High-Q MEMS Resonators for Laser Beam Scanning Displays

Abstract

This paper reports on design, fabrication and characterization of high-Q MEMS resonators to be used in optical applications like laser displays and LIDAR range sensors. Stacked vertical comb drives for electrostatic actuation of single-axis scanners and biaxial MEMS mirrors were realized in a dual layer polysilicon SOI process. High Q-factors up to 145,000 have been achieved applying wafer level vacuum packaging technology including deposition of titanium thin film getters. The effective reduction of gas damping allows the MEMS actuator to achieve large amplitudes at high oscillation frequencies while driving voltage and power consumption can be minimized. Exemplarily shown is a micro scanner that achieves a total optical scan angle of 86 degrees at a resonant frequency of 30.8 kHz, which fulfills the requirements for HD720 resolution. Furthermore, results of a new wafer based glass-forming technology for fabrication of three dimensionally shaped glass lids with tilted optical windows are presented.

An electrostatically driven 2D micro-scanning mirror with capacitive sensing for projection display

“…Contrary to the DLP technology in which majority of the tasks for image production are realized optically, electronic design plays a more important role for scanning-type projectors. As demonstrated in prior studies, micro-scanning mirrors may be driven by electrostatic [5][6][7][8][9][10][11][12][13][14], electromagnetic [15][16][17][18] or piezoelectric [19][20][21][22][23] mechanisms. Each approach has its own advantages and disadvantages.…”

“…Few studies have demonstrated micro-scanning mirrors with on-chip capacitive [12][13], piezoresistive [14] and piezoelectric [21] sensing capabilities. Drabe et al [14] reported a bi-axial electrostatic scanning mirror with piezoresistive sensors.…”

“…Regardless which mechanism is used, the scanner performance is often evaluated based on the resonant frequency, which Page 5 of 31 A c c e p t e d M a n u s c r i p t 5 determines the scan lines per frame, and the  opt D product ( opt is the total optical scan angle and D is the mirror diameter), which determines the resolution of pixels along the scan line. Based on these two metrics, summary of the best performing micro-scanners can be found in [12]. For successful image projection, it is crucial to maintain the synchronization between the calculated pixel position and the actual mirror motion, which requires sensitive detection of mirror's position.…”

An Electromagnetically-Driven Piezoresistively Sensed CMOS MEMS Scanning Mirror for Projection Display

“…However, the idea is often hindered by the microfabrication capability to provide simultaneous driving and sensing. Therefore only few micro-scanners have demonstrated on-chip sensing capabilities [1][2][3]. As a first attempt to integrate CMOS in this work, the implementation conveniently provides piezoresistive sensing to the electromagnetically-driven scanning mirror.…”

Modeling of MOEMS electromagnetic scanning grating mirror for NIR micro-spectrometer

“…[10][11][12][13] Several driving mechanisms can be used for MOEMS SGM, including electromagnetic, electrostatic, electrothermal and piezoelectric techniques. [14][15][16][17][18][19] All of them have their characteristics and can be applied to some specific applications respectively.…”