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Page 1: Mems capacitor
Page 2: Mems capacitor

Capacitance Variation Based on Plate Area,Distance between the Plates and Different Dielectr

ic Materials.

Syed Absar Kazmi (Pakistan)

[email protected]

Department of Electrical and Computer Technology

Kulliyah of Engineering, International Islamic University of Malaysia

Page 3: Mems capacitor

Outline

1.Introduction

2.Research significance

3.Methodology adopted

4.Experimental details

5.Results & discussion

6.conclusion

Fig 1. Comsol model design

Page 4: Mems capacitor

So what exactly is MEMS ?

• Micro-Electro-Mechanical Systems (MEMS) is the

integration of mechanical elements, sensors, actuators, and

electronics on a common substrate through the utilization of

microfabrication technology or “microtechnology”.

Page 5: Mems capacitor

Capacitors

• Composed of two conductive plates separated by an insulator

(or dielectric).

• Commonly illustrated as two parallel metal plates

separated by a distance, d.

C = e A/d

where e = er eo

er is the relative dielectric constant

eo is the vacuum permittivity Fig 2.Prallel plates of capcitor

Page 6: Mems capacitor

Effect of Dimensions

• Capacitance increases with

• increasing surface area of the plates,

• decreasing spacing between plates, and

• increasing the relative dielectric constant of the insulator

between the two plates.

Page 7: Mems capacitor

MEMS Capacitor

• MEMS (Microelectromechanical system)

• Can be a variable capacitor by changing the distance

between electrodes.

• Use in sensing applications as well as in RF electronics.

Page 8: Mems capacitor

Electrical Properties of a Capacitor

• Acts like an open circuit at steady state when connected to a

d.c. voltage or current source.

• Voltage on a capacitor must be continuous

• There are no abrupt changes to the voltage, but there

may be discontinuities in the current.

• An ideal capacitor does not dissipate energy, it takes power

when storing energy and returns it when discharging.

Page 9: Mems capacitor

• Charge is stored on the plates

of the capacitor.

Equation:

Q = CV

Units:

Farad = Coulomb/Voltage

Farad is abbreviated as F

Energy Storage

Fig 3.Prallel plates of capcitor

Page 10: Mems capacitor

Significance

The research is important in the following ways,

1. The capacitance during the varaition of distance between plates

was analyzed

2. The affect on capacitance due to changing the dielectric material

was keenly examined

3. Area of the plates was enlagred and investigated the variation in

capacitance keeping height constant.

4. Overall behavier of capacitor was noticed during all variation

for the implicaiton purposes.

Page 11: Mems capacitor

Methodology Adopted

The over all methodology passed through the fo

llowing phases,

1. COMSOL multiphysic finite element analysis

software is implicated to simulate the capacitor

designed model.

2. Capacitance is analyzed by varying the

destacne between the plates and the dieelctric

materials.

3. By enlarging the plate area and keeping the

height constant capcitance was observed.

4. By getting all results formulated in graphs

and tubulized the data to be analyzed in

simplified way.

COMSOL

Changing Dielectric& Distance

Plate Area

Examined resultsAnalyzed the outcomces

Fig 4.Methodology flow

Page 12: Mems capacitor

Experimental details

Building geometry is used for MEMS capcitor model designed as per desired parameters

Material defination to set up the material properties as conductor and insulator

Meshing of build geometry is performed to achieve the prescise result.

Tabular Compilation of capcitance based on varying factors.

Comprehensive Analysis of Results

Page 13: Mems capacitor

RESULT & DISCUSSION

Capacitance variation is analayzed by two different approach using COMSOL software.The simulated results are shown in table 1 & 2 and by graphs 1 &2

i) Variation of distance between plates and dielectric material ii) Varying the plate area stimation results.

Four different material were chosen for simulation purpose to estimate the capacitance Air,SiO2,Nylon and PVC and distance between plates varied from 9um to 36um

The plate area varied from 50*50 to 230*230um and analyzed the capacitance range.

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RESULT & DISCUSSIONCapacitance variation by dielctric material (Cont....)

Distancebetween the

plates(um)Capacitance (pf) by dielectric materials

Air SiO2 Nylon PVC

10 0.01594 0.01881 0.01875 0.01831

14 0.01475 0.01838 0.01831 0.01777

18 0.01373 0.01799 0.01791 0.01724

22 0.01285 0.01761 0.01751 0.01674

25 0.01226 0.17341 0.01723 0.01639

28 0.01719 0.01707 0.01695 0.01604

31 0.01122 0.01681 0.01668 0.01572

34 0.01076 0.01656 0.01643 0.01541

36 0.01048 0.01641 0.01626 0.01521

Table (1) The Table (1) shows the capacitance analysis by variation of distacne between

plates and for four dielectric materials.By results it can be analyzed that the air as dielctric material has a drastic decay in capacitance as compared to others.Furthermore the SiO2 and Nylon dielectric material’s capacitance varies around the same range for whole variation.Howere PVC capcitance ranges in between the air and other two.

Page 15: Mems capacitor

RESULT & DISCUSSIONCapacitance analysis by varying plate area (Cont....)

plotting values Plate area(um) Capcatance(pf)

1 50*50 0.014757

2 70*70 0.028924

3 90*90 0.04781

4 110*110 0.07142

5 130*130 0.09975

6 150*150 0.013281

7 170*170 0.017059

8 190*190 0.02131

9 210*210 0.026031

10 230*230 0.031226 The second model of MEMS capacitor was designed and examined b

y the plate area variaiton while keeping hight constant at 20um.Above table is tubulized by varying the plate area from 50*50 to 230*230 and its very obvious to estimate that the capacitance enhances by increasing the plate area.

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RESULT & DISCUSSIONCapacitance graph for different dielectric material and plate distance

Figure (8) The graph illustrates capacitance vs plate distance with the four dielectric materials which are Air,SiO2,Nylon and PVC.The graph presents the four line on plotting area.The dielectric material SiO2 and Nylon varies almost in same range of capacitance whereas the PVC capacitance decreases at remarkable rate .However,the dielectric as air has a drastic decay effect then all other dielectric material.

Page 17: Mems capacitor

RESULT & DISCUSSIONCapacitance graph for range of plate area

figure (3)X-axis shows the plate area variation where as the Y-axis shows the capcita

nce with scalling of 0.01 factor to make it more simpler.By figure () it can be alnalyzed that the capacitance increasing gradualy by incresing the plate area

Page 18: Mems capacitor

Conclusion & Implications

This paper provides simplified analysis outcomes for MEMS capacitor.The

capcitance variation were keenly examined by enhancing the plate area,distance

between the plates and dielectric materials. The result demonstrates that , the

capcitance of MEMS capcitor incrememted by plate area and dielelectric strength of

material where as it decays with distance increses between plates.

This variation of capacitance is utillized in wide range of implications like,radio

astronomy, remote sensing, high speed point to point wireless local area networks,

broadband internet access, wireless HD, radar systems, weapon system, security

screening, medicine, aviation air-to-ground communications, shortwave

international and regional broadcasting, maritime sea-to-shore services, terrestrial

microwave links and satellite communication.

Page 19: Mems capacitor

References[1] Tornatta, P.A. ; Cavendish-Kinetics, San Jose, CA, USA ; Gaddi, R.”Aperture tuned

antennas for 3G 4G applications using MEMS digital variable capacitor” Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International

[2]

[3] www.kaust.edu.sa/isl/tools/rf-mems-tutorial [4] www.citycollegiate.com/capacitorXIIa.htm [5] Qizheng Gu*, and Javier R. De Luis Wispry “RF MEMS Tunable Capacitor Applications in Mobile Phones “ Inc., 20 Fairbanks, Suite 190 - 198 [6] www.learningaboutelectronics.com [7] Zhiping Feng, Wenge Zhang, Bingzhi Su, Kevin F. Harsh, K. C. Gupta, V. Bright, and Y. C. Lee ,C AMPmode “Design and Modeling of RF MEMS Tunable Capacitors Using Electro-thermal Actuators “ [8] A. M. Elshurafa and K. N. Salama P. H. Ho

“Modeling and Fabrication of an RF MEMS Variable Capacitor with a Fractal Geometry” [9] DESIGN AND CHARACTERIZATION OF

MEMS VARACTOR [10] Masayuki Miyazaki, Hidetoshi Tanaka, Goichi Ono, Tomohiro Nagano*, Norio Ohkubo,

Takayuki Kawahara, and Kazuo Yano “Electric-Energy Generation Using Variable-Capacitive LSI: Resonator for Power-Free “

[11] Charles L. Goldsmith, Andrew Malczewski, Zhimin J. Yao, Shea Chen, John Ehmke,David H. Hinzel

“RF MEMs Variable Capacitors for Tunable Filters”[12] Aleksander

“Micromachined Electro-Mechanically TunableCapacitors and Their Applications to RF IC’s”Dec, Member, IEEE, and Ken Suyama, Senior Member, IEEE

Page 20: Mems capacitor

Thank you