#### Transcript Sputtering - Royal Institute of Technology

Sputtering The removal of surface atoms due to energetic particle bombardment Sputtering Sputtering First observations of cathode erosion in gas discharges W.R. Grove 1853 Sputtering Removal of surface material as a result of energetic particle bombardment. • • • • • • • • First observations: W.R. Grove 1853, J.P. Gassiot and M. Faraday 1854, 1858. J. Plücker 1858. Useful for thin film coating? First systematic studies: W. Crookes 1891, G. Granquist 1897. Independent of target temperature. J. Stark 1908, 1909. Hot spots? Binary elastic collisions? Cosine emission distribution R. Seeliger 1935. Rules out the collision theory? Crystal structure effects, G.K. Wehner 1956. Collisions back in. Sputtering yields always decrease at high energy : 1/E. Linear collision cascades, relation to nuclear stopping power, J. Lindhard et al. 1963, J. Davies et al. 1960-64. P. Sigmund 1967-69. BCA Monte Carlo, MARLOWE, TRIM. M.T. Robinson 1974, J. Biersack and J.F. Ziegler 1974 Applications in semiconductor industry, coating industry, surface analysis, fusion plasma physics and and space physics Sputter deposition DC- and RF sputter deposition is a convenient and inexpensive coating Technique. Sputter deposition Magnetron sputter deposition is very widely used and allows low pressure discharge, high coating quality and fast deposition Secondary Ion Mass Spectrometry (SIMS) Secondary Ion Mass Spectrometry (SIMS) JET divertor 1999-2001 1998-2004 Elemental mapping by static SIMS J.P. Coad et al. J. Nucl. Mater 363-365(2007) Sputtering Sputtering yield atoms removed Y ( E , ) incident particle Differential sputtering yields Y Y , ,Yq ,Y Yq E1 1 q 105 Y 103 Sputtering yield measurements Sputtering yield measurements Sputtering yield measurements Yield energy dependence. Ejection angle distribution, B. Emmoth, H. Bergsåker et al 1989, 1990 Sputtering Velocity distribution of sputtered atoms, measured by laser induced fluoresence. W. Husinsky et al. 1986 Sputtering Energy distribution of sputtered Tungsten atoms and tungsten clusters. G. Staudenmaier 1984 Crystal structure effect in Sputtering Single crystal effects in sputtering, G. K. Wehner, Phys. Rev. 102(1956)690-704 Non linear Sputtering yield with heavy ions Non linear sputtering yield, evidence of spikes . H.H. Andersen and H. Bay 1974 Three different regimes for theory Single knock-on regime Linear cascade regime Spike regime Nuclear stopping power Electronic stopping power Results from linear cascade theory The linear cascade regime theory got its semi-final form from P. Sigmund, 1969 v G (r , v , v0 , t ) Nv K (v ; v ', v '')d 3v ' d 3v '' G G ' G '' t d ( E , T ) Cm E mT 1 m dT ,0 m 1 F ( E , E0 ) m ( E ) / E02 1 m E1 2Y FD ( E , , 0) m cos 1 3 2 m E11 4 NCm ( E1 U 0 ) Monte Carlo calculations TRIM , J.P. Biersack and W. Eckstein 1984 MARLOWE Monte Carlo calculations Molecular dynamics, C. Erginsoy et al 1964 Monte Carlo calculations TRIM A simple plasma impurity model dN H NH in H dt dN Z NZ in Z dt out inZ YHZ out Y H ZZ Z d j , 0 dt H YHZ YHZ Z , 1 YZZ 1 YZZ in j out j Sputtering in fusion devices Sputtering in fusion devices Impurity fluxes in TEXTOR I. Gudowska, H. Bergsåker et al. J. Nucl. Mater. 176-177(1990)363 Conclusions • Sputtering by particle bombartment has been observed since 150 years. Apart from being a nuisance in many technical systems it alöso has a wide range of useful applications. • Physical sputtering is well understood today, especially in the linear cascade regime. Monte-Carlo methods are very useful in the single-knockon regime and with special boundary conditions. • Physical sputtering is a central physical phenomenon in fusion devices. For plasma modeling Monte Carlo codes and semi-empirical fits are used and give satisfactory results.