Growth by Liquid‐Injection MOCVD and Properties of HfO2 Films for Microelectronic Applications

Abstract

AbstractThin films of HfO2 were deposited on (100)Si/SiO2 by liquid‐injection metal‐organic (MO)CVD using [Hf(OtBu)2(mmp)2] dissolved in octane as the precursor. A precise thickness control on the nanometer scale was obtained by controlling the volume of injected precursor solution. Films of thickness below 10 nm were studied by means of X‐ray reflectometry (XRR), attenuated total reflection infrared spectroscopy (ATR), and atomic force microscopy (AFM). Films are amorphous for deposition temperatures below 350 °C; they are polycrystalline at deposition temperature of 360 °C and above, except for ultrathin films. Under the deposition conditions used, the main crystalline phase is the monoclinic phase as shown by ATR. AFM reveals smooth surfaces for both amorphous and polycrystalline films. The equivalent oxide thickness measured in MOS structures depends linearly on the film's thickness, and a relative dielectric permittivity ϵr of 19 is obtained, which is consistent with that expected for the monoclinic phase of bulk HfO2. Leakage current densities of the order of 1×10–4 A cm–2 for films with a physical thickness of 3.1 nm are obtained. Rapid thermal annealing under ammonia reduces the fixed charges in the oxide (Qox < 1×1011 cm–2) as well as the interfacial charge density (Dit peak = 8×1010 eV–1 cm–2).