SILYLATION OF FOCUSED ION-BEAM EXPOSED RESISTS

Silylation processes for lithography involve the selective incorporation of silicon into a polymeric resist, which can then be patterned using an oxygen reactive ion etching plasma. These processes, like other multilayer approaches, have been developed primarily for optical lithography to minimize substrate reflectivity and allow higher resolution. We have extended this technique to exposure with focused beams of Be, Si, Ga, and Au ions with energies between 49 and 240 keV. Conventional focused ion beam exposure of resists relies upon solvent development and requires ion penetration through the entire resist thickness. With a silylation process, however, higher mass or lower energy ions may be used, and the resist thickness is decoupled from the exposure requirements. Resolution of features smaller than 100 nm has been demonstrated.