Tham khảo tài liệu 'micro electronic and mechanical systems 2009 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 96 Micro Electronic and Mechanical Systems The fabrication of surface-sculpted protrusion arrays is based on the deposition of a nanometric membrane precursor over a sacrificial layer Mamedov et al 2002 Jiang et al 2004b and its subsequent release in etching solution the same method used to produce metal-composite nanomembranes. The difference is that prior to depositing the membrane precursor one first etches an array of micrometer pits in the sacrificial structure. The layout of the pits is determined by the applied photolithographic mask thus defining the diffractive grating for the coupling. The shape of the pits themselves is defined by the chosen etching method. If isotropic etching is used the pits are hemispherical or ellipsoidal. If anisotropic etching is utilized one can produce for instance pyramids or truncated pyramids. The membrane precursor is subsequently deposited over the pits and upon release the fabricated nanomembrane retains the shape of the pits. If the sacrificial layer pits are etched by isotropic etchant the final protrusion are hemispherical Fig. 8b. Variations to this generic form can be obtained by using different shapes of photolithographic masks for instance elliptical openings but also various polygons and by adjusting the etching duration to obtain either flatter or more voluminous structures. The structure in Fig. 8c is obtained in an analogous manner but using anisotropic etching of single crystalline silicon sacrificial layer with 100 surface orientation through square windows aligned along 110 . The variations to this generic form includes truncated pyramids and actually all standard forms obtainable by anisotropic etching. Figure 9 shows the fabricated 15 pmx10 pm pyramid sculpted on the surface of a metalcomposite nanomembrane with a thickness of 20 nm. It is known that nanomembranes become intrinsically stretched during their low-temperature annealing Matovic Jaksic 2009 and thus the sculpted surface features retain their .
