MEM Switches Dr. Lynn Fuller, Artur Nigmatulin, Andrew Estroff

Transcription

1 ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Dr. Lynn Fuller, Artur Nigmatulin, Andrew Estroff 82 Lomb Memorial Drive Rochester, NY Tel (585) Mem_App_Switches.ppt Page 1

2 ADOBE PRESENTER This PowerPoint module has been published using Adobe Presenter. Please click on the Notes tab in the left panel to read the instructors comments for each slide. Manually advance the slide by clicking on the play arrow or pressing the page down key. Page 2

3 OUTLINE Introduction Applications General Purpose Relays RF Switches Electrostatic Actuation Magnetic Actuation Patents Page 3

4 F = k y Analogy: I = G V k is like conductance (G) I is Force, V is potential Cantilever: Ymax = F L 3 /3EI b L h SPRINGS F Z where k is the spring constant and y is the displacement Ymax w F = k y F = (3E(bh 3 /12)/ L 3 ) y k Area of plate, A = W Z where Rochester E Institute = Youngs of Technology Modulus and I = bh 3 /12, moment of inertia Page 4

5 CAPACITIVE ELECTROSTATIC FORCE Energy stored in a parallel plate capacitor W with area A and space between plates of d W = 0.5 QV = 0.5 CV 2 since Q = CV The energy stored in a capacitor can be equated to the force times distance between the plates W = Fd or F = W/d F = o r A V 2 2d 2 C = F o r A d d area A o permitivitty of free space = 8.85e-12 Farads/m r = relative permitivitty (for air r = 1) Page 5

6 ELECTROSTATIC PULL-IN VOLTAGE Example: Two parallel plates a distance d apart, one fixed, one movable with spring constant k. An applied voltage causes a force that works against the spring. At a high enough voltage (Vpull-in) the system becomes unstable and the plates come together. Vpull-in = 8 k d 3 27 o r Area If the spring is a cantilever and the plates have an area of A, the pull in voltage is found from the equation above where k is k = (3E(bh 3 /12)/ L 3 ) Page 6

7 EXAMPLE CALCULATION Page 7

8 INTRODUCTION Excellent Isolation Low Loss Low On Resistance <1 ohm High Q >10,000 Low Power Consumption (almost zero) High Currents ~1 Amp and 10 Amp Peak Small Size Low Actuation Voltage <6 Volts Reliability >10E9 Cycles Fast Operation µsec Small Packaging Page 8

9 APPLICATIONS Area System Device Communication and Radar Systems Phased Array Switching and Reconfigurable Networks Low power oscillators and amplifiers Wireless Communication (portable, base station) switches Satellite (Communication and Radar) Airborne (Communication and Radar) Wireless Satellite Airborne Switch (ground, space, airborne, missile) Switch Varactors and inductors Page 9

10 APPLICATIONS MEMS switches, based on their technical performance specifications, have all the potential for replacing the existing semiconductor switches. The main reasons for this technological shift are properties of virtually no DC power dissipation, excellent linearity and isolation / loss characteristics, as well as relatively small manufacturing costs. On the application front, MEMS switches can be used in satellite communication networks as NxN switching matrices and phase shifters for multibeam satellite communication. They are also widely used in wireless communication systems with basic switching components, such as general SPNT and transmit/receive switches. MEMS are also active components in phase shifters for satellite-based radars, missile systems and long range radars are widely used in defense systems. Page 10

11 CANTILEVER TYPE SWITCH Drain Gate Source F = o r A V 2 2d 2 Gold Gold Silicon Substrate Page 11

12 CANTILEVER TYPE SWITCH SHORTING BAR Source Gate Drain Shorting Bar Gold Poly or Glass Silicon Substrate F = Page 12 o r A V 2 2d 2

13 MEMS SWITCH SHORTING BAR Signal Line Signal Line Electrostatic actuation (V) pulls down contactor to make connection along the signal line. Signal Line Signal Line V Page 13

14 SINGLE CONTACT SWITCH Early MEMS switch using bulk processes Page 14

15 PACKAGED SWITCH Glass cap and deflection bump helps set the gap distance Page 15

16 LATERAL MOVEMENT, Hg CONTACT SWITCH Movement is parallel to the surface of the wafer (most other MEMS switches have movement perpendicular to the wafer surface) Page 16

17 ALL METAL SWITCH All metal switch Page 17

18 MAGNETIC RELAY Switch based on magnetic actuation Page 18

19 MAGNETIC LATCHING RF SWITCH Page 19

20 MAGNETIC LATCHING RF SWITCH Page 20

21 CAPACITIVELY COUPLED RF SWITCH AC switch Page 21

22 INDUCTOR ARRAY WITH THERMAL BIMORPH SWITCHES MEMS switches used in an array to change inductance to change radio channel frequencies. Page 22

23 PATENTS Page 23

24 THERMAL ACTUATION SWITCH Page 24

25 THERMAL ACTUATION SWITCH Thermally actuated MEMS relay switch with a bistable operation was developed in It is fabricated with bulk micromachined technique and thermally actuated with high contact force, stable contact, high current carrying capability and low contact resistance can be achieved. As shown in figure above. When a thermal actuator #1 is bent downward, the mechanically crossbar double beam snaps toward its second stable position, thus the movable crossbar makes contact with two contact bumps simultaneously. The switch demonstrated 2-3 A of current carrying capability and 60 mohms of on resistance. In terms of power efficiency and switching speed, thermal actuation is generally inferior to electrostatic actuation. Page 25

26 ROCKWELL SCIENCE CENTER MEMS DC SWITCH DC to 4 GHz 50 db Isolation 0.1 db loss 50V Actuation Page 26

27 ROCKWELL SCIENCE CENTER MEMS DC SWITCH In 1995, the first DC-contact MEMS series switch in the history was presented by Rockwell Science Center, CA, USA [6]. The switch was fabricated on GaAs substrate with SiO2 micro beam cantilever type arm as a movable structure, anchored on two sides of the switch and platinum-gold contact to short the open circuit, thus allowing the free propagation of the signal from input to output port. The polyimide sacrificial layer was used to form the beam structure, ensuring low temperature fabrication process (typically < 250 ). Very good performance was achieved from DC to up to 4 GHz, having an electrical isolation of 50 db and an insertion loss of 0.1 db. The actuation voltage was within the range of Volts. Page 27

28 UNIVERSITY OF MICHIGAN ALL METAL DC SWITCH DC to 5 GHz 60 db Isolation 0.5 db loss 30V Actuation Page 28

29 UNIVERSITY OF MICHIGAN ALL METAL DC SWITCH Between 1999 and 2000, professor Muldavin, Tan and Rebeiz from University of Michigan came up with a design of all-metal DCcontact MEMS series switch. The fabrication of the switch was performed on high-resistivity silicon substrate with a fixed-fixed bridge design and pull-down electrode placed exactly on both sides of the switch relatively to the signal line. As a sacrificial layer for the suspended bridge structure researches used SiO2. The contact point or dimple was etched in the sacrificial layer and filled with noble metal (Au) afterwards, in order to achieve good switch resistance. The overall performance of the switch was the best available at the time with the isolation of 60 db at 5GHz and insertion loss 0.5 db. Recorded actuation voltage for different pull-down electrode geometries stayed within Volts. Page 29

30 OMRON DC CONTACT MEMS SWITCH DC to 2 GHz 44 db Isolation 0.5 db loss 15V Actuation Page 30

31 OMRON DC CONTACT MEMS SWITCH In 1999 the Omron Company implemented electrostatic DC-contact switch on SOI substrate using single-crystal silicon membrane [9]. In general, the design resembled DC-contact switch of Rockwell Scientific Center with a few exception such that much bigger size actuation pads were integrated directly on the glass substrate. On the purpose of reduced spring constant design the membrane was partially etched away near the anchor points of the switch. Measured isolation value at 2 GHz was 44 db, while the insertion loss was less than 0.5 db. Actuation voltage for this type of switch was in the range between Volts. At that time, it was one of the most advanced metal contact switches that were first commercially packaged in a frit glass cover. Page 31

32 SAMSUNG DC CONTACT SWITCH DC to 4 GHz 35 db Isolation 0.15 db loss 5V Actuation Page 32

33 SAMSUNG DC CONTACT SWITCH DC-contact MEMS series switches was held by Samsung Company in Group of researches headed by Dr.C.M.Song proposed novel design of low voltage MEMS switch with long folded springs [1]. In fact, the design was very similar to the University of Michigan switch and comprised of a gold membrane that was formed on top of aluminum sacrificial layer. The switch had small spring constant and low actuation voltage of 5V. Measured up-state capacitance (1.5pF) resulted in an isolation of 35 db at 4 GHz and insertion loss of 0.15 db from GHz.Fig.2.5 presents micrograph of Samsung DC-contact MEMS switch. Page 33

34 MOTOROLA FOLDED SPRING DC CONTACT SWITCH DC to 50 GHz 35 db Isolation 0.5 db loss?? Actuation Page 34

35 MOTOROLA FOLDED SPRING DC CONTACT SWITCH In the same year Motorola company has issued a patent B1 on Folded Spring Based Micro Electromechanical (MEM) RF switch [10]. According to the patent description, the switch was fabricated on GaAs substrate with microplatform structure suspended on a flexure spring with metal electrodes deposited on top of it for electrostatic actuation. The design was very similar to Samsung, except the shorting bar on a microplatform facing the gap in the signal line and stopping bumpers placed beneath each of four springs, which dramatically reduced the stiction problem between the microplatform and bottom electrodes in ON state. The whole process was performed at a low temperature (< 250 ), thus having polyimide as a sacrificial layer and PECVD SiN as a structure material for the membrane. The device was functional from DC up to 50 GHz with isolation of 35 db and insertion loss of 0.5 db at 20 GHz Page 35

36 UNIVERSITY OF TRENTO LOW ACTIVATION SWITCH DC to 10 GHz 50 db Isolation 0.3 db loss?? Actuation Page 36

37 UNIVERSITY OF TRENTO LOW ACTIVATION SWITCH The most recent work on low-actuation voltage MEMS switch was done in 2005 by Kamal Rangra from University of Trento, Italy [4]. The main emphasis was made on improved low-actuation voltage design and improved RF performance. The actuation voltage optimization was done by better flexure design and beam topology. Realization of the switch was performed on high-resistivity silicon substrate. Electroplated Au bridge was obtained on Cr seed layer thus reducing the residual stress of the film. RF performance enhancement was achieved by incorporating the floating metal design for contact parts of the switch. Measured isolation of the switch was in the range between 50 db to 30 db and the insertion loss of 0.3 db for frequencies from 1-10GHz. Page 37

38 RIT MEMS SWITCH Signal Line Signal Line Electrostatic actuation (V) pulls down contactor to make connection along the signal line. Signal Line Signal Line V Page 38

39 ARTUR NIGMATULIN DESIGN Page 39

40 ARTUR NIGMATULIN DESIGN Page 40

41 ARTUR NIGMATULIN DESIGN Page 41

42 RIT MEMS SWITCH MOVING Video Page 42

43 RIT MULTIPLEXER BY ANDREW ESTROFF Senior Project Page 43

44 RIT SWITCHES BY ANDREW ESTROFF Full Paper Page 44

45 COMMERCIAL MEMS SWITCHES Page 45

46 COMMERCIAL MEMS SWITCHES Omron Co. 2SMES-01 Page 46

47 COMMERCIAL MEMS SWITCHES Page 47

48 RADANT MEMS RMSW200 SWITCH Page 48

49 COMMERCIAL MEMS SWITCHES Page 49

50 REFERENCES 1. Analog Devices Co., 2. G. Rebeiz and J.B. Muldavin, IEEE Microwave Magazine, 2(4),59,(2001) 3. Magnetic latching MEMs RF switches G. M. Rebeiz, RF MEMS Theory, Design and Technology", 1st ed. Wiley Inter-Science, Chiung-I Lee, Chih-Hsiang Ko,and Tsun-Che Huang, Design of Multi-actuation RF MEMS Switch Using CMOS Process,IEEE, Gabriel M. Rebeiz, Jeremy B. Muldavin, RF MEMS switches and Switch Circuits,IEEE Microwave Magazine, December Kamal Jit Rangra, Electrostatic Low Actuation Voltage RF MEMS Switches for Telecommunications, Ph.D thesis, Information and Communication Technologies, DIT-University of Trento, Italy, February L. E. Larson, R. H. Hackett, M. A. Melendes, and R. F. Lohr, Micromachined microwave actuator (MIMAC) technology a new tuning approach for microwave integrated circuits, IEEE Microwave and Millimeter-Wave Monolithic Circuits Symposium Digest, Boston, MA, June 1991, pp J. J. Yao and M. F. Chang, A surface micromachined miniature switch for telecommunications applications with signal frequencies from DC up to 4 GHz, Rockwell Science Center,IEEE, Gabriel M. Rebeiz, RF MEMS Switches: Status of the technology, The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, June 8-12, 2003 Page 50

51 REFERENCES 11. G. L. Tan, High Performance RF MEMS Circuits and Phase Shifters, Ph.D. thesis, University of Michigan, Ann Arbor, MI, M. Sakata, Y. Komura, T. Seki, K. Kobayashi, K. Sano, and S. Horike, Micromachined relay which utilizes single crystal silicon electrostatic actuator, 12th IEEE International Conference on Microelectromechanical Systems, pp , Xi-Qing, Folded spring based micro electromechanical MEM RF switch, United States Patent Number B1, October Dimitrios Peroulis, Electromechanical Considerations in Developing Low-Voltage RF MEMS Switches, IEEE Transactions on microwave theory and techniques, Vol.51, No. 1, January Jérémie Bouchaud, Director and Principal Analyst, MEMS & Sensors, isuppli, RF MEMS switches and varactors finally arrive, MEMS Investor Journal, October R. J. Roark and W. C. Young, Formulas for Stress and Strain, 6th edition,mcgraw-hill, New York, J. M. Gere and S. P. Timoshenko, Mechanics of Materials, 4th edition, PWS Publishing Company, Boston, V. L. Rabinov, R. J. Gupta and S. D. Senturia, The effect of release etch holes on the electromechanical behavior of MEMS structures", International Conference on Solid-State Sensors Actuators,Chicago,IL, June 1997, pp G. K. Fedder, Simulation of Microelectromechanical systems", Ph.D. thesis, Electrical Engineering and Computer Science,University of California at Berkeley,USA, Stephen D. Senturia, Rochester Institute Microsystem of TechnologyDesign", 1st ed. Boston-Dordrecht-London: Kluwer Academic Publishers, 2002 Page 51

52 HOMEWORK MEMS SWITCHES 1. Design a process to make a MEMS switch at RIT. Or 2. Find out who sells mems switches and get some information on their products including price. Or 3. Find a recent technical paper on MEMs switches. Summarize it on one page and attach a copy of the full paper. Page 52