Interfacial, optical properties and band offsets of HfTiON thin films with different nitrogen concentrations

Abstract

The effect of nitrogen concentration on the interfacial and optical properties, as well as band offsets of HfTiO thin films by rf sputtering HfTi alloy target has been systematically investigated. The results indicate that an interfacial layer is unavoidably formed between HfTiON thin films and Si substrate, and the main content of the interfacial layer is silicate. No silicide is formed in the interfacial layer which is partly responsible for the poor electrical properties of high-k gate dielectrics. The optical properties of HfTiON films change, such as the refractive index decreases, while the extinction coefficient increases with the increase of N content, due to the defects increase in the films. The results also indicate that the bandgap and VB offset reduce with the introduction of N into HfTiO thin films. The CB offset of the HfTiON thin films is almost unchanged indicating that the N concentration has little effect on CB offset. However, the bandgap and band offsets are all higher than 1 eV, the sufficient band offsets still makes sputtering-derived HfTiON films by HfTi alloy target a promising high-k gate dielectric for future complementary metal oxide semiconductor technology.

Determination of optical constant and electrical properties of sputtering-derived HfTiON gate dielectrics

“…It is generally known that HfO 2 and TiO 2 are all the indirect band gap semiconductor, as a result the HfTiO(N) film is also regarded as an indirect allowed transition material [25,26]. The optical band gap energies (E g ) are calculated by plotting Tauc's graphs between (a h v) 1/2 versus photon energy (hv) and the intercept of this linear region on the energy axis at (a h v) 1/2 equal to zero gives the optical band gap of deposited thin films from 5.47 to 5.04 eV for HfTiON films with different N content (S1, S2 and S3), as shown in Fig.…”

Improved charge-trapping properties of TiON/HfON dual charge storage layer by tapered band structure

“…For the HfTi sample, an interfacial layer between HfTiON and SiO 2 probably exists because fast diffusion of oxygen vacancies in the hafnium oxide film would lead to an uncontrollable interfacial layer formed between the hafnium oxide film and substrate, 11 which is partly responsible for its poor electrical properties. 12 However, the Ti-rich oxynitride film can limit the release and diffusion of excess oxygen to the interface, thus suppressing the growth of the undesirable interfacial layer. 13 So, the Ti/Hf sample has an enhanced quality of the TiON/SiO 2 interface, which reduces the defects and undesired states generated near/at the interface during operation stress, thus resulting in excellent endurance characteristics.…”