MIM Capacitors Featuring Low EOT and Low Leakage Current Density by Nitrogen-Incorporated HfO₂/ZrO₂/HfO₂

A HfO2/ZrO2/HfO2 (HZH) high-k stack with adequate ZrO2 thickness ratio is proposed as dielectric in metal-insulator–metal (MIM) capacitor for dynamic random access memory (DRAM) applications. The dielectric constant (k) of 43 is achieved when the ZrO2 thickness ratio is 73%. An equivalent oxide thickness (EOT) of 0.46 nm and leakage current density ( Jg ) of 9.4×10−5 A/cm2 are simultaneously achieved with a total HZH physical thickness ( Tox ) of 5 nm. The leakage current may be caused by the interface traps at the HZH multi-interface structure, as well as the oxygen vacancies inside HfO2 and ZrO2. To suppress Jg , a NH3 plasma treatment was in situ conducted during atomic layer deposition (ALD) processes of HZH deposition. Through nitrogen incorporation with in situ NH3 plasma treatment, the oxygen vacancies can be passivated, and Zr-O–N bonds would be formed at the interface to suppress the formation of interface traps. The sample with an in situ NH3 plasma treatment at the interface between ZrO2 and top HfO2 (ZN) can obtain a reduction in leakage current density by 48% when compared with those without ZN, while maintaining the capacitance density (C) at a similar value of around 7.4 μ F/cm2. The approaches of HZH stack and in situ plasma treatment for MIM capacitor are promising to the cell in DRAM technology.