Formation mechanism of interfacial Si–oxide layers during postannealing of Ta2O5/Si

Abstract

The Si–O–Si bonds formed at the Ta2O5/Si interface by annealing were investigated by using Fourier transform infrared absorption spectroscopy. The Ta2O5 thin films deposited on Si substrates were annealed in different ambient (H2O, O2, and N2) at temperatures between 500 and 800 °C. When annealing is done in H2O, the interfacial silicon–oxide grows very rapidly, because the oxidation species can easily diffuse through Ta2O5 films, and because the Si–O formation is controlled by the diffusion of H2O in the interfacial layer. When annealing is done in O2, the oxidation species can also easily diffuse through Ta2O5, but not through the interfacial layer. The interfacial layer is formed by a reaction between Ta2O5 and Si even if the annealing ambient does not contain oxidation species, as is the case when annealing is done in N2. We conclude that the Si–O formation during postannealing in O2 and N2 is controlled by the diffusion of the Si from the substrate through the interfacial layer with an activation energy of 0.7 to 0.8 eV, and that new Si–O bonds are formed at the interface between the Ta2O5 and interfacial layer. Oxidation species from the annealing ambient enhance the frequency factor of the reaction, but do not control Si–O formation.

Dielectric properties enhancement of ZrO2 thin films induced by substrate biasing

“…The surface morphology was evaluated by contact mode atomic force microscopy ͑AFM͒ on a Park Scientific Instrument ͑PSI͒ Autoprobe Research over a scanned area of 5 m ϫ 5 m. The dielectric properties of the thin films deposited at 550°C under different biases were measured using an Agilent 4396B type impedance analyzer. 16 In our experiments, the substrate bias does not affect the deposition temperature but aids to increase the nuclei density in the thin films. [13][14][15] Furthermore, the weak absorption bands at around 720 cm −1 of Zr-O-Si and 800 and 1080 cm −1 of the Si-O vibration mode occur at lower substrate biasing such as 0 and Ϫ100 V, implying the formation of very little SiO x and ZrSiO x at the interface.…”

Influence of oxygen content on the structural and electrical characteristics of thin neodymium oxide gate dielectrics

“…Among them, HfO 2 and ZrO 2 are the potential candidates. This produces rugged surfaces, 5 which are the sources of weak points where local electric fields are enhanced causing increased leakages, deterioration, and breakdown of the MOS structure. 3 Consequently, the thermodynamic stability of high-k metal oxide in contact with silicon is a critical issue for the application of alternative gate dielectrics in ultralarge scale integration ͑ULSI͒ devices.…”

Microstructural improvement of sputtered ZrO2 thin films by substrate biasing

“…Fur- indicating that at a higher substrate biasing, the interfacial structure of the ZrO 2 /Si thin films can be optimized. Ono et al suggested that the formation of the interfacial layers depended on neither the thickness of oxide films nor the annealing atmosphere, but rather the deposition or annealing temperature [20]. In our experiments, the substrate bias does not affect the deposition temperature but aids to increase the nuclei density in the thin films and reduce the critical nucleation energy [15].…”