High-resolution negative e-beam resist

A process-stable, sufficiently sensitive e-beam resist with a resolution of about 30 nm is urgently needed to accelerate the progress in electron beam lithography. Chemically enhanced e-beam resists may meet all demands for a high sensitivity, but so far allow only a resolution of > 100 nm. PMMA resists and non-chemically enhanced e-beam resists (e.g. AR-N 7500 or AR-N 7520 ) have the potential to achieve resolutions of < 30 nm, but these resists are not sensitive enough and require uneconomically long writing times. The long-term research concept of the Allresist is strongly aimed at the development of economical high-resolution e-beam resists. Resist AR-N 7520new (former SX AR-N 7520/4) was presented on the MNE 2010 in Geneva which possessed a sevenfold higher sensitivity as compared to the standard resist AR-N 7520 ( see 21st AR NEWS ). Continuing our recent developments since 2011, new synthetic cross-linkers were tested which resulted in a small further increase of sensitivity. In single measurements, a line width of less than 30 nm was confirmed (see figure).

Fig. 1: 29 nm-ridge with experimental sample SX AR-N 7520/15.2.

A further advantage is the improved solubility in the resist solvent. A higher solid matter content allows the production of films with higher thicknesses. Special applications for electron-beam lithography up to a film thickness of 5 µm can thus be realized with these resists.

It is commonly known that smaller structures require higher exposure doses. This also became evident in our investigations. For a structural width of 5 µm, only a dose of approx. 15 µC/cm² (30 kV) was required. For 100 nm-lines, the required dose ranged from 30 – 50 µC/cm² for the three samples.

Application features of the new resist are significantly improved as compared to the parameters of our standard resist AR-N 7520 . We therefore intend to replace the standard e-beam resist with this new development. Users are already now invited to test the new resists before the standard resist is replaced.