Very good dynamic properties of piezoresistive microprobes for high scanning speeds

High-speed roughness measurements demands high dynamics of the stylus probe. Because of the features of low mass, low probing force and high signal linearity, the investigated silicon microprobe is one of promising candidates for high-speed roughness measurements. To investigate the dynamics of the microprobe, a “Tip flight” test was performed. In this test the microprobe moves across slope features with different speeds. The normalized flight width, i.e. the ratio of the flight width to the structure height, is measured to evaluate the dynamics of the probe quantitively.

The test was carried out with the instrument Profilscanner, a self-developed profilometer at PTB. The microprobe is bonded on a microprobe holder PCB and mounted on a head composed of the XYZ piezo stage which has a motion range of 800 µm × 800 µm × 250 µm (X × Y × Z). The XY axes of the piezo stage can traverse steadily with a speed of up to 10 mm/s. The artefact used in the test is made of Cu with 15 µm Ni and a 5 µm Cr layer. The nominal height is 10 µm and the slope inclination is 30 °.

The initial probing forces at the top surface of the artefact are between 86 µN to 96 µN, which results in probing forces on the bottom surface in the range of 2 µN to 12 µN. The microprobe with the integrated silicon tip traverses across the artefacts with a speed of 20 µm/s, 5 mm/s and 10 mm/s respectively. The measured profiles acquired at different traverse speeds agree well and no perceptible tip flights have been found from the measurement data evaluation. This result proves that the dynamic response of the microprobe with the silicon tip is high enough for the roughness measurements at the traverse speeds up to 10 mm/s.

Further investigation of the tip flight W_f of silicon micro-probes under different traverse speeds v_tip, probing forces F_tip and step height H is under consideration, with the aim to provide sufficient dataset for quantitative modeling of the dynamic performances of micro-probes at high-speed surface topography measurement.





References
[1] Brand, U.; Xu, M.; Doering, L.; Langfahl-Klabes, J.; Behle, H.; Bütefisch, S.; Ahbe, T.; Peiner, E.; Völlmeke, S.; Frank, T.; Mickan, B.; Kiselev, I.; Hauptmannl, M.; Drexel, M. Long Slender Piezo-Resistive Silicon Microprobes for Fast Measurements of Roughness and Mechanical Properties inside Micro-Holes with Diameters below 100 µm. Sensors 2019, 19, 1410.; doi.org/10.3390/s19061410