Generally Surface Acoustic Wave (SAW) gas sensors are based on piezoelectric crystals like silicon oxide or lithium niobate and are often manufactured with a complicated technology. In order to reach high temperature stability, special crystal cuts are used. These cuts often show a small temperature gradient. Further on, a temperature compensation via mixer circuit is often applied. For the detection of specific components in undefined gas mixtures, the mostly very expendable process of pattern recognition is used. In the context of this dissertation, the influence of temperature onto the operation behaviour of SAW gas sensors was examined. For this purpose, mass sensitive SAW gas sensors with temperature regulation were produced based on CMOS compatible technology. Beside the possibility of economic mass production, CMOS compatible technology enables the monolithic integration of the devices. Hereby parasitic effects, caused by hybrid integration in the field of high frequencies, could be avoided. Instabilities like temperature drift mostly have a negative influence onto the functionality and behaviour of SAW gas sensors and consequently reduce significantly the sensitivity and stability of the devices. Therefore, the SAW devices produced in this dissertation were equipped with a polysilicon thermal resistor. To measure the surface temperature, a thin film resistor was located on the surface of each device. As a piezoelectric thin film polycrystalline zinc oxide and aluminium nitride were deposited. In order to achieve the required (002)-texture, the reactive HF sputter process as well as the pulsed DC sputter process were used and compared. The results of these examinations have shown, that the pulsed DC sputter process is especially capable to deposit textured thin films. It was possible to deposit strongly textured layers already at room temperature with high deposition rate. The examinations in context of this dissertation have shown, that often a significant increase of the surface temperature is caused by the adsorption of gases. Especially for SAW devices with a positive temperature gradient the variation of temperature causes an increase of transmitted frequency. Compared with the increase of mass by adsorption it should lead to a decrease of transmitted frequency. These two opposite effects lead to a reduction of sensitivity of SAW gas sensors. It could be shown, that a conventionally temperature compensation via electronic mixer circuit is not sufficient to eliminate these effects. So, the applied control of surface temperature was essential. With using the stabilisation of surface temperature, the SAW devices of this dissertation had shown a significant increase of sensitivity. In opposite to the examinations under laboratory conditions, the compounds as well as separate concentrations of a gas mixture are not known in real conditions. Therefore, the principle of pattern recognition is mostly used. By simultaneous use of gas sensors with different sensitivity and selectivity, a pattern of signals can be obtained. Such a structure needs a lot of cavity and further on a more complicated electronic circuit. It could be shown, that a controlled variation of temperature and the resulting temperature coefficients of sensitivity leaded to an additional information about the adsorbed gas component. So, the number of required SAW devices to analyse gas mixtures could be minimized and the selectivity of the SAW gas sensors could be increased significantly. In addition, the well known transient phenomenon of SAW-devices in the range of up to 2 hours could be reduced significantly by heating the devices. Beside these temperature effects, different layer structures and different polymers have been examined in order to cover / protect the SAW devices. An applicative choice of material and layer structure leaded to a significant reduction of drifts and consequently to an increase of long-term stability of SAW gas sensors for the application under real conditions.
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