Atomic layer deposition of Y-stabilized ZrO₂ for advanced DRAM capacitors

With accelerated shrinking of integrated circuit, the fabrication of metal-insulator-metal (MIM) capacitors having a high capacitance density and low leakage current for dynamic random access memory (DRAM) has become a challenge. In this study, we investigated Y-stabilized ZrO₂ as a novel high-k material for DRAM capacitors. We used atomic layer deposition (ALD) to produce Y-stabilized ZrO₂; this technique enables easy control of the Y concentration by changing the ratio of ZrO₂ to Y₂O₃ ALD cycles. This technique is suitable for future DRAM capacitors, as it provides superior thickness controllability and conformality. Y doping into ZrO₂ increases the oxygen vacancy content in the films and transforms the ZrO₂ crystal structure from monoclinic to cubic. As a result, the dielectric constant is significantly increased from 19.1 to 30.2. Moreover, Y doping shifts the defect level into the conduction band rather than the energy bandgap, resulting in about 60 times lower leakage current density for Y-doped ZrO₂ compared to undoped ZrO₂. It is notable that the dielectric properties and the leakage current density are simultaneously enhanced, indicating that Y-doped ZrO₂ is a promising candidate to satisfy the requirements of future DRAM capacitors.