Kyong-Min Kim

The Property of Ta2O5 on Chemical Vapor Deposited Ru Film Fabricated using Tris(2,4-octanedionato)ruthenium for Application to Dynamic Random Access Memory Capacitor

Chemical vapor deposited (CVD) Ru was adopted as a bottom electrode of Ta2O5 capacitor for application to gigabit scale dynamic random access memory (DRAM). Ru film was deposited with the precursor of tris(2,4-octanedionato)ruthenium, Ru(od)3, at 260°C in O2 ambient. We obtained Ru film with 44 µΩ·cm of electric resistivity after annealing at 700°C. The root mean square (RMS) surface roughness of the film was 3.3 nm on SiO2 and 7.4 nm on TiN. We also obtained a leakage current of 4.45×10-9 A/cm2 at 1 V with a SiO2 equivalent thickness of 1.12 nm in the TiN/Ta2O5/Ru capacitor. Double plasma treatment on Ta2O5 was more effective than single plasma treatment for obtaining low leakage current. The TiN layer under Ru was oxidized into TiOx during the rapid thermal process (RTP) annealing of the Ru film at 600°C in N2 ambient. The remaining oxygen in the Ru film is believed to be an oxygen source for the oxidation of TiN.

Oxidation Characteristics of TiN Film as a Barrier Metal for Bottom-Electrode Ru Film Fabricated from Tris-(2,4-octanedionato)ruthenium

Bottom-electrode Ru films were fabricated on barrier metal TiN films by the reaction of tris-(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] precursor and O2 gas. It was observed that the film incorporated the undesirable impurity of oxygen that could oxidize the TiN underlayer during postthermal treatments. To evaluate the oxidation characteristics of barrier metal TiN by the incorporated oxygen, samples with the Ru/TiN film stack were annealed in N2 ambient up to 700°C for 60 s by rapid thermal processing (RTP). No sign of TiN oxidation was observed in analyses by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. This was also confirmed by measuring the electrical resistance of a contact hole plugged with poly-Si and connected to the Ru/TiN stack, which shows an acceptable value below 1.3×103 Ω. We also investigated the oxidation characteristics of the Ru/TiN stack by atmospheric O2 gas. The samples were annealed in O2 ambient by RTP at 500°C, 600°C, and 700°C for 60 s. The Ru film began to oxidize to RuO2 at 500°C. With increasing temperature, further oxidations of Ru and TiN occurred simultaneously. Finally, at 700°C, Ru and TiN oxidized completely to RuO2 and rutile TiO2 phases, respectively. These results demonstrate the ease of oxidation of Ru and TiN films in O2 ambient.