Abstract
Ruthenium thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) technology using Ru(EtCp)2 and oxygen plasma on the modified surface of silicon and SiO2/Si substrates. The crystal structure, chemical composition, and morphology of films were characterized by grazing incidence XRD (GXRD), secondary ion mass spectrometry (SIMS), and atomic force microscopy (AFM) techniques, respectively. It was found that the mechanism of film growth depends crucially on the substrate temperature. The GXRD and SIMS analysis show that at substrate temperature T = 375 °C, an abrupt change in surface reaction mechanisms occurs, leading to the changing in film composition from RuO2 at low temperatures to pure Ru film at higher temperatures. It was confirmed by electrical resistivity measurements for Ru-based films. Mechanical stress in the films was also analyzed, and it was suggested that this factor increases the surface roughness of growing Ru films. The lowest surface roughness ~1.5 nm was achieved with a film thickness of 29 nm using SiO2/Si-substrate for deposition at 375 °C. The measured resistivity of Ru film is 18–19 µOhm·cm (as deposited).
Highlights
Technology using Ru(EtCp)2 and oxygen plasma on the modified surface of silicon and SiO2 /Si substrates
The crystal structure, chemical composition, and morphology of films were characterized by grazing incidence XRD (GXRD, SmartLab, Rigaku, Tokyo, Japan), secondary ion mass spectrometry (SIMS) at TOF.SIMS5 tool, and by atomic force microscopy (AFM, Nanopics 2100, SII Nanotechnology Inc, Chiba, Japan)
On bare silicon and silicon oxide surface, 3D growth of ruthenium films was observed in the plasma-enhanced atomic layer deposition (PEALD) process and was attributed to poor nucleation
Summary
Technology using Ru(EtCp) and oxygen plasma on the modified surface of silicon and SiO2 /Si substrates. The GXRD and SIMS analysis show that at substrate temperature T = 375 ◦ C, an abrupt change in surface reaction mechanisms occurs, leading to the changing in film composition from RuO2 at low temperatures to pure Ru film at higher temperatures. It was confirmed by electrical resistivity measurements for Ru-based films. Ruthenium is a promising candidate for the electrodes of the dynamic random-access memory (DRAM) capacitors [8], gate electrodes in metal oxide semiconductor transistors (MOSFETs) [9], and high conductive coating for MEMS devices [10,11] It is widely used in heterogeneous catalysis [12]. Considerable interest in ruthenium can be explained by comparably low prices for this noble metal
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