Buried oxide and defects in oxygen implanted Si monitored by positron annihilation

摘要

One- and two-detector Doppler broadening measurements performed on low (～10~(14) to 10~(15) O~(+)/cm~(2)) and high dose (～10~(17) to 10~(18) O~(+)/cm~(2)) oxygen-irradiated Si using variable-energy slow positrons are analyzed in terms of S and W parameters. After annealing the low-dose samples at 800℃, large V_(x)O_(y) complexes are formed at depths around 400 nm. These complexes produce a clear-cut signature when the ratio of S to that of defect-free bulk Si is plotted. Similar behavior is found for samples irradiated with 2 and 4×10~(17)O~(+)/cm~(2) and annealed at 1000℃. After irradiation with 1.7×10~(18)O~(+)/cm~(2) and anneal at 1350℃ a 170 nm thick almost-bulk-quality Si surface layer is formed on top of a 430 nm thick buried oxide layer. This method of preparation is called separation by implantation of oxygen. S-W measurements show that the surface layer contains electrically inactive V_(x)O_(y) complexes not seen by electron microscopy. A method is presented to decompose the Doppler broadening line shape into contributions of the bulk, surface, and defect.