It was noted that oxides which had been grown at low temperatures had a higher density than those which had been grown or annealed at high temperatures. An investigation was made here of the role which the oxide density played in affecting B diffusion through thin-gate dielectrics. Capacitor structures were prepared by depositing polycrystalline Si onto 5.4 to 6nm of oxide which had been grown at 800C in dry O2. Some of these high-density oxides were then annealed at 1100C in order to relax grown-in stresses. After ion implantation of B into the polysilicon, the structures were annealed in an inert ambient at 950C in order to promote B penetration. Capacitance-voltage measurements revealed that B penetration was greatly enhanced in films which had been subjected to high-temperature relaxation annealing. It was concluded that B diffusion in the oxide was retarded by an increased density. The B diffusivity decreased from about 4 x 10-18cm2/s, at an excess density of 0.4%, to a diffusivity of about 10-18cm2/s at an excess density of 4%.

M.Navi, S.T.Dunham: Applied Physics Letters, 1998, 72[17], 2111-3