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Furnaces are versatile, horizontal tube systems which can be used for a wide variety of oxidation, diffusion, heat treatment, and deposition processes. The tube furnaces in the three, four-stack systems at SNF can be divided into two categories: LPCVD systems (Low Pressure Chemical Vapor Deposition of various thin films -- for more information, look for this section of the main Equipment List) and atmospheric systems (for oxidation, doping, and annealing heat treatment.) Process capabilities of each furnace system are detailed in the Furnace Process Summary <PDF>.

Silicon dioxide (SiO₂) is deposited at between 300 and 400C (depending on needs... ie metals 300C), low pressure (~350 mtorr), from silane and oxygen with or without phosphine doping. Doped LTO is also called PSG, or phosphosilicate glass). The refractive index of the film depends on the phosphorous content, lower deposition rate. The refractive index is also influenced by the temperature of the deposition. The oxide deposition rate is mostly dependent on the temperature and is ~ 175A/min at 400C for 4 inch wafers (~200A/min for 3 inch wafers).