Micro/Nanosystems Technology · Magnetron Sputtering device (ALCATEL 450) • Power supply: – RF...

Micro/Nanosystems TechnologyWagner / Meyners 1

Micro/Nanosystems Technology

Prof. Dr. Bernhard Wagner

Dr. Dirk Meyners



Outline

• Cleanroom and vacuum technology

• Cleanroom technology

• Working in a cleanroom

• Kiel’s Nanolab

• Vacuum technology



Outline







Working in a cleanroom

Sources of contamination

form of

contamination

source resulting problem

dust humans, incoming

air, abrasion

shadowing during

lithography

molecular oil, remains of

resist

bad adhesion

ionic contact with skin,

water

electrical

interference

atomic etching electrical

interference

Wrong behavior in a cleanroom can degrade cleanliness by two classes.

Humans are the most important contamination source.

Special behavioral rules



Cleanroom clothes

one-piece coat, shoes, gloves

and cap

Kiel’s Nanolab

special hoods to provide

sterility

Pharmaceutical fabricationMedium standard

mask,

overboots



Particle emission during activities

activity emission of particles with diameter > 0.5µm

min-1

street clothes one-piece coat,

shoes, gloves,

cap, mask

sitting without

movement

0.3 x 106 0.7 x 104

moving head 0.6 x 106 1 x 104

moving body 1 x 106 3 x 104

going slowly 3 x 106 5 x 104

going fast 6 x 106 10 x 104

values according to: R. Zengerle, lecture notes, Mikrosystemtechnik, IMTEK

move slowly, do not rush



Behavioral rules:

- wear cleanroom clothes

- no cosmetics, especially no powders

- avoid skin contact to substrates, chemicals and machines (wear

gloves)

- speaking only with head turned away from substrates

- use wafer boxes for transport and storage of wafers

- do not use pencils, use special paper appropriate for cleanrooms

- do not break silicon wafers into pieces

- do not smoke immediately before entering



Outline







Kiel’s Nanolab

Filter Fan Unit

Process

equipment

Gas exhaust

additional air

gray area white area gray area


Kiel’s Nanolab

Gray Area

White Area

Transmission Electron Microscope

(TEM)

Magnetically

Shielded

Room

lab lab lab

neutralization

P white > P gray > P outside

air

lock

air

lock

(machines)


Kiel’s Nanolab

Gray Area

White Area


(TEM)

lab lab lab

neutralization

P white > P gray > P outside ΔP = 10Pa

Magnetically

Shielded

Room


Kiel’s Nanolab

The lower the particle density the higher the air exchange:

cleanroom class

(209 D)

air flow

[m3/hm2]

air exchange

[number/h]

100 000 60 20

10 000 60 – 120 20 - 40

1 000 700 – 1 100 200 - 300

100 1 600 – 1 800 500 - 600

approximate values according to: R. Zengerle, lecture notes, Mikrosystemtechnik

cleanroom area: 300 m²

technical/utility area: 600 m²

white area: class 100

gray area: class 1000

white area: ca. 150 m²

1800 m³/hm² * 150 m² = 270 000 m³

air conditioning: 20 000 m³/h

air circulation


Kiel’s Nanolab

• additional air

• temperature control: 22°C +/- 2°C

• air humidity control: 45% +/- 10%

• neutralization of sewage water

• cooling water

• central gas supply

• compressed air

• electric power

Detailed description is

part of the first lab course


Kiel’s Nanolab

Gray Area

White Area


(TEM)

2

1

3

1

15

8

9

7

6

1013

13

13

12

11

22

19

20

17

1618

14

15

2

1

4

Airlock

Wet Chemistry

1 Workbenches

2 Electroplating

3 Dicing Saw

4 Magnetron Sputtering

System 6 Inch

5 PVD-Devices

6 Rapid Thermal

Annealing (RTA)

7 Ion Beam Etching (IBE)

8 Inductively Coupled

Plasma (ICP) Etching /

Reactive Ion Etching

(RIE)

9 Plasma Enhanced

Chemical Vapour

Deposition (PECVD)

Thin Film technique 1

10 Magnetron Sputtering

System 4 Inch

11 Pulsed Laser Deposition

12 Evaporative Deposition

13 CVD-Devices

Lithography

14 Optical Microscope

15 Profilometer

16 Mask Aligner 6 Inch

17 Mask Aligner 4 Inch

18 Workbench

19 Spin Coater

20 Oven

21 Scanning Electron

Microscope (SEM) /

Focused Ion Beam

22 Ellipsometer



Wet Chemistry

• Wet Chemistry for Etching, Cleaning and Drying

– Quick dump rinse

– Fine rinse basin with conductivity measurement

– Spin dryer for single wafer

– 3 Ultrasonic bathes

– Fume hood for hydrofluoric acid (HF)

Workbenches


Wet Chemistry

Electroplating

• Electroplating

– 2 basins for electroplating

(Au and Cu)

– Bath for cleaning


Wet Chemistry

Dicing Saw

Automatic Dicing Saw DAD 3350 provided by DISCO

Specifications

• Up to 8“ substrates can be diced.

• Substrate may be made of a variety of materials

such silicon, quartz, borosilicate glass, …

• Max. cutting speed amounts 600 mm/s

• High resolution at both X-, Y-, Z-axis

• Water cooling of spindel and substrate

• Graphical user interface

A special feature:

• Our device can perform round cuts to obtain

for example a 4 inch wafer

from a 8 inch wafer.



Sputter Deposition: Von Ardenne CS 730 S

• Cluster deposition system with 3 chambers and 9 sputter sources

• 8“ and 4“ targets

• Load-lock with 10 x 6“ substrate plate magazine

• RF and DC sputtering up to 3 kW

• 6“ Substrates, radiative heating possible

• Sputter gases: Ar, N2, O2

• Magnetic bias field (100 Oe) possible

• RF etching

Current target list:

• Metals: Ag, Au, Cu, Al, Cr, Ru, Ta, Ti, Mo

• Alloys: FeCo, FeCoBSi, TbFe, NiTi, NiFe, CoFeB, FeAl,

FeB, FeHf, FePd, MnIr, TiNiCu

• Oxides, Nitrides: Al2O3, MgO, Ni3N8, ZnO2, AlN

(other oxides by reactive sputtering)



Magnetron Sputtering device (ALCATEL 450)

• Power supply:

– RF ( 600W)

– DC ( 600W)

• Final Vacuum: 1E-7mbar

• Gas: Ar 6.0 and O2

• Cathodes (3 x 100mm in Ø)

• Substrates:

– Planar

– Tubular

• Heater (up to 600°C)

• Adjustable distance between

substrate and cathode



High Vacuum Evaporating-System PLS 500

• System: Electron-beam evaporator

• Substrate: Dimension: up to 100mm

Substrate heater up to 600°C

• Film-thickness monitoring with oscillating quartz



• PECVD-Tool from Sentech (SI500-PPD)

– SiH4/NH3/NO2 based chemistry to deposite silicon, silicon

oxide, silicon nitride and oxinitrides

• Used for:

– Passivation and insulating

layers for sensors

– Highly selective hard masks

for deep etching

– Dielectric layers for capacitors

– Guiding layer in surface

accoustic waves devices

Plasma enhanced deposition



Pulsed Laser Deposition Workstation

Specifications

• 1“ substrate holder, heatable up to 1000 °C in oxygen

• Coherent Compex Pro 201 excimer Laser

• 4 x 2“ target assembly

• RHEED (reflection high energy electron diffraction)

• Film thickness homogenity over 1“ = ± 5 %

Advantages of the method:

• Stochiometric transfer from multi-element targets (eg.

YBa2Cu3O7)

• Very good thickness control through number of pulses

• Deposition of high quality thin films of different materials

and control of crystallographic structure by RHEED


Lithography

Spin Coater

• Spin Coater OPTIspin ST22P

– Substrate size up to 8“

– Chucks for 4“, 6“, 8“ and

pieces

– spin speed up to 10,000 rpm

• Hot Plate

– HMDS Adhesion promoter

(C6H19NSi2)

– Temperature up to 200°


Lithography

Mask Aligner

– Substrate size: 6“-wafer or 6“ x 6“

– Mask size 7“ x 7“ (e.g. glas wafer with Cr patterns)

– Exposure source 350W Hg lamp

– UV wavelength range 350 – 450 nm

– Resolution down to 0.4 µm

– Top/bottom side alignment

– Modes:

• Vacuum Contact

• Hard Contact

• Soft Contact

• Proximity

(gap 1 – 300µm)

• Mask Aligner Süss Microtec MA6 for UV Lithography

UV

lamp

mask

photoresist

substrate


Lithography

UV Lithography – (Suss Mask align 4”)

• 200W Hg lamp

• UV light wave length: 365nm

• Light intensity : 28mW/cm2

• Exposure uniformity: ± 1,3%

• Sample :

– ≤ 4” wafer (planar)

– From 0,5 to 5 mm

diameter tubes (100 mm

length)

• Cr mask: 5”


• SEM:

– resolution: 0.9nm (1.4nm) @ 15kV (1kV)

– secondary and back scattered electron detection:

– large chamber for inspection of 4’’ (6’’) wafers

• FIB:

– Gallium Ion emitter

– resolution: 5nm @ 30kV

• GIS:

– Platinum and Insulator (SiOx) deposition

– Insulator and Metal Etching

• E-beam-lithography

– pattern size <50nm

• EDX:

– LN2 free Detector (Oxford)

– energy resolution: 129 eV (Mn K)

Lithography

FEI Dualbeam Helios Nanolab



Ion Beam Etching

Ionfab 300 Plus provided by Oxford Technologies

Specifications

• Up to 6“ substrates can be processed.

• A wide variety of materials can be

etched: Metals, oxides, semiconductors, …

• Etch uniformity over 6‘‘ at least

as high as 3%

• End point detection available

• He backside cooling

Advantages of the method:

• Flexibility: since probe material is

„merely“ milled, any layer or multilayer

system can be patterned.

• Reliability: the SIMS (Scanning Ion Mass Spectrometry)

feature allows for an exact monitoring of the etch process

and for the detection of process end point.



Inductively Coupled Plasma etching: Bosch process

• ICP-RIE-Tool from Sentech (SI500)

– SF6 based plasma chemistry step to etch into silicon

– Alternating plasma with C4F8 deposition passivate the sidewall

• Used for:

• Deep etching of silicon structures


Optical Microscope

• Optical Microscope Nikon

Eclipse L200

– magnification up to 1000x

– objectives: 5x, 10x, 20x,

50x, 100x

– 8 x 8 stage with 4“-6“

wafer holder

– filter for photo resists

– bright field/dark field

– polarizer and analyzer

Lithography


Lithography

Profilometer

• Ambios XP-2

– Stylus radius 2µm

– Stylus force 0.05mg – 10mg

– Motorized X-Y-Stage, 6“

– Manual 360° rotation

– Vacuum chuck

– 40x-160x color camera



Outline







Vacuum technologyA definition of vacuum:

• Theoretically: a space without matter

• Practically: a chamber in which the pressure is far below the normal

atmospheric pressure. Processes carried out in this chamber are not

effected by the remaining gas.

Vacuum technology is the entirety of systems and processes applied

for reducing pressure in cavities.

classification of pressure ranges

class pressure [mbar]

low vacuum (Grobvakuum) 103 – 100

fine vacuum 100 – 10-3

high vacuum 10-3 – 10-7

ultra high vacuum < 10-7


Vacuum technology

A

FP

Pressure P is the force F per unit area applied to an object in a

direction perpendicular to the surface.

Pressure Units

pascal bar technical

atmosphere

physical

atmosphere

torr pounds per

square inch

1 Pa 1 N/m² 10-5 1.0197x10-5 9.8692x10-6 7.501x10-3 145.04x10-6

1 bar 105 1 1.0197 0.98692 750.06 14.504

1 at 98 067 0.98067 1 0.96784 735.56 14.223

1 atm 101 325 1.01325 1.0332 1 760 14.696

1 torr 133.32 1.333x10-3 1.3595x10-3 1.3158x10-3 1 19.337x10-3

1 psi 6 894.8 68.95x10-3 70.307x10-3 68.046x10-3 51.715 1


Vacuum technology

Basic assumptions:

• A number N of atomic particles with mass ma is uniformly distributed in

volume V.

• The particle agitation is disordered.

• Each particle moves with its own velocity v.

momentum:

kinetic energy:

vmp a

2

2

1vmE akin


Vacuum technology

The ideal gas law combines the quantities Pressure P, volume V and

temperature T:

In vacuum science the ideal gas low is an accurate approximation since

particle densities are low.

Standard reference conditions:

1-23

23-

mol6.02x10 constant Avogadro :

K)J/(mol 8.31 constant gas :

/1.38x10 constant Boltzmann:

with,

a

a

N

R

KJk

N

NnnRTkTNPV

Tn = 273.15 K = 0°C

Pn = 1.013 bar = 760 Torr


Vacuum technology

The velocity distribution of ideal gas particles is given by the

Maxwellian function F(v):

kT

mv

evkT

mvF

dv

dN

N22

2

32

42

)(1

velocity

particle

number

temperature


Vacuum technologyThe average path a particle moves without collision with another particle is

called the mean free path. In MST many processes (e.g. deposition processes)

demand large values of the mean free path in the range of chamber dimensions.

• Particles behave like firm balls with radius r∞.

• A collision happens if the center of a second particle enters the cross section

of particle 12

R

Image source: W. Menz,

Mikrosystemtechnik für

Ingenieure, 2005


Vacuum technology

On its path particle 1 will hit all the particles contained in the volume lV

Number of collisions:

Mean free path:

The mean free path increases with decreasing particle density ρ and

cross section.

lVN

1

N

l

l


Vacuum technology

Mean free path of molecules [m]

pressure [mbar] air hydrogen

1000 60 x 10-9 200 x 10-9

1 60 x 10-6 200 x 10-6

10-3 6 x 10-2 20 x 10-2

10-6 60 200

10-9 60 x 103 200 x 103

values according to: W. Menz, Mikrosystemtechnik für Ingenieure, 2005


Vacuum technology

Adsorbtion and Desorbtion

If gas atoms collide on a surface, then they remain there with a particluar

probability, i.e. they are adsorbed. The process of liberation of atoms off the

surface is in competition with that and is called desorbtion.

Monolayer

The surface plane is covered as densely as possible with adsorbed gas atoms

adjacent to one another.

Lower coverage

At lower coverage n one

refers to a partial coverage:

Image source: R. Zengerle, lecture notes, Mikrosystemtechnik

monon

n


Vacuum technology

Monolayer formation time (monotime):

• The time necessary in order to cover an initially free surface with a

monolayer:

• Particle flux j depends on gas pressure and temperature. From the ideal gas

law and the Maxwellian function one can derive:

• For nitrogen at room temperatur:

jnt monomono /

RTMNP

nt molar

a

monomono 2

][; 106.3 6

mbarPP

stmono

(assuming a sticking coefficient S = 1)


Vacuum technology

Nitrogen at room temperature

pressure

[mbar]

1 10-3 10-7 10-11

tmono [s] 3.6 x 10-6 3.6 x 10-3 36 100 h

Monolayer formation time:

Sticking coefficient S = rate of adsorbtion / rate of impingement

• strongly material dependent (surface and gas)

• strongly dependent on partial coverage

• e.g.: S = 0.1 … 10-3 for Nitrogen on Si (111) *

* R. E. Schlier, H. E. Farmsworth, Structure and Adsorption Characteristics of Clean Surfaces of

Germanium and Silicon, J. Chem. Phys. 30(4), 917, 1959.


Vacuum technology

Summary:

pressure range pressure mean free path monotime

low vacuum

fine vacuum

high vacuum

ultra high vacuum

b: chamber dimension

Micro/Nanosystems Technology · Magnetron Sputtering device (ALCATEL 450) • Power supply: – RF...

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