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 MEMS 07’ p 143~146

2Outline

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

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

5 A Brief History (1) [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 vertical pistoning 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. Veljko Milanovic´, Member, IEEE Year Publish Contribution

6 [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 Veljko Milanovic´, Member, IEEE A Brief History (2) Year Publish Contribution

7 [1] Basic Manufacture Process 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 releases large areas for out-of plane motion and rotation of micro mirrors. up and down-actuating comb drives Deep reactive ion etch (DRIE) The biggest obstacle in SOI-MEMS mirrors is the inherent lack of out-of-plane motion.,[2001] The biggest obstacle in SOI-MEMS mirrors is the inherent lack of out-of-plane motion.,[2001] Three -level Vertical Comb Three -level Vertical Comb

8 Single axis rotation out-of-wafer-plane degrees of freedom (DoF). providing 1DoF (or single-axis) rotation Laterally actuated,2001 Vertical actuated,2003 Problem: radius of curvature, dynamic deflection, Bucking Problem: radius of curvature, dynamic deflection, Bucking up-actuating comb drives down-actuating comb drives up-actuating comb drives down-actuating comb drives high aspect ratio Rotor & Stator 2 x 2=4 Types Rotor & Stator 2 x 2=4 Types 50V  10 0 angle

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

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

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

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

13 SummarySummary 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

15Referance(1) [1] V. Milanović, L. Doherty, D. Teasdale, C. Zhang, V. Nguyen, M. Last, and K.Pister, "Deep Reactive Ion"Deep Reactive Ion Etching for Lateral Field Emission Devices,"Etching for Lateral Field Emission Devices," IEEE Electron Device Letters, vol. 21, no. 5, May [2] V. Milanović, M. Maharbiz, and K. Pister, "Batch Transfer Integration of RF Microrelays," IEEE Microwave"Batch Transfer Integration of RF Microrelays," and Guided Wave Letters, vol. 10, no. 8, pp , Aug [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 , Jan Micromachining Technology for Lateral Field Emission Devices," [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 , Feb "Laterally Actuated Torsional Micromirrors for Large Static Deflection," [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 "High Aspect Ratio Silicon Micromirrors with Large Static Rotation and Piston Actuation," [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"Gimbal-less Monolithic Silicon Actuators For Tip-Tilt-Piston Micromirror Applications," [7 ]V. Milanović, "Multilevel-Beam SOI-MEMS Fabrication and Applications,“ IEEE/ASME Journal of Microelectromechanical Systems, vol. 13, no. 1, pp , Feb "Multilevel-Beam SOI-MEMS Fabrication and Applications,“ [8 ]V. Milanović, M. Last, K.S.J. Pister, "Torsional Micromirrors with Lateral Actuators,” Trasducers'01 - Eurosensors XV conference, Muenchen, Germany, Jun "Torsional Micromirrors with Lateral Actuators, [9 ]V. Milanović, M. Last, K.S.J. Pister, "Monolithic Silicon Micromirrors with Large Scanning Angle,” Optical MEMS 2001, Okinawa, Japan, Sep "Monolithic Silicon Micromirrors with Large Scanning Angle, [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 pp “Multilevel-Beam SOI-MEMS for Optical Applications,”

16 [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 “A Simple Process for Lateral Single Crystal Silicon Nanowires,” [12]V. Milanović, S. Kwon, L. P. Lee, “Monolithic Vertical Combdrive Actuators for Adaptive Optics,” IEEE/LEOS Optical MEMS 2002, Lugano, Switzerland, Aug “Monolithic Vertical Combdrive Actuators for Adaptive Optics,” [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 , Jan “Monolithic High Aspect Ratio Two-axis Optical Scanner in SOI,” [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, “Tip-Tilt-Piston Actuators for High Fill-Factor Micromirror Arrays," [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, [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.“Fully-Functional Tip-Tilt-Piston Micromirror Array," [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.“Highly Adaptable MEMS-based Display with Wide Projection Angle," [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.“Improved Control of the Vertical Axis Scan for MEMS Projection Displays,"Referance(2)

17 Thank you for your attention!

18 MEMS Dewvices Fish eye wide-angle lens optical scan angle 128 oAppendix

19Appendix Adriatic Research Institute ARI Services : 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. XeF 2 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 IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 10, NO. 3, MAY/JUNE 2004 The transformers allow larger static rotations of the micromirror Transformer rotations