1. NEEP 541 – Sputtering
Fall 2002
Jake Blanchard

2. Outline Sputtering Definitions Models Sample Data Angle of Incidence
Correlations

3. Definitions
Sputtering=ejection of atoms from solid surface under bombardment by energetic ions
Measured as recession rate of surface (m/s)

4. Schematic of Process

5. Modeling Determine scattering cross section
Determine amount of energy deposited near surface
Convert energy to density of recoils near surface
Determine number of recoils which reach surface
Compare energy to binding energy

6. Modeling
Use inverse power law potentials

7. Modeling

8. Sigmund Theory
Assume sputtering is proportional to energy deposited (FD) near surface
Hence, sputtering is proportional to stopping power near surface
Angle of incidence

9. Stopping and Sputtering Distributions – Kr on Cu

10. Modeling
Let G*d3v*dx be the average number of atoms moving at time t with velocity v in the layer between x and x+dx

11. Modeling Expand in Legendre polynomials Take moments
Separate elastic and inelastic collisions
Neglect Ed
Use only leading terms

12. Result
 depends on m, incidence angle, and on mass ratio

13. Copper Target
E (keV)

14. Z1 Dependence

15. He on ??

16. Tungsten Self-Sputtering

17. Mass Ratio Dependence

18. Angle of Incidence
Empirically, the dependence of sputtering on the angle of incidence is:

20. Ar on Copper

21. Copper Target

22. Empirical Correlation
threshold

23. Empirical Correlation
C. Garcia-Rosales, “Revised Formulae for Sputtering Data, J. Nuc. Mat., 218, 1994, p. 8.

24. Some Data Incident Target Eth U0 He Pb 40 2 Ar 45 Ag 3 Ne 23 Kr 85 Cu34
3.5 56