Novel Ir–Ti Alloy Electrodes for High-Density Ferroelectric Memory Applications

概要

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An Ir-based Ir–Ti alloy was improved by controlling the interface layer between Pb(Zr,Ti)O3 (PZT) and an electrode for the high-density ferroelectric memory application. Compared with the Ir electrode, the Ir–Ti alloy electrode was resistant to oxygen annealing and the surface did not roughen much. The increase in resistivity after the annealing was also sufficiently low to maintain its feasibility as an electrode. Furthermore, Ti in the Ir–Ti alloy seemed to assist the growth of (111) grains of PZT, thus resulting in a larger $2P_{\text{r}}$. The Ir–Ti alloy layer also acted as a seed layer for PZT. This means that we can skip the deposition of the seed layer for the purpose of good quality PZT. Furthermore, the Ir–Ti alloy is still applicable to very thin films. In ultra thin films of PZT and a bottom electrode, IrTiOx (20 nm)/IrTi (10 nm) is a good choice as the bottom electrode to conserve $2P_{\text{r}}$ as well as protect the reliability of thin PZT. This is a very different result from IrOx. It is believed that these results could provide a possibility for commercializing embedded or stand-alone FeRAM in high-density ferroelectric memory applications.
2005-06-15