Medusa 84 – the reliable alternative to HSQ resist

Over the past year, intensive work has been carried out to improve the Medusa 84 resist. The synthesis and subsequent purification of the polymers were designed in such a way that the most stable molecular fraction could be isolated. As a result, improved shelf lives are now possible: with a solids content of up to 8% (AR-N 8400.08), storage formore than six months is achievable in a standard refrigerator without any loss of quality.

A comparison between specially prepared 20 nm layers of Medusa 84 and an HSQ powder resist (conducted by Ms. Joanne Schieser, Raith GmbH) showed a slightly better resolution for Medusa 84 (3.6 nm) compared to the HSQ resist (5.2 nm). Even 65 days after coating, Medusa 84 continued to deliver better results (5.9 nm vs. 6.9 nm for HSQ). This highlights the superior quality of Medusa 84 films in comparison with the HSQ polymer.

Medusa 84 samples were furthermore stored for 3.5 months at -30 °C, at 0 °C, and at room temperature. Surprisingly, there was hardly any difference between the three storage conditions with respect to the quality of the resist. Regardless of the storage temperature, all samples exhibited a minimum line width between 3.6 and 4.2 nm.

Fig. 1: Resolution test after different storage conditions. Single pixel lines in Medusa 84 at different storage temperatures after 3.5 months.

We have achieved a substantial improvement in the quality of Medusa 84 and can now offer a reliable and user-friendly alternative to HSQ. This success has prompted us to choose Medusa 84 as Resist of the Month for October.