Fabrication Process of Embedded Silicon Microchannel and Nozzle Structure for Liquid-delivering Atomic Force Microscopy Probe

Abstract

In this paper, we demonstrate the novel fabrication processes of a dual Si atomic force microscopy (AFM) probe with embedded microchannels and a nozzle hole for liquid delivery function. The embedded microchannels and nozzle hole were separately located on the silicon surface to avoid the appearance of unnecessary crystalline (111) planes around the nozzle during the wet etching process for the probe tip formation, yet they were connected underneath the surface. The micronozzle was successfully formed at an inclined (111) plane of the Si AFM tip. The nozzle and embedded microchannels were successfully fabricated with under-surface connection with a path of 1 μm diameter. The narrow trench opening of each microchannel was completely sealed by the combination of Si thermal oxidation and subsequent SiO 2 sputtering deposition. After the sealing process, a microchannel of 1.5 µm diameter was obtained. Applied pressure was estimated as 8 Pa in a microchannel of 1.5 µm diameter and 2 mm length to obtain a flow rate of 0.5 fL/s. A narrow-gapped Si dual tip with a nozzle and embedded microchannels were fabricated. The tip radius was sharpened to several nanometers through the combination of thermal oxidation and low-temperature thermal oxidation with the fabrication processes.