Tip current/positioning close-loop mode of scanning electrochemical microscopy for electrochemical micromachining

Direct Nanomachining on Semiconductor Wafer By Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is one of the most important instrumental methods of modern electrochemistry due to its high spatial and temporal resolution. We introduced SECM into nanomachining by feeding the electrochemical modulations of the tip electrode back to the positioning system, and we demonstrated that SECM is a versatile nanomachining technique on semiconductor wafers using electrochemically induced chemical etching. The removal profile was correlated to the applied tip current when the tip was held stationary and when it was moving slowly (<20 μm s^-1 ), and it followed Faraday's law. Both regular and irregular nanopatterns were translated into a spatially distributed current by the homemade digitally controlled SECM instrument. The desired nanopatterns were "sculpted" directly on a semiconductor wafer by SECM direct-writing mode. The machining accuracy was controlled to the sub-micrometer and even nanometer scales. This advance is expected to play an important role in electrochemical nanomachining for 3D micro/nanostructures in the semiconductor industry.

Scanning Gel Electrochemical Microscopy for Topography and Electrochemical Imaging

Scanning electrochemical probe techniques have been widely applied for analyzing the local electrochemical activity of surfaces and interfaces. In this work, we develop a new concept of carrying out local electrochemical measurements by localizing both the electrode and the electrolyte. This is achieved through a gel probe, which is prepared by electrodepositing chitosan-gelatin gel on a microdisk electrode. It is positioned in contact with the sample surface by shear force feedback. The preliminary results indicate that the topography of the sample can be mapped by tapping the probe and recording the coordinates at a given normalized shear force signal, while the local electrochemical activity can be retrieved from local measurements with the probe touching the sample surface. The technique is denoted as scanning gel electrochemical microscopy. As compared with existing techniques, it has a major advantage of operating in air with the electrolyte immobilized in gel. This would prevent the spreading and leakage of solution on the sample surface and may lead to field applications.