Pulsed liquid-injection MOCVD of high-K oxides for advanced semiconductor technologies

HfO2 and SrTiO3 films were grown on silicon by liquid injection metal organic chemical vapour deposition. The microstructure and structure of the films were characterised by X-ray and electron diffraction, X-ray reflectometry, infrared spectroscopy, and microscopy techniques. In both cases, we emphasised the role of precursors in the resulting composition and microstructure of the films. Dense films of HfO2, either amorphous or crystalline depending on the deposition temperature, were synthesised using Hf(OtBu)2(mmp)2 precursor. Permittivity values of 14–19 were obtained, consistent with the monoclinic structure determined from X-ray diffraction. Optimised films exhibit breakdown field of 6 MV cm−1 and leakage current densities as low as 10−8 A cm−2 at 1 V. ystalline SrTiO3 films were grown using either a mixture of precursors or a heterometallic precursor. The heterometallic precursor provides some advantages such as a lowering of the crystallisation temperature of the perovskite-type phase and a reduction of carbonate impurities at low temperatures. It also allows to keep the films composition constant over a wide temperature range (550–750 °C). The films are highly textured with [ 0   0   1 ] SrTi O 3 parallel to [0 0 1]Si. The permittivity depends strongly on the films thickness (ɛr ∼ 30 for 10 nm and ɛr ∼ 100 for 100 nm). An equivalent oxide thickness of 1.36 nm (for physical thickness of 15.0 nm) was obtained for optimised SrTiO3 film, with a leakage current density of 10−2 A cm−2 at 1 V.