After the circuit patterns have been printed, the wafer is then "doped" with more impurity atoms, such as boron or phosphorus, to form positive and negative
conducting regions. The dopant atoms are ionized (stripped of one or more of their electrons) and accelerated to a high energy in ion implantation chambers. The ions bombard the silicon wafer and penetrate
the holes etched in the protective oxide layer. The depth and concentration of these impurities determine the specific electrical characteristics of the chip.
