Preparation Of Silicon-based Complex Micro/nano Structures Based On ICP Process

Inductively coupled plasma (ICP) etching process in semiconductor processing technology has the merits of high control precision, high etching vertical, a large area etching uniformity, less pollution. Bosch process has been widely used in the ICP etching process in deep silicon etching.The unique feature of ICP-Bosch etching process is its passivation and etching alternately so as to achieve the selective and deep etching of the silicon substrate. Based on the characteristics of the ICP-Bosch etching process, in this thesis, we used ICP-Bosch process to transfer the photoresist pattern structure producing high aspect ratio micro/nano silicon structure with super hydrophobic and broadband antireflection properties. It was followed to use the sidewall corrugated structure prepared by alternate etching processing to fabricate silicon hierarchical micro/nano structure bio-inspired by the ridge-lamellae structures on Morpho scales.The mechanism of ICP-Bosch process etching was firstly introduced. We used ICP-Bosch process to transfer the photoresist pattern structure producing periodic high aspect ratio micro/nano silicon gratings structure with sub-wavelength tapered structures on top of the silicon gratings. The innovation of this approach is the application of diffraction interference lithography process to prepare the sub-wavelength hollow and tapered contour photoresist gratings. Diffraction interference lithography was theoretically simulated by rigorous coupled wave analysis(RCWA), and achieved diffraction lithography on the aligner. The sub-wavelength hollow and tapered contour photoresist gratings were prepared. The sub-wavelength hollow and tapered contour photoresist gratings were transferred to the silicon substrate by ICP-Bosch process that produced periodic high aspect ratio silicon tube gratings with sub-wavelength tapered structures on the top of the gratings. We used an optical test platform to measure the reflectance of high aspect ratio tubular silicon gratings. It was found that the reflectance of periodic high aspect ratio silicon tube gratings with sub-wavelength tapered structures on the top of the gratings was less than5%in the visible band and near-infrared band. The micro/nano-structure has the broadband antireflection property. We used the contact angle measuring instrument to test the wettability of periodic high aspect ratio silicon tube gratings with sub-wavelength tapered structures on the top of the gratings. The average contact angle was about156.2°that has reached the standard of the super-hydrophobic property.Base on the ICP-Bosch process, a novel method for preparation of biomimetic Morpho silicon hierarchical micro/nano structures was proposed. It was ingenious to utilize the micro/nanoscale corrugated structure on the sidewall of{110} crystal faces that were produced by the ICP-Bosch process etching and passivation alternately etching the silicon wafer. This thesis focuses on the main impact factors that influence on the corrugated structure in the etching step:cycle time (etching and passivation time), the gas flow (SF6and C4F8), coil power (Pc) and the RF power (Pp) in the etching step by experimental studies. We designed a feasible solution to measure the etching rate of{110} plane in (111) silicon wafer under the different temperatures and different concentrations of the KOH solution by experimental methods. Electron beam evaporation coating technology was applied inclined evaporation deposited covering layer on bottom of ripples on the {110} plane as mask for the wet etching. Finally, the silicon hierarchical micro/nano structure was prepared by using anisotropic wet etching process. The optical performance of the silicon hierarchical micro/nano structure was test. It was found that when the incident light perpendicular to hierarchy grating lines direction, the measured maximum reflectance in the ultraviolet band was less than15%and about4%in the visible and near-infraredband, that was less than the reflectance of the silicon grating in this angle of incidence. The heat transfer of the silicon hierarchical micro/nano structure was test. Compared with silicon grating, the maximum heat flux of the hierarchical micro/nano structure improved11.2%. Compared with polished silicon, the maximum heat flux of the hierarchical micro/nano structure increased44.6%. Therefore, the structure has a good cooling performance.