Gettering of copper in bonded silicon wafers.

Cross-sectional TEM was used to study the distribution and precipitation of copper in Bonded Silicon (BESOI) wafers intentionally contaminated with an aqueous copper solution. The wafers were contaminated with 10(17) atoms/cm(2), and annealed at 1000 degrees C far 5 minutes, followed by slow quenching to room temperature. Even though the contamination was done from the top-silicon side, defects were observed in tile bulk substrate, and no defects were formed in the top silicon layer, or in the oxide/oxide-silicon interfaces. Furthermore the defects were not concentrated close to the oxide interface, but where uniformly distributed in the bulk. SIMS analysis also did not show copper buildup at either interface We think that this is happening because the bulk offers by far the largest concentration of nucleation sites, and the top silicon layer and oxide-silicon interfaces are relatively speaking, Free of defects or other nucleation sites for the copper.