高密度強誘電体メモリ用のMOCVD合成Pb(Zr,Ti)O_3の高再現性作製のための(111)配向したSrRuO_3/Pt下部電極(非揮発性メモリ及び関連プロセス一般)

概要

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Ferroelectric memories (FeRAM) are used in the microelectronic industry since they provide non volatility, high speed and low power consumption. Actual technologies are mainly based on Pb(Zr,Ti)O_3 ("so-called PZT") which ensures a high remnant polarization and a low coercive field. Nevertheless, the development of next generation PZT-based FeRAM requires the preparation of highly reliable ferroelectric capacitors which combine good electric properties with good resistance to reliability issues (fatigue, imprint and retention). In the present paper we report a comparative study of the structural, morphologic, and electric properties of Pb(Zr,Ti)O_3 films, deposited by pulsed metal-organic chemical vapour deposition (MOCVD), on different (111)-oriented bottom-electrode stacks (SrRuO_3/Pt, Pt, and Ir substrates). The Pb input ratio in the MOCVD chamber was systematically modified for each deposition run to obtain PZT films with various compositions within the Pb process window. Our results clearly demonstrate that only PZT films deposited on SrRuO_3 show high quality and reproducible properties throughout the process window, i.e., high (111) texture, low roughness (<4 nm), high Pr (〜40μC/cm^2), and low V_c (<1 V). This study provides further evidence that SrRuO_3/Pt substrates are good candidates for integration in next-generation high-density FeRAM.
社団法人電子情報通信学会の論文
2007-03-08