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Examples of SiC Sensor R&D Activities

Mehran Mehregany and Srihari Rajgopal

NATO RTO, Granada, Spain, October 6, 2005

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Current SiC Sensor Device Research

Pressure sensors• On-demand production by Kulite• R&D by FLX Micro, STMicroelectronics, Sienna Tech.• Various govt. and academic (NASA, Case, TU Berlin, TU

Delft)Accelerometer

• Various academic (Case, NASA, TU Delft)Gas sensors

• Research by AppliedSensor (S) for automotive exhaust gas and various academic

• Availability >> 5 yearsUV sensors (market < $500K)

• Two devices (sglux, IFW) available, based on Cree chips• Small area limits applications

Radiation sensors• Prototype by Westinghouse (Siemens)

Gas sensor from Boston Microelectronics

UV sensor from IFW

Pressure sensor from KuliteSource: www.wtc-consult.de September

12, 2005

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Example: Micromachined Fuel Atomizers Achieve precise geometries through micromachining Reduce cost through batch fabrication

Si Fuel Atomizers

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Point of highest wear occursat the edge of the exit orifice.The rest of the swirl chamberfloor is largely unaffected.

SEM photo of edge after erosion

Si Fuel Atomizers Fail

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Fabricate a mold by DRIE of a Si wafer Fill with SiC, polish and etch the Si

SiC Fuel Atomizers

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Before After

SiC Fuel Atomizers Pass

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Pressure Sensor – Bulk micromachining

Kulite/NASA example:

– Suspended membrane with piezoresistive elements

– Anisotropic reactive ion etch of 6H-SiC substrate

Source: Leadless sensor packaging for high temperature applicationsMasheeb, F.; et al.,MEMS, 2002

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Accelerometer – Bulk micromachining

NASA example:

– Suspended membrane with piezoresistive elements

– Anisotropic reactive ion etch of 6H-SiC substrate

Source: Ken Bradley 48th Annual NDIA Fuze Conferece, NC April 28, 2004

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Accelerometer – Test Results

Source: Ken Bradley 48th Annual NDIA Fuze Conferece, NC April 28, 2004

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Gas Sensors

MISiCFET (MI – metal insuator

•Gas molecules or reaction species diffuse to the metal-insulator interface and form a polarized layer

•This acts as an applied potential to the gate region

•Variations in the composition of the gas shift the sensor voltage to a higher or lower value

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Packaging

• Thermal conductivity• Minimize thermal resistance in packaging components

• Thermomechanical compatibility• Minimize difference in coefficient of thermal expansion between

components during assembly and operation• Thermal shock resistance

• Ability to withstand sudden thermal excursions during service• Chemical compatibility

• Inhibit electromigration in conductors and metallization reaction with the SiC semiconductor

• Hermiticity• Hermetic seal

• Simplicity, size and weight• Preferably light-weight with small form factor

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Example – Leadless Packaging of Pressure Sensor

Source: Leadless sensor packaging for high temperature applicationsMasheeb, F.; et al.,MEMS, 2002