Diffusion of boron and arsenic in molybdenum disilicide films

Abstract Arsenic and boron diffusion in MoSi 2 has been investigated in the temperature range 450–900° C on the basis of SIMS measurements. The concentration profiles show that a relevant fraction of atoms remains fixed during the annealing. The dopant is mobile only for concentrations lower than about 4 x 10 19 for As and 5 x10 18 cm -3 for B. These values keep constant independently of the implanted dose and suggest the formation of metal-dopant compounds which control the concentration of dopant in solution. The mobile As can be described by the diffusion coefficient D As = 3.2 x 10 -6 exp(-1.4/ kT ) cm 2 /s. This value seems to be related to lattice diffusion, although further investigation will be necessary to better quantify the contribution of grain boundary diffusion. No detectable lattice diffusion has been observed in the B-doped specimens up to 800° C.