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MEMS TECHNOLOGY

BY:

JAYA NAIK

USN:4NM11EC405

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CONTENTS1.Introduction

2.Differences between IC and MEMS

3.Basic elements of MEMS

4.Manufacturing process of MEMS technology

5.RF MEMS

6.RF MEMS switches

7.Fabrication

8.Comparision of MEMS Switches with solid state switches

9.Advantages and Disadvantages

10.Applications

11.Conclusion

12.Reference

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Introduction

• Micro-Electro-Mechanical Systems

• Miniaturized mechanical and electro mechanical elements using micro fabrication.

• Most promising Technology of 21st century.

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Block diagram of IC+MEMS fabrication

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DIFFERENCES: ICs Vs MEMS

MEMS• 3D complex structures

• Doesn’t have any basic building block

• May have moving parts

• May have interface with external media

• Functions include Biological,Chemical,Optical

• Packaging is very complex

ICs• 2D structures

• Transistor is basic building block

• No moving parts

• Totally isolated with media

• Only Electrical

• Packaging Techniques are well developed

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Basic Functional Elements of MEMS

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Manufacturing process of MEMS Technology

1.Photolithography

2.Silicon Micromachining

a)Bulk Micromachining

b)Surface Micromachining

3.Excimer Laser Micromachining

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PHOTOLITHOGRAPHY

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Surface Micromachining

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Basic techniques of Silicon micromachining

•Deposition of thin films•Wet Chemical Etching•Dry Chemical Etching

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Wet Chemical Etching

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Lift off

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Excimer Laser Micromachining

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RF MEMS

•MEMS those with RF range are RE MEMS

•Compound solid state switches have larger insertion loss(on state) and poor electrical isolation (off state)

•RF MEMS Switches provides lower insertion loss, higher isolation, zero static power consumption

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RF MEMS Switches

1.RF series contact switch2.RF shunt capacitive switch

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RF series contact Switch

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RF shunt capacitive Switch

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Limitations

•Series contact switches tend to fail in the open circuit.•Even though the bridge is collapsing and making the contact with transmission line, conductivity of contact metallization area decreases until unacceptable levels of power losses are achieved•Shunt capacitive switches often fail due to charge tapering, both at the surface and bulk states of the dielectric.

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Fabrication

Process flow

(a) Seed layer deposition (b)Dielectric layer deposition and patterning

(c) Spacer coater and patterning

(d)Transmission line electroplating

(e)Membrane deposition and patterning

(f)membrane releasing

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Comparision of MEMS switches with Solid State switches

;PPParameter RFRF MEMS MEMS

PPIN DIODE FFEFET

Voltage(mA) 20-80 3-5 3-5

Current(mA) 0 0-20 0

Power consumption(mW)

0.5-1 5-100 -0.5-0.1

switching 1-300uS 1-100ns 1-100ns

Power handling(W)

<1 <10 <10

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ADVATAGES OF MEMS

•Can reduce the weight,size,power consumption and component counts.

•Promise superior performance

•Can be built with high producibility

•New functionality

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DISADVANTAGES OF MEMS:-

•Due to their size, significant power transfer is impossible•Due to its base material cannot be loaded with large load•Design standards are not well developed•And some Reliability issues..

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Applications

•In Navigation field•Pressure sensors•Medical field•High frequency circuits•Security field

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Conclusion

•Low power consumption, high isolation and ability to integrate with other elements make MEMS switches an alternative to solid state switches.•MEMS is one of the promising technology •Proper design standards have to be build.•High performance RF MEMS switches, high voltage MOSFET and CMOS devices can be integrated on the same chip.

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References

[1] Sazzadur Choudhury, M. Ahmadi, and W.C. Miller, “Micromechanical system for System-on-Chip Connectivity”, IEEE Circuits and Systems, Page(s) 112-132 September 2002

[2] J. B. Muldavin, G. M. Rebeiz, "High Isolation RF MEMS Shunt Switches-Part 2: Design", IEEE Tran. On Microwave Theory and Techniques, Vol.6, Page(s): 253-276.

June 2000,

[3] P. Osterberg, H. Yie, X. Cai, J. White, and S. Senturia, “Self-consistent simulation and modeling of RF MEMS,“ in Proc. IEEE MEMS Conf. January 1994, Page (s)28-32.

[4] Gopinath. A and Ranklin.JB, IEEE Electronic development,” GaAs FET RF switches “, vol. 12, Page(s) 18-37, August 2003

 

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THANK YOU