Germanium doping of Si substrates for improved device characteristics and yield

During the last decade the 300 mm Si wafer has been optimized and one is already studying 450 mm crystals and wafers. The increasing silicon crystal diameter shows two important trends with respect to substrate characteristics: the interstitial oxygen concentration is decreasing while the size of grown in voids (COP's) in vacancy-rich crystals is increasing. The first effect is due the suppression of melt movements by the use of magnetic fields leading to a more limited transport of oxygen to the crystal. This and the decreasing thermal budget of advanced device processing leads to reduced internal gettering capacity. The increasing COP size is due to the combination of decreasing pulling rate and thermal gradient leading to a decreased void nucleation and increased thermal budget for void growth. The effect of Ge doping in the range between 10(16) cm(-3) and 10(19) cm(-3) on both COP's and oxygen precipitation will be discussed.