Pyrolysis of Negative Photoresists to Fabricate Carbon Structures for Microelectromechanical Systems and Electrochemical Applications

Abstract

Carbon structures were fabricated by the pyrolysis of photopatterned negative photoresists ͑SU-8 and photosensitive polyimide͒ on silicon and fused silica wafers. Results here are compared with those of positive resists published earlier by this group. Negative resist films need exposure to ultraviolet light prior to pyrolysis to produce carbon films. The pyrolysis was carried out in a closed quartz tube furnace in a forming gas ͑95% N 2 , 5% H 2 ͒ atmosphere. The pyrolysis process was characterized using a combination of thermogravimetric analysis and differential thermal analysis. The pyrolysis of SU-8 involved gas evolution in a narower range of temperature than polyimide. The adhesion of the carbon film was found to depend on the resist, the substrate, and the heating cycle used. The carbon structures were characterized in terms of their shrinkage during the pyrolysis, the resistivity, the degree of crystallinity and the peak separation in cyclic voltammetry. Carbons derived from pyrolysis of negative resists showed higher resistivity, vertical shrinkage, and peak-to-peak separation voltage than positive resists. Transmission electron microscope results showed a distinct lack of crystallinity even after pyrolysis at 1100°C, unlike the positive resist derived carbon.

Template-free ultraspray pyrolysis synthesis of N/Fe-doped carbon microspheres for oxygen reduction electrocatalysis

“…A more detailed understanding of the mechanism of pore development is however challenging, as is oen highlighted in the literature on the pyrolysis of organic compounds; mechanistic understanding would require detailed analysis of decomposition products as a function of temperature and reaction conditions as previously reported by other groups. [49][50][51][52] Electrochemical characterization of carbon microspheres Electrochemical characterization was carried out in order to understand the electrocatalytic properties of GH710 and GH900 in the oxygen reduction reaction. Fig.…”

SU-8 Photolithography as a Toolbox for Carbon MEMS

“…Masks, a patterned stencil that enables the selective passage of light, must then be designed according to the desired final topography: transparent areas in the mask must correspond to the topography to be fabricated. In 2002, the derivation of carbon films from SU-8 was first reported by Singh and colleagues [16]. In 2005, structures with aspect ratios higher than 10 were reported by Wang et al [17], and since then, a variety of complex carbon microstructures have been derived from SU-8.…”

Transparent ultrathin conducting carbon films

“…Upon pyrolysis the resist forms a thin conductive carbon layer also known as pyrolysed photoresist films (PPF) [12][13][14][15][16][17][18]. The pristine film thickness is A c c e p t e d M a n u s c r i p t controlled by the spin speed, viscosity of photoresist solution, evaporation rate and diffusivity of solute [19].…”