AlO_x Thin Films Synthesized by Mist Chemical Vapor Deposition, Monitored by a Fast-Scanning Mobility Particle Analyzer, and Applied as a Gate Insulating Layer in the Field-Effect Transistors

We investigated the synthesis of aluminum oxide (AlOx) thin films using mist chemical vapor deposition (mist-CVD) from aluminum acetylacetonate (Al(acac)3) and methanol/water (MeOH/H2O) mixture (volume ratio, 7:3). Different deposition parameters, such as the flow rate (Fd) of dilution gas N2, furnace temperature (Tf), solution concentration, and mesh bias (Vm), were optimized via the analysis of the size distribution of mist precursors using a fast-scanning mobility particle analyzer. The film morphology, rigidity of the AlOx network, and junction property at the AlOx/n-type crystalline Si (n-Si) were dominated by the size distribution of the mist precursors determined by the deposition parameters. Further, the mesh bias supply during film growth promoted the miniaturization of the size distribution of the charged mist particles. Consequently, a marked increase in the number density of the mist particles resulted in an increased refractive index (n) of the AlOx thin films with small surface roughness values. Furthermore, such property of the AlOx films improved the junction property at the AlOx/n-Si interface. In this study, the correlation between the size distribution of mist particles, which is dependent on the deposition parameters, and the film and interface properties, is presented together with metal-oxide–semiconductor field-effect transistor (MOS-FET) performance for the AlOx thin films obtained by mist-CVD.