High-yield fabrication of AFM probes with simultaneous formation of both nano-tips and cantilever

Presented is a new micromachining technology for high-yield fabrication of silicon AFM probes. Both tips and cantilevers are simultaneously formed with a masked-maskless-combined anisotropic etching process. The cantilever contour is firstly formed by masked etching. Then, the SiO₂ etching mask is removed while the mask for tip-contour formation is remained. Following the combined etching is performed with the cantilever dived to the bottom of the SOI active layer by maskless etching. Simultaneously, cone-shaped tip contour with about 0.5mum top-diameter is formed by convex-corner undercutting of masked etching process. By specific design based on the rules of the masked-maskless combined etching, the cantilevers and the tips are simultaneously formed. Compared with previous tip-to-cantilever sequential fabrication scheme, this simultaneous formation can effectively increase fabrication yield by avoiding the tips damaged during the process. In addition, the low-cost and mass-producible fabrication techniques, such as anisotropic etching and thermal oxidization, are used instead of expensive and difficult-controlled technique such as the combination of anisotropic and isotropic RIE, etc. Higher than 80% fabrication yield for the AFM probes has been realized in 4-inch wafers. The final tips after oxidation-sharpening treatment are generally with a radius of about 10-30nm and the cantilever spring constant can be well controlled. Sample scanning results from the AFM probes are demonstrated to provide high-resolution image, whose quality is comparable with those from commercialized probes