Ken-ichi Tada

Development of Novel Silicon Precursors for Low-Temperature CVD/ALD Processes

Si-TBES (2) and Si-TBAS (4), novel CVD/ALD precursors bearing a diazasilacyclopentene framework, were synthesized. Thermal analyses revealed that both of them are highly volatile, and their decomposition temperatures were lower than those of comparable silicon precursors, Si(OEt)4 (TEOS) and SiH(NMe2)3 (TDMAS). Deposition properties of SiO2 thin films were investigated by a thermal CVD apparatus. The deposition rates of SiO2 thin films using these new precursors were higher than that of TDMAS. Deposition rate dependency on oxygen partial pressure indicates the high reactivity of the diazasilacyclopentene framework towards oxygen contributes to the high growth rates. Details of the SiO2 thin films were evaluated by XPS, AFM, and SIMS. While Si-TBAS can form conformal SiO2 thin films efficiently, Si-TBES can provide a film with low carbon and nitrogen contamination.

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

Characterization of Ru thin films from a novel CVD/atomic layer deposition precursor “Rudense” for capping layer of Cu interconnects

The authors have succeeded in development of a novel Ru precursor, Ru(EtCp)(η5-CH2C(Me)CHC(Me)O) [Rudense], for CVD and atomic layer deposition (ALD) processes under nonoxidative condition. Rudense has sufficient vapor pressure and good thermal stability (decomposition temperature = ca. 230 °C). Ru thin films were grown on Pt, Ru, Si, and SiO2 substrates using Rudense and NH3 as Ru precursor and reactant, respectively. Rudense gave the conformal, low-impurity (<1021 atoms/cc), and low-resistivity (16 μΩ cm) Ru thin films. Moreover, Rudense showed substrate selectivity; therefore, Rudense will be a candidate for area-selective CVD and ALD precursor for Ru capping layers of Cu interconnects.

Preparation of Ir-Based Electrode Thin Films by Liquid-Delivery MOCVD

We report the preparation of Ir-based electrode thin films by liquid-delivery MOCVD using a vaporizer system. A novel liquid precursor, Ir(EtCp)(C2H4)2, and etylcyclohexane (ECH) were used as a precursor and solvent, respectively. (111)-oriented Ir thin films with a root-mean-square surface roughness of 2.2 nm and an electrical resistivity of 14 muOmega-cm were successfully obtained on SiO2/Si at 400degC. However, it was difficult to form IrO2 films because oxygen was consumed for the decomposition of the solvent, ECH. The step coverage of-40% was obtained for Ir films on SiO2-stepped substrate with an aspect ratio of 0.7.