【Device Papers】Heavy-ion-induced degradation mechanisms and supercritical fluid recovery dynamics in Al₂O₃/β-Ga₂O₃ metal-oxide-semiconductor capacitors

      Researchers from the  Xi’an Jiaotong University have published a dissertation titled "Heavy-ion-induced degradation mechanisms and supercritical fluid recovery dynamics in Al₂O₃/β-Ga₂O₃ metal-oxide-semiconductor capacitors" in Journal of Vacuum Science & Technology A.

Abstract

      This study investigated heavy-ion irradiation effects on Al₂O₃/beta-gallium (β-Ga₂O₃) metal-oxide-semiconductor capacitors (MOSCAPs), which serve as essential building blocks for metal-oxide-semiconductor field effect transistors (MOSFETs), and evaluated the restorative efficacy of N₂O-based supercritical fluid (SCF) treatment. Following tantalum (Ta) ion irradiation at a cumulative fluence of 4 × 10⁷ ions/cm², the net carrier concentration (N_d) degraded from 2.91 × 10¹⁶ to 1.92 × 10¹⁶ cm⁻³. The interface state density (D_it) and interface oxide trap charge density (N_iot) exhibited a slight decrease due to heavy-ion-induced defect restructuring, while the effective oxide charge density (N_eff) declined from 4.22 × 10¹¹ to 3.87 × 10¹¹ cm⁻² via electron capture by oxygen vacancies in the oxide layer. Irradiation-induced latent tracks and a reduction in trap energy level (φ_t) from 1.72 to 1.62 eV led to a tenfold increase in leakage current and reduced breakdown voltage, with trap-assisted tunneling identified as the dominant transport mechanism. To mitigate these effects, N₂O-based SCF treatments were employed to achieve recovery through mild nitridation and oxygen compensation. Initial SCF treatment increased φ_t to 1.78 eV, though persistent latent tracks limited the restoration of leakage characteristics. Subsequent SCF treatments further suppressed leakage current primarily by reducing electrically active trap density and passivating track-associated defects, despite a marginal decline in φ_t. Recovery saturation and N_eff polarity reversal were observed during prolonged exposure, indicating complex charge dynamics. These findings elucidated heavy-ion damage physics in Al₂O₃/β-Ga₂O₃ MOS structures and defined SCF operational boundaries, providing a critical reference for predicting the operational lifetime of future radiation-tolerant MOSFETs.

DOI：

https://doi.org/10.1116/6.0005278