Cantilever-Based Tactile Sensor with Improved Sensitivity for Dimensional Metrology of Deep Narrow Drillings

The paper reports on a tactile force sensor for the dimensional metrology of deep narrow drillings. The sensor consists of an up to 7-mm-long cantilever with a width of 150 mum suspended by a thin silicon membrane hinge comprising an implanted piezoresistive stress sensor. The device is microstructured using deep reactive etching of single-crystal silicon. A quadratic p-well with four peripheral p⁺-contacts serves as stress sensor element. To investigate and improve the stress sensitivity of these elements, 90times90 mum² p-wells comprising non-conducting islands of different sizes were implemented. In comparison to sensor elements without island, the introduction of a non-conducting region of 60times60 mum² improves the sensitivity by 41% consistent with Finite Element simulations. Depending on the size of the island, force sensitivities between 7.74 mV/V/mN and 10.9 mV/V/mN were achieved.