Quantification of Sodium-Ion Migration in Silicon Nitride by Flatband-Potential Monitoring at Device-Operating Temperatures

摘要

A trap-corrected bias–temperature–stress (TraC-BTS) method to quantify the kinetics of ion migration in dielectrics based on capacitance–voltage measurements is presented. The method is based on the extraction of flatband potential (V_(fb)) shifts in metal–insulator–semiconductor test structures an enables the reliability assessment of semiconductor dielectrics and solar cells. Herein, it is shown that carrier trapping in the dielectric must be accounted for, as it strongly affects the measurement of flatband potential in silicon-nitride-based capacitors. This effect is corrected by isolating the contribution of trapping on V_(fb) using contamination-free control devices. A specific drift-diffusion model of the ion kinetics presented herein allows the extraction of ion diffusivity. An Arrhenius relationship is obtained for sodium diffusivity in silicon nitride in a temperature range from 30 °C to 90 °C at an electric field of 1 MV cm~(-1), yielding a prefactor D_0= 1×10~(-14) cm~2 s~(-1) and an activation energy E_a=0.14 eV, with a 95% confidence interval of [0.07, 0.21] eV for the diffusivity. These quantitative kinetics confirm that silicon nitride may be a poor sodium migration barrier under a significant electric field.