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

Abstract

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 × 1600 µm2 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 µm 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.

Design, Modeling, and Control of a Micromachined Nanopositioner With Integrated Electrothermal Actuation and Sensing

“…Closed-loop feedback control of the positioners is highly desirable if a high degree of displacement precision is required, and such a control system needs an accurate source of position information [9], [10]. However, many of the MEMS nanopositioners reported in the literature are not equipped with on-chip sensors due to the restrictions associated with microfabrication processes [11], [12]. Thus, in-plane movements are often measured by laser reflectance microscopes [13], [14] or optical microscopes [15], making the footprint of the whole system fairly large.…”

Non-initial overlap bulk silicon comb-drive actuator with low-voltage and large-displacement

“…Since the first time developed by Tang et al in 1989 [2], comb-drive actuators have be used in a variety of applications including tweezer [3], optical switch [4], micro-tribotester [5] and Micro XY-stage [6][7][8], etc.Generally, comb-drive actuators usually need a high drive voltage to achieve a large displacement. In addition, the desired displacement of the comb-drive actuators is constrained by the side instability.…”

A two directional electrostatic comb-drive X–Y micro-stage for MOEMS applications

“…electromagnetic [13], electrostatic [14,15] or piezoelectric ones [16] have been implemented into the X-Y micro-stages to meet the requirements of fast and high-precision positioning of a micro-component, low energy consumption and low cost of the fabrication. Especially the electrostatic comb-drive actuators are widely used for this purpose due to their ability to provide highly linear, in-plane motion, in relatively large range (typically up to 50 m) and high precision level.…”