Berkeley Sensor Actuator Center MICROROBOTS Richard Yeh Colby

Berkeley Sensor & Actuator Center MICRO-ROBOTS Richard Yeh, Colby Bellew, Seth Hollar, Anita Flynn, … • • Objectives: To create a class of articulated autonomous microrobots with a volume of less than 1 cm 3. Start with simple 2 degree of freedom robot

Berkeley Sensor & Actuator Center Goal To make silicon walk. Need: • Legs and actuators for mobility • Controller for Legs • Power Source

Berkeley Sensor & Actuator Center Smart Dust

Berkeley Sensor & Actuator Center Moore’s Law, take 2 • Nanochips on a dime (Prof. Steve Smith, EECS)

Berkeley Sensor & Actuator Center Micro Mote - Second Attempt

Berkeley Sensor & Actuator Center ~8 mm 3 laser scanner Two 4 -bit mechanical DACs control mirror scan angles. ~6 degrees azimuth, 3 elevation

Berkeley Sensor & Actuator Center ½ of first real Dust attempt Warneke, Leibowitz, Scott, Boser Power input ADC FSM Sensor input Optical RX

Berkeley Sensor & Actuator Center Dust Mock-up

Berkeley Sensor & Actuator Center Dust Delivery • Silicon maple seeds, dandelions 1 mm^3 Solar power, Gossamer wings

Berkeley Sensor & Actuator Center Multi-Chip MEMS Solar cells MUMPs CMOS SOI motors

Berkeley Sensor & Actuator Center Kinematics Sprawled Posture Two co-planar axes of rotation q 1 q 2

Berkeley Sensor & Actuator Center Alternating Tripod Gait f 1 f 2 motion Step size

Berkeley Sensor & Actuator Center Creating a Rigid Link

Berkeley Sensor & Actuator Center First Attempts

Berkeley Sensor & Actuator Center Snaplocks are Key

Berkeley Sensor & Actuator Center Buckling Test glass box HTB rotated by 90 o test chip Maximum Load: 8. 7 gm-10. 2 gm (100 m. N) Pcr ~ 25 m. N per link (26 m. N ideal, 1 m. N flat) 1 cm 2 chip: 0. 1 gm (1. 2 m. N)

Berkeley Sensor & Actuator Center 1 st Link Mechanical Coupling Slider Crank h r D 1 translation q to D = 100 mm, q = 15 o rotation

Berkeley Sensor & Actuator Center Slider Friction Test Device connecting-rod force gauge lever arm shuttle

Berkeley Sensor & Actuator Center Force Gauge Ks ~ 1 u. N/mm

Berkeley Sensor & Actuator Center Unloaded Friction Measurement

Berkeley Sensor & Actuator Center Friction Measurement with Load aluminum foil q Silicon die 2. 5 mm x 20 mm -> ~ 7 m N Half of load supported off-chip

Berkeley Sensor & Actuator Center Friction Measurement with Load

Berkeley Sensor & Actuator Center 2 nd Link Mechanical Coupling Slider Crank + Five Bar Linkage D R 6 R 3 R 2 D 2 R 6 q 3 R 1 R 5 R 4 q 1 D = f(D 2, R 1, R 2, R 3, R 4, R 5, R 6, q 1, q 2, q 3) q 2

Berkeley Sensor & Actuator Center Actuating the Legs 1 st Link Motor 2 nd Link Motor

Berkeley Sensor & Actuator Center Close-Up of MC

Berkeley Sensor & Actuator Center Mechanical Coupling-- 2 nd Link 1 st link

Berkeley Sensor & Actuator Center 2 DOF leg designs Thick SCS: 20 -50 um Low SCS: 4 -10 Top layer (SCS or poly): 2 -5 Thin-substrate: 50 -100 Substrate: 300 -500 50 -100 300 -500 q 1 q 2

Berkeley Sensor & Actuator Center 2 DOF leg designs q 1 q 2

Berkeley Sensor & Actuator Center MICRO-ROBOTS – THREE PROCESSES • CMOS Process • • • National’s 0. 25 micron 5 metal layer process High Voltage Electronics and Solar Cell process • Fabricated in-house • Demonstrated Solar Cells ~ 30 Volts Mechanical Linkages and Actuators Process – Glass Reflow Process

Berkeley Sensor & Actuator Center Proposed Integration Method Thinned Solar Cell/High Voltage Chip Thinned CMOS Chip Inchworm Motors Leg Solar Cells/ High Voltage Assembly CMOS Legs and Motors Wire Bonds Substrate

Berkeley Sensor & Actuator Center Modeling of Mechanical Bug – Anita. Motor Flynn and Linkages Chip Solar Cells, High Voltage CMOS Chip

Berkeley Sensor & Actuator Center CMOS Process • Digital Control Logic • Low Power Oscillator • Voltage Converters … • NS 0. 25 micron 5 metal layer process • Dimensions: 1. 4 mm x. 25 mm • Total Power Dissipation: 6 µW, 50 n. W

Berkeley Sensor & Actuator Center Digital Controller • Controls 2 forward only inch worm actuators 64 steps each – – 1) Motor A 2) Motor B 3) Motor A 4) Motor B • Used Silicon Ensemble for autorouting (xlite_core library) • Clock Input, 8 output lines (4 per motor)

Berkeley Sensor & Actuator Center Oscillator • Current Starved Ring Oscillators – 2 flavors • Initial designed by Brett Warneke ~ 3 MHz, 6 µA @ 1 Volt • Second altered for low power: ~7 KHz, 25 n. A @ 1 volt

Berkeley Sensor & Actuator Center CMOS Voltage Converter • Cross coupled inverters convert 1 V up to 5. 5 V • Uses high voltage transistors in national process

Berkeley Sensor & Actuator Center Icarus Process – High Voltage Electronics and Solar Cells • Developed from Colby Bellew’s Solar Cell process • Isolation Trenches + Solar Cells + CMOS + (mechanical structures) • PMOS Transistors – Vt ~ -3. 8 Volts, 15 Volt breakdown • NMOS Transistors – Vt ~ 1. 5 Volts, 30 Volt breakdown • 8 Masks, 4 ion implants, poly gate

Berkeley Sensor & Actuator Center Fabrication Process Isolation trenches are etched through an SOI wafer and backfilled with nitride and undoped polysilicon.

Berkeley Sensor & Actuator Center Fabrication Process Solar cells and circuits are created by ion implantation, drive-in, oxidation, contact etching, aluminum sputtering and etching.

Berkeley Sensor & Actuator Center Fabrication Process Actuators are deep reactive ion etched through device layer.

Berkeley Sensor & Actuator Center “Rough” Cross section Structures CMOS N+ N+ P- Isolation Trenches – Nitride and Poly Backfill

Berkeley Sensor & Actuator Center Solar Cell Results Individual test cells with increasing area show high degree of consistency. Best estimated efficiency > 14% under solar illumination.

Berkeley Sensor & Actuator Center Solar Cell Results High voltage output has been achieved from up to 60 cells in series.

Berkeley Sensor & Actuator Center Transistor Results NMOS transistors with lengths ranging from 4 to 50 um. Capable of handling Vds of 35 V. Inverters - NMOS transistors with pull-up resistors. Capable of switching 22 V with 3. 3 V input

Berkeley Sensor & Actuator Center Integration Solar powered inverters Solar powered gap closing actuator 12 cell solar array provides Vdd for inverter. 60 cell solar cell array provides power for electrostatic actuator.

Berkeley Sensor & Actuator Center Third Generation Design • Die contains – Large area, configurable solar array – Four buffer designs with CMOS capabilities – Prewired buffer/motor systems

Berkeley Sensor & Actuator Center Icarus Buffer Pad to CMOS chip Dimensions: 1. 8 mm x 1. 0 mm Power Consumption (estimated): < 1 30 Volt Solar Cell Arrays High Voltage Converters CMOS Solar Cell Array (1 Volt) Pad to Inchworm Motors

Berkeley Sensor & Actuator Center High Voltage Converter

Berkeley Sensor & Actuator Center Icarus Schedule • NMOS transistors have significant leakage • Leakage dependent on length of transistor but not the width

Berkeley Sensor & Actuator Center Motors and Linkages Process • Richard Yeh’s Inchworm Motors – Electrostatically Driven Motors – High Efficiency – Large force (~100 u. N), – Large displacement (~100 um) – 23 Million cycles without stiction • Glass reflow process – Planarize 20+ microns of

Berkeley Sensor & Actuator Center Glass Reflow • IP 900 VWG from Ferro Corporation • Si. O 2 (50%), Pb. O (30%), B 2 O 3 (12%), Al 2 O 3 (8%) • TEC 37 x 10 -7/C • Softening Point 771 C • Transition Point 520 C

Berkeley Sensor & Actuator Center Thick Glass Film Technology • • • Planarization using glass reflow Used as sacrificial layer Additional poly-Si layers can be added after planarization Poly Si LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Process Flow SOI Wafer Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Pattern SOI Wafer DRIE - STS Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Spin on glass Alpha Terpineol + Glass Frit Glass Slurry Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Organic Burnout 510 C for 60 minutes in air Glass Frit Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Glass Firing 890 C for 30 minutes Reflowed glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center CMP down to Si-Glass Interface Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center LTO 1 Deposition and Patterning LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Poly 1 Dep and Patterning Poly Si LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center LTO 2 Dep and Patterning Poly Si LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Poly 2 Dep and Patterning Poly Si LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Backside Etch Poly Si LTO Reflowed Glass Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center Release HCL-HF-H 2 O Timed Etch Poly Si Crys. Si Oxide Substrate

Berkeley Sensor & Actuator Center 10 microns

Berkeley Sensor & Actuator Center Preliminary Results 1 ATM Firing Bubbles Vacuum Firing

Berkeley Sensor & Actuator Center MUMPs Inchworm Motors guides shoes Shoe Actuators Shuttle Gap Stop Large Force Large Structures Residual Stress Stiction

Berkeley Sensor & Actuator Center Single-Mask SOI Motors Shuttle Displacement: 48 mm Cycles: 12 Voltage: 6 V (zero load)

Berkeley Sensor & Actuator Center Legs Linkages Motor 7. 6 mm CMOS Motor Solar Cells Current Layout for Motor and Legs

Berkeley Sensor & Actuator Center Thrust and Power from Solid Propellant Microrockets William Lindsay, Dana Teasdale, Veljko Milanovic, Kristofer Pister, and Carlos Fernandez-Pello Berkeley Sensor and Actuator Center University of California Berkeley

Berkeley Sensor & Actuator Center Combustion – Teasdale, Lindsey • Solid rocket propellant • 7 seconds thrust, Isp=15 s • ~1 m. J out

Berkeley Sensor & Actuator Center Altitude vs. Average Thrust Assuming pressure drag, constant total impulse

Berkeley Sensor & Actuator Center Next Generation Design Increase thrust and decrease the mass, while controlling thermal losses

Berkeley Sensor & Actuator Center Thrust Measurements vs. Theory Predicted altitude: 50 m

Berkeley Sensor & Actuator Center Rocket in Action

Berkeley Sensor & Actuator Center ROCKETBOY THANKS YOU! (Bill Lindsay)