PERFORMANCE OF LTCC EMBEDDED SIC GAS SENSORS.

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Maciej Sobocinski; Lida Khajavizadeh; Mike Andersson;Anita Lloyd Spetz; Jari Juuti; Heli Jantunen

Microelectronics and Material Physics Laboratories / Maciej Sobocinski 05/01/2023

SILICON CARBIDE GAS SENSORS

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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Ingemar Lundström et al. (2006)

• Emerged in 1990s• Sensitive to H2, NH3 CO and O2

• Sensing based on changes in VGS

• Operate at high temperatures• Chemically inert material• Used in:

• Combustion control• Ammonia slip control• NOx catalyst recovery• other

TRADITIONAL PACKAGING

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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Mike Andersson et al. (2013)

NASA (2013)

Mike Andersson et al. (2013)

Traditional packaging includes:• Die attachment• Wire bonding• Encapsulation through

brazing etc

Max temperature 350 °C

State of the art packing includes:• Die attachment• Thick wire bonding• Ceramic

encapsulation

Max Temperature: 500 °C

LOW TEMPERATURE CO-FIRED CERAMIC

• Cornerstone of modern electronics• Presented in the 80s of XX century• Dielectric tapes and functional thick film pastes

Benefits of LTCC Fast prototyping Parallel processing Durable, hermetic, resistant Relatively cheap

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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©IMST

©TDK-EPC

HERAEUS HERALOCK 2000

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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Ceramic powder and low melting point glass

Ceramic powder and low melting point glass

Refractory ceramic

Lautzenhiser, F., Amaya, E. & Hochheimer, T., 2004. Self-constrained low temperature glass-ceramic unfired tape for microelectronics and methodes for making and using the same. US Patent nr US 2003/0087136 A1.Rabe, T., Schiller, W., Hochheimer, T., Modes, C., & Kipka, A. (2005). Zero Shrinkage of LTCC by Self-Constrained Sintering. International Journal of Applied Ceramic Technology, 2(5), 374-382.

ONE-STEP PACKAGING

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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INTEGRATION THROUGH CO-FIRING

SiC insertion

Lamination:– 75 º C– 10 MPa pressure

Co-firing:– 865 º C– 30’ in peak T

THE EMBEDDED STRUCTURES

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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Electric via

Gate area

Electric via

Gate area

QUALITY OF INTEGRATION

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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Small cracks in the

passivationS D

G

Remains of via

connections

ELECTRICAL RESPONSE OF THE STRUCTURES

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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• Fully functional MOSFET device• Slight changes in threshold voltage and saturation current

└ Typical for SiC transistor devices exposed to high temperature

GAS SENSING 1

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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• 3 minute pulses of CO• 100 ppm to 1000 ppm• 200 °C

GAS SENSING 2

0 20 40 60 80 100 120 1402

2.2

2.4

2.6

2.8

3

As-processedLTCC packaged

Time [min]

Sens

or S

igna

l [V

]

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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• 5 minute pulses of Ammonia in 6% O2 in N2

• 25 ppm steps from 25 ppm to 175 ppm and back to 25 ppm• Operating temperature: 300 °C

GAS SENSING 3

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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0 25 50 75 100 125 150 175 2000

0.02

0.04

0.06

0.08

0.1

0.12

As-processed LTCC-packagedAs-processed LTCC-packagedAs-processed LTCC-packagedAs-processed LTCC-packaged

NH3 concentration [ppm]

Rel

ativ

e se

nsor

res

pons

e [Δ

V/V

0]

Carrier gas comp: 6% O2 in N2

Operation temp: 300 °C

SUMMARY

• One-step packaging through co-firing is feasible for SiC MOSFET gas sensors• Co-fried structures retain their electrical properties with

small changes• Gas sensing is still present and output signals are

comparable to not packaged structures

05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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05/01/2023Microelectronics and Material Physics Laboratories / Maciej Sobocinski

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THANK YOU FOR YOUR ATTENTION!