At each step of the process, wafers are tested with specially designed equipment under computer control, some of which measure events on an atomic scale.
When the metalization process is completed, all the chips on a wafer are tested again. Those that pass the rigorous electrical tests are then cut from the wafer with high-speed, water-cooled diamond cutting
saws and mounted in metal or plastic packages, called modules. These modules are then tested again.
Each tiny memory cell that holds a bit of information, and every circuit must be tested. Since only one of IBM's advanced eight-inch memory wafers
contain as many memory cells as there are people on earth, it takes extraordinary care and precision to produce reliable chips.
