A typical problem arising from an extreme resolution at an aspect ratio of > 10 is the collapse of bar structures. In Fig. 1, 10-nm bars with a pitch of 50 nm are displayed. These structures were realised with CSAR 62 (SX AR-P 6200/2) at an acceleration voltage of 30 kV and a dose of 230 pC/cm. The CSAR 62 is a further development of the ZEP resist. During the development process, the surface tension of the solvents leads to an undesired “sticking together” of single bars. Currently experiments are carried out to minimize this effect with optimised developers and the use of surface tension-altering substances.
Fig. 1: 10-nm bars still partly stick together (pitch 50 nm)