Highly Adaptable MEMSBased Display with Wide Projection Angle

Highly Adaptable MEMS-Based Display with Wide Projection Angle Veljko Milanović, Kenneth Castelino, Daniel T. Mc. Cormick Adriatic Research Institute 828 San Pablo Ave. , Ste. 109, Berkeley, CA 94706 MEMS 07’ p 143~146 1

Outline Ø Research Brief History Ø Deep reactive ion etch (DRIE) Ø 1 Do. F Mechanism Ø 2 Do. F Mechanism Ø 3 Do. F Mechanism ØProjecter assembly Ø Summary 2

MEMS-BASED DISPLAY Two Basic MEMS-based projection display : Reflective displays, pioneered by Texas Instrument Diffractive display, pioneered by Silicon Light Machines large deflection angles large displacement 3

Research Chart Analysis Year 2000 2001 2002 2003 2004 2005 2006 2007 DRIE Devices tunable field emission devices (FEDs). Torsional Micromirrors Lateral Actuators Sunghoon , Two-Axis [4]Single axis rotation [15] Two-Axis Scanners [7] 2 Do. F linkages to a central stage. [14] 3 Do. F With Large Static Rotation and Piston Actuation Fully-Functional (high-speed /low-power) Large rotation with contact to neighboring elements Display with Wide angle [18] Improve image quality/re-flesh rate/brightness High Temperature Operation Production Engineering 4

A Brief History (1) Year Publish Veljko Milanovic´, Member, IEEE Contribution n [1] 2000 (Journal ) DRIE Devices were fabricated on silicon-on-insulator (SOI) wafers n [2] 2000 (Journal ) Integration of optimized microelectromechanical systems (MEMS) in RF systems on substrates such as sapphire, Ga. As, and even CMOS. n [8] 2001 (Conf. ) Integration of a wide variety of SOI-MEMS sensors, actuators and micromirrors. 1 -axis mirror n [9 ] 2001 (Conf. ) The micromirror structures are laterally electrostatically actuated, torsionally suspended micromirrors with static scanning deflection of over 40° peak-to-peak optical angle. n [10] 2001 (Conf. ) Enabling additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional rotation. n [3] 2001 (Journal ) Utilize MEMS actuators to laterally adjust electrode distances. n [11] 2002 (Conf. ) Add vertical combdrives. + new beam structure which decreases lateral movement while enabling rotation. n [12] 2002 (Conf. ) +19° Providing 1 Do. F and 2 Do. F rotation of micromirrors ; static optical deflection from – 20° to n [4] 2003 (Journal ) Laterally electrostatically actuated, torsionally suspended (SOI) micromirrors with a static optical deflection angle of over 40 peak-to-peak. n [13] 2003 (conf. ) Allow larger static rotations of the micromirror from the combdrive-stroke limited rotation The static optical deflection of the x-axis up to 9. 6° and of the y-axis up to 7. 2°, are achieved for <275 Vdc ; lower-voltage operation exhibits static optical deflection about the x-axis to 5

A Brief History (2) Year Publish Veljko Milanovic´, Member, IEEE Contribution n [5] 2004 (Journal ) vertical comb drives micromachined from the back side and front side of a 50 - μm siliconon- insulator device layer. n [6] 2004 (Journal ) larger static rotations of the micromirror from the comb-drive n [7] 2004 (Journal ) high aspect ratio silicon-on-insulator microelectromechanical systems (SOI-MEMS) by enabling additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional rotation n[14] 2004 (conf. ) Each actuator can rotate bi-directionally to raise or lower its linkage, giving the stage the required (3 Do. F. ) n [15] 2004 (conf. ) Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays, (3 Do. F) n [19] 2004 (joural) Tip-tilt-piston actuators for high fill-factor micromiror arrays n [16] 2006 (conf. ) 95% - chosen such that the mirrors would have sufficient space for large rotations without making contact to neighboring elements. n [17] 2007 (conf. ) display system with a very wide projection angle of up to 120°. n [18] 2007 (conf. ) To improve image quality, reflesh rate, brightness. Horizonal axis resonant frequencies ranging from 10 k. Hz to 21. 5 k. Hz for mirror sizes ranging from 1. 2 mm to 0. 8 mm 6

Basic Manufacture Process Deep reactive ion etch (DRIE) [1] The biggest obstacle in SOI-MEMS mirrors is the nfour-mask process layers with DRIE: inherent lack of out-of-plane motion. , [2001] ntwo for front-side and two for back-side etching. Ø High layers(50 μm) Three -level ØLower layers(30 μm) Vertical Comb ØUpper layers (30 μm) ØBackside opening n releases large areas for out-of plane motion and rotation of micro mirrors. n up and down-actuating comb drives 7

Single axis rotation Laterally actuated , 2001 Problem: radius of curvature, dynamic deflection, Bucking 50 V 100 angle üproviding 1 Do. F (or single-axis) rotation üout-of-wafer-plane degrees of freedom (Do. F). ühigh aspect ratio Vertical actuated , 2003 up-actuating comb drives down-actuating comb drives Rotor & Stator 2 x 2=4 Types 8

Problem: radius of curvature bending Two axis rotation-Vertical, island x rotating Y rotating Øvertical comb drives Ø Isolation island Ø upper-comb and Lower-Comb Ø x rotating + Y rotating Type 1 - vertical combdrives , 2002 A High Aspect Ratio 2 D Gimbaled Microscanner with Large Static Rotation, 2002 9

Two axis rotation-Vertical, rotation transformer 2 generation Comb drive n single-axis+ single-axis n unidirectional rotation Rotation transformer Mechanism Type 2 - vertical combdrives , 2004 low voltage large displacement Veljko Milanović, Int. Conf. on Microelectromechanical Systems, MEMS 2004 10

3 generation( Three axis rotation) 3 Do. F tip-tilt-piston actuators Stator Rotor Linkage + Rotation transformer [19 ]D. T. Mc. Cormick, 2004 Solid State Sensor, Actuator and Microsystems Workshop 11

Micromirrors fully assembled 1. 2 mm Backside silicon micromirrors fully assembled [16] D. T. Mc. Cormick , 2006 IEEE/LEOS Optical MEMS four vertical combdrive rotators four elements being driven by the software 12

Summary A. Specification Achieved : p 3 -level selective DRIE process SOI Wafer p low-inertia mirror-apertures 1 mm x 1 mm p rotations of the micromirror from 20° of peak-to-peak optical deflection p maximum displacement of -12 μm to 12 μm p 125 μm stand-off pedestal p 15 μm thickness( metalized with a 100 nm thick layer of Al) B. The important Milestone & Contribution history 13

C. Key fabrication process presented in this work n All combfingers are fabricated isolated and independently DRIE n Vertical combdrive sets large displacement n Comb-fingers is controlled several μm of overlap n Masks for etching of comb-fingers are self-aligned by a single mask n The process requires selective, high aspect ratio multilevel etching, Etch time is very important 14

Referance(1 ) [1] V. Milanović, L. Doherty, D. Teasdale, C. Zhang, V. Nguyen, M. Last, and K. Pister, "Deep Reactive Ion Etching for Lateral Field Emission Devices, " IEEE Electron Device Letters, vol. 21, no. 5, May. 2000. [2] V. Milanović, M. Maharbiz, and K. Pister, "Batch Transfer Integration of RF Microrelays, " IEEE Microwave and Guided Wave Letters, vol. 10, no. 8, pp. 313 -315, Aug. 2000. [3] V. Milanović, L. Doherty, D. Teasdale, S. Parsa, C. Zhang, and K. Pister, "Micromachining Technology for Lateral Field Emission Devices, " IEEE Tran. On Electron Devices - special issue on vacuum electronics, vol. 48, no. 1, pp. 166 -173, Jan. 2001. [4] V. Milanović, M. Last, K. S. J. Pister, "Laterally Actuated Torsional Micromirrors for Large Static Deflection, " IEEE Photonics Technology Letters, vol. 15, no. 2, pp. 245 -247, Feb. 2003. [5] V. Milanović, S. Kwon, L. P. Lee, "High Aspect Ratio Silicon Micromirrors with Large Static Rotation and Piston Actuation, " IEEE Photonics Technology Letters, vol. 16(8) , Aug. 2004, pp. 1891 - 1893. [6 ]V. Milanović, D. T. Mc. Cormick, G. Matus, "Gimbal-less Monolithic Silicon Actuators For Tip-Tilt-Piston Micromirror Applications, " IEEE J. of Select Topics in Quantum Electronics, Volume: 10 , Issue: 3 , May-June 2004, Pages: 462 – 471 [7 ]V. Milanović, "Multilevel-Beam SOI-MEMS Fabrication and Applications, “ IEEE/ASME Journal of Microelectromechanical Systems, vol. 13, no. 1, pp. 19 -30, Feb. 2004. [8 ]V. Milanović, M. Last, K. S. J. Pister, "Torsional Micromirrors with Lateral Actuators, ” Trasducers'01 Eurosensors XV conference, Muenchen, Germany, Jun. 2001. [9 ]V. Milanović, M. Last, K. S. J. Pister, "Monolithic Silicon Micromirrors with Large Scanning Angle, ” Optical MEMS 2001, Okinawa, Japan, Sep. 2001. [10] V. Milanović, “Multilevel-Beam SOI-MEMS for Optical Applications, ” Proc. 9 th IEEE Int. Conf. on Electronics, Circuits and Systems - ICECS'02, Dubrovnik, Croatia, Sep. 2002. pp. 281 -215 15

Referance(2 ) [11] V. Milanović, L. Doherty, “A Simple Process for Lateral Single Crystal Silicon Nanowires, ” to be presented, Int. Mechanical Eng. Conf. And Exhibit IMECE'02, New Orleans, LA, Nov. 2002. [12]V. Milanović, S. Kwon, L. P. Lee, “Monolithic Vertical Combdrive Actuators for Adaptive Optics, ” IEEE/LEOS Optical MEMS 2002, Lugano, Switzerland, Aug. 2002. [13] V. Milanović, G. Matus, T. Cheng, B. Cagdaser, “Monolithic High Aspect Ratio Two-axis Optical Scanner in SOI, ” Int. Conf. on Microelectromechanical Systems, MEMS 2003, Kyoto, Japan, pp. 255 -258, Jan. 2003. [14] V. Milanović, G. Matus, D. T. Mc. Cormick, “Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays, " at the Hilton Head 2004 Solid State Sensor, Actuator and Microsystems Workshop, Hilton Head, SC, Jun. 6 -10, 2004. [15] V. Milanović, K. Castelino, “Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays, ” Solid State Sensor, Actuator and Microsystems Workshop, Hilton Head, SC, Jun. 6 -10, 2004. [16] Veljko Milanović, Kenneth Castelino, Daniel Mc. Cormick, “Fully-Functional Tip-Tilt-Piston Micromirror Array, " 2006 IEEE/LEOS Optical MEMS and Their Applications Conf. , Big Sky, Montana, Aug. 21, 2006. [17]Veljko Milanović, Kenneth Castelino, Daniel Mc. Cormick, “Highly Adaptable MEMS-based Display with Wide Projection Angle, " 2007 IEEE Int. Conf. on Microelectromechanical Systems (MEMS'07), Kobe, Japan, Jan. 25, 2007. [18] Veljko Milanović, “Improved Control of the Vertical Axis Scan for MEMS Projection Displays , " submitted to: 2007 IEEE/LEOS Optical MEMS and Their Applications Conf. , Hualien, Taiwan, Aug. 12, 2007. 16

Thank you for your attention! 17

Appendix n MEMS Dewvices n Fish eye wide-angle lens n optical scan angle 128 o 18

Appendix Adriatic Research Institute ARI Services : n Custom Microfabrication Services (1) 4” and 6” Wafers for CMOS and MEMS (2) Diffusion , Oxidatin, Depostion (3) Etching a. DRIE b. RIE c. Plasma Etching d. Xe. F 2 Etching (4) E-Gun for W, Al, Cr, Au n Consulting CMOS and MEMS with 6 years experiences n Contract Research and Development ARI Micromirror Development(MPG Fil. E) : 19

Transformer rotations The transformers allow larger static rotations of the micromirror IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 10, NO. 3, MAY/JUNE 2004 20