Microstructural characterization of thin SiO x films obtained by physical vapor deposition

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2010-10, Vol.174 (1), p.132-136
• Main Authors: Curiel, M.A., Nedev, N., Nesheva, D., Soares, J., Haasch, R., Sardela, M., Valdez, B., Sankaran, B., Manolov, E., Bineva, I., Petrov, I.
• Format: Article
• Language: English
• Subjects: Annealing; Materials science; Metal–insulator–semiconductor structures; Nanocrystals; Phase separation; Silicon dioxide; Silicon nanocrystals; Silicon oxide; Silicon substrates; Thermal evaporation; Thin films; Transmission electron microscopy; Tunnels (transportation); X-ray spectroscopy; X-rays
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2010.03.007

X-ray diffraction and reflectivity, X-ray photoelectron spectroscopy and spectroscopic ellipsometry were applied to study the initial composition, thickness, lattice structure and refractive index of ‘fresh’ and annealed thin SiO x films (∼15 nm) on crystalline silicon substrates, prepared by thermal evaporation of SiO in vacuum. It has been ascertained that the film thickness and composition ( x = 1.3) of the ‘fresh’ films are very close to the values set during the deposition. It has been shown that furnace annealing of the films at 1000 °C causes phase separation, film densification and small modification of the Si–SiO x interface. Transmission electron microscopy results have proven that a self-assembling process leads to formation of Si nanocrystals with a diameter of ∼4–5 nm and to epitaxial overgrowth of the Si substrate, increasing the c-Si/SiO x interface transition region to 6–7 monolayers. The nanocrystals are randomly distributed in an amorphous SiO 2 matrix being closer to the Si–SiO x interface. Formation of tunnel oxide layer with a thickness of 3–5 nm has been found upon annealing. Clockwise hysteresis has been observed in the capacitance-voltage characteristics measured which has been explained by assuming charging and discharging of the nanocrystals with holes, which tunnel from the Si substrate.