The ablation characteristics of the SU-8 photoresist (spun on Si wafers) under 248 KrF excimer pulsed laser radiation have been studied. The variation of etch rate with fluence has been investigated in the range 0.05-3.01 J cm −2 . The threshold fluence for ablation of SU-8 is measured to be about 0.05 J cm −2 . The etch rate of SU-8 is found to be higher than that of polyimide (previously reported) under similar conditions. We have investigated the effects of different prebake temperatures (90, 110, 120 and 200 • C) on ablation characteristics, which are found to be similar for all temperatures. The effect of increasing the number of laser shots (from 10 to 10 000) has been examined at different fluences in order to understand the etch-rate variation near the 'end of film' stage of ablation. The results of our analysis using scanning electron microscopy, profilometry and optical microscopy reveal the very smooth morphology of the etched surfaces with no significant debris, no noticeable damage to underlying silicon and the gradual build-up of a carbonaceous film outside and around the etch pits. We find SU-8 very suitable for excimer ablation lithography and have demonstrated this by patterning a gear structure in an SU-8 resist layer with an aspect ratio of 4.5. For the first time, we have shown that the laser micromachining technique has the potential to cleanly remove SU-8 after electroplating a microstructure with copper.

No abstract

No abstract

No abstract

Piezoelectric polymers are increasingly considered as favorable materials for microactuator applications due to their fast response, low operating voltages and greater efficiencies of operation. However, the difficulty of forming structures and shapes has so far limited the range of mechanical design. In this work, the design and fabrication of a unimorph piezoelectric cantilever actuator using piezoelectric polymer polyvinylidene fluoride (PVDF) with an electroplated layer of nickel iron (permalloy) alloy is described. The modeling and simulation of the composite cantilever was performed using CoventorWare to optimize the design parameters in order to achieve large tip deflections. These simulation results indicated that the thicknesses of both the piezo and non-piezo layers of the composite cantilever affect the magnitude of deflection of the cantilever. It was shown that the tip deflection of such a cantilever with a length of 5 mm and a width of 1 mm can reach up to 70 µm, when simulation was carried out using a 28 µm thick PVDF layer at a non-piezo layer thickness of 5 µm. A PVDF polymer cantilever is fabricated using a simple punching technique based on microembossing. The permalloy layer was electroplated on one side of the PVDF to form a composite cantilever. The tip deflection of the cantilever was observed and measured under an optical microscope. The experimental results showed deflection values which are 20% less than those predicted by the simulation and analytical results. The thickness non-uniformity, residual stresses and possible difference in Young’s modulus values of the bulk material to that of electroplated permalloy film are identified as some of the potential issues that might have caused this difference.