1

– Evaporation• Thermal evaporation• E-beam evaporation

– Sputtering• DC sputtering• RF sputtering• Reactive sputtering

– Chemical Vapor Deposition– Laser ablation– Spin-on/liquid deposition

• Spin-on glass and dopants• Sol-gel deposition

Thin film deposition

Vacuum requirement

• Long mean free path – Larger than 1m– pressure less than 5 x 10-6 Torr

• Free of reactive components– Oxygen

• Free of outgassing during evaporation

2

• Physical Vapor Deposition (PVD)– Film is formed by atoms directly

transported from source to the substrate.• Evaporation• Sputtering

• Chemical Vapor Deposition (CVD)– Film is formed by chemical reaction on

the surface of substrate.• SiO2, Si3N4, SiC, W CVD deposition• Atomic layer deposition• Crystal growth

• Evaporation– Thermal evaporation– E-beam evaporation

3

E-beam evaporationMaterial contained in a crucibleEvaporation of almost any material including refractory metalsNo control of volatile components/stoichiometric composition

Thermal E-beam

Temperature range

~ 1800°C ~ 3000°C

Deposition rate

0.1 ~ 2 nm/s 1 ~ 10 nm/s

Typical evaporant

Au, Ag, Al, Cr, Sn, Ga, Ti, NaCl, KCl, MgF2

AlsoPt, W, Ta, Zr, Al2O3, SiO2, TiO2, SnO2

4

Shadowing effectsIncomplete step coverage

Mitigated by rotation & angled evaporation

5

3-Boat Evaporator• 3 separate evaporation

boats• Alloyed layers

– SnAu, AuGe

• Adhesion layers– Cr, Ti

• Protection layer– Au, Pt

Amorphous

Crystalline

6

• Sputtering– DC sputtering– DC magnetron

sputtering– RF sputtering– Reactive sputtering

Magnetron sputtering:Magnetic field concentrates the plasma for more efficient sputtering

7

For SiO2, borosilicate filmsOther insulators

8

• For the deposition of compound thin films

• Addition of appropriate reactive gas (O2, propane, N2)

• Oxide, carbide, nitride

9

Evaporation SputteringLow energy atoms (~0.1 eV) High energy atoms/ions (1~10 eV)

•Denser film•Smaller grain size•Better adhesion

High vacuum•Directional•Good for lift-off•Lower impurity

Low vacuum•Poor directionality•Better step coverage•Gas atom implanted in the film

Point source•Poor uniformity

Parallel plate source•Better uniformity

Component evaporate at different rate•Poor stoichiometry control

All component sputter with similar rate•Maintains stoichiometry

10

– Low-Pressure CVD (LPCVD)

– Plasma-Enhanced CVD (PECVD)

– Atmosphere-Pressure CVD (APCVD)

– Metal-Organic CVD (MOCVD)

Examples: SiO2: SiH4 and O2Si3N4: SiH4 and NH3

11

12

ALD deposition

• Based on two self-limiting half reactions• Deposition of one atomic layer per cycle (slow)• Superior thickness control of very thin layers

0

10 20 30 40 50

0 40 80 120 160 200 240

Time (s)

W

Al2

O3

T = 177°C 1 - 5 - 1 - 5 (W)1 - 5 - 1 - 5 (Al

2O

3)

Process Material Grain size

Film density

Deposition rate

Substrate temperature Directional

Thermal evaporation

Metal or low melting point

materials

10 ~100 nm

poor 0.1 ~ 2 nm/s 50 ~ 100°C yes

E-beam evaporation

Both metal and

dielectrics

10 ~100 nm

poor 1 ~ 10 nm/s 50 ~ 100°C yes

SputteringBoth metal

and dielectrics

~ 10 nm good

Metal: ~ 10 nm/sDielectrics:

0.1 ~ 1 nm/s

~ 200°C Some degree

PECVD Many dielectrics

10 ~100 nm

good 1 ~ 10 nm/s 200 ~ 300°C Some degree

LPCVD Many dielectrics

1 ~ 10 nm excellent 1 ~ 10 nm/s 600 ~ 1200°C isotropic

13

Electroplating/Anodization

Inert Electrode (Pt, C)

CuSO4

H2O

Electrolyte

Wafer

DC source

V

• Metals– Cu, Au, Cr ….

• Efficient use of material• Less dense than evaporation/sputtering• Requires seed layer (Strike/Flash)

Reduction reaction Cu+ + e- → Cu

AnodeCatode Resist process

Resist removal

W/Au Metallization ProcessW/Au flash deposition

Photo Resist process

Electroplating

Resist removal

Au etch (I/KI)

W etch (CF4 RIE)

14

– Laser ablation• Maintains composition• Used for perovskites

– Ferro-electric materials– High-temperature superconductors

– Spin-on/liquid deposition• Spin-on glass and dopants• Sol-gel deposition• Spray-on deposition

Alternate thin film deposition