Ready-to-use spray resists with EVG devices (positive and negative)

Spray coating is often used for the coating of complex topologies. There are various manufacturers of spray coating equipment, probably the best known are EV Group and Süss Microtec. Both producers use different strategies and devices for spraying, and therefore ready-to-use spray resists must be adjusted for the particular equipment.

Chemically enhanced negative resist without cross-linking

In some applications, the substrate on which the negative resist is to be applied cannot be heated. This may be the case for sensitive glass and especially for very big substrates.

Negative poly(hydroxystyrene) and (hydroxystyrene-co-MMA) photoresist with high-temperature stability

As an alternative to the polyimide negative resist, SX AR-N 4340/6 was developed, a highly sensitive CAR negative resist based on polyhydroxystyrene, which can be developed under aqueous-alkaline conditions.

Coloured negative photoresists

Allresist now also offers colored negative resists with the designation SX AR-N 8500. The difference to FUJIFILM resists is that only dyes and no pigments are dissolved in the resists. This allows to achieve a high resolution and high edge sharpness.

CAR 44 on copper

If negative photoresist CAR 44 (AR-N 4400) is directly used on copper or copper-containing substrates, the following points must be observed.

Fabrication of vertical flanks with CAR 44

AR-N 4400-50 was investigated at the TU Braunschweig with particular regard to the fabrication of well-defined resist architectures with vertical flanks.

Dose-dependent structure size with negative resists

The desired structure size also largely depends on the exposure dose used. In the case of overexposure, structures begin to widen which is particularly pronounced during laser exposure.

Generation of undercut structures with negative resists

With laser direct exposure, a slight undercut of the structures can be generated: The upper part of the layer is more strongly irradiated due to the absorption of the resist and consequently more intensely crosslinked.

Sensitive negative resist for 405 nm laser direct exposure

Negative resist AR-N 4400-10 can be structured with laser direct exposure at an exposure wavelength of 405 nm. Different arrays are shown in the figure.

NIR-laser structurable photoresists

By adding suitable dyes to negative-working CAR resists, even a patterning beyond the usual wavelength range is possible if pulsed lasers with sufficiently high intensity are used for exposure.