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Highly Adaptable MEMS-Based Display with Wide Projection Angle

Highly Adaptable MEMS-Based Display with Wide Projection Angle Veljko Milanović, Kenneth Castelino, Daniel T. McCormick Adriatic Research Institute 828 San Pablo Ave., Ste. 109, Berkeley, CA 94706 MEMS 07’ p 143~146. Outline. Research Brief History Deep reactive ion etch (DRIE)

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Highly Adaptable MEMS-Based Display with Wide Projection Angle

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

  2. Outline • Research Brief History • Deep reactive ion etch (DRIE) • 1 DoF Mechanism • 2 DoF Mechanism • 3 DoF Mechanism • Projecter assembly • Summary

  3. MEMS-BASED DISPLAY Two Basic MEMS-based projection display : Reflectivedisplays,pioneered by Texas Instrument Diffractivedisplay,pioneered by Silicon Light Machines large deflection angles large displacement

  4. Research Chart Analysis Year DRIE Devices tunable field emission devices (FEDs). Torsional Micromirrors Lateral Actuators Sunghoon , Two-Axis [4]Single axis rotation [15] Two-Axis Scanners [7] 2 DoF linkages to a central stage. [14] 3 DoF 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

  5. A Brief History (1) Veljko Milanovic´, Member, IEEE • [1] 2000 (Journal)DRIE Devices were fabricated on silicon-on-insulator (SOI) wafers • [2] 2000 (Journal ) Integration of optimized microelectromechanical systems (MEMS) in RF systems on substrates such as sapphire, GaAs, and even CMOS. • [8] 2001 (Conf.) Integration of a wide variety of SOI-MEMS sensors, actuators and micromirrors. 1-axis mirror • [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. • [10] 2001 (Conf.) Enabling additional independent degrees of freedom of operation: both upward and downward • verticalpistoning motion as well as bi-directional rotation. • [3] 2001 (Journal ) Utilize MEMS actuators to laterally adjust electrode distances. • [11] 2002 (Conf.) Add vertical combdrives. + new beam structure which decreases lateral movement while • enabling rotation. • [12] 2002 (Conf.) Providing 1DoF and 2DoF rotation of micromirrors ; static optical deflection from –20° to +19° • [4] 2003 (Journal ) Laterally electrostatically actuated, torsionally suspended (SOI) micromirrors with a static • optical deflection angle of over 40 peak-to-peak. • [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 • 10.8° and about the y-axis to 11.7°, for <85 Vdc. Year Publish Contribution

  6. A Brief History (2) Veljko Milanovic´, Member, IEEE • [5] 2004 (Journal ) vertical comb drives micromachined from the back side and front side of a 50- μm silicon- • on- insulator device layer. • [6] 2004 (Journal ) larger static rotations of the micromirror from the comb-drive • [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 • [14] 2004 (conf.) Each actuator can rotate bi-directionally to raise or lower its linkage,giving the stage the required • (3 DoF. ) • [15] 2004 (conf.) Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays, (3 DoF) • [19] 2004 (joural) Tip-tilt-piston actuators for high fill-factor micromiror arrays • [16]2006 (conf.) 95% - chosen such that the mirrors would have sufficient space for large rotations without making • contact to neighboring elements. • [17] 2007 (conf.) display system with a very wide projection angle of up to 120°. • [18] 2007 (conf.) To improve image quality, reflesh rate, brightness . Horizonal axis resonant frequencies ranging • from 10 kHz to 21.5 kHz for mirror sizes ranging from 1.2mm to 0.8 mm Year Publish Contribution

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

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

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

  10. Two axis rotation-Vertical,rotation transformer 2 generation • Comb drive • single-axis+ single-axis • unidirectional rotation Rotation transformer Mechanism low voltage large displacement Type 2- vertical combdrives ,2004 Veljko Milanović, Int. Conf. on Microelectromechanical Systems, MEMS2004

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

  12. Micromirrors fully assembled 1.2mm Backside silicon micromirrors four vertical combdrive rotators fully assembled four elements being driven by the software [16] D. T. McCormick ,2006 IEEE/LEOS Optical MEMS

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

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

  15. 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. McCormick, 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. 9th IEEE Int. Conf. on Electronics, Circuits and Systems - ICECS'02, Dubrovnik, Croatia, Sep. 2002. pp. 281-215

  16. 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, MEMS2003, Kyoto, Japan, pp. 255-258, Jan. 2003. [14] V. Milanović, G. Matus, D. T. McCormick, “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 McCormick, “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 McCormick, “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.

  17. Thank you for your attention!

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

  19. Appendix Adriatic Research Institute • ARI Services : • Custom Microfabrication Services • (1)  4” and6” Wafersfor CMOS andMEMS • (2)  Diffusion ,Oxidatin, Depostion • (3) Etching • a. DRIE • b. RIE • c. Plasma Etching • d. XeF2 Etching • (4) E-Gun for W, Al, Cr, Au   • Consulting • CMOS and MEMS with 6 years experiences • Contract Research and Development ARI Micromirror Development(MPG FilE) :

  20. 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

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