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Flashcards in Miscellaneous Deck (27):
1

Which wet etchant has the best <111> selectivity?

KOH

2

Name three advantages of using bossed membrane?

1. More Linear (lower deflection)
2. More sensitive (stress concentration)
3. Useful for sensing low pressures

3

Figure shows four resistors on a silicon membrane. Explain why they are located where the are located where they are and in that particular orientation.

Located in the middle of the edge. Left and right (perpendicular to edge) are less sensitive compared to top and bottom (parallel to edge). Stress decreases going into the center of the membrane.

4

What are two advantages of corrugated membranes?

1. Larger deflection for the same pressure
2. More sensitive

5

Capacitive pressure sensors can be sealed under atmospheric or vacuum conditions. Name one advantage and one disadvantage for each.

Atm Adv. - easier to seal in atmosphere
Atm Dis. - Temperature and pressure dependence
Vac. Adv. - No temp dependence
Vac. Dis. - Fabrication

6

Name one advantage and disadvantage of electrostatic actuators as compared to magnetic?

scale better in micro domain
lower power consumption

7

Name two advantages and one disadvantage of capacitive sensors as compared to piezoresistive ones.

More sensitive, less temperature sensitive
Requires a nearby interface chip

8

Name two advantages and one disadvantage of using lower doping for making piezoresistive sensors.

More dynamic range and lower power consumption
Disadv. more temperature sensitive

9

Name three advantages of a full Wheatstone bridge as compared to the half bridge

More sensitive, Linear, automatic temperature compensation

10

Which piezoelectric material has the highest electromechanical coupling factor?

PZT

11

Name two advantages of solid-state diode temperature sensors as compared to thermoelectric ones

smaller, can be integrated with electronics

12

Which of the following deposition methods have the best step coverage?
a - evaporation
b - sputtering
c - PECVD
d - LPCVD

LPCVD

13

Which of the following silicon etchant performs the best when you have aluminum interconnects?

TMAH

14

Thermal oxidation is done at what temperature range?

900-1100 C

15

Why is PSG preferred to thermal oxide as the sacrificial layer in MEMS fabrication?

Faster etch rate in BHF

16

What temperature and voltage range does anodic bonding occur?

300-500C at 800 to 1200 V

17

How is silicon and glass wafer anodically bonded? What is the mobile carrier?

Negative voltage is applied to the glass and positive voltage to the silicon. Mobile carriers of Na+ in the glass cause the bonding to occur.

18

Name four reasons why PDMS is used in soft lithography

1. Cheap
2. Flexible
3. transparent
4. Insulating
5. Biocompatible
6. Gas permeable

19

Name two methods to seal cavities in surface micromachining

Oxidation, LPCVD, Reactive Sealing

20

Name two advantages of using a comb drive structure for an electrostatic actuator as compared to a parallel plate one

1. Higher range of motion
2. Linear force to voltage relationship

21

Piezeresistive coefficient in silicon
-increases with doping
-decreases with doping
-does not depend on doping
-creases up to 10^19 cm3 then decreases

Decreases with doping

22

name two advantages of thermal actuators as compared to electrostatic actuators

1. Limited by breakdown voltage
2. Large range

23

Name two disadvantages of magnetic actuators

Power dissapation
do not scale well in um domain

24

Which of the following piezoelectric materials does not require poling?

ZnO

25

Which of the following cuts of quartz has the smallest temperature sensitivity

AT

26

Which silicon wet etchant has the best p++ selectivity

EDP

27

The TI micromirror array uses X as the structural material and Y as the sacrifical layer

X=AL, Y=PR