how the silicon substrate is used for mems devices

8/11/2019 How the Silicon Substrate is Used for MEMS Devices

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How the silicon substrate is used for MEMS devices.

Discuss the how ANSYS tool is used for transient and static analyses of MEMS devices.

Describe the steps involving in the MEMS process.

Explain the working and features of the MEMS accelerometer.

What is a Microsystems? Explain the working of sensors and actuators in the Microsystems.

Discuss the main building blocks of the MEMS technology



Analysis Types

• Static Analysis

• Dynamic Analysis

– Transient Analysis

–

Modal Analysis

– Harmonic Response Analysis

– etc.

• Buckling Analysis

• Structural Analysis

– Static, Transient, Modal, Harmonic, Buckling, etc.

•

Thermal Analysis

– Steady-state, Transient

• Electric Field Analysis

– Static, Transient, Modal, Harmonic etc.

–



Transient Analysis

• Inertia forces

• Damping forces

• Elastic forces

• External forces

Static Analysis

• When dynamic effects can be neglected, a problem can be solved statically.

• Dynamic effects can be neglected only when the deformation velocity and acceleration are

small.

• Two cases:

– Steady-state solution

approximation solution for a real-world problem

MEMS Accelerometer

MEMS are quietly changing the way you live, in ways that you might never imagine. The device that

senses your car has been in an accident, and fires the airbag is a MEMS device. Most new cars have over

a dozen MEMS devices, making your car safer, more energy efficient, and more environmentally friendly.

MEMS are finding their way into a variety of medical devices, and everyday consumer products. (From

MEMX http://www.memx.com/ )

MEMS Advantages

• Significantly lower manufacturing costs (semiconductor process)

• Small inertial mass

• Particularly realized in the area of:

– sensors – signal switching

FKDDCDM



Materials for MEMS

• Materials are the foundation required to develop microsensors. MEMS are made of:

• Metals

• Polymers

• Ceramic materials

• Semiconductors

• Composite materials

MEMS Process

• Same as the process steps used for making conventional electronic circuits

Fabrication Process



Fabrication Process

MEMS Building Blocks

• Major components in MEMS systems include

– Design

• Much more difficult than IC designs due to the interdisciplinary character of

MEMS

• Design includes packaging

– Packaging is one of the most challenging step both in design and

realization

• Transducers must be integrated with electronics

– Integration with ICs is another challenge for MEMS due to difficult

issues of process compatibility

–

–

–

–

–

–



– Fabrication

• Silicon technology is widely used in MEMS with new step added

– Dimensions are usually much larger than those in ICs even for nano-

transducers. To feel NANO you do not need to be in the nano-scale size!

– Other materials are included to perform required functions of

transducers

• MEMS are frequently integrated with fluidics (polymers, glass…)

– Materials

• Materials that can perform required functions (thermo, piezo-, magneto-

resististance…)

•

Interaction with fluidics (half-cell potential, corrosion…)

Microsystems

Microsystems are miniaturized (silicon or polymer) devices which perform non-electronic functions: typically sensing and actuation.

Typical microsystems have mechanical parts, like microbridges in RF switches or bending cantilevers in atomic

force microscopes (AFMs); electrical parts like piezoresistors in airbag sensors or capacitors in pressure sensors;

or thermal, optical and fluidic structures like heaters and nozzles in inkjet printer or flow sensors. In biomicrosystems

(BioMEMS) cells or microbeads are handled by fluidic streams, magnetic and electric fields, thermal gradients etc. In

chemical microsystems operations like sample pretreatment, separation and detection are built on microchips

Sensors

• Fall into two categories:

– Physical: force, acceleration, pressure, temperaure, magnetic/electric field strength

etc.

– Chemical/biological: pH, reactions, binding between molecules etc.

• Characteristics:

– Sensitivity

–

Linearity

– Responsivity (large signal-to-noise ratio SNR required)

• Johnson noise, a with noise , thermal fluctuation,

(k=Boltzmann’s constant, R=resistance, B=bandwidth), Gaussian distribution

• Shot noise (quantum fluctuation)

http://en.wikipedia.org/wiki/Microbridge



http://en.wikipedia.org/wiki/RF_switches



http://en.wikipedia.org/wiki/Cantilevers



http://en.wikipedia.org/wiki/Atomic_force_microscope




http://en.wikipedia.org/wiki/Piezoresistor



http://en.wikipedia.org/wiki/Airbag


http://en.wikipedia.org/wiki/Sensors



http://en.wikipedia.org/wiki/Inkjet_printer






http://en.wikipedia.org/wiki/BioMEMS



http://en.wikipedia.org/wiki/Microbeads



http://en.wikipedia.org/wiki/Thermal_gradients


















• 1/f noise or flicker (pink) noise,(conductance fluctuation when currents flow)

• Thermal-mechanical noise floor (mechanical motion of elements)

– SNR

– Dynamic range (highest to lowest signals)

– Bandwidth (bandpass)

– Drift (degradation and change of operational points)

– Sensor reliability (related to stability of operation independently of conditions)

– Cross talk or interference (individually tested parameters should not be affected by

other measurements/signals)

– Development cost and time (vary depending on designs and technology, simulations

are very important in shortening the time-to market)

Actuators

• Transform energy from/to the mechanical domain into/from others: electrical

(piezoelectricity, electrostatic), thermal, magnetic etc.

how the silicon substrate is used for mems devices

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