Preparation of Hf-Si-O Thin Films by Simultaneous Deposition and Reaction Process using Pulsed Ion-Beam Evaporation

Abstract

A pulsed ion-beam evaporation method (IBE) has been applied to prepare hafnium silicate (Hf-Si-O) thin films which is one of promising gate dielectrics for metal-oxide-semiconductor (MOS) transistor instead of SiO2. Here, the IBE has a potential to make films containing less impurities due to the ablation of pure hafnium oxide (HfO2) targets in vacuum, while the chemical vapor deposition (CVD) precursor leaves its constituents in the films. From microstructural observation, the thin film consists of two layers; the upper and lower layers. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses reveal that the upper layer is polycrystalline HfO2 and that the lower layer is amorphous hafnium silicate. It may be understood that the hot Hf-O plasma impinging on the Si substrate resulted in the reaction of Si and Hf-O to prepare the Hf-Si-O thin film. The energy given by the intense pulsed ion beam makes it possible to induce such a surface reaction. The film has been found to be uniform distribution of Hf and O in the depth. Content of impurities such as carbon incorporated from the environment into the film are lower than the detection limit of XPS.