1. Jari Koskinen, Sami Franssila jari.koskinen@aalto.fi 19.9.2016
MT P Thin Film Technology Doctoral course (8 credits) 1. Source of material for thin film process
Jari Koskinen, Sami Franssila

2. Contents Material from solid and/or gas Vapourizing ion sputtering
laser processing
Arc evaporation
Sputtering
Gas ambient
neutral gas
reactive gas
Gas kinetic theory
vacuum basics
molecular mean free path,
accumulation of a molecular film
thermalization
Impurities

3. SOURCE solid
liquid
vapor
gas
SUBSTRATE
component
tool

4. Extraction of materials from solid
Evaporation
Sputtering
Arc (evaporation)
Laser heating
Thermal
Kinetic

5. Evaporation
Thomas M. Christensen
UCCS 2000

6. electron beam evaporator view of sample with beam shutter

7. Evaporation temperature for p = 10-2 torr =1.33 10-2 mbar
[Mahan, p149]

8. Vaporization
Evaporation or sublimation of atoms from surface due to thermal energy
If the surface of source is in equilibrium with the vapor, the rate of molecules flowing from the source is:

9. Vapor pressure

10. Vapor pressure

11. Vapor pressure from tabulations

12. Vapor pressure of alloys

13. Vapor pressure of alloys

14. Thomas M. Christensen
UCCS 2000

15. Methods to heat target Resistive electron beam easy to upscale
clean process
cooled crusible may be used

16. Sputtering of target
Erosion of target due to collision of ions to the surface

17. Sputtering
Source of energetic ions
plasma
ion source ( plasma inside)

18. Features of sputter prosses
Acceleration of an ion across the cathode sheath
Penetration of the target, resulting in a series of atomic collisions
Backward ejection of one or more recoiling target atoms
The maximum possible projectile energy – difference between the plasma potential and that of the cathode
Ions,photons, electrons and neutral cause sputtering
The target may emit neutral, ions and clusters

19. Sputtering yield of elements
Thomas M. Christensen
UCCS 2000

20. About binding energy

21. Sputtering yield of elements

23. Thomas M. Christensen
UCCS 2000

24. Filtering of particles from vacuum arc plasma
plasma follows magnetic field lines
plasma bent around corner
particles go straight
Andre Anders LBL

25. Laser ablation

26. Plasma plume
Copper target

27. Laser plasma plume
Carbon plasma from graphite target

28. Particularly suitable for alloyed materials
Organic Spintronics

29. SOURCE solid
liquid
vapor
gas
TRANSPORT
gas phase
vacuum
liquid
SUBSTRATE
component
tool

30. Residual gas Pumping of: Residual gas: Adsorption – Desorption
Diffusion of dissolver or trapped gas
Permeation trough materials
Leaks
diffusion of dissolved molecules
desorption
pump
permeation
leak

31. Total pressure of residual gasses
Average mean free path (distance between collission) in nitrogen residual gas
<λ>
Ultra
Good High
High
Inter-mediate
Rough
Total pressure of residual gasses

32. Total pressure of residual gasses
Average mean free path (distance between collission) in nitrogen residual gas
<λ>
Ultra
Good High
High
Inter-mediate
Rough
Total pressure of residual gasses

33. Vapour and liquid in vacuum - residual gas is a major source of impurity
pump
balance:
condensation = evaporation
balance:
pumping = evaporation
pressure constant until all liquid is pumped

34. Total pressure of residual gasses
Time to form one molecular layer on surface
Ultra
Good High
High
Inter-mediate
Rough
Total pressure of residual gasses

35. Critical temperatures and pressures for some residual gasses
Gas or vapor
pump
Helium
Hydrogen
Nitrogen
Carbon monoxide
Argon
Oxygen
Methane
Carbon dioxide Chlorine
Ether
Ethanol
Carbon tetraclor.
Water
above Tc no liquid

36. Gas sources in reactive sputtering or reactive evaporation
controlled vapor pressure by using mass flow controllers
oxides, nitrides, carbides, hydrides
oxygen containing gas or vapor are main sources of contamination in thin films
e.g. Al, Ti, -> AlOx and TiOx