This page describes selected literature available on atomic layer deposition.
Applications of atomic layer deposition to nanofabrication and emerging nanodevices[1]
Abstract: Recently, with scaling down of semiconductor devices, need for nanotechnology has increased enormously. For nanoscale devices especially, each of the layers should be as thin and as perfect as possible. Thus, the application of atomic layer deposition (ALD) to nanofabrication strategies and emerging nanodevices has sparked a good deal of interest due to its inherent benefits compared to other thin film deposition techniques. Since the ALD process is intrinsically atomic in nature and results in the controlled deposition of films at the atomic scale, ALD produces layers with nanometer scale thickness control and excellent conformality. In this report, we review current research trends in ALD processes, focusing on the application of ALD to emerging nanodevices utilizing fabrication through nanotechnology.
- Atomic layer deposition consists of four essential steps: 1)precursor exposure, 2) evacuation or purging of the precursors and any byproducts from the chamber, 3) exposure of the reactant species, typically oxidants or reagents, and 4) evacuation or purging of the reactants and byproduct molecules from the chamber .
- A clear and distinctive feature of ALD lies in the self-limitation for precursor adsorption and alternate, sequential exposure of precursors and reactants
- A challenge of deposition on nanoscale three-diamension surface is that while saturated adsorption is achieved on the flat surface at a given amount of precursor exposure, incomplete saturation reaction may occur deep inside of nanosize holes or vias, leading to poor overall conformality
- The required exposure to achieve good saturation can be controlled by varying exposure time or working pressure. Higher pressure during precursor exposure was shown to enhance precursor adsorption on the inside surface of the pores, resulting in the reduction of exposure time for saturation.
- Some materials, particularly metal ALD material, may yield islands during ALD process, which affects the growth rate, resulting in a non-linear increase in film thickness vs. growth cycles, and makes it difficult to obtain atomically smooth surfaces
- Another important characteristic of ALD is the ability to deposit relatively high quality films at low temperature, that gives opportunities to material with low evaporation temperature, like InN.( low compared to CVD even at low temperature).
- Another advantage is that ALD can be performed on polymer substrates with nucleation site. TMA molecules into the pores of polymers was found to facilitate the nucleation of ALD Al2O3.
- Method: fluid bed reactor can be used for nanoparticle ALD.
- ALD processes the advantage of biomtemplating from existing materials such as bacteria, butterfly wings, spider silk, etc. due to its high conformality and low growth temperature.
- High aspect ratio AAO with ALD perform as templates for complex nanomorphology fabrication, particular the nanoarrays, nanotube and nanorods.
references
- ↑ Kim, Hyungjun, Han-Bo-Ram Lee, and W.-J. Maeng. “Applications of Atomic Layer Deposition to Nanofabrication and Emerging Nanodevices.” Thin Solid Films 517, no. 8 (February 27, 2009): 2563–2580.