Physical Vapor Deposition (PVD) is – theoretically – a complicated topic. It is the process by which a number of layers of molecules from vapor is deposited onto a solid substrate in a vacuum chamber.
When manufacturing an item, PVD is used quite often. In particular, PVD is used in the manufacturing of aluminized PET film for balloons and snack bags, semiconductor devices, and coated cutting tools for use in metalworking. Outside of PVD tools used for fabrication, smaller tools have also been developed (they are used for scientific purposes). They serve the purpose of being an extreme thin film, like atomic layers, and are used mostly for smaller substrates. Prime examples are mini E-Beam Evaporators which can deposit monolayers of virtually all materials with the use of a high melting point of up to 3500 °C.
A lot of experts say that PVD coatings are harder and more corrosion resistant than coatings applied by the process of electroplating. Because PVD coatings have high impact strength, a high temperature threshold, excellent abrasion resistance and are so durable that protective topcoats are almost never necessary. Common coatings applied by PVD include zirconium nitride, titanium, aluminum nitride, titanium nitride, and chromium nitride.
Two very common types of PVD processes used are Sputtering and Electron Beam Evaporation. Below is a brief explanation of each.
The sputtering process involves simply ejecting material from a “target” onto a source that is a “substrate” – something like a silicon wafer — in a vacuum chamber. The target is bombarded by ionized gas which is often an inert gas, like argon. In the semiconductor industry, sputtering is used to deposit a very thin film on a number of materials in the processing of integrated circuits. Sputtering is key in anti-reflection coatings on glass for optical application.
Sputtering – which uses low substrate temperatures — is a great method to deposit metals for thin-film transistors. One of the most familiar products of sputtering are low-emissivity coatings on glass, which are used in making double-pane windows. An advantage of sputtering is that ever materials with high melting points are easily sputtered while evaporation of the same material in a resistance evaporator is difficult and causes problems.
Electron Beam Evaporation, or E-beam Evaporation, is the process in which a target material is bombarded with an electron beam given off by device with a tungsten filament in a high – intensity vacuum. The electron beam causes atoms from the source material to evaporate into the gaseous phase. The atoms then form into a solid, coating all that is inside the vacuum chamber with a thin layer of the material.
The biggest advantage of E-Beam Evaporation is it permits direct transfer of energy to a source during heating and is very efficient in depositing pure evaporated material to a substrate. Furthermore, deposition rate in this process can be as low as 1 mm per 60 seconds to as high as few micrometers per 60 seconds – these are very solid statistics. Compared to other methods and processes, the material utilization efficiency is remarkably high. Because of the high deposition rate, the industry chooses this process for thermal barrier coatings aerospace machines, hard coatings for cutting tools, and electronic and optical films for semiconductors.
When it comes to choosing between Sputtering and E-Beam Evaporation, it depends what industry PVD is being utilized in. Each have very specific roles, and are important for the future of PVD.