Single-wafer-processed nano-positioning XY-stages with trench-sidewall micromachining technology

• Published in: Journal of micromechanics and microengineering 2006-07, Vol.16 (7), p.1349-1357
• Main Authors: Gu, Lei, Li, Xinxin, Bao, Haifei, Liu, Bin, Wang, Yuelin, Liu, Min, Yang, Zunxian, Cheng, Baoluo
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Micromechanical devices and systems; Physics; Precision engineering, watch making
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/16/7/032

For operation and manipulation with nanometric positioning precision, a single crystalline silicon micro XY-stage is developed by using double-sided bulk-micromachining technology. Front-side deep reactive ion etching combined with backside anisotropic etching constructs the high-aspect-ratio comb-driven XY-stage in a single standard silicon wafer (i.e., no silicon on insulator wafer is used). For integrating several electrostatic actuators in one silicon chip, different actuators are electrically isolated from each other using a trench-sidewall insulating technique. SiO2-refilled trench bars are formed on vertical trench sidewalls to isolate adjacent comb-drive elements. Combined with the reverse-biased p-n junction along the boron-diffused trench sidewall for comb driving, individual actuators can be operated independently. The developed XY-stage of 1600 X 1600 mum2 is suspended by four sets of folded-beam and bending-flexure composite springs. To maximize the moving distance, a two-segment comb finger with a gently curved transition is used for both improving the actuation efficiency and avoiding side instability of the stage. The experimental results verify the stage design including the gentle transition of a two-segment comb-drive scheme. Under 23 V driving voltage, a 10 mum moving stroke is measured in each of the four directions. Compared with a conventional comb structure, the two-segment comb fingers contribute 70% improvement in actuating amplitude. The positioning precision of the stage is evaluated with a nano-mechanical indenting experiment. A scanning probe microscopy probe with an electrical-heated nano tip is put in contact with the surface of a polymethyl methacrylate film that is coated on the stage surface. Along with the movement of the stage, pulsed heating on the nano tip produces serial nano-pitches. With the nano-indenting experiment, better than 18 nm positioning precision is obtained for the XY-stage.