Abstract
The effect of growth temperature on the atomic layer deposition of zirconium oxide (ZrO2) dielectric thin films that were fabricated using a CpZr[N(CH3)2]3/C7H8 cocktail precursor with ozone was investigated. The chemical, structural, and electrical properties of ZrO2 films grown at temperatures from 250 to 350 °C were characterized. Stoichiometric ZrO2 films formed at 250–350 °C with an atomic ratio of O to Zr of 1.8–1.9 and a low content of carbon impurities. The film formed at 300 °C was predominantly the tetragonal crystalline phase, whereas that formed at 350 °C was a mixture of tetragonal and monoclinic phases. Electrical properties, such as capacitance, leakage current, and voltage linearity of TiN/ZrO2/TiN capacitors fabricated using the thin ZrO2 films grown at different temperatures were compared capacitor applications. The ZrO2 film grown at 300 °C exhibited low impurity content, predominantly tetragonal crystalline structure, a high dielectric permittivity of 38.3, a low leakage current of below 10−7 A/cm2 at 2 V, and low-voltage linearity.
Highlights
Zirconium oxide (ZrO2 ) thin films have been extensively studied as dielectrics and insulators because they exhibit a high dielectric constant (k), acceptably low leakage current, and good thermal stability [1]
When compared with the monoclinic phase, the tetragonal and/or cubic phases have higher k and similar Eg, which result in the benefits of a ZrO2 dielectric film that is thinner with higher capacitance
The thicknesses of the ZrO2 films on Si substrates were measured with a spectroscopic ellipsometer (Horiba, UVISEL) and those on TiN were confirmed by transmission electron microscopy (TEM) (FEI, Tecnai G2 F30)
Summary
Zirconium oxide (ZrO2 ) thin films have been extensively studied as dielectrics and insulators because they exhibit a high dielectric constant (k), acceptably low leakage current, and good thermal stability [1]. Because the crystalline phase of ZrO2 depends on the growth process parameters, several methods, such as using an oxidant and doping with another element, have been used to obtain tetragonal ZrO2 films [10,11,12]. The metal precursor used for film growth requires sufficiently high vapor pressure, purity, and thermal and chemical stability, along with low viscosity and cost. Controlling the growth temperature is a very simple method in order to obtain the high-k tetragonal phase of ZrO2 without any additional doping or annealing processes. The influence of the ALD growth temperature on the chemical, structural, and electrical properties of ZrO2 films is systemically investigated. The ability of the growth temperature to regulate the crystalline phase of the films to enhance k without any tradeoff of the leakage current and capacitance linearity is discussed
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