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- ItemLabel free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor(Cambridge : Royal Society of Chemistry, 2015) Guha, S.; Warsinke, A.; Tientcheu, Ch.M.; Schmalz, K.; Meliani, C.; Wenger, Ch.In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88–880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm2 reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process.
- ItemSelf-calibrating highly sensitive dynamic capacitance sensor: Towards rapid sensing and counting of particles in laminar flow systems(Cambridge : Royal Society of Chemistry, 2015) Guha, S.; Schmalz, K.; Wenger, Ch.; Herzel, F.In this report we propose a sensor architecture and a corresponding read-out technique on silicon for the detection of dynamic capacitance change. This approach can be applied to rapid particle counting and single particle sensing in a fluidic system. The sensing principle is based on capacitance variation of an interdigitated electrode (IDE) structure embedded in an oscillator circuit. The capacitance scaling of the IDE results in frequency modulation of the oscillator. A demodulator architecture is employed to provide a read-out of the frequency modulation caused by the capacitance change. A self-calibrating technique is employed at the read-out amplifier stage. The capacitance variation of the IDE due to particle flow causing frequency modulation and the corresponding demodulator read-out has been analytically modelled. Experimental verification of the established model and the functionality of the sensor chip were shown using a modulating capacitor independent of fluidic integration. The initial results show that the sensor is capable of detecting frequency changes of the order of 100 parts per million (PPM), which translates to a shift of 1.43 MHz at 14.3 GHz operating frequency. It is also shown that a capacitance change every 3 μs can be accurately detected.
- ItemHigh-resolution characterization of the forbidden Si 200 and Si 222 reflections(Chester : International Union of Crystallography, 2015) Zaumseil, P.The occurrence of the basis-forbidden Si 200 and Si 222 reflections in specular X-ray diffraction !–2 scans is investigated in detail as a function of the inplane sample orientation. This is done for two different diffractometer types with low and high angular divergence perpendicular to the diffraction plane. It is shown that the reflections appear for well defined conditions as a result of multiple diffraction, and not only do the obtained peaks vary in intensity but additional features like shoulders or even subpeaks may occur within a 2 range of about 2.5 . This has important consequences for the detection and verification of layer peaks in the corresponding angular range.
- ItemInvestigation of the copper gettering mechanism of oxide precipitates in silicon(Pennington, NJ : ECS, 2015) Kissinger, G.; Kot, D.; Klingsporn, M.; Schubert, M.A.; Sattler, A.; Müller, T.One of the reasons why the principal gettering mechanism of copper at oxide precipitates is not yet clarified is that it was not possible to identify the presence and measure the copper concentration in the vicinity of oxide precipitates. To overcome the problem we used a 14.5 nm thick thermal oxide layer as a model system for an oxide precipitate to localize the place where the copper is collected. We also analyzed a plate-like oxide precipitate by EDX and EELS and compared the results with the analysis carried out on the oxide layer. It is demonstrated that both the interface between the oxide precipitate being SiO2 and the silicon matrix and the interface between the thermal oxide and silicon consist of a 2–3 nm thick SiO layer. As the results of these experiments also show that copper segregates at the SiO interface layer of the thermal oxide it is concluded that gettering of copper by oxide precipitates is based on segregation of copper to the SiO interface layer.
- ItemDislocation generation and propagation during flash lamp annealing(Pennington, NJ : ECS, 2015) Kissinger, G.; Kot, D.; Schubert, M.A.; Sattler, A.Dislocation generation and propagation during flash lamp annealing for 20 ms was investigated using wafers with sawed, ground, and etched surfaces. Due to the thermal stress resulting from the temperature profiles generated by the flash pre-existing dislocations propagate into the wafer from both surfaces during flash lamp annealing. A dislocation free zone was observed around 700 μm depth below the surface of a 900 μm thick sawed wafer. The dislocation propagation can be well described by a three-dimensional mechanical model. It was further demonstrated that in wafers being initially free of dislocations no dislocations are generated during flash lamp annealing.