Fabrication of 3D micro-cantilevers based on MBE-grown strained semiconductor layers

Strain-driven bending process proposed for the fabrication of small and precise cantilevers is reported. The process starts from the multi-layer structure grown by molecular beam epitaxy (MBE). The cantilevers consist of the two parts imitating the beam and the tip, each of which has different bending direction and radius. The shape determined by location of strained layer in multi-layer structure controlled with layer design and fabrication process including selective etching technique. We demonstrated cantilevers having a rolling up beam with 5 - 20 mu m length and a rolling down thinner tip with 3 mu m length. However the tips showed tortuous shape. The complex shape might originate from inhomogeneity dissolving of extra compounds generated in sacrifice layer etching process. Moreover, we measured resonant frequencies of the fabricated cantilevers by optical lever method. We obtained high resonant frequency of 2 MHz for the cantilever with 5 mu m length, I gm width, and 100 nm thickness. This frequency seems suitable for video-rate scanning in dynamic mode atomic force microscopy (AFM). These results suggest that the strain-driven bending process is applicable to three-dimensional (3D) micro-cantilevers for video-rate scanning in dynamic AFM. (C) 2007 Elsevier B.V. All rights reserved.