Meng-Hsiung Kiang

Electrostatic combdrive-actuated micromirrors for laser-beam scanning and positioning

We describe the design and fabrication of surface-micromachined resonant microscanners that have large scan angles and fast scan speeds. These scanning micromirrors, which are hundreds of micrometers on a side, are driven by electrostatic-comb actuators and have resonant frequencies in the kilohertz range. Fabricated with two or three structural layers of polysilicon, the scanners are compact, extremely light in weight, and potentially very low in cost. Their power consumption is also minimal because the capacitive motors draw very low currents. High-precision positioning (0.01/spl deg/ dynamically and 0.038/spl deg/ statically) over a large angular range (up to 28/spl deg/ optical angle) makes the micromirrors suitable for a variety of optical applications such as laser scanners and printers, displays, holographic data storage, and fiber-optic switches. We have demonstrated microscanners of this type in bar-code readers, which are important devices with a growing number of applications in many industries.

Micromachined polysilicon microscanners for barcode readers

We describe the design and fabrication of micromachined resonant scanners that have large scan angles at fast scan speeds. Driven by an electrostatic combdrive actuator, these 200 /spl mu/m/spl times/250 /spl mu/m micromirrors have a maximum scan angle of 28/spl deg/ (optical) at a resonant frequency of 3 kHz when driven by a sinusoidal voltage of 9.5 V (amplitude) superimposed on a 30-V dc bias. Fabricated with a four-layer polysilicon-surface-micromachining process, these resonant scanners are compact, extremely light in weight, potentially very low in cost, and operate at very low power levels. Using the scanner as a laser-beam deflector, we have demonstrated a barcode reader system.

Surface-micromachined mirrors for laser-beam positioning

Abstract Actuated surface-micromachined polysilicon micromirrors for laser-beam positioning have been designed and fabricated. Two types of beam-steering mirrors are discussed which use microhinge technology to achieve the required vertical dimensions and functionality. One mirror, intended for precise beam positioning as needed in optical alignment, is actuated by linear microvibromotors. The other mirror is appropriate for laser-beam scanning and uses electrostatic comb-drive actuators. Four layers of polycrystalline silicon are micromachined to form these devices. Environmental stress testing carried out on the beam-positioning mirror has shown its structure to be relatively insensitive to vibrations below 60 kHz. Further testing has shown negligible changes in mirror position for temperatures varying between 25 and 200°C, and stability under the stress of laser irradiation of 375 mW at 1.06 μm wavelength.

Surface-micromachined electrostatic-comb driven scanning micromirrors for barcode scanners

This paper describes the design and fabrication of micromachined resonant scanners that have large scan angles at fast scan speeds. Driven by an electrostatic comb motor, these 200 /spl mu/m by 250 /spl mu/m scanning-micromirrors can scan about 12/spl deg/ (optical) at the resonance frequency of 3 kHz with a sinusoidal voltage input of 20 V in amplitude. Fabricated with a four-poly-layer silicon-surface-micromachining process, these resonant scanners are compact, extremely light in weight, and potentially very low in cost. The power consumption is also minimal since the capacitive motor draws very little current. We have demonstrated the scanner as a laser-beam deflector in a barcode reader, a potentially important application that has a growing popularity in many industries.

Pd/Si plasma immersion ion implantation for selective electroless copper plating on SiO2

Selective deposition of copper in SiO2 trenches has been carried out using Pd/Si plasma immersion ion implantation and electroless Cu plating. To form the seed layer for electroless Cu plating on SiO2, sputtered Pd and Si atoms were partially ionized by the Ar plasma and then deposited at bottoms of SiO2 trenches; Ar ion beam was then applied to assist the mixing of the deposited Pd/Si films with the SiO2 substrate by recoil implantation. We found a threshold Pd dose of 2×1014/cm2 is required to initiate the electroless plating of Cu. By careful control of the anisotropic etching of the oxide trenches and proper choice of the Pd dose, 1‐μm wide Cu filled lines with flat surfaces suitable for planarized multilevel metallization were successfully fabricated.

Silicon-micromachined micromirrors with integrated high-precision actuators for external-cavity semiconductor lasers

We present an actuated silicon-micromachined micromirror with continuous and highly accurate position adjustment designed to be used in the construction of external-cavity semiconductor-laser modules. In our initial design, a positioning accuracy better than /spl plusmn/0.2 /spl mu/m for the actuated micromirrors is obtained. The mechanical robustness, small size, and fine-positional precision of the actuated micromirrors are sufficient for external-cavity-laser applications. In production, the cost of these miniature external-cavity-laser systems should be low because they are batch-processed.

Polysilicon optical microscanners for laser scanning displays

Abstract We have designed and fabricated polysilicon microscanners using surface micromachining technologies. The scanners have electrostatic-comb actuators to drive 300 × 400 μm 2 micromirrors mounted on stationary frames by torsion bars. Torsion-bar mounting improves scanning precision from what is achievable using hinge mounting with journal bearings. The scans are accurate to 0.19 mrad; that is a scan jitter of 0.1% of the full scale, or 9% of a pixel. A 7 × 10-pixel laser-scanning display built with a seven-element, fan-diode-laser array and a scanning polysilicon micromirror is presented. A dual-axis, raster-scanning system based on similar resonant microscanners can be integrated on a chip with the light sources to produce compact microdisplay modules.

Surface-micromachined diffraction gratings for scanning spectroscopic applications

We report the design and fabrication of an actuated diffraction grating using a foundry (Multi-User MEMS ProcesS, or MUMPS, at MCNC) surface-micromachining process. Rectangular gratings with 4 /spl mu/m period and 0.75 /spl mu/m depth are produced on a 500/spl times/1000 /spl mu/m polysilicon plate, which is mounted on torsion bars, and actuated by an electrostatic combdrive. Operated as a first-order reflective grating, it can be used to build an integrated scanning microspectrometer with a resolving power of 250, or, as a grating demultiplexer for multichannel wavelength-switching networks.

Multichannel millimeter wave subcarrier transmission by resonant modulation of monolithic semiconductor lasers

We study the multichannel analog and digital performance of narrowband millimeter-wave optical transmitters based on resonant modulation of monolithic semiconductor lasers. Two-tone measurements are performed under various bias conditions at a cavity round-trip frequency of 41 GHz, and optical transmission over 400 m of single-mode fiber of two simultaneous 2.5 Mb/s BPSK channels centered at a subcarrier frequency of 41 GHz is demonstrated.<<ETX>>

Plasma immersion Pd ion implantation seeding pattern formation for selective electroless Cu plating

Abstract Selective plating of Cu for interconnects was carried out using plasma immersion Pd ion implantation and Cu electroless plating. Pd ions were sputtered from a negatively biased target and ionized in an Ar electron cyclotron resonance (ECR) plasma. The Pd ions were implanted into the SiO 2 substrates biased with negative high pulsed voltages. In our studies, we found the required Pd seeding dose for Cu plating was on the order of5 × 10 14 /cm 2 . With a direct Pd implantation, an intermediate activation step using a PdCl 2 solution was eliminated.