A study was made of the B diffusion in N-doped Si, as deposited from disilane Si2H6 and ammonia NH3 for the development of P+ polysilicon gate metal oxide semiconductor devices. N-doped Si films with varied N content were B implanted, then annealed and finally analyzed by secondary ion mass spectroscopy. In order to simulate the experimental secondary ion mass spectrometry of B concentration profiles in the N-doped Si films, a model adapted to the particular conditions of the samples elaboration, i.e. the very high B concentration and the N content, was established. The B diffusion reduction in N-doped Si films with increasing N rates was evidenced by the profiles as well as by the obtained diffusion coefficients, which showed that the N incorporation reduces the B diffusion. This was confirmed by capacitance–voltage (C–V) measurements performed on metal oxide semiconductor capacitors: the higher the N content, the lower the flat-band voltage. Finally, these results demonstrate that the improvement of the gate oxide quality occurred with the suppression of the B penetration.

Boron Diffusion into Nitrogen-Doped Silicon Films for P+ Polysilicon Gate Structures. F.Mansour, R.Mahamdi, L.Jalabert, P.Temple-Boyer: Thin Solid Films, 2003, 434[1-2], 152-6