Wafer
The blank canvas every chip in the world begins as
Imagine a large, perfectly flat, mirror smooth disc of pure silicon crystal, thin enough to flex slightly, yet precise enough that a fab can print hundreds of individual chip circuits onto its surface in a single production run. That disc is a wafer, the base material every semiconductor chip in the world begins its life as.
Wafers are sliced from a large, ultra pure cylindrical silicon crystal, polished to an almost perfect flatness, and then sent through the fabrication process where circuit patterns are built up on their surface layer by layer. A single wafer typically yields many individual chips at once, which are only separated into distinct dies later, during the ATMP or OSAT stage.
Wafer size, commonly 200 or 300 millimetres in diameter in modern fabs, is itself an important technical detail, since a larger wafer allows more chips to be produced per production run, directly improving a fab's manufacturing efficiency and cost per chip.