In the presence of catalytic working iron salts, gelatine can be cross-linked photochemically in a negative process. A major advantage of these resists lies in their high environmental compatibility,
Polyimides are produced by polycondensation of tetracarboxylic dianhydrides and diamines. For highest thermal strain only polyimides are suitable which contain aromatic building blocks in the polymer chain.
PMMA resists can also be patterned using UV-lithography, but only at exposure wavelengths of 200 – 270 nm (deep UV light). Typically used is the wavelength-range of the lowest line of high-
In certain applications it is desirable to keep the original properties of a polymer unchanged, e.g. without addition of light-sensitive components like for example for a use as moisture sensor.
During e-beam lithography applications on isolating substrates, in particular on quartz-masks or glass, the impact of energy-rich electrons often give rises to strong surface charges.
With the development of photoresists for an exposure in the wavelength range of 500 to 1100 nm using laser light, new procedures became possible. Lithographic processes at an exposure wavelength > 480 nm are not possible with standard photoresists.
Hydrofluoric acid etchings, even those in highly concentrated acids (48%), are technologically used despite the high risk involved with HF applications. Technological problems are discussed in the section “Wet-
As an alternative to the positive polyimide resist (SX AR-PC 5000/82.7), which already contains polyimide as solvent and thus requires no curing at 350-400°C (see “Positive polyimide resist”)