Chemical Fluid Deposition of Hf-Zr-O-based Thin Films using Supercritical Carbon Dioxide Fluid
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Chemical Fluid Deposition of Hf-Zr-O-based Thin Films using Supercritical Carbon Dioxide Fluid Marina Shiokawa,1 Katsushi Izaki,1 Hiroshi Funakubo2 and Hiroshi Uchida1 1
Department of Materials and Life Sciences, Sophia University, Tokyo, 102-8554, Japan
2
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama, 226-8502, Japan
ABSTRACT We propose some chemical processing procedures for fabricating thin films in Hf-Zr-O system by a unique film deposition technique using supercritical carbon dioxide fluid (scCO2), i.e., supercritical fluid deposition (SCFD), which would be an prospective approach for fabricating metal-oxide films for integrated circuits because of its unique characteristics; e.g., extraction ability, transportation capability, and reaction equilibrium etc., are quite favorable for the film deposition from metal-complex precursors. The SCFD was accomplished in a closed batch-type reaction apparatus, consisting of two steps; (a) material deposition and (b) subsequent post-treatment under scCO2 atmosphere. Thin films of amorphous Hf-Zr-O were deposited on platinized silicon [(111)Pt/TiO2/(100)Si] substrates by SCFD using metal-complex precursors M[OCH(CH3)]2(C9H11O2)2 (M = Hf or Zr) at reaction temperature of 100 – 300 oC, significantly lower than those for MOCVD. These films possessed dielectric permittivity’s of approximately 20 – 25, comparable to those from conventional processes, although they still included residue of organic species that prompt the dielectric degradation under lower-frequency bias application. INTRODUCTION Metal oxide thin films are frequently utilized for the fabrication of a variety of electronic devices in modern industry. They are adopted as fundamental components with various functionality, such as insulators, diffusion barriers, dielectric/ferroelectric capacitors, sometimes even as conducting electrodes and mechanical actuators, etc. The components are especially important for construction of integrated circuits that is a core technology for versatile LSI, semiconductive memories (flash, DRAM, FeRAM, RAM, etc.) and, recently, advanced siliconbased MEMS devices. Various kinds of materials from simple oxides (such as SiO2, Al2O3, ZrO2, HfO2, CeO2, RuO2, etc.) to complex oxides (SrTiO3, In2O3-SnO2, SrRuO3, etc.) are applied as thin-film materials on semiconductive silicon (Si) wafers for constructing a wide variety of electronic devices with unique functionalities. A various kind of techniques for fabricating (i.e., depositing) the metal-oxide films have been developed for constructing integrated circuits on Si wafer: Typically, physical vapor deposition (PVD) techniques, such as sputtering and pulsed-laser deposition, chemical vapor deposition (CVD) including atomic layer deposition, and chemical solution deposition (CSD), are adopted by many researchers and manufacturers as conventional techniques. Almost all the
existing devices are fabricated by the combination of these processes. However, we recognize that these techniques include
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