Atomic force microscope probe tips using heavily boron-doped silicon cantilevers realized in a 〈110〉 bulk silicon wafer

A new method of fabricating atomic force microscope (AFM) probe tip is presented. In this process, the probe tips were implemented using self-aligned heavily boron-doped silicon cantilevers in a 〈110〉 bulk silicon wafer. In this structure, a stress-free cantilever can be easily defined by selective etch stop by the heavily boron-doped region in an anisotropic silicon etchant. The proposed tips do not require expensive silicon on insulator (SOI) wafers and double-side alignment. The probe tip dimensions can be exactly defined regardless of wafer thickness by the self-aligned etch from the front side. In addition, the cantilever thickness can be easily controlled by adjusting the diffusion time, and fabricated at low cost by using bulk silicon wafers. The fabricated probe tips showed resonant frequencies of 71.420 kHz with a 1.8-μm-thick probe tip and 122.660 kHz with a 3.0-μm-thick probe tip. Using the two fabricated probe tips, we successfully demonstrate image scanning of a 1 μm grating reference sample in contact and noncontact modes, respectively.