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.

Scanning laser projection using resonant actuated MEMS scanning mirrors is expected to overcome the current limitation of small display size of mobile devices like cell phones, digital cameras and PDAs. Recent progress in the development of compact modulated RGB laser sources enables to set up very small laser projection systems that become attractive not only for consumer products but also for automotive applications like head-up and dash-board displays. Within the last years continuous progress was made in increasing MEMS scanner performance. However, only little is reported on how mass-produceability of these devices and stable functionality even under harsh environmental conditions can be guaranteed. Automotive application requires stable MEMS scanner operation over a wide temperature range from -40° to +85°Celsius. Therefore, hermetic packaging of electrostatically actuated MEMS scanning mirrors becomes essential to protect the sensitive device against particle contamination and condensing moisture. This paper reports on design, fabrication and test of a resonant actuated two-dimensional micro scanning mirror that is hermetically sealed on wafer level. With resonant frequencies of 30kHz and 1kHz, an achievable Theta-D-product of 13mm.deg and low dynamic deformation <20nm RMS it targets Lissajous projection with SVGA-resolution. Inevitable reflexes at the vacuum package surface can be seperated from the projection field by permanent inclination of the micromirror

Low-cost automotive laser scanners for environmental perception are needed to enable the integration of advanced driver assistant systems into all automotive vehicle segments, which is a key to reduce the number of traffic accidents on roads. Within the scope of the European-funded project MiniFaros, partners from five different countries have been cooperating in developing a small-sized low-cost time-of-flight-based range sensor. An omnidirectional 360-deg laser scanning concept has been developed based on the combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. The concept, design, fabrication, and first measurement results of a resonant biaxial 7-mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives is described. Identical resonant frequencies of the two orthogonal axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen, since it minimizes the frequency splitting of the two resonant axes. Low-mirror curvature is achieved by a thickness of the mirror of more than 500 pm. Hermetic wafer-level vacuum packaging of such large mirrors based on multiple wafer bonding has been developed to enable a large mechanical tilt angle of +/- 6.5 deg in each axis. Due to the large targeted tilt angle of +/- 15 deg and because of the MEMS mirror actuator having a diameter of 10 mm, a cavity depth of about 1.6 mm has been realized

Hermetic wafer level packaging of optical MEMS scanning mirrors is essential for mass-market applications. It is the key to enable reliable low-cost mass producible scanning solutions. Vacuum packaging of resonant MEMS scanning mirrors widens the parameter range specifically with respect to scan angle and scan frequency. It also allows extending the utilizable range of mirror aperture size based on the fact that the energy of the high-Q oscillator can be effectively conserved and accumulated. But there are also some drawbacks associated with vacuum packaging. This paper discusses the different advantageous and disadvantageous aspects of vacuum packaging of MEMS scanning mirrors with respect to laser projection displays. Improved MEMS scanning mirror designs are being presented which focus on overcoming previous limitations. Finally an outlook is presented on the suitability of this technology for very large aperture scanning mirrors to be used in high power laser applications

This paper presents design, fabrication and measurements for single-axis piezoelectric MEMS micromirrors with 1 mm2 apertures. These micromirrors, which feature thin-film PZT actuators and mechanical leverage amplification, are dedicated for laser projection and meet the requirements of high resonant frequency and large deflection angles. To identify the optimal micromirror geometries a parametric study by means of FEM simulations and analytic modeling has been performed. Characterization, related to the material qualities of PZT and the mechanical performance of the micromirrors, have verified the reliability of the process, the robustness and the performance of the fabricated prototypes. According to the measurements the fabricated micromirrors feature high Q-factor about 1570. The micromirror reaches the theta(ind opt)·D product of 42.5 °·mm at 32 kHz driven by a low voltage of 7 V. Furthermore, new designs with larger apertures and deflections are currently being developed

Mass-selected distributions of bombardment energies of O+ ions at the powered electrode of a reactive ion etcher are investigated under angles between ±10° with respect to the electrode normal. The energy distributions consist of split high-energy peaks and continuous intensities between 50 eV and the maximal energy defined by the potential drop across the sheath. Ions found in the bimodal split high-energy peaks show angular distributions with widths between 2° and 6° [full width at half-maximum (FWHM)]. The continuous part of the ion energy distributions exhibit angular widths between 7° and 11° (FWHM). The observed phenomena in the ion energy and ion angular distributions are interpreted as combined effects of elastic scattering and dissociative collisions in the sheath.

The design and manufacturing of a piezoelectrically driven translatory MEMS actuator is presented, which features a 7 mm aperture and four thin-film PZT actuators achieving large displacements. The actuator performs piston mode oscillation in resonance which can serve for Fourier Transform Infrared Spectroscopy (FTIR). Thereby vertical displacements in piston mode of up to ± 800 µm at 163 Hz and 25 V driving sinusoidal voltage has been achieved under ambient conditions. Due to the low frequencies and the low driving voltages only low power consumption is required. The effect of residual gas friction and internal friction on the piezo-driven MEMS actuator is analyzed by measuring Qvalues associated with the piston mode. Laser Doppler Vibrometry (LDV) was also used to detect and analyses the parasitic effects especially tilting which superimposes the vertical movement of the mirror. The deviation from the pure vertical piston mode was found to 1.3 µm along the x and 3 µm in the y-axis.

Quadrupole mass spectroscopy has been used to resolve the energy distributions of O2+ on the substrate plane of a parallel plate reactive ion etching reactor. Energy spectra show pronounced structures caused by charge exchange collisions in the plasma sheath in combination with rf modulation. Additionally, continuous distributions are found which are attributed to the effect of elastic scattering of ions.