Atomic Layer Deposition (ALD) is a true nanotechnology, allowing ultra-thin films of a few nanometres to be deposited in a precisely controlled way.

There are two defining characteristics of ALD; self-limiting atomic layer-by-layer growth and highly conformal coating. These characteristics offer many benefits in semiconductor engineering, MEMS and other nanotechnology applications.

The benefits of ALD

As the ALD process deposits precisely one atomic layer in each cycle, complete control over the deposition process is obtained at the nanometre scale:

  • Conformal coating can be achieved even in high aspect ratio and complex structures
  • Pin-hole and particle free deposition is achieved
  • A very wide variety of materials is possible with Atomic Layer Deposition, such as:
    • Oxides: Al2O3, HfO2, SiO2, TiO2, SrTiO3, Ta2O5, Gd2O3, ZrO2, Ga2O3, V2O5, Co3O4, ZnO, ZnO:Al, ZnO:B, In2O3:H, WO3, MoO3, Nb2O5, NiO, MgO, RuO2
    • Fluorides: MgF2, AlF3
    • Organic-hybrid materials: Alucone
    • Nitrides: TiN, TaN, Si3N4, AlN, GaN, WN, HfN, NbN, GdN, VN, ZrN
    • Metals: Pt, Ru, Pd, Ni, W
    • Sulfides: ZnS

ALD tool comparison

Feature OpAL® FlexAL®
Substrates Up to 200mm wafers & pieces directly on stage Up to 200mm wafers handling and pieces on a carrier plate
Bubbled liquid & solid precursors Up to 4 plus water, ozone and gases Up to 8 plus water, ozone and gases
Max precursor source temperature 200ºC 200ºC
Mfc controlled gas lines with rapid delivery system;
1) thermal gas precursors (e.g. NH3, O2)
2) plasma gases (e.g. O2, N2, H2)
2 internally.
Up to 8 in externally
mounted gas pod
Up to 10 in externally mounted gas pod
Plasma Option/field upgrade Option
Loading Open load Loadlock or cassette
Clusterable to other process modules No Yes - inc third party MESC modules as special option
Wafer stage temperature range 25ºC – 400ºC 25ºC – 400ºC (550ºC option)
Ellipsometry ports Yes Yes
Swagelok 10ms rapid pulsing ALD valves Yes Yes

We can now do Atomic Layer Etching as well!

Atomic Layer Deposition (ALD) Cycle

ALD cycle for Al2O3 deposited using TMA and O2 plasma.

Only step 3 varies between H2O for the thermal process or O2 plasma:
A. TMA chemisorbtion       B. TMA purge                  C. O2 plasma                   D. Short post plasma purge

Atomic Layer Deposition (ALD) Applications

ALD can be used for many applications including:

  • High-k gate oxides
  • Storage capacitor dielectrics
  • Pinhole-free passivation layers for OLEDs and polymers
  • Passivation of crystal silicon solar cells
  • High aspect ratio diffusion barriers for Cu interconnects
  • Adhesion layers
  • Organic semiconductors
  • Highly conformal coatings for microfluidic and MEMS applications
  • Other nanotechnology and nano-electronic applications
  • Coating of nanoporous structures
  • Fuel cells, e.g. single metal coating for catalyst layers
  • Bio MEMS

Remote plasma Atomic Layer Deposition (ALD)

In addition to the benefits of thermal ALD, remote plasma allows for a wider choice of precursor chemistry with enhanced film quality:

  • Plasma enables low-temperature ALD processes and the remote source maintains low plasma damage
  • Eliminates the need for water as a precursor, reducing purge times between ALD cycles - especially for low temperatures
  • Higher quality films through improved removal of impurities, leading to lower resistivity, higher density, etc
  • Effective metal chemistry through use of hydrogen plasma
  • Ability to control stoichiometry/phase
  • Reduced nucleation delay
  • Plasma surface treatment
  • Plasma cleaning of chamber is possible for some materials

Download our ALD brochure

ALD Brochure

Atomic layer deposition process solutions

PDF 1.07MB
Optoelectronic Devices brochure

Plasma Solutions for Optoelectronic Semiconductor Device Manufacture

PDF 1.48MB

Related Process Techniques

Nanoscale Growth

Nanoscale Growth

CVD, PECVD and ICP CVD for growth of nanomaterials

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Open loaded thermal ALD tool with plasma option


FlexAL ALD Tool

Remote plasma & thermal ALD in one flexible tool