SiO2-passivation layers formed by thermal oxidation and various chemical vapor deposition (CVD) processes have been investigated by infrared spectroscopy and wet chemical etching studies in ammonium hydroxide water solutions. In order to obtain effects of thermal annealing on the dislocation structure of deposited oxides, these layers have been subjected to an annealing step. Disorder and water-related features in infrared spectra, as compared to activation energies and etch rates received from the etching experiments, show mainly two effects: the annealing of deposited films is accompanied by bond strain relaxation through viscous flow and decreased porosity without a measurable decrease in thickness. Within the infrared study, further evidence was obtained for disorder-induced mechanical mode coupling in oxides with a dislocation structure. In addition, the infrared spectroscopic and etching results for thermally grown oxides are very similar to those for annealed CVD oxides. Such a similarity was also obtained for unmodified CVD oxides processed at two very different temperatures.
A miniaturised transponder system consisting of a chip and a micro coil for measuring intraocular pressure continuously is presented. The system will be integrated in the haptic of a soft artificial intraocular lens. Calculations show that the capacitance of the coil influences the DC voltage drop significantly. With respect to a reliable system function a 20 µm thick coil with an outer diameter of 10.3 mm, an inner diameter of 7.7 mm, 16 windings and a gap of 20 µm between the windings was selected. Measurements show a good agreement between calculated and measured values. Wireless pressure measurements were carried out showing a linear behaviour of the output signal with respect to the applied pressure
To improve the transmission behaviour of a transponder system a new fabrication technique which enables the realisation of multiple layer micro coils by using single layer micro coils is presented. The single layer micro coils were realised by electroplating of 20 pm thick gold on a 9 pm thick polyimide film. Afterwards, the foil was folded together in such a way that the coils were adjusted one above the other. Using this iriiinique double-and 4-layer coils with different number of turns were fabricated. Compared to single layer coils the inductance of the coils increased by a factor of 3.3 for the double layer coils and by a factor of 12.4 for the 4-layer coils. In addition the obtained voltage drop across a 10 k!2 load resistance increased for both coil types (double and 4-layer coils) by more than 20 YO and across a 39 ks2 load resistance by more than 70 %, respectively.
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