BURIED-OXIDE LAYER FORMATION BY HIGH-DOSE OXYGEN-ION IMPLANTATION INTO SI WAFERS - SIMOX (SEPARATION BY IMPLANTED OXYGEN)

Recent advances in SIMOX (separation by implanted oxygen) wafer technology are reviewed. Using a thin surface silicon layer ( less than or equal to 100 nm) should allow the improvement of transistor and integrated-circuit performance without the need for scaling-down. In the SIMOX process, silicon wafers are subjected to high dose oxygen-ion implantation (dose similar to 1 X 10(18)/cm(2), energy similar to 200 keV) and high-temperature annealing (greater than or equal to 1300 degrees C). A buried-oxide layer (several hundred nm thick) is synthesized below a single-crystalline surface-silicon layer (several hundred nm thick). SIMOX structure may be synthesized using a super-stoichiometric oxygen concentration during implantation, or, more recently, a sub-stoichiometric oxygen concentration after annealing. The former method produces a reliable buried-oxide layer, but induces a high density of defects in the surface-silicon layer. The latter cuts implantation time and improves surface-silicon crystallinity, but process window is rather narrow.