ALD Background

What is ALD?

  • The world of nanotechnology and impact on everyday life might seem a few years or even decades away, but in fact nanotechnology already exists in our everyday life.
  • ALD is an enabling nanotechnology platform to produce coatings with nanoscale precision.  Nanocoatings can be produced through liquid and vapor coating platforms, ALD is a unique vapor phase thin film coating platform to deposit coatings with the fine tune of a single atom.  In most cases ALD coatings cannot be seen with the naked eye but the coatings are highly valuable for their ability to improve the performance of products found in everyday life.
  • VaporPulse has direct experience using ALD to functionalize and protect materials used in many industries including Defense, Energy, Medical, Packaging, Optics and Electronics for applications such as UV protection, smart textiles, flexible electronics, corrosion, moisture barriers, and flame retardants.
  • What makes ALD so special and unique?  Provided below is a short primer on ALD, contact us for more information on how to use ALD in your next project.

Introduction to Atomic Layer Deposition (ALD)

Atomic Layer Deposition (ALD) is a vapor thin film deposition process that achieves highly conformal growth with thickness controllable at the nm and sub-nm level. Please see Mikko Ritala – Review – ALD Precusors, Process and Background – 2002 and Greg Parsons – Review – Future ALD Directions – 2011 for topical reviews on the ALD process.

The ALD process is most closely related to Chemical Vapor Deposition (CVD) where the key difference is the precursors used for material formation are introduced in a controlled reaction sequence that forms a binary self-limiting surface reactions on a substrate.  Controlling precursor reaction on a substrate provides atomic level control of the growth of materials.

The ALD process was developed for us in the semiconductor and electronics industries due to the need to deposit ultra-thin pin hole free coatings of oxides, metals, and semiconductors on three-dimensional nano-scale architectures.  ALD is king of all processes to provide this control for the complex structures that enable our cell phones and laptops.  The basics of the ALD process is materials are formed by a two-step reaction process.  First, a precursor (often a metal organic) chemically binds to reactive surface sites.  The bound precursor does not self-react, thereby permitting only a single monolayer of deposition.  Then a co-reactant is introduced to either oxidize or reduce the precursor and reactivate the surface for precursor binding.  In between cycles, an inert purge is used to evacuate all but the chemisorbed species, thus resulting in self-terminating half-reactions.  Each growth cycle deposits an ultra-thin layer of only a few angstroms thickness, making it useful for nano-scale processing.

ALD is chemically distinct from chemical vapor deposition (CVD) which is a continuous growth process with reactions occurring at high temperatures. ALD growth occurs step-wise at lower processing temperatures (commonly below 200 C), where the elementary steps in the overall reaction are isolated in time.  The low temperature operation of ALD has opened us some unique opportunities to produce high performance coatings for thermally sensitive substrates such as plastics and polymers.

At VaporPulse our team scientists and engineers has experience with low and high temperature ALD to produce metal oxide, metal, and nitride coatings on various substrates including metals, polymers and ceramics.

Contact us about how VaporPulse can help on your next ALD project.

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