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 Iron Oxide Mask Etchant Fabrication of Fe2O3 See-through Masks Iron Oxide Mask Etchants are recommended for generating patterns used as electron resist masks or as semi-transparent see-through masks on glass for photoresist imaging in the manufacture of microelectronic devices. The fabrication of solid state devices depends heavily on the use of photolithography for definition of patterns. The current technique using ferric oxide see-through masks represent the best choice when employed with a suitable etchant. Two such etchants are offered: Type ME-10 standard and Type ME-30 for a minimum cost. The ferric oxide see-through mask on glass allows simple alignment and smaller geometries, now requisite for the micro-electronics industry. With ferric oxide masks, unwanted light is absorbed, rather than reflected, as with chromium masks. Halation effects are therefore minimized. In addition, ferric oxide masks offer much lower pinhole density, particularly important in large scale integration. The etch rates are somewhat variable with the thermal history of ferric oxide. At high heat, Fe2O3 becomes insoluble in dilute acids. CVD material produced at over 180 °C exhibits insolubility. Therefore, for ease of etching, the temperature of formation of Fe2O3 film should be less than 160 °C. To provide control in mask-making, a thickness of 2000 ± Å is recommended. PROPERTIES OF IRON OXIDE MASK ETCHANTS
APPLICATION Use standard photo-lithographic techniques for imaging and pattern formation; then follow recommended etch procedure:
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