The evolution of deep trench DRAM capacitors necessitates innovations in material selection as well as in process technology. For the 36 nm generation, crystalline ZrO₂ is intended as high-k dielectric in order to meet the electrical targets. Additionally, the development of suitable ALD processes for the deposition of the dielectric in high aspect ratio trenches is a second essential issue. Therefore, material evaluation adjusted to the process conditions used in trench DRAM production with a capacitor-before-transistor process flow is inevitable, especially, as the thermal stability during the post deposition anneal (PDA) up to 1000°C is one of the most challenging requirements to the dielectric. Growth and crystallization of ALD-ZrO₂ on a SiO-interface depend on both deposition temperature and layer thickness. Un-patterned wafers with as deposited amorphous and after various PDA’s ZrO₂ layers (5 nm physical thickness) were electrically characterized by the non-contact corona charge / Kelvin-probe technique. Physical properties were analyzed by Ellipsometry, AFM, XRD/XRR, ARXPS and SIMS. For the PDA in N₂ up to 400°C, the layers remain amorphous showing the same CET (1.55 nm), thickness and density. PDA’s up to 700°C, however, crystallize the material to the tetragonal phase with an increased density and a reduced layer thickness. Crystallization and nitrogen incorporation induce a CET decrease (1.25 nm). After 800°C PDA, an increased physical thickness and CET (1.35 nm) is observed due to an interfacial layer growth. For the more reactive NH₃ PDA, all above effects especially the changes in CET are more pronounced. Leakage current densities do not change significantly after PDA in both atmospheres up to 700°C, but severe degradations occur for temperatures higher than 800°C. In conclusion, the NH₃ treatment is more promising than N₂ to reduce the CET of ZrO₂ although no improvement in leakage current densities at high temperatures compared to N₂ could be found.

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