Efficient MEMS tests on wafer level with active probe

Chemnitz, /

A new MEMS active probe characterizing MEMS components will be presented at the Sensor + Test – The Measurement Fair – 2014 in Nuremberg, Germany. Fraunhofer ENAS and the Center for Microtechnologies (ZfM) of TU Chemnitz developed a probe which measures very low currents dynamically.

The characterization of micro electro mechanical systems fabricated in batch processing is challenging. The electrical output signals of the MEMS transducer elements are usually very low. The mechanical motion is measured to test the device functionality on wafer level. Until now, extensive optical methods were used for their characterization. Capacitance to voltage conversion (C/V conversion) is a cheap and practical alternative solution. Researchers at the Fraunhofer ENAS and the Center for Microtechnologies (ZfM) of TU Chemnitz developed and built up a MEMS Active Probe for reliable 100-percent testing of components on wafer and chip level. The probe measures very low currents in the pico and nano ampere range dynamically. The new active probe can be positioned very close to the MEMS elements to achieve an optimal signal-to-noise ratio. So the in-plane motion of the micro electro mechanical systems can be electrically detected and characterized. The probe is designed for a frequency range up to 200 kHz and a sensitivity up to 90 mV/nA. The output impedance is matched to 50 Ohm. Therefore the probe can be directly connected with a spectrum analyzer. Moreover it has to be mentioned that it can be fixed to the wafer prober with common positioners. The MEMS Active Probe was primarily developed for the internal use at the Fraunhofer ENAS and ZfM and is proved in practice.

The MEMS Active Probe is introduced at the Sensor + Test – the Measurement Fair – for the first time. It is shown at the joint booth of the Fraunhofer Gesellschaft in hall 12, booth number 537, from June 3 to 5, 2014.

Furthermore, the researches present smart systems for condition monitoring of processes and equipment. An autonomous sensor network for condition monitoring of power lines was developed together with the Fraunhofer IZM and further partners. The working princple is demonstrated with a sensor node at the booth. Moreover Fraunhofer ENAS shows a MEMS based NIR spectrometer, which is applied in biogas plants.