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Method for wide tuning range MEMS varactors

IP.com Disclosure Number: IPCOM000007976D
Publication Date: 2002-May-09
Document File: 6 page(s) / 84K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for wide tuning range micro electro-mechanical systems (MEMS) varactors. Benefits include improved performance.

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Method for wide tuning range MEMS varactors

Disclosed is a method for wide tuning range micro electro-mechanical systems (MEMS) varactors. Benefits include improved performance.

Background

              A parallel-plate MEMS varactor is a MEMS capacitor for which the capacitance can be changed by moving its plates/electrodes closer together using electrostatic forces via bias voltage. This bias voltage is a function of the plates/electrodes dimensions and gap. In general, if the plates/electrodes of the varactor are moved toward each other closer than 2/3 of its zero-bias gap, the plates/electrodes collapse and stick together. The tuning range for the parallel plate MEMS varactor is less than or about 1/3 of its zero-bias gap.

General description

              The disclosed method is a design and process to fabricate MEMS varactors with a tuning range of more than 1/3 of its zero-bias gap. Bumps/stops with height of about 1/3 of the zero-bias gap are placed between the plates/electrodes of the varactor at appropriate positions. As bias voltage increases, the plates/electrodes move toward one another and rest on the bumps/stops. Effectively, the bumps/stops become boundaries of the varactor, which in turn, enable greater applied bias voltage to pull the plates/electrodes even closer together without the stiction problem.

Advantages

      The disclosed method provides advantages including:

§         Improved performance due to an expanded tuning range of more than 1/3 of its zero-bias gap

Detailed description

              The disclosed method is a design and process to make MEMS varactors with a tuning range of more than 1/3 of its zero-bias gap.

Design concept

      A two parallel-plate capacitor resembles fixed-fixed rectangular beams. The actuation voltage and capacitance can be calculated. For example, a parallel-plate capacitor has e...