Investigation of Optical, Electrical, and Mechanical Properties of MOCVD-grown ZrO2 Films†

Abstract

Metal-organic (MO)CVD of ZrO₂ thin films is performed using the precursor [Zr(NMe₂)₂(guan)₂] (guan = η²-(ⁱPrN)₂CNMe₂) as the Zr source, together with oxygen. Film deposition is carried out on both Si(100) and glass substrates at various deposition temperatures. The resulting films are characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) for investigating the crystallinity and morphology, respectively. Optical properties are measured by ellipsometry and UV-vis on Si substrates and glass substrates, respectively, showing a high average refractive index of 2.14 and transmittance of more than 80% in visible light for the film deposited at 500°C. The potential of ZrO₂ thin films as gate dielectrics is verified by carrying out capacitance-voltage (C-V) and current-voltage (I-V) measurements. Dielectric constants are estimated from the accumulation capacitance, and found to be in the range 12 - 19 at an AC frequency of 1 MHz, and a leakage current of the order of 10⁻⁶ A cm⁻² at the applied field of 1 to 2 MV cm⁻¹ is measured for the films deposited at temperatures from 500 to 700°C. The low leakage current and high dielectric constant implies the good quality of the film, relevant for high-k applications. The hardness of the film ranges from 4.2 to 6.3 GPa for the 400 nm thick film, as determined by nano-indentation measurements. The optimum dielectric and hardness is found for the film deposited at 600°C, while the highest refractive index is found to be 2.14 for the film deposited at 500°C, due to higher density of the layers.