Due to the fast-paced development of photolithography since the 1990s, only a short summary of the different techniques and applications can be given here. For in-depth information on the multitude of facts, technologies and procedures presented in each chapter, the added references should be consulted.
We now succeeded in finding a remarkable solution for high-layer e-beam structuring. The negative resist CAR 44 (AR-N 4400-10) was coated to yield a layer with a height of 9.5 μm, dried, and irradiated.
A new application field for Atlas 46 is electron beam lithography, as experiments with a thin Atlas resist layer patterned by e-beam lithography demonstrated. At a layer thickness of 450 nm, 200 nm lines were written into this layer. The sensitivity was 70 μC/cm² at an acceleration voltage of 100 kV.
For an optimum handling of EUV lithography using the RWTH system, a sensitivity range of 30-40 mJ/cm² is desired. A Medusa 82 sample supplemented with 2.5 % photoacid generator (PAG) already reached this target range. These investigations will be continued within the scope of a research project.
The addition of photoacid generators (PAGs) can significantly increase the sensitivity of Medusa 82 (see Resist Wiki “Medusa with photoacid generator”). Another option is to add a PEB after e-beam exposure. Even if substrates were previously stored for several days, the sensitivity significantly increases depending on the temperature and the duration of the PEB.
One disadvantage of HSQ and Medusa 82 is the comparably low sensitivity, which can however be increased by an addition of photoacid generators.
The basic principle of laser ablation is that laser irradiation of a certain wavelength introduces so much energy into the resist material which is modified for ablation that the resist polymer is destroyed and then vaporizes as low molecular weight fragments.
In the final stage of the Eurostar PPA-Litho project which was aimed to develop the resist Phoenix, we achieved to generate far more stable PPA polymers by optimizing the synthesis procedure. Pure polyphthalaldehydes which were subjected to a “stress test” for 14 days at 37 °C showed no decomposition. These resists can thus be shipped without cooling; this however only applies to pure PPA polymers.
Our research team successfully developed a negative resist with high resolution and plasma etching stability in oxygen: Medusa 82. Already with the first samples, it was possible to achieve the properties of HSQ.
Allresist offers the protective coating SX AR-PC 5000/40 for HF and KOH etchings already for a few years. Layers of 5 μm are able to withstand a 48 % hydrofluoric acidic solution for several hours. Also 40 % KOH solutions for silicon etchings do not attack the layer.