High aspect ratio, 3D structuring of photoresist materials by ion beam LIGA

Abstract

IB-LIGA (Ion Beam Lithographie, Galvanoformung and Abformung) is a new technique for the 3D structuring of photoresist materials. It is a direct-write (maskless) technique that uses high energy (0.5–3.5 MeV) light ions (protons or helium ions) for the irradiation of photoresist materials. At CAFI (Centre d’Analyse par Faisceau Ionique), the IB-LIGA technique has been implemented. The experimental parameters for irradiation and the subsequent development have been optimised for PMMA. The results obtained so far are presented. These results include irradiations with different beam energies to control the depth, different sample tilt angles to produce sloping structures, and production of walls by moving the sample. Real 3D structures can be obtained in this way as shown in the examples. These examples show that structures in PMMA can be obtained with smooth near 90° side walls and bottom surfaces with low roughness. High aspect ratios have also been obtained, the current maximum is about 40. An ion-beam focussing system has recently been installed at CAFI, to produce ion-beams with sub-micrometer dimensions which can be accurately scanned in an arbitrary pattern over an area of 2.5×2.5 mm.