What Does Wafer Mean?
A wafer is a thin piece of semiconductor material, usually crystalline silicon, in the shape of a very thin disc that is used as a base for fabricating electronic integrated circuits (ICs) and silicon-based photovoltaic cells. The wafer serves as the substrate for most microelectronic circuits and goes through many processes, such as doping, implantation and etching, before the final product of an an integrated circuit is completed.
A wafer is also known as a slice or substrate.
Techopedia Explains Wafer
A wafer starts out as chunks of polysilicon that are melted and then formed into a cylindrical ingot through a process called Czochralski growth, where a "seed" crystal as thin as a pencil is lowered into the melted silicon to allow monocrystalline silicon to grow around it, which is then rotated and then very slowly pulled in order to form a long cylindrical ingot that varies in diameter depending on the size of the wafer required. The ingot is then sliced into thin pieces using a wafer saw, which uses a very thin wire for cutting. The resulting thin "plates" of the silicon are the wafers, and go through various polishing processes so that the surface are nearly flawless before they are shipped to IC manufacturers. The diameter of a wafer ranges from 2 to 18 inches, and its thickness usually ranges from 275 to 925 µm.