RuO₂ Thin Films as Bottom Electrodes for High Dielectric Constant Materials

Abstract

Ruthenium dioxide ( RuO2) thin films are evaluated as a bottom electrode for SrTiO3. It was found that a thin RuO2(50 nm)/Ru(20 nm) layer on Si is quite effective as a barrier layer for both orygen atoms and metals when depositing SrTiO3 at a relatively low temperature of 450° C. To test its suitability for high-temperature processes such as CVD of SrTiO3, the RuO2/Ru electrode on Si was annealed in air at 600° C for 1 hour. Even under this severe condition, the electrode using 100-nm-thick RuO2 was sufficient for preventing oxygen diffusion into Si.

Microstructural Characterization and Electrochemical Properties of RuO2 Thin Film Electrodes Prepared by Reactive Radio-Frequency Magnetron Sputtering

“…So far, the synthesis of ruthenium oxide by reactive sputtering has been mainly studied for the production of thin film resistors and electrode/diffusion barrier layers for high dielectric constant materials to be used in capacitors for very-large-scale integrated circuits. − Oxide films were mostly prepared by reactive direct-current (dc) magnetron sputtering, ,, and only a few papers reported on the preparation of RuO 2 films by reactive radio frequency (rf) sputtering, as adopted in the present work. A detailed study by Kolawa et al has shown that stoichiometric RuO 2 films can be obtained in a narrow process window, because of the slow oxidation of ruthenium.…”

Growth, microstructure, and resistivity of RuO2 thin films grown by metal-organic chemical vapor deposition

“…[1][2][3][4][5] This oxide behaves as a metal with a bulk resistivity of 35 mV-cm, 23 which is only slightly higher than that of metallic Ru (16 mVcm 2 ). 10 -16 By using RuO 2 thinfilm electrodes as opposed to conventional Pt electrodes, the polarization fatigue resistance of Pb(Zr x Ti 12x )O 3 (PZT)-based thin film capacitors can be dramatically improved, 11,17,18 A variety of thin film deposition techniques, including RF-magnetron 3,13,16 and dc-sputtering, 2,7-9 rf reactive sputtering, 4,5,12,14,15,17 pulsed laser deposition (PLD), 20 and metal-organic chemical vapor deposition (MOCVD), 1,21,22 have been used to fabricate RuO 2 thin films. 3 Ruthenium oxide is an excellent thin film barrier to interdiffusion between silicon and aluminum up to temperatures approaching 600 ± C. 1,4 It is not surprising that RuO 2 is utilized or being developed in a wide variety of thin film applications.…”

(Ba,Sr)TiO3 Thin Films for Dram’s

“…Good electrical properties have been achieved on BST deposited on patterned Ru electrodes on Si with no diffusion barrier [76,97], despite the fact that previous studies showed rapid silicide growth above 5QQ o C [81,82]. In another study, SrTi03 was deposited on RU02 I Ru I Si using a 6QQ o C 1 hr O2 anneal, and the same electrical properties were obtained contacting the RU02 from the front or the heavily doped Si on the backside of the wafer [116]. The chemical stability of Ir I Si and Ir / Ti / Si was studied by RBS and Auger depth profiling and only a thin layer of Ir silicide was found underneath Ir even after a 65Q o C 30. min O2 anneal [86].…”

“…The diffusion of oxygen through polycrystalline Ir films is slower than through polycrystalline Pt [85]. The diffusion of oxygen through RU02 is fairly slow, as shown by the stability of RU02 / Ru / Si to oxidation [85,116].…”