Three dimensional single crystalline force sensor by porous Si micromachining

Porous Si micromachining technique was used for the formation of single crystalline force sensor elements capable to resolve the three vectorial components of the load. Similar structures presented so far, are formed from deposited polycrystalline Si resistors embedded in multilayered SiO234/SiN membranes, using surface micromachining technique for cavity formation. In the present work, in the n-type perforated membrane four implanted piezoresistors were fabricated with their reference pairs on the substrate, in order to form 4 half-bridges for the transduction of the mechanical stress. The HF based porous Si process was successfully combined with conventional doping and Al metallization, thereby offering a possible integration of read-out and amplifying electronics. The 300x300mm2 membrane size allows the formation of large area arrays for tactile sensing using single crystalline sensing elements of superior mechanical properties.