Nanotechnologies are all those deposition techniques that involve thin films.
The most used technologies used to deposit those films are “under vacuum”, but also galvanic coatings in some conditions can be considered nanotechnologies.
The most popular “under vacuum” techniques
PVD. Physical vapor deposition processes are atomistic where material vaporized from a solid or liquid source is transported as a vapor through a vacuum or low-pressure gaseous or plasma environment. When it contacts the target, it condenses.
The vaporized material may be an element, alloy or compound. Some PVD processes can be used to deposit films of compound materials (reactive deposition) by the reaction of depositing material with the gas in the deposition environment (e.g., TiN) or with a co-depositing material such as TiC or even a combination of the two. Picture N°1 shows a typical PVD deposition.
The metal is heated (1) and vaporizes. It deposits on the sample by condensation (2). In the same time, an ion beam (3) shoots the surface of the sample and co-deposits with the metal.
Fig. 1 a PVD plant scheme
Typically, PVD processes are used to deposit films with thicknesses in the range of a few nanometers to thousands of nanometers; however, they can be used to form multilayer coatings, thick deposits and free-standing structures.
CVD Chemical vapor deposition (CVD) deposits atoms or molecules by reducing the decomposition of a chemical-vapor precursor species that contains the material to be deposited. The reduction is normally accomplished using hydrogen at an elevated temperature. Decomposition is accomplished by thermal activation (MOCVD) or using plasma (PECVD) that allows the reduction or decomposition at a lower temperature than using temperature alone.
CVD processing is generally accompanied by volatile reaction by-products, and those, along with unused precursor vapors and other processing gases, must be removed from the deposition system.
Vacuum-deposition processing equipment
The equipment used to generate the deposition environment is an integral part of the process. The principle parts of the deposition system are the deposition chamber, fixturing, which holds the parts to be coated, and the vacuum pumping system, which removes gases and vapors from the deposition chamber.
Generating a vacuum has two purposes:
To reduce the gas pressure enough so that vaporized atoms have a long "mean-free path" and do not nucleate in the vapor to form soot; and
To reduce the contamination level to the point that the desired film can be deposited.
The fixturing holds the substrates to be coated and provides the motion, relative to the vaporization source. This is often necessary to give a uniform deposition over a large area, a complex surface or over many substrates. The fixture and process cycle times determine throughput. The deposition chamber is sized to contain the fixturing and provide room for accessories such as shutters, deposition rate monitors, heaters, etc. Proper design, construction, operation and maintenance are necessary to obtain a reproducible product with high yield and desired product throughput.
Vacuum deposition of thin films and coatings is continually evolving. This is true of processes, equipment, applications and markets. Often, the decision to use vacuum deposition processes is influenced by environmental concerns, since they are "dry processes." Developing applications include clear permeation barrier layers for polymer webs and three-dimensional containers, decorative/wear-resistant coatings for many applications, coatings to replace electroplated chromium, corrosion-resistant coatings to replace cadmium and others.