Karl Hornik

Characteristics of an Oxygen Barrier Based on Bi-layered Ir

For high-density ferroelectric random access memory devices (FeRAMs) with capacitor over plug (COP) structure, oxygen diffusion barriers based on bi-layered Ir have been investigated. This paper describes the detailed characteristics of the barriers. A bi-layered Ir barrier was fabricated by repeating the deposition and RTO treatment of an Ir metal film, which was very effective to obtain excellent barrier properties against oxygen diffusion. Surface roughening was shown after RTO, but can be suppressed by lowering the RTO temperature. The roughening is caused by the formation of a gaseous phase of IrOx during RTO, and not by the formation of Ir hillocks. The stress of the bi-layered Ir barrier is tensile after RTO, which makes further stacking of more layers on the barrier with good adhesion possible. Performance of this barrier was checked using the post annealing in 18O isotope ambient at 650°C for 2 hours. SIMS profile showed the barrier prevented the diffusion of 18O, effectively. The above results strongly suggest that the bi-layered Ir barrier can be applied to the COP structure for high-density FeRAMs.

Oxygen Diffusion Barriers for High-Density FeRAMs

For high-density ferroelectric random access memories (FeRAMs) with capacitor over plug (COP) structure, oxygen diffusion barriers have been investigated. This paper describes the excellent properties of two newly developed diffusion barriers, which are based on a) stoichiometric-IrO 2 films and b) surface treated Ir-films. The IrO 2 barrier was successfully optimized by forming stoichiometric IrO 2 , by deposition temperature control and by decreasing mechanical stress. Surface treatment of Ir-metal layer by using RTO (rapid thermal oxidation) was very effective for obtaining excellent barrier properties, which could be further improved by repeated deposition and RTO treatment leading to bi- or multilayer structures. When applied to fully stacked-PZT capacitors, both barrier types inhibited the oxidation of an underlying W-plug even after annealing at 650C for 2 hours in oxygen ambient. Q sw values of PZT capacitors were around 30 w C/cm 2.