ALD (Atomic Layer Deposition)

As chip node dimensions are continuously shrinking, traditional deposition techniques have reached their limits. Depositing ultra-thin layer at the nanoscale requires Atomic Layer Deposition (ALD) technology, which allows materials to be deposited one atomic layer at a time.
This technology is used to deposit a variety of oxides, nitrides or metals, enabling manufacturing of the most advanced devices including 3D architectures where thickness conformity and uniformity are crucial.

Application requirements

  • High pumping capacity from 1,800 to 4,500 m3/h
  • Vacuum performance stability over time for optimized yield
  • Condensable management by high temperature operation
  • Precursor thermal stability by low temperature operation
  • Corrosion resistance by advanced coating technology
  • Powder handling capabilities
  • High process lifetime at low operating costs: Low power consumption, low repair cost

How does it work?
ALD deposition cycle consists of sequential injections of precursor and reactant in the reactor. Chemical reaction energy is activated either by temperature (Thermal ALD) or by plasma (PE ALD). In between each pulse, N2 purge is injected to evacuate by-products formed by precursor adsorption on the surface and unreacted precursor and reactant. As the reaction is self-limited by nature, film thickness is only dependent on the number of deposition cycles performed, allowing a control of the deposited layer at the atomic scale. ALD process can be performed on single wafer or batch equipment, each of them featuring specific advantages.

Vacuum requirements
Most of ALD processes operate under primary vacuum, in the 10-1 to 5 mbar pressure range. On high volume manufacturing equipment, high pumping capacity in the range of 1,800 to 4,500 m3/h is required for fast evacuation of precursors during purge steps, insuring high throughput. On smaller R&D equipment, smaller dry pumps can be used, between 600 to 1,200 m3/h. Generated by-products are commonly a great challenge for the dry pumps as their nature may vary depending on the type of precursors which are used: Highly corrosive, condensable, or solid, and some applications combining all these simultaneously.

Product portfolio
Pfeiffer Vacuum provides the A4 & ADH Series, full ranges of dry pumps designed to handle these challenges: Sophisticated thermal management prevents deposition, advanced materials reduce corrosion rate and multi-stage Roots design manages powder evacuation.

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