Growth, microstructure, and resistivity of RuO 2 thin films grown by metal-organic chemical vapor deposition
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Growth, microstructure, and resistivity of RuO2 thin films grown by metal-organic chemical vapor deposition J. Vetrone, C. M. Foster,a) G-R. Bai, and A. Wang Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439
J. Patel Physics Department, Northern Illinois University, DeKalb, Illinois 60115
X. Wu Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, and Physics Department, Northern Illinois University, DeKalb, Illinois 60115 (Received 14 January 1997; accepted 15 October 1997)
Polycrystalline RuO2 thin films were grown by metal-organic chemical vapor deposition (MOCVD) on both SiO2ySi(001) and PtyTiySiO2ySi(001) substrates. Films having a controllable and reproducible structural texture and phase purity were synthesized by carefully controlling deposition parameters. Moderate growth temperatures (,350 ±C) and low growth ˚ rates (,30 Aymin) produced highly (110)-textured RuO2 films. Highly (101)-textured RuO2 films were favored at slightly lower temperatures (,300 ±C) and much higher growth rates ˚ (.30 Aymin). The most conductive RuO3 films had resistivities of 34 to 40 mV-cm at ± 25 C, an average grain size of 65 6 15 nm, and a surface roughness (rms) of 3 to 10 nm. Both single-phase Ru and mixed RuyRuO2 phase material were also fabricated at low temperatures (,350 ±C) by using lower oxygen flow concentrations (,10%). I. INTRODUCTION
There has been considerable interest in the deposition of highly conductive metallic oxide thin films as metallization material for Very-Large-Scale-Integrated (VLSI) circuits. Ruthenium oxide, RuO2 , is one of the most promising materials as it has many ideal properties including low resistivity, good thermal stability, and superior diffusion barrier properties.1–5 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 mVcm2 ). RuO2 is thermodynamically stable up to about 800 ±C in air and chemically resistant to common acids and bases.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 RuO2 is utilized or being developed in a wide variety of thin film applications.2,6 –12 In the area of integrated circuits, RuO2 thin films are being most notably studied as an electrode material for random-access memory applications, including both dynamic (DRAM) and nonvolatile (NVRAM) devices.10 –16 By using RuO2 thinfilm electrodes as opposed to conventional Pt electrodes, the polarization fatigue resistance of Pb(Zrx Ti12x )O3 (PZT)-based thin film capacitors can be dramatically improved,11,17,18 particularly for compositions near the morphotropic boundary.19 a)
Present address: Sematech, 2706 Montopolis Drive, Austin, Texas 78741-6499. J. Mater. Res., Vol. 13, No. 8, Aug 1998
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A variety of thin film depo
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