The hydrogen gettering at post-implantation hydrogen plasma treatments of helium- and hydrogen implanted Czochralski silicon

The effect of the gettering of hydrogen at buried defect layers at post-implantation hydrogen plasma treatments and the loss of hydrogen at these layers at high-temperature annealing of helium-implanted (at 300 keV, 1×1016 cm−2; at 1 MeV, 1×1015, 1×1016 and 1×1017 cm−2) and, for comparison, of hydrogen-implanted (at 70 keV, 1×1015, 1×1016 and 3×1016 cm−2) Czochralski silicon was studied. The samples were annealed at 450 and 1000°C in flowing nitrogen or hydrogen ambient. As-implanted and annealed samples were treated by a d.c. hydrogen plasma at 150°C. Secondary ion mass spectroscopy (SIMS) was applied to measure the hydrogen concentration profiles of the samples. The buried defect layers, which were created by hydrogen or helium implantation, act as good getter centers for hydrogen at appropriate hydrogen plasma or heat treatments. It is shown that the loss of hydrogen from the buried layers depends on the temperature, the time of annealing and the annealing ambient. The loss of hydrogen at 450°C and the decrease of the hydrogen SIMS signal do not only result from a formation of H2 molecules captured by cavities and platelets, but also from the penetration of atomic hydrogen into the wafer bulk. This penetration leads to a thermal donor formation, as can be proved by spreading resistance probe analysis.