Synthesis of Mesoporous Organosilicate Films in Supercritical Carbon Dioxide

strate for the resist. After spin-coating, the polymer was gently softbaked at 40 °C to evaporate the solvent. The SU-8 was then structured by UV lithography (k= 365 nm) and post-exposure-baked at 40 °C to polymerize the exposed material. Three-dimensional microsystems were achieved by adding further SU-8 layers and repeating the resist processing steps. The microdevices were finally developed in propylene glycol methyl ether acetate (PGMEA) to remove the unexposed SU-8. After development, the SU-8 structures were released from the fluorocarbon-coated handling wafer by tweezers. The fluorocarbon film exhibits low free surface energy, which reduced the adhesion between the resist and the wafer and eased the release [17]. Before the experiments for stress tailoring, the polymer structures were hardbaked in an oven at 120 °C for 30 min to remove residual resist solvent, which could affect the processing. Moreover, the polymer surface was cleaned in oxygen plasma.