Noriaki Oshima

Ruthenium Film with High Nuclear Density Deposited by MOCVD Using a Novel Liquid Precursor

Ruthenium thin films were deposited on SiO 2 /Si substrates at 260-500°C by metallorganic chemical vapor deposition (MOCVD) using a liquid precursor (2.4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp), DMPD: 2.4-dimethylpentadienyl, EtCp: ethylcyclopentadienyl]. The deposition characteristics and the electrical properties of the deposited films were compared with those using bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp) 2 ] precursor. The Ru films from Ru(DMPD)(EtCp) were deposited more stably than those from Ru(EtCp) 2 . Both films consisted of Ru single phase for the entire deposition temperature range. Initial nucleation of Ru films from Ru(DMPD)(EtCp) was smaller in size and denser than that from Ru(EtCp) 2 . Morover the deposition process from Ru(DMPD)(EtCp) has a much shorter incubation time than that from Ru(EtCp) 2 .

Fatigue-free RuO2/Pb(Zr,Ti)O3/RuO2 capacitor prepared by metalorganic chemical vapor deposition at 395 °C

We deposited an RuO2/Pb(Zr0.40Ti0.60)O3/RuO2 capacitor by metalorganic chemical vapor deposition. RuO2 and Pb(Zr0.40Ti0.60)O3 films were prepared at 350, 395, and 445 °C from respective Ru(C7H11)(C7H9)–O2 and Pb(C11H19O2)2–Zr(O⋅t-C4H9)4–Ti(O⋅i-C3H7)4–O2 systems. Good ferroelectricity was observed for PZT films deposited at 445 °C but not at 395 °C. However, we obtained ferroelectricity with a remanent polarization above 30 μC/cm2 by inserting a 10-nm-thick sputtered-Pt layer between the PZT and RuO2 bottom electrodes, which improved the crystallinity of PZT films even those deposited at 395 °C. This capacitor had hardly any fatigue after 1×1010 switching cycles. This demonstrates the possibility of preparing fatigue-free capacitor all deposited below 400 °C for high-density ferroelectric random-access memory applications.

Low-Temperature Preparation of Metallic Ruthenium Films by MOCVD Using Bis(2,4-dimethylpentadienyl)ruthenium

Physical properties of bis(2,4-dimethylpentadienyl)ruthenium [Ru(DMPD) 2 ] were compared with those of (2,4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp)]. Ru(DMPD) 2 showed a high vapor pressure of 13.3 Pa at 82°C and a decomposition temperature of 210°C, which is 60°C lower than that of Ru(DMPD)(EtCp). Metallic Ru film was deposited on oxidized Si(100) from a Ru(DMPD) 2 -O 2 system in a deposition temperature range from 220 to 400°C by metallorganic chemical vapor deposition (MOCVD), and crystalline metallic Ru films with smooth surfaces were deposited down to 220°C for the first time from a Ru(DMPD) 2 -O 2 system.

Seed Layer Free Conformal Ruthenium Film Deposition on Hole Substrates by MOCVD Using (2,4-Dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium

Ruthenium thin films were deposited at 260-400°C on hole substrates by metallorganic chemical vapor deposition (MOCVD) using (2,4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp)] for the Ru source. The microstructure, conformability, crystallinity, and resistivity of the films were examined. Conformal films whose resistivity was below 30 μΩ-cm were deposited below 300°C on SiO 2 /TiAIN/Ti/SiO 2 /Si(100) hole substrates with aspect ratio of 1.7. Finally, conformal films with a step coverage of 97% were deposited on SiO 2 /Si hole substrates, even those with a high aspect ratio of 6.4, by using Ru(DMPD)(EtCp) without a seed layer.

A Novel Ruthenium Precursor for MOCVD without Seed Ruthenium Layer

The molecular structure of Ru(DMPD)(EtCp) and Ru(EtCp)2 are shown in Fig.1(a) and 1(b), respectively. Ru thin films were deposited on oxidized Si substrates without seed Ru layer by MOCVD at the deposition temperature range from 260°C to 500°C using Ru(DMPD)(EtCp) and Ru(EtCp)2 individually. The vapor of the precursor was generated by bubbling method kept at 60°C where vapor pressure of Ru(DMPD)(EtCp) and Ru(EtCp)2 were the same and showed approximately 5.3Pa. This vapor was transferred to the cold wall type CVD reactor chamber

Conformability of Ruthenium Dioxide Films Prepared on Substrates with Capacitor Holes by MOCVD and Modification by Annealing

Ruthenium dioxide (RuO 2 ) films were prepared at 180-400 °C on SiO 2 /SiN/Si substrates with capacitor holes having an aspect ratio of 3.5 by metallorganic chemical vapor deposition (MOCVD) using (2,4-dimethylpentadienyl) (ethylcyclopentadienyl) ruthenium [Ru(DMPD)(EtCp)] as a Ru source. Conformal film deposition above 86% was ascertained at 200°C. Postannealing at 500 and 600°C under atmospheric N 2 flow improved the film crystallinities and resistivities without any degradation of the conformability.

The Effect of Precursor Ligands on the Deposition Characteristics of Ru Films by MOCVD

To investigate the effects of precursor ligands, metallic ruthenium films were deposited by metallorganic chemical vapor deposition (MOCVD) from three different divalent precursors, bis(2,4-dimethylpentadienyl)ruthenium [Ru(DMPD) 2 ; bis-open ruthenocene type], (2,4-dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium [Ru(DMPD)(EtCp); half-open ruthenocene type], and bis(ethylcyclopentadienyl)ruthenium [Ru(Etcp) 2 ; ruthenocene type]. Their activation energies and the deposition amounts at 400°C were 1.27, 1.68, and 2.32 eV and 1.9, 2.3, and 0.22 μmol/cm 2 h, respectively. The X-ray diffraction patterns indicated that the films prepared from Ru(DMPD) 2 were preferentially oriented to (001), whereas the films from Ru(EtCp) 2 and Ru(DMPD) (EtCp) showed random orientations. The resistivity of the films suggested that thinner films with lower resistivity could be deposited using Ru(DMPD) 2 .

Fabrication of Planar and Three-Dimensional PZT Capacitors with Ir-Based Electrodes Solely by Low-Temperature MOCVD Using a Novel Liquid Ir Precursor

We report on preparation of Ir and IrO2 electrodes and its applications to planar and three-dimensional (3D) PZT capacitors solely by MOCVD using a novel liquid Ir precursor, Ir(EtCp) (CHD). Continuous 15–50 nm-thick Ir films with a pure metallic phase were successfully grown at 250-350°C on SiO2/Si without an incubation time. Ir electrodes showed 40–60% step coverage on stepped substrates with aspect ratios of 0.5–2.0. Fatigue free planar and 3D-Ir/PZT/Ir capacitors with 2Pr of 27–36 μ C/cm2 were successfully fabricated solely by MOCVD. IrO2 electrodes were grown at 400°C by 2-step MOCVD using surface oxidized Ir seeds. Planar PZT capacitors with IrO2 bottom and Ir top electrodes showed D-E hysteresis loops with 2Pr of 27 μ C/cm2 and endurance property with no degradation up to 1010 switching cycles by bipolar pulses of ± 5 V and 500 kHz.

Fabrication of Ir-Based Electrodes by Metal Organic Chemical Vapor Deposition Using Liquid Ir Precursors

Ir-based electrodes were fabricated by metal organic chemical vapor deposition (MOCVD) using a newly developed liquid precursor, (ethylcyclopentadienyl)bis(ethylene) iridium [Ir(EtCp)(C2H4)2], with a lower decomposition temperature than previous precursors, (ethylcyclopentadienyl)(1,5-cyclooctadiene) iridium [Ir(EtCp)(COD)] and (ethylcyclopentadienyl)(1,3-cyclohexadiene) iridium [Ir(EtCp)(CHD)]. Film growth behavior during MOCVD using Ir(EtCp)(C2H4)2 was investigated and compared with that using Ir(EtCp)(COD) and Ir(EtCp)(CHD). When Ir(EtCp)(C2H4)2 was used, significantly higher nucleation was observed at the initial growth stage than that using Ir(EtCp)(COD) and Ir(EtCp)(CHD) owing to the lower thermal decomposition temperature of 220 °C. Ir, IrO2 and Ir/IrO2 films were successfully prepared using Ir(EtCp)(C2H4)2 on underlying SiO2, TiN and Pb(Zr,Ti)O3, showing that Ir-based top and bottom electrodes can be fabricated by MOCVD. The root-mean-square surface roughnesses and electrical resistivities of Ir and IrO2 films on SiO2 were 2.2 nm and 9.4 µΩcm, and 3.3 nm and 1.8×102 µΩcm, respectively. The step coverages of Ir films prepared at 230–400 °C were 35–45%.

A Novel Iridium Precursor for MOCVD

A novel liquid iridium precursor (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD), was synthesized and its physical properties examined. Ir (EtCp) (CHD) showed physical properties suitable for metalorganic chemical vapor deposition (MOCVD). It exhibited enough vapor pressure (0.1 Torr/75°C), excellent volatility, and adequate decomposition temperature. The characteristics of Ir films deposited by MOCVD method using Ir(EtCp)(CHD) and a conventional Ir precursor (1,5-cyclooctadiene) (ethylcyclopentadienyl) iridium Ir(EtCp)(COD) were compared. The Ir films grown using Ir(EtCp)(CHD) showed shorter incubation time and higher nucleation density than those from Ir(EtCp)(COD) at initial growth stage of deposition. 3