the heart of all computers and other electronic devices is the integrated circuit(or IC) Each integrated circuit chip is a thin square wafer hav ing dimensions on the order of 6 mm by 6 mm by 0,4 mm; furthermore, literally millions of inter- connected electronic components and circuits are embedded in one of the chip faces. The base ma erial for ICs is silicon, to which has been added very specific and extremely minute and controlled concentrations of impuritieN that are confined to very small and localized regions For some ICs, the impurities are added using high-temperature dif fusion heat treatments