Electrical Properties in High-k HfO[sub 2] Capacitors with an Equivalent Oxide Thickness of 9 Å on Ru Metal Electrode

Abstract

HfO 2 films with an EOT of 9 Å were deposited at 300°C on Ru/TiN/SiO 2 /Si substrates using an atomic layer deposition technique and the electrical properties of Ru/HfO 2 /Ru capacitors were investigated as a function of the film thickness and annealing temperature. The dielectric constant, dielectric loss, and leakage current density at 1.0 V in the films with a thickness of 7 nm were ϳ19, 0.9 %, and 8 ϫ 10 −7 A/cm 2 , respectively. The capacitors show the stable electrical properties in a thermal treatment up to 600°C.Embedded dynamic random access memory ͑DRAM͒ devices have been used as a technological solution for high-speed and wideband data transfer between logics and memories. Recently, HfO 2 dielectric films have been spotlighted due to its high dielectric constant, large band gap, and thermodynamic stability. 1-3 There are two major requirements for the high-k capacitor dielectric in terms of material properties. Large dielectric constant is favorable to provide sufficient capacitance in the limited capacitor area. Also, the leakage current should be low enough to prevent the refresh problem. The HfO 2 capacitor module has been considered as a most promising candidate for 70 nm generation DRAMs application. 4 In this application, TiN/HfO 2 /TiN capacitor structures are developed for DRAM device below 70 nm design rule. Atomic layer deposition ͑ALD͒ is the most promising technology for deposition of the high-k dielectrics in next generation memories due to excellent film quality and conformal step-coverage. In this study, the Ru/HfO 2 /Ru capacitors are considered instead of TiN/HfO 2 /TiN capacitors because Ru bottom electrode is more stable during deposition in an oxidizing ambient than TiN electrode. The electrical properties in Ru/HfO 2 /Ru capacitors are characterized as a function of film thickness and an annealing temperature.Ruthenium bottom electrode ͑50 nm thick͒ was deposited at 320°C on TiN ͑40 nm͒/Ti ͑4 nm͒/SiO 2 ͑100 nm͒/Si substrate using a precursor of Ru͑EtCp͒ 2 ͕͓͑CH 3 CH 2 ͒C 5 H 4 ͔ 2 Ru͖ by plasmaenhanced ALD technique. The Ru deposition was performed as continuous cycles such as source/purge/NH 3 and plasma/purge. The system pressure and plasma power were maintained as 3 Torr and 300 W, respectively. The HfO 2 dielectric thin films were grown on Ru bottom electrode at 300°C using ALD process. The reactants were TEMAH ͕͓Hf͑N͑CH 3 ͒ 2 ͒ 4 ͔ 2 ͖ and H 2 O. The deposition rate of the films was ϳ0.77 Å/cycle. The surface morphologies of the HfO 2 films were analyzed by an atomic force microscopy ͑AFM͒. For electrical measurements in a metal/insulator/metal ͑MIM͒ structure, Ru top electrodes ͑A = 2.0 ϫ 10 −5 cm 2 ͒ were exactly patterned using lift-off lithography and sputtered by dc magnetron sputtering. The capacitance-voltage characteristics of HfO 2 capacitors as a function of applied frequency are measured at various applied voltages using a Hewlett-Packard 4194A impedance analyzer. Leakage current characteristics of HfO 2 capacitors was investigated by a Keithley 617 electrometer. Fi...

First-Principles Investigation of the Structure, Energetics, and Electronic Properties of Ru/HfO2 Interfaces

“…The variation of the SBH of Ni/ZrO 2 interfaces was found to be as large as 0.76 eV depending upon the surface structure of the dielectric. Much effort has been focused on refining and optimizing metal/dielectric structures to meet engineering requirements. − Various experimental studies have been published within the past few years focusing on the electrical properties of Ru/HfO 2 systems. − However, the structural and chemical nature of the metal/dielectric interface have largely remained unknown due to the complexity of metal/dielectric interfacial structures and the lack of experimental probes for in situ atomic-scale characterization of buried interfaces. Atomistic modeling offers microscopic insight into otherwise inaccessible aspects of complex interface structures.…”

Leakage Current Improvement of Doped and Bilayer High-k for MIM Capacitor

“…However high leakage current of this type of high-k compared to HfO 2 , ZrO 2 , and Al 2 O 3 should be suppressed for being used widely. It was reported that high work function noble metal electrodes have been used to improve the interface-controlled leakage current [5]. In this study, high work function Ru was considered as electrodes and low band gap property of these high-k dielectrics was engineered by the manufacturing methods like doping and multi-layer etc.…”

A Comparison of O3 and H2O as Oxygen Sources for Atomic Layer Deposition Processing of HfAlOx Thin Films for High-k Dielectric Nanocapacitor Applications

“…It has also been shown to be a suitable insulator in metal-insulator-metal (MIM) capacitor devices, although it is susceptible to recrystallization after high temperature processing (14). It has also been reported that the electrical and thermal stability properties of HfO x films are significantly improved by the addition of Al oxide to the hafnia film (15)(16)(17)(18)(19)(20)(21). AlO x is known for its stable thermal and electrical properties; however, it possesses a relatively low dielectric constant of ~8.…”