3-D nanofabrication using nanostructured photoresist film as free-standing appliqué

This paper reports a three-dimensional (3-D) nanofabrication method using a nano-patterned photoresist (PR) film as a free-standing flexible template. In contrast to the conventional usage of PR as a two-dimensional (2-D) pattern transfer layer on a planar substrate in MEMS applications, the lithographically predefined PR layer is released from the supporting substrate in the form of a free-standing film and then applied as an appliqué for the 3-D (e.g., onto a curved surface) and hierarchical (e.g., onto a micro-textured surface) nano-patterning. The ultrathin free-standing PR films show excellent flexibility, integrality, and robustness under various mechanical manipulations and further pattern transfer processes such as deposition and etching after being appliquéd. Enabled by such versatility, periodic nanostructures are successfully demonstrated on various substrates via various fabrication techniques. The results suggest that the application of the free-standing PR films as appliqué will enables them to be used as flexible and re-useable templates or elements in MEMS fabrication and devices, especially for convenient and efficient 3-D nanofabrication over a large area.