OXYNITRIDATION-ENHANCED DIFFUSION OF PHOSPHORUS IN [100] SILICON

Diffusion of phosphorus in silicon in an ambient of pure N-2, pure NH3 , and mixtures of NH3 and N-2 has been investigated to study the effec t of the oxynitridation reaction on the diffusivity. With a thin SiO2 layer on the silicon wafer and a low phosphorus concentration, the dif fusion coefficient of phosphorus can be expressed as a function of the partial pressure of NH3 and temperature as D = 0.145 exp (-3.26 eV/kT ) + 1.718 x 10(-6) exp (-1.72 eV/kT)p(NH3) cm(2) s(-1) At the same tim e, the ratio of the interstitial concentration under oxynitridation co nditions to the concentration under inert conditions can be expressed as C-I/C-I = 1 + 1.183 x 10(-5) exp (1.54 eV/kT)p(NH3) By using P dif fusion as an interstitial monitor, the data (Ref. 1) of oxynitridatian -enhanced B diffusion are analyzed and the fraction of boron diffusion which occurs through the interstitial mechanism is calculated to be 0 .88.