Ultra high Precision 3D Microprobe for CMM Applications

Abstract:
True three dimensional (3D) measurements of micro and nano structures are becoming vital due to the increase in micro mechanical and optical devices used in today’s technologies. Measurements with resolutions less than 100 nm in industry and less than 20 nm in national metrology institutes are desired today. In order to achieve this goal we have developed an ultra high precision micro/nano-coordinate measuring machine (CMM), specifically improving its tactile probe. The first stages of the development of the semiconductor based CMM microprobe have been reported earlier. The probe consists of a compliant silicon micro structure with piezoresistive elements as readout technique. The paper reports on the optimization of the fabrication process and an improved passivation of the piezoresistors. The new fabrication process proved to be robust resulting in high sensitivity and reproducibility of the sensing elements. For micro/nano-CMMs sensitivity and reliability are two of the most desirable characteristics in commercial use. To evaluate the sensor’s performance the microprobe was tested on an ultra high precision CMM (based on a precise nano measuring and positioning machine (NMM)). Measurements on a true 3D artefact are performed proving the functionality of the micro probe. The promising results are reported.