Sinter-Attach of High-Temperature Sensors for Deep-Drilling Monitoring

An optimized fabrication process for high-temperature piezoresistive vibration sensors made of p-doped double-layer SOl material is described. Thus, an easy and straightforward production of very precise sensor geometries is now feasible. Subsequently, it is demonstrated that sintering of silver particles can be successfully applied for die attach of these MEMS sensors. Sintering takes place at a very low pressure of 4 N/mm(2) and a temperature of 250 degrees C for 2 min. Furthermore, the attached sensors are tested according to the requirements of deep drilling projects such as geothermal power generation from deep geologic layers. In doing so, the operation of the bonded sensors under realistic conditions for vibration monitoring is analyzed, i.e. simultaneous temperature (250 degrees C) and vibration (+/- 50 g) stress.