New approaches to improve the endurance of TiN/HfO₂/TiN capacitor during the back-end process for 70nm DRAM device

摘要

We have successfully developed a MIM capacitor process technology with a HfO₂ single layer deposited by ALD (atomic layer deposition), where a Hf(NEtMe)4 and CVD-TiN cylinder-type storage-node were used as a Hf liquid source and bottom electrode for 90 nm-scale DRAMs. Our experimental results indicated that NH₃-plasma treatment on HfO₂ film promoted crystallization below 400° C as well as the formation of a HfO_xN_y layer on the surface of the HfO₂ film. With this treatment, it was possible to solve the degradation problem of the leakage current depending on deposition method of the top electrode, and a stable leakage current without degradation was obtained up to 550° C. As a result, a TiN/HfO₂/TiN (TIT) capacitor with 1.4 μm-height storage node was successfully demonstrated with stable leakage current of 1fA/cell at +1.2 V and high cell capacitance of 40 fF after metal-2 integration.