Gentle deposition process for sensitive substrates, no plasma needed
  • Low temperature deposition possible (RT~400˚C)
  • Coats everything, even on teflon
  • Excellent adhesion due to chemical bonds at the first layer
  • Low stress due to molecular self-assembly