Characterization of time-dependent dielectric degradation and breakdown in bulk hexagonal BN/Si structures

Abstract

Hexagonal boron nitride (h-BN) is a promising material for designing future electronic devices because of its superior dielectric properties. In this study, we fabricated bulk h-BN (sp₂-bonded BN nano-network structure) on Si substrates using magnetically confined arc discharge plasma under various conditions. The effects of process gas conditions (Ar/N₂ and N₂) and impurity [tungsten (W)] incorporation were discussed. Regardless of the gas conditions, the presence of W atoms was found to significantly modulate the optical energy gap, which is supported by first-principles calculations. We investigated time-dependent dielectric breakdown (TDDB) mechanisms under constant voltage stress (CVS) and constant current stress (CCS). The time evolutions of the leakage current and the applied gate voltage during the TDDB measurements were analyzed to clarify the carrier-trapping and defect-generation mechanisms toward the final catastrophic dielectric breakdown. The field acceleration factors in the CVS-TDDB lifetime prediction fell within the general trend of SiO₂-based films and were found to be a weak function of the gas condition and W concentration (CW), whereas the carrier-trapping and defect-generation dynamics during electrical stress depend on the gas conditions and CW. Based on the obtained results, we propose a prediction model for bulk h-BN degradation dynamics during CVS. We found that carrier trapping into preexisting sites and the probability of defect generation were enhanced by the bombardment of ions with higher energy during the bulk h-BN formation and a larger number of incorporated W atoms. These findings provide fundamental guidelines for the reliability assessment of bulk h-BN films for various applications.