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.
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.
With our new development e-beam resist AR-P 6200 (CSAR 62), very fine structures like e.g. 10 nm wide trenches can be manufactured with very high contrast (> 14) and comparably high sensitivity.
T-gate structures are often required for the fabrication of electronic components (MEMS, HEMTs). Corresponding nanostructures can be realized via e-beam lithography in multi-layer processes. Generally, resist layers with different sensitivities like e.g. PMMAs with varying molecular weight distributions are coated on top of each other, irradiated with electrons and then developed in one step.
Layers with a thickness of 1.5 μm were produced using AR-P 6200.18, thick. As shown by investigations at the KIT (IMT, Dr. Lothar Hahn), allows this layer thickness to generate very regular trenches with a width of 300 nm at a period of 300 nm (see Fig. 1).