Slide 15 - 2. Atomic Layer Deposition
Slide 15 - 2. Atomic Layer Deposition
Slide 15 - 2. Atomic Layer Deposition
Metallurgical Engineering
04/13/2021 Slide - 2
Definition ALD
• ALD is a method of applying thin films to various substrates with
atomic scale precision.
• Similar in chemistry to chemical vapor deposition (CVD), except that
the ALD reaction breaks the CVD reaction into two half-reactions,
keeping the precursor materials separate during the reaction.
• ALD film growth is self-limited and based on surface reactions,
which makes achieving atomic scale deposition control possible.
• By keeping the precursors separate throughout the coating process,
atomic layer thickness control of film grown can be obtained as fine
as atomic/molecular scale per monolayer.
04/13/2021 Slide - 3
Brief history of ALD
• Introduced in 1974 by Dr. Tuomo Suntola and co-workers in
Finland to improve the quality of ZnS films used in
electroluminescent displays.
• Recently, it turned out that ALD also produces outstanding
dielectric layers and attracts semiconductor industries for
making High-K dielectric materials.
04/13/2021 Slide - 4
5
Ref: A. Knop–Gericke, "Preparation of Model Systems by Physical Methods," a lecture given at Modern Methods in Heterogeneous Catalysis
Research Lecture Series, Fritz Haber Institute of the Max Planck Society. 24 April 06.
<http://w3.rz-berlin.mpg.de/%7Ejentoft/lehre/catalysis0405.html>.
Ref: A. Knop–Gericke, "Preparation of Model Systems by Physical Methods," a lecture given at Modern Methods in Heterogeneous Catalysis
Research Lecture Series, Fritz Haber Institute of the Max Planck Society. 24 April 06.
<http://w3.rz-berlin.mpg.de/%7Ejentoft/lehre/catalysis0405.html>.
Schematic of
a closed ALD
system
[1] [1]
Acceptable
temperature range
for deposition.
ALD Applications
• High-K dielectrics for CMOS
ALD Applications
• High-K dielectrics for CMOS
Summary
• Advantages
Stoichiometric films with large area uniformity and 3D
conformality.
Precise thickness control.
Low temperature deposition possible.
Gentle deposition process for sensitive substrates.
• Disadvantages
Deposition Rate slower than CVD.
Number of different material that can be deposited is
fair compared to MBE.