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Thin Films > Labs > Flashcards

Labs Flashcards

1
Q

How do we classify the vacuum?

A 
Pressure
Low 10^3 -1 mbar
Medium  1-10^-3 mbar
High 10^-3-10^-7 mbar
Ultra high 10^-7-10^-14
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2
Q

What are the definitions of number density, mean free path and particle flux?

A

Number density - quantity of gas per unit volume
Mean free path - average distance between collisions
Particle flux - rate at which particles hit the surface

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3
Q

How do we specify flow numerically?

A

Viscous
Transitional
Molecular

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4
Q

How many types of pumps are generally included in a vacuum system?

A

2 - primary, secondary

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5
Q

What are the methods used to measure vacuum?

A

Gauges

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6
Q

What are the vacuum gauges used to measure low, high and ultra-high vacuum?

A

low - diaphragm
high - schultz-phelps
ultra-high - hot cathode

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7
Q

How many types of thin film deposition methods are using mostly in nowadays?

A

physical
chemical
mixed

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8
Q

What are the principles of sputtering and e-beam evaporation processes?

A

Sputtering - mixed, noble-gas mixed with plasma forming gas

Ebeam - physical deposition

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9
Q

What are the differences between DC magnetron sputtering and RF sputtering?

A

DC vs AC

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10
Q

What are the main components of sputtering and e-beam evaporation systems (including pumps, gauges etc)?

A

Power source, primary, secondary pump, magnetron, sample stage, electron gun

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11
Q

What is lithography?

A

Pattern transfer

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12
Q

What types of lithography are used depending on radiation sources?

A

Photo
xray
ion beam
ebeam

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13
Q

What are the main stages of a photolithograph process?

A

Photoresist coating, alignment and exposure, development

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14
Q

Why do we need resist materials?

A

Restricts the etchant and prevents it from attacking the substrate

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15
Q

What are the main requirements for the resist material?

A

High resolution, high etch resistance, good adhesion, wider process latitude

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16
Q

What are the differences between negative and positive photoresist?

A

Negative - becomes insoluble after exposure, unexposed parts dissolve during developing
Positive - becomes soluble after exposure, exposed parts dissolve during developing

17
Q

What will effectively limit the feature size?

A

Alignment

18
Q

What is the minimum feature size which can be achieved using mercury lamp?

A

0.25 um

19
Q

Which are the main performance metrics of a patterning process?

A

Resolution - minimum feature size
Registration - how regularly patters are aligned
Throughput - number of wafers that can be exposed

20
Q

Which alignment tools are commonly used?

A

Contact printer
Proximity printer
Projection printer
Stepper

21
Q

What is the definition of etching process?

A

Permanent transfer of pattern from mask onto substrate

22
Q

What are etching methods used in thin film patterning processes?

A

Wet etching
Dry etching
Lift-off

23
Q

What are the important etching parameters?

A

Etch rate, uniformity, throughput, selectivity

24
Q

What are figures of merit of etching process?

A

Uniformity,
selectivity
anisotropy

25
Q

What is the principle of RIE process?

A

Reactive ion etching - no field in centre

26
Q

What are the advantages and disadvantages of lift-off and ion etching processes?

A

Lift-off - cheap, short, easy, low anisotropy, low adhesion, low repeatability, high selectivity
Ion etching - expensive, long, high degree of anisotropy, good adhesion, high repeatability, low selectivity

27
Q

What type of photoresist is used for lift-off and ion etching processes?

A

?

28
Q

What are major steps occur in a RIE process?

A

?

29
Q

Which main factors will affect the etching rate in the RIE process?

A

Sample distance, angle

Voltage

30
Q

What are the main components of a RIE system (including pumps, gauges etc)?

A

?

Thin Films (6 decks)

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