Kazuhisa Kawano

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 .

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.

Chemo-enzymatic synthesis of 3-(2-naphthyl)- L-alanine by an aminotransferase from the extreme thermophile, Thermococcus profundus

Hyper-thermostable aminotransferase from Thermococcus profundus (MsAT) was used to synthesize 3-(2-naphthyl)-l-alanine (Nal) by transamination between its corresponding α-keto acid, 3-(2-naphthyl)pyruvate (NPA) and l-glutamate (Glu) at 70 °C. Equilibrium of this reaction was shifted toward Nal production due to its low solubility, giving rise to Nal precipitate. Optically pure Nal (>99% ee) was synthesized with 93% (mol mol−1) yield from 180 mM NPA and 360 mM Glu.

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

Ligand Structure Effect on A Divalent Ruthenium Precursor for MOCVD

Thermal properties of five divalent ruthenium precursors with three types of structures were examined by thermal analyses. Their volatilities and the relationships between their structure and thermal stability were compared by TG analysis. Precursor volatility was found to be inversely proportional to molecular weight. The DSC result showed that substituting a linear pentadienyl ligand for a cyclopentadienyl ligand decreased the thermal stability of a precursor and precursors could be liquefied by attaching an alkyl group longer than methyl group to a Cp ligand. As a result of TG-MS analyses for Ru(DMPD)(EtCp) and Ru(EtCp) 2 , 2,4-dimethyl-1,3-pentadiene was found to be a thermolysis product of Ru(DMPD)(EtCp) though no thermolysis products of Ru(EtCp) 2 were observed. These results show that the volatility and decomposition temperature of a divalent ruthenium precursor can be designed by adjusting the precursors structure.

Ruthenium and Ruthenium Oxide Films Deposition by MOCVD Using Ru(DMPD)2

Physical properties of bis(2,4-dimethylpentadienyl) ruthenium [Ru(DMPD)2] were examined by comparing with those of (2,4- dimethylpentadienyl)(ethylcyclopentadienyl) ruthenium [Ru(DMPD) (EtCp)]. Ru(DMPD)2 had almost the same vaporizing characteristic as Ru(DMPD)(EtCp) and showed lower decomposition temperature of 210{degree sign}C than those of Ru(DMPD)(EtCp), 270{degree sign}C. Ru- based films was deposited from Ru(DMPD)2 - O2 system. Metallic Ru films were deposited at 400{degree sign}C under the oxygen concentration below 0.25%. Crystalline metallic Ru films were deposited down to 220{degree sign}C under this oxygen concentration for the first time using Ru(DMPD)2.