Characterization of sub-micrometre silicon films (Si-LPCVD) heavily in situ boron-doped and submitted to treatments of dry oxidation
We present the results of a comprehensive investigation concerning changes in the structural and electrical properties of heavily (2 ? 1020 cm?3) in situ boron-doped polysilicon thin films by the low pressure chemical vapour deposition method before and after thermal oxidation treatments. Secondary ion mass spectrometry and transmission electron microscopy, with their associated diffraction diagrams, and four-point probe resistivity measurements are performed on sub-micrometre layers (?300 nm) deposited at two interesting temperatures Td1 = 520 ?C and Td2 = 605 ?C. The thermal oxidation experiments are carried out under dry oxygen (O2) at three oxidation temperatures, Tox, of 840, 945 and 1050 ?C for several durations. After these thermal oxidation processes, remarkable changes in the behaviour of the doping profile, grain growth and electrical conductivity have been observed. This behaviour seems to be typically characteristic of the in situ heavily boron-doped films. In addition, to the presence of some saturation thermal dependence phenomena, we find that these results correlate well with, and support the presence of, another phenomena called the 'differential of oxidation rate' which is evidenced as typical of the in situ doped films.