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The fabrication of pressure sensor dies for precise and stable industrial applications requires a critical high dose implantation process strongly affecting the manufacturing yield of these devices. This paper describes a specific critical process related failure mechanism caused by this implantation process generating local electrical shorts within the piezo resistive structures in-built in the doped silicon substrate surface. The defect signature was investigated by applying site specific localization, advanced target preparation strategy and high-resolution electron microscopy to understand its process related root cause. The electrical shorts could be localized by Lock-in Thermography (LIT) and then were prepared by advanced laser and focused ion beam (FIB) based preparation in both cross-section and plan-view direction for in-depth investigation of the crystal defect signature by high resolution transmission electron microscopy (TEM) analysis in combination with energy dispersive X-ray spectroscopy (EDXS). As a result, the defect mechanism could be identified as segregation of embedded metal residues caused by Fe and Ni contamination from the high dose implantation equipment.

Investigations for non-destructive characterization of MEMS (Micro-Electro-Mechanical-Systems) are presented that can be applied in production monitoring in early stages. Different aspects and experimental results are shown for quadratic and circular silicon membrane structures with artificial structural defects. The quadratic membranes were manufactured with three variations of notches at the edges. The circular membranes had residues on the backside of the membrane resulting from the etching process. The dynamic properties of the structures were measured non-destructively by scanning laser-Doppler vibrometry. The consequences of the generated defects were investigated using the resonant frequencies and mode shapes of the membrane structures in comparison to the dynamic properties of accurate membranes. The results show that the generated defects lead to a variation of the dynamic properties depending on size and position of the defect.

A novel impedimetric and thermal flow sensor chip with perforated membrane for the inline chemical process analysis in micro residence time reactors were developed. Sensors were optimized for reactors made of stainless steel with a hydraulic diameter in the range of ∼1 mm. The impedimetric sensor chip consists of capacitively coupled interdigital electrodes made of MoSi 2 on a silicon substrate. The thermal flow sensor consists of a heater in between two thermocouples on a thin membrane containing small holes for pressure compensation. CFD simulations were conducted to study the influence of medium flow in the cavity below the membrane. A micro fluidic flow cell with sensor electronics was developed for the characterization of both sensors. Experimental results revealed that changes of less than 1% in the thermal and electrical properties of the liquid can be detected. Insofar, the combination of the impedimetric and thermal flow sensor chip enables the analysis of reactive mixtures in overpressure regime by means of 4 independent physical parameters.

A sensor system combining a novel pressure stable thermoelectric flow and impedimetric sensor for monitoring chemical conversion in micro fluidic channels was developed. Devices were optimized for hydraulic diameters ~1 mm and overpressure regime. Impedimetric sensors consist of a pair of interdigital electrodes deposited on a silicon substrate. Thermoelectric flow sensors consist of a perforated membrane with a heater in between two thermocouples. Based on our results both sensors can detect in parallel relative changes in thermal and electrical properties of less than 1 %. Thus the system enables the inline monitoring of chemical conversion by means of 4 parameters.