Definition: wafer

(1) A small magnetic tape cartridge used in the early 1980s. See Stringy Floppy.

(2) The base unit of chip making. A wafer is a slice taken from a salami-like silicon crystal ingot up to 450mm (17.7") in diameter. The larger the wafer, the more chips produced at the same time. The production process comprises a series of photomasking, etching and implantation steps that can take days and weeks to create the final product. See chip manufacturing.

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. The amount of activity that takes place within the chip is truly unbelievable (see active area).

Wafers started out from one to three inches in diameter. Then came 100mm ingots (3.9"), followed by 125mm (4.9"), 150mm (5.9"), 200mm (7.9"), 300mm (11.8") and 450mm (17.7"). See chip, transistor 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.)

Different Sizes

From top to bottom, the wafers are 150, 200 and 300mm (5.9", 7.9" and 11.8") in diameter. (Images from top to bottom courtesy of Texas Instruments, Inc., Advanced Micro Devices, Inc. and Intel Corporation.).

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.)