(1) A small, thin continuous-loop magnetic tape cartridge that has been used from time to time for data storage and specialized applications.
(2) The base unit of chip making. A wafer is a slice taken from a salami-like silicon crystal ingot up to 300mm (11.8") in diameter. The larger the wafer, the more chips produced in a single production pass, which comprises a series of photomasking, etching and implantation steps. Wafers are approximately 1/30th of an inch thick; however, the actual layers of transistors that make up the active circuitry are only a few microns deep.
Wafers started out being very small from one to three inches in diameter. Then came 100mm ingots (3.9"), followed by 125, 150, 200 and 300mm (450mm is expected in the future). Various wafer sizes are used today depending on the type of chip being made. See chip and wafer scale integration.
The Boule Is Sliced
The silicon ingot, which is known as a "boule," is sliced into wafers. (Image courtesy of IBM.)
The person at the top is holding 150mm wafers; in the middle 200mm; and 300mm at the bottom. (Images courtesy of Texas Instruments, Inc., Advanced Micro Devices, Inc. and Intel Corporation, respectively).
Heating the Wafers
The red glow comes from a furnace that reaches 1000 degrees centigrade. The semiconductor wafers are baked in the oven to prepare them for the chip-making process. (Image courtesy of Intel Corporation.)