Effect of post plasma oxidation on Ge gate stacks interface formation

This work investigates the application of slot plane antenna plasma oxidation (SPAO) during dielectric deposition to process TiN/ZrO₂/Al₂O₃/Ge MOS capacitors. The impact of SPAO exposure on effective oxide thickness (EOT), leakage current, interface state density (D_it), C-V hysteresis, oxide breakdown characteristics was studied. Considerable degradation of electrical properties was observed with SPAO being performed before Al₂O₃/ZrO₂ gate stack deposition. When SPAO was performed in between Al₂O₃/ZrO₂ deposition, moderate increase in EOT and significant decrease in D_it was observed. This can be attributed to the formation of a thicker GeO_X layer. On the other hand, when SPAO was performed after the deposition of both the high-k layers, higher D_it was observed suggesting a GeO₂ layer formation. Time zero dielectric breakdown (TZDB) characteristics indicate that plasma exposure after and in between Al₂O₃/ZrO₂ deposition enhances the dielectric quality by film densification due to plasma exposure. It was also demonstrated that improved dielectric and interface quality can be achieved when ALD-Al₂O₃/ZrO₂ gate stacks were exposed to SPAO.