Thermal stability of Co-sputtered Ru-Ti alloy electrodes for dynamic random access memory applications

Ray-Hua Horng*, Dong Sing Wuu, Luh Huei Wu, Ming Kwei Lee, Shih Hsiung Chan, Ching Chich Leu, Tiao Yuan Huang, Simon Min Sze

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Ru-Ti alloy films were studied for use as a bottom electrode of ferroelectric/paraelectric thin film capacitors. These thin films with different Ru/Ti compositions were first prepared by co-sputtering. The Ru/Ti ratio in the alloy was found to strongly affect the resistivity, structure formation and thermal stability. The resistivity of the as-deposited films decreases and closes to that of pure Ru metal films as the amount of Ru atoms increasing. From X-ray diffraction measurement, it was found that the RuTi phase has formed for the as-deposited sample. There also exist Ru and Ti phases for Ru-enriched and Ti-enriched samples, respectively. As-deposited alloy films were also annealed by rapid thermal processing (RTP, 600-750°C, 1 min) in oxygen ambient to simulate the processing of ferroelectric/paraelectric thin film capacitors. It was found that the composition of the thin film has a large effect on the thermal stability. The resistivity of alloy thin films is thermally stable as the Ru composition varies from 0.68 to 0.81. It may be due to the RuTiO2 formation at the surface and play an important role in preventing further oxidation of the Ru-enriched layer. This oxide also presents conductive behavior. On the other hand, the interface between Ru-enriched alloys and Si substrate was still sharp for the RTF-treated sample at 600°C for 1 min. The alloy film with high Ru composition shows excellent thermal stability and barriers against interdiffusion of Si and oxygen. These results suggest that the Ru-enriched alloy films are suitable for the bottom electrode application in ferroelectric/paraelectric thin film capacitors.

Original languageEnglish
JournalJapanese Journal of Applied Physics, Part 2: Letters
Volume37
Issue number10 SUPPL. B
DOIs
StatePublished - 15 Oct 1998

Keywords

  • Alloy
  • Ferroelectric
  • Paraelectric
  • RTP
  • Ru-Ti

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