An electrostatic scanning micromirror with diaphragm mirror plate and diamond-shaped reinforcement frame

Abstract

We present the design, fabrication and measurement results of a comb-driven electrostatic scanning micromirror. Instead of a conventional micromirror having uniform thickness across the entire reflective surface, a diaphragm mirror plate supported by an array of diamond-shaped frame structures is fabricated monolithically. The fabrication process is a simple sequence of silicon deep etch processes on both sides of the silicon-on-insulator (SOI) substrate without the substrate bonding process. The micromirror is fabricated on the device layer of the substrate. The mirror plate undergoes a rotational motion by an electrostatic force between the movable comb electrodes connected to the micromirror and stationary comb electrode formed on the handle wafer. A scanning micromirror with a 10 µm thick diaphragm mirror plate, having a planar dimension of 1.5 × 1.5 mm 2 , supported by an array of 110 µm thick rhombic support frames, was fabricated and tested. A mechanical deflection angle of 8.5 • at a resonance frequency of 19.55 kHz and a pressure of 7 mTorr was obtained. A prototype of the raster scanning laser projection display system was developed using the fabricated micromirror as the horizontal scanner and a galvanomirror as the vertical scanner, respectively.

Mass reduction patterning of silicon-on-oxide–based micromirrors

“…The majority of micromirror designs since then have leveraged some form of an SOI MEMS process and most recognize the benefit of reducing the large mass associated with this approach. Designs that incorporate backside etching of the mirror surface have been presented for a variety of geometries and include hexagon patterns, 10,11 truss structures, 12 three-dimensional conical, 13 and stepped 14 approaches. As apparent from the work cited above, it has long been recognized that accommodating the structural rigidity of the mirror surface must be considered in conjunction with the system dynamic response during the structural design of the micromirror.…”

A Bi-Directional Out-of-Plane Actuator by Electrostatic Force

“…Unlike electromagnetic, piezoelectric, and electrothermal out-of-plane actuators [9][10][11][12], MEMS electrostatic actuators offer a smaller footprint, lower power consumption, and a faster response time.…”

Design, fabrication and vacuum operation characteristics of two-dimensional comb-drive micro-scanner

“…Micromachined optical scanners have also been studied for scientific and industrial applications which range from laser medical imaging to home-office appliances such as facsimile machines, printers, and barcode scanners [1][2][3][4][5][6][7][8][9]. To drive the scanner, one can use several actuation mechanisms such as magnetic, piezoelectric, thermal, and electrostatic [10][11][12][13][14][15][16][17].…”

“…It was recently reported that the operation voltage was decreased substantially by decreasing the air friction of comb-drive micro-mirror at a high resonant frequency when the mirror was operated in vacuum [5,[18][19][20][21]. In Ref.…”