Micro-electromechanical varactor with enhanced tuning range

Abstract

A three-dimensional microelectromechanical (MEM) varactor is described in which a movable beam (50) and a fixed electrode (51) are respectively fabricated on separate substrates coupled to each other. The movable beam with comb drive electrodes is fabricated on the "chip side" and the fixed bottom electrode is fabricated on the "carrier side" of a separate substrate. When the device is fabricated on both surfaces of the substrate, the chip side device is diced and "flipped", aligned and attached to a "carrier" substrate to form the final device. Comb drive (fin) electrodes are used for excitation and movement of the electrodes provides a change in capacitance. Due to the introduction of constant driving force, a large capacitance tuning range can be obtained. The three-dimensional aspect of the device facilitates a large surface area. Low drive voltages may be used when providing high aspect ratio features. During manufacture, the MEM device is fully encapsulated without additional device packaging. In addition, since alignment and bonding are done at the wafer level (wafer-level MEMS packaging), improved device yields can be obtained at low cost.

Description

technical field [0001] The present invention relates generally to microelectromechanical (MEM) switches and methods of fabricating such structures, and more particularly to the use of three-dimensional comb-like drive electrodes (fins) by chip bonding to a carrier substrate. )) of the MEM variable capacitor. Background technique [0002] Variable capacitors or varactors are an essential part of high frequency and radio frequency (RF) circuits. MEM variable capacitors have attracted considerable attention over the past few years due to their excellent electrical characteristics. For applications in aerospace, consumer electronics, and communication systems, variable capacitors using MEM technology can be easily implemented with standard semiconductor devices. [0003] Many researchers have attempted to improve the tuning range of MEMS variable capacitors because the maximum capacitive tuning range obtained by using the parallel-plate electrode method is limited. This is ca...

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Problems solved by technology

Also, most prior art MEMS devices need to be packaged separately, creating some process issues that need to be addressed, at least for MEMS devices with moving parts

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