MEMS Basics Flashcards
Size of MEMS?
1 micron - 1milli
What is a Transducer?
A device that converts one form of energy to another
What is a sensor?
Converts a stimulus to electrical responses
What is an actuator?
Converts electrical signals to non-electrical responses
Classifications of Sensors
Thermal, Mechanical, Chemical, Electrical, Magnetic and Radiant.
Actuator Types
Electrical Motors, Pneumatic Actuators, Hydraulic Actuators, Solenoid Valves
Physical Phenomena
Electrostatics, Mechanical, Resonance, Piezoelectric/Electrostriction, Piezo-resistance, Fluidic Phenomena
What is Piezoelectric?
A mechanical deformation causes an electrical charge. All peizoelectric materials exhibit electrostriction, where the direction of the E field matters
All peizoelectric materials exhibit electrostriction, where the directio
What kind of materials are Piezoelectric?
Barium Titanate (BaTiO3)
Lead Zirconium Titanate (PZT)
PZT and BaTiO3 are ceramics
Zinc Oxide - n-type semiconductor
Gallium Nitrate
Polyvinylidene fluoride (PVDF)
What is Electrostriction and what kind of materials are included?
An applied electric field causes mechanical deformation. All non-conducting materials and dielectrics
What is piezoresistive and what kind of materials are included?
Mechanical Deformation causes a change in resistivity. Metals and Semiconductors
Scaling Laws
Van der Waals, Diffusion, Distance, Surface Tension- Electrostatic Force- Friction-Piezoelectricity-Shape Memory Alloy, Mass-Gravity-Magnetism-Torque
Interplanar Spacing
1/d=sqrt(h^2/a^2+k^2/b^2+l^2/c^2)
Resonance Frequency
omega = sqrt(k/m)
Strongest Plane
(1 1 1)
When do you get good films on a substrate
when the d spacing is the same
Define Anisotropy
When something is direction dependent, like electron movement in crystal
What plane is invulnerable to Alkali etching/Vapor ethcing
(1 1 1)
Memorize flats and wafers
Yes
What is the easiest to etch
( 2 1 1)
Hoe to find of three vectors are co planar?
(A x B) . C = 0
Properties of Silicon
Brittle, not fluorescent
What kind of material do latest transistors use?
Silcon Germanium. The germanium makes the lattice bigger to allow electrons to travel faster.
Bandgap of Silicon
1.12 eV
Lattice Parameter of Si
a = 0.54 nm
At equilibrium, what is the formula for #holes and e-
n_0*p_0 = n_i^2
Most common doping element for n-type and p-type
Phosphorus and Boron
Relationship between Band Gap curvature and
The greater the curvature, the lower the effective mass of the electron. Curvature = 1/radius. Lower r = more curvature = less electron mass = more mobility
Mobility Formula
mu = e*scattering time/effective mass
Velocity?
v = mu*E
sigma in terms of mobility?
e(nmu_n+pmu_p)
J in terms of velocity
e(nv_n+pv_p)
How does Photocurrent work and what is the total current?
If light is used to promote electrons, equal number of holes and electrons are made. I = Dark current + photocurrent
Stress?
Sigma = Force/Area
Strain?
Delta l/l
Modulus?
stresss/strain
Poisson Ratio
-Transverse Strain/Longitudinal Strain
Regions in order on a stress/strain graph
Brittle Fracture, Yeild, Elastometric or flow region, Hardening, ductile fracture
Tensile strength
stress at the maximum of the graph
Toughness
Area under the stress strain graph
Quality factor?
Energy stored/ Energy dissipated per unit cycle per radian
