Internal gettering for Ni contamination in Czochralski silicon wafers

Internal gettering (IG) behavior for Ni contamination in Czochralski silico n wafers was studied. The wafers were initially contaminated with Ni, and t hen isothermally annealed between 800 and 1000 degrees C for up to 16 h. Th e density of Ni-silicides at the polished surfaces and the density of oxide precipitates at the cleaved surfaces were obtained by the preferential etc hing method with Wright etchant. It was confirmed that (i) with an increase in annealing time, Ni-silicide density decreased and became less than the detection limit, and (ii) oxide precipitates were not detected in some of t he wafers, in which Ni-silicides were not detected. The density of oxide pr ecipitates with their size less than the detection limit was obtained after additional annealing at 1000 degrees C for 16 h, and the size of precipita tes was obtained by calculations with assuming diffusion-limited growth. Th e critical size of oxide precipitates for the IG effect was defined as the size above which the Ni-silicides were not detected. It was concluded that (ii the critical size decreased with an increase in precipitate density and (ii) the critical size became less than the detection limit of approximate ly 200 nm by the etching method, when the precipitate density was higher th an about 10(8)/cm(3) (C) 2000 The Electrochemical Society. All rights reser ved.