EXCIMER LASER-MACHINED SU-8 MICROSTRUCTURES FOR POLYDIMETHYLSILOXANE (PDMS) REPLICA MOLDING

Excimer laser ablation is considered a versatile technique to machine three-dimensional (3-D) structures which is difficult to create only by conventional microfabrication technique. We introduce the use of 193 run excimer laser micromachining for fabrication of negative photoresist (SU-8) master molds for polydimethylsiloxane (PDMS) replica molding. Experimental characterization study on the effect of laser parameters (fluence, repetition rate, and number of shots) on the etch performances (etch rate, and aspect ratio) is presented here. Etch rate per shot of SU-8 was proportional to the fluence, but inversely proportional to the number of shots. The repetition rate of laser firing did not show a noteworthy influence to the etch rates. Aspect ratio was also proportional to the fluence and number of laser firing, but was not affected by the repetition rate of laser. For demonstration of replica molding, we made holes with different depth in SU-8 layer and used it to create PDMS micropillar array.