Interface states reduction in atomic layer deposited TiN/ZrO2/Al2O3/Ge gate stacks

In this work, the authors report the application and influence of slot plane antenna plasma oxidation (SPAO) on the quality of Ge/high-k based metal–oxide–semiconductor capacitors. The effect of SPAO exposure on the Ge/high-k interface during atomic layer deposition of the dielectric along with the reliability characteristics has been studied. A significant improvement in the electrical properties has been observed when the high-k stacks are exposed to SPAO treatment. The devices treated with SPAO after Al₂O₃/ZrO₂ deposition (CASE-1) show slightly better equivalent oxide thickness, low leakage current density, and marginally better breakdown characteristics compared to the devices treated with SPAO in-between Al₂O₃/ZrO₂ deposition (CASE-2). This can be attributed to the densification of the gate stack as the plasma exposed to the total stack and the formation of the thick interfacial layer as evident from the X-ray photoelectron spectroscopy (XPS) measurements. A stable and thin interfacial layer formation was observed from XPS data in the samples treated with SPAO in-between high-k stack deposition compared to the samples treated with SPAO after high-k stack deposition. This leads to the low interface state density, low hysteresis, comparable dielectric breakdown, and reliable characteristics in CASE-2 compared to CASE-1. On the other hand, XPS data revealed that the interface is deteriorated in the samples treated with SPAO before high-k stack deposition (CASE-3) and leads to poor electrical properties.