Piezoresistive sensors for scanning probe microscopy

In this article we summarize the efforts devoted to the realization of our ideas of the development of piezoresistive sensor family used in scanning probe microscopy. All the sensors described here are fabricated based on advanced silicon micromachining and standard CMOS processing. The fabrication scenario presented in this article allows for the production of different sensors with the same tip deflection piezoresistive detection scheme. In this way we designed and fabricated, as a basic sensor, piezoresistive cantilever for atomic force microscopy, which enables surface topography measurements with a resolution of 0.1 nm. Next, by introducing a conductive tip isolated from the beam we obtained a microprobe for scanning capacitance microscopy and scanning tunneling microscopy. With this microprobe we measured capacitance between the microtip and the surface in the range of 10−22 F. Furthermore, a modification of the piezoresistors placement, based on the finite element method (FEM) simulation permits fabrication of the multipurpose sensor for lateral force microscopy, which enables measurements of friction forces with a resolution of 1 nN. Finally, using the same basic device idea and only slightly modified process sequence we manufactured femtocalorimeter for the detection of heat energy in the range of 50 pJ.