Abstract
In this work, hafnium oxide (HfO2) thin films are deposited on p-type Si substrates by remote plasma atomic layer deposition on p-type Si at 250 °C, followed by a rapid thermal annealing in nitrogen. Effect of post-annealing temperature on the crystallization of HfO2 films and HfO2/Si interfaces is investigated. The crystallization of the HfO2 films and HfO2/Si interface is studied by field emission transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. The experimental results show that during annealing, the oxygen diffuse from HfO2 to Si interface. For annealing temperature below 400 °C, the HfO2 film and interfacial layer are amorphous, and the latter consists of HfO2 and silicon dioxide (SiO2). At annealing temperature of 450-550 °C, the HfO2 film become multiphase polycrystalline, and a crystalline SiO2 is found at the interface. Finally, at annealing temperature beyond 550 °C, the HfO2 film is dominated by single-phase polycrystalline, and the interfacial layer is completely transformed to crystalline SiO2.
Highlights
Hafnium oxide (HfO2) thin film is an interesting material for a variety of applications
15 nm HfO2 (168 atomic layer deposition (ALD) cycles) thin films were deposited on Si wafers by remote plasma atomic layer deposition (RP-ALD) (Picosun R-200, Finland) using tetrakis hafnium (TEMAH) and oxygen (O2) in alternating pulse with N2 purge of the reaction chamber between pulses
The annealing temperatures were varied from 400 to 600 °C to investigate the effect on crystallization of the HfO2 thin films and HfO2/Si interface
Summary
Hafnium oxide (HfO2) thin film is an interesting material for a variety of applications. It can be used in multilayer optical coating [1], protective coating [2], gate dielectric [3], passivating layer [4–6], and so on due to its excellent properties, such as high density, high refractive index, wide band gap, and relatively high thermal stability. Many methods have been used to prepare HfO2 thin film, such as electron beam evaporation [7], chemical solution deposition [8], reactive sputtering [9], metal organic chemical vapor deposition [10], molecular beam epitaxy [11], and atomic layer deposition (ALD). Post-annealing is found to have significant influences on ALD HfO2 films [12–15]. HfO2 thin films can crystalize for an annealing temperature higher than 500 °C [16–18]. The crystalline structure of HfO2 strongly affects optical and electrical
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