SiO2film

SiO2film, also known as silicon dioxide film, denotes a thin layer of silicon dioxide deposited on a substrate. In microelectronics and optics, such films are typically amorphous and serve as dielectrics, passivation layers, and protective coatings. The film is often stoichiometric SiO2.

Silicon dioxide exists in several polymorphs, but in thin-film form it is usually amorphous; it can form a dense, uniform layer with good electrical insulation. On silicon, thermal oxidation grows SiO2 by consuming the silicon substrate, creating a high-quality gate dielectric; on other substrates, deposition must achieve stoichiometric oxide.

Fabrication methods include thermal oxidation (dry or wet), chemical vapor deposition using silane (SiH4) or tetraethyl orthosilicate (TEOS) with oxidants, atomic layer deposition for precise thickness, sputtering and e-beam evaporation, plasma-assisted deposition, and sometimes sol-gel derived films. Thickness ranges from a few nanometers to several micrometers.

Properties of SiO2films include a wide bandgap (~9 eV), high electrical resistivity, chemical inertness, and optical transparency from the ultraviolet to the near-infrared. The refractive index is around 1.46 at visible wavelengths. Thermally and chemically stable up to roughly 1000 C in inert environments; mechanical properties are in line with glass, with a density near 2.2 g/cm3. Films can be dense and low in moisture diffusion, though hydrogen and hydroxyl groups may be present in as-deposited or annealed states.

Applications span gate dielectrics and diffusion barriers in silicon devices, optical coatings and anti-reflective layers, protective coatings for MEMS and electronics, sensing layers, microfluidic interfaces, and passivation in solar cells.

Common challenges include managing film stress, pinholes, impurities, moisture uptake, and interfacial traps with substrates, as well as achieving precise stoichiometry and film densification during deposition.