Robert E. Frahm

Effects of electrical leakage currents on MEMS reliability and performance

Electrostatically driven MEMS devices commonly operate with electric fields as high at 10/sup 8/ V/m applied across the dielectric between electrodes. Even with the best mechanical design, the electrical design of these devices has a large impact both on performance (e.g., speed and stability) and on reliability (e.g., corrosion and dielectric or gas breakdown). In this paper, we discuss the reliability and performance implications of leakage currents in the bulk and on the surface of the dielectric insulating the drive (or sense) electrodes from one another. Anodic oxidation of poly-silicon electrodes can occur very rapidly in samples that are not hermetically packaged. The accelerating factors are presented along with an efficient early-warning scheme. The relationship between leakage currents and the accumulation of quasistatic charge in dielectrics are discussed, along with several techniques to mitigate charging and the associated drift in electrostatically actuated or sensed MEMS devices. Two key parameters are shown to be the electrode geometry and the conductivity of the dielectric. Electrical breakdown in submicron gaps is presented as a function of packaging gas and electrode spacing. We discuss the tradeoffs involved in choosing gap geometries and dielectric properties that balance performance and reliability.

256/spl times/256 port optical cross-connect subsystem

This paper describes the subsystem design and performance of a 256/spl times/256-port micromechanical beam-steering optical cross-connect with 1.33-dB average loss, which can provide 238/spl times/238-port cross-connect with a maximum loss of less than 2dB. This paper describes the design chosen and analyzes the tolerance ranges required to produce low loss and simulate the expected loss distribution of the fabric. The method of establishing and testing the connections is also described. The simulation is compared with the measured system, and the expected and measured static and dynamic crosstalk are compared.

High-Density Solder Bump Interconnect for MEMS Hybrid Integration

An ultra high-density hybrid integration for micro-electromechanical system (MEMS) mirror chips with several thousand inputs/outputs has been developed. The integration scheme involving flip-chip assembly provides electrical signal to individual mirrors, which is compatible with postprocessing steps of selectively removing the silicon handle and releasing the MEMS mirrors. For the first time, to our knowledge, solder deposition and flip-chip bonding of 3-mum bumps on 5-mum centers of a large array has been demonstrated.

Optical MEMS devices for telecom systems

As telecom networks increase in complexity there is a need for systems capable of manage numerous optical signals. Many of the channel-manipulation functions can be done more effectively in the optical domain. MEMS devices are especially well suited for this functions since they can offer large number of degrees of freedom in a limited space, thus providing high levels of optical integration. We have designed, fabricated and tested optical MEMS devices at the core of Optical Cross Connects, WDM spectrum equalizers and Optical Add-Drop multiplexors based on different fabrication technologies such as polySi surface micromachining, single crystal SOI and combination of both. We show specific examples of these devices, discussing design trade-offs, fabrication requirements and optical performance in each case.

Design for reliability of MEMS/MOEMS for lightwave telecommunications

Optical Micro-Electro-Mechanical Systems (Optical MEMS, or MOEMS) comprise a disruptive technology whose application to telecommunications networks is transforming the horizon for lightwave systems. The influences of materials systems, processing subtleties, and reliability requirements on design flexibility, functionality and commercialization of MOEMS are complex. A tight inter-dependent feedback loop between Component/ Subsystem/ System Design, Fabrication, Packaging, Manufacturing and Reliability is described as a strategy for building reliability into emerging MOEMS products while accelerating their development into commercial offerings.

Integrated array of 1/spl times/N optical switches for wavelength-independent and WDM applications

This paper describes an optical configuration that allows effective arrangement of multiple 1/spl times/N optical switches as an integrated array. An experimental compact module of 16 arrayed 1 /spl times/ 8 optical switches, built by utilizing a cylindrical lens, achieves uniform performance and a mean fiber-to-fiber insertion loss of 2.75 dB. This paper also discusses various layouts that use the proposed optical switching module for both wavelength-independent and wavelength division multiplexing (WDM) applications.

Closed-loop AO demonstration of MEMS SLM with piston, tip, and tilt control

A MEMS SLM with an array of 64×64 pixels, each 120 μm ×120 μm in size, with 98% fill-factor, has been developed. Each reflector in the array is capable of 5 μm of stroke, and ±4° tip and tilt. From a prototype array, 14 contiguous pixels have been independently wired-out to off-chip drive electronics. These 14 pixels have been demonstrated to be effective in an off-the-shelf AO system (with requisite modifications to suit the SLM). For a low-order static aberration, the measured Strehl ratio has been improved from 0.069 to 0.861, a factor of 12 improvement.