教師著作
Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/31266
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Item Fabrication of micro free standing structure in p-type silicon using an electrochemical etching technique(2005-11-25) 楊啟榮; 林明憲; 湯杜翔; 鍾武雄; Yang; Chii-Rong; Lin; Ming-Hsien; Tang; Du-Hsiang; Chung; Wu-HsungAn electrochemical etching technique is suitable to the application of MEMS silicon bulk micromachining. In this work, a HF-ethanol-H2O based electrolyte, modified by adding anionic surfactant MA, was used to evaluate the etching properties of p-type silicon in electrochemical etching. The high-aspect-ratio trench structures and free-standing beams were also fabricated with only single step mask. The results indicate that the pattern of initial pits significantly affects the etching rate of the macropores and the morphology of the etched trench structures. The surfactant MA can drastically reduce the roughness and significantly affect the topology of the etched surface. Because the contact angle of HF-ethanol-H2O-MA based electrolyte is about 6.4 times lower than that in HF-ethanol-H2O based electrolyte. However, the etching rate in MA-added electrolyte is lower than that obtained in electrolyte without MA. Moreover, the wall width of trenches is kept on about 2μm independently of the current density and the width of etching mask. Furthermore, the etched depth is proportional to etching time, but the etching rate is inverse proportional to the etching time. Because the etched depth grows deeper, the concentration of electrolyte at the pore tip decreases linearly with length. The trench structures with aspect ratio of around 40 have been obtained in this study. The free-standing beams are also fabricated with only one mask by controlling the current density.Item Effects of various ion-typed surfactants on silicon anisotropic etching properties in KOH and TMAH solutions(Elsevier, 2005-03-28) Yang, Chii-Rong; Chen, Po-Ying; Yang, Cheng-Hao; Chiou, Yuang-Cherng; Lee, Rong-TsongThree ion-typed surfactants, including anionic SDSS, cationic ASPEG and non-ionic PEG, which are powerful wetting agents in electroforming, were added to 30 wt.% KOH and 10 wt.% TMAH solutions to evaluate the silicon anisotropic etching properties of the (1 0 0) silicon plane without agitation and no IPA additive. The results indicate that the surfactant ion-types are not the main determinants of the silicon anisotropic etching properties in KOH and TMAH solutions. The wetting capacity of the etchants causes the efficacies of the etchants on the roughness to follow the order anionic SDSS, cationic ASPEG, non-ionic PEG and pure solution in KOH solutions, and the order cationic ASPEG, non-ionic PEG, pure solution and anionic SDSS in TMAH solutions, especially at higher etching temperatures. Moreover, the chemical activities of etchants differ so that the etching rates follow the order anionic SDSS, pure solution, non-ionic PEG and cationic ASPEG in KOH solutions, and the order anionic SDSS, pure solution, cationic ASPEG and non-ionic PEG in TMAH solutions at a given etching temperature. Anionic SDSS has the highest etching rate of 5.4 μm/min and the lowest surface roughness of 7.5 nm, which are about 1.69 times higher and 7.87 times lower, respectively, than those obtained in pure KOH solution. The cationic ASPEG has a reasonable etching rate of 0.7 μm/min and the lowest surface roughness of 4 nm in TMAH solutions for etching temperature of 100 °C. Furthermore, the surfactants used here were demonstrated to allow the utilization of usual mask materials and anionic SDSS can even increase the selectivity of silicon dissolution toward silicon dioxide in KOH solutions. A drastic reduction of the undercutting of the convex corners is obtained in TMAH solutions with non-ionic PEG surfactant. This finding reveals that the addition of non-ionic PEG to TMAH solutions is ideal when accurate profiles are required without extremely deep etching.