ULTRASONIC SUPPORTED DEVELOPMENT OF IRRADIATED MICROSTRUCTURES

In the first step of the LIGA process a resist layer typically PMMA (p olymethyl-methacrylate), is patterned by deep etch x-I-ay lithography. Then the exposed parts are dissolved by an organic developer. In orde r to achieve perfect microstructures, the development must. be free of residues, especially, with a view to the following electroforming ste p. In case of microstructures with extreme aspect ratios the developme nt process is not only a problem of solubility- but also of transporta tion. Our studies have proved that the development process can be impr oved through application of ultrasound, especially if the power densit y is raised or the frequency is lowered, because in both cases the amo unt of transient cavitation rises, with the restriction imposed that f ragile microstructures might be destroyed. Therefore, the development parameters need to be optimised for each geometry.