Lattice strain around platelet oxide precipitates in C- and N-doped silicon epitaxial wafers

The effect of heavy C and N doping on local lattice strain around platelet oxide precipitates in Czochralski silicon substrates of p/p- epitaxial (epi ) wafers was investigated quantitatively using convergent beam electron dif fraction (CBED). C- and N-doped p/p- epi wafers, including platelet precipi tates with an edge length of approximately 500 nm, were prepared with an is othermal annealing at 800 degreesC for 700 h. The results of strain analysi s were compared with the reported results of p(-) polished wafers and heavi ly B-doped p/p(+) epi wafers, including an almost equal platelet density an d length to C- and N-doped p/p(-) epi wafers. It was found, with strain ana lysis from high order Laue zone patterns in the CBED disk, that (i) the typ e of lattice strain in C- and N-doped p/p(-) epi wafers was coincided to p( -) polished and B-doped p/p(+) epi wafers. The strain along the normal dire ction to the flat plane of the platelet precipitate was compressive, while the strain along the parallel direction to the flat plane of the platelet w as tensile; (ii) the strain in C-doped p/p(-) epi wafers was as large as th at in B-doped p/p(+) epi wafers, and far relaxed compared with N-doped p/p( -) epi and p(-) polished wafers. Since the substitutional carbon concentrat ion did not change during the isothermal annealing, the strain relaxation i n C-doped p/p(-) epi wafers was caused by the availability of effective sin ks in the matrix for silicon interstitials emitted by the precipitates. (C) 2001 The Electrochemical Society.