No abstract

Pt bottom electrodes for SrBi2Ta2O9 (SBTO) capacitors have been investigated for use in nonvolatile memories. A Pt thin film which is sputtered at a temperature of 300°C consists of enlarged columnar grains, while a film sputtered at room temperature consists of fibrous columnar grains. The formation mechanism of enlarged grains of the Pt film sputtered at 300°C is due to the fact that the film structure changes with substrate temperature based on the structure-zone model. The Pt bottom electrode which consists of the enlarged grains results in a decrease in the Ti diffusion path, leading to effective adhesion of Pt to a SiO2 film.

We have experimentally found a Sn-Zn-Mg 2 Sn eutectic alloy with the eutectic composition of 82Sn-10Zn-8Mg (mol%) and with nearly the same eutectic temperature of 454 K as that of the Pb-Sn eutectic alloy. The eutectic alloy was made in air by covering Sn, Zn and Mg with the 59KCl-41LiCl (mol%) composition eutectic melt in an Al 2 O 3 crucible, melting the metals at 1073 K and washing away the alkali-chlorides with distilled water after cooling to room temperature. The as-cast alloy easily oxidized at temperatures above 503 K in air after melting. It was found that the Sn-Zn-(Mg, Al) 2 Sn eutectic alloys that were made by replacing 0.8 to 4.0 mol% of Mg with Al in the ternary eutectic composition with the same alloying method did not oxidize in air after melting.