John Logan

Process for in-plane and out-of-plane single-crystal-silicon thermal microactuators

Abstract A process to manufacture single-crystal thermal actuators using silicon fusion bonding and electrochemical etch stop is presented. The process permits the simultaneous creation of in-plane and out-of-plane thermal actuators together with levers suitable for both directions of actuation. A final dry-release step is used, permitting the manufacture of MOS or bipolar devices in conjunction with actuators. Out-of-plane actuation of vertically levered devices has been demonstrated. The −3 dB response frequency of out-of-plane actuators is approximately 1000 Hz in air. Novel levered in-plane devices which achieve deflections of up to 200 μm have been fabricated. An estimate of the upper bound of thermal actuator efficiency is presented.

Silicon fusion bonding and deep reactive ion etching: a new technology for microstructures

Abstract New developments in deep reactive ion etching (DRIE) technology, when combined with silicon fusion bonding (SFB), make it possible, for the first time, to span nearly the entire range of microstructure thicknesses between surface and bulk micromachining, using only single-crystal silicon. The combination of these two powerful micromachining tools forms a versatile new technology for the fabrication of micromechanical devices. The two techniques are described and a process technology is presented. Some of the experimental structures and devices that have been demonstrated using this new process technology are discussed.

Fabrication of SOI wafers with buried cavities using silicon fusion bonding and electrochemical etchback

Abstract This paper describes a new technique for batch fabrication of silicon-on-insulator (SOI) wafers for microelectromechanical systems (MEMS) applications by silicon wafer bonding techniques. The process permits the inclusion of buried cavities in the SOI wafers, providing a useful tool for sensor and actuator fabrication using the resulting wafers. A low-cost electrochemical etchback step is used to define accurately the thickness of the remaining single-crystal material even though the two wafers are bonded with an intermediate insulating oxide layer. The results presented include guidelines for backside contact definition which maximize the useful silicon area as a function of doping level. The final single-crystal silicon thickness is uniform to within 0.05 μm (standard deviation) and does not require any costly high-accuracy polishing steps.