GaN Electrochemical Probes and MEMS on Silicon Ulrich Heinle, Peter Benkart, Ingo Daumiller, Mike Kunze, Ertugrul Sönmez
Outline Introduction Electrochemical sensors GaN-on-Silicon MEMS High temperature logic circuits Summary
Start-Up 2002 Foundation (spin-off from Ulm University) Seed Investment (KfW) 1st customers 2004 2-inch production capacity 2005 1st financing (MAZ, TechnoStart, KfW) 2006 4-inch production capacity 2007 Life-Time Test (Temperature & Humidity) First prototype of 1000V power switch and high current diode First prototype of 400 C operational ICs 2008 2nd financing independent 3rd party ISO certification 1st product launch
Added Value Customer MicroGaN GmbH Device/IC Raw Material Epitaxy Supply Application Module Properties adjustable to customer needs Standard - Device/IC Market
Act or-ic Sensor-IC MIC M a r k e t Se gm e n t De vice / IC Pr od uct / Applica t ion HP-IC High Power HFET Recov ery Diode High Power IC Surge Prot ect ion Overv olt age Prot ect ion PFC, Convert er, Inv ert er RF-IC High Frequency IC Foundry Service > 5GHz HT-IC HT-Cont rol Circuit s HT-Mult iplexer, HT-Clock m ech. & surface Sensor Gas Sensor Pressure Sensor Exhaust Sensor HT-Pressure Sensor HT-Liquid Chem. Sensor Act or RF Swit ch RF Varact or SDR, Base St at ion Im pedance Mat ching Filt er Swit ching
GaN-on-Si Technology Substrate Application Advantage Disadvantage Silicon Electronics Sensors Actors low cost large scale backside processing easy assembly losses (RF) Sapphire Optoelectronics Electronics Low cost Insulating heat conductivity no backside processing SiC Optoelectronics Electronics Heat conductivity expensive complex backside processing
MicroGaN Electronics Power Switch Power Diode
GaN Power Technology - MMIC High-Q Diode Optical gate diode Minimized parasitic series resistance Diode configurable Metal Resistor Resistivity: 50 Ω Sheet resistance configurable MIM Capacitor 1fF/µm² (Vmax: 40V) Configurable to higher Vmax
A l G a N /G a N B a s e d S e n s o r s ph sensors (ion-sensitive field effective transistors) fluid detection application areas: food and life science industries Gas sensors application areas: gas monitoring systems, combustion systems
A l G a N /G a N b a s e d IS F E T s ISFET layout Ohm GaN Cap Ohm AlGaN 2DEG GaxOy oxide at the surface H+ - sensitivity GaN-Buffer Native and thermal Ga oxides chemically not stable Si-Substrate common cleaning procedures not possible!
A l G a N /G a N b a s e d I S F E T s modified ISFET layout Oxide Ohm GaN Cap Ohm AlGaN 2DEG GaN-Buffer deposition of dielectrics chemical stability adjustment of sensitivity towards different media Si-Substrate
M e a su re m e n t se tu p VGS = V VDS = potential between a reference electrode (saturated calomel electrode) and the sensor is varied current between sensor and Pt electrode is measured SCE Pt elektrode Elektrolyte
C l e a n -i n -p l a c e t e s t s IV characteristics V D S= 1 V no drift sensitivity 59 mv/ph high transconductance chemically stable dielectrics! CIP: 30 cycles 5min HNO3 & 15 min NaOH @ 60 C
C l e a n -i n -p l a c e t e s t s nitric acid soak 135 min offset between initial measurement and CIP test measurements negligible drift between CIP tests
C l e a n -i n -p l a c e t e s t s caustic soda soak 450 min Reduced offset compared to nitric acid reason not clear diffusion?
GaN-on-Si Gas Sensors Catalytically active Pt layer! Predestinated for use in harsh environments: corrosive ambients elevated temperatures
H2 sensitivity wide thermal operation range detectable H2 concentration spanning from 5 ppm to 2600 ppm
Multi-gas measurement Operation for > 50 h @ 500 C!
GaN-on-Si based MEMS Piezo-driven mechanical systems: modulation of the 2DEG by mechanical stress simple and cost effective backside processing
Top view Mechanical Sensors 8 7 Deflection Beam 2mm (double clamped) 300 C 6 200 C I / I0 (%) 5 Side view GaN 4 3 RT Silicon 2 1 High Signal Ratio 0 Operation @ -1 0 5 deflection (µm) 10 High Temperatures
RF-MEMS Switches and Varactors applications: Reconfigurable Input Matching RF - Input N-th Matching Band N 2nd Matching Band 2 Z0 Z0 RF Switch N-1 1st Matching Band 1 software defined radio impedance matching filter switching Transistor RF Switch 1 low losses low power consumption Stub N-1 Stub 1 low activation voltages
FEM Simulations specifications for materials growth deflection of 5 µm @ -8V (100 x 800 µm) force: 20 µn
GaN-on-Silicon MEMS actors Varactor Processing: standard HEMT process + topside deep GaN etch + backside processing
GaN-on-silicon MEMS switch Front view Low power consumption Low losses
Piezo-electric Actuation Up-State (-8V) Down-State (2V) maximum deflection: 5.6 µm extremely low actuation voltage compared to electrostatic actors movie: rectangular movie: sawtooth movie: resonance
Functional Test input signal: sawtooth (30 mhz; -8V to 2V) input signal: sawtooth (30 mhz; -4V to 2V) 315 320 capacitance (ff) capacitance (ff) 305 310 300 290 295 285 275 280 20 40 60 time (s) 80 100 20 40 60 time (s) 1st evaluation: capacitance shift of 40 ff 80 100
Reviesed Varaktor Layout
High Temperature Logic Circuits Combine sensors / actors for harsh environments Add functionality to sensor / actor systems
Buffered FET Logic Buffered FET Logic CMOS
Schematic Layout
Measurement 2/1 Multiplexer f = 1 khz 1V S0-3 V e0 e1 S0-3 (0 ) -3 (0 ) -3 (0 ) -3 (0 ) 1 (1 ) 1 (1 ) 1 (1 ) 1 (1 ) -3 (0 ) -3 (0 ) 1 (1 ) 1 (1 ) -3 (0 ) -3 (0 ) 1 (1 ) 1 (1 ) 0 1 0 1-3 (0 ) 1 (1 ) 0 1 a 0 0 0 1 1 (1 ) -3 (0 ) 1 1 1V a -3 V Revised layout fully functional at 400 C! T=250 C
Summary Advantages of GaN-on-Silicon for sensor / actor applications: Capable of high temperature operation Chemical stability Backside processing Low cost Very sensitive and chemically stable ph sensors Gas sensors with a wide thermal operation range and a high sensitivity towards different gases Pressure sensors for harsh environments Piezo-driven RF-MEMS (Varactor) High temperature logic circuits
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