GETTERING OF CU AND NI IMPURITIES IN SIMOX WAFERS

The gettering of Cu and Ni impurities in intentionally contaminated SI MOX wafers have been studied by means of cross-sectional transmission electron microscopy, nanoprobe energy dispersive x-ray spectroscopy, s econdary ion mass spectrometry, and selective etching. The wafers with Cu or Ni surface concentrations ranged from about 10(12) up to 10(17) atom/cm(2) were annealed at various temperatures followed by slow coo ling to room temperature. Single and multistep thermal treatments were applied. It has been found that the buried oxide does not prevent the diffusion of both Cu and Ni contaminants from the top silicon layer i nto the bulk substrate at the whole investigated temperature range fro m 600 to 950 degrees C. Moreover the effective gettering of Cu and Ni in the thin silicon substrate layer located just beneath the buried ox ide has been observed and explained as being due to the heterogeneous impurity precipitation at stacking fault tetrahedra formed there durin g the SIMOX manufacturing. The gettering process has remained stable d uring the thermal simulation of CMOS device process of new generation ICs with 0.25 mu m feature size.