High Aspect Ratio Microstructures

The goal of this project is to find a substrate and parameters that allow the realisation of hight aspect ratio microstructures. We tried three substrates (Ti, Cr and Si), two photoresist thicknesses (50 and 100 [m]), two focalisation points (8 and 12 [m]), four laser powers (110, 88, 70 and 66 [mW]). We obtained smaller structures and higher aspect ratios with silicon. The resine thicknesses give us expected results, such as 50 [m] gives smaller structures than 100 [m] but the aspect ratio rules for the resin thickness depend on the structure type. The maximum power of the laser 110 [mW] gives the smallest structures and when the power decreases, the structure size increases. The focus parameter doesn’t have a massive effect, this is more fine-tunning and it depends on the resin thickness. All these results suffer from a significant bias. The development time depends on the substrate type and as we put several substrates on a single wafer, we introduced a bias because some substrates were developed more than others. The walls verticality is around 88:7° but there is a slight bulge in the middle of the walls.