mems sensors for harsh environment

Mems Sensors For Harsh Environment

ARUN K M10MBE0003

Radation meter

Radiation sources in our Environment

• Watch and clock faces (radium dial)• Gas lamp mantles(thorium oxide)• Pink glass and jewelry polishing compound• Smoke detectors• Nuclear power reactor

losses(JAPAN!!!)• Airplane flights• Radon gas• Gemstones

Ambient Conditions• High temperature

• High amount of Vibrations

• High pressure

High Temperature Sensors

• Normal Si sensors fails at >180°C• Cooling required-more weight• SiC and Group 3 nitrides-smart mems

sensor• SiC-Challenges in micromachining• G3 nitrides-piezoelectric functional

elements(upto 1500ºC)• MOEMS-better remote sensing

application

Sic- Properties• Outstanding material and electronic

properties and chemical inertness• hardness of 2480 kg/mm2

• Young’s Modulus of 700 Gpa• SiC has a larger bandgap (2.3-3.4 eV)

a higher thermal conductivity (3.2-4.9 W/cm K)

• high saturation velocity (cm/s)

Types

• Piezoresistive• Capacitive -based sensors• Pressure , force and acceleration• HT applications

MOEMS sensors• Measure

pressure,temperature,stress,displacement• Can easily incorporated in sensor arrays• Can be used for gas and liquid measurements• Highly resistant to electromagnetic

interference (EMI) and radio frequency interference (RFI)

• Eliminate the necessity of onboard electronics

Types• Fibre Optic Sensor• Moems Fabrey Perot Sensor

Fibre Optic Sensors• Robust, highly resistant to EMI and

RFI• Detect displacements on a sub-

nanometer scale• The fabrication is complicated and

expensive.• Misalignments between the sensor

and the fiber

MFPD• Do not require alignment and stabilization

techniques• a cantilever beam fabricated in low-stress LPCVD

silicon nitride forms top mirror of interferometer• silicon substrate below provides the bottom

mirror• substrate vibrates, there is a relative deflection

of the beam with espect to the substrate and hence a change in the microcavity height.

• the amplitude of the substrate motion can be calculated

Polymer Sensor• Design, Fabrication and Optimization

of Thermal Radiation Detectors Based on Thin Polymer Membranes , Claes Mattsson 2009

• a new application of SU-8 as a closed membrane in a thermal sensor.

• Calibrated with bolometer

Reference• New Trends on MEMS Sensor

Technology for Harsh Environment Applications Patricia M. Nieva

• Design, Fabrication and Optimization of Thermal Radiation Detectors Based on Thin Polymer Membranes , Claes Mattsson 2009