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 1E16 cm^-3 and 1E19 cm^-3 on both COP's and oxygen precipitation will be discussed.