In-plane fabrication of insulated gold-tip probes for electrochemical and force spectroscopy molecular experiments

A new and versatile fabrication process of insulated gold tip probes for atomic force microscopy (AFM) is presented by Wu et al. (In-plane fabricated insulated gold-tip probe for electrochemical and molecular experiments, in: 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS), IEEE, 2013, pp. 492–495). The novelty of the process lies in the fact that the length and the thickness of the cantilever are defined by photolithography and Si etching from the wafer top surface. Width of the cantilever is defined by the device layer of a silicon-on-insulator (SOI) wafer. The tip is fabricated in the wafer top plane. E-beam lithography was employed outlining the gold nanowire tip. The chip body is formed with the handling layer of the SOI by deep reactive ion etching in later steps. In a practical operation, the probe chip is rotated by 90 degree. The tip radius of curvature is approximately 20 nm. The high-quality insulation on the probe was demonstrated by performing electrodeposition of gold on the tip-end. The spring constant of the cantilever was obtained by measuring resonance frequency of the cantilever. With this in-plane fabrication process, probes with different spring constants ranging from 0.05 N/m to 13.67 N/m were fabricated on the same wafer.