Fabrication of a ZnO piezoelectric cantilever with a high-aspect-ratio nano tip

This paper reports the fabrication process of a ZnO piezoelectric micro cantilever with a high- aspect-ratio (HAR) nano tip for the scanning probe microscopy (SPM). The HAR nano tip has 5 μm side length, over 15 μm height, and less than 30nm tip radius, which is built on the cantilevers with 200μm and 300μm length. The designed resonance frequency and spring constant of cantilever with 300μm length are 28.41kHz and 0.6986N/m, respectively. To prevent the distortion of data by the cantilever, the HAR nano tip is fabricated using deep RIE process and LPCVD poly-Si deposition. These steps protect nano tips during the whole process and minimize tip damage. To compensate residual stress, the multi-layered structure is used. It is composed of silicon nitride and poly silicon which have tensile and compressive stresses, respectively. And, to prevent ZnO breakdown and metal oxidation during anodic bonding process, internal metal patterns are isolated from the pyrex glass. After the boding process, they are connected with external electrodes through the via holes in pyrex glass.