Gettering Efficiency of Si(110)/Si(100) Directly Bonded Hybrid Crystal Orientation Substrates

摘要

Si(110) and Si(100) directly bonded (DSB) substrates are paid attention as candidate materials for the substrate of next-generation complementary metal oxide semiconductors (CMOSs). From a practical viewpoint on DSB substrates, we have investigated the gettering efficiency at the bonded interfaces of DSB substrates. In our experiments, DSB substrates were intentionally contaminated with 3d transition metals (Fe, Cu, and Ni) and then annealed at 1000℃. The dependence of the concentrations of these metals on the depth of what was evaluated by secondary ionization mass spectrometry (SIMS). It was found that the bonded interface has a good gettering ability for these metals. Results of the preferential etching method support the results of SIMS. Transmission electron microscopy (TEM) showed that (ⅰ) the gettered Fe and Ni formed the silicides FeSi_2 and Ni_2Si_3, respectively; however, (ⅱ) no Cu precipitates formed at the bonded interface. Furthermore, we confirmed that the bonded interface can be effective gettering sites for Cr and Ti. This result indicates that the bonded interface can become effective gettering sites for metals with low diffusivities, if they reach the interface just below the device active layer.