Hiroshi Gokan

Oxygen ion-beam etch resistance of metal-free and organosilicon resist materials

Abstract Oxygen ion-beam etch resistance of metal-free and organosilicon resist materials has been studied, using an etching system with a Kaufman ion gun. The etch rate for metal-free resist materials is inversely proportional to the number of effective carbon atoms in a material. The effective term means subtracting the number of oxygen atoms from that of carbon atoms. This result suggests that the etch-rate determining step is the sputtering of carbon atoms which are not bonded to oxygen atoms. Carbon atoms bonded to oxygen atoms, for example >C=O or ⪰C-O-, may spontaneously desorb to form a volatile product CO under ion bombardment. The etch-rate ratio of an organosilicon resist material P(SiSt-CMS) to AZ1350J markedly increases with decreasing acceleration energy. This is because the rate determining step for an organosilicon resist material is mainly due to the sputtering of silicon atoms in the polymer. This is supported by the fact that the etch rate of an organosilicon resist material increases with increasing beam angle, while that of metal-free resist material monotonically decreases with increasing beam angle.

Low Loss 1–2 GHz SAW Filters with Submicron Finger Period Electrodes

Low loss GHz SAW filters with submicron finger-period double electrodes have been developed. One was a 1 µm period 0.9 GHz filter with 5 dB insertion loss and the other a 0.5 µm period 1.9 GHz filter with 7 dB loss, both having three-transducer configurations on a 128° Y-X LiNbO3 substrate. These filters were realized by a new fabrication process, using direct wafer electron beam writing, two step mask transfer from electron resist PMMA to photoresist AZ-1350J and ion beam etching. The insertion loss was lowered mainly by optimizing ion beam etching conditions to decrease acoustic propagation losses due to electrode edge geometries, ion etched surface damages and electrode film absorption.