Light and Elevated Temperature Induced Degradation in Mono-Like and Float-Zone Silicon: Correlations to Material Types, Silicon Nitride Films, and Dopant Diffusion

Abstract

We compare light and elevated temperature induced degradation (LeTID) in four different silicon substrates, namely p-type boron-doped and n-type phosphorus-doped mono-like Si and float zone silicon, and study the dependence of the degradation behaviors on silicon nitride (SiN x ) film properties and dopant diffusions. The materials exhibit different degradation kinetics, but show a similar dependence on the SiN x deposition conditions, correlating strongly with the Si-N bond density and the refractive index of the SiN x films, measured using Fourier-transform infrared spectroscopy and ellipsometry. It is observed that the degradation severity is reduced by decreasing SiN x deposition temperature and power, revealing a potential solution to mitigate LeTID. Moreover, p-type materials are found to generally suffer a higher degradation extent than their n-type counterparts. Our experimental results are consistent with LeTID depending on the hydrogen concentration in the Si bulk. This model can explain the larger degradation observed in the p-type Si wafers, the dependence of LeTID on the SiN x films, and also the presence of heavily doped regions, all of which affect the diffusion of hydrogen and its final concentration in the bulk after firing.