A wafer, processed as a thin disk composed of semiconducting material, functions as the substrate of semiconductor components. As the semiconducting material, silicon is mainly used. Generally, on each wafer, identical circuit patterns (several millimeters square) are arranged in the form of squares and baked. Each square cut out from the wafer becomes an IC chip. As for wafer sizes, diameters of 8 inches (about 200 mm) and 12 inches (about 300 mm) are standard. As wafer size increases, a greater number of IC chips can be fabricated in one go from one wafer; consequently, wafer size has been increasing as semiconductor technology has advanced.
