Supported pyrolysis for lithographically defined 3D carbon microstructures

Abstract

We present a facile and effective route for the fabrication of carbon microstructures by direct carbonization of polymeric photoresist patterns without distortion or collapse of the microstructure due to high-temperature pyrolysis. The 3D porous structure was a woodpile structure prepared by five-beam interference lithography. Pyrolysis of the SU-8 woodpile structure resulted in shrinkage of the structure into the film with loss of the pore structure. The silica shell support on this SU-8 microstructure provided effective mechanical support to resist pattern distortion or collapse by melting of the photoresist and subsequent large mass loss in the heat treatment. The shrinkages in lattice distance and layer-by-layer distance of the silica-coated SU-8 were measured to be 3% and 60%, respectively. The composition of pyrolyzed SU-8 photoresists was characterized by Raman spectroscopy. Current-sensing AFM was used to measure the local electrical conductivity of a 3D pyrolyzed carbon structure. Our pyrolyzed 3D carbon structures were composed of a glassy carbon and possessed the local conductivity of about 10³ S m⁻¹. The fabrication of lithographically defined carbon structures with high fidelity will open new opportunities for carbon MEMS and various energy-related microdevices.