Byoung-So Choi

Bonding of silicon scanning mirror having vertical comb fingers

A 1500 µm × 1200 µ ms ilicon scanning mirror has been fabricated by using anodic bonding and flip chip bonding. This scanning mirror is mainly composed of two structures having vertical comb fingers. By anodic bonding between the silicon wafer and the Pyrex glass substrate, and following deep inductively coupled plasma reactive ion etching (ICPRIE), isolated comb electrodes were fabricated at the lower structure. However, gold signal lines for electrical connection to the electrodes, which were inserted between silicon and Pyrex glass, were damaged during anodic bonding. This problem was solved by using the proposed processes and signal lines were successfully fabricated with the contact resistance below severa lt en so fohms. By flip chip bonding, the upper and lower structures having vertical comb fingers were assembled. Vertical comb fingers of two structures were aligned with a microscope and the frames of two structures were bonded at 300 ◦ Cf or 20 s using the eutectic bonding material— electroplated AuSn. Finally, the scanning mirror was successfully fabricated and could be used for laser display as a galvanometric vertical scanner. (Some figures in this article are in colour only in the electronic version)

Laser TV for home theater

The laser TV using blue, green diode-pumped solid state lasers and a red diode laser is developed. The wavelengths of the blue, green and red are 457 nm, 532 nm and 648 nm, and the output powers are 350 mW, 700 mW and 500 mW, respectively. The power levels of lasers are adjusted for white color balance. The polygon mirror and the galvanometer are used for horizontal scanning and vertical scanning, respectively. The image size of 80 inches with high-brightness and VGA resolution (640 X 480 Progressive scanning) is obtained. The acousto-optic modulator (AOM) is fabricated for laser beam modulation, for which the carrier frequency of 350 MHz for XGA resolution is applied. TeO2 crystal, which is cut at Brewster angle, is used as an optical medium and LiNbO3 is attached as a transducer. In order to get a compact size, low cost, low-power consumption and lightweight, a scanning mirror using MEMS technology is fabricated by the size of 1500 micrometers X 1200 micrometers . This scanning mirror can be used as a galvanometric vertical scanner for laser TV.

Laser Graphic Video Display using Silicon Scanning Mirrors with Vertical Comb Fingers

We acquired a two-dimensional (2D) laser vector graphic video image using 1500 µm×1200 µm silicon scanning mirrors with vertical comb fingers. Vector image signals from the graphic board were applied to two scanning mirrors, and a SHG green laser was directly modulated to shape independent graphic images. These scanning mirrors were originally designed for laser raster video display as a galvanometric vertical scanner, and are controlled perfectly by the ramp waveform of 60 Hz with the duty cycle of 90%.

Characterization of Silicon Scanning Mirror for Laser Display

To use a scanning mirror for laser display, the size of the mirror must be larger than that of the laser beam and the laser beam must be scanned linearly with analog operation to produce an undistorted image. A 1500 µm×1200 µm silicon scanning mirror having vertical comb fingers, which satisfies such requirements for laser display, has been fabricated and characterized. The open loop responses were measured using a laser doppler vibrometer (LDV) according to the input signal wave forms and the deflection angle was measured according to the control voltage with dc bias voltages. This scanning mirror showed a very linear actuating performance and it could be used for laser display as a galvanometric vertical scanner.

SOI-fabrication of scanning mirror for laser display

A 1500 /spl mu/m/spl times/1200 /spl mu/m scanning mirror having vertical comb fingers has been fabricated by using silicon-on-insulator (SOI)-fabrication processes. It is a vertically driven electrostatic scanner and composed of two structures having vertical comb fingers. We used a buried oxide layer as an etch stop and acquired torsion bars with the uniform thickness. From this, the reliability of the scanning mirror is much improved.

Bonding technologies for silicon scanning mirror having vertical comb fingers

A 1500 micrometers X 1200 micrometers silicon scanning mirror for laser display has been fabricated. This scanning mirror is mainly composed of two structures having vertical comb fingers. By anodic bonding of the silicon wafer and the Pyrex glass substrate, and followed deep ICPRIE (Inductively Coupled Plasma Reactive Ion Etching), isolated comb electrodes were fabricated at the lower structure. But in this anodic bonding, gold signal lines for electrical connection to the electrodes, which were inserted between silicon and Pyrex glass, were cut off by mechanical pressure or damaged to agglomerate by diffusion. To remove these phenomena, Pyrex glass was trenched about 2000 Angstroms in depth in the shape of signal lines, and Cr/Au signal lines were formed along the etched grooves about 500 Angstroms/3500 Angstroms in depth, and then annealed at 400 degree(s)C, N2 atmosphere, for 1 hour before anodic bonding. As a result, gold signal lines were successfully fabricated and the contact resistance was acquired below several tens ohms. By flip chip bonding, the upper and lower structure having vertical comb fingers were assembled. Vertical comb fingers of two structures were aligned with a microscope and the frames of two structures were bonded at 300 degree(s)C for 20 sec. using the eutectic bonding material, electroplated AuSn. Using these bonding technologies, the scanning mirror was successfully fabricated and it could be used for laser display as a galvanometric vertical scanner.