J.-L.A. Yeh

Bio: J.-L.A. Yeh is an academic researcher from Cornell University. The author has contributed to research in topics: Surface micromachining & Deep reactive-ion etching. The author has an hindex of 2, co-authored 2 publications receiving 164 citations.

Integrated polysilicon and DRIE bulk silicon micromachining for an electrostatic torsional actuator

Abstract: This paper presents a fabrication process that integrates polysilicon surface micromachining and deep reactive ion etching (DRIE) bulk silicon micromachining. The process takes advantage of the design flexibility of polysilicon surface micromachining and the deep silicon structures possible with DRIE. As a demonstration, a torsional actuator driven by a combdrive moving in the out-of-plane direction, consisting of polysilicon fingers and bulk silicon fingers, has been fabricated. The integrated process allows the combdrive to be integrated with any structure made by polysilicon surface micromachining.

Copper-encapsulated silicon micromachined structures

Abstract: Selective copper encapsulation on silicon has been used to fabricate micromachined devices such as inductors with quality factors over 30 at frequencies above 5 GHz. The devices are fabricated using either polysilicon surface micromachining, or integrated polysilicon and deep reactive ion etching bulk silicon micromachining. Their exposed silicon surfaces are selectively activated by palladium activation, which allows the subsequent copper deposition on the activated silicon surfaces only. This silicon encapsulated-with-copper technique takes advantage of both the excellent mechanical properties of silicon (to maintain structural integrity), and the high conductivity of copper (for electrical signal transmission). Furthermore, the process not only minimizes interfacial forces typical of physical metal deposition on silicon, but also balances the forces by metal encapsulation on all sides of the silicon structures.

A bulk microfabricated multi-axis capacitive cellular force sensor using transverse comb drives

Abstract: This paper presents design, fabrication and calibration results for a novel 2-DOF capacitive force sensor capable of resolving forces up to 490 µN with a resolution of 0.01 µN in x, and up to 900 µN with a resolution of 0.24 µN in y. A simple fabrication process using deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafers forms the 3D high aspect ratio structure. A transverse mode comb drive movement is used to greatly improve device sensitivity. Among other advantages of the developed process is a dice-free release of wafer structures, allowing fragile structures to be individually packaged. Notching or footing effects and bowing effects are well-known problems in DRIE on SOI wafers. Techniques to overcome notching and bowing effects using a PlasmaTherm SLR-770 etcher are presented that do not require hardware modifications. The application of the force sensor is for providing real-time force feedback during individual cell manipulation tasks.

MEMS: the path to large optical crossconnects

Abstract: Continuous growth in demand for optical network capacity and the sudden maturation of WDM technologies have fueled the development of long-haul optical network systems that transport tens to hundreds of wavelengths per fiber, with each wavelength modulated at 10 Gb/s or more. Micro-electromechanical systems devices are recognized to be the enabling technologies to build the next-generation cost-effective and reliable high-capacity optical crossconnects. While the promises of automatically reconfigurable networks and bit-rate-independent photonic switching are bright, the endeavor to develop a high-port-count MEMS-based OXC involves overcoming challenges in MEMS design and fabrication, optical packaging, and mirror control. Due to the interdependence of many design parameters, manufacturing tolerances, and performance requirements, careful trade-offs must be made in MEMS device design as well as system design. We provide an overview of the market demand, various design trade-offs, and multidisciplinary system considerations for building reliable and manufacturable large MEMS-based OXCs.

On-chip spiral inductors suspended over deep copper-lined cavities

Abstract: A silicon micromachining method has been developed to fabricate on-chip high-performance suspended spiral inductors. The spiral structure of an inductor was formed with polysilicon and was suspended over a 30-/spl mu/m-deep cavity in the silicon substrate beneath. Copper (Cu) was electrolessly plated onto the polysilicon spiral to achieve low resistance. The Cu plating process also metallized the inner surfaces of the cavity, forming both a good radio-frequency (RF) ground and an electromagnetic shield. High quality factors (Qs) over 30 and self-resonant frequencies higher than 10 GHz have been achieved. A study of the mechanical properties of the suspended inductors indicates that they can withstand large shock and vibration. Simulation predicts a reduction of an order of magnitude in the mutual inductance of two adjacent inductors with the 30-/spl mu/m-deep Cu-lined cavity from that with silicon as the substrate. This indicates very small crosstalk between the inductors due to the shielding effect of the cavities.

Theory and experiments of angular vertical comb-drive actuators for scanning micromirrors

Abstract: We report on the theory and experiments of scanning micromirrors with angular vertical comb-drive (AVC) actuators. Parametric analyses of rotational vertical comb-drive actuators using a hybrid model that combines two-dimensional finite-element solutions with analytic formulations are described. The model is applied to both AVC and staggered vertical comb-drive (SVC) actuators. Detailed design tradeoffs and conditions for pull-in-free operations are discussed. Our simulation results show that the fringe fields play an important role in the estimation of maximum continuous rotation angles, particularly for combs with thin fingers, and that the maximum scan angle of the AVC is up to 60% larger than that of the SVC. Experimentally, a large dc continuous scan angle of 28.8/spl deg/ (optical) has been achieved with a moderate voltage (65 V) for a 1-mm-diameter scanning micromirror with AVC actuators. Excellent agreement between the experimental data and the theoretical simulations has been obtained.