Fabrication of Nanometer-Order Dot Patterns by Lift-off Using a Fullerene-Incorporated Bilayer Resist System

We propose a new bilayer resist system consisting of a fullerene-incorporated positive-type electron beam resist, ZEP520, top layer and a pure ZEP bottom layer. In this system, the difference in resist sensitivity between the top and bottom layers can be readily optimized by changing the fullerene content of the top layer so as to create an overhang resist pattern favorable for lift-off. A bilayer system composed of 20 wt% fullerene-incorporated ZEP and pure ZEP produces suitable overhang patterns with a sensitivity of ∼60 µC/cm2. The applicability of the system has been verified through the successful fabrication of a highly-ordered array of self-organized ∼50-nm InGaAs/AlGaAs boxlike structures and a SiC nanoprinting mold with a 150-nm-pitch dot array.