Variable tunable range MEMS capacitor

Details Variable tunable range MEMS capacitor Variable tunable range MEMS capacitor

2000-01-26

2002-03-12

Pham, Long (Department: 2831)

Semiconductor device manufacturing: process

Voltage variable capacitance device manufacture

C333S02400C, C327S566000, C029S025420

Reexamination Certificate

active

06355534

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to microelectromechanical structure (MEMS) fabrication, and, more specifically, the present invention relates to the fabrication of a variable capacitor that is tunable over a wide range.
2. Description of Related Art
As microelectronic technology continues to experience miniaturization and, greater device flexibility, the need has arisen for variable capacitors that can have greater capability and reliability. Prior art on-chip variable capacitors are based on varactor diode technology that have a tuning range of less than about 25%. The varactor diode technology also has a low pull-in effect.
Additionally, prior art membrane capacitors have a capacitance tunable range that is limited due to the voltage exceeding the critical voltage (Vc) thereof. At Vc, the membrane collapses and the capacitor shorts out. Additionally, due to the suspension nature of the prior art capacitors, the center portion of the flexible membrane draws closer to the fixed electrode than the edge portions. This phenomenon creates a greater local capacitance at the center of the flexible membrane than at the edge portions of the flexible membrane where it is anchored.
Between capacitors, it is difficult to control capacitance change in any predictable way such as a linear or even a nonlinear functional correlation between the amount of applied direct current (DC) voltage and the resulting capacitance. Where the edge portions of the flexible membrane occupies a substantial capacitance surface area in relation to the center portion it becomes difficult to achieve an appreciable range of tunable capacitance.
What is needed is a variable capacitor that overcomes the problems in the prior art.


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Kevin F. Harsh et al., “Flip-Chip assembly For Si-Based RF MEMS”, IEEE, MEMS '99 Conference, 12th Intl. Conference, pp. 273-278, Dec., 1999.*
L. Fan, et al., Universal MEMS Platforms For Passive RF Components: Suspended Inductors And Variable Capacitors, IEEE, Micro Electro Mechanical Systems, pp. 29-33, Dec., 1998.*
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Harsh, K.F. et al., “The realization and Design Considerations of a Flip-Chip Integrated MEMS Tunable Capacitor” Proceedings of 12th Int'l Workshop on Micro Electro Mechanical Systems, MEMS, Orlando, FL Jan. 1999, vol. A80, No. 2., pp. 108-118, XP0041192096, Sensors and Actuators A (Physical Mar. 2000, Elsevier, Switzerland.
International Search Report, PCT/US02202, Jan. 22, 2001.

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