Poole-Frenkel conduction and critical charge-to-breakdown in plasma-enhanced chemical vapor deposition silicon-rich silicon nitride films

This work addresses the limited understanding of how stoichiometry influences high-field conduction and breakdown-triggering mechanisms in Silicon-rich silicon nitride (SiNₓ) thin films deposited by plasma-enhanced chemical vapor deposition (PECVD), which is critical for their use as insulating barriers for galvanic isolation in microelectronic devices operating under high electric fields. Amorphous hydrogenated a-SiNₓ:H films with x=[N]/[Si] ratios ranging from 0.86 to 1.06 were deposited by PECVD and integrated into metal–insulator–metal (MIM) structures. Electrical characterization was performed using DC polarization–depolarization measurements and AC high-voltage broadband dielectric spectroscopy over a wide frequency range, allowing extraction of current density–electric field ( J – E ) characteristics under high-field conditions. The experimental results show that Poole–Frenkel (PF) emission governs field-assisted conduction in Silicon-rich SiNₓ films under both DC and AC stress. PF analysis enabled extraction of the zero-field trap barrier height ( ϕ 0 ) ​and the theoretical dielectric permittivity ( ε t h e o ′ ), which were compared to experimental permittivity values. The barrier height ( ϕ 0 ) ​ was found to increase from approximately 0.8 to 1.5 eV with increasing nitrogen content, while ( ε t h e o ′ ) exhibited a decreasing trend, consistent with experimental observations. Breakdown measurements revealed a strong dependence of the breakdown field ( E BD ) ​ on composition, increasing with nitrogen incorporation. In contrast, the charge-to-breakdown ( Q BD ) ​ remained within a narrow range across all compositions, indicating that dielectric failure is governed by a critical injected charge, highlighting a conduction-triggered breakdown process. These results provide design-relevant insights into the role of stoichiometry and frequency on trap-assisted conduction and breakdown behavior in Silicon-rich SiNₓ insulating layers, with direct implications for high-voltage microelectronic and galvanic isolation applications.