Effect of heavy boron doping on the lattice strain around platelet oxide precipitates in Czochralski silicon wafers

The effect of heavy boron doping on local lattice strain around platelet ox ide precipitates in Czochralski silicon wafers was investigated quantitativ ely by convergent beam electron diffraction (CBED). Lightly boron doped (p( -)) polished wafers, including platelet precipitates with density of about 5x10(9)/cm(3) and with an edge length of about 500 nm, were prepared with a n isothermal annealing at 800 degrees C for 700 h. Heavy boron doped (p/p()) epitaxial wafers, including an almost equal precipitate density and leng th to p(-) wafers, were also prepared with an isothermal annealing at 800 d egrees C for 200 h. It was found by strain analysis from high-order Laue zo ne patterns in the CBED disk that (i) the type of lattice strain was coinci dent in p(-) and p/p(+) wafers: the strain along the normal direction of th e platelet precipitate was compressive, while the strain along the parallel direction of the platelet was tensile; (ii) the strain in p/p(+) wafers wa s smaller than that in p(-) wafers; and (iii) the punched-out dislocations were generated by platelets only in p(-) wafers. The results of (ii) and (i ii) indicate that the strain around the platelets is relaxed due to the hea vy boron doping. (C) 2000 American Institute of Physics. [S0021-8979(00)037 13-0].