Physical vapor deposition (PVD)
From Sam's "Semiconductor Fabrication Basics Background Theory" video: "OK, the last 2 topics to talk about in this video. So everything up to this point has talked about how to make discrete devices, so how to make a single transistor, how to make a diode, something like that, but the difference between the ability to make discrete devices and actual integrated circuits is metalization, metalization allows us to make small connections between individual transistors that are on a board and connect them in ways that they have a greater function than just being individual transistors, so metalization is done by taking a wafer that has all these transistors and everything on it already, and then the entire wafer surface will be coated with metal, aluminum or copper something like that, and then same as photo-lithography process will happen, and then we can etch away that metal just to leave little traces and connections that connect all these individual components on the board. There's a few ways of doing that, enter the big umbrella of deposition, thin film deposition. There's so many methods that you can research, mainly there's chemical vapor deposition CVD, and physical vapor deposition PVD. So there are lots of CVD techniques, but mainly they are used to deposit and grow insulators and semiconductors, out of the insulators you can do SiO2 and silicon nitride layers, and out of the semiconductors you can grow epitaxial silicon, also polysilicon as well. Evaporation is a PVD technique and it can be used to deposit conductive metalization layers, like aluminum, copper, gold, nichrome, probably like tungsten if you have enough heat to be able to do that. Sputtering is another PVD technique, you can actually sputter SiO2 interestingly enough, but mainly its used to coat metals, like tungsten, titanium, molybden, aluminum, a huge use for sputtering is ITO, Indium Tin Oxide, you can create clear conductive coatings, and these are used heavily in organic LED technologies and thin film displays, things like that. Molecular beam epitaxy is kind of chemical process but its considered a PVD technique, MBE can be used to do so much stuff its incredible, mainly its used to do complex semiconductors like GaAs devices, set-up with effusion cells that have a small super pure sample of whatever you're trying to deposit wheither its aluminum, silicon, arsenic, gallium and a very pure sample of that is heated up with electron beam, and it basically boils in a vacuum, that can be deposited onto your substrate very nicely."