1. Ion Beam Analysis of the Composition and Structure of Thin Films
Torgny Gustafsson, Physics
and
Eric Garfunkel, Chemistry and Chemical Biology

2. Experimental Details
Medium Energy Ion Scattering: A refinement of Rutherford Backscattering Spectroscopy with enhanced depth and angle resolution (~3Å vs. ~100Å)
A quantitative technique, with well known cross sections and an unusually short distance between data and interpretation
MEIS counts the number of atoms in the sample
By analyzing peak shapes (energy distributions), depth profiles can be obtained

3. MEIS facility at Rutgers*
NRP chamber beam line
ion implanter
XPS system
preparation
chamber
scattering
*Picture taken in 2004

4. Resonant nuclear reactionsp

5. UHV transfer system for growth and other analysis

6. Atomic Layer Deposition

7. Energy distribution for one angle
2D MEIS Data
H+ Energy [keV]
Angle
SiO2/poly-Si/ZrO2/Ge(100)
Energy distribution for one angle
Angular distribution for one element
Energy distributions:
mass (isotope) specific
quantitative (2% accuracy)
depth sensitive (at the sub-nm scale)

8. Energy spectrum and depth profiles
Simulation of the peaks in the energy spectrum:
 scattering cross section
 stopping power (19 eV/Å in ZrO2)
 energy straggling
 detector resolution
 "Near surface" depth resolution  3 Å

9. SiO2/Si(001) oxidation (isotope marking)
Transition zone, SiOx
SiO2
Si (crystalline)
Surface exchange
Growth
800 C
900 C
T (oC)
Time (min)
Oxide growth (Å)
High-k
700 30 11
800 18
950 25
SiO2*
750
165 5
2640 10
900 60
300 21
1860 27
Faster interfacial SiO2 growth in case of high-k oxides in comparison to the SiO2 thickness growth for bare Si
*Gusev, Lu, Gustafsson, Garfunkel, PRB 52 (1995) 1759.

10. Diffusion in gate dielectrics
Si-substrate
O-exchange
in surface
layer
SiO2
growth
at interface
Oxygen (O2) transport in SiO2 O2
Si-substrate
Atomic oxygen (O) transport in high-k films
SiO2 growth,
O-exchange
at interface
O-diffusion and
exchange in bulk
of oxide
High-k
O2 decomp.
at surface O2 O
SiO2 films:
amorphous after annealing
molecular O2 transport in SiO2
decomposition by SiO desorption
(Many) high-k films:
tend to crystallize at low T
atomic O transport in high-k film
high oxygen mobility

11. ZrO2 film re-oxidized in 18O2
30Å Al2O3 annealed in 3 Torr 18O2
ZrO2 film re-oxidized in 18O2
No change in Zr profile
Surface flat by AFM
Deeper O and Si
Isotopic profiling of Zr and Al oxides
Significant interfacial SiO2 growth for ZrO2, less for Al2O3
Dramatic oxygen exchange: 18O replaces 16O
SiO2 growth rate faster than DG-like growth

12. Presence of nitrogen in high-k film: effects on oxygen exchange
(HfO2)2(SiO2)/SiN/Si(001) films have been submitted to various post growth anneals (NH3, N2, O2, Tanneal = oC)
only annealing in NH3/700oC/60s results in nitrogen incorporation in HfSiO6 with oxygen removal (final composition of HfSiO5N (O : N = 5:1))
Sample
as grown
annealed in NH3
N content, 1015 cm-2
2.59
4.09

13. Gettering of O in the dielectric by Ti overlayer
300oC
UHV
Si (100)
HfOx
HfSiOx
TiOx Ti RT
Si (100)
HfO2
SiO2
Si (100)
HfO2.07
SiO2
27Å 6Å
As-deposited amorphous HfO2 film has small amount of interfacial SiO2 (~6-7Å) and excess of oxygen (~HfO2.07)
Deposited Ti forms uniform layer, no strong intermixing with HfO2;
Oxygen concentration in Ti layer is small (TiOx, x<0.10)

14. Composition of Ti/HfO2/SiO2/Si(001) gate stack (as-deposited)
Ti layer oxidizes on the surface and at the Ti/HfO2 interface (TiOx, x<1)
partial depletion of oxygen from HfO2 layer
HfO2 + Ti  HfO2-x + VO (HfO2)+ TiOx
SiO2 remains at the HfO2/Si(001) interface
TiOx
TiOd
Si (100)
HfO2
SiO2 Ti

15. Compositional profile after anneal to 300oC
Ti + xO  TiOx
Decrease of the Si surface peak and decrease of the width of the O peak indicate partial removal of SiO2 layer
Incorporation of some of the Si initially present in the interfacial SiO2 layer in the high-k layer
After air exposure Ti oxidation in the surface layer
Si (100)
HfO1.9
HfSiOx
TiOx
x/2 SiO2 + Ti  x/2 Si + TiOx
TiOx is Ti alloy overlayer
DGo573K(x=0.49) = -54kJ/mol

16. HfO2 deposition on S-passivated InGaAs(001)
Sulfur (1.3×1015atms/cm2) is distributed at the HfO2/InGaAs interface
HfO2 layer has small oxygen excess;
Thin Ga-rich interfacial In0.13Ga0.87Ox:S layer is present,
Elemental As can still present at the interface at small concentration
HfO2
5Å InGaOx
InGaAs(001) S

17. Depth profiling for Al/HfO2/S-pass. InGaAs(001)
a-InGaAsx
InGaAs(001)
AlOx
XPS results: S ?
HfO2
a-InGaAsx
InGaAs(001)
HfO2
a-InGaAsx
InGaAs(001)
AlOx
S expected s

18. Interface composition
Normal incidence, 98keV H+, scattering angle 125o (substrate Si blocking) SrTiO3/SrTiSixOy/Si(001)
Sr, Ti and O are observed in the interface region - they are visible to the ion beam (not blocked) in this scattering geometry
SrTiO3
78Å
TiSixOy 2Å
Si(001) 6Å
SrO
Ti1-xSrxSiyOz 8Å or